181 research outputs found
Cryogenic propellant venting under low pressure conditions final report
Cryogenic propellant venting under low pressure conditions - heat-transfer coefficients for two- phase, single component, solid-gas mixture flow in short, vertical tub
Angular Distribution of -rays from Neutron-Induced Compound States of La
Angular distribution of individual -rays, emitted from a
neutron-induced compound nuclear state via radiative capture reaction of
La(n,) has been studied as a function of incident neutron
energy in the epithermal region by using germanium detectors.
An asymmetry was defined as , where and
are integrals of low and high energy region of a neutron resonance
respectively, and we found that has the angular dependence of
, where is emitted angle of
-rays, with and in 0.74 eV
p-wave resonance.
This angular distribution was analyzed within the framework of interference
between s- and p-wave amplitudes in the entrance channel to the compound
nuclear state, and it is interpreted as the value of the partial p-wave neutron
width corresponding to the total angular momentum of the incident neutron
combined with the weak matrix element, in the context of the mechanism of
enhanced parity-violating effects. Additionally we used the result to quantify
the possible enhancement of the breaking of the time-reversal invariance in the
vicinity of the p-wave resonance.Comment: 14pages, 25 figure
Coupling biochemistry and mechanics in cell adhesion: a model for inhomogeneous stress fiber contraction
Biochemistry and mechanics are closely coupled in cell adhesion. At sites of
cell-matrix adhesion, mechanical force triggers signaling through the
Rho-pathway, which leads to structural reinforcement and increased
contractility in the actin cytoskeleton. The resulting force acts back to the
sites of adhesion, resulting in a positive feedback loop for mature adhesion.
Here we model this biochemical-mechanical feedback loop for the special case
when the actin cytoskeleton is organized in stress fibers, which are
contractile bundles of actin filaments. Activation of myosin II molecular
motors through the Rho-pathway is described by a system of reaction-diffusion
equations, which are coupled into a viscoelastic model for a contractile actin
bundle. We find strong spatial gradients in the activation of contractility and
in the corresponding deformation pattern of the stress fiber, in good agreement
with experimental findings.Comment: Revtex, 35 pages, 13 Postscript figures included, in press with New
Journal of Physics, Special Issue on The Physics of the Cytoskeleto
Electronic, vibrational and transport properties of pnictogen substituted ternary skutterudites
First principles calculations are used to investigate electronic band
structure and vibrational spectra of pnictogen substituted ternary
skutterudites. We compare the results with the prototypical binary composition
CoSb to identify the effects of substitutions on the Sb site, and evaluate
the potential of ternary skutterudites for thermoelectric applications.
Electronic transport coefficients are computed within the Boltzmann transport
formalism assuming a constant relaxation time, using a new methodology based on
maximally localized Wannier function interpolation. Our results point to a
large sensitivity of the electronic transport coefficients to carrier
concentration and to scattering mechanisms associated with the enhanced
polarity. The ionic character of the bonds is used to explain the detrimental
effect on the thermoelectric properties
Perforating eyelid injury extending to the brain stem in a 17-year-old woman: a case report
Long-term effects of amphetamine neurotoxicity on tyrosine hydroxylase mRNA and protein in aged rats
ABSTRACT Four injections (intraperitoneal) of 3 mg/kg amphetamine (2 hr apart) produced pronounced hyperthermia and sustained decreases in dopamine levels and tyrosine hydroxylase (TH) protein levels in the striatum of 15-month-old male rats. A partial recovery of striatal dopamine levels was observed at 4 months after amphetamine. In contrast, TH mRNA and TH protein levels in the midbrain were unaffected at all time points tested up to 4 months after amphetamine treatment. The number of THimmunopositive cells in the midbrain was also unchanged at 4 months after amphetamine, even though the number of THpositive axons in the striatum remained dramatically decreased at this time point. Interestingly, TH-immunopositive cell bodies were observed 4 months after amphetamine in the lateral caudate/putamen, defined anteriorly by the genu of the corpus collosum and posteriorly by the junction of the anterior commissures; these striatal TH-positive cells were not observed in saline-or amphetamine-treated rats that did not become hyperthermic. In addition, low levels (orders of magnitude lower than that present in the midbrain) of TH mRNA were detected using reverse transcription-polymerase chain reaction in the striatum of these amphetamine-treated rats. Our results suggest that even though there is a partial recovery of striatal dopamine levels, which occurs within 4 months after amphetamine treatment, this recovery is not associated with increased TH gene expression in the midbrain. Furthermore, new THpositive cells are generated in the striatum at this 4-month time point
Anel de tensão capsular isolado e associado à lente intraocular acrílica dobrável na opacidade de cápsula posterior após facoemulsificação em cães
Chitosan encapsulation modulates the effect of capsaicin on the tight junctions of MDCK cells
Capsaicin has known pharmacological effects including the ability to reversibly open cellular tight junctions, among others. The aim of this study was to develop a strategy to enhance the paracellular transport of a substance with low permeability (FITC-dextran) across an epithelial cell monolayer via reversible opening of cellular tight junctions using a nanosystem comprised by capsaicin and of chitosan. We compared the biophysical properties of free capsaicin and capsaicin-loaded chitosan nanocapsules, including their cytotoxicity towards epithelial MDCK-C7 cells and their effect on the integrity of tight junctions, membrane permeability and cellular uptake. The cytotoxic response of MDCK-C7 cells to capsaicin at a concentration of 500 μM, which was evident for the free compound, is not observable following its encapsulation. The interaction between nanocapsules and the tight junctions of MDCK-C7 cells was investigated by impedance spectroscopy, digital holographic microscopy and structured illumination fluorescence microscopy. The nanocapsules modulated the interaction between capsaicin and tight junctions as shown by the different time profile of trans-epithelial electrical resistance and the enhanced permeability of monolayers incubated with FITC-dextran. Structured illumination fluorescence microscopy showed that the nanocapsules were internalized by MDCK-C7 cells. The capsaicin-loaded nanocapsules could be further developed as drug nanocarriers with enhanced epithelial permeability
Haloperidol differentially modulates prepulse inhibition and p50 suppression in healthy humans stratified for low and high gating levels
Schizophrenia patients exhibit deficits in sensory gating as indexed by reduced prepulse inhibition (PPI) and P50 suppression, which have been linked to psychotic symptom formation and cognitive deficits. Although recent evidence suggests that atypical antipsychotics might be superior over typical antipsychotics in reversing PPI and P50 suppression deficits not only in schizophrenia patients, but also in healthy volunteers exhibiting low levels of PPI, the impact of typical antipsychotics on these gating measures is less clear. To explore the impact of the dopamine D2-like receptor system on gating and cognition, the acute effects of haloperidol on PPI, P50 suppression, and cognition were assessed in 26 healthy male volunteers split into subgroups having low vs high PPI or P50 suppression levels using a placebo-controlled within-subject design. Haloperidol failed to increase PPI in subjects exhibiting low levels of PPI, but attenuated PPI in those subjects with high sensorimotor gating levels. Furthermore, haloperidol increased P50 suppression in subjects exhibiting low P50 gating and disrupted P50 suppression in individuals expressing high P50 gating levels. Independently of drug condition, high PPI levels were associated with superior strategy formation and execution times in a subset of cognitive tests. Moreover, haloperidol impaired spatial working memory performance and planning ability. These findings suggest that dopamine D2-like receptors are critically involved in the modulation of P50 suppression in healthy volunteers, and to a lesser extent also in PPI among subjects expressing high sensorimotor gating levels. Furthermore, the results suggest a relation between sensorimotor gating and working memory performance
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