2,105 research outputs found
Critical State Flux Penetration and Linear Microwave Vortex Response in YBa_2Cu_3O_{7-x} Films
The vortex contribution to the dc field (H) dependent microwave surface
impedance Z_s = R_s+iX_s of YBa_2Cu_3O_{7-x} thin films was measured using
suspended patterned resonators. Z_s(H) is shown to be a direct measure of the
flux density B(H) enabling a very precise test of models of flux penetration.
Three regimes of field-dependent behavior were observed: (1) Initial flux
penetration occurs on very low field scales H_i(4.2K) 100Oe, (2) At moderate
fields the flux penetration into the virgin state is in excellent agreement
with calculations based upon the field-induced Bean critical state for thin
film geometry, parametrized by a field scale H_s(4.2K) J_c*d 0.5T, (3) for very
high fields H >>H_s, the flux density is uniform and the measurements enable
direct determination of vortex parameters such as pinning force constants
\alpha_p and vortex viscosity \eta. However hysteresis loops are in
disagreement with the thin film Bean model, and instead are governed by the low
field scale H_i, rather than by H_s. Geometric barriers are insufficient to
account for the observed results.Comment: 20 pages, LaTeX type, Uses REVTeX style files, Submitted to Physical
Review B, 600 dpi PostScript file with high resolution figures available at
http://sagar.physics.neu.edu/preprints.htm
Designer lipid-like peptides
A crucial bottleneck in membrane protein studies, particularly G-protein coupled receptors, is the notorious difficulty of finding an optimal detergent that can solubilize them and maintain their stability and function. Here we report rapid production of 12 unique mammalian olfactory receptors using short designer lipid-like peptides as detergents. The peptides were able to solubilize and stabilize each receptor. Circular dichroism showed that the purified olfactory receptors had alpha-helical secondary structures. Microscale thermophoresis suggested that the receptors were functional and bound their odorants. Blot intensity measurements indicated that milligram quantities of each olfactory receptor could be produced with at least one peptide detergent. The peptide detergents' capability was comparable to that of the detergent Brij-35. The ability of 10 peptide detergents to functionally solubilize 12 olfactory receptors demonstrates their usefulness as a new class of detergents for olfactory receptors, and possibly other G-protein coupled receptors and membrane proteins
Long-term marsh growth and retreat in an online coupled hydrodynamic, morphodynamic and ecological model
C-axis Penetration Depth and Inter-layer Conductivity in the Thallium Based Cuprate Superconductors
The c-axis Josephson plasmon in optimally doped single-layer and bi-layer
high Tc cuprates Tl2201 and Tl2212 have been investigated using infrared
spectroscopy. We observed the plasma frequencies for these two compounds at
27.8 and 25.6 cm-1 respectively, which we interpret as a Josephson resonance
across the TlO blocking layers. No maximum in the temperature dependence of the
c-axis conductivity was observed below Tc, indicating that even in the
superconducting state a coherent quasi-particle contribution to the c-axis
conductivity is absent or very weak, in contrast to the behaviour of the
ab-plane conductivity.Comment: 4 pages, 3 figure
Paternal age and first trimester placental size and growth:The Rotterdam Periconceptional Cohort
Introduction: Despite a noticeable trend of delayed fatherhood, less is known about the impact of paternal age on the paternally programmed placenta. We hypothesize that paternal aging affects seminal quality and as such induces ageing-related epigenetic alterations that influence placental growth. Our main aim is to investigate associations between paternal age and first trimester (vascular) placental growth trajectories. Methods: Pregnant women were enrolled before 10 weeks of gestation in the Rotterdam Periconceptional Cohort (Predict study). Placental volumes (PV) and utero-placental vascular volumes (uPVV) were measured at 7, 9, and 11 weeks gestation. Associations between paternal age and PV and uPVV were investigated using linear mixed models and the maximum likelihood ratio test to test non-linear relationships. We adjusted for gestational age, fetal sex, parental smoking and maternal age, BMI, education and parity, and stratified for conception mode. Results: From 808 pregnancies we obtained 1313 PV and from 183 pregnancies 345 uPVV measurements. We show no associations between paternal age and PV (p = 0.934) and uPVV (p = 0.489) in our total population or in pregnancies conceived naturally (PV p = 0.166; uPVV p = 0.446) and after IVF/ICSI (PV p = 0.909; uPVV p = 0.749). For example, PV was 0.9% smaller (95% CI -5.7%—7.1%) in fathers aged 40 compared to 30 years old at 9 weeks gestation in the total study population. Discussion: We are not demonstrating a significant impact of paternal age on first trimester placental growth in a tertiary care population. Given the trend of increasing paternal age, our study should be repeated in the general population.</p
Hepatic lipase is localized at the parenchymal cell microvilli in rat liver
Hepatic lipase (HL) is thought to be located at the vascular endothelium
in the liver. However, it has also been implicated in the binding and
internalization of chylomicron remnants in the parenchymal cells. In view
of this apparent discrepancy between localization and function, we
re-investigated the localization of HL in rat liver using biochemical and
immunohistochemical techniques. The binding of HL to endothelial cells was
studied in primary cultures of rat liver endothelial cells. Endothelial
cells bound HL in a saturable manner with high affinity. However, the
binding capacity accounted for at most 1% of the total HL activity present
in the whole liver. These results contrasted with earlier studies, in
which non-parenchymal cell (NPC) preparations had been found to bind HL
with a high capacity. To study HL binding to the different components of
the NPC preparations, we separated endothelial cells, Kupffer cells and
blebs by counterflow elutriation. Kupffer cells and endothelial cells
showed a relatively low HL-binding capacity. In contrast, the blebs,
representing parenchymal-cell-derived material, had a high HL-binding
capacity (33 m-units/mg of protein) and accounted for more than 80% of the
total HL binding in the NPC preparation. In contrast with endothelial and
Kupffer cells, the HL-binding capacity of parenchymal cells could account
for almost all the HL activity found in the whole liver. These data
strongly suggest that HL binding occurs at parenchymal liver cells. To
confirm this conclusion in situ, we studied HL localization by
immunocytochemical techniques. Using immunofluorescence, we confirmed the
sinusoidal localization of HL. Immunoelectron microscopy demonstrated that
virtually all HL was located at the microvilli of parenchymal liver cells,
with a minor amount at the endothelium. We conclude that, in rat liver, HL
is localized at the microvilli of parenchymal cells
Understanding retreat and expansion of salt marshes by modelling the variability of the salt marsh edge under influence of waves and sediment availability
Is web interviewing a good alternative to telephone interviewing? Findings from the International Tobacco Control (ITC) Netherlands survey
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