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Fundamental Questions (fundamental + question)
Selected AbstractsThe cytoplasmic structure hypothesis for ribosome assembly, vertical inheritance, and phylogeny,BIOESSAYS, Issue 7 2009David S. Thaler Abstract Fundamental questions in evolution concern deep divisions in the living world and vertical versus horizontal information transfer. Two contrasting views are: (i) three superkingdoms Archaea, Eubacteria, and Eukarya based on vertical inheritance of genes encoding ribosomes; versus (ii) a prokaryotic/eukaryotic dichotomy with unconstrained horizontal gene transfer (HGT) among prokaryotes. Vertical inheritance implies continuity of cytoplasmic and structural information whereas HGT transfers only DNA. By hypothesis, HGT of the translation machinery is constrained by interaction between new ribosomal gene products and vertically inherited cytoplasmic structure made largely of preexisting ribosomes. Ribosomes differentially enhance the assembly of new ribosomes made from closely related genes and inhibit the assembly of products from more distal genes. This hypothesis suggests experiments for synthetic biology: the ability of synthetic genomes to "boot," i.e., establish hereditary continuity, will be constrained by the phylogenetic closeness of the cell "body" into which genomes are placed. [source] Sensori-motor experience leads to changes in visual processing in the developing brainDEVELOPMENTAL SCIENCE, Issue 2 2010Karin Harman James Since Broca's studies on language processing, cortical functional specialization has been considered to be integral to efficient neural processing. A fundamental question in cognitive neuroscience concerns the type of learning that is required for functional specialization to develop. To address this issue with respect to the development of neural specialization for letters, we used functional magnetic resonance imaging (fMRI) to compare brain activation patterns in pre-school children before and after different letter-learning conditions: a sensori-motor group practised printing letters during the learning phase, while the control group practised visual recognition. Results demonstrated an overall left-hemisphere bias for processing letters in these pre-literate participants, but, more interestingly, showed enhanced blood oxygen-level-dependent activation in the visual association cortex during letter perception only after sensori-motor (printing) learning. It is concluded that sensori-motor experience augments processing in the visual system of pre-school children. The change of activation in these neural circuits provides important evidence that ,learning-by-doing' can lay the foundation for, and potentially strengthen, the neural systems used for visual letter recognition. [source] RECONSTRUCTING DEWEYAN DEMOCRATIC EDUCATION FOR A GLOBALIZING WORLDEDUCATIONAL THEORY, Issue 4 2009Jessica Ching-Sze Wang As democratic citizenship education gains importance worldwide, one wonders whether common civic education practices in the United States, such as mock elections, are adequate models for other countries, or whether they fall short of realizing the goal of promoting democracy in different regions and cultures. Despite various controversies, one fundamental question remains: How should we teach democracy? Should we teach it as a system of government or as a way of life? Jessica Ching-Sze Wang finds inspiration in Dewey's life and works. She draws on Dewey's experience during the First World War and his insights into the connection between democracy and education to reconstruct a culturally and morally robust form of democratic education, as opposed to the politically dominated one currently being practiced. Wang concludes that Deweyan democratic education thus reconstructed can help us better realize democracy as a way of life for our globalizing world. [source] Why does Candida albicans switch?FEMS YEAST RESEARCH, Issue 7 2009David R. Soll Abstract White,opaque switching in Candida albicans was first discovered in 1987. Fifteen years later, and three years after the discovery of the mating system, it was demonstrated that the switch from white to opaque was an essential step in the mating process. But this latter discovery did not reveal why C. albicans had this requirement, when Saccharomyces cerevisiae and other hemiascomycetes did not. The discovery that mating-competent opaque cells signaled mating-incompetent white cells, through the release of pheromones, to become adhesive and form biofilms provided a clue to this fundamental question. Opaque cells appeared to signal white cells to form biofilms that facilitated mating by protecting the fragile gradients of the pheromone that directed chemotropism, a process necessary for fusion. Here, we explore the discoveries and observations that have led to this hypothesis, and the ancillary questions that have risen that are related to the regulation of the unique pheromone response, the evolution of this response and the relationship between pheromone-enhanced white cell biofilms and ,asexual' biofilms formed by a/, cells. This discussion, therefore, focuses on a unique and complex component of the basic biology of C. albicans that relates switching, mating and pathogenesis. [source] More Peace for Less Money: Measurement and Accountability in the Swedish Armed ForcesFINANCIAL ACCOUNTABILITY & MANAGEMENT, Issue 4 2005Bino Catasús Studies of measurement and accountability are leading public sector transformation. By examining military work, this paper addresses the relationship between measurements and accountability by highlighting the measurements. Evidence was gathered from documents, political statements and field research. Several layers of accountability systems were found in the organisation. The principal can be the weak link in an accountability relationship if the measurement agenda is in the hands of the agent. The problems seem to go beyond performance and output, and a more fundamental question is challenging the public sector: `Are we doing the right things?' Or an even more dramatic existential question arises: `Why do we exist?' [source] Stocks and dynamics of SOC in relation to soil redistribution by water and tillage erosionGLOBAL CHANGE BIOLOGY, Issue 10 2006JIANHUI ZHANG Abstract Soil organic carbon (SOC) displaced by soil erosion is the subject of much current research and the fundamental question, whether accelerated soil erosion is a source or sink of atmospheric CO2, remains unresolved. A toposequence of terraced fields as well as a long slope was selected from hilly areas of the Sichuan Basin, China to determine effects of soil redistribution rates and processes on SOC stocks and dynamics. Soil samples for the determination of caesium-137 (137Cs), SOC, total N and soil particle size fractions were collected at 5 m intervals along a transect down the two toposequences. 137Cs data showed that along the long slope transect soil erosion occurred in upper and middle slope positions and soil deposition appeared in the lower part of the slope. Along the terraced transect, soil was lost over the upper parts of the slopes and deposition occurred towards the downslope boundary on each terrace, resulting in very abrupt changes in soil redistribution over short distances either side of terrace boundaries that run parallel with the contour on the steep slopes. These data reflect a difference in erosion process; along the long slope transect, water erosion is the dominant process, while in the terraced landscape soil distribution is mainly the result of tillage erosion. SOC inventories (mass per unit area) show a similar pattern to the 137Cs inventory, with relatively low SOC content in the erosional sites and high SOC content in depositional areas. However, in the terraced field landscape C/N ratios were highest in the depositional areas, while along the long slope transect, C/N ratios were highest in the erosional areas. When the samples are subdivided based on 137Cs-derived erosion and deposition data, it is found that the erosional areas have similar C/N ratios for both toposequences, while the C/N ratios in depositional areas are significantly different from each other. These differences are attributed to the difference in soil erosion processes; tillage erosion is mainly responsible for high-SOC inventories at depositional positions on terraced fields, whereas water erosion plays a primary role in SOC storage at depositional positions on the long slope. These data support the theory that water erosion may cause a loss of SOC due to selective removal of the most labile fraction of SOC, while on the other hand tillage erosion only transports the soil over short distances with less effect on the total SOC stock. [source] On future non-medical costs in economic evaluationsHEALTH ECONOMICS, Issue 5 2008Bengt Liljas Abstract Economic evaluation in health care is still an evolving discipline. One of the current controversies in cost-effectiveness analysis regards the inclusion or exclusion of future non-medical costs (i.e. consumption net of production) due to increased survival. This paper examines the implications of a symmetry rule stating that there should be consistency between costs included in the numerator and utility aspects included in the denominator. While the observation that no quality-adjusted life year (QALY) instruments explicitly include consumption and leisure seems to give support to the notion that future non-medical costs should be excluded when QALYs are used as the outcome measure, a better understanding of what respondents actually consider when reporting QALY weights is required. However, the more fundamental question is whether QALYs can be interpreted as utilities. Or more precisely, what are the assumptions needed for a general utility model also including consumption and leisure to be consistent with QALYs? Once those assumptions are identified, they need to be experimentally tested to see whether they are at least approximately valid. Until we have answers to these areas for future research, it seems premature to include future non-medical costs. Copyright © 2007 John Wiley & Sons, Ltd. [source] Neural basis of first and second language processing of sentence-level linguistic prosodyHUMAN BRAIN MAPPING, Issue 2 2007Jackson Gandour Abstract A fundamental question in multilingualism is whether the neural substrates are shared or segregated for the two or more languages spoken by polyglots. This study employs functional MRI to investigate the neural substrates underlying the perception of two sentence-level prosodic phenomena that occur in both Mandarin Chinese (L1) and English (L2): sentence focus (sentence-initial vs. -final position of contrastive stress) and sentence type (declarative vs. interrogative modality). Late-onset, medium proficiency Chinese-English bilinguals were asked to selectively attend to either sentence focus or sentence type in paired three-word sentences in both L1 and L2 and make speeded-response discrimination judgments. L1 and L2 elicited highly overlapping activations in frontal, temporal, and parietal lobes. Furthermore, region of interest analyses revealed that for both languages the sentence focus task elicited a leftward asymmetry in the supramarginal gyrus; both tasks elicited a rightward asymmetry in the mid-portion of the middle frontal gyrus. A direct comparison between L1 and L2 did not show any difference in brain activation in the sentence type task. In the sentence focus task, however, greater activation for L2 than L1 occurred in the bilateral anterior insula and superior frontal sulcus. The sentence focus task also elicited a leftward asymmetry in the posterior middle temporal gyrus for L1 only. Differential activation patterns are attributed primarily to disparities between L1 and L2 in the phonetic manifestation of sentence focus. Such phonetic divergences lead to increased computational demands for processing L2. These findings support the view that L1 and L2 are mediated by a unitary neural system despite late age of acquisition, although additional neural resources may be required in task-specific circumstances for unequal bilinguals. Hum. Brain Mapp, 2007. © 2006 Wiley-Liss, Inc. [source] Where Infants Look Determines How They See: Eye Movements and Object Perception Performance in 3-Month-OldsINFANCY, Issue 2 2004Scott P. Johnson A fundamental question of perceptual development concerns how infants come to perceive partly hidden objects as unified across a spatial gap imposed by an occluder. Much is known about the time course of development of perceptual completion during the first several months after birth, as well as some of the visual information that supports unity perception in infants. The goal of this investigation was to examine the inputs to this process. We recorded eye movements in 3-month-old infants as they participated in a standard object unity task and found systematic differences in scanning patterns between those infants whose post-habituation preferences were indicative of unity perception versus those infants who did not perceive unity. Perceivers, relative to nonperceivers, scanned more reliably in the vicinity of the visible rod parts and scanned more frequently across the range of rod motion. These results suggest that emerging object concepts are tied closely to available visual information in the environment, and the process of information pickup. [source] The post-fledging period in a tropical bird: patterns of parental care and survivalJOURNAL OF AVIAN BIOLOGY, Issue 4 2010Corey E. Tarwater How environmental conditions affect the timing and extent of parental care is a fundamental question in comparative studies of life histories. The post-fledging period is deemed critical for offspring fitness, yet few studies have examined this period, particularly in tropical birds. Tropical birds are predicted to have extended parental care during the post-fledging period and this period may be key to understanding geographic variation in avian reproductive strategies. We studied a neotropical passerine, the western slaty-antshrike Thamnophilus atrinucha, and predicted greater care and higher survival during the post-fledging period compared to earlier stages. Furthermore, we predicted that duration of post-fledging parental care and survival would be at the upper end of the distribution for Northern Hemisphere passerines. Correspondingly, we observed that provisioning continued for 6,12 weeks after fledging. In addition, provisioning rate was greater after fledging and offspring survival from fledging to independence was 75%, greater than all estimates from north-temperate passerines. Intervals between nesting attempts were longer when the first brood produced successful fledglings compared to nests where offspring died either in the nest or upon fledging. Parents delayed initiating second nests after the first successful brood until fledglings were near independence. Our results indicate that parents provide greater care after fledging and this extended care likely increased offspring survival. Moreover, our findings of extended post-fledging parental care and higher post-fledging survival compared to Northern Hemisphere species have implications for understanding latitudinal variation in reproductive effort and parental investment strategies. [source] Institutions for Financial Development: What are they and where do they come from?JOURNAL OF ECONOMIC SURVEYS, Issue 1 2006Leopoldo Fergusson Abstract., Among the fundamental causes of long-run economic performance, differences in ,institutions' have received considerable attention in recent years. At the same time, a large body of theoretical and empirical work shows that financial development can have a big effect on economic performance. This raises the more fundamental question as to why some countries have developed financial markets while others do not. This paper reviews the theoretical and empirical research on this issue and shows that one of the channels whereby better institutions may have an effect on economic development is through the consolidation of larger and better financial markets. An issue that is left aside in this paper relates to what regulations and policies lead to better functioning capital markets. At some level, one can think of regulations and policies as particular types of institutions. Nonetheless, institutional problems are deeper causes leading to poor economic performance; bad policies might simply be part of the channels through which they influence performance. Thus, addressing the question of what determines the emergence of ,good' institutions , i.e. institutions that promote financial development , seems particularly important. Recent research providing some answers to this question is also reviewed. [source] Ecological speciation in marine v. freshwater fishesJOURNAL OF FISH BIOLOGY, Issue 5 2009O. Puebla Absolute barriers to dispersal are not common in marine systems, and the prevalence of planktonic larvae in marine taxa provides potential for gene flow across large geographic distances. These observations raise the fundamental question in marine evolutionary biology as to whether geographic and oceanographic barriers alone can account for the high levels of species diversity observed in marine environments such as coral reefs, or whether marine speciation also operates in the presence of gene flow between diverging populations. In this respect, the ecological hypothesis of speciation, in which reproductive isolation results from divergent or disruptive natural selection, is of particular interest because it may operate in the presence of gene flow. Although important insights into the process of ecological speciation in aquatic environments have been provided by the study of freshwater fishes, comparatively little is known about the possibility of ecological speciation in marine teleosts. In this study, the evidence consistent with different aspects of the ecological hypothesis of speciation is evaluated in marine fishes. Molecular approaches have played a critical role in the development of speciation hypotheses in marine fishes, with a role of ecology suggested by the occurrence of sister clades separated by ecological factors, rapid cladogenesis or the persistence of genetically and ecologically differentiated species in the presence of gene flow. Yet, ecological speciation research in marine fishes is still largely at an exploratory stage. Cases where the major ingredients of ecological speciation, namely a source of natural divergent or disruptive selection, a mechanism of reproductive isolation and a link between the two have been explicitly documented are few. Even in these cases, specific predictions of the ecological hypothesis of speciation remain largely untested. Recent developments in the study of freshwater fishes illustrate the potential for molecular approaches to address specific questions related to the ecological hypothesis of speciation such as the nature of the genes underlying key ecological traits, the magnitude of their effect on phenotype and the mechanisms underlying their differential expression in different ecological contexts. The potential provided by molecular studies is fully realized when they are complemented with alternative (e.g. ecological, theoretical) approaches. [source] Successful Aging: Implications for Oral HealthJOURNAL OF PUBLIC HEALTH DENTISTRY, Issue 4 2000H. Asuman Kiyak PhD ABSTRACT The past few years have seen a growing emphasis in gerontology on the concept of "successful" or "robust" aging. This represents a major paradigm shift in the field from a focus on declines in physical and social functioning, assumptions of the aging process as a downward spiral, and studies on how to manage these declines. Leading the way toward this new perspective on aging, the MacArthur Studies of Successful Aging asked the fundamental question: "What genetic, biomedical, behavioral, and social factors are crucial to maintaining health and functional capacities in the later years?" These studies examined longitudinally a large cohort of independent elders on several physical, cognitive, emotional, and social parameters. Other researchers have focused on the theme of robust aging; however, common predictors have emerged, such as remaining active physically and cognitively, maintaining social contacts, and avoiding disease. This research is timely, given the expanding population of the oldest old, and with successive cohorts demonstrating the "compression of morbidity" phenomenon. Such a paradigm shift is critical in geriatric dentistry as well, where successful aging is evident in the growing number of older adults who have retained their natural dentition into advanced old age. This presentation draws parallels between successful aging at the systemic and oral health levels, with illustrations from epidemiologic studies that demonstrate trends in improved health and quality of life among newer cohorts of older adults. [source] Another diet of worms: the applicability of polychaete feeding guilds as a useful conceptual framework and biological variableMARINE ECOLOGY, Issue 3-4 2005Paulo Roberto Pagliosa Abstract A fundamental question in guild studies is how to separate species into guilds. In a seminal manuscript, Fauchald & Jumars [Oceanography and Marine Biology Annual Review17 (1979) 193] summarized polychaete feeding biology and proposed a conceptual framework to test hypotheses on the sympatric occurrence of congeners with limited morphological differentiation. Twenty-six years after this publication, few studies have tested the validity and practical functioning of this scheme of polychaete feeding guilds and then only using part of the classification. The objective of the present study was to analyze the applicability of polychaete feeding guilds to ecological and environment assessments. Two data sets from Santa Catarina Island Bay, southern Brazil, were used. The first data set deals with spatial distribution of natural polychaete assemblages along the bay. The second data set treats fauna in urbanized versus relatively pristine mangroves. Multivariate analysis showed similar patterns in sample groups formed using guilds or densities and composition data. The role of feeding guilds in benthic systems was assessed through comparison with environmental variables. The polychaete assemblage from the Bay was related to sediment type. Motile and discretely motile carnivores and herbivores with jawed probosces matched coarse sands; surface deposit feeders and filter feeders were found in fine sands; and surface and subsurface deposit feeders and carnivores, all with soft probosces matched silt and clay sediments. The data analyses in mangroves showed surface deposit feeders and filter feeders in undisturbed sites and omnivorous species in disturbed ones. The polychaete feeding guilds appear relevant to assembly rules based on resource availability, to resource partitioning and to interspecific competition. [source] Clay mineral-organic matter relationships in the early solar systemMETEORITICS & PLANETARY SCIENCE, Issue 12 2002Victoria K. Pearson These organic-rich meteorites provide a valuable and tangible record of the chemical steps taken towards the origin of life in the early solar system. Chondritic organic matter is present in the inorganic meteorite matrix which, in the CM and CI chondrites, contains evidence of alteration by liquid water on the parent asteroid. An unanswered and fundamental question is to what extent did the organic matter and inorganic products of aqueous alteration interact or display interdependence? We have used an organic labelling technique to reveal that the meteoritic organic matter is strongly associated with clay minerals. This association suggests that clay minerals may have had an important trapping and possibly catalytic role in chemical evolution in the early solar system prior to the origin of life on the early Earth. [source] Biodiversity in microbial communities: system scale patterns and mechanismsMOLECULAR ECOLOGY, Issue 7 2009J. JACOB PARNELL Abstract The relationship between anthropogenic impact and the maintenance of biodiversity is a fundamental question in ecology. The emphasis on the organizational level of biodiversity responsible for ecosystem processes is shifting from a species-centred focus to include genotypic diversity. The relationship between biodiversity measures at these two scales remains largely unknown. By stratifying anthropogenic effects between scales of biodiversity of bacterial communities, we show a statistically significant difference in diversity based on taxonomic scale. Communities with intermediate species richness show high genotypic diversity while speciose and species-poor communities do not. We propose that in species-poor communities, generally comprising stable yet harsh conditions, physiological tolerance and competitive trade-offs limit both the number of species that occur and the loss of genotypes due to decreases in already constrained fitness. In species-rich communities, natural environmental conditions result in well-defined community structure and resource partitioning. Disturbance of these communities disrupts niche space, resulting in lower genotypic diversity despite the maintenance of species diversity. Our work provides a model to inform future research about relationships between species and genotypic biodiversity based on determining the biodiversity consequences of changing environmental context. [source] Natural genetic variation in whole-genome expression in Arabidopsis thaliana: the impact of physiological QTL introgressionMOLECULAR ECOLOGY, Issue 5 2006THOMAS E. JUENGER Abstract A long-standing and fundamental question in biology is how genes influence complex phenotypes. Combining near-isogenic line mapping with genome expression profiling offers a unique opportunity for exploring the functional relationship between genotype and phenotype and for generating candidate genes for future study. We used a whole-genome microarray produced with ink-jet technology to measure the relative expression level of over 21 500 genes from an Arabidopsis thaliana near-isogenic line (NIL) and its recurrent parent. The NIL material contained two introgressions (bottom of chromosome II and top of chromosome III) of the Cvi-1 ecotype in a Ler -2 ecotype genome background. Each introgression ,captures' a Cvi allele of a physiological quantitative trait loci (QTL) that our previous studies have shown increases transpiration and reduces water-use efficiency at the whole-plant level. We used a mixed model anova framework for assessing sources of expression variability and for evaluating statistical significance in our array experiment. We discovered 25 differentially expressed genes in the introgression at a false-discovery rate (FDR) cut-off of 0.20 and identified new candidate genes for both QTL regions. Several differentially expressed genes were confirmed with QRT,PCR (quantitative reverse transcription,polymerase chain reaction) assays. In contrast, we found no statistically significant differentially expressed genes outside of the QTL introgressions after controlling for multiple tests. We discuss these results in the context of candidate genes, cloning QTL, and phenotypic evolution. [source] Representation and Agenda SettingPOLICY STUDIES JOURNAL, Issue 1 2004Bryan D. Jones We develop a new approach to the study of representation based on agenda setting and attention allocation. We ask the fundamental question: do the policy priorities of the public and of the government correspond across time? To assess the policy priorities of the mass public, we have coded the Most Important Problem data from Gallup polls across the postwar period into the policy content categories developed by the Policy Agendas Project (Baumgartner & Jones, 2002). Congressional priorities were assessed by the proportion of total hearings in a given year focusing on those same policy categories, also from the Agendas Project. We then conducted similar analyses on public laws and most important laws, similarly coded. Finally we analyzed the spatial structure of public and congressional agendas using the Shepard-Kruskal non-metric multidimensional scaling algorithm. Findings may be summarized as follows: First, there is an impressive congruence between the priorities of the public and the priorities of Congress across time. Second, there is substantial evidence of congruence between the priorities of the public and lawmaking in the national government, but the correspondence is attenuated in comparison to agendas. Third, although the priorities of the public and Congress are structurally similar, the location of issues within the structure differs between Congress and the general public. The public "lumps" its evaluation of the nations most important problems into a small number of categories. Congress "splits" issues out, handling multiple issues simultaneously. Finally, the public tends to focus on a very constrained set of issues, but Congress juggles many more issues. The article has strong implications for the study of positional representation as well, because for traditional representation to occur, there must be correspondence between the issue-priorities of the public and the government. We find substantial evidence for such attention congruence here. [source] The national innovation system and foreign R&D: the case of TaiwanR & D MANAGEMENT, Issue 5 2007Shin-Horng Chen R&D internationalization has increasingly involved countries outside the developed world. In addition, there has been a growing trend for countries in East Asia to seek to attract the R&D facilities of multinationals (MNCs). For such countries, they are faced with a fundamental question as to what kinds of impact MNCs' offshore R&D facilities will have on their own countries, especially in terms of technological innovation and industrial development. Set against the above backdrop, this paper sets out to examine a relatively new aspect of R&D internationalization related to global innovation networks and to open up the blackbox of the spillover effect regarding foreign R&D by examining the interplay of foreign R&D and Taiwan's national innovation system. The empirical part of the paper draws mainly upon intensive case studies of four high-profile foreign R&D facilities in the IT industry. The way foreign R&D interplays with Taiwan's NIS is examined in terms of the market & technology linkages. [source] The ,NZ' in ,NZ IFRS': Public Benefit Entity AmendmentsAUSTRALIAN ACCOUNTING REVIEW, Issue 3 2008Michael E. Bradbury In 1992, New Zealand adopted a sector-neutral approach to standard setting , where the difference in accounting treatment is driven by differences in the nature of transactions and not by ownership or the objectives of the reporting entity. This study reviews the impact of adaptations of International Financial Reporting Standards (IFRS) to ensure their successful application in a sector-neural environment. A fundamental question of the move to IFRS is whether the public benefit entity amendments in NZ IFRS have contaminated the IFRS for profit-orientated entities or diluted the available guidance for public benefit entities. This suggests that it is worthwhile for Australia and New Zealand to monitor and reconsider their sector-neutral approach to adopting IFRS. [source] Activity-dependent regulation of synaptic size in Drosophila neuromuscular junctionsDEVELOPMENTAL NEUROBIOLOGY, Issue 9 2006Hiroaki Nakayama Abstract One of the fundamental questions in neural development is how neurons form synapses of the appropriate size for the efficient transfer of information across neural circuits. Here we investigated the mechanisms that bring about the size correlation between synapses and postsynaptic cells during development of Drosophila neuromuscular junctions (NMJs). To do this, we made use of a unique system in which two neighboring muscles (M6 and M7) are innervated by the same neurons. In mature NMJs, synaptic size on M6 is normally larger than that on M7, in accordance with the difference in muscle volume; this ensures the same extent of contraction of both muscles, and we refer to this correspondence as "matching". We found that matching was apparent in larvae 8 h after hatching, but not in newly hatched larvae despite the difference in muscle volume. When sensory inputs were suppressed by the expression of tetanus toxin in sensory neurons, matching did not occur, although synapses were able to grow. Matching was also suppressed by the inhibition of motoneuronal activity. These results suggest that matching is induced by regulating the rate of synaptic growth on M6 and M7 in an experience- and activity-dependent manner. It seems most likely that retrograde signals from the postsynaptic to the presynaptic cell convey the information about muscle cell size. We thus examined whether a candidate of retrograde signaling in NMJs, BMP signaling, is involved inmatching. However, there was no effect on matching inBMP type II receptor gene mutants, suggesting thatother experience-driven mechanisms besides BMP signaling are involved in the proper development of synapses. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006 [source] Environmental determinants of amphibian and reptile species richness in ChinaECOGRAPHY, Issue 4 2007Hong Qian Understanding the factors that regulate geographical variation in species richness has been one of the fundamental questions in ecology for decades, but our knowledge of the cause of geographical variation in species richness remains poor. This is particularly true for herpetofaunas (including amphibians and reptiles). Here, using correlation and regression analyses, we examine the relationship of herpetofaunal species richness in 245 localities across China with 30 environmental factors, which include nearly all major environmental factors that are considered to explain broad-scale species richness gradients in such theories as ambient energy, water,energy dynamics, productivity, habitat heterogeneity, and climatic stability. We found that the species richness of amphibians and reptiles is moderately to strongly correlated with most of the environmental variables examined, and that the best fit models, which include explanatory variables of temperature, precipitation, net primary productivity, minimum elevation, and range in elevation, explain ca 70% the variance in species richness for both amphibians and reptiles after accounting for sample area. Although water and temperature are important explanatory variables to both amphibians and reptiles, water variables explain more variance in amphibian species richness than in reptile species richness whereas temperature variables explain more variance in reptile species richness than in amphibian species richness, which is consistent with different physiological requirements of the two groups of organisms. [source] Grinnellian and Eltonian niches and geographic distributions of speciesECOLOGY LETTERS, Issue 12 2007Jorge Soberón Abstract In the recent past, availability of large data sets of species presences has increased by orders of magnitude. This, together with developments in geographical information systems and statistical methods, has enabled scientists to calculate, for thousands of species, the environmental conditions of their distributional areas. The profiles thus obtained are obviously related to niche concepts in the Grinnell tradition, and separated from those in Elton's tradition. I argue that it is useful to define Grinnellian and Eltonian niches on the basis of the types of variables used to calculate them, the natural spatial scale at which they can be measured, and the dispersal of the individuals over the environment. I use set theory notation and analogies derived from population ecology theory to obtain formal definitions of areas of distribution and several types of niches. This brings clarity to several practical and fundamental questions in macroecology and biogeography. [source] Assessing human germ-cell mutagenesis in the Postgenome Era: A celebration of the legacy of William Lawson (Bill) Russell,ENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 2 2007Andrew J. Wyrobek Abstract Birth defects, de novo genetic diseases, and chromosomal abnormality syndromes occur in ,5% of all live births, and affected children suffer from a broad range of lifelong health consequences. Despite the social and medical impact of these defects, and the 8 decades of research in animal systems that have identified numerous germ-cell mutagens, no human germ-cell mutagen has been confirmed to date. There is now a growing consensus that the inability to detect human germ-cell mutagens is due to technological limitations in the detection of random mutations rather than biological differences between animal and human susceptibility. A multidisciplinary workshop responding to this challenge convened at The Jackson Laboratory in Bar Harbor, Maine. The purpose of the workshop was to assess the applicability of an emerging repertoire of genomic technologies to studies of human germ-cell mutagenesis. Workshop participants recommended large-scale human germ-cell mutation studies be conducted using samples from donors with high-dose exposures, such as cancer survivors. Within this high-risk cohort, parents and children could be evaluated for heritable changes in (a) DNA sequence and chromosomal structure, (b) repeat sequences and minisatellites, and (c) global gene expression profiles and pathways. Participants also advocated the establishment of a bio-bank of human tissue samples from donors with well-characterized exposure, including medical and reproductive histories. This mutational resource could support large-scale, multiple-endpoint studies. Additional studies could involve the examination of transgenerational effects associated with changes in imprinting and methylation patterns, nucleotide repeats, and mitochondrial DNA mutations. The further development of animal models and the integration of these with human studies are necessary to provide molecular insights into the mechanisms of germ-cell mutations and to identify prevention strategies. Furthermore, scientific specialty groups should be convened to review and prioritize the evidence for germ-cell mutagenicity from common environmental, occupational, medical, and lifestyle exposures. Workshop attendees agreed on the need for a full-scale assault to address key fundamental questions in human germ-cell environmental mutagenesis. These include, but are not limited to, the following: Do human germ-cell mutagens exist? What are the risks to future generations? Are some parents at higher risk than others for acquiring and transmitting germ-cell mutations? Obtaining answers to these, and other critical questions, will require strong support from relevant funding agencies, in addition to the engagement of scientists outside the fields of genomics and germ-cell mutagenesis. Environ. Mol. Mutagen., 2007. Published 2007 Wiley-Liss, Inc. [source] ENVIRONMENTAL NICHE EQUIVALENCY VERSUS CONSERVATISM: QUANTITATIVE APPROACHES TO NICHE EVOLUTIONEVOLUTION, Issue 11 2008Dan L. Warren Environmental niche models, which are generated by combining species occurrence data with environmental GIS data layers, are increasingly used to answer fundamental questions about niche evolution, speciation, and the accumulation of ecological diversity within clades. The question of whether environmental niches are conserved over evolutionary time scales has attracted considerable attention, but often produced conflicting conclusions. This conflict, however, may result from differences in how niche similarity is measured and the specific null hypothesis being tested. We develop new methods for quantifying niche overlap that rely on a traditional ecological measure and a metric from mathematical statistics. We reexamine a classic study of niche conservatism between sister species in several groups of Mexican animals, and, for the first time, address alternative definitions of "niche conservatism" within a single framework using consistent methods. As expected, we find that environmental niches of sister species are more similar than expected under three distinct null hypotheses, but that they are rarely identical. We demonstrate how our measures can be used in phylogenetic comparative analyses by reexamining niche divergence in an adaptive radiation of Cuban anoles. Our results show that environmental niche overlap is closely tied to geographic overlap, but not to phylogenetic distances, suggesting that niche conservatism has not constrained local communities in this group to consist of closely related species. We suggest various randomization tests that may prove useful in other areas of ecology and evolutionary biology. [source] 360 Feedback from Another AngleHUMAN RESOURCE MANAGEMENT, Issue 1 2001David W. Bracken How do you know if a 360 process has been implemented successfully? What are the factors that influence its success? How can those factors be controlled by those responsible for its implementation? Despite its popularity, there has been little effort to build a comprehensive model that addresses these fundamental questions about 360 feedback. In a quest for such a model, we identify a host of key factors organized according to whether they exert their influence proximally or distally. We discuss how each factor contributes to successful implementation. After identifying how design features of a 360 process affect these key factors, we recommend how to enhance the probability of implementing 360 feedback successfully and sustaining the process over time. © 2001 John Wiley & Sons, Inc. [source] Thymic generation and regenerationIMMUNOLOGICAL REVIEWS, Issue 1 2003Jason Gill Summary:, The thymus is a complex epithelial organ in which thymocyte development is dependent upon the sequential contribution of morphologically and phenotypically distinct stromal cell compartments. It is these microenvironments that provide the unique combination of cellular interactions, cytokines, and chemokines to induce thymocyte precursors to undergo a differentiation program that leads to the generation of functional T cells. Despite the indispensable role of thymic epithelium in the generation of T cells, the mediators of this process and the differentiation pathway undertaken by the primordial thymic epithelial cells are not well defined. There is a lack of lineage-specific cell-surface-associated markers, which are needed to characterize putative thymic epithelial stem cell populations. This review explores the role of thymic stromal cells in T-cell development and thymic organogenesis, as well as the molecular signals that contribute to the growth and expansion of primordial thymic epithelial cells. It highlights recent advances in these areas, which have allowed for a lineage relationship amongst thymic epithelial cell subsets to be proposed. While many fundamental questions remain to be addressed, collectively these works have broadened our understanding of how the thymic epithelium becomes specialized in the ability to support thymocyte differentiation. They should also facilitate the development of novel, rationally based therapeutic strategies for the regeneration and manipulation of thymic function in the treatment of many clinical conditions in which defective T cells have an important etiological role. [source] Molecular versatility of antibodiesIMMUNOLOGICAL REVIEWS, Issue 1 2002Henry Metzger Summary: As immunology developed into a discrete discipline, the principal experimental efforts were directed towards uncovering the molecular basis of the specificity exhibited by antibodies and the mechanism by which antigens induced their production. Less attention was given to how antibodies carry out some of their effector functions, although this subject presents an interesting protein-chemical and evolutionary problem; that is, how does a family of proteins that can bind a virtually infinite variety of ligands, many of which the species producing that protein has never encountered, reproducibly initiate an appropriate response? The experimental data persuasively suggested that aggregation of the antibody was a necessary and likely sufficient initiating event, but this only begged the question: how does aggregation induce a response? I used the IgE:mast cell system as a paradigm to investigate this subject. Data from our own group and from many others led to a molecular model that appears to explain how a cell ,senses' that antigen has reacted with the IgE. The model is directly applicable to one of the fundamental questions cited above, i.e. the mechanism by which antigens induce the production of antibodies. Although the model is conceptually simple, incorporating the actual molecular events into a quantitatively accurate scheme represents an enormous challenge. [source] Mediating between predetermined order and chaos: the role of the teacher in task-based language educationINTERNATIONAL JOURNAL OF APPLIED LINGUISTICS, Issue 3 2009Kris Van den Branden interactie; taakgericht onderwijs; leerkracht; taalleren Tasks are not blueprints for action. A number of empirical studies carried out in authentic classrooms have shown that teachers and students reinterpret the tasks they are offered by syllabus developers in ways that suit their own purposes, learning needs, and interaction styles. This observation has raised fundamental questions about the degree to which teachers who are working with tasks can make any prediction concerning the learning that will come of out of task-based interactional work. In addition, if learners' reactions to tasks are fairly unpredictable, teachers may be inclined to associate task-based work with organisational chaos and with the seemingly unattainable challenge of having to cater to every individual learner's personal whims. Drawing on classroom-based research carried out in Flanders, and describing two task-based lessons that were observed in authentic Dutch as a second language (DSL) classrooms, this paper shows that between the extremes of deterministic predictability on the one hand and complete chaos on the other lies a rich pedagogical space that teachers and learners who work with tasks can exploit to construct shared projects with clearly determined goals. Taaltaken zijn geen blauwdruk voor activiteit in de klas. Uit heel wat onderzoek naar klasinteractie blijkt dat leerkrachten en leerlingen de taken die ze krijgen voorgeschoteld, herinterpreteren, zodat ze beter aansluiten bij hun leerstijlen, interesses en interactiestijl. Dit roept de vraag op of leerkrachten die met taken werken nog wel enige voorspelling kunnen doen over wat hun leerlingen uit de taakuitvoering zullen leren. Bovendien dreigen heel wat leerkrachten taakgericht onderwijs te associëren met chaos in de klas, en met de schier onhaalbare uitdaging om op alle behoeften en reacties van alle individuele leerlingen te moeten inspelen. Op basis van onderzoek in Vlaamse klassen, en voortbouwend op 2 taakgerichte lessen die werden geobserveerd in Vlaamse NT2-klassen, illustreert dit artikel dat er tussen chaos en complete voorspelbaarheid een rijke pedagogische ruimte ligt. Binnen die pedagogische ruimte gaan leerkrachten en leerlingen samen aan de slag rond een gezamenlijk taakgericht project met duidelijke doeleinden. [source] An evaluation of the process and initial impact of disseminating a nursing e-thesisJOURNAL OF ADVANCED NURSING, Issue 5 2009Colin Macduff Abstract Title.,An evaluation of the process and initial impact of disseminating a nursing e-thesis. Aim., This paper is a report of a study conducted to evaluate product, process and outcome aspects of the dissemination of a nursing PhD thesis via an open-access electronic institutional repository. Background., Despite the growth of university institutional repositories which make theses easily accessible via the world wide web, nursing has been very slow to evaluate related processes and outcomes. Method., Drawing on Stake's evaluation research methods, a case study design was adopted. The case is described using a four-phase structure within which key aspects of process and impact are reflexively analysed. Findings., In the conceptualization/re-conceptualization phase, fundamental questions about the purpose, format and imagined readership for a published nursing PhD were considered. In the preparation phase, seven key practical processes were identified that are likely to be relevant to most e-theses. In the dissemination phase email invitations were primarily used to invite engagement. The evaluation phase involved quantitative indicators of initial impact, such as page viewing and download statistics and qualitative feedback on processes and product. Conclusion., Analysis of process and impact elements of e-thesis dissemination is likely to have more than intrinsic value. The advent of e-theses housed in web-based institutional repositories has the potential to transform thesis access and use. It also offers potential to transform the nature and scope of thesis production and dissemination. Nursing scholars can exploit and evaluate such opportunities. [source] |