Variation In Turnover Research Articles

Quantitative proteomics reveals protein profiles underlying major transitions in aspen wood development.

BackgroundWood development is of outstanding interest both to basic research and industry due to the associated cellulose and lignin biomass production. Efforts to elucidate wood formation (which is essential for numerous aspects of both pure and applied plant science) have been made using transcriptomic analyses and/or low-resolution sampling. However, transcriptomic data do not correlate perfectly with levels of expressed proteins due to effects of post-translational modifications and variations in turnover rates. In addition, high-resolution analysis is needed to characterize key transitions. In order to identify protein profiles across the developmental region of wood formation, an in-depth and tissue specific sampling was performed.ResultsWe examined protein profiles, using an ultra-performance liquid chromatography/quadrupole time of flight mass spectrometry system, in high-resolution tangential sections spanning all wood development zones in Populus tremula from undifferentiated cambium to mature phloem and xylem, including cell expansion and cell death zones. In total, we analyzed 482 sections, 20–160 μm thick, from four 47-year-old trees growing wild in Sweden. We obtained high quality expression profiles for 3,082 proteins exhibiting consistency across the replicates, considering that the trees were growing in an uncontrolled environment. A combination of Principal Component Analysis (PCA), Orthogonal Projections to Latent Structures (OPLS) modeling and an enhanced stepwise linear modeling approach identified several major transitions in global protein expression profiles, pinpointing (for example) locations of the cambial division leading to phloem and xylem cells, and secondary cell wall formation zones. We also identified key proteins and associated pathways underlying these developmental landmarks. For example, many of the lignocellulosic related proteins were upregulated in the expansion to the early developmental xylem zone, and for laccases with a rapid decrease in early xylem zones. We observed upregulation of two forms of xylem cysteine protease (Potri.002G005700.1 and Potri.005G256000.2; Pt-XCP2.1) in early xylem and their downregulation in late maturing xylem. Our data also show that Pt-KOR1.3 (Potri.003G151700.2) exhibits an expression pattern that supports the hypothesis put forward in previous studies that this is a key xyloglucanase involved in cellulose biosynthesis in primary cell walls and reduction of cellulose crystallinity in secondary walls.ConclusionOur novel multivariate approach highlights important processes and provides confirmatory insights into the molecular foundations of wood development.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2458-z) contains supplementary material, which is available to authorized users.

Seasonal succession of pollinator floral resources in four types of grasslands

Pollinators are declining globally, and this decline in ecosystem services threatens the stability of agricultural and natural systems. Pollinators depend on a diversity of floral resources that are primarily found in uncultivated areas of agro‐ecosystems such as grasslands. Seasonal succession (the seasonal changes that occur in community composition and structure) of floral resources is an essential consideration for pollinator conservation within agro‐ecosystems. Different types of grasslands common within agricultural landscapes could be expected to differ in their seasonal succession of floral resources. Here we investigated how different types of grasslands important for pollinator conservation in the tallgrass prairie ecoregion (remnant prairies, reconstructed prairies, conservation grazed cattle pastures, and old fields) differ in their seasonal succession of floral resources by sampling the plant community every two weeks from 3 May through 4 October 2013. We found remnant prairies had greater richness of inflorescences when summed over the growing season, and that remnants were least similar to the other grassland types in terms of composition. Reconstructed prairies had high richness of inflorescences and exhibited the most similarity in composition to remnant prairies only during the middle of the growing season. Conservation grazed cattle pastures had more periods where turnover in composition from one survey to the next was low, indicated by the coefficient of variation in turnover throughout the season. Old fields had the lowest richness of inflorescences and were significantly different from reconstructed and remnant prairies.

<sup>14</sup>C in cropland soil of a long-term field trial – experimental variability and implications for estimating carbon turnover

Abstract. Because of their controlled nature, the presence of independent replicates, and their known management history, long-term field experiments are key to the understanding of factors controlling soil carbon. Together with isotope measurements, they provide profound insight into soil carbon dynamics. For soil radiocarbon, an important tracer for understanding these dynamics, experimental variability across replicates is usually not accounted for; hence, a relevant source of uncertainty for quantifying turnover rates is missing. Here, for the first time, radiocarbon measurements of five independent field replicates, and for different layers, of soil from the 66-year-old controlled field experiment ZOFE in Zurich, Switzerland, are used to address this issue. 14C variability was the same across three different treatments and for three different soil layers between the surface and 90 cm depths. On average, experimental variability in 14C content was 12 times the analytical error but still, on a relative basis, smaller than variability in soil carbon concentration. Despite a relative homogeneous variability across the field and along the soil profile, the curved nature of the relationship between radiocarbon content and modelled carbon mean residence time implies that the absolute error of calculated soil carbon turnover time increases with soil depth. In our field experiment findings on topsoil carbon turnover variability would, if applied to subsoil, tend to underweight turnover variability even if experimental variability in the subsoil isotope concentration is the same. Together, experimental variability in radiocarbon is an important component in an overall uncertainty assessment of soil carbon turnover.

Systematic Risk and Share Turnover

I show that the stocks’ contribution to market volatility increases uniformly with their share turnover. The source of this relation is the market force driving the persistence of cross-sectional variation in turnover, namely the rate of investor participation in a stock. A higher rate of participation generates a persistent pattern of relative overreaction to common shocks, resulting in a large cross-sectional dispersion in market beta at both short and long return horizons. This mechanism (i) sheds light on the source of excess market volatility, (ii) introduces a strong mechanical element into the beta-return relation, challenging the traditional interpretation of this relation and the meaningfulness of the existing tests of the CAPM, and (iii) suggests that the low-beta anomaly (Black et al., 1972) reflects a reversal of the beta-driven overreaction in the cross-section of stock returns.

What Does the Pin Model Identify as Private Information?

Some recent papers suggest that the Easley and O’Hara (1987) probability of informed trade (PIN) model fails to capture private information. We investigate this issue by comparing the PIN model with the Duarte and Young (2009) (DY) and Odders-White and Ready (2008) (OWR) models of private information arrival. We find that the PIN and DY models fail to capture private information because they mistakenly associate variations in turnover with the arrival of private information. On the other hand, the OWR model, which uses returns along with order flow imbalance, seems to plausibly identify the arrival of private information.

Non-Financial Disclosure and Value Creation through Consumer Satisfaction in France

In this paper, we are interested in the impact of CSR and social reporting on consumer behavior and thus on the value creation. To enrich the literature and to better understand how CSR reputation can create value for the company, we empirically study the effect of social reporting on the ROS (Return on sales), the variation of turnover and Profit margin through the study of "responsible" behavior of consumers in France. Results show that there is a positive but not significant relationship between social reporting and the change in turnover and profit margins. But there was a significantly positive impact of non-financial disclosure on the return on sales.

Rates and Patterns of Law Enforcement Turnover

Law enforcement agencies invest substantial resources to recruit, hire, and train new police officers. Reducing officer turnover can save significant resources, yet little is known about the rates and patterns of turnover in law enforcement. Using data from the Law Enforcement Management and Administrative Statistics (LEMAS) survey in 2003 and the Census of State and Local Law Enforcement Agencies (CSLLEA) in 2008, this study establishes baseline rates of employee turnover for sworn police officers. In addition to national rates, variations in turnover were compared across states, regions, urbanity, agency size, and agency type. Nationally, the total turnover rate was 10.8% in both 2003 and 2008. There was much consistency in turnover rates between survey years. Turnover rates, however, were higher in smaller agencies, municipal agencies, those in southern regions, and those in rural areas. The turnover rate benchmarks reported here serve to inform future research on law enforcement turnover and retention.

Spatial and temporal variability in species richness in a temperate intertidal community

Understanding changes in estuarine benthic communities has important implications for conservation and yet it is a challenge due to the high natural variability of these systems. We addressed this challenge through the study of temporal and spatial patterns of species richness in an intertidal benthic community in New Zealand North Island. Five different locations within the estuary were monitored seasonally over 12 yr. This data set allowed the study of species–time–area relationships (STAR) and the delineation of patterns in species richness, heterogeneity and turnover in space and time. The site with the highest species richness also had the highest within‐site heterogeneity in species richness, a high number of species occurring infrequently in time, the lowest mud content and the most variable wave climate. Similarities and differences between sites were generally maintained over time, although seasonal and multi‐year patterns in species richness occurred at all sites. The STAR showed a significant negative interaction between space and time, with species accumulation rates in space and time being equivalent at 4 spatial replicates (250 m2) and 2 temporal replicates (6 months). The lowest source of variability in species turnover was within site, and the highest source was over years. This was reflected in the lack of an asymptotic relationship in the species accumulation curve despite the 12 yr of monitoring. These results contribute to the knowledge of the variability in diversity patterns in estuaries and have important implications for long‐term monitoring of natural communities and the estimation of diversity for conservation.

How organizational support impacts affective commitment and turnover among Italian nurses: a multilevel mediation model

This study examines multilevel relationships between perceived organizational support (POS), affective commitment and voluntary turnover among nurses. We explored the mediation role of affective commitment between POS and turnover behavior at both individual and work-unit levels. This cross-level study involved 945 Italian nurses from 60 work units. We hypothesized and showed that collective affective commitment fully mediated the impact of climate for POS on individual and collective turnover among nurses. This study helps explain the variance in turnover among nurses in healthcare organizations by analyzing the influence of unit-level climate on individual behavior. Results stress that social environments within wards are important in explaining the processes by which nurses decide to quit their work unit.

Altered subcutaneous abdominal adipose tissue lipid synthesis in obese, insulin-resistant humans

The purpose of this study was to evaluate the variability of subcutaneous abdominal adipose tissue (AT) dynamics in obese subjects with a wide range of insulin sensitivity (IS) and the correlation between these two metabolic measures. Ten obese (BMI 30-40 kg/m²) nondiabetic subjects with (n = 6) and without (n = 4) the metabolic syndrome were studied following a 12-wk ²H₂O labeling period. Subcutaneous abdominal AT biopsies were collected. Deuterium incorporation into triglyceride (TG)-glycerol and TG-palmitate were measured by gas chromatography-mass spectrometry for the calculation of fractional TG synthesis (fTG) and fractional de novo lipogenesis (fDNL). Muscle IS and insulin-mediated nonesterified fatty acid (NEFA) suppression (a measure for adipose IS) indexes were derived from the oral glucose tolerance test (OGTT). The ability of subcutaneous abdominal AT to synthesize lipids varied significantly in obese subjects (fTG range 7-28%, fDNL range 1.1-4.6%) with significantly lower values (>35% reduction) for both parameters in obese with the metabolic syndrome. fTG correlated positively with muscle IS (r = 0.64, P = 0.04) and inversely with NEFA suppression during the OGTT (r = -0.69, P = 0.03). These results demonstrate a large variability in subcutaneous abdominal AT lipid turnover in obesity. Moreover, a reduced capacity for subcutaneous abdominal AT fat storage is associated with muscle and adipose tissue insulin resistance as well as with the metabolic syndrome, thus identifying a form of obesity at heightened risk for type 2 diabetes and cardiovascular disease.

Is it Time to Voluntarily Turn Over Theories of Voluntary Turnover?

The current research literature on voluntary employee turnover exhibits at least four shortcomings: low predictive validity, excessive exuberance with predictors, low rigor, and little relevance. Existing theories of voluntary employee turnover research are under specified, as none contains the full range of variables originally hypothesized by March and Simon as contributing to individual employees' decisions to quit their jobs. March and Simon (1958) contributed to the current state of affairs by making at least one assumption that subsequent results do not support. Subsequent efforts to expand theory and to detect and integrate new explanatory constructs have led to a much deeper understanding of the same small portion of turnover variance explained in employee decisions to quit. Deficiencies in current approaches and what a nondeficient model of voluntary employee turnover might look like are described. Directions for future voluntary turnover research are identified, as are past trends that need to be discontinued.

Dragonflies: climate canaries for river management

AbstractAimFreshwater ecosystems are highly vulnerable to the effects of climate change. Where long‐term datasets are available, shifts in species phenology, species distributions and community structure consistent with a climate change signal have already been observed. Identifying trends across the wider landscape, to guide management in response to this threat, is limited by the resolution of sampling. Standard biomonitoring of macroinvertebrates for water‐quality purposes is currently not well suited to the detection of climate change effects, and there are risks that substantial changes will occur before a management response can be made. This study investigated whether dragonflies, frequently recommended as general indicators of ecological health, are also suitable as indicators of climate change.LocationData were analysed from standard bio‐assessment monitoring at over 850 sites spanning a 9° latitudinal gradient in eastern Australia.MethodsUsing variation partitioning, we analysed the proportion of assemblage turnover in dragonflies and other macroinvertebrate assemblages that can be explained by climate and other environmental drivers. We also tested whether the utility of dragonflies as indicators improved at higher taxonomic resolution and whether the turnover of dragonfly assemblages was congruent with that of other groups.ResultsClimate explained three times as much variation in turnover of dragonfly species than dragonfly and other macroinvertebrate assemblages at family level. The dissimilarity of dragonflies and varying turnover in each macroinvertebrate assemblage meant surrogacy amongst groups were low.Main conclusionsOn the basis of the influence of climate on turnover of macroinvertebrate assemblages, dragonfly species distribution appears highly sensitive to climatic factors, making this taxon a potential useful indicator of climate change responses. However, the low surrogacy amongst assemblages also suggests that a shift in the focus of conservation management from specific taxa to the functional composition of assemblages across a diverse range of habitats is needed.

Temporal variability in California grasslands: Soil type and species functional traits mediate response to precipitation

Plant communities on infertile soils may be relatively resistant to climatic variation if species in these communities have "stress-tolerant" functional traits that limit their ability to respond to climate. Alternatively, such communities may be more sensitive to climatic variation if their relatively sparse vegetative cover exposes species to more extreme changes in factors such as temperature or wind. We compared temporal variability in species richness and composition over 10 years between grasslands on infertile serpentine and "normal" sedimentary soils. Variability in species richness and species composition tracked mean annual precipitation on both soils, but variability was lower in serpentine grasslands. Communities on serpentine had lower functional diversity and had species with more "stress-tolerant" traits than non-serpentine communities (i.e., shorter stature, lower specific leaf area, and lower leaf area). Within and between soils, variability in species richness and temporal turnover were lower in communities scoring as more stress tolerant on a multivariate index of these traits; however, community variability was unrelated to functional diversity. Within 41 species found commonly on both soils, variability in occurrence and cover were also lower on serpentine soils, even though intraspecific trait differences between soils were minimal; this suggests a direct effect of soil type on species variability in addition to the indirect, trait-mediated effect. Communities with higher biomass had higher annual variability in species occurrence and cover. Our results suggest that infertile soils reduce compositional variability indirectly by selecting for stress-tolerant traits and directly by limiting productivity. We conclude that communities on infertile soils may respond more conservatively to predicted changes in precipitation, including increased variability, than communities on soils of normal fertility.

Local variations in turnover of periodontal collagen fibers in rats

The exact cause of orthodontic relapse is still unclear, although it is often suggested to be caused by periodontal collagen fibers. We hypothesize that long-lived collagen fibers in the periodontium cause relapse. The aim was to determine the half-life of periodontal collagen fibers around rat molars. Thirty weanling rats were repeatedly injected with (3) H-proline, and autoradiography of histological sections was performed at 1, 4, 8, 15, 22, 29, 36, 57, 78 and 113 d after labeling. Grain densities determined in specific areas of the periodontium were used to calculate collagen half-life. The half-life (t(½) ) was found to decrease from the supra-alveolar region to the apical periodontal ligament region. It was longer in the supra-alveolar region (1.39 ± 0.14 wk) compared with the deeper regions (p < 0.05). The t(½) of the upper periodontal ligament region (0.78 ± 0.20 wk) was longer than that of the inter-radicular periodontal ligament region (0.42 ± 0.07 wk, p < 0.05). The t(½) of the apical periodontal ligament region was 0.61 ± 0.15 wk. The data indicate that long-lived collagen fibers do not exist in the soft tissues of the periodontium, and are probably not responsible for relapse. The differences in collagen half-life might be caused by local variations in compressive strain induced by normal function.

Employee Turnover In The Small Business: Practical Insights From Urban Child Care Centers

&lt;p class="MsoNormal" style="text-align: justify; margin: 0in 0.5in 0pt;"&gt;&lt;span style="font-size: 10pt; mso-bidi-font-size: 12.0pt;"&gt;&lt;span style="font-family: Times New Roman;"&gt;This paper investigates the claims of alarming turnover rates in the childcare work force (as claimed by the Center for the Childcare workforce) in the context of organizational literature.&lt;span style="mso-spacerun: yes;"&gt;&amp;nbsp; &lt;/span&gt;Data collected from 70 childcare centers of New York City partially support the traditional claim that behavioral variables (such as job satisfaction and commitment) explain variations in turnover rate.&lt;span style="mso-spacerun: yes;"&gt;&amp;nbsp; &lt;/span&gt;Additionally, it claims that negative work outcomes (or work itself could be cause of voluntary turnover) in this instance, the behavior problem, discipline problem, funding uncertainty and the like may be included in any deterministic model of employee turnover.&lt;span style="mso-spacerun: yes;"&gt;&amp;nbsp; &lt;/span&gt;Finally, this study did not find overwhelming evidence supporting the alarming rate of turnover in the childcare centers.&lt;/span&gt;&lt;/span&gt;&lt;/p&gt;

Are common species sufficient in describing turnover in aquatic metacommunities along environmental and spatial gradients?

Recent findings have suggested that large‐scale diversity patterns are primarily driven by widespread species, while rare species are less important in this regard. The degree to which variation in the diversity of local communities in the context of metacommunity ecology concurs with these findings has not been rigorously examined to date. It is also unknown if community turnover along environmental and spatial gradients is mostly attributable to common as opposed to rare species. We examined spatial turnover for three categories of species, all, common, and rare, in seven aquatic metacommunities using simple and partial Mantel tests. We found that variation in turnover along environmental and spatial gradients was generally similar among all, common, and rare species categories, with five of the seven data sets following this pattern. Our findings thus suggest that spatial turnover in aquatic metacommunities can often be adequately described using common species. More importantly, our findings also suggest that turnover–environment relationships can also be described relatively well using information from common species only.

Effects of the toxin 3-chloroaniline at low concentrations on microbial community dynamics and membrane bioreactor performance

The effects of toxins at ambient concentrations on microbial activity and community dynamics are poorly understood. We operated 4 membrane bioreactors (MBRs) in parallel; two reactors were continuously exposed to the toxin 3-chloroaniline (3-CA) at environmentally relevant levels, representing 25% of the total chemical oxygen demand (COD; Total COD = 400 mg l −1 d −1), and two reactors received no 3-CA. During the 70 d exposure to 3-CA the microbial communities never adapted as evidenced by a 48% and 14% reduction in COD and ammonia removal, respectively, compared to over 92% reduction for both measurements in the controls. The bacterial 16S rRNA gene was monitored using terminal restriction fragment length polymorphism (T-RFLP) analysis ( n = 15 temporal grab samples per reactor) over the 70 d period. T-RFLP spectra analysis compared the rapid species turnover rate (STR) approach with the more computationally intensive non-metric multi-dimensional scaling (NMS) complemented with multi-response permutation procedure (MRPP). The methods revealed comparable findings and the presence of 3-CA selected for a more convergent community with less bacterial turnover. In contrast, the control MBRs were more divergent as evidenced by greater bacterial turnover variability. The importance of studying replicate reactors is highlighted by the fact that one of the two controls was significantly different from the treatment MBRs ( p-value = 0.01, α = 0.05) whereas the other one was not ( p-value = 0.24, α = 0.05). The study suggests that analysis of community dynamics with the rapid STR approach and with NMS/MRPP can lead to comparable results when targeting the 16S rRNA gene. The use of replicate bioreactors is essential for meaningful interpretation of microbial community patterns.

Caregiving in a Patient’s Place of Residence

High turnover and staff shortages among home care and hospice workers may compromise the quality and availability of in-home care. This study explores turnover rates of direct care workers for home care and hospice agencies. OLS (ordinary least square) regression models are run using organizational data from 93 home care agencies and 29 hospice agencies in North Carolina. Home care agencies have higher total turnover rates than hospice agencies, but profit status may be an important covariate. Higher unemployment rates are associated with lower voluntary turnover. Agencies that do not offer health benefits experience higher involuntary turnover. Differences in turnover between hospice and home health agencies suggest that organizational characteristics of hospice care contribute to lower turnover rates. However, the variation in turnover rates is not fully explained by the proposed multivariate models. Future research should explore individual and structural-level variables that affect voluntary and involuntary turnover in these settings.

Factors determining operating cash flow: case of the Tunisian commercial companies

In this article, we studied the problem of the determination of operating cash flows. On the basis of a sample representative of the Tunisian commercial companies, we determined the explanatory power of the operating cycle components on the behaviour of the operating cash-flows. The results of this study prove that our dependent variable, operating cash-flow, is significantly given by the means of four factors dependent on the operating cycle: the timely debt collection, the timely debt payment, the timely flow of stock and the gross commercial margin. However, our dependent variable varies independently of two factors: Earnings and Variation of turnover.

Short admission in an emergency psychiatry unit can prevent prolonged lengths of stay in a psychiatric institution

Characterize and compare acute psychiatric admissions to the psychiatric wards of a general hospital (22 beds), a psychiatric hospital (80) and of an emergency psychiatry unit (6). Survey of the ratios and shares of the demographic, diagnostic and hospitalization variables involved in all acute admissions registered in a catchment area in Brazil between 1998 and 2004. From the 11,208 admissions, 47.8% of the patients were admitted to a psychiatric hospital and 14.1% to a general hospital. The emergency psychiatry unit accounted for 38.1% of all admissions during the period, with a higher variability in occupancy rate and bed turnover during the years. Around 80% of the hospital stays lasted less than 20 days and in almost half of these cases, patients were discharged in 2 days. Although the total number of admissions remained stable during the years, in 2004, a 30% increase was seen compared to 2003. In 2004, bed turnover and occupancy rate at the emergency psychiatry unit increased. The increase in the number of psychiatric admissions in 2004 could be attributed to a lack of new community-based services available in the area beginning in 1998. Changes in the health care network did affect the emergency psychiatric service and the limitations of the community-based network could influence the rate of psychiatric admissions.