text:
Dyadic rational

In mathematics, a dyadic rational or binary rational is a number that can be expressed as a fraction whose denominator is a power of two. For example, 1/2, 3/2, and 3/8 are dyadic rationals, but 1/3 is not. These numbers are important in computer science because they are the only ones with finite binary representations. Dyadic rationals also have applications in weights and measures, musical time signatures, and early mathematics education. They can accurately approximate any real number.

The sum, difference, or product of any two dyadic rational numbers is another dyadic rational number, given by a simple formula. However, division of one dyadic rational number by another does not always produce a dyadic rational result. Mathematically, this means that the dyadic rational numbers form a ring, lying between the ring of integers and the field of rational numbers. This ring may be denoted $$\Z[\tfrac12]$$.

In advanced mathematics, the dyadic rational numbers are central to the constructions of the dyadic solenoid, Minkowski's question-mark function, Daubechies wavelets, Thompson's group, Prüfer 2-group, surreal numbers, and fusible numbers. These numbers are order-isomorphic to the rational numbers; they form a subsystem of the 2-adic numbers as well as of the reals, and can represent the fractional parts of 2-adic numbers. Functions from natural numbers to dyadic rationals have been used to formalize mathematical analysis in reverse mathematics.

In measurement
Many traditional systems of weights and measures are based on the idea of repeated halving, which produces dyadic rationals when measuring fractional amounts of units. The inch is customarily subdivided in dyadic rationals rather than using a decimal subdivision. The customary divisions of the gallon into half-gallons, quarts, pints, and cups are also dyadic. The ancient Egyptians used dyadic rationals in measurement, with denominators up to 64. Similarly, systems of weights from the Indus Valley civilisation are for the most part based on repeated halving; anthropologist Heather M.-L. Miller writes that "halving is a relatively simple operation with beam balances, which is likely why so many weight systems of this time period used binary systems".

In computing
Dyadic rationals are central to computer science as a type of fractional number that many computers can manipulate directly. In particular, as a data type used by computers, floating-point numbers are often defined as integers multiplied by positive or negative powers of two. The numbers that can be represented precisely in a floating-point format, such as the IEEE floating-point datatypes, are called its representable numbers. For most floating-point representations, the representable numbers are a subset of the dyadic rationals. The same is true for fixed-point datatypes, which also use powers of two implicitly in the majority of cases. Because of the simplicity of computing with dyadic rationals, they are also used for exact real computing using interval arithmetic, and are central to some theoretical models of computable numbers.

Generating a random variable from random bits, in a fixed amount of time, is possible only when the variable has finitely many outcomes whose probabilities are all dyadic rational numbers. For random variables whose probabilities are not dyadic, it is necessary either to approximate their probabilities by dyadic rationals, or to use a random generation process whose time is itself random and unbounded.

In music
Time signatures in Western musical notation traditionally are written in a form resembling fractions (for example:, , or ), although the horizontal line of the musical staff that separates the top and bottom number is usually omitted when writing the signature separately from its staff. As fractions they are generally dyadic, although non-dyadic time signatures have also been used. The numeric value of the signature, interpreted as a fraction, describes the length of a measure as a fraction of a whole note. Its numerator describes the number of beats per measure, and the denominator describes the length of each beat.

In mathematics education
In theories of childhood development of the concept of a fraction based on the work of Jean Piaget, fractional numbers arising from halving and repeated halving are among the earliest forms of fractions to develop. This stage of development of the concept of fractions has been called "algorithmic halving". Addition and subtraction of these numbers can be performed in steps that only involve doubling, halving, adding, and subtracting integers. In contrast, addition and subtraction of more general fractions involves integer multiplication and factorization to reach a common denominator. Therefore, dyadic fractions can be easier for students to calculate with than more general fractions.

Definitions and arithmetic
The dyadic numbers are the rational numbers that result from dividing an integer by a power of two. A rational number $$p/q$$ in simplest terms is a dyadic rational when $$q$$ is a power of two. Another equivalent way of defining the dyadic rationals is that they are the real numbers that have a terminating binary representation.

Addition, subtraction, and multiplication of any two dyadic rationals produces another dyadic rational, according to the following formulas:
 * $$\begin{align}

\frac{a}{2^b}+\frac{c}{2^d}&=\frac{2^{d - \min(b,d)}a + 2^{b - \min(b,d)}c} {2^{\max(b,d)} } \\[6px] \frac{a}{2^b}-\frac{c}{2^d}&=\frac{2^{d - \min(b,d)}a - 2^{b - \min(b,d)}c} {2^{\max(b,d)} } \\[6px] \frac{a}{2^b}\cdot \frac{c}{2^d} &= \frac{ a c}{2^{b+d}} \end{align}$$ However, the result of dividing one dyadic rational by another is not necessarily a dyadic rational. For instance, 1 and 3 are both dyadic rational numbers, but 1/3 is not.

Additional properties
Every integer, and every half-integer, is a dyadic rational. They both meet the definition of being an integer divided by a power of two: every integer is an integer divided by one (the zeroth power of two), and every half-integer is an integer divided by two.

Every real number can be arbitrarily closely approximated by dyadic rationals. In particular, for a real number $$x$$, consider the dyadic rationals of the form $\lfloor 2^i x \rfloor / 2^i$, where $$i$$ can be any integer and $$\lfloor\dots\rfloor$$ denotes the floor function that rounds its argument down to an integer. These numbers approximate $$x$$ from below to within an error of $$1/2^i$$, which can be made arbitrarily small by choosing $$i$$ to be arbitrarily large. For a fractal subset of the real numbers, this error bound is within a constant factor of optimal: for these numbers, there is no approximation $$n/2^i$$ with error smaller than a constant times $$1/2^i$$. The existence of accurate dyadic approximations can be expressed by saying that the set of all dyadic rationals is dense in the real line. More strongly, this set is uniformly dense, in the sense that the dyadic rationals with denominator $$2^i$$ are uniformly spaced on the real line.

The dyadic rationals are precisely those numbers possessing finite binary expansions. Their binary expansions are not unique; there is one finite and one infinite representation of each dyadic rational other than 0 (ignoring terminal 0s). For example, 0.112 = 0.10111...2, giving two different representations for 3/4. The dyadic rationals are the only numbers whose binary expansions are not unique.

Algebraic structure
Because they are closed under addition, subtraction, and multiplication, but not division, the dyadic rationals are a ring but not a field. The ring of dyadic rationals may be denoted $$\Z[\tfrac12]$$, meaning that it can be generated by evaluating polynomials with integer coefficients, at the argument 1/2. As a ring, the dyadic rationals are a subring of the rational numbers, and an overring of the integers. Algebraically, this ring is the localization of the integers with respect to the set of powers of two.

As well as forming a subring of the real numbers, the dyadic rational numbers form a subring of the 2-adic numbers, a system of numbers that can be defined from binary representations that are finite to the right of the binary point but may extend infinitely far to the left. The 2-adic numbers include all rational numbers, not just the dyadic rationals. Embedding the dyadic rationals into the 2-adic numbers does not change the arithmetic of the dyadic rationals, but it gives them a different topological structure than they have as a subring of the real numbers. As they do in the reals, the dyadic rationals form a dense subset of the 2-adic numbers, and are the set of 2-adic numbers with finite binary expansions. Every 2-adic number can be decomposed into the sum of a 2-adic integer and a dyadic rational; in this sense, the dyadic rationals can represent the fractional parts of 2-adic numbers, but this decomposition is not unique.

Addition of dyadic rationals modulo 1 (the quotient group $$\Z[\tfrac12]/\Z$$ of the dyadic rationals by the integers) forms the Prüfer 2-group.

Dyadic solenoid
Considering only the addition and subtraction operations of the dyadic rationals gives them the structure of an additive abelian group. Pontryagin duality is a method for understanding abelian groups by constructing dual groups, whose elements are characters of the original group, group homomorphisms to the multiplicative group of the complex numbers, with pointwise multiplication as the dual group operation. The dual group of the additive dyadic rationals, constructed in this way, can also be viewed as a topological group. It is called the dyadic solenoid, and is isomorphic to the topological product of the real numbers and 2-adic numbers, quotiented by the diagonal embedding of the dyadic rationals into this product. It is an example of a protorus, a solenoid, and an indecomposable continuum.

Functions with dyadic rationals as distinguished points
Because they are a dense subset of the real numbers, the dyadic rationals, with their numeric ordering, form a dense order. As with any two unbounded countable dense linear orders, by Cantor's isomorphism theorem, the dyadic rationals are order-isomorphic to the rational numbers. In this case, Minkowski's question-mark function provides an order-preserving bijection between the set of all rational numbers and the set of dyadic rationals.

The dyadic rationals play a key role in the analysis of Daubechies wavelets, as the set of points where the scaling function of these wavelets is non-smooth. Similarly, the dyadic rationals parameterize the discontinuities in the boundary between stable and unstable points in the parameter space of the Hénon map.

The set of piecewise linear homeomorphisms from the unit interval to itself that have power-of-2 slopes and dyadic-rational breakpoints forms a group under the operation of function composition. This is Thompson's group, the first known example of an infinite but finitely presented simple group. The same group can also be represented by an action on rooted binary trees, or by an action on the dyadic rationals within the unit interval.

Other related constructions
In reverse mathematics, one way of constructing the real numbers is to represent them as functions from unary numbers to dyadic rationals, where the value of one of these functions for the argument $$i$$ is a dyadic rational with denominator $$2^i$$ that approximates the given real number. Defining real numbers in this way allows many of the basic results of mathematical analysis to be proven within a restricted theory of second-order arithmetic called "feasible analysis" (BTFA).

The surreal numbers are generated by an iterated construction principle which starts by generating all finite dyadic rationals, and then goes on to create new and strange kinds of infinite, infinitesimal and other numbers. This number system is foundational to combinatorial game theory, and dyadic rationals arise naturally in this theory as the set of values of certain combinatorial games.

The fusible numbers are a subset of the dyadic rationals, the closure of the set $$\{0\}$$ under the operation $$x,y\mapsto(x+y+1)/2$$, restricted to pairs $$x,y$$ with $$|x-y|<1$$. They are well-ordered, with order type equal to the epsilon number $$\varepsilon_0$$. For each integer $$n$$ the smallest fusible number that is greater than $$n$$ has the form $$n+1/2^k$$. The existence of $$k$$ for each $$n$$ cannot be proven in Peano arithmetic, and $$k$$ grows so rapidly as a function of $$n$$ that for $$n=3$$ it is (in Knuth's up-arrow notation for large numbers) already larger than $$2\uparrow^9 16$$.

The usual proof of Urysohn's lemma utilizes the dyadic fractions for constructing the separating function from the lemma.

title: Dyadic rational


text:
Thymus

The thymus (: thymuses or thymi) is a specialized primary lymphoid organ of the immune system. Within the thymus, thymus cell lymphocytes or T cells mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders. The thymus is located in the upper front part of the chest, in the anterior superior mediastinum, behind the sternum, and in front of the heart. It is made up of two lobes, each consisting of a central medulla and an outer cortex, surrounded by a capsule.

The thymus is made up of immature T cells called thymocytes, as well as lining cells called epithelial cells which help the thymocytes develop. T cells that successfully develop react appropriately with MHC immune receptors of the body (called positive selection) and not against proteins of the body (called negative selection). The thymus is the largest and most active during the neonatal and pre-adolescent periods. By the early teens, the thymus begins to decrease in size and activity and the tissue of the thymus is gradually replaced by fatty tissue. Nevertheless, some T cell development continues throughout adult life.

Abnormalities of the thymus can result in a decreased number of T cells and autoimmune diseases such as autoimmune polyendocrine syndrome type 1 and myasthenia gravis. These are often associated with cancer of the tissue of the thymus, called thymoma, or tissues arising from immature lymphocytes such as T cells, called lymphoma. Removal of the thymus is called thymectomy. Although the thymus has been identified as a part of the body since the time of the Ancient Greeks, it is only since the 1960s that the function of the thymus in the immune system has become clearer.

Structure
The thymus is an organ that sits behind the sternum in the upper front part of the chest, stretching upwards towards the neck. In children, the thymus is pinkish-gray, soft, and lobulated on its surfaces. At birth, it is about 4–6 cm long, 2.5–5 cm wide, and about 1 cm thick. It increases in size until puberty, where it may have a size of about 40–50 g, following which it decreases in size in a process known as involution.

The thymus is located in the anterior mediastinum. It is made up of two lobes that meet in the upper midline, and stretch from below the thyroid in the neck to as low as the cartilage of the fourth rib. The lobes are covered by a capsule. The thymus lies behind the sternum, rests on the pericardium, and is separated from the aortic arch and great vessels by a layer of fascia. The left brachiocephalic vein may even be embedded within the thymus. In the neck, it lies on the front and sides of the trachea, behind the sternohyoid and sternothyroid muscles.

Microanatomy
The thymus consists of two lobes, merged in the middle, surrounded by a capsule that extends with blood vessels into the interior. The lobes consist of an outer rich with cells and an inner less dense. The lobes are divided into smaller lobules 0.5-2 mm diameter, between which extrude radiating insertions from the capsule along.

The cortex is mainly made up of thymocytes and epithelial cells. The thymocytes, immature T cells, are supported by a network of the finely-branched epithelial reticular cells, which is continuous with a similar network in the medulla. This network forms an adventitia to the blood vessels, which enter the cortex via septa near the junction with the medulla. Other cells are also present in the thymus, including macrophages, dendritic cells, and a small amount of B cells, neutrophils and eosinophils.

In the medulla, the network of epithelial cells is coarser than in the cortex, and the lymphoid cells are relatively fewer in number. Concentric, nest-like bodies called Hassall's corpuscles (also called thymic corpuscles) are formed by aggregations of the medullary epithelial cells. These are concentric, layered whorls of epithelial cells that increase in number throughout life. They are the remains of the epithelial tubes, which grow out from the third pharyngeal pouches of the embryo to form the thymus.

Blood and nerve supply
The arteries supplying the thymus are branches of the internal thoracic, and inferior thyroid arteries, with branches from the superior thyroid artery sometimes seen. The branches reach the thymus and travel with the septa of the capsule into the area between the cortex and medulla, where they enter the thymus itself; or alternatively directly enter the capsule.

The veins of the thymus, the thymic veins, end in the left brachiocephalic vein, internal thoracic vein, and in the inferior thyroid veins. Sometimes the veins end directly in the superior vena cava.

Lymphatic vessels travel only away from the thymus, accompanying the arteries and veins. These drain into the brachiocephalic, tracheobronchial and parasternal lymph nodes.

The nerves supplying the thymus arise from the vagus nerve and the cervical sympathetic chain. Branches from the phrenic nerves reach the capsule of the thymus, but do not enter into the thymus itself.

Variation
The two lobes differ slightly in size, with the left lobe usually higher than the right. Thymic tissue may be found scattered on or around the gland, and occasionally within the thyroid. The thymus in children stretches variably upwards, at times to as high as the thyroid gland.

Development
The thymocytes and the epithelium of the thymus have different developmental origins. The epithelium of the thymus develops first, appearing as two outgrowths, one on either side, of the third pharyngeal pouch. It sometimes also involves the fourth pharyngeal pouch. These extend outward and backward into the surrounding mesoderm and neural crest-derived mesenchyme in front of the ventral aorta. Here the thymocytes and epithelium meet and join with connective tissue. The pharyngeal opening of each diverticulum is soon obliterated, but the neck of the flask persists for some time as a cellular cord. By further proliferation of the cells lining the flask, buds of cells are formed, which become surrounded and isolated by the invading mesoderm.

The epithelium forms fine lobules, and develops into a sponge-like structure. During this stage, hematopoietic bone-marrow precursors migrate into the thymus. Normal development is dependent on the interaction between the epithelium and the hematopoietic thymocytes. Iodine is also necessary for thymus development and activity.

Involution
The thymus continues to grow after birth reaching the relative maximum size by puberty. It is most active in fetal and neonatal life. It increases to a mass of 20 to 50 grams by puberty. It then begins to decrease in size and activity in a process called thymic involution. After the first year of life the amount of T cells produced begins to fall. Fat and connective tissue fills a part of the thymic volume. During involution, the thymus decreases in size and activity. Fat cells are present at birth, but increase in size and number markedly after puberty, invading the gland from the walls between the lobules first, then into the cortex and medulla. This process continues into old age, where whether with a microscope or with the human eye, the thymus may be difficult to detect, although typically weighs 5–15 grams. Additionally, there is an increasing body of evidence showing that age-related thymic involution is found in most, if not all, vertebrate species with a thymus, suggesting that this is an evolutionary process that has been conserved.[40]

The atrophy is due to the increased circulating level of sex hormones, and chemical or physical castration of an adult results in the thymus increasing in size and activity. Severe illness or human immunodeficiency virus infection may also result in involution.

T cell maturation
The thymus facilitates the maturation of T cells, an important part of the immune system providing cell-mediated immunity. T cells begin as hematopoietic precursors from the bone-marrow, and migrate to the thymus, where they are referred to as thymocytes. In the thymus they undergo a process of maturation, which involves ensuring the cells react against antigens ("positive selection"), but that they do not react against antigens found on body tissue ("negative selection"). Once mature, T cells emigrate from the thymus to provide vital functions in the immune system.

Each T cell has a distinct T cell receptor, suited to a specific substance, called an antigen. Most T cell receptors bind to the major histocompatibility complex on cells of the body. The MHC presents an antigen to the T cell receptor, which becomes active if this matches the specific T cell receptor. In order to be properly functional, a mature T cell needs to be able to bind to the MHC molecule ("positive selection"), and not to react against antigens that are actually from the tissues of body ("negative selection"). Positive selection occurs in the cortex and negative selection occurs in the medulla of the thymus. After this process T cells that have survived leave the thymus, regulated by sphingosine-1-phosphate. Further maturation occurs in the peripheral circulation. Some of this is because of hormones and cytokines secreted by cells within the thymus, including thymulin, thymopoietin, and thymosins.

Positive selection
T cells have distinct T cell receptors. These distinct receptors are formed by process of V(D)J recombination gene rearrangement stimulated by RAG1 and RAG2 genes. This process is error-prone, and some thymocytes fail to make functional T-cell receptors, whereas other thymocytes make T-cell receptors that are autoreactive. If a functional T cell receptor is formed, the thymocyte will begin to express simultaneously the cell surface proteins CD4 and CD8.

The survival and nature of the T cell then depends on its interaction with surrounding thymic epithelial cells. Here, the T cell receptor interacts with the MHC molecules on the surface of epithelial cells. A T cell with a receptor that doesn't react, or reacts weakly will die by apoptosis. A T cell that does react will survive and proliferate. A mature T cell expresses only CD4 or CD8, but not both. This depends on the strength of binding between the TCR and MHC class 1 or class 2. A T cell receptor that binds mostly to MHC class I tends to produce a mature "cytotoxic" CD8 positive T cell; a T cell receptor that binds mostly to MHC class II tends to produce a CD4 positive T cell.

Negative selection
T cells that attack the body's own proteins are eliminated in the thymus, called "negative selection". Epithelial cells in the medulla and dendritic cells in the thymus express major proteins from elsewhere in the body. The gene that stimulates this is AIRE. Thymocytes that react strongly to self antigens do not survive, and die by apoptosis. Some CD4 positive T cells exposed to self antigens persist as T regulatory cells.

Immunodeficiency
As the thymus is where T cells develop, congenital problems with the development of the thymus can lead to immunodeficiency, whether because of a problem with the development of the thymus gland, or a problem specific to thymocyte development. Immunodeficiency can be profound. Loss of the thymus at an early age through genetic mutation (as in DiGeorge syndrome, CHARGE syndrome, or a very rare "nude" thymus causing absence of hair and the thymus) results in severe immunodeficiency and subsequent high susceptibility to infection by viruses, protozoa, and fungi. Nude mice with the very rare "nude" deficiency as a result of FOXN1 mutation are a strain of research mice as a model of T cell deficiency.

The most common congenital cause of thymus-related immune deficiency results from the deletion of the 22nd chromosome, called DiGeorge syndrome. This results in a failure of development of the third and fourth pharyngeal pouches, resulting in failure of development of the thymus, and variable other associated problems, such as congenital heart disease, and abnormalities of mouth (such as cleft palate and cleft lip), failure of development of the parathyroid glands, and the presence of a fistula between the trachea and the oesophagus. Very low numbers of circulating T cells are seen. The condition is diagnosed by fluorescent in situ hybridization and treated with thymus transplantation.

Severe combined immunodeficiency (SCID) are group of rare congenital genetic diseases that can result in combined T, B, and NK cell deficiencies. These syndromes are caused by mutations that affect the maturation of the hematopoietic progenitor cells, which are the precursors of both B and T cells. A number of genetic defects can cause SCID, including IL-2 receptor gene loss of function, and mutation resulting in deficiency of the enzyme adenine deaminase.

Autoimmune polyendocrine syndrome
Autoimmune polyendocrine syndrome type 1, is a rare genetic autoimmune syndrome that results from a genetic defect of the thymus tissues. Specifically, the disease results from defects in the autoimmune regulator (AIRE) gene, which stimulates expression of self antigens in the epithelial cells within the medulla of the thymus. Because of defects in this condition, self antigens are not expressed, resulting in T cells that are not conditioned to tolerate tissues of the body, and may treat them as foreign, stimulating an immune response and resulting in autoimmunity. People with APECED develop an autoimmune disease that affects multiple endocrine tissues, with the commonly affected organs being hypothyroidism of the thyroid gland, Addison's disease of the adrenal glands, and candida infection of body surfaces including the inner lining of the mouth and of the nails due to dysfunction of TH17 cells, and symptoms often beginning in childhood. Many other autoimmune diseases may also occur. Treatment is directed at the affected organs.

Thymoma-associated multiorgan autoimmunity
Thymoma-associated multiorgan autoimmunity can occur in people with thymoma. In this condition, the T cells developed in the thymus are directed against the tissues of the body. This is because the malignant thymus is incapable of appropriately educating developing thymocytes to eliminate self-reactive T cells. The condition is virtually indistinguishable from graft versus host disease.

Myasthenia gravis
Myasthenia gravis is an autoimmune disease most often due to antibodies that block acetylcholine receptors, involved in signalling between nerves and muscles. It is often associated with thymic hyperplasia or thymoma, with antibodies produced probably because of T cells that develop abnormally. Myasthenia gravis most often develops between young and middle age, causing easy fatiguing of muscle movements. Investigations include demonstrating antibodies (such as against acetylcholine receptors or muscle-specific kinase), and CT scan to detect thymoma or thymectomy. With regard to the thymus, removal of the thymus, called thymectomy may be considered as a treatment, particularly if a thymoma is found. Other treatments include increasing the duration of acetylcholine action at nerve synapses by decreasing the rate of breakdown. This is done by acetylcholinesterase inhibitors such as pyridostigmine.

Thymomas
Tumours originating from the thymic epithelial cells are called thymomas. They most often occur in adults older than 40. Tumours are generally detected when they cause symptoms, such as a neck mass or affecting nearby structures such as the superior vena cava; detected because of screening in patients with myasthenia gravis, which has a strong association with thymomas and hyperplasia; and detected as an incidental finding on imaging such as chest x-rays. Hyperplasia and tumours originating from the thymus are associated with other autoimmune diseases – such as hypogammaglobulinemia, Graves disease, pure red cell aplasia, pernicious anaemia and dermatomyositis, likely because of defects in negative selection in proliferating T cells.

Thymomas can be benign; benign but by virtue of expansion, invading beyond the capsule of the thymus ("invasive thymoma"), or malignant (a carcinoma). This classification is based on the appearance of the cells. A WHO classification also exists but is not used as part of standard clinical practice. Benign tumours confined to the thymus are most common; followed by locally invasive tumours, and then by carcinomas. There is variation in reporting, with some sources reporting malignant tumours as more common. Invasive tumours, although not technically malignant, can still spread to other areas of the body. Even though thymomas occur of epithelial cells, they can also contain thymocytes. Treatment of thymomas often requires surgery to remove the entire thymus. This may also result in temporary remission of any associated autoimmune conditions.

Lymphomas
Tumours originating from T cells of the thymus form a subset of acute lymphoblastic leukaemia (ALL). These are similar in symptoms, investigation approach and management to other forms of ALL. Symptoms that develop, like other forms of ALL, relate to deficiency of platelets, resulting in bruising or bleeding; immunosuppression resulting in infections; or infiltration by cells into parts of the body, resulting in an enlarged liver, spleen, lymph nodes or other sites. Blood test might reveal a large amount of white blood cells or lymphoblasts, and deficiency in other cell lines – such as low platelets or anaemia. Immunophenotyping will reveal cells that are CD3, a protein found on T cells, and help further distinguish the maturity of the T cells. Genetic analysis including karyotyping may reveal specific abnormalities that may influence prognosis or treatment, such as the Philadelphia translocation. Management can include multiple courses of chemotherapy, stem cell transplant, and management of associated problems, such as treatment of infections with antibiotics, and blood transfusions. Very high white cell counts may also require cytoreduction with apheresis.

Tumours originating from the small population of B cells present in the thymus lead to primary mediastinal (thymic) large B cell lymphomas. These are a rare subtype of Non-Hodgkins lymphoma, although by the activity of genes and occasionally microscopic shape, unusually they also have the characteristics of Hodgkins lymphomas. that occur most commonly in young and middle-aged, more prominent in females. Most often, when symptoms occur it is because of compression of structures near the thymus, such as the superior vena cava or the upper respiratory tract; when lymph nodes are affected it is often in the mediastinum and neck groups. Such tumours are often detected with a biopsy that is subject to immunohistochemistry. This will show the presence of clusters of differentiation, cell surface proteins – namely CD30, with CD19, CD20 and CD22, and with the absence of CD15. Other markers may also be used to confirm the diagnosis. Treatment usually includes the typical regimens of CHOP or EPOCH or other regimens; regimens generally including cyclophosphamide, an anthracycline, prednisone, and other chemotherapeutics; and potentially also a stem cell transplant.

Thymic cysts
The thymus may contain cysts, usually less than 4 cm in diameter. Thymic cysts are usually detected incidentally and do not generally cause symptoms. Thymic cysts can occur along the neck or in the chest (mediastinum). Cysts usually just contain fluid and are lined by either many layers of flat cells or column-shaped cells. Despite this, the presence of a cyst can cause problems similar to those of thymomas, by compressing nearby structures, and some may contact internal walls and be difficult to distinguish from tumours. When cysts are found, investigation may include a workup for tumours, which may include CT or MRI scan of the area the cyst is suspected to be in.

Surgical removal
Thymectomy is the surgical removal of the thymus. The usual reason for removal is to gain access to the heart for surgery to correct congenital heart defects in the neonatal period. Other indications for thymectomy include the removal of thymomas and the treatment of myasthenia gravis. In neonates the relative size of the thymus obstructs surgical access to the heart and its surrounding vessels.

Removal of the thymus in infancy results in often fatal immunodeficiency, because functional T cells have not developed. In older children and adults, which have a functioning lymphatic system with mature T cells also situated in other lymphoid organs, the effect is reduced, but includes failure to mount immune responses against new antigens, an increase in cancers, and an increase in all-cause mortality.

Society and culture
When used as food for humans, the thymus of animals is known as one of the kinds of sweetbread.

History
The thymus was known to the ancient Greeks, and its name comes from the Greek word θυμός (thumos), meaning "anger", or in Ancient Greek, "heart, soul, desire, life", possibly because of its location in the chest, near where emotions are subjectively felt; or else the name comes from the herb thyme (also in Greek θύμος or θυμάρι), which became the name for a "warty excrescence", possibly due to its resemblance to a bunch of thyme.

Galen was the first to note that the size of the organ changed over the duration of a person's life.

In the nineteenth century, a condition was identified as status thymicolymphaticus defined by an increase in lymphoid tissue and an enlarged thymus. It was thought to be a cause of sudden infant death syndrome but is now an obsolete term.

The importance of the thymus in the immune system was discovered in 1961 by Jacques Miller, by surgically removing the thymus from one-day-old mice, and observing the subsequent deficiency in a lymphocyte population, subsequently named T cells after the organ of their origin. Until the discovery of its immunological role, the thymus had been dismissed as a "evolutionary accident", without functional importance. The role the thymus played in ensuring mature T cells tolerated the tissues of the body was uncovered in 1962, with the finding that T cells of a transplanted thymus in mice demonstrated tolerance towards tissues of the donor mouse. B cells and T cells were identified as different types of lymphocytes in 1968, and the fact that T cells required maturation in the thymus was understood. The subtypes of T cells (CD8 and CD4) were identified by 1975. The way that these subclasses of T cells matured – positive selection of cells that functionally bound to MHC receptors – was known by the 1990s. The important role of the AIRE gene, and the role of negative selection in preventing autoreactive T cells from maturing, was understood by 1994.

Recently, advances in immunology have allowed the function of the thymus in T-cell maturation to be more fully understood.

Other animals
The thymus is present in all jawed vertebrates, where it undergoes the same shrinkage with age and plays the same immunological function as in other vertebrates. Recently, in 2011, a discrete thymus-like lympho-epithelial structure, termed the thymoid, was discovered in the gills of larval lampreys. Hagfish possess a protothymus associated with the pharyngeal velar muscles, which is responsible for a variety of immune responses.

The thymus is also present in most other vertebrates with similar structure and function as the human thymus. A second thymus in the neck has been reported sometimes to occur in the mouse As in humans, the guinea pig's thymus naturally atrophies as the animal reaches adulthood, but the athymic hairless guinea pig (which arose from a spontaneous laboratory mutation) possesses no thymic tissue whatsoever, and the organ cavity is replaced with cystic spaces.

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

title: Thymus


text:
Dutch New Guinea

Dutch New Guinea or Netherlands New Guinea (Nederlands-Nieuw-Guinea, Nugini Belanda) was the western half of the island of New Guinea that was a part of the Dutch East Indies until 1949, later an overseas territory of the Kingdom of the Netherlands from 1949 to 1962. It contained what are now Indonesia's six easternmost provinces, Central Papua, Highland Papua, Papua, South Papua, Southwest Papua, and West Papua, which were administered as a single province prior to 2003 under the name Irian Jaya, and now comprise the Papua region of the country.

During the Indonesian Revolution, the Dutch launched politionele acties to capture territory from the Indonesian Republic. However, the harsh methods of the Dutch had drawn international disapproval. With international opinion shifting towards support of the Indonesian Republic, the Dutch managed in 1949 to negotiate for the separation of Dutch New Guinea from the broader Indonesian settlement, with the fate of the disputed territory to be decided by the close of 1950. However, the Dutch in coming years were able to argue successfully at the UN that the indigenous population of Dutch New Guinea represented a separate ethnic group from the people of Indonesia and thus should not be absorbed into the Indonesian state.

In contrast, the Indonesian Republic, as successor state to the Netherlands East Indies, claimed Dutch New Guinea as part of its natural territorial bounds. The dispute over New Guinea was an important factor in the quick decline in bilateral relations between the Netherlands and Indonesia after Indonesian independence. The dispute escalated into low-level conflict in 1962 following Dutch moves in 1961 to establish a New Guinea Council.

Following the Vlakke Hoek incident, Indonesia launched a campaign of infiltrations designed to place pressure on the Dutch. Facing diplomatic pressure from the United States, fading domestic support and continual Indonesian threats to invade the territory, the Netherlands decided to relinquish control of the disputed territory in August 1962, agreeing to the Bunker Proposal on condition that a referendum to determine the final fate of the territory be conducted at a later date. The territory was administered by the UN temporarily before being transferred to Indonesia on 1 May 1963. A plebiscite, the Act of Free Choice, was eventually held in 1969, but the fairness of the election is disputed.

Pre-World War II
Before 1898, Papuas lived in isolated, competitive, and autonomous clan and tribal environments. However in 1898, the Dutch came and established their presence. Their claim, which was made in 1848, was based on the Sultanate of Ternate's claim on Papua based on Ternatean tributary relation. The Dutch first divided Papua into two afdeelings: Afdeeling Noord-Nieuw-Guinea (Manokwari), and Afdeeling West-En-Zuid-Nieuw-Guinea (Fakfak), both led by controleurs under the Residentie Ternate. The afdeelings were led by controleurs normally responsible for onderafdeeling instead of the usual asistent-resident due to newly established nature of the land. The colonial government set Tanjung Goede Hoop or Jamoer Seba (Yamursba) as the boundary of the two afdeeling

In 1901 to subdue the headhunting ugeris and increase colonial control, Afdeeling West-En-Zuid-Nieuw-Guinea was split into Afdeeling West-Nieuw-Guinea and Afdeeling Zuid-New-Guinea. Afdeeling West-Nieuw-Guinea consisted of the part of Dutch New Guinea from Cape Jamoer Seba to Cape Steenboom and surrounding islands, including the group of Radja Ampat, under a Controller at Fakfak. While Afdeeling Zuid-New-Guinea consisted of the part of Dutch New Guinea from Cape Steenboom to the mouth of the Bensbach river and surrounding islands, under an assistent-resident with a to be determined capital. Later it would be Merauke which was founded on 12th of February, 1902 for the express purpose of being the capital.

Since their creation, Afdeeling West-Nieuw-Guinea would remain part of the Residentie Ternate until it was transferred into Residentie Amboina in 1911. While the Afdeeling Zuid-Nieuw-Guinea would be an independent afdeeling until it was put under Residentie Amboina in 1913.

In 1920, the three Afdeelings were made into its own residentie Nieuw Guinea. However it did not last as in August 1923 the Governor-General decided to merge the residency into Residentie Amboina. It followed the fate of Residentie Ternate which was also merged into Residentie Amboina in 1922. The merging process was done on 1st of April 1924. The Afdeelings themselves were kept the same at the time.

In 1925, the status of the Residentie Amboina was upgraded to the Gouvernement der Molukken, which was divided into two residencies, namely Residentie Amboina and Residentie Ternate. Six onderafdeelings of New Guinea (Manokwari, Sorong, Schouteneilanden, Jappengroep, Hollandia dan West-Nieuw Guinea) were under the Residentie Ternate. While only one, the Onderafdeeling of Zuid-Nieuw Guinea was under the Residentie Amboina. The reduction in the status of the three afdeelings in Papua to onderafdeeling, and before that the Residentie Nieuw Guinea into Amboina, was caused by the decline in the regional income since the ban of hunting Cendrawasih in 1922.

In 1934, the status of the Gouvernement der Molukken was downgraded into Residentie der Molukken. The residency oversaw Afdeeling Ternate, Ambon, Tual, and North and West New Guinea. The Onderafdeeling Zuid-Nieuw-Guinea and Onderafdeeling Boven Digul were placed under Afdeeling Tual. Afdeeling Noord-Nieuw-Guinea and Afdeeling West-Nieuw-Guinea were combined into one afdeeling called Afdeeling Noord-En-West-New Guinea which oversaw 5 onderafdeeling namely Manokwari, Sorong, Serui, Hollandia and Fak-Fak.

In 1936 the Dutch colonial government shuffled a new territorial division in the residency. The residency was divided into two afdeelings, namely the Afdeeling Noord-Nieuw-Guinea which oversaw 5 onderafdeelings (Manokwari, Sorong, Central Vogelkop, Serui and Hollandia); and the West-En-Zuid-Nieuw Guinea Afdeeling also oversaw 5 onderafdeeling (Fak-Fak, Inanwatan, Mimika, Boven Digul and South Nieuw Guinea)

In 1937 Onderafdeeling Boven Digul and Onderafdeeling Zuid-Nieuw-Guinea were placed back under Afdeeling Tual. The Afdeeling West-Niuew-Guinea was separated from the afdeeling of Zuid-Niuew-Guinea. Both Afdeling Noord-Niuew-Guinea and Afdeling West-Niuew-Guinea oversaw 4 onderafdeeling each. Afdeling North New Guinea oversaw Fak-Fak, Central Vogelkop, Inanwatan and Mimika, while Afdeeling West New Guinea oversaw Manokwari, Sorong, Serui and Hollandia. The return of West Guinea's Afdeeling status was related to the increase in private oil exploration activities carried out by the Nederlandsche Nieuw Guinea Petroleum Maatschappij (NNGPM) in Babo which began its activtive in New Guinea on 23 April, 1935.

In 1938, Gouvernement Groote Oost was created to encompass all Dutch East Indies residencies east of Java and Kalimantan.

In 1940 there was another shuffl, and Afdeeling Noord-Niuew-Guinea oversaw five onderafdeeling, namely Manokwari, Sorong, Serui, Sarmi and Hollandia. West New Guinea included three onderafdeelings, namely Fak-Fak, Inanwatan and Mimika. While Onderafdeeling Boven Digul and Onderafdeeling Zuid-Nieuw-Guinea were placed under Afdeeling of Tual.

Until after World War II, the western part of the island of New Guinea was part of the Great East (Groote Oost) governorate of the Dutch East Indies. The Netherlands claimed sovereignty over New Guinea within the colony through its protection over the Sultanate of Tidore, a sultanate on an island west of Halmahera in the Maluku Islands. In a 1660 treaty, the Dutch East India Company (VOC) recognised the Sultanate of Tidore's supremacy over the Papuan people, the inhabitants of New Guinea. Probably this referred to some Papuan islands (Raja Ampat) near the Maluku Islands as well as coastal areas like Fakfak, through familial relations with local rulers, although Tidore never exercised actual control over the interior and highlands of New Guinea. In 1872, Tidore recognised Dutch sovereignty and granted permission to the Kingdom of the Netherlands to establish administration in its territories whenever the Netherlands Indies authorities would want to do so. This allowed the Netherlands to legitimise a claim to the New Guinea area.

The Dutch established the 141st meridian as the eastern frontier of the territory. In 1898, the Netherlands Indies government decided to establish administrative posts in Fakfak and Manokwari, followed by Merauke in 1902. The main reason for this was the expansion of British and German interests in the east. The Dutch wanted to make sure the United Kingdom and Germany would not move the border to the west. This resulted in the partition of the island of New Guinea.

In reality, most of New Guinea remained outside colonial influence. Little was known about the interior; large areas on the map were white and the number of inhabitants of the island was unknown, and numerous explorations were made into the interior from the turn of the 20th century on. The indigenous inhabitants of New Guinea were Papuans, living in tribes. They were hunter-gatherers.

Pre-World War II economic activity was limited. Only coastal and island dwellers traded to some extent, mostly with the Maluku Islands. A development company was founded in 1938 to change this situation, but it was not very active. So, until World War II, New Guinea was a disregarded and unimportant territory within the Netherlands Indies.

Homeland for the Eurasians
The group that was most interested in New Guinea before the war were the Eurasians or Indo people. Before the war, some 150,000 to 200,000 Eurasians were living in the Netherlands Indies. They were of mixed European and Indonesian descent and identified with the Netherlands and the Dutch way of life. In the colonial society of the Netherlands Indies, they held a higher social status than indigenous Indonesians ("inlanders"). They were mostly employed as office workers. As the educational level of indigenous Indonesians was on the rise, more and more Indonesians got jobs previously held by Eurasians. These had no other means of making a living, because, as Europeans, they were forbidden to buy land on Java. This situation caused mental and economic problems to the Eurasians. In 1923, the first plan to designate New Guinea as a settlement territory for Eurasians was devised. In 1926, a separate Vereniging tot Kolonisatie van Nieuw-Guinea (Association for the Settlement of New Guinea) was founded. In 1930, it was followed by the Stichting Immigratie Kolonisatie Nieuw-Guinea (Foundation Immigration and Settlement New Guinea). These organisations regarded New Guinea as an untouched, almost empty land that could serve as a homeland to the sidelined Eurasians, a kind of tropical Holland, where Eurasians could create an existence.

These associations succeeded in sending settlers to New Guinea and lobbied successfully for the establishment of a government agency to subsidise these initiatives (in 1938). However, most settlements ended in failure because of the harsh climate and natural conditions, and because of the fact the settlers, previously office workers, were not skilled in agriculture. The number of settlers remained small. In the Netherlands proper, some organisations existed that promoted a kind of "tropical Holland" in New Guinea, but they were rather marginal. They were linked to the NSB party and other fascist organisations.

Origin of the dispute over New Guinea
In 1942, most parts of the Netherlands Indies were occupied by Japan. Behind Japanese lines in New Guinea, Dutch guerrilla fighters resisted under Mauritz Christiaan Kokkelink. During the occupation the Indonesian nationalist movement went through a rapid development. After Japan's surrender, Sukarno issued the Proclamation of Indonesian Independence, which was to encompass the whole of the Netherlands Indies. The Dutch authorities returned after several months under the leadership of Lieutenant-Governor-General Hubertus van Mook. Van Mook decided to reform Indonesia on a federal basis. This was not a completely new idea, but it was contrary to the administrative practice in the Netherlands Indies until then and contrary to the ideas of the nationalists, who wanted a centralist Indonesia.

Linggadjati agreement
The ethnic diversity of Indonesia was initially discussed at two conferences in Malino and Pangkalpinang. During the Pangkalpinang conference, the right of self-determination of the Eurasian, Chinese, and Arab ethnic minorities was discussed. The new Grooter Nederland-Actie (Extended Netherlands Action) send delegates to this conference, who opined that New Guinea should be declared as separate entities in a similar manner to Surinam. Furthermore, this conference stipulated specific territories could have special relations with the Kingdom of the Netherlands if they wanted to.

Van Mook's plan was to divide Indonesia into several federal states, negaras, with possible autonomous areas, daerahs. The whole would be called the United States of Indonesia and would remain linked to the Netherlands in the Netherlands-Indonesian Union. The Indonesian side agreed to this plan during the Linggadjati conference in November 1946. Van Mook thought a federal structure would safeguard Indonesia's cultural and ethnic diversity. Van Mook and his supporters referred to the right of self-determination in this respect: the different ethnic communities of Indonesia should have the right to govern themselves.

The unilateral amendment of 'Linggadjati'
To many Dutchmen, the idea of parting with Indonesia was shocking. Many Dutch thought their country had a mission to develop Indonesia. The Indonesian wish for independence to many Dutch came as a complete surprise. Because Indonesian nationalists, which had no electoral or official legitimacy—save ethno-state nationalism, under Sukarno cooperated with the Japanese, they were branded as traitors and collaborators. Almost every Dutch political party was against Indonesian independence. The Protestant Anti-Revolutionary Party (ARP) were very supportive of the Dutch Ethical Policy in Indonesia. The newly established liberal People's Party for Freedom and Democracy campaigned for a hard-line policy against the nationalists. Even the Labour Party, which supported Indonesian independence in principle, was hesitant, because of the policies of Sukarno.

Minister of Colonies Jan Anne Jonkman defended the Linggadjati Agreement in Parliament in 1946 by stating that the government wished for New Guinea to remain under Dutch sovereignty, arguing it could be a settlement for Eurasians. A motion entered by the Catholic People's Party (KVP) and the Labour Party, which was accepted by parliament, stated that the declaration of Jonkman in parliament should become a part of the Linggadjati agreement. Duly accepted, the Netherlands thus unilaterally 'amended' the Linggadjati agreement to the effect that New Guinea would remain Dutch. Labour parliamentary group leader Marinus van der Goes van Naters said afterwards the Labour Party entered the motion with the KVP because it feared the Catholics otherwise might reject the Linggadjati agreements.

The Indonesians did not accept this unilateral amendment. In order not to jeopardise the scheduled transfer of sovereignty, the Indonesian vice-president Mohammad Hatta offered to maintain Dutch sovereignty over New Guinea for one year and reopen the negotiations afterwards.

1949–1956
Thus in 1949, when the rest of the Dutch East Indies became fully independent as Indonesia, the Dutch retained sovereignty over western New Guinea, and took steps to prepare it for independence as a separate country. Some five thousand teachers were flown there. The Dutch put an emphasis upon political, business, and civic skills. On 8 February 1950, Stephan Lucien Joseph van Waardenburg was appointed the first Governor (De Gouverneur) of Dutch New Guinea. The first local naval cadets graduated in 1955 and the first army brigade become operational in 1956.

1957–1961
Tensions regarding the Dutch-Indonesian dispute over Dutch New Guinea escalated in December 1957 following Indonesia's defeat in the UN General Assembly on 29 November 1957 to pass a resolution in favour of Indonesia's claim to the territory. Sukarno responded by allowing the seizure of Dutch enterprises operating in Indonesia and announcing the intended expulsion of Dutch residents from Indonesia. The increased tensions surrounding the dispute encouraged the Dutch to accelerate their plans to move the disputed territory towards an act of self-determination. Elections were held in January 1961 and the New Guinea Council officially took office on 5 April 1961, to prepare for full independence by the end of that decade. The Dutch endorsed the council's selection of a new national anthem and the Morning Star as the new national flag on 1 December 1961.

Following the raising of the Papuan National Flag on 1 December 1961, tensions further escalated. On 19 December 1961 Sukarno issued the Tri Komando Rakjat (People's Triple Command), calling the Indonesian people to defeat the formation of an independent state of West Papua, raise the Indonesian flag in that country, and be ready for mobilisation at any time.

Escalation to low-level conflict
In 1962 Indonesia launched a significant campaign of airborne and seaborne infiltrations against the disputed territory, beginning with a seaborne infiltration launched by Indonesian forces on 15 January 1962. The Indonesian attack was comprehensively defeated by Dutch forces including the Dutch destroyers Evertsen and Kortenaer, the so-called Vlakke Hoek incident. Amongst the casualties was the Indonesian Deputy Chief of the Naval Staff; Commodore Yos Sudarso. Unbeknown to the Indonesians, Dutch Signals Intelligence had been able to intercept Indonesian communications, allowing Dutch forces to successfully anticipate Indonesia's infiltration attempts throughout 1962. Forced to regroup, the Indonesians relaunched their campaign of infiltrations in March 1962. In the coming months over 500 Indonesian paratroops and special forces were covertly inserted into Dutch New Guinea, only to be decisively defeated by Dutch forces with the assistance of the indigenous population.

Ellsworth Bunker proposal
Facing mounting international diplomatic pressure and the prospect of an Indonesian invasion force, the Dutch conceded to re-entering negotiations and agreed to the Ellsworth Bunker proposal on 28 July 1962, for a staged transition from Dutch to Indonesian control via UN administration, on the condition that a plebiscite would be held in future in the territory. The agreement was signed on 15 August 1962 at the UN Headquarters in New York and the territory was placed under the United Nations Temporary Executive Authority in October 1962. It was subsequently transferred to Indonesia in May 1963.

The territory formally became part of Indonesia in 1969 after the Indonesian government, who shifted to New Order under President Suharto starting from 1966, conducted a Bunker proposal-based plebiscite termed the Act of Free Choice. The result, which under strong pressure from the military, unanimously wanted to become part of Indonesia. The UN General Assembly later accepted the result via the UN Resolution 2504. This act has been criticised by some in the international community, including the group International Parliamentarians for West Papua, which has termed the act "the act of no choice".

Governors

 * Jan Pieter Karel van Eechoud (29 December 1949 – 8 February 1950; acting)
 * Stephan Lucien Joseph van Waardenburg (8 February 1950 – 24 April 1953)
 * Jan van Baal (24 April 1953 – 31 March 1958)
 * Jan Christoffel Baarspul (31 March 1958 – 1 May 1958; acting)
 * Pieter Johannes Platteel (1 May 1958 – 28 September 1962)
 * Henk Veldkamp (28 September 1962 – 1 October 1962; acting)

In Dutch

 * Doel, H.W. van den, Afscheid van Indië. De val van het Nederlandse imperium in Azië (Amsterdam 2001).
 * Drooglever, P.J., Een daad van vrije keuze. De Papoea’s van westelijk Nieuw-Guinea en de grenzen van het zelfbeschikkingsrecht (Amsterdam 2005).
 * Holst Pellekaan, R.E. van, I.C. de Regt, J.F. Bastiaans, Patrouilleren voor de Papoea's: de Koninklijke Marine in Nederlands Nieuw-Guinea (Amsterdam 1989).
 * Holst Pellekaan, R.E. van, I.C. de Regt, Operaties in de Oost: de Koninklijke Marine in de Indische archipel (1945–1951) (Amsterdam 2003).
 * Huydecoper van Nigteveld, J.L.R., Nieuw-Guinea. Het einde van een koloniaal beleid (Den Haag 1990)
 * Gase, Ronald, Misleiding of zelfbedrog. Een analyse van het Nederlandse Nieuw-Guinea-beleid aan de hand van gesprekken met betrokken politici en diplomaten (Baarn 1984).
 * Geus, P.B.R. de, De Nieuw-Guinea kwestie. Aspecten van buitenlands beleid en militaire macht (Leiden 1984).
 * Jansen van Galen, John, Ons laatste oorlogje. Nieuw-Guinea: de Pax Neerlandica, de diplomatieke kruistocht en de vervlogen droom van een Papoea-natie (Weesp 1984).
 * Klein, W.C. e.a., Nieuw-Guinea, 3 dln. (Den Haag 1953/1954).
 * Meijer, Hans, Den Haag-Djakarta. De Nederlands Indonesische betrekkingen 1950–1962 (Utrecht 1994).
 * Idem, "`Het uitverkoren land'. De lotgevallen van de Indo-Europese kolonisten op Nieuw-Guinea 1949–1962", Tijdschrift voor Geschiedenis 112 (1999) 353–384.
 * Schoorl, Pim (red.), Besturen in Nederlands-Nieuw-Guinea 1945 -1962 (Leiden, 1996).
 * Smit, C., De liquidatie van een imperium. Nederland en Indonesië 1945–1962 (Amsterdam 1962).
 * van Holst-Pellekaan, R.E., de Regst, I.C. and Bastiaans, I.F.J. (ed.), Patrouilleren voor de Papoea's: de Koninklijke Marine in Nederlands Nieuw-Guinea 1945–1960 (Amsterdam, 1989).
 * Vlasblom, Dirk, Papoea. Een geschiedenis (Amsterdam 2004).
 * Wal, Hans van de, Een aanvechtbare en onzekere situatie. De Nederlandse Hervormde Kerk en Nieuw-Guinea 1949–1962 (Hilversum 2006).

title: Dutch New Guinea


text:
Talk:RDRAM

Untitled
Please, read this article and improve: http://www.hardwarecentral.com/hardwarecentral/reviews/article.php/12095_3598601_1 --217.168.89.156 (talk) 22:43, 13 January 2008 (UTC)

 * Rambus memory (RDRAM�) is a revolutionary step from SDRAM

Latency argument fails on its own merrits

SDRAM, DDR and following generations all go back to the Rambus patents which Samsung, Micron and Hynix currently are stealing - that is the only reason Rambus has law suits - they are defending their only product: IP

- Worse than that, the whole article appears to be have been copied from http://www.crucial.com/library/ddr_vs_rdram.asp

Removed for copyright violation. -- Anon.

Density
can anyone please comment on low density and high density? If I remember correctly, the high density memory problem appeared with DDR, and was not an issue with Rambus. thanks
 * I still don't get the xmbit info I find. I've also read that single-side vs double-side is not assured indication. but, I'm quite sure density "problem" began with pc133. early pc133 was still "low density". Soon, pc133 dimms were made with high density chips, which caused trouble for pre-2000 (2001?) mobos. however, all pc133 is OTHERWISE backwards compatible to pc"66" (plain old SDR). more searching might show symptoms, and whether some bios upgrades might fix the problem (or maybe not. chipset may be the problem with high density) I have yt to read what appears only wp info DDR_SDRAM --2z2z (talk) 20:56, 13 October 2010 (UTC)
 * Density in this context refers to the capacity of each chip. The problem occurs when (sometime long after it's initial release) a larger chip is designed, which earlier boards were never designed for.  This problem is not unique to any particular type of memory.  I would be surprised if it were ever a problem with RDRAM simply because of its short lifespan. -Juventas (talk) 01:36, 14 October 2010 (UTC)

I thought the line about weird stuff was un-encyclopedic. I hope that this edit improves things.--Mishac 14:25, 16 Feb 2004 (UTC)

Removed some marketspeak
I removed some (well, a lot of) text because it is clearly Rambus marketspeak (and is hideously outdated):

The Direct RDRAM, hereafter referred to as RDRAM, features an architecture and a protocol designed to achieve high effective bandwidth. The Rambus channel architecture has a single-device upgrade granularity, offering engineers the ability to balance performance requirements against system capacity and component count. The narrow, high-performance channel also offers performance and capacity scalability through the use of multiple channels in parallel. In addition, the validation program created by Intel and Rambus promotes system stability by ensuring that devices and modules conform to published specifications. Although RDRAMs have a low pin count, a single device is capable of providing up to 1.6 GB/s bandwidth. Memory systems that use RIMMs {Rambus inline memory module} or (RDRAM modules) employ a narrow, uniform-impedance transmission line, the Rambus Channel, to connect the memory controller to a set of RIMMs. Low pin count and uniform interconnection topology allow easy routing and reduction of pin count on the memory controller. While a single channel is capable of supplying 1.6 GB/s of bandwidth, multiple channels can be used in parallel to increase this number. Systems that use, for example, the Intel 840 chipset have two parallel Rambus channels, and are able to handle up to 3.2 GB/s.

Providing high bandwidth from a single device also allows memory systems to be constructed from small numbers of RDRAMs. The Sony PlayStation2 uses two RDRAM channels, each with a single RDRAM, to achieve a total of 3.2 GB/s memory bandwidth.

In order to ensure stability of RDRAM memory systems, design guidelines and a validation program have been put in place that surpass requirements set for previous memory technologies. Intel and Rambus have defined system specs to ensure robustness of RDRAMs and of the channel to the memory controller. In addition, they have created a rigorous validation programs for certification of RDRAMs and RIMM modules.

thanks for rewording supa
reads more clearly, was trying to keep as much of the previous entry as possible. Could be improved more, will come back when I have time and citations. That last paragraph sounds like it was pulled from a rambus marketing doc and could be easily be dropped without taking away from the piece.

Using binary prefixes for brandwidth.
Let me explain:

text from the article: - ...which operated at 400 MHz and delivered 1.6 GiB/s of bandwidth over a 16-bit bus... -

Let's calculate:

Brandwidth = Frequency*Bus_Width*2 (2 for DDR)

Frequency = 400 MHz = 400 000 000 Hz

Bus_Width = 16 bit = 2 Byte

So,

Brandwidth = 400 000 000 Hz * 2 byte * 2 = 1 600 000 000 byte/s = 1600 MB/s.

No Mebi- or Gibibytes here. Everything is decimal. I revert to my version.

If you think i am not right - please explain why. --Rotsor 04:06, 26 August 2006 (UTC)
 * Fascinating. I hadn't thought it through before. I'm the person who initially put the binary prefixed bandwidth numbers here. You definitely appear to be correct as long as you're multiplying through with bytes and not mebibytes or kibibytes, say. It would make much sense to do that though lol. Works for me. --Swaaye 06:53, 26 August 2006 (UTC)

17:29, 26 August 2006 Denniss (Rev, all related articles use correct binary prefixes)
Well, i've cheched following articles: None of them used any binary prefixes when speaking about brandwidth. So, you have to provide some more solid argumentation. --Rotsor 13:46, 26 August 2006 (UTC)
 * XDR DRAM
 * DDR SDRAM
 * DDR2 SDRAM
 * DDR3 SDRAM

Neutrality Dispute
I fail to see how this collection of completely true information can be painted as being biased. Can someone explain how this section is not neutral? Please cite specifically the problem wording, and how it would be corrected with semantics.

The cold hard fact of the matter is that RDRam is much more highly priced, and NEVER achieved any market dominance. As a technology enthusiast, it really looks to me like it's a strictly personal thing against the original author of some kind, as I don't see where the truth is being misrepresented. I'll give you guys a little while to respond before I remove the tag.

CameronB 14:28, 13 March 2007 (UTC)

 * Well, seeing as how no-one has found a need to respond to the Neutrality dispute, it's been close enough to a day, I can assume that there is no problem with Neutrality. I'll remove the unnecessary tag then.  CameronB 17:23, 14 March 2007 (UTC)

Raising prices of a competing product to force RDRAM out of market
Pertaining to "In 2004, it was revealed that Infineon, Hynix, Samsung, Micron, Elpida had entered a price-fixing scheme against Rambus during 2001, to force RDRAM out of the market.[18] This gave major memory manufacturers motive to drive Rambus and its RDRAM technology out of market. " I don't understand how price fixing to raise the price of competing memory like DDR, SDRAM can harm RDRAM in the market. Normally dumping or selling below cost is the method used to force a competitor out of the market. It is nice that the statement provides a link, but the concept still appears to make no sense. I'm going to be bold and remove the nonsensical implication. Damle64 01:16, 30 March 2007 (UTC)
 * Well, I think it has to do with the fact that those companies were manufacturing RDRAM and that is what they were price fixing. They were keeping the price higher than DDR to force RDRAM out of the market. OracleGuy01 02:09, 22 July 2007 (UTC)

What actually *is* RDRAM?
The article doesn't actually say anywhere what RDRAM really is. In particular, what is the technical difference between RDRAM and standard DRAM? Also, there is a list of disadvantages of RDRAM compared to the competition, but no list of any advantages whatsoever! —Preceding unsigned comment added by RichardNeill (talk • contribs) 10:29, 22 September 2007 (UTC)

Is howto tag relevant anymore?
Reading through the article, I don't see any how-to instructions anymore. The offending paragraph seems to have been reworded to remove such an objection. Could the tag be removed at this point?

I'd remove it myself, except I don't feel confident making such a judgment call.

No mention of pre-Direct RDRAM
It'd be nice if this article would explain that there have been two incompatible types of memory marketed as RDRAM. The second one, which was adopted by Intel, is the "Direct RDRAM" type. The article should also discuss the first type. 67.164.125.7 (talk) 21:08, 26 February 2009 (UTC)

 * There were two DRDRAM predecessors: Rambus DRAM was the original (c. 1990) Rambus DRAM, which was followed up in the early- to mid-1990s by Concurrent RDRAM. AZ1199 (talk) 01:10, 5 January 2016 (UTC)

Performance and Benchmarks sections
They both have serious POV problems. If the purpose is to provide details on these topics thats fine, but the constant (unfavorable) comparisons smell badly of POV. There is no need to constantly reference what DDR does better. There is also, um, zero references for any of this content?? Very much in need of some clean up. 207.216.253.134 (talk) 07:06, 10 November 2011 (UTC)

Why? The benchmark is objective and nearly all benchmarks found online have similar results. It is possible to do a benchmark that makes RDRAM win (and spectacularly so) by specifically testing things it's good at and ignoring the rest. The website of rambus has such a benchmark that maybe can be included (or linked) to show both sides. I I don't think the performance and benchmark is off-topic, as some users might base purchasing decisions on reading the wikepedia page. I'll add references to the benchmarks when I have time.

193.190.253.146 (talk) —Preceding undated comment added 11:51, 17 November 2011 (UTC).

External links modified
Hello fellow Wikipedians,

I have just added archive links to 1 one external link on RDRAM. Please take a moment to review my edit. If necessary, add after the link to keep me from modifying it. Alternatively, you can add to keep me off the page altogether. I made the following changes:
 * Added archive https://web.archive.org/20150503003151/http://www.computerwriter.com/Star/2000/jun/cw062100_intel_i820_mth_recall.htm to http://www.computerwriter.com/Star/2000/jun/cw062100_intel_i820_mth_recall.htm

When you have finished reviewing my changes, please set the checked parameter below to true or failed to let others know (documentation at ).

Cheers.—cyberbot II  Talk to my owner :Online 20:06, 18 March 2016 (UTC)

External links modified
Hello fellow Wikipedians,

I have just modified 4 external links on RDRAM. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:
 * Added archive https://web.archive.org/web/20080621031911/http://news.zdnet.com/2100-9595_22-523724.html to http://news.zdnet.com/2100-9595_22-523724.html
 * Corrected formatting/usage for http://news.com.com/Intel%2Bdrops%2BRambus%2Bsubsidies/2100-1001_3-270561.html
 * Added tag to http://findarticles.com/p/articles/mi_m0EKF/is_n2161_v43/ai_19288320
 * Added archive https://web.archive.org/web/20090430131325/http://n64.icequake.net/ to http://n64.icequake.net/
 * Added archive https://web.archive.org/web/20090524090904/http://archives.cnn.com/2001/TECH/fun.games/10/24/linux.ps2.idg/index.html to http://archives.cnn.com/2001/TECH/fun.games/10/24/linux.ps2.idg/index.html

When you have finished reviewing my changes, you may follow the instructions on the template below to fix any issues with the URLs.

Cheers.— InternetArchiveBot  (Report bug) 09:10, 24 May 2017 (UTC)

title: Talk:RDRAM


text:
BBC BASIC

BBC BASIC is an interpreted version of the BASIC programming language. It was developed by Acorn Computers Ltd when they were selected by the BBC to supply the computer for their BBC Literacy Project in 1981.

It was originally supplied on an installed ROM for the BBC Microcomputer which used a 6502 microprocessor. When Acorn produced the Archimedes computer which used their ARM processor, further versions of BBC BASIC were produced. Acorn included a built in assembler, first for the 6502 and later for the ARM2 processor.

Initially the BBC specified compatibility with Microsoft BASIC. Acorn were already extending their earlier Atom BASIC to include structured programming constructs. Particularly on the later Archimedes computers as the memory constraints reduced, BBC BASIC incorporated a more complete set of structured programming constructs commonly found in the ALGOL 60 group of computer languages.

Alongside Acorn's version of BBC BASIC on the Archimedes, third party companies produced compiled versions of the language. Development and support has continued after the demise of Acorn Computers Ltd for newer ARM based computers. BBC BASIC is now available on other platforms either for emulators such as on MS Windows or natively.

Precursor languages
Prior to 1957 programming was done using Machine code or Assembly code. These were specific to a processor and not portable.

Then high-level programming languages were developed to allow programs to be more easily transferred between computers:
 * FORTRAN (short for FORmula TRANslation), developed by a team led by John Backus at IBM was commercially released in 1957.
 * LISP (short for LISt Processing) invented by John McCarthy at Massachusetts Institute of Technology in 1958.
 * COBOL (short for COmmon-Business-Oriented Language) came from the 1959 Conference on Data Systems Languages at the University of Pennsylvania resulting in a compiler available in 1962.
 * ALGOL 60 (short for ALGOrithmic Language) designed by an international committee of the Association for Computing Machinery (ACM). The initial ALGOL 58 was followed by the publication of the Revised Report in 1960 (hence ALGOL 60).

Many more computer languages were developed during the 1960-1980 period. Few are now in regular use. Those more generally known were ALGOL W at Stanford University, Pascal plus POP-2 at the University of Edinburgh.

K&R C was designed as the language to write the UNIX operating system. This was formalised as ANSI C from which C++ and JAVA were later derived.

At Dartmouth College two mathematics professors wanted all students to be able to program on their new College computer. The existing high-level languages were used by professionals. In 1964 they created Dartmouth BASIC (short for Beginner’s All-Purpose Symbolic Instruction Code) to be a computer language anyone could use. Having a formula based syntactic structure it is a simplified FORTRAN.

Together, Paul Allen and Bill Gates developed BASIC for the Altair 8800. Development continued to become IBM's BASIC A and Microsoft BASIC.

BBC's involvement
During the 1970s, the BBC Continuing Education Department was considering how advancements in computer related technology would impact British society. Their Microelectronics Report in 1979 to the Manpower Services Commission describes formally their concerns about increasing polarisation and alienation in the workplace that 43 years earlier Charles Chaplin had shown to comic effect in Modern Times.

The BBC required a microcomputer usable for demonstrations in their programming that could be purchased by the general public to enable the viewer to themselves experiment. They decided that such a microcomputer needed to be robust, have expansion capabilities and an implementation of BASIC compatible with Microsoft BASIC VN5.

Jointly the government and the BBC established a public awareness and education campaign. This Computer Literacy Project (1980-1989) used the BBC's choice of the BBC Microcomputer produced by Acorn Computers Ltd. BBC BASIC was central to the user programming experience.

Acorn's involvement
Acorn first developed System BASIC and Atom BASIC for their early 6502 microprocessor computers that were sold to kit-build customers. With the development of the Proton as a Front-end processor, Acorn were designing for more powerful computing.

In order to produce a computer to satisfy the BBC specification, the Proton became the BBC Microcomputer, usable as a stand alone computer. By retaining the capability to be connected to a Z80 computer, Acorn was able to comply with the requirement of a computer supporting CP/M.

Sophie Wilson developed the implementations of BASIC at Acorn. The dialect on the BBC Microcomputer became compatible with Microsoft BASIC and so was acceptable to the BBC. It already had features from the ALGOL 60 group of computer languages that Wilson added to enable some structured programming methodology to be used.

BBC Micro
The full version list is available here:

BASIC I, the original version, was shipped on early BBC Micros.

BASIC II was used on the Acorn Electron and BBC Micros shipped after 1982, including the Model B. It added the  and   keywords, along with offset assembly and bug fixes.

BASIC III was produced in both a UK version and a United States market version for Acorn's abortive attempt to enter the cross-Atlantic computer market. Apart from a few bug fixes, the only change from BASIC II was that the  command could also be spelled  : regardless of which was input, the UK version always listed it as , the US version as. The main place that BASIC III can be found is as the HI-BASIC version for the external second processor.

BASIC IV, also known as CMOS BASIC, available on the BBC Master machines, was changed to use the new instructions available in the 65SC12 processor, reducing the size of the code and therefore allowing the inclusion of,   as a statement,  ,  ,  , | in   statements and faster floating point. Bug fixes were again included.

BASIC IV (1986) was a further improvement to BASIC IV, and was included on the Master Compact machine. The version of BASIC on the Compact included re-coded mathematical routines, said to provide a 30% speed increase over the version included in the rest of the Master series.

HI-BASIC was available in two versions, the first based on BASIC III, and the second based on BASIC IV. Both were built to run from a higher address (&B800) on the second processor, rather than the usual &8000 address on the BBC B. This allowed more program space to be available on either the external or internal 6502 second processors. A version was introduced to support a Zilog Z80 second processor.

Another version of BBC BASIC, called BAS128, was supplied on tape and disc with the BBC Master and Master Compact; it loaded into main RAM and used the 64 kB of Sideways RAM for user programs. This provided support for much larger programs at the cost of being a lot slower than the normal ROM-based version.

The interpreter can deal with both BASIC and 6502 assembly language, which can be included between the [ and ] characters. This contributed to the system's popularity with industrial and research engineers.

Further details/determining BASIC version
As the BBC MOS and RISC OS were usually supplied on ROM, it may be assumed that a specific release of the operating system contained a specific version of BASIC. As such, there is no simple way to determine which version of BASIC is actually running other than by enquiring the operating system identity and thus making an assumption.

See also BeebWiki entry for INKEY.

On the BBC family, it is possible to run both the standard BASIC and an enhanced HIBASIC on the 6502 second processor. One may determine if the program is running on the second processor by examining the initial value of PAGE, it will be &800 if using the second processor. To distinguish between BASIC and HIBASIC, one should examine the initial value of HIMEM. This will be &8000 for BASIC running on the second processor, and &B800 for HIBASIC on the second processor.

A similar situation exists on RISC OS where there may be the normal BASIC or BASIC64 (which offers higher precision maths). Normal BASIC identifies itself as "BASIC V" and BASIC64 identifies itself as "BASIC VI", therefore the following (used before any error has occurred) will distinguish one from the other:

There are better ways of doing this. See the BeebWiki. In almost all cases you shouldn't need to be testing for what BASIC or platform your program is running on, just make the call and read whatever returned data are returned and deal with it.

Acorn Archimedes (RISC OS)
With the move to the 32-bit ARM CPU and the removal of the 16 KB limit on the BASIC code size many new features were added. BASIC V version 1.04 was 61 KB long. Current versions of RISC OS still contain a BBC BASIC V interpreter. The source code to the RISC OS 5 version of BBC BASIC V has been released under the Apache 2.0 license by RISC OS Open.

Amongst the new commands and features supported were:

 * parameters in procedures,
 * local arrays,
 * procedure libraries (, and  ),
 * and  handlers,
 * a relative ,
 * array operations,
 * new operators,
 * Commands for the new sound system, mouse, graphics.
 * array operations,
 * new operators,
 * Commands for the new sound system, mouse, graphics.
 * Commands for the new sound system, mouse, graphics.

The graphics commands were entirely backwards compatible, the sound less so; for example, the  keyword from BASIC V onwards is a command that takes fourteen numeric parameters and effectively does nothing— as in older versions, it calls OS_Word 8, but that does nothing on RISC OS. The in-line 6502 assembler was replaced by an ARM assembler. BASIC V was said, by Acorn, to be "certainly the fastest interpreted BASIC in the world" and "probably the most powerful BASIC found on any computer".

BASIC VI is a version of BASIC V that supports IEEE 754 8-byte format real numbers, as opposed to the standard 5-byte format introduced in BASIC I.

BBC BASIC V and VI were delivered as standard on the Acorn Archimedes and the RiscPC. A version of BBC BASIC V was also available to run on the ARM second processor for the BBC Micro.

A compiler for BBC BASIC V was produced by Paul Fellows, team leader of the Arthur OS development, called the Archimedes BASIC Compiler and published initially by DABS Press. ABC was able to implement almost all of the language, with the obvious exception of the EVAL function, which inevitably required run-time programmatic interpretation. As evidence of its completeness, it was able to support in-line assembler syntax. The compiler was written in BBC BASIC V. The compiler (running under the interpreter in the early development stages) was able to compile itself, and versions that were distributed were self-compiled object code. Many applications initially written to run under the interpreter benefitted from the performance boost that this gave, putting BBC BASIC V on a par with other languages for serious application development.

Other platforms
BBC BASIC has also been ported to many other platforms.

A NS32016 version of BBC BASIC was supplied with the Acorn 32016 coprocessor and Acorn ABC.

In addition to the version of BBC BASIC supplied with the BBC Micro's Zilog Z80 second processor, a Z80-based version of BBC BASIC also exists for CP/M-based systems. A Zilog Z80 version of BBC BASIC was also used on the Tiki 100 desktop computer, Cambridge Z88 portable and the Amstrad NC100 Notepad and Amstrad NC200 Notebook computers. This version has been implemented on the TI-83 Plus and TI-84 Plus series graphing calculators. Due to efforts of J. G. Harston (also responsible for a PDP-11 version ) a version of BBC BASIC for the ZX Spectrum was released in January 2002, with many improvements made in subsequent releases.

For PC-based systems, BBC BASIC was also implemented for DOS as BBCBASIC (86), which aimed for maximum compatibility with the BBC Micro, and BBasic, which concentrated on the BASIC language, with its own enhancements based on BASIC II.

A version of BBC BASIC integrated with the Microsoft Windows graphical user interface, BBC BASIC for Windows created by Richard Russell, developer of the Z80 and x86 versions, was released in 2001. This version is still under active development, seeing much industry use currently. Whilst supporting nearly completely the original BBC BASIC specification (BASIC IV), the Windows version supports much of BASIC V/VI syntax as well as some advanced features of its own. Features unique to BBC BASIC for Windows include interpreter support for record/structure types, and the ability to call Windows API routines or those in an external DLL. Recent versions have included advanced features comparable with languages like C, and an external library has recently added support for objects.

BBC BASIC for SDL was also developed by Richard T. Russell, supporting Windows, Linux and a number of mobile devices supporting the SDL library, as well as a version which allows the running of BBC BASIC programs as applets in a web-page via the Web Assembly framework.

A GPL clone of BBC BASIC named Brandy, written in portable C, is also available. A fork of this, Matrix Brandy, remains under active development.

An emulator of the BBC Micro for the Commodore Amiga was produced by Ariadne Software for CBM (UK). While extremely fast, it did not emulate the 6502 at full speed, so assembly code would run slower than a real BBC while BASIC programs would run much faster. Due to the way the optimised BASIC and the 6502 emulation interacted, almost no commercial games would run but well-behaved code and educational software generally worked. Additionally, it used a slightly less precise floating-point numeric format. For a while it was bundled with a special academic package of the Amiga 500, in the hope that schools would replace their ageing BBC Bs with Amiga 500s.

A version of BBC BASIC V (Z80) has also been made for the TI-83/84+ Texas Instruments calculator families by Benjamin Ryves.

A Commodore 64 version Shado was produced by a small software house Aztec Software in the early 1980s. Patched versions of Acorn's 6502 based HI-BASIC have also been experimentally run on C64, with an interface to the C64 Kernel, replacing the Acorn MOS calls otherwise made.

There have also been efforts to make 6502 based version of BBC BASIC available on the Apple II. Applecorn being one such effort.

BBC BASIC is the programming language used in the Agon Light, an open-sourced 8-bit Z80-based single board computer and microcontroller designed by Bernardo Kastrup and released in 2022.

title: BBC BASIC