Home About us Contact
|
Home About us Contact | ||
|
|
||
Plausible Explanation (plausible + explanation)
Selected AbstractsUnions and the Duration of Workers' Compensation ClaimsINDUSTRIAL RELATIONS, Issue 4 2005MICHELE CAMPOLIETI This paper examines the effect of union status on workers' compensation claim duration in Canada. I find that unionized workers have shorter claims than nonunionized workers and that relatively little of this difference can be attributed to differences in worker or job characteristics. I interpret this as being consistent with a strong union effect that reduces union member's claim duration. Plausible explanations for this finding and directions for future research are also discussed. [source] Formation and photodissociation of M+,C6H6 (M+ = V+ and Ta+) and Ta+,C6H4 complexes in a time-of-flight mass spectrometerJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 5 2001Hsiu-Fang Lee Abstract A series of cyclic hydrocarbons were introduced to react with V+ and Ta+ using a pulsed beam expansion source in a time-of-flight mass spectrometer. The third-row metal Ta+ displayed high reactivity in dehydrogenation to form benzyne complexes, whereas benzene complexes were the terminal products for V+. M+,C6H6 (M+ = V+ and Ta+) and Ta+,C6H4 were selected to perform the photodissociation experiments. In contrast to the V+ fragment formation via simple cleavage of the V+,C6H6 bond, a photoinduced loss of C2H2 occurred in both the Ta+,C6H6 and Ta+,C6H4 complexes. Plausible explanations involved in the formation of Ta+,C6H6 and Ta+,C6H4 complexes are given for observing such photo-induced dissociation. The observed photodissociation in Ta+,C6H6 is analogous to the dissociative process previously investigated in metal ion,molecule reactions. The photodissociation spectrum of Ta+,C6H4 was obtained by recording the appearance of Ta+,C4H2 as a function of wavelength and yielded a dissociation energy of 91 ± 1 kcal mol,1. Copyright © 2001 John Wiley & Sons, Ltd. [source] How do crystal lattice contacts reveal protein crystallization mechanism?CRYSTAL RESEARCH AND TECHNOLOGY, Issue 9 2008Christo N. Nanev Abstract The nature of crystal lattice contacts is discussed because they reflect the selection of the most appropriate (for the given set of conditions) contact patches on the surface of protein molecules. The conclusion is that, along with chemical composition, the protein structure at the crystal lattice contacts is the key to crystallization behavior. The reason is that most stable are conformations, which do not only maximize the number of the bonds but simultaneously minimize van der Waals repulsions. A plausible explanation of the crystallization slot that exists for proteins is given on this basis. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Protein crystal nucleation: Recent notionsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 1 2007Christo N. Nanev Abstract The nucleation of protein crystals is reconsidered taking into account the specificity of the protein molecules. In contrast to the homogeneous surface properties of small molecules, the protein molecule surface is highly inhomogeneous. Over their surfaces proteins exhibit high anisotropic distribution of patches, which are able to form crystalline bonds, the crystallization patch representing only a small fraction of the total surface of the protein molecule. Therefore, an appropriate spatial orientation of the colliding protein molecules is required in order to create a crystalline cluster. This scenario decreases considerably the success ratio of the attempt frequency for crystal nucleation. On the other hand a heterogeneous nucleation of (protein) crystals may be accelerated due to the arrival on some support of under-critical clusters that are formed in bulk solution; when arriving there they may acquire the property of critical nuclei. Thus, a plausible explanation of important peculiarities of protein crystal nucleation, as inferred from the experimental data, is suggested. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Is natural selection a plausible explanation for the distribution of Idh- 1 alleles in the cricket Allonemobius socius?ECOLOGICAL ENTOMOLOGY, Issue 1 2006Diana L. Huestis Abstract., 1.,Allozyme alleles in natural populations have been proposed as either neutral markers of genetic diversity or the product of natural selection on enzyme function, as amino acid substitutions that change electrophoretic mobility may also alter enzyme performance. To address these possibilities, researchers have used both correlative analyses and empirical studies. 2.,Here, geographically structured variation of the enzyme isocitrate dehydrogenase (Idh- 1) in the striped ground cricket Allonemobius socius Scudder (Orthoptera: Gryllidae) is examined. The distributions of Idh- 1 alleles appear to be related to environmental gradients, as allele frequencies showed significant relationships with mean annual temperature and precipitation. Specifically, the slowest mobility allele was more frequent at colder temperatures, while the converse occurred for the fastest mobility allele. 3.,An exploratory experiment was performed to examine fitness effects of possessing different Idh- 1 alleles at two temperatures to test the hypothesis that the geographic structure of this locus may reflect environmental adaptation. Results showed that a significant interaction between temperature and Idh- 1 genotype affected the number of eggs laid, with success of homozygous individuals matching environmental expectations. 4.,The above results show that (1) variation in the frequency of Idh- 1 alleles is significantly related to environmental gradients in the eastern U.S.A. and (2) alternative alleles of Idh- 1 appear to influence the egg-laying ability of individuals differently depending on environmental temperature. Together, these results suggest that natural selection is a plausible mechanism underlying the distribution of Idh- 1 alleles in this species, although more detailed studies are needed. [source] Gender differences in genetic damage induced by the tobacco-specific nitrosamine NNK and the influence of the Thr241Met polymorphism in the XRCC3 geneENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 1 2005Courtney E. Hill Abstract The rapid increase in adenocarcinoma of the lung and mortality amongst women strongly suggests that gender differences exist in sensitivity to certain tobacco carcinogens. In the current study, we performed the mutagen-sensitivity assay, with the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), to test the hypothesis that women are more sensitive to the genotoxic effects of NNK than men. Chromosome aberration (CA) frequencies in peripheral blood lymphocytes (PBLs) from 99 patients were evaluated before and after in vitro exposure to NNK. Because the Thr241Met polymorphism in the DNA-repair gene XRCC3 is associated with increased risk of tobacco-related cancers, especially among women, we also tested the hypothesis that individuals who inherit the homozygous variant 241Met allele are more sensitive to the genotoxic effects of NNK. CA frequency was significantly higher 1 hr after NNK treatment in women, compared with men (P = 0.02). When smoking and gender were considered together, a significant interaction was observed. PBLs from female smokers had significantly higher frequencies of NNK-induced CA, compared with female nonsmokers 1 hr after treatment (P = 0.02). We observed no overall effect of the Thr241Met polymorphism on NNK-induced CA in men, women, smokers, or nonsmokers. Overall, our data indicate that women are more sensitive to the genotoxic effects of NNK than men. Because in past years smoking among women has increased, and in view of the close correlation between NNK exposure and adenocarcinoma of the lung, our data provide a plausible explanation for the recent increase in the incidence of this cancer among women. Environ. Mol. Mutagen., 2005. © 2005 Wiley-Liss, Inc. [source] Differential responses to NMDA receptor activation in rat hippocampal interneurons and pyramidal cells may underlie enhanced pyramidal cell vulnerabilityEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2005E. Avignone Abstract Hippocampal interneurons are generally more resistant than pyramidal cells to excitotoxic insults. Because NMDA receptors play a crucial role in neurodegeneration, we have compared the response to exogenous NMDA in CA1 pyramidal cells and interneurons of the stratum oriens using combined whole-cell patch-clamp recording and ratiometric Ca2+ imaging. In voltage-clamp, current-clamp or in nominally Mg2+ -free medium, NMDA (10 µm; 3,5 min exposure in the presence of tetrodotoxin) induced a markedly larger inward current and Ca2+ rise in pyramidal cells than in interneurons. Pyramidal cells also showed a more pronounced voltage dependence in their response to NMDA. We hypothesized that this enhanced response to NMDA receptor activation in pyramidal cells could underlie their increased vulnerability to excitotoxicity. Using loss of dye as an indicator of degenerative membrane disruption, interneurons tolerated continuous exposure to a high concentration of NMDA (30 µm) for longer periods than pyramidal cells. This acute neurodegeneration in pyramidal cells was independent of intracellular Ca2+, because high intracellular BAPTA (20 mm) did not prolong survival time. Thus, a plausible explanation for the enhanced sensitivity of pyramidal neurons to excitotoxic insults associated with cerebral ischemia is their greater response to NMDA receptor activation, which may reflect differences in NMDA receptor expression and/or subunit composition. [source] INCREASED RATES OF MOLECULAR EVOLUTION IN AN EQUATORIAL PLANT CLADE: AN EFFECT OF ENVIRONMENT OR PHYLOGENETIC NONINDEPENDENCE?EVOLUTION, Issue 1 2005Jeremy M. Brown Abstract A recent study of environmental effects on rates of molecular evolution in the plant subgenus Mearnsia shows that species occurring in more equatorial latitudes have higher rates of substitution in rDNa sequences as compared to their more southerly congeners (Wright et al. 2003). However, we believe that the statistical approach employed by Wright et al. (2003) insufficiently accounts for the phylogenetic nonindependence of the species examined, given that all six equatorial species of Mearnsia form a clade. To distinguish between the effect of latitude and that of phylogenetic nonindependence, we have employed a variety of comparative approaches that use independent contrasts to test for an effect of environment across this entire subgenus. We find very little evidence for an effect of latitude on rate of molecular evolution using these approaches and believe that the shared evolutionary history of the clade is a plausible explanation of the apparent rate difference between equatorial and subequatorial Mearnsia species. [source] A STATISTICAL TEST OF UNBIASED EVOLUTION OF BODY SIZE IN BIRDSEVOLUTION, Issue 12 2002Folmer Bokma Abstract., Of the approximately 9500 bird species, the vast majority is small-bodied. That is a general feature of evolutionary lineages, also observed for instance in mammals and plants. The avian interspecific body size distribution is right-skewed even on a logarithmic scale. That has previously been interpreted as evidence that body size evolution has been biased. However, a procedure to test for unbiased evolution from the shape of body size distributions was lacking. In the present paper unbiased body size evolution is defined precisely, and a statistical test is developed based on Monte Carlo simulation of unbiased evolution. Application of the test to birds suggests that it is highly unlikely that avian body size evolution has been unbiased as defined. Several possible explanations for this result are discussed. A plausible explanation is that the general model of unbiased evolution assumes that population size and generation time do not affect the evolutionary variability of body size; that is, that micro- and macroevolution are decoupled, which theory suggests is not likely to be the case. [source] The influence of fluid-sensitive dispersion and attenuation on AVO analysisGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2006Mark Chapman SUMMARY Analysis of seismic data suggests that hydrocarbon deposits are often associated with higher than usual values of attenuation, but this is generally ignored during amplitude-versus-offset (AVO) analysis. The effect can be modelled with equivalent medium theory based on the squirt flow concept, but the excess attenuation is associated with strong velocity dispersion. Consequently, when we study reflections from the interface between such an equivalent medium and an elastic overburden we find that the reflection coefficient varies with frequency. The impact of this variation depends on the AVO behaviour at the interface; class I reflections tend to be shifted to higher frequency while class III reflections have their lower frequencies amplified. We calculate synthetic seismograms for typical models using the reflectivity method for materials with frequency dependent velocities and attenuations, and find that these effects are predicted to be detectable on stacked data. Two field data sets show frequency anomalies similar to those predicted by the analysis, and we suggest that our modelling provides a plausible explanation of the observations. [source] Innovative Governance and Development in the New Ireland: Social Partnership and the Integrated ApproachGOVERNANCE, Issue 1 2004J. D. House Since the mid-1980s, the economy of the Republic of Ireland has displayed a remarkable turnaround. Its Gross Domestic Product (GDP) has grown at a faster rate than any developed country in the world. The government's deficit has been cut severely and the debt-to-GDP ration sharply reduced. Average incomes have risen significantly, and the unemployment rate reduced dramatically. This article documents these changes. Its main purpose, however, is to provide a plausible explanation for the "Irish miracle." While many factors have been important,support for the Economic Union's regional development programs, a favorable tax structure, locational and language advantages for attracting multinational corporations, strong education and training programs,these factors in themselves do not explain the emergence of the "Celtic tiger." They were in place before the mid-1980s when Ireland was suffering from a fiscal, economic, and political crisis. Instead, the article argues, it was the creative and innovative response of Irish leaders in government, industry, and labor movement and community organizations to the crisis, and the subsequent institutionalization of this response in a new form of governance, that has been the catalyst for the Irish success story. Based on the thorough background research of the Economic and Social Research Council, a farsighted group of leaders developed a strategic plan in 1987 that provided a blueprint for constructive economic and social change. This was then formally instituted for wage restraint on the part of labor in return for income tax and social supposed provisions by government. Irish social Partnership is modeled to some extent on Northern European corporatism. The article reviews corporatism as an early form of innovative governance, using classical corporatism in Sweden and competitive corporatism in the Netherlands to illustrate how this approach has evolved over the years. Dutch economic success in recent years is due in part to its new form of corporatism that has helped it become globally competitive. It is argued, however, that Irish social partnership goes beyond continental corporatism in several important ways. It is more inclusive, covering a large array of social interests; it is more strategic, with a well-articulated integrated approach to social and economic development that is self-corrective and articulated in a new national agreement every three years; and it is more firmly institutionalized in both government and nongovernment agencies in the country. Social partnership and the integrated approach have become part of the culture of the new Ireland. This innovative form of governance underlies the Irish turnaround and augurs well for the future. It can also serve as a model, with appropriate modification tailor-made to each case, for other jurisdictions hoping to emulate Ireland's success. [source] Corporate governance and chief executive officer dismissal following poor performance: Australian evidenceACCOUNTING & FINANCE, Issue 1 2009James Lau G30 Abstract This paper investigates the association between corporate performance and the probability of chief executive officer (CEO) dismissal for large corporations in Australia. Consistent with prior US and UK studies, corporate performance is negatively related to the probability of CEO dismissal, using both accounting and market-based performance measures. This paper also investigates whether key corporate governance characteristics affect the likelihood of CEO dismissal, by examining their effect on the strength of the negative association between corporate performance and CEO dismissal. The only significant variable is size of the board. Although its effect is opposite to that hypothesized, this paper provides a plausible explanation. Overall, the results are consistent with shareholder wealth considerations dominating board behaviour in Australia. [source] Development of a historical ice database for the study of climate change in CanadaHYDROLOGICAL PROCESSES, Issue 18 2002Frédéric Lenormand Abstract The Canadian government has been compiling various observations on freshwater and coastal sea ice conditions for many years. However, the records are not easily accessible and are dispersed within different government departments. Given this, a major effort was undertaken in order to gather all available observations into a common database,the Canadian Ice Database (CID). This database will respond to the needs for climate monitoring in Canada, the validation and improvement of numerical ice models and the development of new remote-sensing methods. Indeed, several studies have shown that freshwater ice and sea ice are good proxy indicators of climate variability and change. The first version of CID contains in situ observations from 757 sites distributed across Canada, which were originally kept on digital or paper records at the Meteorological Service of Canada Headquarters and the Canadian Ice Service (CIS). The CID holds 63 546 records covering the period from ice season 1822,23 to 2000,01. An analysis of the database allows one to trace the temporal evolution of the ice networks. The freeze-up/break-up network of 2000,01 only represents 4% of what it was in 1985,86. A drastic decline of the ice thickness and the snow on ice network is also observable. In 1997,98, it represented only 10% of the network that existed in 1984,85. The major budget cuts in Canadian government agencies during the late 1980s and the 1990s offer the most plausible explanation for the drastic decline in the ice observation networks. Weekly ice coverage determination on large lakes from satellite imagery by the CIS and the national volunteer ice monitoring program, IceWatch, may provide a means of reviving, at least, the freeze-up/break-up network. Copyright © 2002 John Wiley & Sons, Ltd. [source] Parentage analysis in Gabonese colonies of soil-feeding termites belonging to the Cubitermes sp. affinis subarquatus complex of species (Termitidae: Termitinae)INSECT SCIENCE, Issue 2 2010Virginie Roy Abstract,Cubitermes spp. are widely distributed soil-feeding termite species in sub-Saharan Africa which play a fundamental role in soil structure and fertility. A complex of at least four cryptic species (i.e., Cubitermes sp. affinis subarquatus complex of species) has been recently described using molecular markers. In order to investigate the breeding system of these species, five microsatellite markers were used to carry out parentage and relatedness analyses in 15 Gabonese colonies. Monogamy was confirmed as the predominant reproductive organization in Cubitermes spp. (76% of the colonies). Within 30% of these monogamous colonies, a high relatedness between reproductives was shown, suggesting that mating between related individuals occurs. However, Cubitermes colonies can deviate from monogamy. Indeed, parental contributions by at least two related reproductives of the same sex were revealed in four colonies and polyandry was demonstrated in two of them. Infiltration of reproductives in the colony is the most plausible explanation for such cases of polygamy in Cubitermes spp. [source] Decreasing mortality from non-Hodgkin lymphoma in AustraliaINTERNAL MEDICINE JOURNAL, Issue 12 2008M. Coory Abstract Based on the number of new cases (incidence), non-Hodgkin lymphoma is an increasingly common cancer in Australia and many developed countries. Until recently, mortality trends have been stable or slightly increasing. However, since the year 2000, mortality has decreased every year by an average of 5.1% per year (95% confidence interval (CI) ,7.1 to ,3.1%), whereas incidence has continued to increase at 0.9% per year (95%CI 0.6 to 1.2%). It was not possible with the population-based registry data available to us to untangle the causes of the decrease in mortality. The stable mortality rates during the 1990s (in the face of increasing incidence) might have been because of introduction of novel therapies such as autologous stem cell transplant for relapsed diffuse large cell lymphoma or the purine analogue-based therapy for indolent lymphomas. A plausible explanation for the large decrease in mortality since 2000 is the introduction of the monoclonal antibody rituximab. [source] First palaeopathological example of Kienböck's disease from early modern Sakhalin AinuINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 2 2002M. Nakai Abstract A disorder of the carpal lunate has been diagnosed as Kienböck's disease in a skeleton of a middle-aged Ainu male that was excavated from Sakhalin Island, northeast Asia. The bone lesion is primarily and unilaterally associated with the right wrist, where the right carpal lunate is collapsed and the radiocarpal joint shows degenerative arthritis. Interestingly, the left arm is more robust than the right and the left elbow shows considerable osteoarthritis. The most plausible explanation for these pathologies is that after developing Kienböck's disease in the right wrist, excessive use of the left arm made his left arm robust and finally gave rise to osteoarthritis in the left elbow. In archaeology, where only a few osteochondroses have been reported up until now, the present example is the first diagnosis of Kienböck's disease in skeletal remains. Copyright © 2002 John Wiley & Sons, Ltd. [source] Improved Synthesis of Pyrroles and Indoles via Lewis Acid-Catalyzed Mukaiyama,Michael-Type Addition/Heterocyclization of Enolsilyl Derivatives on 1,2-Diaza-1,3-Butadienes.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2007Role of the Catalyst in the Reaction Mechanism Abstract The Mukaiyama,Michael-type addition of various silyl ketene acetals or silyl enol ethers on some 1,2-diaza-1,3-butadienes proceeds at room temperature in the presence of catalytic amounts of Lewis acid affording by heterocyclization 1-aminopyrrol-2-ones and 1-aminopyrroles, respectively. 1-Aminoindoles have been also obtained by the same addition of 2-(trimethylsilyloxy)-1,3-cyclohexadiene on some 1,2-diaza-1,3-butadienes and subsequent aromatization. Mechanistic investigations indicate the coordination by Lewis acid of the enolsilyl derivative and its 1,4-addition on the azo-ene system of 1,2-diaza-1,3-butadienes. The migration of the silyl group from a hydrazonic to an amidic nitrogen, its acidic cleavage and the final internal heterocyclization give the final products. Based on NMR studies and ab initio calculations, a plausible explanation for the migration of the silyl protecting group is presented. [source] Agency and Human RightsJOURNAL OF APPLIED PHILOSOPHY, Issue 1 2010S. MATTHEW LIAO abstract What grounds human rights? How do we determine that something is a human right? James Griffin has persuasively argued that the notion of agency should determine the content of human rights. However, Griffin's agency account faces the question of why agency should be the sole ground for human rights. For example, can Griffin's notion of agency by itself adequately explain such human rights as that against torture? Or, has Griffin offered a plausible explanation as to why one should not broaden the ground for human rights to include other elements of a good life such as freedom from great pain, understanding, deep personal relations, and so on? These concerns have been raised regarding Griffin's agency account, but in his new book, On Human Rights, Griffin has offered new arguments in support of his view that agency is the sole ground for human rights. In this paper, I examine these new arguments, and I argue that Griffin's arguments are ultimately unsuccessful. [source] Effect of activation type on bioregeneration of various activated carbons loaded with phenolJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2006Özgür Akta Abstract Thermally and chemically activated powdered carbons (PAC), and their granular countertypes (GAC) with similar physical characteristics were used to investigate the extent of bioregeneration in laboratory-scale activated sludge reactors. Bioregeneration of activated carbon was determined by measurement of bulk phenol concentrations and loadings remaining on activated carbon. It was also followed by oxygen uptake rate measurements. For the carbons used in this study, bioregeneration of chemically activated carbons was found to be higher than thermally activated ones. This was in accordance with their higher reversibility of adsorption and showed that bioregeneration was controlled by the reversibility of adsorption. Oxidative polymerization of phenol was a plausible explanation for low bioregeneration of thermally activated carbons. However, bioregeneration efficiencies of thermally activated carbons were much higher than their total desorbabilities. This unexpectedly high bioregeneration indicated that some exoenzymatic reactions had occurred. These results suggest that carbon activation type is of crucial importance for bioregeneration. PAC and GAC countertypes showed comparable bioregeneration efficiencies indicating that carbon size was not an effective factor. The environmental scanning electron microscopy (ESEM) studies showed that microorganisms were attached both on the external surface and interval cavities of activated carbon particles. Copyright © 2006 Society of Chemical Industry [source] Breeding system, branching processes, hybrid swarm theory, and the humped-back diversity relationship as additional explanations for apparent monophyly in the Macaronesian island floraJOURNAL OF ECOLOGY, Issue 4 2005N. ELIZABETH SAUNDERS Summary 1Niche pre-emption and competitive exclusion is unsatisfactory as a sole explanation for the apparent paradox of a large number of monophyletic taxa in the Macaronesian island flora. 2Undetected hybridizations have been proposed as an additional plausible explanation. In addition, hybrid swarm theory predicts that hybridizations between invading species would promote adaptive radiation. 3We suggest that branching processes and coalescence offer yet another plausible explanation allowing for multiple colonizations of closely related taxa, which, because of their later local extinction or hybridization, would lead to apparent monophyly in the molecular record. 4The cause of such widespread radiation of a few taxa has not been explained, but may involve intermediate conditions of disturbance or productivity. This proposition has, to date, only been tested in a microbial model system, but it offers a reasonable explanation for the patterns observed in the Macaronesian flora, and perhaps in other island floras worldwide. [source] Getting What We Asked For, Getting What We Paid For, and Not Liking What We Got: The Vanishing Civil TrialJOURNAL OF EMPIRICAL LEGAL STUDIES, Issue 3 2004Stephen C. Yeazell The current rate of civil trials may result from two converging trends in civil practice: 20th-century procedural reforms and associated changes in the organization and financing of legal practice. The procedural reforms required greater pretrial investigation of facts, which in turn often required litigants to make regular investments of substantial capital, access to which was facilitated by changes in the organization of plaintiffs' practices. Together, these procedural reforms and changes in practice structure provide a plausible explanation for the observed phenomenon of declining rate and number of civil trials. [source] ICT and agricultural productivity: evidence from cross-country dataAGRICULTURAL ECONOMICS, Issue 3 2006Monchi Lio Agricultural productivity; ICT adoption; Digital divide Abstract This article carries out agricultural production function estimations, based on data for the period 1995,2000 on 81 countries, to present empirical evidence on the relationship between the adoption of information and communication technology (ICT) and agricultural productivity. It is found that new ICT has a significantly positive impact on agricultural productivity. The evidence suggests that the adoption of modern industrial inputs in agricultural production relies on the information and communication infrastructure. However, the empirical evidence from this study also suggests that new ICT could be a factor for the divergence between countries in terms of overall agricultural productivity. Not only do we find that the ICT adoption levels of the richer countries are much higher than those of the poorer countries, but also that returns from ICT in agricultural production of the richer countries are about two times higher than those of the poorer countries. A plausible explanation for the poorer countries' relatively low productivity elasticity of ICT is the lack of important complementary factors, such as a substantial base of human capital. [source] Energy Dissipation and Photoinhibition in Douglas-Fir Needles with a Fungal-Mediated Reduction in Photosynthetic RatesJOURNAL OF PHYTOPATHOLOGY, Issue 11-12 2002Daniel K. Manter Abstract The dissipation of absorbed light and potential for photooxidative damage was explored in Douglas-fir (Pseudotsuga menziesii ) seedlings with and without Phaeocryptopus gaeumannii infection. The presence of P. gaeumannii significantly reduced net CO2 assimilation rates from ca. 6 ,mol/m2/s to 1.5 ,mol/m2/s, without any significant impact on chloroplast pigments. The partitioning of absorbed light-energy to photochemistry or thermal dissipation was determined from chlorophyll fluorescence measurements. Maximum thermal dissipation for both control and infected needles was ca. 80%, consistent with the similar xanthophyll pool sizes in the two treatments. At high photosynthetic photon flux density (PPFD), when thermal dissipation was maximized, the lower photochemical utilization in infected needles resulted in greater amounts of excess absorbed light (ca. 20 and 10% for the infected and control needles, respectively). A second experiment, monitoring changes in photosystem II (PSII) efficiency (Fv/Fm) in response to a 1 h high light treatment (PPFD=2000 ,mol/m2/s) also suggests that infected needles absorb greater amounts of excess light. In this experiment, declines in Fv/Fm were 1.5 times greater in infected needles, despite the similar xanthophyll pool sizes. Furthermore, increases in minimum fluorescence (178 and 122% of initial values for the infected and control needles, respectively) suggest that the reduction in PSII efficiency is largely attributable to photooxidative damage. Finally, reductions in PSII efficiency under high light conditions provide a plausible explanation for the greater pathogenicity (e.g. premature needle abscission) of P. gaeumannii in sun-exposed foliage. [source] Plant neurobiology and green plant intelligence: science, metaphors and nonsenseJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2008Paul C Struik Abstract This paper analyses the recent debates on the emerging science of plant neurobiology, which claims that the individual green plant should be considered as an intelligent organism. Plant neurobiology tries to use elements from animal physiology as elegant metaphors to trigger the imagination in solving complex plant physiological elements of signalling, internal and external plant communication and whole-plant organisation. Plant neurobiology proposes useful concepts that stimulate discussions on plant behaviour. To be considered a new science, its added value to existing plant biology needs to be presented and critically evaluated. A general, scientific approach is to follow the so-called ,parsimony principle', which calls for simplest ideas and the least number of assumptions for plausible explanation of scientific phenomena. The extent to which plant neurobiology agrees with or violates this general principle needs to be examined. Nevertheless, innovative ideas on the complex mechanisms of signalling, communication, patterning and organisation in higher plants are badly needed. We present current views on these mechanisms and the specific role of auxins in regulating them. Copyright © 2007 Society of Chemical Industry [source] Opposing roles of IL-17A and IL-25 in the regulation of TSLP production in human nasal epithelial cellsALLERGY, Issue 5 2010G. Xu To cite this article: Xu G, Zhang L, Wang DY, Xu R, Liu Z, Han DM, Wang XD, Zuo KJ, Li HB. Opposing roles of IL-17A and IL-25 in the regulation of TSLP production in human nasal epithelial cells. Allergy 2010; 65: 581,589. Abstract Background:, The importance of IL-17A, IL-17F, and IL-25 in allergic rhinitis (AR), as well as their possible role in regulation on thymic stromal lymphopoietin (TSLP) production in nasal epithelial cells, is not well understood. Objective:, To determine the possible regulation of IL-17A, IL-17F, and IL-25 on TSLP production in the initiation of allergic responses. Methods:, The levels of IL-17A, IL-17F, IL-25, and TSLP in nasal lavages of patients with AR were measured using an enzyme-linked immunosorbent assay (ELISA) and compared with that in normal controls. Then, primary human nasal epithelial cells (HNECs) were stimulated with dsRNA (0,75 ,g/ml), as well as IL-17A (100 ng/ml), IL-17F (100 ng/ml), and IL-25(100 ng/ml). The mRNA expression of IL-17A, IL-17F, IL-25, TSLP, as well as the chemokines CCL20, IL-8, and eotaxin was analyzed using quantitative real-time PCR, and their protein levels in the supernatants of cultured HNECs were determined by ELISA. Results:, Both TSLP and IL-17 cytokines are significantly elevated in patients with AR. dsRNA was found to increase the production of IL-17F, IL-25, TSLP, CCL20, and IL-8 in HNECs. Furthermore, IL-25 significantly enhanced dsRNA-induced TSLP production in primary HNECs and was dominant to the inhibitory effect of IL-17A on TSLP regulation. Conclusions:, Our study provides the first evidence that both IL-17F and IL-25 can be induced by dsRNA in HNECs. Despite of the opposing effects of IL-17A and IL-25 on TSLP regulation in HNECs, IL-25 was dominant to IL-17A, providing a plausible explanation for the simultaneous upregulation of IL-17 cytokines and TSLP in patients with AR. [source] Microcirculatory Dysfunction in Chronic Venous Insufficiency (CVI)MICROCIRCULATION, Issue S1 2000MICHAEL JÜNGER ABSTRACT The elevated ambulatory pressure in the peripheral venous system of chronic venous insufficiency (CVI) patients manifests itself not only in the form of disturbed macrocirculation but also and particularly in microangiopathic changes. For this reason, it is closely correlated with trophic disorders of the skin and can ultimately lead to ulceration. Using microcirculation research techniques, we are able to provide clear evidence of a typical microangiopathy in chronic venous insufficiency. Fifty CVI patients in Widmer stages I, II, and III were examined with fluorescence video microscopy, intravital video capillaroscopy, transcutaneous oxygen partial pressure measurement, TcpO2 and laser Doppler flowmetry. The effects of compression therapy with individually fitted compression stockings on capillary morphology were studied over a period of 4 weeks in 20 CVI patients in Widmer stages I and II. The capillary pressure was measured during simulated muscle contraction using a servo-null micropressure system. We periodically drew blood from the dorsalis pedis vein and a brachial vein of 11 healthy test persons and 8 patients with stage III CVI during experimental venous hypertension in order to evaluate the expression pattern of leukocyte adhesion molecules involved in inflammation: LFA-1 (CD11a), Mac-1 (CD11b), p150,95 (CD11c), CD18, VLA-4 (CD49d), and L-selectin (CD62L). In the same patients, we used immunohistochemical methods to examine clinically unaffected skin and the skin near an ulcer, focusing on the adhesion molecules ICAM-1, VCAM-1, and E-selectin. The microangiopathic changes observed with worsening clinical symptoms include a decrease in the number of capillaries, glomerulus-like changes in capillary morphology, a drop in the oxygen content (tcpO2) of the skin, increased permeability of the capillaries to low-molecular-weight substances, increased laser Doppler flux reflecting elevated subcutaneous flow, and diminished vascular reserve. These microangiopathic changes worsen in linear proportion to the clinical severity of chronic venous insufficiency. In patients with venous ulcerations, the baseline expression of LFA-1 and VLA-4 on lymphocytes, Mac-1 expression on the myeloid cell line, and L-selectin expression on all three cell lines was not significantly different from that in healthy controls. During orthostatic stress, there was a significant reduction in the expression of L-selectin in blood cells collected at foot level in the controls (p = 0.002), but not in the patients. Clinical improvement by compression therapy was accompanied by an increase in the number of nutritive capillaries, while the diameter of the capillaries and the dermal papillae was reduced. When ulcers healed in a short period (<6 weeks), we observed a concomitant increase in the number of capillaries (p < 0.05). Microangiopathy appears before trophic disorders of the skin develop. Even trophically normal skin areas may have dilated nutritive capillaries, an early sign of disturbed skin perfusion. These changes represent a plausible explanation for the development and to recurrency tendency of venous ulcers. The reduced expression of lymphocytic L-selectin in healthy controls during the orthostatic stress test may be an indication that the cells are activated by venous stasis. Clinically effective therapeutic measures improve the impaired microcirculation of the skin in the ankle area. [source] The yeast zinc finger regulators Pdr1p and Pdr3p control pleiotropic drug resistance (PDR) as homo- and heterodimers in vivoMOLECULAR MICROBIOLOGY, Issue 5 2002Yasmine M. Mamnun Summary The transcription factors Pdr1p and Pdr3p from Saccharomyces cerevisiae mediate pleiotropic drug resistance (PDR) by controlling expression of ATP-binding cassette (ABC) transporters such as Pdr5p, Snq2p and Yor1p. Previous in vitro studies demonstrated that Pdr1p and Pdr3p recognize so-called pleiotropic drug resistance elements (PDREs) in the promoters of target genes. In this study, we show that both Pdr1p and Pdr3p are phosphoproteins; Pdr3p isoforms migrate as two bands in gel electrophoresis, reflecting two distinct phosphorylation states. Most importantly, native co-immunoprecipitation experiments, using functional epitope-tagged Pdr1p/Pdr3p variants, demonstrate that Pdr1p and Pdr3p can form both homo- and heterodimers in vivo. Furthermore, in vivo footprinting of PDRE-containing promoters demonstrate that Pdr1p/Pdr3p constitutively occupy both perfect and degenerate PDREs in vivo. Thus, in addition to interaction with other regulators, differential dimerization provides a plausible explanation for the observation that Pdr3p and Pdr1p can both positively and negatively control PDR promoters with different combinations of perfect and degenerate PDREs. [source] Tremor induced by thalamic deep brain stimulation in patients with complex regional facial pain,MOVEMENT DISORDERS, Issue 8 2004Constantine Constantoyannis MD Abstract We report on two patients who developed a new postural and action tremor after chronic stimulation of the contralateral thalamus (VPM nucleus) during treatment of a complex regional facial pain syndrome. The tremor was only present during deep brain stimulation (DBS) and was suppressed with adjustment of the stimulation parameters. Tremor was seen only with low frequency stimulation (50 Hz or lower) and disappeared with higher stimulation frequencies. In addition to being an unusual side effect of thalamic DBS, we believe that this phenomenon affords insight into one possible mechanism underlying essential tremor (ET). A central oscillatory mechanism involving the olivocerebellar complex and the thalamus, which is a part of the cerebro,cerebello,cerebral circuit, is thought to play an important role in the genesis of ET. Induction of a tremor resembling ET in our patients indicates an active role for low frequency stimulation. A plausible explanation for this is that low frequency stimulation in the thalamic area enhances the output of the tremor-producing network. This leads credence to the concept of central oscillations in a "tremor circuit," of which the thalamus is a part, as being important in ET. © 2004 Movement Disorder Society [source] Explaining Negotiation Outcomes: Process or Context?NEGOTIATION AND CONFLICT MANAGEMENT RESEARCH, Issue 3 2009Cynthia Irmer Abstract This study evaluates a set of hypotheses about the relative influence of negotiating processes and contexts on outcomes. The investigation proceeds in a sequence of steps. First, a number of process and outcome variables are coded from documented cases of 26 settled violent conflicts that have occurred since the end of World War II. These cases are used also to evaluate the impact of four contextual variables. High partial correlations indicate a strong relationship between process and outcome controlling for context. Second, a set of structured focused comparisons was conducted with four matched and mis-matched cases. By tracing the process in each of these cases through phases of the talks, we showed that there is a causal relationship between process and outcome. Third, a plausibility probe was designed to identify a mechanism responsible for the causal relationship. The probe discovered that the development of trust is a plausible explanation for the relationship between process and outcome. This mode of inquiry, referred to as ACE (association, causation, and explanation), is regarded as a model for research on negotiation and peace processes. [source] Does Political Democracy Enhance Human Development in Developing Countries?AMERICAN JOURNAL OF ECONOMICS AND SOCIOLOGY, Issue 2 2006A Cross-National Analysis Despite the considerable progress of human development (HD) in developing countries (DCs) during recent decades, vast differences still remain among such countries. The question thus arises of why these divergences persist. This cross-national study uses a larger sample of DCs to offer necessary testing of the impact of democracy on HD. This study adopts new measures of democracy featuring majority rule and political contention to estimate their correlation with three physical well-being indicators as well as with three school enrollment indicators. After controlling for several macro-level political and economic characteristics (state revenue and economic growth), the regression modeling for recent data from the 1980s and 1990s showed that democracies indeed achieved higher levels on the HD indicators used here. However, democracy was not a powerful predictor of changes in HD scores during the analysis period. Neither central government health or educational spending significantly altered HD. The conclusions offer a plausible explanation of why democracy in DCs failed to sustain its momentum in improving HD. [source] | ||||||||||||||||||||||||||||||||||