Showing papers by "New York University published in 1998"
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TL;DR: This article developed a dynamic general equilibrium model that is intended to help clarify the role of credit market frictions in business fluctuations, from both a qualitative and a quantitative standpoint, and the model is a synthesis of the leading approaches in the literature.
Abstract: This paper develops a dynamic general equilibrium model that is intended to help clarify the role of credit market frictions in business fluctuations, from both a qualitative and a quantitative standpoint. The model is a synthesis of the leading approaches in the literature. In particular, the framework exhibits a financial accelerator,' in that endogenous developments in credit markets work to amplify and propagate shocks to the macroeconomy. In addition, we add several features to the model that are designed to enhance the empirical relevance. First, we incorporate money and price stickiness, which allows us to study how credit market frictions may influence the transmission of monetary policy. In addition, we allow for lags in investment which enables the model to generate both hump-shaped output dynamics and a lead-lag relation between asset prices and investment, as is consistent with the data. Finally, we allow for heterogeneity among firms to capture the fact that borrowers have differential access to capital markets. Under reasonable parametrizations of the model, the financial accelerator has a significant influence on business cycle dynamics.
5,370 citations
TL;DR: The design and observation of two-dimensional crystalline forms of DNA that self-assemble from synthetic DNA double-crossover molecules that create specific periodic patterns on the nanometre scale are reported.
Abstract: Molecular self-assembly presents a `bottom-up' approach to the fabrication of objects specified with nanometre precision. DNA
molecular structures and intermolecular interactions are particularly
amenable to the design and synthesis of complex molecular objects. We
report the design and observation of two-dimensional crystalline forms
of DNA that self-assemble from synthetic DNA double-crossover
molecules. Intermolecular interactions between the structural units are
programmed by the design of `sticky ends' that associate according to
Watson-Crick complementarity, enabling us to create specific periodic
patterns on the nanometre scale. The patterned crystals have been
visualized by atomic force microscopy.
2,713 citations
TL;DR: This is the first demonstration of the involvement of a G-protein-coupled chemokine receptor in neuronal cell migration and patterning in the central nervous system and may be important for designing strategies to block HIV entry into cells and for understanding mechanisms of pathogenesis in AIDS dementia.
Abstract: Chemokines and their receptors are important in cell migration during inflammation, in the establishment of functional lymphoid microenvironments, and in organogenesis. The chemokine receptor CXCR4 is broadly expressed in cells of both the immune and the central nervous systems and can mediate migration of resting leukocytes and haematopoietic progenitors in response to its ligand, SDF-1. CXCR4 is also a major receptor for strains of human immunodeficiency virus-1 (HIV-1) that arise during progression to immunodeficiency and AIDS dementia. Here we show that mice lacking CXCR4 exhibit haematopoietic and cardiac defects identical to those of SDF-1-deficient mice, indicating that CXCR4 may be the only receptor for SDF-1. Furthermore, fetal cerebellar development in mutant animals is markedly different from that in wild-type animals, with many proliferating granule cells invading the cerebellar anlage. This is, to our knowledge, the first demonstration of the involvement of a G-protein-coupled chemokine receptor in neuronal cell migration and patterning in the central nervous system. These results may be important for designing strategies to block HIV entry into cells and for understanding mechanisms of pathogenesis in AIDS dementia.
2,506 citations
TL;DR: The current understanding of the role of cyclooxygenase‐1 and ‐2 in different physiological situations and disease processes ranging from inflammation to cancer is summarized.
Abstract: Cyclooxygenase (COX), the key enzyme required for the conversion of arachidonic acid to prostaglandins was first identified over 20 years ago. Drugs, like aspirin, that inhibit cyclooxygenase activity have been available to the public for about 100 years. In the past decade, however, more progress has been made in understanding the role of cyclooxygenase enzymes in biology and disease than at any other time in history. Two cyclooxygenase isoforms have been identified and are referred to as COX-1 and COX-2. Under many circumstances the COX-1 enzyme is produced constitutively (i.e., gastric mucosa) whereas COX-2 is inducible (i.e., sites of inflammation). Here, we summarize the current understanding of the role of cyclooxygenase-1 and -2 in different physiological situations and disease processes ranging from inflammation to cancer. We have attempted to include all of the most relevant material in the field, but due to the rapid progress in this area of research we apologize that certain recent findings may have been left out.
2,447 citations
TL;DR: This paper found that since 1979 each of the G3 central banks has pursued an implicit form of inflation targeting, which may account for the broad success of monetary policy in those countries over this time period.
2,227 citations
TL;DR: Compared with the wild type, mouse embryonic fibroblasts derived from chop -/- animals exhibited significantly less programmed cell death when challenged with agents that perturb ER function, and the proximal tubule epithelium of chop -/+ animals exhibited fourfold lower levels of TUNEL-positive cells, and significantly less evidence for subsequent regeneration.
Abstract: Cellular stress, particularly in response to toxic and metabolic insults that perturb function of the endoplasmic reticulum (ER stress), is a powerful inducer of the transcription factor CHOP. The role of CHOP in the response of cells to injury associated with ER stress was examined in a murine deficiency model obtained by homologous recombination at the chop gene. Compared with the wild type, mouse embryonic fibroblasts (MEFs) derived from chop -/- animals exhibited significantly less programmed cell death when challenged with agents that perturb ER function. A similar deficit in programmed cells death in response to ER stress was also observed in MEFs that lack CHOP's major dimerization partner, C/EBPbeta, implicating the CHOP-C/EBP pathway in programmed cell death. An animal model for studying the effects of chop on the response to ER stress was developed. It entailed exposing mice with defined chop genotypes to a single sublethal intraperitoneal injection of tunicamycin and resulted in a severe illness characterized by transient renal insufficiency. In chop +/+ and chop +/- mice this was associated with the early expression of CHOP in the proximal tubules followed by the development of a histological picture similar to the human condition known as acute tubular necrosis, a process that resolved by cellular regeneration. In the chop -/- animals, in spite of the severe impairment in renal function, evidence of cellular death in the kidney was reduced compared with the wild type. The proximal tubule epithelium of chop -/- animals exhibited fourfold lower levels of TUNEL-positive cells (a marker for programmed cell death), and significantly less evidence for subsequent regeneration. CHOP therefore has a role in the induction of cell death under conditions associated with malfunction of the ER and may also have a role in cellular regeneration under such circumstances.
1,935 citations
TL;DR: It is demonstrated that aged humans with significant prolonged cortisol elevations showed reduced hippocampal volume and deficits in hippocampus-dependent memory tasks compared to normal-cortisol controls, and the degree of hippocampal atrophy correlated strongly with both the degree and current basal cortisol levels.
Abstract: Elevated glucocorticoid levels produce hippocampal dysfunction and correlate with individual deficits in spatial learning in aged rats. Previously we related persistent cortisol increases to memory impairments in elderly humans studied over five years. Here we demonstrate that aged humans with significant prolonged cortisol elevations showed reduced hippocampal volume and deficits in hippocampus-dependent memory tasks compared to normal-cortisol controls. Moreover, the degree of hippocampal atrophy correlated strongly with both the degree of cortisol elevation over time and current basal cortisol levels. Therefore, basal cortisol elevation may cause hippocampal damage and impair hippocampus-dependent learning and memory in humans.
1,564 citations
TL;DR: The role of information technology in markets, both in traditional markets, and in the emergence of electronic marketplaces, such as the multitude of Internet-based online auctions, has seen a dramatic increase.
Abstract: Markets play a central role in the economy, facilitating the exchange of information, goods, services and payments. In the process, they create economic value for buyers, sellers, market intermediaries and for society at large. Recent years have seen a dramatic increase in the role of information technology in markets, both in traditional markets, and in the emergence of electronic marketplaces, such as the multitude of Internet-based online auctions.
1,510 citations
TL;DR: A survey of the empirical and theoretical literature on the mechanisms of corporate governance can be found in this article, where the authors focus on the internal mechanisms and their role in ameliorating various classes of agency problems arising from conflicts of interests between managers and equityholders, equityholders and creditors, and capital contributors and other stakeholders.
Abstract: This paper surveys the empirical and theoretical literature on the mechanisms of corporate governance. We focus on the internal mechanisms of corporate governance (e.g., corporate board of directors) and their role in ameliorating various classes of agency problems arising from conflicts of interests between managers and equityholders, equityholders and creditors, and capital contributors and other stakeholders to the corporate firm. We also examine the substitution effect between internal mechanisms of corporate governance and external mechanisms, particularly markets for corporate control. Directions for future research are provided.
1,358 citations
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TL;DR: In this paper, the authors explore the features of affine term structure models that are empirically important for explaining the joint distribution of yields on short and long-term interest rate swaps.
Abstract: In this paper, we explore the features of affine term structure models that are empirically important for explaining the joint distribution of yields on short and long-term interest rate swaps. We begin by showing that the family of N-factor affine models can be classified into N+1 non-nested sub-families of models. For each sub-family, we derive a maximal model with the property that every admissible member of this family is equivalent to or a nested special case of our maximal model. Second, using our classification scheme and maximal models, we show that many of the three-factor models in the literature impose potentially strong over-identifying restrictions on the joint distribution of short- and long-term rates. Third, we compute simulated method-of-moments estimates for several members of one of the four branches of three-factor models, and test the over-identifying restrictions implied by these models. We conclude that many of the extant affine models in the literature fail to describe important features of the distribution of long- and short- term rates. The source of the model misspecification is shown to be overly strong restrictions on the correlations among the state variables. Relaxing these restrictions leads to a model that passes several goodness-of-fit tests over our sample period.
1,343 citations
TL;DR: This article found that stock price reactions to independent director appointments are significantly lower when the CEO is involved in selection, and independent appointees are more likely to serve on large numbers of other boards, a practice disfavored by investor activists.
Abstract: We study whether CEO involvement in the selection of new directors influences the quality of appointments to the board. When the CEO serves on the nominating committee or no nominating committee exists, firms appoint fewer independent outside directors and more gray outsiders with conflicts of interest. Stock price reactions to independent director appointments are significantly lower when the CEO is involved in director selection, and independent appointees are more likely to serve on large numbers of other boards, a practice disfavored by investor activists. Our evidence may illuminate a mechanism used by CEOs to reduce pressure from active monitoring, and we find a recent trend of companies removing CEOs from involvement in director selection.
TL;DR: In this paper, an improved version of a criterion based on the Akaike information criterion (AIC), termed AICc, is derived and examined as a way to choose the smoothing parameter.
Abstract: Summary. Many different methods have been proposed to construct nonparametric estimates of a smooth regression function, including local polynomial, (convolution) kernel and smoothing spline estimators. Each of these estimators uses a smoothing parameter to control the amount of smoothing performed on a given data set. In this paper an improved version of a criterion based on the Akaike information criterion (AIC), termed AICc, is derived and examined as a way to choose the smoothing parameter. Unlike plug-in methods, AICc can be used to choose smoothing parameters for any linear smoother, including local quadratic and smoothing spline estimators. The use of AICc avoids the large variability and tendency to undersmooth (compared with the actual minimizer of average squared error) seen when other 'classical' approaches (such as generalized cross-validation or the AIC) are used to choose the smoothing parameter. Monte Carlo simulations demonstrate that the AICc-based smoothing parameter is competitive with a plug-in method (assuming that one exists) when the plug-in method works well but also performs well when the plug-in approach fails or is unavailable.
TL;DR: Psychiatric research has benefited from attention to measurement theories of reliability, and reliability/agreement statistics for psychopathology ratings and diagnoses are regularly reported in empirical reports.
Abstract: Psychiatric research has benefited from attention to measurement theories of reliability, and reliability/agreement statistics for psychopathology ratings and diagnoses are regularly reported in empirical reports. Nevertheless, there are still controversies regarding how reliability should be measured, and the amount of resources that should be spent on studying measurement quality in research programs. These issues are discussed in the context of recent theoretical and technical contributions to the statistical analysis of reliability. Special attention is paid to statistical studies published since Kraemer's 1992 review of reliability methods in this journal.
TL;DR: It is reported that the large family of IFNα genes can be divided into two groups: an immediate‐early response gene (IFNα4) which is induced rapidly and without the need for ongoing protein synthesis; and a set of genes that display delayed induction, which are induced more slowly and require cellular protein synthesis.
Abstract: Interferon (IFN) genes are among the earliest transcriptional responses to virus infection of mammalian cells. Although the regulation of the IFNβ gene has been well characterized, the induction of the large family of IFNα genes has remained obscure. We report that the IFNα genes can be divided into two groups: an immediate‐early response gene (IFNα4) which is induced rapidly and without the need for ongoing protein synthesis; and a set of genes that display delayed induction, consisting of at least IFNα2, 5, 6 and 8, which are induced more slowly and require cellular protein synthesis. One protein that must be synthesized for induction of the delayed gene set is IFN itself, presumably IFNα4 or IFNβ, which stimulates the Jak–Stat pathway through the IFN receptor, resulting in activation of the transcription factor interferon‐stimulated gene factor 3 (ISGF3). Among the IFN‐stimulated genes induced through this positive feedback loop is the IFN regulatory factor (IRF) protein, IRF7. Induction of IRF7 protein in response to IFN and its subsequent activation by phosphorylation in response to virus‐specific signals, involving two C‐terminal serine residues, are required for induction of the delayed IFNα gene set.
TL;DR: In this paper, a viable transfectant influenza A virus (delNS1) which lacks the NS1 gene has been generated through the use of reverse genetics, and it has been shown that the NS 1 protein plays a crucial role in inhibiting interferon-mediated antiviral responses of the host.
TL;DR: In this paper, the authors empirically examine if entry mode choice (acquisition versus greenfield) influences foreign direct investment survival and find that greenfield entries have survival advantages compared to acquisitions, but the significance of this effect disappears once they account for self-selection of entry mode in the empirical estimates.
Abstract: Firms choose strategies based on their attributes and industry conditions; therefore, strategy choice is endogenous and self-selected. Empirical models that do not account for this and regress performance measures on strategy choice variables are potentially misspecified and their conclusions incorrect. I highlight how self-selection on hard-to-measure or unobservable characteristics can bias strategy performance estimates and recommend an econometric technique that has been developed to account for this effect. Although this concern applies to a wide range of strategy questions, to demonstrate its effect I empirically examine if entry mode choice (acquisition versus greenfield) influences foreign direct investment survival. In specifications that do not account for self-selection, I find that greenfield entries have survival advantages compared to acquisitions. This confirms previous findings. However, the significance of this effect disappears once I account for self-selection of entry mode in the empirical estimates. The results confirm that estimates from models that do not account for self-selection of strategy choice can lead to incorrect or misleading conclusions.
TL;DR: Bank runs can be first-best efficient: they allow efficient risk sharing between early and late withdrawing depositors and they allow banks to hold efficient portfolios as mentioned in this paper. But, if costly runs or markets for risky assets are introduced, central bank intervention of the right kind can lead to a Pareto improvement in welfare.
Abstract: Empirical evidence suggests that banking panics are related to the business cycle and are not simply the result of "sunspots." Panics occur when depositors perceive that the returns on bank assets are going to be unusually low. We develop a simple model of this. In this setting, bank runs can be first-best efficient: they allow efficient risk sharing between early and late withdrawing depositors and they allow banks to hold efficient portfolios. However, if costly runs or markets for risky assets are introduced, central bank intervention of the right kind can lead to a Pareto improvement in welfare. FROM THE EARLIEST TIMES, banks have been plagued by the problem of bank runs in which many or all of the bank's depositors attempt to withdraw their funds simultaneously. Because banks issue liquid liabilities in the form of deposit contracts, but invest in illiquid assets in the form of loans, they are vulnerable to runs that can lead to closure and liquidation. A financial crisis or banking panic occurs when depositors at many or all of the banks in a region or a country attempt to withdraw their funds simultaneously. Prior to the twentieth century, banking panics occurred frequently in Europe and the United States. Panics were generally regarded as a bad thing and the development of central banks to eliminate panics and ensure financial stability has been an important feature of the history of financial systems. It has been a long and involved process. The first cerntral bank, the Bank of Sweden, was established more than 300 years ago. The Bank of England played an especially important role in the development of effective stabilization policies in the eighteenth and nineteenth centuries. By the end of the nineteenth century, banking panics had been eliminated in Europe. The last true panic in England was the Overend, Gurney & Company Crisis of 1866.
TL;DR: These data suggest that many B-CLL cells have been previously stimulated, placing them in the "experienced" or "memory" CD5(+) B cell subset.
Abstract: To better understand the stage(s) of differentiation reached by B-type chronic lymphocytic leukemia (B-CLL) cells and to gain insight into the potential role of antigenic stimulation in the development and diversification of these cells, we analyzed the rearranged VH genes expressed by 83 B-CLL cells (64 IgM+ and 19 non-IgM+). Our results confirm and extend the observations of a bias in the use of certain VH, D, and JH genes among B-CLL cells. In addition, they indicate that the VH genes of approximately 50% of the IgM+ B-CLL cells and approximately 75% of the non-IgM+ B-CLL cells can exhibit somatic mutations. The presence of mutation varies according to the VH family expressed by the B-CLL cell (VH3 expressers displaying more mutation than VH1 and VH4 expressers). In addition, the extent of mutation can be sizeable with approximately 32% of the IgM+ cases and approximately 68% of the non-IgM+ cases differing by > 5% from the most similar germline gene. Approximately 20% of the mutated VH genes display replacement mutations in a pattern consistent with antigen selection. However, CDR3 characteristics (D and JH gene use and association and HCDR3 length, composition, and charge) suggest that selection for distinct B cell receptors (BCR) occurs in many more B-CLL cells. Based on these data, we suggest three prototypic BCR, representing the VH genes most frequently encountered in our study. These data suggest that many B-CLL cells have been previously stimulated, placing them in the "experienced" or "memory" CD5(+) B cell subset.
TL;DR: A 5-residue peptide is demonstrated that inhibits amyloid βprotein fibrillogenesis, disassembles preformed fibrils in vitro and prevents neuronal death induced by fibrILS in cell culture and may provide the basis for a new therapeutic approach to prevent amyloidsosis in Alzheimer's disease.
Abstract: Inhibition of cerebral amyloid beta-protein deposition seems to be an important target for Alzheimer's disease therapy. Amyloidogenesis could be inhibited by short synthetic peptides designed as beta-sheet breakers. Here we demonstrate a 5-residue peptide that inhibits amyloid beta-protein fibrillogenesis, disassembles preformed fibrils in vitro and prevents neuronal death induced by fibrils in cell culture. In addition, the beta-sheet breaker peptide significantly reduces amyloid beta-protein deposition in vivo and completely blocks the formation of amyloid fibrils in a rat brain model of amyloidosis. These findings may provide the basis for a new therapeutic approach to prevent amyloidosis in Alzheimer's disease.
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TL;DR: In this paper, a forward-looking monetary policy reaction function for the postwar US economy, pre- and post-October 1979, is estimated and compared using a simple macroeconomic model, showing that the pre-Volcker rule is consistent with the possibility of persistent, self-fulfilling fluctuations in inflation and output.
Abstract: We estimate a forward-looking monetary policy reaction function for the postwar US economy, pre- and post-October 1979. Our results point to substantial differences in the estimated rule across periods. In particular, interest rate policy in the Volcker-Greenspan period appears to have been much more sensitive to changes in expected inflation than in the pre-Volcker period. We then compare some of the implications of the estimated rules for equilibrium properties of inflation and output, using a simple macroeconomic model. The pre-Volcker rule is shown to be consistent with the possibility of persistent, self-fulfilling fluctuations in inflation and output. In contrast, the Volcker-Greenspan rule is stabilizing.
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TL;DR: The POUM hypothesis as mentioned in this paper states that relatively poor people oppose high rates of redistribution because of the anticipation that they or their children may move up the income ladder. But is it compatible with everyone -- especially the poor -- holding rational expectations that not everyone can simultaneously expect to end up richer than average?
Abstract: Even relatively poor people oppose high rates of redistribution because of the anticipation that they or their children may move up the income ladder. This hypothesis commonly advanced as an explanation of why most democracies do not engage in large-scale expropriation and highly progressive redistribution. But is it compatible with everyone -- especially the poor -- holding rational expectations that not everyone can simultaneously expect to end up richer than average? This paper establishes the formal basis for the POUM hypothesis. There is a range of incomes below the mean where agents oppose lasting redistributions if (and, in a sense, only if) tomorrow's expected income is increasing and concave in today's income. The laissez-faire coalition is larger, the more concave the transition function and the longer the policy horizon. We illustrate the general analysis with an example (calibrated to the U.S.) where, in every period, 3/4 of families are poorer than average, yet a 2/3 majority has expected future incomes above the mean, and therefore desires low tax rates for all future generations. We also analyze empirical mobility matrices from the PSID and find that the POUM effect is indeed a significant feature of the data.
TL;DR: Data support the feasibility of extrasynaptic or volume transmission in the extracellular space by measuring the volume fraction and tortuosity, a measure of hindrance of cellular obstructions.
TL;DR: A new classification system based on co-receptor use is proposed, providing a more accurate description of viral phenotype than the present imprecise and often misleading classification schemes.
Abstract: The phenotype of HIV-1 isolates is defined by the cells in which they replicate in vitro, but these phenotypes can change in vivo with profound implications for viral transmission, pathogenesis and disease progression. Here we propose a new classification system based on co-receptor use, providing a more accurate description of viral phenotype than the present imprecise and often misleading classification schemes.
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TL;DR: In this article, the authors considered the longest increasing subsequence of a random permutation of numbers and proved that the distribution function for the largest eigenvalue of a GUE matrix converges to the Tracy-Widom distribution.
Abstract: The authors consider the length, $l_N$, of the length of the longest increasing subsequence of a random permutation of $N$ numbers. The main result in this paper is a proof that the distribution function for $l_N$, suitably centered and scaled, converges to the Tracy-Widom distribution [TW1] of the largest eigenvalue of a random GUE matrix. The authors also prove convergence of moments. The proof is based on the steepest decent method for Riemann-Hilbert problems, introduced by Deift and Zhou in 1993 [DZ1] in the context of integrable systems. The applicability of the Riemann-Hilbert technique depends, in turn, on the determinantal formula of Gessel [Ge] for the Poissonization of the distribution function of $l_N$.
TL;DR: Angiogenesis in vivo can be modulated by a novel mechanism that involves the autocrine action of vascular endothelial cell-derived FGF-2 and VEGF and is demonstrated to be an important autocrine mediator of F GF-2-induced angiogenesis.
Abstract: FGF-2 and VEGF are potent angiogenesis inducers in vivo and in vitro. Here we show that FGF-2 induces VEGF expression in vascular endothelial cells through autocrine and paracrine mechanisms. Addition of recombinant FGF-2 to cultured endothelial cells or upregulation of endogenous FGF-2 results in increased VEGF expression. Neutralizing monoclonal antibody to VEGF inhibits FGF-2-induced endothelial cell proliferation. Endogenous 18-kD FGF-2 production upregulates VEGF expression through extracellular interaction with cell membrane receptors; high-Mr FGF-2 (22-24-kD) acts via intracellular mechanism(s). During angiogenesis induced by FGF-2 in the mouse cornea, the endothelial cells of forming capillaries express VEGF mRNA and protein. Systemic administration of neutralizing VEGF antibody dramatically reduces FGF-2-induced angiogenesis. Because occasional fibroblasts or other cell types present in the corneal stroma show no significant expression of VEGF mRNA, these findings demonstrate that endothelial cell-derived VEGF is an important autocrine mediator of FGF-2-induced angiogenesis. Thus, angiogenesis in vivo can be modulated by a novel mechanism that involves the autocrine action of vascular endothelial cell-derived FGF-2 and VEGF.
University of Oregon1, New York University2, University of California, San Francisco3, Howard Hughes Medical Institute4, National University of Singapore5, École Normale Supérieure6, University of Bath7, Harvard University8, Brigham and Women's Hospital9, Uppsala University10, Washington University in St. Louis11
TL;DR: This zebrafish gene map will facilitate molecular identification of mutated zebra-fish genes, which can suggest functions for human genes known only by sequence, and is likely that two polyploidization events occurred prior to the divergence of fish and mammal lineages.
Abstract: In chordate phylogeny, changes in the nervous system, jaws, and appendages transformed meek filter feeders into fearsome predators. Gene duplication is thought to promote such innovation. Vertebrate ancestors probably had single copies of genes now found in multiple copies in vertebrates and gene maps suggest that this occurred by polyploidization. It has been suggested that one genome duplication event occurred before, and one after the divergence of ray-finned and lobe-finned fishes. Holland et al., however, have argued that because various vertebrates have several HOX clusters, two rounds of duplication occurred before the origin of jawed fishes. Such gene-number data, however, do not distinguish between tandem duplications and polyploidization events, nor whether independent duplications occurred in different lineages. To investigate these matters, we mapped 144 zebrafish genes and compared the resulting map with mammalian maps. Comparison revealed large conserved chromosome segments. Because duplicated chromosome segments in zebrafish often correspond with specific chromosome segments in mammals, it is likely that two polyploidization events occurred prior to the divergence of fish and mammal lineages. This zebrafish gene map will facilitate molecular identification of mutated zebrafish genes, which can suggest functions for human genes known only by sequence.
TL;DR: The cloning of a murine homolog of yeast IRE1, an essential upstream component of the ER stress‐ response in yeast, is reported on, indicating that a single upstream component, Ire1, plays a role in multiple facets of theER stress‐response in mammalian cells.
Abstract: Cells modify their gene expression pattern in response to stress signals emanating from the endoplasmic reticulum (ER). The well-characterized aspect of this response consists of the activation of genes that encode protein chaperones and other ER resident proteins, and is conserved between mammals and yeast. In mammalian cells, however, ER stress also activates other pathways, including the expression of the transcription factor CHOP/GADD153 and its downstream target genes. ER stress is also linked to the development of programmed cell death, a phenomenon in which CHOP plays an important role. Here we report on the cloning of a murine homolog of yeast IRE1, an essential upstream component of the ER stress-response in yeast. The mammalian Ire1 is located in the ER membrane and its over-expression in mammalian cells activates both the endogenous ER chaperone GRP78/BiP and CHOP-encoding genes. Over-expression of a dominant-negative form of Ire1 blocks the induction of GRP78/BiP and CHOP in response to the ER stress induced by tunicamycin treatment. Over-expression of murine Ire1 also leads to the development of programmed cell death in transfected cells. These results indicate that a single upstream component, Ire1, plays a role in multiple facets of the ER stress-response in mammalian cells.
TL;DR: It is shown that attention can affect performance by signal enhancement for a texture segregation task in which performance is actually diminished when spatial resolution is too high, and that the counterintuitive impairment of performance at the central retinal locations appears to have one possible explanation: attention enhances spatial resolution.
Abstract: Covert attention, the selective processing of visual information at a given location in the absence of eye movements, improves performance in several tasks, such as visual search and detection of luminance and vernier targets1,2,3,4,5,6 An important unsettled issue is whether this improvement is due to a reduction in noise (internal or external)6,7,8,9, a change in decisional criteria10,11, or signal enhancement3,5,12 Here we show that attention can affect performance by signal enhancement For a texture segregation task in which performance is actually diminished when spatial resolution is too high, we observed that attention improved performance at peripheral locations where spatial resolution was too low, but impaired performance at central locations where spatial resolution was too high4,5,6,7,8,9,10,11,12 The counterintuitive impairment of performance that we found at the central retinal locations appears to have only one possible explanation: attention enhances spatial resolution
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TL;DR: This paper examined the performance of the off-shore hedge fund industry over the period 1989 through 1995 using a database that includes both defunct and currently operating hedge fund managers and found that the industry is characterized by high attrition rates of funds, low covariance with the U.S. stock market, evidence consistent with positive risk-adjusted returns over the time, and little evidence of differential manager skill.
Abstract: We examine the performance of the off-shore hedge fund industry over the period 1989 through 1995 using a database that includes both defunct and currently operating funds. The industry is characterized by high attrition rates of funds, low covariance with the U.S. stock market, evidence consistent with positive risk-adjusted returns over the time, and little evidence of differential manager skill.
TL;DR: In this article, the authors employ a carbon-cycle/energy model to estimate the carbon-emission-free power needed for various atmospheric CO2 stabilization scenarios, and find that CO2 stabilization with continued economic growth will require innovative, cost-effective and carbon emission-free technologies that can provide additional tens of terawatts of primary power in the coming decades.
Abstract: The United Nations Framework Convention on Climate Change1 calls for “stabilization of greenhouse-gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system ” A standard baseline scenario2,3 that assumes no policy intervention to limit greenhouse-gas emissions has 10 TW (10 × 1012 watts) of carbon-emission-free power being produced by the year 2050, equivalent to the power provided by all today's energy sources combined Here we employ a carbon-cycle/energy model to estimate the carbon-emission-free power needed for various atmospheric CO2 stabilization scenarios We find that CO2 stabilization with continued economic growth will require innovative, cost-effective and carbon-emission-free technologies that can provide additional tens of terawatts of primary power in the coming decades, and certainly by the middle of the twenty-first century, even with sustained improvement in the economic productivity of primary energy At progressively lower atmospheric CO2-stabilization targets in the 750–350 ppmv range, implementing stabilization will become even more challenging because of the increasing demand for carbon-emission-free power The magnitude of the implied infrastructure transition suggests the need for massive investments in innovative energy research