1,780 research outputs found
Knowledge Exchange and the Trust Institution: a New Look at the Problem
In the knowledge economy, the search and exchange of knowledge is widely recognized as a key factor contributing to the creation and mobilization of company’s knowledge resources to maintain its competitive advantage. This study is devoted to identifying the role of interpersonal trust in the process of searching and sharing knowledge. Theoretical analysis shows that previously conducted studies in this research field are mainly focused on revealing the relationship between interpersonal trust and the willingness to use knowledge. This study is interested in the willingness to establish contact between economic actors for the purpose of knowledge exchange, and this becomes important when discontinuities in innovation result from a lack of knowledge exchange and interaction between stakeholders. The effects of two different types of interpersonal trust (cognition-based trust and affect-based trust) on willingness to share explicit and tacit knowledge between individuals have been separately examined and tested. The analysis conducted is based on data obtained from surveying 295 employees from large organizations in Penza, Russia. To validate the survey, a confirmatory factor analysis using structural equation modeling was undertaken to verify advanced causal hypotheses. To test the hypotheses, a multiple correlation-regression analysis was used. Results reveal that both types of interpersonal trust positively correlate with the willingness to share both explicit and implicit knowledge. Additionally, it has been established that the willingness to share tacit knowledge is more influenced by affect-based trust between individuals, while cognition-based trust is more significant in explaining the willingness to share explicit knowledge. The need to create favorable conditions within organizations to ensure the exchange of knowledge without constraints is highlighted
Amyotrophic lateral sclerosis incidence following exposure to inorganic selenium in drinking water
Background and aim. Some laboratory and epidemiologic studies have documented an association between high intake of the trace element selenium and risk of amyotrophic lateral sclerosis (ALS), a degenerative disease of the motor neurons. There have been few epidemiologic studies of the association.
Methods. From 1986 through 2015, we followed a community cohort in northern Italy that had been inadvertently exposed in the 1974-86 period to drinking water with unusually high levels of selenium, around 8 µg/ml, in its inorganic hexavalent form (selenate). In this cohort, we previously identified a high incidence of ALS during 1986-94. Here we report extended follow-up of this exposed cohort, as well as of an unexposed cohort including over 95,000 municipal residents, for an additional 21 years. We identified incident cases through administrative sources and a specialized registry.
Results. During follow-up, 7 and 112 ALS cases were newly diagnosed in the exposed and unexposed cohorts, respectively, yielding incidence rates of 14 and 5 per 100,000 person-years. A Poisson regression analysis adjusting for age, sex, and calendar year produced an overall rate ratio (RR) for ALS of 2.8 (95% confidence interval (CI) 1.3 - 6) in the entire period of follow-up. The association was stronger earlier than later in follow-up (1986-1994 vs. 1994-2015), and among women than men. All exposed cases were of the sporadic, non-familial form for the disease.
Conclusion. Overall, results from this ‘natural experiment’ indicate a positive association between chronic exposure to inorganic selenium and ALS incidence, with rates in the exposed cohort declining over time after cessation of exposure. Also taking into account the recognized neurotoxicity of selenium, particularly its selective toxicity on motor neurons observed in animal studies, the present study provides additional support for the hypothesis that selenium in its inorganic form increases ALS risk
Fresh Activity in Old Systems: Radio AGN in Fossil Groups of Galaxies
We present the first systematic 1.4 GHz Very Large Array radio continuum
survey of fossil galaxy group candidates. These are virialized systems believed
to have assembled over a gigayear in the past through the merging of galaxy
group members into a single, isolated, massive elliptical galaxy and featuring
an extended hot X-ray halo. We use new photometric and spectroscopic data from
SDSS Data Release 7 to determine that three of the candidates are clearly not
fossil groups. Of the remaining 30 candidates, 67% contain a radio-loud
(L_1.4GHz > 10^23 W Hz^-1) active galactic nucleus (AGN) at the center of their
dominant elliptical galaxy. We find a weak correlation between the radio
luminosity of the AGN and the X-ray luminosity of the halo suggesting that the
AGN contributes to energy deposition into the intragroup medium. We only find a
correlation between the radio and optical luminosity of the central elliptical
galaxy when we include X-ray selected, elliptically dominated non-fossil
groups, indicating a weak relationship between AGN strength and the mass
assembly history of the groups. The dominant elliptical galaxy of fossil groups
is on average roughly an order of magnitude more luminous than normal group
elliptical galaxies in optical, X-ray, and radio luminosities and our findings
are consistent with previous results that the radio-loud fraction in elliptical
galaxies is linked to the stellar mass of a population. The current level of
activity in fossil groups suggests that AGN fueling continues long after the
last major merger. We discuss several possibilities for fueling the AGN at the
present epoch.Comment: Accepted for publication in A
SPIDER VII - Revealing the Stellar Population Content of Massive Early-type Galaxies out to 8Re
Radial trends of stellar populations in galaxies provide a valuable tool to
understand the mechanisms of galaxy growth. In this paper, we present the first
comprehensive analysis of optical-optical and optical-NIR colours, as a
function of galaxy mass, out to the halo region (8Re) of early-type galaxies
(ETGs). We select a sample of 674 massive ETGs (M*>3x10^10MSun) from the
SDSS-based SPIDER survey. By comparing with a large range of population
synthesis models, we derive robust constraints on the radial trends in age and
metallicity. Metallicity is unambiguously found to decrease outwards, with a
measurable steepening of the slope in the outer regions (Re<R<8Re). The
gradients in stellar age are found to be more sensitive to the models used, but
in general, the outer regions of ETGs feature older populations compared to the
cores. This trend is strongest for the most massive galaxies in our sample
(M*>10^11MSun). Furthermore, when segregating with respect to large scale
environment, the age gradient is more significant in ETGs residing in higher
density regions. These results shed light on the processes leading from the
formation of the central core to the growth of the stellar envelope of massive
galaxies. The fact that the populations in the outer regions are older and more
metal-poor than in the core suggests a process whereby the envelope of massive
galaxies is made up of accreted small satellites (i.e. minor mergers) whose
stars were born during the first stages of galaxy formation.Comment: 20 pages, 13 figures, 10 tables. Accepted for publication in MNRA
X-ray Variability and Hardness of ESO 243-49 HLX-1: Clear Evidence for Spectral State Transitions
The ultra-luminous X-ray (ULX) source ESO 243-49 HLX-1 currently provides the
strongest evidence for the existence of intermediate mass black holes. We
conduct an ongoing monitoring campaign with the Swift X-ray Telescope and found
that HLX-1 showed two fast rise and exponential decay with increases in the
count rate of a factor ~40 separated by 375+/-13 days. We obtained new
XMM-Newton and Chandra dedicated pointings that were triggered at the lowest
and highest luminosities, respectively. The unabsorbed luminosities ranged from
1.9x10^40 to 1.25x10^42 erg/s. We confirm here the detection of spectral state
transitions from HLX-1 reminiscent of Galactic black hole binaries: at high
luminosities, the X-ray spectrum showed a thermal state dominated by a disk
component with temperatures of 0.26 keV at most, and at low luminosities the
spectrum is dominated by a hard power law with a photon index in the range
1.4-2.1, consistent with a hard state. The source was also observed in a steep
power law state. In the thermal state, the luminosity of the disk component
appears to scale with the fourth power of the inner disk temperature which
supports the presence of an optically thick, geometrically thin accretion disk.
The low fractional variability (rms of 9+/-9%) in this state also suggests the
presence of a dominant disk. The spectral changes and long-term variability of
the source cannot be explained by variations of the beaming angle and are not
consistent with the source being in a super-Eddington accretion state. HLX-1 is
thus an unusual ULX as it is similar to Galactic black hole binaries, which
have non-beamed and sub-Eddington emission, but with luminosities 3 orders of
magnitude higher. In this picture, a lower limit on the mass of the black hole
of >9000 M_sun can be derived, and the disk temperature in the thermal state
also suggests the presence of a black hole of a few 10^3 M_sun.Comment: accepted for publication in ApJ (October 10, 2011, v740-1); 11
figures, 13 pages with emulateapj styl
All Optical Implementation of Multi-Spin Entanglement in a Semiconductor Quantum Well
We use ultrafast optical pulses and coherent techniques to create spin
entangled states of non-interacting electrons bound to donors (at least three)
and at least two Mn2+ ions in a CdTe quantum well. Our method, relying on the
exchange interaction between localized excitons and paramagnetic impurities,
can in principle be applied to entangle a large number of spins.Comment: 17 pages, 3 figure
(pi,pi)-electronic order in iron arsenide superconductors
The distribution of valence electrons in metals usually follows the symmetry
of an ionic lattice. Modulations of this distribution often occur when those
electrons are not stable with respect to a new electronic order, such as spin
or charge density waves. Electron density waves have been observed in many
families of superconductors[1-3], and are often considered to be essential for
superconductivity to exist[4]. Recent measurements[5-9] seem to show that the
properties of the iron pnictides[10, 11] are in good agreement with band
structure calculations that do not include additional ordering, implying no
relation between density waves and superconductivity in those materials[12-15].
Here we report that the electronic structure of Ba1-xKxFe2As2 is in sharp
disagreement with those band structure calculations[12-15], instead revealing a
reconstruction characterized by a (pi,pi) wave vector. This electronic order
coexists with superconductivity and persists up to room temperature
Color and stellar population gradients in galaxies. Correlation with mass
We analyze the color gradients (CGs) of ~50000 nearby SDSS galaxies. From
synthetic spectral models based on a simplified star formation recipe, we
derive the mean spectral properties, and explain the observed radial trends of
the color as gradients of the stellar population age and metallicity (Z). The
most massive ETGs (M_* > 10^{11} Msun) have shallow CGs in correspondence of
shallow (negative) Z gradients. In the stellar mass range 10^(10.3-10.5) < M_*
< 10^(11) Msun, the Z gradients reach their minimum of ~ -0.5 dex^{-1}. At M_*
~ 10^{10.3-10.5} Msun, color and Z gradient slopes suddenly change. They turn
out to anti-correlate with the mass, becoming highly positive at the very low
masses. We have also found that age gradients anti-correlate with Z gradients,
as predicted by hierarchical cosmological simulations for ETGs. On the other
side, LTGs have gradients which systematically decrease with mass (and are
always more negative than in ETGs), consistently with the expectation from gas
infall and SN feedback scenarios. Z is found to be the main driver of the trend
of color gradients, especially for LTGs, but age gradients are not negligible
and seem to play a significant role too. We have been able to highlight that
older galaxies have systematically shallower age and Z gradients than younger
ones. Our results for high-mass galaxies are in perfect agreement with
predictions based on the merging scenario, while the evolution of LTGs and
younger and less massive ETGs seems to be mainly driven by infall and SN
feedback. (Abridged)Comment: 20 pages, 16 figures, accepted for publication on MNRAS. This version
includes revisions after the referee's report
Deletion of the GABAA α2-subunit does not alter self dministration of cocaine or reinstatement of cocaine seeking
Rationale
GABAA receptors containing α2-subunits are highly represented in brain areas that are involved in motivation and reward, and have been associated with addiction to several drugs, including cocaine. We have shown previously that a deletion of the α2-subunit results in an absence of sensitisation to cocaine.
Objective
We investigated the reinforcing properties of cocaine in GABAA α2-subunit knockout (KO) mice using an intravenous self-administration procedure.
Methods
α2-subunit wildtype (WT), heterozygous (HT) and KO mice were trained to lever press for a 30 % condensed milk solution. After implantation with a jugular catheter, mice were trained to lever press for cocaine (0.5 mg/kg/infusion) during ten daily sessions. Responding was extinguished and the mice tested for cue- and cocaine-primed reinstatement. Separate groups of mice were trained to respond for decreasing doses of cocaine (0.25, 0.125, 0.06 and 0.03 mg/kg).
Results
No differences were found in acquisition of lever pressing for milk. All genotypes acquired self-administration of cocaine and did not differ in rates of self-administration, dose dependency or reinstatement. However, whilst WT and HT mice showed a dose-dependent increase in lever pressing during the cue presentation, KO mice did not.
Conclusions
Despite a reported absence of sensitisation, motivation to obtain cocaine remains unchanged in KO and HT mice. Reinstatement of cocaine seeking by cocaine and cocaine-paired cues is also unaffected. We postulate that whilst not directly involved in reward perception, the α2-subunit may be involved in modulating the “energising” aspect of cocaine’s effects on reward-seeking
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