Empirical Data (empirical + data)

Distribution by Scientific Domains
Distribution within Life Sciences

Selected Abstracts

Evaluating Permanent Disability Ratings Using Empirical Data on Earnings Losses

Jayanta Bhattacharya
Workers' compensation systems are typically designed to assign higher permanent disability benefits to workers with more severe disabilities. However, little or no scientific work exists to guide the design of ratings systems to properly account for the amount of earnings power lost due to disability. In this article, we examine the effectiveness of disability ratings using matched administrative data on ratings and earnings for a large, representative sample of permanent disability claimants in California. We find that while workers with higher ratings do experience larger earnings losses on average, there are large and persistent differences in average earnings losses for similarly rated impairments in different parts of the body. We then explore how adjusting permanent disability ratings to reflect cross-impairment differences in earnings losses can affect the equity of permanent disability benefits. Adjusting disability ratings to account for typical earnings losses reduces cross-impairment differences substantially. The adjusted ratings result in a more equitable distribution of disability benefits across workers with different impairments. [source]

Models of Municipal Budget Allocation: Empirical Data from Spanish Municipalities

The present work empirically analyzes diverse budgetary theories (incrementalism, garbage can, rational) in municipal cost programs, paying special attention to the utility of financial information in decision making. The sample analyzed corresponds to a set of Spanish city councils in the period 1996,2004, and the econometric methodology used is a dynamic panel data model. The main conclusion reached is that the budgetary allocation of municipal costs does not follow a random path; incrementalism is of particular importance, together with financial information variables. The utility of budgetary indicators is reflected in the fact that municipal managers adopt rational elements, although incrementalism remains the habitual behavior. [source]

Modelling and analysing evolution of dispersal in populations at expanding range boundaries

Abstract 1.,Species would be expected to shift northwards in response to current climate warming, but many are failing to do so because of fragmentation of breeding habitats. Dispersal is important for colonisation and an individual-based spatially explicit model was developed to investigate impacts of habitat availability on the evolution of dispersal in expanding populations. Model output was compared with field data from the speckled wood butterfly Pararge aegeria, which currently is expanding its range in Britain. 2.,During range expansion, models simulated positive linear relationships between dispersal and distance from the seed location. This pattern was observed regardless of quantity (100% to 10% habitat availability) or distribution (random vs. gradient distribution) of habitat, although higher dispersal evolved at expanding range margins in landscapes with greater quantity of habitat and in gradient landscapes. Increased dispersal was no longer evident in any landscape once populations had reached equilibrium; dispersal values returned to those of seed populations. However, in landscapes with the least quantity of habitat, reduced dispersal (below that of seed populations) was observed at equilibrium. 3.,Evolutionary changes in adult flight morphology were examined in six populations of P. aegeria along a transect from the distribution core to an expanding range margin in England (spanning a latitudinal distance of >200 km). Empirical data were in agreement with model output and showed increased dispersal ability (larger and broader thoraxes, smaller abdomens, higher wing aspect ratios) with increasing distance from the distribution core. Increased dispersal ability was evident in populations from areas colonised >30 years previously, although dispersal changes were generally evident only in females. 4.,Evolutionary increases in dispersal ability in expanding populations may help species track future climate changes and counteract impacts of habitat fragmentation by promoting colonisation. However, at the highest levels of habitat loss, increased dispersal was less evident during expansion and reduced dispersal was observed at equilibrium indicating that, for many species, continued habitat fragmentation is likely to outweigh any benefits from dispersal. [source]

Ontogenetically stable hydraulic design in woody plants

Summary 1An important component of plant water transport is the design of the vascular network, including the size and shape of water-conducting elements or xylem conduits. 2For over 100 years, foresters and plant physiologists have recognized that these conduits are consistently smaller near branch tips compared with major branches and the main stem. Empirical data, however, have rarely been assembled to assess the whole-plant hydraulic architecture of woody plants as they age and grow. 3In this paper, we analyse vessels of Fraxinus americana (White Ash) within a single tree. Vessels are measured from cross-sections that span 12 m in height and 18 years' growth. 4We show that vessel radii are determined by distance from the top of the tree, as well as by stem size, independently of tree height or age. 5The qualitative form for the scaling of vessel radii agrees remarkably well with simple power laws, suggesting the existence of an ontogenetically stable hydraulic design that scales in the same manner as a tree grows in height and diameter. 6We discuss the implications of the present findings for optimal theories of hydraulic design. [source]

The interplay between learning and the use of ICT in Rwandan student teachers' everyday practice

E. Mukama
Abstract The paper describes a study conducted in Rwanda involving 12 participants selected from a larger cohort of 24 final-year university students who were part of a group-based training programme. The programme was about how to search, retrieve, and use web-based literature. Empirical data were collected through interviews and focus group discussions. The purpose was to explore ways of using information and communication technology (ICT) in student teachers' everyday learning practice. The study draws from a sociocultural perspective and emphasis is put on a literature review involving ICT in teacher education. The findings reveal that utilization of ICT pertains to three major types of variation among student teachers who use ICT: passive, reluctant, and active users. The active ICT users demonstrated a capacity to cross group boundaries and play a central role as agents of change in learning practice. The point is that more experienced student teachers can assist their colleagues in the zone of proximal development and, therefore, enhance the integration of the new technology in teacher education. This implies that having access to ICT together with some instruction is not sufficient to prompt students to start using this technology as a pedagogical tool. Moreover, confrontation of different experiences regarding the use of ICT can spearhead change in student teachers' learning practice through critical reflection. [source]

REVIEW: The evolution of polyembryony in parasitoid wasps

Abstract Polyembryony has evolved independently in four families of parasitoid wasps. We review three main hypotheses for the selective forces favouring this developmental mode in parasitoids: polyembryony (i) reduces the costs of egg limitation; (ii) reduces the genetic conflict among offspring; and (iii) allows offspring to adjust their numbers to the quality of the host. Using comparative data and verbal and mathematical arguments, we evaluate the relative importance of the different selective forces through different evolutionary stages and in the different groups of polyembryonic wasps. We conclude that reducing the cost of egg limitation is especially important when large broods are favoured. Reducing genetic conflict may be most important when broods are small, thus might have been important during, or immediately following, the initial transition from monoembryony to polyembryony. Empirical data provide little support for the brood-size adjustment hypothesis, although it is likely to interact with other selective forces favouring polyembryony. [source]

Effects of Watershed Impervious Cover on Dissolved Silica Loading in Storm Flow,

Socratis Loucaides
Abstract:, Dissolved silica (DSi) availability is a factor that affects the composition of algal populations in aquatic ecosystems. DSi cycling is tightly linked to the hydrological cycle, which is affected by human alterations of the landscape. Development activities that increase impervious cover change watershed hydrology and may increase the discharge of DSi-poor rainwater and decrease the discharge of DSi-rich ground water into aquatic ecosystems, possibly shifting algal community composition toward less desirable assemblages. In this study, DSi loadings from two adjacent coastal watersheds with different percent impervious cover were compared during four rain and five nonrain events. Loadings in the more impervious watershed contained a significantly larger proportion of surface runoff than base flow (ground-water discharge) and had lower [DSi] water during rain events than the less impervious watershed. Application of the Soil Conservation Service Curve Number (CN) method showed that the minimum rainfall height necessary to yield runoff was significantly lower for the more impervious watershed, implying that runoff volumes increase with impervious cover as well as the frequency of runoff-yielding events. Empirical data collected during this study and estimates derived from the CN method suggest that impervious cover may be responsible for both short-term DSi limitation during rain events as well as long-term reduction of DSi inputs into aquatic ecosystems. [source]

Participation in trauma research: Is there evidence of harm?

Michael G. Griffin
Abstract Few studies have examined the impact of trauma research participation upon trauma survivors. Empirical data regarding reactions to research participation would be very useful to address the question of whether it is harmful for trauma survivors to participate in trauma studies. We examined participant reactions to different trauma assessment procedures in domestic violence (N = 260), rape (N = 108), and physical assault (N = 62) samples. Results indicated that participation was very well tolerated by the vast majority of the trauma survivors. Participants generally found that the assessment experience was not distressing and was, in fact, viewed as an interesting and valuable experience. The findings suggest that trauma survivors are not too fragile to participate in trauma research even in the acute aftermath of a traumatic experience. [source]

Inter-firm sharing of process knowledge: exploring knowledge markets

David G. Bell
Markets and communities are two modalities of knowledge exchange between firms; and this study concludes with a model that addresses the tension between the two modalities. The model resulted from an exploratory study conducted under the umbrella of a national consortium, using the methodology of participatory action research. The study involved three large multinational firms, where one firm supplied knowledge of three different processes used in product development to two other non-competitive firms outside their supply chain. The knowledge was shared within the framework of an intervention that included the following: (1) individual work with process-related course materials via the web or compact disc, followed by (2) interactive group sessions supported by videoconference facilities and led by a process expert from the supplying firm. Empirical data were gathered by interviewing participants before and after the intervention, and by observing interactive group sessions. Findings from the empirical data describe rationales for inter-firm sharing of process knowledge, which illustrate a market modality of exchange; and describe practices for effective knowledge sharing, which illustrate aspects of a community modality of exchange. The model induced from these findings compares the situational setting, constellation of meanings and associated knowledge sharing practices for both modalities of exchange: market and community. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Taming the Tiger: Voting Rights and Political Instability in Latin America

Josep M. Colomer
ABSTRACT This article discusses the relationship between certain institutional regulations of voting rights and elections, different levels of electoral participation, and the degree of political instability in several Latin American political experiences. A formal model specifies the hypotheses that sudden enlargements of the electorate may provoke high levels of political instability, especially under plurality and other restrictive electoral rules, while gradual enlargements of the electorate may prevent much electoral and political innovation and help stability. Empirical data illustrate these hypotheses. A historical survey identifies different patterns of political instability and stability in different countries and periods, which can be compared with the adoption of different voting rights regulations and electoral rules either encouraging or depressing turnout. [source]

Power in telephone-advice nursing

Vesa Leppänen
LEPPÄNEN V. Nursing Inquiry 2010; 17: 15,26 Power in telephone-advice nursing Power is a central aspect of nursing, especially in telephone-advice nursing, where nurses assess callers' medical problems and decide what measures that need to be taken. This article presents a framework for understanding how power operates in social interaction between nurses and callers in telephone-advice nursing in primary care in Sweden. Power is analysed as the result of nurses and callers being oriented to five social structures that are relevant to their actions in this context, namely the organization of telephone-advice nursing, the social stock of medical knowledge, the professional division of labour between nurses and doctors, structures of social interaction and structures of emotions. While structural constraints govern some actions to a high degree, calls take place in an organizational free room that give nurses more leeway for acting more creatively. The discussion focuses on the introduction of new technologies of control, for instance computerized decision support systems and audio recording of calls, and on how they reduce the free room. Empirical data consist of 276 audio-recorded telephone calls to 13 nurses at six primary-care centres and of qualitative interviews with 18 nurses. [source]

Negotiating clinical knowledge: a field study of psychiatric nurses' everyday communication

Niels Buus
Negotiating clinical knowledge: a field study of psychiatric nurses' everyday communication Nursing practices at psychiatric hospitals have changed significantly over the last decades. In this paper, everyday nursing practices were interpreted in light of these institutional changes. The objective was to examine how mental health nurses' production of clinical knowledge was influenced by the particular social relations on hospital wards. Empirical data stemming from an extended fieldwork at two Danish psychiatric hospital wards were interpreted using interactionistic theory and the metaphor: ,the game of clinical knowledge'. The results indicated that the nurses' production of clinical knowledge was highly dependent on the individual nurses' practical ability to participate in the game. Furthermore, the nurses colluded in their mutual communication to enable the collective display and sense of knowing that protected them against explicit signs of uncertainty about the clinic. The game of clinical knowledge influenced processes of clinical decision-making among the nurses as the game added to a distorted widening of a ,fictional distance' between patients and the representations produced by the nurses. [source]

Liberating genetic variance through sex

BIOESSAYS, Issue 6 2003
Andrew D. Peters
Genetic variation in fitness is the fundamental prerequisite for adaptive evolutionary change. If there is no variation in survival and reproduction or if this variation has no genetic basis, then the composition of a population will not evolve over time. Consequently, the factors influencing genetic variation in fitness have received close attention from evolutionary biologists. One key factor is the mode of reproduction. Indeed, it has long been thought that sex enhances fitness variation and that this explains the ubiquity of sexual reproduction among eukaryotes. Nevertheless, theoretical studies have demonstrated that sex need not always increase genetic variation in fitness. In particular, if fitness interactions among beneficial alleles (epistasis) are positive, sex can reduce genetic variance in fitness. Empirical data have been sorely needed to settle the issue of whether sex does enhance fitness variation. A recent flurry of studies1,4 has demonstrated that sex and recombination do dramatically increase genetic variation in fitness and consequently the rate of adaptive evolution. Interpreted in light of evolutionary theory, these studies rule out positive in these experiments epistasis as a major source of genetic associations. Further studies are needed, however, to tease apart other possible sources. BioEssays 25:533,537, 2003. © 2003 Wiley Periodicals, Inc. [source]

Redesigning Public Services: Challenges of Practice for Policy

Terry McNulty
The paper observes a challenge within contemporary public policy to change professional practices and relations to improve public services. Policy-makers' advocacy of process redesign as a best-practice mechanism for effecting change in public-sector organizations is the particular focus of attention. In both theory and method the paper engages an interest in public policy and practice with mainstream developments in the field of organization and management studies. The theoretical framework links debate about process organization, organizational change, professional collaboration and business process re-engineering. The public sector is not immune from the hype of transformation that characterizes much current debate about organization form and change. Empirical data about several redesign interventions that occurred in the context of a hospital re-engineering programme are used to analyse the rhetoric and reality of change in public services. Contested processes and limited effects of re-engineering are discussed for what they reveal about the prospects and possibilities for redesign to effect change in public services. [source]

Effectiveness of Conservation Targets in Capturing Genetic Diversity

Maile C. Neel
We used empirical data from four rare plant taxa to assess these consequences in terms of how well allele numbers ( all alleles and alleles occurring at a frequency openface>0.05 in any population ) and expected heterozygosity are represented when different numbers of populations are conserved. We determined sampling distributions for these three measures of genetic diversity using Monte Carlo methods. We assessed the proportion of alleles included in the number of populations considered adequate for conservation, needed to capture all alleles, and needed to meet an accepted standard of genetic-diversity conservation of having a 90,95% probability of including all common alleles. We also assessed the number of populations necessary to obtain values of heterozygosity within ±10% of the value obtained from all populations. Numbers of alleles were strongly affected by the number of populations sampled. Heterozygosity was only slightly less sensitive to numbers of populations than were alleles. On average, currently advocated conservation intensities represented 67,83% of all alleles and 85,93% of common alleles. The smallest number of populations to include all alleles ranged from 6 to 17 ( 42,57% ), but <0.2% of 1000 samples of these numbers of populations included them all. It was necessary to conserve 16,29 ( 53,93% ) of the sampled populations to meet the standard for common alleles. Between 20% and 64% of populations were needed to reliably represent species-level heterozygosity. Thus, higher percentages of populations are needed than are currently considered adequate to conserve genetic diversity if populations are selected without genetic data. Resumen: Cualquier acción de conservación que preserve algunas poblaciones y no otras tendrá consecuencias genéticas. Utilizamos datos empíricos de cuatro taxones de plantas raras para evaluar estas consecuencias en términos de lo bien representados que están los números de alelos ( todos los alelos ocurriendo a una frecuencia>0.05 en cualquier población ) y la heterocigosidad esperada cuando se conservan diferentes números de poblaciones. Las distribuciones de muestreo de estas tres medidas de la diversidad genética fueron determinadas utilizando métodos Monte Carlo. Evaluamos la proporción de alelos incluida en números de poblaciones: consideradas adecuadas para la conservación; requeridas para capturar todos los alelos; y las requeridas para alcanzar un estándar de conservación de diversidad genética aceptable del 90,95% de probabilidad de incluir todos los alelos comunes. También evaluamos el número de poblaciones necesarias para obtener valores de heterocigosidad que caigan dentro de ±10% del valor obtenido de todas las poblaciones. Los números de alelos fueron afectados significativamente por el número de poblaciones muestreadas. La heterocigosidad solo fue ligeramente menos sensible a los números de poblaciones de lo que fueron los alelos. Las intensidades de conservación propugnadas actualmente representaron en promedio el 67,83% de todos los alelos y el 85,93% de los alelos comunes. El menor número de poblaciones para incluir a todos los alelos varió de 6 a 17 ( 42,57% ), pero <0.2% de 1000 muestras de esos números de poblaciones los incluyó a todos. Fue necesario conservar de 16 a 29 ( 53,93% ) de las poblaciones muestreadas para alcanzar el estándar para los alelos comunes. Se requirió entre 20% y 64% de las poblaciones para representar la heterocigosidad a nivel de especie confiablemente. Por lo tanto, se requieren mayores porcentajes de poblaciones que los actualmente considerados adecuados para conservar la diversidad genética si las poblaciones son seleccionadas sin datos genéticos. [source]

Technology Forecasting: From Emotional to Empirical

Michael S. Slocum
Technology Forecasting has evolved from being a methodology based on emotional responses to one predicated on data collection. The Theory of Inventive Problem Solving (TRIZ) is a theory based on empirical data that relates technological evolution to the same stages of biological macro-evolution. This paper will explore the major emotional forecasting methods as well as discuss part of TRIZ Technology Forecasting called Maturity Mapping. The reader will briefly be introduced to eight evolutionary trends based on TRIZ. [source]

Do mood disorders alter crying? a pilot investigation

Jonathan Rottenberg Ph.D.
Abstract Clinical commentators widely interpret crying as a sign of depressed mood. However, there is virtually no empirical data on this topic, and the evidence that mood disorders alter crying is surprisingly weak. This study compared mood disordered patients to a nonpsychiatric reference group on the frequency, antecedents, and consequences of crying behavior using a well-validated questionnaire measure of crying. Forty-four outpatients diagnosed with three forms of mood pathology were age and gender matched to a reference group of 132 participants sampled to be representative of the Dutch population. Both groups completed the Adult Crying Inventory, which provides estimates of the self-reported frequency, antecedents, and consequences of crying behavior. Depression severity and psychiatric symptom severity data were also collected from patients. Compared with the reference group, patients with mood pathology reported increased cry proneness to negative antecedents. By contrast, patients and controls did not differ in reported cry proneness to positive antecedents. Patients reported less mood improvement after crying than did controls. Among male patients, but not female patients, depression severity was associated with increased crying proneness and increased crying frequency. This pilot investigation suggests that mood disorders increase the frequency of negative emotional crying, and may also alter the functions of this behavior. Mood disorders may influence male crying to a greater extent than female crying. Future directions designed to clarify the causal pathways between mood disorders and alterations in crying behavior are discussed. Depression and Anxiety 0:1,7, 2007. © 2007 Wiley-Liss, Inc. [source]

Ethnic Inequalities in the Public Sector: A Comparative Analysis

Yusuf Bangura
This article uses empirical data to discuss the links between ethnicity, inequality and governance in a framework that divides countries according to their levels of ethnic polarization. It makes three main arguments. First, types of diversity, not the existence of diversity per se, explain potentials for conflict or cohesion in multiethnic societies. Ethnic cleavages are configured differently in different social structures and are less conflictual in some countries than in others. Second, relative balance has been achieved in the public sectors of countries that are highly fragmented or those with ethnicity-sensitive policies, but not in those with ethnicity-blind policies. Third, the article is critical of institutional approaches to conflict management that underplay background conditions in shaping choices. Consociational arrangements may not be relevant in unipolar ethnic settings or fragmented multiethnic societies, where governments may be ethnically inclusive under democratic conditions. They seem unavoidable in ethnic settings with two or three main groups or in settings with strong ethnic/regional clusters. [source]

Land Tenure Insecurity and Inequality in Nicaragua

Rikke J. Broegaard
This article uses empirical data from a case study in rural Nicaragua to demonstrate the need for a conceptualization of tenure security as seen from the perspective of the landholder. A large group of farmers in the case study area perceive their tenure situation as being insecure despite the fact that they possess a legal title to their land. The article argues that more attention must be paid to aspects such as inequalities of wealth and power, lack of enforcement and lack of impartiality on the part of the formal institutions when addressing tenure security in an institutionally unstable setting, such as that found in Nicaragua. The article contributes to the ongoing discussion by arguing that future research on how to increase rural land tenure security should explore the concept of tenure security as experienced by farmers. [source]

Unequal Knowledges in Jharkhand, India: De-Romanticizing Women's Agroecological Expertise

Sarah Jewitt
Taking the Jharkhand region of India as a case study, this article uses empirical data to intervene in ,women, environment and development' and ecofeminist debates regarding women's environmental knowledge. The article first outlines the adoption of gender/environmental issues into development planning and considers the dangers of overestimating women's agroecological knowledges and assuming that they can easily participate in development projects. It then highlights the local complexities of environmental knowledge possession and control with reference to gender and other variations in agricultural participation, decision-making and knowledge transfers between villagers' natal and marital places. Particular emphasis is placed on the economic, socio-cultural and ,actor' related factors that supplement gender as an influence on task allocation, decision-making, knowledge distribution and knowledge articulation. The article concludes that given the socio-cultural constraints women face in accumulating and vocalizing environmental knowledge, simplistic participatory approaches are unlikely to empower them. Instead, more flexible, site-specific development initiatives (coupled with wider structural change) are required if opportunities are to be created for women to develop and use their agroecological knowledges. [source]

Psychological effects of prevention: do participants of a type 2 diabetes prevention program experience increased mental distress?

Katrin E. Giel
Abstract Objective To evaluate the mental health outcome of a lifestyle intervention for the prevention of type 2 diabetes and to exclude possible harmful psychological effects. Background There is little empirical data on potential harmful effects of prevention programs. However, information, education, diagnostic procedures, phenotyping and risk assessment may cause or intensify psychological distress such as anxiety, depression or somatization in vulnerable individuals. Methods The Tuebingen Lifestyle Intervention Program (TULIP) for the prevention of type 2 diabetes has assessed mental health outcome in the participants after 9 months of program participation using the Symptom Checklist-90-R (SCL-90-R). The 24-months lifestyle intervention TULIP comprises regular exercise and changes in nutrition and assesses both, a broad range of somatic parameters as well as psychometric variables. For an interim analysis of psychological outcome, complete data sets of the SCL-90-R assessed at baseline and after 9 months of intervention were available for 195 participants (125 females, 70 males; age: 46.1 ± 10.6 years). Data on somatization, anxiety, depression and overall psychological distress were compared to baseline levels. Results SCL-90-R scores of the TULIP-participants did not significantly differ from the German healthy reference population. Compared to baseline, a significant decrease in SCL-90-R scores was found for anxiety, depression and overall psychological distress at re-assessment after 9 months. Conclusion The interim analysis on mental health outcome of a type 2 diabetes prevention program comprising extensive phenotyping and risk assessment rules out adverse psychological effects, suggesting rather beneficial changes concerning symptoms of anxiety, depression and overall psychological distress. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Bridging the gap between field data and global models: current strategies in aeolian research

Joanna Bullard
Abstract Modern global models of earth-atmosphere-ocean processes are becoming increasingly sophisticated but still require validation against empirical data and observations. This commentary reports on international initiatives amongst aeolian researchers that seek to combine field-based data sets and geomorphological frameworks for improving the quality of data available to constrain and validate global models. These include a second iteration of the Dust Indicators and Records from Terrestrial Marine Palaeoenvironments (DIRTMAP2) database, the Digital Atlas of Sand Seas and Dunefields of the World and a new geomorphology-based land surface map produced by the QUEST (Quantifying Uncertainties in the Earth System) Working Group on Dust. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Meltwater discharge through the subglacial bed and its land-forming consequences from numerical experiments in the Polish lowland during the last glaciation

Jan A. Piotrowski
Abstract Numerical experiments suggest that the last glaciation severely affected the upper lithosphere groundwater system in NW Poland: primarily its flow pattern, velocities and fluxes. We have simulated subglacial groundwater flow in two and three spatial dimensions using finite difference codes for steady-state and transient conditions. The results show how profoundly the ice sheet modifies groundwater pressure heads beneath and some distance beyond the ice margin. All model runs show water discharge at the ice forefield driven by ice-sheet-thickness-modulated, down-ice-decreasing hydraulic heads. In relation to non-glacial times, the transient 3D model shows significant changes in the groundwater flow directions in a regionally extensive aquifer ca. 90 m below the ice,bed interface and up to 40 km in front of the glacier. Comparison with empirical data suggests that, depending on the model run, only between 5 and 24% of the meltwater formed at the ice sole drained through the bed as groundwater. This is consistent with field observations documenting abundant occurrence of tunnel valleys, indicating that the remaining portion of basal meltwater was evacuated through a channelized subglacial drainage system. Groundwater flow simulation suggests that in areas of very low hydraulic conductivity and adverse subglacial slopes water ponding at the ice sole was likely. In these areas the relief shows distinct palaeo-ice lobes, indicating fast ice flow, possibly triggered by the undrained water at the ice,bed interface. Owing to the abundance of low-permeability strata in the bed, the simulated groundwater flow depth is less than ca. 200 m. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Seismic vulnerability assessment using regional empirical data

Ahmet Yakut
Abstract This article presents a procedure developed for the seismic performance assessment of low- to mid-rise reinforced concrete buildings in Turkey. The past performance of reinforced concrete buildings during major earthquakes have been compiled and analysed comprehensively using statistical procedures in order to study the empirical correlation between the significant damage inducing parameters and the observed damage. A damage database of nearly 500 representative buildings experiencing the 1999 Kocaeli and Düzce earthquakes have been used and discriminant functions expressing damage score in terms of six damage inducing parameters have been developed. In order to extrapolate the procedure to other regions that are likely to be subjected to major earthquakes a new approach that takes into account different local soil conditions, site-to-source distance and the magnitude of the earthquake has been introduced. The procedure has been applied to a pilot area in Istanbul to estimate expected damage distribution under a credible scenario earthquake. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Density-dependent dispersal in birds and mammals

ECOGRAPHY, Issue 3 2005
Erik Matthysen
Density-dependent dispersal can be caused by various mechanisms, from competition inducing individuals to emigrate (positive density-dependence) to social crowding effects impeding free movement (negative density-dependence). Various spatial population models have incorporated positively density-dependent dispersal algorithms, and recent theoretical models have explored the conditions for density-dependent dispersal (DD) to evolve. However, while the existence of DD is well documented in some taxa such as insects, there is no clear picture on its generality in vertebrates. Here I review the available empirical data on DD in birds and mammals, focusing mainly on variation in dispersal between years and on experimental density manipulations. Surprisingly few studies have explicitly focused on DD, and interpretation of the available data is often hampered by differences in approach, small sample sizes and/or statistical shortcomings. Positive DD was reported in 50 and 33% of the selected mammal and bird studies, respectively, while two studies on mammals (out of eight) reported negative DD. Among bird studies, DD was more often reported for emigration rates or long-distance recoveries than for average distances within finite study areas. Experimental studies manipulating densities (mainly on mammals) have consistently generated positive DD, typically showing reduced emigration in response to partial population removal. Studies that examined dispersal in relation to seasonal changes in density (small mammals only) have more often reported negative DD. Studies that compared dispersal between sites differing in density, also show a mixture of positive and negative DD. This suggests that dispersal changes in a more complex way with seasonal and spatial density variation than with annual densities, and/or that these results are confounded by other factors differing between seasons and sites, such as habitat quality. I conclude that both correlational and experimental studies support the existence of positive, rather than negative, density-dependent dispersal in birds and mammals. [source]

Effects of the North Atlantic Oscillation on growth and phenology of stream insects

ECOGRAPHY, Issue 6 2004
Robert A. Briers
Climatic variation associated with the North Atlantic Oscillation (NAO) influences terrestrial and marine ecosystems, but its effects on river and stream ecosystems are less well known. The influence of the NAO on the growth of stream insects was examined using long-term empirical data on the sizes of mayfly and stonefly nymphs and on water temperature data. Models of egg development and nymphal growth in relation to temperature were used to predict the effect of the NAO on phenology. The study was based in two upland streams in mid-Wales UK that varied in the extent of plantation forestry in their catchments. Winter stream temperatures at both sites were positively related to the winter NAO index, being warmer in positive phases and colder in negative phases. The observed mean size and the simulated developmental period of mayfly nymphs were significantly related to the winter NAO index, with nymphs growing faster in positive phases of the NAO, but the growth of stonefly nymphs was not related to the NAO. This may have been due to the semivoltine stonefly lifecycle, but stonefly nymph growth is also generally less dependent on temperature. There were significant differences in growth rates of both species between streams, with nymphs growing more slowly in the forested stream that was consistently cooler than the open stream. Predicted emergence dates for adult mayflies varied by nearly two months between years, depending on the phase of the NAO. Variation in growth and phenology of stream insects associated with the NAO may influence temporal fluctuations in the composition and dynamics of stream communities. [source]

Stoichiometry of endothermy: shifting the quest from nitrogen to carbon

Marcel Klaassen
Abstract For many animals, notably herbivores, plants are often an inadequate food source given the low content of protein and high content of C-rich material. This conception is mainly based on studies on ectotherms. The validity of this conception for endotherms is unclear given their much higher carbon requirements for maintenance energy metabolism than ectotherms. Applying stoichiometric principles, we hypothesized that endotherms can cope with diets with much higher (metabolizable) carbon to nitrogen ratios than ectotherms. Using empirical data on birds, eutherian mammals, marsupials and reptiles, we compiled and compared measurements and allometric equations for energy metabolism as well as nitrogen requirements. Our analysis supports our hypothesis that plants, and especially their leaves, are generally sufficiently rich in nitrogen to fulfil protein demands in endotherms, at least during maintenance conditions, but less so in ectotherms. This has important implications with respect to community functioning and the evolution of endothermy. [source]

Setting the absolute tempo of biodiversity dynamics

Andrew P. Allen
Abstract Neutral biodiversity theory has the potential to contribute to our understanding of how macroevolutionary dynamics influence contemporary biodiversity, but there are issues regarding its dynamical predictions that must first be resolved. Here we address these issues by extending the theory in two ways using a novel analytical approach: (1) we set the absolute tempo of biodiversity dynamics by explicitly incorporating population-level stochasticity in abundance; (2) we allow new species to arise with more than one individual. Setting the absolute tempo yields quantitative predictions on biodiversity dynamics that can be tested using contemporary and fossil data. Allowing incipient-species abundances greater than one individual yields predictions on how these dynamics, and the form of the species-abundance distribution, are affected by multiple speciation modes. We apply this new model to contemporary and fossil data that encompass 30 Myr of macroevolution for planktonic foraminifera. By synthesizing the model with these empirical data, we present evidence that dynamical issues with neutral biodiversity theory may be resolved by incorporating the effects of environmental stochasticity and incipient-species abundance on biodiversity dynamics. [source]

Antagonistic effects of seed dispersal and herbivory on plant migration

Mark Vellend
Abstract The two factors that determine plant migration rates , seed dispersal and population growth , are generally treated independently, despite the fact that many animals simultaneously enhance plant migration rate via seed dispersal, and decrease it via negative effects of herbivory on population growth. Using extensive empirical data, we modelled the antagonistic effects of seed dispersal and herbivory by white-tailed deer on potential migration rates of Trillium grandiflorum, a forest herb in eastern North America. This novel antagonistic interaction is illustrated by maximum migration rates occurring at intermediate, but low herbivory (< 15%). Assuming herbivory < 20% and favourable conditions for population growth during post-glacial migration, seed dispersal by deer can explain rates of migration achieved in the past, in contrast to previous models of forest herb migration. However, relatively unfavourable conditions for population growth and increasingly intense herbivory by deer may compromise plant migration in the face of present and future climate change. [source]

State Policy, Economic Crisis, Gender, and Family Ties: Determinants of Family Remittances to Cuba

Sarah A. Blue
Abstract: This article advances the argument that changing economic conditions in the home country act as an important determinant for sending remittances. Research on the determinants of remittances has tended to focus on the characteristics of the sending population. In the case of Cuba, disproportionate attention is paid to political disincentives to send remittances and not enough to changing state policy and the growing economic demand for remittances in that country. Using empirical data gathered from households in Havana, this article tests the importance of economic conditions in the home country, political ideology, the relationship of the sender to the receiver, the length of time away from home, and gender as determinants for remittances. Migration during an economic crisis, having immediate relatives in the home country, and female gender positively influenced remittance behavior for Cuban emigrants. Visits to the home country, especially for migrants who had left decades earlier, were found to be critical for reestablishing family connections and increasing remittances. No support was found for political disincentives as a major determinant of remittance sending to Cuba. [source]