4,592 research outputs found
Visualization of Cytoskeletal Elements and Associated Retroviral Antigens by Immunogold Transmission Electron Microscopy of Detergent Extracted Cells
Several investigators have reported an association between the cytoskeleton and viral antigens. In our laboratory, biochemical immunofluorescence and immuno-gold electron microscopy studies were conducted on TX-100 extracted NIH/3T3 cells infected with Moloney-murine leukemia virus. Cytochalasin B treatment causes reversible microfilament disruption and a concomitant decrease in virus production. No effect on microtubules was seen. Immuno-gold electron microscopy reveals an association between cytoskeletal action and the viral antigens gp70 and p15E. The results of these immunocytological and biochemical studies indicate that the cytoskeleton may play an integral role in transport and processing of viral gene-envelope products
Influence of random roughness on the Casimir force at small separations
The influence of random surface roughness of Au films on the Casimir force is
explored with atomic force microscopy in the plate-sphere geometry. The
experimental results are compared to theoretical predictions for separations
ranging between 20 and 200 nm. The optical response and roughness of the Au
films were measured and used as input in theoretical predictions. It is found
that at separations below 100 nm, the roughness effect is manifested through a
strong deviation from the normal scaling of the force with separation distance.
Moreover, deviations from theoretical predictions based on perturbation theory
can be larger than 100%.Comment: 18, 5 figure
Objective determination of image end-members in spectral mixture analysis of AVIRIS data
Spectral mixture analysis has been shown to be a powerful, multifaceted tool for analysis of multi- and hyper-spectral data. Applications of AVIRIS data have ranged from mapping soils and bedrock to ecosystem studies. During the first phase of the approach, a set of end-members are selected from an image cube (image end-members) that best account for its spectral variance within a constrained, linear least squares mixing model. These image end-members are usually selected using a priori knowledge and successive trial and error solutions to refine the total number and physical location of the end-members. However, in many situations a more objective method of determining these essential components is desired. We approach the problem of image end-member determination objectively by using the inherent variance of the data. Unlike purely statistical methods such as factor analysis, this approach derives solutions that conform to a physically realistic model
Genetic, immunological, and cytotoxic comparisons of Legionella proteolytic activities
Several strains of Legionella pneumophila and other species of Legionella with proteolytic activities were compared by assays, including Southern hybridizations and Western immunoblots, to determine their proteolytic, hemolytic, and cytotoxic activities. Only proteases from strains of L. pneumophila were both hemolytic and cytotoxic, and proteolytic activities extracted from other species of legionella possessed only hemolytic activity
Interactions between vaccinia virus and sensitized macrophages in vitro
The action of peritoneal exudate cells (PEC) from normal and vaccinia virus infected mice on infectious vaccinia virus particles was investigatedin vitro. PEC from immune mice showed a significantly higher infectivity titre reduction (virus clearance, VC) than normal cells. This effect could be clearly attributed to the macrophage. Vaccinia virus multiplied in PEC from normal animals while there was no virus propagation in cells from immunized mice. The release of adsorbed or engulfed virus was reduced significantly in PEC from immunized animals. Anti-vaccinia-antibodies seem to activate normal macrophages to increased virus clearance. This stimulating effect was demonstrable only in the IgG fraction of the antiserum.
The activity of macrophages from mice injected three times over a period of 14 days with vaccinia virus could be entirely blocked with anti-mouse-IgG, while PEC from mice injected one time six days previously were not inhibited
Child Psychosocial Adjustment and Parenting in Families Affected by Maternal HIV/AIDS
Child adjustment and parenting were examined in 23 9-through 16-year-old youth from families affected by maternal HIV infection and 20 same-age peers whose mothers were not infected. Children whose mothers were seropositive reported significantly more externalizing problems. Infected mothers reported less age-appropriate supervision/monitoring relative to non-infected mothers. Better mother-child relationship quality and less impairment in parental supervision/monitoring of age-appropriate youth behaviors were associated with fewer externalizing difficulties among the HIV-positive group only. Similarly, only among HIV-infected mothers was refraining from engaging in inconsistent disciplinary tactics associated with lower reports of internalizing and externalizing problems. These data highlight the promise of programs targeting parenting skills to prevent or ameliorate child difficulties
Adiabaticity Conditions for Volatility Smile in Black-Scholes Pricing Model
Our derivation of the distribution function for future returns is based on
the risk neutral approach which gives a functional dependence for the European
call (put) option price, C(K), given the strike price, K, and the distribution
function of the returns. We derive this distribution function using for C(K) a
Black-Scholes (BS) expression with volatility in the form of a volatility
smile. We show that this approach based on a volatility smile leads to relative
minima for the distribution function ("bad" probabilities) never observed in
real data and, in the worst cases, negative probabilities. We show that these
undesirable effects can be eliminated by requiring "adiabatic" conditions on
the volatility smile
EGRET Spectral Index and the Low-Energy Peak Position in the Spectral Energy Distribution of EGRET-Detected Blazars
In current theoretical models of the blazar subclass of active galaxies, the
broadband emission consists of two components: a low-frequency synchrotron
component with a peak in the IR to X-ray band, and a high-frequency inverse
Compton component with a peak in the gamma-ray band. In such models, the
gamma-ray spectral index should be correlated with the location of the
low-energy peak, with flatter gamma-ray spectra expected for blazars with
synchrotron peaks at higher photon energies and vice versa. Using the
EGRET-detected blazars as a sample, we examine this correlation and possible
uncertainties in its construction.Comment: 17 pages including 1 figure, accepted for publication in The
Astrophysical Journa
A search for the radio counterpart of the unidentified gamma-ray source 3EG J1410-6147
We have made radio continuum, HI and X-ray observations in the direction of
the unidentified EGRET source 3EG J1410-6147, using the Australia Telescope
Compact Array and the Chandra X-ray Observatory. The observations encompass the
supernova remnant (SNR) G312.4-0.4 and the two young pulsars PSRs J1412-6145
and J1413-6141.
We derive a lower distance limit of 6 kpc to the SNR, although interpretation
of positive velocity features in the HI spectrum may imply the SNR is more
distant than 14 kpc. PSR J1412-6145, with an age of 50 kyr, is the pulsar most
likely associated with SNR G312.4-0.4. X-rays are not detected from either
pulsar and diffuse X-ray emission near the bright western edge of the SNR is
weak. Although there is circumstantial evidence that this western region is a
pulsar wind nebula (PWN), the embedded pulsar PSR J1412-6145 is apparently not
sufficiently powerful to explain the radio enhancement. The origin of the
electron acceleration in this region and of the gamma-rays remain unidentified,
unless the distance to PSR J1413-6141 is at least a factor of 3 lower than its
dispersion measure distance.Comment: 10 pages, plus 5 jpeg figures, MNRAS, in press. Full postscript or
pdf including all figures is available at http://www.ast.cam.ac.uk/~m
EGRET Gamma-Ray Observations of the Crab P2/P1 Ratio
Recent observations of the Crab pulsar by the Energetic Gamma-Ray Experiment
Telescope (EGRET) on the Compton Gamma Ray Observatory show that the
high-energy gamma-ray light curve has changed little over the lifetime of the
instrument. Previous data collected by SAS-2 and COS-B in the years 1972-82,
along with earlier EGRET data, suggested a 14 year sinusoidal variation in the
flux ratio between the first and second peaks. The new data from EGRET indicate
that the flux ratio is constant.Comment: 6 pages, 3 figures. To be published in Ap
- …