text:
Communication Networks/Channels

Channels
A channel is a communication medium, the path that data takes from source to destination. A channel can be comprised of so many different things: wires, free space, and entire networks. Signals can be routed from one type of network to another network with completely different characteristics. In the Internet, a packet may be sent over a wireless WiFi network to an ethernet lan, to a DSL modem, to a fiber-optic backbone, et cetera. The many unique physical characteristics of different channels determine the three characteristics of interest in communication: the latency, the data rate, and the reliability of the channel.

Bandwidth and Bitrate
Bandwidth is the difference between the upper and lower cutoff frequencies of, for example, a filter, a communication channel, or a signal spectrum. Bandwidth, like frequency, is measured in hertz (Hz). The bandwidth can be physically measured using a spectrum analyzer.

Bandwidth, given by the variables Bw or W is closely related to the amount of digital bits that can be reliably sent over a given channel:

 * $$r_b = 2W$$

where rb is the bitrate. If we have an M-ary signaling scheme with m levels, we can expand the previous equation to find the maximum bit rate for the given bandwidth.

 * $$r_b = 2Wm$$

Channel Capacity
The "capacity" of a channel is the theoretical upper-limit to the bit rate over a given channel that will result in negligible errors. Channel capacity is measured in bits/s.

Shannon's channel capacity is an equation that determines the information capacity of a channel from a few physical characteristics of the channel. A communication systems can attempt to exceed the Shannon's capacity of a given channel, but there will be many errors in transmission, and the expense is generally not worth the effort. Shannon's capacity, therefore, is the theoretical maximum bit rate below which information can be transmitted with negligible errors.

The Shannon channel capacity, C, is measured in units of bits/sec and is given by the equation:

 * $$C = W \log_2 (1 + SNR)$$

C is the maximum capacity of the channel, W is the available bandwidth in the channel, and SNR is the signal to noise ratio, not in DB.

Because channel capacity is proportional to analog bandwidth, some people call it "digital bandwidth".

Acknowledgement
Digital information packets have a number of overhead bits known as a header. This is because most digital systems use statistical TDM (as discussed in the Time-Division Multiplexing chapter). The total amount of bits sent in a transmission must be at least the sum of the data bits and the header bits. The total number of bits transmitted per second (the "throughput") is always less than the theoretical capacity. Because some of this throughput is used for these header bits, the number of data bits transmitted per second (the "goodput") is always less than the throughput.

In addition, since we all want our information to be transmitted reliably, it makes good sense for an intelligent transmitter and an intelligent receiver to check the message for errors.

An essential part of reliable communication is error detection, a subject that we will talk about more in depth later. Error detection is the process of embedding some sort of checksum (called a CRC sum in IP communications) into the packet header. The receiver uses this checksum to detect most errors in the transmission.

forward error correction
Some systems use forward error correction (FEC), a subject that we will talk about more in depth later. In such a system, the transmitter builds a packet and adds error correction codes to the packet. Under normal conditions -- with very few bit errors -- that gives the receiver enough information to not only determine that there was some sort of error, but also pinpoint exactly which bits are in error, and fix those errors.

ARQ: ACK and NAK
In addition, since we all want our information to be transmitted reliably, it makes good sense for an intelligent transmitter and an intelligent receiver to communicate directly to each other, to ensure reliable transmission. This is called acknowledgement, and the process is called hand-shaking.

In an acknowledgement request (ARQ) scheme, the transmitter sends out data packets, and the receiver will then send back an acknowledgement. A positive acknowledgement (called "ACK") means that the packet was received without any detectable errors. A negative acknowledgement (called "NAK") means that the packet was received in error. Generally, when a NAK is received by the transmitter, the transmitter will send the packet again.

If the transmitter fails to receive a ACK in a reasonable amount of time, the transmitter will send the packet again.

Streaming Packets
In some streaming protocols, such as RTP, the transmitter is sending time-sensitive data, and it can therefore not afford to wait for acknowledgement packets. In these types of systems, the receiver will attempt to detect errors in the received packets, and if an error is found, and it cannot be immediately corrected with FEC, the bad packet is simply deleted.

title: Communication Networks/Channels


text:
User talk:68.79.54.175

You have been temporarily blocked from editing Wikibooks. You were warned several times that linking to commercial sites is not allowed. If you wish to make useful contributions, you are welcome to come back after the block expires.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: User talk:68.79.54.175


text:
Communication Systems/M-ary Modulation Schemes

Now what if try to cram more information into a single bittime? If we take 2 bits at a time, and arrange them together, we can assign each set of 2 bits to a different symbol, and then we can transmit the different symbols.

Pronunciation
"M-ary" is pronounced like "em airy".

Example: Q-ASK
Let us use the following scheme:

 * "00" = +5V
 * "01" = +1.66V
 * "10" = -1.66V
 * "11" = -5V

we can see now that we can transmit data twice as fast using this scheme, although we need to have a more complicated receiver, that can decide between 4 different pulses (instead of 2 different pulses, like we have been using).

Bits Per Symbol
All popular communication systems transmit an integer number of bits per symbol. We can relate the number of bits ("k") and the number of different symbols ("m") with the following equation:

 * $$m = 2^k$$

This causes the number of symbols to be a power of two.

With M-ary modulation techniques, the "symbols per second" rate can be much slower than the "bits per second" data rate.

QPSK
Quadrature phase shift keying (aka 4-PSK) is PSK modulation that has four points in the constellation. There are several variations on this technique:
 * simple QPSK
 * DQPSK (differential QPSK)
 * OQPSK (offset QPSK)
 * SOPSK (shaped offset QPSK)
 * π/4 QPSK (shifted constellation QPSK)

CPFSK (MSK)
[MSK]minimum shift keying

For further reading

 * Constellation diagram
 * Quadrature amplitude modulation


text:
User talk:84.94.196.36

You have been temporarily blocked from editing Wikibooks. You were warned several times that linking to commercial sites is not allowed. If you wish to make useful contributions, you are welcome to come back after the block expires.

title: User talk:84.94.196.36


text:
Template talk:Formal Logic/BookNav

Usage
Used to navigate the level of modules immediately below the. In particular, intended for navitating the level of modules immediately below Formal Logic.

Example

Parameter base
 * The parent to the current page.
 * In the example, Formal Logic.
 * Intended and defaults to "Formal Logic" (relosving to Formal Logic ).
 * May be missing, but must not be blank (i.e., you can omit the parameter, but do not use " |base=| ").

Paramteter up
 * The display name for base.
 * In the example, resolves to "Formal Logic".
 * Intended and defaults to "Formal Logic" (resolving to "Formal Logic").
 * May be missing, but must not be blank (i.e., you can omit the parameter, but do not use "|up=| ").

Parameter prev
 * base/prev is the pervious page at the current level.
 * In the example, Formal Logic/Preliminaries.
 * If blank, to Begin is substituted for a link to the previous page.
 * May be blank, but must not be missing (i.e., you can use "|prev=|", but do not omit the parameter entirely).

Parameter next
 * base/next is the next page at the current level.
 * In the example, Formal Logic/Predicate Logic.
 * If blank, to End is substituted for a link to the next page.
 * May be blank, but must not be missing (i.e., you can use "|next=|", but do not omit the parameter entirely).

title: Template talk:Formal Logic/BookNav


text:
Communication Networks/Internet

The Internet
The Internet has become, arguably, the most important and pervasive example of a network on the planet. The Internet connects people from across a street, and from around the globe at nearly the speed of light. The sections in this chapter will discuss some fundamentals about the internet, and some more advanced chapters on the subject will be discussed later in the book.

Client-Server
The exact relationship between a client and a server in the traditional Client-Server relationship can be complicated, and in today's world, the distinctions are more hazy still. This page will attempt to define what a client and a server are, how they are related, and how they communicate.

 * Client : A client is a communications entity that requests information
 * Server : A server is a communications entity that supplies information, or responds to a request.

Packet-Switching Networks
In the page on Time-Division Multiplexing (TDM), we talked about how we can use a method of breaking information up into chunks, and prefixing that data with address information to send multiple streams of data over a single channel. These chunks of data with their headers are called packets, and are the basis for communication in the Internet.

In local area networks (LAN), packets are sent over baseband channels for very short distances. These networks use Statistical TDM (packets) to control access to the channel, and to control the process of moving information from its source to its address. This process of gettings things where they need to go is called routing. Devices that route packets are called (surprise!) routers.

Over larger networks such as Wide Area Networks (WAN), high-capacity broadband channels such as fiber optic cables connect different local LANs. Over a WAN network, packets are then Frequency Division Multiplexed (FDM) to flow simultaneously over these broad channels. At the other end, these packets are moved back down to a baseband system, and routed using TDM techniques again.

When talking about the different components in a computer network, a lot of different words fly around: Routers, Hubs, Switches, and Gateways, are some example. This page will talk about some of the different pieces of hardware that make the Internet possible. This page will only offer brief explanations of each component, opting instead to save complex discussions on the workings of each for later chapters (or even later books!).

Hubs
An Ethernet hub, normally just called a hub, is a networking device used to connect multiple Ethernet segments in order to create a primitive LAN. They are primarily connected using unshielded twisted pairs/shielded twisted pairs (UTP/STP) or Fiber Optic wires, and require no special administration to function. Hubs operate on the physical layer (Layer 1) of the OSI model, and indiscriminately forward frames to every other user in the domain.

Hubs perform a variety of tasks, including:

Acting as a multi-port repeater, Forwarding frames to all users, Allowing for connectivity to networks using 10base2 or 10base5 media, Partitioning ports when excessive collisions occur, which isolates the affected segments, And broadcasting a "jam" signal when collisions take place on Ethernet media.

Hubs also extend but do not control collision domains, absorbing bandwidth and allowing excessive collisions to occur and hinder performance, when switches or bridges can effectively break up a network.

Despite the increase of switches as the connection medium for workgroups, hubs can still operate in a number of situations:

 Small computer clusters,  Careless users/saboteurs cannot interfere with a hub's function,  Connecting outdated networks to newer methods of data transmission, <li> And when budget is a priority over functionality.</li>

Switches and Routers

 * Routers
 * Network Switch

title: Communication Networks/Internet


text:
Template:Formal Logic/TOCPageNav

Usage
Used to navigate modules at the second level below the. In particular, intended for navitating modules at the second level below Formal Logic.

Example

Parameter base
 * The grandparent to the current page.
 * In the example, Formal Logic.
 * Intended and defaults to "Formal Logic" (relosving to Formal Logic ).
 * May be missing, but must not be blank (i.e., you can omit the parameter, but do not use " |base=| ").

Paramteter up
 * base/up is the parent to the current page.
 * In the example, Formal Logic/Sentential Logic.
 * There is no default. The parameter must be neither blank nor missing.

Parameter prev
 * base/up/prev is the pervious page at the current level.
 * In the example, Formal Logic/Sentential Logic/Formal Syntax.
 * If blank, to Begin is substituted for a link to the previous page.
 * May be blank, but must not be missing (i.e., you can use "|prev=|", but do not omit the parameter entirely).

Parameter next
 * base/up/next is the next page at the current level.
 * In the example, Formal Logic/Sentential Logic/Formal Semantics.
 * If blank, to End is substituted for a link to the next page.
 * May be blank, but must not be missing (i.e., you can use "|next=|", but do not omit the parameter entirely).

title: Template:Formal Logic/TOCPageNav


text:
User:Mahanga/test

This is only a test

title: User:Mahanga/test


text:
Communication Networks/Analog and Digital Telephony

Modems Introduction
'''The telephone network was originally designed to carry voice data. The human ear can only really hear sounds up to the 15 kHz range, and most of that is just high-frequency fluff noise that isn't needed to transmit human voice signals. Therefore, the decision was made to limit the telephone network to a maximum transmission frequency of 3400 Hz, and a minimum frequency of 400 Hz (to limit the passage of DC signals, which could damage the circuit). This gives the telephone network an effective bandwidth of 3000 Hz, which is perfect for transmitting voice, but which isn't that good for transmitting anything else.'''

'''Original telephone modems would use the existing telephone network to carry internet signals to a remote ISP. However, new DSP modems use a much larger frequency band, and this information is separated from the phone network almost as soon as it leaves your house. New voice technologies, such as VoIP completely bypass the old telephone infrastructure, and instead transmit voice signals over the internet.'''

The chapters in this section will talk about the analog and digital hybrid nature of the telephone network.

Modems
Modems were the original widespread method for home users to connect to the internet. Modems modulated digital data according to different schemes (that changed as time passed), and transmitted that data through the telephone network.

The telephone network was originally designed to only transmit voice data, so most of the network installed a series of low-pass filters on the different lines, to prevent high-frequency data or noise from damaging the circuits. Because of this, the entire telephone network can be seen as having a hard bandwidth of 3000 Hz. In reality, the lines used have a much higher bandwidth, but the telephone network cuts out all the high-frequency signals. DSL modems make use of that "lost bandwidth", but the original modems had to work within the 3000 Hz limit.

If we take the Shannon channel capacity of a telephone line (assuming a signal SNR of 40db, which is nearly impossible), we can get the following result:

$$C = 3000 \log_2 (1 + 10000) \approx 40 kbps$$

If we then plug this result into Nyquist's equation, we can find how many levels of transmission we need to use to get this bit rate:

$$r_b = 2W log_2(m)$$

which gives

$$m = 2^{\frac{r_b}{2W}} = 2^{\frac{40000}{6000}} = 2^6.67 < 2^7 = 128$$

Therefore, using a 128-level transmission scheme, we can achieve a theoretical maximum bit rate of 40kb/sec through a modem.

56k Modems
If the theoretical Shannon capacity of the telephone network is 40kbps, how can modern modems achieve a speed of 56kb/sec? The V.42 modem standard (which is what a 56k modem is) utilizes a standard implementation of the Lempel-Ziv compression algorithm, to shrink the size of transmitted data, and therefore apparently increase the transmission speed. The telephone companies aren't magically breaking the Shannon bound, they are just finding an interesting path around it.

DSL
A single strand of twisted-pair telephone wire has a bandwidth of nearly 100 kHz, especially over short distances. Over longer distances, noise will play a much bigger role in the received signal, and the wire itself will attenuate the signal more with greater distance. This is why DSL is only offered in locations that are close to the telephone office, and not in remote areas.

DSL signals require the addition of 2 new pieces of hardware: The DSL modem, and the DSL splitter, which is located at the telephone company, and splits the DSL signal (high frequencies) from the voice signal (low frequencies). Also, some houses may require the installation of additional filters, to prevent cross-talk between DSL and voice signals.

VoIP
With the advent of modems and DSL technology, telephone companies have become an integral part of the internet. It's no surprise then, when phone calls start getting digitized, and sent through the internet, instead of the old telephone network. Voice over IP (VoIP) is the logical conclusion to this train of thought.


text:
Communication Networks/Analog and Digital TV

Coaxial Cable
Coaxial cable has an incredibly high bandwidth (compared to twisted pair), and it distorts very little over long distances. For this reason, coax is able to carry a large number of analog television channels to a very large audience.

Bi-Directional Cable
The original implementation of the television network only needed to move data in one direction: from the station to the homes. For this reason, a number of amplifiers were installed in the network that take the signal from the base station, and amplify that signal towards the homes. However, a problem arises when cable internet users want to transmit data back to the base station (upload).

The original cable TV network had a very large amount of available bandwidth, but it wasn't designed to transmit data from the user back to the network. Instead, the entire network was set up with directional amplifiers, that would amplify data going to the user, but wouldnt affect data coming back from the user.

HDTV
HDTV is the next generation of television, and actually allows better resolution, larger frame size, and lower bandwidth than the traditional analog signals. Also, digital signals are less prone to cross-talk between channels, so channels don't need to be spaced as far apart in the frequency domain as analog signals are.

This chapter will discuss the next generations of the cable TV network.

Channels
The TV channels in an analog TV scheme carry channels spaced every 6 MHz from about 150 MHz to 500 MHz. Below 150 MHz was considered originally to be too susceptible to noise, and there was simply no need to expand above 500 MHz. However, with the advent of cable internet, the system needed to be revamped.

Bandwidth
A new band was set aside, from 55 MHz to 75 MHz, to allow traffic to be uploaded from the user. Also, another band was set aside, from 550 to 750 MHz to allow for cable internet downloads. A cable modem would be able to demodulate these two bands of data, without interfering with the TV signal.

Problems
200 MHz of download bandwidth seems like a lot, but every household on a given line (and there could be 100 or more) all need to share this bandwidth, which can slow down the system, especially in heavily populated areas.


text:
Communication Networks/Cable Television Network

The cable television network is something that is very near and dear to the hearts of many people, but few people understand how cable TV works. The chapters in this section will attempt to explain how cable TV works, and later chapters on advanced television networks will discuss topics such as cable internet, and HDTV.

coax cable has a bandwidth in the hundreds of megahertz, which is more than enough to transmit multiple streams of video and audio simultaneously. Some people mistakenly think that the television (or the cable box) sends a signal to the TV station to tell what channel it wants, and then the TV station sends only that channel back to your home. This is not the case. The cable wire transmits every single channel, simultaneously. It does this by using frequency division multiplexing.

TV Channels
Each TV channel consists of a frequency range of 6 MHz. Of this, most of it is video data, some of it is audio data, some of it is control data, and the rest of it is unused buffer space, that helps to prevent cross-talk between adjacent channels.

Scrambled channels, or "locked channels" are channels that are still sent to your house on the cable wire, but without the control signal that helps to sync up the video signal. If you watch a scrambled channel, you can still often make out some images, but they just don't seem to line up correctly. When you call up to order pay-per-view, or when you buy another channel, the cable company reinserts the control signal into the line, and you can see the descrambled channel.

A descrambler, or "cable black box" is a machine that artificially recreates the synchronization signal, and realigns the image on the TV. descrambler boxes are illegal in most places.

NTSC
NTSC, named for the National Television System Committee, is the analog television system used in most of North America, most countries in South America, Burma, South Korea, Taiwan, Japan, Philippines, and some Pacific island nations and territories (see map). NTSC is also the name of the U.S. standardization body that developed the broadcast standard.[1] The first NTSC standard was developed in 1941 and had no provision for color TV.

In 1953 a second modified version of the NTSC standard was adopted, which allowed color broadcasting compatible with the existing stock of black-and-white receivers. NTSC was the first widely adopted broadcast color system. After over a half-century of use, the vast majority of over-the-air NTSC transmissions in the United States were replaced with ATSC on June 12, 2009, and will be, by August 31, 2011, in Canada.

PAL
PAL stands for phase alternating by line.


text:
Handbook of Genetic Counseling/Abnormal Triple Screen and Family History of PKD

Abnormal Triple Screen and Family History of PKD

Introduction

 * What have you been told about why you are here today?
 * We want to discuss the triple screen results and what they really mean
 * We want to get a family history to assess for any other risks related to pregnancy
 * We want to talk about the different testing options available to you.

Family history update (at beginning depending on level of anxiety)

 * Who in the family has been diagnosed with PKD?
 * What age were they diagnosed?
 * Do any of your family members have high blood pressure?
 * Do any other people in your family have kidney problems?

Medical History (related to PKD)

 * Do you see a doctor regularly?
 * Are you currently on any medication?
 * Have you had a renal ultrasound or CT scan?
 * Have you experienced any urinary tract infections?
 * Have you had high blood pressure?
 * Have you experienced any pain in your stomach or back?

Pregnancy History

 * Verify dates
 * Any exposures?
 * Any cig/alcohol/drug use?
 * Any increase in blood pressure?
 * Any ultrasounds so far? When is the next one scheduled?

Triple screen info.

 * The test itself
 * Best results at 16-18 weeks gestation (can be done from 15-22 weeks)
 * Tests mother's blood
 * NOT diagnostic...simply an indication for additional testing
 * Uses three markers to determine indicators for certain fetal problems
 * The three markers
 * produced by the fetus and the placenta
 * Alpha feto protein(AFP)
 * Human chorionic gonadotrophin (HcG)
 * Most sensitive risk factor for DS
 * Greater than 2.5 MOM indicated risk for DS
 * Estriol
 * Median of 0.5 MOM in Trisomy 18

Serum markers results

 * AFP >2.5 MoM indicates a normal AFTN
 * AFP <0.75 MoM indicates a Trisomy 21

 * hCG >2.5 MoM indicates a Trisomy 21
 * hCG <0.55 MoM indicates a Trisomy 18

 * E3 <0.8 MoM indicates a Trisomy 18 or 21

Patient's results

 * AFP =1.oo, HcG=2.21 , UE3=0.99
 * Increased risk for Down syndrome

Explain chromosomes and what Down syndrome is

 * Trisomy 21 (usually - every cell of body)
 * Characteristics
 * mental retardation (mild to moderate)
 * heart difficulties
 * ear infections
 * Do everything a regular kid can…ride a bike, walk, talk
 * Slower to reach milestones
 * Facial features
 * There is no cure

Calculating risk for Down Syndrome (explain how they determine num.)

 * Look at maternal age + AFP MoM + hCG MoM + uE3 MoM = Down Syndrome Risk
 * Risk ³ 1/270 is considered screen positive
 * This is equal to the midtrimester DSR for 35 year-old women
 * AMA woman's risk may be made less by the triple screen results, but it is still considered a test positive because of her age.

Recommendations for abnormal tests

 * Ultrasound for examination of physical abnormalities
 * Down Syndrome
 * Nuchal fold (2nd trimester)
 * detects 34%
 * Nuchal translucency (1st trimester)
 * detects 77%
 * Short femur/humerus (detects 80-90% when combined with one of the following two)
 * Echogenic bowel
 * Short ear
 * Amniocentesis
 * Explain procedure
 * 1/200 risk for complications
 * Can't detect all problems with the baby BUT will determine chromosome status
 * Fetal karyotype
 * Down Syndrome
 * Triploidy
 * Trisomies 13, 18
 * Other chromosomal abnormalities

The Basics of PKD

 * Definition (Polycystic Kidney Disease)
 * Multiple cysts in the kidney leading to kidney dysfunction
 * Prevalence = 1/400 - 1/1000
 * Characteristics
 * 90% penetrant
 * initial signs = high blood pressure, blood in urine (50%), pain in side, back or abdomen, UTI, kidney stones (20-30%)
 * Final stage = renal failure (60%) after age 40
 * Mitral valve prolapse (26% compared to gen pop 2-3%)
 * aneurysms (5-10%) - occurs in familial clusters
 * liver cysts are possible
 * Diagnosis/medical management
 * renal ultrasounds
 * only after age 30 is a negative ultrasound = 5% risk of disease
 * computed tomography (CT) - to detect aneurysm
 * MRI
 * Prevention
 * Diet control = avoid red meat, eat low protein diet, less salt, fresh fruits and veggies, drink lots of water, avoid caffeine
 * Treatment
 * For pain
 * acetaminophren may help
 * laparoscopic surgery to "unroof" cysts
 * For renal failure
 * dialysis
 * renal transplant (75-80% of kidneys work for 5 years)
 * Inheritance (dominant more commonly - recessive is RARE)
 * Description of autosomal dominant and why this is the type
 * Chance of recurrence if the mother has it = 50% chance
 * Chance of recurrence if the mother doesn't have it same as population risk= <1%???? approximately 10% of the PKD patient community became infected through spontaneous mutation, and not through inheritance.
 * Genetics
 * Two genes identified (a third suspected)
 * PKD1 - 16p (90% of PKD) DX is earlier, progresses more rapidly, more likely to be hypertensive
 * PKD2 - chromosome 4
 * Testing is done through linkage

Her options

 * A amniocentesis for chromosome risk
 * A renal ultrasound for herself (PKD surveillance)
 * If it is negative and she is 30+, chance of having PKD is <5%
 * Testing by linkage analysis for herself and family
 * Costs approx. $2200 per family
 * >95% accurate in families
 * Prenatal determination (preferably after linkage has been established)
 * CVS testing for linkage studies (9-15 weeks)
 * Amniocentesis for linkage studies (15+ weeks)

Psychosocial issues

 * How her brothers illness has affected her
 * Scared about the possibility of having PKD?
 * Worried about PKD for baby?
 * Would a diagnosis of PKD influence a pregnancy decision?
 * How would having a child with DS feel?
 * Support and resources at home?
 * Would the dx of DS influence pregnancy planning?

Resources for patient

 * [Polycystic kidney disease access center http://www.nhpress.com/pkd/]
 * [www.adam.com http://www.adam.com]


text:
Talk:GCSE Science/Osmosis in potato slices coursework

Tell me about Independent Variable and Dependent Variable


title: Template:Japanese/Ruby-2


title: Template:Japanese/Rubywikt-2


text:
User:JMRyan/Formal Logic Resources

Templates and images used in or otherwise relevant to Formal Logic.

Book templates
Template:Formal_Logic:equiv Template:Formal_Logic:Recent_Additions Template:Formal_Logic:Preliminaries_TOC Template:Formal_Logic:Sentential_Logic_TOC Template:Formal_Logic:Predicate_Logic_TOC Template:Formal Logic:SpecialNav Template:Formal Logic:BookNav Template:Formal Logic:PageNav Template:Formal Logic:TOCPageNav Template:Formal Logic:TOCcall

Wikibooks templates
Template:Edit Template:Edit2 Template:If Template:Shelf Template:Show1

Images
Image:EquivalenceSign.png     (Template:Formal_Logic:equiv) Image:FormalLogicTitle.png

title: User:JMRyan/Formal Logic Resources


text:
Data Coding Theory/Transmission Codes

Basic Coding
It turns out that we can actually improve the performance of our system simply by changing the bits in our system. We can change the order of bits, or we can change the number of bits that we send, to help decrease error rates. This chapter will talk about transmission codes that can help increase system performance.

Gray Codes
Let us look at a basic QASK system:

 * 1) "00" = +5V
 * 2) "01" = +1.66V
 * 3) "10" = -1.66V
 * 4) "11" = -5V

We will call these "symbol 1" (for 00), "symbol 2" (for 01), "symbol 3" (for 10) and "symbol 4" (for 11).

Now, let us make a basic assumption that the only errors we get will be errors between adjacent symbols. For instance, Symbol 1 can be mistaken for symbol 2, but symbol 1 can never be mistaken for symbol 3. In reality, there is always a very small chance that this could happen, but we will simply ignore it for our purposes.

Now, we have 6 error conditions:

 * 1) Symbol 1 looks like Symbol 2
 * 2) Symbol 2 looks like Symbol 1
 * 3) Symbol 2 looks like Symbol 3
 * 4) Symbol 3 looks like Symbol 2
 * 5) Symbol 3 looks like Symbol 4
 * 6) Symbol 4 looks like Symbol 3

We can also see that in error conditions 1, 2, 5, and 6, a symbol error only produces 1 bit error. The other bit is actually not transmitted in error. The only time where we see 2 bits transmitted in error is when there is a mixup between symbols 2 and 3. We can calculate our probability of bit error as such:

$$P_\mbox{bit error} = \frac{4}{6}(1) P_\mbox{one bit error} + \frac{2}{6}(2)P_\mbox{two bits error}$$

Pone bit error is the probability that 1 bit from the symbol will be in error. Ptwo bits error is the probability that both symbols will be received in error.

To alleviate this problem, we can reorder our symbols, and map them the following way:

 * 1) "00" = +5V
 * 2) "01" = +1.66V
 * 3) "11" = -1.66V
 * 4) "10" = -5V

Now, when any symbol is received in error, there is only one bit error. This small trick is called "Gray Coding", and is a useful (but simple) method to improve system performance in terms of net bit errors.

Using Gray Codes
Gray codes are a simple example of how using an encoding/decoding mechanism in a communications system can have an effect on the error rate of the system. In future chapters we will discuss error correction codes (ECC) that can be used to find and fix single-bit errors in a signal. If we use Gray codes to ensure that the majority of errors are single-bit errors, we can then use more advanced ECC codes to resolve these errors.

Gray codes are typically not used on their own, but are combined with more robust coding methods, like described above.

For further reading

 * Manchester codes
 * MLT-3 Encoding

title: Data Coding Theory/Transmission Codes


text:
User talk:64.136.26.226

Please stop adding nonsense to Wikibooks. It is considered vandalism. If you would like to experiment, use the sandbox. Thank you.

title: User talk:64.136.26.226


text:
Template talk:Formal Logic/TOCPageNav

Usage
Like Template:Formal Logic:PageNav (see Template_talk:Formal Logic:PageNav) except with appended.

Warning. This template has undocumented changes since Template_talk:Formal Logic:PageNav was written.

title: Template talk:Formal Logic/TOCPageNav


text:
Communication Systems/Line Codes

Line Codes
In addition to pulse shaping, there are a number of useful line codes that we can use to help reduce our errors or to have other positive effects on our signal.

Line coding consists of representing the digital signal to be transported, by an amplitude- and time-discrete signal, that is optimally tuned for the specific properties of the physical channel (and of the receiving equipment). The waveform pattern of voltage or current used to represent the 1s and 0s of a digital signal on a transmission link is called line encoding. The common types of line encoding are unipolar, polar, bipolar and Manchester encoding.

Line codes are used commonly in computer communication networks over short distances.

There are numerous ways digital information can be coded onto a transmission medium. Some of the more common include:

 * [[Image:line code table.gif]]

Each of the various line formats has a particular advantage and disadvantage. It is not possible to select one, which will meet all needs. The format may be selected to meet one or more of the following criteria:

 * • Minimize transmission hardware
 * • Facilitate synchronization
 * • Ease error detection and correction
 * • Minimize spectral content
 * • Eliminate a dc component

The Manchester code is quite popular. It is known as a self-clocking code because there is always a transition during the bit interval. Consequently, long strings of zeros or ones do not cause clocking problems.

Non-Return to Zero Codes (NRZ)
Non-Return to Zero (NRZ) codes are a bit awkwardly named, especially considering that the unipolar NRZ code does return to a zero value. In essence, an NRZ code is just a simple square wave, assigning one value to a binary 1, and another amplitude to a binary 0.

NRZ codes are more bandwidth efficient than bipolar ones. However, their spectral components go all the way down to 0 Hz. This prevents them from being used on transmission lines which are transformer coupled, or for some other reason cannot carry DC.

 * [[Image:NRZ spectrum.gif]]

Unipolar NRZ
Unipolar NRZ is simply a square wave with +V being a binary 1, and 0V being a binary 0. NRZ is convenient because computer circuits use unipolar NRZ internally, and it requires little effort to expand this system outside the computer. Unipolar NRZ has a DC term, but a relatively narrow bandwidth.

Bipolar NRZ
Bipolar NRZ operates using a bipolar voltage supply rail. Marks typically are represented using negative voltages (e.g., -9V), while spaces with positive voltages (e.g., +9V). For example, RS-232C/EIA-232 signaling relies on bipolar NRZ.

-5V +5V -5V +5V -5V -5V +5V -5V -5V 1 0   1   0   1   1   0   1   1

Bipolar NRZ has similar bandwidth and DC balance issues as unipolar NRZ.

AMI
AMI (alternate mark inversion) is another example of a bipolar line code. Each successive mark is inverted and the average or DC level of the line is therefore zero.

 * [[Image:AMI.gif]]

AMI is usually implemented as RZ pulses, but NRZ and NRZ-I variants exist as well.

One of the weaknesses of this approach is that long strings of zeros cause the receivers to lose lock. It is therefore necessary to impose other rules on the signal to prevent this. For example, combining NRZ-M with AMI yields MLT-3, the line coding system used with 100-base-T Ethernet.

CDI
The CDI(Conditioned Diphase Interface) bipolar line code is actually a slightly different form of the original FM line coding used in single-density disk drives and audio cassette tapes. Marks are encoded as alternate polarity full period pulses. Spaces are encoded by half a period at the negative voltage and half period at the positive voltage. This coding scheme has the advantage that it requires less logic to implement than HDB3.

 * [[Image:CMI.gif]]

Manchester
Manchester codes were an invention that allows for timing information to be sent along with the data. In an NRZ code, if there is a long stream of ones or zeros, the receiver could conceivably suffer so much compound jitter that it would either lose or gain an entire bit time, and then be out of sync with the transmitter. This is because a long stream of 1s or 0s would not "change state" at all, but instead would simply stay at a single value. Manchester codes say that every single bittime will have a transition in the middle of the bit time, so that a receiver could find that transition, and "lock on" to the signal again, if it started to stray away from center. Because there are more transitions, however, manchester codes also require the highest bandwidth of all the line codes.

Differential Codes
Some communication channels (such as phase-modulated sine waves and differential twisted pairs) have the characteristic that transitions between the 2 symbols used can be easily distinguished, but when first starting to receive it is difficult to tell which of the 2 states it is in. For example, full-speed USB uses a twisted pair and transmits +3.3 V on one line and 0 V on the other line for "1", but 0 V on the one line and +3.3 V on the other line for "0". Because some cables have an extra half-twist in them, it is impossible for a device that was just plugged in to tell whether the symbol it is currently receiving is a "1" or a "0".

Differential codes still work, not even noticing when the 2 wires get switched.

Differential codes, in general, look exactly the same on a oscilloscope or spectrum analyzer as the non-differential code they are based on, and so use exactly the same bandwidth and have exactly the same bitrate.

Differential codes that work when the 2 wires get switched include:
 * Differential Manchester encoding—based on Manchester encoding
 * Non-Return-to-Zero Inverted (NRZI) -- based on non-return-to-zero (NRZ)

(A few non-differential codes also work even when the 2 wires get switched—such as bipolar encoding, and MLT-3 encoding).

Differential Manchester
Differential Manchester encoding, also called biphase mark code (BMC) or FM1, is a line code in which data and clock signals are combined to form a single 2-level self-synchronizing data stream. It is a differential encoding, using the presence or absence of transitions to indicate logical value. It has the following advantages over some other line codes: •	A transition is guaranteed at least once every bit, allowing the receiving device to perform clock recovery. •	Detecting transitions is often less error-prone than comparing against a threshold in a noisy environment. •	Unlike with Manchester encoding, only the presence of a transition is important, not the polarity. Differential coding schemes will work exactly the same if the signal is inverted (wires swapped). (Other line codes with this property include NRZI, bipolar encoding, coded mark inversion, and MLT-3 encoding). •	If the high and low signal levels have the same voltage with opposite polarity, coded signals have zero average DC voltage, thus reducing the necessary transmitting power and minimizing the amount of electromagnetic noise produced by the transmission line.

title: Communication Systems/Line Codes


text:
User:Ralbury

Richard Albury
Just cleaning up typos and awkward phrasing as I go.

title: User:Ralbury


text:
Template:Formal Logic/Equiv

Usage
Displays equivalence-symbol image with alt set to "is equivalent to". Optionally displays first parameter before and after the image. It is intended that the parameter be used for padding by setting it to "&nbsp;", perhaps repeated.

Examples
 * $$\phi\,\!$$ $$\psi\,\!$$
 * $$\phi\,\!$$ $$\psi\,\!$$

Results from of examples above
 * $$\phi\,\!$$ $$\psi\,\!$$
 * $$\phi\,\!$$ $$\psi\,\!$$

title: Template:Formal Logic/Equiv


text:
Handbook of Genetic Counseling/Achondroplasia-1

Achondroplasia

Contracting

 * Make small talk and establish rapport with the family
 * Elicit the families concerns for
 * Elicit Medical History
 * Elicit Family History/Pedigree
 * AAP Guidelines for Newborns:
 * Examination-
 * Confirm diagnosis
 * Document all measurements on achondroplasia growth charts. Also include the following measurements: Occipital frontal circumference, body length, upper to lower segment ratio
 * Guidance-
 * Discuss AD inheritance
 * Most individuals have normal intelligence and normal life expectancy
 * Growth hormone is not an effective treatment
 * Leg lengthening procedures are currently available
 * Final height is approximately 4 foot for both males and females
 * Discuss possible complications:
 * Kyphosis (associated with unsupported sitting)
 * Small foramen magnum-could lead to cord compression
 * Hydrocephalus- OFC size should be monitored
 * Spinal stenosis- rarely occurs in childhood; in older individuals it manifests as numbness, weakness, and altered deep tendon reflexes (individuals with severe kyphosis are at an increased risk for this)
 * Psychosocial issues
 * Refer family to support group such as LPA or HGF
 * Remind parents that most individuals with achondroplasia lead productive, independent lives
 * Discuss with the family how to tell others about the diagnosis
 * Supply family with support material
 * Discuss recurrence risks for future pregnancies

Genetic Etiology

 * Mode of inheritance- autosomal dominant- 75-80% arise from sporadic mutations. Correlated with advanced paternal age; virtually all new mutations arise in the father's germinal cells.
 * Chromosome location- 4p16
 * Molecular genetics-molecular origin arises from a mutation in one copy of the fibroblast growth factor receptor 3 gene.
 * FGFR3 has an ORF of 2520 nucleotides, encoding an 840 residue protein
 * >99% of cases are caused by a nucleotide change (either G to A= 98% of cases or G to C=1% of cases) at nucleotide 1138, resulting in a Gly380Arg amino acid substitution
 * When FGFR3 is mutated, its normal inhibitory function is constitutively activated (turned on regardless of whether or not fibroblast growth factor is bound to it). This results in the increased inhibition of growth of cartilage cells.
 * Mutations in achondroplasia can be interpreted as a gain-of-function mutation that activates the fundamentally negative growth factor exerted by the FGFR3 pathway.
 * Penetrance- fully penetrant.
 * Homozygosity for the mutation usually results in lethality

Incidence

 * Achondroplasia is the most commonly recognizable form of skeletal dysplasia
 * Prevalence is estimated to be 1:26,000-28,000

Clinical Features/Diagnostic Criteria

 * Short stature 100%
 * Rhizomelic (proximal) shortening of the limbs with redundant skin folds
 * Limited elbow extension
 * Short fingers held in a trident configuration
 * Bowed legs
 * Thoracolumbar gibbus (hump or protuberance) in infancy
 * Exaggerated lumbar lordosis (swayback) develops when walking begins
 * Large head with frontal bossing (prominence)
 * Midface hypoplasia
 * Modestly constricted chest

Radiologic Findings

 * Small skull base and foramen magnum
 * Narrowing rather than widening of the interpediculate distance in the lumbar spine; short vertebral bodies
 * Square iliac wings (square pelvis)
 * Flat acetabulae (the cavity that provides the socket in which the head of the femur fits, narrowing of the sacrosciatic notch and characteristic radiolucency (penetrable by radiation) of the proximal femora
 * Short, thick long bones
 * Flared metaphyses (the growing portion of a bone)
 * Short proximal and middle phalanges

Occurrence/Recurrence Risks

 * One parent with achondroplasia-
 * Risk for each pregnancy is 50%
 * Both parents have achondroplasia-
 * 25% normal stature, 50% achondroplasia, 25% homozygous achondroplasia-lethal

Natural History/Life Span

 * Most individuals with achondroplasia have a normal lifespan
 * These individuals are at an increased risk for premature death
 * Usually the risk arises in infancy or childhood
 * One study found a 7.5% increased risk for death in the first year.
 * Usually associated with foraminal compression of the upper cervical cord or lower brain stem
 * Overall, mean survival is 10% less than in the general population

Testing

 * Diagnostic-
 * Clinical diagnosis is a reasonable approach, FGFR3 molecular testing is reserved for rare instances in which the clinical diagnosis is in doubt
 * Molecular test is both straightforward and currently available
 * The molecular PCR-based test is a direct mutation test that looks for a nucleotide change at the 1138th nucleotide.
 * Prenatal-
 * Can be done in a high risk pregnancy, in which one or both parents are affected
 * Uses DNA extracted from fetal cells (First, the mutation must be identified in the affected parent)
 * Can also be done in a low risk pregnancy. Routine ultrasound may reveal short fetal limbs (usually not apparent until the 3rd trimester)
 * Individuals with this indication may be offered amniocentesis so that a diagnosis can be confirmed/rejected.

Explanation of Findings + Management/Treatment Options

 * Growth and Feeding-
 * Height/length should be monitored at each visit and plotted on achondroplasia specific growth charts.
 * Measures should be taken during adolescence to monitor/prevent obesity
 * No treatment will reverse the growth deficiency
 * Growth hormone therapy has not significantly affected growth
 * Extended limb lengthening techniques has been shown to increase height by up to 12 inches. Procedure involves cutting through the bone, and stretching it as the fractured region heals
 * Development and Behavior-
 * Overall individuals have normal cognitive development and function but they also have delayed and unusual motor development
 * Some have language related problems-may be due to high frequency of chronic ear infections/hearing loss
 * A very small amount will have severe learning problems or MR
 * Hypotonia may be indicative of problems at the craniocervical junction
 * Assessment for special needs is crucial
 * Various adaptive devices such as stools and furniture modifications can be used to assist in short stature/hypotonia needs.
 * Neurological-
 * Hydrocephalus-
 * Assessment of ventricular size and volume of extra-axial fluid by ultrasound, MRI, or computerized tomography at diagnosis
 * All children should have serial HC measurements plotted on achondroplasia specific growth charts every 1-2 months until 1 year of age and then at each visit thereafter.
 * Signs of increased intracranial pressure include, accelerated head growth, bulging fontanel, lethargy or irritability, unexplained vomiting and headaches.
 * If any of these signs occur, MRI should be done and compared to the one obtained at diagnosis
 * If hydrocephalus has developed, shunting should be performed- prognosis is usually favorable
 * Cervicomedullary Junction Constriction-
 * Every infant with Achondroplasia has a small and often misplaced foramen magnum due to abnormal growth of the endochondral cranial base
 * Causes risk for apnea-associated death or paralysis
 * These apnea related deaths often arise due to compression at the craniocervical junction, resulting in damage to the respiratory control centers in the lower medulla.
 * Compression can also result in high cervical myelopathy, which leads to hypotonia, weakness, hyperreflexia, asymmetric reflexes and ankle clonus.
 * Doctors should carefully examine the patient
 * Neuroimaging- tomography or MRI of the brain
 * Overnight sleep study in a sleep center should be performed
 * Parents and care providers should be counseled concerning careful neck support and handling. All strollers, jumpers, baby seats etc. should support the head, and limit movement.
 * If evidence of cord compression is present (from MRI) surgical decompression should be done immediately. Approximately 8% of individuals with achondroplasia undergo this type of surgery.
 * Respiratory-
 * Individuals with achondroplasia have small thoraces. This may result in decreased effective lung volumes, decreased respiratory reserve, and increased hypoxemia.
 * Snoring is a uniform feature and should not be reflective of an obstruction of the airway
 * Obstruction of the airway is common in individuals (#'s vary according to study)
 * May be due to hypoplasia of the cranial base and midface (resulting in diminution of the airway size) as well as hypertrophy of the lymphatic ring
 * In some, appropriate positive airway pressure at night is used to maintain appropriate oxygen saturations.
 * Sleep studies are recommended
 * Surgical removal of the tonsils and adenoids may be necessary
 * Tracheostomy may be needed in rare occasions (2% or less)
 * Ears and Hearing-
 * Middle ear dysfunction is a frequent complication, >50% have it severe enough to require myringotomy and ventilation tube placement
 * ENT evaluation should be done at 6months of age and then every 6-9 months throughout preschool.
 * Hearing loss may result in speech and language delays. In these cases, a referral should be made for speech and language therapy.
 * Musculoskeletal-
 * Kyphosis-
 * Present in 90-95% of infants
 * Usually spontaneously resolves
 * Clinical evaluation of the spine every 6 months through 3 years of age
 * If kyphosis is moderate or marked, radiographic assessment should be obtained
 * Parents should be counseled against allowing unsupported sitting during the first year of life
 * Bracing may be needed if the radiograph shows and irreversible curve of >30°
 * Surgical intervention may be necessary
 * Lumbosacral Spinal Stenosis-
 * Stenosis of the entire spinal canal is uniformly present; more problematic in adults
 * Symptoms include: numbness, dysesthesias, radicular pain, leg weakness, clumsiness, gait changes, problems associated with bowel and bladder dribbling
 * MRI will assess the severity and level of the stenosis
 * Intervention methods include: neurosurgical laminectomy,
 * Decompression laminectomy usually results in some improvement of symptoms and function. Only 50% of patients show long-term benefits, additional surgery is often needed.

Knee instability

 * Nearly all young individuals with achondroplasia have knee instability.
 * Hyperextension of between 20-70°
 * Contributes to the motor delays seen in these individuals
 * Bracing may be needed for severe knee instability (rare)
 * Varus deformity-
 * Bowleg deformity
 * Assessment should be made while child is standing
 * Three weight bearing joints should be "in plumb"
 * Surgery may be needed for those with severe misalignment
 * Other-
 * Most develop lordosis- swayback
 * May exacerbate risk for spinal stenosis in the lumbosacral region (in adults)
 * May be associated with pain at the apex resulting in chronic coccydynia
 * Coccydynia can be treated by sewing padding into the underwear
 * Hypermobility of the shoulders
 * Limitation of elbow movement
 * Surgical intervention for elbow limitation is not indicated, rather adaptive devices should be used
 * Hypermobile wrists
 * Discomfort and fatique of wrists from doing fine motor tasks may be relieved by a stabilizing brace
 * Orthodontics
 * Crowding of the teeth
 * Palatal expansion or braces

Differential Diagnosis

 * Thanatophoric dysplasia- nearly always a lethal condition; more severe findings than achondroplasia
 * Homozygous achondroplasia
 * Hypochondroplasia- milder findings than achondroplasia

Common Psychosocial Issues

 * Anxiety concerning the diagnosis
 * Fear of the associated complications
 * Adjusting and adaptation worries for the family
 * Family support- support groups

Support Groups

 * The Little people of America (LPA)
 * P.O. Box 745
 * Lubbock, Texas 79408
 * Phone: 888-LPA-2001
 * [Website http://www.lpaonline.org]

 * MAGIC Foundation for Children's Growth
 * [www.magicfoundation.org http://www.magicfoundation.org]

 * Human Growth Foundation
 * [www.hgfound.org http://www.hgfound.org]

Resources

 * Pauli RM, Chapter 2. (2001). Management of Genetic Syndromes. Ed. Allanson JE, Cassidy SB. New York: Wiley-Liss, Inc.
 * [www.geneclinics.org http://www.geneclinics.org]
 * Jones KL (1997). Smith's Recognizable Patterns of Human Malformation. Philadelphia: W.B. Saunders Company.
 * American Academy of Pediatrics Committee on Genetics (1995) Health supervision for children with achondroplasia. Pediatrics 95: 443-451.


text:
Handbook of Genetic Counseling/Achondroplasia-2

Achondroplasia

Confirm diagnosis
average size trunk, large head relative to the body size
 * Physical features
 * disproportionate short stature, shortening of the proximal segment of the limbs, prominent forehead, shallow nasal bridge, flattened midface,
 * Radiographs
 * contracted base of the skull, square pelvis shape with a small sacrosciatic notch, short pedicles of the vertebrae, rhizomelic (proximal) shortening of the long bones, trident hands, normal length trunk, proximal femoral radiolucency, chevron shape of the distal femoral epiphysis

Medical evaluation

 * Measurements, proportions, and special growth charts
 * height arm span and lower segment
 * weight
 * control eating habits to avoid obesity
 * head circumference
 * Infantile issues
 * airway obstruction
 * sleep apnea
 * hydrocephalus
 * MRI to determine ventricular size
 * upper cord compression
 * MRI of the foramen magnum

Orthopedic

 * thoracolumbar kyphosis/lumbar lordosis
 * truncal weakness
 * bowing of the legs
 * fibular overgrowth at the knees and ankles
 * hip flexion contractures
 * lumbosacral spinal stenosis
 * orthodontics/crowded teeth

Neurological

 * normal intelligence
 * delayed motor milestones
 * equal deep tendon reflexes

Hearing

 * otitis media
 * conductive hearing loss
 * speech evaluation

Psychosocial assessment

 * Family support
 * family and friends' reactions
 * support groups
 * anticipatory guidance/learning from other families

Long-term planning

 * behavior and development
 * avoid gymnastics and contact sports
 * socialization skills
 * adaptation of the home

occupational therapy consultation

 * schooling
 * SSI benefits

Clinical treatments

 * Growth hormone studies
 * Limb-lengthening procedures


text:
Handbook of Genetic Counseling/Advanced Maternal Age - Amniocentesis

Advanced Maternal Age - Amniocentesis

Introduction

 * Welcome and acknowledge any prior phone contact.
 * Discuss the reason for referral. Do they understand why they were sent to genetics?
 * Assess their concerns and what they hope to gain from the session.
 * Assess their degree of knowledge about genetics, heredity, AMA, etc.
 * Provide overview of the session and discussion topics.

Prenatal Intake

 * Obtain client and partner information (age, occupation, ethnicity, religion, consanguinity, health)
 * Elicit family history and construct pedigree.
 * Pregnancy history (dates, procedures, exposures, complications)
 * Discuss population pregnancy information - every pregnancy has a 3-5% risk for congenital malformations; every pregnancy has a 2-3% risk of miscarriage.

What is AMA?

 * Advanced maternal age applies to anyone aged 35 years or above at the expected date of delivery.
 * As maternal age increases, the risk of birth defects (particularly chromosomal abnormalities) increases.
 * Age 35 is the cutoff for AMA because this is the point where the procedural risk equals the risk of aneuploidy.

What are chromosomal abnormalities?

 * Explanation of chromosomes.
 * Explanation of meiosis, haploid germ cells, fertilization to a diploid zygote.
 * Explanation of non-disjunction. Focus on how women are born with all their eggs and they mature with age.
 * Discuss common trisomies/monosomies (13, 18, 21, 47XXY, 45X), show karotypes, and give general description of clinical features and prognoses.

Risk Assessment

 * Discuss client's age-related mid-trimester risks for any chromosomal abnormalities and for Down syndrome in particular.
 * Record data on intake.

What are the testing options?

 * Triple Marker Screening:
 * Maternal blood test performed at 15-22 weeks.
 * Screening test only, NOT diagnostic.
 * Indirect measurement of fetal AFP, hCG, uE3 production.
 * Detects approx. 85% NTDs, up to 85-90% of DS, and up to 80% of Trisomy 18 in women with AMA.
 * False-positive rate of 25% in women over 35 years of age.
 * Does not detect all chromosomal abnormalities assoc. with AMA

Ultrasound

 * Can detect many major birth defects.
 * Some fetuses with chromosomal abnormalities have characteristics that can be seen by ultrasound as "markers", but others have no visible anomalies.
 * Ultrasound can NOT diagnose chromosome abnormalities.

Amniocentesis

 * Medical procedure that removes a small sample of amniotic fluid (made of fetal urine, contains fetal skin cells) from the amniotic sac surrounding the fetus.
 * Usually performed between 15-18 weeks (although some labs will interpret data from 13.5 to 21 weeks)
 * Fluid is used for genetic analysis - fetal karyotyping, biochemical studies, DNA studies, alpha-fetoprotein and acetyl cholinesterase measurements.

Amnio Procedure

 * Procedure takes 20-45 minutes (1-2 minutes for needle insertion).
 * May be required to have a full bladder.
 * Lie down on back with hands folded behind your head.
 * Abdomen cleansed with betadeine.
 * Local anesthetic (xylocaine) may be used to numb the outer layer of skin - this may feel like a pin prick followed by a stinging or burning sensation.
 * Ultrasound is used to locate the fetus and placenta, identify the pocket of fluid, and guide the needle.
 * Physician inserts the needle (22 gauge with a stylet) through the abdomen and into the uterus - some discomfort may be felt when the needle enters the skin and then the uterus (may feel like a menstrual cramp); a sharp pain lasting a few seconds may be felt when the needle enters the amniotic sac.
 * Stylet is removed and the first few cc of fluid are discarded due to possible maternal cell contamination. About 20 cc (1 tablespoon) of amniotic fluid is removed - may feel pressure in the lower abdomen when the fluid is withdrawn; is quickly replaced by the fetus.
 * Needle is removed, bandage applied, fetal heart activity is monitored by ultrasound, no overnight hospital stay.
 * Fluid is sent to lab and results are available in 1-2 weeks. Discuss how results will be received.
 * About 95% of women receive a negative result.
 * Total cost is $600-$900.
 * Afterwards, no strenuous activity for 24 hours. Follow up with MSAFP at 16-18 weeks and ultrasound at 18-20 weeks.

Benefits of Amnio

 * Accuracy of karyotype is >99% (NTD detection is about 90-96%).
 * Can detect chromosomal abnormalities (aneuploidies).
 * Can detect neural tube defects (spina bifida, anencephaly).
 * Tells the sex of the fetus.

Limitations of Amnio

 * Does not detect all possible birth defects (only about 10% of 400 known congenital malformations).
 * Cannot predict the severity of the defect/disorder.
 * If first procedure fails, a second may be attempted that same day. If it doesn't work, then additional procedures should be postponed for 3-7 days.
 * Cell culture failure could occur (rare, <1%).

Risks Associated with Amnio

 * Risk of miscarriage - 1/200 (0.5% beyond background risk).
 * Rh (-) mothers must be given RhoGam in order to prevent blood group sensitization.
 * Uterine cramping is not uncommon.
 * Notify your doctor is you have transient spotting or leakage of amniotic fluid (2-3% of cases).
 * Very rare chance of infection to uterus, hemorrhage, or maternal death.
 * Risk of birth defects due to amnio is remote (risk of clubfoot increased during early amnio).

Conclusion

 * Discuss psychosocial issues that may arise.
 * Remind that no decision has to be made today.
 * Review and summarize.
 * Answer final questions and concerns.
 * Give out patient resources.


text:
Handbook of Genetic Counseling/Advanced Maternal Age - Chorionic Villus Sampling (CVS)

Advanced Maternal Age - Chorionic Villus Sampling (CVS)

Introduction

 * What are your main reasons for seeing us today for genetic counseling?
 * Ask them if they have any particular questions or concerns they would like to discuss.
 * Address any concerns or explain that they will be discussed later
 * Provide an overview of what we will be doing including a discussion of their concerns or questions

Obtain Pregnancy and Family History

 * How far along is the pregnancy?
 * How was that determined?
 * Have you had any complications with your pregnancy?
 * Have you had an ultrasound?
 * When was prenatal care begun?
 * Have you taken any medications since you were pregnant or before you realized you were pregnant?
 * Have you had any alcoholic beverages since you were pregnant?
 * Any drugs?
 * Are you taking prenatal vitamins? When did you start them?
 * How many total pregnancies have you had?
 * Have you had any miscarriages or elective terminations?
 * Do you work outside the home? What is your occupation?
 * Husband's or partner's employment?
 * Do you or your husband/partner have a religious preference?
 * I would like to obtain some family medical history information. Some of the questions I will ask will help us determine if there are any hereditary disorders that we may want to discuss.
 * Take basic 3 generation pedigree unless something else seems significant
 * Ask about: her three pregnancy losses and may want to explain reason for most recent loss. Also ask about MR/learning difficulties in school, birth defects such as cleft lip or palate or heart defects, anyone die young or unexpectedly, anyone with bleeding disorders, cancers, any other health problems that you think might be hereditary?

Explanation of Advanced Maternal Age

 * Are you familiar with the age related risk associated with having a baby with some specific chromosomal abnormalities?
 * As women get older their risk for having a baby with a change in the number of chromosomes in their cells increases. There is no magic age at which a woman goes from no risk to high risk. However, at age 35 the risk is considered high enough to offer some standard testing options that we will discuss today.
 * Explain chromosomes and genes
 * Explain nondisjunction
 * Sometimes when the egg or sperm form, the chromosomes don't separate and an egg or sperm ends up with an extra copy of a chromosome
 * This is called nondisjunction and it is a random, chance event that does not run in families
 * Although it is a random event, it does occur more often as a woman gets older
 * After fertilization, there are now 47 chromosomes rather than the usual 46
 * When there is an extra copy we call it trisomy because there are three copies instead of the usual two copies
 * Often when there is extra genetic material there are changes in the way the fetus grows and develops
 * When a fetus has an extra chromosome there is also a higher risk of having a miscarriage as occurred in your last pregnancy
 * However some fetuses with certain extra chromosomes may survive to birth.

Down syndrome

 * Discuss previous pregnancy loss due to trisomy 21 or Down syndrome
 * Trisomy 21 (most common cause of Down syndrome) is the third most common autosomal trisomy to be observed in fetuses that don't survive
 * Approximately 23% of fetuses with Down syndrome will be lost between midtrimester and term
 * Trisomy 21 is the most common trisomy in babies that are born
 * Are you familiar with the characteristics of Down syndrome?
 * Children with Down syndrome are all unique, but often have distinguishable physical characteristics that you might recognized.
 * They are all cognitively impaired and this is most often mild to moderate
 * Nearly half of children born with Down Syndrome have heart defects and they are at an increased risk for some other specific birth defects or medical concerns

Trisomy 18, 13

 * Two of the other common trisomies are trisomy 18 and 13.
 * Children with these conditions are more severely affected than those with Down Syndrome.
 * They usually have a variety of birth defects and are severely cognitively impaired.
 * Many miscarry and there is a high rate of mortality during infancy

Other chromosome abnormalities involving the sex chromosomes

 * Other chromosome abnormalities that you may be at an increased risk for due to age involves the sex chromosomes (Smith's quotes that there is a marked increase in maternal age associated with maternally derived 47XXY males where the error was in meiosis 1. However, the error can also be in maternal meiosis II and half of males with 47XXY result from paternal meiosis 1 errors)
 * Babies can have an extra copy of one of the sex chromosomes and sometimes they remain undiagnosed until later in life
 * They usually have an average IQ, but may experience learning difficulties in school.
 * They don't usually have serious medical problems associated with having extra sex chromosomes, but they may be infertile.

Age Related Risks

 * Age related risks (refer to chart in visual aids)
 * Live born baby with Down Syndrome 1 in 112 almost 1%
 * at age 42 risk of a live born with any chromosomal abnormality is 1 in 65 around 1.6%
 * chance of having a liveborn child without a chromosomal abnormality detected is 98.4%
 * risks are higher of having an affected fetus during pregnancy though because of the high miscarriage rates in fetuses with a chromosome abnormality
 * quote risks at amnio and CVS if interested at amnio risk is 1 in 41 for all chromosome abnormalities and at time of CVS risk for all is 1 in 28 and at amnio risk for Down syndrome is 1 in 86

Prenatal Testing Options During First and Second Trimester

 * Two tests that are diagnostic and can tell us with greater than 99% [source?] accuracy whether the fetus has a chromosomal abnormality
 * CVS (10-12 weeks)
 * Amniocentesis around 15 weeks
 * (Have you read any information about CVS or amniocentesis?)
 * Option to undergo no testing
 * Screening
 * First trimester prenatal screening plus ultrasound
 * blood test and ultrasound combined will detect 91% of Down syndrome and 97% for trisomy 18, 40% of heart defects and some other birth defects
 * blood tests measures levels of 2 proteins freeBeta-hCG and PAPP-A
 * ultrasound measures nuchal translucency (increased neck width)
 * not diagnostic of a chromosome abnormality but shows whether risks are increased
 * Level II ultrasound in second trimester will help in determining the overall development of the major organs. It will show some birth defects, which may provide a clue about whether or not there is a chromosomal abnormality. However, not all birth defects are detected by amnio, and the presence of a birth defect will not indicate for certain if there is a chromosomal abnormality

Chorionic Villus Sampling Overview

 * Often referred to simply as CVS
 * CVS is a technique in which a sample of placental tissue is obtained
 * The little fingerlike projections of the placenta that are sampled are called chorionic villi
 * The villi are derived from the same original cells as the fetus so these cells should have the same genes and chromosomes as the fetus and we can look at the chromosomes in these cells and detect the chromosomal abnormalities discussed earlier
 * CVS is performed between 10 and 12 weeks gestation

(CVS has been around since 1983 in US)

What Information CVS Can Provide

 * It is a diagnostic test that can determine if the fetus has one of the chromosomal abnormalities we discussed with 98-99% accuracy.
 * It can also determine the sex of the fetus if you would like to know.
 * DNA obtained from the sample can also be used to test for certain specific genetic disorders if the fetus is at risk

Limitations: Information CVS Does Not Provide

 * Most birth defects cannot be detected by CVS or amnio. (Amnio can detect about 10% of birth defects). For example cleft lip, cleft palate, congenital heart defects, and many types of mental retardation will not be detected.
 * CVS doesn't routinely test for heritable disorders such as cystic fibrosis unless there is a risk for a specific disorder and a special test is ordered.
 * CVS does not test for whether the fetus has a neural tube defect (i.e. spina bifida or anencephaly
 * About 95% of women who undergo a CVS will have a negative test result. However, a negative test result from CVS does not guarantee a healthy baby. (3-5 out of every hundred babies have a birth defect).
 * There is a 1-2% chance that the test will be inaccurate (reasons for this will be discussed later)

Associated Risks

 * 1% additional risk for pregnancy loss. This is above the baseline risk of miscarriage that all women have. (At 10-12 weeks this spontaneous loss rate is 2-3%) In other words, about 1 out of every 100 women who have CVS will have a miscarriage that is due directly to the procedure.
 * Extremely low risk of uterine infection
 * Some studies reported a possible risk of limb defects while other studies have not. Most of the defects were noted if the procedure was performed before 10 weeks because the limbs develop between 4-10 wks. The increased risk of limb defects is about 1 in 3000 compared with the norm of 6 per 10,000.

Amniocentsis VS. CVS

 * Amniocentesis is another option that can be performed later in the pregnancy and will test for the same chromosomal abnormalities as well as neural tube defects, but ONTD's can be detected 85% of the time with MSAFP (blood test performed after 14 weeks)
 * Review visual aid that compares the two procedures on timing, risk, accuracy etc.

Reasons Some Women Choose CVS
(This is a personal decision and each woman places different emphasis on the things that are important to her)
 * Permits termination at earlier gestational age
 * 1st trimester and people often don't know that she is pregnant
 * Early termination has been reported to be easier emotionally and physically
 * They want reassurance that the fetus does not have a chromosomal abnormality
 * Allows treatment for a fetus with 21-hydroxylase deficiency (CAH) autosomal recessive condition in which shots of dexamethosone can be given

Reasons Some Women Choose Amniocentesis

 * Lower risk of pregnancy loss 0.5% instead of 1%
 * Results are slightly more accurate >99% compared to 98-99%
 * Offers detection of open neural tube defects (90-96%)
 * However, a maternal blood test (MSAFP) can be performed later in pregnancy (14-22 wks) and will detect 85% of open NTD's
 * Procedure is easier and more hospitals perform it
 * With CVS there is a greater likelihood of needing further testing due to
 * Laboratory failure
 * Maternal cell contamination
 * Frequency 1.9%
 * Not problematic for cytogenetics because they do maternal karyotype also, can be problem for DNA or biochemical testing
 * Mosaic or ambiguous results
 * Presence of two or more groups of cells that differ in their chromosome make up
 * Occurs in 1-2% of CVS samples
 * less concerning in CVS than amnio because the placental cells are more distantly related they split off from the cells in the embryo early on so fetus might not share same genetic make up
 * Insufficient sample

Reasons Women Choose Not to Undergo Either Procedure

 * They don't want to take that added risk of miscarriage
 * They are more anxious about the procedure than they are about having a child with a chromosomal abnormality
 * They feel comfortable not knowing if there is one of these problems until they deliver the child
 * They don't feel a need for reassurance and would not abort the fetus regardless of the result
 * Moral or religious views

Description OF CVS

 * There are two ways the procedure can be performed: Transcervical and Transabdominal Transcervical is the way Dr. Sedicke will usually perform it.
 * Contraindications for both types include:
 * Active vaginal bleeding (must have stopped at least 1 week ago)
 * Don't worry about Rh sensitization because she is O positive
 * Maternal bleeding disorder
 * Fibroids not avoidable
 * Multiple gestation? (usually not attempted)
 * Transcervical
 * Procedure is similar to a pap smear
 * Vagina and cervix are cleaned
 * Under the visual guidance of ultrasound, a thin tube (catheter) inserted through the vagina, cervix, and into the placenta
 * Once the catheter is in place a syringe is attached
 * Suction is applied to remove the villi while the catheter is removed
 * After the sample is obtained it is viewed under a microscope to be sure the size and quality is sufficient and another sample is not needed
 * Sample is placed in a tube of tissue culture medium and sent to a lab for testing
 * Most women report minimal discomfort during the procedure although it varies
 * The actual procedure only takes about 5 minutes
 * The baby's heart beat will be monitored
 * Bleeding occurs in up to 10% of women
 * (Easiest to perform with posterior placenta close to cervix)
 * (Contraindications for transcervical CVS include: cervical polyps, overly curved sampling pathway, active genital herpes or other infections)
 * (Large sample is obtained including whole villi)
 * Transabdominal
 * Abdomen is cleansed and xylocaine injection is given to numb the upper layers (similar to shot given at the dentist)
 * Using ultrasound as visual guidance, spinal needle is guided through the abdominal wall, uterine wall, and into the placenta
 * Once in place a syringe is attached to supply suction
 * While suction is supplied the needle is moved back and forth through the placenta
 * After sample is obtained it is viewed to make sure there is enough and another sample is not required
 * Sample is then placed in a tube of tissue culture medium and sent to a lab for testing
 * There is a wide range of responses when it comes to how women report the procedure felt. When the needle is inserted it may burn for a few seconds. Women report everything from mild cramping to painful, heavy cramping.
 * The actual procedure takes about 5 minutes
 * The heartbeat of the fetus will be monitored
 * Bleeding is rare
 * Contraindications for transabdominal CVS include: interceding bowel, the placenta is too far from the maternal abdominal surface (obesity)
 * (Easiest to perform with anterior or fundal placenta)
 * (Smaller sample size (pieces of the villi) obtained)
 * (Can be performed after 12 weeks, but usually only if there is not enough amniotic fluid for an amniocentesis)

Recommendations for After CVS

 * No exercise or strenuous activity for 24 hours
 * No sexual intercourse, douching, tub baths, or tampon use for 72 hours
 * Notify the OB in any of the following occur:
 * Fever greater than 100.4 degrees F
 * Heavy bleeding or cramping
 * Amniotic fluid leakage
 * Return for follow up ultrasound ?????
 * Blood test (MSAFP) at 16-18 weeks to check for ONTD's
 * Ultrasound is recommended at 18-20 weeks
 * Shot of Rho-gam if Rh negative

Test Results

 * Results will be available anywhere between 1-2 weeks
 * More than 95% of women receive reassuring news
 * Remind them that sometimes further follow-up testing is needed to confirm a result.
 * Ask them how they would like to receive their results and if they want to know the sex of the fetus

Psychosocial Considerations

 * May be nervous about pregnancy loss and may have beliefs that she did something to cause
 * Explain that sometimes women are concerned about how something they did was responsible for pregnancy losses
 * Be reassuring if possible especially about the last one where we know the cause had nothing to do with what she did or didn't do before or during pregnancy
 * May have difficulty deciding on whether to have prenatal test due to risks so help her look at risks and benefits and judge whether the benefit associated with likely reassurance of a normal pregnancy is worth the risk
 * Sometimes the anxiety of the procedure is greater than the anxiety over the risks or vice versa and helping them determine this may be helpful in the decision making process.
 * May feel bad or be very concerned about having a child at an older age so assess what is worrisome. Reassure that many women are having children at that age and the age women have children is increasing. There are many benefits to having children at an older age such as (maturity, financial stability, prior time for career or other goals)
 * May be concerned about alcohol exposures. Can be very reassuring if the alcohol was early on before pregnancy was known. Usually large amount of alcohol or continual exposure is necessary to harm fetus.
 * May be nervous about needles. Explore this and discuss the fear and support she will have present during procedure. Or ask if she would like one of us to accompany her if time will allow.
 * Anxiety and other emotions are likely to be present, but some individuals try to keep them from surfacing.

CF Carrier Screening
http://www.genzymegenetics.com/Our-Services/Reproductive-Testing/cf-plus.aspx
 * Are you familiar with cystic fibrosis?
 * CF is one of the most common inherited diseases (affects 1 in 3300 live births in US)
 * Occurs more frequently in Caucasians than other ethnicities (one in 25,000 affected and 1 in 28 are carriers)
 * causes body to produce thick mucus which leads to a greater risk of infections that sometimes requires hospitalization
 * can affect digestion and cause diarrhea and failure to grow normally
 * with the advancement of treatments over year life span increased average age in the 30's
 * may cause decreased fertility in females and often causes infertility in males
 * AR inheritance, both parents must be carriers to have child with CF
 * a blood test is offered that can determine if an individual is a carrier of CF
 * assess whether interested in this testing
 * testing at CHMC screens for 25 of most common mutations \
 * cost ??
 * cost is $265 when done through CHMC, but sent to Genzyme
 * carrier detection rate with the 97 mutation panel is 90% if of Northern European Descent and 70% if of Southern European descent
 * The 97 mutation analysis by Genzyme detects 85-90% of carriers if Caucasian.
 * Turnaround Time: 5-8 days (when cell culture is required, add ~2 weeks)

Review

 * Assess if there are any questions or other concerns about the procedure that were not addressed.
 * Assess again how she feels about the test options.
 * Acknowledge that it can be a difficult decision and does not need to be made today unless time constraints for testing require a decision right away.
 * Offer patient literature
 * If a decision is reached have her explain how she arrived at that decision to check for understanding.


text:
Handbook of Genetic Counseling/Advanced Maternal Age - Chorionic Villus Sampling (CVS)-2

Advanced Maternal Age - Chorionic Villus Sampling (CVS)

Contracting

 * How has your pregnancy been going? Have there been any complications?
 * What is your understanding of why you were referred for genetic counseling?
 * What specific questions/concerns would you like to address today?

Maternal Age Associated Pregnancy Risks

 * Women over age of 35 considered at "high risk" for chromosomal abnormalities
 * Explain chromosomes and nondisjunction
 * Common trisomies associated with advanced maternal age
 * Trisomy 21 (Down Syndrome)
 * Caused by presence of 3 copies of chromosome 21
 * Can result in characteristic facies, mild to moderate mental retardation, congenital heart disease and other health problems
 * Varying range of severity
 * Many children can go to school, adults may hold jobs and live semi-independently
 * Trisomy 13 (Patau Syndrome) and Trisomy 18 (Edward Syndrome)
 * Caused by presence of 3 copies of chromosome 13 or 18
 * More severe medical issues than those associated with Down Syndrome
 * Usually fatal within first year of life
 * Klinefelter Syndrome (47,XXY)
 * Caused by presence of an extra X chromosome
 * Phenotypic males who may have small testes and androgen deficiency
 * IQ may be 10-15 points lower than average

Testing Options

 * Triple marker screening
 * Blood test performed at 15-22 weeks gestation
 * Screening test, not diagnostic
 * In whole population, detects 62% of problems
 * False positive rate of 3.6%
 * Indirect measurement of AFP, hCG, and uE3 production
 * Detects some chromosomal abnormalities associate with maternal age
 * Down Syndrome (70% in women older than 35)
 * Trisomy 18 (60%)
 * Open neural tube defects (80-90%)
 * Does not detect all chromosomal abnormalities associated with maternal age
 * Amniocentesis may be offered to follow-up on results
 * Ultrasound
 * Capable of detecting many major birth defects
 * May identify ultrasound anomaly that could indicate a chromosomal abnormality
 * Cannot diagnose chromosome abnormality based on ultrasound findings
 * Amniocentesis or CVS may be offered to follow-up on results
 * Chorionic Villus Sampling (CVS)
 * Sample of placental tissue (chorionic villi) obtained
 * Tissue is from same embryonic origin as fetus
 * Should have same genetic composition as fetus
 * Usually performed at 10-12 weeks gestation
 * Technique
 * Transcervical
 * Begin with ultrasound exam to confirm fetal heart activity, appropriate growth, and location of placenta, uterus, and cervix
 * Patient placed in lithotomy position
 * Vagina and cervix cleaned with betadeine
 * Speculum is inserted and some physicians apply a tenaculum to the lip of the cervix to help manipulate the uterus
 * Catheter with a stylet inserted is guided into the placenta using US
 * Stylet removed and syringe inserted
 * Suction is applied to aspirate villi
 * May be slightly uncomfortable
 * Transabdominal
 * Begin with ultrasound exam
 * Abdomen cleaned with betadeine and xylocaine injection given to numb skin
 * Spinal needle with stylet guided through abdominal and uterine walls into placenta using ultrasound guidance
 * Stylet removed and syringe attached
 * Suction applied by syringe plunger and needlemoved back and forth
 * Can be performed at any time during pregnancy
 * May be moderately uncomfortable
 * Transcervical vs. transabdominal
 * Bleeding more common following transcervical (10%)
 * Cramping more common following transabdominal
 * No significant difference in risk for fetal loss
 * Some reports indicate transcervical may have higher risk for infection
 * Recommendations for medical care
 * Rh negative women should be given Rhogam
 * No exercise or strenuous activity for 24 hours
 * No sexual intercourse, douching, tub baths, or use of tampons for 72 hours
 * Notify OB if any of the following signs
 * Fever above 1000F
 * Heavy bleeding or cramping
 * Amniotic fluid leakage
 * Follow up ultrasound in a few days
 * MSAFP at 16-18 weeks
 * Ultrasound at 20 weeks to check fetal anatomy
 * Risks/Benefits of CVS
 * 98-99% accuracy for fetal chromosome analysis
 * Allow identification of affected fetus early in pregnancy
 * Maternal cell contamination risk if 46,XX result
 * 1-2% chance for mosaicism
 * Presence of two or more cell lines that differ in chromosome composition
 * Difficult to interpret because may arise in vitro in lab, may be confined to placenta and not affect fetus, or may represent true fetal mosaicism
 * Can perform molecular DNA analysis or biochemical analysis if at risk fetus
 * Can't detect open neural tube defects
 * Can't detect all birth defects or mental retardation
 * Risk of miscarriage due to procedure is 1% (in addition to 2-3% background risk)
 * Some past studies have cited increased risk for transverse limb anomalies
 * When performed before 10 weeks
 * More recent studies do not indicate any increased risk when performed at 10-12 weeks
 * Some women with elevated MSAFP or unclear CVS results may be offered amniocentesis
 * Not recommended for women with following conditions
 * Active vaginal bleeding
 * Maternal bleeding disorder
 * Cervical polyps, active genital herpes or other infection (transcervical)
 * Interceding bowel or placenta far from maternal abdominal surface (transabdominal)

Amniocentesis

 * Performed after 15 weeks
 * Risks/Benefits
 * 99.7% accuracy for fetal chromosome analysis
 * Detects 96% of open neural tube defects by testing AFAFP
 * Cannot detect all birth defects or mental retardation
 * Risk of miscarriage due to procedure is 0.5%
 * Incidence of mosaicism is 0.1-0.3%


text:
GIMP/Add Speech Bubbles to a Comic Strip

This tutorial will show you how to add text and speech bubbles to pre-made art in The GIMP v2.0 or later.

Make a copy
This step isn't strictly necessary, but it's a good idea that could save you from repeating steps if something goes horribly wrong. It's a very good idea if you're working on the only copy of your source image.

(Better yet, don't work on the only copy of your source image.)

When you open an image in The GIMP, it automatically becomes the background layer. Anything added to the image will be added as a higher layer, sitting above the background layer. You can combine layers by clicking Layers > Merge Down, and you'll probably want to at some stage, so you can work on multiple added items at the same time.

Right-click the Background layer and select Duplicate'. That way, if you accidentally merge the wrong layer down onto a lower one, or perform an operation that seems like a good idea but isn't (and can't be rolled back), you haven't overwritten the only copy of the art you have.

Add a filter
You'll most likely be adding text in black. If the background is dark as well, the text will be almost invisible and difficult to work with. You can make it easier to view dark text on a dark background by adding a semi-opaque layer between them in a light colour. To do this:

Click Layers > New Layer and select a transparent background.

To add the filter, select the Fill tool and select white as the colour to use. Reduce the opacity to 50% and click anywhere on the new layer. You'll see the image turn milky, because you're now viewing the background image through a semi-transparent white layer. Any text you lay down on top of this will be easy to see, and after you've added the speech bubbles around it, the filter can be removed, leaving the background looking like it did to begin with.

Adding the text
To select the Text tool, press T. Select the colour, font and size you prefer. Use anti-alias should be ticked. Jagged edges on your text will make it harder to read, especially if the image is resized. Centre-aligned text is often best, too.

Positioning
After the text box is closed, the text tool automatically changes to the Move tool. At this point, if you try to move the text, you'll see it slide out of the box and vanish completely off the edges of the layer. Since you probably do want to move the text, to get it positioned just right, you'll want to expand the layer to the full size of the image. To do this:

Click Layer > Layer to Image Size.

Now you can select your text with the Rectangular selection tool. As soon as the mouse is released, the selection tool changes to the Move tool and you can simply drag your text to where it needs to be.

Combining styles
The GIMP text tool applies a single style to an entire block of text, so an example of what you can't do is bold or italicise individual words. (In other words, the previous sentence would be impossible.) To mix styles, add all the text of one style in a single layer, taking care to leave the space for the other styled text, then add a second text layer written in the second style, positioning it over the first.

Background
Once you have all the necessary text on the screen and in the right position, you can create the bubbles. First, add a new layer, below the text layer. This part of the process will involve painting out a section of the current layer, so if it's the same layer your text is on, you'll lose it.

Next, change to the Elliptical selection tool. Once again, make sure to anti-alias. Draw an oval around the text, making sure to leave enough white space so the text isn't crowded. This will become the bubble.

To add a stalk pointing to a character, change to the Path tool. (The GIMP's Path tool mirrors the Photoshop Bézier Curve tool.) This allows you to mark out an area to be added to the selection you made with the Ellipse tool.

First, click and release the mouse on a starting point just inside the oval. Next, click where you want the point of the stalk to be. If you want a straight line, release and continue to the next step. If you prefer a curve, hold the mouse button down and drag the pointer away from the second point. The line will deform into a curve. It'll take a bit of experimentation to get it exactly where you want it, but it's a nice effect.

Click back into the oval to complete the other side of the stalk. Now you have an oval around the text, and on top of that, a stalk.

Move back to the dialogues window again, and click the Paths tab. Right-click the uppermost path on the stack and select Add to selection.

Now the entire speech bubble including the stalk will have the blinking dashed line around it.

At this stage, you can experiment a little bit to add some variety among the different speech bubble shapes you have. For instance, the script-fu menu's selection options offers the distress selection tool, which will make the outline a bit more random.

Finally, select an appropriate background colour (white is the classic) and then the Fill tool again. (Make sure you raise the opacity back to 100% unless you prefer the speech bubble to be semi-transparent on top of your background image.) Click inside the selection and it will fill with the selected background colour out to the edges. Your text should now be invisible behind the background colour. Don't try working with the text or any other task yet, because you still need the speech bubble selected.

Border
Now that you have the speech bubble filled, you can add a black (or any other colour) border to it. To do this, first select a foreground colour and then:

Click Edit > Stroke selection....

The default line thickness is 6 pixels, which is probably too thick. 1px or 2px should be plenty. Click to confirm, and a border in the selected foreground colour will appear around the speech bubble.

In order to create a smoother border, first click Select > To Path. Then, click Edit > Stroke Path.... Proceed as stated in the previous paragraph.

Text in bubble
Now that you have speech bubbles, you want the text in them. To accomplish this, go back to the layers window. There's probably a whole range of layers by now, since each block of text and each speech bubble you created added one (or more) new layer. Use the mouse to drag the speech bubble layers below the text layers and you'll see the words appear in the bubbles.

Removing the filter
Using the mouse on the layers window, select the semi-opaque layer you created. Right-click and select Delete. You'll see the background image snap back to its original colours behind your speech bubbles.

Saving your work
If you want to keep the different elements of the image on the separate layers, you'll need to save the image as a .xcf file, which is The GIMP's native file format. To save it in a format you can view in a browser or slideshow program, select the appropriate extension when you save the image and confirm that the file should be exported, (losing the separation between layers in the process).

General practices
We naturally start reading at the top left-hand corner of a box and proceed towards the bottom right. The first words spoken should be higher and further towards the left unless you have some other way in addition to speech bubble stalks of making it clear which character is speaking.

Dark text on a light background is easiest to read. Text and background should never have the same brightness even if they're different colours, since it makes it harder for the eye to distinguish between them. and in general the text should have the 'richer' colour (e.g. red, blue, green) and the background should be a 'washed-out' colour (e.g. white, grey, pale blue).

Start big. It's easy to scale large images down, small images scaled up will tend to be pixelated and won't look as good.

Don't crowd your images with too much talk. Text should give way to art rather than vice versa.

Adding thought bubbles
So far a very effective way of adding speech to your work has been showcased. Now it's time to get thinking!

Tailoring the text to your preferences
A quick note on tool-usage that seems to pass people by:

You must open the Tool Option dialogue and use it as above to get the best out of GIMP. In this case the text editor is selected, but you also need it to use all GIMP tools effectively. It is important in the next section.

Creating the Bubble
Now what you must do is select the tool options as in the screenshot above. This is essential if you want to follow the rest of this tutorial as you will be using it a lot to make sure everything is working correctly. In this instance the Text tool is selected so you can work on all the options such as the font and text size as well as the text justification. This is essential.

Now you need to type in your text as for the speech bubble tutorial. So far all is the same. Note: I have used the same sort of filter as in the earlier tutorial.

Time to add the selections for the bubble. As before select the elliptical marquee tool.

However, this time you need to select the option in the screenshot above from the Tool Options dialogue. This will allow you to draw the several ellipses necessary to create a thought bubble without cancelling the selection each time you click away from it.

After this just fill and stroke as for speech bubbles, move stuff around to your satisfaction, remember to delete the filter and - one thought bubble!


title: User:Adam1213


text:
Talk:Dutch/Lesson 7

/Archive/

title: Talk:Dutch/Lesson 7


text:
Talk:Engineering Thermodynamics/Second Law

Howdy There,

I have an issue with Clausius Statement in this module. I believe you will find that it should read: "..... without external effect ( e.g. external heat or work effect or both)."

A very real example of this distinction is the refrigerator in most recreation vehicles or some large tonnage chillers. Strictly a heat process between three ( or more ) temperatures. These are known generally as absorption refrigerators. No compressor or pumps.

Sincerely and cooperatively,

John Warner

I also have a sneaking suspicion that the Clausius / Kelvin-Planck equivalencies are backwards... I believe the first one actually violates Clausius first, which causes it to violate KP, and the second violates KP, causing it to violate Clausius. A minor quibble, I know.

Kyle

2nd law of thermodynamics..
2nd law of thermodynamics..Italic text

statement about kelvin-planck and clausius is just reverse ..

the true is :

Kelvin-Planck from Clausius

Suppose we have a heat engine which can convert heat into work without rejecting heat anywhere else. We can combine it with a heat pump so that the work produced by the engine is used by the pump. Now the combined system is a heat pump which uses no external work, violating the Kelvin-Planck statement of the second law.

Thus, we see that the Clausius and Kelvin-Planck statements are equivalent, and one necessarily implies the other.  Clausius from Kelvin-Planck

Now suppose we can construct a heat pump which transfers heat from a low temperature reservoir to a high temperature one without using external work. Then, we can couple it with a heat engine in such a way that the heat removed by the heat pump from the low temperature reservoir is the same as the heat rejected by the heat engine, so that the combined system is now a heat engine which converts heat to work without any external effect. This is thus in violation of the Clausius statement of the second law.

Reference from: Book Thermodynamics an Engineering Approach Seventh Edition in SI Units - Latest publish 2011 -


text: User talk:62.231.166.25

title: User talk:62.231.166.25


text: User talk:202.190.55.2

title: User talk:202.190.55.2


text:
User talk:AJK~enwikibooks

Copyright problem with Image:ClassicFinderImage.png
--Derbeth 09:39, 9 November 2005 (UTC)

 * Please stop uploading images without proper copyright tag. Wikibooks have to obey copyrights and cannot accept images without source or used without permission. --Derbeth 09:39, 9 November 2005 (UTC)

Your account will be renamed
Hello,

The developer team at Wikimedia is making some changes to how accounts work, as part of our on-going efforts to provide new and better tools for our users like cross-wiki notifications. These changes will mean you have the same account name everywhere. This will let us give you new features that will help you edit and discuss better, and allow more flexible user permissions for tools. One of the side-effects of this is that user accounts will now have to be unique across all 900 Wikimedia wikis. See the announcement for more information.

Unfortunately, your account clashes with another account also called AJK. To make sure that both of you can use all Wikimedia projects in future, we have reserved the name AJK~enwikibooks that only you will have. If you like it, you don't have to do anything. If you do not like it, you can pick out a different name.

Your account will still work as before, and you will be credited for all your edits made so far, but you will have to use the new account name when you log in.

Sorry for the inconvenience.

Yours, Keegan Peterzell Community Liaison, Wikimedia Foundation 22:54, 17 March 2015 (UTC)

Renamed
 This account has been renamed as part of single-user login finalisation. If you own this account you can |log in using your previous username and password for more information. If you do not like this account's new name, you can choose your own using this form after logging in: . -- Keegan (WMF) (talk) 04:27, 19 April 2015 (UTC)

title: User talk:AJK~enwikibooks


text:
Python Programming/Authors

Authors of Python textbook

 * Quartz25
 * Jesdisciple
 * Hannes Röst
 * David Ross
 * Lawrence D’Oliveiro
 * User:BLibrestez55

title: Python Programming/Authors


text: User talk:202.73.173.197

title: User talk:202.73.173.197