994 research outputs found
Modulation of Ca2+-dependent anion secretion by protein kinase C in normal and cystic fibrosis pancreatic duct cells
AbstractThe study investigated the role of protein kinase C (PKC) in the modulation of agonist-induced Ca2+-dependent anion secretion by pancreatic duct cells. The short-circuit current (ISC) technique was used to examine the effect of PKC activation and inhibition on subsequent ATP, angiotensin II and ionomycin-activated anion secretion by normal (CAPAN-1) and cystic fibrosis (CFPAC-1) pancreatic duct cells. The ISC responses induced by the Ca2+-mobilizing agents, which had been previously shown to be attributed to anion secretion, were enhanced in both CAPAN-1 and CFPAC-1 cells by PKC inhibitors, staurosporine, calphostin C or chelerythrine. On the contrary, a PKC activator, phorbol 12-myristate 13-acetate (PMA), was found to suppress the agonist-induced ISC in CFPAC-1 cells and the ionomycin-induced ISC in CAPAN-1 cells. An inactive form of PMA, 4αd-phorbol 12,13-didecanote (4αD), was found to exert insignificant effect on the agonist-induced ISC, indicating a specific effect of PMA. Our data suggest a role of PKC in modulating agonist-induced Ca2+-dependent anion secretion by pancreatic duct cells. Therapeutic strategy to augment Ca2+-activated anion secretion by cystic fibrosis pancreatic duct cells may be achieved by inhibition or down-regulation of PKC
Spin transport of electrons through quantum wires with spatially-modulated strength of the Rashba spin-orbit interaction
We study ballistic transport of spin-polarized electrons through quantum
wires in which the strength of the Rashba spin-orbit interaction (SOI) is
spatially modulated. Subband mixing, due to SOI, between the two lowest
subbands is taken into account. Simplified approximate expressions for the
transmission are obtained for electron energies close to the bottom of the
first subband and near the value for which anticrossing of the two lowest
subbands occurs. In structures with periodically varied SOI strength, {\it
square-wave} modulation on the spin transmission is found when only one subband
is occupied and its possible application to the spin transistor is discussed.
When two subbands are occupied the transmission is strongly affected by the
existence of SOI interfaces as well as by the subband mixing
Spin-filtering and charge- and spin-switching effects in a quantum wire with periodically attached stubs
Spin-dependent electron transport in a periodically stubbed quantum wire in
the presence of Rashba spin-orbit interaction (SOI) is studied via the
nonequilibrium Green's function method combined with the Landauer-Buttiker
formalism. The coexistence of spin filtering, charge and spin switching are
found in the considered system. The mechanism of these transport properties is
revealed by analyzing the total charge density and spin-polarized density
distributions in the stubbed quantum wire. Furthermore, periodic spin-density
islands with high polarization are also found inside the stubs, owing to the
interaction between the charge density islands and the Rashba SOI-induced
effective magnetic field. The proposed nanostructure may be utilized to devise
an all-electrical multifunctional spintronic device.Comment: 4 pages, 4 figure
Effects of yeast culture on broiler growth performance, nutrient digestibility and caecal microbiota
This study was conducted to evaluate the effects of yeast culture (YC) supplementation on the growth performance, apparent nutrient digestibility and caecal microflora of broiler chickens. A total of 360 one-day-old Arbor Acres broiler chickens were randomly assigned to six dietary treatments containing 0.2%, 0.4%, 0.6%, 0.8% and 1% YC. The experiment lasted for 42 days. Diet and faecal samples were collected for analysis of dry matter, crude protein, ether extract, calcium and phosphorus. Caecal microbiota on days 21 and 42 were measured using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and real-time PCR. Dietary supplementation with YC did not affect feed intake. On day 42, the 0.8% YC group showed optimal growth and feed efficiency, as well as higher levels of apparent digestibility of ether extract, calcium and phosphorus. On day 21, both 0.8% and 1% YC groups exhibited a significant increase in Ruminococcus, Propionibacterium clostridiales, and Bifidobacterium density. The density of Bacteroides in the YC groups was significantly higher than that of the control group. On day 42, the densities of Bacteroides, Sphingomonas and Bifidobacterium were higher in the 0.8% YC group, whereas a significant decrease was observed in the number of Enterobacteriaceae. These results serve as evidence that dietary supplementation with 0.8% YC not only moderately optimized the feed efficiency and the apparent digestibility of ether extract, calcium and phosphorus, but also positively influenced the caecal bacterial density and diversity in broiler chickens.Keywords: Arbor Acres broiler, caecal microflora, yeast culture supplementatio
Quantum State Reconstruction of Many Body System Based on Complete Set of Quantum Correlations Reduced by Symmetry
We propose and study a universal approach for the reconstruction of quantum
states of many body systems from symmetry analysis. The concept of minimal
complete set of quantum correlation functions (MCSQCF) is introduced to
describe the state reconstruction. As an experimentally feasible physical
object, the MCSQCF is mathematically defined through the minimal complete
subspace of observables determined by the symmetry of quantum states under
consideration. An example with broken symmetry is analyzed in detail to
illustrate the idea.Comment: 10 pages, n figures, Revte
The dihadron fragmentation function and its evolution
Dihadron fragmentation functions and their evolution are studied in the
process of annihilation. Under the collinear factorization
approximation and facilitated by the cut-vertex technique, the two hadron
inclusive cross section at leading order (LO) is shown to factorize into a
short distance parton cross section and a long distance dihadron fragmentation
function. We provide the definition of such a dihadron fragmentation function
in terms of parton matrix elements and derive its DGLAP evolution equation at
leading log. The evolution equation for the non-singlet quark fragmentation
function is solved numerically with a simple ansatz for the initial condition
and results are presented for cases of physical interest.Comment: 27 pages, 2 column, Revtex4, 21 figure
Calculating Quenching Weights
We calculate the probability (``quenching weight'') that a hard parton
radiates an additional energy fraction due to scattering in spatially extended
QCD matter. This study is based on an exact treatment of finite in-medium path
length, it includes the case of a dynamically expanding medium, and it extends
to the angular dependence of the medium-induced gluon radiation pattern. All
calculations are done in the multiple soft scattering approximation
(Baier-Dokshitzer-Mueller-Peign\'e-Schiff--Zakharov ``BDMPS-Z''-formalism) and
in the single hard scattering approximation (N=1 opacity approximation). By
comparison, we establish a simple relation between transport coefficient, Debye
screening mass and opacity, for which both approximations lead to comparable
results. Together with this paper, a CPU-inexpensive numerical subroutine for
calculating quenching weights is provided electronically. To illustrate its
applications, we discuss the suppression of hadronic transverse momentum
spectra in nucleus-nucleus collisions. Remarkably, the kinematic constraint
resulting from finite in-medium path length reduces significantly the
transverse momentum dependence of the nuclear modification factor, thus leading
to consistency with the data measured at the Relativistic Heavy Ion Collider
(RHIC).Comment: 45 pages LaTeX, 20 eps-figure
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The roles of sulfuric acid in new particle formation and growth in the mega-city of Beijing
Simultaneous measurements of gaseous sulfuric acid and particle number size distributions were performed to investigate aerosol nucleation and growth during CAREBeijing-2008. The analysis of the measured aerosols and sulfuric acid with an aerosol dynamic model shows the dominant role of sulfuric acid in new particle formation (NPF) process but also in the subsequent growth in Beijing. Based on the data of twelve NPF events, the average formation rates (2–13 cm−3 s−1) show a linear correlation with the sulfuric acid concentrations (R2=0.85). Coagulation seems to play a significant role in reducing the number concentration of nucleation mode particles with the ratio of the coagulation loss to formation rate being 0.41±0.16. The apparent growth rates vary from 3 to 11 nm h−1. Condensation of sulfuric acid and its subsequent neutralization by ammonia and coagulation contribute to the apparent particle growth on average 45±18% and 34±17%, respectively. The 30% higher concentration of sulfate than organic compounds in particles during the seven sulfur-rich NPF events but 20% lower concentration of sulfate during the five sulfur-poor type suggest that organic compounds are an important contributor to the growth of the freshly nucleated particles, especially during the sulfur-poor cases
A novel size independent symplectic analytical singular element for inclined crack terminating at bimaterial interface
Cracks often exist in composite structures, especially at the interface of two different materials. These cracks can significantly affect the load bearing capacity of the structure and lead to premature failure of the structure. In this paper, a novel element for modeling the singular stress state around the inclined interface crack which terminates at the interface is developed. This new singular element is derived based on the explicit form of the high order eigen solution which is, for the first time, determined by using a symplectic approach. The developed singular element is then applied in finite element analysis and the stress intensity factors (SIFs) for a number of crack configurations are derived. It has been concluded that composites with complex geometric configurations of inclined interface cracks can be accurately simulated by the developed method, according to comparison of the results against benchmarks. It has been found that the stiffness matrix of the proposed singular element is independent of the element size and the SIFs of the crack can be solved directly without any post-processing
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