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Substantial Variability (substantial + variability)
Selected AbstractsLate Quaternary vadose carbonate diagenesis in coastal and desert dune and beach sands: is there a palaeoclimatic signal?EARTH SURFACE PROCESSES AND LANDFORMS, Issue 12 2004Sue McLaren Abstract A study of the variation in cement amounts in aeolianite and sandy beach calcarenites that range in age from Holocene to Last Interglacial is used to assess whether a palaeoclimatic control on vadose diagenesis can be identi,ed. Examples are taken from modern-day arid to subhumid settings and represent a geographical distribution ranging from Libya and Oman, to the Mediterranean, the Caribbean and Mexico. The results indicate that a palaeoclimatic signal can be identi,ed in some deposits. However, in other sediments there is substantial variability in mean cement abundance within deposits as well as between these sand bodies. Moreover, many of the better cemented sediments are located in areas where there is accelerated diagenesis, such as in the sea spray zone, close to the groundwater table or near to a palaeosurface, rather than in climatically wet regions. The inference is that palaeoclimatic interpretations are substantially complicated by other factors that affect diagenetic processes and change. Therefore caution is needed when studying the role of climate in vadose diagenesis in the light of the effects of other intrinsic and extrinsic controls. This paper does not aim to provide a de,nitive comparison of sites from different climatic zones. The approach taken here is: (a) to see if there is an overall palaeoclimatic signal in the samples studied; (b) to use examples to illustrate how explanations/controls other than those relating to climate can account for the variabilities observed; and (c) if there is a climatic effect, to see if it is the main over-riding control on vadose diagenesis. The conclusions drawn from this research highlight that it is possible to misinterpret evidence if the study is approached with preconceived notions of simplistic relationships between diagenesis and climate. Copyright © 2004 John Wiley & Sons, Ltd. [source] TEMPORAL VARIATION IN DIVERGENT SELECTION ON SPINE NUMBER IN THREESPINE STICKLEBACKEVOLUTION, Issue 12 2002T. E. Reimchen Abstract., Short-term temporal cycles in ecological pressures, such as shifts in predation regime, are widespread in nature yet estimates of temporal variation in the direction and intensity of natural selection are few. Previous work on threespine stickleback (Gasterosteus aculeatus) has revealed that dorsal and pelvic spines are a defense against gape-limited predators but may be detrimental against grappling insect predators. In this study, we examined a 15-year database from an endemic population of threespine stickleback to look for evidence of temporal shifts in exposure to these divergent predation regimes and correlated shifts in selection on spine number. For juveniles, we detected selection for increased spine number during winter when gape-limited avian piscivores were most common but selection for decreased spine number during summer when odonate predation was more common. For subadults and adults, which are taken primarily by avian piscivores, we predicted selection should generally be for increased spine number in all seasons. Among 59 comparisons, four selection differentials were significant (Bonferroni corrected) and in the predicted direction. However, there was also substantial variability in remaining differentials, including two examples with strong selection for spine reduction. These reversals were associated with increased tendency of the fish to shift to a benthic niche, as determined from examination of stomach contents. These dietary data suggest that increased encounter rates with odonate predation select for spine reduction. Strong selection on spine number was followed by changes in mean spine number during subsequent years and a standard quantitative genetic formula revealed that spine number has a heritable component. Our results provide evidence of rapid morphological responses to selection from predators and suggest that temporal variation in selection may help maintain variation within populations. Furthermore, our findings indicate that variable selection can be predicted if the agents of selection are known. [source] Postfire response of North American boreal forest net primary productivity analyzed with satellite observationsGLOBAL CHANGE BIOLOGY, Issue 8 2003Jeffrey A. Hicke Abstract Fire is a major disturbance in the boreal forest, and has been shown to release significant amounts of carbon (C) to the atmosphere through combustion. However, less is known about the effects on ecosystems following fire, which include reduced productivity and changes in decomposition in the decade immediately following the disturbance. In this study, we assessed the impact of fire on net primary productivity (NPP) in the North American boreal forest using a 17-year record of satellite NDVI observations at 8- km spatial resolution together with a light-use efficiency model. We identified 61 fire scars in the satellite observations using digitized fire burn perimeters from a database of large fires. We studied the postfire response of NPP by analyzing the most impacted pixel within each burned area. NPP decreased in the year following the fire by 60,260 g C m,2 yr,1 (30,80%). By comparing pre- and postfire observations, we estimated a mean NPP recovery period for boreal forests of about 9 years, with substantial variability among fires. We incorporated this behavior into a carbon cycle model simulation to demonstrate these effects on net ecosystem production. The disturbance resulted in a release of C to the atmosphere during the first 8 years, followed by a small, but long-lived, sink lasting 150 years. Postfire net emissions were three times as large as from a model run without changing NPP. However, only small differences in the C cycle occurred between runs after 8 years due to the rapid recovery of NPP. We conclude by discussing the effects of fire on the long-term continental trends in satellite NDVI observed across boreal North America during the 1980s and 1990s. [source] Analysis and comparison of morphological reconstructions of hippocampal field CA1 pyramidal cellsHIPPOCAMPUS, Issue 3 2005José Ambros-Ingerson Abstract Morphological reconstructions have become a routine and valuable tool for neuroscientists. The accuracy of reconstructions is a matter of considerable interest given that they are widely used in computational studies of neural function. Despite their wide usage, comparisons of reconstructions obtained using various methodologies are lacking. We reviewed reconstructions of hippocampal CA1 pyramidal cells from five published studies and found marked differences in some of the most basic measurements. For four of the five studies means of total cell length clustered in the 11,479,13,417-,m range. The remaining study had a significantly larger value for this index at 16,992 ± 5,788 ,m. Surface area means varied more than 4-fold from 16,074 to 67,102 ,m2. Volume means varied more than 8-fold from 3,828 to 30,384 ,m3. Simulated passive input resistance means varied from 38.0 to 172.1 M,, reflecting the variability in cell dimensions. Estimates of the electrotonic length varied from 1.26 to 1.56. In two reconstructions used in previously published studies, simulated somatic excitatory postsynaptic potentials (EPSPs) varied 2,4-fold in amplitude, time to peak and half-width, for synaptic inputs at similar locations. Substantial jitter on the z -axis was identified as one likely source of the discrepancy in total cell length, while substantial differences in diameter measurements across studies, and sometimes within the same study, accounted for the variability in surface area and volume. While some part of the observed variability is surely due to the diversity of CA1 pyramidal cells, our analysis suggests that a substantial portion stemmed from methodological inconsistencies and from technological limitations. Suggestions are made for improving the quality and usefulness of morphological reconstructions. We conclude that reconstructions across studies have substantial variability in measures that are very relevant to neuronal function. Consequently, modelers are advised to use more than just one reconstructed cell in their simulations of neural function. © 2004 Wiley-Liss, Inc. [source] Effect of basin physical characteristics on solute fluxes in nine alpine/subalpine basins, Colorado, USA,HYDROLOGICAL PROCESSES, Issue 14 2001Julie K. Sueker Abstract Alpine/subalpine basins may exhibit substantial variability in solute fluxes despite many apparent similarities in basin characteristics. An evaluation of controls on spatial patterns in solute fluxes may allow development of predictive tools for assessing basin sensitivity to outside perturbations such as climate change or deposition of atmospheric pollutants. Relationships between basin physical characteristics, determined from geographical information system (GIS) tools, and solute fluxes and mineral weathering rates were explored for nine alpine/subalpine basins in Rocky Mountain National Park, Colorado, using correlation analyses for 1993 and 1994 data. Stream-water nitrate fluxes were correlated positively with basin characteristics associated with the talus environment; i.e., the fractional amounts of steep slopes (, 30°), unvegetated terrain and young debris (primarily Holocene till) in the basins, and were correlated negatively with fractional amounts of subalpine meadow terrain. Correlations with nitrate indicate the importance of the talus environment in promoting nitrate flux and the mitigating effect of areas with established vegetation, such as subalpine meadows. Total mineral weathering rates for the basins ranged from about 300 to 600 mol ha,1 year,1. Oligoclase weathering accounted for 30 to 73% of the total mineral weathering flux, and was positively correlated with the amount of old debris (primarily Pleistocene glacial till) in the basins. Although calcite is found in trace amounts in bedrock, calcite weathering accounted for up to 44% of the total mineral weathering flux. Calcite was strongly correlated with steep slope, unvegetated terrain, and young debris,probably because physical weathering in steep-gradient areas exposes fresh mineral surfaces that contain calcite for chemical weathering. Oligoclase and calcite weathering are the dominant sources of alkalinity in the basins. However, atmospherically deposited acids consume much of the alkalinity generated by weathering of calcite and other minerals in the talus environment. Published in 2001 by John Wiley & Sons, Ltd. [source] Eating Disorder Examination-Questionnaire as a measure of change in patients with bulimia nervosaINTERNATIONAL JOURNAL OF EATING DISORDERS, Issue 2 2005Robyn Sysko MS Abstract Objective The current study evaluated the agreement between the Eating Disorder Examination and the Eating Disorder Examination-Questionnaire in assessing eating disorder pathology in a sample of women with bulimia nervosa. Method Patients with broadly defined bulimia nervosa were enrolled in a double-blind, placebo-controlled treatment study of fluoxetine, with and without guided self-help. The current study presents information from 50 patients with data from both the EDE and EDE-Q at study entry and treatment termination. Results The EDE and EDE-Q produced more similar scores for compensatory behaviors (vomiting/laxative use) than complex eating-disordered features (binge eating/importance of shape and weight) at the pretreatment and posttreatment assessments, and for change during the study. Discussion The EDE and EDE-Q are highly correlated for many of the behavioral and attitudinal features of bulimia nervosa. There is substantial variability in agreement for individual patients, but on average, the EDE and EDE-Q will yield similar assessments of eating disorder symptoms and change in symptoms over time. © 2005 by Wiley Periodicals, Inc. [source] (A-)typical and (in-)secure?INTERNATIONAL SOCIAL SECURITY REVIEW, Issue 4 2008"non-standard" forms of employment in Europe, Social protection Abstract Atypical forms of employment (part-time work, mini-jobs, fixed-term contracts and solo self-employment) have gained in importance overall in recent years in many European countries. They are often part of an irregular career pattern and carry a high risk of unemployment. In a 6-country comparison (Germany, the United Kingdom, the Netherlands, Italy, Denmark and Poland) we consider whether and in what way national social protection laws cover the various forms of non-standard employment and the specific risks these entail. Significant variations were found in coverage standards and practices between countries as well as substantial variability within countries in their responses to different types of non-standard employment. A need for further and improved coordination of both social legislation and tax law is identified. [source] High school completion and future youth unemployment: new evidence from High School and BeyondJOURNAL OF APPLIED ECONOMETRICS, Issue 1 2006Professor Mingliang Li In this paper, I provide new evidence from High School and Beyond (HSB) on the effects of compulsory attendance on high school completion and future youth unemployment. I develop Bayesian estimation approaches to the simultaneous equation model with ordered probit and two-limit censored regression and the bivariate duration model, accounting for the heterogeneity in returns to education and the nonlinearity in the effects of compulsory attendance. I find substantial variability in returns to education across schools and evidence of diminishing marginal effects of compulsory attendance on high school completion. The simulation results suggest that increasing the compulsory attendance age raises the probability of completing high school and reduces the proportion of time the individuals are unemployed. These effects are much more pronounced for disadvantaged students but less pronounced for advantaged students, suggesting the potential effects of compulsory attendance on reducing the inequality in education and employment. Copyright © 2005 John Wiley & Sons, Ltd. [source] Survey of consent practices for inpatient colonoscopy and endoscopic retrograde cholangiopancreatography at a tertiary referral centerJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 8 2006Cynthia H Seow Abstract Background:, The purpose of the present paper was to determine informed consent practices for inpatient, open-access colonoscopy and endoscopic retrograde cholangiopancreatography (ERCP) at a tertiary referral center. Methods:, A two-part prospective study incorporating (i) an audit of consent practices for colonoscopy and ERCP; and (ii) a questionnaire directed at gastroenterologists and interns regarding information imparted to patients in the process of acquiring informed consent, was undertaken at Sir Charles Gairdner Hospital, Western Australia. Study subjects consisted of inpatients undergoing open-access colonoscopy and/or ERCP at the study center commencing May 2003; and gastroenterologists and interns at the study center. Results:, Written consent was obtained by junior medical staff in 89% of cases. Response rates for the questionnaire was 100% from interns, and 91% from gastroenterologists. Of interns surveyed, 93% had witnessed a colonoscopy, and 59% had witnessed an ERCP. For 12% of interns, colonoscopic bleeding or perforation were not always mentioned. Colonoscopy failure rate and perforation were overestimated by 51% and 63% of interns, respectively. Only 56% of interns always mentioned pancreatitis as a complication of ERCP. The rate of post-ERCP pancreatitis was overestimated by 25% of interns. Only 40% of gastroenterologists always provided additional information to patients whose consent was obtained by someone else. Written material was not routinely provided for patients. Consent was usually obtained on the day of the procedure. Conclusions:, Written consent for inpatients undergoing open-access colonoscopy and ERCP is rarely obtained by the proceduralist. There is substantial variability in the information provided to patients. Guidelines are required to ensure best practice in this area. [source] Bridging the Gap Between Genomics and EducationMIND, BRAIN, AND EDUCATION, Issue 4 2007Stephen A. Petrill ABSTRACT, Despite several decades of research suggesting the importance of both genetic and environmental factors, these findings are not well integrated into the larger educational literature. Following a discussion of quantitative and molecular genetic methods, this article reviews behavioral genetic findings related to cognitive and academic skills. This literature suggests that (a) the relative importance of genes and environments varies developmentally; (b) genetics, and to a lesser extend the environment, account for a substantial portion of the covariance within and across academic domains; and (c) some forms of disability are qualitatively different from the population, whereas others constitute the lower end of a continuum of ability. Following a discussion of the strengths and limitations of current behavioral genetic research and intervention research, we then discuss the ways in which understanding gene,environment interplay can be used to develop better definitions of learning impairment and better explain the substantial variability in response to intervention. [source] Overcoming the restriction barrier to plasmid transformation of Helicobacter pyloriMOLECULAR MICROBIOLOGY, Issue 5 2000John P. Donahue Helicobacter pylori strains demonstrate substantial variability in the efficiency of transformation by plasmids from Escherichia coli, and many strains are completely resistant to transformation. Among the barriers to transformation are numerous strain-specific restriction-modification systems in H. pylori. We have developed a method to protect plasmid DNA from restriction by in vitro site-specific methylation using cell-free extracts of H. pylori before transformation. In two cases, plasmid DNA treated with cell-free extracts in vitro acquired the restriction pattern characteristic of genomic DNA from the source strain. Among three strains examined in detail, the transformation frequency by treated plasmid shuttle and suicide vectors was significantly increased compared with mock-treated plasmid DNA. The results indicate that the restriction barrier in H. pylori can be largely overcome by specific DNA methylation in vitro. The approach described should significantly enhance the ability to manipulate gene function in H. pylori and other organisms that have substantial restriction barriers to transformation. [source] Effect of defoliation on grass growth.OIKOS, Issue 1 2002A quantitative review The diversity of responses of individual grasses to defoliation created a controversy about 15 years ago, which still needs clarification. We quantitatively assessed the evidence of defoliation effects on individual grass growth, addressing two main questions: 1) what is the average and variability of the effect of defoliation on plant growth? and 2) what are the associated conditions accounting for the diversity of effects? Regarding the first question, the results showed a negative overall effect of defoliation on plant growth and substantial variability in the defoliation responses of different plant components. There was an intermediate negative effect on total production (which included clipped-off biomass), a large negative effect on final live biomass at harvest, and a minimal effect on root biomass. Regarding the second question (conditions accounting for the diversity of effects), defoliation intensity had no effect on the response to defoliation, but both time for recovery from the last defoliation and the period of time between defoliation events significantly decreased the negative effect of defoliation. Nitrogen availability also altered the effect of defoliation, as plants grown at highest nitrogen levels were more negatively affected by clipping than plants with no supplementary addition of nitrogen. These results indicate that the magnitude of defoliation response by an individual plant differs among plant compartments and this response is modulated by other factors, such as time for recovery after defoliation, and nutrient availability. In general, the effect of defoliation on individual plant production was more negative than reported effects of grazing on ecosystem primary production. [source] Psychosocial interventions and quality of life in gynaecological cancer patients: a systematic reviewPSYCHO-ONCOLOGY, Issue 8 2009Jolyn Hersch Abstract Objective: Women with gynaecological cancer are at risk of poor quality of life outcomes. Although various psychosocial interventions have been developed to address these concerns, such interventions have not yet been systematically evaluated in this population. The current review provides an up-to-date and comprehensive summary of the evidence regarding the effectiveness of psychosocial interventions in women with gynaecological cancers. Methods: Relevant studies were identified via Medline, CINAHL, and PsycINFO databases (1980 to June 2008), reference lists of articles and reviews, grey literature databases, and consultations with physicians and other experts in the field. Only controlled trials comparing a psychosocial intervention with a control group in a gynaecological cancer population, with at least one quality of life variable as a main outcome, were included in the review. Two authors independently assessed trial quality and extracted data. Results: Twenty-two studies involving 1926 participants were included. There was substantial variability in study quality and results. Evidence was mixed regarding intervention effects on social and sexual functioning, distress, depression, anxiety, attitude to medical care, self-esteem and body image. Interventions generally did not improve physical or vocational outcomes. Conclusions: There was limited evidence in support of healing touch, whereas information-based interventions seemed largely unable to provide meaningful benefits. Cognitive-behavioural interventions had some positive effects. Counselling appeared to be the most promising intervention strategy for addressing quality of life concerns for women with gynaecological cancers. Copyright © 2008 John Wiley & Sons, Ltd. [source] Method of weighted proportion of reproductive-aged women taking folic acid supplements to predict a neural tube defect rate decline,BIRTH DEFECTS RESEARCH, Issue 12 2003Quanhe Yang Abstract BACKGROUND Neural tube defect (NTD) rates can be lowered by increased consumption of folic acid (FA) by women before and during early pregnancy. The crude proportion of reproductive-aged women taking FA supplements has been used to predict a decline of the NTD rate in the general population. In this study we examine the potential error in using the crude proportion to predict NTD risk reduction, and offer an alternative method. METHODS The crude proportion measures the number of women taking FA. It ignores the substantial variability by maternal age in the probability of giving birth. Age-specific fertility rates (ASFRs) reflect the probability that a woman in a specific age group will give birth in a given year. In this study, we show how to calculate a proportion weighted by ASFRs to predict a decline in the NTD rate, and to assess the effectiveness of FA consumption in preventing NTDs. RESULTS Our results show that a crude proportion of 50% of women (15,49 years old) taking FA is associated with a range of 24,77% in weighted proportions. Assuming a 40% risk reduction from taking 400 ,g of FA daily, the expected NTD rate decline could vary from 9.6% to 30.6%, depending on the age distribution of women taking FA. CONCLUSIONS The ASFR-weighted proportion estimates the proportion of babies born to women taking FA, as opposed to the crude proportion of women taking FA. We recommend using the ASFR-weighted proportion to predict an NTD rate decline and measure the success of FA education campaigns. We found that when women in high-fertility age groups increased their FA consumption, the decline in the NTD rate was greater than when women in low-fertility age groups did so. Our findings suggest that the more efficient approach to NTD prevention is to focus on women with a higher probability of giving birth. For example, by focusing on <50% of women of childbearing age (20,34 years), as much as 76% of the maximum NTD rate reduction can be achieved. Birth Defects Research (Part A), 2003. Published 2003 Wiley-Liss, Inc. [source] Early maladaptive schemas, temperament and character traits in clinically depressed and previously depressed subjects,CLINICAL PSYCHOLOGY AND PSYCHOTHERAPY (AN INTERNATIONAL JOURNAL OF THEORY & PRACTICE), Issue 5 2009Marianne Halvorsen Abstract The Young Schema Questionnaire (YSQ) and the Temperament and Character Inventory (TCI) have been suggested as vulnerability markers for depression. One- hundred forty clinically depressed subjects(CD), previously depressed subjects(PD) and never depressed (ND) controls completed the YSQ, the TCI and the Beck Depression Inventory. Results showed that CD and PD differed significantly on early maladaptive schemas, temperament and character traits compared with ND. In accordance with previous research, higher levels of harm avoidance and lower levels of self-directedness were found in CD and in recovered PD. Moreover, CD and PD showed substantial variability in the scores on the YSQ and the TCI when controlling for concurrent depression severity. In multiple regression analyses, YSQ domain scales of disconnection, impaired autonomy, restricted self-expression and impaired limits emerged as significant predictors of depression severity. Likewise, as concerns TCI higher order scales, high harm avoidance, low self-directedness and high persistence emerged as significant predictors of depression severity. Harm avoidance was positively related to several early maladaptive schemas (EMSs), whereas self-directedness was negatively related to a majority of the EMSs. Our findings indicate the presence of maladaptive personality characteristics in CD and PD. Longitudinal studies are needed to establish their causal role in relation to first-onset and recurrent depression.,Copyright © 2009 John Wiley & Sons, Ltd. Key Practitioner Message: , Early maladaptive schemas, high harm [correction made here after initial online publication] avoidance and low self-directedness may be a part of vulnerability to depression. , The finding of these personality characteristics in subjects recovered from depression indicates malfunctioning to some degree. , Addressing such characteristics in therapy should be considered in order to prevent and treat depression from its relapsing and recurring course. [source] | ||||||||||||||||