197 research outputs found
Dynamics of a driven probe molecule in a liquid monolayer
We study dynamics of a probe molecule, driven by an external constant force
in a liquid monolayer on top of solid surface. In terms of a microscopic,
mean-field-type approach, we calculate the terminal velocity of the probe
molecule. This allows us to establish the analog of the Stokes formula, in
which the friction coefficient is interpreted in terms of the microscopic
parameters characterizing the system. We also determine the distribution of the
monolayer particles as seen from the stationary moving probe molecule and
estimate the self-diffusion coefficient for diffusion in a liquid monolayer.Comment: Latex, 7 pages, 1 figur
Selenoprotein gene expression in an intestinal cell line during selenium depletion: a macroarray approach indicates effects on SelW and glutathione peroxidise 1.
The micronutrient selenium (Se) is incoprprated into a renage of selenoproteins involved in numerous biochemical processes within the body
Molecular Weight Dependence of Spreading Rates of Ultrathin Polymeric Films
We study experimentally the molecular weight dependence of spreading
rates of molecularly thin precursor films, growing at the bottom of droplets of
polymer liquids. In accord with previous observations, we find that the radial
extension R(t) of the film grows with time as R(t) = (D_{exp} t)^{1/2}. Our
data substantiate the M-dependence of D_{exp}; we show that it follows D_{exp}
\sim M^{-\gamma}, where the exponent \gamma is dependent on the chemical
composition of the solid surface, determining its frictional properties with
respect to the molecular transport. In the specific case of hydrophilic
substrates, the frictional properties can be modified by the change of the
relative humidity (RH). We find that \gamma \approx 1 at low RH and tends to
zero when RH gets progressively increased. We propose simple theoretical
arguments which explain the observed behavior in the limits of low and high RH.Comment: 4 pages, 2 figures, to appear in PR
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Efficient Laser-Induced 6 - 8 KeV X-Ray Production From Iron Oxide Aerogel and Foil-Lined Cavity Targets
Efficient laser-induced 6-8 keV x-ray production from iron oxide aerogel and foil-lined cavity targets
The effects of transurethral resection and cystoprostatectomy on dissemination of epithelial cells in the circulation of patients with bladder cancer
This study was undertaken to evaluate the risk of haematogenous dissemination of epithelial cells induced by endoscopic resection and/or cystoprostatectomy for transitional cell carcinoma of the bladder. Thirty-three patients were studied. Thirty-one had different stages and grades of bladder cancer and two patients had benign bladder conditions. Twenty-five cancer patients required transurethral resection of their bladder tumour. Of those, 20 had superficial disease (pTaG1–G2: n = 19; pT1G2: n = 1) and five had muscle invasive tumours (pT2G3: n = 2; pT3aG3: n = 1; pT4G3: n = 2). Five patients underwent radical cystoprostatectomy for muscle invasive cancers (pT2G3: n = 3; pT3bG3: n = 1; pT4G3: n = 1) and one man received chemotherapy for metastatic disease. Venous blood (10 ml) was obtained from the antecubital fossa in each patient, before and 1–2 h after completion of surgery, and prior to treatment in the metastatic patient. An indirect immunocytochemical technique was used to detect circulating epithelial cells after centrifugation on Ficoll gradient and fixation of mononuclear cells on slides, using a monoclonal antibody directed against three cytokeratins: CK8, CK18 and CK19. Circulating epithelial cells were detected only in the patient with metastatic disease. None of the other patients had evidence of epithelial circulating cells before or after surgery. The results suggest that irrespective of disease stage and grade, neither endoscopic nor open bladder surgery leads to detectable dissemination of urothelial cells in the peripheral circulation. These procedures are therefore unlikely to increase the risk of progression and metastasis in transitional cell carcinoma of the bladder. © 1999 Cancer Research Campaig
Theoretical and experimental activities on opacities for a good interpretation of seismic stellar probes
Opacity calculations are basic ingredients of stellar modelling. They play a
crucial role in the interpretation of acoustic modes detected by SoHO, COROT
and KEPLER. In this review we present our activities on both theoretical and
experimental sides. We show new calculations of opacity spectra and comparisons
between eight groups who produce opacity spectra calculations in the domain
where experiments are scheduled. Real differences are noticed with real
astrophysical consequences when one extends helioseismology to cluster studies
of different compositions. Two cases are considered presently: (1) the solar
radiative zone and (2) the beta Cephei envelops. We describe how our
experiments are performed and new preliminary results on nickel obtained in the
campaign 2010 at LULI 2000 at Polytechnique.Comment: 6 pages, 4 figures, invited talk at SOHO2
Computational Study of Hippocampal-Septal Theta Rhythm Changes Due to Beta-Amyloid-Altered Ionic Channels
Electroencephagraphy (EEG) of many dementia patients has been characterized by an increase in low frequency field potential oscillations. One of the characteristics of early stage Alzheimer’s disease (AD) is an increase in theta band power (4–7 Hz). However, the mechanism(s) underlying the changes in theta oscillations are still unclear. To address this issue, we investigate the theta band power changes associated with β-Amyloid (Aβ) peptide (one of the main markers of AD) using a computational model, and by mediating the toxicity of hippocampal pyramidal neurons. We use an established biophysical hippocampal CA1-medial septum network model to evaluate four ionic channels in pyramidal neurons, which were demonstrated to be affected by Aβ. They are the L-type Ca2+ channel, delayed rectifying K+ channel, A-type fast-inactivating K+ channel and large-conductance Ca2+-activated K+ channel. Our simulation results demonstrate that only the Aβ inhibited A-type fast-inactivating K+ channel can induce an increase in hippocampo-septal theta band power, while the other channels do not affect theta rhythm. We further deduce that this increased theta band power is due to enhanced synchrony of the pyramidal neurons. Our research may elucidate potential biomarkers and therapeutics for AD. Further investigation will be helpful for better understanding of AD-induced theta rhythm abnormalities and associated cognitive deficits
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