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Sample records for turnover explain species

  1. Scale dependence in species turnover reflects variance in species occupancy.

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    McGlinn, Daniel J; Hurlbert, Allen H

    2012-02-01

    Patterns of species turnover may reflect the processes driving community dynamics across scales. While the majority of studies on species turnover have examined pairwise comparison metrics (e.g., the average Jaccard dissimilarity), it has been proposed that the species-area relationship (SAR) also offers insight into patterns of species turnover because these two patterns may be analytically linked. However, these previous links only apply in a special case where turnover is scale invariant, and we demonstrate across three different plant communities that over 90% of the pairwise turnover values are larger than expected based on scale-invariant predictions from the SAR. Furthermore, the degree of scale dependence in turnover was negatively related to the degree of variance in the occupancy frequency distribution (OFD). These findings suggest that species turnover diverges from scale invariance, and as such pairwise turnover and the slope of the SAR are not redundant. Furthermore, models developed to explain the OFD should be linked with those developed to explain species turnover to achieve a more unified understanding of community structure.

  2. Explaining the Gap in Charter and Traditional Public School Teacher Turnover Rates

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    Stuit, David A.; Smith, Thomas M.

    2012-01-01

    This study uses national survey data to examine why charter school teachers are more likely to turnover than their traditional public school counterparts. We test whether the turnover gap is explained by different distributions of factors that are empirically and theoretically linked to turnover risk. We find that the turnover rate of charter…

  3. Explaining turnover intention in Korean public community hospitals: occupational differences.

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    Hwang, Jee-In; Chang, Hyejung

    2008-01-01

    Personnel in public hospitals had relatively low job satisfaction despite of tenure employment. High turnover rates degrade hospital image and incur additional costs related to recruitment and training. The purposes of this study were to describe the occupational differences and to identify factors affecting turnover intention among public hospital personnel. A questionnaire survey was conducted as part of Administrative Services Quality Evaluation Program by Seoul metropolitan municipality from 1 November to 1 December in 2003. The subjects were 1251 entire hospital personnel in four hospitals. The questionnaire was designed to measure job satisfaction, organizational commitment, turnover intention, and demographic characteristics. Logistic regression analysis was performed to determine factors influencing turnover intention. There were significant differences in job satisfaction, organizational commitment, and turnover intention according to the occupations. The turnover intention rates were highest among physicians, followed by paramedicals and nursing staffs and then administrators. The significant factors affecting turnover intention were involvement and loyalty among physicians, hospital type, satisfaction with systems and loyalty among nursing staffs, satisfaction with relationship and loyalty among administrators, and loyalty among paramedicals. There were different moderators that influence turnover intentions of hospital personnel. Loyalty had the most important effect upon turnover intention in all occupations. 2007 John Wiley & Sons, Ltd

  4. Pitfalls in quantifying species turnover: the residency effect

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    Kevin Chase Burns

    2014-03-01

    Full Text Available The composition of ecological communities changes continuously through time and space. Understanding this turnover in species composition is a central goal in biogeography, but quantifying species turnover can be problematic. Here, I describe an underappreciated source of bias in quantifying species turnover, namely ‘the residency effect’, which occurs when the contiguous distributions of species across sampling domains are small relative to census intervals. I present the results of a simulation model that illustrates the problem theoretically and then I demonstrate the problem empirically using a long-term dataset of plant species turnover on islands. Results from both exercises indicate that empirical estimates of species turnover may be susceptible to significant observer bias, which may potentially cloud a better understanding of how the composition of ecological communities changes through time.

  5. Seasonal species interactions minimize the impact of species turnover on the likelihood of community persistence.

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    Saavedra, Serguei; Rohr, Rudolf P; Fortuna, Miguel A; Selva, Nuria; Bascompte, Jordi

    2016-04-01

    Many of the observed species interactions embedded in ecological communities are not permanent, but are characterized by temporal changes that are observed along with abiotic and biotic variations. While work has been done describing and quantifying these changes, little is known about their consequences for species coexistence. Here, we investigate the extent to which changes of species composition impact the likelihood of persistence of the predator-prey community in the highly seasonal Białowieza Primeval Forest (northeast Poland), and the extent to which seasonal changes of species interactions (predator diet) modulate the expected impact. This likelihood is estimated extending recent developments on the study of structural stability in ecological communities. We find that the observed species turnover strongly varies the likelihood of community persistence between summer and winter. Importantly, we demonstrate that the observed seasonal interaction changes minimize the variation in the likelihood of persistence associated with species turnover across the year. We find that these community dynamics can be explained as the coupling of individual species to their environment by minimizing both the variation in persistence conditions and the interaction changes between seasons. Our results provide a homeostatic explanation for seasonal species interactions and suggest that monitoring the association of interactions changes with the level of variation in community dynamics can provide a good indicator of the response of species to environmental pressures.

  6. Species turnover and geographic distance in an urban river network

    DEFF Research Database (Denmark)

    Rouquette, James R.; Dallimer, Martin; Armsworth, Paul R.

    2013-01-01

    AimUnderstanding the relationships between species turnover, environmental features and the geographic distance between sites can provide important insights into the processes driving species diversity. This is particularly relevant where the effective distance between sites may be a function...... patterns of species turnover and to determine whether these patterns differ between different taxonomic groups. LocationSheffield area, UK. MethodsAquatic (macroinvertebrates, diatoms) and terrestrial (birds, plants, butterflies) organisms were surveyed at 41 sites across an urban river network. We...... of the geographic distance measures, although network distance remained significant for birds and some plant groups after removing the effect of environmental distance. Water-dispersed and neophyte plant groups were significantly related to network and flow distance. Main conclusionsThe results suggest that aquatic...

  7. Species Turnover through Time: Colonization and Extinction Dynamics across Metacommunities.

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    Nuvoloni, Felipe Micali; Feres, Reinaldo José Fazzio; Gilbert, Benjamin

    2016-06-01

    Island biogeography and metacommunity theory often use equilibrium assumptions to predict local diversity, yet nonequilibrium dynamics are common in nature. In nonequilibrium communities, local diversity fluctuates through time as the relative importance of colonization and extinction change. Here, we test the prevalence and causes of nonequilibrium dynamics in metacommunities of mites associated with rubber trees distributed over large spatial (>1,000 km) and temporal (>30-60 generations) scales in Brazil. We measured colonization and extinction rates to test species turnover and nonequilibrium dynamics over a growing season. Mite metacommunities exhibited nonequilibrium dynamics for most months of the year, and these dynamics tracked climatic conditions. Monthly shifts in temperature of more than 1°C resulted in nonequilibrium dynamics, as did mean temperatures outside of two critical ranges. Nonequilibrium dynamics were caused by a change in colonization with temperature change and changes in both colonization and extinction with absolute temperature. Species turnover showed different trends; high relative humidity increased both colonization and extinction rates, increasing turnover but not nonequilibrium dynamics. Our study illustrates that testing nonequilibrium dynamics can provide new insights into the drivers of colonization, extinction, and diversity fluctuations in metacommunities.

  8. Birds on the move in the face of climate change: High species turnover in northern Europe.

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    Virkkala, Raimo; Lehikoinen, Aleksi

    2017-10-01

    Species richness is predicted to increase in the northern latitudes in the warming climate due to ranges of many southern species expanding northwards. We studied changes in the composition of the whole avifauna and in bird species richness in a period of already warming climate in Finland (in northern Europe) covering 1,100 km in south-north gradient across the boreal zone (over 300,000 km 2 ). We compared bird species richness and species-specific changes (for all 235 bird species that occur in Finland) in range size (number of squares occupied) and range shifts (measured as median of area of occupancy) based on bird atlas studies between 1974-1989 and 2006-2010. In addition, we tested how the habitat preference and migration strategy of species explain species-specific variation in the change of the range size. The study was carried out in 10 km squares with similar research intensity in both time periods. The species richness did not change significantly between the two time periods. The composition of the bird fauna, however, changed considerably with 37.0% of species showing an increase and 34.9% a decrease in the numbers of occupied squares, that is, about equal number of species gained and lost their range. Altogether 95.7% of all species (225/235) showed changes either in the numbers of occupied squares or they experienced a range shift (or both). The range size of archipelago birds increased and long-distance migrants declined significantly. Range loss observed in long-distance migrants is in line with the observed population declines of long-distance migrants in the whole Europe. The results show that there is an ongoing considerable species turnover due to climate change and due to land use and other direct human influence. High bird species turnover observed in northern Europe may also affect the functional diversity of species communities.

  9. Photosynthate consumption and carbon turnover in the rhizosphere depending on plant species and growth conditions

    International Nuclear Information System (INIS)

    Sauerbeck, D.R.; Helal, H.M.; Nonnen, S.; Allard, J.-l.

    1982-01-01

    The root tissue which can be isolated from soils represents only part of the total plant carbon incorporation. Between 20 and 40% of the photosynthetic production of plants is expended for root growth and root metabolism. This indicates a striking turnover of energy in the rhizosphere, because relatively litle root-derived organic matter remains there until harvest time. Plant species and variety, soil conditions and temperature were shown to be the most decisive factors governing the assimilate consumption of plant root systems. A special technique is described which enables to study how this extensive turnover affects the surrounding soil depending on its proximity to the roots. Plant-derived carbon can be detected up to 20mm away from the roots. A priming effect has been found on the decomposition of soil organic matter. This explains why, in spite of the rhizo-deposition mentioned, no net-accumulation of carbon in the rhizosphere has been found. (Author) [pt

  10. Happily ever after?: Explaining turnover and retirement intentions of older workers in The Netherlands

    NARCIS (Netherlands)

    M. Fleischmann (Maria); J.F. Ybema (Jan Fekke); F. Koster (Ferry)

    2013-01-01

    markdownabstractPurpose: This paper aims to provide an empirical test of theories proposed in the literature stating that turnover and retirement (two kinds of work withdrawal) involve different employee decisions. It also aims to provide a more general theoretical framework understanding turnover

  11. Happily ever after? Explaining turnover and retirement intentions of older workers in the Netherlands

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    Munderlein, M.; Ybema, J.F.; Koster, F.

    2013-01-01

    Purpose – This paper aims to provide an empirical test of theories proposed in the literature stating that turnover and retirement (two kinds of work withdrawal) involve different employee decisions. It also aims to provide a more general theoretical framework understanding turnover and retirement

  12. The consequences of time averaging for measuring temporal species turnover in the fossil record

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    Tomašových, Adam; Kidwell, Susan

    2010-05-01

    Modeling time averaging effects with simple simulations allows us to evaluate the magnitude of change in temporal species turnover that is expected to occur in long (paleoecological) time series with fossil assemblages. Distinguishing different modes of metacommunity dynamics (such as neutral, density-dependent, or trade-off dynamics) with time-averaged fossil assemblages requires scaling-up time-averaging effects because the decrease in temporal resolution and the decrease in temporal inter-sample separation (i.e., the two main effects of time averaging) substantially increase community stability relative to assemblages without or with weak time averaging. Large changes in temporal scale that cover centuries to millennia can lead to unprecedented effects on temporal rate of change in species composition. Temporal variation in species composition monotonically decreases with increasing duration of time-averaging in simulated fossil assemblages. Time averaging is also associated with the reduction of species dominance owing to the temporal switching in the identity of dominant species. High degrees of time averaging can cause that community parameters of local fossil assemblages converge to parameters of metacommunity rather that to parameters of individual local non-averaged communities. We find that the low variation in species composition observed among mollusk and ostracod subfossil assemblages can be explained by time averaging alone, and low temporal resolution and reduced temporal separation among assemblages in time series can thus explain a substantial part of the reduced variation in species composition relative to unscaled predictions of neutral model (i.e., species do not differ in birth, death, and immigration rates on per capita basis). The structure of time-averaged assemblages can thus provide important insights into processes that act over larger temporal scales, such as evolution of niches and dispersal, range-limit dynamics, taxon cycles, and

  13. Reversal in the relationship between species richness and turnover in a phytoplankton community.

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    Matthews, Blake; Pomati, Francesco

    2012-11-01

    Negative relationships between species richness and the rate of compositional turnover are common, suggesting that diverse communities have greater stability than depauperate ones; however, the mechanistic basis for this pattern is still widely debated. Species richness and turnover can covary either because they are mechanistically linked or because they share common environmental drivers. Few empirical studies have combined long-term changes in community composition with multiple drivers of environmental change, and so little is known about how the underlying mechanisms of species coexistence interact with changes in the mean and variability of environmental conditions. Here, we use a 33 year long time series (1976-2008) of phytoplankton community composition from Lake Zurich, to examine how environmental variation influences the relationship between richness and annual turnover. We find that the relationship between richness and annual turnover reverses midway through the time series (1992-1993), leading to a hump-shaped relationship between species richness and annual turnover. Using structural equation modeling we show that annual turnover and diversity are independently associated with different drivers of environmental change. Furthermore, we find that the observed annual sequences of community assembly give rise to rates of species accumulation that are more heterogeneous through time than expected by chance, likely owing to a high proportion of species showing significant autocorrelation and to strong positive covariation in the occurrences of species.

  14. Effects of water and nitrogen addition on species turnover in temperate grasslands in northern China.

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    Zhuwen Xu

    Full Text Available Global nitrogen (N deposition and climate change have been identified as two of the most important causes of current plant diversity loss. However, temporal patterns of species turnover underlying diversity changes in response to changing precipitation regimes and atmospheric N deposition have received inadequate attention. We carried out a manipulation experiment in a steppe and an old-field in North China from 2005 to 2009, to test the hypothesis that water addition enhances plant species richness through increase in the rate of species gain and decrease in the rate of species loss, while N addition has opposite effects on species changes. Our results showed that water addition increased the rate of species gain in both the steppe and the old field but decreased the rates of species loss and turnover in the old field. In contrast, N addition increased the rates of species loss and turnover in the steppe but decreased the rate of species gain in the old field. The rate of species change was greater in the old field than in the steppe. Water interacted with N to affect species richness and species turnover, indicating that the impacts of N on semi-arid grasslands were largely mediated by water availability. The temporal stability of communities was negatively correlated with rates of species loss and turnover, suggesting that water addition might enhance, but N addition would reduce the compositional stability of grasslands. Experimental results support our initial hypothesis and demonstrate that water and N availabilities differed in the effects on rate of species change in the temperate grasslands, and these effects also depend on grassland types and/or land-use history. Species gain and loss together contribute to the dynamic change of species richness in semi-arid grasslands under future climate change.

  15. Bird species turnover is related to changing predation risk along a vegetation gradient

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    LaManna, Joseph A.; Hemenway, Amy B.; Boccadori, Vanna; Martin, Thomas E.

    2015-01-01

    Turnover in animal species along vegetation gradients is often assumed to reflect adaptive habitat preferences that are narrower than the full gradient. Specifically, animals may decline in abundance where their reproductive success is low, and these poor-quality locations differ among species. Yet habitat use does not always appear adaptive. The crucial tests of how abundances and demographic costs of animals vary along experimentally manipulated vegetation gradients are lacking. We examined habitat use and nest predation rates for 16 bird species that exhibited turnover with shifts in deciduous and coniferous vegetation. For most bird species, decreasing abundance was associated with increasing predation rates along both natural and experimentally modified vegetation gradients. This landscape-scale approach strongly supports the idea that vegetation-mediated effects of predation are associated with animal distributions and species turnover.

  16. Soil respiration and rates of soil carbon turnover differ among six common European tree species

    DEFF Research Database (Denmark)

    Vesterdal, Lars; Elberling, Bo; Christiansen, Jesper Riis

    2012-01-01

    replicated at six sites in Denmark. The studied tree species were the broadleaves beech (Fagus sylvatica L.), pedunculate oak (Quercus robur L.), lime (Tilia cordata L.), sycamore maple (Acer pseudoplatanus L.) and ash (Fraxinus excelsior L.) and the conifer Norway spruce (Picea abies (L.) Karst.). Rates....... Soil respiration differed significantly among several species and increased in the order beechmaple... moisture. Carbon turnover rates based on the ratio between R h and C stock were significantly higher in ash than in all other species except maple, and maple also had higher C turnover than spruce. A similar influence of tree species on C turnover was indicated by the litterfall C to forest floor C ratio...

  17. Patterns of plant diversity loss and species turnover resulting from land abandonment and intensification in semi-natural grasslands.

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    Uchida, Kei; Koyanagi, Tomoyo F; Matsumura, Toshikazu; Koyama, Asuka

    2018-07-15

    Land-use changes cause biodiversity loss in semi-natural ecosystems worldwide. Biotic homogenization has led to biodiversity loss, mainly through declines in species composition turnover. Elucidating patterns of turnover in species composition could enhance our understanding of how anthropogenic activities affect community assembly. Here, we focused on whether the decreasing patterns in plant diversity and turnover of species composition resulting from land-use change vary in two regions. We estimated the species diversity and composition of semi-natural grasslands surrounding paddy fields in satoyama landscapes. We examined the differences in species diversity and composition across three land-use types (abandoned, traditional, and intensified) in two regions (Hyogo and Niigata Prefectures, Japan), which were characterized by different climatic conditions. We then assessed alpha-, beta-, and gamma-diversity to compare the patterns of diversity losses in the two regions as a result of land-use changes. In each region, gamma-diversity was consistently higher in the traditional sites compared to abandoned or intensified sites. The analyses revealed that most of the beta-diversity in traditional sites differed significantly from those of abandoned and intensified sites in both regions. However, the beta-diversity of total and perennial species did not differ between traditional and abandoned sites in the Hyogo region. We noted that the beta-diversity of total and perennial species in intensified sites was much lower than that in the traditional sites of the Niigata region. Overall, the patterns of alpha- and gamma-diversity loss were similar in both study regions. Although the biotic homogenization was caused by intensified land-use in the Niigata region, this hypothesis did not completely explain the loss of biodiversity in the abandoned sites in the Hyogo region. The present study contributes to the growing body of work investigating changes in biodiversity as a

  18. Tritium water as a marker for the measurement of body water turnover rates in desert livestock, rodent and bird species

    International Nuclear Information System (INIS)

    Khan, M.S.; Ghosh, P.K.; Bohra, R.C.

    1990-01-01

    Tritiated water has been used for estimating body water turnover rates (BWTRs) in desert livestock, rodent and birds. BWTRs in relation to adaption of these animal species to desert environment have been discussed. (author). 5 refs., 2 tabs

  19. Inferring species richness and turnover by statistical multiresolution texture analysis of satellite imagery.

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    Matteo Convertino

    Full Text Available BACKGROUND: The quantification of species-richness and species-turnover is essential to effective monitoring of ecosystems. Wetland ecosystems are particularly in need of such monitoring due to their sensitivity to rainfall, water management and other external factors that affect hydrology, soil, and species patterns. A key challenge for environmental scientists is determining the linkage between natural and human stressors, and the effect of that linkage at the species level in space and time. We propose pixel intensity based Shannon entropy for estimating species-richness, and introduce a method based on statistical wavelet multiresolution texture analysis to quantitatively assess interseasonal and interannual species turnover. METHODOLOGY/PRINCIPAL FINDINGS: We model satellite images of regions of interest as textures. We define a texture in an image as a spatial domain where the variations in pixel intensity across the image are both stochastic and multiscale. To compare two textures quantitatively, we first obtain a multiresolution wavelet decomposition of each. Either an appropriate probability density function (pdf model for the coefficients at each subband is selected, and its parameters estimated, or, a non-parametric approach using histograms is adopted. We choose the former, where the wavelet coefficients of the multiresolution decomposition at each subband are modeled as samples from the generalized Gaussian pdf. We then obtain the joint pdf for the coefficients for all subbands, assuming independence across subbands; an approximation that simplifies the computational burden significantly without sacrificing the ability to statistically distinguish textures. We measure the difference between two textures' representative pdf's via the Kullback-Leibler divergence (KL. Species turnover, or [Formula: see text] diversity, is estimated using both this KL divergence and the difference in Shannon entropy. Additionally, we predict species

  20. Sex chromosome turnover contributes to genomic divergence between incipient stickleback species.

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    Kohta Yoshida

    2014-03-01

    Full Text Available Sex chromosomes turn over rapidly in some taxonomic groups, where closely related species have different sex chromosomes. Although there are many examples of sex chromosome turnover, we know little about the functional roles of sex chromosome turnover in phenotypic diversification and genomic evolution. The sympatric pair of Japanese threespine stickleback (Gasterosteus aculeatus provides an excellent system to address these questions: the Japan Sea species has a neo-sex chromosome system resulting from a fusion between an ancestral Y chromosome and an autosome, while the sympatric Pacific Ocean species has a simple XY sex chromosome system. Furthermore, previous quantitative trait locus (QTL mapping demonstrated that the Japan Sea neo-X chromosome contributes to phenotypic divergence and reproductive isolation between these sympatric species. To investigate the genomic basis for the accumulation of genes important for speciation on the neo-X chromosome, we conducted whole genome sequencing of males and females of both the Japan Sea and the Pacific Ocean species. No substantial degeneration has yet occurred on the neo-Y chromosome, but the nucleotide sequence of the neo-X and the neo-Y has started to diverge, particularly at regions near the fusion. The neo-sex chromosomes also harbor an excess of genes with sex-biased expression. Furthermore, genes on the neo-X chromosome showed higher non-synonymous substitution rates than autosomal genes in the Japan Sea lineage. Genomic regions of higher sequence divergence between species, genes with divergent expression between species, and QTL for inter-species phenotypic differences were found not only at the regions near the fusion site, but also at other regions along the neo-X chromosome. Neo-sex chromosomes can therefore accumulate substitutions causing species differences even in the absence of substantial neo-Y degeneration.

  1. Species turnover in tropical montane forest avifauna links to climatic correlates

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    Chi-Feng Tsai

    2015-01-01

    Full Text Available We examined avifauna richness and composition in Taiwan’s tropical montane forests, and compared to historical records dated 22 years ago. A richness attrition of 44 species caused a discrepancy of 30.2%, and an estimated yearly turnover of 2.2%. More resident species that were narrower or lower in elevation distribution, insectivores/omnivores, small to medium-sized, forest/open-field dwelling, and canopy/ground foragers, vanished; whereas piscivores, carnivores, riparian- and shrub-dwellers, ground and mid-layer foragers, and migrants suffered by higher proportions. Occurrence frequencies of persistent species remained constant but varied among ecological groups, indicating an increased homogeneity for smaller-sized insectivores/omnivores dwelling in the forest canopy, shrub, or understory. While the overall annual temperature slightly increased, a relatively stable mean temperature was replaced by an ascending trend from the mid-1990s until 2002, followed by a cooling down. Mean maximum temperatures increased but minimums decreased gradually over years, resulting in increasing temperature differences up to over 16 °C. This accompanied an increase of extreme typhoons affecting Taiwan or directly striking these montane forests during the last decade. These results, given no direct human disturbances were noted, suggest a link between the species turnover and recent climate change, and convey warning signs of conservation concerns for tropical montane assemblages.

  2. Species turnover (β-diversity) in ectomycorrhizal fungi linked to NH4+ uptake capacity.

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    Kranabetter, J M; Hawkins, B J; Jones, M D; Robbins, S; Dyer, T; Li, T

    2015-12-01

    Ectomycorrhizal (EcM) fungal communities may be shaped by both deterministic and stochastic processes, potentially influencing ecosystem development and function. We evaluated community assembly processes for EcM fungi of Pseudotsuga menziesii among 12 sites up to 400 km apart in southwest British Columbia (Canada) by investigating species turnover (β-diversity) in relation to soil nitrogen (N) availability and physical distance. We then examined functional traits for an N-related niche by quantifying net fluxes of NH4+, NO3- and protons on excised root tips from three contrasting sites using a microelectrode ion flux measurement system. EcM fungal communities were well aligned with soil N availability and pH, with no effect of site proximity (distance-decay curve) on species assemblages. Species turnover was significant (β(1/2) = 1.48) along soil N gradients, with many more Tomentella species on high N than low N soils, in contrast to Cortinarius species. Ammonium uptake was greatest in the spring on the medium and rich sites and averaged over 190 nmol/m(2)/s for Tomentella species. The lowest uptake rates of NH4+ were by nonmycorrhizal roots of axenically grown seedlings (10 nmol/m(2)/s), followed by Cortinarius species (60 nmol/m(2)/s). EcM roots from all sites displayed only marginal uptake of nitrate (8.3 nmol/m(2)/s). These results suggest NH4+ uptake capacity is an important functional trait influencing the assembly of EcM fungal communities. The diversity of EcM fungal species across the region arguably provides critical belowground adaptations to organic and inorganic N supply that are integral to temperate rainforest ecology. © 2015 John Wiley & Sons Ltd.

  3. Partitioning and mapping uncertainties in ensembles of forecasts of species turnover under climate change

    DEFF Research Database (Denmark)

    Diniz-Filho, José Alexandre F.; Bini, Luis Mauricio; Rangel, Thiago Fernando

    2009-01-01

    Forecasts of species range shifts under climate change are fraught with uncertainties and ensemble forecasting may provide a framework to deal with such uncertainties. Here, a novel approach to partition the variance among modeled attributes, such as richness or turnover, and map sources of uncer......Forecasts of species range shifts under climate change are fraught with uncertainties and ensemble forecasting may provide a framework to deal with such uncertainties. Here, a novel approach to partition the variance among modeled attributes, such as richness or turnover, and map sources...... of uncertainty in ensembles of forecasts is presented. We model the distributions of 3837 New World birds and project them into 2080. We then quantify and map the relative contribution of different sources of uncertainty from alternative methods for niche modeling, general circulation models (AOGCM......), and emission scenarios. The greatest source of uncertainty in forecasts of species range shifts arises from using alternative methods for niche modeling, followed by AOGCM, and their interaction. Our results concur with previous studies that discovered that projections from alternative models can be extremely...

  4. Estimating rates of local species extinction, colonization and turnover in animal communities

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    Nichols, James D.; Boulinier, T.; Hines, J.E.; Pollock, K.H.; Sauer, J.R.

    1998-01-01

    Species richness has been identified as a useful state variable for conservation and management purposes. Changes in richness over time provide a basis for predicting and evaluating community responses to management, to natural disturbance, and to changes in factors such as community composition (e.g., the removal of a keystone species). Probabilistic capture-recapture models have been used recently to estimate species richness from species count and presence-absence data. These models do not require the common assumption that all species are detected in sampling efforts. We extend this approach to the development of estimators useful for studying the vital rates responsible for changes in animal communities over time; rates of local species extinction, turnover, and colonization. Our approach to estimation is based on capture-recapture models for closed animal populations that permit heterogeneity in detection probabilities among the different species in the sampled community. We have developed a computer program, COMDYN, to compute many of these estimators and associated bootstrap variances. Analyses using data from the North American Breeding Bird Survey (BBS) suggested that the estimators performed reasonably well. We recommend estimators based on probabilistic modeling for future work on community responses to management efforts as well as on basic questions about community dynamics.

  5. Habitat Heterogeneity Affects Plant and Arthropod Species Diversity and Turnover in Traditional Cornfields.

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    Martínez, Eliana; Rös, Matthias; Bonilla, María Argenis; Dirzo, Rodolfo

    2015-01-01

    The expansion of the agricultural frontier by the clearing of remnant forests has led to human-dominated landscape mosaics. Previous studies have evaluated the effect of these landscape mosaics on arthropod diversity at local spatial scales in temperate and tropical regions, but little is known about fragmentation effects in crop systems, such as the complex tropical traditional crop systems that maintain a high diversity of weeds and arthropods in low-Andean regions. To understand the factors that influence patterns of diversity in human-dominated landscapes, we investigate the effect of land use types on plant and arthropod diversity in traditionally managed cornfields, via surveys of plants and arthropods in twelve traditional cornfields in the Colombian Andes. We estimated alpha and beta diversity to analyze changes in diversity related to land uses within a radius of 100 m to 1 km around each cornfield. We observed that forests influenced alpha diversity of plants, but not of arthropods. Agricultural lands had a positive relationship with plants and herbivores, but a negative relationship with predators. Pastures positively influenced the diversity of plants and arthropods. In addition, forest cover seemed to influence changes in plant species composition and species turnover of herbivore communities among cornfields. The dominant plant species varied among fields, resulting in high differentiation of plant communities. Predator communities also exhibited high turnover among cornfields, but differences in composition arose mainly among rare species. The crop system evaluated in this study represents a widespread situation in the tropics, therefore, our results can be of broad significance. Our findings suggest that traditional agriculture may not homogenize biological communities, but instead could maintain the regional pool of species through high beta diversity.

  6. Habitat Heterogeneity Affects Plant and Arthropod Species Diversity and Turnover in Traditional Cornfields.

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    Eliana Martínez

    Full Text Available The expansion of the agricultural frontier by the clearing of remnant forests has led to human-dominated landscape mosaics. Previous studies have evaluated the effect of these landscape mosaics on arthropod diversity at local spatial scales in temperate and tropical regions, but little is known about fragmentation effects in crop systems, such as the complex tropical traditional crop systems that maintain a high diversity of weeds and arthropods in low-Andean regions. To understand the factors that influence patterns of diversity in human-dominated landscapes, we investigate the effect of land use types on plant and arthropod diversity in traditionally managed cornfields, via surveys of plants and arthropods in twelve traditional cornfields in the Colombian Andes. We estimated alpha and beta diversity to analyze changes in diversity related to land uses within a radius of 100 m to 1 km around each cornfield. We observed that forests influenced alpha diversity of plants, but not of arthropods. Agricultural lands had a positive relationship with plants and herbivores, but a negative relationship with predators. Pastures positively influenced the diversity of plants and arthropods. In addition, forest cover seemed to influence changes in plant species composition and species turnover of herbivore communities among cornfields. The dominant plant species varied among fields, resulting in high differentiation of plant communities. Predator communities also exhibited high turnover among cornfields, but differences in composition arose mainly among rare species. The crop system evaluated in this study represents a widespread situation in the tropics, therefore, our results can be of broad significance. Our findings suggest that traditional agriculture may not homogenize biological communities, but instead could maintain the regional pool of species through high beta diversity.

  7. Species Turnover across Different Life Stages from Seedlings to Canopy Trees in Swamp Forests of Central Brazil

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    Clarissa G. Fontes

    2015-01-01

    Full Text Available Processes driving the assembly of swamp forest communities have been poorly explored. We analyzed natural regeneration and adult tree communities data of a swamp gallery forest in Central Brazil to discuss the role of ecological filters in shaping plant species turnover in a successional gradient. Species data of 120 plots were used to assess species turnover between natural regeneration and adult tree communities. Our analyses were based on 4995 individuals belonging to 72 species. Community patterns were discerned using ordination analyses. A clear floristic turnover among plant life stages was distinguished. Regeneration community of swamp forests was richer in species composition than the adult community. Tree species commonly found in nonflooded gallery forests were present in the regeneration plots but not in the adult community. Differences in the floristic composition of these two strata suggest that not all species in the seedling stage can stand permanent flooding conditions and only a few tolerant species survive to become adult trees. We propose that natural disturbances play an important role by altering limiting resources, allowing seeds of nonflooded forest species to germinate. This paper elucidates the turnover between plant life stages in swamp forests and suggests mechanisms that may shape these communities.

  8. Environmental and historical imprints on beta diversity: insights from variation in rates of species turnover along gradients

    DEFF Research Database (Denmark)

    Fitzpatrick, Matthew C Fitzpatrick; Sanders, Nathan J.; Normand, Signe

    2013-01-01

    A common approach for analysing geographical variation in biodiversity involves using linear models to determine the rate at which species similarity declines with geographical or environmental distance and comparing this rate among regions, taxa or communities. Implicit in this approach are weakly...... justified assumptions that the rate of species turnover remains constant along gradients and that this rate can therefore serve as a means to compare ecological systems. We use generalized dissimilarity modelling, a novel method that accommodates variation in rates of species turnover along gradients...... in rates of species turnover is persistent across regions, taxa and different gradients. Such variation may represent an important but often overlooked component of biodiversity that complicates comparisons of distance–decay relationships and underscores the importance of using methods that accommodate...

  9. Seed dispersal increases local species richness and reduces spatial turnover of tropical tree seedlings.

    Science.gov (United States)

    Wandrag, Elizabeth M; Dunham, Amy E; Duncan, Richard P; Rogers, Haldre S

    2017-10-03

    Dispersal is thought to be a key process underlying the high spatial diversity of tropical forests. Just how important dispersal is in structuring plant communities is nevertheless an open question because it is very difficult to isolate dispersal from other processes, and thereby measure its effect. Using a unique situation, the loss of vertebrate seed dispersers on the island of Guam and their presence on the neighboring islands of Saipan and Rota, we quantify the contribution of vertebrate seed dispersal to spatial patterns of diversity of tree seedlings in treefall gaps. The presence of vertebrate seed dispersers approximately doubled seedling species richness within canopy gaps and halved species turnover among gaps. Our study demonstrates that dispersal plays a key role in maintaining local and regional patterns of diversity, and highlights the potential for ongoing declines in vertebrate seed dispersers to profoundly alter tropical forest composition.

  10. Hierarchical traits distances explain grassland Fabaceae species' ecological niches distances

    Science.gov (United States)

    Fort, Florian; Jouany, Claire; Cruz, Pablo

    2015-01-01

    Fabaceae species play a key role in ecosystem functioning through their capacity to fix atmospheric nitrogen via their symbiosis with Rhizobium bacteria. To increase benefits of using Fabaceae in agricultural systems, it is necessary to find ways to evaluate species or genotypes having potential adaptations to sub-optimal growth conditions. We evaluated the relevance of phylogenetic distance, absolute trait distance and hierarchical trait distance for comparing the adaptation of 13 grassland Fabaceae species to different habitats, i.e., ecological niches. We measured a wide range of functional traits (root traits, leaf traits, and whole plant traits) in these species. Species phylogenetic and ecological distances were assessed from a species-level phylogenetic tree and species' ecological indicator values, respectively. We demonstrated that differences in ecological niches between grassland Fabaceae species were related more to their hierarchical trait distances than to their phylogenetic distances. We showed that grassland Fabaceae functional traits tend to converge among species with the same ecological requirements. Species with acquisitive root strategies (thin roots, shallow root systems) are competitive species adapted to non-stressful meadows, while conservative ones (coarse roots, deep root systems) are able to tolerate stressful continental climates. In contrast, acquisitive species appeared to be able to tolerate low soil-P availability, while conservative ones need high P availability. Finally we highlight that traits converge along the ecological gradient, providing the assumption that species with similar root-trait values are better able to coexist, regardless of their phylogenetic distance. PMID:25741353

  11. Reproductive interference explains persistence of aggression between species.

    Science.gov (United States)

    Drury, Jonathan P; Okamoto, Kenichi W; Anderson, Christopher N; Grether, Gregory F

    2015-04-07

    Interspecific territoriality occurs when individuals of different species fight over space, and may arise spontaneously when populations of closely related territorial species first come into contact. But defence of space is costly, and unless the benefits of excluding heterospecifics exceed the costs, natural selection should favour divergence in competitor recognition until the species no longer interact aggressively. Ordinarily males of different species do not compete for mates, but when males cannot distinguish females of sympatric species, females may effectively become a shared resource. We model how reproductive interference caused by undiscriminating males can prevent interspecific divergence, or even cause convergence, in traits used to recognize competitors. We then test the model in a genus of visually orienting insects and show that, as predicted by the model, differences between species pairs in the level of reproductive interference, which is causally related to species differences in female coloration, are strongly predictive of the current level of interspecific aggression. Interspecific reproductive interference is very common and we discuss how it may account for the persistence of interspecific aggression in many taxonomic groups. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  12. Cell formation by myxozoan species is not explained by dogma

    Science.gov (United States)

    Morris, David J.

    2010-01-01

    Eukaryotes form new cells through the replication of nuclei followed by cytokinesis. A notable exception is reported from the class Myxosporea of the phylum Myxozoa. This assemblage of approximately 2310 species is regarded as either basal bilaterian or cnidarian, depending on the phylogenetic analysis employed. For myxosporeans, cells have long been regarded as forming within other cells by a process referred to as endogenous budding. This would involve a nucleus forming endoplasmic reticulum around it, which transforms into a new plasma membrane, thus enclosing and separating it from the surrounding cell. This remarkable process, unique within the Metazoa, is accepted as occurring within stages found in vertebrate hosts, but has only been inferred from those stages observed within invertebrate hosts. Therefore, I conducted an ultrastructural study to examine how internal cells are formed by a myxosporean parasitizing an annelid. In this case, actinospore parasite stages clearly internalized existing cells; a process with analogies to the acquisition of endosymbiotic algae by cnidarian species. A subsequent examination of the myxozoan literature did not support endogenous budding, indicating that this process, which has been a central tenet of myxozoan developmental biology for over a century, is dogma. PMID:20392735

  13. Cell formation by myxozoan species is not explained by dogma.

    Science.gov (United States)

    Morris, David J

    2010-08-22

    Eukaryotes form new cells through the replication of nuclei followed by cytokinesis. A notable exception is reported from the class Myxosporea of the phylum Myxozoa. This assemblage of approximately 2310 species is regarded as either basal bilaterian or cnidarian, depending on the phylogenetic analysis employed. For myxosporeans, cells have long been regarded as forming within other cells by a process referred to as endogenous budding. This would involve a nucleus forming endoplasmic reticulum around it, which transforms into a new plasma membrane, thus enclosing and separating it from the surrounding cell. This remarkable process, unique within the Metazoa, is accepted as occurring within stages found in vertebrate hosts, but has only been inferred from those stages observed within invertebrate hosts. Therefore, I conducted an ultrastructural study to examine how internal cells are formed by a myxosporean parasitizing an annelid. In this case, actinospore parasite stages clearly internalized existing cells; a process with analogies to the acquisition of endosymbiotic algae by cnidarian species. A subsequent examination of the myxozoan literature did not support endogenous budding, indicating that this process, which has been a central tenet of myxozoan developmental biology for over a century, is dogma.

  14. Estimating the footprint of pollution on coral reefs with models of species turnover.

    Science.gov (United States)

    Brown, Christopher J; Hamilton, Richard J

    2018-01-15

    Ecological communities typically change along gradients of human impact, although it is difficult to estimate the footprint of impacts for diffuse threats such as pollution. We developed a joint model (i.e., one that includes multiple species and their interactions with each other and environmental covariates) of benthic habitats on lagoonal coral reefs and used it to infer change in benthic composition along a gradient of distance from logging operations. The model estimated both changes in abundances of benthic groups and their compositional turnover, a type of beta diversity. We used the model to predict the footprint of turbidity impacts from past and recent logging. Benthic communities far from logging were dominated by branching corals, whereas communities close to logging had higher cover of dead coral, massive corals, and soft sediment. Recent impacts were predicted to be small relative to the extensive impacts of past logging because recent logging has occurred far from lagoonal reefs. Our model can be used more generally to estimate the footprint of human impacts on ecosystems and evaluate the benefits of conservation actions for ecosystems. © 2018 Society for Conservation Biology.

  15. The effect of climate and soil conditions on tree species turnover in a Tropical Montane Cloud Forest in Costa Rica.

    Science.gov (United States)

    Häger, Achim

    2010-12-01

    On a global level, Tropical Montane Cloud Forests constitute important centers of vascular plant diversity. Tree species turnover along environmental gradients plays an important role in larger scale diversity patterns in tropical mountains. This study aims to estimate the magnitude of beta diversity across the Tilardn mountain range in North-Western Costa Rica, and to elucidate the impact of climate and soil conditions on tree species turnover at a local scale. Seven climate stations measuring rainfall, horizontal precipitation (clouds and wind-driven rain) and temperatures were installed along a 2.5km transect ranging from 1200 m.a.s.l. on the Atlantic to 1200 m.a.s.l. on the Pacific slope. The ridge top climate station was located at 1500 m.a.s.l. Climate data were recorded from March through December 2003. Additionally, seven 0.05 ha plots were established. On all plots soil moisture was monitored for one year, furthermore soil type and soil chemistry were assessed. Woody plants with a diameter at breast height (dbh) > or = 5 cm were identified to species. Species' distributions were explored by feeding pairwise Serensen measures between plots into a Principal Component Analysis. Relationships between floristic similarity and environmental variables were analyzed using Mantel tests. Pronounced gradients in horizontal precipitation, temperatures and soil conditions were found across the transect. In total, 483 woody plants were identified, belonging to 132 species. Environmental gradients were paralleled by tree species turnover; the plots could be divided in three distinctive floristic units which reflected different topographic positions on the transect (lower slopes, mid slopes and ridge). Most notably there was a complete species turnover between the ridge and the lower Pacific slope. Floristic similarity was negatively correlated with differences in elevation, horizontal precipitation, temperatures and soil conditions between plots. It is suggested that

  16. Docosahexaenoate-containing molecular species of glycerophospholipids from frog retinal rod outer segments show different rates of biosynthesis and turnover

    International Nuclear Information System (INIS)

    Louie, K.; Wiegand, R.D.; Anderson, R.E.

    1988-01-01

    The authors have studied the de novo synthesis and subsequent turnover of major docosahexaenoate-containing molecular species in frog rod outer segment (ROS) phospholipids following intravitreal injection of [2- 3 H]glycerol. On selected days after injection, ROS were prepared and phospholipids extracted. Phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS) were isolated and converted to diradylglycerols with phospholipase C. Diradylglycerols were derivatized with benzoic anhydride and resolve into diacylglycerobenzoates and ether-linked glycerobenzoates. The diacylglycerobenzoates were fractionated into molecular species by HPLC, quantitated, and counted for radioactivity. Label was incorporated into ROS phospholipids by day 1 and was followed up through the eighth day. The dipolyenoic species 22:6-22:6 from PC showed 1 3-5 times higher radiospecific activity than the same species from either PE or PS. The rate of decline was determined by calculating the half-life of each molecular species, which was used as a measure of the turnover of the species. The percent distribution of radioactivity in the molecular species of PC and PE was quite different from the relative mass distribution at day 1. However, percent dpm approached the mole percent by 31 days. In PS, percent dpm and mole percent were the same at all time points. These results indicate that the molecular species composition of PC and PE in frog retinal ROS is determined by a combination of factors, which include rate of synthesis, rate of degradation, and selective interconversions. In contrast, PS composition appears to be determined at the time of synthesis

  17. Effects of long- and short-term management on the functional structure of meadows through species turnover and intraspecific trait variability.

    Science.gov (United States)

    Volf, Martin; Redmond, Conor; Albert, Ágnes J; Le Bagousse-Pinguet, Yoann; Biella, Paolo; Götzenberger, Lars; Hrázský, Záboj; Janeček, Štěpán; Klimešová, Jitka; Lepš, Jan; Šebelíková, Lenka; Vlasatá, Tereza; de Bello, Francesco

    2016-04-01

    The functional structures of communities respond to environmental changes by both species replacement (turnover) and within-species variation (intraspecific trait variability; ITV). Evidence is lacking on the relative importance of these two components, particularly in response to both short- and long-term environmental disturbance. We hypothesized that such short- and long-term perturbations would induce changes in community functional structure primarily via ITV and turnover, respectively. To test this we applied an experimental design across long-term mown and abandoned meadows, with each plot containing a further level of short-term management treatments: mowing, grazing and abandonment. Within each plot, species composition and trait values [height, shoot biomass, and specific leaf area (SLA)] were recorded on up to five individuals per species. Positive covariations between the contribution of species turnover and ITV occurred for height and shoot biomass in response to both short- and long-term management, indicating that species turnover and intraspecific adjustments selected for similar trait values. Positive covariations also occurred for SLA, but only in response to long-term management. The contributions of turnover and ITV changed depending on both the trait and management trajectory. As expected, communities responded to short-term disturbances mostly through changes in intraspecific trait variability, particularly for height and biomass. Interestingly, for SLA they responded to long-term disturbances by both species turnover and intraspecific adjustments. These findings highlight the importance of both ITV and species turnover in adjusting grassland functional trait response to environmental perturbation, and show that the response is trait specific and affected by disturbance regime history.

  18. Species associations in a species-rich subtropical forest were not well-explained by stochastic geometry of biodiversity.

    Directory of Open Access Journals (Sweden)

    Qinggang Wang

    Full Text Available The stochastic dilution hypothesis has been proposed to explain species coexistence in species-rich communities. The relative importance of the stochastic dilution effects with respect to other effects such as competition and habitat filtering required to be tested. In this study, using data from a 25-ha species-rich subtropical forest plot with a strong topographic structure at Badagongshan in central China, we analyzed overall species associations and fine-scale species interactions between 2,550 species pairs. The result showed that: (1 the proportion of segregation in overall species association analysis at 2 m neighborhood in this plot followed the prediction of the stochastic dilution hypothesis that segregations should decrease with species richness but that at 10 m neighborhood was higher than the prediction. (2 The proportion of no association type was lower than the expectation of stochastic dilution hypothesis. (3 Fine-scale species interaction analyses using Heterogeneous Poisson processes as null models revealed a high proportion (47% of significant species effects. However, the assumption of separation of scale of this method was not fully met in this plot with a strong fine-scale topographic structure. We also found that for species within the same families, fine-scale positive species interactions occurred more frequently and negative ones occurred less frequently than expected by chance. These results suggested effects of environmental filtering other than species interaction in this forest. (4 We also found that arbor species showed a much higher proportion of significant fine-scale species interactions (66% than shrub species (18%. We concluded that the stochastic dilution hypothesis only be partly supported and environmental filtering left discernible spatial signals in the spatial associations between species in this species-rich subtropical forest with a strong topographic structure.

  19. Species associations in a species-rich subtropical forest were not well-explained by stochastic geometry of biodiversity.

    Science.gov (United States)

    Wang, Qinggang; Bao, Dachuan; Guo, Yili; Lu, Junmeng; Lu, Zhijun; Xu, Yaozhan; Zhang, Kuihan; Liu, Haibo; Meng, Hongjie; Jiang, Mingxi; Qiao, Xiujuan; Huang, Handong

    2014-01-01

    The stochastic dilution hypothesis has been proposed to explain species coexistence in species-rich communities. The relative importance of the stochastic dilution effects with respect to other effects such as competition and habitat filtering required to be tested. In this study, using data from a 25-ha species-rich subtropical forest plot with a strong topographic structure at Badagongshan in central China, we analyzed overall species associations and fine-scale species interactions between 2,550 species pairs. The result showed that: (1) the proportion of segregation in overall species association analysis at 2 m neighborhood in this plot followed the prediction of the stochastic dilution hypothesis that segregations should decrease with species richness but that at 10 m neighborhood was higher than the prediction. (2) The proportion of no association type was lower than the expectation of stochastic dilution hypothesis. (3) Fine-scale species interaction analyses using Heterogeneous Poisson processes as null models revealed a high proportion (47%) of significant species effects. However, the assumption of separation of scale of this method was not fully met in this plot with a strong fine-scale topographic structure. We also found that for species within the same families, fine-scale positive species interactions occurred more frequently and negative ones occurred less frequently than expected by chance. These results suggested effects of environmental filtering other than species interaction in this forest. (4) We also found that arbor species showed a much higher proportion of significant fine-scale species interactions (66%) than shrub species (18%). We concluded that the stochastic dilution hypothesis only be partly supported and environmental filtering left discernible spatial signals in the spatial associations between species in this species-rich subtropical forest with a strong topographic structure.

  20. Species turnover drives β-diversity patterns across multiple spatial scales of plant-galling interactions in mountaintop grasslands.

    Science.gov (United States)

    Coelho, Marcel Serra; Carneiro, Marco Antônio Alves; Branco, Cristina Alves; Borges, Rafael Augusto Xavier; Fernandes, Geraldo Wilson

    2018-01-01

    This study describes differences in species richness and composition of the assemblages of galling insects and their host plants at different spatial scales. Sampling was conducted along altitudinal gradients composed of campos rupestres and campos de altitude of two mountain complexes in southeastern Brazil: Espinhaço Range and Mantiqueira Range. The following hypotheses were tested: i) local and regional richness of host plants and galling insects are positively correlated; ii) beta diversity is the most important component of regional diversity of host plants and galling insects; and iii) Turnover is the main mechanism driving beta diversity of both host plants and galling insects. Local richness of galling insects and host plants increased with increasing regional richness of species, suggesting a pattern of unsaturated communities. The additive partition of regional richness (γ) into local and beta components shows that local richnesses (α) of species of galling insects and host plants are low relative to regional richness; the beta (β) component incorporates most of the regional richness. The multi-scale analysis of additive partitioning showed similar patterns for galling insects and host plants with the local component (α) incorporated a small part of regional richness. Beta diversity of galling insects and host plants were mainly the result of turnover, with little contribution from nesting. Although the species composition of galling insects and host plant species varied among sample sites, mountains and even mountain ranges, local richness remained relatively low. In this way, the addition of local habitats with different landscapes substantially affects regional richness. Each mountain contributes fundamentally to the composition of regional diversity of galling insects and host plants, and so the design of future conservation strategies should incorporate multiple scales.

  1. Understory Bird Communities in Amazonian Rainforest Fragments: Species Turnover through 25 Years Post-Isolation in Recovering Landscapes

    Science.gov (United States)

    Stouffer, Philip C.; Johnson, Erik I.; Bierregaard, Richard O.; Lovejoy, Thomas E.

    2011-01-01

    Inferences about species loss following habitat conversion are typically drawn from short-term surveys, which cannot reconstruct long-term temporal dynamics of extinction and colonization. A long-term view can be critical, however, to determine the stability of communities within fragments. Likewise, landscape dynamics must be considered, as second growth structure and overall forest cover contribute to processes in fragments. Here we examine bird communities in 11 Amazonian rainforest fragments of 1–100 ha, beginning before the fragments were isolated in the 1980s, and continuing through 2007. Using a method that accounts for imperfect detection, we estimated extinction and colonization based on standardized mist-net surveys within discreet time intervals (1–2 preisolation samples and 4–5 post-isolation samples). Between preisolation and 2007, all fragments lost species in an area-dependent fashion, with loss of as few as <10% of preisolation species from 100-ha fragments, but up to 70% in 1-ha fragments. Analysis of individual time intervals revealed that the 2007 result was not due to gradual species loss beginning at isolation; both extinction and colonization occurred in every time interval. In the last two samples, 2000 and 2007, extinction and colonization were approximately balanced. Further, 97 of 101 species netted before isolation were detected in at least one fragment in 2007. Although a small subset of species is extremely vulnerable to fragmentation, and predictably goes extinct in fragments, developing second growth in the matrix around fragments encourages recolonization in our landscapes. Species richness in these fragments now reflects local turnover, not long-term attrition of species. We expect that similar processes could be operating in other fragmented systems that show unexpectedly low extinction. PMID:21731616

  2. Understory bird communities in Amazonian rainforest fragments: species turnover through 25 years post-isolation in recovering landscapes.

    Directory of Open Access Journals (Sweden)

    Philip C Stouffer

    Full Text Available Inferences about species loss following habitat conversion are typically drawn from short-term surveys, which cannot reconstruct long-term temporal dynamics of extinction and colonization. A long-term view can be critical, however, to determine the stability of communities within fragments. Likewise, landscape dynamics must be considered, as second growth structure and overall forest cover contribute to processes in fragments. Here we examine bird communities in 11 Amazonian rainforest fragments of 1-100 ha, beginning before the fragments were isolated in the 1980s, and continuing through 2007. Using a method that accounts for imperfect detection, we estimated extinction and colonization based on standardized mist-net surveys within discreet time intervals (1-2 preisolation samples and 4-5 post-isolation samples. Between preisolation and 2007, all fragments lost species in an area-dependent fashion, with loss of as few as <10% of preisolation species from 100-ha fragments, but up to 70% in 1-ha fragments. Analysis of individual time intervals revealed that the 2007 result was not due to gradual species loss beginning at isolation; both extinction and colonization occurred in every time interval. In the last two samples, 2000 and 2007, extinction and colonization were approximately balanced. Further, 97 of 101 species netted before isolation were detected in at least one fragment in 2007. Although a small subset of species is extremely vulnerable to fragmentation, and predictably goes extinct in fragments, developing second growth in the matrix around fragments encourages recolonization in our landscapes. Species richness in these fragments now reflects local turnover, not long-term attrition of species. We expect that similar processes could be operating in other fragmented systems that show unexpectedly low extinction.

  3. Disentangling effects of abiotic factors and biotic interactions on cross-taxon congruence in species turnover patterns of plants, moths and beetles.

    Science.gov (United States)

    Duan, Meichun; Liu, Yunhui; Yu, Zhenrong; Baudry, Jacques; Li, Liangtao; Wang, Changliu; Axmacher, Jan C

    2016-04-01

    High cross-taxon congruence in species diversity patterns is essential for the use of surrogate taxa in biodiversity conservation, but presence and strength of congruence in species turnover patterns, and the relative contributions of abiotic environmental factors and biotic interaction towards this congruence, remain poorly understood. In our study, we used variation partitioning in multiple regressions to quantify cross-taxon congruence in community dissimilarities of vascular plants, geometrid and arciinid moths and carabid beetles, subsequently investigating their respective underpinning by abiotic factors and biotic interactions. Significant cross-taxon congruence observed across all taxon pairs was linked to their similar responses towards elevation change. Changes in the vegetation composition were closely linked to carabid turnover, with vegetation structure and associated microclimatic conditions proposed causes of this link. In contrast, moth assemblages appeared to be dominated by generalist species whose turnover was weakly associated with vegetation changes. Overall, abiotic factors exerted a stronger influence on cross-taxon congruence across our study sites than biotic interactions. The weak congruence in turnover observed particularly between plants and moths highlights the importance of multi-taxon approaches based on groupings of taxa with similar turnovers, rather than the use of single surrogate taxa or environmental proxies, in biodiversity assessments.

  4. Testing the Effectiveness of Environmental Variables to Explain European Terrestrial Vertebrate Species Richness across Biogeographical Scales.

    Directory of Open Access Journals (Sweden)

    Maud Mouchet

    Full Text Available We compared the effectiveness of environmental variables, and in particular of land-use indicators, to explain species richness patterns across taxonomic groups and biogeographical scales (i.e. overall pan-Europe and ecoregions within pan-Europe. Using boosted regression trees that handle non-linear relationships, we compared the relative influence (as a measure of effectiveness of environmental variables related to climate, landscape (or habitat heterogeneity, land-use intensity or energy availability to explain European vertebrate species richness (birds, amphibians, and mammals at the continental and ecoregion scales. We found that dominant land cover and actual evapotranspiration that relate to energy availability were the main correlates of vertebrate species richness over Europe. At the ecoregion scale, we identified four distinct groups of ecoregions where species richness was essentially associated to (i seasonality of temperature, (ii actual evapotranspiration and/or mean annual temperature, (iii seasonality of precipitation, actual evapotranspiration and land cover and (iv and an even combination of the environmental variables. This typology of ecoregions remained valid for total vertebrate richness and the three vertebrate groups taken separately. Despite the overwhelming influence of land cover and actual evapotranspiration to explain vertebrate species richness patterns at European scale, the ranking of the main correlates of species richness varied between regions. Interestingly, landscape and land-use indicators did not stand out at the continental scale but their influence greatly increased in southern ecoregions, revealing the long-lasting human footprint on land-use-land-cover changes. Our study provides one of the first multi-scale descriptions of the variability in the ranking of correlates across several taxa.

  5. KLK6 proteolysis is implicated in the turnover and uptake of extracellular alpha-synuclein species.

    Science.gov (United States)

    Pampalakis, Georgios; Sykioti, Vasia-Samantha; Ximerakis, Methodios; Stefanakou-Kalakou, Ioanna; Melki, Ronald; Vekrellis, Kostas; Sotiropoulou, Georgia

    2017-02-28

    KLK6 is a serine protease highly expressed in the nervous system. In synucleinopathies, including Parkinson disease, the levels of KLK6 inversely correlate with α-synuclein in CSF. Recently, we suggested that recombinant KLK6 mediates the degradation of extracellular α-synuclein directly and via a proteolytic cascade that involves unidentified metalloproteinase(s). Here, we show that recombinant and naturally secreted KLK6 can readily cleave α-synuclein fibrils that have the potential for cell-to-cell propagation in "a prion-like mechanism". Importantly, KLK6-deficient primary cortical neurons have increased ability for α-synuclein fibril uptake. We also demonstrate that KLK6 activates proMMP2, which in turn can cleave α-synuclein. The repertoire of proteases activated by KLK6 in a neuronal environment was analyzed by degradomic profiling, which also identified ADAMTS19 and showed that KLK6 has a limited number of substrates indicating specific biological functions such as the regulation of α-synuclein turnover. We generated adenoviral vectors for KLK6 delivery and demonstrated that the levels of extracellular α-synuclein can be reduced by neuronally secreted KLK6. Our findings open the possibility to exploit KLK6 as a novel therapeutic target for Parkinson disease and other synucleinopathies.

  6. Explaining life history variation in a changing climate across a species' range

    DEFF Research Database (Denmark)

    Neuheimer, Anna B.; MacKenzie, Brian R.

    2014-01-01

    Timing of reproduction greatly influences offspring success and resulting population production. Explaining and predicting species' dynamics necessitates disentangling the intrinsic (genotypic) and extrinsic (climatic) factors controlling reproductive timing. Here we explore temporal and spatial...... changes in spawning time for 21 populations of Atlantic cod (Gadus morhua) across the species' range (40 degrees to 80 degrees N). We estimate spawning time using a physiologically relevant metric that includes information on fish thermal history (degree-days, DD). First, we estimate spawning DD among...... years (within populations) to show how recent changes in spawning time can be explained by local changes in temperature. Second, we employ spawning DD to identify temperature-independent trends in spawning time among populations that are consistent with parallel adaptive evolution and the evolutionary...

  7. Does resource availability, resource heterogeneity or species turnover mediate changes in plant species richness in grazed grasslands?

    NARCIS (Netherlands)

    Bakker, C; Blair, JM; Knapp, AK

    2003-01-01

    Grazing by large ungulates often increases plant species richness in grasslands of moderate to high productivity. In a mesic North American grassland with and without the presence of bison (Bos bison), a native ungulate grazer, three non-exclusive hypotheses for increased plant species richness in

  8. Climate and soil attributes determine plant species turnover in global drylands

    Science.gov (United States)

    Maestre, Fernando T.; Gotelli, Nicholas J.; Quero, José L.; Delgado-Baquerizo, Manuel; Bowker, Matthew A.; Eldridge, David J.; Ochoa, Victoria; Gozalo, Beatriz; Valencia, Enrique; Berdugo, Miguel; Escolar, Cristina; García-Gómez, Miguel; Escudero, Adrián; Prina, Aníbal; Alfonso, Graciela; Arredondo, Tulio; Bran, Donaldo; Cabrera, Omar; Cea, Alex; Chaieb, Mohamed; Contreras, Jorge; Derak, Mchich; Espinosa, Carlos I.; Florentino, Adriana; Gaitán, Juan; Muro, Victoria García; Ghiloufi, Wahida; Gómez-González, Susana; Gutiérrez, Julio R.; Hernández, Rosa M.; Huber-Sannwald, Elisabeth; Jankju, Mohammad; Mau, Rebecca L.; Hughes, Frederic Mendes; Miriti, Maria; Monerris, Jorge; Muchane, Muchai; Naseri, Kamal; Pucheta, Eduardo; Ramírez-Collantes, David A.; Raveh, Eran; Romão, Roberto L.; Torres-Díaz, Cristian; Val, James; Veiga, José Pablo; Wang, Deli; Yuan, Xia; Zaady, Eli

    2015-01-01

    Aim Geographic, climatic, and soil factors are major drivers of plant beta diversity, but their importance for dryland plant communities is poorly known. This study aims to: i) characterize patterns of beta diversity in global drylands, ii) detect common environmental drivers of beta diversity, and iii) test for thresholds in environmental conditions driving potential shifts in plant species composition. Location 224 sites in diverse dryland plant communities from 22 geographical regions in six continents. Methods Beta diversity was quantified with four complementary measures: the percentage of singletons (species occurring at only one site), Whittake’s beta diversity (β(W)), a directional beta diversity metric based on the correlation in species occurrences among spatially contiguous sites (β(R2)), and a multivariate abundance-based metric (β(MV)). We used linear modelling to quantify the relationships between these metrics of beta diversity and geographic, climatic, and soil variables. Results Soil fertility and variability in temperature and rainfall, and to a lesser extent latitude, were the most important environmental predictors of beta diversity. Metrics related to species identity (percentage of singletons and β(W)) were most sensitive to soil fertility, whereas those metrics related to environmental gradients and abundance ((β(R2)) and β(MV)) were more associated with climate variability. Interactions among soil variables, climatic factors, and plant cover were not important determinants of beta diversity. Sites receiving less than 178 mm of annual rainfall differed sharply in species composition from more mesic sites (> 200 mm). Main conclusions Soil fertility and variability in temperature and rainfall are the most important environmental predictors of variation in plant beta diversity in global drylands. Our results suggest that those sites annually receiving ~ 178 mm of rainfall will be especially sensitive to future climate changes. These

  9. Climate and soil attributes determine plant species turnover in global drylands.

    Science.gov (United States)

    Ulrich, Werner; Soliveres, Santiago; Maestre, Fernando T; Gotelli, Nicholas J; Quero, José L; Delgado-Baquerizo, Manuel; Bowker, Matthew A; Eldridge, David J; Ochoa, Victoria; Gozalo, Beatriz; Valencia, Enrique; Berdugo, Miguel; Escolar, Cristina; García-Gómez, Miguel; Escudero, Adrián; Prina, Aníbal; Alfonso, Graciela; Arredondo, Tulio; Bran, Donaldo; Cabrera, Omar; Cea, Alex; Chaieb, Mohamed; Contreras, Jorge; Derak, Mchich; Espinosa, Carlos I; Florentino, Adriana; Gaitán, Juan; Muro, Victoria García; Ghiloufi, Wahida; Gómez-González, Susana; Gutiérrez, Julio R; Hernández, Rosa M; Huber-Sannwald, Elisabeth; Jankju, Mohammad; Mau, Rebecca L; Hughes, Frederic Mendes; Miriti, Maria; Monerris, Jorge; Muchane, Muchai; Naseri, Kamal; Pucheta, Eduardo; Ramírez-Collantes, David A; Raveh, Eran; Romão, Roberto L; Torres-Díaz, Cristian; Val, James; Veiga, José Pablo; Wang, Deli; Yuan, Xia; Zaady, Eli

    2014-12-01

    Geographic, climatic, and soil factors are major drivers of plant beta diversity, but their importance for dryland plant communities is poorly known. This study aims to: i) characterize patterns of beta diversity in global drylands, ii) detect common environmental drivers of beta diversity, and iii) test for thresholds in environmental conditions driving potential shifts in plant species composition. 224 sites in diverse dryland plant communities from 22 geographical regions in six continents. Beta diversity was quantified with four complementary measures: the percentage of singletons (species occurring at only one site), Whittake's beta diversity (β(W)), a directional beta diversity metric based on the correlation in species occurrences among spatially contiguous sites (β(R 2 )), and a multivariate abundance-based metric (β(MV)). We used linear modelling to quantify the relationships between these metrics of beta diversity and geographic, climatic, and soil variables. Soil fertility and variability in temperature and rainfall, and to a lesser extent latitude, were the most important environmental predictors of beta diversity. Metrics related to species identity (percentage of singletons and β(W)) were most sensitive to soil fertility, whereas those metrics related to environmental gradients and abundance ((β(R 2 )) and β(MV)) were more associated with climate variability. Interactions among soil variables, climatic factors, and plant cover were not important determinants of beta diversity. Sites receiving less than 178 mm of annual rainfall differed sharply in species composition from more mesic sites (> 200 mm). Soil fertility and variability in temperature and rainfall are the most important environmental predictors of variation in plant beta diversity in global drylands. Our results suggest that those sites annually receiving ~ 178 mm of rainfall will be especially sensitive to future climate changes. These findings may help to define appropriate

  10. Climate and soil type together explain the distribution of microendemic species in a biodiversity hotspot.

    Directory of Open Access Journals (Sweden)

    Romain Nattier

    Full Text Available The grasshopper genus Caledonula, endemic to New Caledonia, was studied to understand the evolution of species distributions in relation to climate and soil types. Based on a comprehensive sampling of 80 locations throughout the island, the genus was represented by five species, four of which are new to science, of which three are described here. All the species have limited distributions in New Caledonia. Bioclimatic niche modelling shows that all the species were found in association with a wet climate and reduced seasonality, explaining their restriction to the southern half of the island. The results suggest that the genus was ancestrally constrained by seasonality. A molecular phylogeny was reconstructed using two mitochondrial and two nuclear markers. The partially resolved tree showed monophyly of the species found on metalliferous soils, and molecular dating indicated a rather recent origin for the genus. Adaptation to metalliferous soils is suggested by both morphological changes and radiation on these soils. The genus Caledonula is therefore a good model to understand the origin of microendemism in the context of recent and mixed influences of climate and soil type.

  11. Climate and soil type together explain the distribution of microendemic species in a biodiversity hotspot.

    Science.gov (United States)

    Nattier, Romain; Grandcolas, Philippe; Pellens, Roseli; Jourdan, Hervé; Couloux, Arnaud; Poulain, Simon; Robillard, Tony

    2013-01-01

    The grasshopper genus Caledonula, endemic to New Caledonia, was studied to understand the evolution of species distributions in relation to climate and soil types. Based on a comprehensive sampling of 80 locations throughout the island, the genus was represented by five species, four of which are new to science, of which three are described here. All the species have limited distributions in New Caledonia. Bioclimatic niche modelling shows that all the species were found in association with a wet climate and reduced seasonality, explaining their restriction to the southern half of the island. The results suggest that the genus was ancestrally constrained by seasonality. A molecular phylogeny was reconstructed using two mitochondrial and two nuclear markers. The partially resolved tree showed monophyly of the species found on metalliferous soils, and molecular dating indicated a rather recent origin for the genus. Adaptation to metalliferous soils is suggested by both morphological changes and radiation on these soils. The genus Caledonula is therefore a good model to understand the origin of microendemism in the context of recent and mixed influences of climate and soil type.

  12. The effect of climate and soil conditions on tree species turnover in a Tropical Montane Cloud Forest in Costa Rica

    Directory of Open Access Journals (Sweden)

    Achim Häger

    2010-12-01

    Full Text Available On a global level, Tropical Montane Cloud Forests constitute important centers of vascular plant diversity. Tree species turnover along environmental gradients plays an important role in larger scale diversity patterns in tropical mountains. This study aims to estimate the magnitude of beta diversity across the Tilarán mountain range in North-Western Costa Rica, and to elucidate the impact of climate and soil conditions on tree species turnover at a local scale. Seven climate stations measuring rainfall, horizontal precipitation (clouds and wind-driven rain and temperatures were installed along a 2.5km transect ranging from 1 200m.a.s.l. on the Atlantic to 1 200m.a.s.l. on the Pacific slope. The ridge top climate station was located at 1 500m.a.s.l. Climate data were recorded from March through December 2003. Additionally, seven 0.05ha plots were established. On all plots soil moisture was monitored for one year, furthermore soil type and soil chemistry were assessed. Woody plants with a diameter at breast height (dbh ≥5cm were identified to species. Species’ distributions were explored by feeding pairwise Sørensen measures between plots into a Principal Component Analysis. Relationships between floristic similarity and environmental variables were analyzed using Mantel tests. Pronounced gradients in horizontal precipitation, temperatures and soil conditions were found across the transect. In total, 483 woody plants were identified, belonging to 132 species. Environmental gradients were paralleled by tree species turnover; the plots could be divided in three distinctive floristic units which reflected different topographic positions on the transect (lower slopes, mid slopes and ridge. Most notably there was a complete species turnover between the ridge and the lower Pacific slope. Floristic similarity was negatively correlated with differences in elevation, horizontal precipitation, temperatures and soil conditions between plots. It is

  13. Tree species is the major factor explaining C:N ratios in European forest soils

    DEFF Research Database (Denmark)

    Cools, Nathalie; Vesterdal, Lars; De Vos, Bruno

    2014-01-01

    The C:N ratio is considered as an indicator of nitrate leaching in response to high atmospheric nitrogen (N) deposition. However, the C:N ratio is influenced by a multitude of other site-related factors. This study aimed to unravel the factors determining C:N ratios of forest floor, mineral soil...... mineral soil layers it was the humus type. Deposition and climatic variables were of minor importance at the European scale. Further analysis for eight main forest tree species individually, showed that the influence of environmental variables on C:N ratios was tree species dependent. For Aleppo pine...... and peat top soils in more than 4000 plots of the ICP Forests large-scale monitoring network. The first objective was to quantify forest floor, mineral and peat soil C:N ratios across European forests. Secondly we determined the main factors explaining this C:N ratio using a boosted regression tree...

  14. Do competitive interactions in dry heathlands explain plant abundance patterns and species coexistence?

    DEFF Research Database (Denmark)

    Ransijn, Johannes; Damgaard, Christian; Schmidt, Inger K

    2015-01-01

    Plant community patterns in space and time may be explained by the interactions between competing plant species. The presented study investigates this in a nutrient and species poor ecosystem. The study presents a methodology for inferring competitive interactions from yearly vegetation inventories...... to predict the community dynamics of C. vulgaris and D. flexuosa. This was compared with the observed plant community structure at 198 Danish dry heathland sites. Interspecific competition will most likely lead to competitive exclusion of D. flexuosa at the observed temporal and spatial scale...... and uses this to assess the outcome of competitive interactions and to predict community patterns and dynamics in a Northwest-European dry heathland. Inferred competitive interactions from five consecutive years of measurements in permanent vegetation frames at a single dry heathland site were used...

  15. Does competition for phosphate supply explain the invasion pattern of Elodea species?

    Science.gov (United States)

    Thiébaut, Gabrielle

    2005-09-01

    Two invasive aquatic plants, Elodea canadensis and Elodea nuttallii, occurred in north-eastern France. In this study, we examine the influence of phosphorus availability in soft water streams to explain the invasion pattern of exotic species (E. nuttallii and E. canadensis) compared to native plants (Callitriche platycarpa, Ranunculus peltatus). Total phosphorus was measured in these four aquatic macrophytes. Sediment total phosphorus and water-soluble reactive phosphorus were also analysed each season in 2001. Phosphorus content in the two invasive species and in R. peltatus was higher than in C. platycarpa. Elodea species are adapted to the seasonal phosphorus fluctuations as well as R. peltatus and exhibited high phosphorus storage ability. The high fluctuation availability of resources in space or/and time favoured the spread of the invasive plants and confirms the theory of invasibility of Davis et al. [2000. Fluctuating resources in plant communities: a general theory of invasibility. J. Ecol. 88, 528-534]. The eutrophication process increases the invasibility of E. nuttallii's, while inducing competition between E. nuttallii and native macrophyte species.

  16. Geckos as Springs: Mechanics Explain Across-Species Scaling of Adhesion.

    Science.gov (United States)

    Gilman, Casey A; Imburgia, Michael J; Bartlett, Michael D; King, Daniel R; Crosby, Alfred J; Irschick, Duncan J

    2015-01-01

    One of the central controversies regarding the evolution of adhesion concerns how adhesive force scales as animals change in size, either among or within species. A widely held view is that as animals become larger, the primary mechanism that enables them to climb is increasing pad area. However, prior studies show that much of the variation in maximum adhesive force remains unexplained, even when area is accounted for. We tested the hypothesis that maximum adhesive force among pad-bearing gecko species is not solely dictated by toepad area, but also depends on the ratio of toepad area to gecko adhesive system compliance in the loading direction, where compliance (C) is the change in extension (Δ) relative to a change in force (F) while loading a gecko's adhesive system (C = dΔ/dF). Geckos are well-known for their ability to climb on a range of vertical and overhanging surfaces, and range in mass from several grams to over 300 grams, yet little is understood of the factors that enable adhesion to scale with body size. We examined the maximum adhesive force of six gecko species that vary in body size (~2-100 g). We also examined changes between juveniles and adults within a single species (Phelsuma grandis). We found that maximum adhesive force and toepad area increased with increasing gecko size, and that as gecko species become larger, their adhesive systems become significantly less compliant. Additionally, our hypothesis was supported, as the best predictor of maximum adhesive force was not toepad area or compliance alone, but the ratio of toepad area to compliance. We verified this result using a synthetic "model gecko" system comprised of synthetic adhesive pads attached to a glass substrate and a synthetic tendon (mechanical spring) of finite stiffness. Our data indicate that increases in toepad area as geckos become larger cannot fully account for increased adhesive abilities, and decreased compliance must be included to explain the scaling of adhesion in

  17. Selective logging: do rates of forest turnover in stems, species composition and functional traits decrease with time since disturbance? - A 45 year perspective.

    Science.gov (United States)

    Osazuwa-Peters, Oyomoare L; Jiménez, Iván; Oberle, Brad; Chapman, Colin A; Zanne, Amy E

    2015-12-01

    Selective logging, the targeted harvesting of timber trees in a single cutting cycle, is globally rising in extent and intensity. Short-term impacts of selective logging on tropical forests have been widely investigated, but long-term effects on temporal dynamics of forest structure and composition are largely unknown. Understanding these long-term dynamics will help determine whether tropical forests are resilient to selective logging and inform choices between competing demands of anthropogenic use versus conservation of tropical forests. Forest dynamics can be studied within the framework of succession theory, which predicts that temporal turnover rates should decline with time since disturbance. Here, we investigated the temporal dynamics of a tropical forest in Kibale National Park, Uganda over 45 years following selective logging. We estimated turnover rates in stems, species composition, and functional traits (wood density and diameter at breast height), using observations from four censuses in 1989, 1999, 2006, and 2013, of stems ≥ 10 cm diameter within 17 unlogged and 9 logged 200 × 10 m vegetation plots. We used null models to account for interdependencies among turnover rates in stems, species composition, and functional traits. We tested predictions that turnover rates should be higher and decrease with increasing time since the selective logging event in logged forest, but should be less temporally variable in unlogged forest. Overall, we found higher turnover rates in logged forest for all three attributes, but turnover rates did not decline through time in logged forest and was not less temporally variable in unlogged forest. These results indicate that successional models that assume recovery to pre-disturbance conditions are inadequate for predicting the effects of selective logging on the dynamics of the tropical forest in Kibale. Selective logging resulted in persistently higher turnover rates, which may compromise the carbon storage capacity

  18. Selective logging: do rates of forest turnover in stems, species composition and functional traits decrease with time since disturbance? – A 45 year perspective

    Science.gov (United States)

    Osazuwa-Peters, Oyomoare L.; Jiménez, Iván; Oberle, Brad; Chapman, Colin A.; Zanne, Amy E.

    2015-01-01

    Selective logging, the targeted harvesting of timber trees in a single cutting cycle, is globally rising in extent and intensity. Short-term impacts of selective logging on tropical forests have been widely investigated, but long-term effects on temporal dynamics of forest structure and composition are largely unknown. Understanding these long-term dynamics will help determine whether tropical forests are resilient to selective logging and inform choices between competing demands of anthropogenic use versus conservation of tropical forests. Forest dynamics can be studied within the framework of succession theory, which predicts that temporal turnover rates should decline with time since disturbance. Here, we investigated the temporal dynamics of a tropical forest in Kibale National Park, Uganda over 45 years following selective logging. We estimated turnover rates in stems, species composition, and functional traits (wood density and diameter at breast height), using observations from four censuses in 1989, 1999, 2006, and 2013, of stems ≥ 10 cm diameter within 17 unlogged and 9 logged 200 × 10 m vegetation plots. We used null models to account for interdependencies among turnover rates in stems, species composition, and functional traits. We tested predictions that turnover rates should be higher and decrease with increasing time since the selective logging event in logged forest, but should be less temporally variable in unlogged forest. Overall, we found higher turnover rates in logged forest for all three attributes, but turnover rates did not decline through time in logged forest and was not less temporally variable in unlogged forest. These results indicate that successional models that assume recovery to pre-disturbance conditions are inadequate for predicting the effects of selective logging on the dynamics of the tropical forest in Kibale. Selective logging resulted in persistently higher turnover rates, which may compromise the carbon storage capacity

  19. Geckos as Springs: Mechanics Explain Across-Species Scaling of Adhesion.

    Directory of Open Access Journals (Sweden)

    Casey A Gilman

    Full Text Available One of the central controversies regarding the evolution of adhesion concerns how adhesive force scales as animals change in size, either among or within species. A widely held view is that as animals become larger, the primary mechanism that enables them to climb is increasing pad area. However, prior studies show that much of the variation in maximum adhesive force remains unexplained, even when area is accounted for. We tested the hypothesis that maximum adhesive force among pad-bearing gecko species is not solely dictated by toepad area, but also depends on the ratio of toepad area to gecko adhesive system compliance in the loading direction, where compliance (C is the change in extension (Δ relative to a change in force (F while loading a gecko's adhesive system (C = dΔ/dF. Geckos are well-known for their ability to climb on a range of vertical and overhanging surfaces, and range in mass from several grams to over 300 grams, yet little is understood of the factors that enable adhesion to scale with body size. We examined the maximum adhesive force of six gecko species that vary in body size (~2-100 g. We also examined changes between juveniles and adults within a single species (Phelsuma grandis. We found that maximum adhesive force and toepad area increased with increasing gecko size, and that as gecko species become larger, their adhesive systems become significantly less compliant. Additionally, our hypothesis was supported, as the best predictor of maximum adhesive force was not toepad area or compliance alone, but the ratio of toepad area to compliance. We verified this result using a synthetic "model gecko" system comprised of synthetic adhesive pads attached to a glass substrate and a synthetic tendon (mechanical spring of finite stiffness. Our data indicate that increases in toepad area as geckos become larger cannot fully account for increased adhesive abilities, and decreased compliance must be included to explain the scaling of

  20. Environmental niche conservatism explains the accumulation of species richness in Mediterranean-hotspot plant genera.

    Science.gov (United States)

    Skeels, Alexander; Cardillo, Marcel

    2017-03-01

    The causes of exceptionally high plant diversity in Mediterranean-climate biodiversity hotspots are not fully understood. We asked whether a mechanism similar to the tropical niche conservatism hypothesis could explain the diversity of four large genera (Protea, Moraea, Banksia, and Hakea) with distributions within and adjacent to the Greater Cape Floristic Region (South Africa) or the Southwest Floristic Region (Australia). Using phylogenetic and spatial data we estimated the environmental niche of each species, and reconstructed the mode and dynamics of niche evolution, and the geographic history, of each genus. For three genera, there were strong positive relationships between the diversity of clades within a region and their inferred length of occupation of that region. Within genera, there was evidence for strong evolutionary constraint on niche axes associated with climatic seasonality and aridity, with different niche optima for hotspot and nonhotspot clades. Evolutionary transitions away from hotspots were associated with increases in niche breadth and elevated rates of niche evolution. Our results point to a process of "hotspot niche conservatism" whereby the accumulation of plant diversity in Mediterranean-type ecosystems results from longer time for speciation, with dispersal away from hotspots limited by narrow and phylogenetically conserved environmental niches. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

  1. Identification of the sex-determining locus in grass puffer (Takifugu niphobles) provides evidence for sex-chromosome turnover in a subset of Takifugu species

    Science.gov (United States)

    Atsumi, Kazufumi; Kamiya, Takashi; Nozawa, Aoi; Aoki, Yuma; Tasumi, Satoshi; Koyama, Takashi; Nakamura, Osamu; Suzuki, Yuzuru

    2018-01-01

    There is increasing evidence for frequent turnover in sex chromosomes in vertebrates. Yet experimental systems suitable for tracing the detailed process of turnover are rare. In theory, homologous turnover is possible if the new sex-determining locus is established on the existing sex-chromosome. However, there is no empirical evidence for such an event. The genus Takifugu includes fugu (Takifugu rubripes) and its two closely-related species whose sex is most likely determined by a SNP at the Amhr2 locus. In these species, males are heterozygous, with G and C alleles at the SNP site, while females are homozygous for the C allele. To determine if a shift in the sex-determining locus occurred in another member of this genus, we used genetic mapping to characterize the sex-chromosome systems of Takifugu niphobles. We found that the G allele of Amhr2 is absent in T. niphobles. Nevertheless, our initial mapping suggests a linkage between the phenotypic sex and the chromosome 19, which harbors the Amhr2 locus. Subsequent high-resolution analysis using a sex-reversed fish demonstrated that the sex-determining locus maps to the proximal end of chromosome 19, far from the Amhr2 locus. Thus, it is likely that homologous turnover involving these species has occurred. The data also showed that there is a male-specific reduction of recombination around the sex-determining locus. Nevertheless, no evidence for sex-chromosome differentiation was detected: the reduced recombination depended on phenotypic sex rather than genotypic sex; no X- or Y-specific maker was obtained; the YY individual was viable. Furthermore, fine-scale mapping narrowed down the new sex-determining locus to the interval corresponding to approximately 300-kb of sequence in the fugu genome. Thus, T. niphobles is determined to have a young and small sex-determining region that is suitable for studying an early phase of sex-chromosome evolution and the mechanisms underlying turnover of sex chromosome. PMID

  2. Habitat availability does not explain the species richness patterns of European lentic and lotic freshwater animals

    DEFF Research Database (Denmark)

    Dehling, D.M.; Hof, C.; Brandle, M.

    2010-01-01

    Aim In Europe, the relationships between species richness and latitude differ for lentic (standing water) and lotic (running water) species. Freshwater animals are highly dependent on suitable habitat, and thus the distribution of available habitat should strongly influence large-scale patterns...... of species richness. We tested whether habitat availability can account for the differences in species richness patterns between European lentic and lotic freshwater animals. Location Europe. Methods We compiled occurrence data of 1959 lentic and 2445 lotic species as well as data on the amount of lentic...... for previously reported latitudinal patterns in species richness. For lotic species, richness declined with latitude, whereas there was no relationship between habitat availability and latitude. For lentic species, richness showed a hump-shaped relationship with latitude, whereas available habitat increased...

  3. Biotic and abiotic variables show little redundancy in explaining tree species distributions

    DEFF Research Database (Denmark)

    Meier, Elaine S.; Kienast, Felix; Pearman, Peter B.

    2010-01-01

    Abiotic factors such as climate and soil determine the species fundamental niche, which is further constrained by biotic interactions such as interspecific competition. To parameterize this realized niche, species distribution models (SDMs) most often relate species occurrence data to abiotic var...

  4. Historical dynamics and current environmental effects explain the spatial distribution of species richness patterns of New World monkeys

    Directory of Open Access Journals (Sweden)

    Paulo Vallejos-Garrido

    2017-09-01

    -fitting model that explains species richness. OLS and SAR models show that this set of variables explains 69.9% and 64.2% of species richness, respectively. Potential of evapotranspiration is the most important variable within this model, showing a linear positive relationship with species richness, and clear lower and upper limits to the species richness distribution. Discussion We suggest that New World monkeys historically migrated from their biodiversity hotspot (energetically optimal areas for most platyrrine species to adjacent, energetically suboptimal areas, and that the different dispersal abilities of these species, the lack of competitive interactions at a macroecological scale, and environmental constraints (i.e., energy availability, seasonality are key elements which explain the non-uniform pattern of species richness for this clade.

  5. Response of the Fine Root Production, Phenology, and Turnover Rate of Six Shrub Species from a Subtropical Forest to a Soil Moisture Gradient and Shading

    Science.gov (United States)

    Fu, X.; Dai, X.; Wang, H.

    2015-12-01

    Knowledge of the fine root dynamics of different life forms in forest ecosystems is critical to understanding how the overall belowground carbon cycling is affected by climate change. However, our current knowledge regarding how endogenous or exogenous factors regulate the root dynamics of understory vegetation is limited. We selected a suite of study sites representing different habitats with gradients of soil moisture and solar radiation (shading or no shading). We assessed the fine root production phenology, the total fine root production, and the turnover among six understory shrub species in a subtropical climate, and examined the responses of the fine root dynamics to gradients in the soil moisture and solar radiation. The shrubs included three evergreen species, Loropetalum chinense, Vaccinium bracteatum, and Adinandra millettii, and three deciduous species, Serissa serissoides, Rubus corchorifolius, and Lespedeza davidii. We observed that variations in the annual fine root production and turnover among species were significant in the deciduous group but not in the evergreen group. Notably, V. bracteatum and S. serissoides presented the greatest responses in terms of root phenology to gradients in the soil moisture and shading: high-moisture habitat led to a decrease and shade led to an increase in fine root production during spring. Species with smaller fine roots of the 1st+2nd-order diameter presented more sensitive responses in terms of fine root phenology to a soil moisture gradient. Species with a higher fine root nitrogen-to -carbon ratio exhibited more sensitive responses in terms of fine root annual production to shading. Soil moisture and shading did not change the annual fine root production as much as the turnover rate. The fine root dynamics of some understory shrubs varied significantly with soil moisture and solar radiation status and may be different from tree species. Our results emphasize the need to study the understory fine root dynamics

  6. Explaining local-scale species distributions: relative contributions of spatial autocorrelation and landscape heterogeneity for an avian assemblage.

    Directory of Open Access Journals (Sweden)

    Brady J Mattsson

    Full Text Available Understanding interactions between mobile species distributions and landcover characteristics remains an outstanding challenge in ecology. Multiple factors could explain species distributions including endogenous evolutionary traits leading to conspecific clustering and endogenous habitat features that support life history requirements. Birds are a useful taxon for examining hypotheses about the relative importance of these factors among species in a community. We developed a hierarchical Bayes approach to model the relationships between bird species occupancy and local landcover variables accounting for spatial autocorrelation, species similarities, and partial observability. We fit alternative occupancy models to detections of 90 bird species observed during repeat visits to 316 point-counts forming a 400-m grid throughout the Patuxent Wildlife Research Refuge in Maryland, USA. Models with landcover variables performed significantly better than our autologistic and null models, supporting the hypothesis that local landcover heterogeneity is important as an exogenous driver for species distributions. Conspecific clustering alone was a comparatively poor descriptor of local community composition, but there was evidence for spatial autocorrelation in all species. Considerable uncertainty remains whether landcover combined with spatial autocorrelation is most parsimonious for describing bird species distributions at a local scale. Spatial structuring may be weaker at intermediate scales within which dispersal is less frequent, information flows are localized, and landcover types become spatially diversified and therefore exhibit little aggregation. Examining such hypotheses across species assemblages contributes to our understanding of community-level associations with conspecifics and landscape composition.

  7. Traits related to species persistence and dispersal explain changes in plant communities subjected to habitat loss

    DEFF Research Database (Denmark)

    Marini, Lorenzo; Bruun, Hans Henrik; Heikkinen, Risto

    2012-01-01

    Aim Habitat fragmentation is a major driver of biodiversity loss but it is insufficiently known how much its effects vary among species with different life-history traits; especially in plant communities, the understanding of the role of traits related to species persistence and dispersal in dete...... rural landscapes in NW Europe, mitigating the spatial isolation of remaining grasslands should be accompanied by restoration measures aimed at improving habitat quality for low competitors, abiotically dispersed and perennial, clonal species.......Aim Habitat fragmentation is a major driver of biodiversity loss but it is insufficiently known how much its effects vary among species with different life-history traits; especially in plant communities, the understanding of the role of traits related to species persistence and dispersal...... in determining dynamics of species communities in fragmented landscapes is still limited. The primary aim of this study was to test how plant traits related to persistence and dispersal and their interactions modify plant species vulnerability to decreasing habitat area and increasing isolation. Location Five...

  8. Explaining the species richness of birds along a subtropical elevational gradient in the Hengduan Mountains

    DEFF Research Database (Denmark)

    Wu, Yongjie; Colwell, Robert K.; Rahbek, Carsten

    2013-01-01

    AimTo document the species richness pattern of birds in the Hengduan Mountains and to understand its causes. LocationHengduan Mountains, China. MethodsSpecies richness of 738 breeding bird species was calculated for each 100-m elevational band along a gradient from 100 to 6000m a.s.l. Climate data...... were compiled based on monthly records from 182 meteorological stations in the Hengduan Mountains from 1959 to 2004. We calculated the planimetric area, predicted richness under geometric constraints, three-year average NDVI (normalized difference vegetation index) and EVI (enhanced vegetation index...... that climatic and energy factors correlate well with the richness pattern of birds, and that on the surveyed subtropical mountain, the elevational bands with highest seasonality harbour fewer species than areas with less seasonal variation in temperature. The results, however, vary somewhat among taxonomic...

  9. Deficit in community species richness as explained by area and isolation of sites

    DEFF Research Database (Denmark)

    Bruun, Hans Henrik

    2000-01-01

    The potential community species richness was predicted for 85 patches of seminatural grassland in an agricultural landscape in Denmark. The basis of the prediction was a very large dataset on the vegetation, soil pH and topography in Danish grasslands and related communities. Species were inserte......, community richness deficit, varied considerably among patches. Community richness deficit exhibited a negative relationship with patch area, and for small patches a positive relationship with patch isolation....

  10. Turnover Time

    Science.gov (United States)

    Ecosystems contain energy and materials such as carbon, nitrogen, phosphorus, and water, and are open to their flow-through. Turnover time refers to the amount of time required for replacement by flow-through of the energy or substance of interest contained in the system, and is ...

  11. Can commonly measurable traits explain differences in metal accumulation and toxicity in earthworm species?

    NARCIS (Netherlands)

    Qiu, H.; Peijnenburg, W.J.G.M.; van Gestel, C.A.M.; Vijver, M.G.

    2014-01-01

    There is no clear consensus in the literature on the metal accumulation pattern and sensitivity of different earthworm species. In the present study, accumulation and toxicity of Cu, Cd, Ni, and Zn in the earthworms Lumbricus rubellus (epigeic), Aporrectodea longa (anecic), and Eisenia fetida

  12. Can species-specific prey responses to chemical cues explain prey susceptibility to predation?

    Science.gov (United States)

    Šmejkal, Marek; Ricard, Daniel; Sajdlová, Zuzana; Čech, Martin; Vejřík, Lukáš; Blabolil, Petr; Vejříková, Ivana; Prchalová, Marie; Vašek, Mojmír; Souza, Allan T; Brönmark, Christer; Peterka, Jiří

    2018-05-01

    The perception of danger represents an essential ability of prey for gaining an informational advantage over their natural enemies. Especially in complex environments or at night, animals strongly rely on chemoreception to avoid predators. The ability to recognize danger by chemical cues and subsequent adaptive responses to predation threats should generally increase prey survival. Recent findings suggest that European catfish ( Silurus glanis ) introduction induce changes in fish community and we tested whether the direction of change can be attributed to differences in chemical cue perception. We tested behavioral response to chemical cues using three species of freshwater fish common in European water: rudd ( Scardinius erythrophthalmus ), roach ( Rutilus rutilus ), and perch ( Perca fluviatilis ). Further, we conducted a prey selectivity experiment to evaluate the prey preferences of the European catfish. Roach exhibited the strongest reaction to chemical cues, rudd decreased use of refuge and perch did not alter any behavior in the experiment. These findings suggest that chemical cue perception might be behind community data change and we encourage collecting more community data of tested prey species before and after European catfish introduction to test the hypothesis. We conclude that used prey species can be used as a model species to verify whether chemical cue perception enhances prey survival.

  13. Mixed species flock, nest height, and elevation partially explain avian haemoparasite prevalence in Colombia.

    Directory of Open Access Journals (Sweden)

    Angie D González

    Full Text Available The high avian biodiversity present in the Neotropical region offers a great opportunity to explore the ecology of host-parasite relationships. We present a survey of avian haemoparasites in a megadiverse country and explore how parasite prevalences are related to physical and ecological host characteristics. Using light microscopy, we documented the presence of haemoparasites in over 2000 individuals belonging to 246 species of wild birds, from nine localities and several ecosystems of Colombia. We analysed the prevalence of six avian haemoparasite taxa in relation to elevation and the following host traits: nest height, nest type, foraging strata, primary diet, sociality, migratory behaviour, and participation in mixed species flocks. Our analyses indicate significant associations between both mixed species flocks and nest height and Haemoproteus and Leucocytozoon prevalence. The prevalence of Leucocytozoon increased with elevation, whereas the prevalence of Trypanosoma and microfilariae decreased. Plasmodium and Haemoproteus prevalence did not vary significantly with elevation; in fact, both parasites were found up to 3300 m above sea level. The distribution of parasite prevalence across the phylogeny of bird species included in this study showed little host phylogenetic signal indicating that infection rates in this system are evolutionarily labile. Vector distribution as well as the biology of transmission and the maintenance of populations of avian haemoparasites deserve more detailed study in this system.

  14. Species composition and forest structure explain the temperature sensitivity patterns of productivity in temperate forests

    Directory of Open Access Journals (Sweden)

    F. J. Bohn

    2018-03-01

    Full Text Available Rising temperatures due to climate change influence the wood production of forests. Observations show that some temperate forests increase their productivity, whereas others reduce their productivity. This study focuses on how species composition and forest structure properties influence the temperature sensitivity of aboveground wood production (AWP. It further investigates which forests will increase their productivity the most with rising temperatures. We described forest structure by leaf area index, forest height and tree height heterogeneity. Species composition was described by a functional diversity index (Rao's Q and a species distribution index (ΩAWP. ΩAWP quantified how well species are distributed over the different forest layers with regard to AWP. We analysed 370 170 forest stands generated with a forest gap model. These forest stands covered a wide range of possible forest types. For each stand, we estimated annual aboveground wood production and performed a climate sensitivity analysis based on 320 different climate time series (of 1-year length. The scenarios differed in mean annual temperature and annual temperature amplitude. Temperature sensitivity of wood production was quantified as the relative change in productivity resulting from a 1 °C rise in mean annual temperature or annual temperature amplitude. Increasing ΩAWP positively influenced both temperature sensitivity indices of forest, whereas forest height showed a bell-shaped relationship with both indices. Further, we found forests in each successional stage that are positively affected by temperature rise. For such forests, large ΩAWP values were important. In the case of young forests, low functional diversity and small tree height heterogeneity were associated with a positive effect of temperature on wood production. During later successional stages, higher species diversity and larger tree height heterogeneity were an advantage. To achieve such a

  15. Species composition and forest structure explain the temperature sensitivity patterns of productivity in temperate forests

    Science.gov (United States)

    Bohn, Friedrich J.; May, Felix; Huth, Andreas

    2018-03-01

    Rising temperatures due to climate change influence the wood production of forests. Observations show that some temperate forests increase their productivity, whereas others reduce their productivity. This study focuses on how species composition and forest structure properties influence the temperature sensitivity of aboveground wood production (AWP). It further investigates which forests will increase their productivity the most with rising temperatures. We described forest structure by leaf area index, forest height and tree height heterogeneity. Species composition was described by a functional diversity index (Rao's Q) and a species distribution index (ΩAWP). ΩAWP quantified how well species are distributed over the different forest layers with regard to AWP. We analysed 370 170 forest stands generated with a forest gap model. These forest stands covered a wide range of possible forest types. For each stand, we estimated annual aboveground wood production and performed a climate sensitivity analysis based on 320 different climate time series (of 1-year length). The scenarios differed in mean annual temperature and annual temperature amplitude. Temperature sensitivity of wood production was quantified as the relative change in productivity resulting from a 1 °C rise in mean annual temperature or annual temperature amplitude. Increasing ΩAWP positively influenced both temperature sensitivity indices of forest, whereas forest height showed a bell-shaped relationship with both indices. Further, we found forests in each successional stage that are positively affected by temperature rise. For such forests, large ΩAWP values were important. In the case of young forests, low functional diversity and small tree height heterogeneity were associated with a positive effect of temperature on wood production. During later successional stages, higher species diversity and larger tree height heterogeneity were an advantage. To achieve such a development, one could plant

  16. Difference between the vocalizations of two sister species of pigeons explained in dynamical terms.

    Science.gov (United States)

    Alonso, R Gogui; Kopuchian, Cecilia; Amador, Ana; Suarez, Maria de Los Angeles; Tubaro, Pablo L; Mindlin, Gabriel B

    2016-05-01

    Vocal communication is an unique example, where the nonlinear nature of the periphery can give rise to complex sounds even when driven by simple neural instructions. In this work we studied the case of two close-related bird species, Patagioenas maculosa and Patagioenas picazuro, whose vocalizations differ only in the timbre. The temporal modulation of the fundamental frequency is similar in both cases, differing only in the existence of sidebands around the fundamental frequency in the P. maculosa. We tested the hypothesis that the qualitative difference between these vocalizations lies in the nonlinear nature of the syrinx. In particular, we propose that the roughness of maculosa's vocalizations is due to an asymmetry between the right and left vibratory membranes, whose nonlinear dynamics generate the sound. To test the hypothesis, we generated a biomechanical model for vocal production with an asymmetric parameter Q with which we can control the level of asymmetry between these membranes. Using this model we generated synthetic vocalizations with the principal acoustic features of both species. In addition, we confirmed the anatomical predictions by making post mortem inspection of the syrinxes, showing that the species with tonal song (picazuro) has a more symmetrical pair of membranes compared to maculosa.

  17. Topographic heterogeneity and temperature amplitude explain species richness patterns of birds in the Qinghai-Tibetan Plateau.

    Science.gov (United States)

    Zhang, Chunlan; Quan, Qing; Wu, Yongjie; Chen, Youhua; He, Peng; Qu, Yanhua; Lei, Fumin

    2017-04-01

    Large-scale patterns of species richness have gained much attention in recent years; however, the factors that drive high species richness are still controversial in local regions, especially in highly diversified montane regions. The Qinghai-Tibetan Plateau (QTP) and the surrounding mountains are biodiversity hot spots due to a high number of endemic montane species. Here, we explored the factors underlying this high level of diversity by studying the relationship between species richness and environmental variables. The richness patterns of 758 resident bird species were summarized at the scale of 1°×1° grid cell at different taxonomic levels (order, family, genus, and species) and in different taxonomic groups (Passeriformes, Galliformes, Falconiformes, and Columbiformes). These richness patterns were subsequently analyzed against habitat heterogeneity (topographical heterogeneity and land cover), temperature amplitude (annual temperature, annual precipitation, precipitation seasonality, and temperature seasonality) and a vegetation index (net primary productivity). Our results showed that the highest richness was found in the southeastern part of the QTP, the eastern Himalayas. The lowest richness was observed in the central plateau of the QTP. Topographical heterogeneity and temperature amplitude are the primary factors that explain overall patterns of species richness in the QTP, although the specific effect of each environmental variable varies between the different taxonomic groups depending on their own evolutionary histories and ecological requirements. High species richness in the southeastern QTP is mostly due to highly diversified habitat types and temperature zones along elevation gradients, whereas the low species richness in the central plateau of the QTP may be due to environmental and energetic constraints, as the central plateau is harsh environment.

  18. Colony geometry and structural complexity of the endangered species Acropora cervicornis partly explains the structure of their associated fish assemblage.

    Science.gov (United States)

    Agudo-Adriani, Esteban A; Cappelletto, Jose; Cavada-Blanco, Francoise; Croquer, Aldo

    2016-01-01

    In the past decade, significant efforts have been made to describe fish-habitat associations. However, most studies have oversimplified actual connections between fish assemblages and their habitats by using univariate correlations. The purpose of this study was to identify the features of habitat forming corals that facilitate and influences assemblages of associated species such as fishes. For this we developed three-dimensional models of colonies of Acropora cervicornis to estimate geometry (length and height), structural complexity (i.e., volume, density of branches, etc.) and biological features of the colonies (i.e., live coral tissue, algae). We then correlated these colony characteristics with the associated fish assemblage using multivariate analyses. We found that geometry and complexity were better predictors of the structure of fish community, compared to other variables such as percentage of live coral tissue or algae. Combined, the geometry of each colony explained 40% of the variability of the fish assemblage structure associated with this coral species; 61% of the abundance and 69% of fish richness, respectively. Our study shows that three-dimensional reconstructions of discrete colonies of Acropora cervicornis provides a useful description of the colonial structural complexity and may explain a great deal of the variance in the structure of the associated coral reef fish community. This demonstration of the strongly trait-dependent ecosystem role of this threatened species has important implications for restoration and conservation efforts.

  19. Colony geometry and structural complexity of the endangered species Acropora cervicornis partly explains the structure of their associated fish assemblage

    Directory of Open Access Journals (Sweden)

    Esteban A. Agudo-Adriani

    2016-04-01

    Full Text Available In the past decade, significant efforts have been made to describe fish-habitat associations. However, most studies have oversimplified actual connections between fish assemblages and their habitats by using univariate correlations. The purpose of this study was to identify the features of habitat forming corals that facilitate and influences assemblages of associated species such as fishes. For this we developed three-dimensional models of colonies of Acropora cervicornis to estimate geometry (length and height, structural complexity (i.e., volume, density of branches, etc. and biological features of the colonies (i.e., live coral tissue, algae. We then correlated these colony characteristics with the associated fish assemblage using multivariate analyses. We found that geometry and complexity were better predictors of the structure of fish community, compared to other variables such as percentage of live coral tissue or algae. Combined, the geometry of each colony explained 40% of the variability of the fish assemblage structure associated with this coral species; 61% of the abundance and 69% of fish richness, respectively. Our study shows that three-dimensional reconstructions of discrete colonies of Acropora cervicornis provides a useful description of the colonial structural complexity and may explain a great deal of the variance in the structure of the associated coral reef fish community. This demonstration of the strongly trait-dependent ecosystem role of this threatened species has important implications for restoration and conservation efforts.

  20. Individual and species-specific traits explain niche size and functional role in spiders as generalist predators.

    Science.gov (United States)

    Sanders, Dirk; Vogel, Esther; Knop, Eva

    2015-01-01

    The function of a predator within a community is greatly based on its trophic niche, that is the number and the strength of feeding links. In generalist predators, which feed on a wide range of prey, the size and position of the trophic niche is likely determined by traits such as hunting mode, the stratum they occur in, their body size and age. We used stable isotope analyses ((13)C and (15)N) to measure the trophic niche size of nine spider species within a forest hedge community and tested for species traits and individual traits that influence stable isotope enrichment, niche size and resource use. The spiders Enoplognatha, Philodromus, Floronia, and Heliophanus had large isotopic niches, which correspond to a more generalistic feeding behaviour. In contrast, Araneus, Metellina and Agelena, as top predators in the system, had rather narrow niches. We found a negative correlation between trophic position and niche size. Differences in trophic position in spiders were explained by body size, hunting modes and stratum, while niche size was influenced by hunting mode. In Philodromus, the size of the trophic niche increased significantly with age. Fitting spiders to functional groups according to their mean body size, hunting mode and their habitat domain resulted in largely separated niches, which indicates that these traits are meaningful for separating functional entities in spiders. Functional groups based on habitat domain (stratum) caught the essential functional differences between the species with species higher up in the vegetation feeding on flying insects and herb and ground species also preying on forest floor decomposers. Interestingly, we found a gradient from large species using a higher habitat domain and having a smaller niche to smaller species foraging closer to the ground and having a larger niche. This shows that even within generalist predators, such as spiders, there is a gradient of specialism that can be predicted by functional traits.

  1. Can the reproductive system of a rare and narrowly endemic plant species explain its high genetic diversity?

    Directory of Open Access Journals (Sweden)

    Daniele M. Rodrigues

    2018-01-01

    Full Text Available ABSTRACT The reproductive system of flowering plants can be highly variable, affecting their biology, gene flow and genetic variability among populations. Petunia secreta is a rare annual endemic species of Pedra do Segredo, located in the municipality of Caçapava do Sul, state of Rio Grande do Sul, Brazil. Although rare, the species possesses a high level of genetic variability. We investigated the reproductive system of P. secreta, including fruit production and seed germinability, in order to determine if its reproductive system can explain its genetic diversity. We sampled five populations and conducted five greenhouse hand-pollination treatments: 1 autonomous apomixis; 2 self-pollination; 3 hand self-pollination; 4 geitonogamy; and 5 cross-pollination. We analysed a total of 40 plants, 468 flowers, and 6,500 seeds. Only autonomous apomixis and self-pollination did not produce fruit. No differences in fruit weight were observed among pollination treatments (P > 0.05. Seeds of two colours were produced, with no differences in germinability. Considering all plants, populations, and treatments, the average germinability was 73 % (range 9 % to 100 %. These results, along with other previous studies, indicate that the reproductive systems of P. secreta, and its large effective population size, can explain its high genetic diversity.

  2. Common environmental factors explain both ectomycorrhizal species diversity and pine regeneration variability in a post-fire Mediterranean forest.

    Science.gov (United States)

    Buscardo, Erika; Freitas, Helena; Pereira, João Santos; De Angelis, Paolo

    2011-08-01

    Natural seedling regeneration and establishment after stand replacing wildfires is influenced by a series of environmental and biological constraints. In this study, we characterized the diversity and structure of the ectomycorrhizal (ECM) fungal community associated with post-fire naturally regenerated maritime pine saplings, and individuate the environmental factors responsible for fungal species distribution. We also identify the main environmental factors responsible for maritime pine regeneration variability and assessed the relation between saplings performance and ECM fungal diversity indices. Fungal species were identified by direct sequencing of internal transcribed spacer regions. Five years after the disturbance event, a total of 30 taxa colonized the pine saplings. The ECM fungal community was dominated by ruderal species of the genus Rhizopogon (present in almost half of the samples). Almost one third of the identified ECM fungal species belonged to the family Thelephoraceae. Typical k-selected species like Amanita pantherina, Boletus aestivalis, Lactarius chrysorrheus, and Russula densifolia were found on pine saplings collected in proximity of unburnt pine trees, in correspondence with low erosion extents. Pine regeneration varied throughout the study areas and was enhanced at higher elevations, in correspondence with moderate slopes, shallower soils, and a reduced cover of ericaceous shrubs and bare ground. These conditions were found in close proximity to patches of pine trees that survived the disturbance event and were previously characterized by a higher pre-fire pine biomass. Even though no correlations were found between saplings performance and ECM fungal diversity indices, common environmental factors (i.e., ericaceous shrub cover, extent of erosion, slope, and soil depth) were responsible for shaping the ECM fungal distribution and for describing most of the explained regeneration variability.

  3. Differences in U root-to-shoot translocation between plant species explained by U distribution in roots

    Energy Technology Data Exchange (ETDEWEB)

    Straczek, Anne; Duquene, Lise [Belgium Nuclear Research Centre (SCK.CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol (Belgium); Wegrzynek, Dariusz [IAEA, Seibersdorf Laboratories, A-2444 Seibersdorf (Austria); Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Krakow (Poland); Chinea-Cano, Ernesto [IAEA, Seibersdorf Laboratories, A-2444 Seibersdorf (Austria); Wannijn, Jean [Belgium Nuclear Research Centre (SCK.CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol (Belgium); Navez, Jacques [Royal Museum of Africa, Department of Geology, Leuvensesteenweg 13, 3080 Tervuren (Belgium); Vandenhove, Hildegarde, E-mail: hvandenh@sckcen.b [Belgium Nuclear Research Centre (SCK.CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol (Belgium)

    2010-03-15

    Accumulation and distribution of uranium in roots and shoots of four plants species differing in their cation exchange capacity of roots (CECR) was investigated. After exposure in hydroponics for seven days to 100 mumol U L{sup -1}, distribution of uranium in roots was investigated through chemical extraction of roots. Higher U concentrations were measured in roots of dicots which showed a higher CECR than monocot species. Chemical extractions indicated that uranium is mostly located in the apoplasm of roots of monocots but that it is predominantly located in the symplasm of roots of dicots. Translocation of U to shoot was not significantly affected by the CECR or distribution of U between symplasm and apoplasm. Distribution of uranium in roots was investigated through chemical extraction of roots for all species. Additionally, longitudinal and radial distribution of U in roots of maize and Indian mustard, respectively showing the lowest and the highest translocation, was studied following X-ray fluorescence (XRF) analysis of specific root sections. Chemical analysis and XRF analysis of roots of maize and Indian mustard clearly indicated a higher longitudinal and radial transport of uranium in roots of Indian mustard than in roots of maize, where uranium mostly accumulated in root tips. These results showed that even if CECR could partly explain U accumulation in roots, other mechanisms like radial and longitudinal transport are implied in the translocation of U to the shoot.

  4. Differences in U root-to-shoot translocation between plant species explained by U distribution in roots

    International Nuclear Information System (INIS)

    Straczek, Anne; Duquene, Lise; Wegrzynek, Dariusz; Chinea-Cano, Ernesto; Wannijn, Jean; Navez, Jacques; Vandenhove, Hildegarde

    2010-01-01

    Accumulation and distribution of uranium in roots and shoots of four plants species differing in their cation exchange capacity of roots (CECR) was investigated. After exposure in hydroponics for seven days to 100 μmol U L -1 , distribution of uranium in roots was investigated through chemical extraction of roots. Higher U concentrations were measured in roots of dicots which showed a higher CECR than monocot species. Chemical extractions indicated that uranium is mostly located in the apoplasm of roots of monocots but that it is predominantly located in the symplasm of roots of dicots. Translocation of U to shoot was not significantly affected by the CECR or distribution of U between symplasm and apoplasm. Distribution of uranium in roots was investigated through chemical extraction of roots for all species. Additionally, longitudinal and radial distribution of U in roots of maize and Indian mustard, respectively showing the lowest and the highest translocation, was studied following X-ray fluorescence (XRF) analysis of specific root sections. Chemical analysis and XRF analysis of roots of maize and Indian mustard clearly indicated a higher longitudinal and radial transport of uranium in roots of Indian mustard than in roots of maize, where uranium mostly accumulated in root tips. These results showed that even if CECR could partly explain U accumulation in roots, other mechanisms like radial and longitudinal transport are implied in the translocation of U to the shoot.

  5. Employee Turnover: Evidence from a Case Study.

    Science.gov (United States)

    Borland, Jeff

    1997-01-01

    Patterns of employee turnover from a medium-sized law firm in Australia were examined in regard to theories of worker mobility (matching, sectoral shift, and incentive). Results support a role for matching effects, but personnel practices affect the timing of turnover. Matching and incentive-based theories do not explain the high rates of turnover…

  6. Predicting Employee Turnover from Communication Networks.

    Science.gov (United States)

    Feeley, Thomas H.; Barnett, George A.

    1997-01-01

    Investigates three social network models of employee turnover: a structural equivalence model, a social influence model, and an erosion model. Administers a communication network questionnaire to all 170 employees of an organization. Finds support for all three models of turnover, with the erosion model explaining more of the variance than do the…

  7. University Lecturers' Professional Empowerment and Turnover in ...

    African Journals Online (AJOL)

    Many universities in Uganda are grappling with the challenge of academic staff turnover. While research conducted so far has established different factors explaining the problems of turnover, many of which have been addressed, this challenge has not been resolved. Hitherto, attention has not been paid to whether ...

  8. Phylogenetic turnover during subtropical forest succession across environmental and phylogenetic scales.

    Science.gov (United States)

    Purschke, Oliver; Michalski, Stefan G; Bruelheide, Helge; Durka, Walter

    2017-12-01

    Although spatial and temporal patterns of phylogenetic community structure during succession are inherently interlinked and assembly processes vary with environmental and phylogenetic scales, successional studies of community assembly have yet to integrate spatial and temporal components of community structure, while accounting for scaling issues. To gain insight into the processes that generate biodiversity after disturbance, we combine analyses of spatial and temporal phylogenetic turnover across phylogenetic scales, accounting for covariation with environmental differences. We compared phylogenetic turnover, at the species- and individual-level, within and between five successional stages, representing woody plant communities in a subtropical forest chronosequence. We decomposed turnover at different phylogenetic depths and assessed its covariation with between-plot abiotic differences. Phylogenetic turnover between stages was low relative to species turnover and was not explained by abiotic differences. However, within the late-successional stages, there was high presence-/absence-based turnover (clustering) that occurred deep in the phylogeny and covaried with environmental differentiation. Our results support a deterministic model of community assembly where (i) phylogenetic composition is constrained through successional time, but (ii) toward late succession, species sorting into preferred habitats according to niche traits that are conserved deep in phylogeny, becomes increasingly important.

  9. Sucrose-phosphate synthase in tree species: light/dark regulation involves a component of protein turnover in Prosopis juliflora (SW DC).

    Science.gov (United States)

    Sinha, A K; Shirke, P A; Pathre, U; Sane, P V

    1997-10-01

    Light dependent modulation of sucrose-phosphate synthase activity (SPS; EC 2.4.1.14) was studied in a tree species, namely Prosopis juliflora. In this paper we demonstrate that cycloheximide, an inhibitor of cytoplasmic protein synthesis, when fed to detached leaves of P. juliflora through transpiration stream in the dark or in light completely prevents in vivo light activation of Vlim and Vmax activities of SPS. In case of spinach, however, cycloheximide feeding affects only Vlim activity while Vmax activity remained unchanged. In contrast, chloramphenicol, an inhibitor of protein synthesis in chloroplast has no effect on the light activation of SPS in Prosopis. The treatment with cycloheximide showed slight reduction in the rate of O2 evolution indicating that cycloheximide had very little effect on overall photosynthesis. These results indicate that short term protein turnover of the SPS protein and some other essential component(s) (e.g., a putative protein that modifies SPS activity) is one of the primary steps in a complex and unique regulatory cascade effecting the reversible light activation of SPS.

  10. Turnover among healthcare professionals.

    Science.gov (United States)

    Wood, Ben D

    2009-01-01

    Turnover among healthcare professionals is a costly consequence. The existing body of knowledge on healthcare professional turnover is correlated with job satisfaction levels. A landmark study differentiated 2 areas of job satisfaction categories: satisfiers and dissatisfiers (intrinsic and extrinsic motivators). The aim of this article is to examine existing research on precursors of turnover, such as burnout behaviors experienced by healthcare professionals, job satisfaction levels, employee organizational commitment, health complications which precede turnover, some current strategies to reduce turnover, and some effects CEO turnover has on employee turnover intentions.

  11. Strong congruence in tree and fern community turnover in response to soils and climate in central Panama

    DEFF Research Database (Denmark)

    Jones, Mirkka; Ferrier, Simon; Condit, Richard

    2013-01-01

    1. Plant species turnover in central Panamanian forests has been principally attributed to the effects of dispersal limitation and a strong Caribbean to Pacific gradient in rainfall seasonality. Despite marked geological heterogeneity, the role of soil variation has not been rigorously examined. 2....... We modelled the compositional turnover of trees and ferns in the Panama Canal watershed as a function of soil chemistry, climate and geographical separation, using generalized dissimilarity models (GDMs). 3. Predictability in both plant groups was strong, with 74% of turnover explained in trees...... and 49% in ferns. Major trends in the two plant groups were strikingly similar. The independent effects of soils, and of climate for trees, were sizeable, but those of geographical distance were minor. In both plant groups, distance and climatic effects on species turnover covaried strongly. 4. Including...

  12. [New nurse turnover intention and influencing factors].

    Science.gov (United States)

    Han, Sang Sook; Sohn, In Soon; Kim, Nam Eun

    2009-12-01

    The study was done to identify turnover intention in new nurses according to characteristics of the nurses and other factors affecting turnover and to provide data to set up a strategy to reduce the turnover. Data were collected from 1,077 new nurses who had less than 12 months employment experience and worked in one of 188 hospitals. Eight research instruments were used. Data analysis was done using SPSS WIN 15.0 program. Several factors influence new nurse turnover intention. The average score for turnover intention was 2.12. The scores for subscales were self efficacy, 3.76, nursing performance, 3.90, job satisfaction, 2.09, organization commitment, 1.28, stress, 1.32, burnout, 2.82 and nursing organizational culture, 3.29. Turnover intention was related to self efficacy, nursing performance, job satisfaction, organization commitment, stress, burnout, nursing organizational culture, duration of in-class training, duration of on the job training, number of hospital beds, length of employment and duration of employment in current workplace. The predicting factors for turnover intention were burnout, stress, duration of employment in the current workplace, self efficacy and nursing performance. Those factors explained 51.6% of turnover intention. New nurse turnover intention can be reduced by mitigating the factors affecting this intention.

  13. Molecular phylogeny of the genus Asparagus (Asparagaceae) explains interspecific crossability between the garden asparagus (A. officinalis) and other Asparagus species.

    Science.gov (United States)

    Kubota, Shosei; Konno, Itaru; Kanno, Akira

    2012-02-01

    The genus Asparagus comprises approximately 200 species, some of which are commercially cultivated, such as the garden asparagus (A. officinalis). Many Asparagus species, including A. officinalis, are dioecious and have been grouped into a subgenus distinct from that of hermaphroditic species. Although many interspecific crossings have been attempted to introduce useful traits into A. officinalis, only some of the dioecious species were found to be cross-compatible with A. officinalis. Here, molecular phylogenetic analyses were conducted to determine whether interspecific crossability is proportional to the genetic distance between the crossing pairs and to further clarify the evolutionary history of the Asparagus genus. A clade with all cross-compatible species and no cross-incompatible species was recovered in the phylogenetic tree based on analyses of non-coding cpDNA regions. In addition, a sex-linked marker developed for A. officinalis amplified a male-specific region in all cross-compatible species. The phylogenetic analyses also provided some insights about the evolutionary history of Asparagus; for example, by indicating that the genus had its origin in southern Africa, subsequently spreading throughout the old world through intensive speciation and dispersal. The results also suggest that dioecious species were derived from a single evolutionary transition from hermaphroditism in Asparagus. These findings not only contribute towards the understanding of the evolutionary history of the genus but may also facilitate future interspecific hybridization programs involving Asparagus species.

  14. Conflict over non-partitioned resources may explain between-species differences in declines: the anthropogenic competition hypothesis.

    Science.gov (United States)

    Higginson, Andrew D

    2017-01-01

    Human alterations of habitats are causing declines in many species worldwide. The extent of declines varies greatly among closely related species, for often unknown reasons that must be understood in order to maintain biodiversity. An overlooked factor is that seasonally breeding species compete for nest sites, which are increasingly limited in many anthropogenically degraded environments. I used evolutionary game theory to predict the outcome of competition between individuals that differ in their competitive ability and timing of nesting. A range of species following evolutionarily stable strategies can co-exist when there are sufficient nest sites, but my model predicts that a reduction in nest site availability has greater impacts on late-nesting species, especially the stronger competitors, whereas early-nesting, stronger species decline only slightly. These predictions are supported by data on 221 bird and 43 bumblebee species worldwide. Restoration and provision of nest sites should be an urgent priority in conservation efforts. More broadly, these results indicate a new ecological principle of potentially widespread importance: rapid reductions in the abundance of resources for which species' preferences have not diversified will result in unprecedented conflicts that reduce the potential for species co-existence. Understanding the causes of species declines is crucial to preventing the losses. Whilst much work on species vulnerability shows broad scale effects, an enduring mystery is the variation in population trends between closely related species. I combined evolutionary modelling with three global-scale long-term data sets to reveal that competition for scarce nest sites causes variation in declines. The impact of the loss of nest sites on differential declines among closely related species from very different taxa indicates a new ecological principle of widespread importance: the effect of habitat degradation on competition among species. A lack of

  15. Contrasting Holocene environmental histories may explain patterns of species richness and rarity in a Central European landscape

    Czech Academy of Sciences Publication Activity Database

    Hájek, M.; Dudová, Lydie; Hájková, Petra; Roleček, Jan; Moutelíková, J.; Jamrichová, Eva; Horsák, M.

    2016-01-01

    Roč. 133, FEB 1 2016 (2016), s. 48-61 ISSN 0277-3791 Institutional support: RVO:67985939 Keywords : species pool * extreme species richness * biogeography * Carpathians * palaeoecology Subject RIV: EH - Ecology, Behaviour Impact factor: 4.797, year: 2016

  16. Niche filtering, not interspecific resource competition, explains the co-occurrence of butterfly species across the Japanese archipelago

    OpenAIRE

    Iwasaki, Takaya; Sato, Yasuhiro; Nakadai, Ryosuke; Hashimoto, Koya

    2017-01-01

    The relevance of interspecific resource competition in the context of community assembly by herbivorous insects is a well-known topic in ecology. Most previous studies focused on local species assemblies, that shared host plants. Few studies evaluated species pairs within a single taxon when investigating the effects of host plant sharing at the regional scale. Herein, we explore the effect of plant sharing on the geographical co-occurrence patterns of 229 butterflies distributed across the J...

  17. Differences between Lipids Extracted from Five Species Are Not Sufficient To Explain Biomagnification of Nonpolar Organic Chemicals

    DEFF Research Database (Denmark)

    Jahnke, Annika; Holmbäck, Jan; Andersson, Rina Argelia

    2015-01-01

    headspace from spiked olive oil to determine their sorptive capacities. Lipids from seal blubber and pork bacon solely composed of triglycerides had capacities similar to that of olive oil; lipids from mussels, herring, and guillemot egg had quantifiable fractions of phospholipids and cholesterol and showed...... capacities reduced by factors of up to 2.3-fold. Generally, the sorptive capacities of the lipids were not elevated relative to the olive oil controls and are unlikely to explain a substantial part of biomagnification....

  18. Tropical Estuarine Macrobenthic Communities Are Structured by Turnover Rather than Nestedness.

    Science.gov (United States)

    Medeiros, Carlinda Raílly; Hepp, Luiz Ubiratan; Patrício, Joana; Molozzi, Joseline

    2016-01-01

    Turnover (i.e., species substitution) and nestedness (i.e., subsets of species from more diverse locations), the two main mechanisms used to explain the beta diversity of biological communities, have different implications for biodiversity conservation. To better understand how these mechanisms contribute to beta diversity, we tested the following hypotheses: (i) greater dissimilarity in community composition occurs between estuarine zones than other hierarchical level studied; (ii) beta diversity in these communities develops by turnover in estuaries with a lower degree of anthropogenic impact, but by nestedness in estuaries with a greater degree of anthropogenic impact; and (iii) the structuring mechanism is independent of season. We studied two tropical estuaries (dry and wet seasons) that vary in terms of land-use of the drainage basins. Subtidal benthic macroinvertebrates were sampled along the estuarine gradient in each of the two estuaries. The additive partitioning approach to species diversity was used to determine the hierarchical scale with the greatest dissimilarity in community composition. General beta diversity was measured using the Sorensen dissimilarity index, partitioning the turnover and nestedness components. The greatest dissimilarity in the composition of the communities occurred between the zones along the estuarine gradient in both seasons (dry = 58.6%; wet = 46.3%). In the estuary with a lower degree of anthropogenic influence, benthic macroinvertebrate diversity was generated by turnover regardless of the season. In the estuary with a greater degree of anthropogenic impact, beta diversity was structured by turnover during the dry season and a combination of both mechanisms during the wet season. We conclude that turnover is the principal mechanism responsible for beta diversity in benthic macroinvertebrate communities in tropical estuaries.

  19. Analysis of the Rickettsia africae genome reveals that virulence acquisition in Rickettsia species may be explained by genome reduction

    Directory of Open Access Journals (Sweden)

    Audic Stéphane

    2009-04-01

    Full Text Available Abstract Background The Rickettsia genus includes 25 validated species, 17 of which are proven human pathogens. Among these, the pathogenicity varies greatly, from the highly virulent R. prowazekii, which causes epidemic typhus and kills its arthropod host, to the mild pathogen R. africae, the agent of African tick-bite fever, which does not affect the fitness of its tick vector. Results We evaluated the clonality of R. africae in 70 patients and 155 ticks, and determined its genome sequence, which comprises a circular chromosome of 1,278,540 bp including a tra operon and an unstable 12,377-bp plasmid. To study the genetic characteristics associated with virulence, we compared this species to R. prowazekii, R. rickettsii and R. conorii. R. africae and R. prowazekii have, respectively, the less and most decayed genomes. Eighteen genes are present only in R. africae including one with a putative protease domain upregulated at 37°C. Conclusion Based on these data, we speculate that a loss of regulatory genes causes an increase of virulence of rickettsial species in ticks and mammals. We also speculate that in Rickettsia species virulence is mostly associated with gene loss. The genome sequence was deposited in GenBank under accession number [GenBank: NZ_AAUY01000001].

  20. Predictors of Staff Turnover and Turnover Intentions within Addiction Treatment Settings: Change Over Time Matters.

    Science.gov (United States)

    Garner, Bryan R; Hunter, Brooke D

    2014-01-01

    This study examined the extent to which changes over time in clinicians' responses to measures of work attitude (eg, job satisfaction) and psychological climate (eg, supervisor support) could predict actual turnover and turnover intentions above and beyond absolute levels of these respective measures. Longitudinal data for this study were collected from a sample of clinicians (N = 96) being trained to implement an evidence-based treatment for adolescent substance use disorders. Supporting findings from a recent staff turnover study, we found job satisfaction change was able to predict actual turnover above and beyond average levels of job satisfaction. Representing new contributions to the staff turnover literature, we also found that change over time in several other key measures (eg, job satisfaction, role manageability, role clarity) explained a significant amount of variance in turnover intentions above and beyond the absolute level of each respective measure. A key implication of the current study is that organizations seeking to improve their ability to assess risk for staff turnover may want to consider assessing staff at multiple points in time in order to identify systematic changes in key employee attitudes like turnover intentions and job satisfaction.

  1. Predictors of Staff Turnover and Turnover Intentions within Addiction Treatment Settings: Change over Time Matters

    Directory of Open Access Journals (Sweden)

    Bryan R. Garner

    2014-01-01

    Full Text Available This study examined the extent to which changes over time in clinicians’ responses to measures of work attitude (eg, job satisfaction and psychological climate (eg, supervisor support could predict actual turnover and turnover intentions above and beyond absolute levels of these respective measures. Longitudinal data for this study were collected from a sample of clinicians ( N = 96 being trained to implement an evidence-based treatment for adolescent substance use disorders. Supporting findings from a recent staff turnover study, we found job satisfaction change was able to predict actual turnover above and beyond average levels of job satisfaction. Representing new contributions to the staff turnover literature, we also found that change over time in several other key measures (eg, job satisfaction, role manageability, role clarity explained a significant amount of variance in turnover intentions above and beyond the absolute level of each respective measure. A key implication of the current study is that organizations seeking to improve their ability to assess risk for staff turnover may want to consider assessing staff at multiple points in time in order to identify systematic changes in key employee attitudes like turnover intentions and job satisfaction.

  2. Coadsorbed species explain the mechanism of methanol temperature-desorption on CeO2(111)

    Energy Technology Data Exchange (ETDEWEB)

    Sutton, Jonathan E. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Overbury, Steven H. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Beste, Ariana [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-03-24

    Here, we have used density functional theory calculations to investigate the temperature-programmed desorption (TPD) of methanol from CeO2(111). For the first time, low-temperature water formation and high-temperature methanol desorption are explained by our calculations. High coverages of methanol, which correspond to experimental conditions, are required to properly describe these features of the TPD spectrum. We identify a mechanism for the low-temperature formation of water involving the dissociation of two methanol molecules on the same surface O atom and filling of the resulting surface vacancy with one of the methoxy products. After water desorption, methoxy groups are stabilized on the surface and react at higher temperatures to form methanol and formaldehyde by a disproportionation mechanism. Alternatively, the stabilized methoxy groups undergo sequential C–H scission reactions to produce formaldehyde. Calculated energy requirements and methanol/formaldehyde selectivity agree with the experimental data.

  3. ON THE TURNOVER OF THE TULLY-FISHER RELATION

    NARCIS (Netherlands)

    RHEE, MH; PELETIER, RF; VANALBADA, TS

    1995-01-01

    The observed turnover at the high linewidth end of the infrared Tully-Fisher relation can be explained by the stellar population differences among galaxies. When the IRAS 60 mu m fluxes are added to the Tully-Fisher relation as a second parameter, the turnover disappears and the scatter becomes

  4. Can we explain vagrancy in Europe with the autumn migration phenology of Siberian warbler species in East Russia?

    Directory of Open Access Journals (Sweden)

    Bozó László

    2016-06-01

    Full Text Available We examined the autumn migration phenology of nine Siberian breeding songbirds: Thick-billed Warbler (Iduna aedon, Black-browed Reed Warbler (Acrocephalus bistrigiceps, Pallas’s Grasshopper Warbler (Locustella certhiola, Lanceolated Warbler (L. lanceolata, Yellow-browed Warbler (Phylloscopus inornatus, Arctic Warbler (Ph. borealis, Dusky Warbler (Ph. fuscatus, Radde’s Warbler (Ph. schwarzi, Two-barred Warbler (Ph. plumbeitarsus and compared the migration dynamic characteristics with their European occurrence time. The study was carried out within the Amur Bird Project in the Russian Far East along the river Amur at Muraviovka Park between 2011 and 2014. The birds were caught with mistnets and ringed with individually numbered rings. For the characterization of the migration, we used timing, the intervals and the peaks of the migration, the percentage of the recaptures and the average time between the first and the last captures. The timing of migration in the studied species differed in the timing, the intervals (30-67 days and the migration peaks (14 August - 17 September.

  5. Managing teacher turnover

    African Journals Online (AJOL)

    Erna Kinsey

    - ... vacant teaching posts are not filled (Pretorius & Heard, 1999; Anon., ... it reaches critical proportions. This article therefore investigates teacher turnover as a phenome- non to be managed and suggests ways of doing so. The study is based.

  6. To leave or not to leave : When receiving interpersonal citizenship behavior influences an employee's turnover intention

    NARCIS (Netherlands)

    Regts, Gerdien; Molleman, Eric

    Given that few studies have examined relational bases for voluntary employee turnover, the purpose of the article is to examine whether work relationships explain employee turnover intention. Adopting a social relational perspective on employee turnover, we investigated the effect of receiving

  7. Foliar pH as a new plant trait: can it explain variation in foliar chemistry and carbon cycling processes among subarctic plant species and types?

    Science.gov (United States)

    Cornelissen, J H C; Quested, H M; van Logtestijn, R S P; Pérez-Harguindeguy, N; Gwynn-Jones, D; Díaz, S; Callaghan, T V; Press, M C; Aerts, R

    2006-03-01

    Plant traits have become popular as predictors of interspecific variation in important ecosystem properties and processes. Here we introduce foliar pH as a possible new plant trait, and tested whether (1) green leaf pH or leaf litter pH correlates with biochemical and structural foliar traits that are linked to biogeochemical cycling; (2) there is consistent variation in green leaf pH or leaf litter pH among plant types as defined by nutrient uptake mode and higher taxonomy; (3) green leaf pH can predict a significant proportion of variation in leaf digestibility among plant species and types; (4) leaf litter pH can predict a significant proportion of variation in leaf litter decomposability among plant species and types. We found some evidence in support of all four hypotheses for a wide range of species in a subarctic flora, although cryptogams (fern allies and a moss) tended to weaken the patterns by showing relatively poor leaf digestibility or litter decomposability at a given pH. Among seed plant species, green leaf pH itself explained only up to a third of the interspecific variation in leaf digestibility and leaf litter up to a quarter of the interspecific variation in leaf litter decomposability. However, foliar pH substantially improved the power of foliar lignin and/or cellulose concentrations as predictors of these processes when added to regression models as a second variable. When species were aggregated into plant types as defined by higher taxonomy and nutrient uptake mode, green-specific leaf area was a more powerful predictor of digestibility or decomposability than any of the biochemical traits including pH. The usefulness of foliar pH as a new predictive trait, whether or not in combination with other traits, remains to be tested across more plant species, types and biomes, and also in relation to other plant or ecosystem traits and processes.

  8. Sexual selection affects local extinction and turnover in bird communities

    Science.gov (United States)

    Doherty, P.F.; Sorci, G.; Royle, J. Andrew; Hines, J.E.; Nichols, J.D.; Boulinier, T.

    2003-01-01

    Predicting extinction risks has become a central goal for conservation and evolutionary biologists interested in population and community dynamics. Several factors have been put forward to explain risks of extinction, including ecological and life history characteristics of individuals. For instance, factors that affect the balance between natality and mortality can have profound effects on population persistence. Sexual selection has been identified as one such factor. Populations under strong sexual selection experience a number of costs ranging from increased predation and parasitism to enhanced sensitivity to environmental and demographic stochasticity. These findings have led to the prediction that local extinction rates should be higher for species/populations with intense sexual selection. We tested this prediction by analyzing the dynamics of natural bird communities at a continental scale over a period of 21 years (1975-1996), using relevant statistical tools. In agreement with the theoretical prediction, we found that sexual selection increased risks of local extinction (dichromatic birds had on average a 23% higher local extinction rate than monochromatic species). However, despite higher local extinction probabilities, the number of dichromatic species did not decrease over the period considered in this study. This pattern was caused by higher local turnover rates of dichromatic species, resulting in relatively stable communities for both groups of species. Our results suggest that these communities function as metacommunities, with frequent local extinctions followed by colonization. Anthropogenic factors impeding dispersal might therefore have a significant impact on the global persistence of sexually selected species.

  9. ANTESEDEN EMPLOYEE TURNOVER

    Directory of Open Access Journals (Sweden)

    Heryadi Fardilah

    2018-03-01

    Full Text Available This research is concerning the effect of workplace environment, job satisfaction, and  job performance on employee turnover, and the background is to get the convenience of employees condition, the satisfaction of job results, maximum performance, and keep and reduce in and out employees. The purpose of this research is to see how far the influence of workplace environment, job satisfaction, and job performance on employee turnover. Planning of this research uses primary data that is got by handing over questioners to 200 employees in Telecommunication company in East Jakarta. The analysis method which is used is double regresi.  Results of  this  research give conclusion that there's a positive and significant influence of workplace environment, job satisfaction, and job performance on employee turnover.

  10. Impacts of elevated atmospheric CO2 on litter quality, litter decomposability and nitrogen turnover rate of two oak species in a Mediterranean forest ecosystem

    NARCIS (Netherlands)

    Fayez Raiesi Gahrooee,

    1998-01-01

    Elevated CO2 may affect litter quality of plants, and subsequently C and N cycling in terrestrial ecosystems, but changes in litter quality associated with elevated CO2 are poorly known. Abscised leaf litter of two oak species (Quercus cerris L., and Q. pubescens Willd.) exposed to long-term

  11. One hundred years of employee turnover theory and research.

    Science.gov (United States)

    Hom, Peter W; Lee, Thomas W; Shaw, Jason D; Hausknecht, John P

    2017-03-01

    We review seminal publications on employee turnover during the 100-year existence of the Journal of Applied Psychology . Along with classic articles from this journal, we expand our review to include other publications that yielded key theoretical and methodological contributions to the turnover literature. We first describe how the earliest papers examined practical methods for turnover reduction or control and then explain how theory development and testing began in the mid-20th century and dominated the academic literature until the turn of the century. We then track 21st century interest in the psychology of staying (rather than leaving) and attitudinal trajectories in predicting turnover. Finally, we discuss the rising scholarship on collective turnover given the centrality of human capital flight to practitioners and to the field of human resource management strategy. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  12. Costs of employee turnover

    Directory of Open Access Journals (Sweden)

    Jiří Duda

    2013-01-01

    Full Text Available The aim of this paper is to establish a general methodology for calculating the costs incurred by employee turnover. This paper deals with identification of costs incurred by the departure of an employee, and does not deal with the cost of recruitment of a new employee. Economic calculations are adjusted to the tax policy in the Czech Republic. The costs of employee turnover (according to Bliss, 2012 include the costs of substitution of the unoccupied position, costs of conducting the exit interview and termination of the contract. The cost of an executive’s time to understand the causes of leaving and costs of the leaving employee’s training were also determined. Important factors in the costs of employee turnover also include the loss of knowledge and possibly also a loss of customers. Costs of lost employee and department productiveness represent an important part of the costs of employee turnover, as well. For all of these costs there have been proposed general calculations formulas.

  13. Complexity explained

    CERN Document Server

    Erdi, Peter

    2008-01-01

    This book explains why complex systems research is important in understanding the structure, function and dynamics of complex natural and social phenomena. Readers will learn the basic concepts and methods of complex system research.

  14. Differential challenge stressor-hindrance stressor relationships with job attitudes, turnover intentions, turnover, and withdrawal behavior: a meta-analysis.

    Science.gov (United States)

    Podsakoff, Nathan P; LePine, Jeffery A; LePine, Marcie A

    2007-03-01

    In this article, a 2-dimensional work stressor framework is used to explain inconsistencies in past research with respect to stressor relationships with retention-related criteria. Results of meta-analyses of 183 independent samples indicated that whereas hindrance stressors had dysfunctional relationships with these criteria (negative relationships with job satisfaction and organizational commitment and positive relationships with turnover intentions, turnover, and withdrawal behavior), relationships with challenge stressors were generally the opposite (positive relationships with job satisfaction and organizational commitment and negative relationships with turnover intentions and turnover). Results also suggested that the differential relationships between challenge stressors and hindrance stressors and the more distal criteria (withdrawal behavior and turnover) were due, in part, to the mediating effects of job attitudes. (c) 2007 APA, all rights reserved.

  15. Protein turnover in sheep

    International Nuclear Information System (INIS)

    Buttery, P.J.

    1981-01-01

    Considerable advances have been made in the knowledge of the mechanisms and control of synthesis and degradation of proteins in animal tissues during the last decade. Most of the work on the measurement of synthetic and degradative rates of the mixed protein fraction from tissues has been conducted in the rat. There have, unfortunately, been few publications describing results of protein turnover studies with ruminants. Consideration is given here to the techniques used to measure protein turnover, and some of the results obtained, particularly with sheep, are summarized. No attempt has been made to discuss directly the situation in parasitized animals; rather the aim is to provide background information which complements other work dealing with the effects of parasites on the nitrogen metabolism of ruminants. (author)

  16. Measuring temporal turnover in ecological communities

    OpenAIRE

    Shimadzu, Hideyasu; Dornelas, Maria; Magurran, Anne

    2015-01-01

    The authors acknowledge support from the European Research Council (project BioTIME 250189) and the Royal Society. MD acknowledges funding from the Marine Alliance for Science and Technology Scotland (MASTS). MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. 1.Range migrations in response to climate change, invasive species and the emergence of novel ecosystems highlight the importance of temporal turnover in community composition as a...

  17. SPSS explained

    CERN Document Server

    Hinton, Perry R; Brownlow, Charlotte

    2014-01-01

    SPSS Explained provides the student with all that they need to undertake statistical analysis using SPSS. It combines a step-by-step approach to each procedure with easy to follow screenshots at each stage of the process. A number of other helpful features are provided: regular advice boxes with tips specific to each test explanations divided into 'essential' and 'advanced' sections to suit readers at different levels frequently asked questions at the end of each chapter. The first edition of this popular book has been fully updated for IBM SPSS version 21 and also includes: chapters that expl

  18. Determinants of CEO Turnover in Publicand Private Firms in Denmark - CEO and Firm Characteristics

    DEFF Research Database (Denmark)

    Sponholtz, Carina

    In this study we are the first to draw on longitudinal matched employer-employee data to study CEO turnover. Using this data we contribute tothe existing literature by examining the e¤ect of previously unstudied in-dividual characteristics on CEO turnover. Additionally, we are able toexamine CEO...... turnover. Finally, the inverse relationshipbetween firm performance and CEO turnover only exists in LLL firms(larger limited liability firms, both publicly and privately held), whereagency costs are assumed and found to be highest.In this study we are the first to draw on longitudinal matched employer-employee...... turnover across a variety of firm types that di¤er with re-spect to the corporate governance issues they face. Our simple methodol-ogy to define CEO turnover results in turnover rates similar to those foundpreviously. Our results indicate that CEO characteristics are an important factor in explaining CEO...

  19. Causes and consequences of collective turnover: a meta-analytic review.

    Science.gov (United States)

    Heavey, Angela L; Holwerda, Jacob A; Hausknecht, John P

    2013-05-01

    Given growing interest in collective turnover (i.e., employee turnover at unit and organizational levels), the authors propose an organizing framework for its antecedents and consequences and test it using meta-analysis. Based on analysis of 694 effect sizes drawn from 82 studies, results generally support expected relationships across the 6 categories of collective turnover antecedents, with somewhat stronger and more consistent results for 2 categories: human resource management inducements/investments and job embeddedness signals. Turnover was negatively related to numerous performance outcomes, more strongly so for proximal rather than distal outcomes. Several theoretically grounded moderators help to explain average effect-size heterogeneity for both antecedents and consequences of turnover. Relationships generally did not vary according to turnover type (e.g., total or voluntary), although the relative absence of collective-level involuntary turnover studies is noted and remains an important avenue for future research. PsycINFO Database Record (c) 2013 APA, all rights reserved.

  20. Astronomy Explained

    Science.gov (United States)

    North, Gerald

    Every year large numbers of people take up the study of astronomy, mostly at amateur level. There are plenty of elementary books on the market, full of colourful photographs, but lacking in proper explanations of how and why things are as they are. Many people eventually wish to go beyond the 'coffee-table book' stage and study this fascinating subject in greater depth. This book is written for them. In addition, many people sit for public examinations in this subject each year and this book is also intended to be of use to them. All the topics from the GCSE syllabus are covered here, with sample questions at the end of each chapter. Astronomy Explained provides a comprehensive treatment of the subject in more depth than is usually found in elementary works, and will be of interest to both amateur astronomers and students of astronomy.

  1. Elevated CO2 and water addition enhance nitrogen turnover in grassland plants with implications for temporal stability.

    Science.gov (United States)

    Dijkstra, Feike A; Carrillo, Yolima; Blumenthal, Dana M; Mueller, Kevin E; LeCain, Dan R; Morgan, Jack A; Zelikova, Tamara J; Williams, David G; Follett, Ronald F; Pendall, Elise

    2018-05-01

    Temporal variation in soil nitrogen (N) availability affects growth of grassland communities that differ in their use and reuse of N. In a 7-year-long climate change experiment in a semi-arid grassland, the temporal stability of plant biomass production varied with plant N turnover (reliance on externally acquired N relative to internally recycled N). Species with high N turnover were less stable in time compared to species with low N turnover. In contrast, N turnover at the community level was positively associated with asynchrony in biomass production, which in turn increased community temporal stability. Elevated CO 2 and summer irrigation, but not warming, enhanced community N turnover and stability, possibly because treatments promoted greater abundance of species with high N turnover. Our study highlights the importance of plant N turnover for determining the temporal stability of individual species and plant communities affected by climate change. © 2018 John Wiley & Sons Ltd/CNRS.

  2. Salary, Performance, and Superintendent Turnover

    Science.gov (United States)

    Grissom, Jason A.; Mitani, Hajime

    2016-01-01

    Purpose: Superintendent retention is an important goal for many school districts, yet the factors contributing to superintendent turnover are poorly understood. Most prior quantitative studies of superintendent turnover have relied on small, cross-sectional samples, limiting the evidence base. Utilizing longitudinal administrative records from…

  3. Commitment Profiles and Employee Turnover

    Science.gov (United States)

    Stanley, Laura; Vandenberghe, Christian; Vandenberg, Robert; Bentein, Kathleen

    2013-01-01

    We examined how affective (AC), normative (NC), perceived sacrifice (PS), and few alternatives (FA) commitments combine to form profiles and determine turnover intention and turnover. We theorized that three mechanisms account for how profiles operate, i.e., the degree to which membership is internally regulated, the perceived desirability and…

  4. WAP explained

    International Nuclear Information System (INIS)

    Kaiser, M.J.; Pulsipher, A.G.

    2004-01-01

    The Weatherization Assistance Program (WAP) is a federal block grant program administered by all 50 states and the District of Columbia through community action agencies, state energy offices, local government, and other nonprofit organizations to provide weatherization services to eligible households. The WAP was established in 1976 to increase the energy efficiency, reduce the energy expenditures, and improve the health and safety of low-income households, especially those households that are particularly vulnerable such as families with children, persons with disabilities, and the elderly. The manner in which WAP funds have been allocated to states, however, has been a contentious issue since the inception of the program. Southern states have argued that too much of the federal funding goes to cold-climate and rural states. Northern states disagree. In 1990, Congress amended the Energy Conservation and Production Act and required the Department of Energy to develop a new funding formula. The Department of Energy currently uses a three-factor formula developed in 1995 in conjunction with a two-factor formula developed in 1977 and a hold-harmless provision to allocate WAP funding. The purpose of this paper is to explain the WAP allocation mechanism and the assumptions associated with the 1977 and the 1995 funding formula. The factors that compose each funding formula are critically assessed and various implementation issues are reviewed, including the selection of the trigger point and program capacity levels. It is not possible to define the need for weatherization assistance objectively and in a unique manner, and this ambiguity is the main reason why the WAP allocation mechanism is expected to remain a lively topic of debate and contention

  5. Occupational stress and employee turnover.

    Science.gov (United States)

    Bridger, Robert S; Day, Andrea J; Morton, Kate

    2013-01-01

    Questionnaire data captured in January-March 2007 were examined in relation to turnover in males and females during the next five years. In general, most of the workplace stressors (such as role conflict or peer support) were not antecedents of turnover in any group. Junior personnel with psychological strain in 2007 had an increased risk of turnover in the next five years. Low commitment to the service in 2007 increased the odds of turnover in male and female juniors and in female officers. Female juniors with less effective skills for coping with stress and who exercised less frequently on a weekly basis were more likely to leave. An incidental finding was that the odds of turnover were three times greater in female officers with children than in female officers with no children. Stress management interventions focusing on effective coping and sports and exercise participation which are targeted appropriately may improve retention.

  6. Managing voluntary turnover through challenging assignments

    NARCIS (Netherlands)

    Preenen, P.T.Y.; de Pater, I.E.; van Vianen, A.E.M.; Keijzer, L.

    2011-01-01

    This study examines employees’ challenging assignments as manageable means to reduce turnover intentions, job search behaviors, and voluntary turnover. Results indicate that challenging assignments are negatively related to turnover intentions and job search behaviors and that these relationships

  7. Managing voluntary turnover through challenging assignments

    NARCIS (Netherlands)

    Preenen, P.T.Y.; Pater, I.E. de; Vianen, A.E.M. van; Keijzer, L.

    2011-01-01

    This study examines employees' challenging assignments as manageable means to reduce turnover intentions, job search behaviors, and voluntary turnover. Results indicate that challenging assignments are negatively related to turnover intentions and job search behaviors and that these relationships

  8. Examining the Job Search-Turnover Relationship: The Role of Embeddedness, Job Satisfaction, and Available Alternatives

    Science.gov (United States)

    Swider, Brian W.; Boswell, Wendy R.; Zimmerman, Ryan D.

    2011-01-01

    This study examined factors that may help explain under what conditions employee job search effort may most strongly (or weakly) predict subsequent turnover. As predicted, the job search-turnover relationship was stronger when employees had lower levels of job embeddedness and job satisfaction and higher levels of available alternatives. These…

  9. A Study on the Employee Turnover Antecedents in ITES/BPO Sector

    Science.gov (United States)

    Sree Rekha, K. R.; Kamalanabhan, T. J.

    2010-01-01

    This paper aims at testing a conceptual model connecting variables of the internal and external work environment to ITES/BPO employee turnover. Based on the gaps identified from the literature that no single model explains in a comprehensive way as to why, people choose to leave and the lack of turnover studies on call centers located in India.…

  10. Oceanographic mechanisms that possibly explain dominance of neritic-tropical zooplankton species assemblages around the Islas Marías Archipelago, Mexico

    Directory of Open Access Journals (Sweden)

    Jaime Gómez-Gutiérrez

    2014-11-01

    Full Text Available The nearshore zooplankton species assemblage, identified per taxonomic groups (20 and per species for 12 selected groups, was analyzed from samples collected during November 2010 at four volcanic islands of the Islas Marías Archipelago (IMA, located 90-120 km offshore Nayarit, Mexico. From chlorophyll-a concentration and zooplankton biovolume perspective mesotrophic conditions prevailed in comparison with the Gulf of California during November. Crustaceans numerically dominated the zooplankton assemblage (92.3% [Copepoda (79.2%, Decapoda larvae (4.7%, Cladocera (3.7%, Mysidacea (2.7%, and Euphausiacea (2.0%]. The other 15 taxonomic groups (7.7% combined accounted each one less than 1.5% of the relative abundance. Species richness of selected taxa (~56%> included 259 taxa (121 identified to species, 117 to genus, and 21 not identified. Tropical species from neritic affinity clearly dominated zooplankton assemblage around IMA. Five tropical Copepoda species [Calanopia minor (Dana, Clausocalanus jobei Frost & Fleminger, Acrocalanus gibber Giesbrecht, Canthocalanus pauper (Giesbrecht, and Centropages furcatus (Dana], a cladoceran Pseudevadne tergestina (Claus, and a Mysidacea species (Mysidium reckettsi Harrison & Bowman dominated the zooplankton assemblage (accounting about 55% of total abundance of the identified species. Except C. furcatus, all these species are not abundant at oceanic regions of the central and northern Gulf of California. The similarity of multiple neritic and tropical species in the zooplankton assemblage from IMA and Cape Corrientes suggests strong coastal-insular plankton connectivity. Episodic current plumes associated with anomalous intense rivers discharge during rainy years, eddies generated by coastal upwelling event that move offshore, and northward regional oceanic circulation are the most likely mesoscale oceanographic processes that cause costal tropical zooplankton drift enhancing coastal-Archipelago species

  11. Turnover of plant lineages shapes herbivore phylogenetic beta diversity along ecological gradients.

    Science.gov (United States)

    Pellissier, Loïc; Ndiribe, Charlotte; Dubuis, Anne; Pradervand, Jean-Nicolas; Salamin, Nicolas; Guisan, Antoine; Rasmann, Sergio

    2013-05-01

    Understanding drivers of biodiversity patterns is of prime importance in this era of severe environmental crisis. More diverse plant communities have been postulated to represent a larger functional trait-space, more likely to sustain a diverse assembly of herbivore species. Here, we expand this hypothesis to integrate environmental, functional and phylogenetic variation of plant communities as factors explaining the diversity of lepidopteran assemblages along elevation gradients in the Swiss Western Alps. According to expectations, we found that the association between butterflies and their host plants is highly phylogenetically structured. Multiple regression analyses showed the combined effect of climate, functional traits and phylogenetic diversity in structuring butterfly communities. Furthermore, we provide the first evidence that plant phylogenetic beta diversity is the major driver explaining butterfly phylogenetic beta diversity. Along ecological gradients, the bottom up control of herbivore diversity is thus driven by phylogenetically structured turnover of plant traits as well as environmental variables. © 2013 Blackwell Publishing Ltd/CNRS.

  12. How Employee Turnover Affects Productivity

    DEFF Research Database (Denmark)

    Eriksen, Bo

    Research on employee turnover suggests that turnover results in negative organization-level outcomes. This paper provides a firm-level analysis of the impact of the in- and outflows of human resources on productivity and how the presence of organizational slack resources moderates the effects...... moderate this effect so that the negative consequences of employee turnover are less severe for larger, older and capital intensive firms. These moderating variables indicate the presence of slack resources in the firm, and thus that the accumulation of slack reduces the efficiency losses from employee...

  13. Tendon 'turnover lengthening' technique.

    Science.gov (United States)

    Cerovac, S; Miranda, B H

    2013-11-01

    Tendon defect reconstruction is amongst the most technically challenging areas in hand surgery. Tendon substance deficiency reconstruction techniques include lengthening, grafting, two-stage reconstruction and tendon transfers, however each is associated with unique challenges over and above direct repair. We describe a novel 'turnover lengthening' technique for hand tendons that has successfully been applied to the repair of several cases, including a case of attritional flexor and traumatic extensor tendon rupture in two presented patients where primary tenorrhaphy was not possible. In both cases a good post-operative outcome was achieved, as the patients were happy having returned back to normal activities of daily living such that they were discharged 12 weeks post-operatively. Our technique avoids the additional morbidity and complications associated with grafting, transfers and two stage reconstructions. It is quick, simple and reproducible for defects not exceeding 3-4 cm, provides a means of immediate one stage reconstruction, no secondary donor site morbidity and does not compromise salvage by tendon transfer and/or two-stage reconstruction in cases of failure. To our knowledge no such technique has been previously been described to reconstruct such hand tendon defects. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

  14. Turnover, staffing, skill mix, and resident outcomes in a national sample of US nursing homes.

    Science.gov (United States)

    Trinkoff, Alison M; Han, Kihye; Storr, Carla L; Lerner, Nancy; Johantgen, Meg; Gartrell, Kyungsook

    2013-12-01

    The authors examined the relationship of staff turnover to selected nursing home quality outcomes, in the context of staffing and skill mix. Staff turnover is a serious concern in nursing homes as it has been found to adversely affect care. When employee turnover is minimized, better care quality is more likely in nursing homes. Data from the National Nursing Home Survey, a nationally representative sample of US nursing homes, were linked to Nursing Home Compare quality outcomes and analyzed using logistic regression. Nursing homes with high certified nursing assistant turnover had significantly higher odds of pressure ulcers, pain, and urinary tract infections even after controlling for staffing, skill mix, bed size, and ownership. Nurse turnover was associated with twice the odds of pressure ulcers, although this was attenuated when staffing was controlled. This study suggests turnover may be more important in explaining nursing home (NH) outcomes than staffing and skill mix and should therefore be given greater emphasis.

  15. Meta-analysis Reveals that Hydraulic Traits Explain Cross-Species Patterns of Drought-Induced Tree Mortality across the Globe

    Science.gov (United States)

    Anderegg, W.

    2016-12-01

    Drought-induced tree mortality has been observed globally and is expected to increase under climate change scenarios, with large potential consequences for the terrestrial carbon sink. Predicting mortality across species is crucial for assessing the effects of climate extremes on forest community biodiversity, composition, and carbon sequestration. However, the physiological traits associated with elevated risk of mortality in diverse ecosystems remain unknown, though these could greatly improve understanding and prediction of tree mortality in forests. We performed a meta-analysis on species' mortality rates across 475 species from 33 studies around the globe to assess which traits determine a species' mortality risk. We found that species-specific mortality anomalies from community mortality rate in a given drought were associated with plant hydraulic traits. Across all species, mortality was best predicted by a low hydraulic safety margin - the difference between typical minimum xylem water potential and that causing xylem dysfunction - and xylem vulnerability to embolism. Angiosperms and gymnosperms experienced roughly equal mortality risk. Our results provide broad support that hydraulic traits capture key mechanisms determining tree death and highlight that physiological traits can improve vegetation models' prediction of tree mortality during climate extremes. We conclude with thoughts about a revised framework for future tree mortality research.

  16. Collagen turnover after tibial fractures

    DEFF Research Database (Denmark)

    Joerring, S; Krogsgaard, M; Wilbek, H

    1994-01-01

    Collagen turnover after tibial fractures was examined in 16 patients with fracture of the tibial diaphysis and in 8 patients with fracture in the tibial condyle area by measuring sequential changes in serological markers of turnover of types I and III collagen for up to 26 weeks after fracture....... The markers were the carboxy-terminal extension peptide of type I procollagen (PICP), the amino-terminal extension peptide of type III procollagen (PIIINP), and the pyridinoline cross-linked carboxy-terminal telopeptide of type I collagen (ICTP). The latter is a new serum marker of degradation of type I...... collagen. A group comparison showed characteristic sequential changes in the turnover of types I and III collagen in fractures of the tibial diaphysis and tibial condyles. The turnover of type III collagen reached a maximum after 2 weeks in both groups. The synthesis of type I collagen reached a maximum...

  17. Endogenous Turnover of Cyanogenic Glycosides in Plants

    DEFF Research Database (Denmark)

    Picmanova, Martina

    , there is strong evidence that CNglcs serve a no less significant purpose as a transport and storage form of reduced nitrogen which may be remobilized and recycled to balance the needs of primary metabolism during certain developmental events. Reduced nitrogen from CNglcs may be recovered either via HCN refixation...... revealed the formation of glycosides of amides, carboxylic acids and "anitriles", including their di- and triglycosides, evidently derived from CNglcs. Based on results common to the three phylogenetically unrelated plant species, a recycling endogenous turnover pathway for CNglcs was suggested in which...

  18. [Turnover Experience of Male Nurses].

    Science.gov (United States)

    Kim, Hyunsu; Lee, Jeongseop

    2017-02-01

    The aim of this study was to identify turnover experiences of men in nursing and to derive a substantive theory on the turnover experience of men who are nurses. Data were collected through in-depth interviews with 13 men who had worked as a nurse for 1 year or more, and had a turnover experience during that period. Collected data were analyzed on the basis of Strauss and Corbin's grounded theory. The core category in the turnover experiences of the respondents was 'seeking a stable place for me'. In the analysis of the core category, types of 'contentment', 'seeking', 'survival' and 'confusion' were identified. The sequential stages of these nurses' turnover experience were 'confrontation', 'incertitude', 'retrying' and 'realization'. However, when a problem arose in the process, they returned to the stage of confusion. Thus, these stages could occur in a circular fashion. These findings provide a deep understanding of the turnover experience of men in nursing and offers new information about how they adapt to nursing practice. The findings should be useful as foundational data for men who hope to become nurses and also for managers responsible for nurses who are men. © 2017 Korean Society of Nursing Science

  19. Community turnover of wood-inhabiting fungi across hierarchical spatial scales.

    Directory of Open Access Journals (Sweden)

    Nerea Abrego

    Full Text Available For efficient use of conservation resources it is important to determine how species diversity changes across spatial scales. In many poorly known species groups little is known about at which spatial scales the conservation efforts should be focused. Here we examined how the community turnover of wood-inhabiting fungi is realised at three hierarchical levels, and how much of community variation is explained by variation in resource composition and spatial proximity. The hierarchical study design consisted of management type (fixed factor, forest site (random factor, nested within management type and study plots (randomly placed plots within each study site. To examine how species richness varied across the three hierarchical scales, randomized species accumulation curves and additive partitioning of species richness were applied. To analyse variation in wood-inhabiting species and dead wood composition at each scale, linear and Permanova modelling approaches were used. Wood-inhabiting fungal communities were dominated by rare and infrequent species. The similarity of fungal communities was higher within sites and within management categories than among sites or between the two management categories, and it decreased with increasing distance among the sampling plots and with decreasing similarity of dead wood resources. However, only a small part of community variation could be explained by these factors. The species present in managed forests were in a large extent a subset of those species present in natural forests. Our results suggest that in particular the protection of rare species requires a large total area. As managed forests have only little additional value complementing the diversity of natural forests, the conservation of natural forests is the key to ecologically effective conservation. As the dissimilarity of fungal communities increases with distance, the conserved natural forest sites should be broadly distributed in space, yet

  20. Niche segregation in two closely related species of stickleback along a physiological axis: explaining multidecadel changes in fish distribution from iron-induced respiratory impairment

    NARCIS (Netherlands)

    Verberk, W.C.E.P.; Munckhof, van den P.J.J.; Pollux, B.J.A.

    2012-01-01

    Acute exposure to iron can be lethal to fish, but long-term sublethal impacts of iron require further study. Here we investigated whether the spatial and temporal distribution (1967–2004) of two closely related species of stickleback matched the spatial distribution of iron concentrations in the

  1. Variation in levels of reactive oxygen species is explained by maternal identity, sex and body-size-corrected clutch size in a lizard

    Science.gov (United States)

    Olsson, Mats; Wilson, Mark; Uller, Tobias; Mott, Beth; Isaksson, Caroline

    2009-01-01

    Many organisms show differences between males and females in growth rate and crucial life history parameters, such as longevity. Considering this, we may expect levels of toxic metabolic by-products of the respiratory chain, such as reactive oxygen species (ROS), to vary with age and sex. Here, we analyse ROS levels in female Australian painted dragon lizards ( Ctenophorus pictus) and their offspring using fluorescent probes and flow cytometry. Basal level of four ROS species (singlet oxygen, peroxynitrite, superoxide and H2O2) measured with a combined marker, and superoxide measured specifically, varied significantly among families but not between the sexes. When blood cells from offspring were chemically encouraged to accelerate the electron transport chain by mitochondrial uncoupling, net superoxide levels were three times higher in daughters than sons (resulting in levels outside of the normal ROS range) and varied among mothers depending on offspring sex (significant interaction between maternal identity and offspring sex). In offspring, there were depressive effects on ROS of size-controlled relative clutch size, which relies directly on circulating levels of vitellogenin, a confirmed antioxidant in some species. Thus, levels of reactive oxygen species varies among females, offspring and in relation to reproductive investment in a manner that makes its regulatory processes likely targets of selection.

  2. Business Ethics & Employee Turnover: CAFE Matrix

    OpenAIRE

    Sapovadia, Vrajlal; Patel, Sweta

    2013-01-01

    Abstract: Business ethics is in discussion for its importance universally, so is the employee turnover in business. Unethical practices are unwanted, so is the high employee turnover. Unethical practices and high employee turnover in business is ubiquitous. No consensus exists on defining ethics. Employee turnover is well defined, but there is no consensus on when employee turnover is disadvantageous for the company. The Golden Rule or ethic of reciprocity, a maxim states that either ...

  3. Demographic consequences of climate change and land cover help explain a history of extirpations and range contraction in a declining snake species.

    Science.gov (United States)

    Pomara, Lars Y; LeDee, Olivia E; Martin, Karl J; Zuckerberg, Benjamin

    2014-07-01

    Developing conservation strategies for threatened species increasingly requires understanding vulnerabilities to climate change, in terms of both demographic sensitivities to climatic and other environmental factors, and exposure to variability in those factors over time and space. We conducted a range-wide, spatially explicit climate change vulnerability assessment for Eastern Massasauga (Sistrurus catenatus), a declining endemic species in a region showing strong environmental change. Using active season and winter adult survival estimates derived from 17 data sets throughout the species' range, we identified demographic sensitivities to winter drought, maximum precipitation during the summer, and the proportion of the surrounding landscape dominated by agricultural and urban land cover. Each of these factors was negatively associated with active season adult survival rates in binomial generalized linear models. We then used these relationships to back-cast adult survival with dynamic climate variables from 1950 to 2008 using spatially explicit demographic models. Demographic models for 189 population locations predicted known extant and extirpated populations well (AUC = 0.75), and models based on climate and land cover variables were superior to models incorporating either of those effects independently. These results suggest that increasing frequencies and severities of extreme events, including drought and flooding, have been important drivers of the long-term spatiotemporal variation in a demographic rate. We provide evidence that this variation reflects nonadaptive sensitivity to climatic stressors, which are contributing to long-term demographic decline and range contraction for a species of high-conservation concern. Range-wide demographic modeling facilitated an understanding of spatial shifts in climatic suitability and exposure, allowing the identification of important climate refugia for a dispersal-limited species. Climate change vulnerability

  4. Explaining variation in life history timing across a species range: Effects of climate on spawning time in an exploited marine fish

    DEFF Research Database (Denmark)

    Neuheimer, Anna; MacKenzie, Brian

    . Combined, these results shed light on the adaptive capacity of the species in the face of changing climate. We use our results to estimate expected spawning time under future climate regimes, and discuss the implications for codecology and management across the species’ range, and in the greater ecosystem......The capacity of a species to tolerate and/or adapt to environmental conditions will shape its response to future climate change including climate extremes. Of the many life-history processes affected by climate change, timing of reproduction greatly influences offspring success and resulting...... population production. Here we explore temporal and spatial changes in spawning time for Atlantic cod (Gadus morhua) across the species’ range (4 to 80°N). We estimate spawning time using a physiologically relevant metric that includes information on fish thermal history (degree days, DD). First, we estimate...

  5. Employee pathway to voluntary turnover: Testing the direct and ınteractive roles of work family conflict and work family facilitation

    OpenAIRE

    Okechukwu Ethelbert Amah

    2009-01-01

    The direct effect of work family conflict on turnover has received much attention in organizational studies. However, neither the direct effect of work family facilitation on turnover nor the effect of its interaction with work family conflict on voluntary turnover has received similar attention. This has resulted in low explained variance in turnover in models that excluded these relationships. Using 450 participants drawn from employees in Nigeria, I found significant direct and interaction...

  6. Turnover patterns in fish versus macroinvertebrates — implications ...

    African Journals Online (AJOL)

    Spatial patterns in taxonomic richness and turnover for fish and aquatic macroinvertebrates are compared to assess the relative usefulness of each taxonomic group in mapping biodiversity patterns. Fish and aquatic macroinvertebrate species data for sites down the longitudinal axes of nine rivers in four provinces along the ...

  7. Histone turnover within nonproliferating cells

    International Nuclear Information System (INIS)

    Commerford, S.L.; Carsten, A.L.; Cronkite, E.P.

    1982-01-01

    The turnover of DNA and histones in the livers and brains of mice has been determined. These mice had been exposed to constant levels of tritiated water from conception until they were 8 months old. At this point, exposure to tritium was discontinued, and the tritium remaining in DNA and histones was measured at various intervals afterward. The half-lives calculated for these components (with 95% confidence limits given in parentheses) were 117 (85 to 188) days for liver histone, 318 (241 to 466) days for liver DNA, 159 (129 to 208) days for brain histone and 593 (376 to 1406) days for brain DNA. The difference between histone and DNA turnover is statistically significant for both tissues and indicates that histone turnover within tissues cannot be solely accounted for by cell turnover within the tissue but also must include histone turnover within living cells. The half-life of histone within cells is estimated to be 117 (88 to 178) days in liver and 223 (187 to 277) days in brain

  8. Investigating the adequacy of the Competence-Turnover Intention Model: how does nursing competence affect nurses' turnover intention?

    Science.gov (United States)

    Takase, Miyuki; Teraoka, Sachiko; Kousuke, Yabase

    2015-03-01

    The aim of this study was to test the adequacy of the Competence-Turnover Intention Model, which was developed to identify how nursing competence could affect nurses' turnover intention (nurses' intention to voluntarily leave an organisation). Recent studies have suggested that the level of nursing competence is negatively related to nurses' intention to leave their jobs, suggesting that a lack of competence threatens both the quality and quantity of the nursing workforce. However, the mechanism of how nursing competence affects nurses' turnover intention has not been explored previously. A cross-sectional survey design was used. Surveys were distributed to 1337 Japanese registered nurses/midwives in October, 2013. The adequacy of the model was analysed using structural equation modelling. In total, 766 questionnaires were returned, with a return rate of 57%. The model fitted well with the data. The results showed that the level of nursing competence was related positively to the quantity of organisational rewards they felt they had received, and negatively related to the level of exhaustion they experienced. Moreover, the perceived organisational rewards and exhaustion were correlated with nurses' turnover intention through affective commitment. The Competence-Turnover Intention Model is useful for explaining how nursing competence impacts on their turnover intention. Clinical implications derived from the findings are that: promoting nursing competence is key to improving not only the quality of care provided by nurses, but also to retaining the nursing workforce, and the model can be used to develop strategies that would mitigate their turnover intention. © 2014 John Wiley & Sons Ltd.

  9. Why do different oceanic archipelagos harbour contrasting levels of species diversity? The macaronesian endemic genus Pericallis (Asteraceae) provides insight into explaining the 'Azores diversity Enigma'.

    Science.gov (United States)

    Jones, K E; Pérez-Espona, S; Reyes-Betancort, J A; Pattinson, D; Caujapé-Castells, J; Hiscock, S J; Carine, M A

    2016-10-08

    Oceanic archipelagos typically harbour extensive radiations of flowering plants and a high proportion of endemics, many of which are restricted to a single island (Single Island Endemics; SIEs). The Azores represents an anomaly as overall levels of endemism are low; there are few SIEs and few documented cases of intra-archipelago radiations. The distinctiveness of the flora was first recognized by Darwin and has been referred to as the 'Azores Diversity Enigma' (ADE). Diversity patterns in the Macaronesian endemic genus Pericallis (Asteraceae) exemplify the ADE. In this study we used morphometric, Amplified Length Polymorphisms, and bioclimatic data for herbaceous Pericallis lineages endemic to the Azores and the Canaries, to test two key hypotheses proposed to explain the ADE: i) that it is a taxonomic artefact or Linnean shortfall, ie. the under description of taxa in the Azores or the over-splitting of taxa in the Canaries and (ii) that it reflects the greater ecological homogeneity of the Azores, which results in limited opportunity for ecological diversification compared to the Canaries. In both the Azores and the Canaries, morphological patterns were generally consistent with current taxonomic classifications. However, the AFLP data showed no genetic differentiation between the two currently recognized Azorean subspecies that are ecologically differentiated. Instead, genetic diversity in the Azores was structured geographically across the archipelago. In contrast, in the Canaries genetic differentiation was mostly consistent with morphology and current taxonomic treatments. Both Azorean and Canarian lineages exhibited ecological differentiation between currently recognized taxa. Neither a Linnean shortfall nor the perceived ecological homogeneity of the Azores fully explained the ADE-like pattern observed in Pericallis. Whilst variation in genetic data and morphological data in the Canaries were largely congruent, this was not the case in the Azores, where

  10. Job turnover and labor turnover : a taxonomy of employment dynamics

    NARCIS (Netherlands)

    Hassink, Wolter H.J.; Hamermesh, Daniel S.

    1994-01-01

    We present an organized set of stylized facts on the relations among flows of workers,changes in employment and changes in the numer of jobs at the firm level. Job turnover isusually measured by comparing stocks of employment in each firm at two points in time andadding up the absolute employment

  11. Revisiting the impact of job satisfaction and organizational commitment on nurse turnover intention: an individual differences analysis.

    Science.gov (United States)

    De Gieter, Sara; Hofmans, Joeri; Pepermans, Roland

    2011-12-01

    Nurse turnover is an important contributing factor to the worldwide nursing shortage. Many studies have examined the antecedents of nurse turnover to gain a better understanding of the problem and help hospitals reduce their turnover rates. However, an important shortcoming of this research stream is its exclusive focus on explaining turnover behavior of the "average nurse", thereby disregarding individual differences between nurses and groups of nurses. To examine individual differences in the relationships between two crucial turnover antecedents - job satisfaction and organizational commitment - and nurse turnover intention. A sample of 287 nurses working for a variety of Belgian hospitals participated in the study. A survey method was used to collect quantitative data, which were analyzed through standard multiple linear regression, mixture regression models and t-tests. In the total sample of hospital nurses, both job satisfaction and organizational commitment significantly predicted nurse turnover intention. However, subsequent individual differences analyses revealed the existence of two subgroups of nurses. In the satisfaction focused group, only job satisfaction was found to predict nurse turnover intention, whereas in the satisfaction and commitment focused group both job satisfaction and organizational commitment were related to turnover intention. Furthermore, nurses in the latter group displayed stronger turnover intention, were significantly younger and had less job tenure and organizational tenure than nurses in the satisfaction focused group. The debate on the antecedents of nurse turnover still continues, as the existing models fail to fully grasp nurse turnover. The present study identifies individual differences in nurse turnover antecedents among groups of nurses as a possible reason for the absence of one comprehensive turnover model that holds for the general nursing population. Further studies are needed in order to capture the total impact

  12. Employee turnover: measuring the malady.

    Science.gov (United States)

    O'Connor, Stephen

    2002-01-01

    One measure of an organization's value to its employees is turnover. But how do you know if your employees are wondering if the grass is greener elsewhere? Scott Badler in his book What's So Funny about Looking for a Job? suggests a quick quiz to find out.

  13. Biochemical markers of bone turnover

    International Nuclear Information System (INIS)

    Kim, Deog Yoon

    1999-01-01

    Biochemical markers of bone turnover has received increasing attention over the past few years, because of the need for sensitivity and specific tool in the clinical investigation of osteoporosis. Bone markers should be unique to bone, reflect changes of bone less, and should be correlated with radiocalcium kinetics, histomorphometry, or changes in bone mass. The markers also should be useful in monitoring treatment efficacy. Although no bone marker has been established to meet all these criteria, currently osteocalcin and pyridinium crosslinks are the most efficient markers to assess the level of bone turnover in the menopausal and senile osteoporosis. Recently, N-terminal telopeptide (NTX), C-terminal telopeptide (CTX) and bone specific alkaline phosphatase are considered as new valid markers of bone turnover. Recent data suggest that CTX and free deoxypyridinoline could predict the subsequent risk of hip fracture of elderly women. Treatment of postmenopausal women with estrogen, calcitonin and bisphosphonates demonstrated rapid decrease of the levels of bone markers that correlated with the long-term increase of bone mass. Factors such as circadian rhythms, diet, age, sex, bone mass and renal function affect the results of biochemical markers and should be appropriately adjusted whenever possible. Each biochemical markers of bone turnover may have its own specific advantages and limitations. Recent advances in research will provide more sensitive and specific assays

  14. Peptide Level Turnover Measurements Enable the Study of Proteoform Dynamics.

    Science.gov (United States)

    Zecha, Jana; Meng, Chen; Zolg, Daniel Paul; Samaras, Patroklos; Wilhelm, Mathias; Kuster, Bernhard

    2018-05-01

    properties and functions on protein stability in steady-state cells and uncovered that the high turnover of respiratory chain complex I proteins might be explained by oxidative stress. © 2018 Zecha et al.

  15. Antigen-driven T-cell turnover

    NARCIS (Netherlands)

    Fraser, Christophe; Ferguson, Neil M.; de Wolf, Frank; Ghani, Azra C.; Garnett, Geoff P.; Anderson, Roy M.

    2002-01-01

    A mathematical model is developed to characterize the distribution of cell turnover rates within a population of T lymphocytes. Previous models of T-cell dynamics have assumed a constant uniform turnover rate; here we consider turnover in a cell pool subject to clonal proliferation in response to

  16. How Teacher Turnover Harms Student Achievement

    Science.gov (United States)

    Ronfeldt, Matthew; Loeb, Susanna; Wyckoff, James

    2013-01-01

    Researchers and policymakers often assume that teacher turnover harms student achievement, though recent studies suggest this may not be the case. Using a unique identification strategy that employs school-by-grade level turnover and two classes of fixed-effects models, this study estimates the effects of teacher turnover on over 850,000 New York…

  17. Using Turnover as a Recruitment Strategy

    Science.gov (United States)

    Duncan, Sandra

    2009-01-01

    Teacher turnover is notoriously high in the field of early childhood education with an estimated 33% of staff exiting the workplace each year. Turnover is costly. Not only do high levels of turnover negatively impact children's growth and development, it also erodes the program's economic stability and wherewithal to provide effective operations…

  18. Beyond the tradition: test of an integrative conceptual model on nurse turnover.

    Science.gov (United States)

    Battistelli, A; Portoghese, I; Galletta, M; Pohl, S

    2013-03-01

    This paper aimed to extend research on nurse turnover by developing and testing a theoretical model of turnover intention that includes two emergent key off-the-job constructs, work-family conflict (WFC) and community embeddedness (CE). Nurse turnover is considered one of the most significant issues in health care. There is a considerable body of knowledge that has focused on the study of the on-the-job factors of nurse turnover, showing the important role of job attitudes. Recently, WFC and job embeddedness (JE) have been identified as variables that could help explain levels of nurse turnover. Using structural equation modelling from a cross-sectional survey, the relationships between the variables were explored in a sample of 440 nurses from an Italian public hospital. The questionnaire measures demographic data and psychosocial factors such as job satisfaction, organizational commitment, WFC, CE and turnover intentions. The findings supported the importance of non-work dimensions in turnover models. The results suggest that when studying turnover phenomena in health organizations, the extra-work domains (WFC and JE) can contribute to a decrease in the intention to leave, in addition to the more typically emphasized attitude dimension. © 2012 The Authors. International Nursing Review © 2012 International Council of Nurses.

  19. Complexity Science and the Dynamics of Climate and Communication: Reducing Nursing Home Turnover

    Science.gov (United States)

    Anderson, Ruth A.; Corazzini, Kirsten N.; McDaniel, Reuben R.

    2008-01-01

    Purpose Turnover in nursing homes is a widespread problem adversely affecting care quality. Using complexity theory, we tested the effect of administrative climate, communication patterns, and the interaction between the two on turnover, controlling for facility context. Design and Methods Perceptions of administrative climate and communication were collected from 3,449 employees in 164 randomly sampled nursing homes, and they were linked to secondary data on facility characteristics, resource allocation, and turnover. We used hierarchical regression to test the hypotheses. Results Climate and communication both affected turnover, but lower turnover was dependent on the interaction between climate and communication. In nursing homes with reward-based administrative climates, higher levels of communication openness and accuracy explained lower turnover of licensed vocational nurses and certified nurse assistants, relative to nursing homes with an ambiguous climate. Adequate staffing and longer tenure of the nursing director were also important predictors of turnover. Implications Although context is important, managers can also influence turnover by addressing climate and communication patterns and by encouraging stable nursing leadership. PMID:15197292

  20. Analysis and control of employee turnover.

    Science.gov (United States)

    McConnell, Charles R

    2007-01-01

    Turnover is a relatively simple and easily described concept. However, considerable confusion often results when addressing turnover because of differences in how it is defined; that is, what is counted, how it is counted, and how the turnover rates are expressed. Turnover is also costly, although not enough attention is paid to its cost because so much of it is indirect, and thus, not readily visible. There are a variety of causes of turnover, some which can be corrected and some which cannot be avoided. Reducing or otherwise controlling turnover requires continuing management attention to its causes and constant recognition of what can and should be controlled and what cannot be controlled. Ongoing attention to turnover is an essential part of the department manager's role.

  1. Supervisory Turnover in Outpatient Substance Abuse Treatment

    Science.gov (United States)

    Knight, Danica K.; Broome, Kirk M.; Edwards, Jennifer R.; Flynn, Patrick M.

    2009-01-01

    Staff turnover is a significant issue within substance abuse treatment, with implications for service delivery and organizational health. This study examined factors associated with turnover among supervisors in outpatient substance abuse treatment. Turnover was conceptualized as being an individual response to organizational-level influences, and predictors represent aggregate program measures. Participants included 532 staff (including 467 counselors and 65 clinical/program directors) from 90 programs in four regions of the USA. Using logistic regression, analyses of structural factors indicated that programs affiliated with a parent organization and those providing more counseling hours to clients had higher turnover rates. When measures of job attitudes were included, only parent affiliation and collective appraisal of satisfaction were related to turnover. Subsequent analyses identified a trend toward increased supervisory turnover when satisfaction was low following the departure of a previous supervisor. These findings suggest that organizational-level factors can be influential in supervisory turnover. PMID:19949883

  2. Bone turnover in postmenopausal osteoporosis

    International Nuclear Information System (INIS)

    Thomsen, K.

    1988-02-01

    Studies of the bone turnover in postmenopausal osteoporosis are essential, because the associated bone loss is inevitably due to the relative increase of bone resorption compared with bone formation. Measurement of the bone mineral content (BMC) in normal adults is assessed - partly on the uncorrected values and partly in proportion to the body muscle mass. The whole body retention (WBR) method is presented. The WBR and alternative urinary excretion (UE) methods used by the author are characterised and compared with the retention methods described in the literature. The representativity of WBR and UE for the estimation of bone turnover in normal subjects and patients with various bone metabolic diseases is discussed. The conclusion is that the modified retention methods used by the author have a satisfactory precision and accuracy in relation to the clinical studies carried out. The author's modification of the WBR method for determination of bone turnover and the alternative urinary excretion method (UE) consists in continuous scanning in the whole body count, using a gamma camera, and with the collimator a short distance from the volunteer. This procedure has the advantage of restricting the radioactive dose to 2 mCi (72 MBa). This is smaller by a factor of 5-10 than the dose used to measure WBR with equally simple counting equipment: With the author's procedure, using frontal counting, WBR is systematically underestimated by about 4 per cent point compared to the purely dorsal count, but since the frontal position is the most comfortable, requires a smaller radioactive dose, and the error is systematic, it is the preferred counting procedure. Correction of WBR and UE for bone mineral content is in principle a new parameter of bone turnover, whose improved accuracy increases the validity of the retention determinations. 136 refs. (EG)

  3. Effects of breeder turnover and harvest on group composition and recruitment in a social carnivore.

    Science.gov (United States)

    Ausband, David E; Mitchell, Michael S; Waits, Lisette P

    2017-09-01

    Breeder turnover can influence population growth in social carnivores through changes to group size, composition and recruitment. Studies that possess detailed group composition data that can provide insights about the effects of breeder turnover on groups have generally been conducted on species that are not subject to recurrent annual human harvest. We wanted to know how breeder turnover affects group composition and how harvest, in turn, affects breeder turnover in cooperatively breeding grey wolves (Canis lupus Linnaeus 1758). We used noninvasive genetic sampling at wolf rendezvous sites to construct pedigrees and estimate recruitment in groups of wolves before and after harvest in Idaho, USA. Turnover of breeding females increased polygamy and potential recruits per group by providing breeding opportunities for subordinates although resultant group size was unaffected 1 year after the turnover. Breeder turnover had no effect on the number of nonbreeding helpers per group. After breeding male turnover, fewer female pups were recruited in the new males' litters. Harvest had no effect on the frequency of breeder turnover. We found that breeder turnover led to shifts in the reproductive hierarchies within groups and the resulting changes to group composition were quite variable and depended on the sex of the breeder lost. We hypothesize that nonbreeding females direct help away from non-kin female pups to preserve future breeding opportunities for themselves. Breeder turnover had marked effects on the breeding opportunities of subordinates and the number and sex ratios of subsequent litters of pups. Seemingly subtle changes to groups, such as the loss of one individual, can greatly affect group composition, genetic content, and short-term population growth when the individual lost is a breeder. © 2017 The Authors. Journal of Animal Ecology © 2017 British Ecological Society.

  4. A model for reducing health care employee turnover.

    Science.gov (United States)

    Nowak, Paul; Holmes, Gary; Murrow, Jim

    2010-01-01

    Explaining the rationale as to why employees leave their jobs has led to many different strategies to retain employees. The model presented here seeks to explain why employees choose to stay or to leave their place of employment. The information from the analysis will provide managers with well-tested tools to reduce turnover and to ascertain what employees value from their work environment in order to help the organization to retain those employees. The model identifies key factors that management can utilize to provide barriers to exit and retain professional employees in their health care units. Recommendations are provided that reward loyalty and build barriers to exit.

  5. KECENDERUNGAN KEPUASAN KERJA SEBAGAI TRIGGER TURNOVER

    Directory of Open Access Journals (Sweden)

    Raditya Adi Saputra

    2017-06-01

    Full Text Available The purpose of this study are: (1 To determine the effect of job satisfaction on turnover intention; (2 To determine the effect of work stress on turnover intention; (3 To determine the effect of compensation on turnover intention; (4 To determine the effect of organizational climate on turnover intention; and (5 To determine the stress of work, compensation, organizational climate and job satisfaction effect on turnover intention. The population in this study are employees of the Cooperative KOKAPURA AVIA totaling 180 people, while employees who have worked more than three years as many as 128 people. Samples were taken 97 people. The technique of collecting data using questionnaires. The analysis used is multiple regression analysis and path analysis using PLS 3.0 Smart program. Based on the results of the study concluded that: (1 Job satisfaction significantly influence employee turnover intention; (2 Work stress significantly influence employee turnover intention; (3 Compensation incentives significantly influence employee turnover intention; (4 organizational climate significantly influence employee turnover intention; and (5 Work stress, incentive compensation, organizational climate and job satisfaction simultaneously significantly influence employee turnover intention.

  6. Turnover and metabolism of phosphatidylglycerol acyl moieties in E. coli

    International Nuclear Information System (INIS)

    Cooper, C.L.; Rock, C.O.

    1987-01-01

    Fatty acids synthesized in mutants (plsB) blocked in de novo phospholipid biosynthesis were preferentially transferred to phosphatidylglycerol (PtdGro). The ratio of phospholipid species labeled with 32 P and [ 3 H]acetate in the absence of glycerol-3-P acyltransferase activity indicated that [ 3 H]acetate incorporation into PtdGro was due to fatty acid turnover. The magnitude of the turnover process was difficult to estimate due to a significant contraction of the acetyl-CoA pool following the inhibition of phospholipid synthesis. A possible connection between PtdGro turnover and protein acylation was investigated in an E. coli strain containing a lipoprotein expression vector. Cells were prelabeled with [ 3 H]acetate and lipoprotein expression was induced concomitant with the addition of exogenous [ 14 C]-palmitate. [ 14 C] Palmitate was assimilated into the l-position of phosphatidylethanolamine and transferred to the amino terminus of the lipoprotein. In contrast, the ester-linked lipoprotein fatty acids and PtdGro were not enriched in carbon-14 implying a metabolic relationship between these two pools. The data suggest that turnover of PtdGro acyl moieties is related to protein acylation, but a direct link between the two processes remains to be established

  7. Estimating soil turnover rate from tree uprooting during hurricanes in Puerto Rico

    Science.gov (United States)

    Lenart, M.T.; Falk, D.A.; Scatena, F.N.; Osterkamp, W.R.

    2010-01-01

    Soil turnover by tree uprooting in primary and secondary forests on the island of Puerto Rico was measured in 42 study plots in the months immediately after the passage of a Category 3 hurricane. Trunk basal area explained 61% of the variability of mound volume and 53% of the variability of mound area. The proportion of uprooted trees, the number of uprooted trees, or the proportion of uprooted basal area explained 84-85% of the variation in hurricane-created mound area. These same variables explain 79-85% of the variation in mound volume. The study indicates that the soil turnover period from tree uprooting by Puerto Rican hurricanes is between 1600 and 4800 years. These rates are faster than soil turnover by landslides and background treefall in the same area and provide a useful age constraint on soil profile development and soil carbon sequestration in these dynamic landscapes. ?? 2009 Elsevier B.V.

  8. The Structural Model of Psychological Contract Violation, Organizational Commitment, Turnover, Job Satisfaction and Deviant Behaviors

    Directory of Open Access Journals (Sweden)

    M. Golparvar

    2014-12-01

    Full Text Available This research was conducted with the purpose of studying the structural model of the relationships of psychological contract violation with organizational commitment, turnover, job satisfaction and deviant behaviors. Research method was correlation and the statistical population were male employees of an industrial company in Shiraz city, from among which 300 employees were selected using convenience sampling. Assessment instruments consisted of Psychological Contract Violation Questionnaire (Tekleab etal, 2005, Organizational Commitment Questionnaire (Speier & Vankatesh, 2002, Job Satisfaction Questionnaire (Spector, 1985, Turnover Questionnaire (Tekleab etal, 2005 and Deviant Behavior Questionnaire (Bennett & Robinson, 2000. Data was analyzed using Pearson’s correlation coefficient, structure equation modeling (SEM and mediation analysis. Findings showed that psychological contract violation explained 7.1 percent of organizational commitment variance, organizational commitment and job satisfaction explained 16.7 percent of turnover variance, organizational commitment explained 20.3 percent of job satisfaction variance and turnover explained 4.3 percent of deviant behavior variance. Mediation analysis showed that organizational commitment played the complete mediator variable in the relation of psychological contract violation with job satisfaction and job satisfaction was the partial mediator variable in the relation of organizational commitment with turnover. Finally with regard to the limitation of generalization of current research results it is suggested to industrial organizations that they should not violate their obligations to employees in anyway.

  9. Biodiversity effects on resource use efficiency and community turnover of plankton in Lake Nansihu, China.

    Science.gov (United States)

    Tian, Wang; Zhang, Huayong; Zhang, Jian; Zhao, Lei; Miao, Mingsheng; Huang, Hai

    2017-04-01

    The relationship between biodiversity and ecosystem functioning is a central issue in ecology, especially in aquatic ecosystems due to the ecophysiological characteristics of plankton. Recently, ecologists have obtained conflicting conclusions while analyzing the influence of species diversity on plankton resource use efficiency (RUE) and community turnover. In this study, both phytoplankton and zooplankton communities were investigated seasonally from 2011 to 2013 in Lake Nansihu, a meso-eutrophic and recovering lake in China. The effects of phytoplankton diversity on RUE of phytoplankton (RUE PP ), zooplankton (RUE ZP ), and community turnover were analyzed. Results showed that both phytoplankton species richness and evenness were positively correlated with RUE PP . RUE ZP had a negative relationship with phytoplankton species richness, but a weak unimodal relationship with phytoplankton evenness. Cyanobacteria community had the opposite influence on RUE PP and RUE ZP . Thus, cyanobacteria dominance will benefit RUE PP in eutrophic lakes, but the growth and reproduction of zooplankton are greatly limited. The strong negative relationship between total phosphorus and RUE ZP confirmed these results. Phytoplankton community turnover tended to decrease with increasing phytoplankton evenness, which was consistent with most previous studies. The correlation coefficient between phytoplankton species richness and community turnover was negative, but not significant (p > 0.05). Therefore, phytoplankton community turnover was more sensitive to the variation of evenness than species richness. These results will be helpful in understanding the effects of species diversity on ecosystem functioning in aquatic ecosystems.

  10. Tritium turnover in succulent plants

    International Nuclear Information System (INIS)

    Krishnamoorthy, T.M.; Gogate, S.S.; Soman, S.D.

    1977-01-01

    Measurements of turnover rates for tissue free water tritium (TFWT) and tissue bound tritium (TBT) were carried out in three succulent plants, Opuntia sp., E. Trigona and E. Mili using tritiated water as tracer. The estimated half-times were 52, 57.5 and 80 days for TFWT and 212, 318 and 132 days for TBT in the stems of the above plants respectively. Opuntia sp. showed significant incorporation of TBT, 10% of TFWT on weight basis, while the other two plants showed lesser incorporation, 2-3% of TFWT. However, the leaves of E. Mili indicated the same level of fixation of TBT as the stem of Opuntia sp. (author)

  11. Water turnover in reindeer. Some environmental implications

    International Nuclear Information System (INIS)

    Cameron, R.D.; Luick, J.R.; White, R.G.

    1982-01-01

    The nutritional and climatic effects on water turnover (determined using tritiated water) in reindeer are described. At low ambient temperatures (ca. -20 0 C) water turnover is related to protein and mineral intake, which is reflected in the relations of faecal and urinary water to nitrogen and ash excretion via these avenues. As ambient temperature increases, respiratory water, faecal water and urine flow increase, resulting in an increase in water turnover

  12. The costs of turnover in nursing homes

    Science.gov (United States)

    Mukamel, Dana B.; Spector, William D.; Limcangco, Rhona; Wang, Ying; Feng, Zhanlian; Mor, Vincent

    2009-01-01

    Background Turnover rates in nursing homes have been persistently high for decades, ranging upwards of 100%. Objectives To estimate the net costs associated with turnover of direct care staff in nursing homes. Data and sample 902 nursing homes in California in 2005. Data included Medicaid cost reports, the Minimum Data Set (MDS), Medicare enrollment files, Census and Area Resource File (ARF). Research Design We estimated total cost functions, which included in addition to exogenous outputs and wages, the facility turnover rate. Instrumental variable (IV) limited information maximum likelihood techniques were used for estimation to deal with the endogeneity of turnover and costs. Results The cost functions exhibited the expected behavior, with initially increasing and then decreasing returns to scale. The ordinary least square estimate did not show a significant association between costs and turnover. The IV estimate of turnover costs was negative and significant (p=0.039). The marginal cost savings associated with a 10 percentage point increase in turnover for an average facility was $167,063 or 2.9% of annual total costs. Conclusion The net savings associated with turnover offer an explanation for the persistence of this phenomenon over the last decades, despite the many policy initiatives to reduce it. Future policy efforts need to recognize the complex relationship between turnover and costs. PMID:19648834

  13. The costs of turnover in nursing homes.

    Science.gov (United States)

    Mukamel, Dana B; Spector, William D; Limcangco, Rhona; Wang, Ying; Feng, Zhanlian; Mor, Vincent

    2009-10-01

    Turnover rates in nursing homes have been persistently high for decades, ranging upwards of 100%. To estimate the net costs associated with turnover of direct care staff in nursing homes. DATA AND SAMPLE: Nine hundred two nursing homes in California in 2005. Data included Medicaid cost reports, the Minimum Data Set, Medicare enrollment files, Census, and Area Resource File. We estimated total cost functions, which included in addition to exogenous outputs and wages, the facility turnover rate. Instrumental variable limited information maximum likelihood techniques were used for estimation to deal with the endogeneity of turnover and costs. The cost functions exhibited the expected behavior, with initially increasing and then decreasing returns to scale. The ordinary least square estimate did not show a significant association between costs and turnover. The instrumental variable estimate of turnover costs was negative and significant (P = 0.039). The marginal cost savings associated with a 10% point increase in turnover for an average facility was $167,063 or 2.9% of annual total costs. The net savings associated with turnover offer an explanation for the persistence of this phenomenon over the last decades, despite the many policy initiatives to reduce it. Future policy efforts need to recognize the complex relationship between turnover and costs.

  14. The role of job satisfaction, work engagement, self-efficacy and agentic capacities on nurses' turnover intention and patient satisfaction.

    Science.gov (United States)

    De Simone, Silvia; Planta, Anna; Cicotto, Gianfranco

    2018-02-01

    Nurses' voluntary turnover is a worrying global phenomenon which affects service quality. Retaining nursing staff within a hospital is important to eliminate the negative influence of voluntary turnover on the quality of care and organisation costs. This research helps explain nurses' voluntary turnover by analysing the role of self-efficacy, agentic capacities, job satisfaction, and work engagement on hospital turnover intention, and to study the relationships between these variables and patient satisfaction. This study gathered data from 194 nurses and 181 patients from 22 inpatient wards at two hospitals in southern Italy. Correlation analysis revealed that job satisfaction, work engagement, self-efficacy and agentic capacities were positively interrelated and negatively correlated with turnover intention. Path analysis showed that self-efficacy, some agentic capacities (anticipation and self-regulation), job satisfaction, and work engagement had direct or indirect effects on nurses' turnover intention, and that job satisfaction exerted a stronger effect on turnover intention. Also, patient satisfaction was positively correlated with nurses' job satisfaction, work engagement, self-efficacy, self-regulation and anticipation and negatively correlated with nurses' turnover intention. Results highlighted the importance of implementing actions (for example through feedforward methodology and the goal setting technique) to improve self-efficacy, self-regulation skill, work engagement and job satisfaction in order to reduce nurses' turnover intention and increase patient satisfaction with nursing care. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. COMPANIES’FINANCIAL STATUS AND THE BUSINESS TURNOVER ON EMERGENT MARKETS: THE ROMANIAN CASE

    Directory of Open Access Journals (Sweden)

    Stefea Petru

    2013-07-01

    Full Text Available The aim of this study is to test for the relevance of some financial ratios as descriptors of companies’ financial status in explaining the evolutions of their business turnover. We are considering a data sample of 36 companies quoted on the Romanian capital market for a time span between 2007 and 2010.The predictive capacity of some significant financial ratios for the companies’ business turnover is analyzed and a methodology for the evaluation of their financial status based on these ratios is advanced. We found that the predictive capacity of some relevant financial ratios for the dynamic of some quoted companies’ turnovers is non-uniform across the two conventional sectors in which we have grouped these companies according to their field of activity. Based on these results, an synthetic indicator of the companies’ financial status is constructed at the level of each individual sector and the non-linear correlation between this indicator and the business turnover is tested.

  16. Biotic turnover rates during the Pleistocene-Holocene transition

    Science.gov (United States)

    Stivrins, Normunds; Soininen, Janne; Amon, Leeli; Fontana, Sonia L.; Gryguc, Gražyna; Heikkilä, Maija; Heiri, Oliver; Kisielienė, Dalia; Reitalu, Triin; Stančikaitė, Miglė; Veski, Siim; Seppä, Heikki

    2016-11-01

    The Northern Hemisphere is currently warming at the rate which is unprecedented during the Holocene. Quantitative palaeoclimatic records show that the most recent time in the geological history with comparable warming rates was during the Pleistocene-Holocene transition (PHT) about 14,000 to 11,000 years ago. To better understand the biotic response to rapid temperature change, we explore the community turnover rates during the PHT by focusing on the Baltic region in the southeastern sector of the Scandinavian Ice Sheet, where an exceptionally dense network on microfossil and macrofossil data that reflect the biotic community history are available. We further use a composite chironomid-based summer temperature reconstruction compiled specifically for our study region to calculate the rate of temperature change during the PHT. The fastest biotic turnover in the terrestrial and aquatic communities occurred during the Younger Dryas-Holocene shift at 11,700 years ago. This general shift in species composition was accompanied by regional extinctions, including disappearance of mammoth (Mammuthus primigenius) and reindeer (Rangifer tarandus) and many arctic-alpine plant taxa, such as Dryas octopetala, Salix polaris and Saxifraga aizoides, from the region. This rapid biotic turnover rate occurred when the rate of warming was 0.17 °C/decade, thus slightly lower than the current Northern Hemisphere warming of 0.2 °C/decade. We therefore conclude that the Younger Dryas-Holocene shift with its rapid turnover rates and associated regional extinctions represents an important palaeoanalogue to the current high latitude warming and gives insights about the probable future turnover rates and patterns of the terrestrial and aquatic ecosystem change.

  17. Effects of work environment and job characteristics on the turnover intention of experienced nurses: The mediating role of work engagement.

    Science.gov (United States)

    Wan, Qiaoqin; Li, Zhaoyang; Zhou, Weijiao; Shang, Shaomei

    2018-01-19

    To assess turnover intention among experienced nurses and explore the effects of work environment, job characteristics and work engagement on turnover intention. The nursing shortage is an urgent concern in China. A high turnover rate of experienced nurses could have serious effects on the quality of care, costs and the efficiency of hospitals. It is crucial to explore the predictors of turnover intention and develop strategies tailored to experienced nurses. A descriptive, cross-sectional survey design. A total of 778 experienced nurses from seven hospitals was surveyed on their work engagement, job characteristics, work environment and turnover intention in March-May 2017. Structural equation modelling was used to test a theoretical model and the hypotheses. The results showed that 35.9% of experienced nurses had high-level turnover intention. The final model explained 50% of the variance in experienced nurses' turnover intention and demonstrated that: (1) work environment was positively associated with higher work engagement and lower turnover intention and work engagement partially mediated the relationship between work environment and turnover intention; and (2) job characteristics were positively related to higher work engagement and lower turnover intention and work engagement fully mediated the relationship between job characteristics and turnover intention. The study confirms the intrinsic and extrinsic motivators on work engagement posited by job demands-resources model. Theory-driven strategies to improve work environment, enhance job characteristics and promote wok engagement are needed to address the nursing shortage and high turnover intention among experienced nurses. © 2018 John Wiley & Sons Ltd.

  18. Explaining Away Intuitions

    Directory of Open Access Journals (Sweden)

    Jonathan Ichikawa

    2009-12-01

    Full Text Available What is it to explain away an intuition? Philosophers regularly attempt to explain intuitions away, but it is often unclear what the success conditions for their project consist in. I attempt to articulate some of these conditions, taking philosophical case studies as guides, and arguing that many attempts to explain away intuitions underestimate the challenge the project of explaining away involves. I will conclude, therefore, that explaining away intuitions is a more difficult task than has sometimes been appreciated; I also suggest, however, that the importance of explaining away intuitions has often been exaggerated.

  19. Evolutionary Turnover of Kinetochore Proteins: A Ship of Theseus?

    Science.gov (United States)

    Drinnenberg, Ines A; Henikoff, Steven; Malik, Harmit S

    2016-07-01

    The kinetochore is a multiprotein complex that mediates the attachment of a eukaryotic chromosome to the mitotic spindle. The protein composition of kinetochores is similar across species as divergent as yeast and human. However, recent findings have revealed an unexpected degree of compositional diversity in kinetochores. For example, kinetochore proteins that are essential in some species have been lost in others, whereas new kinetochore proteins have emerged in other lineages. Even in lineages with similar kinetochore composition, individual kinetochore proteins have functionally diverged to acquire either essential or redundant roles. Thus, despite functional conservation, the repertoire of kinetochore proteins has undergone recurrent evolutionary turnover. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Employee Turnover among Full-time Public Librarians.

    Science.gov (United States)

    Rubin, Richard

    1989-01-01

    A study of employee turnover in 31 public libraries in the American Midwest established baseline turnover rates and examined the relationship of gender to turnover behavior. Findings showed that: turnover rates are low compared to other occupations; and turnover rates of males and females are similar. (28 references) (Author/MES)

  1. Part of the job: the role of physical work conditions in the nurse turnover process.

    Science.gov (United States)

    Vardaman, James M; Cornell, Paul T; Allen, David G; Gondo, Maria B; Muslin, Ivan S; Mobley, Robin N; Brock, Meagan E; Sigmon, Tracy L

    2014-01-01

    Retention of nursing staff remains an important issue for health care managers. Turnover research has focused primarily on motivational and social factors as keys to retention, whereas the role of the physical work conditions has received considerably less attention. However, work design theory suggests that physical work conditions may be an important factor in fostering retention among nursing staff. The aim of this study was to integrate work design theory with turnover process models to explore the influence of perceptions of physical work conditions on the development of turnover intentions among nursing staff. Drawing on two samples of registered nurses working in cancer units in metropolitan hospitals in the southeastern United States, this study explores the impact of perceptions of physical work conditions on turnover intentions using ordinary least squares regression. Hypotheses are tested in Study 1 and replicated in Study 2. A measure of perceptions of physical work conditions is also developed and validated using exploratory (Study 1) and confirmatory (Study 2) factor analyses. Perceptions of physical work conditions explain variance in turnover intentions above than that explained by motivational and social factors. Specifically, employee perceptions of noisy work conditions are found to significantly increase turnover intentions, whereas perceptions that work conditions facilitate tasks were found to significantly reduce turnover intentions. Perceptions of temperature and health hazard did not show significant effects. Results suggest that health care managers and scholars should re-examine the role of physical work conditions in the turnover process. Investments in upgrades that facilitate tasks may foster retention better than investments that simply improve employee comfort. Negative perceptions of work conditions may have no impact if they are considered a normal "part of the job," although negative perceptions of conditions that are viewed as

  2. On the controlling mechanism of the upper turnover states in the NTC regime

    KAUST Repository

    Ji, Weiqi

    2015-12-18

    Using n-butane, n-heptane and iso-octane as representative fuels exhibiting NTC (negative temperature coefficient) behavior, comprehensive computational studies with detailed mechanisms and theoretical analysis were performed to investigate the upper stationary point, denoted as turnover states, on the NTC curve near the higher temperature regime, where the ignition delay τ exhibits a local maximum. It is found that the global behavior of the turnover states exhibits distinctive thermodynamic and kinetic characteristics under different pressures, in that the ignition delay at the turnover states shows an Arrhenius dependence on the temperature T and an approximate inverse quadratic power law dependence on the pressure P. These global behaviors imply that the temperature and pressure of the turnover states are not independent and can be correlated by Arrhenius dependence, as ln P ∝ 1/T. Further theoretical analyses demonstrate that such turnover states result from the competition between the low-temperature chain branching reactions and the decomposition of the intermediate species, and therefore correspond to a critical value, α, of the ratio of OH production from low-temperature chemistry. In addition, the ignition delay at the turnover state can be well correlated by the analytical expression derived by Peters et al., with the further demonstration that the pressure dependence of the turnover ignition delay mainly result from the H2O2 decomposition reaction. Comparison of the present results with the literature experimental data of n-heptane ignition delay time shows very good agreement.

  3. Employee Turnover: An Empirical and Methodological Assessment.

    Science.gov (United States)

    Muchinsky, Paul M.; Tuttle, Mark L.

    1979-01-01

    Reviews research on the prediction of employee turnover. Groups predictor variables into five general categories: attitudinal (job satisfaction), biodata, work-related, personal, and test-score predictors. Consistent relationships between common predictor variables and turnover were found for four categories. Eight methodological problems/issues…

  4. Relationship between Job Satisfaction and Turnover Intention ...

    African Journals Online (AJOL)

    This study explores the association between job satisfaction and turnover intentions among lecturers in three public universities in Tanzania. It had three objectives: (1) to determine the level of perceived job satisfaction among lecturers; (2) to determine the association between job satisfaction and turnover intention; and (3) ...

  5. Unit-level voluntary turnover rates and customer service quality: implications of group cohesiveness, newcomer concentration, and size.

    Science.gov (United States)

    Hausknecht, John P; Trevor, Charlie O; Howard, Michael J

    2009-07-01

    Despite substantial growth in the service industry and emerging work on turnover consequences, little research examines how unit-level turnover rates affect essential customer-related outcomes. The authors propose an operational disruption framework to explain why voluntary turnover impairs customers' service quality perceptions. On the basis of a sample of 75 work units and data from 5,631 employee surveys, 59,602 customer surveys, and organizational records, results indicate that unit-level voluntary turnover rates are negatively related to service quality perceptions. The authors also examine potential boundary conditions related to the disruption framework. Of 3 moderators studied (group cohesiveness, group size, and newcomer concentration), results show that turnover's negative effects on service quality are more pronounced in larger units and in those with a greater concentration of newcomers.

  6. Piribedil affects dopamine turnover in cochleas stimulated by white noise.

    Science.gov (United States)

    Gil-Loyzaga, P; Vicente-Torres, M A; Fernández-Mateos, P; Arce, A; Esquifino, A

    1994-09-01

    The presence of dopamine (DA) within the cochlea has been previously reported, indicating that its turnover increases under noise stimulation. In the present report, piribedil, a dopaminergic D2 agonist, was used in order to provide evidence of the activity of D2 receptors in the turnover of DA under noise stimulation. Long-Evans rats were intraperitoneally injected with distilled water or with a solution of piribedil one hour previously to either noise or silence exposure. Noise stimulation was performed in an anechoic chamber at 70, 90 or 110 dB SPL for one hour. The animals were then sacrificed and the cochlear contents of DA and its metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were quantified by HPLC with electrochemical detection. The administration of piribedil to animals kept in silence did not modify the cochlear DA, DOPAC and HVA content. Noise stimulation resulted in a decrease of the cochlear DA content and an increase of the cochlear DOPAC and HVA contents in vehicle treated animals. The administration of piribedil resulted in a blockade of this noise induced cochlear DA turnover. These results suggest that piribedil stimulates cochlear D2 receptors controlling the cochlear DA release. Piribedil action on D2 receptors could explain the improvement observed in some cochleo-vestibular diseases signs after piribedil treatment.

  7. Chronic Teacher Turnover in Urban Elementary Schools

    Directory of Open Access Journals (Sweden)

    Kacey Guin

    2004-08-01

    Full Text Available This study examines the characteristics of elementary schools that experience chronic teacher turnover and the impacts of turnover on a school’s working climate and ability to effectively function. Based on evidence from staff climate surveys and case studies, it is clear that high turnover schools face significant organizational challenges. Schools with high teacher turnover rates have difficulty planning and implementing a coherent curriculum and sustaining positive working relationships among teachers. The reality of these organizational challenges is particularly alarming, given that high turnover schools are more likely to serve low-income and minority students. The negative relationship between teacher turnover and school functioning, and the fact that turbulent schools are disproportionately likely to serve lowincome and minority students have important implications for both district and school-level policies. Specifically: Teacher turnover rates are one indicator of school health, which school districts should consider when focusing on school improvements. Districts need to begin by developing the means to identify individual schools that experience high levels of teacher turnover. Current district policies in implementing professional development for teachers in low-performing schools are inefficient when teachers do not remain in the schools in which they are trained. In order for low-performing schools to improve, districts need to consider providing incentive programs so that high quality teachers apply for, and remain in, these schools. Future research is needed to address the causal link between turnover, organizational functioning and student outcomes. Additionally, there is a need for research examining district policies that may facilitate teacher turnover within a district, including how districts place and transfer teachers, as well as how teachers’ salaries are budgeted.

  8. Paleontology to policy: the Quaternary history of Southeast Asian tapirs (Tapiridae) in relation to large mammal species turnover, with a proposal for conservation of Malayan tapir by reintroduction to Borneo.

    Science.gov (United States)

    Cranbrook, Earl Of; Piper, Philip J

    2013-03-01

    The Southeast Asian zoogeographical region is divided into Indochinese, Sundaic and Philippine subregions. Two clades of tapirs, Tapirus spp., have been recognized in Quaternary Southeast Asia. A review of sites at which they occurred shows that representatives of both clades, one of which was the ancestral Malayan tapir Tapirus indicus, co-existed with a diversity of other Pleistocene mammal megafauna. The process of replacement of archaic large mammals was progressive and prolonged through the Quaternary. Zooarcheological investigation has extended knowledge of the former occurrence and distribution of tapirs and other large mammals of the region, with discoveries beyond the outer limits of their previously known ranges. These large mammals were subjected to paleoenvironmental changes as a consequence of the Quaternary cycles of glacial and interglacial periods. Archeological evidence suggests that hunting pressure has intensified the effects of altered environments, leading ultimately to the local disappearance of the Malayan tapir in most of Southeast Asia, including Borneo. The survival of the Malayan tapir through the Quaternary until the present shows that the species is both resilient to environmental change and flexible in its ecological re'uirements and, given proper protection, could continue to inhabit tropical Southeast Asia. To assist the species conservation, reintroduction is proposed from the remaining range of Malayan tapir in the wild, to suitable sites of past occurrence in Borneo, where these ancient survivors of the Quaternary megafauna can be accommodated and safeguarded alongside other forms of land usage. © 2012 Wiley Publishing Asia Pty Ltd, ISZS and IOZ/CAS.

  9. THE EFFECT OF JOB SATISFACTION ON IT EMPLOYEES TURNOVER INTENTION IN ISRAEL

    Directory of Open Access Journals (Sweden)

    Ladelsky Limor

    2014-07-01

    Full Text Available Employee voluntary turnover is very costly for companies, particularly for the Hi-Tech sector, where the costs of their IT labor force is expensive. Employees\\' voluntary turnover has substantial negative impacts on the companies especially costs, potential loss of valuable knowledge, skills and organizational knowledge.That is why it becomes a critical issue to take address. Studies have been carried out on the reasons which lead to this tendency, however the ability to explain and predict it remains restricted.The objective of this paper is to present the reasons for voluntary turnover of employees in the IT sector in Israel from the IT employees` perspective. A broad analysis of the field literature led to the following groups of causes affecting voluntary turnover: organizational causes: Human Resource Management (HRM related, organizational culture, job related, leadership and internal marketing related; extra organizational causes: individual and, respectively, labor market related causes. This could be approached as n light of this review this article will focus on one of the extra organizational causes of voluntary turnover, i.e. the effect of job satisfaction on voluntary turnover intention among IT employees in Hi-Tech companies in Israel. This correlation was researched in an extensive empirical study among two population groups: IT employees and IT managers and by using mixed method research (combination of quantitative and qualitative research.The findings that supported the literature show job satisfaction has a negative effect on voluntary turnover intention among IT employees in Hi-Tech companies in Israel. Additionally, it was found that job satisfaction indirectly affects voluntary turnover intentions and that emotional variables such as commitment, motivation and loyalty mediate voluntary turnover intention.This finding is supported partially in the literature which only pointed out commitment as a mediating factor in the

  10. The mediating effects of job satisfaction on turnover intention for long-term care nurses in Taiwan.

    Science.gov (United States)

    Kuo, Huai-Ting; Lin, Kuan-Chia; Li, I-Chuan

    2014-03-01

    This study explores the mediating effects of job satisfaction on work stress and turnover intention among long-term care nurses in Taiwan. Healthcare institutions face a nursing shortage, and it is important to examine the factors that influence turnover intention among nurses. Excessive levels of work stress may lead to employee dissatisfaction and a significant inverse relationship between work stress and job satisfaction, including subsequent effects on turnover among nurses. However, little is known about the mediating role of job satisfaction on work stress and turnover intention among long-term care nurses. A cross-sectional survey and a correlation design were used. Multistage linear regression was used to test the mediation model. This study showed that job satisfaction significantly mediated the relationship between work stress and turnover intention. Thirty-eight percent of the variance in turnover intention explained by work stress was accounted for by the mediation pathway. The results of this study showed that higher job satisfaction significantly decreased work stress and turnover intention among long-term care nurses. This study provides nursing administrators with a resource to build a supportive environment to increase nurses' job satisfaction and to decrease their stress and turnover. © 2013 John Wiley & Sons Ltd.

  11. The relationship between quality of work life and turnover intention of primary health care nurses in Saudi Arabia.

    Science.gov (United States)

    Almalki, Mohammed J; FitzGerald, Gerry; Clark, Michele

    2012-09-12

    Quality of work life (QWL) has been found to influence the commitment of health professionals, including nurses. However, reliable information on QWL and turnover intention of primary health care (PHC) nurses is limited. The aim of this study was to examine the relationship between QWL and turnover intention of PHC nurses in Saudi Arabia. A cross-sectional survey was used in this study. Data were collected using Brooks' survey of Quality of Nursing Work Life, the Anticipated Turnover Scale and demographic data questions. A total of 508 PHC nurses in the Jazan Region, Saudi Arabia, completed the questionnaire (RR = 87%). Descriptive statistics, t-test, ANOVA, General Linear Model (GLM) univariate analysis, standard multiple regression, and hierarchical multiple regression were applied for analysis using SPSS v17 for Windows. Findings suggested that the respondents were dissatisfied with their work life, with almost 40% indicating a turnover intention from their current PHC centres. Turnover intention was significantly related to QWL. Using standard multiple regression, 26% of the variance in turnover intention was explained by QWL, p turnover intention, after controlling for demographic variables. Creating and maintaining a healthy work life for PHC nurses is very important to improve their work satisfaction, reduce turnover, enhance productivity and improve nursing care outcomes.

  12. Nurse turnover: a literature review - an update.

    Science.gov (United States)

    Hayes, Laureen J; O'Brien-Pallas, Linda; Duffield, Christine; Shamian, Judith; Buchan, James; Hughes, Frances; Laschinger, Heather K Spence; North, Nicola

    2012-07-01

    Concerns related to the complex issue of nursing turnover continue to challenge healthcare leaders in every sector of health care. Voluntary nurse turnover is shown to be influenced by a myriad of inter-related factors, and there is increasing evidence of its negative effects on nurses, patients and health care organizations. The objectives were to conduct a comprehensive review of the related literature to examine recent findings related to the issue of nursing turnover and its causes and consequences, and to identify on methodological challenges and the implications of new evidence for future studies. A comprehensive search of the recent literature related to nursing turnover was undertaken to summarize findings published in the past six years. Electronic databases: MEDLINE, CINAHL and PubMed, reference lists of journal publications. Keyword searches were conducted for publications published 2006 or later that examined turnover or turnover intention in employee populations of registered or practical/enrolled or assistant nurses working in the hospital, long-term or community care areas. Literature findings are presented using an integrative approach and a table format to report individual studies. From about 330 citations or abstracts that were initially scanned for content relevance, 68 studies were included in this summary review. The predominance of studies continues to focus on determinants of nurse turnover in acute care settings. Recent studies offer insight into generational factors that should be considered in strategies to promote stable staffing in healthcare organizations. Nursing turnover continues to present serious challenges at all levels of health care. Longitudinal research is needed to produce new evidence of the relationships between nurse turnover and related costs, and the impact on patients and the health care team. Copyright © 2011 Elsevier Ltd. All rights reserved.

  13. The relationship between quality of work life and turnover intention of primary health care nurses in Saudi Arabia

    Directory of Open Access Journals (Sweden)

    Almalki Mohammed J

    2012-09-01

    Full Text Available Abstract Background Quality of work life (QWL has been found to influence the commitment of health professionals, including nurses. However, reliable information on QWL and turnover intention of primary health care (PHC nurses is limited. The aim of this study was to examine the relationship between QWL and turnover intention of PHC nurses in Saudi Arabia. Methods A cross-sectional survey was used in this study. Data were collected using Brooks’ survey of Quality of Nursing Work Life, the Anticipated Turnover Scale and demographic data questions. A total of 508 PHC nurses in the Jazan Region, Saudi Arabia, completed the questionnaire (RR = 87%. Descriptive statistics, t-test, ANOVA, General Linear Model (GLM univariate analysis, standard multiple regression, and hierarchical multiple regression were applied for analysis using SPSS v17 for Windows. Results Findings suggested that the respondents were dissatisfied with their work life, with almost 40% indicating a turnover intention from their current PHC centres. Turnover intention was significantly related to QWL. Using standard multiple regression, 26% of the variance in turnover intention was explained by QWL, p 2 = .263. Further analysis using hierarchical multiple regression found that the total variance explained by the model as a whole (demographics and QWL was 32.1%, p Conclusions Creating and maintaining a healthy work life for PHC nurses is very important to improve their work satisfaction, reduce turnover, enhance productivity and improve nursing care outcomes.

  14. Estimating soil turnover rate from tree uprooting during hurricanes in Puerto Rico

    Science.gov (United States)

    Melanie T. Lenart; D.A. Falk; F.N. Scatena; W.R. Osterkamp

    2010-01-01

    Soil turnover by tree uprooting in primary and secondary forests on the island of Puerto Rico was measured in 42 study plots in the months immediately after the passage of a Category 3 hurricane. Trunk basal area explained 61% of the variability of mound volume and 53% of the variability of mound area. The proportion of uprooted trees, the number of uprooted trees, or...

  15. Cesium-134 and strontium-85 turnover rates in the centipede Scolopocryptops nigridia McNeill

    International Nuclear Information System (INIS)

    Yates, L.R.; Crossley, D.A. Jr.

    1979-07-01

    Radioactive tracers are providing significant information about the ecology of food chains, including such phenomena as accumulation of radioactive fission products, movement of materials along food chains, assimilation and ingestion rates, and nutrient accumulation and turnover. In this study the ingestion, assimilation and turnover to two radioactive tracers were investigated for Scolopocryptops nigridia, an abundant species in forests of the southeastern United States. The two tracers utilized, cesium-134 and strontium-85, are metabolic analogs of potassium and calcium, respectively. The research was performed as part of a larger investigation on the population ecology of the centipede species, emphasizing its relations to nutrient cycling and energy flow in a forest floor system

  16. AN ECONOMETRIC APPROACH ABOUT VOLUNTARY TURNOVER

    Directory of Open Access Journals (Sweden)

    ADALET EREN

    2013-06-01

    Full Text Available This study analyzes individual and organizational variables that affect voluntary turnover are determined in the special defence and security companies. A binomial logistic regression model is used to estimate voluntary turnover.  Binomial Logistic regression, reliability test (scale alfa, variance (ANOVA, Post-hoc/Tukey, correlation (Pearson and other basic statistical techniques  with SPSS 13 statistical packet program was used in the analyzes ofresearch data. The study finds that; situation of suppose working, number of child, number of death child, number of home’s moving, support of rent, total monthly income of household, last work’s region, number of prizes, affect voluntary turnover are determined.

  17. The validation of the turnover intention scale

    Directory of Open Access Journals (Sweden)

    Chris F.C. Bothma

    2013-04-01

    Full Text Available Orientation: Turnover intention as a construct has attracted increased research attention in the recent past, but there are seemingly not many valid and reliable scales around to measure turnover intention. Research purpose: This study focused on the validation of a shortened, six-item version of the turnover intention scale (TIS-6. Motivation for the study: The research question of whether the TIS-6 is a reliable and a valid scale for measuring turnover intention and for predicting actual turnover was addressed in this study. Research design, approach and method: The study was based on a census-based sample (n= 2429 of employees in an information, communication and technology (ICT sector company (N= 23 134 where the TIS-6 was used as one of the criterion variables. The leavers (those who left the company in this sample were compared with the stayers (those who remained in the employ of the company in this sample in respect of different variables used in the study. Main findings: It was established that the TIS-6 could measure turnover intentions reliably (α= 0.80. The TIS-6 could significantly distinguish between leavers and stayers (actual turnover, thereby confirming its criterion-predictive validity. The scale also established statistically significant differences between leavers and stayers in respect of a number of the remaining theoretical variables used in the study, thereby also confirming its differential validity. These comparisons were conducted for both the 4-month and the 4-year period after the survey was conducted. Practical/managerial implications: Turnover intention is related to a number of variables in the study which necessitates a reappraisal and a reconceptualisation of existing turnover intention models. Contribution/value-add: The TIS-6 can be used as a reliable and valid scale to assess turnover intentions and can therefore be used in research to validly and reliably assess turnover intentions or to

  18. [Organizational socialization in the first three years of nursing profession: strategies to decrease turnover intention].

    Science.gov (United States)

    Tomietto, Marco; Rappogliosi, Cristina Maria; Sartori, Riccardo; Battistelli, Adalgisa

    2014-01-01

    In the first years of nursing profession, new-graduate nurses' turnover intention is a relevant issue due to both the tangible and intangible costs it generates to health care organizations, such as selection and recruitment costs, ward team burden in the onboarding process and the possibility to enhance ward team stability in order to provide an effective and safe nusing care. Organizational socialization is the main factor involved in these dynamics of turnover intention in the first years of nursing profession. This study aims to identify the main factors involved in the organizational socialization process to reduce turnover intention in the first 3 years of nursing profession. 101 new-graduate nurses have been enrolled within the first three years of nursing profession. They have been stratified looking at tenure and years in nursing. Organizational Socialization Inventory scale has been used to assess the onboarding process and 4 items to assess turnover intention. Turnover intention is of 23% in the first year in nursing, and it's over the 26% starting from the second year. The onboarding process explains over the 26% of the variance in turnover intention, and over the 36% in the sub-sample with a stable tenure. Unstable tenured nurses prefer to acquire those competences useful to perform their work, while stable tenure nurses aim to search for professional growth opportunities and integration in the ward-team, in order to reduce turnover intention. Turnover intention is relevant in the first three years of nursing profession. According to the different tenure, different strategies are necessary to plan an effective onboarding process and enhance nursing retention.

  19. Seasonal changes in water content and turnover in cattle, sheep and goats grazing under humid tropical conditions in Ghana

    International Nuclear Information System (INIS)

    Aggrey, E.K.

    1982-01-01

    The effect of seasonal changes on water content and water turnover of cattle, sheep and goats at pasture under humid tropical conditions was studied. Measurement of total body water and water turnover was based on the tritium dilution technique. Total body water was significantly higher in all three species of animal during the dry season, while water turnover was significantly lower in the dry season than in the wet season. In all seasons water turnover was highest in cattle, followed by sheep and then goat. Changes in body weight, body water, body solids and water turnover were associated with seasonal variations in nutrition. The indication was that the goat would be a more suitable animal for production under dry conditions than cattle and sheep. (author)

  20. The longitudinal study of turnover and the cost of turnover in emergency medical services.

    Science.gov (United States)

    Patterson, P Daniel; Jones, Cheryl B; Hubble, Michael W; Carr, Matthew; Weaver, Matthew D; Engberg, John; Castle, Nicholas

    2010-01-01

    Few studies have examined employee turnover and associated costs in emergency medical services (EMS). To quantify the mean annual rate of turnover, total median cost of turnover, and median cost per termination in a diverse sample of EMS agencies. A convenience sample of 40 EMS agencies was followed over a six-month period. Internet, telephone, and on-site data-collection methods were used to document terminations, new hires, open positions, and costs associated with turnover. The cost associated with turnover was calculated based on a modified version of the Nursing Turnover Cost Calculation Methodology (NTCCM). The NTCCM identified direct and indirect costs through a series of questions that agency administrators answered monthly during the study period. A previously tested measure of turnover to calculate the mean annual rate of turnover was used. All calculations were weighted by the size of the EMS agency roster. The mean annual rate of turnover, total median cost of turnover, and median cost per termination were determined for three categories of agency staff mix: all-paid staff, mix of paid and volunteer (mixed) staff, and all-volunteer staff. The overall weighted mean annual rate of turnover was 10.7%. This rate varied slightly across agency staffing mix (all-paid = 10.2%, mixed = 12.3%, all-volunteer = 12.4%). Among agencies that experienced turnover (n = 25), the weighted median cost of turnover was $71,613.75, which varied across agency staffing mix (all-paid = $86,452.05, mixed = $9,766.65, and all-volunteer = $0). The weighted median cost per termination was $6,871.51 and varied across agency staffing mix (all-paid = $7,161.38, mixed = $1,409.64, and all-volunteer = $0). Annual rates of turnover and costs associated with turnover vary widely across types of EMS agencies. The study's mean annual rate of turnover was lower than expected based on information appearing in the news media and EMS trade magazines. Findings provide estimates of two key

  1. The longitudinal study of turnover and the cost of turnover in EMS

    Science.gov (United States)

    Patterson, P. Daniel; Jones, Cheryl B.; Hubble, Michael W.; Carr, Matthew; Weaver, Matthew D.; Engberg, John; Castle, Nicholas

    2010-01-01

    Purpose Few studies have examined employee turnover and associated costs in emergency medical services (EMS). The purpose of this study was to quantify the mean annual rate of turnover, total median cost of turnover, and median cost per termination in a diverse sample of EMS agencies. Methods A convenience sample of 40 EMS agencies was followed over a 6 month period. Internet, telephone, and on-site data collection methods were used to document terminations, new hires, open positions, and costs associated with turnover. The cost associated with turnover was calculated based on a modified version of the Nursing Turnover Cost Calculation Methodology (NTCCM). The NTCCM identified direct and indirect costs through a series of questions that agency administrators answered monthly during the study period. A previously tested measure of turnover to calculate the mean annual rate of turnover was used. All calculations were weighted by the size of the EMS agency roster. The mean annual rate of turnover, total median cost of turnover, and median cost per termination were determined for 3 categories of agency staff mix: all paid staff, mix of paid and volunteer (mixed), and all-volunteer. Results The overall weighted mean annual rate of turnover was 10.7%. This rate varied slightly across agency staffing mix: (all-paid=10.2%, mixed=12.3%, all-volunteer=12.4%). Among agencies that experienced turnover (n=25), the weighted median cost of turnover was $71,613.75, which varied across agency staffing mix: (all-paid=$86,452.05, mixed=$9,766.65, and all-volunteer=$0). The weighted median cost per termination was $6,871.51 and varied across agency staffing mix: (all-paid=$7,161.38, mixed=$1,409.64, and all-volunteer=$0). Conclusions Annual rates of turnover and costs associated with turnover vary widely across types of EMS agencies. The study’s mean annual rate of turnover was lower than expected based on information appearing in the news media and EMS trade magazines. Findings

  2. Plagiarism explainer for students

    OpenAIRE

    Barba, Lorena A.

    2016-01-01

    A slide deck to serve as an explainer of plagiarism in academic settings, with a personal viewpoint. For my students.Also on SpeakerDeck:https://speakerdeck.com/labarba/plagiarism-explainer-for-students(The slide viewer on SpeakerDeck is much nicer.)

  3. Organisational Commitment, Job Satisfaction and Turnover ...

    African Journals Online (AJOL)

    This study investigated organisational commitment, job satisfaction and turnover intentions among records management personnel in Ondo State Civil Service, Akure, Nigeria. Simple random sampling technique was used to draw 240 subjects from a population size of 275 records management personnel.

  4. Rethinking Teacher Turnover: Longitudinal Measures of Instability in Schools

    Science.gov (United States)

    Holme, Jennifer Jellison; Jabbar, Huriya; Germain, Emily; Dinning, John

    2018-01-01

    While there is a robust literature examining the patterns and causes of teacher turnover, few articles to date have critically examined the measures of turnover used in these studies. Yet, an assessment of the way turnover is measured is important, as the measures become the means by which the "problem" of turnover becomes defined and…

  5. Addressing employee turnover and retention: keeping your valued performers.

    Science.gov (United States)

    McConnell, Charles R

    2011-01-01

    Employee turnover and employee retention are inextricably linked; to control turnover is to enhance retention. Turnover is a relatively simple concept; however, considerable confusion often results when addressing turnover because of differences in how it is defined; that is, what is counted, how it is counted, and how the turnover rates are expressed. Turnover is also costly, although not enough attention is paid to its cost because so much of it is indirect and thus not readily visible. There are a variety of causes of turnover, some that can be corrected and some that cannot be avoided. Reducing or otherwise controlling turnover requires continuing management attention to its causes and constant recognition of what can and should be controlled and what cannot be controlled. Ongoing attention to turnover is an essential part of the department manager's role; every improvement in turnover is a direct improvement in retention, with eventual positive effects on the bottom line.

  6. KORELASI ANTARA EMPLOYEES INVOLVEMENT, TURNOVER SERTA PENGARUHNYA TERHADAP PRODUKTIVITAS

    Directory of Open Access Journals (Sweden)

    Purnawan Adi Wicaksono

    2012-02-01

    Full Text Available Praktek yang berkembang menyatakan bahwa employee involvement memiliki efek positif terhadap kinerja organisasi. Perubahan pada kultur organisasi dapat menimbulkan dampak berkurangnya absen, turnover, pengambilan keputusan yang lebih baik dan sebagainya. Sehingga menarik untuk diteliti apakah ada korelasi antara aplikasi perubahan organisasi yaitu employee involvement, turnover serta produktivitas Berdasarkan studi literatur didapatkan hubungan antara employee involvement dengan level turnover, serta hubungan turnover dengan produktivitas. Sehingga employee involvement dapat digunakan sebagai salah satu aspek menghitung produktivitas Keyword : employee involvement, turnover, produktivitas

  7. Denitrification, nitrate turnover, and aerobic respiration by benthic foraminiferans in the oxygen minimum zone off Chile

    DEFF Research Database (Denmark)

    Høgslund, Signe; Revsbech, Niels Peter; Cedhagen, Tomas

    2008-01-01

    Population density, nitrate turnover, and oxygen respiration of benthic foraminiferans were investigated in the oxygen minimum zone (OMZ) off the Chilean coast. Live foraminiferans were found predominantly in the upper 3 mm of the sediment, and the nitrate accumulating species Nonionella cf. stel...

  8. REGIONAL DYNAMICS OF WETLAND-BREEDING FROGS AND TOADS: TURNOVER AND SYNCHRONY

    Science.gov (United States)

    We used data from a statewide frog monitoring network to investigate population turnover and synchrony in eight wetland-breeding species. We found that subpopulations at many sites turn over frequently, with breeding choruses absent or undetectable in most years. Frequencies of d...

  9. Predicting voluntary turnover in employees using demographic characteristics: A South African case study

    Directory of Open Access Journals (Sweden)

    Anton F. Schlechter

    2016-03-01

    Design: An exploratory research design was employed. Secondary quantitative data were extracted from an existing human resources database and analysed. Data obtained for 2592 employees in a general insurance company based in South Africa and Namibia formed the basis for the analysis. Logistic regression analysis was employed to predict employee turnover using various demographic characteristics available within the database. A likelihood ratio test was used to build a predictive model and the Akaike information criterion and Schwarz criterion were used to test how much value each variable added to the model and if its inclusion was warranted. The model was tested by conducting statistical tests of the significance of the coefficients. Deviance and Pearson goodness-of-fit statistics as well as the R-square test of significance were used. The overall goodness-of-fit of the model was also tested using the Hosmer and Lemeshow goodness-of-fit test. Findings: The current findings provide partial support for a predictive model explaining employee turnover. The model tested 14 demographic variables and the following five variables were found to have statistically significant predictive value: age, years of service, cost centre, performance score and the interaction between number of dependants and years of service. It is proposed that these five demographic variables be used as a model to help identify employees at risk of turnover or termed as flight risks. Practical implications: Gaining an understanding of the factors that influence employee voluntary turnover can be instrumental in sustaining workforce stability. The proposed model could help human resources professionals identify employees at risk of turnover using data that are readily available to them. This will further enable the use of targeted interventions to prevent turnover before it happens. Decreased levels of turnover will result in cost saving, enhanced talent management and greater competitive advantage.

  10. The relationship between human resource development factors, career growth and turnover intention: The mediating role of organizational commitment

    Directory of Open Access Journals (Sweden)

    Muhammad Shahid Nawaz

    2016-02-01

    Full Text Available Retaining the best employees is of high concern for most organizations and this issue has become a significant focus of attention for many researchers. For this reason, this paper discusses different factors which influence the employee turnover intention-behavior in the organization, specifically to examine the effect of salary, performance appraisal, training & development and career growth on turnover intention. In addition, based on the social exchange theory this paper explains the mediating role of organizational commitment in the relationship between human resource development factors, career growth and turnover intention. A cross sectional, survey data study is undertaken to investigate the relationships in a sample of 270 full time faculty members employed in different private universities of Pakistan. Partial Least Square two step path modeling is used to test the direct and the indirect hypothesis of the study. The results of PLS (SEM path modeling reveal that human resource development factors specially salary and performance appraisal were negatively associated with turnover intention. In addition, the results also indicate that career growth had significant relationships with turnover intention. Moreover, out of four dimensions of career growth, only two dimensions, namely promotion speed and remuneration growth, have strong influence on turnover intention. Finally, in terms of organizational commitment as mediating variable between the relationships of salary, performance appraisal, career growth and turnover intention, four out of six variables indicate partial mediation including career growth (career goal progress, career growth (promotion speed, career growth (remuneration growth and performance appraisal.

  11. Computer jargon explained

    CERN Document Server

    Enticknap, Nicholas

    2014-01-01

    Computer Jargon Explained is a feature in Computer Weekly publications that discusses 68 of the most commonly used technical computing terms. The book explains what the terms mean and why the terms are important to computer professionals. The text also discusses how the terms relate to the trends and developments that are driving the information technology industry. Computer jargon irritates non-computer people and in turn causes problems for computer people. The technology and the industry are changing so rapidly; it is very hard even for professionals to keep updated. Computer people do not

  12. Glutathione turnover in 14 rat tissues

    International Nuclear Information System (INIS)

    Potter, D.W.; Tran, T.

    1990-01-01

    GSH is a tripeptide found in all tissues and is important in maintaining cellular redox status. First-order rate constants for GSH turnover were determined for various tissues of Fischer male rats. Animals were administered [ 35 S]Cys by tail vein injection and GSH turnover was estimated by the decrease in GSH specific activity following incorporation of Cys, 1-102 hr after administration. Tissue nonprotein sulfhydryls (NPSH) were detected by Ellman's assay and compared with GSH and Cys concentrations determined by HPLC with electrochemical detection. [ 35 S]GSH was analyzed by HPLC equipped with a flow-through radioactivity detector. Although total GSH and Cys were usually slightly lower than NPSH concentrations for the tissues examined, both assay systems gave comparable results. An exception was the glandular stomach which had approximately 2-fold higher NPSH. Liver and kidney had rapid turnover rates with GSH half-lives between 2-5 hr, while heart and skeletal muscle tissue had half-lives of 80-90 hr. Turnover in the blood was slowest, with a half-life of 170 hr. Gastrointestinal tract tissues were shown to have intermediate turnover rates of the following order: glandular stomach > duodenum = small intestine = caecum = large intestine = colon > forestomach. GSH half-life in lung and skin was approximately 45 hr. These studies indicate that tissues utilize GSH at markedly different rates

  13. Nurse turnover: the mediating role of burnout.

    Science.gov (United States)

    Leiter, Michael P; Maslach, Christina

    2009-04-01

    This study tested whether the mediation model of burnout could predict nurses' turnover intentions. A better understanding of what factors support a commitment to a nursing career could inform both policies and workplace practices. The mediation model of burnout provides a way of linking the quality of a nurse's worklife to various outcomes, such as turnover. Data on areas of worklife, burnout, and turnover intentions were collected by surveying 667 Canadian nurses in the Atlantic Provinces. The findings supported the mediation model of burnout, in which areas of worklife predicted burnout, which in turn predicted turnover intentions. Cynicism was the key burnout dimension for turnover, and the most critical areas of worklife were value conflicts and inadequate rewards. The results of this study provide some new insights into how the intention of nurses to leave their job is related to particular aspects of their worklife and to burnout. These results suggest what may be the most appropriate areas to target for interventions to reduce the risk of nurses exiting early from their chosen career.

  14. Growth rate correlates negatively with protein turnover in Arabidopsis accessions.

    Science.gov (United States)

    Ishihara, Hirofumi; Moraes, Thiago Alexandre; Pyl, Eva-Theresa; Schulze, Waltraud X; Obata, Toshihiro; Scheffel, André; Fernie, Alisdair R; Sulpice, Ronan; Stitt, Mark

    2017-08-01

    Previous studies with Arabidopsis accessions revealed that biomass correlates negatively to dusk starch content and total protein, and positively to the maximum activities of enzymes in photosynthesis. We hypothesized that large accessions have lower ribosome abundance and lower rates of protein synthesis, and that this is compensated by lower rates of protein degradation. This would increase growth efficiency and allow more investment in photosynthetic machinery. We analysed ribosome abundance and polysome loading in 19 accessions, modelled the rates of protein synthesis and compared them with the observed rate of growth. Large accessions contained less ribosomes than small accessions, due mainly to cytosolic ribosome abundance falling at night in large accessions. The modelled rates of protein synthesis resembled those required for growth in large accessions, but were up to 30% in excess in small accessions. We then employed 13 CO 2 pulse-chase labelling to measure the rates of protein synthesis and degradation in 13 accessions. Small accessions had a slightly higher rate of protein synthesis and much higher rates of protein degradation than large accessions. Protein turnover was negligible in large accessions but equivalent to up to 30% of synthesised protein day -1 in small accessions. We discuss to what extent the decrease in growth in small accessions can be quantitatively explained by known costs of protein turnover and what factors may lead to the altered diurnal dynamics and increase of ribosome abundance in small accessions, and propose that there is a trade-off between protein turnover and maximisation of growth rate. © 2017 The Authors The Plant Journal © 2017 John Wiley & Sons Ltd.

  15. Biochemical bone turnover markers in diabetes mellitus - A systematic review.

    Science.gov (United States)

    Starup-Linde, Jakob; Vestergaard, Peter

    2016-01-01

    Diabetes mellitus is associated with an increased risk of fractures, which is not explained by bone mineral density. Other markers as bone turnover markers (BTMs) may be useful. To assess the relationship between BTMs, diabetes, and fractures. A systematic literature search was conducted in August 2014. The databases searched were Medline at Pubmed and Embase. Medline at Pubmed was searched by "Diabetes Mellitus" (MESH) and "bone turnover markers" and Embase was searched using the Emtree by "Diabetes Mellitus" and "bone turnover", resulting in 611 studies. The eligibility criteria for the studies were to assess BTM in either type 1 diabetes (T1D) or type 2 diabetes (T2D) patients. Of the 611 eligible studies, removal of duplicates and screening by title and abstract lead to 114 potential studies for full-text review. All these studies were full-text screened for eligibility and 45 studies were included. Two additional studies were added from other sources. Among the 47 studies included there were 1 meta-analysis, 29 cross-sectional studies, 13 randomized controlled trials, and 4 longitudinal studies. Both T1D and T2D were studied. Most studies reported fasting BTM and excluded renal disease. Markers of bone resorption and formation seem to be lower in diabetes patients. Bone specific alkaline phosphatase is normal or increased, which suggests that the matrix becomes hypermineralized in diabetes patients. The BTMs: C-terminal cross-link of collagen, insulin-like growth factor-1, and sclerostin may potentially predict fractures, but longitudinal trials are needed. This article is part of a Special Issue entitled Bone and diabetes. Copyright © 2015 Elsevier Inc. All rights reserved.

  16. The Nexus of Ethical Leadership, Job Performance, and Turnover Intention: The Mediating Role of Job Satisfaction

    Directory of Open Access Journals (Sweden)

    Imran Shafique

    2018-03-01

    Full Text Available This study aims to examine the impact of ethical leadership on employees' job satisfaction, job performance, and turnover intention. A conceptual framework is developed which integrates job satisfaction as a mediating mechanism in explaining the nexus among ethical leadership, employee job performance, and turnover intention. The proposed model is tested by using the data collected from a sample (n = 196 of tourist companies in Pakistan. The results reveal that ethical leadership has a positive effect on employees' job satisfaction, job performance and negative effect on employees' turnover intentions. Further, job satisfaction mediates the effect of ethical leadership on employees' job performance and turnover intentions. The findings recommend that the demonstration of ethical leadership behaviours by managers at the workplace increases the likelihood of employees' job satisfaction and performance, while reducing their intention to leave the job. This study elucidates that, in Pakistani tourism sector, ethical leadership plays a key role in achieving performance goals. Future research could analyse the said nexus in different sectors and across different cultures while considering other measures of individual performance. The originality of this study is theorizing as well as empirically testing the intervening mechanism of job satisfaction in probing the linkages among ethical leadership, job performance, and turnover intention in Pakistani workplace context.

  17. Work Environments and Labor Markets: Explaining Principal Turnover Gap between Charter Schools and Traditional Public Schools

    Science.gov (United States)

    Sun, Min; Ni, Yongmei

    2016-01-01

    Purpose: Knowledge about principals' leadership roles in charter schools' success has become more important as the number of charter schools increases and as we have learned more about the influence of principal leadership on school effectiveness. To contribute to the limited empirical literature on the principal labor market, this study explores…

  18. Explaining Teacher Turnover: School Cohesion and Intrinsic Motivation in Los Angeles

    Science.gov (United States)

    Fuller, Bruce; Waite, Anisah; Irribarra, David Torres

    2016-01-01

    Lifting achievement in many schools depends on reducing the exit of effective teachers. We examine the extent to which teacher perceptions of school cohesion and intrinsic motivators stemming from two theoretical traditions contribute to the intent to leave one's school. We find that elementary teachers report higher levels of organizational…

  19. The wireless internet explained

    CERN Document Server

    Rhoton, John

    2001-01-01

    The Wireless Internet Explained covers the full spectrum of wireless technologies from a wide range of vendors, including initiatives by Microsoft and Compaq. The Wireless Internet Explained takes a practical look at wireless technology. Rhoton explains the concepts behind the physics, and provides an overview that clarifies the convoluted set of standards heaped together under the umbrella of wireless. It then expands on these technical foundations to give a panorama of the increasingly crowded landscape of wireless product offerings. When it comes to actual implementation the book gives abundant down-to-earth advice on topics ranging from the selection and deployment of mobile devices to the extremely sensitive subject of security.Written by an expert on Internet messaging, the author of Digital Press''s successful Programmer''s Guide to Internet Mail and X.400 and SMTP: Battle of the E-mail Protocols, The Wireless Internet Explained describes and evaluates the current state of the fast-growing and crucial...

  20. Self-explaining roads

    NARCIS (Netherlands)

    Horst, A.R.A. van der; Kaptein, N.

    1999-01-01

    As a means to a sustainable safe traffic environment the concept of Self-Explaining Roads (SER) has been developed. The SER concept advocates a traffic environment that elicits safe driving behaviour simply by its design. In order to support safe driving behaviour and appropriate speed choice,

  1. Turnover of sex chromosomes in the stickleback fishes (gasterosteidae.

    Directory of Open Access Journals (Sweden)

    Joseph A Ross

    2009-02-01

    Full Text Available Diverse sex-chromosome systems are found in vertebrates, particularly in teleost fishes, where different systems can be found in closely related species. Several mechanisms have been proposed for the rapid turnover of sex chromosomes, including the transposition of an existing sex-determination gene, the appearance of a new sex-determination gene on an autosome, and fusions between sex chromosomes and autosomes. To better understand these evolutionary transitions, a detailed comparison of sex chromosomes between closely related species is essential. Here, we used genetic mapping and molecular cytogenetics to characterize the sex-chromosome systems of multiple stickleback species (Gasterosteidae. Previously, we demonstrated that male threespine stickleback fish (Gasterosteus aculeatus have a heteromorphic XY pair corresponding to linkage group (LG 19. In this study, we found that the ninespine stickleback (Pungitius pungitius has a heteromorphic XY pair corresponding to LG12. In black-spotted stickleback (G. wheatlandi males, one copy of LG12 has fused to the LG19-derived Y chromosome, giving rise to an X(1X(2Y sex-determination system. In contrast, neither LG12 nor LG19 is linked to sex in two other species: the brook stickleback (Culaea inconstans and the fourspine stickleback (Apeltes quadracus. However, we confirmed the existence of a previously reported heteromorphic ZW sex-chromosome pair in the fourspine stickleback. The sex-chromosome diversity that we have uncovered in sticklebacks provides a rich comparative resource for understanding the mechanisms that underlie the rapid turnover of sex-chromosome systems.

  2. Does Judge Turnover Affect Judicial Performance?

    DEFF Research Database (Denmark)

    Guerra, Alice; Tagliapietra, Claudio

    2017-01-01

    office to another after three years of mandate, and the law prescribes their transfer after ten years to guarantee their independence. Flaws in the process managing the backlog of outbound judges and the existence of asynchrony between outbound and inbound transfers produce a chain of delays...... to the disposition of court cases. Using a novel dataset on Court of Appeal Districts in Italy (2008–2012), we provide evidence of a strong negative relation between high turnover rates and judicial performance. We find that marginal increases in judge turnover rates lead to a statistically significant decrease...... in judicial performance over two years of time...

  3. The rate and cost of nurse turnover in Australia.

    Science.gov (United States)

    Roche, Michael A; Duffield, Christine M; Homer, Caroline; Buchan, James; Dimitrelis, Sofia

    2015-01-01

    Nurse turnover is a critical issue facing workforce planners across the globe, particularly in light of protracted and continuing workforce shortages. An ageing population coupled with the rise in complex and chronic diseases, have contributed to increased demands placed on the health system and importantly, nurses who themselves are ageing. Costs associated with nurse turnover are attracting more attention; however, existing measurements of turnover show inconsistent findings, which can be attributed to differences in study design, metrics used to calculate turnover and variations in definitions for turnover. This paper will report the rates and costs of nurse turnover across three States in Australia.

  4. The quantum Kramers' turnover. IT-23

    Energy Technology Data Exchange (ETDEWEB)

    Barik, Debashis; Shankar Ray, Deb [Indian Association for the Cultivation of Science, Jadavpur, Kolkata (India)

    2004-12-01

    The key result of Kramers' dynamical theory of reaction rate is that the rate varies linearly in the weak dissipative regime and inversely in the high dissipative regime with friction of the reaction medium. That is in between the energy diffusion and spatial diffusion limited regime the rate constant as a function of friction exhibits a bell-shaped curve known as Kramers' turnover.

  5. The quantum Kramers' turnover. IT-23

    International Nuclear Information System (INIS)

    Barik, Debashis; Shankar Ray, Deb

    2004-01-01

    The key result of Kramers' dynamical theory of reaction rate is that the rate varies linearly in the weak dissipative regime and inversely in the high dissipative regime with friction of the reaction medium. That is in between the energy diffusion and spatial diffusion limited regime the rate constant as a function of friction exhibits a bell-shaped curve known as Kramers' turnover

  6. Employee Development and Turnover Intention: Theory Validation

    Science.gov (United States)

    Rahman, Wali; Nas, Zekeriya

    2013-01-01

    Purpose: This study aims to examine the pattern of behavior of turnover intentions in developing countries "vis-a-vis" the one in advanced countries through the empirical data from public universities in Khyber Pakhtunkhwa, Pakistan. The study provides empirical evidence from academia in Pakistan, thereby enriching the understanding of…

  7. A Turnover Model for the Mexican Maquiladoras.

    Science.gov (United States)

    Maertz, Carl P.; Stevens, Michael J.; Campion, Michael A.

    2003-01-01

    From interviews with 47 Mexican maquiladora workers, a model of voluntary turnover was created and compared with models from the United States, Canada, England, and Australia. Despite similarities, the cultural and economic environment affected the precise content of antecedents in the Mexican model. (Contains 63 references.) (SK)

  8. Health care workplace discrimination and physician turnover.

    Science.gov (United States)

    Nunez-Smith, Marcella; Pilgrim, Nanlesta; Wynia, Matthew; Desai, Mayur M; Bright, Cedric; Krumholz, Harlan M; Bradley, Elizabeth H

    2009-12-01

    To examine the association between physician race/ ethnicity, workplace discrimination, and physician job turnover. Cross-sectional, national survey conducted in 2006-2007 of practicing physicians (n = 529) randomly identified via the American Medical Association Masterfile and the National Medical Association membership roster. We assessed the relationships between career racial/ethnic discrimination at work and several career-related dependent variables, including 2 measures of physician turnover, career satisfaction, and contemplation of career change. We used standard frequency analyses, odds ratios and chi2 statistics, and multivariate logistic regression modeling to evaluate these associations. Physicians who self-identified as nonmajority were significantly more likely to have left at least 1 job because of workplace discrimination (black, 29%; Asian, 24%; other race, 21%; Hispanic/Latino, 20%; white, 9%). In multivariate models, having experienced racial/ethnic discrimination at work was associated with high job turnover (adjusted odds ratio, 2.7; 95% CI, 1.4-4.9). Among physicians who experienced workplace discrimination, only 45% of physicians were satisfied with their careers (vs 88% among those who had not experienced workplace discrimination, p value workplace discrimination, p value Workplace discrimination is associated with physician job turnover, career dissatisfaction, and contemplation of career change. These findings underscore the importance of monitoring for workplace discrimination and responding when opportunities for intervention and retention still exist.

  9. Biochemical Markers of Joint Tissue Turnover

    DEFF Research Database (Denmark)

    Bay-Jensen, Anne-Christine; Sondergaard, Bodil Cecilie; Christiansen, Claus

    2009-01-01

    available for the study of tissue turnover in each of the three compartments of the articular joint, that is the bone, the cartilage, and the synovium. Finally, we provide some perspective to future developments in biomarker discovery and discuss the potential impact such technologies could have on the drug...

  10. Turnover of Public School Superintendents in Arizona

    Science.gov (United States)

    Meyer, Joyce Ntsoaki

    2013-01-01

    This study used a descriptive qualitative design utilizing a phenomenological approach to determine and examine the reasons behind the voluntary or involuntary turnover of Arizona school superintendents. Open-ended questions were used to interview five superintendents who had left their districts between 2008 and 2013 about their perceptions on…

  11. Teacher Turnover in Charter Schools. Research Brief

    Science.gov (United States)

    Stuit, David; Smith, Thomas M.

    2010-01-01

    The current study aimed to contribute to a deeper understanding of the organizational conditions of charter schools by examining teacher turnover. Using data from the National Center for Education Statistics (NCES) 2003-04 Schools and Staffing Survey (SASS) and the Teacher Follow-Up Survey (TFS), researchers from the National Center on School…

  12. Director Turnover: An Australian Academic Development Study

    Science.gov (United States)

    Fraser, Kym; Ryan, Yoni

    2012-01-01

    Although it can be argued that directors of central academic development units (ADUs) are critical to the implementation of university teaching and learning strategies, it would appear there is a high director turnover rate. While research in the USA, the UK, and Australia illustrates that ADUs are frequently closed or restructured, that research…

  13. Antecedents of Norwegian Beginning Teachers' Turnover Intentions

    Science.gov (United States)

    Tiplic, Dijana; Brandmo, Christian; Elstad, Eyvind

    2015-01-01

    This study aims at exploring several individual, organizational, and contextual factors that may affect beginning teachers' turnover intentions during their first years of practice. The sample consists of 227 beginning teachers (69% female and 31% male) from 133 schools in Norway. The results show four important antecedents of beginning teachers'…

  14. Habitat associations drive species vulnerability to climate change in boreal forests

    DEFF Research Database (Denmark)

    Mazziotta, Adriano; Triviño, María; Tikkanen, Olli-Pekka

    2016-01-01

    if species sensitivity, the species ability to tolerate climatic variations determined by traits, plays a key role in determining vulnerability. We analyse the role of species’ habitat associations, a proxy for sensitivity, in explaining vulnerability for two poorly-known but species-rich taxa in boreal...... forest, saproxylic beetles and fungi, using three IPCC emissions scenarios. Towards the end of the 21st century we projected an improvement in habitat quality associated with an increase of deadwood, an important resource for species, as a consequence of increased tree growth under high emissions...... scenarios. However, climate change will potentially reduce habitat suitability for ~9–43 % of the threatened deadwood-associated species. This loss is likely caused by future increase in timber extraction and decomposition rates causing higher deadwood turnover, which have a strong negative effect on boreal...

  15. MAGMADIM: Young Explainers Program

    International Nuclear Information System (INIS)

    Paltiel, Z.

    2005-01-01

    Full Text:Physics teachers and educators constantly face the problem of inspiring their students to major in physics. On the other hand, science museums are designed to provide a pleasant environment which will stimulate and encourage a science associated experience to the general public. Typically, there is no intention to teach science as such in science museums. One may, however, use the science museum to teach and inspire certain groups of students in a much deeper sense. In fact they may actually enthusiastically learn much of the school physics curriculum at the museum. This report discusses the Magmadim program through which 10th graders are trained to be young explainers at the Weizmann Institutes Clore Garden of Science. To this end they study the physics underlying its exhibits in an after-school course. The ultimate goal is for the 'magmadim' to become the best possible explainers and be able to face all sorts of museum visitors. Along with learning how to instruct visitors, they must learn the physics behind the exhibits to give a full explanation of the exhibit and be able to answer any question that may arise. Our 5 year experience with the program shows that its self-selected participants not only study a lot of science, but also like it and learn how to explain the content to other people. This program, along with similar programs at the Bloomfield Science Museum and the Madatzim (young physics tutors) program of Ort, help in promoting the interest in science in general and physics in particular among school students. Various ways to expand the programs will also be discussed

  16. Linear Algebra Thoroughly Explained

    CERN Document Server

    Vujičić, Milan

    2008-01-01

    Linear Algebra Thoroughly Explained provides a comprehensive introduction to the subject suitable for adoption as a self-contained text for courses at undergraduate and postgraduate level. The clear and comprehensive presentation of the basic theory is illustrated throughout with an abundance of worked examples. The book is written for teachers and students of linear algebra at all levels and across mathematics and the applied sciences, particularly physics and engineering. It will also be an invaluable addition to research libraries as a comprehensive resource book for the subject.

  17. Turnover among Community Mental Health Workers in Ohio.

    Science.gov (United States)

    Bukach, Ashley M; Ejaz, Farida K; Dawson, Nicole; Gitter, Robert J

    2017-01-01

    This study examined turnover of community mental health workers in 42 randomly selected mental health agencies in Ohio. The turnover rate in 2011 was 26 %. A regression analysis indicated that agencies with lower turnover offered higher maximum pay and were smaller in size, while those offering career advancement opportunities, such as career ladder programs, had higher turnover. The findings suggest that improving wages for workers is likely to reduce turnover. It is also possible that smaller agencies have lower turnover due to stronger relationships with workers and/or more successful hiring practices. Furthermore, turnover that occurs as a result of career advancement could have positive effects and should be examined separate from other types of turnover in the future.

  18. Work-life balance, job satisfaction and turnover intention amongst ...

    African Journals Online (AJOL)

    Work-life balance, job satisfaction and turnover intention amongst ... Employee turnover has signifi cant costs and negative consequences for ... However, no interaction effect was observed between overall work-life balance and job ...

  19. Mercury emission from a temperate lake during autumn turnover

    International Nuclear Information System (INIS)

    Wollenberg, Jennifer L.; Peters, Stephen C.

    2009-01-01

    Lakes in temperate regions stratify during summer and winter months, creating distinct layers of water differentiated by their physical and chemical characteristics. When lakes mix in autumn and spring, mercury cycling may be affected by the chemical changes that occur during mixing. Sampling was conducted in Lake Lacawac, Eastern Pennsylvania, USA, throughout the autumn of 2007 to characterize changes in emission of gaseous elemental mercury (Hg 0 ) from the lake surface and dissolved mercury profiles in the water column during mixing. Water chemistry and weather parameters were also measured, including dissolved organic carbon (DOC), iron, and solar radiation which have been shown to interact with mercury species. Results indicate that emission of Hg 0 from the lake to the atmosphere during turnover was controlled both by solar radiation and by surface water mercury concentration. As autumn turnover progressed through the months of October and November, higher mercury concentration water from the hypolimnion mixed with epilimnetic water, increasing mercury concentration in epilimnetic waters. Dissolved absorbance was significantly correlated with mercury concentrations and with iron, but DOC concentrations were essentially constant throughout the study period and did not exhibit a relationship with either dissolved mercury concentrations or emission rates. Positive correlations between dissolved mercury and iron and manganese also suggest a role for these elements in mercury transport within the lake, but iron and manganese did not demonstrate a relationship with emission rates. This research indicates that consideration of seasonal processes in lakes is important when evaluating mercury cycling in aquatic systems

  20. Turnover of grain legume N rhizodeposits and effect of rhizodeposition on the turnover of crop residues

    DEFF Research Database (Denmark)

    Mayer, J.; Buegger, F.; Jensen, E.S.

    2004-01-01

    The turnover of N derived from rhizodeposition of faba bean (Vicia faba L.), pea (Pisum sativum L.) and white lupin (Lupinus albus L.) and the effects of the rhizodeposition on the subsequent C and N turnover of its crop residues were investigated in an incubation experiment (168 days, 15 degrees....... In the experiment the turnover of C and N was compared in soils with and without previous growth of three legumes and with and without incorporation of crop residues. After 168 days, 21% (lupin), 26% (faba bean) and 27% (pea) of rhizodeposition N was mineralised in the treatments without crop residues. A smaller...... amount of 15-17% was present as microbial biomass and between 30 and 55% of mineralised rhizodeposition N was present as microbial residue pool, which consists of microbial exoenzymes, mucous substances and dead microbial biomass. The effect of rhizodeposition on the C and N turnover of crop residues...

  1. Earnings Management Surrounding CEO Turnover: Evidence from Korea

    OpenAIRE

    JONG-SEO CHOI; YOUNG-MIN KWAK; CHONGWOO CHOE

    2012-01-01

    This article examines the empirical relation between CEO turnover and earnings management in Korea using a sample of 317 CEO turnovers and 634 non-turnover control firms during the period of 2001-2008. We classify CEO turnovers into four types depending on whether the departure of outgoing CEO is peaceful or forced and the incoming CEO is promoted from within or recruited from outside the firm. We measure earnings management by both discretionary accruals and real activities management. We al...

  2. Accelerated extracellular matrix turnover during exacerbations of COPD

    DEFF Research Database (Denmark)

    Sand, Jannie M B; Knox, Alan J; Lange, Peter

    2015-01-01

    progression. Extracellular matrix (ECM) turnover reflects activity in tissues and consequently assessment of ECM turnover may serve as biomarkers of disease activity. We hypothesized that the turnover of lung ECM proteins were altered during exacerbations of COPD. METHODS: 69 patients with COPD hospitalised...... of circulating fragments of structural proteins, which may serve as markers of disease activity. This suggests that patients with COPD have accelerated ECM turnover during exacerbations which may be related to disease progression....

  3. A Ministudy of employee turnover in US hospitals.

    Science.gov (United States)

    Collins, Sandra K; McKinnies, Richard C; Matthews, Eric P; Collins, Kevin S

    2015-01-01

    A ministudy was conducted to collect self-reported employee turnover rates in US hospitals. The results indicate many hospitals are struggling with high employee turnover rates. Widespread variances in ratings were observed across hospitals, which may be due to lack of consistency in how they each calculate their employee turnover. This makes benchmarking for the purposes of performance improvement challenging.

  4. The research methods and model of protein turnover in animal

    International Nuclear Information System (INIS)

    Wu Xilin; Yang Feng

    2002-01-01

    The author discussed the concept and research methods of protein turnover in animal body. The existing problems and the research results of animal protein turnover in recent years were presented. Meanwhile, the measures to improve the models of animal protein turnover were analyzed

  5. Salary and Ranking and Teacher Turnover: A Statewide Study

    Science.gov (United States)

    Garcia, Cynthia Martinez; Slate, John R.; Delgado, Carmen Tejeda

    2009-01-01

    This study examined three years of data obtained from the Academic Excellence Indicator System of the State of Texas regarding teacher turnover rate and teacher salary. Across all public school districts, teacher salary was consistently negatively related to teacher turnover; that is, where salary was lower, turnover rate was higher When data were…

  6. Investing in Leadership: The District's Role in Managing Principal Turnover

    Science.gov (United States)

    Mascall, Blair; Leithwood, Kenneth

    2010-01-01

    This article presents the results of research into the impact of principal turnover on schools, and the ability of schools to mitigate the negative effects of frequent turnover by distributing leadership in the schools. The findings from this qualitative and quantitative analysis show that rapid principal turnover does indeed have a negative…

  7. Superintendent Turnover in Kentucky. Issues & Answers. REL 2011-No. 113

    Science.gov (United States)

    Johnson, Jerry; Huffman, Tyler; Madden, Karen; Shope, Shane

    2011-01-01

    This study examines superintendent turnover in Kentucky public school districts for 1998/99-2007/08, looking at how turnover varies by rural status, Appalachian and non-Appalachian region, and 2007/08 school district characteristics. Key findings include: (1) Kentucky school districts averaged one superintendent turnover during 1998/99-2007/08;…

  8. High School Band Students' Perspectives of Teacher Turnover

    Science.gov (United States)

    Kloss, Thomas E.

    2013-01-01

    Teacher turnover remains an important issue in education. The least researched perspectives, though, are those of the students who experience teacher turnover. The purpose of this study was to examine how high school band students experience teacher turnover. A total of twelve students were interviewed, representing three schools that experienced…

  9. 41 CFR 109-27.5002 - Stores inventory turnover ratio.

    Science.gov (United States)

    2010-07-01

    ... turnover ratio. 109-27.5002 Section 109-27.5002 Public Contracts and Property Management Federal Property....5002 Stores inventory turnover ratio. Comparison of investment in stores inventories to annual issues... comparison may be expressed either as a turnover ratio (dollar value of issues divided by dollar value of...

  10. Turnover of regulated nurses in long-term care facilities.

    Science.gov (United States)

    Chu, Charlene H; Wodchis, Walter P; McGilton, Katherine S

    2014-07-01

    To describe the relationship between nursing staff turnover in long-term care (LTC) homes and organisational factors consisting of leadership practices and behaviours, supervisory support, burnout, job satisfaction and work environment satisfaction. The turnover of regulated nursing staff [Registered Nurses (RNs) and Registered Practical Nurses (RPNs)] in LTC facilities is a pervasive problem, but there is a scarcity of research examining this issue in Canada. The study was conceptualized using a Stress Process model. Distinct surveys were distributed to administrators to measure organisational factors and to regulated nurses to measure personal and job-related sources of stress and workplace support. In total, 324 surveys were used in the linear regression analysis to examine factors associated with high turnover rates. Higher leadership practice scores were associated with lower nursing turnover; a one score increase in leadership correlated with a 49% decrease in nursing turnover. A significant inverse relationship between leadership turnover and nurse turnover was found: the higher the administrator turnover the lower the nurse turnover rate. Leadership practices and administrator turnover are significant in influencing regulated nurse turnover in LTC. Long-term care facilities may want to focus on building good leadership and communication as an upstream method to minimize nurse turnover. © 2013 John Wiley & Sons Ltd.

  11. Literature review of labour turnover and absenteeism costs in the coal mining industry

    Energy Technology Data Exchange (ETDEWEB)

    Woolf, A.

    1977-01-01

    This paper includes labor turnover formulae, turnover costs, and turnover rates for the mining industry. Few meaningful studies or reports on absenteeism costs and labour turnover in mining were retrieved.

  12. Using the Job-Demands-Resources model to predict turnover in the information technology workforce – General effects and gender

    Directory of Open Access Journals (Sweden)

    Peter Hoonakker

    2014-01-01

    Full Text Available High employee turnover has always been a major issue for Information Technology (IT. In particular, turnover of women is very high. In this study, we used the Job Demand/Resources (JD-R model to examine the relationship between job demands and job resources, stress/burnout and job satisfaction/commitment, and turnover intention and tested the model for gender differences. Data were collected in five IT companies. A sample of 624 respondents (return rate: 56%; 54% males; mean age: 39.7 years was available for statistical analyses. Results of our study show that relationships between job demands and turnover intention are mediated by emotional exhaustion (burnout and relationships between job resources and turnover intention are mediated by job satisfaction. We found noticeable gender differences in these relationships, which can explain differences in turnover intention between male and female employees. The results of our study have consequences for organizational retention strategies to keep men and women in the IT work force.

  13. Matlab for engineers explained

    CERN Document Server

    Gustafsson, Fredrik

    2003-01-01

    This book is written for students at bachelor and master programs and has four different purposes, which split the book into four parts: 1. To teach first or early year undergraduate engineering students basic knowledge in technical computations and programming using MATLAB. The first part starts from first principles and is therefore well suited both for readers with prior exposure to MATLAB but lacking a solid foundational knowledge of the capabilities of the system and readers not having any previous experience with MATLAB. The foundational knowledge gained from these interactive guided tours of the system will hopefully be sufficient for an effective utilization of MATLAB in the engineering profession, in education and in research. 2. To explain the foundations of more advanced use of MATLAB using the facilities added the last couple of years, such as extended data structures, object orientation and advanced graphics. 3. To give an introduction to the use of MATLAB in typical undergraduate courses in elec...

  14. PERAN STRES KERJA DAN KEPUASAN KERJA UNTUK MENGURANGI TURNOVER INTENTION

    Directory of Open Access Journals (Sweden)

    Syarifah Nazenin

    2014-09-01

    Full Text Available Tujuan penelitian ini untuk menguji pengaruh variabel stres kerja dan kepuasan kerja pada turnover intention karyawan tetap bagian produksi. Sampel penelitian ini adalah 86 responden, menggunakan metode Slovin dengan teknik probability sampling dengan jenis proportionate random sampling. Berdasarkan hasil penelitian, menunjukkan bahwa stres kerja berpengaruh positif signifikan pada turnover intention. Kemudian, kepuasan kerja berpengaruh negatif signifikan. Penelitian ini menyimpulkan, bahwa stres kerja berpengaruh positif dan signifikan pada turnover intention karyawan dan kepuasan kerja berpengaruh negatif dan signifikan terhadap turnover intention karyawan. Implikasi manajerial yang bisa dilakukan adalah dengan pengurangan tingkat stres karyawan dan membuat program untuk tujuan menekan turnover intention, seperti kesempatan promosi dan meningkatkan reward karyawan. The purpose of this study conducted to examine the effect of work stress and job satisfaction on turnover intention of employee in production department. The sample was 86 respondent, using Slovin method with proportionate random sampling technique. The result showed that job stress has a positive effect on turnover intention while job satisfaction has a negative effect on turnover intention. This study conclude that job stress has positive and significant impact on employee turnover intention and job satisfaction significantly and negatively related to turnover intention of employees. Therefore, it is recommended to managerial level people to reduce stress levels in employees and to create a program for pressing turnover intention, such as promotional opportunities and improve employee rewards.

  15. Temporal assemblage turnovers of intertidal foraminiferal communities from tropical (SE Caribbean) and temperate (NE England and SW Spain) regions

    Science.gov (United States)

    Costelloe, Ashleigh; Wilson, Brent; Horton, Benjamin P.; Hayek, Lee-Ann C.

    2018-05-01

    This is the first quantitative study of temporal assemblage turnovers of the relationships between intertidal foraminifera. Time series datasets collected from tropical Caroni Swamp and Claxton Bay (Trinidad, SE Caribbean) and temperate Cowpen Marsh (NE England, U.K.) and Bay of Cadiz (SW Spain) were used. The assemblage turnover index (ATI) examined species interrelationships through comparisons of monthly or biweekly species proportional abundances over one or two years. Species contributing to major assemblage turnovers (ATI > x + σ) were identified using the conditioned on-boundary index (CoBI). Foraminiferal species are heterogeneously distributed within the sediment; multiple sample stations at a study location cumulatively represent the foraminiferal metacommunity and clusters represent foraminiferal assemblages. The ATI and CoBI were applied to the proportional abundances of live specimens recorded for the metacommunity and assemblages at each location. At Caroni Swamp and Claxton Bay, major assemblage turnovers were driven by the most abundant species and the majority coincided with seasonal change or the arrival of the seasonal Orinoco plume in the Gulf of Paria. Seasonal turnovers of the foraminiferal metacommunities at temperate Cowpen Marsh and Bay of Cádiz occurred during the summer and winter. Major assemblage turnovers in the upper Cowpen Marsh occurred in the summer, and the lower marsh in the winter. Foraminiferans are useful bioindicators for monitoring the health of coastal environments. Understanding foraminiferal population dynamics will allow cyclical changes to be differentiated from abrupt and persistent changes, which are related to anthropogenic disturbances or long-term climate change. The ATI and CoBI are useful indices for quantitatively exploring relationships of foraminiferal populations over time.

  16. Job satisfaction and turnover intent of primary healthcare nurses in rural South Africa: a questionnaire survey.

    Science.gov (United States)

    Delobelle, Peter; Rawlinson, Jakes L; Ntuli, Sam; Malatsi, Inah; Decock, Rika; Depoorter, Anne Marie

    2011-02-01

    This paper is a report of a correlational study of the relationships between demographic variables, job satisfaction, and turnover intent among primary healthcare nurses in a rural area of South Africa. Health systems in Southern Africa face a nursing shortage fuelled by migration, but research on job satisfaction and turnover intent of primary healthcare nurses remains poorly described. A cross-sectional study with survey design was conducted in 2005 in all local primary healthcare clinics, including nurses on duty at the time of visit (n = 143). Scale development, anova, Spearman's rank correlation, and logistic regression were applied. Nurses reported satisfaction with work content and coworker relationships and dissatisfaction with pay and work conditions. Half of all nurses considered turnover within two years, of whom three in ten considered moving overseas. Job satisfaction was statistically significantly associated with unit tenure (P job satisfaction, age and education (P Satisfaction with supervision was the only facet significantly explaining turnover intent when controlling for age, education, years of nursing and unit tenure (P job satisfaction and retention of primary healthcare nurses in rural South Africa should rely not only on financial rewards and improved work conditions but also on adequate human resource management. © 2010 Blackwell Publishing Ltd.

  17. How Wage Compression Affects Job Turnover

    OpenAIRE

    Heyman, Fredrik

    2008-01-01

    I use Swedish establishment-level panel data to test Bertola and Rogerson’s (1997) hypothesis of a positive relation between the degree of wage compression and job reallocation. Results indicate that the effect of wage compression on job turnover is positive and significant in the manufacturing sector. The wage compression effect is stronger on job destruction than on job creation, consistent with downward wage rigidity. Further results include a strong positive relationship between the fract...

  18. Stock Option Compensation and Managerial Turnover

    OpenAIRE

    Raluca Georgiana NASTASESCU

    2009-01-01

    This study examines the association between managerial turnover and equity-based compensation. I investigate whether stock options act to bond executives to their firms and whether retention of managers is a motivation of companies in designing CEO incentive contracts. The results show that stock options do negatively influence the probability of a CEO leaving the company. The monetary cost of losing the value of equity-based compensation package keeps the manager with his company. I also fin...

  19. High bone turnover in Irish professional jockeys.

    LENUS (Irish Health Repository)

    Waldron-Lynch, F

    2012-02-01

    SUMMARY: Professional jockeys are routinely exposed to high impact trauma and sustain fractures frequently. We found that jockeys restrict their caloric intake in order to maintain regulation weights, and that bone turnover is high. There are significant health and safety implications for the racing industry. INTRODUCTION: Professional jockeys routinely sustain fractures from high impact falls. Jockeys maintain a low percentage body fat and a low body mass index (BMI) to achieve low weight targets in order to race. We evaluated dietary habits and bone metabolism in jockeys. METHODS: Bone mineral density (BMD) was measured in 27 male jockeys of the 144 jockeys licensed in Ireland. Fourteen (52%) had BMD T score below -1.0, of whom 12 consented to clinical review, nutritional survey, endocrine studies, and bone turnover markers (BTM). BTM were compared to age- and sex-matched controls (n = 16). RESULTS: BMI was 20.6 +\\/- 1.7 kg\\/m(2); previous fracture frequency was 3.2 +\\/- 2.0 per rider. All had normal endocrine axes. The jockeys\\' diet as determined by a 7-day dietary recall was deficient in energy, calcium, and vitamin D intake. Compared with the control group, the jockey group had evidence of increased bone turnover. CONCLUSIONS: A substantial proportion of the professional jockeys in Ireland have low-normal BMD, low BMI, and high bone turnover that may result from weight and dietary restrictions. These factors seem to have a deleterious effect on their bone health and predispose the jockeys to a high fracture risk that should be remediated.

  20. Bone mass and turnover in fibromyalgia

    DEFF Research Database (Denmark)

    Jacobsen, Søren; Gam, A; Egsmose, C

    1993-01-01

    Physical inactivity accelerates bone loss. Since patients with fibromyalgia are relatively physically inactive, bone mass and markers of bone metabolism were determined in 12 premenopausal women with fibromyalgia and in healthy age matched female control subjects. No differences were found in lum.......01. This was linked to lower urinary creatinine excretion (p = 0.02) probably reflecting lower physical activity in the patients with fibromyalgia. We conclude that bone mass and turnover are generally not affected in premenopausal women with fibromyalgia....

  1. Community Structure of Leaf-Litter Ants in a Neotropical Dry Forest: A Biogeographic Approach to Explain Betadiversity

    Directory of Open Access Journals (Sweden)

    Rogério Silvestre

    2012-01-01

    Full Text Available This paper describes habitat and geographic correlates of ant diversity in Serra da Bodoquena, a poorly surveyed region of central-western Brazil. We discuss leaf-litter ant diversity on a regional scale, with emphasis on the contribution of each of the processes that form the evolutionary basis of contemporary beta diversity. The diversity of leaf-litter ants was assessed from a series of 262 Winkler samples conducted in two microbasins within a deciduous forest domain. A total of 170 litter-dwelling ant species in 45 genera and 11 subfamilies was identified. The data showed that the study areas exhibited different arrangements of ant fauna, with a high turnover in species composition between sites, indicating high beta diversity. Our analysis suggests that the biogeographic history of this tropical dry forest in the centre of South America could explain ant assemblage structure more than competitive dominance. The co-occurrence analysis showed that species co-occur less often than expected by chance in only two of the localities, suggesting that, for most of the species, co-occurrences are random. The assessment of the structure of the diversity of litter-dwelling ants is the first step in understanding the beta diversity patterns in this region of great biogeographic importance.

  2. Treatment staff turnover in organizations implementing evidence-based practices: Turnover rates and their association with client outcomes

    Science.gov (United States)

    Garner, Bryan R.; Hunter, Brooke D.; Modisette, Kathryn C.; Ihnes, Pamela C.; Godley, Susan H.

    2011-01-01

    High staff turnover has been described as a problem for the substance use disorder treatment field. This assertion is based primarily on the assumption that staff turnover adversely impacts treatment delivery and effectiveness. This assumption, however, has not been empirically tested. In this study, we computed annualized rates of turnover for treatment staff (n=249) participating in an evidence-based practice implementation initiative and examined the association between organizational-level rates of staff turnover and client-level outcomes. Annualized rates of staff turnover were 31% for clinicians and 19% for clinical supervisors. Additionally, multilevel analyses did not reveal the expected relationship between staff turnover and poorer client-level outcomes. Rather, organizational-level rates of staff turnover were found to have a significant positive association with two measures of treatment effectiveness: less involvement in illegal activity and lower social risk. Possible explanations for these findings are discussed. PMID:22154040

  3. The effect of positive interactions on temporal turnover of community composition along an environmental gradient.

    Directory of Open Access Journals (Sweden)

    Youshi Wang

    Full Text Available It has been demonstrated that the interplay between negative and positive interactions simultaneously shapes community structure and composition. However, few studies have attempted to examine the effect of facilitation on compositional changes in communities through time. Additionally, due to the difficulties in collecting the long-term data, it would be useful to indicate the rate of temporal turnover using a readily obtainable metric. Using an individual-based model incorporating plant strategies, we examined the role of facilitation on the temporal turnover of communities located at different positions along an environmental gradient for three model scenarios: CM without facilitation; CFM-U, a unimodal relationship between facilitation and environmental severity; and CFM-L, a positively linear relationship between facilitation and environmental severity. Our results demonstrated that facilitation could increase, decrease or have no remarkable effect on temporal turnover. The specific outcome depended on the location of the focal community across the environmental gradient and the model employed. Compared with CM, the inclusion of positive interactions (i.e. CFM-U and CFM-L, at intermediate environmental stress levels (such as S = 0.7 and 0.8 resulted in lower Bray-Curtis similarity values; at other severity levels, facilitation slowed down (such as S = 0.3 and 0.4 at low to medium stress levels, and S = 0.9 at high stress levels or had only a subtle effect (such as at S = 0.1 on temporal turnover. We also found that the coefficient of variation (CV in species abundances and the rate of temporal variability showed a significant quadratic relationship. Our theoretical analysis contributes to the understanding of factors driving temporal turnover in biotic communities, and presents a potential metric (i.e. CV in species abundances assessing the consequences of ongoing environmental change on community structure.

  4. The effect of positive interactions on temporal turnover of community composition along an environmental gradient.

    Science.gov (United States)

    Wang, Youshi; Yang, Zhiyong; Zhou, Shurong; Soininen, Janne; Ai, Dexiecuo; Li, Yali; Chu, Chengjin

    2013-01-01

    It has been demonstrated that the interplay between negative and positive interactions simultaneously shapes community structure and composition. However, few studies have attempted to examine the effect of facilitation on compositional changes in communities through time. Additionally, due to the difficulties in collecting the long-term data, it would be useful to indicate the rate of temporal turnover using a readily obtainable metric. Using an individual-based model incorporating plant strategies, we examined the role of facilitation on the temporal turnover of communities located at different positions along an environmental gradient for three model scenarios: CM without facilitation; CFM-U, a unimodal relationship between facilitation and environmental severity; and CFM-L, a positively linear relationship between facilitation and environmental severity. Our results demonstrated that facilitation could increase, decrease or have no remarkable effect on temporal turnover. The specific outcome depended on the location of the focal community across the environmental gradient and the model employed. Compared with CM, the inclusion of positive interactions (i.e. CFM-U and CFM-L), at intermediate environmental stress levels (such as S = 0.7 and 0.8) resulted in lower Bray-Curtis similarity values; at other severity levels, facilitation slowed down (such as S = 0.3 and 0.4 at low to medium stress levels, and S = 0.9 at high stress levels) or had only a subtle effect (such as at S = 0.1) on temporal turnover. We also found that the coefficient of variation (CV) in species abundances and the rate of temporal variability showed a significant quadratic relationship. Our theoretical analysis contributes to the understanding of factors driving temporal turnover in biotic communities, and presents a potential metric (i.e. CV in species abundances) assessing the consequences of ongoing environmental change on community structure.

  5. Turnover in health care: the mediating effects of employee engagement.

    Science.gov (United States)

    Collini, Stevie A; Guidroz, Ashley M; Perez, Lisa M

    2015-03-01

    This study aimed to understand the interaction between interpersonal respect, diversity climate, mission fulfilment and engagement to better predict turnover in health care. Registered nurse turnover has averaged 14% and current nursing shortages are expected to spread. Few studies have studied employee engagement as a mediator between organisational context and turnover. Study participants were employees working within 185 departments across ten hospitals within a large healthcare organisation in the USA. Although a total of 5443 employees work in these departments, employee opinion survey responses were aggregated by department before being linked to turnover rates gathered from company records. Engagement fully mediated the relationship between respect and turnover and the relationship between mission fulfilment and turnover. Diversity climate was not related to turnover. Turnover in health care poses a significant threat to the mission of creating a healing environment for patients and these results demonstrate that workplace respect and connection to the mission affect turnover by decreasing engagement. The findings demonstrated that to increase engagement, and improve turnover rates in health care, it would be beneficial for organisations, and nurse management to focus on improving mission fulfilment and interpersonal relationships. © 2013 John Wiley & Sons Ltd.

  6. Workforce turnover at local health departments: nature, characteristics, and implications.

    Science.gov (United States)

    Newman, Sarah J; Ye, Jiali; Leep, Carolyn J

    2014-11-01

    Employee turnover, defined as total separations from employment, is expensive, can result in lost capacity, and can limit local health departments' (LHDs') ability to respond to public health needs. Despite the importance of workforce capacity in public health, little is known about workforce turnover in LHDs. To examine the extent to which LHDs experience turnover and identify LHD characteristics that are associated with turnover. A cross-sectional data set of employee turnover and LHD characteristics from the 2013 National Profile of LHDs was analyzed. Descriptive statistics and bivariate analyses were conducted in 2014 on turnover rates. The effect of the following LHD characteristics on turnover rates were examined: population size, governance type, degree of urbanization, top executive experience level, expenditures per capita, and LHD budget cuts. In 2013, LHDs experienced a mean turnover rate of 9.88%; approximately one third of turnover was due to retirements. LHDs with shared state and local governance experienced a higher turnover rate than LHDs with exclusive state or local governance. LHDs that are units of state agencies had a significantly higher retirement rate than those governed by local authorities. Top executive experience level, per capita expenditures, and LHD budget cuts were also related to turnover rates. LHDs experienced a lower overall turnover rate than state health departments in 2011 and lower than all local and state government agencies in 2012. Strengthening leadership skills of new top executives and ensuring adequate funding may reduce turnover in LHDs. Copyright © 2014 American Journal of Preventive Medicine. Published by Elsevier Inc. All rights reserved.

  7. ON THE ORIGIN OF THE HIGH COLUMN DENSITY TURNOVER IN THE H I COLUMN DENSITY DISTRIBUTION

    International Nuclear Information System (INIS)

    Erkal, Denis; Gnedin, Nickolay Y.; Kravtsov, Andrey V.

    2012-01-01

    We study the high column density regime of the H I column density distribution function and argue that there are two distinct features: a turnover at N H I ≈ 10 21 cm –2 , which is present at both z = 0 and z ≈ 3, and a lack of systems above N H I ≈ 10 22 cm –2 at z = 0. Using observations of the column density distribution, we argue that the H I-H 2 transition does not cause the turnover at N H I ≈ 10 21 cm –2 but can plausibly explain the turnover at N H I ∼> 10 22 cm –2 . We compute the H I column density distribution of individual galaxies in the THINGS sample and show that the turnover column density depends only weakly on metallicity. Furthermore, we show that the column density distribution of galaxies, corrected for inclination, is insensitive to the resolution of the H I map or to averaging in radial shells. Our results indicate that the similarity of H I column density distributions at z = 3 and 0 is due to the similarity of the maximum H I surface densities of high-z and low-z disks, set presumably by universal processes that shape properties of the gaseous disks of galaxies. Using fully cosmological simulations, we explore other candidate physical mechanisms that could produce a turnover in the column density distribution. We show that while turbulence within giant molecular clouds cannot affect the damped Lyα column density distribution, stellar feedback can affect it significantly if the feedback is sufficiently effective in removing gas from the central 2-3 kpc of high-redshift galaxies. Finally, we argue that it is meaningful to compare column densities averaged over ∼ kpc scales with those estimated from quasar spectra that probe sub-pc scales due to the steep power spectrum of H I column density fluctuations observed in nearby galaxies.

  8. The potential effects of climate change on amphibian distribution, range fragmentation and turnover in China.

    Science.gov (United States)

    Duan, Ren-Yan; Kong, Xiao-Quan; Huang, Min-Yi; Varela, Sara; Ji, Xiang

    2016-01-01

    Many studies predict that climate change will cause species movement and turnover, but few have considered the effect of climate change on range fragmentation for current species and/or populations. We used MaxEnt to predict suitable habitat, fragmentation and turnover for 134 amphibian species in China under 40 future climate change scenarios spanning four pathways (RCP2.6, RCP4.5, RCP6 and RCP8.5) and two time periods (the 2050s and 2070s). Our results show that climate change may cause a major shift in spatial patterns of amphibian diversity. Amphibians in China would lose 20% of their original ranges on average; the distribution outside current ranges would increase by 15%. Suitable habitats for over 90% of species will be located in the north of their current range, for over 95% of species in higher altitudes (from currently 137-4,124 m to 286-4,396 m in the 2050s or 314-4,448 m in the 2070s), and for over 75% of species in the west of their current range. Also, our results predict two different general responses to the climate change: some species contract their ranges while moving westwards, southwards and to higher altitudes, while others expand their ranges. Finally, our analyses indicate that range dynamics and fragmentation are related, which means that the effects of climate change on Chinese amphibians might be two-folded.

  9. The potential effects of climate change on amphibian distribution, range fragmentation and turnover in China

    Directory of Open Access Journals (Sweden)

    Ren-Yan Duan

    2016-07-01

    Full Text Available Many studies predict that climate change will cause species movement and turnover, but few have considered the effect of climate change on range fragmentation for current species and/or populations. We used MaxEnt to predict suitable habitat, fragmentation and turnover for 134 amphibian species in China under 40 future climate change scenarios spanning four pathways (RCP2.6, RCP4.5, RCP6 and RCP8.5 and two time periods (the 2050s and 2070s. Our results show that climate change may cause a major shift in spatial patterns of amphibian diversity. Amphibians in China would lose 20% of their original ranges on average; the distribution outside current ranges would increase by 15%. Suitable habitats for over 90% of species will be located in the north of their current range, for over 95% of species in higher altitudes (from currently 137–4,124 m to 286–4,396 m in the 2050s or 314–4,448 m in the 2070s, and for over 75% of species in the west of their current range. Also, our results predict two different general responses to the climate change: some species contract their ranges while moving westwards, southwards and to higher altitudes, while others expand their ranges. Finally, our analyses indicate that range dynamics and fragmentation are related, which means that the effects of climate change on Chinese amphibians might be two-folded.

  10. Cereal aphid colony turnover and persistence in winter wheat.

    Directory of Open Access Journals (Sweden)

    Linton Winder

    Full Text Available An understanding of spatial and temporal processes in agricultural ecosystems provides a basis for rational decision-making with regards to the management and husbandry of crops, supporting the implementation of integrated farming strategies. In this study we investigated the spatial and temporal distribution of aphid pests (Sitobion avenae and Metopolophium dirhodum within winter wheat fields. Using an intensive sampling programme we investigated distributions at both the small (single shoot and large (field scales. Within two fields, a grid with 82 locations was established (area 120 m by 168 m. At each location, 25 shoots were individually marked and aphid counts by observation conducted on 21 and 22 occasions as the crop matured, resulting in 43,050 and 45,100 counts being conducted in the two fields respectively. We quantified field scale spatial distributions, demonstrating that spatial pattern generally emerged, with temporal stability being both species- and field- dependent. We then measured turnover of colonies at the small (individual shoot and large (field scales by comparing consecutive pairs of sampling occasions. Four turnover categories were defined: Empty (no aphids recorded on either occasion; Colonised (aphids recorded on the second occasion but not the first; Extinction (aphids recorded on the first occasion but not the second; Stable (aphids recorded on both occasions. At the field scale, population stability soon established, but, at the small scale there was a consistently high proportion of unoccupied shoots with considerable colonisation and extinction and low stability. The redistribution of aphids within the crop at the local scale is a vulnerability which could be used to disrupt population development--by mediating exposure to ground-active natural enemies and by incurring a metabolic cost caused by the physiological demands to re-establish on a nearby host plant.

  11. PENGARUH KEPUASAN KERJA DAN KOMITMEN ORGANISASI TERHADAP TURNOVER INTENTION

    Directory of Open Access Journals (Sweden)

    V. Mardi Widyadmono

    2017-04-01

    Full Text Available This study assesses the influence of job satisfaction and organizational commitment on Turnover Intention. Futhermore, the study identify the mediation role of organizational commitment in the relationship between job satifaction and Turnover Intention. The participants of the study are 98 employees working in private companies operated in Yogyakarta, (36 men and 62 women. Respondents complete questionnaire containing questions on job satisfaction variable, questions on organizational commitment and questions on Turnover Intention. The statistics tools applied are regression analysis to assess the relation between variables and Sobel test to measure the mediation role of organizational commitment. The results of the investigation revealed that job satisfication and organizational commitment influence negatively and significantly Turnover Intention. The higher the job satisfication and the organizational commitment of employees lead to the lower Turnover Intention. The organizational commitment does not play mediation role in the relationship between job satisfication and Turnover Intention

  12. Mentor program boosts new nurses' satisfaction and lowers turnover rate.

    Science.gov (United States)

    Fox, Kathy C

    2010-07-01

    In 2004, the turnover rate among first-year registered nurses (RNs) at St. Francis Hospital and Health Centers had mushroomed to 31%. Based on research, in 2006, the hospital embarked on a journey to implement an RN mentor program to improve satisfaction and reduce turnover. A pilot program was initiated, including 12 RN mentors and 12 RN protégés from select nursing units. The results showed a 0% turnover rate during the 1-year pilot program. Based on these findings, the mentor program was expanded to include RNs working in inpatient nursing units and surgery and emergency departments. Each year, the RN turnover rate has decreased. In 2009, the turnover rate was 10.3%. Because of the success of the program, it has been expanded in scope to include other professionals experiencing high turnover in targeted departments, including radiological technicians, respiratory therapists, pharmacists, and physical therapists.

  13. Combined effects of positive and negative affectivity and job satisfaction on job performance and turnover intentions.

    Science.gov (United States)

    Bouckenooghe, Dave; Raja, Usman; Butt, Arif Nazir

    2013-01-01

    Capturing data from employee-supervisor dyads (N = 321) from eight organizations in Pakistan, including human service organizations, an electronics assembly plant, a packaging material manufacturing company, and a small food processing plant, we used moderated regression analysis to examine whether the relationships between trait affect (positive affectivity [PA] and negative affectivity [NA]) and two key work outcome variables (job performance and turnover) are contingent upon the level of job satisfaction. We applied the Trait Activation Theory to explain the moderating effect of job satisfaction on the relationship between affect and performance and between affect and turnover. Overall, the data supported our hypotheses. Positive and negative affectivity influenced performance and the intention to quit, and job satisfaction moderated these relationships. We discuss in detail the results of these findings and their implications for research and practice.

  14. Turnover of circulating hematopoietic stem cells

    Energy Technology Data Exchange (ETDEWEB)

    Dorie, M J; Maloney, M A; Patt, H M

    1979-10-01

    Short-term parabiosis of male and female CBA/CaJ mice was used to investigate the turnover of circulating hematopoietic stem cells. The change and subsequent disappearance of donor stem cells were monitored by spleen colony assay and chromosome analysis of individual colonies. The results revealed an exponential disappearance of pluripotent stem cells from blood with a characteristic half time of 1.7 h. Blood-borne stem cells were shown to be equilibrated with a subpopulation of marrow stem cells exhibiting a disappearance half time of 9.5 h. Splenectomy did not change the apparent rate of stem cell removal from the blood.

  15. Role stress and turnover intentions among information technology personnel in South Africa: The role of supervisor support

    Directory of Open Access Journals (Sweden)

    Rennie Naidoo

    2018-04-01

    Full Text Available Orientation: High turnover of information technology (IT personnel is a major problem facing many global and local organisations. An increasingly important area of turnover research of IT personnel experiencing role stress involves examining their perceptions of supervisor support. Research purpose: This study aimed to examine the effects of role-related stress and supervisor support on job satisfaction, job performance and IT turnover intentions. Motivations for the study: It is important to assess from both a theoretical and a practical perspective the extent to which turnover can be explained by relational factors such as supervisor support. Research design, approach and method: An online voluntary survey yielded a sample of 163 respondents. Six constructs were measured: turnover intention, job performance, job satisfaction, supervisor support, role ambiguity and role conflict. A total of 158 usable responses were subjected to descriptive, correlation and regression analysis. Mediation and moderation effects were assessed using a multiple regression bootstrapping procedure. Main findings: Role ambiguity has a greater impact on job satisfaction than role conflict. Job satisfaction fully mediated the relationship between role stress and turnover intention. Supervisor support mediated the relationship between role stressors and job satisfaction and role stressors and job performance. There was no evidence in favour of a moderating role of supervisor support. Practical and managerial implications: Higher priority should be given to tackling role ambiguity. Supervisor support can increase job satisfaction, improve job performance and ultimately reduce turnover intentions, despite the presence of role stress. Contribution or value-add: Human resource managers and IT managers could use these results to improve job performance and staff retention.

  16. A dimensionless ordered pull-through model of the mammalian lens epithelium evidences scaling across species and explains the age-dependent changes in cell density in the human lens

    Science.gov (United States)

    Wu, Jun Jie; Wu, Weiju; Tholozan, Frederique M.; Saunter, Christopher D.; Girkin, John M.; Quinlan, Roy A.

    2015-01-01

    We present a mathematical (ordered pull-through; OPT) model of the cell-density profile for the mammalian lens epithelium together with new experimental data. The model is based upon dimensionless parameters, an important criterion for inter-species comparisons where lens sizes can vary greatly (e.g. bovine (approx. 18 mm); mouse (approx. 2 mm)) and confirms that mammalian lenses scale with size. The validated model includes two parameters: β/α, which is the ratio of the proliferation rate in the peripheral and in the central region of the lens; and γGZ, a dimensionless pull-through parameter that accounts for the cell transition and exit from the epithelium into the lens body. Best-fit values were determined for mouse, rat, rabbit, bovine and human lens epithelia. The OPT model accounts for the peak in cell density at the periphery of the lens epithelium, a region where cell proliferation is concentrated and reaches a maximum coincident with the germinative zone. The β/α ratio correlates with the measured FGF-2 gradient, a morphogen critical to lens cell survival, proliferation and differentiation. As proliferation declines with age, the OPT model predicted age-dependent changes in cell-density profiles, which we observed in mouse and human lenses. PMID:26236824

  17. The phase model of burnout and employee turnover.

    Science.gov (United States)

    Goodman, Eric A; Boss, R Wayne

    2002-01-01

    This study explores the phase model of burnout and investigates its relationship to actual turnover in a hospital. The results indicate that employees who turnover have significantly higher burnout phase scores that those who stay in the organization. A further comparison of voluntary and involuntary turnover demonstrates that there is no significant differences on burnout phase scores. The findings lend support to the usefulness of the phase model of burnout.

  18. Job and industry turnover for registered and licensed vocational nurses.

    Science.gov (United States)

    Spetz, Joanne; Rickles, Jordan; Chapman, Susan; Ong, Paul M

    2008-09-01

    Most studies of nurse turnover focus on job turnover, which could reflect nurse advancement and thus not be detrimental to the workforce. The authors discuss findings from a study that involved 2 cohorts of graduates from registered nursing and licensed vocational nursing community college programs in California. The duration of employment in the healthcare industry, as well as with specific employers, is tracked, lending a more thorough analysis of nursing job and industry turnover than found in other studies.

  19. The Impact of Human Resource Management Practices on Employee Turnover

    OpenAIRE

    Ozoliņa-Ozola, I

    2014-01-01

    The aim of this research was to identify the human resource management practices that are effective for employee turnover reducing. For this purpose the methods of document analysis and expert survey were used. On the basis of analysis of the scientific literature retrieved from academic databases the human resource management practices, which were mentioned in connection with employee turnover, were detected and described its effect on employee turnover. By conducting two separate expert sur...

  20. Does public service performance affect top management turnover?

    OpenAIRE

    Boyne, George A.; James, Oliver; John, Peter; Petrovsky, Nicolai

    2010-01-01

    Political and organizational theories suggest that the turnover of chief executives and other members of senior management teams are likely to be influenced by public service performance. We use a panel data set of 148 English local governments over 4 years to test this proposition. The empirical results show that performance has a negative effect on turnover, but that this effect is weaker for chief executives than for members of their senior management teams. In addition, top team turnover ...

  1. Frog species richness, composition and beta-diversity in coastal Brazilian restinga habitats.

    Science.gov (United States)

    Rocha, C F D; Hatano, F H; Vrcibradic, D; Van Sluys, M

    2008-02-01

    We studied the species richness and composition of frogs in 10 restinga habitats (sand dune environments dominated by herbaceous and shrubby vegetation) along approximately 1500 km of coastal areas of three Brazilian States: Rio de Janeiro (Grumari, Maricá, Massambaba, Jurubatiba and Grussaí), Espírito Santo (Praia das Neves and Setiba) and Bahia (Prado and Trancoso). We estimated beta-diversity and similarity among areas and related these parameters to geographic distance between areas. All areas were surveyed with a similar sampling procedure. We found 28 frog species belonging to the families Hylidae, Microhylidae, Leptodactylidae and Bufonidae. Frogs in restingas were in general nocturnal with no strictly diurnal species. The richest restinga was Praia das Neves (13 species), followed by Grussaí and Trancoso (eight species in each). The commonest species in the restingas was Scinax alter (found in eight restingas), followed by Aparasphenodon brunoi (seven areas). Our data shows that richness and composition of frog communities vary consistently along the eastern Brazilian coast and, in part, the rate of species turnover is affected by the distance among areas. Geographic distance explained approximately 12% of species turnover in restingas and about 9.5% of similarity among frog assemblages. Although geographic distance somewhat affects frog assemblages, other factors (e.g. historical factors, disturbances) seem to be also involved in explaining present frog assemblage composition in each area and species turnover among areas. The frog fauna along restinga habitats was significantly nested (matrix community temperature = 26.13 degrees; p = 0.007). Our data also showed that the most hospitable restinga was Praia das Neves and indicated that this area should be protected as a conservation unit. Frog assemblage of each area seems to partially represent a nested subset of the original assemblage, although we should not ignore the importance of historical

  2. Frog species richness, composition and beta-diversity in coastal Brazilian restinga habitats

    Directory of Open Access Journals (Sweden)

    CFD. Rocha

    Full Text Available We studied the species richness and composition of frogs in 10 restinga habitats (sand dune environments dominated by herbaceous and shrubby vegetation along approximately 1500 km of coastal areas of three Brazilian States: Rio de Janeiro (Grumari, Maricá, Massambaba, Jurubatiba and Grussaí, Espírito Santo (Praia das Neves and Setiba and Bahia (Prado and Trancoso. We estimated beta-diversity and similarity among areas and related these parameters to geographic distance between areas. All areas were surveyed with a similar sampling procedure. We found 28 frog species belonging to the families Hylidae, Microhylidae, Leptodactylidae and Bufonidae. Frogs in restingas were in general nocturnal with no strictly diurnal species. The richest restinga was Praia das Neves (13 species, followed by Grussaí and Trancoso (eight species in each. The commonest species in the restingas was Scinax alter (found in eight restingas, followed by Aparasphenodon brunoi (seven areas. Our data shows that richness and composition of frog communities vary consistently along the eastern Brazilian coast and, in part, the rate of species turnover is affected by the distance among areas. Geographic distance explained approximately 12% of species turnover in restingas and about 9.5% of similarity among frog assemblages. Although geographic distance somewhat affects frog assemblages, other factors (e.g. historical factors, disturbances seem to be also involved in explaining present frog assemblage composition in each area and species turnover among areas. The frog fauna along restinga habitats was significantly nested (matrix community temperature = 26.13°; p = 0.007. Our data also showed that the most hospitable restinga was Praia das Neves and indicated that this area should be protected as a conservation unit. Frog assemblage of each area seems to partially represent a nested subset of the original assemblage, although we should not ignore the importance of historical

  3. Plant traits and environment: floating leaf blade production and turnover of waterlilies

    Directory of Open Access Journals (Sweden)

    Peter F. Klok

    2017-04-01

    Full Text Available Floating leaf blades of waterlilies fulfill several functions in wetland ecosystems by production, decomposition and turnover as well as exchange processes. Production and turnover rates of floating leaf blades of three waterlily species, Nuphar lutea (L. Sm., Nymphaea alba L. and Nymphaea candida Presl, were studied in three freshwater bodies, differing in trophic status, pH and alkalinity. Length and percentages of leaf loss of marked leaf blades were measured weekly during the growing season. Area and biomass were calculated based on leaf length and were used to calculate the turnover rate of floating leaf blades. Seasonal changes in floating leaf production showed that values decreased in the order: Nymphaea alba, Nuphar lutea, Nymphaea candida. The highest production was reached for Nuphar lutea and Nymphaea alba in alkaline, eutrophic water bodies. The production per leaf was relatively high for both species in the acid water body. Nymphaea candida showed a very short vegetation period and low turnover rates. The ratio Total potential leaf biomass/Maximum potential leaf biomass (P/Bmax of the three species ranged from 1.35–2.25. The ratio Vegetation period (Period with floating leaves/Mean leaf life span ranged from 2.94–4.63, the ratio Growth period (Period with appearance of new floating leaves/Vegetation period from 0.53–0.73. The clear differences between Nymphaea candida versus Nuphar lutea and Nymphaea alba, may be due to adaptations of Nymphaea candida to an Euro-Siberic climate with short-lasting summer conditions.

  4. Plant traits and environment: floating leaf blade production and turnover of waterlilies.

    Science.gov (United States)

    Klok, Peter F; van der Velde, Gerard

    2017-01-01

    Floating leaf blades of waterlilies fulfill several functions in wetland ecosystems by production, decomposition and turnover as well as exchange processes. Production and turnover rates of floating leaf blades of three waterlily species, Nuphar lutea (L.) Sm., Nymphaea alba L. and Nymphaea candida Presl, were studied in three freshwater bodies, differing in trophic status, pH and alkalinity. Length and percentages of leaf loss of marked leaf blades were measured weekly during the growing season. Area and biomass were calculated based on leaf length and were used to calculate the turnover rate of floating leaf blades. Seasonal changes in floating leaf production showed that values decreased in the order: Nymphaea alba , Nuphar lutea , Nymphaea candida . The highest production was reached for Nuphar lutea and Nymphaea alba in alkaline, eutrophic water bodies. The production per leaf was relatively high for both species in the acid water body. Nymphaea candida showed a very short vegetation period and low turnover rates. The ratio Total potential leaf biomass/Maximum potential leaf biomass (P/B max ) of the three species ranged from 1.35-2.25. The ratio Vegetation period (Period with floating leaves)/Mean leaf life span ranged from 2.94-4.63, the ratio Growth period (Period with appearance of new floating leaves)/Vegetation period from 0.53-0.73. The clear differences between Nymphaea candida versus Nuphar lutea and Nymphaea alba , may be due to adaptations of Nymphaea candida to an Euro-Siberic climate with short-lasting summer conditions.

  5. Dynamics of Adipocyte Turnover in Humans

    Energy Technology Data Exchange (ETDEWEB)

    Spalding, K; Arner, E; Westermark, P; Bernard, S; Buchholz, B; Bergmann, O; Blomqvist, L; Hoffstedt, J; Naslund, E; Britton, T; Concha, H; Hassan, M; Ryden, M; Frisen, J; Arner, P

    2007-07-16

    Obesity is increasing in an epidemic fashion in most countries and constitutes a public health problem by enhancing the risk for cardiovascular disease and metabolic disorders such as type 2 diabetes. Owing to the increase in obesity, life expectancy may start to decrease in developed countries for the first time in recent history. The factors determining fat mass in adult humans are not fully understood, but increased lipid storage in already developed fat cells is thought to be most important. We show that adipocyte number is a major determinant for the fat mass in adults. However, the number of fat cells stays constant in adulthood in lean and obese and even under extreme conditions, indicating that the number of adipocytes is set during childhood and adolescence. To establish the dynamics within the stable population of adipocytes in adults, we have measured adipocyte turnover by analyzing the integration of {sup 14}C derived from nuclear bomb tests in genomic DNA. Approximately 10% of fat cells are renewed annually at all adult ages and levels of body mass index. Neither adipocyte death nor generation rate is altered in obesity, suggesting a tight regulation of fat cell number that is independent of metabolic profile in adulthood. The high turnover of adipocytes establishes a new therapeutic target for pharmacological intervention in obesity.

  6. Efficacy of /sup 22/Na turnover in ecophysiological studies of carnivores

    Energy Technology Data Exchange (ETDEWEB)

    Wilkinson, I S; Skinner, J D

    1988-01-01

    /sup 22/Na turnover rates gave overestimates of mean /sup 23/Na intake in both brown hyaenas (449,9%, range 54,7-991,2) and aardwolf (336,0%, range 118,4-776,0). There was also no significant relationship between /sup 22/Na turned over and /sup 23/Na ingested in either species. It would therefore be impossible to utilize this technique to determine food intake in these species. Further uncertainties pertaining to the dietary content of the predator and the distribution of body sodium in the prey, cast doubts on the applicability of the technique for use in carnivore studies

  7. Similar processes but different environmental filters for soil bacterial and fungal community composition turnover on a broad spatial scale.

    Directory of Open Access Journals (Sweden)

    Nicolas Chemidlin Prévost-Bouré

    Full Text Available Spatial scaling of microorganisms has been demonstrated over the last decade. However, the processes and environmental filters shaping soil microbial community structure on a broad spatial scale still need to be refined and ranked. Here, we compared bacterial and fungal community composition turnovers through a biogeographical approach on the same soil sampling design at a broad spatial scale (area range: 13300 to 31000 km2: i to examine their spatial structuring; ii to investigate the relative importance of environmental selection and spatial autocorrelation in determining their community composition turnover; and iii to identify and rank the relevant environmental filters and scales involved in their spatial variations. Molecular fingerprinting of soil bacterial and fungal communities was performed on 413 soils from four French regions of contrasting environmental heterogeneity (Landesturnovers. The relative importance of processes and filters was assessed by distance-based redundancy analysis. This study demonstrates significant community composition turnover rates for soil bacteria and fungi, which were dependent on the region. Bacterial and fungal community composition turnovers were mainly driven by environmental selection explaining from 10% to 20% of community composition variations, but spatial variables also explained 3% to 9% of total variance. These variables highlighted significant spatial autocorrelation of both communities unexplained by the environmental variables measured and could partly be explained by dispersal limitations. Although the identified filters and their hierarchy were dependent on the region and organism, selection was systematically based on a common group of environmental variables: pH, trophic resources, texture and land use. Spatial autocorrelation was also important at

  8. Similar processes but different environmental filters for soil bacterial and fungal community composition turnover on a broad spatial scale.

    Science.gov (United States)

    Chemidlin Prévost-Bouré, Nicolas; Dequiedt, Samuel; Thioulouse, Jean; Lelièvre, Mélanie; Saby, Nicolas P A; Jolivet, Claudy; Arrouays, Dominique; Plassart, Pierre; Lemanceau, Philippe; Ranjard, Lionel

    2014-01-01

    Spatial scaling of microorganisms has been demonstrated over the last decade. However, the processes and environmental filters shaping soil microbial community structure on a broad spatial scale still need to be refined and ranked. Here, we compared bacterial and fungal community composition turnovers through a biogeographical approach on the same soil sampling design at a broad spatial scale (area range: 13300 to 31000 km2): i) to examine their spatial structuring; ii) to investigate the relative importance of environmental selection and spatial autocorrelation in determining their community composition turnover; and iii) to identify and rank the relevant environmental filters and scales involved in their spatial variations. Molecular fingerprinting of soil bacterial and fungal communities was performed on 413 soils from four French regions of contrasting environmental heterogeneity (Landescommunities' composition turnovers. The relative importance of processes and filters was assessed by distance-based redundancy analysis. This study demonstrates significant community composition turnover rates for soil bacteria and fungi, which were dependent on the region. Bacterial and fungal community composition turnovers were mainly driven by environmental selection explaining from 10% to 20% of community composition variations, but spatial variables also explained 3% to 9% of total variance. These variables highlighted significant spatial autocorrelation of both communities unexplained by the environmental variables measured and could partly be explained by dispersal limitations. Although the identified filters and their hierarchy were dependent on the region and organism, selection was systematically based on a common group of environmental variables: pH, trophic resources, texture and land use. Spatial autocorrelation was also important at coarse (80 to 120 km radius) and/or medium (40 to 65 km radius) spatial scales, suggesting dispersal limitations at these scales.

  9. Explaining Physics – What Skills does a good Explainer Need?

    CERN Multimedia

    CERN. Geneva; Bartels, Hauke

    2018-01-01

    Explaining physics in a way that it is both scientifically correct and comprehensible is a highly demanding practice. But are explanations an effective way to teach physics? Under which circumstances should a physics teacher explain – and is there such a thing as a guideline for effective instructional explanations? Of course, explaining is more than just presenting content knowledge in clear language – but what more? In our talk, we want to discuss empirical studies on instructional explanations from science education and psychology to address these questions. Among other things, we will refer to results from a large study aiming to research whether teacher education contributes to the development of explaining skills. Besides, we will give insights into a project that seeks to measure explaining skills with an interactive online test instrument.

  10. Organisational commitment and turnover intentions in humanitarian organisations

    NARCIS (Netherlands)

    Wijnmaalen, Julia; Heyse, Liesbet; Voordijk, Johannes T.

    2016-01-01

    Unwanted staff turnover is a prominent HRM problem in humanitarian organisations. In the profit sector, HRM tools such as pay, benefits, socialisation and training have proven to be effective in increasing organisational commitment and decreasing staff turnover. This study explores whether such

  11. How Multiple Interventions Influenced Employee Turnover: A Case Study.

    Science.gov (United States)

    Hatcher, Timothy

    1999-01-01

    A 3-year study of 46 textile industry workers identified causes of employee turnover (supervision, training, organizational communication) using performance analysis. A study of multiple interventions based on the analysis resulted in changes in orientation procedures, organizational leadership, and climate, reducing turnover by 24%. (SK)

  12. Survey of pay satisfaction, job satisfaction and employee turnover in ...

    African Journals Online (AJOL)

    Survey of pay satisfaction, job satisfaction and employee turnover in selected business organisations in Lagos, Nigeria. ... Global Journal of Social Sciences ... The study was an attempt at investigating the relatedness of pay satisfaction, job satisfaction and employee turnover in business organizations in Lagos Nigeria.

  13. Performance and turnover intentions: a social exchange perspective

    NARCIS (Netherlands)

    Biron, M.; Boon, C.

    2013-01-01

    Purpose - Prior research has yielded mixed results regarding the relationship between performance and turnover intentions. Drawing from social exchange theory, the purpose of this paper is to propose that the performance-turnover intentions association may be contingent upon individuals' exchange

  14. Telaah Hubungan Kepuasan Kerja Dan Komitmen Organisasional Terhadap Turnover Intention

    OpenAIRE

    Ali Amran; Acep Rohendi

    2017-01-01

    ABSTRAK Karyawan merupakan elemen yang sangat penting bagi perusahaan. Karyawan sebagai sumber daya manusia adalah penggerak utama berjalannya roda perusahaan sehingga perusahaan harus menjaga kepuasan kerja dan komitmen organisasional agar karyawan tidak berkeinginan untuk berpindah ke perusahaan lain (turnover intention). Hal ini perlu dikaji pengaruh kepuasan kerja dan komitmen organisasional terhadap turnover intention sehingga dapat bermanfaat untuk mengetahui nilai penting dari kepu...

  15. A Review of the Literature on Principal Turnover

    Science.gov (United States)

    Snodgrass Rangel, Virginia

    2018-01-01

    Among the many challenges facing public schools are high levels of principal turnover. Given the important role that principals play and are expected to play in the improvement process, concerns about principal turnover have resulted in a growing body of research on its causes and consequences. The purpose of this review is to take stock of what…

  16. Health workforce acquisition, retention and turnover in southwest ...

    African Journals Online (AJOL)

    Background: Skill mix of health professionals, staff acquisition and turnover rate are among the major challenges for the delivery of quality health care. This study assessed the health workforce acquisition, retention, turnover rate and their intention to leave. Methods: A cross-sectional survey with quantitative and qualitative ...

  17. The Link between Training Satisfaction, Work Engagement and Turnover Intention

    Science.gov (United States)

    Memon, Mumtaz Ali; Salleh, Rohani; Baharom, Mohamed Noor Rosli

    2016-01-01

    Purpose: The purpose of this paper is to examine the casual relationship between training satisfaction, work engagement (WE) and turnover intention and the mediating role of WE between training satisfaction and turnover intention. Design/methodology/approach: Data were collected from 409 oil and gas professionals using an email survey…

  18. Estimating Cause: Teacher Turnover and School Effectiveness in Michigan

    Science.gov (United States)

    Keesler, Venessa; Schneider, Barbara

    2010-01-01

    The purpose of this paper is investigate issues related to within-school teacher supply and school-specific teacher turnover within the state of Michigan using state administrative data on Michigan's teaching force. This paper 1) investigates the key predictors of teacher turnover and mobility, 2) develops a profile of schools that are likely to…

  19. Efficacy of 22Na turnover in ecopbysiological studies of carnivores

    African Journals Online (AJOL)

    Efficacy of 22Na turnover in ecopbysiological studies of carnivores. loS. Wilkinson and J.D. Skinner*. Mammal Research Institute, University of Pretoria, Pretoria, 0002 Republic of South Africa. Received 8 December 1986; accepted 11 August 1987. 22Na turnover rates gave overestimates of mean 23Na intake in both ...

  20. Below the Surface of Special Education Administrator Turnover

    Science.gov (United States)

    Meeks, Amy

    2016-01-01

    The field of special education administration has experienced a shortage of high quality special education leadership candidates for several decades. If school districts are to effectively address the turnover of educational leaders, they must know what is happening that affects turnover of their leadership team. The intent of this study was to…

  1. Bone mass and turnover in fibromyalgia

    DEFF Research Database (Denmark)

    Jacobsen, Søren; Gam, A; Egsmose, C

    1993-01-01

    Physical inactivity accelerates bone loss. Since patients with fibromyalgia are relatively physically inactive, bone mass and markers of bone metabolism were determined in 12 premenopausal women with fibromyalgia and in healthy age matched female control subjects. No differences were found...... in lumbar bone mineral density, femoral neck bone mineral density, serum levels of alkaline phosphatase, osteocalcin, ionized calcium and phosphate. The urinary excretion of both hydroxyproline and calcium relative to urinary creatinine excretion was significantly higher in patients with fibromyalgia, p = 0.......01. This was linked to lower urinary creatinine excretion (p = 0.02) probably reflecting lower physical activity in the patients with fibromyalgia. We conclude that bone mass and turnover are generally not affected in premenopausal women with fibromyalgia....

  2. Regulatory mechanisms of skeletal muscle protein turnover during exercise

    DEFF Research Database (Denmark)

    Rose, Adam John; Richter, Erik

    2009-01-01

    Skeletal muscle protein turnover is a relatively slow metabolic process that is altered by various physiological stimuli such as feeding/fasting and exercise. During exercise, catabolism of amino acids contributes very little to ATP turnover in working muscle. With regards to protein turnover......, there is now consistent data from tracer studies in rodents and humans showing that global protein synthesis is blunted in working skeletal muscle. Whether there is altered skeletal muscle protein breakdown during exercise remains unclear. The blunting of protein synthesis is believed to be mediated...... downstream of changes in intracellular Ca(2+) and energy turnover. In particular, a signaling cascade involving Ca(2+)-calmodulin-eEF2 kinase-eEF2 is implicated. The possible functional significance of altered protein turnover in working skeletal muscle during exercise is discussed. Further work...

  3. PENGARUH KEPUASAN KERJA TERHADAP KOMITMEN ORGANISASI DAN TURNOVER INTENTION

    Directory of Open Access Journals (Sweden)

    Agi Syarif Hidayat

    2018-03-01

    Full Text Available The high level of employee turnover in the marketing department at PT. Toyamilindo indicates low organizational commitment and high turnover intention. The purpose of this study is to determine the effect of job satisfaction on organizational commitment and turnover intention. Quantitative methods are used in this study. Population is the  employees of marketing department at PT. Toyamilindo with 50 people. Sampling technique used is sampling saturated with the number of samples of 50 people. Data collection technique uses questionnaires and regression analysis. Finding on the research results shows that there are positive and significant influence of job satisfaction on organizational commitment and negative and significant influence of job satisfaction on turnover intention, and also the influence of organizational commitment on work satisfaction to turnover intention. The managerial implications of corporate leaders must improve employee work satisfaction, especially in terms of salary.

  4. Perceptions of hospital CEOs about the effects of CEO turnover.

    Science.gov (United States)

    Khaliq, Amir A; Thompson, David M; Walston, Stephen L

    2006-01-01

    Empirical evidence is scarce on chief executive officer (CEO) turnover in U.S. hospitals, with potentially serious implications for many of these organizations. This study, based on a nationwide survey of CEOs at non-federal general surgical and medical community hospitals conducted in the spring of 2004, reports the perceptions of hospital CEOs regarding the circumstances and impact of CEO turnover on U.S. hospitals. In the opinion of the respondents, the impact includes competitors taking advantage of turnover by luring employees and physicians away from the target hospital, significantly increasing the likelihood of other senior executives leaving the hospital, and many of the important strategic activities being delayed or cancelled altogether. Interestingly, the perceptions of CEOs regarding the effects of turnover do not seem to differ regardless of voluntary or involuntary circumstances of turnover. However, there is a notable bias in emphasizing the perceived negative implications of respondents' own departures and allegedly positive effects of their predecessors' departures.

  5. Conserving the stage: climate change and the geophysical underpinnings of species diversity.

    Directory of Open Access Journals (Sweden)

    Mark G Anderson

    Full Text Available Conservationists have proposed methods for adapting to climate change that assume species distributions are primarily explained by climate variables. The key idea is to use the understanding of species-climate relationships to map corridors and to identify regions of faunal stability or high species turnover. An alternative approach is to adopt an evolutionary timescale and ask ultimately what factors control total diversity, so that over the long run the major drivers of total species richness can be protected. Within a single climatic region, the temperate area encompassing all of the Northeastern U.S. and Maritime Canada, we hypothesized that geologic factors may take precedence over climate in explaining diversity patterns. If geophysical diversity does drive regional diversity, then conserving geophysical settings may offer an approach to conservation that protects diversity under both current and future climates. Here we tested how well geology predicts the species diversity of 14 US states and three Canadian provinces, using a comprehensive new spatial dataset. Results of linear regressions of species diversity on all possible combinations of 23 geophysical and climatic variables indicated that four geophysical factors; the number of geological classes, latitude, elevation range and the amount of calcareous bedrock, predicted species diversity with certainty (adj. R(2 = 0.94. To confirm the species-geology relationships we ran an independent test using 18,700 location points for 885 rare species and found that 40% of the species were restricted to a single geology. Moreover, each geology class supported 5-95 endemic species and chi-square tests confirmed that calcareous bedrock and extreme elevations had significantly more rare species than expected by chance (P<0.0001, strongly corroborating the regression model. Our results suggest that protecting geophysical settings will conserve the stage for current and future biodiversity and may

  6. Job and career satisfaction and turnover intentions of newly graduated nurses.

    Science.gov (United States)

    Laschinger, Heather K Spence

    2012-05-01

    To describe new graduate nurses' worklife experiences in Ontario hospital settings in the first 2 years of practice and to examine predictors of job and career satisfaction and turnover intentions. With a large cohort of nurses approaching retirement, every effort must be made to ensure that the work environments of new graduate nurses are positive, promoting job satisfaction and commitment to the profession to address the nursing workforce shortage. A cross-sectional analysis of data from a mail survey of new graduate nurses (n=342) in their first and second year of experience was used to address the research objectives. Overall, new graduate nurses were positive about their working conditions and there were few differences between nurses in their first and second years of practice. Structural and personal factors explained significant amounts of variance (31-68%) in both job and career satisfaction and turnover intentions. Empowerment, work engagement and burnout were important significant predictors. Modifiable workplace factors play an important role in influencing new graduates' job and career satisfaction and turnover intentions. Managers can employ strategies to enhance quality work environments that promote retention of new graduates and lessen the nursing workforce shortage. © 2011 Blackwell Publishing Ltd.

  7. Retaining your high performers: moderators of the performance-job satisfaction-voluntary turnover relationship.

    Science.gov (United States)

    Nyberg, Anthony

    2010-05-01

    Two divergent ideas explain the relationship between performance and voluntary turnover. One suggests that higher performing employees, who are rewarded for their superior work product, will desire to remain with an organization that values their performance and will, consequently, be less likely than lower performing employees to voluntarily leave. An alternative idea suggests that higher performing employees, who are more desirable to external companies as a result of their superior work product, will have more external job opportunities and will, consequently, be more likely than their lower performing colleagues to voluntarily leave. The current study evaluated the behaviors and attitudes of 12,545 insurance employees over a 3-year period to examine how these 2 divergent expectations influence the performance-voluntary turnover relationship. Results show that both pay growth and the relevant unemployment rate interact with performance to influence the performance-voluntary turnover relationship and that they work independently of employee job satisfaction influences. PsycINFO Database Record (c) 2010 APA, all rights reserved.

  8. Bone turnover, calcium homeostasis, and vitamin D status in Danish vegans.

    Science.gov (United States)

    Hansen, Tue H; Madsen, Marie T B; Jørgensen, Niklas R; Cohen, Arieh S; Hansen, Torben; Vestergaard, Henrik; Pedersen, Oluf; Allin, Kristine H

    2018-01-23

    A vegan diet has been associated with increased bone fracture risk, but the physiology linking nutritional exposure to bone metabolism has only been partially elucidated. This study investigated whether a vegan diet is associated with increased bone turnover and altered calcium homeostasis due to insufficient intake of calcium and vitamin D. Fractionated and total 25-hydroxyvitamin D (25(OH)-D), parathyroid hormone (PTH), calcium, and four bone turnover markers (osteocalcin, N-terminal propeptide of type I procollagen (PINP), bone-specific alkaline phosphatase (BAP), and C-terminal telopeptide of type I collagen (CTX)) were measured in serum from 78 vegans and 77 omnivores. When adjusting for seasonality and constitutional covariates (age, sex, and body fat percentage) vegans had higher concentrations of PINP (32 [95% CI: 7, 64]%, P = 0.01) and BAP (58 [95% CI: 27, 97]%, P Vegans had higher serum PTH concentration (38 [95% CI: 19, 60]%; P Vegans have higher levels of circulating bone turnover markers compared to omnivores, which may in the long-term lead to poorer bone health. Differences in dietary habits including intake of vitamin D and calcium may, at least partly, explain the observed differences.

  9. DNA turnover in buffer-held Escherichia coli and its effect on repair of UV damage

    International Nuclear Information System (INIS)

    Tang, M.S.; Wang, T.C.V.; Patrick, M.H.

    1979-01-01

    Continuous DNA degradation and resynthesis, without a net change in cellular DNA content, were observed in buffer-held, non-irradiated E. coli B/r. This constant DNA turnover probably involves most of the genome and reflects random sites of DNA repair due to the polA-dependent excision-resynthesis repair pathway. Under these non-growth conditions it appears that at any given time there is a minimum of one repair site per 6.5 x 10 6 daltons DNA, each of which is at least 160 nucleotides long. While the amount of DNA degradation is not influenced by prior exposure to UV radiation, the synthetic activity decreases with increasing UV fluence. It is suggested that when sites of DNA turnover occur opposite to cyclobutyl dipyrimidines in UV-irradiated cells, repair of the latter damage can be prevented. This implies that both beneficial and deleterious processes take place in irradiated buffer-held cells, and that cell survival depends on the delicate balance between DNA turnover and repair of UV-damage. Based on these findings, a model is proposed to explain the limit repair observed during post-irradiation liquid-holding and to account for the large difference in cell survival between irradiation at low fluence rates (fluence-rate dependent recovery) and at high fluence rates followed by liquid-holding (liquid-holding recovery). (author)

  10. Increased platelet aggregation and turnover in the acute phase of ST-elevation myocardial infarction

    DEFF Research Database (Denmark)

    Jensen, Kristian Løkke Funck; Dalsgaard, Jens; Grove, Erik Lerkevang

    2013-01-01

    Newly produced platelets are present in the acute phase of ST-elevation myocardial infarction (STEMI). This may influence the antiplatelet effect of aspirin and clopidogrel administered prior to primary percutaneous coronary intervention (PPCI). The aims of this study were to investigate the anti...... turnover may partly explain the reduced efficacy of antiplatelet drugs in the acute phase of STEMI....... the antiplatelet effect of aspirin and clopidogrel and evaluate platelet turnover in the acute phase of STEMI compared to a stable phase 3 months later. In this observational follow-up study on 48 STEMI patients transferred for PPCI, loading doses of aspirin (300 mg) and clopidogrel (600 mg) were given orally...... in the ambulance. Blood samples were obtained immediately prior to PPCI, at 4 and 12 hours after administration of bolus doses and at follow-up after 3 months. Residual platelet aggregation was evaluated by Multiplate® and VerifyNow® aggregometry. Platelet turnover was evaluated by automated flow cytometry...

  11. How Serious of a Problem is Staff Turnover in Substance Abuse Treatment? A Longitudinal Study of Actual Turnover1

    Science.gov (United States)

    Eby, Lillian T.; Burk, Hannah; Maher, Charleen P.

    2010-01-01

    In the substance abuse treatment field, the annual turnover rate is cited as being anywhere between 19 and 50 percent (Johnson & Roman, 2002; Gallon, Gabriel, & Knudsen, 2003; Knudsen et al., 2003; McLellan et al., 2003). However, no research to date has evaluated these claims by tracking turnover longitudinally using organizational turnover data from substance abuse treatment centers. This research presents the results of a longitudinal study designed to systematically examine actual turnover among counselors and clinical supervisors. Twenty-seven geographically dispersed treatment organizations, serving a wide range of clients in the public and private sector, provided data for the study over a two year time span (2008–2009). The annual turnover rate was 33.2% for counselors and 23.4% for clinical supervisors. For both groups the majority of turnover was voluntary (employee-initiated). Specific reasons for turnover were largely consistent across the two groups, with the most common reason being a new job or new opportunity. The findings are discussed in terms of the unique employment context of substance abuse treatment. Practical recommendations are also discussed to help stem the tide of turnover in the field of substance abuse treatment. PMID:20675097

  12. How serious of a problem is staff turnover in substance abuse treatment? A longitudinal study of actual turnover.

    Science.gov (United States)

    Eby, Lillian T; Burk, Hannah; Maher, Charleen P

    2010-10-01

    In the substance abuse treatment field, the annual turnover rate is cited as being anywhere between 19% and 50% (J.A. Johnson & P.M. Roman, 2002; S.L. Gallon, R.M. Gabriel, J.R.W. Knudsen, 2003; H.K. Knudsen, J.A. Johnson, & P.M. Roman, 2003; A.T. McLellan, D. Carise, & H.D. Kleber, 2003). However, no research to date has evaluated these claims by tracking turnover longitudinally using organizational turnover data from substance abuse treatment centers. This research presents the results of a longitudinal study designed to systematically examine actual turnover among counselors and clinical supervisors. Twenty-seven geographically dispersed treatment organizations, serving a wide range of clients in the public and private sector, provided data for the study over a 2-year time span (2008-2009). The annual turnover rate was 33.2% for counselors and 23.4% for clinical supervisors. For both groups, the majority of turnover was voluntary (employee-initiated). Specific reasons for turnover were largely consistent across the two groups, with the most common reason being a new job or new opportunity. The findings are discussed in terms of the unique employment context of substance abuse treatment. Practical recommendations are also discussed to help stem the tide of turnover in the field of substance abuse treatment. Copyright (c) 2010 Elsevier Inc. All rights reserved.

  13. Biotic homogenization of urban floras by alien species: the role of species turnover and richness differences

    Czech Academy of Sciences Publication Activity Database

    Lososová, Z.; Chytrý, M.; Danihelka, Jiří; Tichý, L.; Ricotta, C.

    2016-01-01

    Roč. 27, č. 3 (2016), s. 452-459 ISSN 1100-9233 Institutional support: RVO:67985939 Keywords : archaeophyte * neophyte * environmental filter Subject RIV: EF - Botanics Impact factor: 2.924, year: 2016

  14. Staff turnover in statewide implementation of ACT: relationship with ACT fidelity and other team characteristics

    OpenAIRE

    Rollins, Angela L.; Salyers, Michelle P.; Tsai, Jack; Lydick, Jennifer M.

    2010-01-01

    Staff turnover on assertive community treatment (ACT) teams is a poorly understood phenomenon. This study examined annual turnover and fidelity data collected in a statewide implementation of ACT over a 5-year period. Mean annual staff turnover across all observations was 30.0%. Turnover was negatively correlated with overall fidelity at Year 1 and 3. The team approach fidelity item was negatively correlated with staff turnover at Year 3. For 13 teams with 3 years of follow-up data, turnover ...

  15. Relationship between ethical work climate and nurses' perception of organizational support, commitment, job satisfaction and turnover intent.

    Science.gov (United States)

    Abou Hashish, Ebtsam Aly

    2017-03-01

    Healthcare organizations are now challenged to retain nurses' generation and understand why they are leaving their nursing career prematurely. Acquiring knowledge about the effect of ethical work climate and level of perceived organizational support can help organizational leaders to deal effectively with dysfunctional behaviors and make a difference in enhancing nurses' dedication, commitment, satisfaction, and loyalty to their organization. This study aims to determine the relationship between ethical work climate, and perceived organizational support and nurses' organizational commitment, job satisfaction, and turnover intention. A descriptive correlational research design was conducted in all inpatient care units at three major hospitals affiliated to different health sectors at Alexandria governorate. All nurses working in these previous hospitals were included in the study (N = 500). Ethical Climate Questionnaire, Survey of Perceived Organizational Support, Organizational Commitment Questionnaire, Index of Job Satisfaction, and Intention to Turnover scale were used to measure study variables. Ethical considerations: Approval was obtained from Ethics Committee at Faculty of Nursing, Alexandria University. Privacy and confidentiality of data were maintained and assured by obtaining subjects' informed consent to participate in the research before data collection. The result revealed positive significant correlations between nurses' perception of overall ethical work climate and each of perceived organizational support, commitment, as well as their job satisfaction. However, negative significant correlations were found between nurses' turnover intention and each of these variables. Also, approximately 33% of the explained variance of turnover intention is accounted by ethical work climate, organizational support, organizational commitment, and job satisfaction, and these variables independently contributed significantly in the prediction of turnover intention

  16. Team climate, intention to leave and turnover among hospital employees: Prospective cohort study

    Directory of Open Access Journals (Sweden)

    Virtanen Marianna

    2007-10-01

    Full Text Available Abstract Background In hospitals, the costs of employee turnover are substantial and intentions to leave among staff may manifest as lowered performance. We examined whether team climate, as indicated by clear and shared goals, participation, task orientation and support for innovation, predicts intention to leave the job and actual turnover among hospital employees. Methods Prospective study with baseline and follow-up surveys (2–4 years apart. The participants were 6,441 (785 men, 5,656 women hospital employees under the age of 55 at the time of follow-up survey. Logistic regression with generalized estimating equations was used as an analysis method to include both individual and work unit level predictors in the models. Results Among stayers with no intention to leave at baseline, lower self-reported team climate predicted higher likelihood of having intentions to leave at follow-up (odds ratio per 1 standard deviation decrease in team climate was 1.6, 95% confidence interval 1.4–1.8. Lower co-worker assessed team climate at follow-up was also association with such intentions (odds ratio 1.8, 95% confidence interval 1.4–2.4. Among all participants, the likelihood of actually quitting the job was higher for those with poor self-reported team climate at baseline. This association disappeared after adjustment for intention to leave at baseline suggesting that such intentions may explain the greater turnover rate among employees with low team climate. Conclusion Improving team climate may reduce intentions to leave and turnover among hospital employees.

  17. Team climate, intention to leave and turnover among hospital employees: prospective cohort study.

    Science.gov (United States)

    Kivimäki, Mika; Vanhala, Anna; Pentti, Jaana; Länsisalmi, Hannakaisa; Virtanen, Marianna; Elovainio, Marko; Vahtera, Jussi

    2007-10-23

    In hospitals, the costs of employee turnover are substantial and intentions to leave among staff may manifest as lowered performance. We examined whether team climate, as indicated by clear and shared goals, participation, task orientation and support for innovation, predicts intention to leave the job and actual turnover among hospital employees. Prospective study with baseline and follow-up surveys (2-4 years apart). The participants were 6,441 (785 men, 5,656 women) hospital employees under the age of 55 at the time of follow-up survey. Logistic regression with generalized estimating equations was used as an analysis method to include both individual and work unit level predictors in the models. Among stayers with no intention to leave at baseline, lower self-reported team climate predicted higher likelihood of having intentions to leave at follow-up (odds ratio per 1 standard deviation decrease in team climate was 1.6, 95% confidence interval 1.4-1.8). Lower co-worker assessed team climate at follow-up was also association with such intentions (odds ratio 1.8, 95% confidence interval 1.4-2.4). Among all participants, the likelihood of actually quitting the job was higher for those with poor self-reported team climate at baseline. This association disappeared after adjustment for intention to leave at baseline suggesting that such intentions may explain the greater turnover rate among employees with low team climate. Improving team climate may reduce intentions to leave and turnover among hospital employees.

  18. Job Demands, Engagement, and Turnover Intentions in Polish Nurses: The Role of Work-Family Interface

    Directory of Open Access Journals (Sweden)

    Anna Maria Dåderman

    2016-11-01

    Full Text Available Background: Poland has lower ratios of employed registered nurses per 1,000 inhabitants than the EU average. Polish nurses work under miserable conditions without assisting personnel, and they reconcile their professional demands with responsibilities for their families; 96% of them are women. Rationale/Aims: This study uses Hobfoll’s Conservation of Resources (COR theory to explain the role of various resources in the improvement of work conditions in the nursing profession. Work-family conflict (WFC and family-work conflict (FWC threaten to deplete nurses’ resources. This paper set out to (1 examine the extent to which perceived job demands (workload and interpersonal conflicts at work and engagement (vigour, dedication and absorption are associated with turnover intentions (the intention to leave the present workplace and the intention to leave the nursing profession; (2 attempt to determine whether levels of WFC and FWC moderate these associations. Design/Method: This study comprised 188 female registered nurses. The inclusion criterion was to live with a partner and/or have children. Results: WFC was moderately related to FWC. Hierarchical regression analyses showed that only high job demands and low vigour were significantly associated with turnover intentions. WFC was experienced more intensively than FWC. Job demands, vigour, dedication and turnover intentions had a strong effect on WFC, while absorption had a strong effect on FWC. However, levels of WFC and FWC did not significantly moderate these associations. Originality/Conclusion: The study produces new knowledge by examining a constellation of job demands, work engagement and WFC, which reflect the management of personal resources. Results from such a constellation in nurses from countries with a post-transformational economic system have not previously been discussed in the light of COR theory. Most importantly, we conclude that WFC does not intensify turnover intentions.

  19. Job Demands, Engagement, and Turnover Intentions in Polish Nurses: The Role of Work-Family Interface.

    Science.gov (United States)

    Dåderman, Anna M; Basinska, Beata A

    2016-01-01

    Background: Poland has lower ratios of employed registered nurses per 1,000 inhabitants than the EU average. Polish nurses work under miserable conditions without assisting personnel, and they reconcile their professional demands with responsibilities for their families; 96% of them are women. Rationale/Aims: This study uses Hobfoll's conservation of resources (CORs) theory to explain the role of various resources in the improvement of work conditions in the nursing profession. Work-family conflict (WFC) and family work conflict (FWC) threaten to deplete nurses' resources. This paper set out to (1) examine the extent to which perceived job demands (workload and interpersonal conflicts at work) and engagement (vigor, dedication, and absorption) are associated with turnover intentions (the intention to leave the present workplace and the intention to leave the nursing profession); (2) attempt to determine whether levels of WFC and FWC moderate these associations. Design/Method: This study comprised 188 female registered nurses. The inclusion criterion was to live with a partner and/or have children. Results: WFC was moderately related to FWC. Hierarchical regression analyses showed that only high job demands and low vigor were significantly associated with turnover intentions. WFC was experienced more intensively than FWC. Job demands, vigor, dedication, and turnover intentions had a strong effect on WFC, while absorption had a strong effect on FWC. However, levels of WFC and FWC did not significantly moderate these associations. Originality/Conclusion: The study produces new knowledge by examining a constellation of job demands, work engagement and WFC, which reflect the management of personal resources. Results from such a constellation in nurses from countries with a post-transformational economic system have not previously been discussed in the light of COR theory. Most importantly, we conclude that WFC does not intensify turnover intentions.

  20. Turnover of Glycerolipid Metabolite Pool and Seed Viability

    Directory of Open Access Journals (Sweden)

    Xiao-Long Hu

    2018-05-01

    Full Text Available Hydration–dehydration cycles can frequently cause stress to seeds, but can also be used to improve germination. However, the molecular basis of the stress caused is poorly understood. Herein, we examine the effects of hydration–dehydration cycles on seed viability and profile the membrane glycerolipid molecular species. We find that seed viability was not affected during the first two cycles, but significantly decreased as further cycles were applied, until all viability was lost. The abundances of seven glycerolipid classes increased and decreased through hydration and dehydration, respectively, but the phosphatidic acid and diacylglycerol abundances changed in the opposite sense, while total glycerolipid contents remained constant. This suggests that during hydration–dehydration cycles, turnover of glycerolipid metabolite pools take place, while no significant lipid synthesis or degradation is involved. As further hydration–dehydration cycles occurred, lipid unsaturation increased, plastidic lipids decreased, and phosphatidylserine acyl chains lengthened. The latter two could be lethal for seeds. Our findings reveal a novel model of membrane lipid changes, and provide new insights into the responses of seeds to hydration–dehydration cycles.

  1. Fundamental species traits explain provisioning services of tropical American palms

    DEFF Research Database (Denmark)

    Cámara Leret, Rodrigo; Faurby, Søren; Macía, Manuel

    2017-01-01

    we show that our findings hold even when accounting for phylogenetic clustering of traits and utility due to phylogenetic relatedness5. Beyond expanding our understanding of how local stakeholders perceive and explore biodiversity in mega-diverse forests, our trait- and phylogeny-based approach helps...

  2. Mycorrhizal status helps explain invasion success of alien plant species

    Czech Academy of Sciences Publication Activity Database

    Menzel, A.; Hempel, S.; Klotz, S.; Moora, M.; Pyšek, Petr; Rillig, M. C.; Zobel, M.; Kühn, I.

    2017-01-01

    Roč. 98, č. 1 (2017), s. 92-102 ISSN 0012-9658 R&D Projects: GA ČR GB14-36079G Grant - others:AV ČR(CZ) AP1002 Program:Akademická prémie - Praemium Academiae Institutional support: RVO:67985939 Keywords : plant invasion * mycorrhiza * naturalization Subject RIV: EH - Ecology, Behaviour OBOR OECD: Ecology Impact factor: 4.809, year: 2016

  3. An Analysis of the Effects of Deployment on Turnover in the United States Army Reserve

    National Research Council Canada - National Science Library

    McCloskey, Michele

    1999-01-01

    .... Survey questions were developed using motivation and turnover theories, and a Integrated Turnover Model relating a Reservist's deployment experience to the presence or absence of six major factors...

  4. Staff turnover in statewide implementation of ACT: relationship with ACT fidelity and other team characteristics.

    Science.gov (United States)

    Rollins, Angela L; Salyers, Michelle P; Tsai, Jack; Lydick, Jennifer M

    2010-09-01

    Staff turnover on assertive community treatment (ACT) teams is a poorly understood phenomenon. This study examined annual turnover and fidelity data collected in a statewide implementation of ACT over a 5-year period. Mean annual staff turnover across all observations was 30.0%. Turnover was negatively correlated with overall fidelity at Year 1 and 3. The team approach fidelity item was negatively correlated with staff turnover at Year 3. For 13 teams with 3 years of follow-up data, turnover rates did not change over time. Most ACT staff turnover rates were comparable or better than other turnover rates reported in the mental health and substance abuse literature.

  5. Understanding the factors that determine registered nurses' turnover intentions.

    Science.gov (United States)

    Osuji, Joseph; Uzoka, Faith-Michael; Aladi, Flora; El-Hussein, Mohammed

    2014-01-01

    Turnover among registered nurses (RNs) produces a negative impact on the health outcomes of any health care organization. It is also recognized universally as a problem in the nursing profession. Little is known about the turnover intentions and career orientations of RNs working in Calgary, Alberta, Canada. The aim of this study is to contribute to the knowledge of and to advance the discussion on the turnover of nursing professionals. The study population consisted of RNs employed in the five major hospitals in Calgary. There were 193 surveys returned, representing a response rate of 77.2%. The results show that age and education have a negative effect on turnover intention. Education was found to have a significant negative effect on career satisfaction but not on job satisfaction and organizational commitment. Length of service has a significant negative effect on turnover intention. Role ambiguity has significant highly negative effect on career satisfaction. Growth opportunity and supervisor support have a very significant positive effect on job satisfaction, career satisfaction, and organizational commitment. External career opportunities and organizational commitment do not seem to have a significant effect on turnover intention. Career satisfaction, on the other hand, had negative significant effects on turnover intention.

  6. Turnover rates in microorganisms by laser ablation electrospray ionization mass spectrometry and pulse-chase analysis

    Energy Technology Data Exchange (ETDEWEB)

    Stopka, Sylwia A.; Mansour, Tarek R.; Shrestha, Bindesh [Department of Chemistry, W.M. Keck Institute for Proteomics Technology and Applications, The George Washington University, Washington, DC 20052 (United States); Maréchal, Éric; Falconet, Denis [Laboratoire de Physiologie Cellulaire et Végétale, UMR 5168, CEA-CNRS-INRA-Univ. Grenoble Alpes, Grenoble (France); Vertes, Akos, E-mail: vertes@gwu.edu [Department of Chemistry, W.M. Keck Institute for Proteomics Technology and Applications, The George Washington University, Washington, DC 20052 (United States)

    2016-01-01

    Biochemical processes rely on elaborate networks containing thousands of compounds participating in thousands of reaction. Rapid turnover of diverse metabolites and lipids in an organism is an essential part of homeostasis. It affects energy production and storage, two important processes utilized in bioengineering. Conventional approaches to simultaneously quantify a large number of turnover rates in biological systems are currently not feasible. Here we show that pulse-chase analysis followed by laser ablation electrospray ionization mass spectrometry (LAESI-MS) enable the simultaneous and rapid determination of metabolic turnover rates. The incorporation of ion mobility separation (IMS) allowed an additional dimension of analysis, i.e., the detection and identification of isotopologs based on their collision cross sections. We demonstrated these capabilities by determining metabolite, lipid, and peptide turnover in the photosynthetic green algae, Chlamydomonas reinhardtii, in the presence of {sup 15}N-labeled ammonium chloride as the main nitrogen source. Following the reversal of isotope patterns in the chase phase by LAESI-IMS-MS revealed the turnover rates and half-lives for biochemical species with a wide range of natural concentrations, e.g., chlorophyll metabolites, lipids, and peptides. For example, the half-lives of lyso-DGTS(16:0) and DGTS(18:3/16:0), t{sub 1/2} = 43.6 ± 4.5 h and 47.6 ± 2.2 h, respectively, provided insight into lipid synthesis and degradation in this organism. Within the same experiment, half-lives for chlorophyll a, t{sub 1/2} = 24.1 ± 2.2 h, and a 2.8 kDa peptide, t{sub 1/2} = 10.4 ± 3.6 h, were also determined. - Highlights: • High-throughput pulse-chase analysis using direct sampling of biological cells. • Ion mobility separation for the elucidation of isotopologs. • Identification of isotopologs in difference heat plots of DT vs. m/z. • Simultaneous determination of turnover rates for lipids and

  7. Your Radiologist Explains Nuclear Medicine

    Medline Plus

    Full Text Available ... Disorders Video: The Basketball Game: An MRI Story Radiology and You Sponsored by Image/Video Gallery Your Radiologist Explains Nuclear Medicine Transcript Welcome to Radiology Info dot org Hello! I’m Dr. Ramji ...

  8. Your Radiologist Explains Nuclear Medicine

    Medline Plus

    Full Text Available ... by Image/Video Gallery Your Radiologist Explains Nuclear Medicine Transcript Welcome to Radiology Info dot org Hello! ... d like to talk to you about nuclear medicine. Nuclear medicine offers the potential to identify disease ...

  9. Your Radiologist Explains Nuclear Medicine

    Medline Plus

    Full Text Available ... An MRI Story Radiology and You Sponsored by Image/Video Gallery Your Radiologist Explains Nuclear Medicine Transcript ... by a special camera and computer to create images of the inside of your body. If you’ ...

  10. Your Radiologist Explains Nuclear Medicine

    Medline Plus

    Full Text Available ... Sponsored by Image/Video Gallery Your Radiologist Explains Nuclear Medicine Transcript Welcome to Radiology Info dot org ... I’d like to talk to you about nuclear medicine. Nuclear medicine offers the potential to identify ...

  11. Explaining variation in nascent entrepreneurship

    NARCIS (Netherlands)

    A.J. van Stel (André); A.R.M. Wennekers (Sander); P. Reynolds (Paul); A.R. Thurik (Roy)

    2004-01-01

    textabstractThis paper aims at explaining cross-country variation in nascent entrepreneurship. Regression analysis is applied using various explanatory variables derived from three different approaches. We make use of the Global Entrepreneurship Monitor database, including nascent entrepreneurship

  12. Explaining nascent entrepreneurship across countries

    NARCIS (Netherlands)

    A.R. Thurik (Roy); A.J. van Stel (André); A.R.M. Wennekers (Sander); P. Reynolds (Paul)

    2003-01-01

    textabstractThis paper aims at explaining cross-country variation in nascent entrepreneurship. Regression analysis is applied using various explanatory variables derived from three different approaches. We make use of the Global Entrepreneurship Monitor database, including nascent entrepreneurship

  13. Different relationships between temporal phylogenetic turnover and phylogenetic similarity and in two forests were detected by a new null model.

    Science.gov (United States)

    Huang, Jian-Xiong; Zhang, Jian; Shen, Yong; Lian, Ju-yu; Cao, Hong-lin; Ye, Wan-hui; Wu, Lin-fang; Bin, Yue

    2014-01-01

    Ecologists have been monitoring community dynamics with the purpose of understanding the rates and causes of community change. However, there is a lack of monitoring of community dynamics from the perspective of phylogeny. We attempted to understand temporal phylogenetic turnover in a 50 ha tropical forest (Barro Colorado Island, BCI) and a 20 ha subtropical forest (Dinghushan in southern China, DHS). To obtain temporal phylogenetic turnover under random conditions, two null models were used. The first shuffled names of species that are widely used in community phylogenetic analyses. The second simulated demographic processes with careful consideration on the variation in dispersal ability among species and the variations in mortality both among species and among size classes. With the two models, we tested the relationships between temporal phylogenetic turnover and phylogenetic similarity at different spatial scales in the two forests. Results were more consistent with previous findings using the second null model suggesting that the second null model is more appropriate for our purposes. With the second null model, a significantly positive relationship was detected between phylogenetic turnover and phylogenetic similarity in BCI at a 10 m×10 m scale, potentially indicating phylogenetic density dependence. This relationship in DHS was significantly negative at three of five spatial scales. This could indicate abiotic filtering processes for community assembly. Using variation partitioning, we found phylogenetic similarity contributed to variation in temporal phylogenetic turnover in the DHS plot but not in BCI plot. The mechanisms for community assembly in BCI and DHS vary from phylogenetic perspective. Only the second null model detected this difference indicating the importance of choosing a proper null model.

  14. Measurements of protein turnover in man with nitrogen-15

    International Nuclear Information System (INIS)

    Garlick, P.J.; Waterlow, J.C.

    1977-01-01

    Past and present methods of measuring total body protein turnover with 15 N-labelled compounds are reviewed, and a short assessment made of results achieved. Protein turnover in man was first measured by Sprinson and Rittenberg (1949) using 15 N glycine as tracer. The rate of turnover was calculated from the fraction of the dose excreted in urine in the days following a single oral dose of the isotope. In the following years a number of similar methods were devised but interest waned, perhaps because consistent changes in turnover rate under different conditions were not detected. A revival of interest came with the measurement of changes in protein turnover in malnourished and recovering children by Picou and Taylor-Roberts (1969). Nitrogen-15-glycine was infused and measurements were made of the abundance of 15 N in urinary urea, which reached a plateau in about 24 hours. Turnover rates were calculated from the proportion of the infused dose excreted in urea after the plateau had been reached. This method has also been used successfully on adults when the isotope has been given as three-hourly oral doses. In adults, however, plateau labelling in urea is not usually reached for two days. In our laboratory the use of urinary ammonia, which reaches a plateau more quickly than urea, has been examined. In addition, comparisons have been made between constant infusion and single dose of isotope. Halliday and McKeran (1975) infused 15 N-lysine and measured the 15 N abundance in the free lysine of plasma, which reached a plateau in about 12 hours. Turnover in the whole body and turnover of muscle proteins and of plasma albumin were estimated separately. These methods of measuring protein turnover with 15 N are described and results reviewed of the effects of food intake, nutritional status and age. (author)

  15. Employee turnover and productivity among small business entities in Nigeria

    Directory of Open Access Journals (Sweden)

    John N. N. Ugoani

    2016-12-01

    Full Text Available This study was designed to evaluate the problems of employee turnover on productivity among small business entities in Nigeria, and recommend remedial actions. Employee turnover is the separation of employees from employers and replacement with other employees. Productive manpower is a critical element for the economic survival of any small business entity. The survey research design was used for the study. The sample comprised of 320 respondents. Data generated were analyzed by using descriptive, and Z-test statistical techniques. It was found that employee turnover adversely affects productivity in small business entities.

  16. Turnover and employment in the German wind energy industry

    International Nuclear Information System (INIS)

    Keuper, A.

    1995-01-01

    Results of the fast growing wind energy market in 1994 are the turnover reaching more than 800 million DM, and the number of employees to about 3,700. In 1995 the manufacturers expect to need less than 4 employees to build and to install 1 MW rated power and to decrease the ratio of manufacturer's turnover per installed power unit to about 1900 DM/kW. In spite of this development it is expected that the turnover and the number of employees will increase due to the still fast growing market. (orig.)

  17. The curvilinear effect of work engagement on employees' turnover intentions.

    Science.gov (United States)

    Caesens, Gaëtane; Stinglhamber, Florence; Marmier, Virginie

    2016-04-01

    Numerous studies have shown the positive consequences of work engagement for both organisations and employees experiencing it. For instance, research has demonstrated that work-engaged employees have lower levels of turnover intentions than non-engaged employees. However, in this research, we examined whether there is a dark side of work engagement. More precisely, we investigated whether the relationship between work engagement and employees' turnover intentions might be non-linear. Based on two different samples, our results indicated that the relationship between work engagement and employees' turnover intentions is curvilinear. The theoretical and practical implications of these results are discussed. © 2014 International Union of Psychological Science.

  18. Sildenafil Stimulates Aqueous Humor Turnover in Rabbits

    Science.gov (United States)

    Alvarez, Lawrence J.; Zamudio, Aldo C.; Candia, Oscar A.

    2013-01-01

    Sildenafil citrate increases ocular blood flow and accelerates the rate of anterior chamber refilling after paracentesis. The latter effect could have resulted from a reduction in outflow facility or from an increase in aqueous humor (AH) production. In this study, we used scanning ocular fluorophotometry to examine the effects of sildenafil on AH turnover, and thus, AH production in eyes of live normal rabbits. For this, the rate of aqueous humor flow (AHF) was quantified with a commercially available fluorophotometer that measured the rate of fluorescein clearance from the anterior segment, which predominantly occurs via the trabecular meshwork. After ≈ 2 hrs of control scans to determine the baseline rate of AHF, the rabbits were fed 33 mg of sildenafil and allowed ≈ 45 min for the drug to enter the systemic circulation. Thereafter, fluorescence scans were retaken for an additional 90–120 min. Sildenafil ingestion increased AHF by about 36%, from 2.31 μL/min to 3.14 μL/min (PViagra, Revatio), stimulates AHF in rabbits. Our results seem consistent with reports indicating that the drug dilates intraocular arteries and augments intraocular vascular flow. These physiological responses to the agent apparently led to increased fluid entry into the anterior chamber. As such, the drug might have utility in patients with ocular hypotony resulting from insufficient AH formation. PMID:23562660

  19. A Comprehensive Model of the Employee's Turnover Decision Process

    National Research Council Canada - National Science Library

    Donnelly, David

    2002-01-01

    .... In any environment in which retention is a primary goal, an essential first step in controlling attrition is the development of an in-depth understanding of the employee turnover decision process...

  20. Wind energy industry in Germany. Turnover and employment

    International Nuclear Information System (INIS)

    Keuper, A.; Schmidt, A.

    1994-01-01

    As a consequence of the growing wind energy market in Germany the importance of the industry in this business are has grown. In 1994 the turnover will go beyond 500 million DM, and the number of employees will reach 2,900. The turnover and the number of employees are increasing in spite of the higher efficiency. In 1994 only 5 employees are needed by a manufacturer to install 1 MW rated power instead of 15 in 1989, and the ratio of installed power to manufacturer's turnover has risen from 0,25 W/DM in 1988 to 0,455 W/DM in 1994. On the other hand the turnover of the manufacturers per employee has increased from 80,000 DM in 1988 to 440,000 DM in 1994. Economic development has considerably been advanced by subsidies for the application of wind energy technology. (orig.)

  1. SOME FEATURES OF CONTROL STAFF TURNOVER IN PERSONNEL MANAGEMENT

    Directory of Open Access Journals (Sweden)

    S. N. Kaznacheeva

    2015-01-01

    Full Text Available The author refers to the decision of the actual problem of staff turnover in the transformation of the Russian economy. In light of the problem of the effectiveness of human resources management the author indicates the most frequent problems faced by the company and focus on the problem of staff turnover. The author presents a different interpretation, defining "Marketing personnel" as a kind of administrative activity aimed at ensuring the long-term organization of human resources (identifying staffing needs, and these needs, that is, covering the organization's needs for personnel. It highlights the main features and distinctive features of marketing staff. We consider the objective (external and subjective reasons (internal reasons for staff turnover. The author proposes a number of measures to help identify the causes of turnover.

  2. Bone turnover and oxidative stress markers in estrogen- deficient ...

    African Journals Online (AJOL)

    Bone turnover and oxidative stress markers in estrogen- ... reproduction in any medium, provided the original work is properly credited. ..... Institute for Laboratory Animal Research: Guide for the ... American Veterinary Medical Association.

  3. Autoradiographic imaging of phosphoinositide turnover in the brain

    International Nuclear Information System (INIS)

    Hwang, P.M.; Bredt, D.S.; Snyder, S.H.

    1990-01-01

    With [ 3 H]cytidine as a precursor, phosphoinositide turnover can be localized in brain slices by selective autoradiography of the product [ 3 H]cytidine diphosphate diacylglycerol, which is membrane-bound. In the cerebellum, glutamatergic stimulation elicits an increase of phosphoinositide turnover only in Purkinje cells and the molecular layer. In the hippocampus, both glutamatergic and muscarinic cholinergic stimulation increase phosphoinositide turnover, but with distinct localizations. Cholinergic stimulation affects CA1, CA3, CA4, and subiculum, whereas glutamatergic effects are restricted to the subiculum and CA3. Imaging phosphoinositide turnover in brain slices, which are amenable to electrophysiologic studies, will permit a dynamic localized analysis of regulation of this second messenger in response to synaptic stimulation of specific neuronal pathways

  4. survey of pay satisfaction, job satisfaction and employee turnover

    African Journals Online (AJOL)

    employee turnover in business organizations in Lagos Nigeria. Data were .... to be making more money than them were more dissatisfied with ... postulates that an employee is a rational decision maker, hence, he makes efforts that lead to a ...

  5. Report: Remedial Project Manager Turnover at Superfund Sites

    Science.gov (United States)

    Report #2001-M-000015, June 15, 2001. We determined that EPA Region III did not have formal procedures in place to mitigate continuity problems caused by turnover of EPA personnel in the Superfund program.

  6. Regulation of endoplasmic reticulum turnover by selective autophagy

    NARCIS (Netherlands)

    Khaminets, Aliaksandr; Heinrich, Theresa; Mari, Muriel; Grumati, Paolo; Huebner, Antje K; Akutsu, Masato; Liebmann, Lutz; Stolz, Alexandra; Nietzsche, Sandor; Koch, Nicole; Mauthe, Mario; Katona, Istvan; Qualmann, Britta; Weis, Joachim; Reggiori, Fulvio; Kurth, Ingo; Hübner, Christian A; Dikic, Ivan

    2015-01-01

    The endoplasmic reticulum (ER) is the largest intracellular endomembrane system, enabling protein and lipid synthesis, ion homeostasis, quality control of newly synthesized proteins and organelle communication. Constant ER turnover and modulation is needed to meet different cellular requirements and

  7. Regulation of endoplasmic reticulum turnover by selective autophagy

    NARCIS (Netherlands)

    Khaminets, Aliaksandr; Heinrich, Theresa; Mari, Muriel; Grumati, Paolo; Huebner, Antje K.; Akutsu, Masato; Liebmann, Lutz; Stolz, Alexandra; Nietzsche, Sandor; Koch, Nicole; Mauthe, Mario; Katona, Istvan; Qualmann, Britta; Weis, Joachim; Reggiori, Fulvio; Kurth, Ingo; Huebner, Christian A.; Dikic, Ivan

    2015-01-01

    The endoplasmic reticulum (ER) is the largest intracellular endomembrane system, enabling protein and lipid synthesis, ion homeostasis, quality control of newly synthesized proteins and organelle communication(1). Constant ER turnover and modulation is needed to meet different cellular requirements

  8. Rationale for the evaluation of trabecular bone turnover

    International Nuclear Information System (INIS)

    Kimmel, D.B.; Jee, W.S.S.

    1976-01-01

    A procedure for the morphometric evaluation of trabecular bone is identified. Its scrupulous use allows total identification of bone formation and resorption rates, items necessary for the direct histologic analysis of bone turnover

  9. Employee motivation development opportunities seeking to reduce employee turnover

    OpenAIRE

    Pilukienė, Laura; Kšivickaitė, Gertūda

    2014-01-01

    In this article, the authors analyse one of the main nowadays human resources problem – growing employee turnover. Employee motivation process is analysed as a key competitive advantage in employee retention that leads to the growth of the business company’s productivity and competitive stability. The main goal of the article is to analyse the employee motivation and employee turnover relationship and its development possibilities in Lithuania’s business sector.

  10. Liquid Crystal Gel Reduces Age Spots by Promoting Skin Turnover

    OpenAIRE

    Mina Musashi; Ariella Coler-Reilly; Teruaki Nagasawa; Yoshiki Kubota; Satomi Kato; Yoko Yamaguchi

    2014-01-01

    Studies have shown that liquid crystals structurally resembling the intercellular lipids in the stratum corneum can beneficially affect the skin when applied topically by stimulating the skin’s natural regenerative functions and accelerating epidermal turnover. In the present study, the effects of applying low concentrations of a liquid crystal gel of our own creation were evaluated using epidermal thickening in mouse skin as an assay for effective stimulation of epidermal turnover. A liquid ...

  11. Turnover rate of hypoxic cells in solid tumors

    International Nuclear Information System (INIS)

    Ljungkvist, A.S.E.; Bussink, J.; Rijken, P.F.J.W.; Van Der Kogel, A.J.

    2003-01-01

    Most solid tumors contain hypoxic cells, and both the amount and duration of tumor hypoxia has been shown to influence the effect of radiation treatment negatively. It is important to understand the dynamic processes within the hypoxic cell population in non-treated tumors, and the effect of different treatment modalities on the kinetics of hypoxic cells to be able to design optimal combined modality treatments. The turnover rate of hypoxic cells was analyzed in three different solid tumor models with a double bio-reductive hypoxic marker assay with sequential injection of the two hypoxic markers. Previously it was shown that this assay could be used to detect both a decrease and an increase of tumor hypoxia in relation to the tumor vasculature with high spatial resolution. In this study the first hypoxic marker, pimonidazole, was administered at variable times relative to tumor harvest, and the second hypoxic marker, CCI-103F, was injected at a fixed time before harvest. The hypoxic cell turnover rate was calculated as the loss of pimonidazole positive cells relative to CCI-103F. The murine C38 line had the fastest hypoxic turnover rate of 60% /24h and the human xenograft line SCCNij3 had the slowest hypoxic turnover rate of 30% /24 h. The hypoxic turnover rate was most heterogeneous in the SCCNij3 line that even contained viable groups of cells that had been hypoxic for at least 5 days. The human xenograft line MEC82 fell in between with a hypoxic turnover rate of 50% /24 h. The hypoxic cell turnover was related to the potential tumor volume doubling time (Tpot) with a Tpot of 26h in C38 and 103h in SCCNij3. The dynamics of hypoxic cells, quantified with a double hypoxic marker method, showed large differences in hypoxic cell turnover rate and were related to Tpot

  12. Physician and staff turnover in community primary care practice.

    Science.gov (United States)

    Ruhe, Mary; Gotler, Robin S; Goodwin, Meredith A; Stange, Kurt C

    2004-01-01

    The effect of a rapidly changing healthcare system on personnel turnover in community family practices has not been analyzed. We describe physician and staff turnover and examine its association with practice characteristics and patient outcomes. A cross-sectional evaluation of length of employment of 150 physicians and 762 staff in 77 community family practices in northeast Ohio was conducted. Research nurses collected data using practice genograms, key informant interviews, staff lists, practice environment checklists, medical record reviews, and patient questionnaires. The association of physician and staff turnover with practice characteristics, patient satisfaction, and preventive service data was tested. During a 2-year period, practices averaged a 53% turnover rate of staff. The mean length of duration of work at the current practice location was 9.1 years for physicians and 4.1 years for staff. Longevity varied by position, with a mean of 3.4 years for business employees, 4.0 years for clinical employees, and 7.8 years for office managers. Network-affiliated practices experienced higher turnover than did independent practices. Physician longevity was associated with a practice focus on managing chronic illness, keeping on schedule, and responding to insurers' requests. No association was found between turnover and patient satisfaction or preventive service delivery rates. Personnel turnover is pervasive in community primary care practices and is associated with employee role, practice network affiliation, and practice focus. The potentially disruptive effect of personnel turnover on practice functioning, finances, and longitudinal relationships with patients deserves further study despite the reassuring lack of association with patient satisfaction and preventive service delivery rates.

  13. Corporate governance mechanisms in family firms: Evidence from CEO turnovers

    OpenAIRE

    González, Maximiliano; Guzmán, Alexander; Pombo, Carlos; Trujillo, María Andréa

    2013-01-01

    Research Question/Issue: How sensitive is CEO turnover to firm performance in the context of family firms? Research Findings/Insights: Using a detailed database of mostly non-listed Colombian firms, we found that family ownership (direct and indirect through pyramidal structures) reduces the probability of CEO turnover when financial performance has been poor; however, we found that the opposite effect is true when families participate actively on the board of directors. These results hold tr...

  14. The Modern Technologies to Reduce Turnover of Company Staff

    OpenAIRE

    Zaiko Tetiana O.; Poplavska Oksana M.

    2017-01-01

    The article is aimed at analyzing and substantiating the use in practice of modern technologies to reduce turnover of staff, which do not bear significant financial costs for the company. The authors have proved that non-material measures to reduce staff turnover in companies are becoming predominant nowadays. Among them as the most important are indicated: introduction of flexible schedule (mode) of work, transition to the remote form of employment, and distribution of internal shares, in pa...

  15. Prediction of Employee Turnover in Organizations using Machine Learning Algorithms

    OpenAIRE

    Rohit Punnoose; Pankaj Ajit

    2016-01-01

    Employee turnover has been identified as a key issue for organizations because of its adverse impact on work place productivity and long term growth strategies. To solve this problem, organizations use machine learning techniques to predict employee turnover. Accurate predictions enable organizations to take action for retention or succession planning of employees. However, the data for this modeling problem comes from HR Information Systems (HRIS); these are typically under-funded compared t...

  16. Kramers Turnover Theory for a Triple Well Potential

    International Nuclear Information System (INIS)

    Pollak, E.; Talkner, P.

    2001-01-01

    Kramers turnover theory is solved for a particle in a symmetric triple well potential for temperatures above the crossover temperature between tunneling and activated barrier crossing. Comparison with the turnover theory for a double well potential shows that the presence of the intermediate well always leads to a decrease of the reaction rate. At most though, the rate is a factor of two smaller than in the case of a double well potential. (author)

  17. Spatio-temporal segregation and size distribution of fish assemblages as related to non-native species occurrence in the middle rio Doce Valley, MG, Brazil

    Directory of Open Access Journals (Sweden)

    Henrique Corrêa Giacomini

    Full Text Available The lakes in the middle rio Doce Valley (MG are suffering impacts due to the introduction of invasive fish species, mainly piscivorous species like red piranha Pygocentrus nattereri and peacock bass Cichla kelberi. Fishes were collected in bimonthly samples conducted at ten lakes along a year. The present study showed that the composition of native fish assemblages is significantly related to the presence and type of non-native species. Fish species distribution among lakes can be explained by differences in species body size: smaller native species are less concentrated in lakes with invasive piscivores, which is in accordance with the hypothesis that they have greater susceptibility to predation by invaders. Another probable cause for this correlation is the proximity of lakes to the drainage system, which could explain both the non-native incidence and the turnover of native species composition. Furthermore, temporal variability in species composition was significantly higher in invaded lakes. This last factor may be linked to seasonal flood pulses, which carry immigrant fishes from streams in the vicinity. The metacommunity framework can bring insights for future studies in such spatially structured systems, and the approach should improve our understanding of processes underlying species composition as well as help direct conservation-focused management plans.

  18. Resource specialists lead local insect community turnover associated with temperature - analysis of an 18-year full-seasonal record of moths and beetles.

    Science.gov (United States)

    Thomsen, Philip Francis; Jørgensen, Peter Søgaard; Bruun, Hans Henrik; Pedersen, Jan; Riis-Nielsen, Torben; Jonko, Krzysztof; Słowińska, Iwona; Rahbek, Carsten; Karsholt, Ole

    2016-01-01

    Insect responses to recent climate change are well documented, but the role of resource specialization in determining species vulnerability remains poorly understood. Uncovering local ecological effects of temperature change with high-quality, standardized data provides an important first opportunity for predictions about responses of resource specialists, and long-term time series are essential in revealing these responses. Here, we investigate temperature-related changes in local insect communities, using a sampling site with more than a quarter-million records from two decades (1992-2009) of full-season, quantitative light trapping of 1543 species of moths and beetles. We investigated annual as well as long-term changes in fauna composition, abundance and phenology in a climate-related context using species temperature affinities and local temperature data. Finally, we explored these local changes in the context of dietary specialization. Across both moths and beetles, temperature affinity of specialists increased through net gain of hot-dwelling species and net loss of cold-dwelling species. The climate-related composition of generalists remained constant over time. We observed an increase in species richness of both groups. Furthermore, we observed divergent phenological responses between cold- and hot-dwelling species, advancing and delaying their relative abundance, respectively. Phenological advances were particularly pronounced in cold-adapted specialists. Our results suggest an important role of resource specialization in explaining the compositional and phenological responses of insect communities to local temperature increases. We propose that resource specialists in particular are affected by local temperature increase, leading to the distinct temperature-mediated turnover seen for this group. We suggest that the observed increase in species number could have been facilitated by dissimilar utilization of an expanded growing season by cold- and hot

  19. Telaah Hubungan Kepuasan Kerja Dan Komitmen Organisasional Terhadap Turnover Intention

    Directory of Open Access Journals (Sweden)

    Ali Amran

    2017-04-01

    ABSTRACT       Employees are the most important resources of company. They are human resources to do and move all of the activities of company. Therefore, company needs to keep and maintain their job satisfaction and organizational commitment in order to reduce the intention to leave the company (turnover intention. It is necessary to study the relationship among job satisfaction, organizational commitment and turnover intention. This will give benefit to determine the important values of employees’ job satisfaction and organizational commitment and its influences on turnover intention. The research methods are descriptive survey and verificative survey that is used to assess the performance of independent variables: those are job satisfaction and organizational commitment,  and dependent variable: that is turnover intention with doing observation to employees of PT. Alexindo Bekasi. The result of this research is there is influence of job satisfaction and organizational commitment on turnover intention. This research is the improvement of existing researches which can be applied in the other companies specially for the human resource or employee behavior field.   Keywords: Job Satisfaction, Organizational Commitment, Turnover Intention

  20. The tear turnover and tear clearance tests - a review.

    Science.gov (United States)

    Garaszczuk, Izabela K; Montes Mico, Robert; Iskander, D Robert; Expósito, Alejandro Cerviño

    2018-03-01

    The aim is to provide a summary of methods available for the assessment of tear turnover and tear clearance rates. The review defines tear clearance and tear turnover and describes their implication for ocular surface health. Additionally, it describes main types of techniques for measuring tear turnover, including fluorescein tear clearance tests, techniques utilizing electromagnetic spectrum and tracer molecule and novel experimental techniques utilizing optical coherence tomography and fluorescein profilometry. Areas covered: Internet databases (PubMed, Science Direct, Google Scholar) and most frequently cited references were used as a principal resource of information on tear turnover rate and tear clearance rate, presenting methodologies and equipment, as well as their definition and implications for the anterior eye surface health and function. Keywords used for data-search were as follows: tear turnover, tear clearance, fluorescein clearance, scintigraphy, fluorophotometry, tear flow, drainage, tear meniscus dynamics, Krehbiel flow and lacrimal functional unit. Expert commentary: After decades, the topic of tear turnover assessment has been reintroduced. Recently, new techniques have been developed to propose less invasive, less time consuming and simpler methodologies for the assessment of tear dynamics that have the potential to be utilized in clinical practice.

  1. Turnover intention among intensive care unit nurses in Alexandria, Egypt.

    Science.gov (United States)

    Mosallam, Rasha; Hamidi, Samer; Elrefaay, Manal

    2015-06-01

    Given the difficulty in recruiting new nurses, it is imperative to retain those already in the profession. This cross-sectional study explored the relationship of demographic and work-related factors, burnout, conflict management and relationship between nurses and physicians on turnover intentions among ICU nurses in eight major hospitals in Alexandria, Egypt. Data on burnout, conflict management, nurse-physician communication, and turnover intention were collected by surveying 100 nurses in eight hospitals in Alexandria governorate. All nurses at the ICU of selected hospitals were approached (n=100) and a 47-item Likert scale questionnaire was administered to explore the factors affecting the turnover intention of ICU nurses in Alexandria. ICU nurses exhibited a mean score for turnover intention of 3.23 (mean score percentage 65.0%). There was a moderately positive statistically significant correlation between turnover intention and emotional exhaustion (r=0.29, Pturnover intention were emotional exhaustion and age. Nurses turnover intention at the ICU of the selected hospitals is high and is significantly associated with nurses' emotional exhaustion, poor nurse-physician communication, and nurses age.

  2. Stable isotopic constraints on global soil organic carbon turnover

    Science.gov (United States)

    Wang, Chao; Houlton, Benjamin Z.; Liu, Dongwei; Hou, Jianfeng; Cheng, Weixin; Bai, Edith

    2018-02-01

    Carbon dioxide release during soil organic carbon (SOC) turnover is a pivotal component of atmospheric CO2 concentrations and global climate change. However, reliably measuring SOC turnover rates on large spatial and temporal scales remains challenging. Here we use a natural carbon isotope approach, defined as beta (β), which was quantified from the δ13C of vegetation and soil reported in the literature (176 separate soil profiles), to examine large-scale controls of climate, soil physical properties and nutrients over patterns of SOC turnover across terrestrial biomes worldwide. We report a significant relationship between β and calculated soil C turnover rates (k), which were estimated by dividing soil heterotrophic respiration rates by SOC pools. ln( - β) exhibits a significant linear relationship with mean annual temperature, but a more complex polynomial relationship with mean annual precipitation, implying strong-feedbacks of SOC turnover to climate changes. Soil nitrogen (N) and clay content correlate strongly and positively with ln( - β), revealing the additional influence of nutrients and physical soil properties on SOC decomposition rates. Furthermore, a strong (R2 = 0.76; p turnover and thereby improving predictions of multiple global change influences over terrestrial C-climate feedback.

  3. Turnover intention of graduate nurses in South Korea.

    Science.gov (United States)

    Lee, Haejung; Lim, Yeonjung; Jung, Hee Young; Shin, Youn-Wha

    2012-06-01

    The purpose of this study was to identify the turnover intention of graduate nurses in South Korea and to explore the correlates of turnover intention. A descriptive, correlational design was used. The participants comprised 225 female nurses who were working at 13 general hospitals and who had accumulated turnover intention was 7.51. Turnover intention was found to be related to the number of beds in the hospital, workplace, and duration of job orientation (theory and practice), instruction by a preceptor, job stress, clinical competence, self-efficacy, and the practice environment. In the multivariate approach, the practice environment, job stress, and the workplace were found to be significantly related to turnover intention and accounted for 36% of the said intention in the studied graduate nurses. The results support that the characteristics of magnet hospitals that improve the practice environment could play a critical role in retaining nurses in hospitals. Managerial interventions that enhance the practice environment, reduce job stress, and place graduate nurses in nursing units with a single specialty could benefit the hospitals employing such nurses. Further research to explore the effects of managerial strategies on graduate nurses' turnover intention is warranted. © 2011 The Authors; Japan Journal of Nursing Science © 2011 Japan Academy of Nursing Science.

  4. Factors influencing turnover intention among registered nurses in Samar Philippines.

    Science.gov (United States)

    Labrague, Leodoro J; Gloe, Donna; McEnroe, Denise M; Konstantinos, Kostas; Colet, Paolo

    2018-02-01

    Despite the massive nurse migration and turnover of nurses in the Philippines, there remains a lack of studies describing factors influencing the migration of Filipino nurses. This study explored the effects of nurses' characteristics, work satisfaction, and work stress with the intent to leave an organization among registered nurses in the Philippines. This study utilized a descriptive, cross-sectional approach. One hundred sixty six (166) nurses participated in the study during the months of September 2015 to December 2015. Three standardized instruments were used in the study: Job Satisfaction Index (JSI), Job Stress Scale (JSS), and Turnover Intention Inventory Scale (TIIS). Data were analyzed using descriptive and inferential statistical tools. Nurses' ages were found to significantly influence their turnover intentions. Job satisfaction (β=-0.47, p=0.001) and job stress (β=0.23, p=0.001) strongly predicted turnover intentions in the nurses. The mean values for the job satisfaction scale, job stress scale, and turnover intention inventory scale were 3.13 (SD=0.60), 2.74 (SD=0.71), and 2.43 (SD=0.67) respectively. Several predictors of turnover intentions were determined in this study through nurses' age, job satisfaction, and job stress as being the most influential factors. Efforts to increase nurses' job satisfaction and reduce job stress should be implemented to halt further loss of these skilled groups of healthcare professionals. Copyright © 2017 Elsevier Inc. All rights reserved.

  5. Organisational commitment and turnover intentions: evidence from Nigerian paramilitary organisation

    Directory of Open Access Journals (Sweden)

    Dotun Olaleye Faloye

    2014-09-01

    Full Text Available This study explores the empirical link between different dimensions of organizational commitment and turnover intentions on Nigeria paramilitary organisation. A literature review of organizational commitment and employee turnover provides the basis for the research hypotheses. Four research hypotheses were formulated and tested at 95% and 99% confidence level. The study adopted a survey research design. A self-administered questionnaire was used, involving 144 respondents from selected paramilitary organisation in Akure, Nigeria to collect data and testing the existing theory. Data collected were analysed using both descriptive and inferential statistical techniques. In contrary to theory, the study revealed a weak positive relationship between organizational commitment dimensions (affective, continuance and normative and turnover intentions. The relationships are statistically significant expect the one between turnover intention and normative commitment which is statistically insignificant. The study concluded that the commitment of an employee to organisational goals, missions, and values is not enough to predict his/her stay in the organisation. There are other variables apart from organisational commitment that are predictor of employees’ intentions to quit. Thus, organisations should look beyond forces in their internal environment, when considering reduction in employee’s turnover intentions and the actual employee’s turnover.

  6. Reviewing Employee Turnover: Focusing on Proximal Withdrawal States and an Expanded Criterion

    Science.gov (United States)

    Hom, Peter W.; Mitchell, Terence R.; Lee, Thomas W.; Griffeth, Rodger W.

    2012-01-01

    We reconceptualize employee turnover to promote researchers' understanding and prediction of why employees quit or stay in employing institutions. A literature review identifies shortcomings with prevailing turnover dimensions. In response, we expand the conceptual domain of the turnover criterion to include multiple types of turnover (notably,…

  7. Multiscale change in reef coral species diversity and composition in the Tropical Eastern Pacific

    Science.gov (United States)

    Gomez, Catalina G.; Gonzalez, Andrew; Guzman, Hector M.

    2018-03-01

    Both natural and anthropogenic factors are changing coral-reef structure and function worldwide. Long-term monitoring has revealed declines in the local composition and species diversity of reefs. Here we report changes in coral-reef community structure over 12 yr (2000-2012) at 17 sites and three spatial scales (reef, gulf and country) in the Tropical Eastern Pacific (Panama). We found a significant 4% annual decline in species population sizes at the country and gulf scales, with significant declines ranging from 3 to 32% at all but one reef. No significant temporal change in expected richness was found at the country scale or in the Gulf of Chiriquí, but a 7% annual decline in expected species richness was found in the Gulf of Panama. There was a 2% increase in community evenness in the Gulf of Chiriquí, but no change in the Gulf of Panama. Significant temporal turnover was found at the country and gulf scales and at 29% of the reefs, a finding mostly explained by changes in species abundance, and losses and gains of rare species. Temporal trends in alpha and beta diversity metrics were explained by water temperature maxima, anomalies and variation that occurred even in the absence of a strong El Niño warming event.

  8. Journalism and Explaining News Content

    NARCIS (Netherlands)

    Albæk, E.; Skovsgaard, M.; de Vreese, C.H.; Nussbaum, J.F.

    Three models are presented to explain variation in news content. In the first model the explanation is based on the individual journalist, in the second model on the professional journalist, and in the third model on the organized journalist. The individual journalist model focuses on how the

  9. Can Marxism Explain America's Racism?

    Science.gov (United States)

    Willhelm, Sidney M.

    1980-01-01

    The Marxist interpretation of the Black experience in America has always had difficulty explaining various noneconomic aspects of racism. A perspective is needed that can blend racism as a variable in relationship with economic variables. To reach this perspective, the labor process within capitalism must be more fully understood. (Author/GC)

  10. Does market competition explain fairness?

    Science.gov (United States)

    Descioli, Peter

    2013-02-01

    The target article by Baumard et al. uses their previous model of bargaining with outside options to explain fairness and other features of human sociality. This theory implies that fairness judgments are determined by supply and demand but humans often perceive prices (divisions of surplus) in competitive markets to be unfair.

  11. Predicting rates of isotopic turnover across the animal kingdom: a synthesis of existing data.

    Science.gov (United States)

    Thomas, Stephen M; Crowther, Thomas W

    2015-05-01

    The stable isotopes of carbon ((12)C, (13)C) and nitrogen ((14)N, (15)N) represent powerful tools in food web ecology, providing a wide range of dietary information in animal consumers. However, identifying the temporal window over which a consumer's isotopic signature reflects its diet requires an understanding of elemental incorporation, a process that varies from days to years across species and tissue types. Though theory predicts body size and temperature are likely to control incorporation rates, this has not been tested empirically across a morphologically and phylogenetically diverse range of taxa. Readily available estimates of this relationship would, however, aid in the design of stable isotope food web investigations and improve the interpretation of isotopic data collected from natural systems. Using literature-derived turnover estimates from animal species ranging in size from 1 mg to 2000 kg, we develop a predictive tool for stable isotope ecologists, allowing for estimation of incorporation rates in the structural tissues of entirely novel taxa. In keeping with metabolic scaling theory, we show that isotopic turnover rates of carbon and nitrogen in whole organisms and muscle tissue scale allometrically with body mass raised approximately to the power -0.19, an effect modulated by body temperature. This relationship did not, however, apply to incorporation rates in splanchnic tissues, which were instead dependent on the thermoregulation tactic employed by an organism, being considerably faster in endotherms than ectotherms. We believe the predictive turnover equations we provide can improve the design of experiments and interpretation of results obtained in future stable isotopic food web studies. © 2014 The Authors. Journal of Animal Ecology © 2014 British Ecological Society.

  12. Mycorrhizal Glomus spp. vary in their effects on the dynamics and turnover of fine alfalfa (Medicago sativa L.) roots

    International Nuclear Information System (INIS)

    Ren, A.; Waly, N.; Chunhui, M.; Zhang, Q.; Liu, H.; Yang, J.

    2016-01-01

    The distribution of fine roots in the soil profile has important implications related to water and nutrient uptake. The Objective of this study was to compare the effects of different arbuscular mycorrhizal fungi (AMF) on the fine root dynamics of Medicago sativa L. cv. Sanditi. We used minirhizotrons to observe changes in fine root length density (FRLD, mm/cm2) and fine root surface area density (FRSAD, mm2/cm2) during the growing season. Fine root P concentrations and turnover rate were also measured. The colonization rate of fine roots varied depending on the AMF species. Colonization rates were highest when roots were inoculated with Glomus mosseae and lowest when roots were inoculated G. intraradices. Inoculation with AMF significantly increased both FRLD and FRSAD. G. versiforme increased FRLD and FRSAD most, whereas G. mosseae had the least effect. Inoculation with AMF also decreased fine root turnover rates. Inoculation with a mixture of AMF species increased fine root turnover and P concentrations more than inoculation with a single AMF species. Fine root length density increased to a maximum on Aug. 6 and then decreased. In comparison, FRSAD exhibited two peaks during the growing season. Overall, the Results indicated that inoculation with AMF can significantly promote fine root growth and P uptake by alfalfa growing on soil with low P availability. The AMF may preserve fine root function late in the growing season. (author)

  13. The small-scale species mobility in calcareous grasslands - example from southern Poland

    Directory of Open Access Journals (Sweden)

    Wojciech Bąba

    2011-01-01

    Full Text Available In this paper I use the different measures of species mobility to describe the fine small-scale dynamics of calcareous grassland built mainly by perennial species and developed in the highly heterogeneous habitat of calcareous rocks. The community showed the low dynamics on a plot-scale (100 m2 and a high one on the scale of 1 m2. However, the studied species differed greatly in calculated indices: turnover rate, (T; 6-64, residence time (RT; 0.5-21.8 y and carousel time (CT; 4-420 y as well as the observed tendency to persistence on the spots (PERSIST and their re-colonisation (AGAIN. This allowed to distinguish the three groups of species: (1 "core species" characterized by high frequency and low T and high CT and RT values, which determine the low dynamics of a community on the plot scale, (2 species with intermediate mobility rate and (3 the group with high mobility rate. The observed cumulative frequencies of all the studied species (CFobs were much lower than expected under the random re-assignation model (CFRR. Moreover, they were also lower than those predicted by random immigration model (CFRI. The results showed that the "complex carousel" model rather than "single carousel" one explained better the small-scale dynamics of calcareous grasslands.

  14. Turnover of registered nurses in Israel: characteristics and predictors.

    Science.gov (United States)

    Toren, Orly; Zelker, Revital; Lipschuetz, Michal; Riba, Shoshana; Reicher, Sima; Nirel, Nurit

    2012-05-01

    In an era of global and local nursing shortages, nursing turnover has negative consequences in terms of diminished quality of care, increased costs and economic losses and decreased job satisfaction. To examine the turnover rate of registered nurses in Israel by assessing the varying degree of turnover between economic sectors, between hospital and community facilities, and/or between types of hospitals; and by examining potential predicting factors of turnover among registered nurses. A national phone survey was undertaken in Israel consisting of a random sampling of registered nurses of working age (up to age 60). The subjects comprised 10% of a national database of 32,000 registered nurses. The turnover rate among working nurses in Israel currently stands at 23%. In addition, 13% of employed nurses have taken a temporary leave of absence for a period greater than 6 months in the past 10 years, most up to 1 year. While job satisfaction rates were relatively high (72%), Professional satisfaction rates were 60% with no significant difference between hospital and community nurses. The turnover rate of registered nurses from a hospital setting to the community was significantly higher (pcommunity registered nurses to hospitals. Predicting factors of turnover were found to be: young age, part-time work, lack of advanced professional education, academic education and low satisfaction with the nursing profession. The shift of nursing workforce is mainly from hospitals to community health settings. There is a need to monitor and understand the characteristics of job and professional satisfaction among hospital nurses in order to implement crucial organizational interventions and retain hospital nursing staffs. Since young nurses, nurses working part time and nurses with no advanced professional and academic education, tend to move more than others, efforts should be targeted at these specific groups. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

  15. A case study into labour turnover within an NHS Trust.

    Science.gov (United States)

    Bamford, David; Hall, Catherine

    2007-02-01

    This paper investigates turnover in a British NHS Trust, to find out why staff left and whether factors identified in the literature with regards to improving turnover were pertinent to the organization. The research also investigated staff groups with high turnover--staff with less than 12 months service, and the unqualified nursing staff group--to ascertain whether there were any reasons for leaving or areas of dissatisfaction particular to these groups. The outcomes of the research complied with much of the published research with some interesting differences. The main reasons for leaving were identified as moving house, promotion or career development and taking up education and training opportunities elsewhere. There was no evidence of 'level of pay', commonly given as a significant influence behind turnover, as a reason for leaving. It was also found that the retention strategies identified in the published research were mainly applicable to the research, with evidence to support the improvement of line management skills, training and development, career development, appraisal, communications and induction in order to reduce turnover. There was less evidence for introducing work-life balance policies, improving communications, pay and working relationships as retention strategies. Recommendations for future management of labour turnover within the NHS Trust and elsewhere are made, with observations about the validity of some existing models. The core contribution of this research is in adding to the body of knowledge about labour turnover issues. This is of value to those working in the UK health-care and wider public sector. Specific recommendations for future research are made.

  16. Explaining Disparities in Unemployment Dynamics

    OpenAIRE

    Karanassou, Marika; Snower, Dennis J.

    1993-01-01

    This paper attempts to explain disparities among the unemployment experiences of different OECD countries in terms of the `fragility' of the short-run unemployment equilibrium (the impact of labour market shocks on the short-run unemployment rate) and the lag structure of the employment determination, wage setting, and labour force participation decisions. The effects of this lag structure on unemployment dynamics are captured through two general measures of `unemployment persistence' (occurr...

  17. Explaining the Gender Wealth Gap

    Science.gov (United States)

    Ruel, Erin; Hauser, Robert M.

    2013-01-01

    To assess and explain the United States’ gender wealth gap, we use the Wisconsin Longitudinal Study to examine wealth accumulated by a single cohort over 50 years by gender, by marital status, and limited to the respondents who are their family’s best financial reporters. We find large gender wealth gaps between currently married men and women, and never-married men and women. The never-married accumulate less wealth than the currently married, and there is a marital disruption cost to wealth accumulation. The status-attainment model shows the most power in explaining gender wealth gaps between these groups explaining about one-third to one-half of the gap, followed by the human-capital explanation. In other words, a lifetime of lower earnings for women translates into greatly reduced wealth accumulation. A gender wealth gap remains between married men and women after controlling for the full model that we speculate may be related to gender differences in investment strategies and selection effects. PMID:23264038

  18. Carbon Turnover during Effluent Application to the Land: A Potential Role for Vegetation?

    Directory of Open Access Journals (Sweden)

    Vasileios A. Tzanakakis

    2015-01-01

    Full Text Available This work investigates the effect of plant species (Eucalyptus camaldulensis vs. Arundo donax on carbon (C turnover during wastewater application to the land. The study was carried out in 40-liter pots under field conditions and plant species were treated either with pre-treated municipal wastewater or freshwater. Plant species had a strong effect on soil organic matter with pots planted with E. camaldulensis showing greater values than pots planted with A. donax. In accordance, greater respiration rates were measured in E. camaldulensis pots compared to those planted with A. donax. The respiration rate followed a decreasing trend with the progress of the season for both species. These findings suggest differences in soil microbial community composition and/or activity in the rhizosphere of plant species. Minor effects of plant species or effluent were observed in dissolved organic carbon, protein, and hexoses content. In conclusion, the results of the present study reveal an important role of plant species on C cycling in terrestrial environments with potential implications on the sequestration of C and release of nutrients and pollutants.

  19. Cu uptake and turnover in both Cu-acclimated and non-acclimated rainbow trout (Oncorhynchus mykiss)

    DEFF Research Database (Denmark)

    Grosell, M.; Hogstrand, C.; Wood, C.M.

    1997-01-01

    -acclimation clearly involves changes in copper accumulation kinetics in the plasma. The acclimated fish showed a 65% reduced Cu-64 accumulation after 65 h and an increased turnover of Cu in the plasma compared to the non-acclimated fish. Total Cu in the plasma increased by 59% after 3 h of exposure in the non...... aortic catheter. By measuring both Cu-64 accumulation and total Cu concentrations, we were able to analyse the ongoing uptake and turnover of ambient Cu, independent of any Cu already present in the fish. Plasma accounted for at least 90% of the Cu-64 labelled Cu present in the blood and Cu...... h of exposure. Acclimation did not have an unambiguous effect on branchial Cu uptake and differences in branchial uptake could not explain the reduced accumulation in the plasma. The rapidly exchangeable Cu pools were 54% in the gills and 33% in the liver, suggesting a considerable hepatic Cu...

  20. Dead wood biomass and turnover time, measured by radiocarbon, along a subalpine elevation gradient.

    Science.gov (United States)

    Kueppers, Lara M; Southon, John; Baer, Paul; Harte, John

    2004-12-01

    Dead wood biomass can be a substantial fraction of stored carbon in forest ecosystems, and coarse woody debris (CWD) decay rates may be sensitive to climate warming. We used an elevation gradient in Colorado Rocky Mountain subalpine forest to examine climate and species effects on dead wood biomass, and on CWD decay rate. Using a new radiocarbon approach, we determined that the turnover time of lodgepole pine CWD (340+/-130 years) was roughly half as long in a site with 2.5-3 degrees C warmer air temperature, as that of pine (630+/-400 years) or Engelmann spruce CWD (800+/-960 and 650+/-410 years) in cooler sites. Across all sites and both species, CWD age ranged from 2 to 600 years, and turnover time was 580+/-180 years. Total standing and fallen dead wood biomass ranged from 4.7+/-0.2 to 54+/-1 Mg ha(-1), and from 2.8 to 60% of aboveground live tree biomass. Dead wood biomass increased 75 kg ha(-1) per meter gain in elevation and decreased 13 Mg ha(-1) for every degree C increase in mean air temperature. Differences in biomass and decay rates along the elevation gradient suggest that climate warming will lead to a loss of dead wood carbon from subalpine forest.

  1. The relationship between job satisfaction, burnout, and turnover intention among physicians from urban state-owned medical institutions in Hubei, China: a cross-sectional study

    Directory of Open Access Journals (Sweden)

    Zhang Yimin

    2011-09-01

    Full Text Available Abstract Background Throughout China, a growing number of physicians are leaving or intending to depart from their organizations owing to job dissatisfaction. Little information is available about the role of occupational burnout in this association. We set out to analyze the relationship between job satisfaction, burnout, and turnover intention, and further to determine whether occupational burnout can serve as a mediator among Chinese physicians from urban state-owned medical institutions. Methods A cross-sectional survey was carried out in March 2010 in Hubei Province, central China. The questionnaires assessed sociodemographic characteristics, job satisfaction, burnout, and turnover intention. The job satisfaction and occupational burnout instruments were obtained by modifying the Chinese Physicians' Job Satisfaction Questionnaire (CPJSQ and the Chinese Maslach Burnout Inventory (CMBI, respectively. Such statistical methods as one-way ANOVA, Pearson correlation, GLM-univariate and structural equation modeling were used. Results Of the 1600 physicians surveyed, 1451 provided valid responses. The respondents had medium scores (3.18 +/-0.73 on turnover intention, in which there was significant difference among the groups from three urban areas with different development levels. Turnover intention, which significantly and negatively related to all job-satisfaction subscales, positively related to each subscale of burnout syndrome. Work environment satisfaction (b = -0.074, p , job rewards satisfaction (b = -0.073, p , organizational management satisfaction (b = -0.146, p , and emotional exhaustion (b = 0.135, p were identified as significant direct predictors of the turnover intention of physicians, with 41.2% of the variance explained unitedly, under the control of sociodemographic variables, among which gender, age, and years of service were always significant. However, job-itself satisfaction no longer became significant, with the estimated

  2. Health insurance, cost expectations, and adverse job turnover.

    Science.gov (United States)

    Ellis, Randall P; Albert Ma, Ching-To

    2011-01-01

    Because less healthy employees value health insurance more than the healthy ones, when health insurance is newly offered job turnover rates for healthier employees decline less than turnover rates for the less healthy. We call this adverse job turnover, and it implies that a firm's expected health costs will increase when health insurance is first offered. Health insurance premiums may fail to adjust sufficiently fast because state regulations restrict annual premium changes, or insurers are reluctant to change premiums rapidly. Even with premiums set at the long run expected costs, some firms may be charged premiums higher than their current expected costs and choose not to offer insurance. High administrative costs at small firms exacerbate this dynamic selection problem. Using 1998-1999 MEDSTAT MarketScan and 1997 Employer Health Insurance Survey data, we find that expected employee health expenditures at firms that offer insurance have lower within-firm and higher between-firm variance than at firms that do not. Turnover rates are systematically higher in industries in which firms are less likely to offer insurance. Simulations of the offer decision capturing between-firm health-cost heterogeneity and expected turnover rates match the observed pattern across firm sizes well. 2010 John Wiley & Sons, Ltd.

  3. [Cost of nursing turnover in a Teaching Hospital].

    Science.gov (United States)

    Ruiz, Paula Buck de Oliveira; Perroca, Marcia Galan; Jericó, Marli de Carvalho

    2016-02-01

    To map the sub processes related to turnover of nursing staff and to investigate and measure the nursing turnover cost. This is a descriptive-exploratory study, classified as case study, conducted in a teaching hospital in the southeastern, Brazil, in the period from May to November 2013. The population was composed by the nursing staff, using Nursing Turnover Cost Calculation Methodology. The total cost of turnover was R$314.605,62, and ranged from R$2.221,42 to R$3.073,23 per employee. The costs of pre-hire totaled R$101.004,60 (32,1%), and the hiring process consumed R$92.743,60 (91.8%) The costs of post-hire totaled R$213.601,02 (67,9%), for the sub process decreased productivity, R$199.982,40 (93.6%). The study identified the importance of managing the cost of staff turnover and the financial impact of the cost of the employee termination, which represented three times the average salary of the nursing staff.

  4. Investigation on the turnover of plant proteins. 2

    International Nuclear Information System (INIS)

    Becker, R.; Winkler, E.; Jung, K.; Huebner, G.

    1981-01-01

    Based on kinetic analyses of amino acid and protein turnover by means of compartment models the synthesis and degradation of the soluble proteins in etiolated epicotyl segments of Pisum sativum L. as well as their dependence on the herbicide 2'-methyl-4'-chlorophenoxyacetic acid (MCPA) were determined quantitatively. The segments were incubated for 10 h in a medium containing 14 C-leucine and subsequently placed in an inactive medium. The radioactivity in the soluble proteins and in the amino acid fraction was followed up for a total of 24 h. A 3-pool model in which the total measurable amino acid pool was divided into a direct precursor pool for protein synthesis and into a degradation pool was best suited to interpret the data. The turnover rate for the soluble proteins of untreated epicotyl segments was determined to be 0.058 h -1 ; at an MCPA concentration of 10 -4 M this value was nearly doubled. An increased proteolytic activity in the epicotyl segments ran parallel to the change of the turnover rate in dependence on MCPA concentration. The heterogeneity of the soluble protein with respect to the turnover rate was investigated by means of 3 H/ 14 C double labelling for individual protein fractions separated by gel electrophoresis. The results obtained in this way were comparable with those of the total pool turnover. (author)

  5. Relating microbial community structure to functioning in forest soil organic carbon transformation and turnover.

    Science.gov (United States)

    You, Yeming; Wang, Juan; Huang, Xueman; Tang, Zuoxin; Liu, Shirong; Sun, Osbert J

    2014-03-01

    Forest soils store vast amounts of terrestrial carbon, but we are still limited in mechanistic understanding on how soil organic carbon (SOC) stabilization or turnover is controlled by biotic and abiotic factors in forest ecosystems. We used phospholipid fatty acids (PLFAs) as biomarker to study soil microbial community structure and measured activities of five extracellular enzymes involved in the degradation of cellulose (i.e., β-1,4-glucosidase and cellobiohydrolase), chitin (i.e., β-1,4-N-acetylglucosaminidase), and lignin (i.e., phenol oxidase and peroxidase) as indicators of soil microbial functioning in carbon transformation or turnover across varying biotic and abiotic conditions in a typical temperate forest ecosystem in central China. Redundancy analysis (RDA) was performed to determine the interrelationship between individual PFLAs and biotic and abiotic site factors as well as the linkage between soil microbial structure and function. Path analysis was further conducted to examine the controls of site factors on soil microbial community structure and the regulatory pathway of changes in SOC relating to microbial community structure and function. We found that soil microbial community structure is strongly influenced by water, temperature, SOC, fine root mass, clay content, and C/N ratio in soils and that the relative abundance of Gram-negative bacteria, saprophytic fungi, and actinomycetes explained most of the variations in the specific activities of soil enzymes involved in SOC transformation or turnover. The abundance of soil bacterial communities is strongly linked with the extracellular enzymes involved in carbon transformation, whereas the abundance of saprophytic fungi is associated with activities of extracellular enzymes driving carbon oxidation. Findings in this study demonstrate the complex interactions and linkage among plant traits, microenvironment, and soil physiochemical properties in affecting SOC via microbial regulations.

  6. The Impact of Job Satisfaction on the Turnover Intent of Executive Level Central Office Administrators in Texas Public School Districts: A Quantitative Study of Work Related Constructs

    Directory of Open Access Journals (Sweden)

    Johnny O’Connor

    2018-05-01

    Full Text Available The purpose of this study was to examine the relationship between job satisfaction and turnover intent of executive level central office administrators in Texas public school districts. For the intent of this study, executive level central office administrators were defined as staff members who serve in one of the following roles in a school district: assistant, associate, area, or deputy superintendent. The data were collected from a random sample of 234 participants in which survey instruments of job satisfaction and turnover intent were used. Each instrument was created on a five-point Likert scale. Based on the results of the study, it was concluded that a moderate inverse relationship exists between job satisfaction and turnover intent and job satisfaction explained 41.3% of an executive level central office administrator’s intent for turnover. Research related to this employee group is lacking. Therefore, not much is known regarding how it relates to their attitude towards work-related factors. Learning more about job satisfaction and turnover intention of these individuals could have long term implications since it relates to mitigating the shortage of superintendent candidates available to fill the growing number of vacancies as well as recruitment, retention, and increased work productivity of these staff.

  7. Explaining the Evolution of Poverty

    DEFF Research Database (Denmark)

    Arndt, Channing; Hussain, Azhar; Jones, Edward Samuel

    2012-01-01

    We provide a comprehensive approach for analyzing the evolution of poverty using Mozambique as a case study. Bringing together data from disparate sources, we develop a novel “back-casting” framework that links a dynamic computable general equilibrium model to a micro-simulation poverty module....... This framework provides a new approach to explaining and decomposing the evolution of poverty, as well as to examining rigorously the coherence between poverty, economic growth, and inequality outcomes. Finally, various simple but useful and rarely-applied approaches to considering regional changes in poverty...

  8. Changes of Protein Turnover in Aging Caenorhabditis elegans

    Energy Technology Data Exchange (ETDEWEB)

    Dhondt, Ineke; Petyuk, Vladislav A.; Bauer, Sophie; Brewer, Heather M.; Smith, Richard D.; Depuydt, Geert; Braeckman, Bart P.

    2017-07-05

    Protein turnover rates severely decline in aging organisms, including C. elegans. However, limited information is available on turnover dynamics at the individual protein level during aging. We followed changes in protein turnover at one-day resolution using a multiple-pulse 15Nlabeling and accurate mass spectrometry approach. Forty percent of the proteome shows gradual slowdown in turnover with age, whereas only few proteins show increased turnover. Decrease in protein turnover was consistent for only a minority of functionally related protein subsets, including tubulins and vitellogenins, whereas randomly diverging turnover patterns with age were the norm. Our data suggests increased heterogeneity of protein turnover of the translation machinery, whereas protein turnover of ubiquitin-proteasome and antioxidant systems are well-preserved over time. Hence, we presume that maintenance of quality control mechanisms is a protective strategy in aging worms, although the ultimate proteome collapse is inescapable.

  9. Quality of working life: an antecedent to employee turnover intention.

    Science.gov (United States)

    Mosadeghrad, Ali Mohammad

    2013-06-01

    The purpose of this study was to measure the level of quality of work life (QWL) among hospital employees in Iran. Additionally, it aimed to identify the factors that are critical to employees' QWL. It also aimed to test a theoretical model of the relationship between employees' QWL and their intention to leave the organization. A survey study was conducted based on a sample of 608 hospital employees using a validated questionnaire. Face, content and construct validity were conducted on the survey instrument. Hospital employees reported low QWL. Employees were least satisfied with pay, benefits, job promotion, and management support. The most important predictor of QWL was management support, followed by job proud, job security and job stress. An inverse relationship was found between employees QWL and their turnover intention. This study empirically examined the relationships between employees' QWL and their turnover intention. Managers can take appropriate actions to improve employees' QWL and subsequently reduce employees' turnover.

  10. Estimation of Employee Turnover with Competing Risks Models

    Directory of Open Access Journals (Sweden)

    Grzenda Wioletta

    2015-12-01

    Full Text Available Employee turnover accompanies every business organization, regardless of the industry and size. Nowadays, many companies struggle with problems related to the lack of sufficient information about the nature of employee turnover processes. Therefore, comprehensive analysis of these processes is necessary. This article aims to examine the turnover of employees from a big manufacturing company using competing risks models with covariates and without covariates. This technique allows to incorporate the information about the type of employment contract termination. Moreover, Cox proportional hazard model enables the researcher to analyse simultaneously multiple factors that affect employment duration. One of the major observations is that employee remuneration level differentiates most strongly the risk of job resignation.

  11. PENGARUH JOB SATISFACTION TERHADAP OCB DAN TURNOVER INTENTION

    Directory of Open Access Journals (Sweden)

    Febru Rida Ningsih

    2015-06-01

    Full Text Available This article aims to provide the impact of job satisfaction to OCB and turnover intention. This study used a quantitative method with a statistical analysis. Simple analysis regression used to test each hypotheses. The object of this research is a branch of national bank. Population in this research are entire employees of a brach of national bank that is e non frontliner employees. Non-probability sampling is used of this reseach. The measurement of job satiafaction and turnover intention variables used likert scale that developed by Rinaldi (2008 and measurement of OCB variable adopted from  Organ (1988.  The result of this research has shown that hypotheses one is rejected and hypotheses two is accepted. Eventually, through this article, an understanding that job satisfaction does not significantly influence to OCB but job satisfaction has significant influence to turnover intention.

  12. No turnover in lens lipids for the entire human lifespan.

    Science.gov (United States)

    Hughes, Jessica R; Levchenko, Vladimir A; Blanksby, Stephen J; Mitchell, Todd W; Williams, Alan; Truscott, Roger J W

    2015-03-11

    Lipids are critical to cellular function and it is generally accepted that lipid turnover is rapid and dysregulation in turnover results in disease (Dawidowicz 1987; Phillips et al., 2009; Liu et al., 2013). In this study, we present an intriguing counter-example by demonstrating that in the center of the human ocular lens, there is no lipid turnover in fiber cells during the entire human lifespan. This discovery, combined with prior demonstration of pronounced changes in the lens lipid composition over a lifetime (Hughes et al., 2012), suggests that some lipid classes break down in the body over several decades, whereas others are stable. Such substantial changes in lens cell membranes may play a role in the genesis of age-related eye disorders. Whether long-lived lipids are present in other tissues is not yet known, but this may prove to be important in understanding the development of age-related diseases.

  13. Cogema in 1996: increasing turnover and stable net results

    International Nuclear Information System (INIS)

    Anon.

    1997-01-01

    This short article gives some financial informations about the Cogema group for 1996. The net result for 1996 reached 977 millions of French Francs (FF) with respect to 973 for the previous year. The turnover reached 34.427 billions of FF in 1996 and 30.611 in 1995, which represents a 12.5% growth. In the mining sector, the turnover has decreased to 2.853 billions of FF with respect to 3.238 in 1995. In the engineering and industry services sector the turnover of the overall companies, with the exception of Cogema, has considerably progressed (2.199 billions of FF in 1996, 1.738 in 1995). (J.S.)

  14. DNA turnover and strand breaks in Escherichia coli

    International Nuclear Information System (INIS)

    Hanawalt, P.; Grivell, A.; Nakayama, H.

    1975-01-01

    The extent of DNA turnover has been measured in a dnaB mutant of Escherichia coli, temperature sensitive for semiconservative DNA replication. At the nonpermissive temperature about 0.02 percent of the deoxynucleotides in DNA are exchanged per generation period. This turnover rate is markedly depressed in the presence of rifampicin. During thymine starvation strand breaks accumulate in the DNA of E. coli strains that are susceptible to thymineless death. Rifampicin suppresses the appearance of these breaks, consistent with our hypothesis that transcription may be accompanied by repairable single-strand breaks in DNA. DNA turnover is enhanced severalfold in strands containing 5-bromodeoxyuridine in place of thymidine, possibly because the analog (or the deoxyuridine, following debromination) is sometimes recognized and excised

  15. Peningkatan Komitmen Organisasi untuk Menurunkan Angka Turnover Karyawan

    Directory of Open Access Journals (Sweden)

    Elita Halimsetiono

    2014-05-01

    Full Text Available Komitmen organisasi dapat diartikan sebagai suatu sikap yang harus dimiliki oleh setiap pegawai untuk menunjukkan loyalitas terhadap organisasi tempat mereka bekerja. Pada dasarnya, komitmen organisasi berkaitan erat dengan aspek-aspek psikologis dalam menerima dan memercayai nilai-nilai dan tujuan organisasi yang muncul sebagai keinginan untuk tetap mempertahankan keanggotaan dalam organisasi. Permasalahan yang sering dikaitkan dengan rendahnya komitmen organisasi adalah pindah kerja (turnover. Masalah ini memiliki dampak yang merugikan organisasi karena dapat menghambat efektivitas dan efisiensi kerja yang selanjutnya akan menurunkan tingkat produktivitas organisasi. Oleh karena itu, untuk mencegah tingginya turnover karyawan, organisasi perlu meningkatkan komitmen organisasi karyawannya. Caranya adalah dengan mengetahui faktor-faktor apa saja yang memengaruhi komitmen organisasi dan bagaimana cara untuk meningkatkan komitmen organisasi tersebut. Artikel ini membahas faktor-faktor apa saja yang memengaruhi komitmen organisasi dan cara-cara yang dapat digunakan untuk meningkatkan komitmen organisasi sebagai upaya untuk menurunkan angka turnover karyawan. Organizational commitment can be interpreted as an attitude that should be owned by every employee to demonstrate loyalty to the organization where they work. Basically, organizational commitment is closely related to the psychological aspects in the acceptance and confidence to the values and objectives of the organization that are presented through the existence of a desire to maintain membership in the organization. Problems which are associated with low organizational commitment is turnover. This problem has an adverse impact on the organization because it can inhibit the effectiveness and efficiency of the work that would lower the level of productivity of the organization. Therefore, to prevent the high employee turnover, the organization should increase the organizational commitment of

  16. 'Memory and molecular turnover,' 30 years after inception.

    Science.gov (United States)

    Meagher, Richard B

    2014-01-01

    In 1984 Sir Francis Crick hypothesized that memory is recorded in the brain as reversible modifications to DNA and protein, but acknowledged that most biomolecules turn over too rapidly to account for long-term memories. To accommodate this possible paradox he modeled an enzymatic mechanism to maintain modifications on hemi-modified multimeric symmetrical molecules. While studies on the turnover of chromatin modifications that may be involved in memory are in their infancy, an exploration of his model in the light of modern epigenetics produced somewhat surprising results. The molecular turnover rates for two classes of chromatin modifications believed to record and store durable memories were approximated from experiments using diverse approaches and were found to be remarkably short. The half-lives of DNA cytosine methylation and post-translationally modified nucleosomal histones are measured in hours and minutes, respectively, for a subset of sites on chromatin controlling gene expression. It appears likely that the turnover of DNA methylation in the brain and in neurons, in particular, is even more rapid than in other cell types and organs, perhaps accommodating neuronal plasticity, learning, and memory. The machinery responsible for the rapid turnover of DNA methylation and nucleosomal histone modifications is highly complex, partially redundant, and appears to act in a sequence specific manner. Molecular symmetry plays an important part in maintaining site-specific turnover, but its particular role in memory maintenance is unknown. Elucidating Crick's paradox, the contradiction between rapid molecular turnover of modified biomolecules and long-term memory storage, appears fundamental to understanding cognitive function and neurodegenerative disease.

  17. Employees' responses to an organizational merger: Intraindividual change in organizational identification, attachment, and turnover.

    Science.gov (United States)

    Sung, Wookje; Woehler, Meredith L; Fagan, Jesse M; Grosser, Travis J; Floyd, Theresa M; Labianca, Giuseppe Joe

    2017-06-01

    The authors used pre-post merger data from 599 employees experiencing a major corporate merger to compare 3 conceptual models based on the logic of social identity theory (SIT) and exchange theory to explain employees' merger responses. At issue is how perceived change in employees' own jobs and roles (i.e., personal valence) and perceived change in their organization's status and merger appropriateness (i.e., organizational valence) affect their changing organizational identification, attachment attitudes, and voluntary turnover. The first model suggests that organizational identification and organizational attachment develop independently and have distinct antecedents. The second model posits that organizational identification mediates the relationships between change in organizational and personal valence and change in attachment and turnover. The third model posits that change in personal valence moderates the relationship between changes in organizational valence and in organizational identification and attachment. Using latent difference score (LDS) modeling in an SEM framework and survival analysis, the results suggest an emergent fourth model that integrates the first and second models: Although change in organizational identification during the merger mediates the relationship between change in personal status and organizational valence and change in attachment, there is a direct and unmediated relationship between change in personal valence and attachment. This integrated model has implications for M&A theory and practice. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  18. Platelet monoamine oxidase: specific activity and turnover number in headache

    International Nuclear Information System (INIS)

    Summers, K.M.; Brown, G.K.; Craig, I.W.; Peatfield, R.; Rose, F.C.

    1982-01-01

    Monoamine oxidase turnover numbers (molecules of substrate converted to product per minute per active site) have been calculated for the human platelet enzyme using [ 3 H]pargyline. Headache patients with high and low monoamine oxidase specific activities relative to controls were found to have turnover numbers very close to those for controls. This finding suggests that their specific activities vary because of differences in the concentration of active monoamine oxidase molecules, rather than differences in the ability of those enzyme molecules to catalyse the deamination reaction. (Auth.)

  19. [Pharmaceutical logistic in turnover of pharmaceutical products of Azerbaijan].

    Science.gov (United States)

    Dzhalilova, K I

    2009-11-01

    Development of pharmaceutical logistic system model promotes optimal strategy for pharmaceutical functioning. The goal of such systems is organization of pharmaceutical product's turnover in required quantity and assortment, at preset time and place, at a highest possible degree of consumption readiness with minimal expenses and qualitative service. Organization of the optimal turnover chain in the region is offered to start from approximate classification of medicaments by logistic characteristics. Supplier selection was performed by evaluation of timeliness of delivery, quality of delivered products (according to the minimum acceptable level of quality) and time-keeping of time spending for orders delivery.

  20. Explaining the harmonic sequence paradox.

    Science.gov (United States)

    Schmidt, Ulrich; Zimper, Alexander

    2012-05-01

    According to the harmonic sequence paradox, an expected utility decision maker's willingness to pay for a gamble whose expected payoffs evolve according to the harmonic series is finite if and only if his marginal utility of additional income becomes zero for rather low payoff levels. Since the assumption of zero marginal utility is implausible for finite payoff levels, expected utility theory - as well as its standard generalizations such as cumulative prospect theory - are apparently unable to explain a finite willingness to pay. This paper presents first an experimental study of the harmonic sequence paradox. Additionally, it demonstrates that the theoretical argument of the harmonic sequence paradox only applies to time-patient decision makers, whereas the paradox is easily avoided if time-impatience is introduced. ©2011 The British Psychological Society.

  1. Substance Abuse-Specific Knowledge Transfer or Loss? Treatment Program Turnover versus Professional Turnover among Substance Abuse Clinicians

    Science.gov (United States)

    Eby, Lillian T.; Curtis, Sara L.

    2014-01-01

    This longitudinal study investigated the extent to which substance abuse (SA) clinician turnover is associated with SA-specific knowledge loss due to change in professions (professional turnover) versus SA-specific knowledge transfer due to movement from one SA clinical setting to another (treatment program turnover). For this study, clinicians had to voluntarily leave their current treatment program. Eligible clinicians completed a quantitative survey while employed and a qualitative post-employment exit interview 1 year later. Compared to those that exited the SA profession (N = 99), clinicians who changed treatment programs (N = 120) had greater SA-specific formal knowledge and were more likely to be personally in recovery. No differences were found between the two groups in terms of SA-specific practical knowledge. PMID:25115318

  2. Nitric oxide turnover in permeable river sediment

    DEFF Research Database (Denmark)

    Schreiber, Frank; Stief, Peter; Kuypers, Marcel M M

    2014-01-01

    We measured nitric oxide (NO) microprofiles in relation to oxygen (O2) and all major dissolved N-species (ammonium, nitrate, nitrite, and nitrous oxide [N2O]) in a permeable, freshwater sediment (River Weser, Germany). NO reaches peak concentrations of 0.13 μmol L-1 in the oxic zone and is consumed......-nitroso-N-acetylpenicillamine (SNAP) (1) confirmed denitrification as the main NO consumption pathway, with N2O as its major product, (2) showed that denitrification combines one free NO molecule with one NO molecule formed from nitrite to produce N2O, and (3) suggested that NO inhibits N2O reduction....

  3. Exploring correlates of turnover among nursing assistants in the National Nursing Home Survey.

    Science.gov (United States)

    Temple, April; Dobbs, Debra; Andel, Ross

    2011-01-01

    High turnover of nursing assistants (NAs) has implications for the quality of nursing home care. Greater understanding of correlates of NA turnover is needed to provide insight into possible retention strategies. This study examined nursing home organizational characteristics and specific job characteristics of staff in relation to turnover of NAs. Cross-sectional data on 944 nationally representative nursing homes were derived from the 2004 National Nursing Home Survey. Using a 3-month turnover rate, 25% of the facilities with the lowest turnover rates were classified as low turnover, 25% of the facilities with the highest turnover were classified as high turnover, and the remaining 50% of the facilities were classified as moderate turnover. Multinomial logistic regression was used to examine organizational and job characteristics associated with low and high turnover compared with moderate turnover. One organizational characteristic, staffing levels at or greater than 4.0 hours per patient day, was associated with greater odds of low NA turnover and reduced odds of high NA turnover. Job characteristics including higher wages and union membership were associated with greater odds of low NA turnover, whereas wages, fully paid health insurance, employee assistance benefits, and involvement in resident care planning were associated with reduced odds of high NA turnover. The results of this study suggest that job characteristics of NA staff may be particularly important for turnover. Specifically, the provision of competitive wages and benefits (particularly health insurance) and involvement of NAs in resident care planning could potentially reduce NA turnover, as could maintaining high levels of nurse staffing.

  4. Testing deep-sea biodiversity paradigms on abyssal nematode genera and Acantholaimus species

    Science.gov (United States)

    Lins, Lidia; da Silva, Maria Cristina; Neres, Patrícia; Esteves, André Morgado; Vanreusel, Ann

    2018-02-01

    Biodiversity patterns in the deep sea have been extensively studied in the last decades. In this study, we investigated whether reputable concepts in deep-sea ecology also explain diversity and distribution patterns of nematode genera and species in the abyss. Among them, three paradigms were tackled: (1) the deep sea is a highly diverse environment at a local scale, while on a regional and even larger geographical scale, species and genus turnover is limited; (2) the biodiversity of deep-sea nematode communities changes with the nature and amount of organic matter input from the surface; and (3) patch-mosaic dynamics of the deep-sea environment drive local diversity. To test these hypotheses, diversity and density of nematode assemblages and of species of the genus Acantholaimus were studied along two abyssal E-W transects. These two transects were situated in the Southern Ocean ( 50°S) and the North Atlantic ( 10°N). Four different hierarchical scales were used to compare biodiversity: at the scale of cores, between stations from the same region, and between regions. Results revealed that the deep sea harbours a high diversity at a local scale (alpha diversity), but that turnover can be shaped by different environmental drivers. Therefore, these results question the second part of the paradigm about limited species turnover in the deep sea. Higher surface primary productivity was correlated with greater nematode densities, whereas diversity responses to the augmentation of surface productivity showed no trend. Areas subjected to a constant and low food input revealed similar nematode communities to other oligotrophic abyssal areas, while stations under high productivity were characterized by different dominant genera and Acantholaimus species, and by a generally low local diversity. Our results corroborate the species-energy hypothesis, where productivity can set a limit to the richness of an ecosystem. Finally, we observed no correlation between sediment

  5. Explaining evolution via constrained persistent perfect phylogeny

    Science.gov (United States)

    2014-01-01

    Background The perfect phylogeny is an often used model in phylogenetics since it provides an efficient basic procedure for representing the evolution of genomic binary characters in several frameworks, such as for example in haplotype inference. The model, which is conceptually the simplest, is based on the infinite sites assumption, that is no character can mutate more than once in the whole tree. A main open problem regarding the model is finding generalizations that retain the computational tractability of the original model but are more flexible in modeling biological data when the infinite site assumption is violated because of e.g. back mutations. A special case of back mutations that has been considered in the study of the evolution of protein domains (where a domain is acquired and then lost) is persistency, that is the fact that a character is allowed to return back to the ancestral state. In this model characters can be gained and lost at most once. In this paper we consider the computational problem of explaining binary data by the Persistent Perfect Phylogeny model (referred as PPP) and for this purpose we investigate the problem of reconstructing an evolution where some constraints are imposed on the paths of the tree. Results We define a natural generalization of the PPP problem obtained by requiring that for some pairs (character, species), neither the species nor any of its ancestors can have the character. In other words, some characters cannot be persistent for some species. This new problem is called Constrained PPP (CPPP). Based on a graph formulation of the CPPP problem, we are able to provide a polynomial time solution for the CPPP problem for matrices whose conflict graph has no edges. Using this result, we develop a parameterized algorithm for solving the CPPP problem where the parameter is the number of characters. Conclusions A preliminary experimental analysis shows that the constrained persistent perfect phylogeny model allows to

  6. Job Demand and Job Resources related to the turnover intention of public health nurses: An analysis using a Job Demands-Resources model.

    Science.gov (United States)

    Iguchi, Aya

    2016-01-01

    Objectives The purpose of this study was to investigate the job demands and job resources of public health nurses based on the Job Demands-Resources (JD-R) model, and to build a model that can estimate turnover intention based on job demands and job resources.Method By adding 12 items to the existing questionnaire, the author created a questionnaire consisting of 10 factors and 167 items, and used statistical analysis to examine job demands and job resources in relation to turnover intention.Results Out of 2,668 questionnaires sent, 1993 (72.5%) were returned. Considering sex-based differences in occupational stress, I analyzed women's answers in 1766 (66.2%) mails among the 1798 valid responses. The average age of respondents was 41.0±9.8 years, and the mean service duration was 17.0±10.0 years. For public health nurses, there was a turnover intention of 9.2%. The "job demands" section consisted of 29 items and 10 factors, while the "job resources" section consisted of 54 items and 22 factors. The result of examining the structure of job demands and job resources, leading to turnover intention was supported by the JD-R model. Turnover intention was strong and the Mental Component Summary (MCS) is low in those who had many job demands and few job resources (experiencing 'burn-out'). Enhancement of work engagement and turnover intention was weak in those who had many job resources. This explained approximately 60% of the dispersion to "burn-out", and approximately 40% to "work engagement", with four factors: work suitability, work significance, positive work self-balance, and growth opportunity of job resources.Conclusion This study revealed that turnover intention is strong in those who are burned out because of many job demands. Enhancement of work engagement and turnover intention is weak in those with many job resources. This suggests that suitable staffing and organized efforts to raise awareness of job significance are effective in reducing

  7. Firm-level innovation activity, employee turnover and HRM practices

    DEFF Research Database (Denmark)

    Eriksson, Tor; Qin, Zhihua; Wang, Wenjing

    2014-01-01

    This paper examines the relationship between employee turnover, HRM practices and innovation in Chinese firms in five high technology sectors. We estimate hurdle negative binomial models for count data on survey data allowing for analyses of the extensive as well as intensive margins of firms' in...

  8. Employees as Customers: Exploring Service Climate, Employee Patronage, and Turnover

    Science.gov (United States)

    Abston, Kristie A.; Kupritz, Virginia W.

    2011-01-01

    The role of retail employees as customers was explored by quantitatively examining the influence of service climate and employee patronage on employee turnover intentions. Employees representing all shifts in two stores of a national retailer participated. Results indicated that employee patronage partially mediates the effects of service climate…

  9. Psychological contract as precursor for turnover and self-employment

    NARCIS (Netherlands)

    Stormbroek-Burgers, van R.G.B.M.; Blomme, R.J.

    2017-01-01

    Purpose The purpose of this paper is to examine the effect of psychological contract (PC) fulfilment and violation on turnover intention and self-employment intentions. Design/methodology/approach A sample of 132 Dutch organizationally employed individuals was used to test the effect of PC

  10. Some Determinants of Employee Turnover in a Psychiatric Facility.

    Science.gov (United States)

    Zautra, Alex J.; And Others

    1987-01-01

    Used research from illness-prevention and job-enrichment approaches to enhancing quality of work environments to create instruments assessing number of job stressors and level of task interest on psychiatric hospital units. Instruments successfully predicted employee turnover during one year. Job stress and interaction between job stress and task…

  11. System wide cofactor turnovers can propagate metabolic stability between pathways

    DEFF Research Database (Denmark)

    Yang, Y.; Guan, Y.H.; Villadsen, John

    2016-01-01

    . Furthermore, we elaborated the criteria to tell if a multi-enzyme over-all reaction path is of in vivo nature or not at the metabolic level. As new findings, we discovered that there are interactions between the enzyme feedback inhibition and the CI turnover, and such interactions may well lead to metabolic...

  12. Turnover of nursing employees in a Gauteng hospital group

    Directory of Open Access Journals (Sweden)

    Japie Greyling

    2010-11-01

    Research purpose: The purpose of this study was to investigate individual determinants of voluntary turnover to identify a risk-group profile. Motivation for the study: Nursing employers should have a clearer understanding of the dynamics around nurses’ turnover behaviour and embark on strategies to retain their talent. Research design, approach and method: A survey measuring voluntary turnover was conducted among 262 professional and assistant nurses in three selected hospitals in Gauteng province using the McCarthy, Tyrrell and Cronin (2002 instrument. Pearson’s chi square with Yates’s continuity correction tested the relationship among the variables presented in a contingency table, in other words the risk group and each of the individual determinants. Main findings: Discontent with salaries was the major determinant of the nurses’ resignation. Organisational causes were nursing practices, the work environment, physical-emotional costs and employment opportunities after resignation. Practical/managerial implications: Hospital management could indeed establish a good rapport with nursing staff while facilitating respectful and ethical conduct by doctors towards nursing staff. Putting into place effective labour practices and business strategies could improve job satisfaction in the workplace. Contribution/value-add: This study contributed to a greater understanding of the personal and organisational determinants of the turnover of nurses in South African hospitals.

  13. Chinese Teachers' Work Stress and Their Turnover Intention

    Science.gov (United States)

    Liu, Shujie; Onwuegbuzie, Anthony J.

    2012-01-01

    This survey study employed qualitative dominant mixed research to explore the sources of teacher stress in China and the possible reasons for Chinese teachers' turnover intention. The data were collected in Jilin Province of China, and 510 teachers participated in the survey. Quantitatively, 40.4% of the surveyed teachers reported that they…

  14. Relationships between Emotional Labor, Job Performance, and Turnover

    Science.gov (United States)

    Goodwin, Robyn E.; Groth, Markus; Frenkel, Stephen J.

    2011-01-01

    The present study investigates the relationship between the emotional labor strategies surface acting and deep acting and organizational outcomes, specifically, employees' overall job performance and turnover. Call center employees from two large financial service organizations completed an online survey about their use of surface and deep acting.…

  15. The Prediction of Teacher Turnover Employing Time Series Analysis.

    Science.gov (United States)

    Costa, Crist H.

    The purpose of this study was to combine knowledge of teacher demographic data with time-series forecasting methods to predict teacher turnover. Moving averages and exponential smoothing were used to forecast discrete time series. The study used data collected from the 22 largest school districts in Iowa, designated as FACT schools. Predictions…

  16. Teachers' Perceptions of Administrative Support and Antecedents of Turnover

    Science.gov (United States)

    Russell, Elizabeth Morgan; Williams, Sue W.; Gleason-Gomez, Cheryl

    2010-01-01

    The purpose of this pilot study was to determine the degree to which teachers' age, perceptions of fair pay, receipt of employer-sponsored health insurance, and administrative support, as operationalized by the Competing Values Framework, predicted antecedents of turnover. Teachers' thoughts of leaving their current job and commitment to a center…

  17. Systematic analysis of protein turnover in primary cells.

    Science.gov (United States)

    Mathieson, Toby; Franken, Holger; Kosinski, Jan; Kurzawa, Nils; Zinn, Nico; Sweetman, Gavain; Poeckel, Daniel; Ratnu, Vikram S; Schramm, Maike; Becher, Isabelle; Steidel, Michael; Noh, Kyung-Min; Bergamini, Giovanna; Beck, Martin; Bantscheff, Marcus; Savitski, Mikhail M

    2018-02-15

    A better understanding of proteostasis in health and disease requires robust methods to determine protein half-lives. Here we improve the precision and accuracy of peptide ion intensity-based quantification, enabling more accurate protein turnover determination in non-dividing cells by dynamic SILAC-based proteomics. This approach allows exact determination of protein half-lives ranging from 10 to >1000 h. We identified 4000-6000 proteins in several non-dividing cell types, corresponding to 9699 unique protein identifications over the entire data set. We observed similar protein half-lives in B-cells, natural killer cells and monocytes, whereas hepatocytes and mouse embryonic neurons show substantial differences. Our data set extends and statistically validates the previous observation that subunits of protein complexes tend to have coherent turnover. Moreover, analysis of different proteasome and nuclear pore complex assemblies suggests that their turnover rate is architecture dependent. These results illustrate that our approach allows investigating protein turnover and its implications in various cell types.

  18. Turn-over of Stratijm Corneum in Leprosy

    Directory of Open Access Journals (Sweden)

    R P Okhandiar

    1987-01-01

    Full Text Available Stratum corneum showed increased proliferative activity on the patches of leprosy as evidenced by a significantly fast stratum corneum turnover time (p 0.001 measured by fluorescent staining technic with dansyl chloride. These findings suggest imperfect keratinization on the patches of leprosy leading to formation of structurally weak stratum corneum.

  19. Principal Turnover: Upheaval and Uncertainty in Charter Schools?

    Science.gov (United States)

    Ni, Yongmei; Sun, Min; Rorrer, Andrea

    2015-01-01

    Purpose: Informed by literature on labor market and school choice, this study aims to examine the dynamics of principal career movements in charter schools by comparing principal turnover rates and patterns between charter schools and traditional public schools. Research Methods/Approach: This study uses longitudinal data on Utah principals and…

  20. Steroid implants and markers of bone turnover in steers | Knetter ...

    African Journals Online (AJOL)

    The current study was designed to test the hypothesis that recently identified indicators of bone and cartilage turnover could be detected in the peripheral circulation, and that these markers might reflect accelerated ageing effects of the widely used steroidal implants, trenbolone acetate (TBA) and estradiol-17β (E2).

  1. Influence of Religiosity on Turnover Intention: Empirical Evidence ...

    African Journals Online (AJOL)

    This study examined the influence of employees' religiosity on their turnover intentions. The ex-post facto research design and the convenient sampling technique were employed in this study. A hundred and forty-nine (149) employees in Lagos and Ogun States of Nigeria were sampled as the study participants.

  2. Adeprene influence on the turnover rate of brain noradrenaline

    International Nuclear Information System (INIS)

    Tyutyulkova, N.I.; Gorancheva, J.I.; Ankov, V.K.

    1978-01-01

    The influence of Adeprene - Bulgarian antidepressant - on the content and the turnover rate of the rat brain noradrenaline was studied. The animals were injected intraperitoneally during 5 days with 20 mg/kg Adeprene. One hour after the last administration of Adeprene, Tyrosine, labelled with 14 C was injected. The animals were sacrified on the 1st, 2nd and 4th hours after the injection of 14 C-Tyrosine. The tyrosine and noradrenaline concentration were determined spectrofluorimetrically the concentration of the compounds labelled with 14 C by means of a liquid scintillator. The turnover rate constant of noradrenaline was calculated on the basis of the obtained results and the respective formula. It was established that under the influence of Adeprene, the noradrenaline concentration in the brain rises from 0,5 g/g in the control animals to 0,6 in treated mice. The turnover rate constant of noradrenaline, however, drops to 0,9 g/g/hour as compared to 0,15 g/g/hours in the controls. The determination of the turnover rate provides an idea about the intensity of utilization and synthesis of the mediator and is considered consequently as a more radiosensitive index for the neuronal activity then the total amine content. (A.B.)

  3. The Effects of Turnover: What We Know about Teacher Attrition

    Science.gov (United States)

    DeAngelis, Karen

    2012-01-01

    School business officials are likely to know better than anyone else about the financial costs to districts and schools associated with teacher attrition. Perhaps less well-known, though, is what else has been learned about this issue in recent years--information that may affect how one thinks about teacher turnover. Here is some of that research:…

  4. Bone turnover biomarkers in obese postmenopausal Saudi women ...

    African Journals Online (AJOL)

    Background: There is a high prevalence of diabetes mellitus type-2 (T2DM) and osteoporosis are problems worldwide. In this study, we evaluated the correlation between T2DM and bone turnover in diabetic obese postmenopausal Saudi women. Subjects and Methods: The present study included total of 65 T2-DM obese ...

  5. Effects of ractopamine and gender on protein turnover in skeletal ...

    African Journals Online (AJOL)

    Effects of the β-agonist, ractopamine-HCl (ractopamine), on skeletal muscle protein turnover were evaluated in 16 steers (512 kg) and 16 heifers (473 kg). Treatments were arranged in a 2 × 2 factorial design and included gender (steer vs. heifer) and ractopamine (0 or 200 mg/d). Steers were implanted with 120 mg ...

  6. Organizational Career Growth, Affective Occupational Commitment and Turnover Intentions

    Science.gov (United States)

    Weng, Qingxiong; McElroy, James C.

    2012-01-01

    Survey data, collected from the People's Republic of China, were used to test Weng's (2010) four facet model of career growth and to examine its effect on occupational commitment and turnover intentions. Weng conceptualized career growth as consisting of four factors: career goal progress, professional ability development, promotion speed, and…

  7. Oxidative Criteria And Somebone Turnover Markers In Beta ...

    African Journals Online (AJOL)

    Bone disease in beta-thalassemic patients has multifactorial etiology; increased iron stores and per-oxidative stress are involved factors. This study aimed to investigate the relationship between some bone turnover markers and some oxidants, antioxidants parameters of betathalassemic patients. The study included 50 ...

  8. Calculation of turnover rates in stable-isotope studies

    International Nuclear Information System (INIS)

    Wootton, R.; Ford, G.C.; Cheng, K.N.; Halliday, D.

    1985-01-01

    In a comparison of glucose turnover measured with 2 H-glucose and with 13 C-glucose Tserng and Kalhan used five apparently different equations and obtained conflicting answers. There is, however, no difference in principle between the use of a stable isotope as a tracer and the use of a radioactive isotope, and the rate of appearance of tracee in a steady-state system (the turnover) can therefore be shown to be proportional to the equilibrium dilution of the infused tracer. Because the sensitivity of measurement of this dilution made using a gas chromatograph-mass spectrometer is lower than that made by radioactivity measurement, the contribution to the measured turnover rate due to the infusate cannot be neglected, as it usually is in radioisotope work. A convenient calibration curve to establish this dilution is the mole ratio of the pure infusate against the area ratio for the relevant ions. Tserng and Kalhan's apparently conflicting results for glucose-turnover using 13 C-glucose as the tracer can all be shown to amount to approximately 11.6 μmol min -1 kg -1 . This value is only slightly lower (0.05 2 H-glucose as the tracer and supports the use of 13 C-glucose as an alternative. (author)

  9. Exercise Enhances Whole-Body Cholesterol Turnover in Mice

    NARCIS (Netherlands)

    Meissner, Maxi; Havinga, Rick; Boverhof, Renze; Kema, Ido; Groen, Albert K.; Kuipers, Folkert

    MEISSNER, M., R. HAVINGA, R. BOVERHOF, I. KEMA, A. K. GROEN, and F. KUIPERS. Exercise Enhances Whole-Body Cholesterol Turnover in Mice. Med. Sci. Sports Exerc., Vol. 42, No. 8, pp. 1460-1468, 2010. Purpose: Regular exercise reduces cardiovascular risk in humans by reducing cholesterol levels, but

  10. Factors Affecting Turnover Intention among Nurses in Ethiopia

    NARCIS (Netherlands)

    Ayalew, Firew; Kols, Adrienne; Kim, Young-Mi; Schuster, Anne; Emerson, Mark R; Roosmalen, J van; Stekelenburg, Jelle; Woldemariam, Damtew; Gibson, Hannah

    2015-01-01

    BACKGROUND: Reducing turnover is essential to address health worker shortages in the public sector and improve the quality of services. This study examines factors associated with Ethiopian nurses' intention to leave their jobs. METHODS: Survey respondents (a sample of 425 nurses at 122 facilities)

  11. Electronic alerts and clinician turnover: the influence of user acceptance.

    Science.gov (United States)

    Hysong, Sylvia J; Spitzmuller, Christiane; Espadas, Donna; Sittig, Dean F; Singh, Hardeep

    2014-11-01

    Use of certain components of electronic health records (EHRs), such as EHR-based alerting systems (EASs), might reduce provider satisfaction, a strong precursor to turnover. We examined the impact of factors likely to influence providers' acceptance of an alerting system, designed to facilitate electronic communication in outpatient settings, on provider satisfaction, intentions to quit, and turnover. We conducted a cross-sectional Web-based survey of EAS-related practices from a nationwide sample of primary care providers (PCPs) practicing at Department of Veterans Affairs (VA) medical facilities. Of 5001 invited VA PCPs, 2590 completed the survey. We relied on Venkatesh's Unified Theory of Acceptance and Use of Technology to create survey measures of 4 factors likely to impact user acceptance of EAS: supportive norms, monitoring/ feedback, training, and providers' perceptions of the value (PPOV) of EASs to provider effectiveness. Facility-level PCP turnover was measured via the VA's Service Support Center Human Resources Cube. Hypotheses were tested using structural equation modeling. After accounting for intercorrelations among predictors, monitoring/feedback regarding EASs significantly predicted intention to quit (b = 0.30, P < .01), and PPOV of EASs predicted both overall provider satisfaction (b = 0.58, P < .01) and facility-level provider turnover levels (b = -0.19, P < .05), all without relying on any intervening mechanisms. Design, implementation, and use of EASs might impact provider satisfaction and retention. Institutions should consider strategies to help providers perceive greater value in these clinical tools.

  12. The Modern Technologies to Reduce Turnover of Company Staff

    Directory of Open Access Journals (Sweden)

    Zaiko Tetiana O.

    2017-12-01

    Full Text Available The article is aimed at analyzing and substantiating the use in practice of modern technologies to reduce turnover of staff, which do not bear significant financial costs for the company. The authors have proved that non-material measures to reduce staff turnover in companies are becoming predominant nowadays. Among them as the most important are indicated: introduction of flexible schedule (mode of work, transition to the remote form of employment, and distribution of internal shares, in particular related to the strengthening of cohesion of staff, its team spirit. Also the reasons of transition from material to intangible factors of influence on conduct of workers have been disclosed. The advantages of non-material measures of the staff turnover reduction for both employees and employers were analyzed. For the first ones the most important are motivation and job satisfaction, while for the others it is reduction of staff turnover, formation of the responsible worker, improvement of quality and productivity of work.

  13. The relationship between bone turnover and insulin sensitivity and secretion

    DEFF Research Database (Denmark)

    Frost, Morten; Balkau, Beverley; Hatunic, Mensud

    2018-01-01

    Bone metabolism appears to influence insulin secretion and sensitivity, and insulin promotes bone formation in animals, but similar evidence in humans is limited. The objectives of this study are to explore if bone turnover markers were associated with insulin secretion and sensitivity and to det...

  14. Approximation algorithms for replenishment problems with fixed turnover times

    NARCIS (Netherlands)

    T. Bosman (Thomas); M. van Ee (Martijn); Y. Jiao (Yang); A. Marchetti Spaccamela (Alberto); R. Ravi; L. Stougie (Leen)

    2018-01-01

    textabstractWe introduce and study a class of optimization problems we coin replenishment problems with fixed turnover times: a very natural model that has received little attention in the literature. Nodes with capacity for storing a certain commodity are located at various places; at each node the

  15. Gender Differences in Perceptions of Resources and Turnover Intentions of Work-Linked Couples in Masculine Occupations.

    Science.gov (United States)

    Huffman, Ann Hergatt; Olson, Kristine J

    2017-10-01

    Employees in work-linked marriages have spouses that share the same family and the same workplace and/or occupation. Whereas, in recent years, there has been increasingly more research on dual-career marriages (i.e. both spouses work, but not necessarily at the same workplace and/or occupation), there has been very little research on work-linked marriages. The current study focuses on work resources (i.e. family supportive supervisor behaviour and job control) as key mediating processes that explain the effect of gender on turnover intentions among work-linked employees in masculine occupations (i.e. military). Investigating gender differences is important because, compared with men, women are more likely to be in work-linked marriages and to leave their jobs. Based on role theory and conservation of resource theory, we predicted that gender was related to turnover intentions, and this relationship would be mediated by key explanatory variables (i.e. family supportive supervisor behaviours, job control and psychological distress). Mediation analyses, conducted on a sample of men and women in work-linked marriages (n = 309), provide support for the hypothesized model. These findings offer guidance for understanding gender differences among work-linked employees in masculine occupations, and how these differences can affect important outcomes such as turnover intentions. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  16. Rhizosphere bacterial carbon turnover is higher in nucleic acids than membrane lipids: implications for understanding soil carbon cycling

    Directory of Open Access Journals (Sweden)

    Ashish A. Malik

    2015-04-01

    Full Text Available Using a pulse-chase 13CO2 plant labeling experiment we compared the flow of plant carbon into macromolecular fractions of root-associated soil microorganisms. Time dependent 13C dilution patterns in microbial cellular fractions were used to calculate their turnover time. The turnover times of microbial biomolecules were found to vary: microbial RNA (19 h and DNA (30 h turned over fastest followed by chloroform fumigation extraction-derived soluble cell lysis products (14 d, while phospholipid fatty acids (PLFAs had the slowest turnover (42 d. PLFA/NLFA 13C analyses suggest that both mutualistic arbuscular mycorrhizal and saprophytic fungi are dominant in initial plant carbon uptake. In contrast, high initial 13C enrichment in RNA hints at bacterial importance in initial C uptake due to the dominance of bacterial derived RNA in total extracts of soil RNA. To explain this discrepancy, we observed low renewal rate of bacterial lipids, which may therefore bias lipid fatty acid based interpretations of the role of bacteria in soil microbial food webs. Based on our findings, we question current assumptions regarding plant-microbe carbon flux and suggest that the rhizosphere bacterial contribution to plant assimilate uptake could be higher. This highlights the need for more detailed quantitative investigations with nucleic acid biomarkers to further validate these findings.

  17. Bone turnover in postmenopausal osteoporosis. Effect of calcitonin treatment.

    Science.gov (United States)

    Civitelli, R; Gonnelli, S; Zacchei, F; Bigazzi, S; Vattimo, A; Avioli, L V; Gennari, C

    1988-10-01

    To investigate the effectiveness of calcitonin treatment of postmenopausal osteoporosis in relation to bone turnover, we examined 53 postmenopausal osteoporotic women before and after one year of therapy with salmon calcitonin (sCT), at the dose of 50 IU every other day. Baseline evaluation revealed that 17 (32%) patients had high turnover (HTOP), and 36 (68%) normal turnover osteoporosis (NTOP) as assessed by measurement of whole body retention (WBR) of 99mTc-methylene diphosphonate. The two groups did not differ in terms of bone mineral content (BMC) measured by dual photon absorptiometry at both lumbar spine and femoral diaphysis. However, HTOP patients had higher levels of serum osteocalcin (OC) and urinary hydroxyproline excretion (HOP/Cr). Multivariate regression analysis showed no correlation between parameters of bone turnover (WBR, OC, HOP/Cr) and both femoral and vertebral bone density; the latter being negatively correlated only with the years elapsed since menopause (R2 = 0.406). Treatment with sCT resulted in a significant increase of vertebral BMC in the 53 patients taken as a whole group (+/- 7%, P less than 0.001). When the results obtained in HTOP and NTOP were analyzed separately, only those with HTOP showed a marked increment of spinal BMC (+22%, P less than 0.001), NTOP subjects neither gained nor lost bone mineral during the study. Femoral BMC decreased in the whole group after sCT therapy (-3%, P less than 0.003). However, HTOP patients maintained initial BMC values, whereas those with NTOP lost a significant amount of bone during the study period (-5%, P less than 0.001). The increase of vertebral bone mass was associated with a marked depression of bone turnover detectable in both subsets of patients and in the whole group. (a) assessment of bone turnover cannot help predict the severity of bone loss in postmenopausal osteoporosis; (b) calcitonin therapy appears to be particularly indicated for patients with high-turnover osteoporosis

  18. A social network perspective on turnover intentions: The role of distributive justice and social support

    NARCIS (Netherlands)

    Soltis, S.; Agneessens, F.; Sasovova, Z.; Labianca, G.

    2013-01-01

    Organizations are increasingly concerned about retaining human talent, particularly within knowledge-based industries where turnover is expensive. Our study employs a social network perspective to explore the influence of employees' formal and informal workplace relationships on their turnover

  19. A Social Network Perspective on Turnover Intentions : The Role of Distributive Justice and Social Support

    NARCIS (Netherlands)

    Soltis, Scott M.; Agneessens, Filip; Sasovova, Zuzana; Labianca, Giuseppe (Joe)

    Organizations are increasingly concerned about retaining human talent, particularly within knowledge-based industries where turnover is expensive. Our study employs a social network perspective to explore the influence of employees' formal and informal workplace relationships on their turnover

  20. Career Anchors of United States Air Force Information Systems Workers: A Turnover Predictor

    National Research Council Canada - National Science Library

    Wynne, Lee

    2002-01-01

    ...) and the work of Schein (1987) to measure the career anchors, job satisfaction, and turnover intention of AF IS workers to determine if those whose job type and career anchor match report higher satisfaction and lower turnover...

  1. The effects of sexual harassment on turnover in the military: time-dependent modeling.

    Science.gov (United States)

    Sims, Carra S; Drasgow, Fritz; Fitzgerald, Louise F

    2005-11-01

    Sexual harassment has consistently negative consequences for working women, including changes in job attitudes (e.g., lower satisfaction) and behaviors (e.g., increased work withdrawal). Cross-sectional evidence suggests that harassment influences turnover intentions. However, few studies have used actual turnover; rather, they rely on proxies. With a sample of 11,521 military servicewomen with turnover data spanning approximately 4 years, the authors used the appropriate method for longitudinal turnover data--Cox's regression--to investigate the impact of harassment on actual turnover. Experiences of harassment led to increased turnover, even after controlling for job satisfaction, organizational commitment, and marital status. Among officers, harassment also affected turnover over and above rank. Given turnover's relevance to organizational bottom lines, these findings have important implications not only for individual women but also for organizations. ((c) 2005 APA, all rights reserved).

  2. A Theoretical Framework for Turnover Intention of Air Force Enlisted Information Systems Personnel

    Science.gov (United States)

    2003-03-25

    removal of poor performers, advancement opportunities for talented replacements, and decreases in pre-turnover withdrawal behaviors such as absenteeism ...in Employee Turnover Intentions and Its Determinants Among Telecommuters and Non- Telecommuters ,” Journal of Management Information Systems, 16: 147

  3. Prostate Cancer Metastases to Bone: Role of High Bone Turnover Induced by Androgen Deprivation

    National Research Council Canada - National Science Library

    Padalecki, Susan

    2002-01-01

    .... Treatment with androgen deprivation therapy leads to an increase in bone turnover as indicated by the loss of bone mineral density and the increase in markers of bone turnover in patients on treatment...

  4. A New Insight to Bone Turnover: Role of -3 Polyunsaturated Fatty Acids

    Directory of Open Access Journals (Sweden)

    Naroa Kajarabille

    2013-01-01

    Full Text Available Background. Evidence has shown that long-chain polyunsaturated fatty acids (LCPUFA, especially the ω-3 fatty acids such as eicosapentaenoic acid (EPA and docosahexaenoic acid (DHA are beneficial for bone health and turnover. Objectives. This review summarizes findings from both in vivo and in vitro studies and the effects of LC PUFA on bone metabolism, as well as the relationship with the oxidative stress, the inflammatory process, and obesity. Results. Some studies in humans indicate that LCPUFA can increase bone formation, affect peak bone mass in adolescents, and reduce bone loss. However, the cellular mechanisms of action of the LCPUFA are complex and involve modulation of fatty acid metabolites such as prostaglandins, resolvins and protectins, several signaling pathways, cytokines, and growth factors, although in certain aspects there is still some controversy. LCPUFA affect receptor activator of nuclear factor κβ (RANK, a receptor found on the osteoclast, causing bone resorption, which controls osteoclast formation. Conclusions. Since fatty acids are an endogenous source of reactive oxygen species, free radicals alter the process of bone turnover; however, although there are clinical evidences linking bone metabolism and dietary lipids, more clinical trials are necessary to prove whether ω-3 PUFA supplementation plays a major role in bone health.

  5. Whole body and tissue cholesterol turnover in the baboon

    International Nuclear Information System (INIS)

    Dell, R.B.; Mott, G.E.; Jackson, E.M.; Ramakrishnan, R.; Carey, K.D.; McGill, H.C. Jr.; Goodman, D.S.

    1985-01-01

    Cholesterol turnover was studied in four baboons by injecting [ 14 C]cholesterol 186 days and [ 3 H]cholesterol 4 days before necropsy, and fitting a two- or three-pool model to the resulting specific activity-time data. At necropsy, cholesterol mass and specific activity were determined for the total body and for many tissues. The principal aim of this study was to estimate the extent of cholesterol synthesis in the side pools of the model, by computing the amount of side pool synthesis needed to equal the measured total body cholesterol. Central pool synthesis varied from 61 to 89% of the total cholesterol production rate. Moreover, the finding that the measured total body cholesterol fell within the range obtained from the kinetic analysis by using reasonable assumptions, provides evidence for the physiological validity of the model. A second aim of this study was to explore cholesterol turnover in various tissues. A pool model predicts that rapidly turning over tissues will have higher specific activities at early times and lower specific activities at later times after injection of tracer relative to slowly turning over tissues, except where significant synthesis occurs. Results in all four baboons were similar. Turnover rates for the different tissues loosely fell into three groups which were turning over at fast, intermediate, and slow rates. Finally, the magnitude of variation of cholesterol specific activity was moderate for several distributed tissues (fat, muscle, arteries, and the alimentary tract), but was small for liver. Cholesterol turnover in serial biopsies of skin, muscle, and fat could, however, be fitted with a single pool to estimate tissue turnover rates

  6. Hypoxic cell turnover in different solid tumor lines

    International Nuclear Information System (INIS)

    Ljungkvist, Anna S.E.; Bussink, Johan; Kaanders, Johannes H.A.M.; Rijken, Paulus F.J.W.; Begg, Adrian C.; Raleigh, James A.; Kogel, Albert J. van der

    2005-01-01

    Purpose: Most solid tumors contain hypoxic cells, and the amount of tumor hypoxia has been shown to have a negative impact on the outcome of radiotherapy. The efficacy of combined modality treatments depends both on the sequence and timing of the treatments. Hypoxic cell turnover in tumors may be important for optimal scheduling of combined modality treatments, especially when hypoxic cell targeting is involved. Methods and Materials: Previously we have shown that a double bioreductive hypoxic marker assay could be used to detect changes of tumor hypoxia in relation to the tumor vasculature after carbogen and hydralazine treatments. This assay was used in the current study to establish the turnover rate of hypoxic cells in three different tumor models. The first hypoxic marker, pimonidazole, was administered at variable times before tumor harvest, and the second hypoxic marker, CCI-103F, was injected at a fixed time before harvest. Hypoxic cell turnover was defined as loss of pimonidazole (first marker) relative to CCI-103F (second marker). Results: The half-life of hypoxic cell turnover was 17 h in the murine C38 colon carcinoma line, 23 h and 49 h in the human xenograft lines MEC82 and SCCNij3, respectively. Within 24 h, loss of pimonidazole-stained areas in C38 and MEC82 occurred concurrent with the appearance of pimonidazole positive cell debris in necrotic regions. In C38 and MEC82, most of the hypoxic cells had disappeared after 48 h, whereas in SCCNij3, viable cells that had been labeled with pimonidazole were still observed after 5 days. Conclusions: The present study demonstrates that the double hypoxia marker assay can be used to study changes in both the proportion of hypoxic tumor cells and their lifespan at the same time. The present study shows that large differences in hypoxic cell turnover rates may exist among tumor lines, with half-lives ranging from 17-49 h

  7. Exit interviews to reduce turnover amongst healthcare professionals.

    Science.gov (United States)

    Webster, Joan; Flint, Anndrea

    2014-08-19

    Exit interviews are widely used in healthcare organisations to identify reasons for staff attrition, yet their usefulness in limiting turnover is unclear. To determine the effectiveness of various exit interview strategies in decreasing turnover rates amongst healthcare professionals. We searched the Cochrane EPOC Group Specialised Register; Cochrane Central Register of Controlled Trials (CENTRAL), Issue 11, 2012; MEDLINE, Ovid (1950- ); EMBASE, Ovid (1947- ); CINAHL, EbscoHost (1980- ), and PsycINFO, OVID (1806-) between October 31 and November 6, 2012. We also screened the reference lists of included studies and relevant reviews; and searched trial registries for planned and on-going studies. We did not restrict searches by language or publication date. Randomised controlled trials, controlled clinical trials, controlled before-after studies and interrupted time series studies comparing turnover rates between healthcare professionals who had undergone one form of exit interview with another form of exit interview or with no interview. Two review authors independently assessed trial quality and extracted data. The original search identified 1560 citations, of which we considered 19 potentially relevant. The two authors independently reviewed the abstracts of these studies and retrieved the full texts of eight studies. We excluded all eight following independent assessment; they were either interviews, commentaries on how to do an exit interview or descriptive studies about reasons for leaving. We found no studies that matched our inclusion criteria. For this first update, we screened 2220 citations and identified no new studies. Evidence about the effectiveness of exit interviews to reduce turnover is currently not available. However, exit interviews may provide useful information about the work environment which, in turn, may be useful in the development of interventions to reduce turnover.

  8. Mitochondrial Signaling in Plants Under Hypoxia: Use of Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS)

    DEFF Research Database (Denmark)

    Hebelstrup, Kim; Møller, Ian Max

    2015-01-01

    Hypoxia commonly occurs in roots in water-saturated soil and in maturing and germinating seeds. We here review the role of the mitochondria in the cellular response to hypoxia with an emphasis on the turnover of Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS) and their potential...

  9. Organic Matter Quality and its Influence on Carbon Turnover and Stabilization in Northern Peatlands

    Science.gov (United States)

    Turetsky, M. R.; Wieder, R. K.

    2002-12-01

    Peatlands cover 3-5 % of the world's ice-free land area, but store about 33 % of global terrestrial soil carbon. Peat accumulation in northern regions generally is controlled by slow decomposition, which may be limited by cold temperatures and water-logging. Poor organic matter quality also may limit decay, and microbial activity in peatlands likely is regulated by the availability of labile carbon and/or nutrients. Conversely, carbon in recalcitrant soil structures may be chemically protected from microbial decay, particularly in peatlands where carbon can be buried in anaerobic soils. Soil organic matter quality is controlled by plant litter chemical composition and the susceptibility of organic compounds to decomposition through time. There are a number of techniques available for characterizing organic quality, ranging from chemical proximate or elemental analysis to more qualitative methods such as nuclear magenetic resonance, pyrolysis/mass spectroscopy, and Fourier transform infrared spectroscopy. We generally have relied on proximate analysis for quantitative determination of several organic fractions (i.e., water-soluble carbohydrates, soluble nonpolars, water-soluble phenolics, holocellulose, and acid insoluble material). Our approaches to studying organic matter quality in relation to C turnover in peatlands include 1) 14C labelling of peatland vegetation along a latitudinal gradient in North America, allowing us to follow the fate of 14C tracer in belowground organic fractions under varying climates, 2) litter bag studies focusing on the role of individual moss species in litter quality and organic matter decomposition, and 3) laboratory incubations of peat to explore relationships between organic matter quality and decay. These studies suggest that proximate organic fractions vary in lability, but that turnover of organic matter is influenced both by plant species and climate. Across boreal peatlands, measures of soil recalcitrance such as acid

  10. The perceived stress and turnover intention of direct-care staff of community residential facilities

    OpenAIRE

    Lightle, Kevin Eugene

    1990-01-01

    This study examines turnover among direct-care staff of community residential facilities. Turnover is of concern as the projected rate indicated by direct-care staff is 34%. A review of personnel records project an annual turnover rate of 40%. Stress is examined for its relationship to turnover. The Maslach Burnout Inventory is used to measure the perceived stress level of staff. Results indicate direct-care staff are not stressed to the point of burnout in two of ...

  11. Effects of growth state and 3H labeling level on RNA turnover in WI-38 fibroblasts and HeLa cells

    International Nuclear Information System (INIS)

    Sameshima, M.; Schlessinger, D.

    1981-01-01

    The rate of turnover of prelabeled RNA in WI-38 human diploid fibroblasts varied with the level of 3 H incorporated, the cell density of cultures, and the arrest of growth by senescence. The half-life of RNA in sparse cultures of growing WI-38 diploid fibroblasts depended on the level of [ 3 H]uridine incorporated; extrapolated to zero levels of incorporation, the half-life was 15 to 20 days. At any level of incorporated [ 3 H]uridine, however, RNA half-life decreased to 4 to 5 days in superconfluent cultures as the culture growth slowed. A similar shortening of half-life was observed when growth was stopped by 3 H irradiation or clonal senescence. However, the rate of turnover was not simply dependent on whether cells were growing; for example, turnover did not increase when growth was arrested by incubating cells in conditioned medium. HeLa and L cells also showed an RNA half-life of about 14 to 20 days with an increase in turnover rate of crowded cultures. However, this increase occurred at higher cell densities than with the diploid fibroblasts. Also, the growth rate and rate of RNA turnover of HeLa and L cells were much less affected by incorporated 3 H. The differential responses to confluence and 3 H label can explain the higher turnover rate of RNA in normal human fibroblasts compared to SV40-transformed cells [S.A. Liebhaber, S. Wolf, and D. Schlessinger, Cell 13, 121-127 (1978)

  12. When the Going Gets Tough: Direct, Buffering and Indirect Effects of Social Support on Turnover Intention

    Science.gov (United States)

    Pomaki, Georgia; DeLongis, Anita; Frey, Daniela; Short, Kathy; Woehrle, Trish

    2010-01-01

    We examined the role of social support in turnover intention among new teachers. First, we tested and found evidence for a direct negative relationship between social support and turnover intention. Second, we tested the social support buffer hypothesis, and found that teachers with higher social support had lower turnover intention in the face of…

  13. Pengaruh Budaya Organisasi dan Gaya Kepemimpinan Transformasional terhadap Intensi Turnover Karyawan

    OpenAIRE

    Ginting, Artiwinata

    2016-01-01

    This study aims to determine the influence of organization culture and transformational leadership style toward to employee turnover intention. Data were collected by using employee turnover intention scale, organization culture scale and transformational leadership style scale. This research involved 206 employees. The results showed that organization culture and transformational leadership style not significant influenced to employee turnover intention. The organizational culture negatively...

  14. Is high employee turnover really harmful?: An empirical test using company records

    NARCIS (Netherlands)

    Glebbeek, A.C.; Bax, E.H.

    2004-01-01

    We tested the hypothesis that employee turnover and firm performance have an inverted U-shaped relationship: overly high or low turnover is harmful. Our analysis was based on economic performance data from 110 offices of a temporary employment agency. These offices had high variation in turnover but

  15. Blind Spots: Small Rural Communities and High Turnover in the Superintendency

    Science.gov (United States)

    Kamrath, Barry; Brunner, C. Cryss

    2014-01-01

    This article examines high superintendency turnover through rural community members' perceptions of such attrition in their districts. Findings indicate that community members perceived high turnover as negative and believed that turnover was created by financial pressures, rural community resistance to educational trends, and bias against…

  16. How Teacher Turnover Harms Student Achievement. NBER Working Paper No. 17176

    Science.gov (United States)

    Ronfeldt, Matthew; Lankford, Hamilton; Loeb, Susanna; Wyckoff, James

    2011-01-01

    Researchers and policymakers often assume that teacher turnover harms student achievement, but recent evidence calls into question this assumption. Using a unique identification strategy that employs grade-level turnover and two classes of fixed-effects models, this study estimates the effects of teacher turnover on over 600,000 New York City 4th…

  17. Superintendent Turnover in Kentucky. Summary. Issues & Answers. REL 2011-No. 113

    Science.gov (United States)

    Johnson, Jerry; Huffman, Tyler; Madden, Karen; Shope, Shane

    2011-01-01

    This study examines superintendent turnover in Kentucky public school districts for 1998/99-2007/08, looking at how turnover varies by rural status, Appalachian and non-Appalachian region, and 2007/08 school district characteristics. Key findings include: (1) Kentucky school districts averaged one superintendent turnover during 1998/99-2007/08;…

  18. Predictors of actual turnover in a national sample of newly licensed registered nurses employed in hospitals.

    Science.gov (United States)

    Brewer, Carol S; Kovner, Christine T; Greene, William; Tukov-Shuser, Magdalene; Djukic, Maja

    2012-03-01

    This paper is a report of a study of factors that affect turnover of newly licensed registered nurses in United States hospitals. There is a large body of research related to nursing retention; however, there is little information specific to newly licensed registered nurse turnover. Incidence rates of turnover among new nurses are unknown because most turnover data are not from nationally representative samples of nurses. This study used a longitudinal panel design to obtain data from 1653 registered nurses who were recently licensed by examination for the first time. We mailed surveys to a nationally representative sample of hospital registered nurses 1 year apart. The analytic sample consisted of 1653 nurses who responded to both survey mailings in January of 2006 and 2007. Full-time employment and more sprains and strains (including back injuries) result in more turnover. Higher intent to stay and hours of voluntary overtime and more than one job for pay reduces turnover. When we omitted intent to stay from the probit model, less job satisfaction and organizational commitment led to more turnover, confirming their importance to turnover. Magnet Recognition Award(®) hospitals and several other work attributes had no effect on turnover.   Turnover problems are complex, which means that there is no one solution to decreasing turnover. Multiple points of intervention exist. One specific approach that may improve turnover rates is hospital policies that reduce strains and sprains. © 2011 The Authors. Journal of Advanced Nursing © 2011 Blackwell Publishing Ltd.

  19. Diagnosing Causes of Teacher Retention, Mobility and Turnover: Guidelines for TIF Grantees

    Science.gov (United States)

    Finster, Matthew

    2015-01-01

    To effectively address teacher turnover, Teacher Incentive Fund (TIF) grantees need to follow an approach that entails aligning the tracking, diagnosing, and intervening processes. Unfortunately, too often retention strategies are implemented without regard to the various types of teacher turnover and specific data about the causes of turnover.…

  20. Stayers, Leavers, and Switchers Among Certified Nursing Assistants in Nursing Homes: A Longitudinal Investigation of Turnover Intent, Staff Retention, and Turnover

    Science.gov (United States)

    Rosen, Jules

    2011-01-01

    Purpose: Studies of certified nursing assistant (CNA) turnover in nursing homes are typically cross-sectional and include full-time and part-time workers. We conducted a longitudinal study to evaluate the job factors and work attitudes associated with just full-time staying or leaving. For those who did not stay, we assessed reasons for leaving and satisfaction following job transition. Design and Methods: A random sample of CNAs identified through the Pennsylvania Department of Health's CNA registry, working≥30 hr weekly in a nursing facility was surveyed by telephone at baseline and 1 year later. Results: Of the 620 responding to both surveys, 532 (85.8%) remained (stayers), 52 (8.4%) switched to another facility (switchers), and 36 (5.8%) left the industry (leavers). At baseline, switchers reported higher turnover intentions and fewer benefits compared with stayers and left for new opportunities. Leavers had lower job satisfaction and emotional well-being and left for health reasons. Turnover intentions were predicted by low job satisfaction and low emotional well-being. Actual turnover was predicted only by turnover intentions and by the absence of health insurance. Pay was not a predictor of turnover intent or turnover. Implications: There are two distinct groups of CNAs contributing to turnover. Attitudinal factors, such as job satisfaction and emotional well-being, are mediated via turnover intentions to effect actual turnover. Even accounting for methodological differences, this turnover rate is lower than previous studies, which use alternative methods and include part-time workers. This study should help nursing home administrators better understand the work-related factors associated with staff turnover. PMID:21498629

  1. Social Capital and Turnover. Towards a Theoretically Informed Model for Social Capital in Turnover Research: Applications to the U.S. Military

    Science.gov (United States)

    2007-03-01

    Hamilton College, Clinton, NY. Porter L. & Steers R. (1973). Organizational, work, and personal factors in employee turnover and absenteeism ...in Modern Sociology. Annual Review of Sociology 24, pp. 1-24. Price, J. (1977). A Theory of Turnover. In Labour turnover and retention (Chapter 3...for measurement. Research Paper, University of Rome La Sapienza, Department of Public Economics: June 2005. Sabatini, F. Social capital, labour

  2. Bone Turnover Status: Classification Model and Clinical Implications

    Science.gov (United States)

    Fisher, Alexander; Fisher, Leon; Srikusalanukul, Wichat; Smith, Paul N

    2018-01-01

    Aim: To develop a practical model for classification bone turnover status and evaluate its clinical usefulness. Methods: Our classification of bone turnover status is based on internationally recommended biomarkers of both bone formation (N-terminal propeptide of type1 procollagen, P1NP) and bone resorption (beta C-terminal cross-linked telopeptide of type I collagen, bCTX), using the cutoffs proposed as therapeutic targets. The relationships between turnover subtypes and clinical characteristic were assessed in1223 hospitalised orthogeriatric patients (846 women, 377 men; mean age 78.1±9.50 years): 451(36.9%) subjects with hip fracture (HF), 396(32.4%) with other non-vertebral (non-HF) fractures (HF) and 376 (30.7%) patients without fractures. Resalts: Six subtypes of bone turnover status were identified: 1 - normal turnover (P1NP>32 μg/L, bCTX≤0.250 μg/L and P1NP/bCTX>100.0[(median value]); 2- low bone formation (P1NP ≤32 μg/L), normal bone resorption (bCTX≤0.250 μg/L) and P1NP/bCTX>100.0 (subtype2A) or P1NP/bCTX0.250 μg/L) and P1NP/bCTXturnover (both markers elevated ) and P1NP/bCTX>100.0 (subtype 4A) or P1NP/bCTX75 years and hyperparathyroidism. Hypoalbuminaemia and not using osteoporotic therapy were two independent indicators common for subtypes 3, 4A and 4B; these three subtypes were associated with in-hospital mortality. Subtype 3 was associated with fractures (OR 1.7, for HF OR 2.4), age>75 years, chronic heart failure (CHF), anaemia, and history of malignancy, and predicted post-operative myocardial injury, high inflammatory response and length of hospital stay (LOS) above10 days. Subtype 4A was associated with chronic kidney disease (CKD), anaemia, history of malignancy and walking aids use and predicted LOS>20 days, but was not discriminative for fractures. Subtype 4B was associated with fractures (OR 2.1, for HF OR 2.5), age>75 years, CKD and indicated risks of myocardial injury, high inflammatory response and LOS>10 days. Conclusions: We

  3. Does positive selection drive transcription factor binding site turnover? A test with Drosophila cis-regulatory modules.

    Directory of Open Access Journals (Sweden)

    Bin Z He

    2011-04-01

    Full Text Available Transcription factor binding site(s (TFBS gain and loss (i.e., turnover is a well-documented feature of cis-regulatory module (CRM evolution, yet little attention has been paid to the evolutionary force(s driving this turnover process. The predominant view, motivated by its widespread occurrence, emphasizes the importance of compensatory mutation and genetic drift. Positive selection, in contrast, although it has been invoked in specific instances of adaptive gene expression evolution, has not been considered as a general alternative to neutral compensatory evolution. In this study we evaluate the two hypotheses by analyzing patterns of single nucleotide polymorphism in the TFBS of well-characterized CRM in two closely related Drosophila species, Drosophila melanogaster and Drosophila simulans. An important feature of the analysis is classification of TFBS mutations according to the direction of their predicted effect on binding affinity, which allows gains and losses to be evaluated independently along the two phylogenetic lineages. The observed patterns of polymorphism and divergence are not compatible with neutral evolution for either class of mutations. Instead, multiple lines of evidence are consistent with contributions of positive selection to TFBS gain and loss as well as purifying selection in its maintenance. In discussion, we propose a model to reconcile the finding of selection driving TFBS turnover with constrained CRM function over long evolutionary time.

  4. Store turnover as a predictor of food and beverage provider turnover and associated dietary intake estimates in very remote Indigenous communities.

    Science.gov (United States)

    Wycherley, Thomas; Ferguson, Megan; O'Dea, Kerin; McMahon, Emma; Liberato, Selma; Brimblecombe, Julie

    2016-12-01

    Determine how very-remote Indigenous community (RIC) food and beverage (F&B) turnover quantities and associated dietary intake estimates derived from only stores, compare with values derived from all community F&B providers. F&B turnover quantity and associated dietary intake estimates (energy, micro/macronutrients and major contributing food types) were derived from 12-months transaction data of all F&B providers in three RICs (NT, Australia). F&B turnover quantities and dietary intake estimates from only stores (plus only the primary store in multiple-store communities) were expressed as a proportion of complete F&B provider turnover values. Food types and macronutrient distribution (%E) estimates were quantitatively compared. Combined stores F&B turnover accounted for the majority of F&B quantity (98.1%) and absolute dietary intake estimates (energy [97.8%], macronutrients [≥96.7%] and micronutrients [≥83.8%]). Macronutrient distribution estimates from combined stores and only the primary store closely aligned complete provider estimates (≤0.9% absolute). Food types were similar using combined stores, primary store or complete provider turnover. Evaluating combined stores F&B turnover represents an efficient method to estimate total F&B turnover quantity and associated dietary intake in RICs. In multiple-store communities, evaluating only primary store F&B turnover provides an efficient estimate of macronutrient distribution and major food types. © 2016 Public Health Association of Australia.

  5. Ocean Acidification Causes Increased Calcium Carbonate Turnover during Larval Shell Formation

    Science.gov (United States)

    Frieder, C.; Pan, F.; Applebaum, S.; Manahan, D. T.

    2016-02-01

    Mollusca is a major taxon for studies of the evolution and mechanisms of calcification. Under current and future ocean change scenarios, decreases in shell size have been observed in many molluscan species during early development. The mechanistic basis for these decreases are of significant interest. In this study, Pacific oyster larvae (Crassostrea gigas) reared at aragonite undersaturation (Ω > 1). Coupling radioisotope tracer assays with mineral mass measurements allowed calculation of calcification budgets for first shell formation in veliger stage larvae. Three primary mechanisms (in order of increasing effect) contributed to the change in shell mass at undersaturation: delayed onset of calcification, increased dissolution rates, and decreased net calcification rates. The observation of dissolution indicates turnover of the newly formed shell, and physicochemical constraints of undersaturation provide a mechanistic basis for decreased calcification.

  6. Staff Turnover in Assertive Community Treatment (Act) Teams: The Role of Team Climate.

    Science.gov (United States)

    Zhu, Xi; Wholey, Douglas R; Cain, Cindy; Natafgi, Nabil

    2017-03-01

    Staff turnover in Assertive Community Treatment (ACT) teams can result in interrupted services and diminished support for clients. This paper examines the effect of team climate, defined as team members' shared perceptions of their work environment, on turnover and individual outcomes that mediate the climate-turnover relationship. We focus on two climate dimensions: safety and quality climate and constructive conflict climate. Using survey data collected from 26 ACT teams, our analyses highlight the importance of safety and quality climate in reducing turnover, and job satisfaction as the main mediator linking team climate to turnover. The findings offer practical implications for team management.

  7. PENGARUH WORK OVERLOAD DAN WORK FAMILY CONFLICT TERHADAP TURNOVER INTENTION YANG DIMEDIASI OLEH WORK EXHAUSTION

    Directory of Open Access Journals (Sweden)

    Nurul Hidayatin Nisa

    2016-01-01

    Full Text Available The purpose of this research was to examine factors that determine turnover intention in medical representative at PT. APL. To be known before that medical representatives have high percentage in turnover. The research using work exhaustion as mediation to determine the relationship between works overload and work family conflict of turnover intention. Research method is quantitative approach in causal research. The analysis tools are AMOS and T-Sobel. Findings of this research are both work overload and work family conflict berpengaruh with work exhaustion and turnover intention, work exhaustion mediated work overload and work family conflict over turnover intention.

  8. Nonrandom community assembly and high temporal turnover promote regional coexistence in tropics but not temperate zone.

    Science.gov (United States)

    Freestone, Amy L; Inouye, Brian D

    2015-01-01

    A persistent challenge for ecologists is understanding the ecological mechanisms that maintain global patterns of biodiversity, particularly the latitudinal diversity gradient of peak species richness in the tropics. Spatial and temporal variation in community composition contribute to these patterns of biodiversity, but how this variation and its underlying processes change across latitude remains unresolved. Using a model system of sessile marine invertebrates across 25 degrees of latitude, from the temperate zone to the tropics, we tested the prediction that spatial and temporal patterns of taxonomic richness and composition, and the community assembly processes underlying these patterns, will differ across latitude. Specifically, we predicted that high beta diversity (spatial variation in composition) and high temporal turnover contribute to the high species richness of the tropics. Using a standardized experimental approach that controls for several confounding factors that hinder interpretation of prior studies, we present results that support our predictions. In the temperate zone, communities were more similar across spatial scales from centimeters to tens of kilometers and temporal scales up to one year than at lower latitudes. Since the patterns at northern latitudes were congruent with a null model, stochastic assembly processes are implicated. In contrast, the communities in the tropics were a dynamic spatial and temporal mosaic, with low similarity even across small spatial scales and high temporal turnover at both local and regional scales. Unlike the temperate zone, deterministic community assembly processes such as predation likely contributed to the high beta diversity in the tropics. Our results suggest that community assembly processes and temporal dynamics vary across latitude and help structure and maintain latitudinal patterns of diversity.

  9. Buckwheat seedling flavonoids do not undergo rapid turnover

    International Nuclear Information System (INIS)

    Margna, U.; Vainjaerv, T.

    1981-01-01

    Pulse-labelling with exogenous [1- 14 C]-L-phenylalanine showed that of all flavonoids of buckwheat seedling cotyledons only anthocyanins underwent a slow turnover (not more than 6-8 per cent a day) whilst the major flavonoids, rutin and four C-glycosylflavones, remained metabolically stable within at least 7 days. From excised hypocotyls pulse-labelled flavonoids (anthocyanins and rutin) began to disappear gradually beginning with the second day of incubation. As hypocotyls, however, during prolonged incubation soon began to autolyse a considerable part of that loss was obviously due to abnormal shifts in cell metabolic activities with a possibility that some microbial process was also involved. In hypocotyls of intact seedlings pulse-labelled rutin, similar to rutin in cotyledons, showed no signs of turnover. (author)

  10. Workplace threats to health and job turnover among women workers.

    Science.gov (United States)

    Gucer, Patricia W; Oliver, Marc; McDiarmid, Melissa

    2003-07-01

    Is job turnover related to concern about workplace health risks? Using data from a national sample of working women, we examined the relationships among workplace risk communications, worker concerns about workplace threats from hazardous substances, indoor air quality, and job change. Eight percent reported changing a job as a result of concern over workplace threats to health. Previous workplace injury predicted concern about hazardous materials and indoor air quality as well as job change, but employer communication about workplace health risks was associated with less job change and less concern about indoor air quality. Women worry about workplace threats to their health enough to change their jobs, but employers may have the power to cut turnover costs and reduce disruption to workers' lives through the use of risk communication programs.

  11. Indicators Used in the Dynamic Analysis of Turnover

    Directory of Open Access Journals (Sweden)

    Mihaela Loredana Ecobici

    2016-01-01

    Full Text Available The dynamic evolution of an indicator is an important aspect to be taken into consideration when analyzing the evolution in a company. Dynamic evolution uses a number of indicators that reveal aspects that the management of a company must introduce in the development strategy or in the rehabilitation process of a company. The purpose of this article is to analyse the dynamic evolution of the turnover at a company that operates in the field of industry. The finality of this article will result in a number of conclusions concerning the evolution of turnover analysed in the light of absolute modification, indices, growth rates and annual average rate of growth. The importance of the analysis of its evolution, stemming from the fact that it is in a relationship of perpetuous interdependence with the main economic factors that participate in the activity of production and marketing.

  12. Rapid Development, Build-Out Ratio and Subsequent Neighborhood Turnover

    Directory of Open Access Journals (Sweden)

    George O. Rogers

    2018-04-01

    Full Text Available Neighborhood development is primarily comprised of structural elements that include design elements, nearby amenities and ecological attributes. This paper assumes that the process of development itself also influences the character of the neighborhood—specifically, that the rate of development and build-out ratio influences neighborhood turnover. While the structural components clearly set a framework for development, the process of development expresses the character of the neighborhood in subtle messages conveyed through the market. Neighborhoods in the rapidly growing university town of College Station, Texas are analyzed in terms of neighborhood design, nearby amenities and landscape ecology components. Residential property records are used to characterize each neighborhood in terms of the rate of development and current build-out ratio. The multivariate analysis indicates that the development rate increases subsequent neighborhood turnover rates while the build-out ratio decreases it.

  13. The natural selection of metabolism explains curvature in allometric scaling

    OpenAIRE

    Witting, Lars

    2016-01-01

    I simulate the evolution of metabolism and mass to explain the curvature in the metabolic allometry for placental and marsupial mammals. I assume that the release of inter-specific competition by the extinction of dinosaurs 65 million years ago made it possible for each clade to diversity into a multitude of species across a wide range of niches. The natural selection of metabolism and mass was then fitted to explain the maximum observed body masses over time, as well as the current inter-spe...

  14. THE EARNINGS PER SHARE AND INVENTORY TURNOVER RATIOS IN THE GLOBAL FINANCIAL CRISIS: A COMPARATIVE STUDY FOR FOOD AND TEXTILE SECTORS IN ISTANBUL STOCK EXCHANGE

    Directory of Open Access Journals (Sweden)

    Sudi APAK

    2009-01-01

    Full Text Available The ongoing financial crisis in the global markets, which originated in the US subprime mortgage segment (real estate and quickly spread into other market segments and countries, is already seen today as one of the biggest financial crises in history. Underlying the subprime crisis had essentially two interrelated factors; the boom in US real estate markets, and the high liquidity demand in the global financial markets. The later period was, in turn, fuelled by the significant easing of US monetary policy over an extended period of time and by the additional boost to global liquidity as many emerging markets had tied their exchange rates to the US dollar and therefore had to match the expansive US monetary policy. The occurrence of market crash or financial crisis is possible key factor of earning per share (EPS and inventory turnover ratios (ITR inefficiency. This paper empirically investigates that the effects of the current financial crisis on the efficiency -earning per share (EPS and inventory turnover ratios- listed food and textile companies in Istanbul Stock Exchange (ISE. The EPS and inventory turnover ratios, applying the multivariate test statistics for the two sub-periods of pre-crisis and the crisis time. The article proceeds in the following manner. Firstly, the study will explain main reasons of global financial crises. Secondly the study will analyze all EPS and inventory turnover ratios changing are of related companies. Finally, that will be argued for adjustment of related ratios of sectors.

  15. Examining the temporal relationship between psychological climate, work attitude, and staff turnover

    Science.gov (United States)

    Garner, Bryan R.; Hunter, Brooke D.

    2012-01-01

    Relative to the broader industrial-organizational (I-O) psychology field, research on the turnover of substance use disorder (SUD) treatment staff is in its infancy. Despite its long and rich history, recent reviews of the turnover literature within I-O psychology have noted there remains considerable room for improvement. In particular, recommendations have been made for research that considers time in the turnover process and explores more distal causes of staff turnover. Addressing these gaps, this paper examined the temporal relationship between latent measures of psychological climate, work attitude, and staff turnover. Using data from 95 SUD treatment staff clustered within 29 treatment organizations, multilevel discrete-time survival analyses revealed that a latent measure of work attitude (e.g., job satisfaction, pay satisfaction, turnover intentions) fully mediated the temporal relationship between latent measures of psychological climate (e.g., supervisor support, coworker support, role conflict) and subsequent staff turnover. PMID:22658290

  16. The relationship between clinician turnover and adolescent treatment outcomes: An examination from the client perspective

    Science.gov (United States)

    Garner, Bryan R.; Funk, Rodney R.; Hunter, Brooke D.

    2012-01-01

    The turnover of substance use disorder (SUD) treatment staff has been assumed to adversely impact treatment effectiveness, yet only limited research has empirically examined this assumption. Representing an extension of prior organizational-level analyses of the impact of staff turnover on client outcomes, this study examined the impact of SUD clinician turnover on adolescent treatment outcomes using a client perspective. Multilevel regression analysis did reveal that relative to those adolescents who did not experience clinician turnover, adolescents who experienced both direct and indirect clinician turnover reported a significantly higher percentage of days using alcohol or drugs at 6-month follow-up. However, clinician turnover was not found to have significant associations (negative or positive) with the other five treatment outcomes examined (e.g., substance-related problems, involvement in illegal activity). Thus, consistent with our prior findings, the current study provides additional evidence that turnover of SUD clinicians is not necessarily associated with adverse treatment outcomes. PMID:23083980

  17. An Integrative Literature Review of Patient Turnover in Inpatient Hospital Settings.

    Science.gov (United States)

    Park, Shin Hye; Weaver, Lindsay; Mejia-Johnson, Lydia; Vukas, Rachel; Zimmerman, Julie

    2016-05-01

    High patient turnover can result in fragmentation of nursing care. It can also increase nursing workload and thus impede the ability of nurses to provide safe and high-quality care. We reviewed 20 studies that examined patient turnover in relation to nursing workload, staffing, and patient outcomes as well as interventions in inpatient hospital settings. The studies consistently addressed the importance of accounting for patient turnover when estimating nurse staffing needs. They also showed that patient turnover varied by time, day, and unit type. Researchers found that higher patient turnover was associated with adverse events; however, further research on this topic is needed because evidence on the effect of patient turnover on patient outcomes is not yet strong and conclusive. We suggest that researchers and administrators need to pay more attention to patterns and levels of patient turnover and implement managerial strategies to reduce nursing workload and improve patient outcomes. © The Author(s) 2015.

  18. The effect of culture on the curvilinear relationship between performance and turnover.

    Science.gov (United States)

    Sturman, Michael C; Shao, Lian; Katz, Jan H

    2012-01-01

    Although researchers have theorized that there exists a curvilinear relationship between job performance and voluntary turnover, their research has been tested in the United States or culturally similar Switzerland. Through a study of the performance-turnover relationship from a multinational service-oriented organization in 24 countries, we demonstrate that the general relationship between performance and turnover is similar across countries but the details of that relationship change across countries. Using 4 cultural dimensions--in-group collectivism, power distance, uncertainty avoidance, and performance orientation--we find that cultural factors alter the overall probability of voluntary turnover and influence the degree of curvilinearity in the performance-turnover relationship. Our findings have implications for research on the performance-turnover relationship, turnover research, and practice.

  19. Nitrogen Turnover on Organic and Conventional Mixed Farms

    OpenAIRE

    Halberg, Niels; Kristensen, Erik Steen; Kristensen, Ib Sillebak

    1995-01-01

    Separate focus on crop fertilization or feeding practices inadequately describes nitrogen (N) loss from mixed dairy farms because of (1) interaction between animal and crop production and between the production system and the manager, and (2) uncertainties of herd N production and crop N utilization. Therefore a systems approach was used to study N turnover and N efficiency on 16 conventional and 14 organic private Danish farms with mixed animal (dairy) and crop production. There were signifi...

  20. Kinetics of corneal epithelium turnover in vivo. Studies of lovastatin

    International Nuclear Information System (INIS)

    Cenedella, R.J.; Fleschner, C.R.

    1990-01-01

    The authors developed a direct chemical approach for estimating the rate of turnover of the corneal epithelium in vivo. The method was used to examine the effects of lovastatin, a potent inhibitor of cholesterol biosynthesis, on proliferation and turnover of the epithelium. Corneal DNA was labeled by pulse injection (IP) of the rat with 3H-thymidine, and 3H-labeled DNA was recovered from peripheral and central corneas over the next 15 days. Only the epithelium became labeled, and the loss of label by cell desquamation began 3 days after injection. The loss of 3H-DNA from the cornea (peripheral plus central region) followed first-order kinetics. The half-life of the disappearance was about 3 days. The peripheral cornea became more highly labeled than the central cornea and began to lose 3H-DNA before the central cornea. These observations support the possibility of a higher mitotic rate in the peripheral region and the centripetal movement of a population of peripheral epithelial cells in the normal cornea. The half-lives of the disappearance of 3H-DNA from peripheral and central corneas measured between days 5 and 15 postinjection were identical, both at 3 days. Complete turnover of the corneal epithelium would, therefore, require about 2 weeks (4-5 half-lives). Treatment of the rat with lovastatin had no obvious effects upon the proliferation or turnover of the corneal epithelium. Although lovastatin inhibited corneal 3-hydroxy-3-methylglutaryl coenzyme A reductase, the key regulatory enzyme of cholesterol synthesis, the cornea compensated by induction of this enzyme so that there was no net inhibition of cholesterol synthesis in the cornea

  1. The Relationship Between Army CRNA Job Satisfaction and Turnover

    Science.gov (United States)

    1998-10-01

    performance . These factors would be predicted to influence job satisfaction . The third component in Stage II, interpersonal relations which includes group...produce more although this is not consistently substantiated ( Vroom , 1964). Vroom (1964) found that job satisfaction was directly related to the...from the job, and what is supplied by the job in terms of needs. Vroom identified an inverse relationship between job satisfaction and turnover. 16

  2. Bone turnover markers: Emerging tool in the management of osteoporosis

    Directory of Open Access Journals (Sweden)

    Sahana Shetty

    2016-01-01

    Full Text Available Bone is a dynamic tissue which undergoes constant remodeling throughout the life span. Bone turnover is balanced with coupling of bone formation and resorption at various rates leading to continuous remodeling of bone. A study of bone turnover markers (BTMs provides an insight of the dynamics of bone turnover in many metabolic bone disorders. An increase in bone turnover seen with aging and pathological states such as osteoporosis leads to deterioration of bone microarchitecture and thus contributes to an increase in the risk of fracture independent of low bone mineral density (BMD. These microarchitectural alterations affecting the bone quality can be assessed by BTMs and thus may serve as a complementary tool to BMD in the assessment of fracture risk. A systematic search of literature regarding BTMs was carried out using the PubMed database for the purpose of this review. Various reliable, rapid, and cost-effective automated assays of BTMs with good sensitivity are available for the management of osteoporosis. However, BTMs are subjected to various preanalytical and analytical variations necessitating strict sample collection and assays methods along with utilizing ethnicity-based reference standards for different populations. Estimation of fracture risk and monitoring the adherence and response to therapy, which is a challenge in a chronic, asymptomatic disease such as osteoporosis, are the most important applications of measuring BTMs. This review describes the physiology of bone remodeling, various conventional and novel BTMs, and BTM assays and their role in the assessment of fracture risk and monitoring response to treatment with antiresorptive or anabolic agents.

  3. Employee turnover reducing tools in the transport companies

    OpenAIRE

    Lydekienė, Alina

    2016-01-01

    Employee turnover is an employee’s choice to leave a company. To keep employees and protect them from being attracted by competitors, companies must seek to know the personnel, to understand their needs and problems, guarantee satisfaction to an existing staff. The aspect of job change has been examined for decades in worldwide practice, because loyalty of employees, especially of skilled specialists, is one of the main factors to run a successful business (Pilkauskaitė – Valickienė, Valickas...

  4. The Link between HR Attributions and Employees’ Turnover Intentions

    Directory of Open Access Journals (Sweden)

    Juliana Caesaria Tandung

    2016-02-01

    Full Text Available Human Resources Management (HRM is part of the organizational functions that contribute to the effectiveness of a firm’s performance, and brings an organization a competitive advantage through the implementation of its Human Resources (HR practices. HR practices adopted by management are perceived or attributed subjectively by individual employees, and can in turn affect the employees’ attitudes and behavior (e.g. Job satisfaction and turnover intention. The purpose of this study is to contribute to the process-based approach by investigating the effect of HR attributions on turnover intentions, with job satisfaction playing a mediating role. The analysis is on the individual level, with 454 respondents from various organizations within the Netherlands. The results show that HR attributions can affect the turnover intention, through the presence of job satisfaction. Thus, it can be said that it is important to always consider the employees’ attitudes and behavior when examining their perception of HR practices, and in predicting their intention to leave.

  5. Control of the Protein Turnover Rates in Lemna minor

    Science.gov (United States)

    Trewavas, A.

    1972-01-01

    The control of protein turnover in Lemna minor has been examined using a method described in the previous paper for determining the rate constants of synthesis and degradation of protein. If Lemna is placed on water, there is a reduction in the rate constants of synthesis of protein and an increase (3- to 6-fold) in the rate constant of degradation. The net effect is a loss of protein from the tissue. Omission of nitrate, phosphate, sulfate, magnesium, or calcium results in increases in the rate constant of degradation of protein. An unusual dual effect of benzyladenine on the turnover constants has been observed. Treatment of Lemna grown on sucrose-mineral salts with benzyladenine results in alterations only in the rate constant of synthesis. Treatment of Lemna grown on water with benzyladenine alters only the rate constant of degradation. Abscisic acid on the other hand alters both rate constants of synthesis and degradation of protein together. Inclusion of growth-inhibiting amino acids in the medium results in a reduction in the rate constants of synthesis and increases in the rate constant of degradation of protein. It is concluded that the rate of turnover of protein in Lemna is very dependent on the composition of the growth medium. Conditions which reduce growth rates also reduce the rates of synthesis of protein and increase those of degradation. PMID:16657895

  6. Cholesterol turnover and metabolism in two patients with abetalipoproteinemia

    International Nuclear Information System (INIS)

    Goodman, D.S.; Deckelbaum, R.J.; Palmer, R.H.; Dell, R.B.; Ramakrishnan, R.; Delpre, G.; Beigel, Y.; Cooper, M.

    1983-01-01

    Total body turnover of cholesterol was studied in two patients with abetalipoproteinemia, a 32-year-old man and a 31-year-old woman. The patients received [14C]cholesterol intravenously, and the resulting specific activity-time curves (for 40 and 30 weeks, respectively) were fitted with a three-pool model. Parameters were compared with those from studies of cholesterol turnover in 82 normal and hyperlipidemic subjects. A three-pool model gave the best fit for the abetalipoproteinemic patients, as well as for the 82 previously studied subjects, suggesting general applicability of this model. Cholesterol production rates in the two abetalipoproteinemic subjects (0.82 and 0.89 g/day) were close to values predicted for persons of their body weight. Thus, total body turnover rate of cholesterol was quite normal in abetalipoproteinemia, confirming previous reports. Very low values (9.2 and 8.4 g) were found for M1, the size of the rapidly exchanging compartment pool 1, in the two abetalipoproteinemic subjects. These values were well below the values predicted (from the comparison study population) for normal persons of this size with low plasma cholesterol levels. For one patient, total body exchangeable cholesterol was very low, although not significantly below the predicted values for a person of his size. In the second patient, the observed estimate for total body exchangeable cholesterol was well within the range of values predicted for persons of her size with low to extremely low cholesterol levels

  7. Turnover in intracranial aneurysm phantoms: its relation to neck size

    International Nuclear Information System (INIS)

    Chung, Tae Sub; Lee, Young Jun; Rhim, Yoon Chul

    2003-01-01

    To evaluate the physiologic background of aneurysms poorly visualized during 3D-TOF MRA, contrast-enhanced MRA (CEMRA) and DSA due to hemodynamic isolation. Using handmade elastic silicon phantoms to represent terminal basilar tip aneurysms, 3D-TOF MRA, CEMRA and DSA were used to determine blood turnover. Aneurysmal neck size was 2 mm and 10 mm, and the use of a pulsatile pump also helped recreate human physiologic parameters. We compared the results with those of computational fluid dynamics. DSA images of the narrow-necked aneurysm showed that a small volume of contrast medium washed into it during the systolic phase. As the width of its neck increased, the turnover volume of fragments of contrast bolus also increased. At CEMRA, the broad-necked aneurysm was visualized as the main bolus of Gd-DTPA passed through it, and at delayed CEMRA, the narrow-necked aneurysm was visualized faintly after the passage of bolus Gd-DTPA. The results correlated closely with those of 3D-TOF MRA and computational fluid dynamics. The visualization of intracranial aneurysms at 3D-TOF MRA, CEMRA and DSA was greatly dependent upon blood turnover, which varied according to aneurysmal neck size. A narrow-necked aneurysm might be missed at 3D-TOF MRA, CEMRA and DSA due to hemodynamic isolation

  8. Computational model of collagen turnover in carotid arteries during hypertension.

    Science.gov (United States)

    Sáez, P; Peña, E; Tarbell, J M; Martínez, M A

    2015-02-01

    It is well known that biological tissues adapt their properties because of different mechanical and chemical stimuli. The goal of this work is to study the collagen turnover in the arterial tissue of hypertensive patients through a coupled computational mechano-chemical model. Although it has been widely studied experimentally, computational models dealing with the mechano-chemical approach are not. The present approach can be extended easily to study other aspects of bone remodeling or collagen degradation in heart diseases. The model can be divided into three different stages. First, we study the smooth muscle cell synthesis of different biological substances due to over-stretching during hypertension. Next, we study the mass-transport of these substances along the arterial wall. The last step is to compute the turnover of collagen based on the amount of these substances in the arterial wall which interact with each other to modify the turnover rate of collagen. We simulate this process in a finite element model of a real human carotid artery. The final results show the well-known stiffening of the arterial wall due to the increase in the collagen content. Copyright © 2015 John Wiley & Sons, Ltd.

  9. KEAHLIAN AUDITOR DAN TURNOVER INTENTION SEBAGAI MEDIASI DETERMINAN KINERJA AUDITOR

    Directory of Open Access Journals (Sweden)

    Ceacilia Srimindarti

    2015-12-01

    Full Text Available This research aims to examine the effect of locus of control and organizational commitment on auditors’ performance as well as to examine whether auditors’ expertise and turnover intention mediate the effect of locus of control and organizational commitment on auditors’ performance. Samples of this study were auditors who worked at audit firms in Semarang. Samples were selected using the purposive sampling method. The data were analyzed using SEM with AMOS program. This study found that locus of control had a negative effect on auditors’ performance, organizational commitment had a positive effect on auditors’ performance, and auditors’ expertise and turnover intention had no effect on auditors’ performance. Furthermore, locus of control had a negative effect on auditors’ expertise, and organizational commitment had a negative effect on turnover intention. Based on this result, managers of public accounting firm (partners should provide some trainings to the auditors who had the external locus of control so that they can achieve the standardized performances. They should also confirm the company’s values to the auditor to increase emotional attachment to the company as well as try to comply to the demands of the company thus its performance will be in accordance with company’s expectations.

  10. Using Job Embeddedness to Explain New Teacher Retention

    Science.gov (United States)

    Watson, Jennifer Moradian; Olson-Buchanan, Julie

    2016-01-01

    The high turnover rates among teachers, particularly novice teachers, is a significant problem in the field of education. This study examines the relationship between teacher turnover and a construct found in organizational literature--job embeddedness. Job embeddedness is the extent to which an employee connects socially and emotionally to their…

  11. Paleocommunity turnover in an Early Pliocene seamount from southeastern Spain

    Science.gov (United States)

    García-Ramos, Diego Antonio; Zuschin, Martin

    2017-04-01

    Seamounts are topographic elevations under the sea, regardless of their size and relief. They support rich living communities and are important biodiversity hotspots, but many of the fundamental ecological processes that maintain seamount communities remain poorly understood. In contrast to snapshot observations conducted on extant seamounts, fossil examples may provide the opportunity to assess how temporal changes in physico-chemical parameters relate to paleocommunity turnovers in these particular biotopes. Here we deal with an Early Pliocene (Zanclean) small seamount in southeastern Spain. This classic locality is extremely rich in fossil macroinvertebrates and was subject to studies of some taxonomic groups in the late seventies. However, the detailed stratigraphy is herein outlined for the first time. The overall feature is a shallowing upward succession about 35 m thick which onlaps a Miocene volcanic ridge. The occurrence of the planktonic foraminifera Globorotalia margaritae and G. puncticulata allow attribution to the MPl3 biozone of the Mediterranean Pliocene. We measured two sections that can be divided in a lower interval of fine-grained bryozoan-rich deposits and a upper interval of biocalcarenite increasingly rich in rhodoliths upsection. The whole series is bioturbated, with Thalassinoides traces being more common upsection. Biofabrics comprise mostly densely-packed suites of disarticulated and fragmented shells of calcitic fauna (large oysters are often bioeroded by clionid sponges), suggesting relatively low sedimentation rates and reworking by storms (e.g., channelized shell-beds, tubular tempestites). The prevailing taxonomic groups are cheilostome bryozoans, oysters, brachiopods, pectinids, echinoderms, cirripedes and corals. The lower interval contains octocoral internodes (Isididae) (only recorded at the base of the section). Scleratinians like Balanophyllia? decrease in abundance upsection. Bryozoans are extremely abundant and diverse, with

  12. How energetic and environmental constraints of microorganisms determine the carbon turnover in soils

    Science.gov (United States)

    Don, A.; Rödenbeck, C.; Gleixner, G.

    2012-04-01

    Microorganisms are the main catalysts driving carbon fluxes from soils. Traditional concepts of soil carbon stabilization failed to account for environmental and energy constraints of microorganisms. The distribution and density of organic carbon in the soil profile maybe a key factor determining the carbon stability and carbon flux. Decomposition is a two-step process following the Michaelis Menten kinetics: In a first step enzyme and substrate form a joint complex and then the decomposition reaction is catalyzed. Thus, biological decomposition relies on the encounter of substrate and the degradation catalyst, the microorganisms. Lower substrate concentration decreases the likelihood of an enzyme to hit a substrate molecule, to form an enzyme-substrate complex, and thus to catalyze the reaction. However, it was unproofen if this concept can be appliued to soils also. A long-term lab experiment revealed that the soil carbon turnover decreased with increasing carbon dilution due to mixture with soil minerals. The ability of microorganisms to move towards substrate in soils seems to be limited. To elucidate the effect of concentration-controlled carbon turnover, we devised the simple simulation model SCAMP based on the two-step kinetic with microorganism and carbon particles been simulated explicitly. The SCAMP model was able to simulate soil carbon profiles and age profiles in a realistic manner. The only carbon stabilization mechanism implemented in the model is the distribution of microorganisms and carbon particles in the soil and thus the availability of carbon for microorganism, which is especially important for subsoil carbon dynamics. The experiments and the model help to explain why large fractions of soil carbon have been stabilized for millennia and decoupled from the global carbon cycle.

  13. The Effect of Parasite Infection on Stable Isotope Turnover Rates of δ15N, δ13C and δ34S in Multiple Tissues of Eurasian Perch Perca fluviatilis.

    Directory of Open Access Journals (Sweden)

    Elizabeth Yohannes

    Full Text Available Stable isotope analysis of commercially and ecologically important fish can improve understanding of life-history and trophic ecology. However, accurate interpretation of stable isotope values requires knowledge of tissue-specific isotopic turnover that will help to describe differences in the isotopic composition of tissues and diet. We performed a diet-switch experiment using captive-reared parasite-free Eurasian perch (Perca fluviatilis and wild caught specimens of the same species, infected with the pike tapeworm Triaenophorus nodulosus living in host liver tissue. We hypothesize that metabolic processes related to infection status play a major role in isotopic turnover and examined the influence of parasite infection on isotopic turn-over rate of carbon (δ13C, nitrogen (δ15N and sulphur (δ34S in liver, blood and muscle. The δ15N and δ13C turnovers were fastest in liver tissues, followed by blood and muscle. In infected fish, liver and blood δ15N and δ13C turnover rates were similar. However, in infected fish, liver and blood δ13C turnover was faster than that of δ15N. Moreover, in infected subjects, liver δ15N and δ13C turnover rates were three to five times faster than in livers of uninfected subjects (isotopic half-life of ca.3-4 days compared to 16 and 10 days, respectively. Blood δ34S turnover rate were about twice faster in non-infected individuals implying that parasite infection could retard the turnover rate of δ34S and sulphur containing amino acids. Slower turnover rate of essential amino acid could probably decrease individual immune function. These indicate potential hidden costs of chronic and persistent infections that may have accumulated adverse effects and might eventually impair life-history fitness. For the first time, we were able to shift the isotope values of parasites encapsulated in the liver by changing the dietary source of the host. We also report variability in isotopic turnover rates between tissues

  14. Promoting retention of nurses: A meta-analytic examination of causes of nurse turnover.

    Science.gov (United States)

    Nei, Darin; Snyder, Lori Anderson; Litwiller, Brett J

    2015-01-01

    Because the health care field is expected to be the fastest growing job field until 2020, an urgent need to focus on nurse retention exists. The aim of this study was to examine the relationships between predictors of turnover (i.e., personal characteristics, role states, job characteristics, group/leader relations, organizational/environmental perceptions, attitudinal reactions) and turnover cognitions and intentions, as well as actual turnover among nurses, in an effort to determine the strongest predictors of voluntary turnover. Meta-analysis was used to determine best estimates of the effect of predictors on turnover based on 106 primary studies of employed nurses. Meta-analyzed correlations were subjected to path analysis to establish the structural relationships among the study variables. Supportive and communicative leadership, network centrality, and organizational commitment are the strongest predictors of voluntary turnover based on meta-analytic correlations. Additional variables that relate to nurse turnover intentions include job strain, role tension, work-family conflict, job control, job complexity, rewards/recognition, and team cohesion. The findings suggest that some factors, such as salary, are relatively less important in prediction of turnover. Administrators concerned about nurse turnover may more effectively direct resources toward altering certain job characteristics and work conditions in the effort to reduce voluntary turnover among nurses.

  15. Tree Species Identity Shapes Earthworm Communities

    DEFF Research Database (Denmark)

    Schelfhout, Stephanie; Mertens, Jan; Verheyen, Kris

    2017-01-01

    Earthworms are key organisms in forest ecosystems because they incorporate organic material into the soil and affect the activity of other soil organisms. Here, we investigated how tree species affect earthworm communities via litter and soil characteristics. In a 36-year old common garden...... of soil and foliar litter, and determined the forest floor turnover rate and the density and biomass of the earthworm species occurring in the stands. Tree species significantly affected earthworm communities via leaf litter and/or soil characteristics. Anecic earthworms were abundant under Fraxinus, Acer...

  16. What Explains Patterns of Diversification and Richness among Animal Phyla?

    Science.gov (United States)

    Jezkova, Tereza; Wiens, John J

    2017-03-01

    Animal phyla vary dramatically in species richness (from one species to >1.2 million), but the causes of this variation remain largely unknown. Animals have also evolved striking variation in morphology and ecology, including sessile marine taxa lacking heads, eyes, limbs, and complex organs (e.g., sponges), parasitic worms (e.g., nematodes, platyhelminths), and taxa with eyes, skeletons, limbs, and complex organs that dominate terrestrial ecosystems (arthropods, chordates). Relating this remarkable variation in traits to the diversification and richness of animal phyla is a fundamental yet unresolved problem in biology. Here, we test the impacts of 18 traits (including morphology, ecology, reproduction, and development) on diversification and richness of extant animal phyla. Using phylogenetic multiple regression, the best-fitting model includes five traits that explain ∼74% of the variation in diversification rates (dioecy, parasitism, eyes/photoreceptors, a skeleton, nonmarine habitat). However, a model including just three (skeleton, parasitism, habitat) explains nearly as much variation (∼67%). Diversification rates then largely explain richness patterns. Our results also identify many striking traits that have surprisingly little impact on diversification (e.g., head, limbs, and complex circulatory and digestive systems). Overall, our results reveal the key factors that shape large-scale patterns of diversification and richness across >80% of all extant, described species.

  17. Intraspecific trait variation and covariation in a widespread tree species (Nothofagus pumilio) in southern Chile.

    Science.gov (United States)

    Fajardo, Alex; Piper, Frida I

    2011-01-01

    • The focus of the trait-based approach to study community ecology has mostly been on trait comparisons at the interspecific level. Here we quantified intraspecific variation and covariation of leaf mass per area (LMA) and wood density (WD) in monospecific forests of the widespread tree species Nothofagus pumilio to determine its magnitude and whether it is related to environmental conditions and ontogeny. We also discuss probable mechanisms controlling the trait variation found. • We collected leaf and stem woody tissues from 30-50 trees of different ages (ontogeny) from each of four populations at differing elevations (i.e. temperatures) and placed at each of three locations differing in soil moisture. • The total variation in LMA (coefficient of variation (CV) = 21.14%) was twice that of WD (CV = 10.52%). The total variation in traits was never less than 23% when compared with interspecific studies. Differences in elevation (temperature) for the most part explained variation in LMA, while differences in soil moisture and ontogeny explained the variation in WD. Traits covaried similarly in the altitudinal gradient only. • Functional traits of N. pumilio exhibited nonnegligible variation; LMA varied for the most part with temperature, while WD mostly varied with moisture and ontogeny. We demonstrate that environmental variation can cause important trait variation without species turnover. © The Authors (2010). Journal compilation © New Phytologist Trust (2010).

  18. Endangered Species

    Science.gov (United States)

    EPA's Endangered Species Protection Program helps promote recovery of listed species. The ESPP determines if pesticide use in a geographic area may affect any listed species. Find needed limits on pesticide use in Endangered Species Protection Bulletins.

  19. An engine for global plant diversity: Highest evolutionary turnover and emigration in the American tropics

    Directory of Open Access Journals (Sweden)

    Alexandre eAntonelli

    2015-04-01

    Full Text Available Understanding the processes that have generated the latitudinal biodiversity gradient and the continental differences in tropical biodiversity remains a major goal of evolutionary biology. Here we estimate the timing and direction of range shifts of extant flowering plants (angiosperms between tropical and non-tropical zones, and into and out of the major tropical regions of the world. We then calculate rates of speciation and extinction taking into account incomplete taxonomic sampling. We use a recently published fossil calibrated phylogeny and apply novel bioinformatic tools to code species into user-defined polygons. We reconstruct biogeographic history using stochastic character mapping to compute relative numbers of range shifts in proportion to the number of available lineages through time. Our results, based on the analysis of c. 22,600 species and c. 20 million geo-referenced occurrence records, show no significant differences between the speciation and extinction of tropical and non-tropical angiosperms. This suggests that at least in plants, the tropical biodiversity gradient primarily derives from other factors than differential rates of diversification. In contrast, the outstanding species richness found today in the American tropics (the Neotropics, as compared to tropical Africa and tropical Asia, is associated with significantly higher speciation and extinction rates. This suggests an exceedingly rapid evolutionary turnover, i.e. Neotropical species being formed and replaced by one another at unparalleled rates. In addition, tropical America stands out from other continents by having ‘pumped out’ more species than it received through most of the last 66 million years. These results imply that the Neotropics have acted as an engine for global plant diversity.

  20. Centennial black carbon turnover observed in a Russia steppe soil

    Energy Technology Data Exchange (ETDEWEB)

    Hammes, K.; Torn, M.S.; Lapenas, A.G.; Schmidt, M.W.I.

    2008-09-15

    Black carbon (BC), from incomplete combustion of fuels and biomass, has been considered highly recalcitrant and a substantial sink for carbon dioxide. Recent studies have shown that BC can be degraded in soils. We use two soils with very low spatial variability sampled 100 years apart in a Russian steppe preserve to generate the first whole-profile estimate of BC stocks and turnover in the field. Quantities of fire residues in soil changed significantly over a century. Black carbon stock was 2.5 kg m{sup -2}, or about 7-10% of total organic C in 1900. With cessation of biomass burning, BC stocks decreased 25% over a century, which translates into a centennial soil BC turnover (293 years best estimate; range 182-541 years), much faster than so-called inert or passive carbon in ecosystem models. The turnover time presented here is for loss by all processes, namely decomposition, leaching, and erosion, although the latter two were probably insignificant in this case. Notably, at both time points, the peak BC stock was below 30 cm, a depth interval, which is not typically accounted for. Also, the quality of the fire residues changed with time, as indicated by the use benzene poly carboxylic acids (BPCA) as molecular markers. The proportions of less-condensed (and thus more easily degradable) BC structures decreased, whereas the highly condensed (and more recalcitrant) BC structures survived unchanged over the 100-year period. Our results show that BC cannot be assumed chemically recalcitrant in all soils, and other explanations for very old soil carbon are needed.