4,667 research outputs found
IMPACT ON PRESENTEEISM OF THE CONSCIENTIOUSNESS TRAIT: A HEALTH SECTOR CASE STUDY
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
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
The hot core towards the intermediate mass protostar NGC7129 FIRS 2: Chemical similarities with Orion KL
NGC 7129 FIRS 2 (hereafter FIRS 2) is an intermediate-mass (2 to 8 Msun)
protostar located at a distance of 1250 pc. High spatial resolution
observations are required to resolve the hot core at its center. We present a
molecular survey from 218200 MHz to 221800 MHz carried out with the IRAM
Plateau de Bure Interferometer. These observations were complemented with a
long integration single-dish spectrum taken with the IRAM 30m telescope. We
used a Local Thermodynamic Equilibrium (LTE) single temperature code to model
the whole dataset. The interferometric spectrum is crowded with a total of ~300
lines from which a few dozens remain unidentified yet. The spectrum has been
modeled with a total of 20 species and their isomers, isotopologues and
deuterated compounds. Complex molecules like methyl formate (CH3OCHO), ethanol
(CH3CH2OH), glycolaldehyde (CH2OHCHO), acetone (CH3COCH3), dimethyl ether
(CH3OCH3), ethyl cyanide (CH3CH2CN) and the aGg' conformer of ethylene glycol
(aGg'-(CH2OH)_2) are among the detected species. The detection of vibrationally
excited lines of CH3CN, CH3OCHO, CH3OH, OCS, HC3N and CH3CHO proves the
existence of gas and dust at high temperatures. In fact, the gas kinetic
temperature estimated from the vibrational lines of CH3CN, ~405 K, is similar
to that measured in massive hot cores. Our data allow an extensive comparison
of the chemistry in FIRS~2 and the Orion hot core. We find a quite similar
chemistry in FIRS 2 and Orion. Most of the studied fractional molecular
abundances agree within a factor of 5. Larger differences are only found for
the deuterated compounds D2CO and CH2DOH and a few molecules (CH3CH2CN, SO2,
HNCO and CH3CHO). Since the physical conditions are similar in both hot cores,
only different initial conditions (warmer pre-collapse phase in the case of
Orion) and/or different crossing time of the gas in the hot core can explain
this behavior.Comment: 30 pages, 9 figure
Water distribution in shocked regions of the NGC1333-IRAS4A protostellar outflow
We present the study of the H2O spatial distribution at two bright shocked
regions along IRAS4A, one of the strongest H2O emitters among the Class 0
outflows. We obtained Herschel-PACS maps of the IRAS4A outflow and HIFI
observations of two shocked positions. The largest HIFI beam of 38 arcsec at
557 GHz was mapped in several key water lines with different upper energy
levels, to reveal possible spatial variations of the line profiles. We detect
four H2O lines and CO (16-15) at the two selected positions. In addition,
transitions from related outflow and envelope tracers are detected. Different
gas components associated with the shock are identified in the H2O emission. In
particular, at the head of the red lobe of the outflow, two distinct gas
components with different excitation conditions are distinguished in the HIFI
emission maps: a compact component, detected in the ground-state water lines,
and a more extended one. Assuming that these two components correspond to two
different temperature components observed in previous H2O and CO studies, the
excitation analysis of the H2O emission suggests that the compact (about 3
arcsec) component is associated with a hot (T~1000 K) gas with densities
~(1-4)x10^5 cm^{-3}, whereas the extended one (10-17 arcsec) traces a warm
(T~300-500 K) and dense gas (~(3-5)x10^7 cm^{-3}). Finally, using the CO
(16-15) emission observed at R2, we estimate the H2O/H2 abundance of the warm
and hot components to be (7-10)x10^{-7} and (3-7)x10^{-5}. Our data allowed us,
for the first time, to resolve spatially the two temperature components
previously observed with HIFI and PACS. We propose that the compact hot
component may be associated with the jet that impacts the surrounding material,
whereas the warm, dense, and extended component originates from the compression
of the ambient gas by the propagating flow.Comment: 13 pages, 11 figures. Accepted for publication in Astronomy and
Astrophysic
Deuterated water in the solar-type protostars NGC 1333 IRAS 4A and IRAS 4B
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
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
Are quantitative trait-dependent sampling designs cost-effective for analysis of rare and common variants?
Use of trait-dependent sampling designs in whole-genome association studies of sequence data can reduce total sequencing costs with modest losses of statistical efficiency. In a quantitative trait (QT) analysis of data from the Genetic Analysis Workshop 17 mini-exome for unrelated individuals in the Asian subpopulation, we investigate alternative designs that sequence only 50% of the entire cohort. In addition to a simple random sampling design, we consider extreme-phenotype designs that are of increasing interest in genetic association analysis of QTs, especially in studies concerned with the detection of rare genetic variants. We also evaluate a novel sampling design in which all individuals have a nonzero probability of being selected into the sample but in which individuals with extreme phenotypes have a proportionately larger probability. We take differential sampling of individuals with informative trait values into account by inverse probability weighting using standard survey methods which thus generalizes to the source population. In replicate 1 data, we applied the designs in association analysis of Q1 with both rare and common variants in the FLT1 gene, based on knowledge of the generating model. Using all 200 replicate data sets, we similarly analyzed Q1 and Q4 (which is known to be free of association with FLT1) to evaluate relative efficiency, type I error, and power. Simulation study results suggest that the QT-dependent selection designs generally yield greater than 50% relative efficiency compared to using the entire cohort, implying cost-effectiveness of 50% sample selection and worthwhile reduction of sequencing costs
Early growth performances of various seed sources of black (Prunus serotina Erhr.) and wild cherry (Prunus avium L.) seedlings on low and high elevation sites in the western Black Sea Region of Turkey
The growth performances of one-year old seedlings of various black cherry (BC) and wild cherry (WC) seed sources (SSs) that were planted on low elevation sites (LES) and high elevation sites (HES) in the western Black Sea Region (BSR) of Turkey were assessed one and five years after planting (YAP). Significance between and within-species variations were found for seedling growth. On species basis, WC was superior to BC for seedling groundline diameter and height growth for the low elevation sites(LES) of one and five years after planting (YAP), whereas no substantial survival and growth differences were found between the species for the high elevation sites (HES) of five YAP. Generally, seedlings averaged a greater survival on the LES, when compared with those on the HES. Local WC SSs (Tefen, Yayla and Dirgine) demonstrated an enhanced seedling survival and growth on LES than the other SSs. Unlike the LES results, a collection of BC (Michigan 1 and Ukraine) and WC SSs (Dirgine, Germany, and Tefen) displayed the best seedling growth over five years. The HES seedlings frequently experienced diebacks and forking due to heavy snow fall and wildlife browsing. Selection of the local WC SSs was vital for the LES. However, BC SSs may present a potential for planting on the HES with harsher environmental conditions.Keywords: Black cherry, provenance test, seedling growth and survival, wild cherry
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Configuration and Technology Implications of Potential Nuclear Hydrogen System Applications.
Nuclear technologies have important distinctions and potential advantages for large-scale generation of hydrogen for U.S. energy services. Nuclear hydrogen requires no imported fossil fuels, results in lower greenhouse-gas emissions and other pollutants, lends itself to large-scale production, and is sustainable. The technical uncertainties in nuclear hydrogen processes and the reactor technologies needed to enable these processes, as well waste, proliferation, and economic issues must be successfully addressed before nuclear energy can be a major contributor to the nation's energy future. In order to address technical issues in the time frame needed to provide optimized hydrogen production choices, the Nuclear Hydrogen Initiative (NHI) must examine a wide range of new technologies, make the best use of research funding, and make early decisions on which technology options to pursue. For these reasons, it is important that system integration studies be performed to help guide the decisions made in the NHI. In framing the scope of system integration analyses, there is a hierarchy of questions that should be addressed: What hydrogen markets will exist and what are their characteristics? Which markets are most consistent with nuclear hydrogen? What nuclear power and production process configurations are optimal? What requirements are placed on the nuclear hydrogen system? The intent of the NHI system studies is to gain a better understanding of nuclear power's potential role in a hydrogen economy and what hydrogen production technologies show the most promise. This work couples with system studies sponsored by DOE-EE and other agencies that provide a basis for evaluating and selecting future hydrogen production technologies. This assessment includes identifying commercial hydrogen applications and their requirements, comparing the characteristics of nuclear hydrogen systems to those market requirements, evaluating nuclear hydrogen configuration options within a given market, and identifying the key drivers and thresholds for market viability of nuclear hydrogen options
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