1,052 research outputs found
Electrowetting on superhydrophobic SU-8 patterned surfaces
Electrowetting on micro-patterned layers of SU-8 photoresist with an amorphous Teflon (R) coating has been observed. The cosine of the contact angle is shown to be proportional to the square of the applied voltage for increasing bias. However, this does not apply below 40 V and we suggest that this may be explained in terms of penetration of fluid into the pattern of the surface. Assuming that the initial application of a bias voltage converts the drop from Cassie-Baxter to Wenzel regime, we have used this as a technique to estimate the roughness factor of the surface
Disk illumination by black hole superradiance of electromagnetic perturbations
Using the Kerr-Schild formalism to solve the Einstein-Maxwell equations, we
study energy transport due to time-dependent electromagnetic perturbations
around a Kerr black hole, which may work as a mechanism to illuminate a disk
located on the equatorial plane. For such a disk-hole system it is found that
the energy extraction from the hole can occur under the well-known
superradiance condition for wave frequency, even though the energy absorption
into the hole should be rather dominant near the polar region of the horizon.
We estimate the efficiency of the superradiant amplification of the disk
illumination. Further we calculate the time-averaged energy density
distribution to show explicitly the existence of a negative energy region near
the horizon and to discuss the possible generation of a hot spot on the disk.Comment: 11 pages, 4 figures, corrected typos, published in Physical Review
Polyelectrolyte Multilayering on a Charged Planar Surface
The adsorption of highly \textit{oppositely} charged flexible
polyelectrolytes (PEs) on a charged planar substrate is investigated by means
of Monte Carlo (MC) simulations. We study in detail the equilibrium structure
of the first few PE layers. The influence of the chain length and of a (extra)
non-electrostatic short range attraction between the polycations and the
negatively charged substrate is considered. We show that the stability as well
as the microstructure of the PE layers are especially sensitive to the strength
of this latter interaction. Qualitative agreement is reached with some recent
experiments.Comment: 28 pages; 11 (main) Figs - Revtex4 - Higher resolution Figs can be
obtained upon request. To appear in Macromolecule
Roles of bone-derived hormones in type 2 diabetes and cardiovascular pathophysiology
Background: Emerging evidence demonstrates that bone is an endocrine organ capable of influencing multiple physiological and pathological processes through the secretion of hormones. Recent research suggests complex crosstalk between the bone and other metabolic and cardiovascular tissues. It was uncovered that three of these bone-derived hormones—osteocalcin, lipocalin 2, and sclerostin—are involved in the endocrine regulations of cardiometabolic health and play vital roles in the pathophysiological process of developing cardiometabolic syndromes such as type 2 diabetes and cardiovascular disease. Chronic low-grade inflammation is one of the hallmarks of cardiometabolic diseases and a major contributor to disease progression. Novel evidence also implicates important roles of bone-derived hormones in the regulation of chronic inflammation. Scope of review: In this review, we provide a detailed overview of the physiological and pathological roles of osteocalcin, lipocalin 2, and sclerostin in cardiometabolic health regulation and disease development, with a focus on the modulation of chronic inflammation. Major conclusions: Evidence supports that osteocalcin has a protective role in cardiometabolic health, and an increase of lipocalin 2 contributes to the development of cardiometabolic diseases partly via pro-inflammatory effects. The roles of sclerostin appear to be complicated: It exerts pro-adiposity and pro-insulin resistance effects in type 2 diabetes and has an anti-calcification effect during cardiovascular disease. A better understanding of the actions of these bone-derived hormones in the pathophysiology of cardiometabolic diseases will provide crucial insights to help further research develop new therapeutic strategies to treat these diseases
Topography driven spreading
Roughening a hydrophobic surface enhances its nonwetting properties into superhydrophobicity. For liquids other than water, roughness can induce a complete rollup of a droplet. However, topographic effects can also enhance partial wetting by a given liquid into complete wetting to create superwetting. In this work, a model system of spreading droplets of a nonvolatile liquid on surfaces having lithographically produced pillars is used to show that superwetting also modifies the dynamics of spreading. The edge speed-dynamic contact angle relation is shown to obey a simple power law, and such power laws are shown to apply to naturally occurring surfaces
Spectral Cross-calibration of the Konus-Wind, the Suzaku/WAM, and the Swift/BAT Data using Gamma-Ray Bursts
We report on the spectral cross-calibration results of the Konus-Wind, the
Suzaku/WAM, and the Swift/BAT instruments using simultaneously observed
gamma-ray bursts (GRBs). This is the first attempt to use simultaneously
observed GRBs as a spectral calibration source to understand systematic
problems among the instruments. Based on these joint spectral fits, we find
that 1) although a constant factor (a normalization factor) agrees within 20%
among the instruments, the BAT constant factor shows a systematically smaller
value by 10-20% compared to that of Konus-Wind, 2) there is a systematic trend
that the low-energy photon index becomes steeper by 0.1-0.2 and Epeak becomes
systematically higher by 10-20% when including the BAT data in the joint fits,
and 3) the high-energy photon index agrees within 0.2 among the instruments.
Our results show that cross-calibration based on joint spectral analysis is an
important step to understanding the instrumental effects which could be
affecting the scientific results from the GRB prompt emission data.Comment: 82 pages, 88 figures, accepted for publication in PAS
On the offset of Short Gamma-ray Bursts
Short Gamma-Ray Bursts (SGRBs) are expected to form from the coalescence of
compact binaries, either of primordial origin or from dynamical interactions in
globular clusters. In this paper, we investigate the possibility that the
offset and afterglow brightness of a SGRB can help revealing the origin of its
progenitor binary. We find that a SGRB is likely to result from the primordial
channel if it is observed within 10 kpc from the center of a massive galaxy and
shows a detectable afterglow. The same conclusion holds if it is 100 kpc away
from a small, isolated galaxy and shows a weak afterglow. On the other hand, a
dynamical origin is suggested for those SGRBs with observable afterglow either
at a large separation from a massive, isolated galaxy or with an offset of
10-100 kpc from a small, isolated galaxy. We discuss the possibility that SGRBs
from the dynamical channel are hosted in intra-cluster globular clusters and
find that GRB 061201 may fall within this scenario.Comment: 5 pages, 3 figures, MNRAS in pres
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