Chapter 1-----Julia Case Bradley Programming In Visual Basic 6.0 - Free download as PDF File (.pdf), Text File (.txt) or read online for free.
Programming Visual Basic.NET 9 Preface The purpose of this book is to provide experienced software developers with the means to quickly become productive in Microsoft's Visual Basic.NET development environment. The only assumption I make about you as a programmer is that you're comfortable with the concepts and processes of software development. Har Gobind Khorana (9 January 1922 â 9 November 2011) was an Indian-American. Later, his lab went on to study the structurally related visual pigment known as. The mission of the Khorana Program is to build a seamless community of. And the Lasker Foundation Award for Basic Medical Research, both in 1969, the.
Har Gobind Khorana (9 January 1922 â 9 November 2011)[1][2][3] was an Indian-born American biochemist.[4] While on the faculty of the University of WisconsinâMadison, he shared the 1968 Nobel Prize for Physiology or Medicine with Marshall W. Nirenberg and Robert W. Holley for research that showed the order of nucleotides in nucleic acids, which carry the genetic code of the cell and control the cell's synthesis of proteins. Khorana and Nirenberg were also awarded the Louisa Gross Horwitz Prize from Columbia University in the same year.[5][6]
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Born in British India, Khorana served on the faculties of three universities in North America. He became a naturalized citizen of the United States in 1966,[7] and received the National Medal of Science in 1987.[8]
![]() Biography[edit]
Khorana was born to Krishna Devi Khorana and Ganpat Rai Khorana, in Raipur, a village in Punjab, British India (now in present-day Pakistan) in a Hindu family.[9]The exact date of his birth is not certain but he believed that it might have been 9 January 1922;[10] this date was later shown in some documents, and has been widely accepted.[11] He was the youngest of five children. His father was a patwari, a village agricultural taxation clerk in the British Indian government. In his autobiography, Khorana wrote this summary: 'Although poor, my father was dedicated to educating his children and we were practically the only literate family in the village inhabited by about 100 people.'[12] The first four years of his education were provided under a tree, a spot that was, in effect, the only school in the village.[9]
He attended D.A.V. High School in Multan, in West Punjab.[9] Later, he studied at the Punjab University in Lahore, with the assistance of scholarships, where he obtained a bachelor's degree in 1943[12] and a Master of Science degree in 1945.[4][13]
Khorana lived in British India until 1945, when he moved to England to study organic chemistry at the University of Liverpool on a Government of India Fellowship. He received his PhD in 1948 advised by Roger J. S. Beer.[14][15][16][12] The following year, he pursued postdoctoral studies with Professor Vladimir Prelog at ETH Zurich in Switzerland.[12] He worked for nearly a year on alkaloid chemistry in an unpaid position.[9][16]
During a brief period in 1949, he was unable to find a job in his original home area in the Punjab.[9] He returned to England on a fellowship to work with George Wallace Kenner and Alexander R. Todd on peptides and nucleotides.[16] He stayed in Cambridge from 1950 until 1952.
He moved to Vancouver, British Columbia, with his family in 1952 after accepting a position with the British Columbia Research Council at University of British Columbia.[12][17] Khorana was excited by the prospect of starting his own lab, a colleague later recalled.[9] His mentor later said that the Council had few facilities at the time but gave the researcher 'all the freedom in the world'.[18] His work in British Columbia was on 'nucleic acids and synthesis of many important biomolecules' according to the American Chemical Society.[14]
In 1960 Khorana accepted a position as co-director of the Institute for Enzyme research at the Institute for Enzyme Research at the University of Wisconsin at Madison.[14][19] He became a professor of biochemistry in 1962 and was named Conrad A. Elvehjem Professor of Life Sciences at WisconsinâMadison.[20] While at Wisconsin, 'he helped decipher the mechanisms by which RNA codes for the synthesis of proteins' and 'began to work on synthesizing functional genes' according to the American Chemical Society.[14] During his tenure at this University, he completed the work that led to sharing the Nobel prize. The Nobel web site states that it was 'for their interpretation of the genetic code and its function in protein synthesis'. Har Gobind Khorana's role is stated as follows: he 'made important contributions to this field by building different RNA chains with the help of enzymes. Using these enzymes, he was able to produce proteins. The amino acid sequences of these proteins then solved the rest of the puzzle.'[21]
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He became a US citizen in 1966.[22] Beginning in 1970, Khorana was the Alfred P. Sloan Professor of Biology and Chemistry at the Massachusetts Institute of Technology[23][12][24] and later, a member of the Board of Scientific Governors at The Scripps Research Institute. He retired from MIT in 2007.[22]
Har Gobind Khorana married Esther Elizabeth Sibler in 1952. They had met in Switzerland and had three children, Julia Elizabeth, Emily Anne, and Dave Roy.
Research[edit]
Ribonucleic acid (RNA) with two repeating units (UCUCUCU â UCU CUC UCU) produced two alternating amino acids. This, combined with the Nirenberg and Leder experiment, showed that UCU genetically codes for serine and CUC codes for leucine. RNAs with three repeating units (UACUACUA â UAC UAC UAC, or ACU ACU ACU, or CUA CUA CUA) produced three different strings of amino acids. RNAs with four repeating units including UAG, UAA, or UGA, produced only dipeptides and tripeptides thus revealing that UAG, UAA, and UGA are stop codons.[25]
Their Nobel lecture was delivered on 12 December 1968.[25] Khorana was the first scientist to chemically synthesize oligonucleotides.[26] This achievement, in the 1970s, was also the world's first synthetic gene; in later years, the process has become widespread.[23] Subsequent scientists referred to his research while advancing genome editing with the CRISPR/Cas9 system.[22]
Subsequent research[edit]
He extended the above to long DNA polymers using non-aqueous chemistry and assembled these into the first synthetic gene, using polymerase and ligase enzymes that link pieces of DNA together,[26] as well as methods that anticipated the invention of polymerase chain reaction (PCR).[27] These custom-designed pieces of artificial genes are widely used in biology labs for sequencing, cloning and engineering new plants and animals, and are integral to the expanding use of DNA analysis to understand gene-based human disease as well as human evolution. Khorana's invention(s) have become automated and commercialized so that anyone now can order a synthetic oligonucleotide or a gene from any of a number of companies. One merely needs to send the genetic sequence to one of the companies to receive an oligonucleotide with the desired sequence.
After the middle of the 1970s, his lab studied the biochemistry of bacteriorhodopsin, a membrane protein that converts light energy into chemical energy by creating a proton gradient.[28] Later, his lab went on to study the structurally related visual pigment known as rhodopsin.[29]
A summary of his work was provided by a former colleague at the University of Wisconsin: 'Khorana was an early practitioner, and perhaps a founding father, of the field of chemical biology. He brought the power of chemical synthesis to bear on deciphering the genetic code, relying on different combinations of trinucleotides.'[14][4]
Awards and honors[edit]
In addition to sharing the Nobel prize (while he was working at the University of WisconsinâMadison in the U.S.),[13] Khorana was elected as Foreign Member of the Royal Society (ForMemRS) in 1978.[30] In 2007, the University of WisconsinâMadison, the Government of India (DBT Department of Biotechnology), and the Indo-US Science and Technology Forum jointly created the Khorana Program, jointly. The mission of the Khorana Program is to build a seamless community of scientists, industrialists, and social entrepreneurs in the United States and India.
The program is focused on three objectives:[31] Providing graduate and undergraduate students with a transformative research experience, engaging partners in rural development and food security, and facilitating public-private partnerships between the U.S. and India. The WisconsinâIndia Science and Technology Exchange Program (WINStep Forward, WSF) adopted administration responsibilities for the Khorana program in 2007.[32] WINStep Forward was jointly created by Drs. Aseem Ansari and Ken Shapiro at the University of WisconsinâMadison. WINStep Forward also administers the nationally competitive S.N. Bose Programs for Indian and American students, respectively, to promote both fundamental and applied research not only in biotechnology but broadly across all STEM (science, technology, engineering, and mathematics) fields, including medicine, pharmacy, agriculture, wildlife and climate change.
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In 2009, Khorana was hosted by the Khorana Program and honored at the 33rd Steenbock Symposium in Madison, Wisconsin.[19]
Other honours included the Louisa Gross Horwitz Prize from Columbia University and the Lasker Foundation Award for Basic Medical Research, both in 1969, the Willard Gibbs Medal of the Chicago section of the American Chemical Society, in 1974, the Gairdner Foundation Annual Award, in 1980 and the Paul Kayser International Award of Merit in Retina Research, in 1987.[12]
On 9 January 2018, a Google Doodle celebrated the achievements[33] of Har Gobind Khorana on what would have been his 96th birthday.[34][35]
Death[edit]
Har Gobind Khorana died on 9 November 2011, in Concord, Massachusetts, at the age of 89.[36]His wife, Esther, and daughter, Emily Anne, had died earlier,[14] but Khorana was survived by his other two children.[10] Julia later wrote about his work as a professor. 'Even while doing all this research, he was always really interested in education, in students and young people.'[12]
In his obituary, the Washington Post provided this summary of the man: 'Dr. Khorana was known for a modest, ingratiating manner. He tended to shun publicity, making many of his most important scientific announcements at departmental seminars and in scientific publications'.[36]
References[edit]
External links[edit]
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Har_Gobind_Khorana&oldid=900878161'
Alan Baddeley and Graham Hitch proposed a model of working memory in 1974, in an attempt to present a more accurate model of primary memory (often referred to as short-term memory). Working memory splits primary memory into multiple components, rather than considering it to be a single, unified construct.[1]
Baddeley & Hitch proposed their three part working memory model as an alternative to the short-term store in Atkinson & Shiffrin's 'multi-store' memory model (1968). This model is later expanded upon by Baddeley and other co-workers to add a fourth component, and has become the dominant view in the field of working memory. However, alternative models are developing (see working memory) providing a different perspective on the working memory system.
The original model of Baddeley & Hitch was composed of three main components; the central executive which acts as supervisory system and controls the flow of information from and to its slave systems: the phonological loop and the visuo-spatial sketchpad. The phonological loop stores verbal content, whereas the visuo-spatial sketchpad caters to visuo-spatial data. Both the slave systems only function as short-term storage centers. In 2000 Baddeley added a third slave system to his model, the episodic buffer.
Baddeley & Hitch's argument for the distinction of two domain-specific slave systems in the older model was derived from experimental findings with dual-task paradigms. Performance of two simultaneous tasks requiring the use of two separate perceptual domains (i.e. a visual and a verbal task) is nearly as efficient as performance of the tasks individually. In contrast, when a person tries to carry out two tasks simultaneously that use the same perceptual domain, performance is less efficient than when performing the tasks individually.[2]
A fourth component of Baddeley's model was added 25 years later to complement the central executive system. The third slave system was designated as episodic buffer. It is considered a limited capacity system that provides temporary storage of information capable by conjoining information from the subsidiary systems, and long-term memory, into a single episodic representation.[3]
Components[edit]
Baddeley's first model of working memory (without the episodic buffer)
Programming In Visual Basic 2010 Bradley Pdf Download Windows 7Central executive[edit]
The central executive is a flexible system responsible for the control and regulation ofcognitive processes. It directs focus and targets information, making working memory and long term memory work together. It can be thought of as a supervisory system that controls cognitive processes making sure short term store is actively working and intervenes when they go astray and prevents distractions.[4]
It has the following functions:
The central executive has two main systems: the visuo-spatial sketchpad, for visual information, and the phonological loop, for verbal information.[5]
Using the dual-task paradigm, Baddeley and Erses have found, for instance, that patients with Alzheimer's dementia are impaired when performing multiple tasks simultaneously, even when the difficulty of the individual tasks is adapted to their abilities.[6] Two tasks include a memory tasks and a tracking task. Individual actions are completed well, but as the Alzheimer's becomes more prominent in a patient, performing two or more actions becomes more and more difficult. This research has shown the deteriorating of the central executive in individuals with Alzheimer's.[7]
Recent research on executive functions suggests that the 'central' executive is not as central as conceived in the Baddeley & Hitch model. Rather, there seem to be separate executive functions that can vary largely independently between individuals and can be selectively impaired or spared by brain damage.[8]
Phonological loop[edit]
Baddeley's model of the phonological loop
The phonological loop (or 'articulatory loop') as a whole deals with sound or phonological information. It consists of two parts: a short-term phonological store with auditory memory traces that are subject to rapid decay and an articulatory rehearsal component (sometimes called the articulatory loop) that can revive the memory traces.
Any auditory verbal information is assumed to enter automatically into the phonological store. Visually presented language can be transformed into phonological code by silent articulation and thereby be encoded into the phonological store. This transformation is facilitated by the articulatory control process. The phonological store acts as an 'inner ear', remembering speech sounds in their temporal order, whilst the articulatory process acts as an 'inner voice' and repeats the series of words (or other speech elements) on a loop to prevent them from decaying. The phonological loop may play a key role in the acquisition of vocabulary, particularly in the early childhood years.[9] It may also be vital for learning a second language.
Five main findings provide evidence for the phonological loop:
Evidence in support of phonological short term store[edit]
An accumulation of literature across decades has lent strong support to the theory of phonological STS. In a 1971 study, Stephen Madigan demonstrated that a larger recency effect is seen during forward serial recall when people are presented a list auditorally as opposed to visually. (A smaller effect is seen in backwards serial recall.)[15] In his study, auditory presentation led to greater recall of the most recently studied items. Catherine Penney expanded on this discovery to observe that modality effects can also be found in the case of free recall tasks.[16] In 1965, Dallett had discovered that this observed modality effect is greatly reduced by the addition of a 'suffix' item to the presented list; this suffix is a distractor item that is not to be recalled.[17] Robert Greene utilized this observation in 1987 to discover that this suffix effect has a larger impact on lists learned auditorally as opposed to visually.[18] The culmination of all of these findings results in strong support of the theory that there is a short-term store that phonologically stores recently learned items. In addition, Bloom and Watkins found that the suffix effect is greatly diminished when the suffix is not interpreted as linguistic sound, which agrees with the phonological short term store theory as it would be largely unaffected by non-linguistic distractors.[19]
Visuo-spatial working memory[edit]
Alan Baddeley's theory of working memory has yet another aspect to which memory can be stored short term. The visuo-spatial sketchpad is this store that holds visual information for manipulation.[20] The visuo-spatial sketchpad is thought to be its own storage of working memory in that it does not interfere with the short term processes of the phonological loop. In research, it has been found that the visuo-spatial sketchpad can work simultaneously with the phonological loop to process both auditory and visual stimuli without either of the processes affecting the efficacy of the other.[21] Baddeley re-defined the theory of short-term memory as a working memory to explain this phenomenon. In the original theory of short-term memory, it is understood that a person only has one store of immediate information processing which could only hold a total of 7 items plus or minus two items to be stored in a very short period of time, sometimes a matter of seconds. The digit-span test is a perfect example of a measurement for classically defined short-term memory. Essentially, if one is not able to encode the 7 plus or minus two items within a few minutes by finding an existing association for the information to be transferred into long-term memory, then the information is lost and never encoded.[22]
However, visuo-spatial short-term memory can retain visual and/or spatial information over brief periods of time.[22] When this memory is in use, individuals are able to momentarily create and revisit a mental image that can be manipulated in complex or difficult tasks of spatial orientation.There are some who have disparities in the areas of the brain that allow for this to happen from different types of brain damage.[21] There can also be a misunderstanding here in the differences between transient memories such as the visual sensory memory. A transient memory is merely a fleeting type of sensory memory. Therefore, as the visual sensory memory is a type of sensory memory, there is a store for the information, but the store last for only a second or so. A common effect of the visual sensory memory is that individuals may remember seeing things that weren't really there or not remembering particular things that were in their line of sight. The memory is only momentary, and if it isn't attended to within a matter of seconds, it is gone.[20]
There are two different pathways in the brain that control different functions of what is known inclusively as the visuo-spatial sketchpad. The sketchpad consists of the spatial short-term memory and the object memory. The spatial short-term memory is how one is able to learn and thus remember 'where' they are in comparative representation to other objects. The object memory of the visuo-spatial sketchpad is essential in learning and remembering 'what' an object is.[22] It should be noted that the differences between these two differing visual abilities is due in large part because of different pathways of each of the abilities in the brain. The visual pathway in the brain that detects spatial representation of a person to and within their environment is the dorsal stream. The visual pathway that determines objects shapes, sizes, colors and other definitive characteristics is called the ventral stream.[21] Each of these two streams runs independent of one another so that the visual system may process one without the other (like in brain damage for instance) or both simultaneously. The two streams do not depend on one another, so if one is functioning manipulatively, the other can still send its information through.
Logie's elaboration of the visuospatial sketchpad[edit]
Logie has proposed that the visuo-spatial sketchpad can be further subdivided into two components:
Three main findings provide evidence for the distinction between visual and spatial parts of the visuospatial sketchpad:
Episodic buffer[edit]
In 2000 Baddeley added a fourth component to the model, the episodic buffer. This component is a limited capacity passive system,[27] dedicated to linking information across domains to form integrated units of visual, spatial, and verbal information with time sequencing (or episodic chronological ordering[27]), such as the memory of a story or a movie scene. The episodic buffer is also assumed to have links to long-term memory and semantic meaning.[28]
'It acts as a buffer store, not only between the components of Working Memory, but also linking Working Memory to perception and Long-Term Memory'.[27] Baddeley assumes that 'retrieval from the buffer occurred through conscious awareness'.[27] The episodic buffer allows individuals to use integrated units of information they already have to imagine new concepts. Since this is likely 'an attention-demanding process..the buffer would depend heavily on the Central Executive'.[27]
The main motivation for introducing this component was the observation that some (in particular, highly intelligent) patients with amnesia, who presumably have no ability to encode new information in long-term memory, nevertheless have good short-term recall of stories, recalling much more information than could be held in the phonological loop.[29] 'The episodic buffer appears..capable of storing bound features and making them available to conscious awareness but not itself responsible for the process of binding'.[30]
It is assumed that 'conscious access to the phonological loop or sketchpad may operate via the buffer'.[31] This is based on the assumption that both the visuo-spatial sketchpad and phonological loop act as minor buffers, combining information within their sensory area. The episodic buffer may also interact with smell and taste.[31]
Biology/neuroscience[edit]
There is much evidence for a brief memory buffer, as distinct from the long term store. The phonological loop seems to be connected to activation in the left hemisphere, more specifically the temporal lobe. The visuo-spatial sketchpad activates different areas depending on task difficulty; less intense tasks seem to activate in the occipital lobe, whereas more complex tasks appear in the parietal lobe. The central executive is still a mystery, although it would seem to be more or less located in the frontal lobes of the brain. The episodic buffer seems to be in both hemispheres (bilateral) with activations in both the frontal and temporal lobes, and even the left portion of the hippocampus.[32] In terms of genetics, the gene ROBO1 has been associated with phonological buffer integrity or length.[33][34]
Validity of the model[edit]
The strength of Baddeley's model is its ability to integrate a large number of findings from work on short-term and working memory. Additionally, the mechanisms of the slave systems, especially the phonological loop, has inspired a wealth of research in experimental psychology, neuropsychology, and cognitive neuroscience.
However, criticisms have been raised, for instance of the phonological-loop component, because some details of the findings are not easily explained by the original Baddeley & Hitch model, including the controversy regarding the 7+/-2 rule. [35][36]
The episodic buffer is seen as a helpful addition to the model of working memory, but it has not been investigated extensively and its functions remain unclear.[37]
See also[edit]References[edit]Notes[edit]
Bibliography[edit]
External links[edit]
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Baddeley%27s_model_of_working_memory&oldid=892836369'
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