5,056 research outputs found


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    Our purpose in this study was to examine the relationship between presenteeism and the conscientiousness trait as an individual-level predictor of employee health and productivity. We used convenience sampling to recruit 168 Turkish health employees, who completed measures of conscientiousness and presenteeism. The findings revealed that in a work outcomes context, the conscientiousness trait was positively related to the noncompletion of work dimension of presenteeism, the focus of which is on work outcomes. However, the relationship between the conscientiousness trait and the distraction dimension of presenteeism was nonsignificant. Our findings have implications for managers and organizations, who should be proactive in taking preventative precautions to mitigate the possible negative effects of presenteeism behaviors

    Interaction Between Motor Domains Can Explain the Complex Dynamics of Heterodimeric Kinesins

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    Motor proteins are active enzyme molecules that play a crucial role in many biological processes. They transform the chemical energy into the mechanical work and move unidirectionally along rigid cytoskeleton filaments. Single-molecule experiments suggest that motor proteins, consisting of two motor domains, move in a hand-over-hand mechanism when each subunit changes between trailing and leading positions in alternating steps, and these subunits do not interact with each other. However, recent experiments on heterodimeric kinesins suggest that the motion of motor domains is not independent, but rather strongly coupled and coordinated, although the mechanism of these interactions are not known. We propose a simple discrete stochastic model to describe the dynamics of homodimeric and heterodimeric two-headed motor proteins. It is argued that interactions between motor domains modify free energy landscapes of each motor subunit, and motor proteins still move via the hand-over-hand mechanism but with different transitions rates. Our calculations of biophysical properties agree with experimental observations. Several ways to test the theoretical model are proposed.Comment: To appear in New J. Phy

    Physiological responses of the calcifying rhodophyte, Corallina officinalis (L.), to future CO2 levels

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    Future atmospheric CO2 levels will most likely have complex consequences for marine organisms, particulary photosynthetic calcifying organisms. Corallina officinalis L. is an erect calcifying macroalga found in the inter- and subtidal regions of temperate rocky coastlines and provides important substrate and refugia for marine meiofauna. The main goal of the current study was to determine the physiological responses of C. officinalis to increased CO2 concentrations expected to occur within the next century and beyond. Our results show that growth and production of inorganic material decreased under high CO2 levels, while carbonic anhydrase activity was stimulated and negatively correlated to algal inorganic content. Photosynthetic efficiency based on oxygen evolution was also negatively affected by increased CO2. The results of this study indicate that C. officinalis may become less competitive under future CO2 levels, which could result in structural changes in future temperate intertidal communities

    Simulated Performance of a Renewable Energy Technology – Heat Pump Systems in Semi-Arid California Greenhouses

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    In addition to the labor, energy and water consumption are the two main cost drivers in current greenhouse systems. Consequently, considerable effort is expended to conserve energy and water, and look for alternative energy sources, especially environmentally friendly renewable energy sources and technologies. Greenhouses in hot and arid regions also require large quantities of water for irrigation. Using proper technologies and environmental management systems can significantly change the energy and moisture dynamics of greenhouse production systems. This study aims to focus on reducing natural gas, electricity, and water consumption in semi-arid California greenhouses introducing renewable energy heat pump technologies to both open and confined greenhouses in California. The confined system has no external aeration and has no need for further water supply. It has a great potential to reduce the demand for natural gas, the load on the power grid, and the demand for irrigation water in greenhouse operations. It also allows plant protection without using chemical insecticides and the accumulation of carbon dioxide without aeration losses

    Decay resistance of scotch pine wood impregnated with Agaricus campestris bio-protective extract

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    In this study, it was investigated the possibilities of the use of fungal extract as wood protection solution against wood-degrading fungi. For that purpose, the decay resistance of Scotch pine wood samples, impregnated with Agaricus campestris fungal extract, was observed against the brown rot fungus Coniophora puteana. Impregnation procedure was applied at four different concentration levels and with two different extraction methods (hot water and methanol). The concentration levels were arranged as 1%, 3%, 5%, 7% for hot water and as 1.25%, 3.75%, 6.25%, 8.75% for methanol. The wood protective efficacy of extract solutions was determined by means of fungi decay test. The mass losses of the samples treated with both fungal extracts ranged from 3.53 to 20.91. The lowest mass losses in hot water (4.57%) and methanol extractions (3.53%) were seen in the samples treated at the highest concentration levels (7% and 8.75%). The wood samples impregnated at 7% and 8.75% concentration levels met the requirements of durability class 1 and were classified as very durable. Antifungal activity of methanol extract was stronger than that of the hot water extract. The variations which concentration levels were less than 7% did not have adequate protection to meet the requirements of the European norms

    Deuterated water in the solar-type protostars NGC 1333 IRAS 4A and IRAS 4B

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    Aims. The aim of this paper is to study deuterated water in the solar-type protostars NGC1333 IRAS4A and IRAS4B, to compare their HDO abundance distribution with other star-forming regions, and to constrain their HDO/H2O ratios. Methods. Using the Herschel/HIFI instrument as well as ground-based telescopes, we observed several HDO lines covering a large excitation range (Eup/k=22-168 K) towards these protostars and an outflow position. Non-LTE radiative transfer codes were then used to determine the HDO abundance profiles in these sources. Results. The HDO fundamental line profiles show a very broad component, tracing the molecular outflows, in addition to a narrower emission component and a narrow absorbing component. In the protostellar envelope of NGC1333 IRAS4A, the HDO inner (T>100 K) and outer (T<100 K) abundances with respect to H2 are estimated at 7.5x10^{-9} and 1.2x10^{-11}, respectively, whereas, in NGC1333 IRAS4B, they are 1.0x10^{-8} and 1.2x10^{-10}, respectively. Similarly to the low-mass protostar IRAS16293-2422, an absorbing outer layer with an enhanced abundance of deuterated water is required to reproduce the absorbing components seen in the fundamental lines at 465 and 894 GHz in both sources. This water-rich layer is probably extended enough to encompass the two sources as well as parts of the outflows. In the outflows emanating from NGC1333 IRAS4A, the HDO column density is estimated at about (2-4)x10^{13} cm^{-2}, leading to an abundance of about (0.7-1.9)x10^{-9}. An HDO/H2O ratio between 7x10^{-4} and 9x10^{-2} is derived in the outflows. In the warm inner regions of these two sources, we estimate the HDO/H2O ratios at about 1x10^{-4}-4x10^{-3}. This ratio seems higher (a few %) in the cold envelope of IRAS4A, whose possible origin is discussed in relation to formation processes of HDO and H2O.Comment: 16 pages, 13 figure

    Effect of anisotropy and destructuration on behavior of Haarajoki test embankment

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    This paper investigates the influence of anisotropy and destructuration on the behavior of Haarajoki test embankment, which was built by the Finnish National Road Administration as a noise barrier in 1997 on a soft clay deposit. Half of the embankment is constructed on an area improved with prefabricated vertical drains, while the other half is constructed on the natural deposit without any ground improvement. The construction and consolidation of the embankment is analyzed with the finite-element method using three different constitutive models to represent the soft clay. Two recently proposed constitutive models, namely S-CLAY1 which accounts for initial and plastic strain induced anisotropy, and its extension, called S-CLAY1S which accounts, additionally, for interparticle bonding and degradation of bonds, were used in the analysis. For comparison, the problem is also analyzed with the isotropic modified cam clay model. The results of the numerical analyses are compared with the field measurements. The simulations reveal the influence that anisotropy and destructuration have on the behavior of an embankment on soft clay