text:
Radiation Oncology/Radiobiology

Radiobiology

 * Basic Radiobiology
 * American Board of Radiology Curriculum
 * DNA Damage
 * DNA Damage Response
 * DNA Repair
 * Cell Death
 * Cell Cycle
 * Growth Factors
 * Hypoxia
 * Cancer Syndromes
 * Cancer Genetics
 * Cancer Biology
 * Radiosensitivity
 * /Radioresistance/
 * Radiation Oncology/Radiobiology/Radiosensitizer
 * Radiation Oncology/Radiobiology/Radioprotector
 * Linear-Quadratic Model
 * Normal Tissue Tolerance
 * Whole Body Irradiation (TBI)
 * Radiation Syndrome
 * Radiation Hormesis
 * Radiation Protection
 * Protein Overview
 * Radiobiology Equations
 * Bioassays
 * Radioimmunoassays
 * Radiopathology
 * Radiation Induced Secondary Malignancies
 * Reirradiation
 * Hyperthermia
 * Hyperbaric Oxygen
 * Agricultural Applications

Other Resources
 * Radiobiology Lecture SeriesThe lecture series is provided courtesy of William Mcbride PhD, DSc
 * ASTRO Radiobiology Study Guides
 * Radiation Biology for Physical Scientists

Note: Majority of the text in these pages has been adopted from
 * Radiobiology for the Radiologist, 6th Edition (Hall, 2005)
 * Basic Clinical Radiobiology, 3rd Edition (Steele, 2002)
 * Basic Clinical Radiobiology, 4th Edition (Joiner, 2009)
 * Radiation and Cancer Biology, Review by Richard C. Miller, 2009

title: Radiation Oncology/Radiobiology


text:
Radiation Oncology/Cost-Effectiveness

Quality of Care

 * American College of Surgeons; 2009 PMID 19466738 -- "Using the NCDB for cancer care improvement: an introduction to available quality assessment tools." (Raval MV, J Surg Oncol. 2009 Jun 15;99(8):488-90.)
 * Description of National Cancer Database (NCDB) and how it can be used to improve quality of cancer care in the U.S.

Utilization

 * Ghent University; 2008 PMID 18374290 -- "Evidence behind use of intensity-modulated radiotherapy: a systematic review of comparative clinical studies." (Veldeman L, Lancet Oncol. 2008 Apr;9(4):367-75.)
 * Review of IMRT evidence
 * Conclusion: Evidence of reduced toxicity; local control and overall survival inconclusive

 * CCORE, Australia; 2005 PMID 16080176 -- "The role of radiotherapy in cancer treatment: estimating optimal utilization from a review of evidence-based clinical guidelines." (Delaney G, Cancer. 2005 Sep 15;104(6):1129-37.)
 * Evidence-based estimate of RT ~52% of patients with cancer. Monte Carlo estimates ranged from 51.7 - 53.1%

 * University of Minnesota; 2002 (1991-1996) PMID 12187168 -- "Studying radiation therapy using SEER-Medicare-linked data." (Virnig BA, Med Care. 2002 Aug;40(8 Suppl):IV-49-54.)
 * Comparison of SEER and Medicare (MedPAR Part B and Outpatient) data. Cohort of breast, endometrial, lung, prostate, or rectal cancer patients.
 * Outcome: Agreement between SEER and Medicare for lung 88%, prostate 93%, rectal cancer 94%, breast cancer 94%, endometrial cancer 95%
 * Conclusion: High level of agreement between SEER and Medicare data, suggesting either source can be used to asses RT-related treatment patterns

Health Policy

 * Memorial Sloan Kettering; 2009 Full paper -- "Limits on Medicare's Ability to Control Rising Spending on Cancer Drugs" (Bach PB, New England Journal Of Medicine, 2009)

 * 21st Century Oncology; 2008 PMID 18954812 -- "A changing paradigm in the study and adoption of emerging health care technologies: coverage with evidence development." (Wallner PE, J Am Coll Radiol. 2008 Nov;5(11):1125-9.)
 * Introduction of new technologies without "significant evidence" places an increasing burden on health care delivery system. Review of "coverage with evidence development" reimbursement strategy

Economic Analysis

 * Tufts; 2010 PMID 20056956 -- "When is cancer care cost-effective? A systematic overview of cost-utility analyses in oncology." (Greenberg D, J Natl Cancer Inst. 2010 Jan 20;102(2):82-8. Epub 2010 Jan 7.)

 * MD Anderson; 2008 PMID 18596196 -- "Economic evaluations of medical care interventions for cancer patients: how, why, and what does it mean?" (Shih YC, CA Cancer J Clin. 2008 Jul-Aug;58(4):231-44.)
 * Overview of economic evaluations

 * Harvard; 1996 PMID 8690653 -- "Economic analyses in health care: an introduction to the methodology with an emphasis on radiation therapy." (Hayman J, Int J Radiat Oncol Biol Phys. 1996 Jul 1;35(4):827-41.)
 * Intervention ("NEW") is always compared to another intervention strategy, including "no treatment" strategy ("STANDARD")
 * Cost Minimization
 * Assumes that intervention benefit is comparable; it can thus be eliminated from analysis
 * Only cost of NEW intervention is compared to the cost of STANDARD intervention
 * Unit = dollars
 * Cost Effectiveness
 * Cost of intervention is related to its impact on a clinically relevant endpoint ("effectiveness")
 * Years of life saved (survival) is most commonly used endpoint
 * Incremental cost-effectiveness ratio (ICER) is the incremental cost divided by the incremental benefit of NEW intervention over STANDARD intervention
 * Unit = dollars per year-life-saved
 * Commonly accepted "cost-effectiveness" threshold is $50,000 - $100,000 per year life saved
 * Cost Utility
 * The endpoint (eg survival) is modified by quality of life measures ("utility") due to:
 * Survival is insensitive to treatment-related side-effects (eg xerostomia), which may make survival not as valuable to a patient
 * Survival is insensitive to palliative benefits of treatment (eg relief of dyspnea in NSCLC)
 * Survival is insensitive to prolongation of disease-free period (eg longer life without painful bone mets)
 * Utility is generally 0-1 (0 represents death, 1 represents perfect health)
 * Effectiveness (survival benefit) is then multiplied by utility to get Quality-Adjusted Life Year (QALY)
 * Incremental cost-effectiveness ratio is the incremental cost divided by the incremental QALY benefit of NEW intervention over STANDARD intervention
 * Unit = dollars per QALY
 * Commonly accepted "cost-effectiveness" threshold is $50,000 - $100,000 per QALY
 * Cost Benefit
 * The benefit of intervention (improved survival, less toxicity, longer DFS) is converted to dollars
 * Cost of intervention is in dollars
 * The cost-benefit of NEW and STANDARD treatments is calculated as benefit (dollars) minus cost (dollars)
 * The incremental cost-benefit is the difference between NEW and STANDARD, and is beneficial if it is >0
 * There is a lot of controversy about assigning dollar value to benefits such as lower toxicity

RT Cost Estimates

 * Lyon; 2009 PMID 19493690 -- "[The cost of respiration-gated radiotherapy in the framework of a clinical research programme "STIC"] - [Article in French]" (Remonnay R, Cancer Radiother. 2009 Jun 1. [Epub ahead of print])
 * Prospective nonrandomized cost study. 365 patients breast or lung cancer, RT +/- respiratory gating.
 * Outcome: Cost lung no gating euro 1256 vs. gating 1807; breast 996 vs. 1510. Overcosts due to extra working time of staff, and extra use of equipment
 * Conclusion: Medical reimbursement largely underestimate costs related to innovation

 * Calgary, Canada; 2008 PMID 18237802 -- "The cost of radiation therapy." (Ploquin NP, Radiother Oncol. 2008 Feb;86(2):217-23. Epub 2008 Jan 30.)
 * Literature review. 11 publications
 * Conclusion: Costs for RT seem to be converging

 * Michigan 2000 PMID 10802374 -- "A comparison of two methods for estimating the technical costs of external beam radiation therapy." (Hayman JA, Int J Radiat Oncol Biol Phys. 2000 May 1;47(2):461-7.)
 * Comparison of using Medicare data (converting Medicare charges into costs via Medicare Cost-to-Charge Ratios, CCR) vs. direct procedure-specific cost estimates from cost-accounting systems (CAS)
 * CCR vs CAS: Palliative simple $1,285 vs. $1,195 (+8%); palliative complex $2,345 vs. $1,769 (+33%); curative breast $6,757 vs. $4,850 (+39%); curative prostate $9,453 vs. $7,498 (+26%)
 * Conclusion: for complex treatments (most of EBRT), technical cost estimates much higher using Medicare CCR vs. internal CAS. This may impact cost-effectiveness analysis

Breast

 * Harvard
 * 2009 PMID 18963542 -- "Partial-breast irradiation versus whole-breast irradiation for early-stage breast cancer: a cost-effectiveness analysis" (Sher DJ, Int J Radiat Oncol Biol Phys. 2009 Jun 1;74(2):440-6. Epub 2008 Oct 27.)
 * Markov model. ICER estimate for PBI vs WBRT for ER+ postmenopausal women with early stage BCA. External beam PBI (EB-PBI) and Mamosite PBI (MS-PBI) compared
 * ICER for WBRT compared with EB-PBI $630,000/QALY, but MS-PBI much worse than both
 * Conclusion: EB-PBI most cost-effective over a wide range of assumptions
 * 2008 PMID 17967514 -- "Partial breast irradiation versus whole breast radiotherapy for early-stage breast cancer: a decision analysis." (Sher DJ, Int J Radiat Oncol Biol Phys. 2008 Feb 1;70(2):469-76. Epub 2007 Oct 29.)
 * Markov model to compare quality-adjusted life expectancy (QALE) for APBI vs WBRT in ER+ early stage BCA over 15 years
 * Outcome: QALE for 40-year old 12.6 years, for 55-year old 12.1 years. QALE highly sensitive to patient preferences
 * Conclusion: For most utility values, APBI preferred treatment modality
 * Michigan
 * 2005 PMID 15936561 -- "A cost comparison analysis of partial versus whole-breast irradiation after breast-conserving surgery for early-stage breast cancer." (Suh WW, Int J Radiat Oncol Biol Phys. 2005 Jul 1;62(3):790-6.)
 * Payer costs (2003 Medicare) and patient costs estimated for 1) WBRT-Boost 60/30, 2) WBRT 50/25, 3) WBRT-AC 42.5/16, 4) WBRT-IMRT 60/30, 5) APBI-MammoSite, 6) APBI-HDR, 7) APBI-3DCRT 38.5/10 BID, 8) APBI-IMRT 38.5/10 BID
 * Least costly: WBRT using External Beam (APBI-3DCRT)
 * 2005 PMID 15752884 -- "Cost-effectiveness of radiation therapy following conservative surgery for ductal carcinoma in situ of the breast." (Suh WW, Int J Radiat Oncol Biol Phys. 2005 Mar 15;61(4):1054-61.)
 * Markov model, 55-yeard old woman, DCIS, BCS. 12-year rates: invasive 18% vs. 8%, noninvasive 16% vs. 9% (NSABP B-17 data)
 * RT incemental cost: overall $3300 (2002 Medicare schedule), initial $8700, due to higher LR salvage costs.
 * Incremental cost-effectiveness rate (ICER): $36,700 per QALY
 * Conclusion: should not withold RT because of cost-effectiveness
 * 2000 PMID 10637242 -- "Cost-effectiveness of adding an electron-beam boost to tangential radiation therapy in patients with negative margins after conservative surgery for early-stage breast cancer." (Hayman JA, J Clin Oncol. 2000 Jan;18(2):287-95.)
 * Markov model. Early stage BCA, BCS with SM-. Addition of E-boost to tangential fields. Data from Lyon trial (reduction of LR by 2% at 10 years, no OS impact)
 * Cost $2,008; 0.0065 QALY, ICER >$300,000
 * Conclusion: Cost-effectiveness for E-boost well above commonly cited threshold of $50,000
 * 1999 PMID 10378968 -- "Is the use of radiation therapy after mastectomy cost-effective?" (Hayman JA, Semin Radiat Oncol. 1999 Jul;9(3):287-91.)
 * Review
 * 1998 PMID 9508186 -- "Cost-effectiveness of routine radiation therapy following conservative surgery for early-stage breast cancer." (Hayman JA, J Clin Oncol. 1998 Mar;16(3):1022-9.)
 * Markov model, 60-year old women, BCS +/- RT
 * Addition of RT: cost increase $9,800 per patient; no change in life expectancy; increase in 0.35 QALY/patient = ICER $28,000/QALY
 * Conclusion: RT after BCS is cost-effective compared to other accepted medical interventions

 * Stockholm 2005 (Sweden) PMID 15885828 -- "Economic evaluation of proton radiation therapy in the treatment of breast cancer." (Lundkvist J, Radiother Oncol. 2005 May;75(2):179-85.)
 * Markov model. 55-year old women, left-sided BCA. Treated with proton RT
 * Cost per QALY: Euro 67,000 (considered not cost-effective). However, high risk-population for cardiac disease (mortality risk 2X) cost Euro 35,000. This is ~5% of treated patients in Sweden

 * Penn 2002 PMID 12039934 -- "Decision-analytic model and cost-effectiveness evaluation of postmastectomy radiation therapy in high-risk premenopausal breast cancer patients." (Lee JH, J Clin Oncol. 2002 Jun 1;20(11):2713-25.)
 * Markov model. Premenopausal, LN+ women. Postmastecomy +/- RT. 15-year outcome, discount 3%
 * 15-year predicted relapse-free survival: no RT 48% vs. RT 55%, 0.29 years life gained
 * Cost: no RT $40,800 vs. 48,100. ICER $24,900, QALY 22,600

 * Ontario 2000 PMID 11072153 -- "A cost-outcome analysis of adjuvant postmastectomy locoregional radiotherapy in premenopausal node-positive breast cancer patients." (Dunscombe P, Int J Radiat Oncol Biol Phys. 2000 Nov 1;48(4):977-82.)
 * Premenopausal, LN+ women. Post-mastectomy + RT
 * Cost CAD 7,000 (in 1997 canadian dollars); benefit 0.5 life years, ICER CAD 14,000; 0.45 QALY at 10 years, QALY CAD 15,600

Medulloblastoma

 * Karolinska 2005 PMID 15637691 -- "Cost-effectiveness of proton radiation in the treatment of childhood medulloblastoma." (Lundkvist J, Cancer. 2005 Feb 15;103(4):793-801.)
 * Markov model. 5-year old children. Consequences of proton RT
 * Euro 23,600 cost saving (mainly due to reduction in IQ loss and GHD); 0.68 QALY/patient
 * Conclusion: Protons cost-effective, and cost-saving compared to photons with proper patient selection

Lung

 * Toronto, 2004 PMID 15609808 -- "Estimating the benefit and cost of radiotherapy for lung cancer." (Barbera L, Int J Technol Assess Health Care. 2004 Fall;20(4):545-51.)
 * Benefit from lit review, cost using published canadian data; 2001 Canadian Dollars (CAD).
 * Mean benefit: Curative intent 7 months of survival, palliative intent 3 months of symptom control
 * Cost: CAD 9,881 per life year gained, CAD 13,938 per year symptom control gained
 * Conclusion: RT relatively inexpensive

Rectum

 * Swedish Rectal Trial, 2002 PMID 12377315 -- "Cost-effectiveness of preoperative radiotherapy in rectal cancer: results from the Swedish Rectal Cancer Trial." (Dahlberg M, Int J Radiat Oncol Biol Phys. 2002 Nov 1;54(3):654-60.)
 * 8 year F/U. 98/1168 randomly selected patients from main trial from single region.
 * Total costs: RT USD 35,300 vs. surgery alone USD 30,000
 * Survival benefit 21 months - cost of year saved USD 3,654. Sensitivity analysis worst case USD 15,228

Spinal Cord Mets

 * Please see RTOG 97-14 on the Bone metastases page

Protons

 * Also see above in organ-specific sections
 * Stockholm 2005 (Sweden) PMID 16332592 -- "Proton therapy of cancer: potential clinical advantages and cost-effectiveness." (Lundkvist J, Acta Oncol. 2005;44(8):850-61.)
 * Markov model. Four scenarios: left-sided breast cancer, prostate cancer, H&N cancer, and medulloblastoma
 * Conclusion: average cost per QALY: GBP 10,130. Proton facility investment may be cost-effective

Erythropoietin

 * Princess Margaret, 1998 PMID 9874467 -- "What are cancer patients willing to pay for prophylactic epoetin alfa? A cost-benefit analysis." (Ortega A, Cancer. 1998 Dec 15;83(12):2588-96.)
 * Willingness to pay (WTP) analysis
 * Editorial PMID 9874443

Conflict of Interest

 * Georgetown; 1992 PMID 1406881 -- "Consequences of physicians' ownership of health care facilities--joint ventures in radiation therapy." (Mitchell JM, N Engl J Med. 1992 Nov 19;327(21):1497-501.)
 * Radiation therapy joint ventures in Florida reviewed, and data compared to rest of US
 * Outcome: None in inner city or rural areas. Delivered 53% more RT, had 42% higher charges, and spent 18% less time with each patient. Mortality comparable
 * Conclusion: Joint ventures in RT have adverse effects on patients' access to care, increase use of services and costs substantially, and cause no improvement in quality

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

title: Radiation Oncology/Cost-Effectiveness


text:
User talk:Abhinambiar

Radiation Oncology book
Abhinambiar, thank you for your contributions to the Radiation Oncology wikibook! Brim 04:03, 27 August 2006 (UTC)

RTOG 97-04

 * Thanks for your input on esophagus! I have removed the 97-04 reference from that page, as the trial deal with pancreas, and we have it already under resectable pancreas . Tomas

title: User talk:Abhinambiar


text:
WebObjects/LEWOStuff

Note: This framework has been discontinued.

LEWOStuff is a framework for aiding the general development of WebObjects and java software products and vertical solutions. It has been developed by Andrew Lindesay for his projects and is generally used by him and his clients. It is released under a BSD-style license and so is effectively an open-source project which can be used at your own risk. Please read the license distributed with the framework for further details on the usage of this software.

The framework has been used on a handful of application server projects which are deployed in the Australia / New Zealand region. There is presently no support for collaboration on source code, but any corrections or suggestions would be welcome. A new source distribution is generally released every few months. An overview PDF document is distributed with the framework and this covers basic architecture as well as the general functionality afforded by the framework.

Download and Info
You can obtain the most recent public distribution from the Lindesay Electric website at http://www.lindesay.co.nz/. Click on LEStuff.

lejstuff
lejstuff is a java library for J2SE development which is suitable for the development of general java software.

LEWOStuff
LEWOStuff is a java framework for aiding the development of WebObjects application server development. The framework includes and extends many aspects of lejstuff mentioned above.

LECocoaStuff
LECocoaStuff is an Objective-C framework for aiding the development of Cocoa client applications.

title: WebObjects/LEWOStuff


text:
CCNA Certification/Appendix B - Cisco Router Commands and their Usages

=Cisco Router Commands and their Usages=

User Mode Commands
These commands can only be entered from user mode.

Privileged Mode Commands
These commands can only be entered from privileged mode. To enter privileged mode, use the enable command.

Config Commands
These commands can only be entered from config mode. To enter config mode, use the "conf t" command.


text:
Rosacea/Print version

 * 1) What Is Rosacea? [[File:25%.svg]]
 * 2) Basic Skin Care [[File:25%.svg]]
 * 3) Treatments [[File:25%.svg]]
 * 4) Intense Pulsed Light and Laser [[File:50%.svg]]
 * 5) Insurance [[File:50%.svg]]
 * 6) Researching [[File:25%.svg]]
 * 7) Resources [[File:75%.svg]]
 * 8) Glossary

= What Is Rosacea? =

= Basic Skin Care =

= Treatments =

= Insurance =

= Researching =

= Resources =

= Glossary =

= Authors and Contributors =

= License =

title: Rosacea/Print version


text:
WebObjects/Web Applications/Deployment/Tomcat Deployment

This article was written by Andrew Lindesay (http://www.lindesay.co.nz) around May 2005. It first appeared as LaTeX PDF and has been transcribed into this Wiki. You use the information contained in this document at your own risk. Please contact the author if you feel there may have been an error in the conversion to Wiki markup.

Abstract
From WebObjects 5.2, it has been possible to derive a build product from a WebObjects application project that can be deployed into a J2EE servlet container. This article shows how it is possible to deploy a WebObjects 5.2 application into a Tomcat environment and achieve a very similar topology to the ”native” WebObjects deploy.

Introduction
This document was originally written assuming a Tomcat 5 deployment, but after some difficulties with web services and AXIS, I have modified this document to also cater for a Tomcat 3 deployment. This document covers both circumstances.

Assumptions
This article assumes the following:

 * WebObjects 5.2 (likely to work fine with newer versions)
 * Java 1.4
 * Latest Tomcat release of version 5 (5.5.12 at the time of writing) or 3 (3.3.2 at the time of writing)
 * Some sort of UNIX deployment.
 * The reader has some conception of the concepts behind servlet technology.
 * The reader is familiar with a standard WebObjects deployment topology which will be referred to as wotaskd deployment.

For the purposes of this document, it is assumed that Tomcat has been installed at a directory on the local disc called $TOMCATDIR. It is also assumed that you will have another directory with the files required to configure and run an instance called $INSTDIR. It is assumed also that you will have a directory called $JKDIR with the Tomcat apache adaptor in it. In this article, some configuration files require the paths to be shown and these are tabulated below.

In reality, these directories could be located anywhere.

Objective
The objective of this article is to show that a WebObjects application can be deployed into a servlet container and keep some of the desirable attributes of a WebObjects deployment topology. Some of these traits are itemised below.

 * Clustering over a number of hardware nodes to prevent system downtime from a single hardware failure incident.
 * Clustering over a number of virtual machine instances on each hardware node to avoid downtime from a single software failure incident.
 * Ability to make efficient use of lower cost server hardware rather than encouraging use of large, expensive servers.
 * Make maximum use of memory availabile in each virtual machine as cache to minimise database traffic and lower stress on the database server.
 * Ability to make sessions "sticky" to a given virtual machine instance, whilst being multiplexed through a single web server front-end adaptor.
 * Ability to load-balance requests to instances which are operational.

A standard WebObjects deployment topology is shown in the figure below alongside what is to be achieved with Tomcat. A typical J2EE deployment may have a different topology from this.

Servlet Build Products
Creating a servlet build product from a WebObjects application project is covered in some depth by documentation that is supplied by Apple for WebObjects. This is not going to be repeated here, but here is a brief overview of the process.

 * Include the JavaWOJSPServlet.framework framework into your project.
 * In the build settings, set the SERVLET_SINGLE_DIR_DEPLOY value to YES to create the most trouble-free form of deployment servlet.
 * Edit the SERVLET_DEPLOY_LICENSE to contain your valid deployment license key if you need one for the version of WebObjects you are using.
 * Edit the SERVLET_WEBAPPS_DIR to point to <tt>$INSTDIR/webapps/</tt> or some place where you want the build product to go.

Now when you choose a Deployment build, you will also get the servlet assembled. The end result is a directory structure similar to that shown in the figure below.

Removing the DOCTYPE from .plist Files
Many property-list files (often called plist files) have a document type at the top. This can refer to files on a MacOS-X machine or to files on Apple servers. In either case this can cause problems with deployments which are not on MacOS-X servers. The following script can be run with the argument of the <tt>WEB-INF</tt> folder to remove these. The WebObjects application runs fine without this information in the plist files. This script can easily be incorporated one way or another as a step in the build process for your WebObjects project.

 * 1) [apl 3.may.2006]
 * 2) This will remove any DOCTYPE's from the top of plists so that
 * 3) they do not attempt to validate the DTD which is either
 * 4) extracted from /System or the internet over HTTP.

if [ -z $1 ]; then echo "syntax: stripdocype.sh " exit 1 fi

for PLISTFILE in `find $1 -name *.plist` do sed \ '/<!DOCTYPE [^>]*>/s/.*//' \ $PLISTFILE \ > /tmp/remove-plist-temp

cp /tmp/remove-plist-temp $PLISTFILE done

Application Configuration with Tomcat
A WebObjects project with servlet support has a file called <tt>web.xml.template</tt> in it. By default, this is located in <tt>/Resources/Servlet Resources/WEB-INF</tt> in your project. The <tt>web.xml.template</tt> file is used as a template for creating <tt>web.xml</tt> which is also known as the <tt>servlet deployment descriptor</tt>. This deployment descriptor is used as the means of communicating settings to the application as well as the servlet container in which the application runs. This section covers some common changes to that file as well as a discussion around a means of general configuration of the application when it is running inside a servlet container.

Data Source for Model Database Configuration
Some WebObjects engineers use the <tt>setConnectionDictionary(...)</tt> method on a model to set the JDBC database connection parameters for the model. However, the servlet container has it's own <tt>data source</tt> mechanism for supplying database information which will override any connection dictionary information which is set into the model. If you don't want this to happen, and you want your <tt>setConnectionDictionary(...)</tt> to take effect, comment out the <tt>resource-ref</tt> item with the title <tt>jdbc/DefaultDataSource</tt> in the <tt>web.xml.template</tt> file.

Serving WebServerResources
To stop the web server resources (images, CSS files and other static data) from being served out of the java environment, you need to configure the <tt>context-param</tt> with the name <tt>WOAppMode</tt> to be <tt>Deployment</tt> in the <tt>web.xml.template</tt> file.

Application Specific Configuration
This area of configuration covers items such as the following fictitious examples;

 * 1) Email address of person to contact when system fails.
 * 2) Frequency of polling some resource.
 * 3) Optional connection information for databases.
 * 4) GST rate for New Zealand.

In other words, these are application-specific configuration values. One way to configure your application specific parameters in a servlet container is to load your config into <tt>env-entry</tt>-s in your <tt>web.xml</tt> file. Here is such an example of one such entry;

<env-entry> <env-entry-name>foo/nz.co.foo.FooAppMailFrom</env-entry-name> <env-entry-value>bar@foo.co.nz</env-entry-value> <env-entry-type>java.lang.String</env-entry-type> </env-entry>

You can retrieve these value inside the application with some code as shown below. See the LEConfig class from LEWOStuff, the WebObjects framework from Lindesay Electric for an example. LEWOStuff also comes with a tool to help load standard java properties files into the servlet deployment descriptor.

import javax.naming.*;

// ...later in the same class...

Object valueO = null; try { InitialContext context = new InitialContext; valueO = context.lookup("java:comp/env/foo/nz.co.foo.FooAppMailFrom"); } catch(javax.naming.NamingException ne) { /* handle gracefully */ }

It is probably easiest to apply these settings in some automated fashion to the <tt>web.xml</tt> file as part of a further automated build or deploy process.

Application Binary
Put your application servlet build product at <tt>$INSTDIR</tt> such that the following path exists.

$INSTDIR/webapps/FooApp/WEB-INF

Tomcat Server Configuration Files
You need to create a tomcat configuration file for each of the instances that you would like to have. The pattern is followed here of having an instance number proceeded by the lower case letter "i". Put the first server configuration file at the following location.

$INSTDIR/server_i1.xml

Here is an example of how this file might look. There is no coverage of the individual settings here as the reader is expected to review the tomcat documentation to discover the specific meanings of these settings.

Tomcat 5
<Server port="7071" shutdown="SHUTDOWN"> <Service name="Catalina"> <Connector port="8081" maxHttpHeaderSize="8192" maxThreads="150" minSpareThreads="25" maxSpareThreads="75" enableLookups="false" acceptCount="100" connectionTimeout="20000" disableUploadTimeout="true" />

<Connector port="9091" enableLookups="false" protocol="AJP/1.3" />

<Engine name="i1" defaultHost="appserver1.foo.co.nz" jvmRoute="i1"> <Host name="appserver1.foo.co.nz" appBase="/home/fooapp/webapps" unpackWARs="true" autoDeploy="false" xmlValidation="false" xmlNamespaceAware="false"> <Context cookies="false" docBase="FooApp" path="FooApp" reloadable="false"> <Manager distributable="false" /> </Context> </Host> </Engine>

</Service> </Server>

Tomcat 3
<?xml version="1.0" encoding="ISO-8859-1"?>

<Server> <ContextManager workDir="work">

<LoaderInterceptor11 useApplicationLoader="true" />

<AutoDeploy source="modules" target="modules" redeploy="true" /> <AutoWebApp dir="modules" host="DEFAULT" trusted="true"/> <AutoWebApp dir="/home/fooapp/webapps" trusted="true" reloadable="false" />

<SimpleMapper1 />

<SessionExpirer checkInterval="60" /> <SessionIdGenerator randomClass="java.security.SecureRandom" />

<WebXmlReader validate="false" /> <ErrorHandler showDebugInfo="true" />

<Jdk12Interceptor /> <LoadOnStartupInterceptor /> <Servlet22Interceptor />

<SessionId cookiesFirst="false" noCookies="true" /> <SimpleSessionStore maxActiveSessions="256" />

<Http10Connector port="8081" secure="false" /> <Ajp13Connector port="9091" tomcatAuthentication="false" shutdownEnable="true" />

</ContextManager> </Server>

Assuming that there will be three instances in this example deploy, this entire file should be replicated and modified twice for the other two instances. For the other instances' server configuration files, change the "i1" (Tomcat 5 only) by modifying the numerical component and change the port numbers by making the last digit the instance number. For example, the ports <tt>7071</tt>, <tt>8081</tt> and <tt>9091</tt> are used here. For "i2", use <tt>7072</tt>, <tt>8082</tt> and <tt>9092</tt>.

You should have three files now present called <tt>server_i1.xml</tt>, <tt>server_i2.xml</tt> and <tt>server_i3.xml</tt> in the directory <tt>$INSTDIR</tt>.

Startup An Instance
To startup an instance, issue a command as follows. You should issue this command for each of the server configuration files. The <tt>$JAVA_HOME</tt> shell environment variable should have been setup correctly before launching an instance.

Tomcat 5
$TOMCATDIR/bin/startup.sh -config $INSTDIR/server_i1.xml

Tomcat 3
$TOMCATDIR/bin/startup -config $INSTDIR/server_i1.xml -home $TOMCATDIR

Tomcat 3 Environment Variables
To pass java environment variables to your application, set the <tt>TOMCAT_OPTS</tt> shell environment variable before starting up the Tomcat 3 environment. An example of this would be as follows;

TOMCAT_OPTS=-Dabc=xyz export TOMCAT_OPTS

Check Availability
You can now see if your instance is up using the following URL.

http://appserver1.foo.co.nz:8081/FooApp/WebObjects/FooApp.woa

Note that both the AJP (This is the protocol between the apache adaptor and the individual Tomcat instances.) and the regular HTTP engines are accessing the same running application. This means that a test straight onto the application via HTTP is actually testing the application that is being accessed via AJP. This behaviour provides an opportunity to be able to monitor specific instances of Tomcat over direct HTTP.

Check each of your instances.

Problems
Under Tomcat 5, check the log file at <tt>$TOMCATHOME/logs/catalina.out</tt> if you are unable to access your instance.

Shutdown An Instance
To shutdown an instance, issue a command as follows.

Tomcat 5
$TOMCATDIR/bin/shutdown.sh -config $INSTDIR/server_i1.xml

It is also possible to use the UNIX <tt>telnet</tt> command to connect to the port described in the server configuration file's <tt>Server</tt> tag and type the word supplied in the <tt>shutdown</tt> attribute to take out the Tomcat instance.

Tomcat 3
TOMCATDIR/bin/shutdown -ajp13 -port 9091

Apache Adaptor Setup
A final deployment usually involves apache feeding inbound requests to instances and handling situations where an instance has gone down and balancing load over the instances that are currently running. This job is undertaken by <tt>mod_jk</tt> which is a module for apache written by the Tomcat group. This module communicates with the tomcat instances using a protocol called <tt>AJP</tt>. This protocol carries all the information required to check instances are operational as well as relaying requests to the instances. It is assumed that the configuration as well as binaries for the <tt>mod_jk</tt> apache module will be located at <tt>$JKDIR</tt>.

Compiling and Installing
Instructions for downloading and installing <tt>mod_jk</tt> can be obtained from the Tomcat website. The <tt>mod_jk.so</tt> binary should be located at the following path.

$JKDIR/mod_jk.so

Add a line to your system's apache httpd configuration file like this:

Include /opt/modjk/apache.conf

Edit this file to look like this:

LoadModule jk_module /opt/modjk/mod_jk.so AddModule mod_jk.c

JkLogFile /opt/modjk/mod_jk.log JkLogLevel info

JkWorkerProperty worker.list=i1,i2,i3,loadbalancer JkWorkerProperty worker.i1.type=ajp13 JkWorkerProperty worker.i1.port=9091 JkWorkerProperty worker.i1.host=appserver1.foo.co.nz JkWorkerProperty worker.i1.lbfactor=1 JkWorkerProperty worker.i2.type=ajp13 JkWorkerProperty worker.i2.port=9092 JkWorkerProperty worker.i2.host=appserver1.foo.co.nz JkWorkerProperty worker.i2.lbfactor=1 JkWorkerProperty worker.i3.type=ajp13 JkWorkerProperty worker.i3.port=9093 JkWorkerProperty worker.i3.host=appserver1.foo.co.nz JkWorkerProperty worker.i3.lbfactor=1 JkWorkerProperty worker.loadbalancer.type=lb JkWorkerProperty worker.loadbalancer.sticky_session=1 JkWorkerProperty worker.loadbalancer.local_worker_only=1 JkWorkerProperty worker.loadbalancer.balance_workers=i1,i2,i3

JkMount /FooApp/* loadbalancer

Again, the details of the exact settings will not be covered in this article, but this should provide a simple guide to setting up this file to provide for a multi-instance deploy under Tomcat.

Restart Apache
Now restart apache with the following command:

sudo apachectl restart

Test Application
Now you can test your application using a URL such as this one.

http://www.foo.co.nz/FooApp/WebObjects/FooApp.woa

All three instances that you have setup should take some of the inbound requests.

Choosing the Right Instance
<tt>mod_jk</tt> ensures that requests that have started a session will be directed to the correct instance where the session originated. This behaviour is known as {\it sticky sessions}. It does not appear to be possible to nominate the instance from the servlet container in another way.

More Information
../Tomcat Deployment Details/


text:
Rosacea/Intense Pulsed Light and Laser manufacturers

Candela
Candela corporation (http://www.candelalaser.com/) was founded in 1970 and produce and sell laser systems. Their current lineup of laser systems include the GentleLASE® for hair removal, C-beam™ for psoriasis, Smooth beam™ for acne scars and wrinkles and the Vbeam® for vascular lesions (including rosacea). Candela have recently announced a distribution agreement with Danish Dermatologic Development to sell Intense Pulsed Light (IPL) machines in the U.S.

Vbeam®
The Vbeam® is a pulsed dye 595nm laser and is commonly used for treating rosacea. The Vbeam features an integrated Dynamic Cooling Device™ that sprays the top layer of skin with cryogen milliseconds before each laser pulse. This reduces purpura normally associated with laser treatments.

Ellipse I2PL
Candela branded IPL machine manufactured by Danish Dermatologic Development.

Lumenis
Lumenis (http://www.aesthetic.lumenis.com/) formed after the merger of ESC™ Medical Systems and Coherent Medical Group and are based in Israel.

Lumenis One
All in one machine with 3 modules; an IPL module, Nd:YAG laser module and a LightSheer module. The IPL module incorporates Optimal Pulse Technology (OPT) which results in a more even distribution of energy within each pulse, this makes it more effective and a lower energy levels can be used to achieve the same results.

VascuLight
Combination machine with cooled Nd:Yag laser head and IPL head.

D-Light SR
Cheaper IPL machine.

IPL Quantum SR
IPL machine dedicated to skin photorejuvenation treatments.

Danish Dermatologic Development
Danish Dermatologic Development A/S (DDD) (http://www.ellipse.org) manufacturer and sell Intense Pulsed Light (IPL) machines. They developed Dual Mode Filtering, a method of using two filters to filter out wavelengths both shorter and longer than the optimal range. DDD entered into an agreement with Candela corporation where Candela will distribute the Ellipse systems in the U.S.

Ellipse Light
The Ellipse Light is designed for beauticians and is used for the treatment of unwanted hair or sun-damaged skin (including diffuse redness). The Ellipse Light calculates the treatment parameters automatically using information about your skin inputted by the machine operator.

Ellipse Flex
The Ellipse Flex is designed for physicians and treats a larger number of conditions including facial telangiectasias, vascular malformations and rosacea.

Laserscope
Laserscope (http://www.laserscope.com/) are a US based company that manufacturer and sell medical laser systems primarily for urology and aesthetic surgery.

List of machines indicated for rosacea:
 * Gemini - A combination 1064nm Nd:YAG laser and 532nm KTP laser
 * Aura-i - Frequency doubled Nd:YAG (532nm)
 * Lyra-i - 1064 Nd:YAG laser

Syneron
Syneron Medical Ltd. (http://www.syneron.com/) is a rapidly expanding company founded in 2000. Syneron use their patented ELOS system that combines Bi-Polar Radio Frequency (RF) and optical energies. Syneron sell a number of platforms with the Aurora, Galaxy and Pitanga being suitable for vascular and pigmented lesions including rosacea.

Galaxy
The Galaxy is a all-in-one platform with an Intense Pulsed Light (IPL) head and a 900nm diode laser head. Physicians using this device are trained using the FotoFacial RF™ procedure.

Aurora
Combined Intense Pulsed Light (IPL) and Bi-Polar Radio Frequency (elos). Physicians using this device are trained using the FotoFacial RF™ procedure.

Cynosure
Cynosure, inc (http://www.cynosurelaser.com/) was founded in 1991 and produce and sell medical laser systems.

Cutera
Cutera (http://www.cutera.com) manufacture and sell the CoolGlide family of Laser and IPL machines for aesthetic treatments

List of machines indicated for rosacea:
 * CoolGlide Xeo - has both a long-pulse Nd:YAG laser and a IPL module
 * CoolGlide Genesis Plus - has both a long-pulse Nd:YAG laser and a IPL module
 * CoolGlide Vantage - long-pulse Nd:YAG Laser
 * CoolGlide Excel - long-pulse Nd:YAG Laser

Sciton
Sciton Inc., (Palo Alto, CA) is a privately owned medical device company formed in 1997 to provide advanced lasers and light sources to the aesthetic medical markets. Their BBL (Broadband Light) system is a specialized version of IPL with two flashlamps and swappable filters.

Palomar
Palomar Medical Technologies, Inc. (Palomar) designs, manufactures, markets and sells lasers and other light-based products and related disposable items and accessories for use in medical and cosmetic procedures. It offers a range of products based on its technologies that include, but are not limited to hair removal; removal of vascular lesions, such as rosacea, spider veins, port wine stains and hemangiomas...

EsteLux
During 2001, Palomar received United States Food and Drug Administration (FDA) clearance to market and sell the Palomar EsteLux Pulsed Light System. In 2002, and 2003, the Company offered six hand pieces for the EsteLux system: LuxY, LuxG, LuxR, LuxRs, LuxB and LuxV. These hand pieces emit pulses of intense light to treat unwanted hair, solar lentigo (sunspots), rosacea, actinic bronzing, spider veins, birthmarks, telangiectasias and acne.

MediLux
In March 2003, the Company launched the Palomar MediLux Pulsed Light System with the six hand pieces also available on the EsteLux. The MediLux provides a snap-on connector enabling it to switch among hand pieces and provide treatments tailored to each individual being treated.

StarLux
In February 2004, Palomar launched the StarLux Pulsed Light System. The StarLux has a single power supply capable of operating both lasers and lamps. The StarLux operates five of the EsteLux/MediLux hand pieces: LuxY, LuxG, LuxR, LuxRs, and LuxV.

StarLux 500
In February 2007, Palomar launched the StarLux 500 Laser and Pulsed Light System, and began shipping in March 2007.


text:
Rosacea/Authors and Contributors

Listed alphabetically as their contributions appear in the wikibooks edit summary
 * Warren

title: Rosacea/Authors and Contributors


text: Category:Book:Automobile Repair

title: Category:Book:Automobile Repair


text:
Genealogy/Mailing lists

Genealogical Mailing lists first began with Roots-L in the 1990's. The list provides a wonderful, relaxed way to connect with possible cousins sharing the same surnames, locality, and other special interest groups pertaining to Genealogy and Family History work. The list is archived and searchable at http://lists.rootsweb.com/ If you prefer, you can subscribe to the email list that you are interested in the digest mode (one email with all of the posted emails for the day) or list mode (where you get an email for each email posted).

This great resource is available to all at no charge to subscribe or to search the archives. Either way works well and is worth your time.

title: Genealogy/Mailing lists


text:
Catholicism

{| width="100%" cellpadding="20" cellspacing="0"
 * bgcolor="#DEE7F5" width="60%" valign="top"|
 * bgcolor="#DEE7F5" width="60%" valign="top"|

Introduction to Catholicism

 * }

title: Catholicism


text:
GCSE Science/Momentum

Momentum is the tendency for objects at rest to stay at rest, and for objects in motion to stay in motion.

The greater the mass of an object, the greater its resistance to changes in motion. Also, intuitively, the greater the velocity of an object, the greater the momentum it possesses. Therefore, the momentum of an object can be quantified mathematically as p=mv, or as mass x velocity.

The greatest usefulness of the concept of momentum lies in the fact that the total momentum of a system of objects is always conserved, i.e., in isolation the total momentum always stays the same. This knowledge allows the solution of many problems in physics with great elegance. For example, in rocket propulsion; the mass of propellant a rocket carried multiplied by the exhaust velocity of the engine, will be equal to the final forward velocity of the empty rocket multiplied by its empty mass. Without understanding the principle of conservation, finding the final velocity of the rocket would be very puzzling; but applying the simple equation mv = m’v’,  and rearranging to v’=mv/m’, finding the velocity becomes a very simple calculation.

The principle of conservation of momentum applies to all states of matter, i.e., solids, liquids, gases, and plasma (and subatomic particles), and with all forms of interaction through all forces, such as gravity, magnetism, direct contact, electrostatic force, etc. etc., so the scope and range of application of this principle is vast. It is easily one of the most important concepts to understand in solving problems involving motion.

The concept of momentum can also be applied to rotating objects, in which case the momentum possessed by such rotating objects is called 'angular momentum'. Angular momentum is also conserved.

title: GCSE Science/Momentum


text:
User:Kelbel

Hi! I'm Kelly. I'm new to Wikipedia, but I signed on so that I could contribute to the Muggle's Guide to Harry Potter pages. Wikibooks are such a great resource--I'm excited to be a part!

title: User:Kelbel


text:
Online OsiriX Documentation/Using OsiriX Plugins/Align

WARNING! '''This plugin overrides a lot of fundamental OsiriX rendering routines. Many bugs are to be expected if this plugin is installed while doing anything other than creating mosaics of 8-bit images.'''

This plugin will make OsiriX tile images internally to increase the speed of texture uploads to the video card. This plugin has been tested using 8-bit black-on-white EM images. Some work has gone into making this plugin work with other images types. Your milage may vary. The faster texture upload speed may make this plugin useful for viewing very large images. Report bugs to [mailto:spalte@gmail.com| Joël Spaltenstein].

= Tools for the construction of EM image mosaics by manual registration =

Using the Align plugin
Open two image viewers. One will be the tile being added to the mosaic, the other is the mosaic being constructed. It may be useful to have a small white 8-bit tiff with a single pixel set to 0x00 (in order to define the dynamic range of the image) to use as the first image of the mosaic. Define the viewers as as the tile and  mosaic by using the Make Align Tile and Make Align Mosaic menu items. Now drag the file icon in the tile 's menu-bar to the mosaic, exactly as if making an image fusion. The tile should appear over the image in the mosaic window. In order to position the image correctly you will move control points on the images. Select the number of control points you wish to use with the appropriate menu items. Drag the control points in the tile to define their position. Drag the control points in the mosaic to define where the control points should map to. Once the alignment is satisfactory, make sure the mosaic viewer is the active window, and use the Merge Images menu item to paste the tile onto the mosaic. To save the mosaic, export it to a tiff, making sure of course that Set to original image size is selected in the OsiriX export preferences.

Make Align Background
When creating a new mosaic, you may wish to take into account a mosaic created from EM images of a nearby slice. In order to do this, open up a viewer onto the said mosaic, Make Align Background and drag the newly created background onto the mosaic. In order to save memory, the mosaic viewer copies the image data from the background, making it safe to close the background viewer without the background disappearing from the mosaic. Of course this also means that no live link is kept between the mosaic and the background. The background can be positioned by selecting the Pan tool and panning while pressing the command (open-apple) key.

Tips
Define three new CLUTs before using the plugin. One that goes from white to mostly Red and Blue, another that goes from white to mostly Red and Green, and yet another that goes from white to mostly Green and Blue. By using these newly created CLUTs, it will be very easy to see it the alignment of the new tile is good. For example, if the Red and Blue CLUT is used for the mosaic and the Green and Blue CLUT is used for the tile, the intersection of the images will appear as a sharp blue image.


text:
User talk:Pir/Book1

Hi Pir,

Why don't you work on this in the main namespace? There's a few otehr books on unix aps (like the gimp) already on wikibooks, and you might be able to garner help from the folks who worked on those. -- SB_Johnny | talk 17:33, 27 August 2006 (UTC)

title: User talk:Pir/Book1


text:
User:Akira.pl

pl:Wikipedysta:Akira

title: User:Akira.pl


text:
User:Piotr~enwikibooks

Click

pl:User:Piotr

title: User:Piotr~enwikibooks


text:
Wikijunior:How Things Work/Lever

A lever is an object that is used with a pivot point, or 'fulcrum', to multiply the force applied to another object. Levers are often long and skinny and made of rigid material. Levers are one of the six simple machines.

Who invented it?
Levers occur in nature. In fact, your arm and your jaw are both examples of levers. It is impossible to say who invented the first mechanical lever. Human beings have used mechanical levers since the stone age.

The earliest remaining writings regarding levers date from the 3rd century BC and were provided by Archimedes. "Give me the place to stand, and I shall move the earth." is a remark of Archimedes who was the first to mathematically describe how levers multiply force.

In ancient Egypt, builders used the lever to move and uplift obelisks weighing more than 100 tons. A shadoof is type of lever that was used in Egypt. It is a pole with a weight on one end. It is used to lift water from a well or river for irrigation. It was in common use by 2000 BC. It is still used in many areas of Africa and Asia to draw water.

What does it do?
A lever enables people to do work using less force. A lever usually is used to move or lift objects. Sometimes it is used to push against objects, but not actually move them. Levers can be used to exert a large force over a small distance at one end by exerting only a small force over a greater distance at the other.

How does it get power?
Its power comes from outside forces acting on it. In order to use the lever successfully and achieve its mechanical advantage, you must exert force into this simple machine. The force applied to one end of the lever is transferred to the other end on the lever. The real power of levers comes from a mechanical advantage. The lever allows less effort to be expended when moving an object, but there's a trade-off. The object will move a shorter distance than the person or thing exerting the force. For example, a crowbar can be used to pry up a board because it applies a lot of force over a short distance when the person using the crowbar uses much less force over a much greater distance. Another example is a catapult. You put the load onto the catapult, pull it back, and it throws the object(s) to where they were desired to go. This simple machine was also used in very early times.

How does it work?
The lever has two important parts. The lever itself and the fulcrum. The placement of the fulcrum determines how far the levered object will move, and how much force is required to move it.

If a weight was resting on a lever a person could lift the weight by pressing on the lever on the other side. The farther away from the fulcrum that person pressed, the less force that person would need to apply. In order to lift the weight the same distance, the force would have to be applied over a longer distance. In science, we call how much effort it takes to move something a certain distance "work." With a lever, you always do the same amount of work no matter how long your lever is. But if you are moving the lever further, then you don't have to push as hard to do the same amount of work.

How dangerous is it?
Levers can be dangerous because they multiply force. But everyone uses levers all the time without ever thinking they are dangerous. Every time you open a door, you are using a lever. Most levers we use are safe. But throughout human history, levers have also been used as weapons. Some examples of weapons that are levers are nunchucks, catapults, and atlatls.

How does it vary?
There are actually three types of levers! They are called first-class levers, second-class levers, and third-class levers.

A see-saw is an example of a first-class lever. A first-class lever the fulcrum is located between the force pushing down- the input force-(on a see-saw that would be the person going down) and the output force (the person going up).

A wheel barrow is an example of a second-class lever. In a second class lever, the resistance is located between the effort and the fulcrum. The input force would be the handles, where you need to pull up in order to lift the weight in the barrow. The fulcrum located on the axle of the front wheel.

A baseball bat is an example of a third-class lever. In a third class lever the effort is between the fulcrum and the resistance. In the case of a baseball bat, you exert effort by swinging the bat at the handle. The heavier part of the bat is the resistance. In this case, the force at the end of the bat is actually reduced, but the speed is increased. The end of the bat moves faster than the grip where the force is applied, giving it greater momentum, causing it to strike the ball harder.

How has it changed the world?
The lever has changed the way we work immensely. It has helped us to do more work with fewer resources. It played an essential role in developing agriculture. It also played a crucial role in building shelters and other types of buildings. In fact, levers are so useful and common, that they have played a role in every other technological advancement.

What idea(s) and/or inventions had to be developed before it could be created?
Levers are one of the six simple machines. They did not require any prior invention. The very first machine ever invented by a human being may very well have been a lever.

title: Wikijunior:How Things Work/Lever


text:
Wikijunior:How Things Work/Wedge

Who invented it?
The origin of the wedge is unknown, because it has been in use from as early as the stone age. The first wedge was probably used as a knife or scraper and was probably just a broken piece of a stone. Stones that fit easily in your hand and are sharp enough to cut meat, grass and bark are not hard to find. You can find pieces of stone that can be used as a knife just lying on the ground in some places.

The wedge is one of the very first inventions of humans. The wedge is one of the six simple machines and may have been the first or second developed (along with the Lever. When early humans made scrapers, axes and knives from stone, they were making a wedge. The earliest known wedges made by people were made 2.6 million years ago. Simple stone tools like these are called "Oldowan" tools by archaeologists.

In ancient Egyptian quarries, bronze wedges were used to break away blocks of stone used in construction. Wooden wedges, that swelled after being saturated with water, were also used. Some indigenous peoples of the Americas used antler wedges for splitting and working wood to make canoes, dwellings and other objects.

A wedge is a triangular shaped tool that is thicker on one end (the blunt end) and thinner on the other end (the edge.) A slice of pie is the shape of a wedge. Wedges are one of the six simple machines. It can be used to separate two objects, split an object, lift an object, or hold an object in place.

How does it get power?
Its power comes from outside forces acting on it. A wedge converts a force applied to its blunt end into forces perpendicular (at a right angle) to its inclined surfaces. A short wedge with a wide angle may do a job faster, but it requires more force than a long wedge with a narrow angle.

How dangerous is it?
Because a wedge is thin on the edge, it is sharp. There are many wedges you have to be careful with, like knives and scissors. However, some wedges can be blunt and not dangerous at all...

How does it vary?
Some wedges are used to separate. Common examples of this type of wedge include knives, axes, nails, scissors, and plows (British English: ploughs). Others are used to lift things or adjust the distance between them. A long tapered piece of wood called a shim is used in carpentry to make fine adjustments. Still other wedges are used to hold things in place. A doorstop is an example of this kind of wedge.

How has it changed the world?
The wedge might be the most important invention in human history. Without wedges, we would not have been able to cut wood, hunt animals, or make clothing. A particular kind of wedge called the plow allowed human beings to farm the land.

What idea(s) and/or inventions had to be developed before it could be created?
The only thing that people had to know was how to chip rock to make it sharp. Now we usually use metal for most wedges.

title: Wikijunior:How Things Work/Wedge


text:
Wikijunior:How Things Work/Screw

Screws are one kind of simple machines. They have a corkscrew-shaped ridge, known as a thread, wrapped around a cylinder. The head is specially shaped to allow a screwdriver or wrench to grip the screw when driving it in.

The most common uses of screws are to hold objects together — such as wood — and to position objects. Often screws have a head on one end of the screw that allows it to be turned. The head is usually larger than the body of the screw. The cylindrical portion of the screw from the underside of the head to the tip is called the shank.

Bolts are a type of screw that usually is designed to work with a nut or another threaded fastener.

Who invented it?
Historians do not know who invented the screw. Although it seems to have been invented only in the last few thousand years. The first known use of a screw was as part of the screw pump of Sennacherib, King of Assyria, for the water systems at the Hanging Gardens of Babylon and Nineveh in the 7th century BC.

Around 250 BC, the Greek inventor Archimedes made a screw pump. Archimedes' machine had a revolving screw-shaped blade inside a cylinder. The blade was turned by hand. This type of machine is called the Archimedes screw. It is still used today for pumping liquids and other materials like coal and grain. By the 1st century BC, wooden screws were commonly used throughout the Mediterranean world in devices such as oil and wine presses.

The metal screw did not become a common fastener until machines for mass production were developed at the end of the 18th century, because nails, which are straight, are much easier to make than screws. In the 1770s, English instrument maker Jesse Ramsden invented a machine that made metal screws. Handheld screwdrivers first appeared around 1800. These developments caused a great increase in the use of threaded fasteners.

Throughout the 19th century, the most common types of screw heads were round with simple slots that were turned using screwdrivers and square and hexagonal heads that were turned with wrenches. In the early 1930s, the Phillips-head screw was invented by Henry F. Phillips. This screw has a cross-shaped recess in the head for the driver tool.

What does it do?
Screws do one basic thing. They convert a force that goes around and around into a force that goes up and down. This force can be used to push against an object.

Machines that use screws to push against other objects are called presses. A press is used to make cider or wine by squashing fruit to extract the juice from it. Printing presses were also used to make books.

The up and down force generated by a screw can also be used to hold things together. Screws can thread into a metal nut and the up and down force holds the two together. One big advantage of screws used as fasteners is that they can be removed and reinserted many times without losing their effectiveness. They have greater holding power than nails and can be easily disassembled and reused.

Screws can also be used to lift things. A device called an auger is used for lifting or pumping water or another liquid. As the screw turns in the water, the water is lifted. This is also how a concrete mixer (truck) unloads its load of concrete.

How does it get power?
A screw is powered by the movement of the screw driver. It converts this rotational force (called torque) into up and down force. A screw's power depends on how close together the threads are and how far away from the center of the screw force is applied. You can get more power by making the threads closer together. If the threads are close together, then with each turn of the screw it travels a shorter distance but exerts more force. With tighter threads you have to turn the screw more times before it is tight. You can also get more power by using an object that allows you to apply force farther from the center of the screw. This is why it's easier to turn a screw or bolt with a long wrench than a shorter one. But there is a downside to using a longer wrench. With a longer wrench, you have to move the wrench farther in order to turn the screw the same distance.

How dangerous is it?
Screws can be dangerous around anyone especially children. Screws with a sharp point on the shank are designed to pierce material and they can puncture and really damage your skin or wherever you hurt yourself, if you are not being careful and cautious.

How does it vary?
Certain screws may have different shapes, sizes, etc. to suit different needs. Some screw threads are designed to mate with a complementary thread, known as an internal thread, often in the form of a nut or an object that has the internal thread formed into it. Other screw threads are designed to cut a helical groove in a softer material as the screw is inserted. Most screws are tightened by clockwise rotation, which is termed a right-hand thread. Screws with left-hand threads are used in exceptional cases. For example, when the screw will be subject to anticlockwise forces (which would work to undo a right-hand thread), a left-hand-threaded screw would be an appropriate choice. Threaded fasteners either have a tapered shank or a non-tapered shank. Fasteners with tapered shanks are designed to either be driven into a substrate directly or into a pilot hole in a substrate. Mating threads are formed in the substrate as these fasteners are driven in. Fasteners with a non-tapered shank are designed to mate with a nut or to be driven into a tapped hole.

How has it changed the world?
Inventions like the automobile would not be possible without the screw.

What idea(s) and/or inventions had to be developed before it could be created?
The screw is like a ramp or inclined plane wrapped around a pole so the ramp had to be invented first. Although some screws have been made from wood, screws made from metal are much more useful because they can be more precise. Smelters to purify ore and forges to work metal were needed to make screws that were effective fasteners. In order to mass produce screws, a special lathe had to be developed.

title: Wikijunior:How Things Work/Screw


text:
Wikijunior:How Things Work/Flush Toilet

When most of us go do things everyday, we have questions that sometimes are a little weird. That’s ok! For years, people have been making things complicated, but we’re here to answer the question, how do flush toilets work?

Who invented it?
Flush toilets were first used in parts of India and Pakistan about 2,700 years ago. The cities of Harappa and Mohenjo-daro had a flush toilet in almost every house, attached to a sophisticated sewage system. Remains of sewage systems have been found in the houses of the Minoan cities of Crete and Santorini in Greece. There were also toilets in ancient Egypt, Persia and China. "In Roman civilization, toilets were sometimes part of public bath houses where men and women were together in mixed company." Toilets are usually connected to a septic tank, or to a sewer.

In 1775 Alexander Cummings invented the S-trap, which is still used today, that used standing water to seal the outlet of the bowl, preventing the escape of foul air from the sewer. His design had a sliding valve in the bowl outlet above the trap.

The flush toilet is sometimes called a water closet ("WC").

How does it get power?
A toilet works because of gravity. When a flush lever is pulled, a plug opens, allowing water to flow out to fill the basin. When the basin is full enough, gravity causes the liquid to flow out through a bend in the pipe, called an S trap.

Historically, other traps were used but found to have various issues. L traps would clog due to the 90 degree angle. U traps would also clog due to lack of water pressure not pulling the water through the pipe properly. Finally, T traps were used in a series of toilet stalls but would not allow water to flow downward, instead pushing water back and forth without properly draining.

How does it work?
A flush toilet disposes of our waste products by using water to send them through a drainpipe to another location.

The picture below shows a typical toilet. The toilet bowl usually has a ring-shaped seat on top, which is covered by the lid when not in use. Alternatively, you may remove the lid, leading to an upper decker design.

The handle/button is pressed to flush the toilet. The water used for flushing is stored in the tank (also called a cistern)

The tank contains some important parts. The next picture shows the parts of a typical tank. The inlet valve controls the water supply coming into the tank. It lets water in when the tank is empty and stops water coming in when the tank is full.

The "float ball" rises as the tank fills with water. As it rises, the float rod attached to it presses against the inlet valve. When the tank is full, the rod is pressing against the inlet valve hard enough to turn the water off. This stops the tank from overflowing.

When you press the handle, a lever inside the tank pulls the piston up, forcing some water through the siphon. This provides suction in the siphon, and the rest of the water within the siphon 'U' tube follows. The piston is usually covered by a plastic membrane, which is constructed to be "sucked" out of the way by the emptying siphon tube water, allowing the rest of the water in the tank to rush past the piston, and over the top of the siphon, emptying the rest of the tank. The piston membrane then drops back onto the piston, ready for the next flush operation.

The tank empties quite quickly, and the float ball floats to the bottom. That means the float rod is no longer pressing against the valve, so water begins to flow into the tank, filling it up again.

The water which left the tank goes through a short pipe to the toilet bowl. It sloshes around the rim, down the sides of the bowl, and out through the drainpipe, cleaning the bowl and carrying the waste with it.

Some of the clean water coming behind remains at the bottom of the toilet bowl. That's because modern toilets have a 'S' bend which remains filled with water between flushing. The water in the 'S' bend stops bad odours escaping from the drainpipe. During flushing the 'S' bend also provides siphon action which helps speed up the flushing process.

However, since this type of toilet does not generally handle waste on site, separate waste treatment systems must be built.

What does it do?
The flush cleans the bowl of the toilet, and under the rim where it is difficult to clean. It carries waste matter to a drain, which then takes it to a treatment plant or septic tank.

How does it vary?
Toilets come in many different types. There are chemical toilets, which use chemicals to neutralize the waste instead of water. There are composting toilets, which are better for the environment because they turn the waste into natural compost. There are even incinerating toilets, which burn the waste.

Some toilets have extra fixtures such as grab-bars for wheelchair users. Some toilets have a water jet built into them like a bidet. Some have heated seats, and lids that open and close automatically. And some will even check your blood pressure and temperature.

Different toilets use different amounts of water per flush. Older models use 13 or even 19 liters per flush while newer models use 6 liters (1.6 gallons) per flush. Today, some well-designed 6 liter toilets flush better than lesser toilets that use 2-3 times more water per flush. The design of the surfaces that control the flow of water make a big difference!

How has it changed the world?
The toilet has made homes, towns and cities cleaner places to live in. Because water cleans the toilets very well, highly contagious diseases cannot spread as easily as in the past, where very often thousands of people died at the same time, and to keep epidemics under control, cities and villages weren't allowed to grow beyond a certain population. Toilets help public health of today to keep higher standards than in the past. That allows us today to live in much bigger cities than in the past, not being afraid of getting sick. Big cities were a requirement to start the industrial revolution in the 1800s. We see that although toilets might not look like such an important invention, they have had a huge impact on our modern world. The toilet has also created a whole new profession called plumbers and its associated industry.

What idea(s) and/or inventions had to be developed before it could be created?
To have a flush toilet in your house, first of all one has to have fresh and clean water supply. A better organization of the cities was needed for that. The lever and the siphon also had to be invented before the flush toilet could have come into being.

title: Wikijunior:How Things Work/Flush Toilet


text:
Wikijunior:How Things Work/Car Engine

A car engine uses internal combustion engine which is a mechanical device which burns a fuel to produce power rotation which moves a vehicle.

Who invented it?
Nicolaus Otto was the first person to successfully build the 4-stroke type of engine that would later become an car engine in 1876. In 1885 Karl Benz used an engine similar to Otto's engine to make a three-wheeled automobile move. In the same year, Benz began producing and selling automobiles.

The first commercial two-stroke engine involving in-cylinder compression is attributed to Scottish engineer Dugald Clerk, who patented his design in 1881

How does it get power?
The internal combustion engine gets its power from the heat generated from the burning of liquid fuels mixed with air (vaporized).

These are mostly  'fossil fuels'  like gasoline, diesel, compressed natural gas (CNG) and liquefied petroleum gas (LPG) that are mined from the ground, and are becoming harder to find and extract,  but some recent technologies use synthetic or renewable fuels such as hydrogen, which can be produced by electrolysis using renewable energy sources.

What does it do?
It is a mechanical device that converts chemical energy (the fuel) to heat energy, and then to mechanical energy. Reciprocating (back and forth) motion is converted to rotary (spinning) motion, and transmitted through a clutch, gear box etc. to move the wheels of the car.

How does it work?
An engine is properly called a motor because it makes things move! Engine really means ingenious devices, but we use the term because the process of burning a fuel and delivering power usually requires much more than a simple motor spinning an axle. (clever things like gears, levers and cables to get the power to where it is really needed).

A motor burns a mixture of fuel and air in one or more metal tubes called cylinders. The hot, expanding gas from the combustion drives a piston downwards, causing a crankshaft to rotate, and spin a flywheel, absorbs energy from the burned fuel and keeps things rotating until the next cycle. The power from the rotating crankshaft and flywheel is what ultimately drives the wheels.

There are lots of different types of motor, but only two common sorts: the cheap, noisy and rather limited 2-stroke usually only found on small motorcycles and garden machines, and the more sophisticated Otto or 4-stroke used for cars, trucks and buses, which motor (pictured here) has a fun mnemonic, starting with the piston at the 'top' (but note: this is  not always actually at the top, but - as in the picture left - that is how most folks call the end of the cylinder with the spark-plug or igniter which is also furthest from the  'bottom-end'   or crankshaft):
 * SUCK (1) in a mixture of air and fuel vapor (actually called induction stroke as the piston starts at the 'top' of the cylinder near the spark plug or igniter and goes down to the 'bottom' near the crankshaft)
 * SQUEEZE (2) the mixture (a compression stroke as the piston goes 'up' towards the spark plug or igniter)
 * BANG! (3) the spark plug or igniter sets fire to the compressed fuel and air (a power stroke to force the piston 'down' towards the crankshaft) - When the piston is furthest from the crankshaft, it is said to be at  'top-dead-center'  - the actual spark usually occurs when the flywheel inertia has moved the crankshaft a few degrees further, so the piston has actually already started its 'decent' before it gets a push from the expanding hot burning gasses!
 * BLOW (4) out the exhausted (burned) gasses form the burnt fuel (the exhaust stroke - the piston returns to the 'top' of the cylinder ready to suck-in some fresh fuel and restart the cycle.

Two Stroke Motor
These were used in only a few small cars in the mid 20th century, notably the mass-produced East German Trabant, but also more famous makers of 'super-compacts' or 'ultra-lights' such as DKW, Saab, Wartburg, Suzuki and Subaru produced small numbers of 2-stroke vehicles.

A special mixture of fuel and lubricating oil is needed, because the fuel-and-air mixture is drawn in through the crankcase, with the end of the combustion stroke and the beginning of the compression stroke happening at the same time so that it performs the intake and exhaust functions together!

Although they have a better power-to-weight ratio than 4-strokes, they are more prone to wear and very polluting. Many industrial machines or ship engines use large 2-stroke diesel motors.

Gasoline and diesel
The speed of gasoline (or petrol) engines is easier to control and usually lighter than an equivalent diesel, which work best at constant speed and really needs a turbo-charger to compensate for the diesel inertia.

Gasoline is a 'light' fuel, highly combustible and ignited with an electrical spark-plug. Diesel (sometimes called 'vaporising oil) is a thicker 'heavy' fuel which is much less inflammable, and is fired by very high compression within the cylinder. The diesel is 'injected' by a tube fitted about where a gasoline engine has its spark-plug. Diesel fuel is apt to become solid at low temperatures, and often has an 'anti-wax-agent' to prevent this.

The diesel engine may require heating before it will work. This is usually done with an electrical heater, but some tractors motors designed for cold climates in the mid 20th century could use either fuel, and had to be started using petrol, then when hot, the driver could choose to use either expensive gasoline or cheap 'tractor vaporizing oil' which was in some European countries was subsidised and stained to detect its use in 'unauthorized' vehicles.

How dangerous is it?
VERY! Engines use flammable liquid fuel that can leak, they produce heat which can ignite spilled fuel, they are heavy and massive, so they stay hot long after they stop, they produce power,  and have lots of moving parts which can crush fingers or catch clothing to trap and injure the unwary, so the main motor (called the  'prime mover' ) has to be turned off long before you can work on an engine. Remember there are other motors that are around to power such as cooling fans  that may be designed to work for some period of time  after the prime mover engine ignition is switched off).

Never open the hood or touch an engine unless you are certain it has properly cooled off -probably for at least an hour after stopping.

Always check that everything in the engine bay is cool and is not leaking fuel or oil - plus make sure that any other motors have also actually stopped running before inserting anything under the hood (including particularly unprotected  fingers, loose long hair or dangling clothing).

How does it vary?
Internal combustion engines vary in the number of cylinders they have, and the size and positioning of those cylinders. For example, an Inline-4 has four cylinders in a line, and a V-6 has three pairs of cylinders in a "V" shape illustrated above.

Some Volkswagen designs used an unusual four-stroke air cooled engine, with two cylinders either side ( 'horizontally opposed, four-cylinder motor' ) which was originally designed for light aircraft. Illustrated here is one such, a Volkswagen Beetle motor of 1131 cubic centimetres (69 Cubic inches) total capacity, 25 PS (DIN) horsepower from 1945. It has been cut to show a better view of the interior. The orange colour is the cut surfaces and the green colour is the fuel-air  inlet  from the carburettor (mixer) which is in the middle, because it has to feed either side. The exhaust, cooling fan, and electrical generator or  alternator is not shown. The oil filter and cooler is at the top left.

Automotive (vehicle) internal combustion engines may be either 2-stroke or 4-stroke engines, and can use spark-ignition (SI) for 'volatile' gasoline or liquid petroleum gas (LPG) fuels and/or compression ignited (CI) diesel engines (as mentioned).

How has it changed the world?
Very dramatically. Before the automobile, there was only horse-power for personal transport at around 10 - 15 km/h (less than 10 mph or roughly twice walking speed) and steam powered public transport managed about two or three times that speed. The internal combustion engine has made personal transportation very much faster, up to about 100 km/h (60mph) on ordinary roads. Unfortunately both gasoline and diesel are what ar called 'fossil fuels' because they are made by natural forces over many millions of years, and our rate of consumption means they may not last forever. Scientists have tried many other 'synthetic fuels' but with only limited success. So the car is also responsible, indirectly, for the way we in the western world now live, with separate residential, industrial and commercial areas, which means most people need a car for work, shopping and social activities.

Unfortunately massive car use has led to an increase in world pollution - the so-called  'greenhouse-gasses'  which are thought to be warming the world and changing the weather. The polar ice caps seem to be melting, so the sea might rise, flooding coastal areas, and storms may become more violent because the air-flow is temperature sensitive.

What idea(s) and/or inventions had to be developed before it could be created?
The ideas of converting reciprocatory (back and forth) motion of the to rotary (spinning) motion was known since ancient times, and used in lathes to make round posts and spindles.

The idea of using external heat to make steam was known to the ancient Greeks, but steam engines as we know them only emerged from reciprocating steam pumps developed since the 17th century. Later, in the 18th century more sophisticated steam engines had cranks and flywheels to produce rotary motion and speed control using governors. In the early 19th century steam locomotives were developed, and with them some of the accessories such as cabin heaters (to say nothing of steering mechanisms and brakes).

The big breakthrough was finding ways of burning the fuel inside the piston (internal combustion engine), rather than making high-pressure steam or gas and then pumping that into the engine cylinders as occurs in steam and pneumatic motors.

title: Wikijunior:How Things Work/Car Engine


text:
Wikijunior:How Things Work/Airplane Wing

The wing is the part of airplane that enables it to rise into the air.

Who invented it?
Many people tried to invent a wing that would let people fly. Even the famous inventor, Leonardo da Vinci drew up plans for different ways of flying with wings like a bird. The first wing that let a person fly was in ancient China in the year 559. It was really just a large kite. In 877, long before Marco Polo and other explorers brought back information about Chinese kites to Europe, an Arab inventor in Spain named Abbas Ibn Firnas made the first hang glider, and tested it himself.

Sir George Cayley and later Otto Lilienthal created working gliders that allowed people to fly as long ago as the 1800s. The Wright Brothers were famous for the airplane that they first demonstrated in 1903 in Kitty Hawk, North Carolina, but their airplane's wings worked in the same way as Otto Lilienthal's glider wings from 1891.

How does it get power?
The only power that a wing needs is to be moved forward through the air. In a glider the wing is either pushed to get it started, or it is brought somewhere high up and dropped, like a hang glider pilot starting from the top of a cliff. In a powered airplane, the engines either push or pull the wings through the air.

The shape and positioning of a wing is very important. Most wings are curved, which makes the air going over them go faster than the air going under them. Because the air above the wing moves faster, it is more spread out than the air below the wing. Air presses on everything around it, even though you can't feel it. When there is more air it pushes more on the things around it. The fast-moving, spread-out air over the top of the wing lets the air on the bottom of the wing push the wing up, creating lift.

Another way to think of it is that the wing of an airplane is usually tilted so that the front is higher than the back. The air that follows the upper and lower surfaces of the wing is directed downward by the wing's shape and tilt. This creates an opposing upward lifting force on the wing itself. It is the lift from the wings that carries a plane through the air.

How dangerous is it?
Airplane wings are not dangerous. Airplanes themselves have a good safety record when they are well maintained and handled. Wings are as dangerous as any fast moving object can be and so depends also on the material it is made. First planes were made of very flimsy material because of weight and wings strength evolved accordingly to the speed requirements, the faster the plane the stronger the material must be.

What does it do?
A wing is a part of airplane that lifts it up. There are mainly four forces acting on airplane while in air. Wings provide the force to the airplane that takes it up against the force of gravity due to earth. An airplane wing is specially designed so that air that passes around it actually helps lift up the plane. It is also streamlined in shape so that the plane can move at maximum speed.

The horizontal 'front' or 'leading edge' splits the air so that the airstream over the top of the wing has to travel further than the airstream beneath the wing. When the two streams meet again at the 'trailing edge' the upper airstream has been stretched and the lower airstream has been compressed. The wing tries to equalize the air pressure above and below by moving up, but of course it can not move upwards without also lifting the airplane!

The reason an airplane is so called is because each wing provides two flat surfaces or planes which are joined by a thick, almost semicircular leading edge, and which meet at the sharp trailing edge. Because they split the air wings are properly called Aero-planes or (mostly in the USA) airplanes. Helicopter blades and propellers also technically possess 'airplanes' but today for most people who are not aviation specialists or 'aerodynamicists' the term simply means the complete 'fixed wing aircraft'

Wing shape can be modified to increase or decrease lift using flaps and ailerons

How does it vary?
All airplane wings contain flaps to increase lift and drag. Some airplane wings, especially those of larger jets, have spoilers that will further slow down the airplane. This is important in landing, where one must land at the slowest speed possible without stalling and then stop the airplane's movement as quickly as possible.

In larger airplanes the wings often have the engines fixed onto them.

How has it changed the world?
An airplane wing is one of the most fundamental things that allow a plane to fly. Without it, a plane does not fly and it has brought planes all over the world.

What idea(s) and/or inventions had to be developed before it could be created?
The first plane had to be invented before any experimentation with the wing could occur. The earliest wings were simply light framed wooden planks, with no such inbuilt drag or lift functions.


text:
Wikijunior:How Things Work/Hard Drive

When was it invented?
Hard disks were first invented in the 1950s and were initially called fixed disks or 'Winchesters' (the name of a popular IBM offering introduced in 1972.) The first magnetic hard disc for storage was the IBM 305 RAMAC which appeared in 1956. RAMAC (Random Access Method of Accounting and Control) quickly became the industry standard. For years hard drives were confined to mainframes and servers.

How does it get power?
The hard disk gets its power from one of the variable electrical output leads of the SMPS (switch mode power supply) of the computer.

How does it work?
First take a close look at the hard drive image here. This will give you a great idea of how each part is working together inside a hard drive.

Imagine a bunch of bar magnets all in a row, with the ends sticking towards you. Imagine that the first one has the north side sticking up, then the next 2 have south sticking up, and then 5 have north sticking up again. If you place a bunch of magnets together like this, you can start creating a code. A code created out of only north and south signals. In fact, computers are based on a very simple code based on only 0s and 1s called binary. North and South can be translated into 0 and 1 very easily.

A hard disk turns this line of magnets into a disk. Imagine spinning the long line of magnets like a thread around, like rolling up a piece of paper. To read the hard disk, all you have to do is spin the disk, and place another very small detection magnet close to it. The detection magnet is called a magneto-resistive read sensor. From the pattern of north and south, you can translate the code from "North and South" into everything on a computer.

The hard disk is also able to flip the magnets any time, so it can turn a magnet from "north" into "south" very easily. This allows it to not only read the disk, but write to it. Basically, it can change the "code" of north-south any time the computer wants it to.

When computers do this, they spin the disk very fast. They can read the code millions of times a second. Much work has been done to help make the disk spin faster and faster.

How dangerous is it?
Not very dangerous unless you open one up while attached to a power supply. A big mistake!

What does it do?
It is a mass storage device which can be used to store operating systems and a number of pieces of software. It is one of the main components of Desktop and Laptop computers. One hard disk can be partitioned to create a number of different virtual disks. Each such virtual disk can store (and work) a different operating system. The newer hard disks are much smaller than the original ones, but can store much much more than their ancestors. Not forgetting about their speeds. The newer hard disks can fetch data (stored in them) at the wink of an eye.... sometimes even faster.

How does it vary?
Not that many hard drives vary, except for the amount of data that they hold. There are different types of hard drives, like external hard drives and internal hard drives. Some types of hard drives are explained below.

Parallel Advanced Technology Attachment (PATA)
These types of drives are also known as Integrated Drive Electronics (IDE) and Enhanced Integrated Drive Electronics (EIDE) drives. These hard drives are very slow.

Serial ATA (SATA)
SATA drives are more efficient, and use less power than PATA drives. They are also faster than the PATA drives.

Solid State Drives (SSD)
These hard disks, unlike the other types, don't consist of moving components. The other hard drives explained above comprise of a spinning magnetic disk that performs the function of storing data, but SSDs use semi-conductors for this purpose. Since there are no moving components, these hard disks are much faster than the other drives.

How has it changed the world?
Hard drives enable computers and other electronic devices such as MP3 players to store massive amounts of information for use later.

Hard drives have allowed computer programmers to build enormously complex programs and store them for use on computers. Complex programs such as the one you are using to read this would not have been available prior to the introduction of hard drives.

Before hard drives were used in computers, popular storage mediums included cardboard cards, paper tape (with holes punched in it), magnetic tape, and magnetic tape formed into disks called floppy disks.

As computer programs have increased in size, hard drives have had to also increase in size to store the data.

What idea(s) and/or inventions had to be developed before it could be created?

 * The computer
 * Magnetic data storage

title: Wikijunior:How Things Work/Hard Drive


text:
Wikijunior:How Things Work/Mobile Phone

Who invented it?
The invention of the mobile phone, or cellphone as it is often called, is credited to Dr. Martin Cooper at Motorola. He made the first successful call over the system on April 3 of 1973.

How does it get power?
All portable cellphones use an electrical battery.

The batteries are usually rechargeable, so they can be used over and over again with recharging. To recharge the battery, the cellphone is plugged into a charger that connects to either a car battery or an electrical wall socket. Charging stores electrical energy onto the battery, which is then slowly used up by the cell phone after it has been unplugged.

Most cellphones typically use a 3.6 volt battery. The battery will usually last 2-3 days before it needs to be recharged depending on how much the phone is used.

How does it work?
The cellphone is a combination of a telephone and a radio. Like a telephone, you can listen and talk to someone on the other end, and like a radio, you can do it wirelessly over the air. The signals that come into and go out of a cellphone are like the ones TV and radio are received on, just formatted differently.

Signals are sent back and forth between the cellphone and a base station. The base station is a device that is usually a mile or two away from where the cellphone is being used and has an antenna that is high up on a tower. Since radio signals can bounce around and go through walls and windows, you don't have to be within sight of the base station in order to communicate with it. Once the signals arrive at the base station, they are converted into regular telephone signals and sent over the public telephone network to whomever you are calling, or sent back out from another base station if you are calling another cellphone.

The reason why it is called a cellphone is that it operates inside a "cell". A cell is a geographic region in which a base station is located. If you are located in that cell, your cellphone communicates to the base station inside that cell. If you move into a different cell, you are transferred seamlessly to a different base station inside the other cell. By keeping the cells small and having many base stations located every couple of miles, more users can talk at the same time from different places.

Also since there are many cells, one is located close to where you are using the phone, so the phone does not have to transmit with too much power. Less power means the phone can be made smaller and use less battery. Think of it as if you were at a party in a large room with a lot of people talking. If you were talking to a person just 3 feet way, you don't have to shout for them to hear you. Meanwhile, someone at the other end of the room could be talking to someone else near them and not interfere with what you are saying.

How dangerous is it?
When properly used a cellphone is not dangerous at all. A cellphone uses microwave frequency to communicate over the air to a base station. To do so, it transmits about 1 Watt of power from its antenna. You can compare that with the amount of power a single Christmas light bulb consumes.

Since talking on a mobile phone is distracting, it can be dangerous to use one while driving. Several studies have shown that drivers have more accidents while using cellphones, even when using "hands-free" systems. Many countries and some U.S. states have passed laws to restrict use of mobile phones while driving.

Many gas stations have signs warning people not to use mobile phones while pumping gas. There is a small chance that a broken cellphone can cause a spark that can ignite gas vapors. Although this is very unlikely, it's best to be safe than sorry, and not use electronic equipment such as mobile phones where explosive gas may be present.

Addiction
Addiction to mobile phones is a serious thing. It’s when you want to keep playing/using it but it’s time to stop. This happens because when you use a phone to play games, you receive something called dopamine. Your brain wants more and more, so your brain will want to play the phone more for more dopamine. But the brain works against itself.

The brain does something called "desensitization", which makes it even harder to get the desired dopamine, making the required playtime longer and longer, and longer. We call this addiction "mobile phone addiction".

What does it do?
A mobile phone allows you to use telephone service from almost anywhere. Most telephones are what is called "land line" or "fixed line" meaning they are physically tied to the land by a wire that plugs into a jack that goes to the phone company. A portable or cordless phone allows you to talk wirelessly but the receiver is still connected to the same land line. The cordless phone can only work within 100 - 200 feet of your receiver that is connected to the land line.

A mobile phone allows you more range and allows you to communicate much further from virtually anywhere in the city, country, or world. You have the ability to make a telephone call or receive one wherever you happen to be with your mobile phone. But only if you have a signal.

How does it vary?
Mobile phones or cellphones come in many different configurations. Most are about the size of a candy bar, have a display and a keypad. Some configurations come with a flip that opens up to show the display and the keypad, thereby keeping it protected. More recently, mobile phones come with touchscreens.

Cellphones are available both big and small, simple and complex. Some just make simple phone calls, others have tiny cameras, MP3 players, digital organizers built into them. Some of the newer models, can even allow you to use the internet over them, browse various services such as news, movie listings, or chat using instant messaging services.

New models are always being introduced. New fashions, new technology, more features, cheaper cost, better performance, keep the market place filled with plenty of choices.

How has it changed the world?
The mobile phone has radically changed the world since its introduction in 1973. With each year more and more people are owning one. Most families typically have two or three.

The ability to easily communicate to anyone, anywhere, is a powerful concept. This was true when the telegraph was first invented, and then taken to a new level with the advent of the telephone. The mobile phone is just the next extension of that technology.

Ease of communication, leads to more efficient communication, and thus to an efficient use of time and resources. More efficient communication leads to better collaboration, better ideas, better use of time, more peace of mind. It provides an important lifeline in times of emergency.

But aside from practical applications, it also provides benefits socially and is fun. It allows communications with friends and family regardless of location. Whether you're calling to say something important, or just to chat about nothing at all.

Many mobile phones now have cameras built into them, allowing you to take a photo anywhere at any time, some people buy mobile phones just for the camera and don't even use it to phone or text people!

Plenty of important events and controversies have happened because people could organise things quicker with mobile phones. In Britain, a series of strikes by cargo lorry drivers over rising fuel prices was supposedly organised by one man and a mobile phone. Mobile phones with cameras and video are increasingly being used to capture important events when television crews are not available.

What idea(s) and/or inventions had to be developed before it could be created?
Since the mobile phone is a combination of a telephone and a radio, these two devices are the building blocks upon which the mobile phone was developed. In addition, tiny computers (microprocessors) are needed to control the radio and its connection to the nearest base station.

The telephone was invented by Alexander Graham Bell in 1876.

The radio was invented by Guglielmo Marconi in 1896.

The microprocessor was invented by Gary Boone in 1971.

title: Wikijunior:How Things Work/Mobile Phone