Science.gov

Sample records for huxley correspondence letters

  1. Secondary Students' Internalization of Letter-Sound Correspondences.

    ERIC Educational Resources Information Center

    Ryder, Randall J.; Graves, Michael F.

    1980-01-01

    A study of seventh-, ninth-, and eleventh-grade students' ability to apply letter-sound correspondence to synthetic words indicates that, although by seventh grade, students have largely mastered letter-sound correspondences, low ability students do not approach the same mastery as average and high ability students until the eleventh grade. (JMF)

  2. 19 CFR 145.3 - Opening of letter class mail; reading of correspondence prohibited.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 19 Customs Duties 2 2011-04-01 2011-04-01 false Opening of letter class mail; reading of... Opening of letter class mail; reading of correspondence prohibited. (a) Matter in addition to... addressee has given written authorization for the opening. (c) Reading of correspondence. No Customs...

  3. 19 CFR 145.3 - Opening of letter class mail; reading of correspondence prohibited.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 19 Customs Duties 2 2010-04-01 2010-04-01 false Opening of letter class mail; reading of... Opening of letter class mail; reading of correspondence prohibited. (a) Matter in addition to... addressee has given written authorization for the opening. (c) Reading of correspondence. No Customs...

  4. Use of Simple and Conditional Letter-Sound Correspondences in Children's Pronunciations of Synthetic Words.

    ERIC Educational Resources Information Center

    Chapman, Robin S.; And Others

    Conditional letter sound correspondences (LSC) in which the pronunciation of a letter is determined by its graphemic environment were studied. Conditional LSC patterns selected for investigation were the c, g, and vowel-in-final-e patterns. The study had two aims: (1) to gather normative data for LSC generalizations and (2) to examine, for each…

  5. Pronunciation of Synthetic Words with Predictable and Unpredictable Letter-Sound Correspondences. Technical Report No. 71.

    ERIC Educational Resources Information Center

    Calfee, Robert C.; And Others

    The acquisition of Literacy Project's basic goal is to determine the processes by which children learn to read, and to identify reasons many fail to learn. One part of the process is the formation of correspondences between letter patterns and the sounds for which they stand. To determine the extent of such correspondences, tests of pronunciation…

  6. Instruction in Letter-Sound Correspondences for Children with Autism and Limited Speech

    ERIC Educational Resources Information Center

    Benedek-Wood, Elizabeth; McNaughton, David; Light, Janice

    2016-01-01

    This study used a multiple probe across participants' research design to evaluate the effects of instruction on the acquisition of letter-sound correspondences (LSCs) by three young children with autism spectrum disorder and limited speech. All three children (ages 3-5 years) reached criterion for identifying the LSCs targeted during instruction,…

  7. 124 High-Impact Letters for Busy Principals: A Guide to Handling Difficult Correspondence.

    ERIC Educational Resources Information Center

    Grady, Marilyn L.

    This work's 124 sample letters and accompanying CD-ROM provide templates for important letters busy principals often do not have time to prepare. Chapter 1, "Thank-You Letters," includes 14 letters for staff, students, parents, guest and conference speakers, and donations. Chapter 2, "Appreciation Letters," contains seven letters for staff,…

  8. Brain sensitivity to print emerges when children learn letter-speech sound correspondences.

    PubMed

    Brem, Silvia; Bach, Silvia; Kucian, Karin; Guttorm, Tomi K; Martin, Ernst; Lyytinen, Heikki; Brandeis, Daniel; Richardson, Ulla

    2010-04-27

    The acquisition of reading skills is a major landmark process in a human's cognitive development. On the neural level, a new functional network develops during this time, as children typically learn to associate the well-known sounds of their spoken language with unfamiliar characters in alphabetic languages and finally access the meaning of written words, allowing for later reading. A critical component of the mature reading network located in the left occipito-temporal cortex, termed the "visual word-form system" (VWFS), exhibits print-sensitive activation in readers. When and how the sensitivity of the VWFS to print comes about remains an open question. In this study, we demonstrate the initiation of occipito-temporal cortex sensitivity to print using functional MRI (fMRI) (n = 16) and event-related potentials (ERP) (n = 32) in a controlled, longitudinal training study. Print sensitivity of fast (<250 ms) processes in posterior occipito-temporal brain regions accompanied basic associative learning of letter-speech sound correspondences in young (mean age 6.4 +/- 0.08 y) nonreading kindergarten children, as shown by concordant ERP and fMRI results. The occipito-temporal print sensitivity thus is established during the earliest phase of reading acquisition in childhood, suggesting that a crucial part of the later reading network first adopts a role in mapping print and sound. PMID:20395549

  9. Thomas Birch's 'Weekly Letter' (1741-66): correspondence and history in the mid-eighteenth-century Royal Society.

    PubMed

    Ellis, Markman

    2014-09-20

    Thomas Birch (1705-66), Secretary of the Royal Society from 1752 to 1765, and Philip Yorke, second Earl of Hardwicke (1720-90), wrote a 'Weekly Letter' from 1741 to 1766, an unpublished correspondence of 680 letters now housed in the British Library (Additional Mss 35396-400). The article examines the dimensions and purposes of this correspondence, an important conduit of information for the influential coterie of the 'Hardwicke circle' gathered around Yorke in the Royal Society. It explores the writers' self-conception of the correspondence, which was expressed in deliberately archaic categories of seventeenth-century news exchange, such as the newsletter, aviso and a-la-main. It shows how the letter writers negotiated their difference in status through the discourse of friendship, and concludes that the 'Weekly Letter' constituted for the correspondents a form of private knowledge, restricted in circulation to their discrete group, and as such unlike the open and networked model of Enlightenment science. PMID:25254279

  10. Building Practical Knowledge of Letter-Sound Correspondences: A Beginner's Word Wall and Beyond.

    ERIC Educational Resources Information Center

    Wagstaff, Janiel M.

    1998-01-01

    Describes how one kindergarten teacher developed self-monitoring and searching behaviors in her class of beginning readers. Describes an array of reading and writing activities that advanced students' phonemic awareness, letter-sound knowledge, and facility with reading and writing--learning that was proudly constructed with ownership shared…

  11. Friendly Letters on the Correspondence of Helen Keller, Anne Sullivan, and Alexander Graham Bell.

    ERIC Educational Resources Information Center

    Blatt, Burton

    1985-01-01

    Excerpts from the letters between Alexander Graham Bell and Anne Sullivan and Helen Keller are given to illustrate the educational and personal growth of Helen Keller as well as the educational philosophy of Bell regarding the education of the deaf blind. (DB)

  12. Letters

    NASA Astrophysics Data System (ADS)

    2001-03-01

    The Editor welcomes letters, by e-mail to ped@iop.org or by post to Dirac House, Temple Back, Bristol BS1 6BE Contents: Force on a pendulum Sound slows down Bond is back Force on a pendulum The simple pendulum has been used by several educationalists for investigating the patterns of thinking among students and their observations that Aristotelian thinking persists among students at college level. I had also considered the simple pendulum in my 1985 letter in Physics Today [1], so I was interested to read the test given by Lenka Czudková and Jana Musilová [2]. When students were asked to draw net forces acting on the particle at various positions, 31.9% of students believed that the net force was tangential to the particle's path the whole time. To me this is no surprise because in our derivation of the equation for the period of a simple pendulum we assume that the unbalanced sine component provides the restoring force for the harmonic motion of the bob. Of course, Czudková and Musilová's question asked students for the net force on the particle, not the component. The student's answer fits well with the logic of the equilibrium of forces and the parallelogram law. Lastly, let me bring out the similarity between the student's answer and the thinking of George Gamow. He used to call positrons 'donkey' electrons because of their displacement against the applied force, before Paul Dirac termed them positrons. Victor Weisskeptf told me this anecdote in a letter in May 1982. References [1] Sathe D 1985 Phys. Today 38 144 [2] Czudková L and Musilová J 2000 Phys. Educ. 35 428 Dileep V Sathe Dadawala Jr College, Pune, India Sound slows down Without wanting to stir up more trouble amongst the already muddy waters of Physics teaching, consider how many times you have heard (or, more worryingly, read) this: 'Sound waves travel faster in a denser material' But...The velocity of simple longitudinal waves in a bulk medium is given by v = (K/ρ)1/2 where K is

  13. Letters

    NASA Astrophysics Data System (ADS)

    2001-03-01

    The Editor welcomes letters, by e-mail to ped@iop.org or by post to Dirac House, Temple Back, Bristol BS1 6BE Contents: Force on a pendulum Sound slows down Bond is back Force on a pendulum The simple pendulum has been used by several educationalists for investigating the patterns of thinking among students and their observations that Aristotelian thinking persists among students at college level. I had also considered the simple pendulum in my 1985 letter in Physics Today [1], so I was interested to read the test given by Lenka Czudková and Jana Musilová [2]. When students were asked to draw net forces acting on the particle at various positions, 31.9% of students believed that the net force was tangential to the particle's path the whole time. To me this is no surprise because in our derivation of the equation for the period of a simple pendulum we assume that the unbalanced sine component provides the restoring force for the harmonic motion of the bob. Of course, Czudková and Musilová's question asked students for the net force on the particle, not the component. The student's answer fits well with the logic of the equilibrium of forces and the parallelogram law. Lastly, let me bring out the similarity between the student's answer and the thinking of George Gamow. He used to call positrons 'donkey' electrons because of their displacement against the applied force, before Paul Dirac termed them positrons. Victor Weisskeptf told me this anecdote in a letter in May 1982. References [1] Sathe D 1985 Phys. Today 38 144 [2] Czudková L and Musilová J 2000 Phys. Educ. 35 428 Dileep V Sathe Dadawala Jr College, Pune, India Sound slows down Without wanting to stir up more trouble amongst the already muddy waters of Physics teaching, consider how many times you have heard (or, more worryingly, read) this: 'Sound waves travel faster in a denser material' But...The velocity of simple longitudinal waves in a bulk medium is given by v = (K/ρ)1/2 where K is

  14. The correspondence of Thomas Dale (1700-1750): Botany in the transatlantic Republic of Letters.

    PubMed

    Cook, William J

    2012-03-01

    This paper seeks to provide a full account of the life and career of Dr. Thomas Dale (1700-1750), with particular reference to his botanical works and correspondence. Born in Hoxton, London, Dale studied medicine at Leiden and engaged fully in the social, literary and epistolary network in which botany was practised in eighteenth-century England. In 1730, however, Dale relocated to the British colonial port of Charles Town, South Carolina. Here he continued to engage in a transatlantic network of botanical exchange and discussion, corresponding on equal and reciprocal terms with his former colleagues in England. Where Dale differs from naturalists in South Carolina before him is that his motives for pursuing botany and for corresponding with English naturalists were located firmly in the New World. Such a conclusion forms a valuable, albeit small contribution to models for the development of national scientific cultures in the imperial world. Similarly, Dale's pursuit of botanical information in South Carolina provides a small amount of material with which to illustrate currently fashionable models for the mediated exchange and circulation of scientific knowledge. PMID:22326093

  15. Evolution and Education: Lessons from Thomas Huxley

    ERIC Educational Resources Information Center

    Lyons, Sherrie Lynne

    2010-01-01

    Thomas Huxley more than anyone else was responsible for disseminating Darwin's theory in the western world and maintained that investigating the history of life should be regarded as a purely scientific question free of theological speculation. The content and rhetorical strategy of Huxley's defense of evolution is analyzed. Huxley argued that the…

  16. Letters

    NASA Astrophysics Data System (ADS)

    2001-07-01

    The Editor welcomes letters, by e-mail to ped@iop.org or by post to Dirac House, Temple Back, Bristol BS1 6BE, UK. Contents: Alternative view of education in Zambia Pedantry or compromise Alternative view of education in Zambia I have just read the 'On the Map' report of the International School of Lusaka with very mixed feelings (Physics Education, March 2001). I have recently spent some time in Zambia, in Lusaka, and share Sue Pears' love for the country and the Zambians. The ISL is indeed a good, prestigious school, similar to International Schools in many other countries. But, as in most other developing countries, there is enormous variation between the different types of schooling, and the ISL is at one end of the spectrum. Most schools in Zambia are less favoured. Zambia is a wonderful, beautiful country full of the most friendly and resourceful people I know. It is also a very poor country. It is a country of enormous contrasts and its schools reflect that variation. It has a tiny, affluent 'middle' class of professionals, politicians, businessmen, employees of international businesses and NGOs—nearly all paid from overseas budgets. It has an enormous majority of poor folk, cheerfully living in very basic conditions but sharing their lives in extended families without complaint. The government is virtually bankrupt, and consequently those paid by the government—teachers, police, nurses etc—get a pittance. The wage for a teacher in a typical school is #20 per month (compared to a typical teacher in the UK who gets 100 times more, about #2000 per month). The GNP in Zambia is about 1 per day per person, and this has to pay for all the schools, hospitals, police, and the civic infrastructure that we take so much for granted (the GNP in UK is about 60 per day per person). Consequently most state schools do not have resources; they have a classroom and a teacher but little else. What resources the school has will be paid for by the school fees that every

  17. Letters

    NASA Astrophysics Data System (ADS)

    2001-07-01

    The Editor welcomes letters, by e-mail to ped@iop.org or by post to Dirac House, Temple Back, Bristol BS1 6BE, UK. Contents: Alternative view of education in Zambia Pedantry or compromise Alternative view of education in Zambia I have just read the 'On the Map' report of the International School of Lusaka with very mixed feelings (Physics Education, March 2001). I have recently spent some time in Zambia, in Lusaka, and share Sue Pears' love for the country and the Zambians. The ISL is indeed a good, prestigious school, similar to International Schools in many other countries. But, as in most other developing countries, there is enormous variation between the different types of schooling, and the ISL is at one end of the spectrum. Most schools in Zambia are less favoured. Zambia is a wonderful, beautiful country full of the most friendly and resourceful people I know. It is also a very poor country. It is a country of enormous contrasts and its schools reflect that variation. It has a tiny, affluent 'middle' class of professionals, politicians, businessmen, employees of international businesses and NGOs—nearly all paid from overseas budgets. It has an enormous majority of poor folk, cheerfully living in very basic conditions but sharing their lives in extended families without complaint. The government is virtually bankrupt, and consequently those paid by the government—teachers, police, nurses etc—get a pittance. The wage for a teacher in a typical school is #20 per month (compared to a typical teacher in the UK who gets 100 times more, about #2000 per month). The GNP in Zambia is about 1 per day per person, and this has to pay for all the schools, hospitals, police, and the civic infrastructure that we take so much for granted (the GNP in UK is about 60 per day per person). Consequently most state schools do not have resources; they have a classroom and a teacher but little else. What resources the school has will be paid for by the school fees that every

  18. Letters

    NASA Astrophysics Data System (ADS)

    2001-09-01

    The Editor welcomes letters, by e-mail to ped@iop.org or by post to Dirac House, Temple Back, Bristol BS1 6BE, UK. Contents: M-set as metaphor The abuse of algebra M-set as metaphor 'To see a World in a Grain of Sand And a Heaven in a Wild Flower Hold Infinity in the palm of your hand And Eternity in an hour' William Blake's implied relativity of spatial and temporal scales is intriguing and, given the durability of this worlds-within-worlds concept (he wrote in 1803) in art, literature and science, the blurring of distinctions between the very large and the very small must strike some kind of harmonious chord in the human mind. Could this concept apply to the physical world? To be honest, we cannot be absolutely sure. Most cosmological thinking still retains the usual notions of a finite universe and an absolute size scale extending from smallest to largest objects. In the boundless realm of mathematics, however, the story is quite different. The M-set was discovered by the French mathematician Benoit Mandelbrot in 1980, created by just a few simple lines of computer code that are repeated recursively. As in Blake's poem, this 'world' has no bottom we have an almost palpable archetype for the concept of infinity. I would use the word 'tangible', but one of the defining features of the M-set is that nowhere in the labyrinth can one find a surface smooth enough for a tangent. Upon magnification even surfaces that appeared to be smooth explode with quills and scrolls and lightning bolts and spiral staircases. And there is something more, something truly sublime. Observe a small patch with unlimited magnifying power and, as you observe the M-set on ever-smaller scales, down through literally endless layers of ornate structure, you occasionally come upon a rapidly expanding cortex of dazzling colour with a small black structure at its centre. The black spot appears to be the M-set itself! There is no end to the hierarchy, no bottom-most level, just endless recursive

  19. Letters

    NASA Astrophysics Data System (ADS)

    2001-01-01

    The Editor welcomes letters, by e-mail to ped@iop.org or by post to Dirac House, Temple Back, Bristol BS1 6BE, UK. Contents: Maths for physics? Help! Fire! Energy and mass Maths for physics? As a maths graduate working as a university research associate I should be well qualified to support my daughter, who has just started AS-level physics, with the maths she needs for the course. There seems to be little integration between the maths and physics departments, so that maths needed for physics has not yet been covered in maths lessons. This is a problem I remember from my own school days, but the shorter timescale and modular nature of the AS and A2 levels means that it is essential that this mismatch of knowledge is resolved now. I would like to know whether physics teachers in the UK have encountered this problem and whether there is a deficiency in the maths syllabus in relation to the requirements of the AS and A2 levels in Physics or whether this is a problem peculiar to my daughter's school. Eleanor Parent of A-level student, Sheffield, UK Help! Fire! Is there a crisis in physics education? Is physics didactics coming to an end? Yes and no. Being a delegate from Norway at the on-going conference Physics on Stage (6-10 November 2000) at CERN in Geneva, I have had the opportunity to discuss this with people from all over Europe. Yes, there is a crisis. (Look at the proceedings for details on this.) I'd like to take a broader look at this situation. Like Hari Seldon in Isaac Asimov's Foundation Trilogy, I believe that there is nothing like a real crisis to get things going... Famous is the quote from the American Patent Office around 1890: 'Everything has been invented that could be invented'. Fortunately, this spurred action. The Michelson and Morley experiment heralded a most exciting period for physics. Just a cosmic blink later we put a person on the Moon. Coming back to the crisis - I am certain that in the near future we will see an interesting development

  20. Letters

    NASA Astrophysics Data System (ADS)

    2001-09-01

    The Editor welcomes letters, by e-mail to ped@iop.org or by post to Dirac House, Temple Back, Bristol BS1 6BE, UK. Contents: M-set as metaphor The abuse of algebra M-set as metaphor 'To see a World in a Grain of Sand And a Heaven in a Wild Flower Hold Infinity in the palm of your hand And Eternity in an hour' William Blake's implied relativity of spatial and temporal scales is intriguing and, given the durability of this worlds-within-worlds concept (he wrote in 1803) in art, literature and science, the blurring of distinctions between the very large and the very small must strike some kind of harmonious chord in the human mind. Could this concept apply to the physical world? To be honest, we cannot be absolutely sure. Most cosmological thinking still retains the usual notions of a finite universe and an absolute size scale extending from smallest to largest objects. In the boundless realm of mathematics, however, the story is quite different. The M-set was discovered by the French mathematician Benoit Mandelbrot in 1980, created by just a few simple lines of computer code that are repeated recursively. As in Blake's poem, this 'world' has no bottom we have an almost palpable archetype for the concept of infinity. I would use the word 'tangible', but one of the defining features of the M-set is that nowhere in the labyrinth can one find a surface smooth enough for a tangent. Upon magnification even surfaces that appeared to be smooth explode with quills and scrolls and lightning bolts and spiral staircases. And there is something more, something truly sublime. Observe a small patch with unlimited magnifying power and, as you observe the M-set on ever-smaller scales, down through literally endless layers of ornate structure, you occasionally come upon a rapidly expanding cortex of dazzling colour with a small black structure at its centre. The black spot appears to be the M-set itself! There is no end to the hierarchy, no bottom-most level, just endless recursive

  1. Letters

    NASA Astrophysics Data System (ADS)

    2001-05-01

    The Editor welcomes letters, by e-mail to ped@iop.org or by post to Dirac House, Temple Back, Bristol BS1 6BE, UK. Contents: Quantum uncertainties Reflections in a plastic box A brief history of quantum physics Correction Grammar and gender Quantum uncertainties Whilst I enjoyed Gesche Pospiech's article ('Uncertainty and complementarity: the heart of quantum physics' 2000 Phys. Educ. 35 393 9) I would like to expand on two comments he makes. Firstly the author claims that QM is linear, and a consequence of this is that any two superimposed states form an admissible third state. This is rather too sweeping, as it is true only for degenerate states. Otherwise quantum mechanics would allow a continuum of energies between states by a simple admixture of levels. The proof of this statement is trivial. For a Hamiltonian H and two orthogonal wavefunctions, ψ1 and ψ2 with energies E1 and E2 then (ψ1 + ψ2) is not an eigenfunction of that Hamiltonian as H(ψ1 + ψ2) = E1ψ1 + E2ψ2 ≠ E(ψ1 + ψ2) for any value of E, unless E1 = E2. Secondly Pospiech states that quantum objects show wave- or particle-like behaviour, depending on the measuring apparatus, and that occasionally experiments (such as Taylor's) reveal both. I would contest the validity of this type of thinking. All experiments on quantum objects reveal both types of behaviour—even ones which simply show straight line motion of photons. What is important, in addition, is our interpretation of the results. It takes an understanding of QED, for example, to see that an experiment which otherwise shows particle behaviour is, in fact, showing quantum behaviour. More contentiously though I would suggest that detection apparatus is incapable of detecting anything other than particles. Wave-like behaviour is revealed only by an analysis of the paths the particle could have taken. In other words, the interference of continuous fields sometimes predicts the same results when the detection is averaged over many events

  2. Supplemental Flashcard Drill Methods for Efficiently Helping At-Risk Kindergartners Make Letter-Sound Correspondences: Does Presentation Arrangement of Words Matter?

    ERIC Educational Resources Information Center

    Griffin, Crystal; Joseph, Laurice M.

    2015-01-01

    Variations of supplemental flashcard drill and practice instructional procedures (i.e., massed practice and interspersal presentation arrangements of words) were examined for six kindergartners who struggled making letter-sound correspondences. Findings revealed that the children demonstrated the highest learning rates when the presentation…

  3. Thomas Henry Huxley and neuroscience.

    PubMed

    Smith, C U

    1999-01-01

    In the latter decades of the nineteenth century Thomas Henry Huxley was at the heart of British Science: President of the British Association for the Advancement of Science (1870), President of the Royal Society (1883-86), Chairman of innumerable committees. His thought in many ways characterises the spirit of the 'high' Victorian age in Britain. He was not only the most eminent academic biologist of his time but also deeply interested in philosophical issues. His re-examination of the evolution of the brain in response to Richard Owen's 'telenomic' views formed the kernel of the notorious debate at the 1860 meeting of the British Association in Oxford. From his early youth until old age he thought long and hard about the mind/body problem. This paper follows the development of his ideas and shows how in debate with many of the leading thinkers of his age, in the X-club and the Metaphysical Society, he struggled to develop a biologically-based account of the relationship between mind and brain. However, at the end, he seems to have recognized that his position was not entirely satisfactory and ultimately famously confessing himself 'agnostic' turned from metaphysics to devote himself to more practical issues. The unresolved problems of mind and brain which perplexed Huxley remain to torment his epigoni. PMID:11640239

  4. Circles of Confidence in Correspondence: Modeling Confidentiality and Secrecy in Knowledge Exchange Networks of Letters and Drawings in the Early Modern Period.

    PubMed

    van den Heuvel, Charles; Weingart, Scott B; Spelt, Nils; Nellen, Henk

    2016-01-01

    Science in the early modern world depended on openness in scholarly communication. On the other hand, a web of commercial, political, and religious conflicts required broad measures of secrecy and confidentiality; similar measures were integral to scholarly rivalries and plagiarism. This paper analyzes confidentiality and secrecy in intellectual and technological knowledge exchange via letters and drawings. We argue that existing approaches to understanding knowledge exchange in early modern Europe--which focus on the Republic of Letters as a unified entity of corresponding scholars--can be improved upon by analyzing multilayered networks of communication. We describe a data model to analyze circles of confidence and cultures of secrecy in intellectual and technological knowledge exchanges. Finally, we discuss the outcomes of a first experiment focusing on the question of how personal and professional/official relationships interact with confidentiality and secrecy, based on a case study of the correspondence of Hugo Grotius. PMID:27071301

  5. Correspondence standards

    NASA Technical Reports Server (NTRS)

    1992-01-01

    This revised handbook covers the drafting, preparation, and review of NASA letters, memorandums, informal communications, electronic communications, envelopes and mailing, and classified correspondence. The appendices address specific guidelines for administrator's correspondence, White House and Congressional correspondance, Privacy Act correspondence, and foreign correspondence. Also incorporated as appendices are quick references for forms of address, compound words, and capitalization of words frequently used at NASA.

  6. Evolution and Education: Lessons from Thomas Huxley

    NASA Astrophysics Data System (ADS)

    Lyons, Sherrie Lynne

    2010-05-01

    Thomas Huxley more than anyone else was responsible for disseminating Darwin’s theory in the western world and maintained that investigating the history of life should be regarded as a purely scientific question free of theological speculation. The content and rhetorical strategy of Huxley’s defense of evolution is analyzed. Huxley argued that the classification of humans should be determined independent of any theories of origination of species. Besides providing evidence that demonstrated the close relationship between apes and humans, he also argued that a pithecoid ancestry in no way degraded humankind. In his broader defense of evolution he drew on his agnosticism to define what science could and could not explain. Theology made empirical claims and needed to be subject to the same standards of evidence as scientific claims. He maintained that even most scientific objections to evolution were religiously based. The objections to the theory fundamentally remain the same as in the nineteenth century and much can be learned from Huxley to develop effective strategies for educating the public about evolution. Huxley’s own scientific articles as well as his popular writings provide numerous examples that could be harnessed not only for the teaching of evolution, but also for understanding science as a process.

  7. Brave new world revisited revisited: Huxley's evolving view of behaviorism

    PubMed Central

    Newman, Bobby

    1992-01-01

    Aldous Huxley's Brave New World has served as a popular and powerful source of antibehavioral sentiment. Several of Huxley's works are examined in order to ascertain his true thoughts regarding behaviorism. Early in his career Huxley failed to appreciate aspects of behavioral theory (e.g., an appreciation of heredity) or the good ends to which it could be employed. Huxley's later works portrayed behaviorism in a much more positive light, and he believed that behavioral science, along with spiritual enlightenment, might help save humanity from the Brave New World he predicted. PMID:22478115

  8. Brave new world revisited revisited: Huxley's evolving view of behaviorism.

    PubMed

    Newman, B

    1992-01-01

    Aldous Huxley's Brave New World has served as a popular and powerful source of antibehavioral sentiment. Several of Huxley's works are examined in order to ascertain his true thoughts regarding behaviorism. Early in his career Huxley failed to appreciate aspects of behavioral theory (e.g., an appreciation of heredity) or the good ends to which it could be employed. Huxley's later works portrayed behaviorism in a much more positive light, and he believed that behavioral science, along with spiritual enlightenment, might help save humanity from the Brave New World he predicted. PMID:22478115

  9. Thomas Henry Huxley's developmental view of the cell.

    PubMed

    Richmond, Marsha L

    2002-01-01

    In 1853, the British physiologist Thomas Henry Huxley roundly criticized German cell theory. Historians have had difficulty explaining how such a 'progressive' biologist could have rejected cellular autonomy and the central role of the nucleus in cell life. The key to Huxley's thinking is provided by understanding his 'epigenetic' philosophy of biology. PMID:11823799

  10. How a Neurologically Integrated Approach Which Teaches Sound-Symbol Correspondence and Legible Letter Formations Impacts At-Risk First Graders

    ERIC Educational Resources Information Center

    Shaw, Donita Massengill; Sundberg, Mary Lou

    2008-01-01

    The setting of this study took place in an inner city. The purpose was to determine the effectiveness of a neurologically integrated approach in teaching 43 at-risk pre-first graders their letter sounds and formations during 45-50 hours of summer school. There were four sequential phases to teaching this alphabetic approach: imagery, auditory,…

  11. Schizophrenia, evolution and the borders of biology: on Huxley et al.'s 1964 paper in Nature.

    PubMed

    De Bont, Raf

    2010-06-01

    In October 1964, Julian Huxley, Ernst Mayr, Humphrey Osmond and Abram Hoffer co-published a controversial paper in Nature, in which they tried to explain the persistence of schizophrenia from an evolutionary perspective. This article will elucidate how the reputed authors composed this paper to make it a strong argument for biological psychiatry. Through a close reading of their correspondence, it will furthermore clarify the elements which remained unspoken in the paper, but which were elementary in its genesis. The first was the dominance of psychoanalytical theory in (American) psychiatry--a dominance which the authors wanted to break. The second was the ongoing discussion on the boundaries of biological determinism and the desirability of a new kind of eugenics. As such, the Huxley et al. paper can be used to study the central issues of psychiatry in a pivotal era of its history. PMID:21877369

  12. Julian Huxley, Uca pugnax and the allometric method.

    PubMed

    Packard, Gary C

    2012-02-15

    The allometric method, which often is attributed to Julian Huxley, entails fitting a straight line to logarithmic transformations of the original bivariate data and then back-transforming the resulting equation to form a power function in the arithmetic scale. Development of the technique was strongly influenced by Huxley's own research on growth by the enlarged 'crusher' claw in male fiddler crabs (Uca pugnax). Huxley reported a discontinuity in the log-log plot of chela mass vs body mass, which he interpreted as an abrupt change in relative growth of the chela at about the time crabs attain sexual maturity. My analysis of Huxley's arithmetic data indicates, however, that the discontinuity was an artifact caused by logarithmic transformation and that dynamics of growth by the crusher claw do not change at any point during development. Arithmetic data are well described by a power function fitted by nonlinear regression but not by one estimated by back-transforming a line fitted to logarithms. This finding and others like it call into question the continued reliance on the allometric method in contemporary research. PMID:22279062

  13. A compact and stable hydraulic micromanipulator patterned after a Huxley-style approach.

    PubMed

    Krueger, J W

    1991-11-01

    I describe a remote-controlled micromanipulator platform that is stable, durable, precise, and easy to construct. Small metallic bellows are used for hydraulic control, where all fluid connections are made by standard 1/16-in. high-performance liquid chromatography fittings. Inspired by the parallelogram suspension utilized in the larger Huxley-style micromanipulator (A. F. Huxley. J. Physiol. Lond. 157: 6-5P, 1961), the device is a compact cradle suspension of folded lever arms that creates vertical motions which have minimal cross-coupled horizontal error. A simple arrangement for securing the bellows in the remote controller counteracts the vertical cross-coupling error that arises in the parallelogram suspension so that the position of the microtool more faithfully corresponds to the micrometer settings. Being compact, the micromanipulator can be mounted on a microscope stage to eliminate the microscope's resonance as a source of vibration. This feature also reduces the cantilevering of the microtool that 1) is a source of parasitic vibrations and 2) limits the load bearing in larger devices which can only be placed alongside the microscope. The device has a good dynamic response, and one design suits both right- and left-handed use. PMID:1951677

  14. Statistical mechanics of the Huxley-Simmons model

    NASA Astrophysics Data System (ADS)

    Caruel, M.; Truskinovsky, L.

    2016-06-01

    The chemomechanical model of Huxley and Simmons (HS) [A. F. Huxley and R. M. Simmons, Nature 233, 533 (1971), 10.1038/233533a0] provides a paradigmatic description of mechanically induced collective conformational changes relevant in a variety of biological contexts, from muscles power stroke and hair cell gating to integrin binding and hairpin unzipping. We develop a statistical mechanical perspective on the HS model by exploiting a formal analogy with a paramagnetic Ising model. We first study the equilibrium HS model with a finite number of elements and compute explicitly its mechanical and thermal properties. To model kinetics, we derive a master equation and solve it for several loading protocols. The developed formalism is applicable to a broad range of allosteric systems with mean-field interactions.

  15. EXPONENTIAL TIME DIFFERENCING FOR HODGKIN–HUXLEY-LIKE ODES

    PubMed Central

    Börgers, Christoph; Nectow, Alexander R.

    2013-01-01

    Several authors have proposed the use of exponential time differencing (ETD) for Hodgkin–Huxley-like partial and ordinary differential equations (PDEs and ODEs). For Hodgkin–Huxley-like PDEs, ETD is attractive because it can deal effectively with the stiffness issues that diffusion gives rise to. However, large neuronal networks are often simulated assuming “space-clamped” neurons, i.e., using the Hodgkin–Huxley ODEs, in which there are no diffusion terms. Our goal is to clarify whether ETD is a good idea even in that case. We present a numerical comparison of first- and second-order ETD with standard explicit time-stepping schemes (Euler’s method, the midpoint method, and the classical fourth-order Runge–Kutta method). We find that in the standard schemes, the stable computation of the very rapid rising phase of the action potential often forces time steps of a small fraction of a millisecond. This can result in an expensive calculation yielding greater overall accuracy than needed. Although it is tempting at first to try to address this issue with adaptive or fully implicit time-stepping, we argue that neither is effective here. The main advantage of ETD for Hodgkin–Huxley-like systems of ODEs is that it allows underresolution of the rising phase of the action potential without causing instability, using time steps on the order of one millisecond. When high quantitative accuracy is not necessary and perhaps, because of modeling inaccuracies, not even useful, ETD allows much faster simulations than standard explicit time-stepping schemes. The second-order ETD scheme is found to be substantially more accurate than the first-order one even for large values of Δt. PMID:24058276

  16. EXPONENTIAL TIME DIFFERENCING FOR HODGKIN-HUXLEY-LIKE ODES.

    PubMed

    Börgers, Christoph; Nectow, Alexander R

    2013-01-01

    Several authors have proposed the use of exponential time differencing (ETD) for Hodgkin-Huxley-like partial and ordinary differential equations (PDEs and ODEs). For Hodgkin-Huxley-like PDEs, ETD is attractive because it can deal effectively with the stiffness issues that diffusion gives rise to. However, large neuronal networks are often simulated assuming "space-clamped" neurons, i.e., using the Hodgkin-Huxley ODEs, in which there are no diffusion terms. Our goal is to clarify whether ETD is a good idea even in that case. We present a numerical comparison of first- and second-order ETD with standard explicit time-stepping schemes (Euler's method, the midpoint method, and the classical fourth-order Runge-Kutta method). We find that in the standard schemes, the stable computation of the very rapid rising phase of the action potential often forces time steps of a small fraction of a millisecond. This can result in an expensive calculation yielding greater overall accuracy than needed. Although it is tempting at first to try to address this issue with adaptive or fully implicit time-stepping, we argue that neither is effective here. The main advantage of ETD for Hodgkin-Huxley-like systems of ODEs is that it allows underresolution of the rising phase of the action potential without causing instability, using time steps on the order of one millisecond. When high quantitative accuracy is not necessary and perhaps, because of modeling inaccuracies, not even useful, ETD allows much faster simulations than standard explicit time-stepping schemes. The second-order ETD scheme is found to be substantially more accurate than the first-order one even for large values of Δt. PMID:24058276

  17. Hippocampus minor, calcar avis, and the Huxley-Owen debate.

    PubMed

    Owen, Christopher M; Howard, Allyson; Binder, Devin K

    2009-12-01

    On the bicentennial of Darwin's birth, we describe the origin of the calcar avis and summarize the debate around this structure, which played a central role in the evolution debate in the mid-19th century. We performed a comprehensive review of relevant neuroanatomic literature, bibliographic sources, and 19th century primary sources. Once known as the hippocampus minor, the structure now known as the calcar avis is an involution of the ventricular wall produced by the calcarine fissure. A heated debate raged between 2 prominent scientific theorists, Sir Richard Owen and Thomas Henry Huxley, over the presence of the hippocampus minor in apes versus humans. Owen put forward the lack of an identifiable hippocampus minor in humans as part of an attempt to debunk evolution. A bitter personal and academic rivalry ensued, as Huxley conducted his own dissections to refute Owen's claims. Huxley ultimately dismantled Owen's premises, securing the epithet "Darwin's bulldog" for his defense of the theory of evolution. Thus, this relatively obscure neuroanatomic landmark served as a pivotal point of contention in the most popularized and acrimonious evolutionary debate of the 19th century. PMID:19934969

  18. What would T. H. Huxley have made of prion diseases?

    PubMed

    Ridley, Rosalind M

    2003-07-01

    T. H. Huxley was "Darwin's bulldog," and took the offensive in championing the cause of evolution against skeptical scientists and outraged theologians. As such, he took part in one of the great "paradigm shifts" of biology, at the end of the nineteenth century. Huxley was a rigorous scientist and wrote important articles on scientific method, as well as publishing extensively on a wide range of subjects in natural history. In the second half of the twentieth century, the "prion hypothesis" was put forward to explain the pathogenesis of a curious group of diseases known as the transmissible spongiform encephalopathies. This also involved a "paradigm shift" because the prion hypothesis postulated that biologically relevant information could be enciphered in protein conformation (rather than encoded in nucleic acid base sequences), and could be transmitted from one molecule to another, thereby causing infectious disease. This article examines a few of Huxley's remarks to speculate on how he might have responded to the scientific debate about prion disease had he lived a century later. PMID:12777692

  19. Analytical solutions of the Frankenhaeuser-Huxley equations I: minimal model for backpropagation of action potentials in sparsely excitable dendrites.

    PubMed

    Poznanski, Roman R

    2004-09-01

    Hodgkin and Huxley's ionic theory of the nerve impulse embodies principles, applicable also to the impulses in vertebrate nerve fibers, as demonstrated by Bernhard Frankenhaeuser and Andrew Huxley 40 years ago. Frankenhaeuser and Huxley reformulated the classical Hodgkin-Huxley equations, in terms of electrodiffusion theory, and computed action potentials specifically for saltatory conduction in myelinated axons. In this paper, we obtain analytical solutions to the most difficult nonlinear partial differential equations in classical neurophysiology. We solve analytically the Frankenhaeuser-Huxley equations pertaining to a model of sparsely excitable, nonlinear dendrites with clusters of transiently activating, TTX-sensitive Na(+) channels, discretely distributed as point sources of inward current along a continuous (non-segmented) leaky cable structure. Each cluster or hot-spot, corresponding to a mesoscopic level description of Na(+) ion channels, includes known cumulative inactivation kinetics observed at the microscopic level. In such a third-order system, the 'recovery' variable is an electrogenic sodium-pump imbedded in the passive membrane, and the system is stabilized by the presence of a large leak conductance mediated by a composite number of ligand-gated channels permeable to monovalent cations Na(+) and K(+). In order to reproduce antidromic propagation and attenuation of action potentials, a nonlinear integral equation must be solved (in the presence of suprathreshold input, and a constant-field equation of electrodiffusion at each hot-spot with membrane gates controlling the flow of current). A perturbative expansion of the non-dimensional membrane potential (Phi) is used to obtain time-dependent analytical solutions, involving a voltage-dependent Na(+) activation (micro) and a state-dependent inactivation (eta) gating variables. It is shown that action potentials attenuate in amplitude in accordance with experimental findings, and that the spatial

  20. Correspondence: A Medium Rediscovered.

    ERIC Educational Resources Information Center

    Dilworth, Collett B., Jr.; Wilde, Pat

    Two English teachers, one in North Carolina and one in Missouri, structured a correspondence project for their senior English classes so that 60 students at each school exchanged personal letters once each week during the semester. The students responded to the project with an interest and drive that overshadowed their interest in the normal…

  1. Memristor, Hodgkin-Huxley, and Edge of Chaos

    NASA Astrophysics Data System (ADS)

    Chua, Leon

    2013-09-01

    From a pedagogical point of view, the memristor is defined in this tutorial as any 2-terminal device obeying a state-dependent Ohm’s law. This tutorial also shows that from an experimental point of view, the memristor can be defined as any 2-terminal device that exhibits the fingerprints of ‘pinched’ hysteresis loops in the v-i plane. It also shows that memristors endowed with a continuum of equilibrium states can be used as non-volatile analog memories. This tutorial shows that memristors span a much broader vista of complex phenomena and potential applications in many fields, including neurobiology. In particular, this tutorial presents toy memristors that can mimic the classic habituation and LTP learning phenomena. It also shows that sodium and potassium ion-channel memristors are the key to generating the action potential in the Hodgkin-Huxley equations, and that they are the key to resolving several unresolved anomalies associated with the Hodgkin-Huxley equations. This tutorial ends with an amazing new result derived from the new principle of local activity, which uncovers a minuscule life-enabling ‘Goldilocks zone’, dubbed the edge of chaos, where complex phenomena, including creativity and intelligence, may emerge. From an information processing perspective, this tutorial shows that synapses are locally-passive memristors, and that neurons are made of locally-active memristors.

  2. Memristor, Hodgkin-Huxley, and edge of chaos.

    PubMed

    Chua, Leon

    2013-09-27

    From a pedagogical point of view, the memristor is defined in this tutorial as any 2-terminal device obeying a state-dependent Ohm's law. This tutorial also shows that from an experimental point of view, the memristor can be defined as any 2-terminal device that exhibits the fingerprints of 'pinched' hysteresis loops in the v-i plane. It also shows that memristors endowed with a continuum of equilibrium states can be used as non-volatile analog memories. This tutorial shows that memristors span a much broader vista of complex phenomena and potential applications in many fields, including neurobiology. In particular, this tutorial presents toy memristors that can mimic the classic habituation and LTP learning phenomena. It also shows that sodium and potassium ion-channel memristors are the key to generating the action potential in the Hodgkin-Huxley equations, and that they are the key to resolving several unresolved anomalies associated with the Hodgkin-Huxley equations. This tutorial ends with an amazing new result derived from the new principle of local activity, which uncovers a minuscule life-enabling 'Goldilocks zone', dubbed the edge of chaos, where complex phenomena, including creativity and intelligence, may emerge. From an information processing perspective, this tutorial shows that synapses are locally-passive memristors, and that neurons are made of locally-active memristors. PMID:23999613

  3. A Stimulus Sampling Theory of Letter Identity and Order

    ERIC Educational Resources Information Center

    Norris, Dennis; Kinoshita, Sachiko; van Casteren, Maarten

    2010-01-01

    Early on during word recognition, letter positions are not accurately coded. Evidence for this comes from transposed-letter (TL) priming effects, in which letter strings generated by transposing two adjacent letters (e.g., "jugde") produce large priming effects, more than primes with the letters replaced in the corresponding position (e.g.,…

  4. What would Thomas Henry huxley have made of prion diseases?

    PubMed

    Ridley, R M

    2001-01-01

    "Science is nothing but trained and organized common sense, differing from the latter only as a veteran may differ from a raw recruit."(a) Prion disease is a disease of the second half of the twentieth century, but the scientific method that has elucidated this fascinating group of diseases is much older. As an illustration of this, this chapter considers the way in which a nineteenth century scientist might have reacted to the challenge that prion disease has presented. T. H. Huxley (1825-1895) was an ardent naturalist, who traveled around the world collecting specimens, and who peered down the microscope (1). He amassed vast amounts of data, and could work prodigiously hard. His approach to science can be judged from some of things that he said. He was a confrontational character, and would undoubtedly have joined in the arguments that led to the concept of prion disease, if he had lived a century later. PMID:21374495

  5. Hodgkin–Huxley revisited: reparametrization and identifiability analysis of the classic action potential model with approximate Bayesian methods

    PubMed Central

    Daly, Aidan C.; Holmes, Chris

    2015-01-01

    As cardiac cell models become increasingly complex, a correspondingly complex ‘genealogy’ of inherited parameter values has also emerged. The result has been the loss of a direct link between model parameters and experimental data, limiting both reproducibility and the ability to re-fit to new data. We examine the ability of approximate Bayesian computation (ABC) to infer parameter distributions in the seminal action potential model of Hodgkin and Huxley, for which an immediate and documented connection to experimental results exists. The ability of ABC to produce tight posteriors around the reported values for the gating rates of sodium and potassium ion channels validates the precision of this early work, while the highly variable posteriors around certain voltage dependency parameters suggests that voltage clamp experiments alone are insufficient to constrain the full model. Despite this, Hodgkin and Huxley's estimates are shown to be competitive with those produced by ABC, and the variable behaviour of posterior parametrized models under complex voltage protocols suggests that with additional data the model could be fully constrained. This work will provide the starting point for a full identifiability analysis of commonly used cardiac models, as well as a template for informative, data-driven parametrization of newly proposed models. PMID:27019736

  6. Hodgkin-Huxley revisited: reparametrization and identifiability analysis of the classic action potential model with approximate Bayesian methods.

    PubMed

    Daly, Aidan C; Gavaghan, David J; Holmes, Chris; Cooper, Jonathan

    2015-12-01

    As cardiac cell models become increasingly complex, a correspondingly complex 'genealogy' of inherited parameter values has also emerged. The result has been the loss of a direct link between model parameters and experimental data, limiting both reproducibility and the ability to re-fit to new data. We examine the ability of approximate Bayesian computation (ABC) to infer parameter distributions in the seminal action potential model of Hodgkin and Huxley, for which an immediate and documented connection to experimental results exists. The ability of ABC to produce tight posteriors around the reported values for the gating rates of sodium and potassium ion channels validates the precision of this early work, while the highly variable posteriors around certain voltage dependency parameters suggests that voltage clamp experiments alone are insufficient to constrain the full model. Despite this, Hodgkin and Huxley's estimates are shown to be competitive with those produced by ABC, and the variable behaviour of posterior parametrized models under complex voltage protocols suggests that with additional data the model could be fully constrained. This work will provide the starting point for a full identifiability analysis of commonly used cardiac models, as well as a template for informative, data-driven parametrization of newly proposed models. PMID:27019736

  7. Letter Imperfect

    ERIC Educational Resources Information Center

    Kramer, Stephen

    2003-01-01

    In this essay, the author, a 5th-grade teacher, questions how well a standardized test can measure his students. This article presents a letter he wrote for the Washington state science test scorer regarding his students' test scores. He shares stories about some of the students in his class. He points out that tests can turn out to be more like…

  8. The ISI distribution of the stochastic Hodgkin-Huxley neuron

    PubMed Central

    Rowat, Peter F.; Greenwood, Priscilla E.

    2014-01-01

    The simulation of ion-channel noise has an important role in computational neuroscience. In recent years several approximate methods of carrying out this simulation have been published, based on stochastic differential equations, and all giving slightly different results. The obvious, and essential, question is: which method is the most accurate and which is most computationally efficient? Here we make a contribution to the answer. We compare interspike interval histograms from simulated data using four different approximate stochastic differential equation (SDE) models of the stochastic Hodgkin-Huxley neuron, as well as the exact Markov chain model simulated by the Gillespie algorithm. One of the recent SDE models is the same as the Kurtz approximation first published in 1978. All the models considered give similar ISI histograms over a wide range of deterministic and stochastic input. Three features of these histograms are an initial peak, followed by one or more bumps, and then an exponential tail. We explore how these features depend on deterministic input and on level of channel noise, and explain the results using the stochastic dynamics of the model. We conclude with a rough ranking of the four SDE models with respect to the similarity of their ISI histograms to the histogram of the exact Markov chain model. PMID:25339894

  9. Correspondence analysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Correspondence analysis is a powerful exploratory multivariate technique for categorical variables with many levels. It is a data analysis tool that characterizes associations between levels of 2 or more categorical variables using graphical representations of the information in a contingency table...

  10. Principal Dynamic Mode Analysis of the Hodgkin–Huxley Equations

    PubMed Central

    Eikenberry, Steffen E.; Marmarelis, Vasilis Z.

    2015-01-01

    We develop an autoregressive model framework based on the concept of Principal Dynamic Modes (PDMs) for the process of action potential (AP) generation in the excitable neuronal membrane described by the Hodgkin–Huxley (H–H) equations. The model's exogenous input is injected current, and whenever the membrane potential output exceeds a specified threshold, it is fed back as a second input. The PDMs are estimated from the previously developed Nonlinear Autoregressive Volterra (NARV) model, and represent an efficient functional basis for Volterra kernel expansion. The PDM-based model admits a modular representation, consisting of the forward and feedback PDM bases as linear filterbanks for the exogenous and autoregressive inputs, respectively, whose outputs are then fed to a static nonlinearity composed of polynomials operating on the PDM outputs and cross-terms of pair-products of PDM outputs. A two-step procedure for model reduction is performed: first, influential subsets of the forward and feedback PDM bases are identified and selected as the reduced PDM bases. Second, the terms of the static nonlinearity are pruned. The first step reduces model complexity from a total of 65 coefficients to 27, while the second further reduces the model coefficients to only eight. It is demonstrated that the performance cost of model reduction in terms of out-of-sample prediction accuracy is minimal. Unlike the full model, the eight coefficient pruned model can be easily visualized to reveal the essential system components, and thus the data-derived PDM model can yield insight into the underlying system structure and function. PMID:25630480

  11. Stimulus-dependent refractoriness in the Frankenhaeuser-Huxley model.

    PubMed

    Morse, R P; Allingham, D; Stocks, N G

    2015-10-01

    Phenomenological neural models, such as the leaky integrate-and-fire model, normally have a fixed refractory time-course that is independent of the stimulus. The recovery of threshold following an action potential is typically based on physiological experiments that use a two-pulse paradigm in which the first pulse is suprathreshold and causes excitation and the second pulse is used to determine the threshold at various intervals following the first. In such experiments, the nerve is completely unstimulated between the two pulses. This contrasts the receptor stimuli in normal physiological systems and the electrical stimuli used by cochlear implants and other neural prostheses. A numerical study of the Frankenhaeuser-Huxley conductance-based model of nerve fibre was therefore undertaken to investigate the effect of stimulation on refractoriness. We found that the application of a depolarizing stimulus during the later part of what is classically regarded as the absolute refractory period could effectively prolong the absolute refractory period, while leaving the refractory time-constants and other refractory parameters largely unaffected. Indeed, long depolarizing pulses, which would have been suprathreshold if presented to a resting nerve fibre, appeared to block excitation indefinitely. Stimulation during what is classically regarded as the absolute refractory period can therefore greatly affect the temporal response of a nerve. We conclude that the classical definition of absolute refractory period should be refined to include only the initial period following an action potential when an ongoing stimulus would not affect threshold; this period was found to be about half as long as the classical absolute refractory period. We further conclude that the stimulus-dependent nature of the relative refractory period must be considered when developing a phenomenological nerve model for complex stimuli. PMID:26187096

  12. Principal dynamic mode analysis of the Hodgkin-Huxley equations.

    PubMed

    Eikenberry, Steffen E; Marmarelis, Vasilis Z

    2015-03-01

    We develop an autoregressive model framework based on the concept of Principal Dynamic Modes (PDMs) for the process of action potential (AP) generation in the excitable neuronal membrane described by the Hodgkin-Huxley (H-H) equations. The model's exogenous input is injected current, and whenever the membrane potential output exceeds a specified threshold, it is fed back as a second input. The PDMs are estimated from the previously developed Nonlinear Autoregressive Volterra (NARV) model, and represent an efficient functional basis for Volterra kernel expansion. The PDM-based model admits a modular representation, consisting of the forward and feedback PDM bases as linear filterbanks for the exogenous and autoregressive inputs, respectively, whose outputs are then fed to a static nonlinearity composed of polynomials operating on the PDM outputs and cross-terms of pair-products of PDM outputs. A two-step procedure for model reduction is performed: first, influential subsets of the forward and feedback PDM bases are identified and selected as the reduced PDM bases. Second, the terms of the static nonlinearity are pruned. The first step reduces model complexity from a total of 65 coefficients to 27, while the second further reduces the model coefficients to only eight. It is demonstrated that the performance cost of model reduction in terms of out-of-sample prediction accuracy is minimal. Unlike the full model, the eight coefficient pruned model can be easily visualized to reveal the essential system components, and thus the data-derived PDM model can yield insight into the underlying system structure and function. PMID:25630480

  13. T.H. Huxley's criticism of German cell theory: an epigenetic and physiological interpretation of cell structure.

    PubMed

    Richmond, M L

    2000-01-01

    In 1853, the young Thomas Henry Huxley published a long review of German cell theory in which he roundly criticized the basic tenets of the Schleiden-Schwann model of the cell. Although historians of cytology have dismissed Huxley's criticism as based on an erroneous interpretation of cell physiology, the review is better understood as a contribution to embryology. "The Cell-theory" presents Huxley's "epigenetic" interpretation of histological organization emerging from changes in the protoplasm to replace the "preformationist" cell theory of Schleiden and Schwann (as modified by Albert von Kolliker), which posited the nucleus as the seat of organic vitality. Huxley's views influenced a number of British biologists, who continued to oppose German cell theory well into the twentieth century. Yet Huxley was pivotal in introducing the new German program of "scientific zoology" to Britain in the early 1850s, championing its empiricist methodology as a means to enact broad disciplinary and institutional reforms in British natural history. PMID:11640226

  14. The "History" of Victorian Scientific Naturalism: Huxley, Spencer and the "End" of natural history.

    PubMed

    Lightman, Bernard

    2016-08-01

    As part of their defence of evolutionary theory, T. H. Huxley and Herbert Spencer argued that natural history was no longer a legitimate scientific discipline. They outlined a secularized concept of life from biology to argue for the validity of naturalism. Despite their support for naturalism, they offered two different responses to the decline of natural history. Whereas Huxley emphasized the creation of a biological discipline, and all that that entailed, Spencer was more concerned with constructing an entire intellectual system based on the idea of evolution. In effect, Spencer wanted to create a new scientific worldview based on evolutionary theory. This had consequences for their understanding of human history, especially of how science had evolved through the ages. It affected their conceptions of human agency, contingency, and directionality in history. Examining Huxley's and Spencer's responses to the "end" of natural history reveals some of the deep divisions within scientific naturalism and the inherent problems of naturalism in general. Whereas Huxley chose to separate the natural and the historical, Spencer opted to fuse them into a single system. PMID:26751794

  15. Tunicates: exploring the sea shores and roaming the open ocean. A tribute to Thomas Huxley.

    PubMed

    Lemaire, Patrick; Piette, Jacques

    2015-06-01

    This review is a tribute to the remarkable contributions of Thomas Huxley to the biology of tunicates, the likely sister group of vertebrates. In 1851, the great biologist and philosopher published two landmark papers on pelagic tunicates in the Philosophical Transactions of the Royal Society. They were dedicated to the description of the adult anatomy and life cycle of thaliaceans and appendicularians, the pelagic relatives of ascidians. In the first part of this review, we discuss the novel anatomical observations and evolutionary hypotheses made by Huxley, which would have a lasting influence on tunicate biology. We also briefly comment on the more philosophical reflections of Huxley on individuality. In the second part, we stress the originality and relevance of past and future studies of tunicates in the resolution of major biological issues. In particular, we focus on the complex relationship between genotype and phenotype and the phenomenon of developmental system drift. We propose that more than 150 years after Huxley's papers, tunicate embryos are still worth studying in their own right, independently of their evolutionary proximity to vertebrates, as they provide original and crucial insights into the process of animal evolution. Tunicates are still at the forefront of biological research. PMID:26085517

  16. Tunicates: exploring the sea shores and roaming the open ocean. A tribute to Thomas Huxley

    PubMed Central

    Lemaire, Patrick; Piette, Jacques

    2015-01-01

    This review is a tribute to the remarkable contributions of Thomas Huxley to the biology of tunicates, the likely sister group of vertebrates. In 1851, the great biologist and philosopher published two landmark papers on pelagic tunicates in the Philosophical Transactions of the Royal Society. They were dedicated to the description of the adult anatomy and life cycle of thaliaceans and appendicularians, the pelagic relatives of ascidians. In the first part of this review, we discuss the novel anatomical observations and evolutionary hypotheses made by Huxley, which would have a lasting influence on tunicate biology. We also briefly comment on the more philosophical reflections of Huxley on individuality. In the second part, we stress the originality and relevance of past and future studies of tunicates in the resolution of major biological issues. In particular, we focus on the complex relationship between genotype and phenotype and the phenomenon of developmental system drift. We propose that more than 150 years after Huxley's papers, tunicate embryos are still worth studying in their own right, independently of their evolutionary proximity to vertebrates, as they provide original and crucial insights into the process of animal evolution. Tunicates are still at the forefront of biological research. PMID:26085517

  17. Letter Writing Seminar for Word Processing Principals

    ERIC Educational Resources Information Center

    Wunsch, Alan P.

    1978-01-01

    A business letter writing seminar was developed by the Center for Executive Development at Arizona State University at the request of the American Express Company's credit card division in Phoenix. Sessions were held on company premises and included basic correspondence and writing techniques for company production form letters, pattern…

  18. The What and Where of Adding Channel Noise to the Hodgkin-Huxley Equations

    PubMed Central

    Goldwyn, Joshua H.; Shea-Brown, Eric

    2011-01-01

    Conductance-based equations for electrically active cells form one of the most widely studied mathematical frameworks in computational biology. This framework, as expressed through a set of differential equations by Hodgkin and Huxley, synthesizes the impact of ionic currents on a cell's voltage—and the highly nonlinear impact of that voltage back on the currents themselves—into the rapid push and pull of the action potential. Later studies confirmed that these cellular dynamics are orchestrated by individual ion channels, whose conformational changes regulate the conductance of each ionic current. Thus, kinetic equations familiar from physical chemistry are the natural setting for describing conductances; for small-to-moderate numbers of channels, these will predict fluctuations in conductances and stochasticity in the resulting action potentials. At first glance, the kinetic equations provide a far more complex (and higher-dimensional) description than the original Hodgkin-Huxley equations or their counterparts. This has prompted more than a decade of efforts to capture channel fluctuations with noise terms added to the equations of Hodgkin-Huxley type. Many of these approaches, while intuitively appealing, produce quantitative errors when compared to kinetic equations; others, as only very recently demonstrated, are both accurate and relatively simple. We review what works, what doesn't, and why, seeking to build a bridge to well-established results for the deterministic equations of Hodgkin-Huxley type as well as to more modern models of ion channel dynamics. As such, we hope that this review will speed emerging studies of how channel noise modulates electrophysiological dynamics and function. We supply user-friendly MATLAB simulation code of these stochastic versions of the Hodgkin-Huxley equations on the ModelDB website (accession number 138950) and http://www.amath.washington.edu/~etsb/tutorials.html. PMID:22125479

  19. Einstein/Roosevelt Letters: A Unit.

    ERIC Educational Resources Information Center

    Bodle, Walter S.

    1985-01-01

    The letters in this unit of study intended for secondary students are facsimile reproductions of the correspondence between Albert Einstein and President Roosevelt on the possibility of constructing an atomic bomb. Classroom activities are also suggested. (RM)

  20. Controlling the onset of Hopf bifurcation in the Hodgkin-Huxley model

    NASA Astrophysics Data System (ADS)

    Xie, Yong; Chen, Luonan; Kang, Yan Mei; Aihara, Kazuyuki

    2008-06-01

    It is a challenging problem to establish safe and simple therapeutic methods for various complicated diseases of the nervous system, particularly dynamical diseases such as epilepsy, Alzheimer’s disease, and Parkinson’s disease. From the viewpoint of nonlinear dynamical systems, a dynamical disease can be considered to be caused by a bifurcation induced by a change in the values of one or more regulating parameter. Therefore, the theory of bifurcation control may have potential applications in the diagnosis and therapy of dynamical diseases. In this study, we employ a washout filter-aided dynamic feedback controller to control the onset of Hopf bifurcation in the Hodgkin-Huxley (HH) model. Specifically, by the control scheme, we can move the Hopf bifurcation to a desired point irrespective of whether the corresponding steady state is stable or unstable. In other words, we are able to advance or delay the Hopf bifurcation, so as to prevent it from occurring in a certain range of the externally applied current. Moreover, we can control the criticality of the bifurcation and regulate the oscillation amplitude of the bifurcated limit cycle. In the controller, there are only two terms: the linear term and the nonlinear cubic term. We show that while the former determines the location of the Hopf bifurcation, the latter regulates the criticality of the Hopf bifurcation. According to the conditions of the occurrence of Hopf bifurcation and the bifurcation stability coefficient, we can analytically deduce the linear term and the nonlinear cubic term, respectively. In addition, we also show that mixed-mode oscillations (MMOs), featuring slow action potential generation, which are frequently observed in both experiments and models of chemical and biological systems, appear in the controlled HH model. It is well known that slow firing rates in single neuron models could be achieved only by type-I neurons. However, the controlled HH model is still classified as a type

  1. Neurotic love letters.

    PubMed

    Tierra, Tatiana De La

    2004-01-01

    Abstract The intensity of falling in love is expressed through sexual longing and is focused on pleasures of the body. Fresh fruits and vegetables and other elements of nature-wind, birds, foliage-form part of the setting of seduction. Being in love with another woman makes the entire world beautiful. But the lesbian paradise is eventually eclipsed by bitter realities that intrude upon the relationship-the ever-present ex-lover (still in the picture), family ties (with homophobic overtones), business connections (that imperil lesbian economic independence), and issues of commitment and honesty that eventually lead to betrayal and a bittersweet breakup. Based on correspondence originally written in Spanish, "Neurotic Love Letters" is a testament to an unfortunate fact-that all the love and lust between two women cannot always conquer dubious circumstances and harsh realities unique to lesbian relationships. PMID:24821038

  2. How the Hodgkin–Huxley equations inspired the Cardiac Physiome Project

    PubMed Central

    Noble, Denis; Garny, Alan; Noble, Penelope J

    2012-01-01

    Early modelling of cardiac cells (1960–1980) was based on extensions of the Hodgkin–Huxley nerve axon equations with additional channels incorporated, but after 1980 it became clear that processes other than ion channel gating were also critical in generating electrical activity. This article reviews the development of models representing almost all cell types in the heart, many different species, and the software tools that have been created to facilitate the cardiac Physiome Project. PMID:22473779

  3. On letter frequency effects.

    PubMed

    New, Boris; Grainger, Jonathan

    2011-10-01

    In four experiments we examined whether the frequency of occurrence of letters affects performance in the alphabetic decision task (speeded letter vs. pseudo-letter classification). Experiments 1A and 1B tested isolated letters and pseudo-letters presented at fixation, and Experiments 2A and 2B tested the same stimuli inserted at the 1st, 3rd, or 5th position in a string of Xs. Significant negative correlations between letter frequency and response times to letter targets were found in all experiments. The correlations were found to be stronger for token frequency counts compared with both type frequency and frequency rank, stronger for frequency counts based on a book corpus compared with film subtitles, and stronger for measures counting occurrences as the first letter of words compared with inner letters and final letters. Correlations for letters presented in strings of Xs were found to depend on letter case and position-in-string. The results are in favor of models of word recognition that implement case-specific and position-specific letter representations. PMID:21855049

  4. Computational and Electronic Analog Implementation of the Hodgkin-Huxley Model of Action Potentials in Neurons

    NASA Astrophysics Data System (ADS)

    Smith, Peter; Link, Justin

    2012-02-01

    Alan Loyd Hodgkin and Andrew Huxley's mathematical model of action potential initiation and propagation in neurons is one of the greatest hallmarks of biophysics. Two techniques for implementing the Hodgkin-Huxley model were explored: computational and electronic analog. Computational modeling was done using NEURON 7.1. NEURON is a free, robust, and relatively user friendly simulation environment that enables quantitatively accurate computational modeling of neurons and neural networks. An analog electronic circuit was built using field-effect transistors (FETs) to simulate the non-linear, voltage-dependent (sodium and potassium) conductances that are responsible for membrane excitability. While the electronic analog qualitatively reproduces many of the key features of the action potential including overall shape, inactivation period, and propagation, it was difficult to quantitatively reproduce the Hodgkin-Huxley model. In addition, while the relative cost to build circuits equivalent to small membrane patches is minimal (˜50), implementation of larger cells or networks would prove uneconomical. Still, both techniques are viable avenues toward introducing interdisciplinary research into either a computational or electronics lab setting at the undergraduate level.

  5. Past as Prediction: Newcomb, Huxley, The Eclipse of Thales, and The Power of Science

    NASA Astrophysics Data System (ADS)

    Stanley, Matthew

    2009-12-01

    The ancient eclipse of Thales was an important, if peculiar, focus of scientific attention in the 19th century. Victorian-era astronomers first used it as data with which to calibrate their lunar theories, but its status became strangely malleable as the century progressed. The American astronomer Simon Newcomb re-examined the eclipse and rejected it as the basis for lunar theory. But strangely, it was the unprecedented accuracy of Newcomb's calculations that led the British biologist T.H. Huxley to declare the eclipse to be the quintessential example of the power of science. Huxley argued that astronomy's ability to create "retrospective prophecy” showed how scientific reasoning was superior to religion (and incidentally, helped support Darwin's theories). Both Newcomb and Huxley declared that prediction (of past and future) was what gave science its persuasive power. The eclipse of Thales's strange journey through Victorian astronomy reveals how these two influential scientists made the case for the social and cultural authority of science.

  6. Thomas Henry Huxley (1825-1895) puts us in our place.

    PubMed

    Weiss, Kenneth M

    2004-05-15

    Thomas Huxley was one of the 19th century's most active defenders of Darwin's idea that life has evolved through natural processes. An anatomist and paleontologist, he extended his energies to science and education policy, the democratization of science, and the broad societal implications of evolution. Since his time the fossil record has greatly improved and the genetic 'revolution' has occurred, deepening our understanding of primate and human evolution in ways that would please Huxley: improved systematics relies heavily on genetic data, and molecular technologies are opening our understanding of the genetic basis of complex traits of traditional anthropological interest-but in ways that are thoroughly dependent on the fact of evolution. A more unified biological synthesis is forming that unites genes, developmental process, structure, and inheritance. But the tempo and mode of evolution remain unresolved. Huxley was one of many who have had trouble accepting Darwin's gradual natural selection as the central evolutionary mechanism, and views spanning the antipodes of gradualism and saltation find advocates even in our genetic era. PMID:15211682

  7. Exploring the Role of Mechanotransduction Activation and Adaptation Kinetics in Hair Cell Filtering Using a Hodgkin-Huxley Approach

    NASA Astrophysics Data System (ADS)

    Wells, Gregg B.; Ricci, Anthony J.

    2011-11-01

    In the auditory system, mechanotransduction occurs in the hair cell sensory hair bundle and is the first major step in the translation of mechanical energy into electrical. Tonotopic variations in the activation kinetics of this process are posited to provide a low pass filter to the input. An adaptation process, also associated with mechanotransduction, is postulated to provide a high pass filter to the input in a tonotopic manner. Together a bandpass filter is created at the hair cell input. Corresponding mechanical components to both activation and adaptation are also suggested to be involved in generating cochlear amplification. A paradox to this story is that hair cells where the mechanotransduction properties are most robust possess an intrinsic electrical resonance mechanism proposed to account for all required tuning and amplification. A simple Hodgkin-Huxley type model is presented to attempt to determine the role of the activation and adaptation kinetics in further tuning hair cells that exhibit electrical resonance. Results further support that steady state mechanotransduction properties are critical for setting the resting potential of the hair cell while the kinetics of activation and adaptation are important for sharpening tuning around the characteristic frequency of the hair cell.

  8. Dynamics from seconds to hours in Hodgkin-Huxley model with time-dependent ion concentrations and buffer reservoirs.

    PubMed

    Hübel, Niklas; Dahlem, Markus A

    2014-12-01

    The classical Hodgkin-Huxley (HH) model neglects the time-dependence of ion concentrations in spiking dynamics. The dynamics is therefore limited to a time scale of milliseconds, which is determined by the membrane capacitance multiplied by the resistance of the ion channels, and by the gating time constants. We study slow dynamics in an extended HH framework that includes time-dependent ion concentrations, pumps, and buffers. Fluxes across the neuronal membrane change intra- and extracellular ion concentrations, whereby the latter can also change through contact to reservoirs in the surroundings. Ion gain and loss of the system is identified as a bifurcation parameter whose essential importance was not realized in earlier studies. Our systematic study of the bifurcation structure and thus the phase space structure helps to understand activation and inhibition of a new excitability in ion homeostasis which emerges in such extended models. Also modulatory mechanisms that regulate the spiking rate can be explained by bifurcations. The dynamics on three distinct slow times scales is determined by the cell volume-to-surface-area ratio and the membrane permeability (seconds), the buffer time constants (tens of seconds), and the slower backward buffering (minutes to hours). The modulatory dynamics and the newly emerging excitable dynamics corresponds to pathological conditions observed in epileptiform burst activity, and spreading depression in migraine aura and stroke, respectively. PMID:25474648

  9. Writing Letters of Recommendation

    ERIC Educational Resources Information Center

    Withers, Jennie

    2009-01-01

    The purpose of this essay is to instruct teachers how to write a letter of recommendation for their students. It includes when to say no, what the student needs to provide the teacher and how to write a strong letter. I am a teacher with sixteen years experience and therefore have written many letters for students. This instructional essay will…

  10. All About Letters.

    ERIC Educational Resources Information Center

    Post Office Dept., Washington, DC.

    This booklet, designed to promote the letter writing habit, provides information about writing letters in a variety of situations. It is divided into several short sections with illustrations. Reasons to write letters and postcards are offered by several authors and celebrites including Stevie Wonder, Darryl Stingley, and "Dear Abby." Addresses…

  11. RED-LETTER DAYS

    EPA Science Inventory

    The word "red-letter" is an adjective meaning "of special significance." It's origin is from the practice of marking Christian holy days in red letters on calendars. The "red-letter days" to which I refer occurred while I was a graduate student of ...

  12. Stochastic sensitivity analysis of noise-induced suppression of firing and giant variability of spiking in a Hodgkin-Huxley neuron model.

    PubMed

    Bashkirtseva, Irina; Neiman, Alexander B; Ryashko, Lev

    2015-05-01

    We study the stochastic dynamics of a Hodgkin-Huxley neuron model in a regime of coexistent stable equilibrium and a limit cycle. In this regime, noise may suppress periodic firing by switching the neuron randomly to a quiescent state. We show that at a critical value of the injected current, the mean firing rate depends weakly on noise intensity, while the neuron exhibits giant variability of the interspike intervals and spike count. To reveal the dynamical origin of this noise-induced effect, we develop the stochastic sensitivity analysis and use the Mahalanobis metric for this four-dimensional stochastic dynamical system. We show that the critical point of giant variability corresponds to the matching of the Mahalanobis distances from attractors (stable equilibrium and limit cycle) to a three-dimensional surface separating their basins of attraction. PMID:26066242

  13. Learning to write letters: examination of student and letter factors.

    PubMed

    Puranik, Cynthia S; Petscher, Yaacov; Lonigan, Christopher J

    2014-12-01

    Learning to write the letters of the alphabet is an important part of learning how to write conventionally. In this study, we investigated critical factors in the development of letter-writing skills using exploratory item response models to simultaneously account for variance in responses due to differences between students and between letters. Letter-writing skills were assessed in 415 preschool children aged 3 to 5 years. At the student level, we examined the contribution of letter-name knowledge, letter-sound knowledge, and phonological awareness to letter-writing skills. At the letter level, we examined seven intrinsic and extrinsic factors in understanding how preschool children learn to write alphabet letters: first letter of name, letters in name, letter order, textual frequency, number of strokes, symmetry, and letter type. Results indicated that variation in letter-writing skills was accounted for more by differences between students rather than by differences between letters, with most of the variability accounted for by letter-name knowledge and age. Although significant, the contribution of letter-sound knowledge and phonological awareness was relatively small. Student-level mechanisms underlying the acquisition of letter-writing skills are similar to the mechanisms underlying the learning of letter sounds. However, letter characteristics, which appear to play a major role in the learning of letter names and letter sounds, did not appear to influence learning how to write letters in a substantial way. The exception was if the letter was in the child's name. PMID:25181463

  14. Mud, Blood, and Bullet Holes: Teaching History with War Letters

    ERIC Educational Resources Information Center

    Carroll, Andrew

    2013-01-01

    From handwritten letters of the American Revolution to typed emails from Iraq and Afghanistan, correspondence from U.S. troops offers students deep insight into the specific conflicts and experiences of soldiers. Over 100,000 correspondences have been donated to the Legacy Project, a national initiative launched in 1998 to preserve war letters by…

  15. With Love, Grandma: Letters to Grandchildren.

    ERIC Educational Resources Information Center

    Smith, Carl B.; Ritter, Naomi

    Based on years of experience with intergenerational correspondence at the "Senior Partners Network," this book is designed to help grandparents (and grandchildren) to find the right topics for correspondence, all laid out in clear steps. The book also offers sample letters, cards, and e-mail messages, and provides dozens of themes. The book's goal…

  16. Huxley's Model for Muscle Contraction Revisited: The Importance of Microscopic Reversibility.

    PubMed

    Astumian, R Dean

    2015-01-01

    Andrew Huxley's model for muscle contraction is the first mechanistic description of how an energy-providing chemical reaction, ATP hydrolysis, can be coupled by a molecule (myosin) to do work in the environment in a cyclic process. The model was originally used to fit experimentally obtained force vs velocity curves, and has served as a paradigm for understanding mechanochemical coupling ever since. Despite the remarkable success in fitting kinetic data, Huxley's model is thermodynamically inconsistent in several regards, most notably in its failure to include thermal noise in the description of the mechanical transitions by which motion occurs. This inconsistency has led subsequent workers to incorrect conclusions regarding the importance of mechanical transitions for determining the direction of motion, the efficiency of energy conversion, the ratio of forward to backward steps, and the applied force necessary to stop the motion of chemically driven molecular motors. In this chapter an extension of Huxley's model is described where the principle of microscopic reversibility provides a framework for developing a thermodynamically consistent description of a molecular machine. The results show clearly that mechanical strain and the so-called "power stroke" are irrelevant for determining the directionality and thermodynamic properties of any chemically driven molecular motor. Instead these properties are controlled entirely by the chemical specificity that describes how the relative rates of the ATP hydrolysis reaction depend, by allosteric interactions, on the mechanical state of the molecule. This mechanism has been termed an "information ratchet" in the literature. In contrast to the results for chemical driving, a power stroke can be a key component for the operation of an optically driven motor, the transitions of which do not obey microscopic reversibility. PMID:26122749

  17. Rival Visions: J.J. Rousseau and T.H. Huxley on the Nature (or Nurture) of Inequality and What It Means for Education

    ERIC Educational Resources Information Center

    Currie-Knight, Kevin

    2011-01-01

    Jean-Jacques Rousseau (1712-1778) and Thomas Huxley (1852-1895) had different, but substantial, effects on the history of education. Rousseau's educational theories supplied the intellectual foundation for pedagogical progressivism. Huxley's educational writings helped to enlarge the scope of the British curriculum to include such things as…

  18. The time course of visual influences in letter recognition.

    PubMed

    Madec, Sylvain; Le Goff, Kévin; Riès, Stéphanie K; Legou, Thierry; Rousselet, Guillaume; Courrieu, Pierre; Alario, F-Xavier; Grainger, Jonathan; Rey, Arnaud

    2016-06-01

    This study builds on a specific characteristic of letters of the Roman alphabet-namely, that each letter name is associated with two visual formats, corresponding to their uppercase and lowercase versions. Participants had to read aloud the names of single letters, and event-related potentials (ERPs) for six pairs of visually dissimilar upper- and lowercase letters were recorded. Assuming that the end product of processing is the same for upper- and lowercase letters sharing the same vocal response, ERPs were compared backward, starting from the onset of articulatory responses, and the first significant divergence was observed 120 ms before response onset. Given that naming responses were produced at around 414 ms, on average, these results suggest that letter processing is influenced by visual information until 294 ms after stimulus onset. This therefore provides new empirical evidence regarding the time course and interactive nature of visual letter perception processes. PMID:26742753

  19. The Business Letter.

    ERIC Educational Resources Information Center

    Nederland Independent School District, TX.

    GRADES OR AGES: Grades 9-12. SUBJECT MATTER: Business. ORGANIZATION AND PHYSICAL APPEARANCE: This guide, designed for direct student use, indicates the parts of a business letter, a placement guide, and steps for typing letters. Worksheets and illustrations indicate forms of block and indented styles; open, closed, and mixed punctuation; the…

  20. Metamorphopsia and letter recognition

    PubMed Central

    Wiecek, Emily; Dakin, Steven C.; Bex, Peter

    2014-01-01

    Acuity is the most commonly used measure of visual function, and reductions in acuity are associated with most eye diseases. Metamorphopsia—a perceived distortion of visual space—is another common symptom of visual impairment and is currently assessed qualitatively using Amsler (1953) charts. In order to quantify the impact of metamorphopsia on acuity, we measured the effect of physical spatial distortion on letter recognition. Following earlier work showing that letter recognition is tuned to specific spatial frequency (SF) channels, we hypothesized that the effect of distortion might depend on the spatial scale of visual distortion just as it depends on the spatial scale of masking noise. Six normally sighted observers completed a 26 alternate forced choice (AFC) Sloan letter identification task at five different viewing distances, and the letters underwent different levels of spatial distortion. Distortion was controlled using spatially band-pass filtered noise that spatially remapped pixel locations. Noise was varied over five spatial frequencies and five magnitudes. Performance was modeled with logistic regression and worsened linearly with increasing distortion magnitude and decreasing letter size. We found that retinal SF affects distortion at midrange frequencies and can be explained with the tuning of a basic contrast sensitivity function, while object-centered distortion SF follows a similar pattern of letter object recognition sensitivity and is tuned to approximately three cycles per letter (CPL). The interaction between letter size and distortion makes acuity an unreliable outcome for metamorphopsia assessment. PMID:25453116

  1. Letters from a Suicide

    ERIC Educational Resources Information Center

    Barnes, Donna Holland; Lawal-Solarin, Foluso Williams; Lester, David

    2007-01-01

    There has been no published study on personal letters written before an individual's suicidal death hitherto, although studies have been done using diaries. The purpose of this study was to search for trends in the use of particular linguistic categories in a series of personal letters written before an individual's suicidal death. A linguistic…

  2. Which Children Benefit from Letter Names in Learning Letter Sounds?

    ERIC Educational Resources Information Center

    Treiman, Rebecca; Pennington, Bruce F.; Shriberg, Lawrence D.; Boada, Richard

    2008-01-01

    Typical U.S. children use their knowledge of letters' names to help learn the letters' sounds. They perform better on letter sound tests with letters that have their sounds at the beginnings of their names, such as v, than with letters that have their sounds at the ends of their names, such as m, and letters that do not have their sounds in their…

  3. Teaching Letter Formation.

    ERIC Educational Resources Information Center

    Graham, Steve; Madan, Avi J.

    1981-01-01

    The authors describe a remedial technique for teaching letter formation to students with handwriting difficulties. The approach blends traditional procedures (modeling, physical prompts, tracing, self correction, etc.) with cognitive behavior modification principles. (CL)

  4. IMPLEMENTATION REVIEW LETTERS, 2002

    EPA Science Inventory

    The following letters provide a summary of the Environmental Protection Agencys comments regarding 2002 Implementation Review of nineteen estuary programs in the National Estuary Program. Various strengths within the programs included use of implementation progress and tracking s...

  5. Students as Letter Writers: How Letters Inform Instructors

    ERIC Educational Resources Information Center

    Kirms, Lynn M.

    2004-01-01

    Letters from students, serve to enhance the insight toward students at a personal level while adding a familiar form and friendly voice to the classroom community. The biographical letter and study-skill letter are the two sets of students' letters discussed. It is found that one needs to know one's student better versus the time needed for this…

  6. Launch of Zoological Letters.

    PubMed

    Fukatsu, Takema; Kuratani, Shigeru

    2016-02-01

    A new open-access journal, Zoological Letters, was launched as a sister journal to Zoological Science, in January 2015. The new journal aims at publishing topical papers of high quality from a wide range of basic zoological research fields. This review highlights the notable reviews and research articles that have been published in the first year of Zoological Letters, providing an overview on the current achievements and future directions of the journal. PMID:26853862

  7. Writing effective consultation letters: 12 tips for teachers.

    PubMed

    Keely, Erin; Dojeiji, Suzan; Myers, Kathryn

    2002-11-01

    Written correspondence is the standard mode of communication between healthcare providers. Despite the importance of this skill and increased emphasis on ambulatory care, communication skills and professionalism in training programs, there has been very little written on the teaching and evaluation of consultation letter writing. Consultation letter writing is an essential skill that cannot be learned simply by reading others' letters and should be taught in a formal manner. This article describes the authors' experience in teaching the skill of writing effective consultation letters to residents and describes strategies for evaluating this skill. PMID:12623449

  8. Predicting the past: ancient eclipses and Airy, Newcomb, and Huxley on the authority of science.

    PubMed

    Stanley, Matthew

    2012-06-01

    Greek historical accounts of ancient eclipses were an important, if peculiar, focus of scientific attention in the nineteenth century. Victorian-era astronomers tried to correct the classical histories using scientific methods, then used those histories as data with which to calibrate their lunar theories, then rejected the histories as having any relevance at all. The specific dating of these eclipses--apparently a simple exercise in celestial mechanics--became bound up with tensions between scientific and humanistic approaches to the past as well as with wider social debates over the power and authority of science in general. The major figures discussed here, including G. B. Airy, Simon Newcomb, and T. H. Huxley, argued that the critical question was whether science could speak authoritatively about the past. To them, the ability of science to talk about the past indicated its power to talk about the future; it was also the fulcrum of fierce boundary disputes among science, history, and religion. PMID:22908421

  9. Rhythmic Oscillations of Excitatory Bursting Hodkin-Huxley Neuronal Network with Synaptic Learning

    PubMed Central

    Shi, Qi; Han, Fang; Wang, Zhijie; Li, Caiyun

    2016-01-01

    Rhythmic oscillations of neuronal network are actually kind of synchronous behaviors, which play an important role in neural systems. In this paper, the properties of excitement degree and oscillation frequency of excitatory bursting Hodkin-Huxley neuronal network which incorporates a synaptic learning rule are studied. The effects of coupling strength, synaptic learning rate, and other parameters of chemical synapses, such as synaptic delay and decay time constant, are explored, respectively. It is found that the increase of the coupling strength can weaken the extent of excitement, whereas increasing the synaptic learning rate makes the network more excited in a certain range; along with the increasing of the delay time and the decay time constant, the excitement degree increases at the beginning, then decreases, and keeps stable. It is also found that, along with the increase of the synaptic learning rate, the coupling strength, the delay time, and the decay time constant, the oscillation frequency of the network decreases monotonically. PMID:27073393

  10. Autaptic activity-induced synchronization transitions in Newman-Watts network of Hodgkin-Huxley neurons.

    PubMed

    Wu, Yanan; Gong, Yubing; Wang, Qi

    2015-04-01

    In this paper, we numerically study the effect of autapse on the synchronization of Newman-Watts small-world Hodgkin-Huxley neuron network. It is found that the neurons exhibit synchronization transitions as autaptic self-feedback delay is varied, and the phenomenon becomes strongest when autaptic self-feedback strength is optimal. This phenomenon also changes with the change of coupling strength and network randomness and become strongest when they are optimal. There are similar synchronization transitions for electrical and chemical autapse, but the synchronization transitions for chemical autapse occur more frequently and are stronger than those for electrical synapse. The underlying mechanisms are briefly discussed in quality. These results show that autaptic activity plays a subtle role in the synchronization of the neuronal network. These findings may find potential implications of autapse for the information processing and transmission in neural systems. PMID:25933661

  11. Autaptic activity-induced synchronization transitions in Newman-Watts network of Hodgkin-Huxley neurons

    NASA Astrophysics Data System (ADS)

    Wu, Yanan; Gong, Yubing; Wang, Qi

    2015-04-01

    In this paper, we numerically study the effect of autapse on the synchronization of Newman-Watts small-world Hodgkin-Huxley neuron network. It is found that the neurons exhibit synchronization transitions as autaptic self-feedback delay is varied, and the phenomenon becomes strongest when autaptic self-feedback strength is optimal. This phenomenon also changes with the change of coupling strength and network randomness and become strongest when they are optimal. There are similar synchronization transitions for electrical and chemical autapse, but the synchronization transitions for chemical autapse occur more frequently and are stronger than those for electrical synapse. The underlying mechanisms are briefly discussed in quality. These results show that autaptic activity plays a subtle role in the synchronization of the neuronal network. These findings may find potential implications of autapse for the information processing and transmission in neural systems.

  12. Control of bursting synchronization in networks of Hodgkin-Huxley-type neurons with chemical synapses

    NASA Astrophysics Data System (ADS)

    Batista, C. A. S.; Viana, R. L.; Ferrari, F. A. S.; Lopes, S. R.; Batista, A. M.; Coninck, J. C. P.

    2013-04-01

    Thermally sensitive neurons present bursting activity for certain temperature ranges, characterized by fast repetitive spiking of action potential followed by a short quiescent period. Synchronization of bursting activity is possible in networks of coupled neurons, and it is sometimes an undesirable feature. Control procedures can suppress totally or partially this collective behavior, with potential applications in deep-brain stimulation techniques. We investigate the control of bursting synchronization in small-world networks of Hodgkin-Huxley-type thermally sensitive neurons with chemical synapses through two different strategies. One is the application of an external time-periodic electrical signal and another consists of a time-delayed feedback signal. We consider the effectiveness of both strategies in terms of protocols of applications suitable to be applied by pacemakers.

  13. Homoclinic bifurcation in a Hodgkin-Huxley model of thermally sensitive neurons

    SciTech Connect

    Feudel, Ulrike; Neiman, Alexander; Pei, Xing; Wojtenek, Winfried; Braun, Hans; Huber, Martin; Moss, Frank

    2000-03-01

    We study global bifurcations of the chaotic attractor in a modified Hodgkin-Huxley model of thermally sensitive neurons. The control parameter for this model is the temperature. The chaotic behavior is realized over a wide range of temperatures and is visualized using interspike intervals. We observe an abrupt increase of the interspike intervals in a certain temperature region. We identify this as a homoclinic bifurcation of a saddle-focus fixed point which is embedded in the chaotic attractors. The transition is accompanied by intermittency, which obeys a universal scaling law for the average length of trajectory segments exhibiting only short interspike intervals with the distance from the onset of intermittency. We also present experimental results of interspike interval measurements taken from the crayfish caudal photoreceptor, which qualitatively demonstrate the same bifurcation structure. (c) 2000 American Institute of Physics.

  14. Emergent Central Pattern Generator Behavior in Gap-Junction-Coupled Hodgkin-Huxley Style Neuron Model

    PubMed Central

    Memelli, Heraldo; Solomon, Irene C.

    2012-01-01

    Most models of central pattern generators (CPGs) involve two distinct nuclei mutually inhibiting one another via synapses. Here, we present a single-nucleus model of biologically realistic Hodgkin-Huxley neurons with random gap junction coupling. Despite no explicit division of neurons into two groups, we observe a spontaneous division of neurons into two distinct firing groups. In addition, we also demonstrate this phenomenon in a simplified version of the model, highlighting the importance of afterhyperpolarization currents (IAHP) to CPGs utilizing gap junction coupling. The properties of these CPGs also appear sensitive to gap junction conductance, probability of gap junction coupling between cells, topology of gap junction coupling, and, to a lesser extent, input current into our simulated nucleus. PMID:23365558

  15. Students' Perceptions of Reference Letters

    ERIC Educational Resources Information Center

    Payne, Brian K.; Appel, Jonathan; Smith, Donald H.; Hoofnagle, Kara

    2006-01-01

    This study examines students' perceptions of reference letters. Students (n = 444) were asked to describe how they perceived reference letters. Four themes were uncovered. First, some students perceived reference letters as useful for employers. Second, some students perceived the letters as important for students seeking employment or admission…

  16. Letter Names, Letter Sounds and Phonological Awareness: An Examination of Kindergarten Children across Letters and of Letters across Children

    ERIC Educational Resources Information Center

    Evans, Mary Ann; Bell, Michelle; Shaw, Deborah; Moretti, Shelley; Page, Jodi

    2006-01-01

    In this study 149 kindergarten children were assessed for knowledge of letter names and letter sounds, phonological awareness, and cognitive abilities. Through this it examined child and letter characteristics influencing the acquisition of alphabetic knowledge in a naturalistic context, the relationship between letter-sound knowledge and…

  17. Epistolary and Emotional Education: The Letters of an Irish Father to His Daughter, 1747-1752

    ERIC Educational Resources Information Center

    Ruberg, Willemijn

    2008-01-01

    The letters Bishop Edward Synge (1691-1762) wrote to his daughter Alicia (1733-1807) in 1747-1752 are discussed to show how correspondence from a father to a daughter could be used to teach a teenage girl how to spell and write letters. Moreover, these letters are an excellent source to show how emotional behaviour was taught. Instructions on…

  18. Walking a Fine Line: Writing Negative Letters in an Insurance Company.

    ERIC Educational Resources Information Center

    Schryer, Catherine F.

    2000-01-01

    Examines the situated-language practices associated with the production of negative letters in an insurance company. Combines textual analyses of a set of negative letters together with writers' accounts of producing these letters to identify effective strategies for composing this correspondence. Identifies some strategies that characterize…

  19. Taxicab Correspondence Analysis

    ERIC Educational Resources Information Center

    Choulakian, V.

    2006-01-01

    Taxicab correspondence analysis is based on the taxicab singular value decomposition of a contingency table, and it shares some similar properties with correspondence analysis. It is more robust than the ordinary correspondence analysis, because it gives uniform weights to all the points. The visual map constructed by taxicab correspondence…

  20. Harvard Education Letter, 1999.

    ERIC Educational Resources Information Center

    Graves-Desai, Kelly, Ed.

    1999-01-01

    This document is comprised of the six issues in volume 15 of the Harvard Education Letter, a bimonthly newsletter addressing current issues in elementary and secondary education. Articles in this volume include the following: (1) January-February--"Retention vs. Social Promotion: Schools Search for Alternatives" (Kelly), and "School Design Can Say…

  1. Inside the Letter

    ERIC Educational Resources Information Center

    Duke, Roger; Graham, Alan

    2007-01-01

    In this article, the authors describe how a Java applet can help to build learners' intuitions about basic ideas of algebra. "Matchbox Algebra" is a Java applet the authors have designed to enable learners to grasp a key idea in learning algebra: that the letter "x" may be thought of as representing an as-yet-unknown number. They describe the…

  2. Four-Letter Words.

    ERIC Educational Resources Information Center

    Luster, Robert G.

    1983-01-01

    Describes a computer program (for Apple II) that tests knowledge of four-letter words. The program, which includes four games and a dictionary, can be used in one of two modes (inquiry or game) by students at any level depending on version of dictionary selected. Dictionary operations and classroom applications are discussed. (JN)

  3. Five Long Letters.

    ERIC Educational Resources Information Center

    Bone, Eric

    1990-01-01

    Describes the life of former Louisiana governor Huey Long through five fictitious letters. Discusses Long's experiences as a state public service commissioner, governor, and senator. Attributes Long's assassination to his killer's personal motives. Concludes that Long's life showed how much personal power could be gained even in a democracy. (SG)

  4. Harvard Education Letter, 2001.

    ERIC Educational Resources Information Center

    Gordon, David, T., Ed.

    2001-01-01

    This document is comprised of the six issues in volume 17 of the Harvard Education Letter, a bimonthly newsletter addressing current issues in elementary and secondary education. Articles in this volume include the following: (1) January-February--"Charters and Districts: Three Stages in an Often Rocky Relationship" (Kelly) and "'We Don't Allow…

  5. Harvard Education Letter, 2002.

    ERIC Educational Resources Information Center

    Gordon, David T., Editor

    2002-01-01

    This document is comprised of the 6 issues in volume 18 of the Harvard Education Letter, a bimonthly newsletter addressing current issues in elementary and secondary education. Articles in this volume include the following: (1) January/February--"Curriculum Access in the Digital Age" (David T. Gordon) and "Using Charters To Improve Urban Schools"…

  6. Letter to Doxiadis

    ERIC Educational Resources Information Center

    Fuller, Buckminster

    1969-01-01

    The second half of a lengthy letter to Dr. Constantine Doxiadis (published in full in Main Currents in Modern Thought, XXV, March-April 1969) summarizes Buckminster Fuller's personal reflections on the impact of industrialization and on the effect of technological change in uniting mankind. (MF)

  7. Letters and American Literacy.

    ERIC Educational Resources Information Center

    Kevis, David E.

    The work itself should help a person who is going to teach reading and writing. Practical suggestions are offered in the final two chapters, while the opening three give intellectual perspectives. A theme binds the work of letting the consciousness of writing as a visual system be increased and of breaking the spell by which letter phonetics can…

  8. Letters in this Issue

    NASA Astrophysics Data System (ADS)

    1998-01-01

    Reforming the General Chemistry Textbook individual letters by Edward T. Samulski; Stephen J. Hawkes; Stephen J. Fisher; J. Stephen Hartman; A. R. H. Cole; Stanley Pine, Ronald Archer, and Herbert Kaesz; Jimmy Reeves; Robert Hill; and Brock Spencer, C. Bradley Moore and Nedah Rose. Re: article by R. J. Gillespie The author replies

  9. The Fuzzy Scarlet Letter

    ERIC Educational Resources Information Center

    Pallas, Aaron M.

    2012-01-01

    Critics of the public release of teacher evaluation scores sometimes liken these ratings to the scarlet letter worn by Hester Prynne in Nathaniel Hawthorne's classic novel. The comparison is apt. But public school teachers who are subjected to public shaming because of their students' test scores can rarely expect the opportunities for redemption…

  10. Harvard Education Letter, 2000.

    ERIC Educational Resources Information Center

    Gordon, David T., Ed.

    2000-01-01

    This document is comprised of the six issues in volume 16 of the Harvard Education Letter, a bimonthly newsletter addressing current issues in elementary and secondary education. Articles in this volume include the following: (1) January-February--"Grade Inflation: What's Really behind All Those A's?" (Birk) and "Every Friday was Fight Day"…

  11. Vowel Cluster-Phoneme Correspondences in 20,000 English Words.

    ERIC Educational Resources Information Center

    Johnson, Dale D.

    The symbol-sound correspondence status of vowel-cluster (two or more adjacent vowel letters) spelling in American English was investigated. The source of the study was Venezky's 1963 revision of the Thorndike Frequency Count. A computer print-out of the 20,000 word corpus was analyzed to determine the letter-sound correspondence of vowel cluster…

  12. Priming of abstract letter representations may be universal: the case of Arabic.

    PubMed

    Carreiras, Manuel; Perea, Manuel; Abu Mallouh, Reem

    2012-08-01

    Recent research on the Roman alphabet has demonstrated that the magnitudes of masked repetition priming are equivalent for letter pairs that have similar visual features across cases (e.g., c-C) and for letter pairs with dissimilar features (e.g., g-G). Here, we examined whether priming of abstract letter representations occurs in an orthographic system, Arabic, in which the letters show an intricate number of contextual forms. Arabic does not have a lowercase/uppercase distinction, but the letters exhibit different forms that depend on their position (initial, medial, final, or isolated) and their connectivity. Importantly, some letters look quite different across positions (e.g., (symbol in text) and (symbol in text), which correspond to the letter 'ayn), whereas others look very similar (e.g. (symbol in text), and (symbol in text), which correspond to the letter fā'). We employed a masked priming same-different task, in which native speakers of Arabic decided whether a target letter was the same as or different from a reference letter presented in a different position (middle vs. isolated). The results showed masked repetition priming effects of the same magnitude for letter pairs with similar and with dissimilar visual features across letter positions. These data support the view that priming of abstract letter representations is a universal phenomenon. PMID:22569990

  13. President Nixon's Letter of Resignation.

    ERIC Educational Resources Information Center

    Alexander, Mary; Childress, Marilyn

    1982-01-01

    Contains a primary source document--President Nixon's resignation letter--and suggests teaching strategies for its use with secondary level students. To refresh students' memories of the events surrounding the letter, a selective chronology is also presented. (RM)

  14. FPGA implementation of a biological neural network based on the Hodgkin-Huxley neuron model

    PubMed Central

    Yaghini Bonabi, Safa; Asgharian, Hassan; Safari, Saeed; Nili Ahmadabadi, Majid

    2014-01-01

    A set of techniques for efficient implementation of Hodgkin-Huxley-based (H-H) model of a neural network on FPGA (Field Programmable Gate Array) is presented. The central implementation challenge is H-H model complexity that puts limits on the network size and on the execution speed. However, basics of the original model cannot be compromised when effect of synaptic specifications on the network behavior is the subject of study. To solve the problem, we used computational techniques such as CORDIC (Coordinate Rotation Digital Computer) algorithm and step-by-step integration in the implementation of arithmetic circuits. In addition, we employed different techniques such as sharing resources to preserve the details of model as well as increasing the network size in addition to keeping the network execution speed close to real time while having high precision. Implementation of a two mini-columns network with 120/30 excitatory/inhibitory neurons is provided to investigate the characteristic of our method in practice. The implementation techniques provide an opportunity to construct large FPGA-based network models to investigate the effect of different neurophysiological mechanisms, like voltage-gated channels and synaptic activities, on the behavior of a neural network in an appropriate execution time. Additional to inherent properties of FPGA, like parallelism and re-configurability, our approach makes the FPGA-based system a proper candidate for study on neural control of cognitive robots and systems as well. PMID:25484854

  15. FPGA implementation of a biological neural network based on the Hodgkin-Huxley neuron model.

    PubMed

    Yaghini Bonabi, Safa; Asgharian, Hassan; Safari, Saeed; Nili Ahmadabadi, Majid

    2014-01-01

    A set of techniques for efficient implementation of Hodgkin-Huxley-based (H-H) model of a neural network on FPGA (Field Programmable Gate Array) is presented. The central implementation challenge is H-H model complexity that puts limits on the network size and on the execution speed. However, basics of the original model cannot be compromised when effect of synaptic specifications on the network behavior is the subject of study. To solve the problem, we used computational techniques such as CORDIC (Coordinate Rotation Digital Computer) algorithm and step-by-step integration in the implementation of arithmetic circuits. In addition, we employed different techniques such as sharing resources to preserve the details of model as well as increasing the network size in addition to keeping the network execution speed close to real time while having high precision. Implementation of a two mini-columns network with 120/30 excitatory/inhibitory neurons is provided to investigate the characteristic of our method in practice. The implementation techniques provide an opportunity to construct large FPGA-based network models to investigate the effect of different neurophysiological mechanisms, like voltage-gated channels and synaptic activities, on the behavior of a neural network in an appropriate execution time. Additional to inherent properties of FPGA, like parallelism and re-configurability, our approach makes the FPGA-based system a proper candidate for study on neural control of cognitive robots and systems as well. PMID:25484854

  16. Null space in the Hodgkin-Huxley Equations. A critical test.

    PubMed Central

    Best, E N

    1979-01-01

    Voltage perturbation methods based upon topological concepts are used to elicit responses from the Hodgkin-Huxley (HH) nonlinear differential equations. These responses present a critical check upon the validity of the HH model for electrical activity across squid axon membrane. It is shown that when a constant current is applied such that a stable equilibrium and rhythmic firing are present, the following predictions are inherent in the HH system of equations: (a) Small instantaneous voltage perturbations to the axon given at points along its firing spike result in phase resetting curves (when new phase versus old phase is plotted) with an average slope of 1. (b) A larger voltage perturbation (from certain points along the firing spike) results in the permanent cessation of periodic firing, with membrane voltage rapidly approaching the equilibrium value. (c) A still larger perturbation yields phase resetting curves with an average slope equal to 0. These predictions, coupled with Tasaki's experimental demonstration that squid axons in excellent condition do give repetitive firing under constant current, provide a critical test of the validity of the HH model. Images FIGURE 3 PMID:262379

  17. Quantification of degeneracy in Hodgkin-Huxley neurons on Newman-Watts small world network.

    PubMed

    Man, Menghua; Zhang, Ya; Ma, Guilei; Friston, Karl; Liu, Shanghe

    2016-08-01

    Degeneracy is a fundamental source of biological robustness, complexity and evolvability in many biological systems. However, degeneracy is often confused with redundancy. Furthermore, the quantification of degeneracy has not been addressed for realistic neuronal networks. The objective of this paper is to characterize degeneracy in neuronal network models via quantitative mathematic measures. Firstly, we establish Hodgkin-Huxley neuronal networks with Newman-Watts small world network architectures. Secondly, in order to calculate the degeneracy, redundancy and complexity in the ensuing networks, we use information entropy to quantify the information a neuronal response carries about the stimulus - and mutual information to measure the contribution of each subset of the neuronal network. Finally, we analyze the interdependency of degeneracy, redundancy and complexity - and how these three measures depend upon network architectures. Our results suggest that degeneracy can be applied to any neuronal network as a formal measure, and degeneracy is distinct from redundancy. Qualitatively degeneracy and complexity are more highly correlated over different network architectures, in comparison to redundancy. Quantitatively, the relationship between both degeneracy and redundancy depends on network coupling strength: both degeneracy and redundancy increase with complexity for small coupling strengths; however, as coupling strength increases, redundancy decreases with complexity (in contrast to degeneracy, which is relatively invariant). These results suggest that the degeneracy is a general topologic characteristic of neuronal networks, which could be applied quantitatively in neuroscience and connectomics. PMID:27155043

  18. Responses of a Hodgkin-Huxley neuron to various types of spike-train inputs

    NASA Astrophysics Data System (ADS)

    Hasegawa, Hideo

    2000-01-01

    Numerical investigations have been made of responses of a Hodgkin-Huxley (HH) neuron to spike-train inputs whose interspike interval (ISI) is modulated by deterministic, semi-deterministic (chaotic), and stochastic signals. As deterministic one, we adopt inputs with the time-independent ISI and with time-dependent ISI modulated by sinusoidal signal. The Rössler and Lorentz models are adopted for chaotic modulations of ISI. Stochastic ISI inputs with the gamma distribution are employed. It is shown that distribution of output ISI data depends not only on the mean of ISIs of spike-train inputs but also on their fluctuations. The distinction of responses to the three kinds of inputs can be made by return maps of input and output ISIs, but not by their histograms. The relation between the variations of input and output ISIs is shown to be different from that of the integrate and fire (IF) model because of the refractory period in the HH neuron.

  19. Response of a Hodgkin-Huxley neuron to a high-frequency input.

    PubMed

    Borkowski, L S

    2009-11-01

    We study the response of a Hodgkin-Huxley neuron stimulated by a periodic sequence of conductance pulses arriving through the synapse in the high-frequency regime. In addition to the usual excitation threshold there is a smooth crossover from the firing to the silent regime for increasing pulse amplitude gsyn. The amplitude of the voltage spikes decreases approximately linearly with gsyn. In some regions of parameter space the response is irregular, probably chaotic. In the chaotic regime between the mode-locked regions 3:1 and 2:1 near the lower excitation threshold, the output interspike interval histogram (ISIH) undergoes a sharp transition. If the driving period is below the critical value, TT* even multiples of Ti also appear in the histogram, starting from the largest values. Near T* the ISIH scales logarithmically on both sides of the transition. The coefficient of variation of ISIH has a cusp singularity at T*. The average response period has a maximum slightly above T*. Near the excitation threshold in the chaotic regime the average firing rate rises sublinearly from frequencies of order 1 Hz. PMID:20365013

  20. Channel-noise-induced critical slowing in the subthreshold Hodgkin-Huxley neuron

    NASA Astrophysics Data System (ADS)

    Bukoski, Alex; Steyn-Ross, D. A.; Steyn-Ross, Moira L.

    2015-03-01

    The dynamics of a spiking neuron approaching threshold is investigated in the framework of Markov-chain models describing the random state-transitions of the underlying ion-channel proteins. We characterize subthreshold channel-noise-induced transmembrane potential fluctuations in both type-I (integrator) and type-II (resonator) parametrizations of the classic conductance-based Hodgkin-Huxley equations. As each neuron approaches spiking threshold from below, numerical simulations of stochastic trajectories demonstrate pronounced growth in amplitude simultaneous with decay in frequency of membrane voltage fluctuations induced by ion-channel state transitions. To explore this progression of fluctuation statistics, we approximate the exact Markov treatment with a 12-variable channel-based stochastic differential equation (SDE) and its Ornstein-Uhlenbeck (OU) linearization and show excellent agreement between Markov and SDE numerical simulations. Predictions of the OU theory with respect to membrane potential fluctuation variance, autocorrelation, correlation time, and spectral density are also in agreement and illustrate the close connection between the eigenvalue structure of the associated deterministic bifurcations and the observed behavior of the noisy Markov traces on close approach to threshold for both integrator and resonator point-neuron varieties.

  1. Theoretical Analysis of Transcranial Magneto-Acoustical Stimulation with Hodgkin-Huxley Neuron Model.

    PubMed

    Yuan, Yi; Chen, Yudong; Li, Xiaoli

    2016-01-01

    Transcranial magneto-acoustical stimulation (TMAS) is a novel stimulation technology in which an ultrasonic wave within a magnetostatic field generates an electric current in an area of interest in the brain to modulate neuronal activities. As a key part of the neural network, neurons transmit information in the nervous system. However, the effect of TMAS on the neuronal firing pattern remains unknown. To address this problem, we investigated the stimulatory mechanism of TMAS on neurons, by using a Hodgkin-Huxley neuron model. The simulation results indicated that the magnetostatic field intensity and ultrasonic power affect the amplitude and interspike interval of neuronal action potential under a continuous wave ultrasound. The simulation results also showed that the ultrasonic power, duty cycle and repetition frequency can alter the firing pattern of neural action potential under pulsed wave ultrasound. This study may help to reveal and explain the biological mechanism of TMAS and to provide a theoretical basis for TMAS in the treatment or rehabilitation of neuropsychiatric disorders. PMID:27148032

  2. Effect of autaptic activity on the response of a Hodgkin-Huxley neuron.

    PubMed

    Wang, Hengtong; Wang, Longfei; Chen, Yueling; Chen, Yong

    2014-09-01

    An autapse is a special synapse that connects a neuron to itself. In this study, we investigated the effect of an autapse on the responses of a Hodgkin-Huxley neuron to different forms of external stimuli. When the neuron was subjected to a DC stimulus, the firing frequencies and the interspike interval distributions of the output spike trains showed periodic behaviors as the autaptic delay time increased. When the input was a synaptic pulse-like train with random interspike intervals, we observed low-pass and band-pass filtering behaviors. Moreover, the region over which the output ISIs are distributed and the mean firing frequency display periodic behaviors with increasing autaptic delay time. When specific autaptic parameters were chosen, most of the input ISIs could be filtered, and the response spike trains were nearly regular, even with a highly random input. The background mechanism of these observed dynamics has been analyzed based on the phase response curve method. We also found that the information entropy of the output spike train could be modified by the autapse. These results also suggest that the autapse can serve as a regulator of information response in the nervous system. PMID:25273202

  3. Minimal Hodgkin-Huxley type models for different classes of cortical and thalamic neurons.

    PubMed

    Pospischil, Martin; Toledo-Rodriguez, Maria; Monier, Cyril; Piwkowska, Zuzanna; Bal, Thierry; Frégnac, Yves; Markram, Henry; Destexhe, Alain

    2008-11-01

    We review here the development of Hodgkin-Huxley (HH) type models of cerebral cortex and thalamic neurons for network simulations. The intrinsic electrophysiological properties of cortical neurons were analyzed from several preparations, and we selected the four most prominent electrophysiological classes of neurons. These four classes are "fast spiking", "regular spiking", "intrinsically bursting" and "low-threshold spike" cells. For each class, we fit "minimal" HH type models to experimental data. The models contain the minimal set of voltage-dependent currents to account for the data. To obtain models as generic as possible, we used data from different preparations in vivo and in vitro, such as rat somatosensory cortex and thalamus, guinea-pig visual and frontal cortex, ferret visual cortex, cat visual cortex and cat association cortex. For two cell classes, we used automatic fitting procedures applied to several cells, which revealed substantial cell-to-cell variability within each class. The selection of such cellular models constitutes a necessary step towards building network simulations of the thalamocortical system with realistic cellular dynamical properties. PMID:19011929

  4. Chimera states in a Hodgkin-Huxley model of thermally sensitive neurons.

    PubMed

    Glaze, Tera A; Lewis, Scott; Bahar, Sonya

    2016-08-01

    Chimera states occur when identically coupled groups of nonlinear oscillators exhibit radically different dynamics, with one group exhibiting synchronized oscillations and the other desynchronized behavior. This dynamical phenomenon has recently been studied in computational models and demonstrated experimentally in mechanical, optical, and chemical systems. The theoretical basis of these states is currently under active investigation. Chimera behavior is of particular relevance in the context of neural synchronization, given the phenomenon of unihemispheric sleep and the recent observation of asymmetric sleep in human patients with sleep apnea. The similarity of neural chimera states to neural "bump" states, which have been suggested as a model for working memory and visual orientation tuning in the cortex, adds to their interest as objects of study. Chimera states have been demonstrated in the FitzHugh-Nagumo model of excitable cells and in the Hindmarsh-Rose neural model. Here, we demonstrate chimera states and chimera-like behaviors in a Hodgkin-Huxley-type model of thermally sensitive neurons both in a system with Abrams-Strogatz (mean field) coupling and in a system with Kuramoto (distance-dependent) coupling. We map the regions of parameter space for which chimera behavior occurs in each of the two coupling schemes. PMID:27586615

  5. On the noise-enhancing ability of stochastic Hodgkin-Huxley neuron systems.

    PubMed

    Chen, Bor-Sen; Li, Cheng-Wei

    2010-07-01

    Recently noise has been shown to be useful in enhancing neuron sensitivity by stochastic resonance. In this study, in order to measure the noise-enhancing factor (NEF), a nonlinear stochastic model is introduced for the Hodgkin-Huxley (HH) neuron system with synaptic noise input stimulation and channel noises in the sodium and potassium channels. The enhancing factor of the HH neuron system is measured from the point of view of the noise-exploiting level of nonlinear stochastic H(infinity) signal processing. Since the nonlinear stochastic-enhancing measure problem of HH neuron systems requires a solution for the difficulty presented by the Hamilton Jacobi inequality (HJI), a fuzzy interpolation of locally linearized systems is employed to simplify the nonlinear noise-enhancing problems by solving only a set of linear matrix inequalities. The NEF of the HH neuron system is found to be related to the locations of eigenvalues of linearized HH neuron systems and can be estimated through the H(infinity) signal processing method. Based on a stochastic fuzzy linearized HH neuron system, we found that channel noises are enhanced by the active eigenvalues of ionic channels while synaptic noises are attenuated by the passive eigenvalues of synaptic process. PMID:20235824

  6. Theoretical Analysis of Transcranial Magneto-Acoustical Stimulation with Hodgkin-Huxley Neuron Model

    PubMed Central

    Yuan, Yi; Chen, Yudong; Li, Xiaoli

    2016-01-01

    Transcranial magneto-acoustical stimulation (TMAS) is a novel stimulation technology in which an ultrasonic wave within a magnetostatic field generates an electric current in an area of interest in the brain to modulate neuronal activities. As a key part of the neural network, neurons transmit information in the nervous system. However, the effect of TMAS on the neuronal firing pattern remains unknown. To address this problem, we investigated the stimulatory mechanism of TMAS on neurons, by using a Hodgkin-Huxley neuron model. The simulation results indicated that the magnetostatic field intensity and ultrasonic power affect the amplitude and interspike interval of neuronal action potential under a continuous wave ultrasound. The simulation results also showed that the ultrasonic power, duty cycle and repetition frequency can alter the firing pattern of neural action potential under pulsed wave ultrasound. This study may help to reveal and explain the biological mechanism of TMAS and to provide a theoretical basis for TMAS in the treatment or rehabilitation of neuropsychiatric disorders. PMID:27148032

  7. Demonstrating the Correspondence Bias

    ERIC Educational Resources Information Center

    Howell, Jennifer L.; Shepperd, James A.

    2011-01-01

    Among the best-known and most robust biases in person perception is the correspondence bias--the tendency for people to make dispositional, rather than situational, attributions for an actor's behavior. The correspondence bias appears in virtually every social psychology textbook and in many introductory psychology textbooks, yet the authors'…

  8. New Insights about Letter Learning

    ERIC Educational Resources Information Center

    Dougherty Stahl, Katherine A.

    2015-01-01

    The acquisition of alphabetic knowledge (letter names, letter sounds, and letter forms) is an important predictor of later literacy achievement. This article describes research findings that provide new insights about how children learn the alphabetic principle and the implications for effective and efficient instruction of the alphabet. Teachers…

  9. Task switching and response correspondence in the psychological refractory period paradigm

    NASA Technical Reports Server (NTRS)

    Lien, Mei-Ching; Schweickert, Richard; Proctor, Robert W.

    2003-01-01

    Three experiments examined the effects of task switching and response correspondence in a psychological refractory period paradigm. A letter task (vowel-consonant) and a digit task (odd-even) were combined to form 4 possible dual-task pairs in each trial: letter-letter, letter-digit, digit-digit, and digit-letter. Foreknowledge of task transition (repeat or switch) and task identity (letter or digit) was varied across experiments: no foreknowledge in Experiment 1, partial foreknowledge (task transition only) in Experiment 2, and full foreknowledge in Experiment 3. For all experiments, the switch cost for Task 2 was additive with stimulus onset asynchrony, and the response-correspondence effect for Task 2 was numerically smaller in the switch condition than in the repeat condition. These outcomes suggest that reconfiguration for Task 2 takes place after the central processing of Task 1 and that the crosstalk correspondence effect is due to response activation by way of stimulus-response associations.

  10. Letter of the Law.

    ERIC Educational Resources Information Center

    Dowling-Sendor, Benjamin

    2003-01-01

    A recent decision by the 8th U.S. Circuit Court of Appeals in a case from Arkansas centered on a vicious letter written by an 8th-grade boy about his former girlfriend and turned over to school officials. The court ruled for the school district in expelling the student for the year, without allowing him to attend an alternative school. Argues that…

  11. Letters to the Editor

    NASA Astrophysics Data System (ADS)

    1997-03-01

    All the Letters to the Editor in this issue are in the same PostScript or PDF file. Contents Criticisms of hands-on pseudoscience David J Fisher 27 Elderberry Road, Cardiff CF5 3RG, UK Measuring varying fields Don Koks Adelaide University, Australia Relativity at A-level: a comment David Sang 3 Ellasdale Road, Bognor Regis, PO21 2SG, UK

  12. Letters to the Editor

    NASA Astrophysics Data System (ADS)

    2000-11-01

    All the Letters to the Editor in this issue are in the same PostScript or PDF file. Contents The equivalence of mass and energy Peter Stansbury Head of Physics, Christ Church Grammar School, Claremont, Western Australia 6010 Comment on `A simple experiment to study parabolic surfaces' N Gauthier Department of Physics, The Royal Military College of Canada, Kingston, Ontario K7K 7B4, Canada

  13. Phoneme Isolation Ability Is Not Simply a Consequence of Letter-Sound Knowledge

    ERIC Educational Resources Information Center

    Hulme, Charles; Caravolas, Marketa; Malkova, Gabriela; Brigstocke, Sophie

    2005-01-01

    Two studies investigated whether knowledge of specific letter-sound correspondences is a necessary precursor of children's ability to isolate phonemes in speech. In both studies, Czech and English children reliably isolated phonemes for which they did not know the corresponding letter. These data refute the idea that phoneme manipulation ability…

  14. Sodium currents activate without a Hodgkin-and-Huxley-type delay in central mammalian neurons.

    PubMed

    Baranauskas, Gytis; Martina, Marco

    2006-01-11

    Hodgkin and Huxley established that sodium currents in the squid giant axons activate after a delay, which is explained by the model of a channel with three identical independent gates that all have to open before the channel can pass current (the HH model). It is assumed that this model can adequately describe the sodium current activation time course in all mammalian central neurons, although there is no experimental evidence to support such a conjecture. We performed high temporal resolution studies of sodium currents gating in three types of central neurons. The results show that, within the tested voltage range from -55 to -35 mV, in all of these neurons, the activation time course of the current could be fit, after a brief delay, with a monoexponential function. The duration of delay from the start of the voltage command to the start of the extrapolated monoexponential fit was much smaller than predicted by the HH model. For example, in prefrontal cortex pyramidal neurons, at -46 mV and 12 degrees C, the observed average delay was 140 micros versus the 740 micros predicted by the two-gate HH model and the 1180 micros predicted by the three-gate HH model. These results can be explained by a model with two closed states and one open state. In this model, the transition between two closed states is approximately five times faster than the transition between the second closed state and the open state. This model captures all major properties of the sodium current activation. In addition, the proposed model reproduces the observed action potential shape more accurately than the traditional HH model. PMID:16407565

  15. Comparison between Hodgkin-Huxley and Markov formulations of cardiac ion channels.

    PubMed

    Carbonell-Pascual, Beatriz; Godoy, Eduardo; Ferrer, Ana; Romero, Lucia; Ferrero, Jose M

    2016-06-21

    When simulating the macroscopic current flowing through cardiac ion channels, two mathematical formalisms can be adopted: the Hodgkin-Huxley model (HHM) formulation, which describes openings and closings of channel 'gates', or the Markov model (MM) formulation, based on channel 'state' transitions. The latter was first used in 1995 to simulate the effects of mutations in ionic currents and, since then, its use has been extended to wild-type channels also. While the MMs better describe the actual behavior of ion channels, they are mathematically more complex than HHMs in terms of parameter estimation and identifiability and are computationally much more demanding, which can dramatically increase computational time in large-scale (e.g. whole heart) simulations. We hypothesize that a HHM formulation obtained from classical patch-clamp protocols in wild-type and mutant ion channels can be used to correctly simulate cardiac action potentials and their static and dynamic properties. To validate our hypothesis, we selected two pivotal cardiac ionic currents (the rapid delayed rectifier K(+) current, IKr, and the inward Na(+) current, INa) and formulated HHMs for both wild-type and mutant channels (LQT2-linked T474I mutation for IKr and LQT3-linked ΔKPQ mutation for INa). Action potentials were then simulated using the MM and HHM versions of the currents, and the action potential waveforms, biomarkers and action potential duration rate dependence properties were compared in control conditions and in the presence of physiological variability. While small differences between ionic currents were found between the two models (correlation coefficient ρ>0.92), the simulations yielded almost identical action potentials (ρ>0.99), suggesting that HHMs may also be valid to simulate the effects of mutations affecting IKr and INa on the action potential. PMID:27059892

  16. A nonlinear autoregressive Volterra model of the Hodgkin-Huxley equations.

    PubMed

    Eikenberry, Steffen E; Marmarelis, Vasilis Z

    2013-02-01

    We propose a new variant of Volterra-type model with a nonlinear auto-regressive (NAR) component that is a suitable framework for describing the process of AP generation by the neuron membrane potential, and we apply it to input-output data generated by the Hodgkin-Huxley (H-H) equations. Volterra models use a functional series expansion to describe the input-output relation for most nonlinear dynamic systems, and are applicable to a wide range of physiologic systems. It is difficult, however, to apply the Volterra methodology to the H-H model because is characterized by distinct subthreshold and suprathreshold dynamics. When threshold is crossed, an autonomous action potential (AP) is generated, the output becomes temporarily decoupled from the input, and the standard Volterra model fails. Therefore, in our framework, whenever membrane potential exceeds some threshold, it is taken as a second input to a dual-input Volterra model. This model correctly predicts membrane voltage deflection both within the subthreshold region and during APs. Moreover, the model naturally generates a post-AP afterpotential and refractory period. It is known that the H-H model converges to a limit cycle in response to a constant current injection. This behavior is correctly predicted by the proposed model, while the standard Volterra model is incapable of generating such limit cycle behavior. The inclusion of cross-kernels, which describe the nonlinear interactions between the exogenous and autoregressive inputs, is found to be absolutely necessary. The proposed model is general, non-parametric, and data-derived. PMID:22878687

  17. Power-Law Dynamics of Membrane Conductances Increase Spiking Diversity in a Hodgkin-Huxley Model.

    PubMed

    Teka, Wondimu; Stockton, David; Santamaria, Fidel

    2016-03-01

    We studied the effects of non-Markovian power-law voltage dependent conductances on the generation of action potentials and spiking patterns in a Hodgkin-Huxley model. To implement slow-adapting power-law dynamics of the gating variables of the potassium, n, and sodium, m and h, conductances we used fractional derivatives of order η≤1. The fractional derivatives were used to solve the kinetic equations of each gate. We systematically classified the properties of each gate as a function of η. We then tested if the full model could generate action potentials with the different power-law behaving gates. Finally, we studied the patterns of action potential that emerged in each case. Our results show the model produces a wide range of action potential shapes and spiking patterns in response to constant current stimulation as a function of η. In comparison with the classical model, the action potential shapes for power-law behaving potassium conductance (n gate) showed a longer peak and shallow hyperpolarization; for power-law activation of the sodium conductance (m gate), the action potentials had a sharp rise time; and for power-law inactivation of the sodium conductance (h gate) the spikes had wider peak that for low values of η replicated pituitary- and cardiac-type action potentials. With all physiological parameters fixed a wide range of spiking patterns emerged as a function of the value of the constant input current and η, such as square wave bursting, mixed mode oscillations, and pseudo-plateau potentials. Our analyses show that the intrinsic memory trace of the fractional derivative provides a negative feedback mechanism between the voltage trace and the activity of the power-law behaving gate variable. As a consequence, power-law behaving conductances result in an increase in the number of spiking patterns a neuron can generate and, we propose, expand the computational capacity of the neuron. PMID:26937967

  18. Power-Law Dynamics of Membrane Conductances Increase Spiking Diversity in a Hodgkin-Huxley Model

    PubMed Central

    Teka, Wondimu; Stockton, David; Santamaria, Fidel

    2016-01-01

    We studied the effects of non-Markovian power-law voltage dependent conductances on the generation of action potentials and spiking patterns in a Hodgkin-Huxley model. To implement slow-adapting power-law dynamics of the gating variables of the potassium, n, and sodium, m and h, conductances we used fractional derivatives of order η≤1. The fractional derivatives were used to solve the kinetic equations of each gate. We systematically classified the properties of each gate as a function of η. We then tested if the full model could generate action potentials with the different power-law behaving gates. Finally, we studied the patterns of action potential that emerged in each case. Our results show the model produces a wide range of action potential shapes and spiking patterns in response to constant current stimulation as a function of η. In comparison with the classical model, the action potential shapes for power-law behaving potassium conductance (n gate) showed a longer peak and shallow hyperpolarization; for power-law activation of the sodium conductance (m gate), the action potentials had a sharp rise time; and for power-law inactivation of the sodium conductance (h gate) the spikes had wider peak that for low values of η replicated pituitary- and cardiac-type action potentials. With all physiological parameters fixed a wide range of spiking patterns emerged as a function of the value of the constant input current and η, such as square wave bursting, mixed mode oscillations, and pseudo-plateau potentials. Our analyses show that the intrinsic memory trace of the fractional derivative provides a negative feedback mechanism between the voltage trace and the activity of the power-law behaving gate variable. As a consequence, power-law behaving conductances result in an increase in the number of spiking patterns a neuron can generate and, we propose, expand the computational capacity of the neuron. PMID:26937967

  19. Proposed modification of the Huxley-Simmons model for myosin head motion along an actin filament.

    PubMed

    Mitsui, T; Chiba, H

    1996-09-21

    A model is proposed for myosin head motion along an actin filament which accommodates recent experimental data. The model includes three attached states of a myosin head and is thus similar to the classical Huxley & Simmons (1971) model, but differs in that an explicit expression is given for the spatial distribution of potential energy wells for the myosin head. Our model also differs from the classical model, in that it assumes that the proportion of myosin heads attached to actin filament is constant and independent of shortening velocity, as suggested by X-ray diffraction data. Furthermore, it posits that the crossbridge is string-like rather than spring-like. This modified model fits well to the experimental data in the following respects. (1) The calculated tension dependence of muscle stiffness agrees with the observation by Ford et al. (1985 J. Physiol. 361, 131-150). (2) A myosin head under low load can move as far as 60 nm along an actin filament during one ATP hydrolysis cycle in muscle, in agreement with the results by Yanagida et al. (1985 Nature 316, 366-369) and others. (3) The model predicts that such movements consist of a series of elementary steps of 11 nm. (4) A single myosin head hardly moves after the first step of 11 nm under the condition of in vitro experiment carried out by Finer et al. (1994 Nature 368, 113-119), in agreement with their observation. (5) The calculated energy liberation rate reproduces the characteristics of Hill's equation. (6) The "double-hyperbolic force-velocity relation" reported by Edman (1988 J. Physiol. 404, 301-321) can be understood in terms of a potential barrier against movement of a potential well in which a myosin head is trapped. PMID:8944146

  20. Stochastic differential equation models for ion channel noise in Hodgkin-Huxley neurons.

    PubMed

    Goldwyn, Joshua H; Imennov, Nikita S; Famulare, Michael; Shea-Brown, Eric

    2011-04-01

    The random transitions of ion channels between conducting and nonconducting states generate a source of internal fluctuations in a neuron, known as channel noise. The standard method for modeling the states of ion channels nonlinearly couples continuous-time Markov chains to a differential equation for voltage. Beginning with the work of R. F. Fox and Y.-N. Lu [Phys. Rev. E 49, 3421 (1994)], there have been attempts to generate simpler models that use stochastic differential equation (SDEs) to approximate the stochastic spiking activity produced by Markov chain models. Recent numerical investigations, however, have raised doubts that SDE models can capture the stochastic dynamics of Markov chain models.We analyze three SDE models that have been proposed as approximations to the Markov chain model: one that describes the states of the ion channels and two that describe the states of the ion channel subunits. We show that the former channel-based approach can capture the distribution of channel noise and its effects on spiking in a Hodgkin-Huxley neuron model to a degree not previously demonstrated, but the latter two subunit-based approaches cannot. Our analysis provides intuitive and mathematical explanations for why this is the case. The temporal correlation in the channel noise is determined by the combinatorics of bundling subunits into channels, but the subunit-based approaches do not correctly account for this structure. Our study confirms and elucidates the findings of previous numerical investigations of subunit-based SDE models. Moreover, it presents evidence that Markov chain models of the nonlinear, stochastic dynamics of neural membranes can be accurately approximated by SDEs. This finding opens a door to future modeling work using SDE techniques to further illuminate the effects of ion channel fluctuations on electrically active cells. PMID:21599202

  1. Multiclass Continuous Correspondence Learning

    NASA Technical Reports Server (NTRS)

    Bue, Brian D,; Thompson, David R.

    2011-01-01

    We extend the Structural Correspondence Learning (SCL) domain adaptation algorithm of Blitzer er al. to the realm of continuous signals. Given a set of labeled examples belonging to a 'source' domain, we select a set of unlabeled examples in a related 'target' domain that play similar roles in both domains. Using these 'pivot samples, we map both domains into a common feature space, allowing us to adapt a classifier trained on source examples to classify target examples. We show that when between-class distances are relatively preserved across domains, we can automatically select target pivots to bring the domains into correspondence.

  2. Letters to the Editor

    NASA Astrophysics Data System (ADS)

    1998-03-01

    All the Letters to the Editor in this issue are in the same PostScript or PDF file. Contents Comment on `Magnetic and electric field strengths of high voltage power lines and household appliances' José Luis Giordano Dept. de Ciencia y Tecnología de Materiales y Fluidos, CPSI, Universidad de Zaragoza, Spain Twins paradox S R Carson Norton College, Malton, North Yorkshire, UK On alternative ways of finding the ratio of specific heats of gases Tomas Ficker Physics Department, Technical University of Brno, Czech Republic

  3. Letters to the Editor

    NASA Astrophysics Data System (ADS)

    1998-11-01

    All the Letters to the Editor in this issue are in the same PostScript or PDF file. Contents Narrow-band interference filters for lecture demonstrations A P Ovcharenko, B M Valiyov and V D Yegorenkov Kharkov State University, Ukraine Static electricity and the gas lift chair P Cooke Department of Physics, University of South Australia, Levels Campus, Pooraka, South Australia Relativistic mass Simon Carson Norton College, Langton Road, Norton, Malton, North Yorkshire YO17 9PT, UK Magazine or journal? Philip Britton Head of Physics, Leeds Grammar School, UK

  4. Letters to the Editor

    NASA Astrophysics Data System (ADS)

    2000-09-01

    All the Letters to the Editor in this issue are in the same PostScript or PDF file. Contents Heat and temperature Kevin Carlton Canterbury Christ Church University College, North Holmes Road, Canterbury, Kent CT1 1QU, UK James Bond's shoes J Oliver Linton Head of Physics, Wolverhampton Grammar School, Compton Road, Wolverhampton WV3 9RB, UK Of springs and strings Ronald Newburgh Extension School, Harvard University, Cambridge, MA 02138, USA Clarifying the concept Keith Atkin 14 Cortworth Road, Ecclesall, Sheffield S11 9LP, UK

  5. Letters to the Editor

    NASA Astrophysics Data System (ADS)

    1998-01-01

    All the Letters to the Editor in this issue are in the same PostScript or PDF file. Contents Physics and history Arthur I Miller Department of Science & Technology Studies, University College London, Gower Street, London WC1E 6BT, UK Physics and history: a reply David Miller Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK Cathode rays, the electron and Thomson's discovery John Harris 33 Glentham Road, London SW13 9JD, UK Vectors: swallow them whole! David Wheeler Mahanakorn University of Technology, Bangkok, Thailand

  6. The Correspondence Principle Revisited.

    ERIC Educational Resources Information Center

    Liboff, Richard L.

    1984-01-01

    Addresses the question of frequency correspondence in the domain of large quantum numbers, with reference to periodic systems. Provides two simple counterexamples (a particle in a cubical box and a rigid rotator) to show that the classical result is not always recovered in the limit of large quantum numbers. (JM)

  7. The letter height superiority illusion.

    PubMed

    New, Boris; Doré-Mazars, Karine; Cavézian, Céline; Pallier, Christophe; Barra, Julien

    2016-02-01

    Letters are identified better when they are embedded within words rather than within pseudowords, a phenomenon known as the word superiority effect (Reicher in Journal of Experimental Psychology, 81, 275-280, 1969). This effect is, inter alia, accounted for by the interactive-activation model (McClelland & Rumelhart in Psychological Review, 88, 375-407, 1981) through feedback from word to letter nodes. In this study, we investigated whether overactivation of features could lead to perceptual bias, wherein letters would be perceived as being taller than pseudoletters, or words would be perceived as being taller than pseudowords. In two experiments, we investigated the effects of letter and lexical status on the perception of size. Participants who had to compare the heights of letters and pseudoletters, or of words and pseudowords, indeed perceived the former stimuli as being taller than the latter. Possible alternative interpretations of this height superiority effect for letters and words are discussed. PMID:26370216

  8. Half a Century of Physical Review Letters

    ScienceCinema

    Garisto, Robert

    2010-01-08

    Fifty years ago, Sam Goudsmit started an experiment: the journal Physical Review Letters.  Since 1958, the experiment has thrived. PRL has gone through many changes, published many important papers, and become a leader in international scientific publication.  I will trace the rise of PRL from its early 20th century roots as "Letters to the Editor," through changes in editorial process and advents of new technology. Along the way I'll show what has gone on behind the scenes, and give a glimpse of our plans for the future.  I'll also give some advice to would-be authors and referees, illustrated with interesting correspondence we've received.

  9. Michael Maier--nine newly discovered letters.

    PubMed

    Lenke, Nils; Roudet, Nicolas; Tilton, Hereward

    2014-02-01

    The authors provide a transcription, translation, and evaluation of nine newly discovered letters from the alchemist Michael Maier (1568-1622) to Gebhardt Johann von Alvensleben (1576-1631), a noble landholder in the vicinity of Magdeburg. Stemming from the final year of his life, this correspondence casts new light on Maier's biography, detailing his efforts to secure patronage amid the financial crisis of the early Thirty Years' War. While his ill-fated quest to perfect potable gold continued to form the central focus of his patronage suits, Maier also offered his services in several arts that he had condemned in his printed works, namely astrology and "supernatural" magic. Remarks concerning his previously unknown acquaintance with Heinrich Khunrath call for a re-evaluation of Maier's negotiation of the discursive boundaries between Lutheran orthodoxy and Paracelsianism. The letters also reveal Maier's substantial contribution to a work previously ascribed solely to the English alchemist Francis Anthony. PMID:25241502

  10. The letters of John Dastin.

    PubMed

    Thiesen, Wilfred

    2008-07-01

    John Dastin, a noted alchemist who lived ca. 1300, followed the lead of many of his contemporaries and predecessors in using letters to propagate his views on alchemy. This article identifies a number of letters that Dastin wrote, and includes one text addressed to a cardinal of the city of Naples. This letter is virtually a copy of a work by Arnold of Villanova. I believe that other works ascribed to Dastin will also show a great dependence on Arnold's works. PMID:19048973

  11. The Visuo-Haptic and Haptic Exploration of Letters Increases the Kindergarten-Children's Understanding of the Alphabetic Principle

    ERIC Educational Resources Information Center

    Bara, Florence; Gentaz, Edouard; Cole, Pascale; Sprenger-Charolles, Liliane

    2004-01-01

    This study examined the effect of incorporating a visuo-haptic and haptic (tactual-kinaesthetic) exploration of letters in a training designed to develop phonemic awareness, knowledge of letters and letter/sound correspondences, on 5-year-old children's understanding and use of the alphabetic principle. Three interventions, which differed in the…

  12. A correspondence principle

    NASA Astrophysics Data System (ADS)

    Hughes, Barry D.; Ninham, Barry W.

    2016-02-01

    A single mathematical theme underpins disparate physical phenomena in classical, quantum and statistical mechanical contexts. This mathematical "correspondence principle", a kind of wave-particle duality with glorious realizations in classical and modern mathematical analysis, embodies fundamental geometrical and physical order, and yet in some sense sits on the edge of chaos. Illustrative cases discussed are drawn from classical and anomalous diffusion, quantum mechanics of single particles and ideal gases, quasicrystals and Casimir forces.

  13. What Can Reduce Letter Migrations in Letter Position Dyslexia?

    ERIC Educational Resources Information Center

    Friedmann, Naama; Rahamim, Einav

    2014-01-01

    Letter position dyslexia (LPD) is a peripheral dyslexia that causes errors of letter position within words, such as reading "cloud" as "could." In this study, we assessed the effect of various display manipulations and reading methods on the reading of 10 Hebrew readers with developmental LPD. These manipulations included…

  14. Visually discriminating upper case letters, lower case letters and numbers.

    PubMed

    Richmond, Janet; Waugh, Russell F; Konza, Deslea

    2015-01-01

    English and number literacy are important for successful learning and testing student literacy and numeracy standards enables early identification and remediation of children who have difficulty. Rasch measures were created with the RUMM2020 computer program for the perceptual constructs of visual discrimination upper case letters, lower case letters and numbers. Thirty items for Visual Discrimination of Upper Case Letters (VDUCL), 36 for Lower Case Letters (VDLCL) and 20 for Visual Discrimination of Numbers (VDN) were presented to 324 Pre-Primary through Year 4 children, aged 4-9 years old. All students attended school in Perth, Western Australia. Eighteen of the initial 30 items for VDUCL, thirty-one of the original 36 items for VDLCL and thirteen of the original 20 items for VDN were used to create linear scales (the others were deleted due to misfit) and these clearly showed which letters and numbers children said were easy and which were hard. PMID:25562334

  15. Correspondence: Searching sequence space

    SciTech Connect

    Youvan, D.C.

    1995-08-01

    This correspondence debates the efficiency and application of genetic algorithms (GAs) to search protein sequence space. The important experimental point is that such sparse searches utilize physically realistic syntheses. In this regard, all GA-based technologies are very similar; they {open_quotes}learn{close_quotes} from their initial sparse search and then generate interesting new proteins within a few iterations. Which GA-based technology is best? That probably depends on the protein and the specific engineering goal. Given the fact that the field of combinatorial chemistry is still in its infancy, it is probably wise to consider all of the proven mutagenesis methods. 19 refs.

  16. The Syllabic Bridge: The First Step in Learning Spelling-to-Sound Correspondences

    ERIC Educational Resources Information Center

    Doignon-Camus, Nadege; Zaga, Daniel

    2014-01-01

    It is widely agreed that learning to read starts with the establishment of letter-to-phoneme correspondences. However, it is also widely agreed that prereaders do not have access to phoneme units. Here we show that the building of associations between letters and syllables, which we call the "syllabic bridge", might be a faster and more…

  17. Letters in Biographies and Novels.

    ERIC Educational Resources Information Center

    Paterra, Elizabeth

    1997-01-01

    This is an annotated bibliography of biographies, historical fiction, contemporary stories, and discussion questions related to letter writing. A sidebar suggests an activity that involves reading a book about Ludwig van Beethoven, listening to Beethoven's music, and discussing letters in the story. (DGM)

  18. 48 CFR 42.504 - Postaward letters.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... CONTRACT ADMINISTRATION AND AUDIT SERVICES Postaward Orientation 42.504 Postaward letters. In some... orientation (in lieu of a conference). The letter should identify the Government representative...

  19. Two New Letters by Denning

    NASA Astrophysics Data System (ADS)

    Beech, Martin

    2010-06-01

    Two letters written by W. F. Denning to R. P. Greg in March and April of 1879 that had been tucked into the folds of an 1876 edition of the British Association for the Advancement of Science Reports were recently found at the Carnegie Institution in Washington D.C. The letters are wonderfully preserved, and offer us a snap-shot of the work being performed by a young Denning at the time when his influence in the field of meteor studies was in its ascendency. The contents of these two letters is analyzed and placed within context to Denning's other publications and private life.

  20. The Letter-Sound Generalization of First, Second, and Third Grade Finnish Children.

    ERIC Educational Resources Information Center

    Venezky, Richard L.

    To find how well children learn letter-sound correspondences when an orthography is highly regular, and how this ability relates to socioeconomic status (SES) and to reading ability, 240 Finnish children were tested for letter-sound generalizations. The test consisted of 25 synthetic words, constructed to look like Finnish words and to contain the…

  1. Effect of Autaptic Activity on Intrinsic Coherence Resonance in Newman-Watts Networks of Stochastic Hodgkin-Huxley Neurons

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Gong, Yubing

    2016-06-01

    In this paper, we study the effect of autaptic activity on intrinsic coherence resonance (CR) induced by channel noise in Newman-Watts (NW) networks of stochastic Hodgkin-Huxley (HH) neurons. It is found that autaptic strength and autaptic delay have a big effect on the intrinsic CR. As autaptic strength increases, there is optimal autaptic strength by which the intrinsic CR is most highly enhanced. Autaptic delay can enhance, reduce, or destroy the intrinsic CR, depending on the delay length. Moreover, there are optimal coupling strength and network randomness by which autaptic activity can most highly enhance the intrinsic CR. These results show that autaptic activity has different effects on the intrinsic CR in the neuronal networks, and it can most highly enhance the intrinsic CR at optimal coupling strength and network randomness. These findings could find potential implications of channel noise and autaptic activity for the information processing and transmission in neural systems.

  2. Effects of the spike timing-dependent plasticity on the synchronisation in a random Hodgkin-Huxley neuronal network

    NASA Astrophysics Data System (ADS)

    Borges, R. R.; Borges, F. S.; Lameu, E. L.; Batista, A. M.; Iarosz, K. C.; Caldas, I. L.; Viana, R. L.; Sanjuán, M. A. F.

    2016-05-01

    In this paper, we study the effects of spike timing-dependent plasticity on synchronisation in a network of Hodgkin-Huxley neurons. Neuron plasticity is a flexible property of a neuron and its network to change temporarily or permanently their biochemical, physiological, and morphological characteristics, in order to adapt to the environment. Regarding the plasticity, we consider Hebbian rules, specifically for spike timing-dependent plasticity (STDP), and with regard to network, we consider that the connections are randomly distributed. We analyse the synchronisation and desynchronisation according to an input level and probability of connections. Moreover, we verify that the transition for synchronisation depends on the neuronal network architecture, and the external perturbation level.

  3. [Hardware Implementation of Numerical Simulation Function of Hodgkin-Huxley Model Neurons Action Potential Based on Field Programmable Gate Array].

    PubMed

    Wang, Jinlong; Lu, Mai; Hu, Yanwen; Chen, Xiaoqiang; Pan, Qiangqiang

    2015-12-01

    Neuron is the basic unit of the biological neural system. The Hodgkin-Huxley (HH) model is one of the most realistic neuron models on the electrophysiological characteristic description of neuron. Hardware implementation of neuron could provide new research ideas to clinical treatment of spinal cord injury, bionics and artificial intelligence. Based on the HH model neuron and the DSP Builder technology, in the present study, a single HH model neuron hardware implementation was completed in Field Programmable Gate Array (FPGA). The neuron implemented in FPGA was stimulated by different types of current, the action potential response characteristics were analyzed, and the correlation coefficient between numerical simulation result and hardware implementation result were calculated. The results showed that neuronal action potential response of FPGA was highly consistent with numerical simulation result. This work lays the foundation for hardware implementation of neural network. PMID:27079105

  4. Two new species of South American freshwater crayfish genus Parastacus Huxley, 1879 (Crustacea: Decapoda: Parastacidae).

    PubMed

    Ribeiro, Felipe Bezerra; Buckup, Ludwig; Gomes, Kelly Martinez; Araujo, Paula Beatriz

    2016-01-01

    Two new species of Parastacus Huxley, 1879 are described from material collected in the state of Rio Grande do Sul, southern Brazil: Parastacus fluviatilis sp. nov. from highland streams and Parastacus caeruleodactylus sp. nov. from wetlands. Parastacus fluviatilis sp. nov. is distinguished mainly by large chelipeds with dense setae cover on the cutting edge of fingers, telson subtriangular with two lateral blunt spines and strongly concave ventral surface of lateral process of thoracic sternites 6 and 7. Parastacus caeruleodactylus sp. nov. is distinguished mainly by blue cheliped fingers and a large gap between them, reduced abdomen, dorsal and ventral margins of dactylus, propodus and carpus of second pair of pereiopods with tufts of long setae and mid-dorsal carina of exopod of uropods unarmed. According to IUCN Red List criteria both species are considered endangered. Habitat characterization and a method for defining the shape of second abdominal pleura are also provided. PMID:27615888

  5. Letters to a Young Writer.

    ERIC Educational Resources Information Center

    Waldman, Anne; Becker, Robin

    2002-01-01

    Presents words of encouragement to a young poet. Includes empathetic words and motivating ideas. Presents a letter including a quote from "Tintern Abbey" by William Wordsworth and ideas about that quote. (SG)

  6. Early predictors of letter knowledge.

    PubMed

    de Jong, P F; Olson, R K

    2004-07-01

    This study examined the influence of phonological memory and rapid naming on the development of letter knowledge. Participants were 77 Dutch children, who were followed from the start of their first kindergarten year (mean age 4 years 6.8 months) to the end of their second kindergarten year. Phonological memory was assessed by a nonword repetition test and a sentence repetition test. Rapid naming involved object naming. The study revealed found a substantial effect of phonological memory on the acquisition of letter knowledge that was particularly related to the ability to repeat nonwords. Vocabulary knowledge did not have an independent effect on letter learning after phonological memory was controlled. The study also showed a small effect of rapid naming on the acquisition of letter knowledge that was independent of the effect of phonological memory. Finally, the study also provided further evidence for a specific relation between phonological memory and vocabulary acquisition. PMID:15203300

  7. Letter from the Friends Chairman

    MedlinePlus

    ... Home Current Issue Past Issues Letter from the Friends Chairman Past Issues / Fall 2006 Table of Contents ... FNLM Chairman Paul Rogers converse at a recent Friends function at the National Library of Medicine. Photo ...

  8. Color associations for days and letters across different languages

    PubMed Central

    Rouw, Romke; Case, Laura; Gosavi, Radhika; Ramachandran, Vilayanur

    2014-01-01

    While colors are commonplace in everyday metaphors, relatively little is known about implicit color associations to linguistic or semantic concepts in a general population. In this study, we test color associations for ordered linguistic concepts (letters and days). The culture and language specificity of these effects was examined in a large group (457) of Dutch-speaking participants, 92 English-speaking participants, and 49 Hindi-speaking participants. Non-random distributions of color choices were revealed; consistencies were found across the three language groups in color preferences for both days and letters. Interestingly, while the Hindi-speaking participants were presented with letter stimuli matched on phonology, their pattern of letter-to-color preferences still showed similarities with Dutch- and English-speaking participants. Furthermore, we found that that the color preferences corresponded between participants indicating to have conscious color experiences with letters or days (putative synesthetes) and participants who do not (non-synesthetes). We also explored possible mechanisms underlying the color preferences. There were a few specific associations, including red for “A,” red for “Monday,” and white for “Sunday.” We also explored more general mechanisms, such as overall color preferences as shown by Simner et al. (2005). While certainly not all variation can be explained or predicted, the results show that regularities are present in color-to-letter or color-to-day preferences in both putative synesthetes and non-synesthetes across languages. Both letter-to-color and day-to-color preferences were influenced by multiple factors. The findings support a notion of abstract concepts (such as days and letters) that are not represented in isolation, but are connected to perceptual representational systems. Interestingly, at least some of these connections to color representations are shared across different language/cultural groups. PMID

  9. 46 CFR 115.306 - Stability letter.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... stability letter must be posted under glass or other suitable transparent material, such that all pages are... 46 Shipping 4 2014-10-01 2014-10-01 false Stability letter. 115.306 Section 115.306 Shipping COAST... of Certificates, Permits, and Stability Letters § 115.306 Stability letter. When, in accordance...

  10. 46 CFR 115.306 - Stability letter.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... stability letter must be posted under glass or other suitable transparent material, such that all pages are... 46 Shipping 4 2013-10-01 2013-10-01 false Stability letter. 115.306 Section 115.306 Shipping COAST... of Certificates, Permits, and Stability Letters § 115.306 Stability letter. When, in accordance...

  11. 46 CFR 176.306 - Stability letter.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... letter, the stability letter must be posted under glass or other suitable transparent material, such that... 46 Shipping 7 2012-10-01 2012-10-01 false Stability letter. 176.306 Section 176.306 Shipping COAST...) INSPECTION AND CERTIFICATION Posting of Certificates, Permits, and Stability Letters § 176.306...

  12. 46 CFR 115.306 - Stability letter.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... stability letter must be posted under glass or other suitable transparent material, such that all pages are... 46 Shipping 4 2012-10-01 2012-10-01 false Stability letter. 115.306 Section 115.306 Shipping COAST... of Certificates, Permits, and Stability Letters § 115.306 Stability letter. When, in accordance...

  13. 46 CFR 176.306 - Stability letter.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... letter, the stability letter must be posted under glass or other suitable transparent material, such that... 46 Shipping 7 2010-10-01 2010-10-01 false Stability letter. 176.306 Section 176.306 Shipping COAST...) INSPECTION AND CERTIFICATION Posting of Certificates, Permits, and Stability Letters § 176.306...

  14. 46 CFR 115.306 - Stability letter.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... stability letter must be posted under glass or other suitable transparent material, such that all pages are... 46 Shipping 4 2010-10-01 2010-10-01 false Stability letter. 115.306 Section 115.306 Shipping COAST... of Certificates, Permits, and Stability Letters § 115.306 Stability letter. When, in accordance...

  15. 46 CFR 176.306 - Stability letter.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... letter, the stability letter must be posted under glass or other suitable transparent material, such that... 46 Shipping 7 2011-10-01 2011-10-01 false Stability letter. 176.306 Section 176.306 Shipping COAST...) INSPECTION AND CERTIFICATION Posting of Certificates, Permits, and Stability Letters § 176.306...

  16. 46 CFR 176.306 - Stability letter.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... letter, the stability letter must be posted under glass or other suitable transparent material, such that... 46 Shipping 7 2014-10-01 2014-10-01 false Stability letter. 176.306 Section 176.306 Shipping COAST...) INSPECTION AND CERTIFICATION Posting of Certificates, Permits, and Stability Letters § 176.306...

  17. Letter Writing: A Tool for Counselor Educators

    ERIC Educational Resources Information Center

    Hoffman, Rachel M.

    2008-01-01

    Letter writing is an integral component of narrative therapy practice. In addition to the benefits of letter writing in counseling practice, letter writing may hold interesting possibilities for use in counselor education. This article provides a brief review of the benefits of letter writing in counseling practice and discusses the potential use…

  18. Embedded Picture Mnemonics to Learn Letters

    ERIC Educational Resources Information Center

    Shmidman, Adina; Ehri, Linnea

    2010-01-01

    Can embedded mnemonics ease the task of learning a foreign alphabet? English-speaking preschoolers (N = 36, M = 5;2 years) were taught 10 Hebrew letter-sound relations. Experimental letters were learned with mnemonics that embedded letter shapes in drawings of objects whose shapes resembled the letters and whose English names began with the…

  19. 42 CFR 93.202 - Charge letter.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Charge letter. 93.202 Section 93.202 Public Health... MISCONDUCT Definitions § 93.202 Charge letter. Charge letter means the written notice, as well as any... HHS administrative actions. If the charge letter includes a debarment or suspension action, it may...

  20. 19 CFR 356.16 - Charging letter.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 19 Customs Duties 3 2010-04-01 2010-04-01 false Charging letter. 356.16 Section 356.16 Customs... Undertaking § 356.16 Charging letter. (a) Contents of letter. The Deputy Under Secretary will initiate proceedings by issuing a charging letter to each charged party and affected party which includes: (1)...

  1. 42 CFR 93.202 - Charge letter.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 1 2011-10-01 2011-10-01 false Charge letter. 93.202 Section 93.202 Public Health... MISCONDUCT Definitions § 93.202 Charge letter. Charge letter means the written notice, as well as any... HHS administrative actions. If the charge letter includes a debarment or suspension action, it may...

  2. 19 CFR 356.16 - Charging letter.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 19 Customs Duties 3 2011-04-01 2011-04-01 false Charging letter. 356.16 Section 356.16 Customs... Undertaking § 356.16 Charging letter. (a) Contents of letter. The Deputy Under Secretary will initiate proceedings by issuing a charging letter to each charged party and affected party which includes: (1)...

  3. Effects of Letter-Identification Training on Letter Naming in Prereading Children

    ERIC Educational Resources Information Center

    Hayashi, Yusuke; Schmidt, Anna C.; Saunders, Kathryn J.

    2013-01-01

    Three prereading children who named 0 to 3 of 20 targeted letters were taught to select the 20 printed letters when they heard spoken letter names. For all participants, letter-identification training resulted in naming for the majority of letters.

  4. Language General and Specific Factors in Letter Acquisition: Considering Child and Letter Characteristics in Korean

    ERIC Educational Resources Information Center

    Kim, Young-Suk; Petscher, Yaacov

    2013-01-01

    In the present study we investigated the extent to which child level factors (i.e., phonological awareness) and letter level factors (i.e., letter name structures, letter frequency, visual similarity, and letter order) contributed to letter name and sound acquisition, using data from Korean-speaking children (N = 169) and cross-classified…

  5. Letters from ainsworth: contesting the 'organization' of attachment.

    PubMed

    Landa, Sophie; Duschinsky, Robbie

    2013-05-01

    As Main (1999) noted in her obituary for Mary Ainsworth, 'she was interacting weekly by letter and manuscript with her mentor and friend, John Bowlby, and their academic correspondence formed an important part of her, and implicitly our, life.' These letters of Ainsworth to John Bowlby during the 1980s, available in the Wellcome Trust Library in London, contain valuable reflections on the work of her pupils to extend her system of classifying infant behaviour in the Strange Situation Procedure. Mary Main proposed a D classification and interpreted such behaviour as a breakdown in an ABC strategy caused by a conflict between a disposition to approach and flee from the caregiver. Patricia Crittenden extended the subtypes of A and C, using a developmental model of information processing, and observed that they could be used together in A/C combinations. These letters offer insight into Ainsworth's intellectual rationale for encouraging both Main and Crittenden in their conflicting endeavours. PMID:23667365

  6. Correspondence

    PubMed Central

    Almli, Lynn M.; Srivastava, Amita; Fani, Negar; Kerley, Kimberly; Mercer, Kristina B.; Feng, Hao; Bradley, Bekh; Ressler, Kerry J.

    2014-01-01

    Follow-up and Extension of a Prior Genome-wide Association Study of Posttraumatic Stress Disorder: Gene × Environment Associations and Structural Magnetic Resonance Imaging in a Highly Traumatized African-American Civilian Population PMID:24576688

  7. The Lyttleton-Hoyle correspondence 1939-42

    NASA Astrophysics Data System (ADS)

    Mitton, S.

    2005-12-01

    Fred Hoyle started to collaborate with his older colleague Raymond Lyttleton in 1938. Hoyle's doctoral research had been in nuclear physics, and his supervisors were Rudolph Peierls and Paul Dirac. His first papers were in quantum electrodynamics. When Hoyle decided to change his research field to astronomy, Lyttleton acted as a mentor, and it was he who suggested that Hoyle should look at the physics of accretion. From late-1939, Lyttleton and Hoyle were both scientific civil servants drafted in for war work. They were in different establishments and could communicate only by the postal service. Some 70 letters from Lyttleton to Hoyle have survived, but we do not have any copies of Hoyle's correspondence. Many letters are undated, so it required detective work to assemble them in the correct sequence. The correspondence shows that Lyttleton played the senior role in determining what problems they should tackle, and in what order. Apart from the scientific content, these letters are remarkable for the sharp personal remarks Lyttleton makes of other colleagues, and particularly the Council of the Royal Astronomical Society. I make the suggestion that the poisonous and prolonged nature of the correspondence considerably influenced Hoyle's subsequent attitude to the establishment, to government-employed astronomers, and to the RAS. This was detrimental when Hoyle found, later in his career, that he would have to provide answers to these stakeholders. This research has been supported by St Edmund's College, Cambridge, UK.

  8. CORRESPONDENCE EDUCATION IN THE NETHERLANDS.

    ERIC Educational Resources Information Center

    SLOOS, ISAAEC; AND OTHERS

    RECENT TRENDS AND EVIDENCES OF PROGRESS IN CORRESPONDENCE EDUCATION IN THE NETHERLANDS ARE CONSIDERED, TOGETHER WITH RESEARCH ON THE SOCIOCULTURAL AND MOTIVATIONAL ASPECTS OF PARTICIPATION IN CORRESPONDENCE STUDY, AND THE SPECIAL FUNCTIONS AND ADVANTAGES OF THE CORRESPONDENCE METHOD. THEORIES AND IDEAS UNDERLYING THE DIDACTICS OF CORRESPONDENCE…

  9. "The Scarlet Letter". [Lesson Plan].

    ERIC Educational Resources Information Center

    Discovery Communications, Inc., Bethesda, MD.

    Based on Nathaniel Hawthorne's novel "The Scarlet Letter," this lesson plan presents activities designed to help students understand that the ending of a novel does not resolve all of the questions that may occur to readers; and that readers may imagine characters living out their lives beyond the ending the author gave to a novel. The main…

  10. The Harvard Education Letter, 1995.

    ERIC Educational Resources Information Center

    Miller, Edward, Ed.

    1995-01-01

    This document is comprised of volume 11 of the Harvard Education Letter, published bimonthly and addressing current issues in elementary and secondary education. Articles in the volume's six issues are: (1) January-February--"The Old Model of Staff Development Survives in a World Where Everything Else Has Changed" (Miller), "Giving Voice to Our…

  11. Resource Letter N-1: Nanotechnology

    NASA Astrophysics Data System (ADS)

    Cela, Devin; Dresselhaus, Mildred; Helen Zeng, Tingying; Terrones, Mauricio; Souza Filho, Antonio G.; Ferreira, Odair P.

    2014-01-01

    This Resource Letter provides a guide to the literature on Nanotechnology. Journal articles, books, websites, and other documents are cited on the following topics: attributes of various types of nanomaterials, nanotechnology in the context of different academic fields, and the effects of nanotechnology on society.

  12. The Harvard Education Letter, 1998.

    ERIC Educational Resources Information Center

    Graves-Desai, Kelly, Ed.; Eaton, Susan, Ed.; Walser, Nancy, Ed.

    1998-01-01

    This document is comprised of volume 14 of the Harvard Education Letter, published bimonthly and addressing current issues in elementary and secondary education. Articles in the six issues of this volume include the following: (1) January-February--"Multi-Age Classrooms: An Age-Old Grouping Method Is Still Evolving" (Walser), "Teachers Wanted:…

  13. Letter to the next President

    ERIC Educational Resources Information Center

    Rotherham, Andrew J.; Mikuta, Julie; Freeland, Julia

    2008-01-01

    This article takes the form of a letter to the 44th president of the United States, urging the president to pursue an aggressive agenda to improve teacher quality. The authors assert that because teacher quality is the single most important factor shown to impact student outcomes, the next administration must dedicate resources to human capital…

  14. The Principal and Reference Letters.

    ERIC Educational Resources Information Center

    Smith, Agnes E.; Permuth, Steve; Gray, David L.

    1999-01-01

    Requests to write letters of reference for former teachers can be legally problematic. Principals should know relevant state laws; have employees sign a release from liability; provide only factual information; maintain fair personnel files; avoid telephone recommendations; disclose information on a need-to-know basis; and avoid performance…

  15. Resource Letter RC-1: Cosmology

    ERIC Educational Resources Information Center

    Ryan, Michael P., Jr.; Shepley, L. C.

    1976-01-01

    This is one of a series of resource letters on different topics intended to guide college physicists, astronomers, and other scientists to some of the literature and other teaching aids that may help improve course content in specified fields. (Author/CP)

  16. The Harvard Education Letter, 1996.

    ERIC Educational Resources Information Center

    Miller, Edward Ed.; Graves-Desai, Kelly, Ed.; Maloney, Karen, Ed.

    1996-01-01

    This document is comprised of volume 12 of the Harvard Education Letter, published bimonthly and addressing current issues in elementary-secondary education. Articles in this volume include the following: (1) January-February--"Early Reports From Kentucky on Cash Rewards for 'Successful' Schools Reveal Many Problems" (Miller), "New Ideas Like…

  17. Letter to Russia

    SciTech Connect

    Tobin, J G

    2012-03-15

    find it puzzling that the authors nonetheless claim in their conclusions that 'An evaluation of state occupations supports the proposal that the occupation of the 5f levels in bulk Pu must be near 5'. Apart from the aforementioned conceptual inconsistencies, there are a number of more technical aspects that are not discussed in sufficient detail. Among these are: (1) The authors use LDA to approximate the electron correlations. A lively debate takes place in the literature whether this approximation can adequately describe the electronic structure of Pu metal or not, yet the authors do not discuss the choice of the approximation at all, which they should, in my opinion. They should also specify if their solutions are spin polarized or whether they use spin-restricted LDA. (2) The quality of the employed basis set is not clear. Are the results converged with respect to the basis size? What is the estimated magnitude of the residual errors? (3) There are statements in the manuscript indicating that the cluster calculations depend somehow on the calculations of the diatomic molecule. Namely: 'Underpinning these calculations, there is a geometry optimization of diatomic molecules...' and 'Underlying the Pu cluster simulations is the calculation of the electronic structure of a Pu2 dimer with the bond length 3.28 {angstrom} corresponding to the inter-atomic distances in delta-Pu.' What does this underpinning/underlying mean in more technical terms? What role does the geometry optimization play when the cluster calculations seem to be performed at a fixed geometry corresponding to the delta-Pu? Lastly, the manuscript contains a lot of material that was previously (and often multiple times) published elsewhere, including the Physical Review journals. For instance, the experimental part of Fig. 2 was shown already in Refs. 26, 27 and 28 in essentially the same graphical form; the top part of Fig. 9 appeared in Refs. 19, 4 and in PRL 90, 196404 (2003). I think that reprinting

  18. 77 FR 56635 - List of Correspondence From January 1, 2012, Through March 31, 2012

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-13

    ...The Secretary is publishing the following list of correspondence from the U.S. Department of Education (Department) to individuals during the previous quarter. The correspondence on this list describes the Department's interpretations of the Individuals with Disabilities Education Act (IDEA) or the regulations that implement the IDEA. This list and the letters or other documents described in......

  19. 77 FR 17050 - List of Correspondence From October 1, 2011, through December 31, 2011

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-23

    ...The Secretary is publishing the following list of correspondence from the U.S. Department of Education (Department) to individuals during the previous quarter. The correspondence describes the Department's interpretations of the Individuals with Disabilities Education Act (IDEA) or the regulations that implement the IDEA. This list and the letters or other documents described in this list,......

  20. Similar Sound Separation and Cumulative Introduction in Learning Letter-Sound Correspondences

    ERIC Educational Resources Information Center

    Carnine, Douglas W.

    1976-01-01

    Since similarity inhibits learning, children will have greater difficulty learning responses that are more similar to each other; the instructional procedure of separating similar sounds was evaluated in two experiments. (DMT)

  1. Finland, Phonics, and Whole Language: Beginning Reading in a Regular Letter-Sound Correspondence Language.

    ERIC Educational Resources Information Center

    Korkeamaki, Riitta-Liisa; Dreher, Mariam Jean

    1993-01-01

    Reviews the typical approach (synthetic phonics) to teaching reading in Finland. Suggests that teachers in English-speaking countries can learn from problems Finnish teachers face and vice versa. Finds that, despite a highly regular writing system, Finnish teachers find that a heavy phonics emphasis does not solve their reading instruction…

  2. Effect of duration of synaptic activity on spike rate of a Hodgkin-Huxley neuron with delayed feedback

    NASA Astrophysics Data System (ADS)

    Hashemi, M.; Valizadeh, A.; Azizi, Y.

    2012-02-01

    A recurrent loop consisting of a single Hodgkin-Huxley neuron influenced by a chemical excitatory delayed synaptic feedback is considered. We show that the behavior of the system depends on the duration of the activity of the synapse, which is determined by the activation and deactivation time constants of the synapse. For the fast synapses, those for which the effect of the synaptic activity is small compared to the period of firing, depending on the delay time, spiking with single and multiple interspike intervals is possible and the average firing rate can be smaller or larger than that of the open loop neuron. For slow synapses for which the synaptic time constants are of order of the period of the firing, the self-excitation increases the firing rate for all values of the delay time. We also show that for a chain consisting of few similar oscillators, if the synapses are chosen from different time constants, the system will follow the dynamics imposed by the fastest element, which is the oscillator that receives excitations via a slow synapse. The generalization of the results to other types of relaxation oscillators is discussed and the results are compared to those of the loops with inhibitory synapses as well as with gap junctions.

  3. Spontaneous voltage oscillations and response dynamics of a Hodgkin-Huxley type model of sensory hair cells

    PubMed Central

    2011-01-01

    We employ a Hodgkin-Huxley-type model of basolateral ionic currents in bullfrog saccular hair cells for studying the genesis of spontaneous voltage oscillations and their role in shaping the response of the hair cell to external mechanical stimuli. Consistent with recent experimental reports, we find that the spontaneous dynamics of the model can be categorized using conductance parameters of calcium-activated potassium, inward rectifier potassium, and mechano-electrical transduction (MET) ionic currents. The model is demonstrated for exhibiting a broad spectrum of autonomous rhythmic activity, including periodic and quasi-periodic oscillations with two independent frequencies as well as various regular and chaotic bursting patterns. Complex patterns of spontaneous oscillations in the model emerge at small values of the conductance of Ca2+-activated potassium currents. These patterns are significantly affected by thermal fluctuations of the MET current. We show that self-sustained regular voltage oscillations lead to enhanced and sharply tuned sensitivity of the hair cell to weak mechanical periodic stimuli. While regimes of chaotic oscillations are argued to result in poor tuning to sinusoidal driving, chaotically oscillating cells do provide a high sensitivity to low-frequency variations of external stimuli. PMID:22282726

  4. A single order-disorder transition generates tension during the Huxley-Simmons phase 2 in muscle.

    PubMed

    Davis, J S; Harrington, W F

    1993-11-01

    Increasing temperature was used to progressively interconvert non-force-generating into force-generating states in skinned rabbit psoas muscle fibers contracting isometrically. Laser temperature-jump and length-jump experiments were used to characterize tension generation in the time domain of the Huxley-Simmons phase 2. In our experiments, phase 2 is subdivisible into two kinetic steps each with quite different physical properties. The fast kinetic component has rate constant of 950 s-1 at 1 degrees C and a Q10 of approximately 1.2. Its rate is tension insensitive and its normalized amplitude declines with rising temperature--behavior that closely parallels the instantaneous stiffness of the cross-bridge. It is likely that this kinetic step is a manifestation of a damped elastic element/s in the fiber. The slow component of phase 2 is temperature-dependent with a Q10 of approximately 3.0. Its rate is sensitive to tension. Unlike the fast component, its amplitude remains in fixed proportion to isometric tension at different temperatures indicating direct participation in tension generation. Similar T-jump studies on frog fibers are also included. The combined results (frog and rabbit) suggest that tension generation occurs in a single endothermic (entropy driven) step in phase 2. PMID:8298018

  5. Effects of channel noise on synchronization transitions in delayed scale-free network of stochastic Hodgkin-Huxley neurons

    NASA Astrophysics Data System (ADS)

    Wang, Bao-Ying; Gong, Yu-Bing

    2015-11-01

    We numerically study the effect of the channel noise on the spiking synchronization of a scale-free Hodgkin-Huxley neuron network with time delays. It is found that the time delay can induce synchronization transitions at an intermediate and proper channel noise intensity, and the synchronization transitions become strongest when the channel noise intensity is optimal. The neurons can also exhibit synchronization transitions as the channel noise intensity is varied, and this phenomenon is enhanced at around the time delays that can induce the synchronization transitions. It is also found that the synchronization transitions induced by the channel noise are dependent on the coupling strength and the network average degree, and there is an optimal coupling strength or network average degree with which the synchronization transitions become strongest. These results show that by inducing synchronization transitions, the channel noise has a big regulation effect on the synchronization of the neuronal network. These findings could find potential implications for the information transmission in neural systems. Project supported by the Natural Science Foundation of Shandong Province of China (Grant No. ZR2012AM013).

  6. Membrane Capacitive Memory Alters Spiking in Neurons Described by the Fractional-Order Hodgkin-Huxley Model

    PubMed Central

    Weinberg, Seth H.

    2015-01-01

    Excitable cells and cell membranes are often modeled by the simple yet elegant parallel resistor-capacitor circuit. However, studies have shown that the passive properties of membranes may be more appropriately modeled with a non-ideal capacitor, in which the current-voltage relationship is given by a fractional-order derivative. Fractional-order membrane potential dynamics introduce capacitive memory effects, i.e., dynamics are influenced by a weighted sum of the membrane potential prior history. However, it is not clear to what extent fractional-order dynamics may alter the properties of active excitable cells. In this study, we investigate the spiking properties of the neuronal membrane patch, nerve axon, and neural networks described by the fractional-order Hodgkin-Huxley neuron model. We find that in the membrane patch model, as fractional-order decreases, i.e., a greater influence of membrane potential memory, peak sodium and potassium currents are altered, and spike frequency and amplitude are generally reduced. In the nerve axon, the velocity of spike propagation increases as fractional-order decreases, while in a neural network, electrical activity is more likely to cease for smaller fractional-order. Importantly, we demonstrate that the modulation of the peak ionic currents that occurs for reduced fractional-order alone fails to reproduce many of the key alterations in spiking properties, suggesting that membrane capacitive memory and fractional-order membrane potential dynamics are important and necessary to reproduce neuronal electrical activity. PMID:25970534

  7. Membrane capacitive memory alters spiking in neurons described by the fractional-order Hodgkin-Huxley model.

    PubMed

    Weinberg, Seth H

    2015-01-01

    Excitable cells and cell membranes are often modeled by the simple yet elegant parallel resistor-capacitor circuit. However, studies have shown that the passive properties of membranes may be more appropriately modeled with a non-ideal capacitor, in which the current-voltage relationship is given by a fractional-order derivative. Fractional-order membrane potential dynamics introduce capacitive memory effects, i.e., dynamics are influenced by a weighted sum of the membrane potential prior history. However, it is not clear to what extent fractional-order dynamics may alter the properties of active excitable cells. In this study, we investigate the spiking properties of the neuronal membrane patch, nerve axon, and neural networks described by the fractional-order Hodgkin-Huxley neuron model. We find that in the membrane patch model, as fractional-order decreases, i.e., a greater influence of membrane potential memory, peak sodium and potassium currents are altered, and spike frequency and amplitude are generally reduced. In the nerve axon, the velocity of spike propagation increases as fractional-order decreases, while in a neural network, electrical activity is more likely to cease for smaller fractional-order. Importantly, we demonstrate that the modulation of the peak ionic currents that occurs for reduced fractional-order alone fails to reproduce many of the key alterations in spiking properties, suggesting that membrane capacitive memory and fractional-order membrane potential dynamics are important and necessary to reproduce neuronal electrical activity. PMID:25970534

  8. Teaching and learning the Hodgkin-Huxley model based on software developed in NEURON’s programming language hoc

    PubMed Central

    2013-01-01

    Background We present a software tool called SENB, which allows the geometric and biophysical neuronal properties in a simple computational model of a Hodgkin-Huxley (HH) axon to be changed. The aim of this work is to develop a didactic and easy-to-use computational tool in the NEURON simulation environment, which allows graphical visualization of both the passive and active conduction parameters and the geometric characteristics of a cylindrical axon with HH properties. Results The SENB software offers several advantages for teaching and learning electrophysiology. First, SENB offers ease and flexibility in determining the number of stimuli. Second, SENB allows immediate and simultaneous visualization, in the same window and time frame, of the evolution of the electrophysiological variables. Third, SENB calculates parameters such as time and space constants, stimuli frequency, cellular area and volume, sodium and potassium equilibrium potentials, and propagation velocity of the action potentials. Furthermore, it allows the user to see all this information immediately in the main window. Finally, with just one click SENB can save an image of the main window as evidence. Conclusions The SENB software is didactic and versatile, and can be used to improve and facilitate the teaching and learning of the underlying mechanisms in the electrical activity of an axon using the biophysical properties of the squid giant axon. PMID:23675833

  9. FROM THE HISTORY OF PHYSICS: Correspondence between G A Gamow and P L Kapitza

    NASA Astrophysics Data System (ADS)

    Frenkel', Viktor Ya

    1994-08-01

    The letters exchanged between Peter Kapitza and George Gamow are published here for the first time. The correspondence throws light on the active support accorded by Kapitza to his Russian colleagues and on his work as the coeditor of a prestigious series of physics monographs published by Clarendon Press, Oxford. Gamow comes over in his letters, relating to one of the most interesting periods of his creative activity (1929 - 1934), in full blaze of his personality.

  10. How to write an editorial letter?

    PubMed

    Süer, Evren; Yaman, Önder

    2013-09-01

    In most journals, there are letters or answers sections. Letters to the editor are usually a type of short communication that can be written on any topic that attracts the attention of the readers. Although articles are stringently vetted before publication in a journal, some issues can still go unnoticed. In this situation, readers can offer their interpretations by writing a letter to the editor. Thus, letters are also a control mechanism that facilitates progress after an article has been published. One of the most important aspects of a letter to the editor is that it must be short. It is known that a letter is more easily accessible to readers when the message is short and brief. The letter to the editor or author must make reference to objectives or discussions on medical, scientific or general topics that may attract attention. A letter must have a purpose, and it should convey its message in a short and definitive fashion. PMID:26328135

  11. Letters of Reprimand: The Important Questions.

    ERIC Educational Resources Information Center

    Zirkel, Perry A.; Gluckman, Ivan B.

    1986-01-01

    Outlines two legal cases involving letters of reprimand written by administrators and put in teachers' files. Shows how in these cases the letters did not constitute defamation or a violation of First or Fourteenth Amendment rights. (MD)

  12. Texture-Based Correspondence Display

    NASA Technical Reports Server (NTRS)

    Gerald-Yamasaki, Michael

    2004-01-01

    Texture-based correspondence display is a methodology to display corresponding data elements in visual representations of complex multidimensional, multivariate data. Texture is utilized as a persistent medium to contain a visual representation model and as a means to create multiple renditions of data where color is used to identify correspondence. Corresponding data elements are displayed over a variety of visual metaphors in a normal rendering process without adding extraneous linking metadata creation and maintenance. The effectiveness of visual representation for understanding data is extended to the expression of the visual representation model in texture.

  13. Making Routine Letters Have Positive Effects.

    ERIC Educational Resources Information Center

    Walsh, S. M.

    While few business people dispute the importance of carefully crafting persuasive, demanding, conciliatory, and bad-news letters, the regular flow of routine communications receives very little meaningful consideration or scrutiny. These routine communications (letters, inquiries, requests, collection letters, complaints, confirmations,…

  14. Are Letter Detection and Proofreading Tasks Equivalent?

    ERIC Educational Resources Information Center

    Saint-Aubin, Jean; Losier, Marie-Claire; Roy, Macha; Lawrence, Mike

    2015-01-01

    When readers search for misspellings in a proofreading task or for a letter in a letter detection task, they are more likely to omit function words than content words. However, with misspelled words, previous findings for the letter detection task were mixed. In two experiments, the authors tested the functional equivalence of both tasks. Results…

  15. Educators' Liability for Negative Letters of Recommendation.

    ERIC Educational Resources Information Center

    Tidwell, James A.

    1986-01-01

    Discusses the protection of "qualified privilege" provided by the law to teachers writing letters of recommendation for students. The letter must be written in good faith and with a belief that it contains no inaccurate information. Reviews some related court decisions and provides seven recommendations for writing such letters. (MD)

  16. 24 CFR 200.1505 - Warning letter.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... URBAN DEVELOPMENT GENERAL INTRODUCTION TO FHA PROGRAMS Multifamily Accelerated Processing (MAP): MAP... letter, which specifies problems or violations identified by HUD, to a MAP lender. (b) Effect of warning letter. The warning letter: (1) Does not suspend a lender's MAP privileges; (2) May impose a higher...

  17. 48 CFR 3416.603 - Letter contracts.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 48 Federal Acquisition Regulations System 7 2013-10-01 2012-10-01 true Letter contracts. 3416.603... CONTRACTING METHODS AND CONTRACT TYPES TYPES OF CONTRACTS Time-and-Materials, Labor-Hour, and Letter Contracts 3416.603 Letter contracts....

  18. 48 CFR 3016.603 - Letter contracts.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 48 Federal Acquisition Regulations System 7 2013-10-01 2012-10-01 true Letter contracts. 3016.603... ACQUISITION REGULATION (HSAR) CONTRACT METHODS AND CONTRACT TYPES TYPES OF CONTRACTS Time-and-Materials, Labor-Hour, and Letter Contracts 3016.603 Letter contracts....

  19. Beyond Zebra: Preschoolers' Knowledge about Letters.

    ERIC Educational Resources Information Center

    Treiman, Rebecca; Richmond-Welty, E. Daylene; Tincoff, Ruth

    1997-01-01

    Argues that an important type of child knowledge about letters is knowledge of the phonological structure of the letters' names in English. Concludes that learning the alphabet forms the basis for generalizations about the structure of letter names. (22 references) (Author/CK)

  20. 46 CFR 176.306 - Stability letter.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 7 2013-10-01 2013-10-01 false Stability letter. 176.306 Section 176.306 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS (UNDER 100 GROSS TONS) INSPECTION AND CERTIFICATION Posting of Certificates, Permits, and Stability Letters § 176.306 Stability letter. When, in accordance with § 178.210...

  1. 24 CFR 200.1505 - Warning letter.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... URBAN DEVELOPMENT GENERAL INTRODUCTION TO FHA PROGRAMS Multifamily Accelerated Processing (MAP): MAP... letter, which specifies problems or violations identified by HUD, to a MAP lender. (b) Effect of warning letter. The warning letter: (1) Does not suspend a lender's MAP privileges; (2) May impose a higher...

  2. 24 CFR 200.1505 - Warning letter.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... URBAN DEVELOPMENT GENERAL INTRODUCTION TO FHA PROGRAMS Multifamily Accelerated Processing (MAP): MAP... letter, which specifies problems or violations identified by HUD, to a MAP lender. (b) Effect of warning letter. The warning letter: (1) Does not suspend a lender's MAP privileges; (2) May impose a higher...

  3. 24 CFR 200.1505 - Warning letter.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... URBAN DEVELOPMENT GENERAL INTRODUCTION TO FHA PROGRAMS Multifamily Accelerated Processing (MAP): MAP... letter, which specifies problems or violations identified by HUD, to a MAP lender. (b) Effect of warning letter. The warning letter: (1) Does not suspend a lender's MAP privileges; (2) May impose a higher...

  4. 24 CFR 200.1505 - Warning letter.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... URBAN DEVELOPMENT GENERAL INTRODUCTION TO FHA PROGRAMS Multifamily Accelerated Processing (MAP): MAP... letter, which specifies problems or violations identified by HUD, to a MAP lender. (b) Effect of warning letter. The warning letter: (1) Does not suspend a lender's MAP privileges; (2) May impose a higher...

  5. 19 CFR 354.7 - Charging letter.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 19 Customs Duties 3 2011-04-01 2011-04-01 false Charging letter. 354.7 Section 354.7 Customs... VIOLATION OF AN ANTIDUMPING OR COUNTERVAILING DUTY ADMINISTRATIVE PROTECTIVE ORDER § 354.7 Charging letter. (a) Contents of Letter. The Deputy Under Secretary will initiate proceedings by issuing a...

  6. 19 CFR 354.7 - Charging letter.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 19 Customs Duties 3 2010-04-01 2010-04-01 false Charging letter. 354.7 Section 354.7 Customs... VIOLATION OF AN ANTIDUMPING OR COUNTERVAILING DUTY ADMINISTRATIVE PROTECTIVE ORDER § 354.7 Charging letter. (a) Contents of Letter. The Deputy Under Secretary will initiate proceedings by issuing a...

  7. Letter Dice. Technical Note No. 6.

    ERIC Educational Resources Information Center

    Gunter, Jock

    Letter and syllable dice devised for a project in rural Ecuador provide inexpensive, easily reproducible learning materials for practice in basic literary skills. Eleven wooden cubes with six letters on each cube are cast onto a surface and the player constructs words from the letters on the top side of the dice. After a word is formed and…

  8. Learning Letter Names and Sounds: Effects of Instruction, Letter Type, and Phonological Processing Skill

    ERIC Educational Resources Information Center

    Piasta, Shayne B.; Wagner, Richard K.

    2010-01-01

    Preschool-age children (N = 58) were randomly assigned to receive instruction in letter names and sounds, letter sounds only, or numbers (control). Multilevel modeling was used to examine letter name and sound learning as a function of instructional condition and characteristics of both letters and children. Specifically, learning was examined in…

  9. What Do Letter Migration Errors Reveal About Letter Position Coding in Visual Word Recognition?

    ERIC Educational Resources Information Center

    Davis, Colin J.; Bowers, Jeffrey S.

    2004-01-01

    Dividing attention across multiple words occasionally results in misidentifications whereby letters apparently migrate between words. Previous studies have found that letter migrations preserve within-word letter position, which has been interpreted as support for position-specific letter coding. To investigate this issue, the authors used word…

  10. An Attempt to Simulate Letter-by-Letter Dyslexia in Normal Readers

    ERIC Educational Resources Information Center

    Fiset, Stephanie; Arguin, Martin; Fiset, Daniel

    2006-01-01

    We attempted to simulate the main features of letter-by-letter (LBL) dyslexia in normal readers through stimulus degradation (i.e. contrast reduction and removal of high spatial frequencies). The results showed the word length and the letter confusability effects characteristic of LBL dyslexia. However, the interaction of letter confusability and…

  11. Generalized Constrained Multiple Correspondence Analysis.

    ERIC Educational Resources Information Center

    Hwang, Heungsun; Takane, Yoshio

    2002-01-01

    Proposes a comprehensive approach, generalized constrained multiple correspondence analysis, for imposing both row and column constraints on multivariate discrete data. Each set of discrete data is decomposed into several submatrices and then multiple correspondence analysis is applied to explore relationships among the decomposed submatrices.…

  12. 50 years of JETP Letters

    NASA Astrophysics Data System (ADS)

    Pastukhov, V. P.

    2015-04-01

    This paper briefly traces the 50-year history of the journal Pis'ma v Zhurnal Eksperimental'noi i Teoreticheskoi Fiziki (JETP Letters), whose first issue was published on 1 April 1965. The journal is intended for a wide circle of physicists-readers as a fast publication channel for short communications on new results from research of the highest significance and highest priority in all areas of experimental and theoretical physics. Today, the journal celebrates numerous important contributions to the development of physics both in Russia and worldwide. Over a historically short period, JETP Letters developed into a highly authoritative and influential source for physicists engaged in a wide range of fields. Due to the wise and well-timed editorial policy, the journal continues to retain its leadership position, despite the difficulties the entire science periodical literature - and indeed the whole of science - is currently experiencing in Russia.

  13. Open letter to the Vatican.

    PubMed

    1999-01-01

    An open letter was published by Latin American and Caribbean women during the Special Session of the UN General Assembly on the International Conference on Population and Development. The letter generally focused on the Church¿s stand on women's reproductive rights. In particular, it questioned the Church on the following aspects of reproductive health, which include: 1) maternal death related to lack of access to reproductive health care; 2) Vatican representatives insisting that only parents can supervise their children education and health, which also lead to many cases of sexual abuse and incest; 3) women's sexual inequality and daily violence; 4) the Vatican delegation blocking the advances of contraception, sexual education, and HIV prevention; 5) problems of migrants and allocation of resources; and 6) the Church failing to recognize the capacity of young people to make decisions based on their own conscience. PMID:12178905

  14. Spatio-temporal properties of letter crowding.

    PubMed

    Chung, Susana T L

    2016-04-01

    Crowding between adjacent letters has been investigated primarily as a spatial effect. The purpose of this study was to investigate the spatio-temporal properties of letter crowding. Specifically, we examined the systematic changes in the degradation effects in letter identification performance when adjacent letters were presented with a temporal asynchrony, as a function of letter separation and between the fovea and the periphery. We measured proportion-correct performance for identifying the middle target letter in strings of three lowercase letters at the fovea and 10° in the inferior visual field, for a range of center-to-center letter separations and a range of stimulus onset asynchronies (SOA) between the target and flanking letters (positive SOAs: target preceded flankers). As expected, the accuracy for identifying the target letters reduces with decreases in letter separation. This crowding effect shows a strong dependency on SOAs, such that crowding is maximal between 0 and ∼100 ms (depending on conditions) and diminishes for larger SOAs (positive or negative). Maximal crowding does not require the target and flanking letters to physically coexist for the entire presentation duration. Most importantly, crowding can be minimized even for closely spaced letters if there is a large temporal asynchrony between the target and flankers. The reliance of letter identification performance on SOAs and how it changes with letter separations imply that the crowding effect can be traded between space and time. Our findings are consistent with the notion that crowding should be considered as a spatio-temporal, and not simply a spatial, effect. PMID:27088895

  15. Spatio-temporal properties of letter crowding

    PubMed Central

    Chung, Susana T. L.

    2016-01-01

    Crowding between adjacent letters has been investigated primarily as a spatial effect. The purpose of this study was to investigate the spatio-temporal properties of letter crowding. Specifically, we examined the systematic changes in the degradation effects in letter identification performance when adjacent letters were presented with a temporal asynchrony, as a function of letter separation and between the fovea and the periphery. We measured proportion-correct performance for identifying the middle target letter in strings of three lowercase letters at the fovea and 10° in the inferior visual field, for a range of center-to-center letter separations and a range of stimulus onset asynchronies (SOA) between the target and flanking letters (positive SOAs: target preceded flankers). As expected, the accuracy for identifying the target letters reduces with decreases in letter separation. This crowding effect shows a strong dependency on SOAs, such that crowding is maximal between 0 and ∼100 ms (depending on conditions) and diminishes for larger SOAs (positive or negative). Maximal crowding does not require the target and flanking letters to physically coexist for the entire presentation duration. Most importantly, crowding can be minimized even for closely spaced letters if there is a large temporal asynchrony between the target and flankers. The reliance of letter identification performance on SOAs and how it changes with letter separations imply that the crowding effect can be traded between space and time. Our findings are consistent with the notion that crowding should be considered as a spatio-temporal, and not simply a spatial, effect. PMID:27088895

  16. Thoughts on the condolence letter.

    PubMed

    Feldmann, B M

    2000-11-15

    Genuine, specific, timely emotional support of caregivers at the time of euthanasia is an important part of the veterinary professional obligation. Such support helps ease client pain during the grieving process. However, caution and sensitivity are essential when assessing and responding to caregiver-companion animal relationships.(1) For example, some caregivers are highly bonded but conceal their emotions, so our perceptions and responses must be thoughtful and discerning. My veterinary technician and I are supportive of our clients during euthanasia. I later write the condolence letter according to our perceptions of that particular human-companion animal bond. The only exceptions to our attempt to be thoroughly supportive at the time of euthanasia are those instances when we perceive that there has been obvious and willful abuse or neglect. At such times, we try to maintain emotional neutrality. The condolence letter and its variations described here are intended to serve as a guide. We send the condolence letter to caregivers within 24 hours of euthanasia, and it is addressed to the entire family. In addition, a euthanasia packet is provided at the time of euthanasia. The packet includes 2 brochures on coping with the loss of a companion animal, (2,3) contact information for a pet loss support hotline and a pet loss support group, an essay and a poem about the death of a companion animal, and a how-to article on dealing with children and their emotions on the loss of a pet. (4) My veterinary technician almost always phones the caregiver 1 to 3 days after euthanasia of their companion animal. The timing of the call depends on the circumstances of death and our judgment as to the emotional needs of the caregiver and family. Where emotions around euthanasia and loss are especially deep, the follow-up call may be made as early as that night or the next morning, with a second call 2 to 3 days later. The nature of the conversation depends on the technician

  17. Writing More Informative Letters of Reference

    PubMed Central

    Wright, Scott M; Ziegelstein, Roy C

    2004-01-01

    Writing a meaningful and valuable letter of reference is not an easy task. Several factors influence the quality of any letter of reference. First, the accuracy and reliability of the writer's impressions and judgment depend on how well he knows the individual being described. Second, the writer's frame of reference, which is determined by the number of persons at the same level that he has worked with, will impact the context and significance of his beliefs and estimations. Third, the letter-writing skills of the person composing the letter will naturally affect the letter. To support the other components of a candidate's application, a letter of reference should provide specific examples of how an individual's behavior or attitude compares to a reference group and should assess “intangibles” that are hard to glean from a curriculum vitae or from test scores. This report offers suggestions that should help physicians write more informative letters of reference. PMID:15109330

  18. Letter Knowledge in Parent–Child Conversations

    PubMed Central

    Robins, Sarah; Treiman, Rebecca; Rosales, Nicole

    2014-01-01

    Learning about letters is an important component of emergent literacy. We explored the possibility that parent speech provides information about letters, and also that children’s speech reflects their own letter knowledge. By studying conversations transcribed in CHILDES (MacWhinney, 2000) between parents and children aged one to five, we found that alphabetic order influenced use of individual letters and letter sequences. The frequency of letters in children’s books influenced parent utterances throughout the age range studied, but children’s utterances only after age two. Conversations emphasized some literacy-relevant features of letters, such as their shapes and association with words, but not letters’ sounds. Describing these patterns and how they change over the preschool years offers important insight into the home literacy environment. PMID:25598577

  19. Synesthesia for manual alphabet letters and numeral signs in second-language users of signed languages.

    PubMed

    Atkinson, Joanna; Lyons, Tanya; Eagleman, David; Woll, Bencie; Ward, Jamie

    2016-08-01

    Many synesthetes experience colors when viewing letters or digits. We document, for the first time, an analogous phenomenon among users of signed languages who showed color synesthesia for fingerspelled letters and signed numerals. Four synesthetes experienced colors when they viewed manual letters and numerals (in two cases, colors were subjectively projected on to the hands). There was a correspondence between the colors experienced for written graphemes and their manual counterparts, suggesting that the development of these two types of synesthesia is interdependent despite the fact that these systems are superficially distinct and rely on different perceptual recognition mechanisms in the brain. PMID:27351751

  20. Letters

    NASA Astrophysics Data System (ADS)

    2000-04-01

    Coulombic Models in Chemical Bonding by Lawrence J. Sacks and by Derek W. Smith Re: articles by R. J. Gillespie and by D. W. Smith D. W. Smith replies Capsaicin Hazard by Paul E. Vorndam Re: article by J. D. Batchelor and B. T. Jones B. T. Jones reply Editor's Note: Hazards Re: JCE 1999, 76, 240 and JCE 2000, 77, 266.

  1. The long learning route to abstract letter units.

    PubMed

    Thompson, G Brian

    2009-02-01

    This is a review of theory and evidence on how abstract letter units (ALUs) are initially learnt by the developing individual. Despite the predominance of the lower-case form of letters in the print environment, naming identification of upper case has precedence over lower case among preschool children. Such children showed a significant lag in extending their categories of upper-case variants to include the corresponding lower-case forms that are visually dissimilar. As late as 11 years of age children gave longer naming latencies for the lower-case than the upper-case forms. Initial learning of ALUs proceeded slowly over many months, consistent with the "common contexts" hypothesis but not consistent with the early acquisition predicted by the "common letter name" hypothesis. Evidence from cross-case transfer in a training experiment indicated that prior to acquiring full use of ALUs the children had formed representations of words that were letter based but specific to lower-case forms. PMID:18649251

  2. Voltage dependence of Hodgkin-Huxley rate functions for a multistage K+ channel voltage sensor within a membrane

    NASA Astrophysics Data System (ADS)

    Vaccaro, S. R.

    2014-11-01

    The activation of a K+channel sensor in two sequential stages during a voltage clamp may be described as the translocation of a Brownian particle in an energy landscape with two large barriers between states. A solution of the Smoluchowski equation for a square-well approximation to the potential function of the S4 voltage sensor satisfies a master equation and has two frequencies that may be determined from the forward and backward rate functions. When the higher-frequency terms have small amplitude, the solution reduces to the relaxation of a rate equation, where the derived two-state rate functions are dependent on the relative magnitude of the forward rates (α and γ ) and the backward rates (β and δ ) for each stage. In particular, the voltage dependence of the Hodgkin-Huxley rate functions for a K+channel may be derived by assuming that the rate functions of the first stage are large relative to those of the second stage—α ≫γ and β ≫δ . For a Shaker IR K+ channel, the first forward and backward transitions are rate limiting (α <γ and δ ≪β ), and for an activation process with either two or three stages, the derived two-state rate functions also have a voltage dependence that is of a similar form to that determined for the squid axon. The potential variation generated by the interaction between a two-stage K+ ion channel and a noninactivating Na+ ion channel is determined by the master equation for K+channel activation and the ionic current equation when the Na+channel activation time is small, and if β ≪δ and α ≪γ , the system may exhibit a small amplitude oscillation between spikes, or mixed-mode oscillation, in which the slow closed state modulates the K+ ion channel conductance in the membrane.

  3. Kinetic Effects of Fiber Type on the Two Subcomponents of the Huxley-Simmons Phase 2 in Muscle

    PubMed Central

    Davis, Julien S.; Epstein, Neal D.

    2003-01-01

    The Huxley-Simmons phase 2 controls the kinetics of the first stages of tension recovery after a step-change in fiber length and is considered intimately associated with tension generation. It had been shown that phase 2 is comprised of two distinct unrelated phases. This is confirmed here by showing that the properties of phase 2fast are independent of fiber type, whereas those of phase 2slow are fiber type dependent. Phase 2fast has a rate of 1000–2000 s−1 and is temperature insensitive (Q10 ∼ 1.16) in fast, medium, and slow speed fibers. Regardless of fiber type and temperature, the amplitude of phase 2fast is half (∼0.46) that of phase 1 (fiber instantaneous stiffness). Consequently, fiber compliance (cross-bridge and thick/thin filament) appears to be the common source of both phase 1 elasticity and phase 2fast viscoelasticity. In fast fibers, stiffness increases in direct proportion to tension from an extrapolated positive origin at zero tension. The simplest explanation is that tension generation can be approximated by two-state transition from attached preforce generating (moderate stiffness) to attached force generating (high stiffness) states. Phase 2slow is quite different, progressively slowing in concert with fiber type. An interesting interpretation of the amplitude and rate data is that reverse coupling of phase 2slow back to Pi release and ATP hydrolysis appears absent in fast fibers, detectable in medium speed fibers, and marked in slow fibers contracting isometrically. Contracting slow and heart muscles stretched under load could employ this enhanced reversibility of the cross-bridge cycle as a mechanism to conserve energy. PMID:12829493

  4. Mean-field description and propagation of chaos in networks of Hodgkin-Huxley and FitzHugh-Nagumo neurons

    PubMed Central

    2012-01-01

    We derive the mean-field equations arising as the limit of a network of interacting spiking neurons, as the number of neurons goes to infinity. The neurons belong to a fixed number of populations and are represented either by the Hodgkin-Huxley model or by one of its simplified version, the FitzHugh-Nagumo model. The synapses between neurons are either electrical or chemical. The network is assumed to be fully connected. The maximum conductances vary randomly. Under the condition that all neurons’ initial conditions are drawn independently from the same law that depends only on the population they belong to, we prove that a propagation of chaos phenomenon takes place, namely that in the mean-field limit, any finite number of neurons become independent and, within each population, have the same probability distribution. This probability distribution is a solution of a set of implicit equations, either nonlinear stochastic differential equations resembling the McKean-Vlasov equations or non-local partial differential equations resembling the McKean-Vlasov-Fokker-Planck equations. We prove the well-posedness of the McKean-Vlasov equations, i.e. the existence and uniqueness of a solution. We also show the results of some numerical experiments that indicate that the mean-field equations are a good representation of the mean activity of a finite size network, even for modest sizes. These experiments also indicate that the McKean-Vlasov-Fokker-Planck equations may be a good way to understand the mean-field dynamics through, e.g. a bifurcation analysis. Mathematics Subject Classification (2000): 60F99, 60B10, 92B20, 82C32, 82C80, 35Q80. PMID:22657695

  5. 76 FR 65703 - List of Correspondence

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-24

    ... learning disability. ] Letter dated February 10, 2011, to non-attorney advocate Amber Mintz, regarding the... Secretary is publishing the following list pursuant to section 607(f) of the Individuals with Disabilities.... Individuals with disabilities can obtain a copy of this list and the letters or other Departmental...

  6. A lab-controlled simulation of a letter-speech sound binding deficit in dyslexia.

    PubMed

    Aravena, Sebastián; Snellings, Patrick; Tijms, Jurgen; van der Molen, Maurits W

    2013-08-01

    Dyslexic and non-dyslexic readers engaged in a short training aimed at learning eight basic letter-speech sound correspondences within an artificial orthography. We examined whether a letter-speech sound binding deficit is behaviorally detectable within the initial steps of learning a novel script. Both letter knowledge and word reading ability within the artificial script were assessed. An additional goal was to investigate the influence of instructional approach on the initial learning of letter-speech sound correspondences. We assigned children from both groups to one of three different training conditions: (a) explicit instruction, (b) implicit associative learning within a computer game environment, or (c) a combination of (a) and (b) in which explicit instruction is followed by implicit learning. Our results indicated that dyslexics were outperformed by the controls on a time-pressured binding task and a word reading task within the artificial orthography, providing empirical support for the view that a letter-speech sound binding deficit is a key factor in dyslexia. A combination of explicit instruction and implicit techniques proved to be a more powerful tool in the initial teaching of letter-sound correspondences than implicit training alone. PMID:23708733

  7. Taming supersymmetric defects in 3d–3d correspondence

    NASA Astrophysics Data System (ADS)

    Gang, Dongmin; Kim, Nakwoo; Romo, Mauricio; Yamazaki, Masahito

    2016-07-01

    We study knots in 3d Chern–Simons theory with complex gauge group {SL}(N,{{C}}), in the context of its relation with 3d { N }=2 theory (the so-called 3d–3d correspondence). The defect has either co-dimension 2 or co-dimension 4 inside the 6d (2,0) theory, which is compactified on a 3-manifold \\hat{M}. We identify such defects in various corners of the 3d–3d correspondence, namely in 3d {SL}(N,{{C}}) CS theory, in 3d { N }=2 theory, in 5d { N }=2 super Yang–Mills theory, and in the M-theory holographic dual. We can make quantitative checks of the 3d–3d correspondence by computing partition functions at each of these theories. This Letter is a companion to a longer paper [1], which contains more details and more results.

  8. How automatic are crossmodal correspondences?

    PubMed

    Spence, Charles; Deroy, Ophelia

    2013-03-01

    The last couple of years have seen a rapid growth of interest (especially amongst cognitive psychologists, cognitive neuroscientists, and developmental researchers) in the study of crossmodal correspondences - the tendency for our brains (not to mention the brains of other species) to preferentially associate certain features or dimensions of stimuli across the senses. By now, robust empirical evidence supports the existence of numerous crossmodal correspondences, affecting people's performance across a wide range of psychological tasks - in everything from the redundant target effect paradigm through to studies of the Implicit Association Test, and from speeded discrimination/classification tasks through to unspeeded spatial localisation and temporal order judgment tasks. However, one question that has yet to receive a satisfactory answer is whether crossmodal correspondences automatically affect people's performance (in all, or at least in a subset of tasks), as opposed to reflecting more of a strategic, or top-down, phenomenon. Here, we review the latest research on the topic of crossmodal correspondences to have addressed this issue. We argue that answering the question will require researchers to be more precise in terms of defining what exactly automaticity entails. Furthermore, one's answer to the automaticity question may also hinge on the answer to a second question: Namely, whether crossmodal correspondences are all 'of a kind', or whether instead there may be several different kinds of crossmodal mapping (e.g., statistical, structural, and semantic). Different answers to the automaticity question may then be revealed depending on the type of correspondence under consideration. We make a number of suggestions for future research that might help to determine just how automatic crossmodal correspondences really are. PMID:23370382

  9. Spiral wave death, breakup induced by ion channel poisoning on regular Hodgkin-Huxley neuronal networks

    NASA Astrophysics Data System (ADS)

    Ma, Jun; Huang, Long; Tang, Jun; Ying, He-Ping; Jin, Wu-Yin

    2012-11-01

    The electric activities of neurons are often affected by ion channel poisoning, in particularly, interrupting normal transduction of signals within the brain. This may be due to changes in conductance and the number of active channels. Tetraethylammonium, for example, is known to cause ion channel poisoning of potassium channels, while tetrodotoxin has similar detrimental effects on sodium channels. The occurrence of spiral waves in neuronal systems was observed frequently in the past, and it was argued that these waves of excitation may play an important role by the propagation of electric signals across the quiescent regions of the brain. In this work, the parameters xk and xNa determine the ratio, with regards to the total number of ion channels, of active potassium and sodium channels, respectively, and they are taken to be representative also for the degree of channel poisoning. In the numerical studies, a well developed stable rotating spiral wave is used as the initial state to be controlled by the ion channel poisoning. We show that, under noise-free conditions, spiral waves are terminated whenever xk and xNa are set lower than a given threshold. However, breakup of spiral wave occurs if the intensity of the channel noise increases. In order to quantify these observations, we use a simple but robust synchronization measure, which captures succinctly the transition from spiral waves to homogeneous neuronal activity and/or broken turbulent state. The critical thresholds can be inferred from the abrupt changes occurring in the corresponding dependencies of synchronization versus the xk and xNa ratios. Furthermore, the sampled membrane potentials of a single neuron are recorded to detect the periodical spiral wave in a feasible way and the results could be dependent of the position of node (or site) to be monitored. Notably, small synchronization factors can be tightly associated to states where the formation of spiral waves is robust to channel poisoning and

  10. [Protestant clergymen among Hahnemann's clientele. Patient histories in letters].

    PubMed

    Kreher, Simone; Schlott, Melanie; Schlott, Thilo

    2016-01-01

    As part of the research project, developments in the history of science and in the regional and ecclesiastic history of the late feudal petty state of Köthen-Anhalt have been assessed and numerous documents of the Nagel and Mühlenbein family histories examined that place the transcribed patient letters of the two Protestant clergymen within the context of the Hahnemann Archives. These findings complement and extend previous insights into Hahnemann's Köthen clientele, especially when it comes to the structure and milieu of the local clerical elite. Inspired by the interpretive methods of sequential textual analysis, form and content of the letters of the two clergymen and their relatives were also investigated as methodically structured lines of communication. The body of sources published here presents--embedded in the body-image (of sickness and health) prevalent at the time--the medical cultures of educated patients as well as the increasingly professionalized medical practices of Samuel Hahnemann in a flourishing urban doctor's surgery. The correspondence between the pastors Albert Wilhelm Gotthilf Nagel (1796-1835) and August Carl Ludwig Georg Mühlenbein (1797-1866), presented here in a standard edition, has been investigated at Fulda University as part of the project 'Homöopathisches Medicinieren zwischen alltäglicher Lebensführung und professioneller Praxis' ('Homeopathic medicine between everyday use and professional practice'). Of the altogether 78 transcribed documents, 53 are letters written by either of the two pastors, 16 are patient journals by Samuel Hahnemann, 9 letters by the pastors' wives and Mühlenbein's mother. The two series of letters, originally composed between 1831 and 1833 in old German cursive script, can now be used as sources for research into the history of homeopathy. PMID:27263219