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Re-examine
Selected AbstractsSupraspinal input is dispensable to generate glycine-mediated locomotive behaviors in the zebrafish embryoDEVELOPMENTAL NEUROBIOLOGY, Issue 5 2006Gerald B. Downes Abstract The anatomy of the developing zebrafish spinal cord is relatively simple but, despite this simplicity, it generates a sequence of three patterns of locomotive behaviors. The first behavior exhibited is spontaneous movement, then touch-evoked coiling, and finally swimming. Previous studies in zebrafish have suggested that spontaneous movements occur independent of supraspinal input and do not require chemical neurotransmission, while touch-evoked coiling and swimming depend on glycinergic neurotransmission as well as supraspinal input. In contrast, studies in other vertebrate preparations have shown that spontaneous movement requires glycine and other neurotransmitters and that later behaviors do not require supraspinal input. Here, we use lesion analysis combined with high-speed kinematic analysis to re-examine the role of glycine and supraspinal input in each of the three behaviors. We find that, similar to other vertebrate preparations, supraspinal input is not essential for spontaneous movement, touch-evoked coiling, or swimming behavior. Moreover, we find that blockade of glycinergic neurotransmission decreases the rate of spontaneous movement and impairs touch-evoked coiling and swimming, suggesting that glycinergic neurotransmission plays critical yet distinct roles for individual patterns of locomotive behaviors. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006 [source] Changes within maturing neurons limit axonal regeneration in the developing spinal cordDEVELOPMENTAL NEUROBIOLOGY, Issue 4 2006Murray Blackmore Abstract Embryonic birds and mammals display a remarkable ability to regenerate axons after spinal injury, but then lose this ability during a discrete developmental transition. To explain this transition, previous research has emphasized the emergence of myelin and other inhibitory factors in the environment of the spinal cord. However, research in other CNS tracts suggests an important role for neuron-intrinsic limitations to axon regeneration. Here we re-examine this issue quantitatively in the hindbrain-spinal projection of the embryonic chick. Using heterochronic cocultures we show that maturation of the spinal cord environment causes a 55% reduction in axon regeneration, while maturation of hindbrain neurons causes a 90% reduction. We further show that young neurons transplanted in vivo into older spinal cord can regenerate axons into myelinated white matter, while older axons regenerate poorly and have reduced growth cone motility on a variety of growth-permissive ligands in vitro, including laminin, L1, and N-cadherin. Finally, we use video analysis of living growth cones to directly document an age-dependent decline in the motility of brainstem axons. These data show that developmental changes in both the spinal cord environment and in brainstem neurons can reduce regeneration, but that the effect of the environment is only partial, while changes in neurons by themselves cause a nearly complete reduction in regeneration. We conclude that maturational events within neurons are a primary cause for the failure of axon regeneration in the spinal cord. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006 [source] Matching motivation enhancement treatment to client motivation: re-examining the Project MATCH motivation matching hypothesisADDICTION, Issue 8 2010Katie Witkiewitz ABSTRACT Aims The current study was designed to re-examine the motivation matching hypothesis from Project MATCH using growth mixture modeling, an analytical technique that models variation in individual drinking patterns. Design, setting and participants Secondary data analyses of data from Project MATCH (n = 1726), a large multi-site alcoholism treatment-matching study. Measurements Percentage of drinking days was the primary outcome measure, assessed from 1 month to 12 months following treatment. Treatment assignment, alcohol dependence symptoms and baseline percentage of drinking days were included as covariates. Findings The results provided support for the motivation matching hypothesis in the out-patient sample and among females in the aftercare sample: the majority of individuals with lower baseline motivation had better outcomes if assigned to motivation enhancement treatment (MET) compared to those assigned to cognitive behavioral treatment (CBT). In the aftercare sample there was a moderating effect of gender and alcohol dependence severity, whereby males with lower baseline motivation and greater alcohol dependence drank more frequently if assigned to MET compared to those assigned to CBT. Conclusions Results from the current study lend partial support to the motivation-matching hypothesis and also demonstrated the importance of moderating influences on treatment matching effectiveness. Based upon these findings, individuals with low baseline motivation in out-patient settings and males with low levels of alcohol dependence or females in aftercare settings may benefit more from motivational enhancement techniques than from cognitive,behavioral techniques. [source] TERRORISM AND THE RETURNS TO OILECONOMICS & POLITICS, Issue 3 2009BROCK BLOMBERG The effect of terrorism on global oil prices has been largely explained through demand-side effects. We estimate an empirical model to re-examine the effect of terrorism on the price of global oil stocks across oil market regimes that reflect different supply constraints. We believe that terrorism will have larger impacts when global capacity is tight (i.e. when global demand is close to global supply). This means that any shock to capacity (say by conflict) should have the largest impact on profits before the first OPEC shock in the early 1970s. Since then, conflict shocks would not allow firms to exploit production in the same way, thus reducing the available profits that could be garnered by such production manipulation. If capacity constraints are binding when a conflict occurs, then we predict that a positive stock price reaction can be expected for oil firms from such a shock. We exploit a new panel dataset to investigate the relationship between oil profitability and conflict, using conflict data from the top 20 oil producing and exporting countries in the world. We show that in the later part of our sample, 1974,2005, as cartel behavior of OPEC member countries has diminished and as conflict has become more regular and thus the information surrounding it noisier, oil stock prices do not increase in response to conflict. However, in earlier capacity constrained eras, we find that oil stocks can in fact increase in response to conflict. In some cases, the impact of conflict may cause the return of oil stocks to increase by as much as 10 percentage points. [source] Multiple bacterial symbionts in two species of co-occurring gutless oligochaete worms from Mediterranean sea grass sedimentsENVIRONMENTAL MICROBIOLOGY, Issue 12 2008Caroline Ruehland Summary Gutless oligochaete worms are found worldwide in the pore waters of marine sediments and live in symbiosis with chemoautotrophic sulfur-oxidizing bacteria. In the Mediterranean, two species of gutless oligochaete worms, Olavius algarvensis and O. ilvae, co-occur in sediments around sea grass beds. These sediments have extremely low sulfide concentrations (< 1 ,M), raising the question if O. ilvae, as shown previously for O. algarvensis, also harbours sulfate-reducing symbionts that provide its sulfur-oxidizing symbionts with reduced sulfur compounds. In this study, we used fluorescence in situ hybridization (FISH) and comparative sequence analysis of genes for 16S rRNA, sulfur metabolism (aprA and dsrAB), and autotrophic carbon fixation (cbbL) to examine the microbial community of O. ilvae and re-examine the O. algarvensis symbiosis. In addition to the four previously described symbionts of O. algarvensis, in this study a fifth symbiont belonging to the Spirochaetes was found in these hosts. The symbiotic community of O. ilvae was similar to that of O. algarvensis and also included two gammaproteobacterial sulfur oxidizers and two deltaproteobacterial sulfate reducers, but not a spirochete. The phylogenetic and metabolic similarity of the symbiotic communities in these two co-occurring host species that are not closely related to each other indicates that syntrophic sulfur cycling provides a strong selective advantage to these worms in their sulfide-poor environment. [source] From protozoa to mammalian cells: a new paradigm in the life cycle of intracellular bacterial pathogensENVIRONMENTAL MICROBIOLOGY, Issue 3 2000Minireview It is becoming apparent that several intracellular bacterial pathogens of humans can also survive within protozoa. This interaction with protozoa may protect these pathogens from harsh conditions in the extracellular environment and enhance their infectivity in mammals. This relationship has been clearly established in the case of the interaction between Legionella pneumophila and its protozoan hosts. In addition, the adaptation of bacterial pathogens to the intracellular life within the primitive eukaryotic protozoa may have provided them with the means to infect the more evolved mammalian cells. This is evident from the existence of several similarities, at both the phenotypic and the molecular levels, between the infection of mammalian and protozoan cells by L. pneumophila. Thus, protozoa appear to play a central role in the transition of bacteria from the environment to mammals. In essence, protozoa may be viewed as a ,biological gym', within which intracellular bacterial pathogens train for their encounters with the more evolved mammalian cells. Thus, intracellular bacterial pathogens have benefited from the structural and biochemical conservation of cellular processes in eukaryotes. The interaction of intracellular bacterial pathogens and protozoa highlights this conservation and may constitute a simplified model for the study of these pathogens and the evolution of cellular processes in eukaryotes. Furthermore, in addition to being environmental reservoirs for known intracellular pathogens of humans and animals, protozoa may be sources of emerging pathogenic bacteria. It is thus critical to re-examine the relationship between bacteria and protozoa to further our understanding of current human bacterial pathogenesis and, possibly, to predict the appearance of emerging pathogens. [source] Mechanistic links between climate and fisheries along the east coast of the United States: explaining population outbursts of Atlantic croaker (Micropogonias undulatus)FISHERIES OCEANOGRAPHY, Issue 1 2007JONATHAN A. HARE Abstract Climate has been linked to variation in marine fish abundance and distribution, but often the mechanistic processes are unknown. Atlantic croaker (Micropogonias undulatus) is a common species in estuarine and coastal areas of the mid-Atlantic and southeast coasts of the U.S. Previous studies have identified a correlation between Atlantic croaker abundance and winter temperatures in Chesapeake Bay, and have determined thermal tolerances of juveniles. Here we re-examine the hypothesis that winter temperature variability controls Atlantic croaker population dynamics. Abundance indices were analyzed at four life history stages from three regions along the east coast of the U.S. Correlations suggest that year-class strength is decoupled from larval supply and is determined by temperature-linked, overwinter survival of juveniles. Using a relation between air and water temperatures, estuarine water temperature was estimated from 1930 to 2002. Periods of high adult catch corresponded with warm winter water temperatures. Prior studies indicate that winter temperature along the east coast is related to the North Atlantic Oscillation (NAO); variability in catch is also correlated with the NAO, thereby demonstrating a link between Atlantic croaker dynamics, thermal limited overwinter survival, and the larger climate system of the North Atlantic. We hypothesize that the environment drives the large-scale variability in Atlantic croaker abundance and distribution, but fishing and habitat loss decrease the resiliency of the population to periods of poor environmental conditions and subsequent weak year classes. [source] Can the Earth's dynamo run on heat alone?GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2003David Gubbins SUMMARY The power required to drive the geodynamo places significant constraints on the heat passing across the core,mantle boundary and the Earth's thermal history. Calculations to date have been limited by inaccuracies in the properties of liquid iron mixtures at core pressures and temperatures. Here we re-examine the problem of core energetics in the light of new first-principles calculations for the properties of liquid iron. There is disagreement on the fate of gravitational energy released by contraction on cooling. We show that only a small fraction of this energy, that associated with heating resulting from changes in pressure, is available to drive convection and the dynamo. This leaves two very simple equations in the cooling rate and radioactive heating, one yielding the heat flux out of the core and the other the entropy gain of electrical and thermal dissipation, the two main dissipative processes. This paper is restricted to thermal convection in a pure iron core; compositional convection in a liquid iron mixture is considered in a companion paper. We show that heat sources alone are unlikely to be adequate to power the geodynamo because they require a rapid secular cooling rate, which implies a very young inner core, or a combination of cooling and substantial radioactive heating, which requires a very large heat flux across the core,mantle boundary. A simple calculation with no inner core shows even higher heat fluxes are required in the absence of latent heat before the inner core formed. [source] Impact of Human Genome Project on treatment of frail and edentulous patients,GERODONTOLOGY, Issue 1 2004Ichiro Nishimura Objective:, Because of ongoing increases in life expectancy and deferment of edentulousness to older age, dentists are facing a different challenge to satisfy elderly denture wearers with a higher prevalence of chronic diseases. This discussion introduces the Human Genome databases as novel and powerful resources to re-examine the core problems experienced by frail and edentulous patients. Background:, Recent studies demonstrated that mandibular implant overdentures do not necessarily increase masticatory function, perception and satisfaction in denture wearers with adequate edentulous residual ridges. It has been demonstrated that the rate of edentulous residual ridge resorption significantly varies among individuals. The prognosis and cost-effectiveness of denture treatment, with or without implants, may largely depend on how the edentulous ridge is maintained. However, reliable clinical methods permitting dentists to predict the long-term health of the edentulous residual ridge are lacking. Materials and methods:, With the completion of the Human Genome Project, the genomic sequence database from this multinational consortium will provide a unique resource to determine the genetic basis of similarity and diversity of humans. Results:, One base pair in every 100 to 300 base pairs of the genome sequence varies among humans, suggesting that genetic diagnosis using the single nucleotide polymorphisms (SNPs) may provide a novel opportunity to differentiate our edentulous patients. Conclusions:, Future dental service for the elderly will require a personalized care paradigm, using highly sensitive diagnostic technology such as SNP genomic analysis, for recommending the treatment with greatest potential benefit. [source] Revisiting the corroboration effects of earnings and dividend announcementsACCOUNTING & FINANCE, Issue 2 2006Louis T. W. Cheng D82; G14; M41 Abstract Using a unique market setting in Hong Kong, where (i) all firms release earnings and dividend information in the same announcement; (ii) corporate transparency is low; (iii) dividend income is non-taxable and (iv) corporate ownership is highly concentrated, we re-examine the corroboration effects of earnings and dividends. We use the control firm approach to avoid the return estimation bias resulting from observation clustering. We also add in variables and use econometric procedure to control for the potential impacts of earnings management, special dividends and heteroskedasticity. Our findings show that there exists a corroboration effect between the jointly announced signals. [source] Takeover activity in Australia: endogenous and exogenous influencesACCOUNTING & FINANCE, Issue 3 2005Frank Finn G34 Abstract The present paper analyses the population of takeover bids for listed Australian companies using quarterly data over a 25-year period to re-examine the predictability of takeover activity and to determine if there is a flow on impact on macroeconomic variables. We examine whether takeover activity: (i) is endogenous; that is, determined by own activity; (ii) is jointly determined by macroeconomic and capital market variables; and (iii) has an exogenous spillover impact across the economy. We find that stock prices and takeover activity share a long-term common trend, the relative success of takeover bids is independent of sharemarket activity, and conclude that aggregate takeover activity is driven by fundamental economic factors rather than by speculative activity. [source] Cell culture,produced hepatitis C virus does not infect peripheral blood mononuclear cells,HEPATOLOGY, Issue 6 2008Svetlana Marukian Hepatitis C virus (HCV) replicates primarily in the liver, but HCV RNA has been observed in association with other tissues and cells including B and T lymphocytes, monocytes, and dendritic cells. We have taken advantage of a recently described, robust system that fully recapitulates HCV entry, replication and virus production in vitro to re-examine the issue of HCV infection of blood cell subsets. The HCV replicase inhibitor 2,C-methyl adenosine was used to distinguish HCV RNA replication from RNA persistence. Whereas cell culture,grown HCV replicated in Huh-7.5 hepatoma cells, no HCV replication was detected in B or T lymphocytes, monocytes, macrophages, or dendritic cells from healthy donors. No blood cell subset tested expressed significant levels of Claudin-1, a tight junction protein needed for HCV infection of Huh-7.5 cells. A B cell line expressing high levels of Claudin-1, CD81, and scavenger receptor BI remained resistant to HCV pseudoparticle infection. We bypassed the block in HCV entry by transfecting HCV RNA into blood cell subsets. Transfected RNA was not detectably translated and induced high levels of interferon-,. Supernatants from HCV RNA,transfected macrophages inhibited HCV replication in Huh-7.5 cells. Conclusion: We conclude that multiple blocks prevent blood cells from supporting HCV infection. (HEPATOLOGY 2008;48:1843-1850.) [source] The difficulties of empire: present, past and future*HISTORICAL RESEARCH, Issue 205 2006Linda Colley Although empire is now an intensely fashionable subject of enquiry, much contemporary comment is relatively uninformed and lacks historical context. This is particularly significant in the light of the United States' purported new imperialism. This article considers the problems faced by those attempting to define empire, whether in the past or the present. It traces the origins of American imperialism to the beginnings of the republic and before, and compares it with the British experience, arguing in all cases for the importance of a wide-ranging and comparative approach to empire. Finally, it urges historians and political commentators to move beyond a concentration on dead European empires, to look as well at other and at present-day versions of the phenomenon, and to re-examine the overlap between nation and empire. [source] A 20-year follow-up study of endodontic variables and apical status in a Swedish populationINTERNATIONAL ENDODONTIC JOURNAL, Issue 12 2007M. Eckerbom Abstract Aim, To re-examine a population after 20 years and evaluate changes in prevalence of endodontic treatment and apical periodontitis, as well as the technical quality of root fillings. Methodology, One hundred and fifteen out of an original 200 patients living in the northern part of Sweden were re-examined with a full mouth radiographic survey after 20 years. Frequencies of root canal treated teeth, apical periodontitis and quality parameters of root fillings were registered. Results, The frequency of root canal treated teeth increased significantly (P < 0.05) from 13.9% at the first investigation to 17.7% after 20 years. There was also a statistically significant increase (P < 0.05) in teeth with apical periodontitis from 3.3% to 6.8%. Apical periodontitis both in connection with root canal treated teeth and teeth without endodontic treatment, had increased during the follow-up period. Even though the quality of the root fillings had improved, there was no corresponding improvement of the apical status in teeth with root fillings. Conclusions, There is still a great need for endodontic treatment in the Swedish population, and no improvement in apical health was found during this 20-year follow up. [source] Fast iterative solution of large undrained soil-structure interaction problemsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 3 2003Kok-Kwang Phoon Abstract In view of rapid developments in iterative solvers, it is timely to re-examine the merits of using mixed formulation for incompressible problems. This paper presents extensive numerical studies to compare the accuracy of undrained solutions resulting from the standard displacement formulation with a penalty term and the two-field mixed formulation. The standard displacement and two-field mixed formulations are solved using both direct and iterative approaches to assess if it is cost-effective to achieve more accurate solutions. Numerical studies of a simple footing problem show that the mixed formulation is able to solve the incompressible problem ,exactly', does not create pressure and stress instabilities, and obviate the need for an ad hoc penalty number. In addition, for large-scale problems where it is not possible to perform direct solutions entirely within available random access memory, it turns out that the larger system of equations from mixed formulation also can be solved much more efficiently than the smaller system of equations arising from standard formulation by using the symmetric quasi-minimal residual (SQMR) method with the generalized Jacobi (GJ) preconditioner. Iterative solution by SQMR with GJ preconditioning also is more elegant, faster, and more accurate than the popular Uzawa method. Copyright © 2003 John Wiley & Sons, Ltd. [source] The Re-Assessment and Reconstruction of Excavated BoatsINTERNATIONAL JOURNAL OF NAUTICAL ARCHAEOLOGY, Issue 2 2007Seán McGrail In response to papers by John Coates and by Owain Roberts, the author re-evaluates mid- to late-20th-century reconstruction drawings and models of prehistoric sewn-plank boats Ferriby 1 and Brigg 2. He concludes that an impartial and informed group should re-examine all surviving evidence for these boats and then build a small-scale ,as-found' model of each one. After being subjected to criticism, these models could become the basis for generally-agreed reconstruction models of the original form and structure of these two boats. A similar process would be the best way ahead for the Dover sewn-plank boat. © 2007 The Author [source] International Regimes: The Case of Western Corporate GovernanceINTERNATIONAL STUDIES REVIEW, Issue 2 2006DAVID A. DETOMASI Accounting and financial scandals of unprecedented scale have recently occurred in the United States, Europe, and elsewhere. Much of the cause for these scandals has been attributed to the poor corporate governance standards practiced by the offending companies, leading researchers to re-examine how corporate governance affects economic development. One topic receiving significant research attention has been whether national corporate governance systems are likely to converge, what form that convergence may take, and what barriers currently inhibit convergence. This essay argues that the tools of regime theory hold significant potential for helping to structure empirical inquiry into the process of corporate governance convergence. It then draws upon the recent experience of Western corporate governance systems to illustrate how a consensus on norms, values, and principles in the issue area of corporate governance is emerging. The essay concludes by drawing out the implications of the developing corporate governance regime for emerging market economies and the general topic of global governance. It also poses questions for continued empirical research in the area of corporate governance and international relations. [source] A phylogeny of Vetigastropoda and other "archaeogastropods": re-organizing old gastropod cladesINVERTEBRATE BIOLOGY, Issue 3 2010Stephanie W. Aktipis Abstract. The phylogenetic relationships among the "archaeogastropod" clades Patellogastropoda, Vetigastropoda, Neritimorpha, and Neomphalina are uncertain; the phylogenetic placement of these clades varies across different analyses, and particularly among those using morphological characteristics and those relying on molecular data. This study explores the relationships among these groups using a combined analysis with seven molecular loci (18S rRNA, 28S rRNA, histone H3, 16S rRNA, cytochrome c oxidase subunit I [COI], myosin heavy-chain type II, and elongation factor-1, [EF-1,]) sequenced for 31 ingroup taxa and eight outgroup taxa. The deep evolutionary splits among these groups have made resolution of stable relationships difficult, and so EF-1, and myosin are used in an attempt to re-examine these ancient radiation events. Three phylogenetic analyses were performed utilizing all seven genes: a single-step direct optimization analysis using parsimony, and two-step approaches using parsimony and maximum likelihood. A single-step direct optimization parsimony analysis was also performed using only five molecular loci (18S rRNA, 28S rRNA, histone H3, 16S rRNA, and COI) in order to determine the utility of EF-1, and myosin in resolving deep relationships. In the likelihood and POY optimal phylogenetic analyses, Gastropoda, Caenogastropoda, Neritimorpha, Neomphalina, and Patellogastropoda were monophyletic. Additionally, Neomphalina and Pleurotomariidae fell outside the remaining vetigastropods, indicating the need for further investigation into the relationship of these groups with other gastropods. [source] Reciprocal phenotypic plasticity can lead to stable predator,prey interactionJOURNAL OF ANIMAL ECOLOGY, Issue 6 2009Akihiko Mougi Summary 1.,Inducible defences of prey and inducible offences of predators are prevalent strategies in trophic interactions with temporal variation. Due to the inducible properties of the functional traits themselves, which drive the dynamic predator,prey relationship on an ecological time-scale, predator and prey may reciprocally interact through their inducible traits (i.e. reciprocal phenotypic plasticity). 2.,Although overwhelming evidence of the stabilizing effect of inducible traits in either species on community dynamics forcefully suggests a critical ecological role for reciprocal plasticity in predator,prey population dynamics, our understanding of its ecological consequences is very limited. 3.,Within a mathematical modelling framework, we investigated how reciprocal plasticity influences the stability of predator,prey systems. 4.,By assuming two types of phenotypic shift, a density-dependent shift and an adaptive phenotypic shift, we examined two interaction scenarios with reciprocal plasticity: (i) an arms-race-like relationship, in which the defensive prey phenotype is more protective against both predator phenotypes (i.e. normal and offensive) than the normal prey phenotype, and the offensive predator is a more efficient consumer, preying upon both prey phenotypes (i.e. normal and defensive), than the normal predator and (ii) a matching response-like relationship, in which the offensive predator consumes more defensive prey and fewer normal prey than the normal predator. 5.,Results of both phenotypic shift models consistently suggest that given the used set of parameter values, the arms-race-like reciprocal plasticity scenario has the largest stability area, when compared with the other scenarios. In particular, higher stability is achieved when the prey exhibits a high-performance inducible defence. Furthermore, this stabilization is so strong that the destabilizing effects of enrichment may be eliminated, even though the higher flexibility of plasticity does not always stabilize a system. 6.,Recent empirical studies support our model predictions. Clear-cut examples of reciprocal phenotypic plasticity show an arms-race-like relationship in which prey species exhibit induced high-performance defences. We may need to re-examine reported predator,prey interactions in which predator or prey exhibits inducible plasticity to determine whether arms-race-like reciprocal plasticity is a general ecological phenomenon. [source] Family decision at the turn of the century: has the changing structure of households impacted the family decision-making process?JOURNAL OF CONSUMER BEHAVIOUR, Issue 2 2002Michael A. Belch Professor of Marketing Abstract Evaluation of husbands' and wives' influence in family decision making is heavily reliant on studies conducted in the 1970s and 1980s. Since that time, profound changes have occurred in the American family. These changes may have affected the nature of decision making in the household. To examine the degree to which earlier findings are still generalisable today, hypotheses are developed and tested with a contemporary sample of 458 men and women. Results suggest that there have been significant changes in the roles assumed in the family decision-making process, with the wife gaining more influence in all decision areas. The results indicate that marketers must re-examine their marketing strategies for some products and/or services. Possible theoretical explanations are suggested to explain why these changes may have occurred. Copyright © 2002 Henry Stewart Publications. [source] VARIANCE-RATIO TESTS OF RANDOM WALK: AN OVERVIEWJOURNAL OF ECONOMIC SURVEYS, Issue 3 2009Amélie Charles Abstract This paper reviews the recent developments in the field of the variance-ratio (VR) tests of the random walk and martingale hypothesis. In particular, we present the conventional individual and multiple VR tests as well as their improved modifications based on power-transformed statistics, rank and sign tests, subsampling and bootstrap methods, among others. We also re-examine the weak-form efficiency for five emerging equity markets in Latin America. [source] Are 16-month-ahead forecasts useful?JOURNAL OF FORECASTING, Issue 3 2006A directional analysis of Japanese GDP forecasts Abstract Past literature casts doubt on the ability of long-term macroeconomic forecasts to predict the direction of change. We re-examine this issue using the Japanese GDP forecast data of 37 institutions, and find that their 16-month-ahead forecasts contain valuable information on whether the growth rate accelerates or not. Copyright © 2006 John Wiley _ Sons, Ltd. [source] Career success and weak paradigms: the role of activity, resiliency, and true scoresJOURNAL OF ORGANIZATIONAL BEHAVIOR, Issue 8 2007John R. Hollenbeck Questions have been raised about the significant influence that weak paradigm development has on the careers of individuals struggling to make a life in the field of organization science. Based on the fact that a weak paradigm leads to low levels of agreement about the quality of any manuscript, it has been suggested that the marketplace for ideas is beyond comprehension to even the most talented individuals, and that career outcomes are determined largely by chance events over which people have no control. We re-examine this argument and the influence of weak paradigms on the reliability of evaluations at the career level of analysis. Using Spearman,Brown Prophecy formula, we show that the reliability of evaluations at the career level is very high, even if one makes very pessimistic assumptions regarding inter-rater agreement at the manuscript/journal level. Although weak paradigms create high levels of uncertainty on any one single pass through the review system, our results suggest that within 5 years, researchers are likely to be reliability evaluated. This reliability converges on 1.0 under specific conditions that are easily controlled by authors (activity level and resiliency) and editors (forming independent judgments and the use of three reviewers rather than two). Copyright © 2007 John Wiley & Sons, Ltd. [source] Relationship between the structural distortion and the Mn electronic state in La1,xCaxMnO3: a Mn K -edge XANES studyJOURNAL OF SYNCHROTRON RADIATION, Issue 4 2009Jesús Chaboy A theoretical study of the X-ray absorption near-edge structure (XANES) spectra at the Mn K -edge in the La1,xCaxMnO3 series is reported. The relationship between the edge shift, the Ca,La substitution and the distortion of the MnO6 octahedra in these systems has been studied. It is shown that, by correctly considering these effects simultaneously, the experimental XANES data are consistent with the presence of two different Mn local environments in the intermediate La1,xCaxMnO3 compounds. By taking into account the energy shift associated with the modification of the MnO6 distortion as Ca substitutes for La, it is possible to reproduce the XANES spectra of the intermediate-doped compounds starting from the experimental spectra of the end-members LaMnO3 and CaMnO3. These results point out the need to re-examine the conclusions derived in the past from the simple analysis of the Mn K -edge XANES edge-shift in these materials. In particular, it is shown that the modification of the Mn K -edge absorption through the La1,xCaxMnO3 series is well reproduced by considering the simultaneous presence of both distorted and undistorted octahedra and, consequently, that the existence of charge-ordering phenomena cannot be ruled out from the XANES data. [source] The credit crunch , the right time for credit unions to strike?LEGAL STUDIES, Issue 1 2009Dr Nicholas Ryder The origins of the cooperative movement can be traced to the Rochdale Society of Equitable Pioneers in 1844, from which similar institutions emerged in Central Europe, the North American continent and the rest of the world. Modern credit unions evolved from these small cooperative societies and have developed into mainstream providers of financial services in many jurisdictions. However, credit unions in the UK have not made a similar impact. There are several factors that have limited their growth , an inadequate legislative framework, an ineffective credit union regulatory system, inappropriate development models, an over-reliance on state subsidies and a disunited movement. The aim of this paper is to re-examine these factors in light of the level of political support provided by the government since 1997. [source] Confucian Capitalism and the Paradox of Closure and Structural Holes in East Asian FirmsMANAGEMENT AND ORGANIZATION REVIEW, Issue 1 2010Sun-Ki Chai abstract A long-standing debate has taken place in the organizational sociology and social network literatures about the relative advantages of network closure versus structural holes in the generation of social capital. There is recent evidence that these advantages differ across cultures and between East Asia and the West in particular, but existing network models are unable to explain why or address cultural variation in general. This paper seeks to provide a solution by integrating a culture-embedded rational model of action into the social network model of structure, using this not only to re-examine the closure versus structural hole debate, but also to tie it to the literature on Confucian capitalism and the ,East Asian Model' of the firm. We argue that this integrated approach allows us to systematically analyse the relationship between culture and behaviour in networks and, more specifically, to explain why closure has been a more powerful source of productivity in East Asia than the West. [source] A restoration genetics guide for coral reef conservationMOLECULAR ECOLOGY, Issue 12 2008ILIANA B. BAUMS Abstract Worldwide degradation of coral reef communities has prompted a surge in restoration efforts. They proceed largely without considering genetic factors because traditionally, coral populations have been regarded as open over large areas with little potential for local adaptation. Since, biophysical and molecular studies indicated that most populations are closed over shorter time and smaller spatial scales. Thus, it is justified to re-examine the potential for site adaptation in corals. There is ample evidence for differentiated populations, inbreeding, asexual reproduction and the occurrence of ecotypes, factors that may facilitate local adaptation. Discovery of widespread local adaptation would influence coral restoration projects mainly with regard to the physical and evolutionary distance from the source wild and/or captive bred propagules may be moved without causing a loss of fitness in the restored population. Proposed causes for loss of fitness as a result of (plant) restoration efforts include founder effects, genetic swamping, inbreeding and/or outbreeding depression. Direct evidence for any of these processes is scarce in reef corals due to a lack of model species that allow for testing over multiple generations and the separation of the relative contributions of algal symbionts and their coral hosts to the overall performance of the coral colony. This gap in our knowledge may be closed by employing novel population genetic and genomics approaches. The use of molecular tools may aid managers in the selection of appropriate propagule sources, guide spatial arrangement of transplants, and help in assessing the success of coral restoration projects by tracking the performance of transplants, thereby generating important data for future coral reef conservation and restoration projects. [source] Local kinematics and the local standard of restMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2010Ralph Schönrich ABSTRACT We re-examine the stellar kinematics of the solar neighbourhood in terms of the velocity ,, of the Sun with respect to the local standard of rest. We show that the classical determination of its component V, in the direction of Galactic rotation via Strömberg's relation is undermined by the metallicity gradient in the disc, which introduces a correlation between the colour of a group of stars and the radial gradients of its properties. Comparing the local stellar kinematics to a chemodynamical model which accounts for these effects, we obtain (U, V, W),= (11.1+0.69,0.75, 12.24+0.47,0.47, 7.25+0.37,0.36) km s,1, with additional systematic uncertainties ,(1, 2, 0.5) km s,1. In particular, V, is 7 km s,1 larger than previously estimated. The new values of (U, V, W), are extremely insensitive to the metallicity gradient within the disc. [source] The PSCz dipole revisitedMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2006Spyros Basilakos ABSTRACT We re-examine the gravitational acceleration (dipole) induced on the Local Group of galaxies by the Infrared Astronomical Satellite (IRAS) galaxy distribution of the Point Source Catalog redshift (PSCz) survey. We treat the cirrus-affected low galactic latitudes by utilizing a spherical harmonic expansion of the galaxy surface density field up to the octapole order. We find strong indications for significant contributions to the Local Group motion from depths up to ,185 h,1 Mpc and a possible contribution even from ,210 h,1 Mpc, in agreement with the recent analysis of Kocevski & Ebeling of a whole-sky X-ray cluster survey. What changes with respect to the previous PSCz dipole analyses is: (i) the large-scale dipole contributions and (ii) an increase of the overall dipole amplitude due to the important contribution of the local volume (, 4 h,1 Mpc), which we now take into account. This results in a lower value of the , (,,0.6m/b) parameter, which we find to be ,IRAS, 0.49 in real space. Therefore, for the concordance cosmological model (,m= 1 ,,,= 0.3), the IRAS galaxies bias factor is bIRAS, 1, which means that IRAS galaxies are good tracers of the underlying matter distribution. [source] The effect of a finite mass reservoir on the collapse of spherical isothermal clouds and the evolution of protostellar accretionMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2005E. I. Vorobyov ABSTRACT Motivated by recent observations that detect an outer boundary for starless cores, and evidence for time-dependent mass accretion in the Class 0 and Class I protostellar phases, we re-examine the case of spherical isothermal collapse in the case of a finite mass reservoir. The presence of a core boundary, implemented through a constant-volume approximation in our simulation, results in the generation of an inward-propagating rarefaction wave. This steepens the gas density profile from r,2 (self-similar value) to r,3 or steeper. After a protostar forms, the mass accretion rate evolves through three distinct phases: (1) an early phase of decline in , which is a non-self-similar effect due to rapid and spatially non-uniform infall in the pre-stellar phase; (2) for large cores, an intermediate phase of near-constant from the infall of the outer part of the self-similar density profile, which has low (subsonic) infall speed in the pre-stellar phase; and (3) a late phase of rapid decline in when accretion occurs from the region affected by the inward-propagating rarefaction wave. Our model clouds of small to intermediate size make a direct transition from phase (1) to phase (3) above. Both the first and second phase (if the latter is indeed present) are characterized by a temporally increasing bolometric luminosity Lbol, while Lbol is decreasing in the third (final) phase. We identify the period of temporally increasing Lbol with the Class 0 phase, and the later period of terminal accretion and decreasing Lbol with the Class I phase. The peak in Lbol corresponds to the evolutionary time when 50 ± 15 per cent of the cloud mass has been accreted by the protostar. This is in agreement with the classification scheme proposed in the early 1990s by André et al.; our model adds a physical context to their interpretation. We show how our results can be used to explain tracks of envelope mass Menv versus Lbol for protostars in Taurus and Ophiuchus. We also develop an analytic formalism that successfully reproduces the protostellar accretion rate from profiles of density and infall speed in the pre-stellar phase. It shows that the spatial gradient of infall speed that develops in the pre-stellar phase is a primary cause of the temporal decline in during the early phase of protostellar accretion. [source] | ||||||||||||||||||||||||||||