125 research outputs found
Air flow conditions in workspace of mulcher
ArticleCurrently, there has been a great effort on increasing the efficiency of agricultural
machinery. The energy demands of mulching with the
vertical
axis of rotation
depends
on the
amount
of pr
ocessed material per unit of time, its properties and efficiency of material processing.
Another
important
factor that is affecting the overall energy demands is the energy losses, which
can be even higher than energy, required
for
the processing of materi
al.
The efficiency
of the
material processing and the energy losses
are influenced
to a large extent by the air flow inside
the mulcher workspace, which
is created
by the movement of working tools. The air flow ensures
the repeated contact of the processed
material with the working tools, affects the energy losses
and the quality of work. The contribution deals with the air flow conditions inside the workspace
of mulcher with the
vertical
axis of rotation. The velocity of the
air flow
was measured
my
means
of LDA (Laser Doppler Anemometry) method in three planes above the surface (180, 100 and
20
mm
) and
in
two directions (peripheral and radial). The laboratory model of one mulcher rotor
from mulcher MZ 6000 made by BEDNAR Ltd. company
was used
for the measu
rement. From
the
results
it is evident that the maximum values of peripheral velocity of the air flow reach
approx. 50% of the velocity of the tools. In the radial
plane
an air vortex is created between 20
and 100
mm
planes above the surface around the tip
of the blade
Markers of thrombogenesis are activated in unmedicated patients with acute psychosis: a matched case control study
<p>Abstract</p> <p>Background</p> <p>Antipsychotic treatment has been repeatedly found to be associated with an increased risk for venous thromboembolism in schizophrenia. The extent to which the propensity for venous thromboembolism is linked to antipsychotic medication alone or psychosis itself is unclear. The objective of this study was to determine whether markers of thrombogenesis are increased in psychotic patients who have not yet been treated with antipsychotic medication.</p> <p>Methods</p> <p>We investigated the plasma levels of markers indicating activation of coagulation (D-dimers and Factor VIII) and platelets (soluble P-selectin, sP-selectin) in an antipsychotic-naive group of fourteen men and eleven women with acute psychosis (age 29.1 ± 8.3 years, body mass index 23.6 ± 4.7), and twenty-five healthy volunteers were matched for age, gender and body mass index.</p> <p>Results</p> <p>D-dimers (median 0.38 versus 0.19 mg/l, mean 1.12 ± 2.38 versus 0.28 ± 0.3 mg/l; P = 0.003) and sP-selectin (median 204.1 versus 112.4 ng/ml, mean 209.9 ± 124 versus 124.1 ± 32; P = 0.0005) plasma levels were significantly increased in the group of patients with acute psychosis as compared with healthy volunteers. We found a trend (median 148% versus 110%, mean 160 ± 72.5 versus 123 ± 62.5; P = 0.062) of increased plasma levels of factor VIII in psychotic patients as compared with healthy volunteers.</p> <p>Conclusions</p> <p>The results suggest that at least a part of venous thromboembolic events in patients with acute psychosis may be induced by pathogenic mechanisms related to psychosis rather than by antipsychotic treatment. Finding an exact cause for venous thromboembolism in psychotic patients is necessary for its effective treatment and prevention.</p
Exciton spin dynamics in spherical CdS quantum dots
Exciton spin dynamics in quasi-spherical CdS quantum dots is studied in
detail experimentally and theoretically. Exciton states are calculated using
the 6-band k.p Hamiltonian. It is shown that for various sets of Luttinger
parameters, when the wurtzite lattice crystal field splitting and Coulomb
interaction between the electron-hole pair are taken into account exactly, both
the electron and hole wavefunction in the lowest exciton state are of S-type.
This rules out the spatial-symmetry-induced origin of the dark exciton in CdS
quantum dots. The exciton bleaching dynamics is studied using time- and
polarization-resolved transient absorption technique of ultrafast laser
spectroscopy. Several samples with a different mean size of CdS quantum dots in
different glass matrices were investigated. This enabled the separation of
effects that are typical for one particular sample from those that are general
for this type of material. The experimentally determined dependence of the
electron spin relaxation rate on the radius of quantum dots agrees well with
that computed theoretically.Comment: 24 pages, 10 figure
Experimental observation of the optical spin transfer torque
The spin transfer torque is a phenomenon in which angular momentum of a spin
polarized electrical current entering a ferromagnet is transferred to the
magnetization. The effect has opened a new research field of electrically
driven magnetization dynamics in magnetic nanostructures and plays an important
role in the development of a new generation of memory devices and tunable
oscillators. Optical excitations of magnetic systems by laser pulses have been
a separate research field whose aim is to explore magnetization dynamics at
short time scales and enable ultrafast spintronic devices. We report the
experimental observation of the optical spin transfer torque, predicted
theoretically several years ago building the bridge between these two fields of
spintronics research. In a pump-and-probe optical experiment we measure
coherent spin precession in a (Ga,Mn)As ferromagnetic semiconductor excited by
circularly polarized laser pulses. During the pump pulse, the spin angular
momentum of photo-carriers generated by the absorbed light is transferred to
the collective magnetization of the ferromagnet. We interpret the observed
optical spin transfer torque and the magnetization precession it triggers on a
quantitative microscopic level. Bringing the spin transfer physics into optics
introduces a fundamentally distinct mechanism from the previously reported
thermal and non-thermal laser excitations of magnets. Bringing optics into the
field of spin transfer torques decreases by several orders of magnitude the
timescales at which these phenomena are explored and utilized.Comment: 11 pages, 4 figure
Experimental observation of the optical spin-orbit torque
Spin polarized carriers electrically injected into a magnet from an external
polarizer can exert a spin transfer torque (STT) on the magnetization. The phe-
nomenon belongs to the area of spintronics research focusing on manipulating
magnetic moments by electric fields and is the basis of the emerging
technologies for scalable magnetoresistive random access memories. In our
previous work we have reported experimental observation of the optical
counterpart of STT in which a circularly polarized pump laser pulse acts as the
external polarizer, allowing to study and utilize the phenomenon on several
orders of magnitude shorter timescales than in the electric current induced
STT. Recently it has been theoretically proposed and experimentally
demonstrated that in the absence of an external polarizer, carriers in a magnet
under applied electric field can develop a non-equilibrium spin polarization
due to the relativistic spin-orbit coupling, resulting in a current induced
spin-orbit torque (SOT) acting on the magnetization. In this paper we report
the observation of the optical counterpart of SOT. At picosecond time-scales,
we detect excitations of magnetization of a ferromagnetic semiconductor
(Ga,Mn)As which are independent of the polarization of the pump laser pulses
and are induced by non-equilibrium spin-orbit coupled photo-holes.Comment: 4 figure, supplementary information. arXiv admin note: text overlap
with arXiv:1101.104
On non-local variational problems with lack of compactness related to non-linear optics
We give a simple proof of existence of solutions of the dispersion manage-
ment and diffraction management equations for zero average dispersion,
respectively diffraction. These solutions are found as maximizers of non-linear
and non-local vari- ational problems which are invariant under a large
non-compact group. Our proof of existence of maximizer is rather direct and
avoids the use of Lions' concentration compactness argument or Ekeland's
variational principle.Comment: 30 page
Towards a unified theory of Sobolev inequalities
We discuss our work on pointwise inequalities for the gradient which are
connected with the isoperimetric profile associated to a given geometry. We
show how they can be used to unify certain aspects of the theory of Sobolev
inequalities. In particular, we discuss our recent papers on fractional order
inequalities, Coulhon type inequalities, transference and dimensionless
inequalities and our forthcoming work on sharp higher order Sobolev
inequalities that can be obtained by iteration.Comment: 39 pages, made some changes to section 1
Regularity of Infinity for Elliptic Equations with Measurable Coefficients and Its Consequences
This paper introduces a notion of regularity (or irregularity) of the point
at infinity for the unbounded open subset of \rr^{N} concerning second order
uniformly elliptic equations with bounded and measurable coefficients,
according as whether the A-harmonic measure of the point at infinity is zero
(or positive). A necessary and sufficient condition for the existence of a
unique bounded solution to the Dirichlet problem in an arbitrary open set of
\rr^{N}, N\ge 3 is established in terms of the Wiener test for the regularity
of the point at infinity. It coincides with the Wiener test for the regularity
of the point at infinity in the case of Laplace equation. From the topological
point of view, the Wiener test at infinity presents thinness criteria of sets
near infinity in fine topology. Precisely, the open set is a deleted
neigborhood of the point at infinity in fine topology if and only if infinity
is irregular.Comment: 20 page
Plasma proteome changes in cardiovascular disease patients: novel isoforms of apolipoprotein A1
<p>Abstract</p> <p>Background</p> <p>The aim of this proteomic study was to look for changes taking place in plasma proteomes of patients with acute myocardial infarction (AMI), unstable angina pectoris (UAP), and stable angina pectoris (SAP).</p> <p>Methods</p> <p>Depleted plasma proteins were separated by 2D SDS-PAGE (pI 4-7), and proteomes were compared using Progenesis SameSpots statistical software. Proteins were identified by nanoLC-MS/MS. Proteins were quantified using commercial kits. Apolipoprotein A1 was studied using 1D and 2D SDS-PAGE, together with western blotting.</p> <p>Results</p> <p>Reciprocal comparison revealed 46 unique, significantly different spots; proteins in 34 spots were successfully identified and corresponded to 38 different proteins. Discrete comparisons of patient groups showed 45, 41, and 8 significantly different spots when AMI, UAP, and SAP were compared with the control group. On the basis of our proteomic data, plasma levels of two of them, alpha-1 microglobulin and vitamin D-binding protein, were determined. The data, however, failed to prove the proteins to be suitable markers or risk factors in the studied groups. The plasma level and isoform representation of apolipoprotein A1 were also estimated. Using 1D and 2D SDS-PAGE, together with western blotting, we observed extra high-molecular weight apolipoprotein A1 fractions presented only in the patient groups, indicating that the novel high-molecular weight isoforms of apolipoprotein A1 may be potential new markers or possible risk factors of cardiovascular disease.</p> <p>Conclusion</p> <p>The reported data show plasma proteome changes in patients with AMI, UAP, and SAP. We propose some apolipoprotein A1 fractions as a possible new disease-associated marker of cardiovascular disorders.</p
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