The spectacular rise and fall of stock prices during the recent dot-com bubble period has been accompanied by a surge of interest in the topic of short-selling. For the most part, this work is ...cross-sectional in nature, examining the causes and consequences of short-sales constraints at the individual-stock level, and it suggests the following two broad conclusions. First, consistent with the notion that short-selling is undertaken by rational arbitrageurs, the demand for short positions is greatest among stocks that appear to be overvalued. Second, because of frictions in the market for borrowing stock, as well as various institutional rigidities, arbitrage by would-be short-sellers is incomplete. Thus, those stocks where the demand for shorting is greatest tend to have abnormally low future returns.
The aurorae are dynamic, luminous displays that grace the night skies of Earth’s high latitude regions. The solar wind emanating from the Sun is their ultimate energy source, but the chain of plasma ...physical processes leading to auroral displays is complex. The special conditions at the interface between the solar wind-driven magnetosphere and the ionospheric environment at the top of Earth’s atmosphere play a central role. In this Auroral Acceleration Region (AAR) persistent electric fields directed along the magnetic field accelerate magnetospheric electrons to the high energies needed to excite luminosity when they hit the atmosphere. The “ideal magnetohydrodynamics” description of space plasmas which is useful in much of the magnetosphere cannot be used to understand the AAR. The AAR has been studied by a small number of single spacecraft missions which revealed an environment rich in wave-particle interactions, plasma turbulence, and nonlinear acceleration processes, acting on a variety of spatio-temporal scales. The pioneering 4-spacecraft Cluster magnetospheric research mission is now fortuitously visiting the AAR, but its particle instruments are too slow to allow resolve many of the key plasma physics phenomena. The Alfvén concept is designed specifically to take the next step in studying the aurora, by making the crucial high-time resolution, multi-scale measurements in the AAR, needed to address the key science questions of auroral plasma physics. The new knowledge that the mission will produce will find application in studies of the Sun, the processes that accelerate the solar wind and that produce aurora on other planets.
The development and characterization of a quartz crystal microbalance (QCM) sensor for the direct detection of aerosolized influenza A virions is reported. Self-assembled monolayers (SAMs) of ...mercaptoundecanoic acid (MUA) are formed on QCM gold electrodes to provide a surface amenable for the immobilization of anti-influenza A antibodies using NHS/EDC coupling chemistry. The surface-bound antibody provides a selective and specific sensing interface for the capture of influenza virions. A nebulizer is used to create aerosolized samples and is directly connected to a chamber housing the antibody-modified crystal (“immunochip”). Upon exposure to the aerosolized virus, the interaction between the antibody and virus leads to a dampening of the oscillation frequency of the quartz crystal. The magnitude of frequency change is directly related to virus concentration. Control experiments using aerosols from chicken egg allantoic fluid and an anti-murine antibody based immunosensor confirm that the observed signal originates from specific viral binding on the chip surface. Step-by-step surface modification of MUA assembly, antibody attachment, and antibody–virus interaction are characterized by atomic force microscopy (AFM) imaging analysis. Using the
S/
N
=
3 principle, the limit of detection is estimated to be 4 virus particles/mL. The high sensitivity and real-time sensing scheme presented here can play an important role in the public health arena by offering a new analytical tool for identifying bio-contaminated areas and assisting in timely patient diagnosis.
Objective: This study’s aim was to determine whether maintenance therapy with terbutaline administered by pump prolongs gestation in women after treatment with intravenous magnesium sulfate tocolysis ...for suspected preterm labor. Study Design: Consenting women with a singleton gestation and intact membranes who had uterine contractions and >1 cm cervical dilation, 80% effacement, or progressive cervical change and whose contractions were successfully arrested with intravenous magnesium were randomly assigned to receive either terbutaline or normal saline solution placebo by subcutaneous infusion pump. Pump therapy was administered with a standardized protocol. Pump therapy was discontinued and parenteral magnesium was resumed if recurrent preterm labor developed while women were on the therapeutic regimen at <34 weeks’ gestation and no contraindication for tocolysis existed. If recurrent labor was arrested, pump therapy was restarted according to the original treatment group. A sample size of 48 women was required to detect a 2-week intergroup difference in mean time to delivery. Analyses were based on intent to treat. Results: Fifty-two women received terbutaline (n = 24) or placebo (n = 28). At random assignment the groups were similar with respect to age, race, parity, previous preterm delivery, gestational age, and cervical examination. Overall there was a 1-day difference in mean time to delivery between the groups (terbutaline 29 ± 22 days and placebo 28 ± 23 days, P = .78). There were no differences in the rates of preterm delivery at <34 and <37 weeks’ gestation. Neonatal outcomes were similar. Conclusions: Maintenance terbutaline therapy administered by pump does not prolong gestation in women successfully treated for suspected preterm labor. (Am J Obstet Gynecol 1998;179:874-8.)
Thirty-four sows (parity=1.8; BW=206
kg) were used to determine the influence of
l-carnitine and/or chromium tripicolinate on plasma leptin concentrations of gestating sows fed one meal daily. ...Treatments were arranged in a 2×2 factorial with main effects of carnitine (0 or 50
ppm) and chromium (0 or 200
ppb). Diets were fed for approximately 167 days (through one gestation, the following lactation, the interval from weaning to estrus, and 28 days into the following gestation) prior to blood collection. Leptin concentration was determined in plasma that was collected at feeding, every 15
min for the first 3
h after feeding, and at 6, 9, 15, 20, and 24
h after feeding. Sows fed diets containing carnitine had greater (
P<0.02) overall mean plasma leptin concentrations and greater (
P<0.05) leptin concentrations at 2.25, 3, 6, 15, 20, and 24
h after feeding compared to sows fed either the control diet or the diet containing chromium. Leptin concentrations of sows fed diets containing carnitine also were greater (
P<0.05) than control sows at 2.5 and 2.75
h postprandial and greater than (
P<0.05) sows fed diets with both carnitine and chromium at 6
h after feeding. Chromium had no effect (
P>0.10) on plasma leptin concentration. These results suggest that dietary carnitine, but not chromium, increases circulating leptin in gestating sows fed one meal per day. These results may help to explain the improvements in reproductive function previously observed from feeding sows diets containing carnitine.
The neurobehavioral effects of inhaled cyclohexane in rats and humans are investigated to define relationships between internal doses and acute central nervous system effects. Rats are exposed for 3 ...consecutive days at target concentrations of 0, 1.4, 8, and 28 g/m3, 8 h/d. Measurements include standardized observational measures, spontaneous motor activity assessments, and learned visual discrimination performance. Cyclohexane concentrations in blood and brain are measured to assess internal exposure. Human volunteers are exposed for 4 hours to 86 or 860 mg/m3 in 2 test sessions. Neurobehavioral effects are measured using a computerized neurobehavioral test battery. In rats, there are slight reductions in psychomotor speed in the high-exposure group but minimal central nervous system effects. In humans, there are no significant treatment-related effects at the levels tested.
Aging and degeneration of the intervertebral disk are accompanied by decreases in water and proteoglycan contents, and structural alterations. The aim of this study was to determine the impact of ...compositional changes on the material properties of intervertebral disk tissues. Confined compression stress-relaxation experiments were applied to bovine caudal annulus fibrosus and nucleus pulposus tissue specimens that were separated into three experimental groups: in situ, free-swelling control (PBS), and digestion (chondroitinase-ABC). Measurements of glycosaminoglycan (GAG) and water content, as well as nonlinear finite deformation biphasic theory and multiple linear regression analyses were performed. The compressive modulus HA0 and permeability k0 of in situ specimens were 0.37+/-0.06 MPa and 0.49+/-0.08x10(-15) m4 N-1 s-1 for nucleus, and 0.74+/-0.13 MPa and 0.42+/-0.05x10(-15) m4 N-1 s-1 for annulus, respectively. There was a larger effect of swelling and digestion on the material properties and biochemical composition of nucleus pulposus than for annulus fibrosus. Alterations in proteoglycan and water content affected the compressive modulus and permeability, although the permeability was somewhat more strongly affected by water content than by proteoglycan content. Correlation coefficients r<or=0.75 for the multiple regression indicated water and GAG content can moderately predict material properties, however other compositional and structural factors must be considered.
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