Science.gov

Sample records for affect aggregate turnover

  1. Anaerobic Nitrogen Turnover by Sinking Diatom Aggregates at Varying Ambient Oxygen Levels

    PubMed Central

    Stief, Peter; Kamp, Anja; Thamdrup, Bo; Glud, Ronnie N.

    2016-01-01

    In the world’s oceans, even relatively low oxygen levels inhibit anaerobic nitrogen cycling by free-living microbes. Sinking organic aggregates, however, might provide oxygen-depleted microbial hotspots in otherwise oxygenated surface waters. Here, we show that sinking diatom aggregates can host anaerobic nitrogen cycling at ambient oxygen levels well above the hypoxic threshold. Aggregates were produced from the ubiquitous diatom Skeletonema marinoi and the natural microbial community of seawater. Microsensor profiling through the center of sinking aggregates revealed internal anoxia at ambient 40% air saturation (∼100 μmol O2 L-1) and below. Accordingly, anaerobic nitrate turnover inside the aggregates was evident within this range of ambient oxygen levels. In incubations with 15N-labeled nitrate, individual Skeletonema aggregates produced NO2- (up to 10.7 nmol N h-1 per aggregate), N2 (up to 7.1 nmol N h-1), NH4+ (up to 2.0 nmol N h-1), and N2O (up to 0.2 nmol N h-1). Intriguingly, nitrate stored inside the diatom cells served as an additional, internal nitrate source for dinitrogen production, which may partially uncouple anaerobic nitrate turnover by diatom aggregates from direct ambient nitrate supply. Sinking diatom aggregates can contribute directly to fixed-nitrogen loss in low-oxygen environments in the ocean and vastly expand the ocean volume in which anaerobic nitrogen turnover is possible, despite relatively high ambient oxygen levels. Depending on the extent of intracellular nitrate consumption during the sinking process, diatom aggregates may also be involved in the long-distance export of nitrate to the deep ocean. PMID:26903977

  2. Factors Affecting Turnover among Family Child Care Providers: A Longitudinal Study.

    ERIC Educational Resources Information Center

    Todd, Christine M., Deery-Schmitt, Deanna M.

    1996-01-01

    This study investigated 57 family child caregivers longitudinally to identify turnover precursors. Providers most likely to leave had more education, less training, and more stress than providers who stayed. Training and caring for one's own children indirectly affected turnover through job stress. Job satisfaction was unrelated to turnover. Job…

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

    USGS Publications Warehouse

    Doherty, P.F., Jr.; 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.

  4. Chemical Nature and Turnover of Carbon Associated with Diagnostic Aggregate Fractions

    NASA Astrophysics Data System (ADS)

    Six, J.

    2004-12-01

    Recently, many studies have shown the importance of aggregation in controlling soil organic C dynamics and storage. Nevertheless, very few studies have characterized the chemical nature of aggregated associated C fractions to elucidate the origin and degree of microbial alteration of these C fractions. Here, I summarize several studies employing biomarker analyses for plant-derived lignin, bacterial-derived muramic acid, and fungal-derived glucosamine to aggregate associated C fractions. A comparison of different particulate organic matter (POM) fractions indicated that fine POM occluded within microaggregates-within-macroaggregates (mM) had the greatest amino sugar content, greatest ratio of glucosamine over muramic acid, and lowest phenolic CuO oxidation products. The latter result suggest that the fine POM is the most degraded POM fraction, which was confirmed by C isotope analyses. However, side chain oxidation of lignin compounds of fine POM was intermediate, suggesting an average microbial alteration of lignin. These results suggest a significant microbial contribution, especially fungal, to this relative older C fraction protected within the mM. Carbon and isotopic analyses of the mM confirmed that this structural unit within the soil protects C from fast decomposition and facilitates the long-term stabilization of C in undisturbed soil. Furthermore, amino sugar analyses indicated that microbial-derived C is stabilized in the mM, due primarily to a greater fungal-mediated improvement of soil structural stability and concurrent deposition of fungal-derived C. In conclusion, the characterizing the chemical nature and turnover of aggregate associated C fractions elucidated that the mM fraction plays an important role in the long term stabilization of C and seems to be an ideal indicator or diagnostic fraction for C sequestration potential in soils.

  5. Soil aggregates, organic matter turnover and carbon balance in a Mediterranean eroded vineyard

    NASA Astrophysics Data System (ADS)

    Novara, Agata; Lo Papa, Giuseppe; Dazzi, Carmelo; Gristina, Luciano; Cerdà, Artemi

    2014-05-01

    . 103-120. Dimoyiannis, D. 2012. Wet aggregate stability as affected by excess carbonate and other soil properties. Land Degradation & Development, 23: 450- 455. DOI 10.1002/ldr.1085 Fernández-Calviño, D., Garrido-Rodríguez, B., López-Periago, J. E., Paradelo, M., and Arias-Estévez, M. 2013. Spatial distribution of copper fractions in a vineyard soil. Land Degradation & Development, 24: 556- 563. DOI 10.1002/ldr.1150 García-Orenes, F., Cerdà, A., Mataix-Solera, J., Guerrero, C., Bodí, M.B., Arcenegui, V., Zornoza, R. & Sempere, J.G. 2009. Effects of agricultural management on surface soil properties and soil-water losses in eastern Spain. Soil and Tillage Research 106, 117-123. 10.1016/j.still.2009.06.002 Jacinthe, P.A., R. Lal, L.B. Owens, and D.L. Hothem. (2004) Transport of labile carbon in runoff as affected by land use and rainfall characteristics. Soil and Tillage Research 77: 111-123 Kocyigit, R., Demirci, S. 2012. Long-term changes of aggregate-associated and labile soil organic carbon and nitrogen after conversion from forest to grassland and cropland in northern Turkey. Land Degradation & Development, 23: 475- 482. DOI 10.1002/ldr.1092 Lal, R., 2003. Soil erosion and the global carbon budget. Environment International 29, 437-450 Novara, A., Gristina, L., Bodì, M.B., Cerdà, A. 2011. The impact of fire on redistribution of soil organic matter on a Mediterranean hillslope under maquia vegetation type. Land Degradation and Development, 2: 530 - 536. DOI: 10.1002/ldr.1027 Novara, A., Gristina, L., Kuzyakov, Y., Schillaci, C., Laudicina, V.A., La Mantia, T., 2013. Turnover and availability of soil organic carbon under different Mediterranean land use as estimated by 13C natural abundance. European Journal ofSoil science, 64, 466-475. DOI: 10.1111/ejss.12038 Novara, A., Gristina, L., Saladino, S., Santoro, A., Cerda, A. 2011. Soil erosion assessment on tillage and alternative soil managements in a Sicilian vineyard. Soil & Tillage Research 117

  6. Organizational Career Growth, Affective Occupational Commitment and Turnover Intentions

    ERIC Educational Resources Information Center

    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. Turnover of subsoil organic carbon controlled by substrate limitation and aggregation?

    NASA Astrophysics Data System (ADS)

    Dietrich, Patrick; Don, Axel; Helfrich, Mirjam

    2014-05-01

    Subsoils (>30 cm depth) store more than 50% of the total soil organic carbon (SOC) and subsoil SOC is characterised by high mean residence times compared to topsoil SOC. However, little is known about the mechanisms controlling the turnover of SOC in the subsoil. The purpose of this study was to evaluate the effect of temperature, substrate limitation and aggregation disturbance on subsoil SOC turnover. We assumed that temperature limits SOC turnover in subsoil, but the temperature response of SOC is obscured by an increasing stabilization of organic material with soil depth. In a laboratory incubation experiment the production of CO2 from undisturbed and disturbed soil samples and disturbed soil samples with added 13C labelled roots were investigated at two different temperatures (10 and 20° C). Soil samples were taken from 2-12 cm (depth 1), 30-60 cm (depth2) and 130-160 cm (depth 3) in a deciduous forest from a podzolic Cambisol and were placed in microcosms with an inner diameter of 14.2 cm and a height of 20 cm for depth 1 and 40 cm for depth 2 and 3. The microcosms were incubated for 30 days at 60% of water holding capacity. The incubation experiment showed an average increase of 80-150% in CO2 production for disturbed and undisturbed samples in depth 1 and depth 2 with increasing temperature. However, this was not observed in depth 3. This temperature influence was not found in the disturbed samples with added substrate. Instead, the increase in CO2 production of the labelled samples from depth 2 and 3 had a lag time of 5 to 8 days compared to samples from depth 1. Reasons for this delayed reaction on substrate might be dormant microorganisms in the subsoil at the beginning of the incubation experiment or spatial separation of microorganisms and the labelled substrate. Disturbance of the samples from depth 1 and 2 initially increase the CO2 production, but this effect was minor after day 15. Contrary to expectation, the CO2 production in depth 3 was greater

  8. Can intra-aggregate pore structures affect the aggregate's effectiveness in protecting carbon?

    SciTech Connect

    Ananyeva, K; Wang, W; Smucker, A J.M.; Rivers, M L; Kravchenko, A N

    2012-11-15

    Aggregates are known to provide physical protection to soil organic matter shielding it from rapid decomposition. Spatial arrangement and size distribution of intra-aggregate pores play an important role in this process. This study examined relationships between intra-aggregate pores measured using X-ray computed micro-tomography images and concentrations of total C in 4–6 mm macro-aggregates from two contrasting land use and management practices, namely, conventionally tilled and managed row crop agricultural system (CT) and native succession vegetation converted from tilled agricultural land in 1989 (NS). Previous analyses of these aggregates indicated that small (<15 μm) and large (>100 μm) pores prevail in NS aggregates while medium (30–90 μm) pores are more abundant in CT aggregates (Kravchenko et al., 2011; Wang et al., 2012). We hypothesized that these differences in pore size distributions affect the ability of macro-aggregates to protect C. The results of this study supported this hypothesis. Consistent with greater heterogeneity of pore distributions within NS aggregates we observed higher total C and greater intra-aggregate C variability in NS as compared with CT aggregates. Total C concentrations and intra-aggregate C standard deviations were negatively correlated with fractions of medium sized pores, indicating that presence of such pores was associated with lower but more homogeneously distributed total C. While total C was positively correlated with presence of small and large pores. The results suggest that because of their pore structure NS macro-aggregates provide more effective physical protection to C than CT aggregates.

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

    PubMed

    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. PMID:23469474

  10. Interplay of model ingredients affecting aggregate shape plasticity in diffusion-limited aggregation

    NASA Astrophysics Data System (ADS)

    Duarte-Neto, P.; Stošić, T.; Stošić, B.; Lessa, R.; Milošević, M. V.

    2014-07-01

    We analyze the combined effect of three ingredients of an aggregation model—surface tension, particle flow and particle source—representing typical characteristics of many aggregation growth processes in nature. Through extensive numerical experiments and for different underlying lattice structures we demonstrate that the location of incoming particles and their preferential direction of flow can significantly affect the resulting general shape of the aggregate, while the surface tension controls the surface roughness. Combining all three ingredients increases the aggregate shape plasticity, yielding a wider spectrum of shapes as compared to earlier works that analyzed these ingredients separately. Our results indicate that the considered combination of effects is fundamental for modeling the polymorphic growth of a wide variety of structures in confined geometries and/or in the presence of external fields, such as rocks, crystals, corals, and biominerals.

  11. Interplay of model ingredients affecting aggregate shape plasticity in diffusion-limited aggregation.

    PubMed

    Duarte-Neto, P; Stošić, T; Stošić, B; Lessa, R; Milošević, M V

    2014-07-01

    We analyze the combined effect of three ingredients of an aggregation model--surface tension, particle flow and particle source--representing typical characteristics of many aggregation growth processes in nature. Through extensive numerical experiments and for different underlying lattice structures we demonstrate that the location of incoming particles and their preferential direction of flow can significantly affect the resulting general shape of the aggregate, while the surface tension controls the surface roughness. Combining all three ingredients increases the aggregate shape plasticity, yielding a wider spectrum of shapes as compared to earlier works that analyzed these ingredients separately. Our results indicate that the considered combination of effects is fundamental for modeling the polymorphic growth of a wide variety of structures in confined geometries and/or in the presence of external fields, such as rocks, crystals, corals, and biominerals. PMID:25122308

  12. The Dynamics and Turnover of Tau Aggregates in Cultured Cells: INSIGHTS INTO THERAPIES FOR TAUOPATHIES.

    PubMed

    Guo, Jing L; Buist, Arjan; Soares, Alberto; Callaerts, Kathleen; Calafate, Sara; Stevenaert, Frederik; Daniels, Joshua P; Zoll, Bryan E; Crowe, Alex; Brunden, Kurt R; Moechars, Diederik; Lee, Virginia M Y

    2016-06-17

    Filamentous tau aggregates, the hallmark lesions of Alzheimer disease (AD), play key roles in neurodegeneration. Activation of protein degradation systems has been proposed to be a potential strategy for removing pathological tau, but it remains unclear how effectively tau aggregates can be degraded by these systems. By applying our previously established cellular model system of AD-like tau aggregate induction using preformed tau fibrils, we demonstrate that tau aggregates induced in cells with regulated expression of full-length mutant tau can be gradually cleared when soluble tau expression is suppressed. This clearance is at least partially mediated by the autophagy-lysosome pathway, although both the ubiquitin-proteasome system and the autophagy-lysosome pathway are deficient in handling large tau aggregates. Importantly, residual tau aggregates left after the clearance phase leads to a rapid reinstatement of robust tau pathology once soluble tau expression is turned on again. Moreover, we succeeded in generating monoclonal cells persistently carrying tau aggregates without obvious cytotoxicity. Live imaging of GFP-tagged tau aggregates showed that tau inclusions are dynamic structures constantly undergoing "fission" and "fusion," which facilitate stable propagation of tau pathology in dividing cells. These findings provide a greater understanding of cell-to-cell transmission of tau aggregates in dividing cells and possibly neurons. PMID:27129267

  13. Soil aggregates, organic matter turnover and carbon balance in a Mediterranean eroded vineyard

    NASA Astrophysics Data System (ADS)

    Novara, Agata; Lo Papa, Giuseppe; Dazzi, Carmelo; Gristina, Luciano; Cerdà, Artemi

    2014-05-01

    The carbon cycle is being affected by the human impacts (Novara et al., 2011; Yan-Gui et al., 2013), and one of those is the intensification in the soil erosion in agriculture land (Cerdà et al., 2009; García Orenes et al., 2009). Vineyards also are affected by the human activities (Fernández Calviño, 2012). Vineyards in Sicily are cultivated on 110.000 ha, 10% of which on >10% slope. Deficiencies of soil organic matter are typical of the semi arid Mediterranean environment especially where traditional intensive cropping practices are adopted (Novara et al., 2012; 2013). These practices in vineyards could lead soil to intensive erosion processes (Novara et al., 2011). The fate of SOC under erosion processes is difficult to understand because of the influence of the erosion impact on SOC pathway, which depends on the different features of the process involved (detachment, transport and/or deposition). Soil erosion must be considered a net C source (Lal, 2003), as eroded soils have lower net primary productivity (NPP) (Dick and Gregorich, 2004) caused by reduction in the effective rooting depth and all in all determining decline in soil quality. Breakdown of aggregates and soil dispersion expose SOM to microbial/enzymatic processes and chemical soil properties (Dimoyiannis, 2012; Kocyigit and Demirci, 2012). Moreover the light fraction, transported by runoff, is labile and easily mineralized determining CO2 emission in the atmosphere (Jacinthe and Lal, 2004). Therefore, the carbon pool is lower in eroded than in un-eroded soil scapes and the rate of mineralization of soil organic matter is higher in sediments than in original soil. In this survey we show a research conducted on a slope sequence of three soil profiles in an irrigated vineyard located in Sambuca di Sicilia, Italy (UTM33-WGS84: 4169367N; 325011E). The SOC content was measured at depth intervals of 10 cm up to a depth of 60 cm in each pedon. Wet aggregate-size fractions with no prior chemical

  14. How Does Supervisor Support Influence Turnover Intent Among Frontline Hospital Workers? The Mediating Role of Affective Commitment.

    PubMed

    Nichols, Helen M; Swanberg, Jennifer E; Bright, Charlotte Lyn

    2016-01-01

    Turnover among frontline hospital service workers can disrupt organizational effectiveness, reduce profitability, and limit the ability to provide high-quality, patient-centered care. This concern is compounded by the increasing reliance on frontline supervisors to manage this workforce, often without necessary training and support. However, research addressing the relationship between frontline supervisor support and intent to turnover among service workers and the process by which these variables are related is limited. By surveying 270 housekeeping and dietary service workers employed at 2 US hospitals, this study examined the relationship between supervisor support and turnover intent and assessed the mediating role of affective commitment between supervisor support and intent to turnover. Turnover intentions were lower for workers who reported greater levels of supervisor support and affective commitment; both supervisor support and affective commitment were significant predictors of turnover intent when tested individually. However, when controlling for affective commitment, supervisor support no longer predicted turnover intent, indicating that affective commitment fully mediated the relationship between supervisor support and intent to turnover. Implications for further research and organizational practice are discussed. PMID:27455369

  15. Secondary nucleating sequences affect kinetics and thermodynamics of tau aggregation

    PubMed Central

    Moore, Christopher L.; Huang, Michael H.; Robbennolt, Shauna A.; Voss, Kellen R.; Combs, Benjamin; Gamblin, T. Chris; Goux, Warren J.

    2011-01-01

    Tau protein was scanned for highly amyloidogenic sequences in amphiphilic motifs (X)nZ, Z(X)nZ (n≥2) or (XZ)n (n≥2), where X is a hydrophobic residue and Z is a charged or polar residue. N-acetyl peptides homologous to these sequences were used to study aggregation. Transmission electron microscopy (TEM) showed 7 peptides, in addition to well known primary nucleating sequences c275VQIINK (AcPHF6*) and Ac306VQIVYK (AcPHF6), formed fibers, tubes, ribbons or rolled sheets. Of the peptides shown by TEM to form amyloid, Ac10VME, AcPHF6*, Ac375KLTFR, and Ac393VYK were found to enhance the fraction of β-structure of AcPHF6 formed at equilibrium, and Ac375KLTFR was found to inhibit AcPHF6 and AcPHF6* aggregation kinetics in a dose-dependent manner, consistent with its participation in a hybrid steric zipper model. Single site mutants were generated which transformed predicted amyloidogenic sequences in tau into non-amyloidogenic ones. A M11K mutant had fewer filaments and showed a decrease in aggregation kinetics and an increased lag time compared to wild type tau, while a F378K mutant showed significantly more filaments. Our results infer that sequences throughout tau, in addition to PHF6 and PHF6*, can seed amyloid formation or affect aggregation kinetics or thermodynamics. PMID:22085312

  16. Effect of organic fertilizer and biochar application on soil macro-aggregate formation and organic carbon turnover

    NASA Astrophysics Data System (ADS)

    Grunwald, Dennis; Kaiser, Michael; Ludwig, Bernard

    2015-04-01

    Macro-aggregates are important for the organic matter dynamic and thus the productivity of sustainably managed soils. To date, less is known about the influence of biochar in comparison to other commonly used organic soil additives on the formation of macro-aggregates and organic carbon turnover. Here we aimed to analyze the effects of biochar applied individually and in combination with slurry versus the effects of the individual application of slurry and manure on macro-aggregate yield, the associated organic carbon concentration, and the organic carbon mineralization. For this, we crushed the macro-aggregate fraction (>250 μm) of two different soils that were then mixed with biochar (combustion temperature: 550° C, feedstock: woodchips) and/or cattle-slurry or cattle-manure and incubated within a microcosm experiment at 5° C, 15° C, and 25° C. We monitored the CO2 evolution during the incubation experiment. After four and eight weeks, we determined the dry mass and the carbon concentration of the newly formed macro-aggregates (>250 μm) and the microbial biomass carbon concentration. Carbon mineralization was modelled assuming first-order kinetics and using a rate modifying factor for the temperature (taken from the RothC-26.3 model). Two pools were considered (mineralization of the native organic matter from the control soils and mineralization of the substrates added) in each treatment and the models were calibrated to the C mineralization data at 25° C, whereas the data for 15° C and 5° C were used for validation. Independent from the incubation temperature and the duration of the experiment, the individual application of biochar did not show significant effects on the macro-aggregate yield, the associated carbon concentration, or the CO2 emission rate compared to the control sample receiving no amendments. For the application of biochar in combination with slurry, we observed only for the 15° C treatment higher CO2 emission rates in combination with

  17. Dietary arginine affects energy metabolism through polyamine turnover in juvenile Atlantic salmon (Salmo salar).

    PubMed

    Andersen, Synne M; Holen, Elisabeth; Aksnes, Anders; Rønnestad, Ivar; Zerrahn, Jens-Erik; Espe, Marit

    2013-12-14

    In the present study, quadruplicate groups of juvenile Atlantic salmon (Salmo salar) were fed plant protein-based diets with increasing arginine inclusions (range 28·8-37·4 g/kg DM) to investigate whether arginine supplementation affects growth and lipid accumulation through an elevated polyamine turnover. Dietary lysine was held at a constant concentration, just below the requirement. All other amino acids were balanced and equal in the diets. Arginine supplementation increased protein and fat accretion, without affecting the hepatosomatic or visceralsomatic indices. Dietary arginine correlated with putrescine in the liver (R 0·78, P= 0·01) and with ornithine in the muscle, liver and plasma (P= 0·0002, 0·003 and 0·0002, respectively). The mRNA of ornithine decarboxylase, the enzyme producing putrescine, was up-regulated in the white adipose tissue of fish fed the high-arginine inclusion compared with those fed the low-arginine diet. Concomitantly, spermidine/spermine-(N1)-acetyltransferase, the rate-limiting enzyme for polyamine turnover that consumes acetyl-CoA, showed an increased activity in the liver of fish fed the arginine-supplemented diets. In addition, lower acetyl-CoA concentrations were observed in the liver of fish fed the high-arginine diet, while ATP, which is used in the process of synthesising spermidine and spermine, did not show a similar trend. Gene expression of the rate-limiting enzyme for β-oxidation of long-chain fatty acids, carnitine palmitoyl transferase-1, was up-regulated in the liver of fish fed the high-arginine diet. Taken together, the data support that increased dietary arginine activates polyamine turnover and β-oxidation in the liver of juvenile Atlantic salmon and may act to improve the metabolic status of the fish. PMID:23656796

  18. Response to platelet-activating factor in human platelets stored and aged in plasma. Decrease in aggregation, phosphoinositide turnover, and receptor affinity

    SciTech Connect

    Shukla, S.D.; Morrison, W.J.; Klachko, D.M.

    1989-07-01

    Human platelet concentrates were stored in polyolefin bags at 22 to 24 degrees C on a horizontal shaker for up to 8 days. At different intervals, aliquots of platelet-rich plasma (PRP) were removed aseptically and five variables, i.e., platelet counts, morphology, platelet-activating factor (PAF)-stimulated aggregation, phosphoinositide turnover, and (3H)PAF binding to platelet receptors, were studied. The number of platelets did not change during the 8 days of storage. Scanning electron microscopy of the platelets revealed a gradual morphologic change from biconcave flat discs to irregular, crenated forms. The PAF-induced aggregation of platelets declined with time of storage. A decrease to 50 percent of the Day 1 aggregatory response to PAF was evident on Day 2, and there was a further decline to about 20 percent by Day 6. Similarly, PAF receptor-coupled phosphoinositide turnover, as monitored by 32P incorporation into individual phosphoinositides, decreased dramatically with storage. After 2 to 3 days of storage, the phosphoinositide turnover was reduced to 50 percent of the original response, and it continued to decline to about 25 percent of original response by Day 5 or 6. The binding of (3H)PAF to washed human platelets indicated subtle changes between Days 2 and 4, which became more noticeable by Day 6. These results have raised the possibility of changes in the number of the receptors and/or their affinity for the ligand during storage. We conclude that although the number of platelets was maintained during storage for 8 days, a general deterioration of their responses to PAF occurred at the levels of cell surface receptor, transmembrane signaling (phosphoinositide turnover), and response (aggregation).

  19. The Influence of Haemoglobin A1c Levels on Platelet Aggregation and Platelet Turnover in Patients with Coronary Artery Disease Treated with Aspirin

    PubMed Central

    Neergaard-Petersen, Søs; Hvas, Anne-Mette; Grove, Erik Lerkevang; Larsen, Sanne Bøjet; Gregersen, Søren; Kristensen, Steen Dalby

    2015-01-01

    Background Hyperglycaemia may attenuate the antiplatelet effect of aspirin and thereby increase the risk of cardiovascular events. We investigated the influence of increased haemoglobin A1c (HbA1c) levels on platelet aggregation and turnover in a large cohort of patients with coronary artery disease (CAD) with type 2 diabetes, prediabetes or no diabetes. Methods In this observational study, we included 865 stable CAD patients on 75 mg aspirin as mono-therapy of whom 242 patients had type 2 diabetes and were receiving antidiabetic drugs. Among 623 patients without diabetes, we classified 303 patients with prediabetes (HbA1c ≥5.7–6.4% [39–47 mmol/mol]) naive to antidiabetic drugs. Platelet aggregation was evaluated by the Multiplate Analyzer using arachidonic acid and collagen and by the VerifyNow Aspirin. Platelet turnover was evaluated by immature platelets using flow cytometry and platelet activation by soluble P-selectin. Results CAD patients with type 2 diabetes had higher platelet aggregation (all p-values <0.01), platelet turnover (immature platelet count, p<0.01) and platelet activation (p<0.001) than patients without diabetes. CAD patients with prediabetes had increased platelet aggregation (p = 0.02) and platelet count (p = 0.02) compared with patients without diabetes. Increased levels of HbA1c correlated positively with increased platelet aggregation using arachidonic acid (r = 0.19, p<0.0001), collagen (r = 0.10, p<0.01) and VerifyNow (r = 0.15, p<0.0001), and with platelet count (r = 0.08, p = 0.01), immature platelet count (r = 0.11, p<0.001) and soluble P-selectin (r = 0.15, p<0.0001). These associations were mainly evident in non-diabetic and prediabetic CAD patients. Conclusions CAD patients with prediabetes and diabetes may have attenuated antiplatelet effect of aspirin compared with CAD patients without diabetes. This may be related to increased platelet count in patients with prediabetes. Increased levels of HbA1c correlated positively

  20. Water level changes affect carbon turnover and microbial community composition in lake sediments

    PubMed Central

    Weise, Lukas; Ulrich, Andreas; Moreano, Matilde; Gessler, Arthur; E. Kayler, Zachary; Steger, Kristin; Zeller, Bernd; Rudolph, Kristin; Knezevic-Jaric, Jelena; Premke, Katrin

    2016-01-01

    Due to climate change, many lakes in Europe will be subject to higher variability of hydrological characteristics in their littoral zones. These different hydrological regimes might affect the use of allochthonous and autochthonous carbon sources. We used sandy sediment microcosms to examine the effects of different hydrological regimes (wet, desiccating, and wet-desiccation cycles) on carbon turnover. 13C-labelled particulate organic carbon was used to trace and estimate carbon uptake into bacterial biomass (via phospholipid fatty acids) and respiration. Microbial community changes were monitored by combining DNA- and RNA-based real-time PCR quantification and terminal restriction fragment length polymorphism (T-RFLP) analysis of 16S rRNA. The shifting hydrological regimes in the sediment primarily caused two linked microbial effects: changes in the use of available organic carbon and community composition changes. Drying sediments yielded the highest CO2 emission rates, whereas hydrological shifts increased the uptake of allochthonous organic carbon for respiration. T-RFLP patterns demonstrated that only the most extreme hydrological changes induced a significant shift in the active and total bacterial communities. As current scenarios of climate change predict an increase of drought events, frequent variations of the hydrological regimes of many lake littoral zones in central Europe are anticipated. Based on the results of our study, this phenomenon may increase the intensity and amplitude in rates of allochthonous organic carbon uptake and CO2 emissions. PMID:26902802

  1. Water level changes affect carbon turnover and microbial community composition in lake sediments.

    PubMed

    Weise, Lukas; Ulrich, Andreas; Moreano, Matilde; Gessler, Arthur; Kayler, Zachary E; Steger, Kristin; Zeller, Bernd; Rudolph, Kristin; Knezevic-Jaric, Jelena; Premke, Katrin

    2016-05-01

    Due to climate change, many lakes in Europe will be subject to higher variability of hydrological characteristics in their littoral zones. These different hydrological regimes might affect the use of allochthonous and autochthonous carbon sources. We used sandy sediment microcosms to examine the effects of different hydrological regimes (wet, desiccating, and wet-desiccation cycles) on carbon turnover. (13)C-labelled particulate organic carbon was used to trace and estimate carbon uptake into bacterial biomass (via phospholipid fatty acids) and respiration. Microbial community changes were monitored by combining DNA- and RNA-based real-time PCR quantification and terminal restriction fragment length polymorphism (T-RFLP) analysis of 16S rRNA. The shifting hydrological regimes in the sediment primarily caused two linked microbial effects: changes in the use of available organic carbon and community composition changes. Drying sediments yielded the highest CO2 emission rates, whereas hydrological shifts increased the uptake of allochthonous organic carbon for respiration. T-RFLP patterns demonstrated that only the most extreme hydrological changes induced a significant shift in the active and total bacterial communities. As current scenarios of climate change predict an increase of drought events, frequent variations of the hydrological regimes of many lake littoral zones in central Europe are anticipated. Based on the results of our study, this phenomenon may increase the intensity and amplitude in rates of allochthonous organic carbon uptake and CO2 emissions. PMID:26902802

  2. Human Apolipoprotein E Isoforms differentially affect Bone Mass and Turnover in vivo

    PubMed Central

    Dieckmann, Marco; Beil, F. Timo; Mueller, Brigitte; Bartelt, Alexander; Marshall, Robert P.; Koehne, Till; Amling, Michael; Ruether, Wolfgang; Cooper, Jackie A.; Humphries, Steve E.; Herz, Joachim; Niemeier, Andreas

    2012-01-01

    The primary role of apolipoprotein E (apoE) is to mediate the cellular uptake of lipoproteins. However, a new role for apoE as a regulator of bone metabolism in mice has recently been established. In contrast to mice, the human APOE gene is characterized by three common isoforms APOE ε2, ε3 and ε4 that result in different metabolic properties of the apoE isoforms, but it remains controversial whether the APOE polymorphism influences bone traits in humans. To clarify this, we investigated bone phenotypes of apoE knock-in mice, which express one human isoform each (apoE2 k.i., apoE3 k.i., apoE4 k.i.) in place of the mouse apoE. Analysis of 12 week-old female knock-in mice revealed increased levels of biochemical bone formation and resorption markers in apoE2 k.i. animals as compared to apoE3 k.i. and apoE4 k.i., with a reduced OPG/RANKL ratio in apoE2 k.i., indicating increased turnover with prevailing resorption in apoE2 k.i.. Accordingly, histomorphometric and μCT analyses demonstrated significantly lower trabecular bone mass in apoE2 than in apoE3 and apoE4 k.i. animals, which was reflected by a significant reduction of lumbar vertebrae maximum force resistance. Unlike trabecular bone, femoral cortical thickness, and stability was not differentially affected by the apoE isoforms. To extend these observations to the human situation, plasma from middle-aged healthy men homozygous for ε2/ε2, ε3/ε3, and ε4/ε4 (n=21, n=80, n=55 respectively) was analyzed with regard to bone turnover markers. In analogy to apoE2 k.i. mice, a lower OPG/RANKL ratio was observed in the serum of ε2/ε2 carriers as compared to ε3/ε3 and ε4/ε4 individuals (p=0.02 for ε2/ε2 vs ε4/ε4). In conclusion, the current data strongly underline the general importance of apoE as a regulator of bone metabolism and identifies the APOE ε2 allele as a potential genetic risk factor for low trabecular bone mass and vertebral fractures in humans. PMID:22991192

  3. Long-Term Tillage Affects on Soil Aggregation and Carbon Sequestration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Continuous cultivation affects soil structure due to the destruction of soil aggregates and the lost of soil organic carbon (SOC). Different management practices, such as different tillage applications, affect the formation and the stabilization of soil aggregates through management effects on SOC l...

  4. Does Aggregation Affect the Redistribution and Quality of Eroded SOC?

    NASA Astrophysics Data System (ADS)

    Hu, Yaxian; Kuhn, Nikolaus

    2015-04-01

    A substantial amount of literature has discussed the impacts of soil erosion on global carbon cycling. However, numerous gaps in our knowledge remain unaddressed, for instance, the biogeochemical fate of displaced SOC during transport being one of them. The transport distance and the quality of eroded SOC are the two major factors that determine its fate. Previous laboratory-based research had demonstrated that the effects of aggregation can potentially shorten the transport distance of eroded SOC. The mineralization potential of SOC also differs in sediment fractions of different likely transport distances. It is therefore essential to examine the transport distance and quality of eroded SOC under field conditions with natural rainfall as the agent of erosion. Soil samples from a silty clay soil from Switzerland and a sandy soil from Denmark, were collected in the field this summer after natural rainfall events. The soil from Switzerland was sampled from a field of maize in St. Ursanne (47°20' N 7°09' E) on August 6th, 2014 after a natural rainfall event. A depositional fan consisting of aggregated sediment was formed outside the lower edge of the field. The sandy soil from Denmark was sampled from a farm in Foulum (56°30' N, 9°35' W) on September 4, 2014, after a series of natural rainfall events. Soil samples were collected at different topographic positions along the two slopes. All the soil samples from the two farms were fractionated by a settling tube. Bulk soil from Switzerland and Denmark was also dispersed by ultrasound. The SOC contents of all bulk soils and associated fractions were determined using a carbon analyzer Leco 612 at 1000°C. The quality of SOC in different settling fractions collected from various topographic positions were also determined by stable isotopes of C and N (13C and 15N). Our results show that 1) the aggregate specific SOC distribution evidently differs from the mineral particle specific SOC distribution, indicating that re

  5. Three Genes Which Affect Founding of Aggregations in Polysphondylium Pallidum

    PubMed Central

    Francis, D.; Shaffer, A.; Smoyer, K.

    1991-01-01

    PN6024 is an extraordinary mutant strain of the cellular slime mold Polysphondylium pallidum, characterized by having defects in many unlinked genes. New strains with altered development appeared spontaneously as aberrant clones of PN6024. Genetic crosses using the macrocyst sexual cycle were used to show that PN6030 (a clone like PN6024 in phenotype) carries mutations at two loci, emm and hge, whereas PN6031 (a clone of altered morphology) carries in addition a mutation at a third locus, mgt. hge and possibly mgt are linked to the mating type locus mat. The relatively high frequency of recombination between mat and hge is strong evidence that meiosis precedes macrocyst germination. The mutant genes themselves are of interest. A major effect of the emm-1 mutation is to remove the requirement for light to trigger aggregation. hge-1 greatly reduces the frequency of aggregation, whereas mgt-1 greatly increases it under standard conditions. None of these mutations interrupts later development leading to stalks and spore cells. It is hypothesized that all three genes act on steps immediately preceding the differentiation of the founder cells which initiate aggregation. PMID:1874416

  6. Long-term Differences in Tillage and Land Use Affect Intra-aggregate Pore Heterogeneity

    SciTech Connect

    Kravchenko, A.N.; Wang, A.N.W.; Smucker, A.J.M.; Rivers, M.L.

    2012-10-25

    Recent advances in computed tomography provide measurement tools to study internal structures of soil aggregates at micrometer resolutions and to improve our understanding of specific mechanisms of various soil processes. Fractal analysis is one of the data analysis tools that can be helpful in evaluating heterogeneity of the intra-aggregate internal structures. The goal of this study was to examine how long-term tillage and land use differences affect intra-aggregate pore heterogeneity. The specific objectives were: (i) to develop an approach to enhance utility of box-counting fractal dimension in characterizing intra-aggregate pore heterogeneity; (ii) to examine intra-aggregate pores in macro-aggregates (4-6 mm in size) using the computed tomography scanning and fractal analysis, and (iii) to compare heterogeneity of intra-aggregate pore space in aggregates from loamy Alfisol soil subjected to 20 yr of contrasting management practices, namely, conventional tillage (chisel plow) (CT), no-till (NT), and native succession vegetation (NS). Three-dimensional images of the intact aggregates were obtained with a resolution of 14.6 {micro}m at the Advanced Photon Source, Argonne National Laboratory, Argonne, IL. Proposed box-counting fractal dimension normalization was successfully implemented to estimate heterogeneity of pore voxel distributions without bias associated with different porosities in soil aggregates. The aggregates from all three studied treatments had higher porosity associated with large (>100 {micro}m) pores present in their centers than in their exteriors. Pores 15 to 60 {micro}m were equally abundant throughout entire aggregates but their distributions were more heterogeneous in aggregate interiors. The CT aggregates had greater numbers of pores 15 to 60 {micro}m than NT and NS. Distribution of pore voxels belonging to large pores was most heterogeneous in the aggregates from NS, followed by NT and by CT. This result was consistent with presence of

  7. Turnover Begets Turnover

    ERIC Educational Resources Information Center

    Castle, Nicholas G.

    2005-01-01

    Purpose: This study examined the association between turnover of caregivers and turnover of nursing home top management. The top managers examined were administrators and directors of nursing, and the caregivers examined were registered nurses, licensed practical nurses, and nurse aides. Design and Methods: The data came from a survey of 419…

  8. A Protein Aggregation Based Test for Screening of the Agents Affecting Thermostability of Proteins

    PubMed Central

    Eronina, Tatyana; Borzova, Vera; Maloletkina, Olga; Kleymenov, Sergey; Asryants, Regina; Markossian, Kira; Kurganov, Boris

    2011-01-01

    To search for agents affecting thermal stability of proteins, a test based on the registration of protein aggregation in the regime of heating with a constant rate was used. The initial parts of the dependences of the light scattering intensity (I) on temperature (T) were analyzed using the following empiric equation: I = Kagg(T−T0)2, where Kagg is the parameter characterizing the initial rate of aggregation and T0 is a temperature at which the initial increase in the light scattering intensity is registered. The aggregation data are interpreted in the frame of the model assuming the formation of the start aggregates at the initial stages of the aggregation process. Parameter T0 corresponds to the moment of the origination of the start aggregates. The applicability of the proposed approach was demonstrated on the examples of thermal aggregation of glycogen phosphorylase b from rabbit skeletal muscles and bovine liver glutamate dehydrogenase studied in the presence of agents of different chemical nature. The elaborated approach to the study of protein aggregation may be used for rapid identification of small molecules that interact with protein targets. PMID:21760963

  9. Relations of job characteristics from multiple data sources with employee affect, absence, turnover intentions, and health.

    PubMed

    Spector, P E; Jex, S M

    1991-02-01

    Much of the evidence in support of job characteristics theory is limited to incumbent reports of job characteristics. In this study, job characteristics data from three independent sources--incumbents, ratings from job descriptions, and the Dictionary of Occupational Titles--were used. Convergent validities of incumbent reports with other sources were quite modest. Although incumbent reports of job characteristics correlated significantly with several employee outcomes (job satisfaction, work frustration, anxiety on the job, turnover intentions, and number of doctor visits), the other sources showed few significant correlations, except for number of doctor visits. Caution is urged in the use of incumbent self-reports of job characteristics as indicators of actual work environments. New methods for studying job characteristics are suggested. PMID:2016216

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

    PubMed Central

    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. PMID:26197473

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

    PubMed

    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. PMID:26197473

  12. FBXW7 and USP7 regulate CCDC6 turnover during the cell cycle and affect cancer drugs susceptibility in NSCLC

    PubMed Central

    Merolla, Francesco; Poser, Ina; Visconti, Roberta; Ilardi, Gennaro; Paladino, Simona; Inuzuka, Hiroyuki; Guggino, Gianluca; Monaco, Roberto; Colecchia, David; Monaco, Guglielmo; Cerrato, Aniello; Chiariello, Mario; Denning, Krista; Claudio, Pier Paolo; Staibano, Stefania; Celetti, Angela

    2015-01-01

    CCDC6 gene product is a pro-apoptotic protein substrate of ATM, whose loss or inactivation enhances tumour progression. In primary tumours, the impaired function of CCDC6 protein has been ascribed to CCDC6 rearrangements and to somatic mutations in several neoplasia. Recently, low levels of CCDC6 protein, in NSCLC, have been correlated with tumor prognosis. However, the mechanisms responsible for the variable levels of CCDC6 in primary tumors have not been described yet. We show that CCDC6 turnover is regulated in a cell cycle dependent manner. CCDC6 undergoes a cyclic variation in the phosphorylated status and in protein levels that peak at G2 and decrease in mitosis. The reduced stability of CCDC6 in the M phase is dependent on mitotic kinases and on degron motifs that are present in CCDC6 and direct the recruitment of CCDC6 to the FBXW7 E3 Ubl. The de-ubiquitinase enzyme USP7 appears responsible of the fine tuning of the CCDC6 stability, affecting cells behaviour and drug response. Thus, we propose that the amount of CCDC6 protein in primary tumors, as reported in lung, may depend on the impairment of the CCDC6 turnover due to altered protein-protein interaction and post-translational modifications and may be critical in optimizing personalized therapy. PMID:25885523

  13. Soil Aggregation and Carbon Sequestration as affected by Long-Term Tillage Practices

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In agricultural systems, soil structure is an important property that mediates many soil physical and biological processes and controls soil organic carbon (SOC) content. Cultivation affects soil structure due to the destruction of soil aggregates and the lost of SOC. Different management practices...

  14. Antecedents of Student Teachers' Affective Commitment to the Teaching Profession and Turnover Intention

    ERIC Educational Resources Information Center

    Christophersen, Knut-Andreas; Elstad, Eyvind; Solhaug, Trond; Turmo, Are

    2016-01-01

    Several European countries have experienced both a dearth of and reduction in the quality of applicants to teacher education study programmes. There is also significant leakage from these programmes. The rationale for this study therefore lies in the need to reduce teacher attrition. Research indicates that affective commitment to a profession is…

  15. Cerium oxide nanoparticle aggregates affect stress response and function in Caenorhabditis elegans

    PubMed Central

    Rogers, Steven; Rice, Kevin M; Manne, Nandini DPK; Shokuhfar, Tolou; He, Kun; Selvaraj, Vellaisamy

    2015-01-01

    Objective: The continual increase in production and disposal of nanomaterials raises concerns regarding the safety of nanoparticles on the environmental and human health. Recent studies suggest that cerium oxide (CeO2) nanoparticles may possess both harmful and beneficial effects on biological processes. The primary objective of this study is to evaluate how exposure to different concentrations (0.17–17.21 µg/mL) of aggregated CeO2 nanoparticles affects indices of whole animal stress and survivability in Caenorhabditis elegans. Methods: Caenorhabditis elegans were exposed to different concentrations of CeO2 nanoparticles and evaluated. Results: Our findings demonstrate that chronic exposure of CeO2 nanoparticle aggregates is associated with increased levels of reactive oxygen species and heat shock stress response (HSP-4) in Caenorhabditis elegans, but not mortality. Conversely, CeO2 aggregates promoted strain-dependent decreases in animal fertility, a decline in stress resistance as measured by thermotolerance, and shortened worm length. Conclusion: The data obtained from this study reveal the sublethal toxic effects of CeO2 nanoparticle aggregates in Caenorhabditis elegans and contribute to our understanding of how exposure to CeO2 may affect the environment. PMID:26770770

  16. Increased nitrogen deposition did not affect the composition and turnover of plant and microbial biomarkers in forest soil density fractions

    NASA Astrophysics Data System (ADS)

    Griepentrog, Marco; Bodé, Samuel; Boeckx, Pascal; Hagedorn, Frank; Wiesenberg, Guido L. B.; Schmidt, Michael W. I.

    2013-04-01

    Increased atmospheric nitrogen (N) deposition and elevated CO2 concentrations affect many forests and their ecosystem functions, including organic matter cycling in soils, the largest carbon pool of terrestrial ecosystems. However, it is still not clear how, and what the underlying mechanisms are. Specific molecules of plant and microbial origin (biomarkers) might respond differently to N deposition, depending on their internal N content. Microbial cell-wall-constituents with high-N content like amino sugars are reliable biomarkers to distinguish between fungal- and bacterial-derived organic residues. Individual lipids are plant-specific biomarkers that lack N in their molecular structure. Here, we tested the effects of elevated CO2 and increased N deposition on the dynamics of plant and microbial biomarkers by studying their composition and turnover in forest soil density fractions. Furthermore, we tested the hypothesis that these biomarkers respond differently to increased N deposition, depending on their internal N content. We used soil samples from a 4-year elevated CO2 and N deposition experiment in model forest ecosystems (open-top chambers), that were fumigated with ambient and 13C-depleted CO2 and treated with two levels of 15N-labeled fertilizer. Bulk soil was separated into free light fraction, occluded light fraction and heavy fraction by density fractionation and ultrasonic dispersion. The heavy fraction was further particle-size fractionated with 20 μm as a cut-off. We determined carbon and N concentrations and their isotopic compositions (δ13C, δ15N) within bulk soil and density fractions. Therein, we extracted and quantified individual amino sugars and lipids and conducted compound-specific stable-isotope-analysis using GC- and LC-IRMS. Results show that amino sugars were mainly stabilized in association with soil minerals. Especially bacterial amino sugars were preferentially associated with soil minerals, exemplified by a consistent decrease

  17. Soil-aggregating bacterial community as affected by irrigation, tillage, and cropping system in the Northern Great Plains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Management of irrigated agriculture that influences organic carbon availability can affect soil aggregation in dryland. We compared irrigation, tillage and cropping system effects on aggregate distribution and the community structure of the predominant culturable bacteria that can function as soil a...

  18. ATTACHMENT OF ESCHERICHIA COLI TO SOIL AGGREGATES AS AFFECTED BY AGGREGATE WATER CONTENT AND PRESENCE OF MANURE COLLOIDS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many soils contain relatively large structural units that do not slack when soil is being wetted. Soil aggregates, obtained from dry soil samples by sieving, present a model media to study the interactions of intact soils with dissolved or suspended contaminants. Land-applied manures may contain var...

  19. Different Factors Affecting Human ANP Amyloid Aggregation and Their Implications in Congestive Heart Failure

    PubMed Central

    Millucci, Lia; Paccagnini, Eugenio; Ghezzi, Lorenzo; Bernardini, Giulia; Braconi, Daniela; Laschi, Marcella; Consumi, Marco; Spreafico, Adriano; Tanganelli, Piero; Lupetti, Pietro; Magnani, Agnese; Santucci, Annalisa

    2011-01-01

    Aims Atrial Natriuretic Peptide (ANP)-containing amyloid is frequently found in the elderly heart. No data exist regarding ANP aggregation process and its link to pathologies. Our aims were: i) to experimentally prove the presumptive association of Congestive Heart Failure (CHF) and Isolated Atrial Amyloidosis (IAA); ii) to characterize ANP aggregation, thereby elucidating IAA implication in the CHF pathogenesis. Methods and Results A significant prevalence (85%) of IAA was immunohistochemically proven ex vivo in biopsies from CHF patients. We investigated in vitro (using Congo Red, Thioflavin T, SDS-PAGE, transmission electron microscopy, infrared spectroscopy) ANP fibrillogenesis, starting from α-ANP as well as the ability of dimeric β-ANP to promote amyloid formation. Different conditions were adopted, including those reproducing β-ANP prevalence in CHF. Our results defined the uncommon rapidity of α-ANP self-assembly at acidic pH supporting the hypothesis that such aggregates constitute the onset of a fibrillization process subsequently proceeding at physiological pH. Interestingly, CHF-like conditions induced the production of the most stable and time-resistant ANP fibrils suggesting that CHF affected people may be prone to develop IAA. Conclusions We established a link between IAA and CHF by ex vivo examination and assessed that β-ANP is, in vitro, the seed of ANP fibrils. Our results indicate that β-ANP plays a crucial role in ANP amyloid deposition under physiopathological CHF conditions. Overall, our findings indicate that early IAA-related ANP deposition may occur in CHF and suggest that these latter patients should be monitored for the development of cardiac amyloidosis. PMID:21814559

  20. Soil aggregate stability as affected by clay mineralogy and polyacrylamide addition

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The addition of polyacrylamide (PAM) to soil leads to stabilization of existing aggregates and improved bonding between, and aggregation of adjacent soil particles However, the dependence of PAM efficacy as an aggregate stabilizing agent on soil-clay mineralogy has not been studied. Sixteen soil sam...

  1. How the Timing of Climate Change Policy Affects Infrastructure Turnover in the Electricity Sector: Engineering, Economic and Policy Considerations

    NASA Astrophysics Data System (ADS)

    Izard, Catherine Finlay

    The electricity sector is responsible for producing 35% of US greenhouse gas (GHG) emissions. Estimates suggest that ideally, the electricity sector would be responsible for approximately 85% of emissions abatement associated with climate polices such as America's Clean Energy and Security Act (ACES). This is equivalent to ˜50% cumulative emissions reductions below projected cumulative business-as-usual (BAU) emissions. Achieving these levels of emissions reductions will require dramatic changes in the US electricity generating infrastructure: almost all of the fossil-generation fleet will need to be replaced with low-carbon sources and society is likely to have to maintain a high build rate of new capacity for decades. Unfortunately, the inertia in the electricity sector means that there may be physical constraints to the rate at which new electricity generating capacity can be built. Because the build rate of new electricity generating capacity may be limited, the timing of regulation is critical---the longer the U.S. waits to start reducing GHG emissions, the faster the turnover in the electricity sector must occur in order to meet the same target. There is a real, and thus far unexplored, possibility that the U.S. could delay climate change policy implementation for long enough that it becomes infeasible to attain the necessary rate of turnover in the electricity sector. This dissertation investigates the relationship between climate policy timing and infrastructure turnover in the electricity sector. The goal of the dissertation is to answer the question: How long can we wait before constraints on infrastructure turnover in the electricity sector make achieving our climate goals impossible? Using the Infrastructure Flow Assessment Model, which was developed in this work, this dissertation shows that delaying climate change policy increases average retirements rates by 200-400%, increases average construction rates by 25-85% and increases maximum construction

  2. Daytime pattern of post-exercise protein intake affects whole-body protein turnover in resistance-trained males

    PubMed Central

    2012-01-01

    Background The pattern of protein intake following exercise may impact whole-body protein turnover and net protein retention. We determined the effects of different protein feeding strategies on protein metabolism in resistance-trained young men. Methods Participants were randomly assigned to ingest either 80g of whey protein as 8x10g every 1.5h (PULSE; n=8), 4x20g every 3h (intermediate, INT; n=7), or 2x40g every 6h (BOLUS; n=8) after an acute bout of bilateral knee extension exercise (4x10 repetitions at 80% maximal strength). Whole-body protein turnover (Q), synthesis (S), breakdown (B), and net balance (NB) were measured throughout 12h of recovery by a bolus ingestion of [15N]glycine with urinary [15N]ammonia enrichment as the collected end-product. Results PULSE Q rates were greater than BOLUS (~19%, P<0.05) with a trend towards being greater than INT (~9%, P=0.08). Rates of S were 32% and 19% greater and rates of B were 51% and 57% greater for PULSE as compared to INT and BOLUS, respectively (P<0.05), with no difference between INT and BOLUS. There were no statistical differences in NB between groups (P=0.23); however, magnitude-based inferential statistics revealed likely small (mean effect±90%CI; 0.59±0.87) and moderate (0.80±0.91) increases in NB for PULSE and INT compared to BOLUS and possible small increase (0.42±1.00) for INT vs. PULSE. Conclusion We conclude that the pattern of ingested protein, and not only the total daily amount, can impact whole-body protein metabolism. Individuals aiming to maximize NB would likely benefit from repeated ingestion of moderate amounts of protein (~20g) at regular intervals (~3h) throughout the day. PMID:23067428

  3. Multiwalled carbon nanotube dispersion methods affect their aggregation, deposition, and biomarker response.

    PubMed

    Chang, Xiaojun; Henderson, W Matthew; Bouchard, Dermont C

    2015-06-01

    To systematically evaluate how dispersion methods affect the environmental behaviors of multiwalled carbon nanotubes (MWNTs), MWNTs were dispersed in various solutions (e.g., surfactants, natural organic matter (NOM), and etc.) via ultrasonication (SON) and long-term stirring (LT). The two tested surfactants [anionic sodium dodecyl sulfate (SDS) and nonionic poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) (PEO-PPO-PEO) triblock copolymers (Pluronic)] could only disperse MWNTs via ultrasonication; while stable aqueous SON/MWNT and LT/MWNT suspensions were formed in the presence of the two model NOMs (Suwannee river humic acid and fulvic acid). Due to the inherent stochastic nature for both methods, the formed MWNT suspensions were highly heterogeneous. Their physicochemical properties, including surface charge, size, and morphology, greatly depended upon the dispersant type and concentration but were not very sensitive to the preparation methods. Aggregation and deposition behaviors of the dispersed MWNTs were controlled by van der Waal and electrostatic forces, as well as other non-DLVO forces (e.g., steric, hydrophobic forces, etc.). Unlike the preparation method-independent physicochemical properties, LT/NOM-MWNTs and SON/NOM-MWNTs differed in their fathead minnow epithelial cell metabolomics profiles. PMID:25924000

  4. SOIL AGGREGATE STABILITY AS AFFECTED BY LONG-TERM TILLAGE AND CLAY TYPE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil aggregate stability and dispersivity depend on clay mineralogy. However, little is known about the effect of soil mineralogy on soil crustability for long-term cultivated soil. The effect of long-term tillage on aggregate stability was the objective of our study. More than 20 soil samples chara...

  5. Commitment Profiles and Employee Turnover

    ERIC Educational Resources Information Center

    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…

  6. Spatial pattern formation of microbes at the soil microscale affect soil C and N turnover in an individual-based microbial community model

    NASA Astrophysics Data System (ADS)

    Kaiser, Christina; Evans, Sarah; Dieckmann, Ulf; Widder, Stefanie

    2016-04-01

    At the μm-scale, soil is a highly structured and complex environment, both in physical as well as in biological terms, characterized by non-linear interactions between microbes, substrates and minerals. As known from mathematics and theoretical ecology, spatial structure significantly affects the system's behaviour by enabling synergistic dynamics, facilitating diversity, and leading to emergent phenomena such as self-organisation and self-regulation. Such phenomena, however, are rarely considered when investigating mechanisms of microbial soil organic matter turnover. Soil organic matter is the largest terrestrial reservoir for organic carbon (C) and nitrogen (N) and plays a pivotal role in global biogeochemical cycles. Still, the underlying mechanisms of microbial soil organic matter buildup and turnover remain elusive. We explored mechanisms of microbial soil organic matter turnover using an individual-based, stoichiometrically and spatially explicit computer model, which simulates the microbial de-composer system at the soil microscale (i.e. on a grid of 100 x 100 soil microsites). Soil organic matter dynamics in our model emerge as the result of interactions among individual microbes with certain functional traits (f.e. enzyme production rates, growth rates, cell stoichiometry) at the microscale. By degrading complex substrates, and releasing labile substances microbes in our model continusly shape their environment, which in turn feeds back to spatiotemporal dynamics of the microbial community. In order to test the effect of microbial functional traits and organic matter input rate on soil organic matter turnover and C and N storage, we ran the model into steady state using continuous inputs of fresh organic material. Surprisingly, certain parameter settings that induce resource limitation of microbes lead to regular spatial pattern formation (f.e. moving spiral waves) of microbes and substrate at the μm-scale at steady-state. The occurrence of these

  7. Sunlight affects aggregation and deposition of graphene oxide in the aquatic environment.

    EPA Science Inventory

    In this study, we investigate the role of simulated sunlight on the physicochemical properties, aggregation, and deposition of graphene oxide (GO) in aquatic environments. Results show that light exposure under varied environmental conditions significantly impacts the physicochem...

  8. Geologic and societal factors affecting the international oceanic transport of aggregate

    USGS Publications Warehouse

    Langer, W.H.

    1995-01-01

    Crushed stone and sand and gravel are the two main sources of natural aggregate, and together comprise approximately half the volume and tonnage of mined material in the United States. Natural aggregate is a bulky, heavy material without special or unique properties, and it is commonly used near its source of production to minimize haulage cost. However, remoteness is no longer an absolute disqualifier for the production of aggregate. Today interstate aggregate routinely is shipped hundreds of kilometers by rail and barge. In addition, during 1992, the United States imported 1,317,000 metric tons of aggregate from Canada and 1,531,000 metric tons from Mexico. A number of ports on the Atlantic Coast and Gulf Coast of the United States receive imports of crushed stone from foreign sources for transport to various parts of the eastern United States. These areas either lack adequate supplies of aggregate or are augmenting their supplies because they have difficulties meeting current demand. These difficulties may include poor stone quality, environmental permitting problems, or transportation. Certain societal and geologic conditions of New York City and Philadelphia along the Atlantic Coast, and Tampa and New Orleans along the Gulf Coast, are discussed to demonstrate the different combinations of issues that contribute to the economic viability of importing crushed stone. ?? 1995 Oxford University Press.

  9. Supervisory Turnover in Outpatient Substance Abuse Treatment

    PubMed Central

    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

  10. Turnover Time

    EPA Science Inventory

    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. Pig slurry acidification and separation techniques affect soil N and C turnover and N2O emissions from solid, liquid and biochar fractions.

    PubMed

    Gómez-Muñoz, B; Case, S D C; Jensen, L S

    2016-03-01

    The combined effects of pig slurry acidification, subsequent separation techniques and biochar production from the solid fraction on N mineralisation and N2O and CO2 emissions in soil were investigated in an incubation experiment. Acidification of pig slurry increased N availability from the separated solid fractions in soil, but did not affect N2O and CO2 emissions. However acidification reduced soil N and C turnover from the liquid fraction. The use of more advanced separation techniques (flocculation and drainage > decanting centrifuge > screw press) increased N mineralisation from acidified solid fractions, but also increased N2O and CO2 emissions in soil amended with the liquid fraction. Finally, the biochar production from the solid fraction of pig slurry resulted in a very recalcitrant material, which reduced N and C mineralisation in soil compared to the raw solid fractions. PMID:26716355

  12. Design of peptidyl compounds that affect beta-amyloid aggregation: importance of surface tension and context.

    PubMed

    Gibson, Todd J; Murphy, Regina M

    2005-06-21

    Self-association of beta-amyloid (Abeta) peptide into cross-beta-sheet fibrils induces cellular toxicity in vitro and is linked with progression of Alzheimer's disease. Previously, we demonstrated that hybrid peptides, containing a recognition domain that binds to Abeta and a disrupting domain consisting of a chain of charged amino acids, inhibited Abeta-associated toxicity in vitro and increased the rate of Abeta aggregation. In this work we examine the design parameter space of the disrupting domain. Using KLVFFKKKKKK as a base case, we tested hybrid compounds with a branched rather than linear lysine oligomer, with l-lysine replaced by d-lysine, and with lysine replaced by diaminopropionic acid. We synthesized a compound with a novel anionic disrupting domain that contained cysteine thiols oxidized to sulfates, as well as other compounds in which alkyl or ether chains were appended to KLVFF. In all cases, the hybrid compound's ability to increase solvent surface tension was the strongest predictor of its effect on Abeta aggregation kinetics. Finally, we investigated the effects of arginine on Abeta aggregation. Arginine is a well-known chaotrope but increases surface tension of water. Arginine modestly decreased Abeta aggregation. In contrast, RRRRRR slightly, and KLVFFRRRRRR greatly, increased Abeta aggregation. Thus, the influence of arginine on Abeta aggregation depends strongly on the context in which it is presented. The effect of arginine, RRRRRR, and KLVFFRRRRRR on Abeta aggregation was examined in detail using laser light scattering, circular dichroism spectroscopy, Fourier transform infrared spectroscopy, thioflavin T fluorescence, and transmission electron microscopy. PMID:15952797

  13. Dynamics of aggregate stability and soil organic C distribution as affected by climatic aggressiveness: a mesocosm approach

    NASA Astrophysics Data System (ADS)

    Pellegrini, Sergio; Elio Agnelli, Alessandro; Costanza Andrenelli, Maria; Barbetti, Roberto; Castelli, Fabio; Costantini, Edoardo A. C.; Lagomarsino, Alessandra; Pasqui, Massimiliano; Tomozeiu, Rodica; Razzaghi, Somayyeh; Vignozzi, Nadia

    2014-05-01

    changed at the end of the trial, depending of soil types. In CAS and MED a decrease of C content was observed in fractions larger than 0.250 mm, while an accumulation occurred only in CAS microaggregates. BOV showed a singular pattern, with an increase of organic C in all fractions. In this site an improvement of aggregation, involving the coarser fractions, seems to have been favoured during the experiment. Overall, the imposed climate did not affect significantly these trends, except in CAS, where TYP and SIM climates showed an increase of macroaggregates and their C concentration. Soil pedoclimatic characteristics showed to be the main factors affecting C and aggregates dynamics in this mesocosm experiment.

  14. Stability and heavy metal distribution of soil aggregates affected by application of apatite, lime, and charcoal.

    PubMed

    Cui, Hongbiao; Ma, Kaiqiang; Fan, Yuchao; Peng, Xinhua; Mao, Jingdong; Zhou, Dongmei; Zhang, Zhongbin; Zhou, Jing

    2016-06-01

    Only a few studies have been reported on the stability and heavy metal distribution of soil aggregates after soil treatments to reduce the availability of heavy metals. In this study, apatite (22.3 t ha(-1)), lime (4.45 t ha(-1)), and charcoal (66.8 t ha(-1)) were applied to a heavy metal-contaminated soil for 4 years. The stability and heavy metal distribution of soil aggregates were investigated by dry and wet sieving. No significant change in the dry mean weight diameter was observed in any treatments. Compared with the control, three-amendment treatments significantly increased the wet mean weight diameter, but only charcoal treatment significantly increased the wet aggregate stability. The soil treatments increased the content of soil organic carbon, and the fraction 0.25-2 mm contained the highest content of soil organic carbon. Amendments' application slightly increased soil total Cu and Cd, but decreased the concentrations of CaCl2 -extractable Cu and Cd except for the fraction <0.053 mm. The fractions >2 and 0.25-2 mm contained the highest concentrations of CaCl2-extractable Cu and Cd, accounted for about 74.5-86.8 % of CaCl2-extractable Cu and Cd in soil. The results indicated that amendments' application increased the wet soil aggregate stability and decreased the available Cu and Cd. The distribution of available heavy metals in wet soil aggregates was not controlled by soil aggregate stability, but possibly by soil organic carbon. PMID:26893180

  15. Does the Level of Occupational Aggregation Affect Estimates of the Gender Wage Gap?

    ERIC Educational Resources Information Center

    Kidd, Michael P.; Shannon, Michael

    1996-01-01

    Using data from the 1989 Canadian Labour-Market Activity Survey, when occupation is treated as a productivity-related characteristic, gender wage gap estimates are distorted. Using a larger number of occupations, the occupational aggregation by gender reflects barriers women face in attempting to enter male-dominated occupations. (SK)

  16. Environmental factors affecting twitching motility, biofilm development, and aggregation by Xylella fastidiosa

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The bacterial pathogen Xylella fastidiosa causes many important plant diseases in different crops such as citrus, grapes, almond and coffee. While disease symptoms expressed by this pathogen are not completely understood, it is widely accepted that blockage of xylem vessels by aggregates of the bact...

  17. Primary particle size distribution of eroded material affected by degree of aggregate slaking and seal development

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Primary particle size distribution (PSD) of eroded sediments can be used to estimate potential nutrient losses from soil and pollution hazards to the environment. We studied eroded sediment PSDs from three saturated soils, packed in trays (20 x 40 x 4 cm), that had undergone either minimal aggregate...

  18. Organic Matter and Water Stability of Field Aggregates Affected by Tillage in South Dakota

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Increased tillage intensity has been associated with declines in soil organic matter (SOM). A case study was conducted (2001-2004) on adjacent farms (both in a two-year crop rotation) in eastern South Dakota to quantify tillage effects on components of SOM and soil aggregate stability. One farm used...

  19. Leucine supplementation does not affect protein turnover and impairs the beneficial effects of endurance training on glucose homeostasis in healthy mice.

    PubMed

    Costa Júnior, José M; Rosa, Morgana R; Protzek, André O; de Paula, Flávia M; Ferreira, Sandra M; Rezende, Luiz F; Vanzela, Emerielle C; Zoppi, Cláudio C; Silveira, Leonardo R; Kettelhut, Isis C; Boschero, Antonio C; de Oliveira, Camila A M; Carneiro, Everardo M

    2015-04-01

    Endurance exercise training as well as leucine supplementation modulates glucose homeostasis and protein turnover in mammals. Here, we analyze whether leucine supplementation alters the effects of endurance exercise on these parameters in healthy mice. Mice were distributed into sedentary (C) and exercise (T) groups. The exercise group performed a 12-week swimming protocol. Half of the C and T mice, designated as the CL and TL groups, were supplemented with leucine (1.5 % dissolved in the drinking water) throughout the experiment. As well known, endurance exercise training reduced body weight and the retroperitoneal fat pad, increased soleus mass, increased VO2max, decreased muscle proteolysis, and ameliorated peripheral insulin sensitivity. Leucine supplementation had no effect on any of these parameters and worsened glucose tolerance in both CL and TL mice. In the soleus muscle of the T group, AS-160(Thr-642) (AKT substrate of 160 kDa) and AMPK(Thr-172) (AMP-Activated Protein Kinase) phosphorylation was increased by exercise in both basal and insulin-stimulated conditions, but it was reduced in TL mice with insulin stimulation compared with the T group. Akt phosphorylation was not affected by exercise but was lower in the CL group compared with the other groups. Leucine supplementation increased mTOR phosphorylation at basal conditions, whereas exercise reduced it in the presence of insulin, despite no alterations in protein synthesis. In trained groups, the total FoxO3a protein content and the mRNA for the specific isoforms E2 and E3 ligases were reduced. In conclusion, leucine supplementation did not potentiate the effects of endurance training on protein turnover, and it also reduced its positive effects on glucose homeostasis. PMID:25575490

  20. Aggregation of adverse behaviors and its affecting factors among young military conscripts in Taiwan.

    PubMed

    Wu, Der-Min; Chu, Nain-Feng; Lin, Yaoh-Shiang; Lai, Hsiang-Ru

    2007-06-01

    The authors studied the prevalence of the aggregation in common lifestyle habits, namely, cigarette smoking, alcohol drinking, and betel-nut chewing and the demographic correlates of individual aggregation in these lifestyle behaviors among young military conscripts in Taiwan. Cross-sectional screening was conducted among conscripts in southern and eastern sections of Taiwan from Aug. 1st to Dec. 31st 2001. Totally, 3913 conscripts who had more than 1 month of service were included in this multistage sampling study. Information on smoking, drinking, and betel-nut chewing habits were ascertained as part of a self-administered questionnaire completed by examinees at the service unit. Aggregation in lifestyle habits was studied by comparing the observed and expected proportions (O/E ratio) with their 95% confidence intervals (CI) for zero, one, two, and three simultaneously occurring lifestyle habits. The study results showed a significant clustering of lifestyle habits studied; the number of subjects was greater than expected in groups with two (for cigarette smoking and betel-nut chewing, O/E ratio=1.17, 95%CI=1.06-1.28), and three (O/E ratio=5.63, 95%CI=5.06-6.20) lifestyle habits. Determinants for this clustering of lifestyle habits included lower educational levels and residential area in southern and eastern sections of Taiwan. There was a significant individual aggregation in lifestyle habits including cigarette smoking, alcohol drinking, and betel-nut chewing in the health survey among young military conscripts. In addition, young military conscripts with low educational levels and residential area in southern and eastern sections of Taiwan had an apparent tendency toward the aggregation in these lifestyle habits. PMID:17107751

  1. Chemical properties of lipids strongly affect the kinetics of the membrane-induced aggregation of α-synuclein

    PubMed Central

    Brown, James W. P.; Ouberai, Myriam M.; Flagmeier, Patrick; Vendruscolo, Michele; Buell, Alexander K.; Sparr, Emma; Dobson, Christopher M.

    2016-01-01

    Intracellular α-synuclein deposits, known as Lewy bodies, have been linked to a range of neurodegenerative disorders, including Parkinson’s disease. α-Synuclein binds to synthetic and biological lipids, and this interaction has been shown to play a crucial role for both α-synuclein’s native function, including synaptic plasticity, and the initiation of its aggregation. Here, we describe the interplay between the lipid properties and the lipid binding and aggregation propensity of α-synuclein. In particular, we have observed that the binding of α-synuclein to model membranes is much stronger when the latter is in the fluid rather than the gel phase, and that this binding induces a segregation of the lipids into protein-poor and protein-rich populations. In addition, α-synuclein was found to aggregate at detectable rates only when interacting with membranes composed of the most soluble lipids investigated here. Overall, our results show that the chemical properties of lipids determine whether or not the lipids can trigger the aggregation of α-synuclein, thus affecting the balance between functional and aberrant behavior of the protein. PMID:27298346

  2. Dabigatran and rivaroxaban do not affect AA- and ADP-induced platelet aggregation in patients receiving concomitant platelet inhibitors.

    PubMed

    Olivier, Christoph B; Weik, Patrick; Meyer, Melanie; Weber, Susanne; Diehl, Philipp; Bode, Christoph; Moser, Martin; Zhou, Qian

    2016-08-01

    Dabigatran and rivaroxaban are novel, vitamin K-independent oral anticoagulants (NOACs) and act via antagonism of the coagulation factor (F) IIa (dabigatran) or FXa (rivaroxaban), respectively. Compared to vitamin-K-antagonists, NOACs have shown non-inferiority of risk and benefit in patients with non valvular atrial fibrillation (AF). In clinical practice there is increasing use of NOACs combined with platelet inhibitors in patients with AF and coronary artery disease. However, whether NOACs affect the function of platelet inhibitors remains incompletely known. This observational study aimed to assess the platelet function in patients receiving dabigatran or rivaroxaban and concomitant platelet inhibitors. A single centre observational study was performed analysing the platelet aggregation of patients treated with dabigatran or rivaroxaban with or without concomitant platelet inhibitors. Measurements before the initiation of NOAC therapy served as the respective control group. Platelet aggregation was measured by multiple electrode aggregometry and was induced with adenosine diphosphate (ADP, 6.5 µM) and arachidonic acid (AA, 0.5 mM), respectively. In order to evaluate whether NOACs interact with platelet inhibition by ASA or the P2Y12-antagonist clopidogrel, 87 patients were grouped according to their concomitant antiplatelet medication. Comparing the ADP- and AA-induced platelet aggregation in patients without concomitant platelet inhibitors (n = 45) no significant differences under therapy with dabigatran (d) or rivaroxaban (r) compared to the control group (c) were observed. In patients taking clopidogrel as a concomitant platelet inhibitor (n = 21), neither dabigatran nor rivaroxaban affected the ADP-induced platelet aggregation (c 20 ± 11, d 21 ± 14, r 18 ± 8 AU*min, p = 0.200). Patients receiving dabigatran or rivaroxaban in combination with ASA (n = 42; 21 ASA only, 21 ASA + clopidogrel) showed no significant differences of the AA

  3. Factors affecting crystallization, dispersion, and aggregation of calcium oxalate monohydrate in various urinary environments

    NASA Astrophysics Data System (ADS)

    Christmas, Kimberly Gail

    The mechanisms for the formation of kidney stones are not well understood. One possible mechanism is the formation of aggregates in the nephron tubules of the kidneys. However, altering the urinary environment may be a method to help prevent the recurrence of the formation of kidney stones. The primary inorganic constituent found in kidney stones of North American patients is calcium oxalate monohydrate (COM). In this research, studies on the effect of mixing rate on COM precipitation showed that rapid mixing compared to slow mixing produced smaller particle sizes and a narrower particle size distribution due to the more uniform supersaturation level. The findings are consistent with the general contention that mixing directly influences nucleation rate while mixing rate has relatively little influence over rate of growth in precipitation processes. Screening and central composite experimental designs are used to determine the effect of various factors on the aggregation and dispersion characteristics of previously grown calcium oxalate monohydrate (COM) crystals in artificial urinary environments of controlled variables. The variables examined are pH, calcium, oxalate, pyrophosphate, citrate, and protein concentrations in ultrapure water and artificial urine. Optical density measurements, zeta potential analysis, particle size analyzer, optical microscopy, AFM force measurements, protein adsorption, and ions and small molecule adsorption have been used to assess the state of aggregation and dispersion of the COM crystals and to elucidate the mechanisms involved in such a complex system. The data indicate that our model protein, mucin, acts as a dispersant. This is attributed to steric hindrance resulting from the adsorbed mucoprotein. Oxalate, however, promotes aggregation. Interesting interactions between protein and oxalate along with protein and citrate are observed. Such interactions (synergistic or antagonistic) are found to depend on the concentrations of

  4. Methylations of tryptophan-modified naphthoquinone affect its inhibitory potential toward Aβ aggregation.

    PubMed

    Scherzer-Attali, Roni; Convertino, Marino; Pellarin, Riccardo; Gazit, Ehud; Segal, Daniel; Caflisch, Amedeo

    2013-02-14

    Aggregation of amyloid beta (Aβ) is the hallmark of Alzheimer's disease (AD). Small molecules inhibiting Aβ can be valuable therapeutics for AD. We have previously reported that 1,4-naphthoquinon-2-yl-l-tryptophan (NQTrp), reduces aggregation and oligomerization of Aβ in vitro and in vivo. In silico analysis further showed that certain functional groups of NQTrp, not in the aromatic rings, are also involved in binding and inhibiting Aβ. To better understand the exact mode of action and identify the groups crucial for NQTrp inhibitory activity, we conducted structure-activity analysis. Four derivatives of NQTrp were studied in silico: a D-isomer, two single-methylated and one double-methylated derivative. In silico results showed that the NQTrp groups involved in hydrogen bonds are the anilinic NH (i.e., the NH linker between the quinone and tryptophan moieties), the quinonic carbonyls, and the carboxylic acid. These predictions were supported by in vitro results. Our results should aid in designing improved small-molecule inhibitors of Aβ aggregation for treating AD. PMID:23259849

  5. Indole affects the formation of multicellular aggregate structures in Pantoea agglomerans YS19.

    PubMed

    Yu, Xuemei; Jiang, Jing; Liang, Chen; Zhang, Xiao; Wang, Jieru; Shen, Delong; Feng, Yongjun

    2016-01-01

    Pantoea agglomerans YS19 is an endophytic diazotrophic bacterium isolated from rice. As well as having the ability to form a biofilm, as do most bacteria, it is characterized by the formation of a unique multicellular aggregate structure called symplasmata. Indole is traditionally known as a metabolite of the amino acid tryptophan, which, however, has recently been shown to participate in various regulations of bacterial physiological processes, including stress resistance, quorum sensing and biofilm formation. Here, an indole signal was found to promote symplasmata formation, yet inhibit biofilm formation, indicating different regulatory pathways of indole in the construction of the two structures. However, symplasmata showed almost an equivalent stress-resistant capability, as compared with biofilms, for YS19 to confront acids, heavy metals (Cu(2+)), and UV treatments. Moreover, indole was tested to show a promoting effect on exopolysaccharides (EPS) production and an inhibition effect on the expression of an outer membrane protein OmpW. These results provide evidence for understanding the regulatory mechanisms of indole on such multicellular aggregates. PMID:26923129

  6. Multiwalled Carbon Nanotube Dispersion Methods Affect Their Aggregation, Deposition, and Biomarker Response

    EPA Science Inventory

    To systematically evaluate how dispersion methods affect the environmental behaviors of multiwalled carbon nanotubes (MWNTs), MWNTs were dispersed in various solutions (e.g., surfactants, natural organic matter (NOM), and etc.) via ultrasonication (SON) and long-term stirring (LT...

  7. Tripeptide SQL Inhibits Platelet Aggregation and Thrombus Formation by Affecting PI3K/Akt Signaling.

    PubMed

    Su, Xing-li; Su, Wen; He, Zhi-long; Ming, Xin; Kong, Yi

    2015-09-01

    Centipede has been prescribed for the treatment of cardiovascular diseases in Asian countries for several hundred years. Previously, a new antiplatelet tripeptide SQL (H-Ser-Gln-Leu-OH) was isolated and characterized from centipede. In this study, we investigated its antithrombotic activities in vivo and underlying mechanism. It was found that SQL inhibited platelet aggregation induced by adenosine diphosphate, thrombin, epinephrine, and collagen and attenuated thrombus formation in both the ferric chloride-induced arterial thrombosis model and arteriovenous shunt thrombosis model in rats. It did not prolong the bleeding time in mice even at the dose of 10 mg/kg that showed potent antithrombosis effects. Molecular docking revealed that SQL binds PI3Kβ with the binding free energy of -24.341 kcal/mol, which is close to that of cocrystallized ligand (-24.220 kcal/mol). Additionally, SQL displayed inhibition on the late (180 seconds) but did not influence the early (60 seconds) Akt Ser473 phosphorylation in the immunoblot assay. These results suggest that SQL inhibits thrombus formation in vivo and that SQL inhibits PI3K-mediated signaling or even the PI3K itself in platelets. This study may help elucidate the mechanism for centipede treating cardiovascular diseases. PMID:25923322

  8. Understanding how the aggregation structure of starch affects its gastrointestinal digestion rate and extent.

    PubMed

    Chen, Pei; Wang, Kai; Kuang, Qirong; Zhou, Sumei; Wang, Dazheng; Liu, Xingxun

    2016-06-01

    Regulating the starch gastrointestinal digestion rate by control of its aggregation structure is an effective way, but the mechanism is still not clear. Multi-scale structure of waxy and normal wheat starches were studied by confocal laser scanning and scanning electron microscopes, as well as wide-angle and small-angle X-ray techniques in this study. In vitro digestion kinetics of those two starches and structure-digestion relationship were also discussed. Both waxy and normal starches show A-type diffraction pattern, but waxy variety shows a slightly higher crystallinity. Small-angle X-ray scattering results show that waxy wheat starch has higher scattering peak intensity (Imax) and a larger crystallinity lamellar repeat distance (Lp) compared with the normal wheat starch. We suggested that the higher digestion rate of waxy starch at initial stage is mainly due to more small-size particles, but the higher crystallinity and the larger crystalline lamellar size limit the digestion extent. PMID:26899172

  9. In situ characterization of protein aggregates in human tissues affected by light chain amyloidosis: a FTIR microspectroscopy study.

    PubMed

    Ami, Diletta; Lavatelli, Francesca; Rognoni, Paola; Palladini, Giovanni; Raimondi, Sara; Giorgetti, Sofia; Monti, Luca; Doglia, Silvia Maria; Natalello, Antonino; Merlini, Giampaolo

    2016-01-01

    Light chain (AL) amyloidosis, caused by deposition of amyloidogenic immunoglobulin light chains (LCs), is the most common systemic form in industrialized countries. Still open questions, and premises for developing targeted therapies, concern the mechanisms of amyloid formation in vivo and the bases of organ targeting and dysfunction. Investigating amyloid material in its natural environment is crucial to obtain new insights on the molecular features of fibrillar deposits at individual level. To this aim, we used Fourier transform infrared (FTIR) microspectroscopy for studying in situ unfixed tissues (heart and subcutaneous abdominal fat) from patients affected by AL amyloidosis. We compared the infrared response of affected tissues with that of ex vivo and in vitro fibrils obtained from the pathogenic LC derived from one patient, as well as with that of non amyloid-affected tissues. We demonstrated that the IR marker band of intermolecular β-sheets, typical of protein aggregates, can be detected in situ in LC amyloid-affected tissues, and that FTIR microspectroscopy allows exploring the inter- and intra-sample heterogeneity. We extended the infrared analysis to the characterization of other biomolecules embedded within the amyloid deposits, finding an IR pattern that discloses a possible role of lipids, collagen and glycosaminoglycans in amyloid deposition in vivo. PMID:27373200

  10. In situ characterization of protein aggregates in human tissues affected by light chain amyloidosis: a FTIR microspectroscopy study

    PubMed Central

    Ami, Diletta; Lavatelli, Francesca; Rognoni, Paola; Palladini, Giovanni; Raimondi, Sara; Giorgetti, Sofia; Monti, Luca; Doglia, Silvia Maria; Natalello, Antonino; Merlini, Giampaolo

    2016-01-01

    Light chain (AL) amyloidosis, caused by deposition of amyloidogenic immunoglobulin light chains (LCs), is the most common systemic form in industrialized countries. Still open questions, and premises for developing targeted therapies, concern the mechanisms of amyloid formation in vivo and the bases of organ targeting and dysfunction. Investigating amyloid material in its natural environment is crucial to obtain new insights on the molecular features of fibrillar deposits at individual level. To this aim, we used Fourier transform infrared (FTIR) microspectroscopy for studying in situ unfixed tissues (heart and subcutaneous abdominal fat) from patients affected by AL amyloidosis. We compared the infrared response of affected tissues with that of ex vivo and in vitro fibrils obtained from the pathogenic LC derived from one patient, as well as with that of non amyloid-affected tissues. We demonstrated that the IR marker band of intermolecular β-sheets, typical of protein aggregates, can be detected in situ in LC amyloid-affected tissues, and that FTIR microspectroscopy allows exploring the inter- and intra-sample heterogeneity. We extended the infrared analysis to the characterization of other biomolecules embedded within the amyloid deposits, finding an IR pattern that discloses a possible role of lipids, collagen and glycosaminoglycans in amyloid deposition in vivo. PMID:27373200

  11. Inhalation of Whole Diesel Exhaust but not Gas-Phase Components Affects In Vitro Platelet Aggregation in Hypertensive Rats

    EPA Science Inventory

    Rationale: Intravascular thrombosis and platelet aggregation are enhanced following exposure to diesel exhaust (DE) and other respirable particulate matter; however, the roles of endothelial and circulating mediators on platelet aggregation remain unclear. We hypothesized that ad...

  12. Contextual Factors Related to Elementary Principal Turnover

    ERIC Educational Resources Information Center

    Partlow, Michelle C.

    2007-01-01

    The issue of school leadership instability and how it affects schools and student achievement has been studied. The question of how to predict turnover of the principal remains an unknown. The purpose of this research was to search for possible relationships between certain contextual variables and principal turnover and to test the independent…

  13. Employee Turnover: Evidence from a Case Study.

    ERIC Educational Resources Information Center

    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…

  14. Global skeletal uptake of 99mTc-methylene diphosphonate (GSU) in patients affected by endocrine diseases: comparison with biochemical markers of bone turnover.

    PubMed

    Scillitani, A; Dicembrino, F; Chiodini, I; Minisola, S; Fusilli, S; Di Giorgio, A; Garrubba, M; D'Aloiso, L; Frusciante, V; Torlontano, M; Modoni, S; Trischitta, V; Trischitta, V; Carnevale, V

    2002-10-01

    This study aimed to clinically validate the global skeletal uptake (GSU) of (99m)Tc-methylene diphosphonate ((99m)Tc-MDP), and to compare it with a marker of bone formation (i.e. serum osteocalcin or OC) and an index of bone resorption (i.e. urinary deoxypyridinoline or U-DPD) in different endocrine disorders affecting the skeleton. We studied 29 female patients with thyrotoxicosis (TT), 27 with primary hyperparathyroidism (PHPT), 16 with acromegaly (AC), 15 with Cushing's syndrome (CS), and altogether 110 healthy women matched for age, BMI and menstrual status. In all subjects total body digital scan images (TBDS) were acquired at 5 min and at 4 h after the administration of (99m)Tc-MDP; the whole body retention (WBR) of the tracer was measured by counting two identical sets of rectangular ROIs, and GSU was subsequently calculated by drawing an irregular ROI on 4 h TBDS images. Serum OC was assessed by IRMA and urinary DPD by fluorometric detection after reverse phase high pressure chromatography. In TT patients GSU (40.0 +/- 5.1 vs 36.5 +/- 4.8%), OC (19.1 +/- 11.8 vs 7.1 +/- 2.9 microg/l) and U-DPD (62.4 +/- 42.7 vs 19.5 +/- 5.3 pmol/pmol) were significantly ( p<0.01) higher than in controls. PHPT patients showed GSU (47.2 +/- 6.6 vs 37.8 +/- 5.3%), OC (38.6 +/- 40.9 vs 8.2 +/- 2.5 microg/l), and U-DPD (55.0 +/- 51.3 vs 21.9 +/- 6.1 pmol/pmol) values significantly ( p<0.001) higher than controls. In CS patients, GSU (39.6 +/- 6.4 vs 32.7 +/- 3.5%; p<0.01) and U-DPD (22.8 +/- 8.4 vs 16.5 +/- 2.7 pmol/pmol; p<0.05) were higher, whereas OC (3.6 +/- 2.4 vs 5.2 +/- 1.9 mg/l; p<0,05) was lower than in controls. In AC patients, GSU (34.9 +/- 5.3 vs 35.2 +/- 3.4%) did not differ significantly from controls, whereas OC (16.8 +/- 8.8 vs 6.9 +/- 2.9 microg/l; p<0.001) and U-DPD (30.9 +/- 13.6 vs 21.0 +/- 5.7 pmol/pmol; p<0.01) were higher. Stepwise multivariate linear regression analysis was performed with disease activity, creatinine clearance, age, and years since

  15. Hyrdo-Quebec`s experience using deep slot cutting to rehabilitate concrete gravity dams affected by alkali-aggregate reaction

    SciTech Connect

    Veilleux, M.

    1995-12-31

    In recent years, Hydro-Qu{acute e}bec has cut vertical slots in concrete dams to solve structural problems stemming from aging of concrete subject to thermal cycles and alkali-aggregate reaction (AAR). In most cases, the structural disorders caused large cracks and permanent displacement. This paper describes Hydro-Qu{acute e}bec`s experience using a new slot-cutting and sealing technology to rehabilitate concrete gravity dams affected by AAR, among them rehabilitation of the Paugan (1991), La Tuque (1992-1993), Rapides Farmers (1993-1994) and Chelsea (1994) hydroelectric developments. The aim of this technology is to relieve internal stress and to create an effective expansion joint which can accommodate reversible and irreversible displacement induced by thermal cycles as well as permanent movement due to chemical concrete swelling caused by AAR. This method of rehabilitation is generally used in conjunction with grouting and drainage work and sometimes with post-tensioned anchor rods or cables.

  16. Carbon and Nitrogen Fractions in Dryland Soil Aggregates Affected by Long-term Tillage and Cropping Sequence

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Tillage and cropping sequence may influence C and N sequestration, microbial activities, and N mineralization in dryland soil aggregates. We evaluated the 21-yr effect of tillage and cropping sequence combinations on C and N fractions in aggregates of a Dooley sandy loam (fine-loamy, mixed, frigid, ...

  17. How Do the Size, Charge and Shape of Nanoparticles Affect Amyloid β Aggregation on Brain Lipid Bilayer?

    PubMed

    Kim, Yuna; Park, Ji-Hyun; Lee, Hyojin; Nam, Jwa-Min

    2016-01-01

    Here, we studied the effect of the size, shape, and surface charge of Au nanoparticles (AuNPs) on amyloid beta (Aβ) aggregation on a total brain lipid-based supported lipid bilayer (brain SLB), a fluid platform that facilitates Aβ-AuNP aggregation process. We found that larger AuNPs induce large and amorphous aggregates on the brain SLB, whereas smaller AuNPs induce protofibrillar Aβ structures. Positively charged AuNPs were more strongly attracted to Aβ than negatively charged AuNPs, and the stronger interactions between AuNPs and Aβ resulted in fewer β-sheets and more random coil structures. We also compared spherical AuNPs, gold nanorods (AuNRs), and gold nanocubes (AuNCs) to study the effect of nanoparticle shape on Aβ aggregation on the brain SLB. Aβ was preferentially bound to the long axis of AuNRs and fewer fibrils were formed whereas all the facets of AuNCs interacted with Aβ to produce the fibril networks. Finally, it was revealed that different nanostructures induce different cytotoxicity on neuroblastoma cells, and, overall, smaller Aβ aggregates induce higher cytotoxicity. The results offer insight into the roles of NPs and brain SLB in Aβ aggregation on the cell membrane and can facilitate the understanding of Aβ-nanostructure co-aggregation mechanism and tuning Aβ aggregate structures. PMID:26782664

  18. How Do the Size, Charge and Shape of Nanoparticles Affect Amyloid β Aggregation on Brain Lipid Bilayer?

    NASA Astrophysics Data System (ADS)

    Kim, Yuna; Park, Ji-Hyun; Lee, Hyojin; Nam, Jwa-Min

    2016-01-01

    Here, we studied the effect of the size, shape, and surface charge of Au nanoparticles (AuNPs) on amyloid beta (Aβ) aggregation on a total brain lipid-based supported lipid bilayer (brain SLB), a fluid platform that facilitates Aβ-AuNP aggregation process. We found that larger AuNPs induce large and amorphous aggregates on the brain SLB, whereas smaller AuNPs induce protofibrillar Aβ structures. Positively charged AuNPs were more strongly attracted to Aβ than negatively charged AuNPs, and the stronger interactions between AuNPs and Aβ resulted in fewer β-sheets and more random coil structures. We also compared spherical AuNPs, gold nanorods (AuNRs), and gold nanocubes (AuNCs) to study the effect of nanoparticle shape on Aβ aggregation on the brain SLB. Aβ was preferentially bound to the long axis of AuNRs and fewer fibrils were formed whereas all the facets of AuNCs interacted with Aβ to produce the fibril networks. Finally, it was revealed that different nanostructures induce different cytotoxicity on neuroblastoma cells, and, overall, smaller Aβ aggregates induce higher cytotoxicity. The results offer insight into the roles of NPs and brain SLB in Aβ aggregation on the cell membrane and can facilitate the understanding of Aβ-nanostructure co-aggregation mechanism and tuning Aβ aggregate structures.

  19. Coniston Dam: The rehabiliation of a 50-year-old concrete dam affected by alkali aggregate reaction

    SciTech Connect

    Read, P.H.; Thomas, M.

    1995-12-31

    This paper discusses the rehabilitation of the Coniston main dam in Ontario, with particular emphasis on the alkali-aggregate reaction (AAR) related aspects of the investigation and the influence of these on the design approach adopted, including measures taken to allow for possible future expansion of the original gravity section concrete. The rehabilitation program was primarily undertaken to increase the stability of the gravity sections and log chute which did not meet current dam safety criteria. However, all parts of the structure were found to be affected by AAR and the downstream face of the gravity sections were severely deteriorated due to the combined effects of AAR and freeze-thaw cycles. Field and laboratory investigations were undertaken to determine the extent of deterioration of the dam structures and to assess the potential for continued deterioration. Based on the findings from these studies, a rehabilitation and upgrade strategy was developed which included removal of badly deteriorated concrete, placement of reinforced concrete liners (upstream and downstream), addition of mass concrete buttresses along the length of the gravity sections, replacement of the deck and epoxy injection of the cracked sluiceway piers. Particular attention was paid to the design of the new concrete mixes (to limit the supply of alkalis to the existing concrete) and to the relief of stress between the original concrete core and new concrete liners. The new gravity section liner was debonded from the core concrete to reduce the transfer of stress due to continued expansion of the core; furthermore, the reinforcement of the liner was designed to resist tensile stresses induced by future expansion. Consideration was also given to minimizing the ingress of water to the dam core in order to reduce the degree of saturation and likelihood of further AAR and freeze-thaw action.

  20. Cathodoluminescence microscopy and petrographic image analysis of aggregates in concrete pavements affected by alkali-silica reaction

    SciTech Connect

    Stastna, A.; Sachlova, S.; Pertold, Z.; Prikryl, R.; Leichmann, J.

    2012-03-15

    Various microscopic techniques (cathodoluminescence, polarizing and electron microscopy) were combined with image analysis with the aim to determine a) the modal composition and degradation features within concrete, and b) the petrographic characteristics and the geological types (rocks, and their provenance) of the aggregates. Concrete samples were taken from five different portions of Highway Nos. D1, D11, and D5 (the Czech Republic). Coarse and fine aggregates were found to be primarily composed of volcanic, plutonic, metamorphic and sedimentary rocks, as well as of quartz and feldspar aggregates of variable origins. The alkali-silica reaction was observed to be the main degradation mechanism, based upon the presence of microcracks and alkali-silica gels in the concrete. Use of cathodoluminescence enabled the identification of the source materials of the quartz aggregates, based upon their CL characteristics (i.e., color, intensity, microfractures, deformation, and zoning), which is difficult to distinguish only employing polarizing and electron microscopy. - Highlights: Black-Right-Pointing-Pointer ASR in concrete pavements on the Highways Nos. D1, D5 and D11 (Czech Republic). Black-Right-Pointing-Pointer Cathodoluminescence was combined with various microscopic techniques and image analysis. Black-Right-Pointing-Pointer ASR was attributed to aggregates. Black-Right-Pointing-Pointer Source materials of aggregates were identified based on cathodoluminescence characteristics. Black-Right-Pointing-Pointer Quartz comes from different volcanic, plutonic and metamorphic parent rocks.

  1. Structure Stability and Carbon Distribution in Silty Loam Soil Aggregates as Affected Tillage and Corn-Soybean Crop Rotation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Different tillage intensities may influence soil physical and chemical properties, distribution of nutrients and organic carbon between and within the aggregates. We studied the effect of long term (25 years) conservation tillage on structure stability and the total C and N distribution in Miami sil...

  2. Heat-denaturation and aggregation of quinoa (Chenopodium quinoa) globulins as affected by the pH value.

    PubMed

    Mäkinen, Outi E; Zannini, Emanuele; Koehler, Peter; Arendt, Elke K

    2016-04-01

    The influence of heating (100 °C; 0-15 min) on the relative molecular mass, protein unfolding and secondary structure of quinoa globulins was studied at pH 6.5 (low solubility), 8.5 and 10.5 (high solubility). The patterns of denaturation and aggregation varied with pH. Heating triggered the disruption of the disulfide bonds connecting the acidic and basic chains of the chenopodin subunits at pH 8.5 and 10.5, but not at pH 6.5. Large aggregates unable to enter a 4% SDS-PAGE gel were formed at pH 6.5 and 8.5, which became soluble under reducing conditions. Heating at pH 10.5 lead to a rapid dissociation of the native chenopodin and to the disruption of the subunits, but no SDS-insoluble aggregates were formed. No major changes in secondary structure occurred during a 15 min heating, but an increase in hydrophobicity indicated unfolding of the tertiary structure in all samples. PMID:26593460

  3. Supplementation with calcium and short-chain fructo-oligosaccharides affects markers of bone turnover but not bone mineral density in postmenopausal women.

    PubMed

    Slevin, Mary M; Allsopp, Philip J; Magee, Pamela J; Bonham, Maxine P; Naughton, Violetta R; Strain, J J; Duffy, Maresa E; Wallace, Julie M; Mc Sorley, Emeir M

    2014-03-01

    This 24-mo randomized, double-blind, controlled trial aimed to examine whether supplementation with a natural marine-derived multi-mineral supplement rich in calcium (Ca) taken alone and in conjunction with short-chain fructo-oligosaccharide (scFOSs) has a beneficial effect on bone mineral density (BMD) and bone turnover markers (BTMs) in postmenopausal women. A total of 300 non-osteoporotic postmenopausal women were randomly assigned to daily supplements of 800 mg of Ca, 800 mg of Ca with 3.6 g of scFOS (CaFOS), or 9 g of maltodextrin. BMD was measured before and after intervention along with BTMs, which were also measured at 12 mo. Intention-to-treat ANCOVA identified that the change in BMD in the Ca and CaFOS groups did not differ from that in the maltodextrin group. Secondary analysis of changes to BTMs over time identified a greater decline in osteocalcin and C-telopeptide of type I collagen (CTX) in the Ca group compared with the maltodextrin group at 12 mo. A greater decline in CTX was observed at 12 mo and a greater decline in osteocalcin was observed at 24 mo in the CaFOS group compared with the maltodextrin group. In exploratory subanalyses of each treatment group against the maltodextrin group, women classified with osteopenia and taking CaFOS had a smaller decline in total-body (P = 0.03) and spinal (P = 0.03) BMD compared with the maltodextrin group, although this effect was restricted to those with higher total-body and mean spinal BMD at baseline, respectively. Although the change in BMD observed did not differ between the groups, the greater decline in BTMs in the Ca and CaFOS groups compared with the maltodextrin group suggests a more favorable bone health profile after supplementation with Ca and CaFOS. Supplementation with CaFOS slowed the rate of total-body and spinal bone loss in postmenopausal women with osteopenia-an effect that warrants additional investigation. This trial was registered at www.controlled-trials.com as ISRCTN63118444. PMID

  4. Interannual Changes in Biomass Affect the Spatial Aggregations of Anchovy and Sardine as Evidenced by Geostatistical and Spatial Indicators

    PubMed Central

    Barra, Marco; Petitgas, Pierre; Bonanno, Angelo; Somarakis, Stylianos; Woillez, Mathieu; Machias, Athanasios; Mazzola, Salvatore; Basilone, Gualtiero; Giannoulaki, Marianna

    2015-01-01

    Geostatistical techniques were applied and a series of spatial indicators were calculated (occupation, aggregation, location, dispersion, spatial autocorrelation and overlap) to characterize the spatial distributions of European anchovy and sardine during summer. Two ecosystems were compared for this purpose, both located in the Mediterranean Sea: the Strait of Sicily (upwelling area) and the North Aegean Sea (continental shelf area, influenced by freshwater). Although the biomass of anchovy and sardine presented high interannual variability in both areas, the location of the centres of gravity and the main spatial patches of their populations were very similar between years. The size of the patches representing the dominant part of the abundance (80%) was mostly ecosystem- and species-specific. Occupation (area of presence) appears to be shaped by the extent of suitable habitats in each ecosystem whereas aggregation patterns (how the populations are distributed within the area of presence) were species-specific and related to levels of population biomass. In the upwelling area, both species showed consistently higher occupation values compared to the continental shelf area. Certain characteristics of the spatial distribution of sardine (e.g. spreading area, overlapping with anchovy) differed substantially between the two ecosystems. Principal component analysis of geostatistical and spatial indicators revealed that biomass was significantly related to a suite of, rather than single, spatial indicators. At the spatial scale of our study, strong correlations emerged between biomass and the first principal component axis with highly positive loadings for occupation, aggregation and patchiness, independently of species and ecosystem. Overlapping between anchovy and sardine increased with the increase of sardine biomass but decreased with the increase of anchovy. This contrasting pattern was attributed to the location of the respective major patches combined with the

  5. Interannual Changes in Biomass Affect the Spatial Aggregations of Anchovy and Sardine as Evidenced by Geostatistical and Spatial Indicators.

    PubMed

    Barra, Marco; Petitgas, Pierre; Bonanno, Angelo; Somarakis, Stylianos; Woillez, Mathieu; Machias, Athanasios; Mazzola, Salvatore; Basilone, Gualtiero; Giannoulaki, Marianna

    2015-01-01

    Geostatistical techniques were applied and a series of spatial indicators were calculated (occupation, aggregation, location, dispersion, spatial autocorrelation and overlap) to characterize the spatial distributions of European anchovy and sardine during summer. Two ecosystems were compared for this purpose, both located in the Mediterranean Sea: the Strait of Sicily (upwelling area) and the North Aegean Sea (continental shelf area, influenced by freshwater). Although the biomass of anchovy and sardine presented high interannual variability in both areas, the location of the centres of gravity and the main spatial patches of their populations were very similar between years. The size of the patches representing the dominant part of the abundance (80%) was mostly ecosystem- and species-specific. Occupation (area of presence) appears to be shaped by the extent of suitable habitats in each ecosystem whereas aggregation patterns (how the populations are distributed within the area of presence) were species-specific and related to levels of population biomass. In the upwelling area, both species showed consistently higher occupation values compared to the continental shelf area. Certain characteristics of the spatial distribution of sardine (e.g. spreading area, overlapping with anchovy) differed substantially between the two ecosystems. Principal component analysis of geostatistical and spatial indicators revealed that biomass was significantly related to a suite of, rather than single, spatial indicators. At the spatial scale of our study, strong correlations emerged between biomass and the first principal component axis with highly positive loadings for occupation, aggregation and patchiness, independently of species and ecosystem. Overlapping between anchovy and sardine increased with the increase of sardine biomass but decreased with the increase of anchovy. This contrasting pattern was attributed to the location of the respective major patches combined with the

  6. Doxorubicin enhances nucleosome turnover around promoters.

    PubMed

    Yang, Fan; Kemp, Christopher J; Henikoff, Steven

    2013-05-01

    Doxorubicin is an anthracycline DNA intercalator that is among the most commonly used anticancer drugs. Doxorubicin causes DNA double-strand breaks in rapidly dividing cells, although whether it also affects general chromatin properties is unknown. Here, we use a metabolic labeling strategy to directly measure nucleosome turnover to examine the effect of doxorubicin on chromatin dynamics in squamous cell carcinoma cell lines derived from genetically defined mice. We find that doxorubicin enhances nucleosome turnover around gene promoters and that turnover correlates with gene expression level. Consistent with a direct action of doxorubicin, enhancement of nucleosome turnover around promoters gradually increases with time of exposure to the drug. Interestingly, enhancement occurs both in wild-type cells and in cells lacking either the p53 tumor suppressor gene or the master regulator of the DNA damage response, ATM, suggesting that doxorubicin action on nucleosome dynamics is independent of the DNA damage checkpoint. In addition, another anthracycline drug, aclarubicin, shows similar effects on enhancing nucleosome turnover around promoters. Our results suggest that anthracycline intercalation promotes nucleosome turnover around promoters by its effect on DNA topology, with possible implications for mechanisms of cell killing during cancer chemotherapy. PMID:23602475

  7. Mediator tail subunits can form amyloid-like aggregates in vivo and affect stress response in yeast

    PubMed Central

    Zhu, Xuefeng; Chen, Lihua; Carlsten, Jonas O. P.; Liu, Qian; Yang, Junsheng; Liu, Beidong; Gustafsson, Claes M.

    2015-01-01

    The Med2, Med3 and Med15 proteins form a heterotrimeric subdomain in the budding yeast Mediator complex. This Med15 module is an important target for many gene specific transcription activators. A previous proteome wide screen in yeast identified Med3 as a protein with priogenic potential. In the present work, we have extended this observation and demonstrate that both Med3 and Med15 form amyloid-like protein aggregates under H2O2 stress conditions. Amyloid formation can also be stimulated by overexpression of Med3 or of a glutamine-rich domain present in Med15, which in turn leads to loss of the entire Med15 module from Mediator and a change in stress response. In combination with genome wide transcription analysis, our data demonstrate that amyloid formation can change the subunit composition of Mediator and thereby influence transcriptional output in budding yeast. PMID:26138482

  8. A weak pulsed magnetic field affects adenine nucleotide oscillations, and related parameters in aggregating Dictyostelium discoideum amoebae.

    PubMed

    Davies, E; Olliff, C; Wright, I; Woodward, A; Kell, D

    1999-02-01

    A model eukaryotic cell system was used to explore the effect of a weak pulsed magnetic field (PMF) on time-varying physiological parameters. Dictyostelium discoideum cells (V12 strain) were exposed to a pulsed magnetic field (PMF) of flux density 0.4 mT, generated via air-cored coils in trains of 2 ms pulses gated at 20 ms. This signal is similar to those used to treat non-uniting fractures. Samples were taken over periods of 20 min from harvested suspensions of amoebae during early aggregation phase, extracted and derivatised for HPLC fluorescent assay of adenine nucleotides. Analysis of variance showed a significant athermal damping effect (P < 0.002, n = 22) of the PMF on natural adenine nucleotide oscillations and some consistent changes in phase relationships. The technique of nonlinear dielectric spectroscopy (NLDS) revealed a distinctive effect of PMF, caffeine and EGTA in modulating the cellular harmonic response to an applied weak signal. Light scattering studies also showed altered frequency response of cells to PMF, EGTA and caffeine. PMF caused a significant reduction of caffeine induced cell contraction (P < 0.0006, n = 19 by paired t-test) as shown by Malvern particle size analyser, suggesting that intracellular calcium may be involved in mediating the effect of the PMF. PMID:10228582

  9. Aggregate-cement paste transition zone properties affecting the salt-frost damage of high-performance concretes

    SciTech Connect

    Cwirzen, Andrzej; Penttala, Vesa

    2005-04-01

    The influence of the cement paste-aggregate interfacial transition zone (ITZ) on the frost durability of high-performance silica fume concrete (HPSFC) has been studied. Investigation was carried out on eight non-air-entrained concretes having water-to-binder (W/B) ratios of 0.3, 0.35 and 0.42 and different additions of condensed silica fume. Studies on the microstructure and composition of the cement paste have been made by means of environmental scanning electron microscope (ESEM)-BSE, ESEM-EDX and mercury intrusion porosimetry (MIP) analysis. The results showed that the transition zone initiates and accelerates damaging mechanisms by enhancing movement of the pore solution within the concrete during freezing and thawing cycles. Cracks filled with ettringite were primarily formed in the ITZ. The test concretes having good frost-deicing salt durability featured a narrow transition zone and a decreased Ca/Si atomic ratio in the transition zone compared to the bulk cement paste. Moderate additions of silica fume seemed to densify the microstructure of the ITZ.

  10. QTL mapping of genetic determinants of lipoprotein metabolism in mice: Mutations of the apolipoprotein A-II gene affecting lipoprotein turnover

    SciTech Connect

    Weinreb, A.; Purcell-Huynh, D.A.; Castellani, L.W.

    1994-09-01

    Cholesterol and lipoproteins represent important risk factors for atherosclerosis. In order to better understand the genes involved in determining lipoprotein levels, quantitative trait locus (QTL) mapping was performed using a cross between NZB and SM/J mice. Significant LOD scores for loci determining total cholesterol, HDL cholesterol, LDL and VLDL cholesterol, triglycerides, free fatty acids, and apolipoprotein A-II (apoA-II) were obtained. NZB mice have a 7-10 fold higher apoA-II level SM/J. LOD scores of 19.6 (chow) and 10.3 (high fat) were obtained at the apoA-II gene locus. Comparison of apoA-II levels by apoA-II genotype reveals that {approximately}30% of the variance in apoA-II levels can be accounted for by differences within the apoA-II gene. Northern analysis of mRNA from NZB and SM/J mice fed a high fat diet failed to show any significant differences in mRNA levels. The rates of apoA-II protein synthesis relative to total protein synthesis between the two strains were similar, with a rate of 0.16% for NZB and 0.18% for SM/J. Sequencing of NZB and SM/J apoA-II cDNAs revealed a pro5 to gln5 substitution in SM/J. Therefore, differences in the apoA-II levels between NZB and SM/J may be partly due to a structural difference in apoA-II resulting in an increased rate of apoA-II clearance in SM/J. A coincident QTL for HDL at the same chromosome 1 locus suggests that a structural difference in apoA-II may be affecting the rate of HDL clearance. It is of interest to note that the pro5 to gln5 substitution leads to apoA-II amyloid deposition in the SAM mouse.

  11. Antecedents of Norwegian Beginning Teachers' Turnover Intentions

    ERIC Educational Resources Information Center

    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'…

  12. A Turnover Model for the Mexican Maquiladoras.

    ERIC Educational Resources Information Center

    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)

  13. Growth and aggregation behavior of representative phytoplankton as affected by the environmental contaminant di-n-butyl phthalate

    SciTech Connect

    Acey, R.; Healy, P.; Unger, T.F.; Ford, C.E.; Hudson, R.A.

    1987-07-01

    The authors' continuing efforts to characterize the molecular basis for the development-stage-dependent phthalate ester toxicity in the brine shrimp, Artemia, led them to consider a number of microorganisms as foraging species for Artemia. The sensitivity of these microorganisms to phthalate esters was surprising and suggests that the nature and distribution of fresh water phytoplankton may already have been significantly altered by phthalates. The purpose of our experiments was to demonstrate the extent to which present levels of oceanic contamination by phthalates may be approaching those necessary to affect the distribution and survival of phytoplankton in the biosphere.

  14. A co culture approach show that polyamine turnover is affected during inflammation in Atlantic salmon immune and liver cells and that arginine and LPS exerts opposite effects on p38MAPK signaling.

    PubMed

    Holen, Elisabeth; Espe, Marit; Andersen, Synne M; Taylor, Richard; Aksnes, Anders; Mengesha, Zebasil; Araujo, Pedro

    2014-04-01

    This study assess which pathways and molecular processes are affected by exposing salmon head kidney cells or liver cells to arginine supplementation above the established requirements for growth support. In addition to the conventional mono cultures of liver and head kidney cells, co cultures of the two cell types were included in the experimental set up. Responses due to elevated levels of arginine were measured during inflammatory (lipopolysaccharide/LPS) and non -inflammatory conditions. LPS up regulated the genes involved in polyamine turnover; ODC (ornithine decarboxylase), SSAT (spermidine/spermine-N1-acetyltransferase) and SAMdc (S-adenosyl methionine decarboxylase) in head kidney cells when co cultured with liver cells. Regardless of treatment, liver cells in co culture up regulated ODC and down regulated SSAT when compared to liver mono cultures. This suggests that polyamines have anti-inflammatory properties and that both salmon liver cells and immune cells seem to be involved in this process. The transcription of C/EBP β/CCAAT, increased during inflammation in all cultures except for liver mono cultures. The observed up regulation of this gene may be linked to glucose transport due to the highly variable glucose concentrations found in the cell media. PPARα transcription was also increased in liver cells when receiving signals from head kidney cells. Gene transcription of Interleukin 1β (IL-1β), Interleukin-8 (IL-8), cyclooxygenase 2 (COX2) and CD83 were elevated during LPS treatment in all the head kidney cell cultures while arginine supplementation reduced IL-1β and IL-8 transcription in liver cells co cultured with head kidney cells. This is probably connected to p38MAPK signaling as arginine seem to affect p38MAPK signaling contrary to the LPS induced p38MAPK signaling, suggesting anti-inflammatory effects of arginine/arginine metabolites. This paper shows that co culturing these two cell types reveals the connection between metabolism and

  15. Perception of Lay People Regarding Determinants of Health and Factors Affecting It: An Aggregated Analysis from 29 Countries

    PubMed Central

    ZAHRA, Aqeela; LEE, Eun-Whan; SUN, Li-Yuan; PARK, Jae-Hyun

    2015-01-01

    Background: This study aimed to evaluate the perception of lay people regarding determinants of health at global level and factors affecting it. Methods: Data was collected from International Social Survey Program (ISSP) and World Bank website. Multilevel regression analysis was done and lay people’s perception regarding health behavior, environment, poverty and genes as health determinants was assessed. Various socio demographic factors were used as independent variables. Results: The highest percentage of people agreed environment as determinant of health. An inverse relationship was observed between GNI quartiles and an individual’s agreement with poverty, health behavior, and environment as health determinant. There was a significant negative association of females with health damaging behavior (P<0.05) and positive association with environment and genes (P<0.05) as health determinants. Elderly people agreed with poverty as determinant of health (P<0.05). GNI was negatively related to environment (P<0.05) and poverty (P<0.05) as health determinant. Conclusion: The common public is now becoming aware of a broadened concept of health and people belonging to different backgrounds have different perceptions regarding determinants of health. Our results show that highest percentage of people agreed with environment as determinant of health, which is consistent with scientific view of increased burden of disease, caused by environmental factors. Thus, tailored health programs and policies that address an individual’s specific problems are likely to induce a change in behavior and attitude, hence decreasing the disease burden. PMID:26811813

  16. Integrating Turnover Reasons and Shocks with Turnover Decision Processes

    ERIC Educational Resources Information Center

    Maertz, Carl P., Jr.; Kmitta, Kayla R.

    2012-01-01

    We interviewed and classified 186 quitters from many jobs and organizations via a theoretically-based protocol into five decision process types. We then tested exploratory hypotheses comparing users of these types on their propensity to report certain turnover reasons and turnover shocks. "Impulsive-type quitters," with neither a job offer in hand…

  17. Gaussian Process Modeling of Protein Turnover.

    PubMed

    Rahman, Mahbubur; Previs, Stephen F; Kasumov, Takhar; Sadygov, Rovshan G

    2016-07-01

    We describe a stochastic model to compute in vivo protein turnover rate constants from stable-isotope labeling and high-throughput liquid chromatography-mass spectrometry experiments. We show that the often-used one- and two-compartment nonstochastic models allow explicit solutions from the corresponding stochastic differential equations. The resulting stochastic process is a Gaussian processes with Ornstein-Uhlenbeck covariance matrix. We applied the stochastic model to a large-scale data set from (15)N labeling and compared its performance metrics with those of the nonstochastic curve fitting. The comparison showed that for more than 99% of proteins, the stochastic model produced better fits to the experimental data (based on residual sum of squares). The model was used for extracting protein-decay rate constants from mouse brain (slow turnover) and liver (fast turnover) samples. We found that the most affected (compared to two-exponent curve fitting) results were those for liver proteins. The ratio of the median of degradation rate constants of liver proteins to those of brain proteins increased 4-fold in stochastic modeling compared to the two-exponent fitting. Stochastic modeling predicted stronger differences of protein turnover processes between mouse liver and brain than previously estimated. The model is independent of the labeling isotope. To show this, we also applied the model to protein turnover studied in induced heart failure in rats, in which metabolic labeling was achieved by administering heavy water. No changes in the model were necessary for adapting to heavy-water labeling. The approach has been implemented in a freely available R code. PMID:27229456

  18. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1995-01-01

    Part of the 1994 Industrial Minerals Review. The production, consumption, and applications of construction aggregates are reviewed. In 1994, the production of construction aggregates, which includes crushed stone and construction sand and gravel combined, increased 7.7 percent to 2.14 Gt compared with the previous year. These record production levels are mostly a result of funding for highway construction work provided by the Intermodal Surface Transportation Efficiency Act of 1991. Demand is expected to increase for construction aggregates in 1995.

  19. Occupational stress and employee turnover.

    PubMed

    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. PMID:24047248

  20. Modification of the degree of branching of a beta-(1,3)-glucan affects aggregation behavior and activity in an oxidative burst assay.

    PubMed

    Magee, Andrew S; Langeslay, Ryan R; Will, Paul M; Danielson, Michael E; Wurst, Lindsay R; Iiams, Vanessa A

    2015-12-01

    Scleroglucan is a β-(1,3)-glucan which is highly branched at the 6-position with a single glucose residue. Acid hydrolysis of a high molecular weight scleroglucan gave a medium molecular weight, freely soluble material. Linkage analysis by the partially methylated alditol acetate method showed that the solubilized material had 30% branching. When the material was subjected to partial Smith degradations, the percent branching was reduced accordingly to 12% or 17%. After the percent branching was reduced, the average molecular weight of the samples increased considerably, indicating the assembly of higher ordered aggregate structures. An aggregate number distribution analysis was applied to confirm the higher aggregated structures. These aggregated structures gave the material significantly enhanced activity in an in vitro oxidative burst assay compared to the highly branched material. PMID:26015027

  1. Weighted aggregation

    NASA Technical Reports Server (NTRS)

    Feiveson, A. H. (Principal Investigator)

    1979-01-01

    The use of a weighted aggregation technique to improve the precision of the overall LACIE estimate is considered. The manner in which a weighted aggregation technique is implemented given a set of weights is described. The problem of variance estimation is discussed and the question of how to obtain the weights in an operational environment is addressed.

  2. Autoradiographic imaging of phosphoinositide turnover in the brain

    SciTech Connect

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

    1990-08-17

    With ({sup 3}H)cytidine as a precursor, phosphoinositide turnover can be localized in brain slices by selective autoradiography of the product ({sup 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.

  3. Improvements to Kramers turnover theory

    NASA Astrophysics Data System (ADS)

    Pollak, Eli; Ankerhold, Joachim

    2013-04-01

    The Kramers turnover problem, that is, obtaining a uniform expression for the rate of escape of a particle over a barrier for any value of the external friction was solved in the 1980s. Two formulations were given, one by Mel'nikov and Meshkov (MM) [V. I. Mel'nikov and S. V. Meshkov, J. Chem. Phys. 85, 1018 (1986), 10.1063/1.451844], which was based on a perturbation expansion for the motion of the particle in the presence of friction. The other, by Pollak, Grabert, and Hänggi (PGH) [E. Pollak, H. Grabert, and P. Hänggi, J. Chem. Phys. 91, 4073 (1989), 10.1063/1.456837], valid also for memory friction, was based on a perturbation expansion for the motion along the collective unstable normal mode of the particle. Both theories did not take into account the temperature dependence of the average energy loss to the bath. Increasing the bath temperature will reduce the average energy loss. In this paper, we analyse this effect, using a novel perturbation theory. We find that within the MM approach, the thermal energy gained from the bath diverges, the average energy gain becomes infinite implying an essential failure of the theory. Within the PGH approach increasing the bath temperature reduces the average energy loss but only by a finite small amount of the order of the inverse of the reduced barrier height. Then, this does not seriously affect the theory. Analysis and application for a cubic potential and Ohmic friction are presented.

  4. Cell number and chondrogenesis in human mesenchymal stem cell aggregates is affected by the sulfation level of heparin used as a cell coating.

    PubMed

    Lei, Jennifer; Trevino, Elda; Temenoff, Johnna

    2016-07-01

    For particular cell-based therapies, it may be required to culture mesenchymal stem cell (MSC) aggregates with growth factors to promote cell proliferation and/or differentiation. Heparin, a negatively charged glycosaminoglycan (GAG) is known to play an important role in sequestration of positively charged growth factors and, when incorporated within cellular aggregates, could be used to promote local availability of growth factors. We have developed a heparin-based cell coating and we believe that the electrostatic interaction between native heparin and the positively charged growth factors will result in (1) higher cell number in response to fibroblast growth factor-2 (FGF-2) and 2) greater chondrogenic differentiation in response to transforming growth factor-β1 (TGF-β1), compared to a desulfated heparin coating. Results revealed that in the presence of FGF-2, by day 14, heparin-coated MSC aggregates increased in DNA content 8.5 ± 1.6 fold compared to day 1, which was greater than noncoated and desulfated heparin-coated aggregates. In contrast, when cultured in the presence of TGF-β1, by day 21, desulfated heparin-coated aggregates upregulated gene expression of collagen II by 86.5 ± 7.5 fold and collagen X by 37.1 ± 4.7 fold, which was higher than that recorded in the noncoated and heparin-coated aggregates. These observations indicate that this coating technology represents a versatile platform to design MSC culture systems with pairings of GAGs and growth factors that can be tailored to overcome specific challenges in scale-up and culture for MSC-based therapeutics. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1817-1829, 2016. PMID:26990913

  5. Construction aggregates

    USGS Publications Warehouse

    Langer, W.H.; Tepordei, V.V.; Bolen, W.P.

    2000-01-01

    Construction aggregates consist primarily of crushed stone and construction sand and gravel. Total estimated production of construction aggregates increased in 1999 by about 2% to 2.39 Gt (2.64 billion st) compared with 1998. This record production level continued an expansion that began in 1992. By commodities, crushed stone production increased 3.3%, while sand and gravel production increased by about 0.5%.

  6. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1994-01-01

    Part of a special section on industrial minerals in 1993. The 1993 production of construction aggregates increased 6.3 percent over the 1992 figure, to reach 2.01 Gt. This represents the highest estimated annual production of combined crushed stone and construction sand and gravel ever recorded in the U.S. The outlook for construction aggregates and the issues facing the industry are discussed.

  7. Turnover of soil monosaccharides: Recycling versus Stabilization

    NASA Astrophysics Data System (ADS)

    Basler, Anna; Dyckmans, Jens

    2014-05-01

    Soil organic matter (SOM) represents a mixture of differently degradable compounds. Each of these compounds are characterised by different dynamics due to different chemical recalcitrance, transformation or stabilisation processes in soil. Carbohydrates represent one of these compounds and contribute up to 25 % to the soil organic matter. Vascular plants are the main source of pentose sugars (Arabinose and Xylose), whereas hexoses (Galactose and Mannose) are primarily produced by microorganisms. Several studies suggest that the mean turnover times of the carbon in soil sugars are similar to the turnover dynamics of the bulk carbon in soil. The aim of the study is to characterise the influence of stabilisation and turnover of soil carbohydrates. Soil samples are collected from (i) a continuous maize cropping experiment ('Höhere Landbauschule' Rotthalmünster, Bavaria) established 1979 on a Stagnic Luvisol and (ii) from a continuous wheat cropping, established 1969, as reference site. The effect of stabilisation is estimated by the comparison of turnover times of microbial and plant derived soil carbohydrates. As the dynamics of plant derived carbohydrate are solely influenced by stabilisation processes, whereas the dynamics of microbial derived carbohydrates are affected by recycling of organic carbon compounds derived by C3 plant substrate as well as stabilisation processes. The compound specific isotopic analysis (CSIA) of soil carbohydrates was performed using a HPLC/o/IRMS system. The chromatographic and mass spectrometric subunits were coupled with a LC-Isolink interface. Soil sugars were extracted after mild hydrolysis using 4 M trifluoroacetic acid (TFA). Chromatographic separation of the sugars was achieved using a low strength 0.25 mM NaOH solution as mobile phase at a ?ow rate of 250 μL min-1 at 10 ° C.

  8. Changes in eroded material and runoff as affected by rain depth and aggregate slaking in three semi-arid region soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Seal formation, runoff and interrill soil erosion are controlled by, among other factors, soil texture, rain properties (kinetic energy and intensity), and aggregate slaking. Previous studies typically reported the total amounts of runoff and soil loss for an entire storm.We examined, at intervals o...

  9. Horse chestnut extract contracts bovine vessels and affects human platelet aggregation through 5-HT(2A) receptors: an in vitro study.

    PubMed

    Felixsson, Emma; Persson, Ingrid A-L; Eriksson, Andreas C; Persson, Karin

    2010-09-01

    Extract from seeds and bark of horse chestnut (Aesculus hippocastanum L) is used as an herbal medicine against chronic venous insufficiency. The effect and mechanism of action on veins, arteries, and platelets are not fully understood. The aim of this study was to investigate the effects and mechanisms of action of horse chestnut on the contraction of bovine mesenteric veins and arteries, and human platelet aggregation. Contraction studies showed that horse chestnut extract dose-dependently contracted both veins and arteries, with the veins being the most sensitive. Contraction of both veins and arteries were significantly inhibited by the 5-HT(2A) receptor antagonist ketanserin. No effect on contraction was seen with the cyclooxygenase inhibitor indomethacin, the alpha(1) receptor antagonist prazosin or the angiotensin AT(1) receptor antagonist saralasin neither in veins nor arteries. ADP-induced human platelet aggregation was significantly reduced by horse chestnut. A further reduction was seen with the extract in the presence of ketanserin. In conclusion, horse chestnut contraction of both veins and arteries is, at least partly, mediated through 5-HT(2A) receptors. Human platelet aggregation is reduced by horse chestnut. The clinical importance of these findings concerning clinical use, possible adverse effects, and drug interactions remains to be investigated. PMID:20148408

  10. Composition analysis of fractions of extracellular polymeric substances from an activated sludge culture and identification of dominant forces affecting microbial aggregation.

    PubMed

    Guo, Xuan; Wang, Xu; Liu, Junxin

    2016-01-01

    Extracellular polymeric substances (EPS) appear to play a critical role in the formation of bioaggregates, such as sludge flocs, in activated sludge processes. Here, we systematically investigated the composition and chemical structure of various EPS fractions excreted from an activated sludge culture using multi-analysis techniques to examine the ability of the sludge to aggregate. Chemical analysis was used with a three-dimensional excitation emission matrix and Fourier transform infrared spectroscopy, applying inter-particle forces theory. The combined findings revealed that hydrophobic groups, especially protein-related N-H, were present in a greater proportion in tightly bound EPS (TB-EPS). This result, which explained the specificity of TB-EPS in the chemical structure, was consistent with data indicating that TB-EPS contained a large amount of protein-like substances (86.7 mg/g of mixed liquor volatile suspended solids, 39.7% of the total EPS). Subsequently, a novel experimental procedure was developed to pinpoint key inter-particle forces in sludge aggregation. The result revealed that hydrogen bonds are the predominant triggers that promote sludge aggregation. This comprehensive analysis indicated that hydrophobic proteins in TB-EPS are responsible for the critical role played by hydrogen bonds in sludge formation. Our findings highlight the need to elucidate the mechanisms of TB-EPS-mediated flocculation in future efforts. PMID:27311788

  11. Composition analysis of fractions of extracellular polymeric substances from an activated sludge culture and identification of dominant forces affecting microbial aggregation

    NASA Astrophysics Data System (ADS)

    Guo, Xuan; Wang, Xu; Liu, Junxin

    2016-06-01

    Extracellular polymeric substances (EPS) appear to play a critical role in the formation of bioaggregates, such as sludge flocs, in activated sludge processes. Here, we systematically investigated the composition and chemical structure of various EPS fractions excreted from an activated sludge culture using multi-analysis techniques to examine the ability of the sludge to aggregate. Chemical analysis was used with a three-dimensional excitation emission matrix and Fourier transform infrared spectroscopy, applying inter-particle forces theory. The combined findings revealed that hydrophobic groups, especially protein-related N–H, were present in a greater proportion in tightly bound EPS (TB-EPS). This result, which explained the specificity of TB-EPS in the chemical structure, was consistent with data indicating that TB-EPS contained a large amount of protein-like substances (86.7 mg/g of mixed liquor volatile suspended solids, 39.7% of the total EPS). Subsequently, a novel experimental procedure was developed to pinpoint key inter-particle forces in sludge aggregation. The result revealed that hydrogen bonds are the predominant triggers that promote sludge aggregation. This comprehensive analysis indicated that hydrophobic proteins in TB-EPS are responsible for the critical role played by hydrogen bonds in sludge formation. Our findings highlight the need to elucidate the mechanisms of TB-EPS-mediated flocculation in future efforts.

  12. Composition analysis of fractions of extracellular polymeric substances from an activated sludge culture and identification of dominant forces affecting microbial aggregation

    PubMed Central

    Guo, Xuan; Wang, Xu; Liu, Junxin

    2016-01-01

    Extracellular polymeric substances (EPS) appear to play a critical role in the formation of bioaggregates, such as sludge flocs, in activated sludge processes. Here, we systematically investigated the composition and chemical structure of various EPS fractions excreted from an activated sludge culture using multi-analysis techniques to examine the ability of the sludge to aggregate. Chemical analysis was used with a three-dimensional excitation emission matrix and Fourier transform infrared spectroscopy, applying inter-particle forces theory. The combined findings revealed that hydrophobic groups, especially protein-related N–H, were present in a greater proportion in tightly bound EPS (TB-EPS). This result, which explained the specificity of TB-EPS in the chemical structure, was consistent with data indicating that TB-EPS contained a large amount of protein-like substances (86.7 mg/g of mixed liquor volatile suspended solids, 39.7% of the total EPS). Subsequently, a novel experimental procedure was developed to pinpoint key inter-particle forces in sludge aggregation. The result revealed that hydrogen bonds are the predominant triggers that promote sludge aggregation. This comprehensive analysis indicated that hydrophobic proteins in TB-EPS are responsible for the critical role played by hydrogen bonds in sludge formation. Our findings highlight the need to elucidate the mechanisms of TB-EPS-mediated flocculation in future efforts. PMID:27311788

  13. Transformational leadership moderates the relationship between emotional exhaustion and turnover intention among community mental health providers.

    PubMed

    Green, Amy E; Miller, Elizabeth A; Aarons, Gregory A

    2013-08-01

    Public sector mental health care providers are at high risk for burnout and emotional exhaustion which negatively affect job performance and client satisfaction with services. Few studies have examined ways to reduce these associations, but transformational leadership may have a positive effect. We examine the relationships between transformational leadership, emotional exhaustion, and turnover intention in a sample of 388 community mental health providers. Emotional exhaustion was positively related to turnover intention, and transformational leadership was negatively related to both emotional exhaustion and turnover intention. Transformational leadership moderated the relationship between emotional exhaustion and turnover intention, indicating that having a transformational leader may buffer the effects of providers' emotional exhaustion on turnover intention. Investing in transformational leadership development for supervisors could reduce emotional exhaustion and turnover among public sector mental health providers. PMID:22052429

  14. Transformational Leadership Moderates the Relationship between Emotional Exhaustion and Turnover Intention among Community Mental Health Providers

    PubMed Central

    Green, Amy E.; Miller, Elizabeth A.; Aarons, Gregory A.

    2014-01-01

    Public sector mental health care providers are at high risk for burnout and emotional exhaustion which negatively affect job performance and client satisfaction with services. Few studies have examined ways to reduce these associations, but transformational leadership may have a positive effect. We examine the relationships between transformational leadership, emotional exhaustion, and turnover intention in a sample of 388 community mental health providers. Emotional exhaustion was positively related to turnover intention, and transformational leadership was negatively related to both emotional exhaustion and turnover intention. Transformational leadership moderated the relationship between emotional exhaustion and turnover intention, indicating that having a transformational leader may buffer the effects of providers’ emotional exhaustion on turnover intention. Investing in transformational leadership development for supervisors could reduce emotional exhaustion and turnover among public sector mental health providers. PMID:22052429

  15. When and how is job embeddedness predictive of turnover? a meta-analytic investigation.

    PubMed

    Jiang, Kaifeng; Liu, Dong; McKay, Patrick F; Lee, Thomas W; Mitchell, Terence R

    2012-09-01

    The present meta-analytic study introduces an overall model of the relationships between job embeddedness and turnover outcomes. Drawing on 65 independent samples (N = 42,907), we found that on-the-job and off-the-job embeddedness negatively related to turnover intentions and actual turnover, after controlling for job satisfaction, affective commitment, and job alternatives. In addition, the negative relationships between on-the-job embeddedness (off-the-job embeddedness) and turnover criteria were stronger in female-dominated samples and public organizations (collectivistic countries). Finally, turnover intentions, job search behavior, and job performance fully (partially) mediated the effect of on-the-job embeddedness (off-the-job embeddedness) on actual turnover. The research and practical implications of our findings are noted, in light of study limitations and future research needs. PMID:22663557

  16. Teacher Turnover Impact on 1st-8th Grade Student Academic Achievement: A Correlational Study

    ERIC Educational Resources Information Center

    Reid, Johnnie M.

    2010-01-01

    The impact of schools and students not meeting academic achievement standards affects the community and the nation's future workforce. This paper examines many of the factors influencing achievement with special attention given to the facts of teacher turnover in the schools. Teacher turnover and the sad state of the academic achievement of…

  17. Three-Component Commitment and Turnover: An Examination of Temporal Aspects

    ERIC Educational Resources Information Center

    Culpepper, Robert A.

    2011-01-01

    SEM (N = 182) was employed to examine implied temporal aspects of three-component commitment theory as they relate to turnover. Consistent with expectations, affective commitment predicted subsequent turnover in an immediate and relatively short interval of 4 months, but failed to do in a much longer but outlying interval of 5-12 months. Side bet…

  18. The Effects of Turnover: What We Know about Teacher Attrition

    ERIC Educational Resources Information Center

    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:…

  19. The High Cost of Teacher Turnover. Policy Brief

    ERIC Educational Resources Information Center

    National Commission on Teaching and America's Future, 2007

    2007-01-01

    In 2007, the National Commission on Teaching and America's Future (NCTAF) completed an 18-month study of the costs of teacher turnover in five school districts. The selected districts varied in size, location, and demographics enabling exploration of how these variations affected costs. Costs of recruiting, hiring, processing, and training…

  20. Relation of Principal Transformational Leadership to School Staff Job Satisfaction, Staff Turnover, and School Performance

    ERIC Educational Resources Information Center

    Griffith, James

    2004-01-01

    In the present study, the direct effect of principal transformational leadership to school staff turnover and school performance was examined, in addition to its indirect effect through school staff job satisfaction. Survey data were obtained from elementary school staff and students, and school-aggregated student achievement test scores were…

  1. Turnover in the Advancement Profession

    ERIC Educational Resources Information Center

    Iarrobino, Jon D.

    2006-01-01

    Recruitment and retention is an area with which most organizations are concerned. Excessive turnover has exorbitant costs and wastes valuable time. Institutions of higher education are no exception. One of the most vital operations in nonprofit colleges and universities is its Office of Institutional Advancement. More and more, an institution of…

  2. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1993-01-01

    Part of a special section on the market performance of industrial minerals in 1992. Production of construction aggregates increased by 4.6 percent in 1992. This increase was due, in part, to the increased funding for transportation and infrastructure projects. The U.S. produced about 1.05 Gt of crushed stone and an estimated 734 Mt of construction sand and gravel in 1992. Demand is expected to increase by about 5 percent in 1993.

  3. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1996-01-01

    Part of the Annual Commodities Review 1995. Production of construction aggregates such as crushed stone and construction sand and gravel showed a marginal increase in 1995. Most of the 1995 increases were due to funding for highway construction work. The major areas of concern to the industry included issues relating to wetlands classification and the classification of crystalline silica as a probable human carcinogen. Despite this, an increase in demand is anticipated for 1996.

  4. Construction aggregates

    USGS Publications Warehouse

    Nelson, T.I.; Bolen, W.P.

    2007-01-01

    Construction aggregates, primarily stone, sand and gravel, are recovered from widespread naturally occurring mineral deposits and processed for use primarily in the construction industry. They are mined, crushed, sorted by size and sold loose or combined with portland cement or asphaltic cement to make concrete products to build roads, houses, buildings, and other structures. Much smaller quantities are used in agriculture, cement manufacture, chemical and metallurgical processes, glass production and many other products.

  5. Surface characteristics of spacecraft components affect the aggregation of microorganisms and may lead to different survival rates of bacteria on Mars landers

    NASA Technical Reports Server (NTRS)

    Schuerger, Andrew C.; Richards, Jeffrey T.; Hintze, Paul E.; Kern, Roger G.

    2005-01-01

    Layers of dormant endospores of Bacillus subtilis HA101 were applied to eight different spacecraft materials and exposed to martian conditions of low pressure (8.5 mbar), low temperature (-10 degrees C), and high CO(2) gas composition and irradiated with a Mars-normal ultraviolet (UV-visible- near-infrared spectrum. Bacterial layers were exposed to either 1 min or 1 h of Mars-normal UV irradiation, which simulated clear-sky conditions on equatorial Mars (0.1 tau). When exposed to 1 min of Mars UV irradiation, the numbers of viable endospores of B. subtilis were reduced three to four orders of magnitude for two brands of aluminum (Al), stainless steel, chemfilm-treated Al, clear-anodized Al, and black-anodized Al coupons. In contrast, bacterial survival was reduced only one to two orders of magnitude for endospores on the non-metal materials astroquartz and graphite composite when bacterial endospores were exposed to 1 min of Mars UV irradiation. When bacterial monolayers were exposed to 1 h of Mars UV irradiation, no viable bacteria were recovered from the six metal coupons listed above. In contrast, bacterial survival was reduced only two to three orders of magnitude for spore layers on astroquartz and graphite composite exposed to 1 h of Mars UV irradiation. Scanning electron microscopy images of the bacterial monolayers on all eight spacecraft materials revealed that endospores of B. subtilis formed large aggregates of multilayered spores on astroquartz and graphite composite, but not on the other six spacecraft materials. It is likely that the formation of multilayered aggregates of endospores on astroquartz and graphite composite is responsible for the enhanced survival of bacterial cells on these materials.

  6. Surface Characteristics of Spacecraft Components Affect the Aggregation of Microorganisms and May Lead to Different Survival Rates of Bacteria on Mars Landers

    NASA Astrophysics Data System (ADS)

    Schuerger, Andrew W.; Richards, Jeffrey T.; Hintze, Paul E.; Kern, Roger G.

    2005-08-01

    Layers of dormant endospores of Bacillus subtilis HA101 were applied to eight different spacecraft materials and exposed to martian conditions of low pressure (8.5 mbar), low temperature (-10°C), and high CO2 gas composition and irradiated with a Mars-normal ultraviolet (UV-visible- near-infrared spectrum. Bacterial layers were exposed to either 1 min or 1 h of Mars-normal UV irradiation, which simulated clear-sky conditions on equatorial Mars (0.1 tau). When exposed to 1 min of Mars UV irradiation, the numbers of viable endospores of B. subtilis were reduced three to four orders of magnitude for two brands of aluminum (Al), stainless steel, chemfilm-treated Al, clear-anodized Al, and black-anodized Al coupons. In contrast, bacterial survival was reduced only one to two orders of magnitude for endospores on the non-metal materials astroquartz and graphite composite when bacterial endospores were exposed to 1 min of Mars UV irradiation. When bacterial monolayers were exposed to 1 h of Mars UV irradiation, no viable bacteria were recovered from the six metal coupons listed above. In contrast, bacterial survival was reduced only two to three orders of magnitude for spore layers on astroquartz and graphite composite exposed to 1 h of Mars UV irradiation. Scanning electron microscopy images of the bacterial monolayers on all eight spacecraft materials revealed that endospores of B. subtilis formed large aggregates of multilayered spores on astroquartz and graphite composite, but not on the other six spacecraft materials. It is likely that the formation of multilayered aggregates of endospores on astroquartz and graphite composite is responsible for the enhanced survival of bacterial cells on these materials.

  7. Using Turnover as a Recruitment Strategy

    ERIC Educational Resources Information Center

    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…

  8. How Teacher Turnover Harms Student Achievement

    ERIC Educational Resources Information Center

    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…

  9. Chronic Teacher Turnover in Urban Elementary Schools

    ERIC Educational Resources Information Center

    Guin, Kacey

    2004-01-01

    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.…

  10. Estimating Teacher Turnover Costs: A Case Study

    ERIC Educational Resources Information Center

    Levy, Abigail Jurist; Joy, Lois; Ellis, Pamela; Jablonski, Erica; Karelitz, Tzur M.

    2012-01-01

    High teacher turnover in large U.S. cities is a critical issue for schools and districts, and the students they serve; but surprisingly little work has been done to develop methodologies and standards that districts and schools can use to make reliable estimates of turnover costs. Even less is known about how to detect variations in turnover costs…

  11. Measuring Staff Turnover in Nursing Homes

    ERIC Educational Resources Information Center

    Castle, Nicholas G.

    2006-01-01

    Purpose: In this study the levels of staff turnover reported in the nursing home literature (1990-2003) are reviewed, as well as the definitions of turnover used in these prior studies. With the use of primary data collected from 354 facilities, the study addresses the various degrees of bias that result, depending on how staff turnover is defined…

  12. Benchmarking of homogeneous electrocatalysts: overpotential, turnover frequency, limiting turnover number.

    PubMed

    Costentin, Cyrille; Passard, Guillaume; Savéant, Jean-Michel

    2015-04-29

    In relation to contemporary energy challenges, a number of molecular catalysts for the activation of small molecules, mainly based on transition metal complexes, have been developed. The time has thus come to develop tools allowing the benchmarking of these numerous catalysts. Two main factors of merit are addressed. One involves their intrinsic catalytic performances through the comparison of "catalytic Tafel plots" relating the turnover frequency to the overpotential independently of the characteristics of the electrochemical cell. The other examines the effect of deactivation of the catalyst during the course of electrolysis. It introduces the notion of the limiting turnover number as a second key element of catalyst benchmarking. How these two factors combine with one another to control the course of electrolysis is analyzed in detail, leading to procedures that allow their separate estimation from measurements of the current, the charge passed, and the decay of the catalyst concentration. Illustrative examples from literature data are discussed. PMID:25757058

  13. Cytoplasmic mRNA turnover and ageing

    PubMed Central

    Borbolis, Fivos; Syntichaki, Popi

    2015-01-01

    Messenger RNA (mRNA) turnover that determines the lifetime of cytoplasmic mRNAs is a means to control gene expression under both normal and stress conditions, whereas its impact on ageing and age-related disorders has just become evident. Gene expression control is achieved at the level of the mRNA clearance as well as mRNA stability and accessibility to other molecules. All these processes are regulated by cis-acting motifs and trans-acting factors that determine the rates of translation and degradation of transcripts. Specific messenger RNA granules that harbor the mRNA decay machinery or various factors, involved in translational repression and transient storage of mRNAs, are also part of the mRNA fate regulation. Their assembly and function can be modulated to promote stress resistance to adverse conditions and over time affect the ageing process and the lifespan of the organism. Here, we provide insights into the complex relationships of ageing modulators and mRNA turnover mechanisms. PMID:26432921

  14. Immunogenicity of Therapeutic Protein Aggregates.

    PubMed

    Moussa, Ehab M; Panchal, Jainik P; Moorthy, Balakrishnan S; Blum, Janice S; Joubert, Marisa K; Narhi, Linda O; Topp, Elizabeth M

    2016-02-01

    Therapeutic proteins have a propensity for aggregation during manufacturing, shipping, and storage. The presence of aggregates in protein drug products can induce adverse immune responses in patients that may affect safety and efficacy, and so it is of concern to both manufacturers and regulatory agencies. In this vein, there is a lack of understanding of the physicochemical determinants of immunological responses and a lack of standardized analytical methods to survey the molecular properties of aggregates associated with immune activation. In this review, we provide an overview of the basic immune mechanisms in the context of interactions with protein aggregates. We then critically examine the literature with emphasis on the underlying immune mechanisms as they relate to aggregate properties. Finally, we highlight the gaps in our current understanding of this issue and offer recommendations for future research. PMID:26869409

  15. Construction aggregates

    USGS Publications Warehouse

    Bolen, W.P.; Tepordei, V.V.

    2001-01-01

    The estimated production during 2000 of construction aggregates, crushed stone, and construction sand and gravel increased by about 2.6% to 2.7 Gt (3 billion st), compared with 1999. The expansion that started in 1992 continued with record production levels for the ninth consecutive year. By commodity, construction sand and gravel production increased by 4.5% to 1.16 Gt (1.28 billion st), while crushed stone production increased by 1.3% to 1.56 Gt (1.72 billion st).

  16. Altered bone turnover during spaceflight

    NASA Technical Reports Server (NTRS)

    Turner, R. T.; Morey, E. R.; Liu, C.; Baylink, D. J.

    1982-01-01

    Modifications in calcium metabolism during spaceflight were studied, using parameters that reflect bone turnover. Bone formation rate, medullary area, bone length, bone density, pore size distribution, and differential bone cell number were evaluated in growing rate both immediately after and 25 days after orbital spaceflights aboard the Soviet biological satellites Cosmos 782 and 936. The primary effect of space flight on bone turnover was a reversible inhibition of bone formation at the periosteal surface. A simultaneous increase in the length of the periosteal arrest line suggests that bone formation ceased along corresponding portions of that surface. Possible reasons include increased secretion of glucocorticoids and mechanical unloading of the skeleton due to near-weightlessness, while starvation and immobilization are excluded as causes.

  17. Turnover: strategies for staff retention.

    PubMed

    SnowAntle, S

    1990-01-01

    This discussion has focused on a number of areas where organizations may find opportunities for more effectively managing employee retention. Given the multitude of causes and consequences, there is no one quick fix. Effective management of employee retention requires assessment of the entire human resources process, that is, recruitment, selection, job design, compensation, supervision, work conditions, etc. Regular and systematic diagnosis of turnover and implementation of multiple strategies and evaluation are needed (Mobley, 1982). PMID:10106673

  18. Methyl group turnover on methyl-accepting chemotaxis proteins during chemotaxis by Bacillus subtilis

    SciTech Connect

    Thoelke, M.S.; Casper, J.M.; Ordal, G.W. )

    1990-02-05

    The addition of attractant to Bacillus subtilis briefly exposed to radioactive methionine causes an increase of labeling of the methyl-accepting chemotaxis proteins. The addition of attractant to cells radiolabeled for longer times shows no change in the extent of methylation. Therefore, the increase in labeling for the briefly labeled cells is due to an increased turnover of methyl groups caused by attractant. All amino acids gave enhanced turnover. This turnover lasted for a prolonged time, probably spanning the period of smooth swimming caused by the attractant addition. Repellent did not affect the turnover when added alone or simultaneously with attractant. Thus, for amino acid attractants, the turnover is probably the excitatory signal, which is seen to extend long into or throughout the adaptation period, not just at the start of it.

  19. Serum phosphorus adds to value of serum parathyroid hormone for assessment of bone turnover in renal osteodystrophy.

    PubMed

    Gentry, Jimmy; Webb, Jonathan; Davenport, Daniel; Malluche, Hartmut H

    2016-07-01

    It is well-established that parathyroid hormone (PTH) correlates with the level of bone turnover in patients with chronic kidney disease stage 5D (CKD-5D). Hyperphosphatemia is a well-established complication of end-stage renal disease and is usually attributed to dietary intake. This study evaluates the relationship between serum phosphorus levels and bone turnover in patients with CKD-5D. 93 patients with CKD-5D from the Kentucky Bone Registry who had sequentially undergone anterior iliac bone biopsies were reviewed. Undecalcified bone sections were qualitatively assessed for turnover and placed into a group with low turnover and a group with non-low (normal/high) turnover. Results of PTH and phosphorus concentrations in blood drawn at the time of biopsies were compared between the groups. PTH and phosphorus levels were significantly higher in the non-low turnover group compared to the low turnover group. Cutoff levels for PTH and phosphorus were tested for predictive power of bone turnover. Both PTH and phosphorus correlated with turnover. Adding serum phosphorus to serum PTH enhanced predictive power of PTH for low turnover. The vast majority of patients with serum phosphorus levels ≥ 6.0 mg/dL had non-low turnover, while the majority of those with low turnover had phosphorus values < 6.0 mg/dL. Classification and regression-tree analysis showed that elevated serum phosphorus (> 6.2 mg/dL) in patients with PTH < 440 pg/mL was helpful in diagnosing nonlow turnover in this range of PTH. In patients with PTH ranges of 440 - 814 pg/mL, serum phosphorus levels > 4.55 mg/dL ruled out low turnover bone disease. This suggests that not only dietary intake but also bone affects serum phosphorus levels. PMID:27191663

  20. Sex-chromosome turnovers induced by deleterious mutation load.

    PubMed

    Blaser, Olivier; Grossen, Christine; Neuenschwander, Samuel; Perrin, Nicolas

    2013-03-01

    In sharp contrast with mammals and birds, many cold-blooded vertebrates present homomorphic sex chromosomes. Empirical evidence supports a role for frequent turnovers, which replace nonrecombining sex chromosomes before they have time to decay. Three main mechanisms have been proposed for such turnovers, relying either on neutral processes, sex-ratio selection, or intrinsic benefits of the new sex-determining genes (due, e.g., to linkage with sexually antagonistic mutations). Here, we suggest an additional mechanism, arising from the load of deleterious mutations that accumulate on nonrecombining sex chromosomes. In the absence of dosage compensation, this load should progressively lower survival rate in the heterogametic sex. Turnovers should occur when this cost outweighs the benefits gained from any sexually antagonistic genes carried by the nonrecombining sex chromosome. We use individual-based simulations of a Muller's ratchet process to test this prediction, and investigate how the relevant parameters (effective population size, strength and dominance of deleterious mutations, size of nonrecombining segment, and strength of sexually antagonistic selection) are expected to affect the rate of turnovers. PMID:23461315

  1. Revisiting nurse turnover costs: adjusting for inflation.

    PubMed

    Jones, Cheryl Bland

    2008-01-01

    Organizational knowledge of nurse turnover costs is important, but gathering these data frequently may not always be feasible in today's fast-paced and complex healthcare environment. The author presents a method to inflation adjust baseline nurse turnover costs using the Consumer Price Index. This approach allows nurse executives to gain current knowledge of organizational nurse turnover costs when primary data collection is not practical and to determine costs and potential savings if nurse retention investments are made. PMID:18157000

  2. Guide to good practices for operations turnover

    SciTech Connect

    1998-12-01

    This Guide to Good Practices is written to enhance understanding of, and provide direction for, Operations Turnover, Chapter XII of Department of Energy (DOE) Order 5480.19, Conduct of Operations Requirements for DOE Facilities. The practices in this guide should be considered when planning or reviewing operations turnover programs. Contractors are advised to adopt procedures that meet the intent of DOE Order 5480.19. Operations Turnover is an element of an effective Conduct of Operations program. The complexity and array of activities performed in DOE facilities dictate the necessity for a formal operations turnover program to promote safe and efficient operations.

  3. Structure of Viral Aggregates

    NASA Astrophysics Data System (ADS)

    Barr, Stephen; Luijten, Erik

    2010-03-01

    The aggregation of virus particles is a particular form of colloidal self-assembly, since viruses of a give type are monodisperse and have identical, anisotropic surface charge distributions. In small-angle X-ray scattering experiments, the Qbeta virus was found to organize in different crystal structures in the presence of divalent salt and non-adsorbing polymer. Since a simple isotropic potential cannot explain the occurrence of all observed phases, we employ computer simulations to investigate how the surface charge distribution affects the virus interactions. Using a detailed model of the virus particle, we find an asymmetric ion distribution around the virus which gives rise to the different phases observed.

  4. Dynamic Aspects of Voluntary Turnover: An Integrated Approach to Curvilinearity in the Performance-Turnover Relationship

    ERIC Educational Resources Information Center

    Becker, William J.; Cropanzano, Russell

    2011-01-01

    Previous research pertaining to job performance and voluntary turnover has been guided by 2 distinct theoretical perspectives. First, the push-pull model proposes that there is a quadratic or curvilinear relationship existing between these 2 variables. Second, the unfolding model of turnover posits that turnover is a dynamic process and that a…

  5. Employee Turnover among Full-time Public Librarians.

    ERIC Educational Resources Information Center

    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)

  6. Employee Turnover: An Empirical and Methodological Assessment.

    ERIC Educational Resources Information Center

    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…

  7. Principal Turnover. Information Capsule. Volume 0914

    ERIC Educational Resources Information Center

    Blazer, Christie

    2010-01-01

    Recent studies indicate that school districts are facing increasing rates of principal turnover. Frequent principal changes deprive schools of the leadership stability they need to succeed, disrupt long-term school reform efforts, and may even be linked to increased teacher turnover and lower levels of student achievement. This Information Capsule…

  8. Predicting Employee Turnover from Communication Networks.

    ERIC Educational Resources Information Center

    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…

  9. Mitochondrial Turnover in the Heart

    PubMed Central

    Gustafsson, Åsa B.

    2010-01-01

    Mitochondrial quality control is increasingly recognized as an essential element in maintaining optimally functioning tissues. Mitochondrial quality control depends upon a balance between biogenesis and autophagic destruction. Mitochondrial dynamics (fusion and fission) allows for the redistribution of mitochondrial components. We speculate that this permits sorting of highly functional components into one end of a mitochondrion, while damaged components are segregated at the other end, to be jettisoned by asymmetric fission followed by selective mitophagy. Ischemic preconditioning requires autophagy/mitophagy, resulting in selective elimination of damaged mitochondria, leaving behind a population of robust mitochondria with a higher threshold for opening of the mitochondrial permeability transition pore. In this review we will consider the factors that regulate mitochondrial biogenesis and destruction, the machinery involved in both processes, and the biomedical consequences associated with altered mitochondrial turnover. PMID:21147177

  10. Social Disadvantage and Network Turnover

    PubMed Central

    2015-01-01

    Objectives. Research shows that socially disadvantaged groups—especially African Americans and people of low socioeconomic status (SES)—experience more unstable social environments. I argue that this causes higher rates of turnover within their personal social networks. This is a particularly important issue among disadvantaged older adults, who may benefit from stable networks. This article, therefore, examines whether social disadvantage is related to various aspects of personal network change. Method. Social network change was assessed using longitudinal egocentric network data from the National Social Life, Health, and Aging Project, a study of older adults conducted between 2005 and 2011. Data collection in Wave 2 included a technique for comparing respondents’ confidant network rosters between waves. Rates of network losses, deaths, and additions were modeled using multivariate Poisson regression. Results. African Americans and low-SES individuals lost more confidants—especially due to death—than did whites and college-educated respondents. African Americans also added more confidants than whites. However, neither African Americans nor low-SES individuals were able to match confidant losses with new additions to the extent that others did, resulting in higher levels of confidant network shrinkage. These trends are partly, but not entirely, explained by disadvantaged individuals’ poorer health and their greater risk of widowhood or marital dissolution. Discussion. Additional work is needed to shed light on the role played by race- and class-based segregation on group differences in social network turnover. Social gerontologists should examine the role these differences play in explaining the link between social disadvantage and important outcomes in later life, such as health decline. PMID:24997286

  11. Kinetic model for erythrocyte aggregation.

    PubMed

    Bertoluzzo, S M; Bollini, A; Rasia, M; Raynal, A

    1999-01-01

    It is well known that light transmission through blood is the most widely utilized method for the study of erythrocyte aggregation. The curves obtained had been considered empirically as exponential functions. In consequence, the process becomes characterized by an only parameter that varies with all the process factors without discrimination. In the present paper a mathematical model for RBC aggregation process is deduced in accordance with von Smoluchowski's theory about the kinetics of colloidal particles agglomeration. The equation fitted the experimental pattern of the RBC suspension optical transmittance closely and contained two parameters that estimate the most important characteristics of the aggregation process separately, i.e., (1) average size of rouleaux at equilibrium and (2) aggregation rate. The evaluation of the method was assessed by some factors affecting erythrocyte aggregation, such as temperature, plasma dilutions, Dextran 500, Dextran 70 and PVP 360, at different media concentrations, cellular membrane alteration by the alkylating agent TCEA, and decrease of medium osmolarity. Results were interpreted considering the process characteristics estimated by the parameters, and there were also compared with similar studies carried out by other authors with other methods. This analysis allowed us to conclude that the equation proposed is reliable and useful to study erythrocyte aggregation. PMID:10660481

  12. Concurrent and Lagged Effects of Registered Nurse Turnover and Staffing on Unit-Acquired Pressure Ulcers

    PubMed Central

    Park, Shin Hye; Boyle, Diane K; Bergquist-Beringer, Sandra; Staggs, Vincent S; Dunton, Nancy E

    2014-01-01

    Objective We examined the concurrent and lagged effects of registered nurse (RN) turnover on unit-acquired pressure ulcer rates and whether RN staffing mediated the effects. Data Sources/Setting Quarterly unit-level data were obtained from the National Database of Nursing Quality Indicators for 2008 to 2010. A total of 10,935 unit-quarter observations (2,294 units, 465 hospitals) were analyzed. Methods This longitudinal study used multilevel regressions and tested time-lagged effects of study variables on outcomes. Findings The lagged effect of RN turnover on unit-acquired pressure ulcers was significant, while there was no concurrent effect. For every 10 percentage-point increase in RN turnover in a quarter, the odds of a patient having a pressure ulcer increased by 4 percent in the next quarter. Higher RN turnover in a quarter was associated with lower RN staffing in the current and subsequent quarters. Higher RN staffing was associated with lower pressure ulcer rates, but it did not mediate the relationship between turnover and pressure ulcers. Conclusions We suggest that RN turnover is an important factor that affects pressure ulcer rates and RN staffing needed for high-quality patient care. Given the high RN turnover rates, hospital and nursing administrators should prepare for its negative effect on patient outcomes. PMID:24476194

  13. Licensing and due process in the turnover of bacterial RNA.

    PubMed

    Bandyra, Katarzyna J; Luisi, Ben F

    2013-04-01

    RNA enables the material interpretation of genetic information through time and in space. The creation, destruction and activity of RNA must be well controlled and tightly synchronized with numerous cellular processes. We discuss here the pathways and mechanism of bacterial RNA turnover, and describe how RNA itself modulates these processes as part of decision-making networks. The central roles of RNA decay and other aspects of RNA metabolism in cellular control are also suggested by their vulnerability to sabotage by phages; nonetheless, RNA can be used in defense against phage infection, and these processes are described here. Salient aspects of RNA turnover are drawn together to suggest how it could affect complex effects such as phenotypic diversity in populations and responses that persist for multiple generations. PMID:23580162

  14. Signaling Pathways That Control mRNA Turnover

    PubMed Central

    Thapar, Roopa; Denmon, Andria P.

    2013-01-01

    Cells regulate their genomes mainly at the level of transcription and at the level of mRNA decay. While regulation at the level of transcription is clearly important, the regulation of mRNA turnover by signaling networks is essential for a rapid response to external stimuli. Signaling pathways result in posttranslational modification of RNA binding proteins by phosphorylation, ubiquitination, methylation, acetylation etc. These modifications are important for rapid remodeling of dynamic ribonucleoprotein complexes and triggering mRNA decay. Understanding how these posttranslational modifications alter gene expression is therefore a fundamental question in biology. In this review we highlight recent findings on how signaling pathways and cell cycle checkpoints involving phosphorylation, ubiquitination, and arginine methylation affect mRNA turnover. PMID:23602935

  15. Global covariation of carbon turnover times with climate in terrestrial ecosystems.

    PubMed

    Carvalhais, Nuno; Forkel, Matthias; Khomik, Myroslava; Bellarby, Jessica; Jung, Martin; Migliavacca, Mirco; Mu, Mingquan; Saatchi, Sassan; Santoro, Maurizio; Thurner, Martin; Weber, Ulrich; Ahrens, Bernhard; Beer, Christian; Cescatti, Alessandro; Randerson, James T; Reichstein, Markus

    2014-10-01

    The response of the terrestrial carbon cycle to climate change is among the largest uncertainties affecting future climate change projections. The feedback between the terrestrial carbon cycle and climate is partly determined by changes in the turnover time of carbon in land ecosystems, which in turn is an ecosystem property that emerges from the interplay between climate, soil and vegetation type. Here we present a global, spatially explicit and observation-based assessment of whole-ecosystem carbon turnover times that combines new estimates of vegetation and soil organic carbon stocks and fluxes. We find that the overall mean global carbon turnover time is 23(+7)(-4) years (95 per cent confidence interval). On average, carbon resides in the vegetation and soil near the Equator for a shorter time than at latitudes north of 75° north (mean turnover times of 15 and 255 years, respectively). We identify a clear dependence of the turnover time on temperature, as expected from our present understanding of temperature controls on ecosystem dynamics. Surprisingly, our analysis also reveals a similarly strong association between turnover time and precipitation. Moreover, we find that the ecosystem carbon turnover times simulated by state-of-the-art coupled climate/carbon-cycle models vary widely and that numerical simulations, on average, tend to underestimate the global carbon turnover time by 36 per cent. The models show stronger spatial relationships with temperature than do observation-based estimates, but generally do not reproduce the strong relationships with precipitation and predict faster carbon turnover in many semi-arid regions. Our findings suggest that future climate/carbon-cycle feedbacks may depend more strongly on changes in the hydrological cycle than is expected at present and is considered in Earth system models. PMID:25252980

  16. The Impact of Staff Turnover on Workplace Demands and Coworker Relationships

    PubMed Central

    Knight, Danica K.; Becan, Jennifer E.; Flynn, Patrick M.

    2016-01-01

    Turnover among clinical staff can have detrimental effects on service provision and organizational efficiency. But how does it affect staff who remain employed at the agency? Researchers at the Institute of Behavioral Research at Texas Christian University sought to answer this question by examining the impact of staff turnover on perceptions of workplace demands and support among 353 clinical staff members from 63 outpatient substance abuse treatment programs. Study results documented that counselors in high-turnover programs reported higher demands (job stress, inadequate staffing) and lower support (communication, collaboration) within their organization, even after controlling for other factors such as decreasing budgets, increasing census, and individual measures of workload. Findings underscore the need to intentionally promote workplace communication and collaboration among staff following the departure of a coworker in order to reduce stress and minimize subsequent turnover among remaining clinical staff.

  17. Triacylglycerol turnover in the failing heart.

    PubMed

    Carley, Andrew N; Lewandowski, E Douglas

    2016-10-01

    No longer regarded as physiologically inert the endogenous triacylglyceride (TAG) pool within the cardiomyocyte is now recognized to play a dynamic role in metabolic regulation. Beyond static measures of content, the relative rates of interconversion among acyl intermediates are more closely linked to dynamic processes of physiological function in normal and diseased hearts, with the potential for both adaptive and maladaptive contributions. Indeed, multiple inefficiencies in cardiac metabolism have been identified in the decompensated, hypertrophied and failing heart. Among the intracellular responses to physiological, metabolic and pathological stresses, TAG plays a central role in the balance of lipid handling and signaling mechanisms. TAG dynamics are profoundly altered from normal in both diabetic and pathologically stressed hearts. More than just expansion or contraction of the stored lipid pool, the turnover rates of TAG are sensitive to and compete against other enzymatic pathways, anabolic and catabolic, for reactive acyl-CoA units. The rates of TAG synthesis and lipolysis thusly affect multiple components of cardiomyocyte function, including energy metabolism, cell signaling, and enzyme activation, as well as the regulation of gene expression in both normal and diseased states. This review examines the multiple etiologies and metabolic consequences of the failing heart and the central role of lipid storage dynamics in the pathogenic process. This article is part of a Special Issue entitled: Heart Lipid Metabolism edited by G.D. Lopaschuk. PMID:26993578

  18. Lysosomal Acid Lipase Hydrolyzes Retinyl Ester and Affects Retinoid Turnover.

    PubMed

    Grumet, Lukas; Eichmann, Thomas O; Taschler, Ulrike; Zierler, Kathrin A; Leopold, Christina; Moustafa, Tarek; Radovic, Branislav; Romauch, Matthias; Yan, Cong; Du, Hong; Haemmerle, Guenter; Zechner, Rudolf; Fickert, Peter; Kratky, Dagmar; Zimmermann, Robert; Lass, Achim

    2016-08-19

    Lysosomal acid lipase (LAL) is essential for the clearance of endocytosed cholesteryl ester and triglyceride-rich chylomicron remnants. Humans and mice with defective or absent LAL activity accumulate large amounts of cholesteryl esters and triglycerides in multiple tissues. Although chylomicrons also contain retinyl esters (REs), a role of LAL in the clearance of endocytosed REs has not been reported. In this study, we found that murine LAL exhibits RE hydrolase activity. Pharmacological inhibition of LAL in the human hepatocyte cell line HepG2, incubated with chylomicrons, led to increased accumulation of REs in endosomal/lysosomal fractions. Furthermore, pharmacological inhibition or genetic ablation of LAL in murine liver largely reduced in vitro acid RE hydrolase activity. Interestingly, LAL-deficient mice exhibited increased RE content in the duodenum and jejunum but decreased RE content in the liver. Furthermore, LAL-deficient mice challenged with RE gavage exhibited largely reduced post-prandial circulating RE content, indicating that LAL is required for efficient nutritional vitamin A availability. In summary, our results indicate that LAL is the major acid RE hydrolase and required for functional retinoid homeostasis. PMID:27354281

  19. Crystal aggregation in kidney stones; a polymer aggregation problem?

    NASA Astrophysics Data System (ADS)

    Wesson, J.; Beshensky, A.; Viswanathan, P.; Zachowicz, W.; Kleinman, J.

    2008-03-01

    Kidney stones most frequently form as aggregates of calcium oxalate monohydrate (COM) crystals with organic layers between them, and the organic layers contain principally proteins. The pathway leading to the formation of these crystal aggregates in affected people has not been identified, but stone forming patients are thought to have a defect in the structure or distribution of urinary proteins, which normally protect against stone formation. We have developed two polyelectrolyte models that will induce COM crystal aggregation in vitro, and both are consistent with possible urinary protein compositions. The first model was based on mixing polyanionic and polycationic proteins, in portions such that the combined protein charge is near zero. The second model was based on reducing the charge density on partially charged polyanionic proteins, specifically Tamm-Horsfall protein, the second most abundant protein in urine. Both models demonstrated polymer phase separation at solution conditions where COM crystal aggregation was observed. Correlation with data from other bulk crystallization measurements suggest that the anionic side chains form critical binding interactions with COM surfaces that are necessary along with the phase separation process to induce COM crystal aggregation.

  20. Mechanisms and Rates of Bacterial Colonization of Sinking Aggregates

    PubMed Central

    Kiørboe, Thomas; Grossart, Hans-Peter; Ploug, Helle; Tang, Kam

    2002-01-01

    Quantifying the rate at which bacteria colonize aggregates is a key to understanding microbial turnover of aggregates. We used encounter models based on random walk and advection-diffusion considerations to predict colonization rates from the bacteria's motility patterns (swimming speed, tumbling frequency, and turn angles) and the hydrodynamic environment (stationary versus sinking aggregates). We then experimentally tested the models with 10 strains of bacteria isolated from marine particles: two strains were nonmotile; the rest were swimming at 20 to 60 μm s−1 with different tumbling frequency (0 to 2 s−1). The rates at which these bacteria colonized artificial aggregates (stationary and sinking) largely agreed with model predictions. We report several findings. (i) Motile bacteria rapidly colonize aggregates, whereas nonmotile bacteria do not. (ii) Flow enhances colonization rates. (iii) Tumbling strains colonize aggregates enriched with organic substrates faster than unenriched aggregates, while a nontumbling strain did not. (iv) Once on the aggregates, the bacteria may detach and typical residence time is about 3 h. Thus, there is a rapid exchange between attached and free bacteria. (v) With the motility patterns observed, freely swimming bacteria will encounter an aggregate in <1 day at typical upper-ocean aggregate concentrations. This is faster than even starving bacteria burn up their reserves, and bacteria may therefore rely solely on aggregates for food. (vi) The net result of colonization and detachment leads to a predicted equilibrium abundance of attached bacteria as a function of aggregate size, which is markedly different from field observations. This discrepancy suggests that inter- and intraspecific interactions among bacteria and between bacteria and their predators may be more important than colonization in governing the population dynamics of bacteria on natural aggregates. PMID:12147501

  1. Plagued by Turnover? Train Your Managers.

    ERIC Educational Resources Information Center

    Dobbs, Kevin

    2000-01-01

    Dissatisfaction with managers is a major cause of employee turnover The Charles Schwab Corporation surveys employees annually and holds employee focus groups and online town meetings. The information is used for the coaching and training of department heads. (JOW)

  2. Biomimetic catalysis: Taking on the turnover challenge

    NASA Astrophysics Data System (ADS)

    Hooley, Richard J.

    2016-03-01

    Emulating the efficiency with which enzymes catalyse reactions has often been used as inspiration to develop self-assembled cages. Now two studies present approaches to achieving catalyst turnover -- one of the biggest challenges in achieving truly biomimetic catalysis.

  3. Coping with Turnovers in School Food Service.

    ERIC Educational Resources Information Center

    Pannell, Dorothy V.

    1988-01-01

    Labor shortages, cost increases, and turnover have prompted Fairfax County Schools, Virginia, food service managers to offer training programs and recruitment bonuses, to use more convenience foods, and to price out every service. (MLF)

  4. Modelling the impact of soil tillage on SOM turnover

    NASA Astrophysics Data System (ADS)

    Franko, Uwe; Spiegel, Heide

    2013-04-01

    The CCB model of the soil organic matter (SOM) turnover has been proved to be valid over a wide range of site conditions and cropping systems. It is based on the aggregation of different fresh organic matter to the flux of SOM reproducing carbon (Crep) and on the aggregation of the complexity of site conditions as Biologic Active Time (BAT). Next to carbon input and site conditions the soil tillage is known to have an impact on SOM. The CCB model calculates the BAT value from a statistically based meta model using soil texture and climate data. The CANDY model as ancestor of CCB is also based on the BAT calculation - but under consideration of soil temperature, soil moisture and the depth of the reaction layer in the top soil. Especially the latter effect takes into account that gas exchange between the reaction space in the soil pores and the atmosphere may be hindered in deeper soil layers as well as the filling of pore space with water. Depending on soil type and soil moisture dynamics the BAT at the base of the plough layer may be considerably lower than in the layers above. If the soil is ploughed regularly, there are no long-term effects on SOM dynamics in the different depth steps (10 cm) of the top soil. In contrast, on ploughless systems with reduced cultivation depth we expect depth depending effects of SOM storage. The integration of this mechanism had to be based on a simplified approach because the CCB model is working in annual time steps and is based on very few soil parameters. An analysis of the general mechanisms of BAT calculation led to a simplified solution to calculate a site specific correction factor of the BAT estimation from the meta model. Therefore, we assume a texture dependent reduction of the turnover activity with depth, indicated by the coefficient alpha. A first examination of this approach has been performed using the dataset of the Fuchsenbigl experiment in Austria with three tillage variants (conventional ploughing, reduced and

  5. The costs of nurse turnover, part 2: application of the Nursing Turnover Cost Calculation Methodology.

    PubMed

    Jones, Cheryl Bland

    2005-01-01

    This is the second article in a 2-part series focusing on nurse turnover and its costs. Part 1 (December 2004) described nurse turnover costs within the context of human capital theory, and using human resource accounting methods, presented the updated Nursing Turnover Cost Calculation Methodology. Part 2 presents an application of this method in an acute care setting and the estimated costs of nurse turnover that were derived. Administrators and researchers can use these methods and cost information to build a business case for nurse retention. PMID:15647669

  6. On gigahertz spectral turnovers in pulsars

    NASA Astrophysics Data System (ADS)

    Rajwade, K.; Lorimer, D. R.; Anderson, L. D.

    2016-01-01

    Pulsars are known to emit non-thermal radio emission that is generally a power-law function of frequency. In some cases, a turnover is seen at frequencies around 100 MHz. Kijak et al. have reported the presence of a new class of `Gigahertz Peaked Spectrum' (GPS) pulsars that show spectral turnovers at frequencies around 1 GHz. We apply a model based on free-free thermal absorption to explain these turnovers in terms of surrounding material such as the dense environments found in H II regions, pulsar wind nebulae, or in cold, partially ionized molecular clouds. We show that the turnover frequency depends on the electron temperature of the environment close to the pulsar, as well as the emission measure along the line of sight. We fitted this model to the radio fluxes of known GPS pulsars and show that it can replicate the GHz turnover. From the thermal absorption model, we demonstrate that normal pulsars would exhibit a GPS-like behaviour if they were in a dense environment. We discuss the application of this model in the context of determining the population of neutron stars within the central parsec of the Galaxy. We show that a non-negligible fraction of this population might exhibit high-frequency spectral turnovers, which has implications on the detectability of these sources in the Galactic Centre.

  7. Spatial turnover in the global avifauna

    PubMed Central

    Gaston, Kevin J; Davies, Richard G; Orme, C. David L; Olson, Valerie A; Thomas, Gavin H; Ding, Tzung-Su; Rasmussen, Pamela C; Lennon, Jack J; Bennett, Peter M; Owens, Ian P.F; Blackburn, Tim M

    2007-01-01

    Despite its wide implications for many ecological issues, the global pattern of spatial turnover in the occurrence of species has been little studied, unlike the global pattern of species richness. Here, using a database on the breeding distributions of birds, we present the first global maps of variation in spatial turnover for an entire taxonomic class, a pattern that has to date remained largely a matter of conjecture, based on theoretical expectations and extrapolation of inconsistent patterns from different biogeographic realms. We use these maps to test four predictions from niche theory as to the form that this variation should take, namely that turnover should increase with species richness, towards lower latitudes, and with the steepness of environmental gradients and that variation in turnover is determined principally by rare (restricted) species. Contrary to prediction, we show that turnover is high both in areas of extremely low and high species richness, does not increase strongly towards the tropics, and is related both to average environmental conditions and spatial variation in those conditions. These results are closely associated with a further important and novel finding, namely that global patterns of spatial turnover are driven principally by widespread species rather than the restricted ones. This complements recent demonstrations that spatial patterns of species richness are also driven principally by widespread species, and thus provides an important contribution towards a unified model of how terrestrial biodiversity varies both within and between the Earth's major land masses. PMID:17472910

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

    PubMed

    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. PMID:19594245

  9. Platelet aggregation test

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/003669.htm Platelet aggregation test To use the sharing features on this page, please enable JavaScript. The platelet aggregation blood test checks how well platelets , a ...

  10. Thermodynamics of Protein Aggregation

    NASA Astrophysics Data System (ADS)

    Osborne, Kenneth L.; Barz, Bogdan; Bachmann, Michael; Strodel, Birgit

    Amyloid protein aggregation characterizes many neurodegenerative disorders, including Alzheimer's, Parkinson's, and Creutz- feldt-Jakob disease. Evidence suggests that amyloid aggregates may share similar aggregation pathways, implying simulation of full-length amyloid proteins is not necessary for understanding amyloid formation. In this study we simulate GNNQQNY, the N-terminal prion-determining domain of the yeast protein Sup35 to investigate the thermodynamics of structural transitions during aggregation. We use a coarse-grained model with replica-exchange molecular dynamics to investigate the association of 3-, 6-, and 12-chain GNNQQNY systems and we determine the aggregation pathway by studying aggregation states of GN- NQQNY. We find that the aggregation of the hydrophilic GNNQQNY sequence is mainly driven by H-bond formation, leading to the formation of /3-sheets from the very beginning of the assembly process. Condensation (aggregation) and ordering take place simultaneously, which is underpinned by the occurrence of a single heat capacity peak only.

  11. Platelet aggregation test

    MedlinePlus

    The platelet aggregation blood test checks how well platelets , a part of blood, clump together and cause blood to clot. ... Decreased platelet aggregation may be due to: Autoimmune ... Fibrin degradation products Inherited platelet function defects ...

  12. HEMC: A sensitive aggregate stability method for soil quality evaluation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil aggregate stability is an important soil quality index, representing mainly soil structural stability and affecting, among others, hydraulic conductivity, seal formation, runoff, water and wind erosion. The most common method of assessing aggregate stability is wet sieving where aggregate stabi...

  13. The costs of nurse turnover: part 1: an economic perspective.

    PubMed

    Jones, Cheryl Bland

    2004-12-01

    Nurse turnover is costly for healthcare organizations. Administrators and nurse executives need a reliable estimate of nurse turnover costs and the origins of those costs if they are to develop effective measures of reducing nurse turnover and its costs. However, determining how to best capture and quantify nurse turnover costs can be challenging. Part 1 of this series conceptualizes nurse turnover via human capital theory and presents an update of a previously developed method for determining the costs of nurse turnover, the Nursing Turnover Cost Calculation Method. Part 2 (January 2005) presents a recent application of the methodology in an acute care hospital. PMID:15632752

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

    PubMed

    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. PMID:21808181

  15. Analysis of Soil Structure Turnover with Garnet Particles and X-Ray Microtomography.

    PubMed

    Schlüter, Steffen; Vogel, Hans-Jörg

    2016-01-01

    Matter turnover in soil is tightly linked to soil structure which governs the heterogeneous distribution of habitats, reaction sites and pathways in soil. Thereby, the temporal dynamics of soil structure alteration is deemed to be important for essential ecosystem functions of soil but very little is known about it. A major reason for this knowledge gap is the lack of methods to study soil structure turnover directly at microscopic scales. Here we devise a conceptual approach and an image processing workflow to study soil structure turnover by labeling some initial state of soil structure with small garnet particles and tracking their fate with X-ray microtomography. The particles adhere to aggregate boundaries at the beginning of the experiment but gradually change their position relative to the nearest pore as structure formation progresses and pores are destructed or newly formed. A new metric based on the contact distances between particles and pores is proposed that allows for a direct quantification of soil structure turnover rates. The methodology is tested for a case study about soil compaction of a silty loam soil during stepwise increase of bulk density (ρ = {1.1, 1.3, 1.5} g/cm3). We demonstrate that the analysis of mean contact distances provides genuinely new insights about changing diffusion pathways that cannot be inferred neither from conventional pore space attributes (porosity, mean pore size, pore connectivity) nor from deformation analysis with digital image correlation. This structure labeling approach to quantify soil structure turnover provides a direct analogy to stable isotope labeling for the analysis of matter turnover and can be readily combined with each other. PMID:27453995

  16. Analysis of Soil Structure Turnover with Garnet Particles and X-Ray Microtomography

    PubMed Central

    Vogel, Hans-Jörg

    2016-01-01

    Matter turnover in soil is tightly linked to soil structure which governs the heterogeneous distribution of habitats, reaction sites and pathways in soil. Thereby, the temporal dynamics of soil structure alteration is deemed to be important for essential ecosystem functions of soil but very little is known about it. A major reason for this knowledge gap is the lack of methods to study soil structure turnover directly at microscopic scales. Here we devise a conceptual approach and an image processing workflow to study soil structure turnover by labeling some initial state of soil structure with small garnet particles and tracking their fate with X-ray microtomography. The particles adhere to aggregate boundaries at the beginning of the experiment but gradually change their position relative to the nearest pore as structure formation progresses and pores are destructed or newly formed. A new metric based on the contact distances between particles and pores is proposed that allows for a direct quantification of soil structure turnover rates. The methodology is tested for a case study about soil compaction of a silty loam soil during stepwise increase of bulk density (ρ = {1.1, 1.3, 1.5} g/cm3). We demonstrate that the analysis of mean contact distances provides genuinely new insights about changing diffusion pathways that cannot be inferred neither from conventional pore space attributes (porosity, mean pore size, pore connectivity) nor from deformation analysis with digital image correlation. This structure labeling approach to quantify soil structure turnover provides a direct analogy to stable isotope labeling for the analysis of matter turnover and can be readily combined with each other. PMID:27453995

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

    PubMed Central

    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. PMID:25336960

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

    PubMed

    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. PMID:25336960

  19. Do Employees Leave Just Because They Can? Examining the Perceived Employability-Turnover Intentions Relationship.

    PubMed

    Acikgoz, Yalcin; Sumer, H Canan; Sumer, Nebi

    2016-07-01

    The relationship between perceived employability and turnover intentions seems much more complicated than what the common sense would suggest. Based on the reviewed literature, it was expected that job satisfaction, affective commitment, and perceived job security would moderate this relationship. Using a sample of working individuals from different occupations and sectors (N = 721), it was found that employees who perceived themselves as highly employable were more likely to have turnover intentions when their affective commitment was low and perceived job security was high; and the relationship was negative for employees with shorter tenures. Understanding the conditions under which perceived employability is associated with turnover intentions may help organizations design human resource policies that allow them to retain an educated and competent workforce. PMID:27043746

  20. Proteasome regulates turnover of toxic human amylin in pancreatic cells.

    PubMed

    Singh, Sanghamitra; Trikha, Saurabh; Sarkar, Anjali; Jeremic, Aleksandar M

    2016-09-01

    Toxic human amylin (hA) oligomers and aggregates are implicated in the pathogenesis of type 2 diabetes mellitus (T2DM). Although recent studies demonstrated a causal connection between hA uptake and toxicity in pancreatic cells, the mechanism of amylin's clearance following its internalization and its relationship to toxicity is yet to be determined, and hence was investigated here. Using pancreatic rat insulinoma β-cells and human islets as model systems, we show that hA, following its internalization, first accumulates in the cytosol followed by its translocation into nucleus, and to a lesser extent lysosomes, keeping the net cytosolic amylin content low. An increase in hA accumulation in the nucleus of pancreatic cells correlated with its cytotoxicity, suggesting that its excessive accumulation in the nucleus is detrimental. hA interacted with 20S core and 19S lid subunits of the β-cell proteasomal complex, as suggested by immunoprecipitation and confocal microscopy studies, which subsequently resulted in a decrease in the proteasome's proteolytic activity in these cells. In vitro binding and activity assays confirmed an intrinsic and potent ability of amylin to interact with the 20S core complex thereby modulating its proteolytic activity. Interestingly, less toxic and aggregation incapable rat amylin (rA) showed a comparable inhibitory effect on proteasome activity and protein ubiquitination, decoupling amylin aggregation/ toxicity and amylin-induced protein stress. In agreement with these studies, inhibition of proteasomal proteolytic activity significantly increased intracellular amylin content and toxicity. Taken together, our results suggest a pivotal role of proteasomes in amylin's turnover and detoxification in pancreatic cells. PMID:27340132

  1. Why managers should care about fairness: the effects of aggregate justice perceptions on organizational outcomes.

    PubMed

    Simons, Tony; Roberson, Quinetta

    2003-06-01

    This work examines the aggregation of justice perceptions to the departmental level and the business-unit level, the impact of these aggregate perceptions on business-unit-level outcomes, and the usefulness of the distinction between procedural and interpersonal justice at different levels of analysis. Latent variables analyses of individual-level and department-level data from 4,539 employees in 783 departments at 97 hotel properties showed that the 2 justice types exercise unique paths of impact on employees' organizational commitment and thus on turnover intentions and discretionary service behavior. Business-unit-level analyses further demonstrate paths of association between aggregate justice perceptions, aggregate commitment levels, and the business-unit-level outcomes of employee turnover rates and customer satisfaction ratings. PMID:12814293

  2. Aggregate structure, morphology and the effect of aggregation mechanisms on viscosity at elevated protein concentrations.

    PubMed

    Barnett, Gregory V; Qi, Wei; Amin, Samiul; Neil Lewis, E; Roberts, Christopher J

    2015-12-01

    Non-native aggregation is a common issue in a number of degenerative diseases and during manufacturing of protein-based therapeutics. There is a growing interest to monitor protein stability at intermediate to high protein concentrations, which are required for therapeutic dosing of subcutaneous injections. An understanding of the impact of protein structural changes and interactions on the protein aggregation mechanisms and resulting aggregate size and morphology may lead to improved strategies to reduce aggregation and solution viscosity. This report investigates non-native aggregation of a model protein, α-chymotrypsinogen, under accelerated conditions at elevated protein concentrations. Far-UV circular dichroism and Raman scattering show structural changes during aggregation. Size exclusion chromatography and laser light scattering are used to monitor the progression of aggregate growth and monomer loss. Monomer loss is concomitant with increased β-sheet structures as monomers are added to aggregates, which illustrate a transition from a native monomeric state to an aggregate state. Aggregates grow predominantly through monomer-addition, resulting in a semi-flexible polymer morphology. Analysis of aggregation growth kinetics shows that pH strongly affects the characteristic timescales for nucleation (τn) and growth (τg), while the initial protein concentration has only minor effects on τn or τg. Low-shear viscosity measurements follow a common scaling relationship between average aggregate molecular weight (Mw(agg)) and concentration (σ), which is consistent with semi-dilute polymer-solution theory. The results establish a link between aggregate growth mechanisms, which couple Mw(agg) and σ, to increases in solution viscosity even at these intermediate protein concentrations (less than 3w/v %). PMID:26284891

  3. Quantification of isotopic turnover in agricultural systems

    NASA Astrophysics Data System (ADS)

    Braun, A.; Auerswald, K.; Schnyder, H.

    2012-04-01

    The isotopic turnover, which is a proxy for the metabolic rate, is gaining scientific importance. It is quantified for an increasing range of organisms, from microorganisms over plants to animals including agricultural livestock. Additionally, the isotopic turnover is analyzed on different scales, from organs to organisms to ecosystems and even to the biosphere. In particular, the quantification of the isotopic turnover of specific tissues within the same organism, e.g. organs like liver and muscle and products like milk and faeces, has brought new insights to improve understanding of nutrient cycles and fluxes, respectively. Thus, the knowledge of isotopic turnover is important in many areas, including physiology, e.g. milk synthesis, ecology, e.g. soil retention time of water, and medical science, e.g. cancer diagnosis. So far, the isotopic turnover is quantified by applying time, cost and expertise intensive tracer experiments. Usually, this comprises two isotopic equilibration periods. A first equilibration period with a constant isotopic input signal is followed by a second equilibration period with a distinct constant isotopic input signal. This yields a smooth signal change from the first to the second signal in the object under consideration. This approach reveals at least three major problems. (i) The input signals must be controlled isotopically, which is almost impossible in many realistic cases like free ranging animals. (ii) Both equilibration periods may be very long, especially when the turnover rate of the object under consideration is very slow, which aggravates the first problem. (iii) The detection of small or slow pools is improved by large isotopic signal changes, but large isotopic changes also involve a considerable change in the input material; e.g. animal studies are usually carried out as diet-switch experiments, where the diet is switched between C3 and C4 plants, since C3 and C4 plants differ strongly in their isotopic signal. The

  4. Intraorganizational Career Advancement and Voluntary Turnover in a Multinational Bank in Taiwan

    ERIC Educational Resources Information Center

    Zhao, Wei; Zhou, Xueguang

    2008-01-01

    Purpose: This study aims to investigate how various aspects of intraorganizational career advancement--current career attainments, recent pace of upward mobility, and future prospect of career advancement--affect voluntary turnover, drawing empirical evidence from a multinational corporation (MNC) in Taiwan's cultural and labor market environment.…

  5. Mitochondrial protein turnover: methods to measure turnover rates on a large scale

    PubMed Central

    Chan, X’avia CY; Black, Caitlin M; Lin, Amanda J; Ping, Peipei; Lau, Edward

    2016-01-01

    Mitochondrial proteins carry out diverse cellular functions including ATP synthesis, ion homeostasis, cell death signaling, and fatty acid metabolism and biogenesis. Compromised mitochondrial quality control is implicated in various human disorders including cardiac diseases. Recently it has emerged that mitochondrial protein turnover can serve as an informative cellular parameter to characterize mitochondrial quality and uncover disease mechanisms. The turnover rate of a mitochondrial protein reflects its homeostasis and dynamics under the quality control systems acting on mitochondria at a particular cell state. This review article summarizes some recent advances and outstanding challenges for measuring the turnover rates of mitochondrial proteins in health and disease. PMID:25451168

  6. Mitochondrial Turnover and Aging of Long-Lived Postmitotic Cells: The Mitochondrial–Lysosomal Axis Theory of Aging

    PubMed Central

    Kurz, Tino; Navratil, Marian; Arriaga, Edgar A.; Brunk, Ulf T.

    2010-01-01

    Abstract It is now generally accepted that aging and eventual death of multicellular organisms is to a large extent related to macromolecular damage by mitochondrially produced reactive oxygen species, mostly affecting long-lived postmitotic cells, such as neurons and cardiac myocytes. These cells are rarely or not at all replaced during life and can be as old as the whole organism. The inherent inability of autophagy and other cellular-degradation mechanisms to remove damaged structures completely results in the progressive accumulation of garbage, including cytosolic protein aggregates, defective mitochondria, and lipofuscin, an intralysosomal indigestible material. In this review, we stress the importance of crosstalk between mitochondria and lysosomes in aging. The slow accumulation of lipofuscin within lysosomes seems to depress autophagy, resulting in reduced turnover of effective mitochondria. The latter not only are functionally deficient but also produce increased amounts of reactive oxygen species, prompting lipofuscinogenesis. Moreover, defective and enlarged mitochondria are poorly autophagocytosed and constitute a growing population of badly functioning organelles that do not fuse and exchange their contents with normal mitochondria. The progress of these changes seems to result in enhanced oxidative stress, decreased ATP production, and collapse of the cellular catabolic machinery, which eventually is incompatible with survival. Antioxid. Redox Signal. 12, 503–535. PMID:19650712

  7. Staff training and turnover in Alzheimer special care units: comparisons with non-special care units.

    PubMed

    Grant, L A; Kane, R A; Potthoff, S J; Ryden, M

    1996-01-01

    Nursing facility staff may not be properly trained to deal with behavioral symptoms of Alzheimer's disease. We collected data about specialized dementia training and turnover among licensed nurses and nursing assistants in 400 nursing units in 124 Minnesota nursing facilities. Staff training may affect the retention of paraprofessional and professional nursing staff. A diversity of training methods, including workshops or seminars, films or videos, outside consultants, reading materials, training manuals, in-house experts, role playing techniques, or an orientation program for new staff, might be used to develop more effective training programs and reduce rates of nursing assistant turnover. PMID:9060276

  8. Turnover of Public School Superintendents in Arizona

    ERIC Educational Resources Information Center

    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…

  9. Cusp catastrophe model of employee turnover.

    PubMed

    Sheridan, J E; Abelson, M A

    1983-09-01

    A cusp catastrophe model is developed to explain job turnover of nursing employees. The temporal dynamics of the catastrophe model suggest that leavers experience lower organization commitment than do stayers prior to termination. Leavers' perceptions of job tension and commitment appear to cross the threshold levels prior to the termination dates. PMID:10262614

  10. Employee Development and Turnover Intention: Theory Validation

    ERIC Educational Resources Information Center

    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…

  11. Home Visitor Job Satisfaction and Turnover.

    ERIC Educational Resources Information Center

    Buchbinder, Sharon B.; Duggan, Anne K.; Young, Elizabeth; Fuddy, Loretta; Sia, Cal

    This paper summarizes findings of a 3-year study of the job satisfaction and turnover of home visitors, both professional and paraprofessional, in programs which link families-at-risk for impaired functioning to medical home care and other resources. Specifically, the study examined: (1) home visitor personal characteristics that influence…

  12. Job Turnover Intentions Among Pharmacy Faculty

    PubMed Central

    Conklin, Mark H.

    2007-01-01

    Objectives To determine the primary reasons why pharmacy faculty intend to remain or leave their current institution and why they left their most recent academic institution, and the relative contribution of various organizational and individual characteristics toward explaining variance in turnover intentions. Methods A survey instrument was e-mailed to pharmacy faculty members asking respondents to indicate up to 5 reasons for their intentions and up to 5 reasons why they left a previous institution. The survey also elicited perceptions on quality of work life in addition to demographic and institutional data, upon which turnover intentions were regressed using a forward-conditional procedure. Organizational commitment as a moderator of turnover intentions was regressed over the remaining variables not acting directly on employer intentions. Results Just over 1 in 5 respondents indicated intentions to leave their current academic institution. Excessive workload, seeking a new challenge, poor salary, and poor relationships with college or school administrators were frequently cited as reasons for leaving. Turnover intentions are influenced directly by department chair support and organizational commitment, which moderates various support and satisfaction variables. Conclusions Pharmacy faculty members’ decision to remain or leave an institution is dependent upon developing a sense of commitment toward the institution. Commitment is facilitated by support from the institution and department chair, in addition to a sense of satisfaction with the teaching environment. PMID:17786250

  13. Teacher Turnover in Charter Schools. Research Brief

    ERIC Educational Resources Information Center

    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…

  14. Costing Child Protective Services Staff Turnover.

    ERIC Educational Resources Information Center

    Graef, Michelle I.; Hill, Erick L.

    2000-01-01

    Details process of determining a child welfare agency's actual dollar costs directly attributed to protective services staff turnover, using the agency's human resources database and interviews with administrative personnel. Provides formulas and process for calculating specific cost elements due to employee separation, replacement, and training.…

  15. Director Turnover: An Australian Academic Development Study

    ERIC Educational Resources Information Center

    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…

  16. Normal Bone Turnover in Transient Hyperphosphatasemia

    PubMed Central

    Kutilek, Stepan; Cervickova, Barbora; Bebova, Pavla; Kmonickova, Marie; Nemec, Vladimir

    2012-01-01

    Transient hyperphosphatasemia of infancy and early childhood (THI) is characterized by a temporary isolated elevation of serum alkaline phosphatase activity (ALP), predominantly its bone or liver isoform, in either sick or healthy children under 5 years of age. Return to normal ALP levels usually occurs within four months. Spontaneous rise of ALP might concern the physician, especially when treating seriously ill children. However, THI is considered a benign biochemical disorder with no clinical consequences. Some existing reports support the hypothesis that THI is a result of increased bone turnover. We present evidence of normal bone turnover in two children with THI. In a one-year-old girl and a boy of the same age, high ALP levels (31 and 109 μkat/L, respectively) were accidentally detected. The children had no signs of metabolic bone disease or of liver disease. The high ALP levels returned to normal in two months, thus fulfilling the diagnosis of THI. In both patients, serum parathyroid hormone and bone turnover markers, serum CrossLaps, and serum osteocalcin were neither elevated, nor did these markers follow the ALP dynamics, thus reflecting normal bone turnover in THI. Children with THI should be spared from extensive investigations and unnecessary vitamin D treatment. Conflict of interest:None declared. PMID:22664360

  17. Work-Related Variables and Turnover Intention among Registered Nurses.

    ERIC Educational Resources Information Center

    Pooyan, Abdullah; And Others

    1990-01-01

    Health institutions have become more interested in the causes of job turnover among registered nurses. Proper management of job turnover can improve the financial health and long-term survival of health care institutions. (Author)

  18. Looking for a Challenge? Watch That Labour Turnover!

    ERIC Educational Resources Information Center

    Wilkinson, Roderick

    1975-01-01

    Low labor turnover is an essential factor in the success of an enterprise. Steps in dealing with the turnover problem include: establish the objective, get the facts, decide what to do, take action, and check results. (MW)

  19. Staff turnover: occasional friend, frequent foe, and continuing frustration.

    PubMed

    McConnell, C R

    1999-09-01

    Turnover appears to be a relatively simple concept. However, considerable confusion results when discussing turnover because of differences in how it is defined--what is counted, how it is counted, and how the rate of turnover is expressed. Turnover is also costly, although not enough attention is paid to turnover's 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. PMID:10747463

  20. A concept analysis of turnover intention: implications for nursing management.

    PubMed

    Takase, Miyuki

    2010-01-01

    This paper provides a review and concept analysis of turnover intention. The aim was to promote Nurse Managers' understanding of the meanings and mechanisms of turnover intention, which could help them counteract nurse turnover. Sixty-six papers published between January 1998 and August 2007 were collected from CINAHL, PubMed, and PsycINFO databases, and were subjected to Rogers' concept analysis. The results showed that turnover intention is a multi-stage process involving the voluntary departure of employees from their current position, and is triggered by negative psychological responses to internal/external job context. These psychological responses evolve into withdrawal cognition and behaviours, and lead to actual turnover. To prevent nurse turnover, Nurse Managers should closely observe the internal and external causes of turnover, and the stage of nurses' turnover intention. PMID:20394269

  1. Constituent attachment and voluntary turnover in low-wage/low-skill service work.

    PubMed

    Ellingson, Jill E; Tews, Michael J; Dachner, Alison M

    2016-01-01

    This paper draws on life stage theory, ethnographic research conducted in the service sector, and evidence for secondary segmentation within the low-wage/low-skill labor force to offer evidence that social bond development with coworkers can help reduce the high rate of turnover observed in low-wage/low-skill service work. Contrary to the belief that these employees will leave before social ties can develop, constituent attachment was found to be the only significant predictor of turnover in 2 samples of front-line service workers in a casual dining, national restaurant chain after controlling for other aspects of work that can create a sense of attachment to a job, and other job attitudes, such as satisfaction and commitment. However, the effect was dependent on developmental life stage. Constituent attachment reduced turnover among workers classified as emerging adults, whereas constituent attachment did little to affect turnover among nonemerging adults. Implications of the results are discussed with respect to the value of considering segmentation in future research on turnover in the service sector and the use of life stage theory for understanding the leaving behavior of workers in different stages of adulthood. PMID:26121092

  2. Nursing churn and turnover in Australian hospitals: nurses perceptions and suggestions for supportive strategies

    PubMed Central

    2014-01-01

    Background This study aimed to reveal nurses’ experiences and perceptions of turnover in Australian hospitals and identify strategies to improve retention, performance and job satisfaction. Nursing turnover is a serious issue that can compromise patient safety, increase health care costs and impact on staff morale. A qualitative design was used to analyze responses from 362 nurses collected from a national survey of nurses from medical and surgical nursing units across 3 Australian States/Territories. Method A qualitative design was used to analyze responses from 362 nurses collected from a national survey of nurses from medical and surgical nursing units across 3 Australian States/Territories. Results Key factors affecting nursing turnover were limited career opportunities; poor support; a lack of recognition; and negative staff attitudes. The nursing working environment is characterised by inappropriate skill-mix and inadequate patient-staff ratios; a lack of overseas qualified nurses with appropriate skills; low involvement in decision-making processes; and increased patient demands. These issues impacted upon heavy workloads and stress levels with nurses feeling undervalued and disempowered. Nurses described supportive strategies: improving performance appraisals, responsive preceptorship and flexible employment options. Conclusion Nursing turnover is influenced by the experiences of nurses. Positive steps can be made towards improving workplace conditions and ensuring nurse retention. Improving performance management and work design are strategies that nurse managers could harness to reduce turnover. PMID:24708565

  3. Aggregations in Flatworms.

    ERIC Educational Resources Information Center

    Liffen, C. L.; Hunter, M.

    1980-01-01

    Described is a school project to investigate aggregations in flatworms which may be influenced by light intensity, temperature, and some form of chemical stimulus released by already aggregating flatworms. Such investigations could be adopted to suit many educational levels of science laboratory activities. (DS)

  4. Comparative Proteome Analysis of hAT-MSCs Isolated from Chronic Renal Failure Patients with Differences in Their Bone Turnover Status

    PubMed Central

    Akpinar, Gurler; Tuncay, Mehmet; Aksoy, Ayça; Karaoz, Erdal

    2015-01-01

    The relationship between the stem cells and the bone turnover in uremic bone disease due to chronic renal failure (CRF) is not described. The aim of this study was to investigate the effect of bone turnover status on stem cell properties. To search for the presence of such link and shed some light on stem-cell relevant mechanisms of bone turnover, we carried out a study with mesenchymal stem cells. Tissue biopsies were taken from the abdominal subcutaneous adipose tissue of a CRF patient with secondary hyperparathyroidism with the high turnover bone disease. This patient underwent parathyroidectomy operation (PTX) and another sample was taken from this patient after PTX. A CRF patient with adynamic bone disease with low turnover and a healthy control were also included. Mesenchymal stem cells isolated from the subjects were analyzed using proteomic and molecular approaches. Except ALP activity, the bone turnover status did not affect common stem cell properties. However, detailed proteome analysis revealed the presence of regulated protein spots. A total of 32 protein spots were identified following 2D gel electrophoresis and MALDI-TOF/TOF analyzes. The identified proteins were classified into seven distinct groups and their potential relationship to bone turnover were discussed. Distinct protein expression patterns emerged in relation to the bone turnover status indicate a possible link between the stem cells and bone turnover in uremic bone disease due to CRF. PMID:26575497

  5. Job Satisfaction, Commitment, Withdrawal Cognitions and Turnover: A Longitudinal Study.

    ERIC Educational Resources Information Center

    Kerber, Kenneth W.; Campbell, James P.

    Recent research on organizational turnover has examined the validity of the turnover decision process, in particular, the model of employee turnover proposed by Mobley (1977). This study followed-up on a previous (Kerber and Campbell, 1986) study of new employees of a large computer company in which participants completed a questionnaire that…

  6. A Ministudy of employee turnover in US hospitals.

    PubMed

    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. PMID:25627851

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

    ERIC Educational Resources Information Center

    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…

  8. Job Turnover and Job Satisfaction among Nursing Home Aides.

    ERIC Educational Resources Information Center

    Waxman, Howard M.; And Others

    1984-01-01

    Interviewed 234 aides in seven nursing homes concerning job turnover rate, job satisfaction, and perception of milieu. A positive association found between turnover rate and aides' perceptions of the homes' order, organization, and control suggested that job turnover would lessen with more involvement in the decision-making process. (JAC)

  9. Employee Turnover in the Federal Government. A Special Study.

    ERIC Educational Resources Information Center

    Musell, R. Mark

    A study of employee turnover in the Federal government showed that in 1984, about 195,000 full-time, nonpostal Federal workers with permanent appointments left Federal jobs or transferred to other Federal agencies--representing a turnover rate of 11.5 percent. The turnover was about three percentage points higher for white-collar workers than for…

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

    ERIC Educational Resources Information Center

    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;…

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

    ERIC Educational Resources Information Center

    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…

  12. High School Band Students' Perspectives of Teacher Turnover

    ERIC Educational Resources Information Center

    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…

  13. Global distribution of carbon turnover times in terrestrial ecosystems

    NASA Astrophysics Data System (ADS)

    Carvalhais, Nuno; Forkel, Matthias; Khomik, Myroslava; Bellarby, Jessica; Jung, Martin; Migliavacca, Mirco; Mu, Mingquan; Saatchi, Sassan; Santoro, Maurizio; Thurner, Martin; Weber, Ulrich; Ahrens, Bernhard; Beer, Christian; Cescatti, Alessandro; Randerson, James T.; Reichstein, Markus

    2015-04-01

    The response of the carbon cycle in terrestrial ecosystems to climate variability remains one of the largest uncertainties affecting future projections of climate change. This feedback between the terrestrial carbon cycle and climate is partly determined by the response of carbon uptake and by changes in the residence time of carbon in land ecosystems, which depend on climate, soil, and vegetation type. Thus, it is of foremost importance to quantify the turnover times of carbon in terrestrial ecosystems and its spatial co-variability with climate. Here, we develop a global, spatially explicit and observation-based assessment of whole-ecosystem carbon turnover times (τ) to investigate its co-variation with climate at global scale. Assuming a balance between uptake (gross primary production, GPP) and emission fluxes, τ can be defined as the ratio between the total stock (C_total) and the output or input fluxes (GPP). The estimation of vegetation (C_veg) stocks relies on new remote sensing-based estimates from Saatchi et al (2011) and Thurner et al (2014), while soil carbon stocks (C_soil) are estimated based on state of the art global (Harmonized World Soil Database) and regional (Northern Circumpolar Soil Carbon Database) datasets. The uptake flux estimates are based on global observation-based fields of GPP (Jung et al., 2011). Globally, we find an overall mean global carbon turnover time of 23-4+7 years (95% confidence interval). A strong spatial variability globally is also observed, from shorter residence times in equatorial regions to longer periods at latitudes north of 75°N (mean τ of 15 and 255 years, respectively). The observed latitudinal pattern reflect the clear dependencies on temperature, showing increases from the equator to the poles, which is consistent with our current understanding of temperature controls on ecosystem dynamics. However, long turnover times are also observed in semi-arid and forest-herbaceous transition regions. Furthermore

  14. Local aggregation characteristics of microscale blood flows

    NASA Astrophysics Data System (ADS)

    Kaliviotis, Efstathios; Sherwood, Joseph M.; Dusting, Jonathan; Balabani, Stavroula

    2015-11-01

    Erythrocyte aggregation (EA) is an important aspect of microvascular flows affecting blood flow and viscosity. Microscale blood flows have been studied extensively in recent years using computational and microfluidic based approaches. However, the relationship between the local structural characteristics of blood and the velocity field has not been quantified. We report simultaneous measurements of the local velocity, aggregation and haematocrit distributions of human erythrocytes flowing in a microchannel. EA was induced using Dextran and flows were imaged using brightfield microscopy. Local aggregation characteristics were investigated using statistical and edge-detection image processing techniques while velocity profiles were obtained using PIV algorithms. Aggregation intensity was found to strongly correlate with local variations in velocity in both the central and wall regions of the channel. The edge detection method showed that near the side wall large aggregates are associated with high local velocities and low local shear rates. In the central region large aggregates occurred in regions of low velocity and high erythrocyte concentration. The results demonstrate the combined effect of haematocrit and velocity distributions on local aggregation characteristics.

  15. Diffusion-limited aggregation on curved surfaces

    NASA Astrophysics Data System (ADS)

    Choi, J.; Crowdy, D.; Bazant, M. Z.

    2010-08-01

    We develop a general theory of transport-limited aggregation phenomena occurring on curved surfaces, based on stochastic iterated conformal maps and conformal projections to the complex plane. To illustrate the theory, we use stereographic projections to simulate diffusion-limited aggregation (DLA) on surfaces of constant Gaussian curvature, including the sphere (K>0) and the pseudo-sphere (K<0), which approximate "bumps" and "saddles" in smooth surfaces, respectively. Although the curvature affects the global morphology of the aggregates, the fractal dimension (in the curved metric) is remarkably insensitive to curvature, as long as the particle size is much smaller than the radius of curvature. We conjecture that all aggregates grown by conformally invariant transport on curved surfaces have the same fractal dimension as DLA in the plane. Our simulations suggest, however, that the multifractal dimensions increase from hyperbolic (K<0) to elliptic (K>0) geometry, which we attribute to curvature-dependent screening of tip branching.

  16. Charged Dust Aggregate Interactions

    NASA Astrophysics Data System (ADS)

    Matthews, Lorin; Hyde, Truell

    2015-11-01

    A proper understanding of the behavior of dust particle aggregates immersed in a complex plasma first requires a knowledge of the basic properties of the system. Among the most important of these are the net electrostatic charge and higher multipole moments on the dust aggregate as well as the manner in which the aggregate interacts with the local electrostatic fields. The formation of elongated, fractal-like aggregates levitating in the sheath electric field of a weakly ionized RF generated plasma discharge has recently been observed experimentally. The resulting data has shown that as aggregates approach one another, they can both accelerate and rotate. At equilibrium, aggregates are observed to levitate with regular spacing, rotating about their long axis aligned parallel to the sheath electric field. Since gas drag tends to slow any such rotation, energy must be constantly fed into the system in order to sustain it. A numerical model designed to analyze this motion provides both the electrostatic charge and higher multipole moments of the aggregate while including the forces due to thermophoresis, neutral gas drag, and the ion wakefield. This model will be used to investigate the ambient conditions leading to the observed interactions. This research is funded by NSF Grant 1414523.

  17. Turnover intention in new graduate nurses: a multivariate analysis

    PubMed Central

    Beecroft, Pauline C; Dorey, Frederick; Wenten, Madé

    2008-01-01

    Title Turnover intention in new graduate nurses: a multivariate analysis Aim This paper is a report of a study to determine the relationship of new nurse turnover intent with individual characteristics, work environment variables and organizational factors and to compare new nurse turnover with actual turnover in the 18 months of employment following completion of a residency. Background Because of their influence on patient safety and health outcomes nurse turnover and turnover intent have received considerable attention worldwide. When nurse staffing is inadequate, especially during nursing shortages, unfavourable clinical outcomes have been documented. Method Prospective data collection took place from 1999 to 2006 with 889 new paediatric nurses who completed the same residency. Scores on study instruments were related to likelihood of turnover intent using logistic regression analysis models. Relationships between turnover intent and actual turnover were compared using Kaplan–Meier survivorship. Results The final model demonstrated that older respondents were more likely to have turnover intent if they did not get their ward choice. Also higher scores on work environment and organizational characteristics contributed to likelihood that the new nurse would not be in the turnover intent group. These factors distinguish a new nurse with turnover intent from one without 79% of the time. Increased seeking of social support was related to turnover intent and older new graduates were more likely to be in the turnover intent group if they did not get their ward choice. Conclusion When new graduate nurses are satisfied with their jobs and pay and feel committed to the organization, the odds against turnover intent decrease. What is already known about this topic There is concern in many countries about nurse turnover and the resulting effects on patient safety and quality of care. Decreasing ability to recruit experienced nurses has increased the emphasis on

  18. Organisation turnover among registered nurses: an exploratory model.

    PubMed

    Bloom, J R; Alexander, J A; Flatt, S

    1988-11-01

    In light of current concerns over nursing shortages and productivity, turnover among hospital nurses has assumed renewed importance as a managerial issue. This study examines the thesis that organisation of hospital work is a determinant of voluntary turnover among registered nurses. This perspective differs from previous work in this area in that both turnover and its determinants are conceptualised at the organisational rather than individual level, thus opening the way for administrative intervention to reduce turnover. The conceptual model is tested using multiple regression techniques on a sample of 310 community hospitals. Results suggest the importance of administrative work structures and the professionalisation of the workforce as contributors to higher turnover. PMID:10296903

  19. Aggregate and the environment

    USGS Publications Warehouse

    Langer, William H.; Drew, Lawrence J.; Sachs, J.S.

    2004-01-01

    This book is designed to help you understand our aggregate resources-their importance, where they come from, how they are processed for our use, the environmental concerns related to their mining and processing, how those concerns are addressed, and the policies and regulations designed to safeguard workers, neighbors, and the environment from the negative impacts of aggregate mining. We hope this understanding will help prepare you to be involved in decisions that need to be made-individually and as a society-to be good stewards of our aggregate resources and our living planet.

  20. Replicator dynamics with turnover of players

    NASA Astrophysics Data System (ADS)

    Juul, Jeppe; Kianercy, Ardeshir; Bernhardsson, Sebastian; Pigolotti, Simone

    2013-08-01

    We study adaptive dynamics in games where players abandon the population at a given rate and are replaced by naive players characterized by a prior distribution over the admitted strategies. We demonstrate how such a process leads macroscopically to a variant of the replicator equation, with an additional term accounting for player turnover. We study how Nash equilibria and the dynamics of the system are modified by this additional term for prototypical examples such as the rock-paper-scissors game and different classes of two-action games played between two distinct populations. We conclude by showing how player turnover can account for nontrivial departures from Nash equilibria observed in data from lowest unique bid auctions.

  1. Health Care Workplace Discrimination and Physician Turnover

    PubMed Central

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

    2013-01-01

    Objective To examine the association between physician race/ethnicity, workplace discrimination, and physician job turnover. Methods 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 χ2 statistics, and multivariate logistic regression modeling to evaluate these associations. Results 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 odes ratio, 2.7; 95% CI, 1.4–4.9]. Among physicians who experienced work-place discrimination, only 45% of physicians were satisfied with their careers (vs 88% among those who had not experienced workplace discrimination, p value < .01], and 40% were con-templating a career change (vs 10% among those who had not experienced workplace discrimination, p value < .001). Conclusion 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. PMID:20070016

  2. Strategies to manage low-bone turnover.

    PubMed

    Spasovski, G

    2009-01-01

    A change in paradigm occurred lately whereby not hypocalcemia but hypercalcemia and positive calcium balance were considered negative factors. Namely, the use of calcium- based binders in combination with vitamin D analogues, has been shown to lead to an over-suppression of parathyroid hormone (PTH) and development of low-bone turnover adynamic bone disease (ABD). The changing prevalence of various types of bone diseases from a high to low-bone turnover goes in line with the presence of increased risk for vascular calcification (VC), morbidity and mortality in the dialysis population. The attenuation of the previous great expectations in calcium-based phosphate binders and vitamin D-analogues entailed a new treatment strategy to preserve bone and vascular health. Hence, a new evidence for treatment of ABD with various types of non calcium based binders and low calcium dialysate is presented. Sevelamer treatment has reduced calcium concentration and increased PTH levels, resulting in the improvement of markers of bone turnover, increased bone formation and improved trabecular architecture, providing a slower progression of VC. Data on lanthanum beneficial effect on ABD histology have been demonstrated in long-term clinical studies. Although there is a slow release of lanthanum from its bone deposits after discontinuation of the treatment and no association with aluminium- like bone toxicity, there is still an ongoing scientific debate about its long-term toxic potential. Finally, reducing the number of calcium based binders and low calcium dialysate (1.25 mmol/l) has been reported to have an impact on the evolution towards markers reflecting higher bone turnover. Then, adoption of the non calcium-based binders should be reserved to high risk patients with ABD and progression of vascular calcifications associated with increased morbidity and mortality. PMID:19668299

  3. Forest turnover rates follow global and regional patterns of productivity

    USGS Publications Warehouse

    Stephenson, N.L.; van Mantgem, P.J.

    2005-01-01

    Using a global database, we found that forest turnover rates (the average of tree mortality and recruitment rates) parallel broad-scale patterns of net primary productivity. First, forest turnover was higher in tropical than in temperate forests. Second, as recently demonstrated by others, Amazonian forest turnover was higher on fertile than infertile soils. Third, within temperate latitudes, turnover was highest in angiosperm forests, intermediate in mixed forests, and lowest in gymnosperm forests. Finally, within a single forest physiognomic type, turnover declined sharply with elevation (hence with temperature). These patterns of turnover in populations of trees are broadly similar to the patterns of turnover in populations of plant organs (leaves and roots) found in other studies. Our findings suggest a link between forest mass balance and the population dynamics of trees, and have implications for understanding and predicting the effects of environmental changes on forest structure and terrestrial carbon dynamics. ??2005 Blackwell Publishing Ltd/CNRS.

  4. Generational differences in registered nurse turnover.

    PubMed

    LeVasseur, Sandra A; Wang, Chen-Yen; Mathews, Barbara; Boland, Mary

    2009-08-01

    The chronic nature of the nursing workforce shortage in the United States is a continuing concern. As the nationwide gap between supply and demand grows, it remains unknown what impact turnover will have on nursing, access to care, and efforts to improve quality and safety of health care. It also remains unclear whether the recent turnover trends among new graduate registered nurses differ from past generational cohorts of new nurses. The aims of this study were to identify the reasons why registered nurses turnover by generational cohort (Veterans, Baby Boomers, and GenXMs) and to compare the length of time nurses were employed in their first five nursing positions by generational cohort. The findings suggest the three generational cohorts displayed similar reasons for leaving nursing positions with relocation, career advancement, and personal/family reasons reported most frequently. Except for the first nursing position, significant generational effects were found in the length of time Veterans, Baby Boomer, and GenXMs stayed employed in their nursing positions. It remains unknown why the GenXMs displayed a significantly shorter length of employment time in their second, third, fourth, and fifth nursing positions. The decline in length of employment time displayed in both the Baby Boomers and GenXMs may be an issue of concern requiring future research. PMID:20026454

  5. Protein Colloidal Aggregation Project

    NASA Technical Reports Server (NTRS)

    Oliva-Buisson, Yvette J. (Compiler)

    2014-01-01

    To investigate the pathways and kinetics of protein aggregation to allow accurate predictive modeling of the process and evaluation of potential inhibitors to prevalent diseases including cataract formation, chronic traumatic encephalopathy, Alzheimer's Disease, Parkinson's Disease and others.

  6. Calvarial doughnut lesions associated with high-turnover osteoporosis presenting in childhood.

    PubMed

    Stock, J L; Coderre, J A; Overdorf, J H; Fitzpatrick, L A; Shapiro, J R

    1999-01-01

    Osteogenesis imperfecta and juvenile osteoporosis are two well-described syndromes of osteoporosis presenting in childhood. There are also several references in the radiology literature to calvarial doughnut lesions (CDLs), areas of radiolucency surrounded by a dense and well-defined area of sclerotic bone, either as an incidental finding or associated with childhood fracture. We have characterized the metabolic abnormalities in a 13-yr-old boy with CDLs and multiple fractures and followed him during his progression through puberty. The patient's paternal grandmother; father; and paternal aunt, uncle, and first cousin were similarly affected, and a mandibular lesion in the uncle was pathologically described as fibrous dysplasia. The subject's physical examination was significant for bony protuberances of the skull and normal hearing, sclearal hue, dentition, and joint flexibility. Radiographs revealed calvarial CDLs and osteopenia which was confirmed by bone mineral density (BMD) testing. Biochemical markers of bone formation and resorption were elevated compared to normal adult and a transiliac crest bone biopsy confirmed high-turnover osteoporosis. Over 6 yr, with no specific therapy, BMD gradually normalized, but the CDLs increased in size, bone turnover remained elevated by biochemical markers, and he continued to fracture. The subject's affected father and maternal grandmother had normal BMD and no history of adult fracture. CDLs with high-turnover osteoporosis should be considered in the differential diagnosis of pediatric osteoporosis. During puberty the BMD normalizes but the high-turnover state persists, and the propensity to fracture eventually decreases in older affected adults. The CDLs may be a variant of fibrous dysplasia, and further study is necessary in order to elucidate the stimulus for increased bone turnover and the familial nature of this syndrome. PMID:23547313

  7. Turnover of messenger RNA: Polysome statistics beyond the steady state

    NASA Astrophysics Data System (ADS)

    Valleriani, A.; Ignatova, Z.; Nagar, A.; Lipowsky, R.

    2010-03-01

    The interplay between turnover or degradation and ribosome loading of messenger RNA (mRNA) is studied theoretically using a stochastic model that is motivated by recent experimental results. Random mRNA degradation affects the statistics of polysomes, i.e., the statistics of the number of ribosomes per mRNA as extracted from cells. Since ribosome loading of newly created mRNA chains requires some time to reach steady state, a fraction of the extracted mRNA/ribosome complexes does not represent steady state conditions. As a consequence, the mean ribosome density obtained from the extracted complexes is found to be inversely proportional to the mRNA length. On the other hand, the ribosome density profile shows an exponential decrease along the mRNA for prokaryotes and becomes uniform in eukaryotic cells.

  8. Dynamic aspects of voluntary turnover: an integrated approach to curvilinearity in the performance-turnover relationship.

    PubMed

    Becker, William J; Cropanzano, Russell

    2011-03-01

    Previous research pertaining to job performance and voluntary turnover has been guided by 2 distinct theoretical perspectives. First, the push-pull model proposes that there is a quadratic or curvilinear relationship existing between these 2 variables. Second, the unfolding model of turnover posits that turnover is a dynamic process and that a downward performance change may increase the likelihood of organizational separation. Drawing on decision theory, we propose and test an integrative framework. This approach incorporates both of these earlier models. Specifically, we argue that individuals are most likely to voluntarily exit when they are below-average performers who are also experiencing a downward performance change. Furthermore, the interaction between this downward change and performance partially accounts for the curvilinear relationship proposed by the push-pull model. Findings from a longitudinal field study supported this integrative theory. PMID:20853945

  9. Sectoral shifts and aggregate unemployment

    SciTech Connect

    Loungani, P.

    1986-01-01

    Some recent research has taken the view that sectoral or industry-specific shocks significantly affect aggregate unemployment by increasing the amount of inter-industry labor reallocation required. The empirical evidence for this view rests on the finding that during the 1950s - and again during the 1970s - there was a positive correlation between aggregate unemployment and the dispersion of employment growth rates. This thesis demonstrates that this correlation arises largely because oil price shocks affect both unemployment and the dispersion of employment growth. Once the dispersion due to oil shocks is accounted for, the residual dispersion in employment has very low explanatory power for unemployment. Since the dispersion index does not measure pure sectoral shifts, an alternate measure of dispersion is developed that serves as a better proxy for the amount of inter-industry labor reallocation required each period. Estimates using this measure suggest that, during the 1950s, temporary increases in the relative price of oil were responsible for generating the observed correlation. On the other hand, sectoral shifts were important during the 1970s; in particular, the 1973 oil price increase has had significant reallocative effects on the economy. This contention is subjected to further tests by looking at the time-series behavior of employment in durable-goods industries and also by following the inter-industry movements of workers over time through the use of panel data.

  10. Influence of Phenylalanine on Carotenoid Aggregation

    NASA Astrophysics Data System (ADS)

    Lu, L.; Ni, X.; Luo, X.

    2015-01-01

    The carotenoids lutein and β-carotene form, in 1:1 ethanol-water mixtures H-aggregates, of different strengths. The effects of phenylalanine on these aggregates were recorded by UV-Vis absorption, steady-state fluorescence, and Raman spectra. The H-aggregate of lutein was characterized by a large 78 nm blue shift in the absorption spectra, confirming the strong coupling between hydroxyl groups of adjacent molecules. The 15 nm blue shift in the β-carotene mixture also indicates that it was assembled by weak coupling between polyenes. After adding phenylalanine, the reducing absorption strength of the aggregates of lutein and reappearance of vibrational substructure indicate that the hydroxyl and amino groups of phenylalanine may coordinate to lutein and disaggregate the H-aggregates. However, phenylalanine had no effect on aggregates of β-carotene. The Raman spectra show three bands of carotenoids whose intensities decreased with increasing phenylalanine concentration. The frequency of ν1 corresponding to the length of the conjugated region was more sensitive to the solution of lutein. This coordination of phenylalanine to lutein could increase the length of the conjugated region. In addition, phenylalanine significantly affected the excited electronic states of carotenoids, which were crucial in the energy transfer from carotenoids to chlorophyll a in vivo.

  11. 24 CFR 55.24 - Aggregation.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ..., require compliance with subpart C of this part, affect the same floodplain or wetland, and are currently under review by HUD (or by a responsible entity authorized by 24 CFR part 58), individual or aggregated... FLOODPLAIN MANAGEMENT AND PROTECTION OF WETLANDS Procedures for Making Determinations on...

  12. 32 CFR 701.46 - Aggregating requests.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... National Defense Department of Defense (Continued) DEPARTMENT OF THE NAVY UNITED STATES NAVY REGULATIONS AND OFFICIAL RECORDS AVAILABILITY OF DEPARTMENT OF THE NAVY RECORDS AND PUBLICATION OF DEPARTMENT OF THE NAVY DOCUMENTS AFFECTING THE PUBLIC FOIA Fees § 701.46 Aggregating requests. Except for...

  13. 32 CFR 701.46 - Aggregating requests.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... National Defense Department of Defense (Continued) DEPARTMENT OF THE NAVY UNITED STATES NAVY REGULATIONS AND OFFICIAL RECORDS AVAILABILITY OF DEPARTMENT OF THE NAVY RECORDS AND PUBLICATION OF DEPARTMENT OF THE NAVY DOCUMENTS AFFECTING THE PUBLIC FOIA Fees § 701.46 Aggregating requests. Except for...

  14. 32 CFR 701.46 - Aggregating requests.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... National Defense Department of Defense (Continued) DEPARTMENT OF THE NAVY UNITED STATES NAVY REGULATIONS AND OFFICIAL RECORDS AVAILABILITY OF DEPARTMENT OF THE NAVY RECORDS AND PUBLICATION OF DEPARTMENT OF THE NAVY DOCUMENTS AFFECTING THE PUBLIC FOIA Fees § 701.46 Aggregating requests. Except for...

  15. 32 CFR 701.46 - Aggregating requests.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... National Defense Department of Defense (Continued) DEPARTMENT OF THE NAVY UNITED STATES NAVY REGULATIONS AND OFFICIAL RECORDS AVAILABILITY OF DEPARTMENT OF THE NAVY RECORDS AND PUBLICATION OF DEPARTMENT OF THE NAVY DOCUMENTS AFFECTING THE PUBLIC FOIA Fees § 701.46 Aggregating requests. Except for...

  16. 32 CFR 701.46 - Aggregating requests.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... National Defense Department of Defense (Continued) DEPARTMENT OF THE NAVY UNITED STATES NAVY REGULATIONS AND OFFICIAL RECORDS AVAILABILITY OF DEPARTMENT OF THE NAVY RECORDS AND PUBLICATION OF DEPARTMENT OF THE NAVY DOCUMENTS AFFECTING THE PUBLIC FOIA Fees § 701.46 Aggregating requests. Except for...

  17. Aggregate Unemployment Decreases Individual Returns to Education

    ERIC Educational Resources Information Center

    Ammermueller, Andreas; Kuckulenz, Anja; Zwick, Thomas

    2009-01-01

    Aggregate unemployment may affect individual returns to education through qualification-specific responses in participation and wage bargaining. This paper shows that an increase in regional unemployment by 1% decreases returns to education by 0.005 percentage points. This implies that higher skilled employees are better sheltered from labour…

  18. Turnover of eroded soil organic carbon after deposition in terrestrial and aquatic environments

    NASA Astrophysics Data System (ADS)

    Kirkels, Frédérique; Cammeraat, Erik; Kalbitz, Karsten; van Oost, Kristof; Ellerbrock, Ruth; Follain, Stéphane; Fuchslueger, Lucia; Gerke, Horst; Heckrath, Goswin; Kögel-Knabner, Ingrid; Kuhn, Nikolaus; van Loon, Emiel; Quinton, John; Richter, Andreas; Salvador-Blanes, Sébastien; Sommer, Michael; Steffens, Markus

    2015-04-01

    The fate of eroded soil organic carbon (SOC) after deposition is a large uncertainty in assessing the impact of soil erosion on C budgets. Globally, large amounts of SOC are transported by erosion and a substantial part is transferred into adjacent inland waters, linking terrestrial and aquatic C cycling. However, the net effect on C fluxes between soils, inland waters and atmosphere remains uncertain. In this study, we determined SOC turnover in terrestrial and aquatic environments and indentified its major controls. A European gradient of agricultural sites was sampled, spanning a wide range soil properties (e.g. texture, aggregation, etc.), SOC quantity and quality. In a 16-week incubation experiment, SOC turnover was determined for conditions reflecting downslope soils or inland waters. Moreover, we studied the impact of labile C inputs ('priming') on SOC stability using 13C labeled cellulose. Physical and chemical soil properties and SOC molecular composition were assessed as potential controls on C turnover. SOC deposition in aquatic environments resulted in upto 3.5 times higher C turnover than deposition on downslope soils. Labile C inputs enlarged total CO2 emissions, with the largest increase for aquatic conditions. Solid-state 13C NMR and FT-IR spectroscopy showed broad similarities in SOC molecular composition. Soil and SOC properties could not (yet) fully explain variation in SOC turnover between the sites. However, temporal trends in CO2 emissions clearly differed between downslope soils and inland waters. We established a quantitative model, based on the ten sites of the European gradient, that is capable to describe CO2 emissions for SOC deposited on soils and in inland waters and upon different levels of labile C inputs. Our findings indicate that deposition conditions (soils vs. inland waters) play a crucial role in determining C turnover. Erosion measures preventing deposition in aquatic environments could therefore be an important carbon saving

  19. Carbon Turnover and Dynamics from Biochemically Diverse Microbial Groups in Temperate and Tropical Forest Soils

    NASA Astrophysics Data System (ADS)

    Throckmorton, H.; Bird, J. A.; Firestone, M.; Horwath, W. R.

    2009-12-01

    Microorganisms represent an important source of actively cycling carbon (C) in terrestrial ecosystems, yet little is known of the fate or stability of microbial C in soils or the relative importance of microbial biochemistry as a factor influencing C stabilization. This project utilized uniformly 13C-labeled, biochemically diverse, non-living microbial residues including fungi, actinomycetes, bacteria Gm+, and bacteria Gm- as substrates in a reciprocal transplant experiment in a temperate forest in the Sierra Nevada and a tropical forest in Puerto Rico. Microbes were isolated from each site, grown with 13C media, autoclaved and lypholyzed, and non-living residues were added back to soils at each site. The temperate and tropical soils were analyzed over a 3 and 2 year period, respectively. Microbial C turnover differed substantially between the two sites, with microbial C levels stabilizing at 35% of initial input C after 12 months in the temperate site, while in Puerto Rico microbial C does not to begin to stabilize until about 16 months at less than 10% of initial input C. Physical fractionation of soils indicate that, despite the substantial difference in microbial C turnover between the two sites, microbial C turnover in the fraction occluded within aggregates and in the fraction associated with mineral surfaces did not differ between the two sites; the only physical fraction where microbial C turnover differed between the two sites was the light fraction, which is unassociated with the mineral matrix. These results underline the importance of the soil mineral matrix for protecting soil organic matter from mineralization. Although microbial groups did not differ in their relative partitioning among soil physical fractions, there was some evidence for slower overall decomposition of bacteria Gm+ and fungi relative to bacteria Gm- and actinomycetes; however, the observed effect was not substantial. Pyrolysis-GC-MS-IRMS results suggest there are some differences in

  20. Lanosterol reverses protein aggregation in cataracts.

    PubMed

    Zhao, Ling; Chen, Xiang-Jun; Zhu, Jie; Xi, Yi-Bo; Yang, Xu; Hu, Li-Dan; Ouyang, Hong; Patel, Sherrina H; Jin, Xin; Lin, Danni; Wu, Frances; Flagg, Ken; Cai, Huimin; Li, Gen; Cao, Guiqun; Lin, Ying; Chen, Daniel; Wen, Cindy; Chung, Christopher; Wang, Yandong; Qiu, Austin; Yeh, Emily; Wang, Wenqiu; Hu, Xun; Grob, Seanna; Abagyan, Ruben; Su, Zhiguang; Tjondro, Harry Christianto; Zhao, Xi-Juan; Luo, Hongrong; Hou, Rui; Perry, J Jefferson P; Gao, Weiwei; Kozak, Igor; Granet, David; Li, Yingrui; Sun, Xiaodong; Wang, Jun; Zhang, Liangfang; Liu, Yizhi; Yan, Yong-Bin; Zhang, Kang

    2015-07-30

    The human lens is comprised largely of crystallin proteins assembled into a highly ordered, interactive macro-structure essential for lens transparency and refractive index. Any disruption of intra- or inter-protein interactions will alter this delicate structure, exposing hydrophobic surfaces, with consequent protein aggregation and cataract formation. Cataracts are the most common cause of blindness worldwide, affecting tens of millions of people, and currently the only treatment is surgical removal of cataractous lenses. The precise mechanisms by which lens proteins both prevent aggregation and maintain lens transparency are largely unknown. Lanosterol is an amphipathic molecule enriched in the lens. It is synthesized by lanosterol synthase (LSS) in a key cyclization reaction of a cholesterol synthesis pathway. Here we identify two distinct homozygous LSS missense mutations (W581R and G588S) in two families with extensive congenital cataracts. Both of these mutations affect highly conserved amino acid residues and impair key catalytic functions of LSS. Engineered expression of wild-type, but not mutant, LSS prevents intracellular protein aggregation of various cataract-causing mutant crystallins. Treatment by lanosterol, but not cholesterol, significantly decreased preformed protein aggregates both in vitro and in cell-transfection experiments. We further show that lanosterol treatment could reduce cataract severity and increase transparency in dissected rabbit cataractous lenses in vitro and cataract severity in vivo in dogs. Our study identifies lanosterol as a key molecule in the prevention of lens protein aggregation and points to a novel strategy for cataract prevention and treatment. PMID:26200341

  1. Stimulation of r- vs. K- selected microorganisms by elevated atmospheric CO2 depends on soil aggregate size

    NASA Astrophysics Data System (ADS)

    Dorodnikov, M.; Blagodatskaya, E.; Blagodatsky, S.; Fangmeier, A.; Kuzyakov, Y.

    2009-04-01

    Increased root exudation under elevated atmospheric CO2 and the contrasting environments in soil macro- and microaggregates could affect microbial growth strategy. We investigated the effect of elevated CO2 on the contribution of fast- (r-strategists) and slow-growing microorganisms (K-strategists) in soil macro- and microaggregates. We fractionated the bulk soil from the ambient and elevated (for 5 years) CO2 treatments of FACE-Hohenheim (Stuttgart) into large macro- (>2 mm), small macro- (0.25-2.00 mm), and microaggregates (<0.25 mm) using an "optimal moist" sieving. Microbial biomass (Cmic), the maximal specific growth rate (μ), growing microbial biomass (GMB) and lag-period (tlag) were estimated by the kinetics of CO2 emission from bulk soil and aggregates amended with glucose and nutrients. Although Corg and Cmic were unaffected by elevated CO2, μ values were significantly higher under elevated than ambient CO2 for bulk soil, small macroaggregates, and microaggregates. The substrate induced respiratory response increased with the decreasing of aggregates size under both CO2 treatments. Based on changes in μ, GMB, and lag-period, we conclude that elevated atmospheric CO2 stimulated the r-selected microorganisms, especially in soil microaggregates. Such an increase in r-selected microorganisms could increase C turnover in terrestrial ecosystems in a future elevated atmospheric CO2 environment.

  2. Organizational commitment and turnover of nursing home administrators.

    PubMed

    Castle, Nicholas G

    2006-01-01

    In this investigation, the associations between organizational commitment (OC), intent-to-turnover, and actual turnover of a large sample of nursing home administrators (NHAs) are examined. Data used come from a mail survey, from which 632 responses were received from the NHAs (response rate = 63%). The one-year turnover rate of NHAs was 39 percent, and in almost all cases (87%) these NHAs had also exhibited low OC scores. The intent-to-turnover results show thinking about quitting comes before searching for a new position, which in turn both comes before the intention to quit. Multivariate analyses show work overload has a strong and robust association with both intent-to-turnover and turnover of NHAs, and may indicate that NHAs are leaving their positions because they are understaffed. PMID:16648695

  3. The implications of linking the dynamic performance and turnover literatures.

    PubMed

    Sturman, M C; Trevor, C O

    2001-08-01

    This article examines how the literatures of dynamic performance and the performance-turnover relationship inform each other. The nonrandom performance turnover relationship suggests that dynamic performance studies may be biased by their elimination of participants who do not remain for the entire study period. The authors demonstrated that the performance slopes of those who leave an organization differ from the performance slopes of those who remain. This finding suggests that studies of the performance-turnover relationship need to consider employee performance trends when predicting turnover. Replicating and extending the research of D. A. Harrison, M. Virick, and S. William (1996), the authors found that performance changes from the previous month and performance trends measured over a longer time period explained variance in voluntary turnover beyond current performance. Finally, the authors showed that performance trends interacted with current performance in the prediction of voluntary turnover. PMID:11519652

  4. Evaluating the Role of Microbial Internal Storage Turnover on Nitrous Oxide Accumulation During Denitrification

    PubMed Central

    Liu, Yiwen; Peng, Lai; Guo, Jianhua; Chen, Xueming; Yuan, Zhiguo; Ni, Bing-Jie

    2015-01-01

    Biological wastewater treatment processes under a dynamic regime with respect to carbon substrate can result in microbial storage of internal polymers (e.g., polyhydroxybutyrate (PHB)) and their subsequent utilizations. These storage turnovers play important roles in nitrous oxide (N2O) accumulation during heterotrophic denitrification in biological wastewater treatment. In this work, a mathematical model is developed to evaluate the key role of PHB storage turnovers on N2O accumulation during denitrification for the first time, aiming to establish the key relationship between N2O accumulation and PHB storage production. The model is successfully calibrated and validated using N2O data from two independent experimental systems with PHB storage turnovers. The model satisfactorily describes nitrogen reductions, PHB storage/utilization, and N2O accumulation from both systems. The results reveal a linear relationship between N2O accumulation and PHB production, suggesting a substantial effect of PHB storage on N2O accumulation during denitrification. Application of the model to simulate long-term operations of a denitrifying sequencing batch reactor and a denitrifying continuous system indicates the feeding pattern and sludge retention time would alter PHB turnovers and thus affect N2O accumulation. Increasing PHB utilization could substantially raise N2O accumulation due to the relatively low N2O reduction rate when using PHB as carbon source. PMID:26463891

  5. Evaluating the Role of Microbial Internal Storage Turnover on Nitrous Oxide Accumulation During Denitrification.

    PubMed

    Liu, Yiwen; Peng, Lai; Guo, Jianhua; Chen, Xueming; Yuan, Zhiguo; Ni, Bing-Jie

    2015-01-01

    Biological wastewater treatment processes under a dynamic regime with respect to carbon substrate can result in microbial storage of internal polymers (e.g., polyhydroxybutyrate (PHB)) and their subsequent utilizations. These storage turnovers play important roles in nitrous oxide (N2O) accumulation during heterotrophic denitrification in biological wastewater treatment. In this work, a mathematical model is developed to evaluate the key role of PHB storage turnovers on N2O accumulation during denitrification for the first time, aiming to establish the key relationship between N2O accumulation and PHB storage production. The model is successfully calibrated and validated using N2O data from two independent experimental systems with PHB storage turnovers. The model satisfactorily describes nitrogen reductions, PHB storage/utilization, and N2O accumulation from both systems. The results reveal a linear relationship between N2O accumulation and PHB production, suggesting a substantial effect of PHB storage on N2O accumulation during denitrification. Application of the model to simulate long-term operations of a denitrifying sequencing batch reactor and a denitrifying continuous system indicates the feeding pattern and sludge retention time would alter PHB turnovers and thus affect N2O accumulation. Increasing PHB utilization could substantially raise N2O accumulation due to the relatively low N2O reduction rate when using PHB as carbon source. PMID:26463891

  6. Ichthyosaurs from the French Rhaetian indicate a severe turnover across the Triassic-Jurassic boundary

    NASA Astrophysics Data System (ADS)

    Fischer, Valentin; Cappetta, Henri; Vincent, Peggy; Garcia, Géraldine; Goolaerts, Stijn; Martin, Jeremy E.; Roggero, Daniel; Valentin, Xavier

    2014-12-01

    Mesozoic marine reptiles went through a severe turnover near the end of the Triassic. Notably, an important extinction event affected ichthyosaurs, sweeping a large part of the group. This crisis is, however, obscured by an extremely poor fossil record and is regarded as protracted over the entire Norian-earliest Jurassic interval, for the lack of a more precise scenario. The iconic whale-sized shastasaurid ichthyosaurs are regarded as early victims of this turnover, disappearing by the middle Norian. Here we evaluate the pattern of this turnover among ichthyosaurs by analysing the faunal record of two Rhaetian localities. One locality is Autun, eastern France; we rediscovered in this material the holotypes or partial `type' series of Rachitrema pellati, Actiosaurus gaudryi, Ichthyosaurus rheticus, Ichthyosaurus carinatus and Plesiosaurus bibractensis; a revised taxonomic scheme is proposed. The second assemblage comes from a new locality: Cuers, southeastern France. Both these assemblages provide several lines of evidence for the presence of shastasaurid-like ichthyosaurs in the Rhaetian of Europe. These occurrences suggest that both the demise of shastasaurids and the sudden radiation of neoichthyosaurians occurred within a short time window; this turnover appears not only more abrupt but also more complex than previously postulated and adds a new facet of the end-Triassic mass extinction.

  7. Job satisfaction and turnover intent among hospital social workers in the United States.

    PubMed

    Pugh, Greg L

    2016-08-01

    Feelings of job satisfaction and turnover intentions among social workers affect work quality for both social workers and the people for whom they provide services. Existing literature on job satisfaction among hospital social workers is limited, and is overly focused on issues of compensation. There is job satisfaction research with hospital nurses available for comparison. Other informative social work research on job satisfaction and turnover exists in mental health and generally, across settings. Research on turnover intent in social work is primarily from child welfare settings and may not generalize. The literature notes gaps and contradictions about predictors of job satisfaction and turnover intent. Using a large national dataset of hospital social workers, this research clarifies and fills gaps regarding hospital social workers, and explores how Herzberg's theory of work can clarify the difference between sources of job dissatisfaction and job satisfaction. Findings include hospital social workers reporting high job satisfaction and that demographics do not contribute to the predictive models. The findings do support centralized social work departments and variety in the job functions of hospital social workers, and are consistent with the theoretical framework. PMID:27322030

  8. Protein turnover in Azotobacter vinelandii during encystment and germination.

    PubMed

    Ruppen, M E; Garner, G; Sadoff, H L

    1983-12-01

    Protein turnover occurs during differentiation of Azotobacter vinelandii 12837 to the extent of 50% during encystment and 7% during germination. The addition of rifampin at the initiation of encystment prevents encystment and inhibits turnover. In germinating cysts, protein turnover is essential owing to an apparent lack of certain amino acid biosynthetic enzymes. The capacity to synthesize sulfur-containing amino acids from inorganic precursors is regained about halfway through the germination process. PMID:6643391

  9. Technology meets aggregate

    SciTech Connect

    Wilson, C.; Swan, C.

    2007-07-01

    New technology carried out at Tufts University and the University of Massachusetts on synthetic lightweight aggregate has created material from various qualities of fly ash from coal-fired power plants for use in different engineered applications. In pilot scale manufacturing tests an 'SLA' containing 80% fly ash and 20% mixed plastic waste from packaging was produced by 'dry blending' mixed plastic with high carbon fly ash. A trial run was completed to produce concrete masonry unit (CMU) blocks at a full-scale facility. It has been shown that SLA can be used as a partial substitution of a traditional stone aggregate in hot asphalt mix. 1 fig., 2 photos.

  10. Sclerostin as a novel marker of bone turnover in athletes

    PubMed Central

    Jóźków, P; Mędraś, M; Majda, M; Słowińska-Lisowska, M

    2016-01-01

    Sclerostin is a protein secreted by osteocytes that acts as an inhibitor of bone formation. It has been shown that physical activity affects sclerostin concentration and thus bone remodelling. The aim of the study was to evaluate serum concentrations of sclerostin, selected bone turnover markers (PTH, P1NP), 25(OH)D3 and the intake of calcium and vitamin D in physically active versus sedentary men. A total of 59 healthy men aged 17-37 were enrolled in the study (43 athletes and 16 non-athletes). The mean sclerostin concentration in the group of athletes (A) was significantly higher than in non-athletes (NA) (35.3±8.9 vs 28.0±5.6 pmol·l-1, p= 0.004). A compared with NA had higher concentrations of P1NP (145.6±77.5 vs 61.2±22.3 ng·ml-1, p= <0.0001) and 25(OH)D3 (16.9±8.4 vs 10.3±4.3 ng·ml-1, p= 0.004) and lower concentrations of PTH (25.8±8.3 vs 38.2±11.5 pg·ml-1, p= <0.0001). Vitamin D deficiency was found in 77% of A and 100% of NA. A and NA had similar daily energy intake. They did not differ as to the intake of calcium and vitamin D. We observed a negative correlation between the serum concentrations of sclerostin and calcium in the studied subjects. Our results suggest that regular, long-lasting physical training may be associated with higher concentration of sclerostin. It seems that increased sclerostin is not related to other bone turnover markers (PTH, P1NP). PMID:26929475