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Search Results: 1 - 10 of 530 matches for " Atkinson "
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Same formula, different figures: Change and persistence in class inequalities
Sociologia, Problemas e Práticas , 2010,
Abstract: many contemporary social theorists have argued that the social changes of the last few decades have shattered the hold of class over life histories, identities and politics and put in its place reflexive choice and individualism. this paper presents a summary of a recently completed research project in the uk designed to put these claims to the test. starting out from a “phenomeno-bourdieusian” model of class and deploying life history interviews it reveals not the decline of class in advanced capitalism, but its reinvention. new practices and pathways have emerged, but they represent only the shifting substance of class - the underlying structure of relational difference that defines class and produces different outcomes remains as patent as ever.
Signs of selection in our genes
Nick Atkinson
Genome Biology , 2005, DOI: 10.1186/gb-spotlight-20050506-01
Abstract: Building on an earlier study, Cornell University's Rasmus Nielsen and colleagues compared over 13,000 annotated human genes and their chimp equivalents, using the ratio of synonymous to nonsynonymous mutations as evidence of positive selection. Their aim, Nielsen said, was to determine "which genes have been changing as humans and chimpanzees have evolved into their modern forms."The team subjected orthologous human–chimp gene pairs from published human data and polymerase chain reaction data obtained from a single male chimpanzee to likelihood analysis, which revealed any differences in mutation type ratio. They excluded genes with fewer than three nucleotide differences.Nielsen's team made several surprising discoveries, including increased positive selection on the X chromosome and a relative lack of positive selection on genes expressed in the brain. Many genes that showed signs of positive selection were involved in sensory perception or immune defenses, they report, and some of the strongest evidence for selection was seen in genes involved in apoptosis. The latter finding offers "a possible link between selfish mutations during spermatogenesis and cancer prevalence," Nielsen told The Scientist.Apoptosis kills a large proportion of cells during spermatogenesis. A mutation allowing a cell to avoid such a fate should spread in the population because it would confer a selective advantage. However, cancer cells are also eliminated by apoptosis, so any positive selection would be balanced against an increased risk of cancer. "Much of the same molecular machinery is used to destroy cancer cells," Nielsen explained.Justin Fay, a geneticist at Washington University's School of Medicine, said Nielsen's team has done "a great job of squeezing out any evidence for positive selection on protein coding sequences." However, he pointed to the limitations of their statistical modeling technique, which is only able to detect positive selection on a gene when it has multiple se
Little fire ant males are clones
Nick Atkinson
Genome Biology , 2005, DOI: 10.1186/gb-spotlight-20050630-01
Abstract: Denis Fournier, from Université Libre de Bruxelles in Belgium, and colleagues studied the DNA of queens, workers, males, and their sperm from 34 little ant nests in French Guiana. They expected to find a typical haplodiploidy genetic system, but instead discovered that queens possessed only maternally derived DNA, and males possessed only paternally derived DNA."If males are potentially in an evolutionary dead end, as is true in the little fire ant where workers are sterile and all queens are clonally produced, they do not have a means to transmit their genes to the next generation," said Fournier. Queens produce gynes (reproductively competent females) clonally, a strategy that denies males the opportunity to pass on their genes. Males are still required, however, in the production of workers, upon which a queen's own reproductive success depends even though males themselves gain nothing.The males' response has been to evolve their own means of clonal reproduction, Fournier and colleagues say. They propose that at some stage after fertilization, maternal genetic material is lost and a haploid male offspring, encoded solely by the sperm's DNA, develops. "We could think of the males as a separate, parasitic species that uses host eggs for its own reproduction," said Fournier."The reality with natural history is that if you look close enough, you find remarkable patterns," commented Greg Hurst, at University College London. This well-known ant species was previously thought to have a "classic bee-ant system of genetics," in which diploid females exist alongside maternally derived haploid males. But the "fascinating bit of natural history" uncovered by Fournier and colleagues tells a more complex story, in which males and females both reproduce asexually and have thus separated into distinct genetic lineages."In essence, the male-female interaction in this species has become like an obligate symbiosis—the females need the males for worker production and the males need
Lice tell mankind's story
Nick Atkinson
Genome Biology , 2004, DOI: 10.1186/gb-spotlight-20041006-01
Abstract: Modern humans - Homo sapiens - are generally thought to have passed through a tight population genetic "bottleneck" somewhere between 10,000 and 20,000 years ago. Parasites such as lice tend to be highly species specific, so by unravelling their evolutionary history it's possible to see past the bottleneck, according to the Florida Museum of Natural History's David Reed, lead author of the paper."The addition of parasite data to studies of primate and human evolutionary history is similar to having multiple camera angles recording an event," Reed told us. "We aim to create a better picture of human evolutionary history by studying lice, which might tell us something that human genetic studies alone either have not or cannot."Humans today play host to two separate genetic lineages of head and body lice. Although both occupy the same ecological niche, their most recent common ancestor lived over a million years ago, the study reports. One lineage has a global distribution, whereas the other appears to be limited to the New World.Reed and his colleagues present evidence that the New World lineage originally co-evolved with Homo erectus, but switched hosts to Homo sapiens around 25,000 years ago. The switch took place in Asia, the authors suggest, before the colonization of North America across the Bering Straits. The effective isolation of New World human populations until only a few hundred years ago allowed this second louse lineage to persist.Todd Disotell, of New York University's Department of Anthropology, was impressed by the study. "When I read this paper I was both intrigued and excited by Reed et al.'s findings," he said."I think that the conclusion that there was contact [in Asia] between remnant Homo erectus populations and modern Homo sapiens is correct, but the exact nature of that contact will be a continuing controversy," said Disotell. Physical contact certainly took place for the transmission of lice to be possible, but this doesn't necessarily equate
Platypus has 10 sex chromosomes
Nick Atkinson
Genome Biology , 2004, DOI: 10.1186/gb-spotlight-20041029-01
Abstract: "The platypus has long been known to have an unusual multiple set of sex chromosomes," said the University of Melbourne's professor Marilyn Renfree, who was not involved in the studies. However, the use of fluorescence in situ hybridization (FISH) confirmed how the ten elements segregate. "Remarkably, the five X chromosomes go into one cell, and the five Y into another," she continued. "This results in two kinds of sperm - half with XXXXX that determine female young and half with YYYYY that determine male young.""This sex chromosome system is unique in mammals," said the Australian National University's Frank Grützner, lead author of the Nature paper. "The only way to ensure that five X chromosomes end up in one sperm and five Y chromosomes in another is for all of the sex chromosomes to assemble in a certain pattern - X1Y1X2Y2X3Y3X4Y4X5Y5 - during meiosis. That's precisely what we found - a chain of alternating X and Y chromosomes."Willem Rens, lead author on paper in PNAS, said that his team used FISH to visualize each chromosome. "The paints are hybridized to metaphase cell preparations and reveal which chromosomes are present," said Rens, of Cambridge University's Resource Centre for Comparative Genomics. The technique allowed the researchers to discover how sex is determined at the chromosomal level, he told us, although at the level of the gene it remains a mystery.Peter Temple-Smith, at the University of Melbourne, met the new findings with enthusiasm. "The use of several extremely powerful, recently developed genetic techniques have unlocked some of the long-held secrets of sex determination in monotremes," he said. "The results suggest an otherwise unexpected evolutionary connection between bird and mammal sex chromosomes.""The complexity and intricacy of this system is mind-blowing," said Katherine Belov, of the Australian Museum's Evolutionary Biology Unit. "The fact that monotremes can manage such a large number of chromosomes is interesting in itself, b
Kinetics of the gas-phase reactions of OH radicals with alkanes and cycloalkanes
R. Atkinson
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2003,
Abstract: The available database concerning rate constants for gas-phase reactions of the hydroxyl (OH) radical with alkanes through early 2003 is presented over the entire temperature range for which measurements have been made (~180-2000 K). Measurements made using relative rate methods are re-evaluated using recent rate data for the reference compound (generally recommendations from this review). In general, whenever more than one study has been carried out over an overlapping temperature range, recommended rate constants or temperature-dependent rate expressions are presented. The recommended 298 K rate constants, temperature-dependent parameters, and temperature ranges over which these recommendations are applicable are listed in Table 1.
Literacy and Accountability: The High Stakes of High-Stakes Assessments
Terry Atkinson
Journal of Curriculum and Instruction , 2007,
Singularities of Type-Q ABS Equations
James Atkinson
Symmetry, Integrability and Geometry : Methods and Applications , 2011,
Abstract: The type-Q equations lie on the top level of the hierarchy introduced by Adler, Bobenko and Suris (ABS) in their classification of discrete counterparts of KdV-type integrable partial differential equations. We ask what singularities are possible in the solutions of these equations, and examine the relationship between the singularities and the principal integrability feature of multidimensional consistency. These questions are considered in the global setting and therefore extend previous considerations of singularities which have been local. What emerges are some simple geometric criteria that determine the allowed singularities, and the interesting discovery that generically the presence of singularities leads to a breakdown in the global consistency of such systems despite their local consistency property. This failure to be globally consistent is quantified by introducing a natural notion of monodromy for isolated singularities.
Qualitative Forschung – Einheit und Vielfalt Qualitative Research—Unity and Diversity Investigación cualitativa: unidad y diversidad
Paul Atkinson
Forum : Qualitative Social Research , 2005,
Abstract: In diesem Beitrag wird zu zeigen versucht, dass qualitative Forschung zwar in vielen sozialwissenschaftlichen Bereichen Anerkennung gewonnen hat, dies aber um den Preis wachsender Fragmentierung und Inkoh renz. Auch verbleiben die unterschiedlichen qualitativen "Dom nen", die im Laufe dieser Entwicklung etabliert werden konnten, meist isoliert voneinander. Es wird deshalb die These vertreten, dass eine Rückbesinnung auf einige grundlegende Prinzipien ethnographischer Forschung unbedingt erforderlich ist, Prinzipien, die die multiplen Modalit ten von sozialem Handeln und kultureller Pr sentation anerkennen und diese zugleich in einem breiteren ethnographischen Rahmen lokalisieren. Hierzu ist es erforderlich, die intrinsischen Ordnungs- und Organisationsprinzipien zu verstehen, die die soziale Form konstituieren und "durchdringen" – diskursive, visuelle und materiale. Eine solche formale Ethnographie würde es auch erlauben, klassische Ideen wie "datengegründete Theoriebildung", "Triangulation" und "dichte Beschreibung" neu zu konzeptualisieren. URN: urn:nbn:de:0114-fqs0503261 The paper argues that while qualitative research has been flourishing in many fields of the social sciences, it has become unhelpfully fragmented and incoherent. Equally, there have developed a number of specialist domains of qualitative research that are too often treated in isolation. It is argued that we need to return to some fundamental principles of ethnographic inquiry that recognise the multiple modalities of social action and cultural representation, while locating them within a wider ethnographic framework. We need to recognise the intrinsic, indigenous principles of order and organisation that permeate social forms—discursive, visual, and material. Such formal ethnography provides a way of renewing classic ideas such as "grounded theory", "triangulation" and "thick description". URN: urn:nbn:de:0114-fqs0503261 El artículo discute que mientras la investigación cualitativa ha estado floreciendo en muchos campos de las ciencias sociales, se ha vuelto inconvenientemente fragmentada e incoherente. Igualmente, se han desarrollado varios dominios especializados de investigación cualitativa que frecuentemente se tratan de modo aislado. Se discute que necesitamos volver a algunos principios fundamentales de la investigación etnográfica que reconocen las modalidades múltiples de acción social y la representación cultural, mientras se sitúan en un marco etnográfico más amplio. Necesitamos reconocer los principios intrínsecos indígenas de orden y organización que penetran las formas s
Interrupció, reproducció i colonització pedagògica de la vida quotidiana: classificació i emmarcament de l'experiència del treball i l'educació
Paul Atkinson
Temps d'Educació , 1989,
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