699 research outputs found
Specialized osmotic stress response systems involve multiple SigB-like sigma factors in Streptomyces coelicolor
Tunable variation of optical properties of polymer capped gold nanoparticles
Optical properties of polymer capped gold nanoparticles of various sizes
(diameter 3-6 nm) have been studied. We present a new scheme to extract size
dependent variation of total dielectric function of gold nanoparticles from
measured UV-Vis absorption data. The new scheme can also be used, in principle,
for other related systems as well. We show how quantum effect, surface atomic
co - ordination and polymer - nanoparticle interface morphology leads to a
systematic variation in inter band part of the dielectric function of gold
nanoparticles, obtained from the analysis using our new scheme. Careful
analysis enables identification of the possible changes to the electronic band
structure in such nanoparticles.Comment: 13 pages,7 figures, 1 tabl
Primary Proton Spectrum of Cosmic Rays measured with Single Hadrons
The flux of cosmic-ray induced single hadrons near sea level has been
measured with the large hadron calorimeter of the KASCADE experiment. The
measurement corroborates former results obtained with detectors of smaller size
if the enlarged veto of the 304 m^2 calorimeter surface is encounted for. The
program CORSIKA/QGSJET is used to compute the cosmic-ray flux above the
atmosphere. Between E_0=300 GeV and 1 PeV the primary proton spectrum can be
described with a power law parametrized as
dJ/dE_0=(0.15+-0.03)*E_0^{-2.78+-0.03} m^-2 s^-1 sr^-1 TeV^-1. In the TeV
region the proton flux compares well with the results from recent measurements
of direct experiments.Comment: 13 pages, accepted by Astrophysical Journa
Living phosphatic stromatolites in a low-phosphorus environment: Implications for the use of phosphorus as a proxy for phosphate levels in paleosystems
In the geological record, fossil phosphatic stromatolites date back to the Great Oxidation Event in the Paleoproterozoic, but living phosphatic stromatolites have not been described previously. Here, we report on cyanobacterial stromatolites in a supratidal freshwater environment at Cape Recife, South African southern coast, precipitating Ca carbonate alternating with episodes of Ca phosphate deposition. In their structure and composition, the living stromatolites from Cape Recife closely resemble their fossilized analogues, showing phosphatic zonation, microbial casts, tunnel structures and phosphatic crusts of biogenic origin. The microbial communities appear to be also similar to those proposed to have formed fossil phosphatic stromatolites. Phosphatic domains in the material from Cape Recife are spatially and texturally associated with carbonate precipitates, but form distinct entities separated by sharp boundaries. Electron Probe Micro-Analysis shows that Ca/P ratios and the overall chemical compositions of phosphatic precipitates are in the range of octacalcium phosphate, amorphous tricalcium phosphate and apatite. The coincidence in time of the emergence of phosphatic stromatolites in the fossil record with a major episode of atmospheric oxidation led to the assumption that at times of increased oxygen release the underlying increased biological production may have been linked to elevated phosphorus availability. The stromatolites at Cape Recife, however, form in an environment where ambient phosphorus concentrations do not exceed 0.28μM, one to two orders of magnitude below the previously predicted minimum thresh-old of >5 μM for biogenic phosphate precipitation in paleo-systems. Accordingly, we contest the previously proposed suitability of phosphatic stromatolites as a proxy for high ambient phosphate concentrations in supratidal to shallow ocean settings in earth history
Culture, entrepreneurship and uneven development: a spatial analysis
Interest in the proposed connection between culture and entrepreneurship has grown significantly in recent years. However, less attention has been given to the nature of the overall impact of this proposed association on development outcomes, particularly at a local level. In response, this paper analyses the relationship between the nature of the culture, entrepreneurship and development experienced across localities, proposing that the link between culture and development is mediated by entrepreneurship. It focuses upon the concept of community culture, as well as embracing a notion of development incorporating both economic and social well-being outcomes. Drawing upon a multivariate spatial analysis of data from localities in Great Britain, the findings indicate that differences in rates of entrepreneurship are strongly influenced by the community culture present in these localities. Furthermore, a bidirectional relationship is found to exist between entrepreneurship and economic and social development outcomes. It is concluded that the embeddedness of local community culture presents a significant challenge for those places seeking to promote entrepreneurially-driven development
Fracton pairing mechanism for "strange" superconductors: Self-assembling organic polymers and copper-oxide compounds
Self-assembling organic polymers and copper-oxide compounds are two classes
of "strange" superconductors, whose challenging behavior does not comply with
the traditional picture of Bardeen, Cooper, and Schrieffer (BCS)
superconductivity in regular crystals. In this paper, we propose a theoretical
model that accounts for the strange superconducting properties of either class
of the materials. These properties are considered as interconnected
manifestations of the same phenomenon: We argue that superconductivity occurs
in the both cases because the charge carriers (i.e., electrons or holes)
exchange {\it fracton excitations}, quantum oscillations of fractal lattices
that mimic the complex microscopic organization of the strange superconductors.
For the copper oxides, the superconducting transition temperature as
predicted by the fracton mechanism is of the order of K. We suggest
that the marginal ingredient of the high-temperature superconducting phase is
provided by fracton coupled holes that condensate in the conducting
copper-oxygen planes owing to the intrinsic field-effect-transistor
configuration of the cuprate compounds. For the gate-induced superconducting
phase in the electron-doped polymers, we simultaneously find a rather modest
transition temperature of K owing to the limitations imposed by
the electron tunneling processes on a fractal geometry. We speculate that
hole-type superconductivity observes larger onset temperatures when compared to
its electron-type counterpart. This promises an intriguing possibility of the
high-temperature superconducting states in hole-doped complex materials. A
specific prediction of the present study is universality of ac conduction for
.Comment: 12 pages (including separate abstract page), no figure
Infrared behavior of the gluon propagator in lattice Landau gauge: the three-dimensional case
We evaluate numerically the three-momentum-space gluon propagator in the
lattice Landau gauge, for three-dimensional pure-SU(2) lattice gauge theory
with periodic boundary conditions. Simulations are done for nine different
values of the coupling , from (strong coupling) to (in the scaling region), and for lattice sizes up to . In the
limit of large lattice volume we observe, in all cases, a gluon propagator
decreasing for momenta smaller than a constant value . From our data
we estimate MeV. The result of a gluon propagator
decreasing in the infrared limit has a straightforward interpretation as
resulting from the proximity of the so-called first Gribov horizon in the
infrared directions.Comment: 14 pages, BI-TP 99/03 preprint, correction in the Acknowledgments
section. To appear in Phys.Rev.
Antecedents and Outcomes of Managing Diversity in a UK Context: Test of a Mediation Model
Extant research on diversity management has primarily examined the main effects of diversity management practices on outcomes from an organizational perspective. Meta-analysis in this field corroborates the conclusion that this approach is unable to account for the outcomes of diversity management effectively. The current study extends the literature by examining organizational antecedents of diversity management practices (DMP). This study also examines the mediating influences of perception of overall justice (POJ) and social exchange with organization (SEWO) on the relationships between DMP and work outcomes of career satisfaction and turnover intention. Results of data obtained from a cross section of 191 minority employees in UK revealed: (i) the reasons why organisations adopted and implemented DMP influenced employees’ outcomes of turnover intention and career satisfaction; (ii) the relationship between diversity management and social exchange with organization is mediated by perception of overall justice; (iii) social exchange with organization relates to increased career satisfaction; and (iv) DMP related positively to career satisfaction through perception of overall justice and SEWO
Original article polymorphisms in CTNNBL1 in relation to colorectal cancer with evolutionary implications
Dynamical mean-field approach to materials with strong electronic correlations
We review recent results on the properties of materials with correlated
electrons obtained within the LDA+DMFT approach, a combination of a
conventional band structure approach based on the local density approximation
(LDA) and the dynamical mean-field theory (DMFT). The application to four
outstanding problems in this field is discussed: (i) we compute the full
valence band structure of the charge-transfer insulator NiO by explicitly
including the p-d hybridization, (ii) we explain the origin for the
simultaneously occuring metal-insulator transition and collapse of the magnetic
moment in MnO and Fe2O3, (iii) we describe a novel GGA+DMFT scheme in terms of
plane-wave pseudopotentials which allows us to compute the orbital order and
cooperative Jahn-Teller distortion in KCuF3 and LaMnO3, and (iv) we provide a
general explanation for the appearance of kinks in the effective dispersion of
correlated electrons in systems with a pronounced three-peak spectral function
without having to resort to the coupling of electrons to bosonic excitations.
These results provide a considerable progress in the fully microscopic
investigations of correlated electron materials.Comment: 24 pages, 14 figures, final version, submitted to Eur. Phys. J. for
publication in the Special Topics volume "Cooperative Phenomena in Solids:
Metal-Insulator Transitions and Ordering of Microscopic Degrees of Freedom
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