454 research outputs found
Chern numbers for two families of noncommutative Hopf fibrations
We consider noncommutative line bundles associated with the Hopf fibrations
of SUq(2) over all Podles spheres and with a locally trivial Hopf fibration of
S^3_{pq}. These bundles are given as finitely generated projective modules
associated via 1-dimensional representations of U(1) with Galois-type
extensions encoding the principal fibrations of SUq(2) and S^3_{pq}. We show
that the Chern numbers of these modules coincide with the winding numbers of
representations defining them.Comment: 6 page
Enantiomerically pure β-phenylalanine analogues from α–β-phenylalanine mixtures in a single reactive extraction step
An efficient and selective method for the extraction of α-amino acids in preference over their β-isomers using PdCl2(PPh3)2 was discovered, which enables the separation of product mixtures obtained in the enantioselective enzymatic formation of β-amino acids.
One pot ‘click’ reactions: tandem enantioselective biocatalytic epoxide ring opening and [3+2] azide alkyne cycloaddition
Halohydrin dehalogenase (HheC) can perform enantioselective azidolysis of aromatic epoxides to 1,2-azido alcohols which are subsequently ligated to alkynes producing chiral hydroxy triazoles in a one-pot procedure with excellent enantiomeric excess.
Modified polysaccharides as alternative binders for foundry industry
Polysaccharides constitute a wide group of important polymers with many commercial applications, for example food packaging, fibres, coatings, adhesives etc. This review is devoted to the presentation of polysaccharide application in foundry industry. In this paper the selected properties of foundry moulding sand and core sand containing modified polysaccharides as binders are presented according to foreign literature data. Also, author’s own research about effect of using moulding sand binder consisting of modified polysaccharide (modified starch) or its composition with non-toxic synthetic polymers are discussed. Based on technologies taken under consideration in this paper, it could be concluded that polysaccharides are suitable as an alternative for use as binder in foundry moulding applications
Intermediate valence of CeNi2Al3 compound and its evidences: Theoretical and experimental approach
We present measurements of magnetic, transport and electronic properties obtained for polycrystalline CeNi2Al3
intermetallic compound. Magnetic susceptibility χ(T) was investigated in the range from 2 to 700 K, and its
behavior is characteristic of a compound with unstable valence, varying between Ce3þ and Ce4þ. In the temperature
range down to 2 K there was no trace of magnetic order, no anomalies in the temperature dependence of
the specific heat were found. The Sommerfeld coefficient extracted from the linear term of the heat capacity
takes a value of γ ¼ 21 mJ/(mol K2). The dependence of S(T) is linear up to about 25 K, which is symptomatic of
a thermopower in the Fermi’s liquid regime.
The structure of satellites in the Ce(3d) electron spectrum obtained by the X-ray photoelectron spectroscopy
(XPS) method indicates that the states of Ce(4f) are of mixed valence character. Analysis of Ce(3d) states based
on Gunnarsson-Sch€onhammer theory shows that the energy of hybridization of Ce(4f) states with a conduction
band is about 78 meV. For more detailed information about electronic states the fully relativistic band structure
was calculated within the density functional theory (DFT) for the first time. Below Fermi’s energy, the density of
states is mainly formed by Ni(3d) states hybridized with Ce(4f) ones
Interface Mixing in Fe/Si Multilayers Observed by the In Situ Conductance Measurements
In this contribution the in situ conductance vs. deposition time dependences of Fe/Si multilayers are analysed. The plot of resistance multiplied by the square of the thickness as a function of iron thickness shows that during the iron deposition initially amorphous-like Fe-Si mixture is formed, next the mixture crystallises, and finally bcc-Fe phase appears. The interface mixing is also manifested by the reduction of the total multilayer thickness measured by small angle X-ray diffraction
Planetary Detection Efficiency of the Magnification 3000 Microlensing Event OGLE-2004-BLG-343
OGLE-2004-BLG-343 was a microlensing event with peak magnification
A_{max}=3000+/-1100, by far the highest-magnification event ever analyzed and
hence potentially extremely sensitive to planets orbiting the lens star. Due to
human error, intensive monitoring did not begin until 43 minutes after peak, at
which point the magnification had fallen to A~1200, still by far the highest
ever observed. As the light curve does not show significant deviations due to a
planet, we place upper limits on the presence of such planets by extending the
method of Yoo et al. (2004b), which combines light-curve analysis with priors
from a Galactic model of the source and lens populations, to take account of
finite-source effects. This is the first event so analyzed for which
finite-source effects are important, and hence we develop two new techniques
for evaluating these effects. Somewhat surprisingly, we find that
OGLE-2004-BLG-343 is no more sensitive to planets than two previously analyzed
events with A_{max}~100, despite the fact that it was observed at ~12 times
higher magnification. However, we show that had the event been observed over
its peak, it would have been sensitive to almost all Neptune-mass planets over
a factor of 5 of projected separation and even would have had some sensitivity
to Earth-mass planets. This shows that some microlensing events being detected
in current experiments are sensitive to very low-mass planets. We also give
suggestions on how extremely high-magnification events can be more promptly
monitored in the future.Comment: 50 pages, 13 figures, published in The Astrophysical Journa
First Space-based Microlens Parallax Measurement of an Isolated Star: Spitzer Observations of OGLE-2014-BLG-0939
We present the first space-based microlens parallax measurement of an
isolated star. From the striking differences in the lightcurve as seen from
Earth and from Spitzer (~1 AU to the West), we infer a projected velocity
v_helio,projected ~ 250 km/s, which strongly favors a lens in the Galactic Disk
with mass M=0.23 +- 0.07 M_sun and distance D_L=3.1 +- 0.4 kpc. An ensemble of
such measurements drawn from our ongoing program could be used to measure the
single-lens mass function including dark objects, and also is necessary for
measuring the Galactic distribution of planets since the ensemble reflects the
underlying Galactic distribution of microlenses. We study the application of
the many ideas to break the four-fold degeneracy first predicted by Refsdal 50
years ago. We find that this degeneracy is clearly broken, but by two
unanticipated mechanisms.Comment: 26 pages, 3 figures, submitted to Ap
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