click links in text for more info

Williams tube

The Williams tube, or the Williams–Kilburn tube after inventors Freddie Williams and Tom Kilburn, is an early form of computer memory. It was the first random-access digital storage device, was used in several early computers; the Williams tube works by displaying a grid of dots on a cathode ray tube. Due to the way CRTs work, this creates a small charge of static electricity over each dot; the charge at the location of each of the dots is read by a thin metal sheet just in front of the display. Since the display faded over time, it was periodically refreshed, it cycles faster than earlier acoustic delay line memory, at the speed of the electrons inside the vacuum tube, rather than at the speed of sound. However, the system was adversely affected by any nearby electrical fields, required constant alignment to keep operational. Williams–Kilburn tubes were used on high-speed computer designs. Williams and Kilburn applied for British patents on 11 December 1946, 2 October 1947, followed by United States patent applications on 10 December 1947, 16 May 1949.

The Williams tube depends on an effect called secondary emission. When the electron beam strikes the phosphor that forms the display surface, it causes it to light up; these electrons travel a short distance before being attracted back to the CRT surface and falling on it a short distance away. The overall effect is to cause a slight positive charge in the immediate region of the beam where there is a deficit of electrons, a slight negative charge around the dot where those electrons land; the resulting charge well remains on the surface of the tube for a fraction of a second while the electrons flow back to their original locations. The lifetime depends on the size of the well; the process of creating the charge well is used as the write operation in a computer memory, storing a single binary digit, or bit. A collection of dots or spaces one horizontal row on the display, represents a computer word. There is a relationship between the size and spacing of the dots and their lifetime, as well as the ability to reject crosstalk with adjacent dots.

This places an upper limit on the memory density, each Williams tube could store about 1024 to 2560 bits of data. Because the electron beam is inertia-free and can be moved anywhere on the display, the computer can access any location, making it a random access memory; the computer would load the address as an X and Y pair into the driver circuitry and trigger a time base generator that would sweep the selected locations, reading from or writing to the internal registers implemented as flip-flops. Reading the memory took place via a secondary effect caused by the writing operation. During the short period when the write takes place, the redistribution of charges in the phosphor creates an electrical current that induces voltage in any nearby conductors; this is read by placing a thin metal sheet just in front of the display side of the CRT. During a read operation, the beam writes to the selected bit locations on the display; those locations that were written to are depleted of electrons, so no current flows, no voltage appears on the plate.

This allows the computer to determine. If the location had not been written to the write process will create a well and a pulse will be read on the plate, indicating a "0". Reading a memory location creates a charge well whether or not one was there, destroying the original contents of that location, so any read has to be followed by a write to reinstate the original data. In some systems this was accomplished using a second electron gun inside the CRT that could write to one location while the other was reading the next. Since the display would fade over time, the entire display had to be periodically refreshed using the same basic method. However, as the data is read and immediately written, this operation can be carried out by external circuitry while the central processing unit was busy carrying out other operations; this refresh operation is similar to the memory refresh cycles of DRAM in modern systems. Since the refresh process caused the same pattern to continually reappear on the display, there was a need to be able to erase written values.

This was accomplished by writing to the display just beside the original location. The electrons released by this new write would fall into the written well, filling it back in; the original systems produced this effect by writing a small dash, easy to accomplish without changing the master timers and producing the write current for a longer period. The resulting pattern was a series of dashes. There was a considerable amount of research on more effective erasing systems, with some systems using out-of-focus beams or complex patterns; some Williams tubes were made from radar-type cathode ray tubes with a phosphor coating that made the data visible, while other tubes were purpose-built without such a coating. The presence or absence of this coating had no effect on the operation of the tube, was of no importance to the operators, since the face of the tube was covered by the pickup plate. If a visible output was needed, a second tube connected in parallel with the storage tube, with a phosphor coating, but without a pickup plate, was used as a display device.

Developed at the University of Manchester in England, it provided the medium on which the first electronically stored-memory program was implemented in the M

Rajiv Dayal Mathur

Air Marshal Rajiv Dayal Mathur, PVSM, AVSM, VSM,ADC is an officer in the Indian Air Force. He is the Air Officer Commanding-in-Chief, Eastern Air Command, he assumed the office on 1 March 2019 succeeding Air Marshal Raghunath Nambiar. Mathur did his schooling from Dehradun, he joined National Defence Academy in 1978. He is an alumnus of the Defence Services Staff College and the National Defence College, New Delhi, he holds M. Sc and M Phil degrees in Defence and Strategic Studies from Madras University. Mathur was commissioned as a fighter pilot in the Indian Air Force on June 4, 1982, he is a qualified flight instructor and has flying experience of over 5000 hours on a variety of fighter aircraft and helicopters. He has commanded a front-line air base, he has held various other appointments including Principal Director of information and electronics warfare, Assistant Chief of Air Staff at air headquarters New Delhi, air defence commander at headquarters Eastern Air Command. He has been in-charge of air force's Air Warfare Strategy Cell as well as space, air traffic services and media and public relations directorate.

He took over the position of Senior Air Staff Officer, South Western Air Command in August 2018. During his career, Mathur has been awarded the Vishisht Seva Medal in 2003, the Ati Vishisht Seva Medal in 2014, the Param Vishisht Seva Medal in 2020 for his service. Air Marshal Mathur is married to Shipra Mathur, the president of Air Force Wives Welfare Association

Marco Antonio Rivera Useche

Marco Antonio Rivera Useche was a Venezuelan musician and composer. He was born in San Cristóbal on 19 June 1895 and died on 15 July 1990, he married Juanita Moreno Morales, with whom he had five children in 1937. Rivera was of humble origins. After completing primary education he began to work practicing the trades of carpentry, jewelry and shoemaking. In 1910 he began studying music with the Italian master Nicolas Constantino Chicaroni, who had arrived in San Cristóbal in the company of other Italian musicians to be incorporated into the Táchira State Band, including Angelo Mottola, author the state Hymn of Anzoátegui. From 1912 Rivera became a full member of the TáchiraState band and from 1913 he started to receive a salary of Bs 100 per month. In 1916 he was exiled for a short period in Colombia for a confrontation with the president of the state, Eustace Gomez, cousin to the president of Venezuela, Juan Vicente Gómez. On his return he began to study English with a German professor named Sildner.

He again continued his musical studies there. He returned to Venezuela to join a band in Maracaibo with the misfortune that Eustace Gomez was present at the premiere of the band, who had him arrested along with other Tachira musicians, he was imprisoned for two years. During his confinement he began composing his first waltz, on his release in 1921 he moved back to Maracaibo where he contracted malaria. While in Maracaibo and through an American friend, he studied orchestration and harmony by correspondence in an American school, he returned to San Cristóbal in 1924 where he dedicated himself to the composition of waltzes, fox trot, bambucos. In 1927, on the death of Nicolas Constantine who directed the Infantil de la Iglesia band, the pastor, made Rivera responsible for the management of this band, he took charge of the Táchira Band from 1929. Rivera was co-founder of the Táchira School of Music, directed by his cousin Luis Felipe Ramón y Rivera. Among his extensive work is the San Cristóbal State hymn.

In 1934 he founded the state Chamber Orchestra. He was among the founders of the Atheneum Reading Room of Táchira, an initiative of Charles Rangel Lamus. Following a trip to America to attend a meeting of bands, he conceived the idea of changing the band into on the Symphonic Concert Band. In 1968 he retired to San Pedro del Río. Marco Antonio Rivera Useche left a long list of musical production in various genres, including bambuco, fox trot, fantasies for concert, the galerón, intermezzo, joropo and marches. Today the Official Concert Band of Táchira is named after him


Lyngør is a village area on a group of small islands in the municipality of Tvedestrand in Aust-Agder county, off the southeast coast of Norway. The village is about 12 kilometres southeast of the town of Tvedestrand and about 12 kilometres southwest of the town of Risør; the village is located on several islands located close together and separated by small straits that are less than 100 metres wide. The village is located on the islands of Holmen, Lyngøya and Steinsøya; the Lyngør Lighthouse lies at the northeast edge of the village area. The village was a popular home for sea captains since it is only accessible by boat and it has no cars; the village is well-known for charming wooden houses. It is recognized as one of the best-preserved communities in Europe. Most of the buildings are now summer homes, but there are still about 75 permanent, year-round residents. A hugely popular destination in the summer months, it has more struggled to maintain a stable permanent population since it has no road connections to the mainland.

The community has a sail-making factory, a few restaurants that are open during the tourist season, a famous general store. The strait that goes through Lyngør is well known for the dramatic Battle of Lyngør during the Napoleonic Wars, in which the British Royal Navy put an end to the last of Dano-Norwegian naval forces; the wreck of the Danish frigate Najaden was discovered in the strait in 1957

Marco Wölfli

Marco Wölfli is a Swiss professional football goalkeeper who plays for Young Boys in the Swiss Super League. Wölfli made his league debut for Young Boys during their 1999–2000 Nationalliga B campaign. Two years limited opportunities with the first team saw him move to FC Thun, where he won promotion to the Nationalliga A and established himself as a good prospect, he returned to Young Boys in the summer of 2003 cementing himself as the Bern club's first choice goalkeeper. After the retirement of veteran striker Thomas Häberli, Wölfli was named club captain by manager Vladimir Petkovic prior to the 2009–10 season, he is the longest tenured player at the club. In November 2010 he extended his contract to last until 30 June 2015, he was part of the Young Boys squad that won the Swiss Super League for the first time in 32 years in 2017–18 season. He earned his first international cap for Switzerland in the friendly match against Finland on 19 November 2008. After his injury on 9 December Wölfli lost his number one status at Young Boys and has since not played for Switzerland anymore.

Young Boys Swiss Super League: 2017–18 Marco Wölfli at profile Marco Wölfli at Marco Wölfli on the website of the Swiss Football League

Ornithine transcarbamylase deficiency

Ornithine transcarbamylase deficiency is the most common urea cycle disorder in humans. It is an inherited disorder. Ornithine transcarbamylase, the defective enzyme in this disorder, is the final enzyme in the proximal portion of the urea cycle, it is responsible for converting carbamoyl ornithine into citrulline. OTC deficiency is inherited in an X-linked recessive manner, meaning males are more affected than females. In affected individuals, ammonia concentrations increase causing ataxia and death without rapid intervention. OTC deficiency is diagnosed using a combination of clinical findings and biochemical testing, while confirmation is done using molecular genetics techniques. Once an individual has been diagnosed, the treatment goal is to avoid precipitating episodes that can cause an increased ammonia concentration; the most common treatment combines a low protein diet with nitrogen scavenging agents. Liver transplant is considered curative for this disease. Experimental trials of gene therapy using adenoviral vectors resulted in the death of one participant, Jesse Gelsinger, have been discontinued.

OTC deficiency can become apparent at any age. Early-onset OTC deficiency is most found in males. In life, the disease may present in both males and females. In the classic presentation, a male infant appears well but by the second day of life becomes irritable and stops feeding. Infants may have poorly-controlled body temperature and respiratory rates, may experience seizures. Without urgent intervention, a metabolic encephalopathy develops. High levels of ammonia cause preferential damage to the brain. Onset forms of OTC deficiency can have variable presentations. Although late onset forms of the disease are considered milder than the classic infantile presentation, any affected individual is at risk for an episode of hyperammonemia that could still be life-threatening if presented with the appropriate stressors; these patients will present with headaches, vomiting, erratic behavior, or seizures. A detailed dietary history of an affected individual with undiagnosed OTC deficiency will reveal a history of protein avoidance.

The prognosis of a patient with severe OTC deficiency is well correlated with the length of the hyperammonemic period rather than the degree of hyperammonemia or the presence of other symptoms, such as seizures. For patients with late onset forms of the disease, their overall clinical picture is dependent on the extent of hyperammonemia they have experienced if it has remained unrecognized. OTC deficiency is caused by mutations in the OTC gene, located on the X chromosome. OTC codes for the mitochondrial enzyme ornithine transcarbamylase, expressed only in liver; the functional enzyme consists of three identical subunits. OTC is the last enzyme in the proximal portion of the urea cycle, which consists of the reactions that take place in the mitochondria; the substrates of the reaction catalyzed by ornithine transcarbamylase are ornithine and carbamyl phosphate, while the product is citrulline. There are no common mutations that cause disease, however 10 - 15% of disease causing mutations are deletions.

It is inherited in an X-linked recessive manner, meaning males are more affected than females. Females who carry a defective copy of the gene can be affected or asymptomatic depending on the random nature of X-inactivation. There is some degree of genotype - phenotype correlation with OTC deficiency, but this depends on a number of situations. Individuals with milder mutations associated with late onset disease can still present with severe illness when exposed to sufficient metabolic stress. Correlations are more difficult to ascertain in females, since the residual activity of OTC in the liver is impacted not only by the nature of the mutation, but by the random pattern of X-inactivation. OTC deficiency is estimated to be the most common urea cycle disorder. An exact incidence is difficult to calculate, due to the varying clinical presentations of onset forms of the disease. Early estimates of the incidence were as high as 1:14,000 live births, however studies have decreased these estimates to 1:60,000 - 1:72,000.

In individuals with marked hyperammonemia, a urea cycle disorder is high on the list of possible causes. While the immediate focus is lowering the patient's ammonia concentrations, identifying the specific cause of increased ammonia levels is key as well. Diagnostic testing for OTC deficiency, or any individual with hyperammonemia involves plasma and urine amino acid analysis, urine organic acid analysis and plasma acylcarnitines. An individual with untreated OTC deficiency will show decreased citrulline and arginine concentrations and increased orotic acid; the increased orotic acid concentrations result from the buildup of carbamoyl phosphate. This biochemical phenotype is classic for OTC deficiency, but can be seen in neonatal presentations of ornithine aminotransferase deficiency. Only affected males demonstrate this classic biochemical phenotype. Heterozygous females can be difficult to diagnose. With the rise of sequencing techniques, molecular testing has become preferred when the disease causing mutati