Showing papers by "Boston University published in 2000"
TL;DR: The construction of a genetic toggle switch is presented—a synthetic, bistable gene-regulatory network—in Escherichia coli and a simple theory is provided that predicts the conditions necessary for bistability.
Abstract: It has been proposed' that gene-regulatory circuits with virtually any desired property can be constructed from networks of simple regulatory elements. These properties, which include multistability and oscillations, have been found in specialized gene circuits such as the bacteriophage lambda switch and the Cyanobacteria circadian oscillator. However, these behaviours have not been demonstrated in networks of non-specialized regulatory components. Here we present the construction of a genetic toggle switch-a synthetic, bistable gene-regulatory network-in Escherichia coli and provide a simple theory that predicts the conditions necessary for bistability. The toggle is constructed from any two repressible promoters arranged in a mutually inhibitory network. It is flipped between stable states using transient chemical or thermal induction and exhibits a nearly ideal switching threshold. As a practical device, the toggle switch forms a synthetic, addressable cellular memory unit and has implications for biotechnology, biocomputing and gene therapy.
4,222 citations
TL;DR: It is discovered that changes in tissue rigidity and strain could play an important controlling role in a number of normal and pathological processes involving cell locomotion, including morphogenesis, the immune response, and wound healing.
3,189 citations
TL;DR: Evidence of the occurrence of three classes of small-world networks, characterized by a vertex connectivity distribution that decays as a power law law, and the nature of such constraints may be the controlling factor for the emergence of different classes of networks are presented.
Abstract: We study the statistical properties of a variety of diverse real-world networks. We present evidence of the occurrence of three classes of small-world networks: (a) scale-free networks, characterized by a vertex connectivity distribution that decays as a power law; (b) broad-scale networks, characterized by a connectivity distribution that has a power law regime followed by a sharp cutoff; and (c) single-scale networks, characterized by a connectivity distribution with a fast decaying tail. Moreover, we note for the classes of broad-scale and single-scale networks that there are constraints limiting the addition of new links. Our results suggest that the nature of such constraints may be the controlling factor for the emergence of different classes of networks.
3,074 citations
Book•
01 Jan 2000TL;DR: Economists and workers in the financial world will find useful the presentation of empirical analysis methods and well-formulated theoretical tools that might help describe systems composed of a huge number of interacting subsystems.
Abstract: This book concerns the use of concepts from statistical physics in the description of financial systems. The authors illustrate the scaling concepts used in probability theory, critical phenomena, and fully developed turbulent fluids. These concepts are then applied to financial time series. The authors also present a stochastic model that displays several of the statistical properties observed in empirical data. Statistical physics concepts such as stochastic dynamics, short- and long-range correlations, self-similarity and scaling permit an understanding of the global behaviour of economic systems without first having to work out a detailed microscopic description of the system. Physicists will find the application of statistical physics concepts to economic systems interesting. Economists and workers in the financial world will find useful the presentation of empirical analysis methods and well-formulated theoretical tools that might help describe systems composed of a huge number of interacting subsystems.
2,826 citations
TL;DR: Two small RNAs regulate the timing of Caenorhabditis elegans development and may control late temporal transitions during development across animal phylogeny.
Abstract: Two small RNAs regulate the timing of Caenorhabditis elegans development. Transition from the first to the second larval stage fates requires the 22-nucleotide lin-4 RNA and transition from late larval to adult cell fates requires the 21-nucleotide let-7 RNA. The lin-4 and let-7 RNA genes are not homologous to each other, but are each complementary to sequences in the 3' untranslated regions of a set of protein-coding target genes that are normally negatively regulated by the RNAs. Here we have detected let-7 RNAs of ~21 nucleotides in samples from a wide range of animal species, including vertebrate, ascidian, hemichordate, mollusc, annelid and arthropod, but not in RNAs from several cnidarian and poriferan species, Saccharomyces cerevisiae, Escherichia coli or Arabidopsis. We did not detect lin-4 RNA in these species. We found that let-7 temporal regulation is also conserved: let-7 RNA expression is first detected at late larval stages in C. elegans and Drosophila , at 48 hours after fertilization in zebrafish, and in adult stages of annelids and molluscs. The let-7 regulatory RNA may control late temporal transitions during development across animal phylogeny.
2,532 citations
TL;DR: This article is part 1 of a two-part summary of an NIH conference, Stepping Away with OA: Prevention of Onset, Progression, and Disability of Osteoarthritis, which brought together experts in osteoarth arthritis from diverse backgrounds and provided a multidisciplinary and comprehensive summary of recent advances in the prevention.
Abstract: Osteoarthritis is the most common form of arthritis, affecting millions of people in the United States. It is a complex disease whose etiology bridges biomechanics and biochemistry. Evidence is growing for the role of systemic factors (such as genetics, dietary intake, estrogen use, and bone density) and of local biomechanical factors (such as muscle weakness, obesity, and joint laxity). These risk factors are particularly important in weightbearing joints, and modifying them may present opportunities for prevention of osteoarthritis-related pain and disability. Major advances in management to reduce pain and disability are yielding a panoply of available treatments ranging from nutriceuticals to chondrocyte transplantation, new oral anti-inflammatory medications, and health education. This article is part 1 of a two-part summary of a National Institutes of Health conference. The conference brought together experts on osteoarthritis from diverse backgrounds and provided a multidisciplinary and comprehensive summary of recent advances in the prevention of osteoarthritis onset, progression, and disability. Part 1 focuses on a new understanding of what osteoarthritis is and on risk factors that predispose to disease occurrence. It concludes with a discussion of the impact of osteoarthritis on disability. Ann Intern Med. 2000;133:635-646. www.annals.org For author affiliations and current addresses, see end of text.
2,313 citations
TL;DR: The authors found that when the contract offers money the environment is perceived as monetary, and participants respond in a qualitatively different way in monetary and non-monetary environments in a set of experiments.
Abstract: Economics seems largely based on the assumption that monetary incentives improve performance. By contrast, a large literature in psychology, including a rich tradition of experimental work, claims just the opposite. In this paper we present and discuss a set of experiments designed to test the effect of different monetary compensations on performance. In our experiments we find that whenever money is offered, a larger amount yields a higher performance. It is not true, however, that offering money always induces a higher performance: participants who were offered a small payoff gave a worse performance than those who were offered no compensation at all. These results suggest that the behavior of participants is influenced by their perception of the contract that is offered to them. When the contract offers money the environment is perceived as monetary, and participants respond in a qualitatively different way in monetary and non-monetary environments. In a different set of experiments we test subjects who, acting as principals, have to provide the appropriate incentive to agents. We show that principals do not anticipate the drastic difference in behavior. The vast majority of principals seem to think incorrectly that a larger compensation is unambiguously a better incentive.
2,094 citations
Posted Content•
TL;DR: In this article, the authors present an empirical examination of the determinants of country-level production of international patents and introduce a novel framework based on the concept of national innovative capacity, the ability of a country to produce and commercialize a flow of innovative technology over the long term.
Abstract: Motivated by differences in R&D productivity across advanced economies, this paper presents an empirical examination of the determinants of country-level production of international patents. We introduce a novel framework based on the concept of national innovative capacity. National innovative capacity is the ability of a country to produce and commercialize a flow of innovative technology over the long term. National innovative capacity depends on the strength of a nation's common innovation infrastructure (cross-cutting factors which contribute broadly to innovativeness throughout the economy), the environment for innovation in its leading industrial clusters, and the strength of linkages between these two areas. We use this framework to guide our empirical exploration into the determinants of country-level R&D productivity, specifically examining the relationship between international patenting (patenting by foreign countries in the United States) and variables associated with the national innovative capacity framework. While acknowledging important measurement issues arising from the use of patent data, we provide evidence for several findings. First, the production function for international patents is surprisingly well-characterized by a small but relatively nuanced set of observable factors, including R&D manpower and spending, aggregate policy choices such as the extent of IP protection and openness to international trade, and the share of research performed by the academic sector and funded by the private sector. As well, international patenting productivity depends on each individual country's knowledge stock.' Further, the predicted level of national innovative capacity has an important impact on more downstream commercialization and diffusion activities (such as achieving a high market share of high-technology export markets). Finally, there has been convergence among OECD countries in terms of the estimated level of innovative capacity over the past quarter century.
2,006 citations
TL;DR: A common receptor activation pathway can initiate innate immune responses to both bacterial and viral pathogens.
Abstract: The innate immune system contributes to the earliest phase of the host defense against foreign organisms and has both soluble and cellular pattern recognition receptors for microbial products. Two important members of this receptor group, CD14 and the Toll-like receptor (TLR) pattern recognition receptors, are essential for the innate immune response to components of Gram-negative and Gram-positive bacteria, mycobacteria, spirochetes and yeast. We now find that these receptors function in an antiviral response as well. The innate immune response to the fusion protein of an important respiratory pathogen of humans, respiratory syncytial virus (RSV), was mediated by TLR4 and CD14. RSV persisted longer in the lungs of infected TLR4-deficient mice compared to normal mice. Thus, a common receptor activation pathway can initiate innate immune responses to both bacterial and viral pathogens.
1,679 citations
TL;DR: Individuals of 50 years and older who were prescribed statins had a substantially lowered risk of developing dementia, independent of the presence or absence of untreated hyperlipidaemia, or exposure to nonstatin LLAs.
1,637 citations
Journal Article•
Lawrence Berkeley National Laboratory1, University of Zurich2, Stanford University3, College of William & Mary4, University of Genoa5, University of Urbino6, CERN7, Budker Institute of Nuclear Physics8, Cornell University9, Argonne National Laboratory10, ETH Zurich11, Tata Institute of Fundamental Research12, Hillsdale College13, Spanish National Research Council14, Tohoku University15, Ohio State University16, University of California, San Diego17, University of California, Berkeley18, Aix-Marseille University19, University of Minnesota20, University of Alabama21, University of Helsinki22, California Institute of Technology23, George Washington University24, University of Kansas25, RWTH Aachen University26, Boston University27, University of California, Los Angeles28, Institut des Hautes Études Scientifiques29, University of Pennsylvania30, University of Tokyo31, University of Delaware32, Fermilab33, Carnegie Mellon University34, University of California, Santa Cruz35, Lawrence Livermore National Laboratory36, University of Washington37, Karlsruhe Institute of Technology38, Heidelberg University39, Florida State University40, Carleton University41, National Science Foundation42, University of Mainz43, University of Edinburgh44, University of Chicago45, Brookhaven National Laboratory46, Kent State University47, Paul Scherrer Institute48, Max Planck Society49, Massachusetts Institute of Technology50, Nagoya University51, Harvard University52
TL;DR: In this article, a biennial review summarizes much of particle physics using data from previous editions., plus 2778 new measurements from 645 papers, including measurements of gauge bosons, leptons, quarks, mesons, and baryons.
Abstract: This biennial Review summarizes much of particle physics. Using data from previous editions., plus 2778 new measurements from 645 papers, we list, evaluate, and average measured properties of gauge bosons, leptons, quarks, mesons, and baryons. We also summarize searches for hypothetical particles such as Higgs bosons, heavy neutrinos, and supersymmetric particles. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables, figures, formulae, and reviews of topics such as the Standard Model, particle detectors., probability, and statistics. Among the 108 reviews are many that are new or heavily revised including those on CKM quark-mixing matrix, V-ud & V-us, V-cb & V-ub, top quark, muon anomalous magnetic moment, extra dimensions, particle detectors, cosmic background radiation, dark matter, cosmological parameters, and big bang cosmology.
TL;DR: How the cognitive and neural coding mechanisms that underlie declarative memory work together to create and re-create fully networked representations of previous experiences and knowledge about the world are described.
Abstract: Recent neurobiological studies have begun to reveal the cognitive and neural coding mechanisms that underlie declarative memory--our ability to recollect everyday events and factual knowledge. These studies indicate that the critical circuitry involves bidirectional connections between the neocortex, the parahippocampal region and the hippocampus. Each of these areas makes a unique contribution to memory processing. Widespread high-order neocortical areas provide dedicated processors for perceptual, motor or cognitive information that is influenced by other components of the system. The parahippocampal region mediates convergence of this information and extends the persistence of neocortical memory representations. The hippocampus encodes the sequences of places and events that compose episodic memories, and links them together through their common elements. Here I describe how these mechanisms work together to create and re-create fully networked representations of previous experiences and knowledge about the world.
TL;DR: It is suggested that a quantitative loss in muscle CSA is a major contributor to the decrease in muscle strength seen with advancing age and accounts for 90% of the variability in strength at T2.
Abstract: The present study examines age-related changes in skeletal muscle size and function after 12 yr. Twelve healthy sedentary men were studied in 1985–86 (T1) and nine (initial mean age 65.4 ± 4.2 yr) ...
TL;DR: The author builds a general theory of modular systems, drawing on systems research from many disciplines, and then uses this general theory to derive a model of interfirm product modularity, including testable research propositions.
Abstract: Many systems migrate toward increasing or decreasing modularity, yet no explicit causal models exist to explain this process. In this article the author builds a general theory of modular systems, drawing on systems research from many disciplines, and then uses this general theory to derive a model of interfirm product modularity, including testable research propositions. The product model provides a valuable tool for predicting technological trajectories, and it demonstrates how the general theory can be applied to specific systems.
TL;DR: In this paper, the authors show that large technology shocks are needed to produce realistic business cycles, while Solow residuals are sufficiently volatile, these imply frequent technological regress, suggesting the imminent demise of real business cycles.
Abstract: The Real Business Cycle (RBC) research program has grown spectacularly over the last decade, as its concepts and methods have diffused into mainstream macroeconomics. Yet, there is increasing skepticism that technology shocks are a major source of business fluctuations. This chapter exposits the basic RBC model and shows that it requires large technology shocks to produce realistic business cycles. While Solow residuals are sufficiently volatile, these imply frequent technological regress. Productivity studies permitting unobserved factor variation find much smaller technology shocks, suggesting the imminent demise of real business cycles. However, we show that greater factor variation also dramatically amplifies shocks: a RBC model with varying capital utilization yields realistic business cycles from small, nonnegative changes in technology.
TL;DR: The present results indicate that a knock-out of GSHPx may be adequately compensated under nonstressed conditions, but that after administration of mitochondrial toxins GSHpx plays an important role in detoxifying increases in oxygen radicals.
Abstract: Glutathione peroxidase (GSHPx) is a critical intracellular enzyme involved in detoxification of hydrogen peroxide (H 2 O 2 ) to water. In the present study we examined the susceptibility of mice with a disruption of the glutathione peroxidase gene to the neurotoxic effects of malonate, 3-nitropropionic acid (3-NP), and 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP). Glutathione peroxidase knock-out mice showed no evidence of neuropathological or behavioral abnormalities at 2–3 months of age. Intrastriatal injections of malonate resulted in a significant twofold increase in lesion volume in homozygote GSHPx knock-out mice as compared to both heterozygote GSHPx knock-out and wild-type control mice. Malonate-induced increases in conversion of salicylate to 2,3- and 2,5-dihydroxybenzoic acid, an index of hydroxyl radical generation, were greater in homozygote GSHPx knock-out mice as compared with both heterozygote GSHPx knock-out and wild-type control mice. Administration of MPTP resulted in significantly greater depletions of dopamine, 3,4-dihydroxybenzoic acid, and homovanillic acid in GSHPx knock-out mice than those seen in wild-type control mice. Striatal 3-nitrotyrosine (3-NT) concentrations after MPTP were significantly increased in GSHPx knock-out mice as compared with wild-type control mice. Systemic 3-NP administration resulted in significantly greater striatal damage and increases in 3-NT in GSHPx knock-out mice as compared to wild-type control mice. The present results indicate that a knock-out of GSHPx may be adequately compensated under nonstressed conditions, but that after administration of mitochondrial toxins GSHPx plays an important role in detoxifying increases in oxygen radicals.
TL;DR: A solution for the time- and age-dependent connectivity distribution of a growing random network is presented and the power law N(k) approximately k(-nu) is found, where the exponent nu can be tuned to any value in the range 2.
Abstract: A solution for the time- and age-dependent connectivity distribution of a growing random network is presented. The network is built by adding sites that link to earlier sites with a probability A(k) which depends on the number of preexisting links k to that site. For homogeneous connection kernels, A(k) approximately k(gamma), different behaviors arise for gamma 1, and gamma = 1. For gamma 1, a single site connects to nearly all other sites. In the borderline case A(k) approximately k, the power law N(k) approximately k(-nu) is found, where the exponent nu can be tuned to any value in the range 2
TL;DR: It is reported that minocycline delays disease progression, inhibits casp enzyme-1 and caspase-3 mRNA upregulation, and decreases inducible nitric oxide synthetase activity, in the R6/2 mouse model of Huntington disease.
Abstract: Huntington disease is an autosomal dominant neurodegenerative disease with no effective treatment. Minocycline is a tetracycline derivative with proven safety. After ischemia, minocycline inhibits caspase-1 and inducible nitric oxide synthetase upregulation, and reduces infarction. As caspase-1 and nitric oxide seem to play a role in Huntington disease, we evaluated the therapeutic efficacy of minocycline in the R6/2 mouse model of Huntington disease. We report that minocycline delays disease progression, inhibits caspase-1 and caspase-3 mRNA upregulation, and decreases inducible nitric oxide synthetase activity. In addition, effective pharmacotherapy in R6/2 mice requires caspase-1 and caspase-3 inhibition. This is the first demonstration of caspase-1 and caspase-3 transcriptional regulation in a Huntington disease model.
TL;DR: A simplified model is used to show that the different rhythms in the CA1 region of the hippocampus employ different dynamical mechanisms to synchronize, based on different ionic currents, which are consistent with data suggesting that gamma rhythms are used for relatively local computations whereas beta rhythms are use for higher level interactions involving more distant structures.
Abstract: Experimental and modeling efforts suggest that rhythms in the CA1 region of the hippocampus that are in the beta range (12–29 Hz) have a different dynamical structure than that of gamma (30–70 Hz). We use a simplified model to show that the different rhythms employ different dynamical mechanisms to synchronize, based on different ionic currents. The beta frequency is able to synchronize over long conduction delays (corresponding to signals traveling a significant distance in the brain) that apparently cannot be tolerated by gamma rhythms. The synchronization properties are consistent with data suggesting that gamma rhythms are used for relatively local computations whereas beta rhythms are used for higher level interactions involving more distant structures.
TL;DR: In this paper, the authors describe a model of two-party electoral competition with "probabilistic" voting behavior and lobbying by special interest groups that helps identify determinants of relative capture at different levels of government.
Abstract: 135 Despite the importance of this issue, not much systematic research appears to have been devoted to assessing the relative susceptibility of national and local governments to interestgroup capture. Here we describe a model of two-party electoral competition with “probabilistic” voting behavior and lobbying by specialinterest groups based on David Baron (1994) and Gene Grossman and Elhanan Helpman (1996) that helps identify determinants of relative capture at different levels of government. These include relative levels of voter awareness and interest-group cohesiveness, electoral uncertainty, electoral competition, heterogeneity of districts with respect to inequality, and the electoral system. While some of these uphold the traditional Madisonian presumption, others are likely to create a tendency for lower capture at the local level, so the net effect is theoretically ambiguous. This suggests that the extent of relative capture may be context-specific and needs to be assessed empirically.
TL;DR: Chemical and physical definition of the fibrils in tissues will be needed to relate the in vitro properties of amyloid protein fibril formation in vivo to the pathogenesis ofAmyloid fibrillar formation in vitro.
TL;DR: Nicastrin and presenilins are likely to be functional components of a multimeric complex necessary for the intramembranous proteolysis of proteins such as Notch/GLP-1 and βAPP.
Abstract: Nicastrin, a transmembrane glycoprotein, forms high molecular weight complexes with presenilin 1 and presenilin 2. Suppression of nicastrin expression in Caenorhabditis elegans embryos induces a subset of notch/glp-1 phenotypes similar to those induced by simultaneous null mutations in both presenilin homologues of C. elegans (sel-12 and hop-1). Nicastrin also binds carboxy-terminal derivatives of β-amyloid precursor protein (βAPP), and modulates the production of the amyloid β-peptide (Aβ) from these derivatives. Missense mutations in a conserved hydrophilic domain of nicastrin increase Aβ42 and Aβ40 peptide secretion. Deletions in this domain inhibit Aβ production. Nicastrin and presenilins are therefore likely to be functional components of a multimeric complex necessary for the intramembranous proteolysis of proteins such as Notch/GLP-1 and βAPP.
TL;DR: The algorithm presented may be employed to derive albedo from space-based multiangular measurements and also serves as a guide for the use of the MODIS BRDF/albedo product.
Abstract: Spectral albedo may be derived from atmospherically corrected, cloud-cleared multiangular reflectance observations through the inversion of a bidirectional reflectance distribution function (BRDF) model and angular integration. This paper outlines an algorithm suitable for this task that makes use of kernel-based BRDF models. Intrinsic land surface albedos are derived, which may be used to derive actual albedo by taking into account the prevailing distribution of diffuse skylight. Spectral-to-broadband conversion is achieved using band-dependent weighting factors. The validation of a suitable BRDF model, the semiempirical Ross-Li (reciprocal RossThick-LiSparse) model and its performance under conditions of sparse angular sampling and noisy reflectances are discussed, showing that the retrievals obtained are generally reliable. The solar-zenith angle dependence of albedo may be parameterized by a simple polynomial that makes it unnecessary for the user to be familiar with the underlying BRDF model. The algorithm given is that used for the production of a BRDF/albedo standard data product from NASA's EOS-MODIS sensor, for which an at-launch status is provided. Finally, the algorithm is demonstrated on combined AVHRR and GOES observations acquired over New England, from which solar zenith angle-dependent albedo maps with a nominal spatial resolution of 1 km are derived in the visible band. The algorithm presented may be employed to derive albedo from space-based multiangular measurements and also serves as a guide for the use of the MODIS BRDF/albedo product.
TL;DR: This review will provide the reader with a brief outline of the basic properties of inhibition-based oscillations in the CNS by combining research from laboratory models, large-scale neuronal network simulations, and mathematical analysis.
TL;DR: Combining imipramine and CBT appeared to confer limited advantage acutely but more substantial advantage by the end of maintenance, and each treatment worked well immediately following treatment and during maintenance;CBT appeared durable in follow-up.
Abstract: ContextPanic disorder (PD) may be treated with drugs, psychosocial intervention,
or both, but the relative and combined efficacies have not been evaluated
in an unbiased fashion.ObjectiveTo evaluate whether drug and psychosocial therapies for PD are each
more effective than placebo, whether one treatment is more effective than
the other, and whether combined therapy is more effective than either therapy
alone.Design and SettingRandomized, double-blind, placebo-controlled clinical trial conducted
in 4 anxiety research clinics from May 1991 to April 1998.PatientsA total of 312 patients with PD were included in the analysis.InterventionsPatients were randomly assigned to receive imipramine, up to 300 mg/d,
only (n=83); cognitive-behavioral therapy (CBT) only (n=77); placebo only
(n=24); CBT plus imipramine (n=65); or CBT plus placebo (n=63). Patients were
treated weekly for 3 months (acute phase); responders were then seen monthly
for 6 months (maintenance phase) and then followed up for 6 months after treatment
discontinuation.Main Outcome MeasuresTreatment response based on the Panic Disorder Severity Scale (PDSS)
and the Clinical Global Impression Scale (CGI) by treatment group.ResultsBoth imipramine and CBT were significantly superior to placebo for the
acute treatment phase as assessed by the PDSS (response rates for the intent-to-treat
[ITT] analysis, 45.8%, 48.7%, and 21.7%; P=.05 and P=.03, respectively), but were not significantly different
for the CGI (48.2%, 53.9%, and 37.5%, respectively). After 6 months of maintenance,
imipramine and CBT were significantly more effective than placebo for both
the PDSS (response rates, 37.8%, 39.5%, and 13.0%, respectively; P=.02 for both) and the CGI (37.8%, 42.1%, and 13.0%, respectively).
Among responders, imipramine produced a response of higher quality. The acute
response rate for the combined treatment was 60.3% for the PDSS and 64.1%
for the CGI; neither was significantly different from the other groups. The
6-month maintenance response rate for combined therapy was 57.1% for the PDSS
(P=.04 vs CBT alone and P=.03
vs imipramine alone) and 56.3% for the CGI (P=.03
vs imipramine alone), but not significantly better than CBT plus placebo in
either analysis. Six months after treatment discontinuation, in the ITT analysis
CGI response rates were 41.0% for CBT plus placebo, 31.9% for CBT alone, 19.7%
for imipramine alone, 13% for placebo, and 26.3% for CBT combined with imipramine.ConclusionsCombining imipramine and CBT appeared to confer limited advantage acutely
but more substantial advantage by the end of maintenance. Each treatment worked
well immediately following treatment and during maintenance; CBT appeared
durable in follow-up.
TL;DR: Firing patterns of hippocampal complex-spike neurons were examined for the capacity to encode information important to the memory demands of a task even when the overt behavior and location of the animal are held constant, suggesting some of the information necessary for representing specific memory episodes is encoded.
TL;DR: Evaluation of benefit of glucosamine and chondroitin preparations for OA symptoms using meta-analysis combined with systematic quality assessment of clinical trials of these preparations in knee and/or hip OA suggests some degree of efficacy appears probable for these preparations.
Abstract: Data Synthesis Quality scores ranged from 12.3% to 55.4% of the maximum, with a mean (SD) of 35.5% (12%). Only 1 study described adequate allocation concealment and 2 reported an intent-to-treat analysis. Most were supported or performed by a manufacturer. Funnel plots showed significant asymmetry (P#.01) compatible with publication bias. Tests for heterogeneity were nonsignificant after removing 1 outlier trial. The aggregated effect sizes were 0.44 (95% confidence interval [CI], 0.240.64) for glucosamine and 0.78 (95% CI, 0.60-0.95) for chondroitin, but they were diminished when only high-quality or large trials were considered. The effect sizes were relatively consistent for pain and functional outcomes. Conclusions Trials of glucosamine and chondroitin preparations for OA symptoms demonstrate moderate to large effects, but quality issues and likely publication bias suggest that these effects are exaggerated. Nevertheless, some degree of efficacy appears probable for these preparations.
TL;DR: In this paper, the authors argue that corporate social performance has become a legitimizing identity (brand) for researchers in the business and society field, but it has not developed into a viable theoretical or operational construct, and they suggest that researchers remove the CSP label from their operational variables, and instead narrowly define their studies in operational terms.
Abstract: We argue that corporate social performance (CSP) has become a legitimizing identity (brand) for researchers in the business and society field, but it has not developed into a viable theoretical or operational construct. Because measuring CSP is contingent on the operational setting (industry, issues, etc.), it is difficult to produce worthwhile comparisons across studies or generalizing beyond the boundaries of a specific study. The authors suggest that researchers remove the CSP label from their operational variables, and instead narrowly define their studies in operational terms. They provide aworking example of the proposed research direction by examining the theory underlying the popular CSP–financial performance (FP) debate. In the authors’ conceptualization, stakeholder action provides the underlying logic connecting CSP-FP, and we recast the research question to investigate the conditions under which stakeholders will take action to influence the focal organization and when those actions will influ...
TL;DR: The current major hypotheses are outlined, predictions relevant to integrated molecular approaches are developed, and the current evidence is evaluated, focusing on central African, Australian, and South American systems.
Abstract: ▪ Abstract Understanding the evolutionary processes that generate and sustain diversity in tropical faunas has challenged biologists for over a century and should underpin conservation strategies. Molecular studies of diversity within species and relationships among species, when integrated with more traditional approaches of biogeography and paleoecology, have much to contribute to this challenge. Here we outline the current major hypotheses, develop predictions relevant to integrated molecular approaches, and evaluate the current evidence, focusing on central African, Australian, and South American systems. The available data are sparse relative to the scale of the questions. However, the following conclusions can be drawn: (a) in most cases, the divergence of extant sister taxa predates the Pleistocene; (b) areas with high habitat heterogeneity and recent climatic or geological instability appear to harbor more species of recent origin; (c) there is support for both allopatric and gradient models of di...
TL;DR: Comparison between the simulations and magnetic resonance measurements in the ascending aorta and nine peripheral locations in one individual shows excellent agreement between the two.
Abstract: Blood flow in the large systemic arteries is modeled using one-dimensional equations derived from the axisymmetric Navier–Stokes equations for flow in compliant and tapering vessels. The arterial tree is truncated after the first few generations of large arteries with the remaining small arteries and arterioles providing outflow boundary conditions for the large arteries. By modeling the small arteries and arterioles as a structured tree, a semi-analytical approach based on a linearized version of the governing equations can be used to derive an expression for the root impedance of the structured tree in the frequency domain. In the time domain, this provides the proper outflow boundary condition. The structured tree is a binary asymmetric tree in which the radii of the daughter vessels are scaled linearly with the radius of the parent vessel. Blood flow and pressure in the large vessels are computed as functions of time and axial distance within each of the arteries. Comparison between the simulations and magnetic resonance measurements in the ascending aorta and nine peripheral locations in one individual shows excellent agreement between the two. © 2000 Biomedical Engineering Society.