7,186 research outputs found
New immunolatex spheres: visual markers of antigens on lymphocytes for scanning electron microscopy
New immunochemical reagents consisting of antibodies bound to small latex spheres were used as visual markers for the detection and localization of cell surface antigens by scanning electron microscopy. Cross-linked latex spheres of various sizes from 300 to 3,4000 Ã… in diameter were synthesized by aqueous emulsion copolymerization of methacrylate derivatives containing hydroxyl and carboxyl functional groups. Proteins and other molecules containing primary amino groups were covalently bonded to the acrylic spheres under a variety of mild conditions by the aqueous carbodiimide, cyanogen bromide, and glutaraldehyde methods. For use in the indirect immunochemical-labeling technique, goat antibodies directed against rabbit immunoglobulins were bonded to the spheres. These immunolatex reagents were shown to bind only to cells (red blood and lymphocytes) which had previously been sensitized with rabbit antibodies against cell surface antigens. Mouse spleen lymphocytes with exposed immunoglobulins on their surface (B cells) were labeled with these spheres and distinguished from unlabeled or T lymphocytes by scanning electron microscopy. The distribution of Ig receptors on lymphocytes was also studied using the spheres as visual markers. When lymphocytes were fixed with glutaraldehyde and subsequently labeled with the immunolatex reagents, a random distribution was observed by scanning electron microscopy; a patchy distribution was observed when unfixed lymphocytes were used. These results are consistent with studies using ferritin-labeled antibodies (S. De Petris and M. Raff. 1973. Nature [Lond.]. 241:257.) and support the view that Ig receptors on lymphocytes undergo translational diffusion. In addition to serving as visual markers for scanning electron microscopy, these latex spheres tagged with fluorescent or radioactive molecules have applications as highly sensitive markers for fluorescent microscopy and as reagents for quantitative studies of cell surface antigens and other receptors
Entropy in Spin Foam Models: The Statistical Calculation
Recently an idea for computing the entropy of black holes in the spin foam
formalism has been introduced. Particularly complete calculations for the three
dimensional euclidean BTZ black hole were done. The whole calculation is based
on observables living at the horizon of the black hole universe. Departing from
this idea of observables living at the horizon, we now go further and compute
the entropy of BTZ black hole in the spirit of statistical mechanics. We
compare both calculations and show that they are very interrelated and equally
valid. This latter behaviour is certainly due to the importance of the
observables.Comment: 11 pages, 1 figur
Protein specific polymeric immunomicrospheres
Small, round, bio-compatible microspheres capable of covalently bonding proteins and having a uniform diameter below about 3500 A are prepared by substantially instantaneously initiating polymerization of an aqueous emulsion containing no more than 35% total monomer including an acrylic monomer substituted with a covalently bondable group such as hydroxyl, amino or carboxyl and a minor amount of a cross-linking agent
Preparation of small bio-compatible microspheres
Small, round, bio-compatible microspheres capable of covalently bonding proteins and having a uniform diameter below about 3500 A are prepared by substantially instantaneously initiating polymerization of an aqueous emulsion containing no more than 35% total monomer including an acrylic monomer substituted with a covalently bondable group such a hydroxyl, amino or carboxyl and a minor amount of a cross-linking agent
A Mechanism for Chronic Filarial Hydrocele with Implications for Its Surgical Repair
Chronic hydrocele is the accumulation of fluid around the testis leading to an increase in the volume of the scrotal contents. Depending on the volume of fluid, hydrocele can be disfiguring and even incapacitating. Chronic hydrocele has multiple etiologies, but irrespective of the cause, surgery is the standard form of treatment and this can be done using different surgical techniques. The prevalence of chronic hydrocele in bancroftian filariasis endemic areas—a parasitic disease transmitted by mosquito—is very high and represents the most common clinical manifestation of bancroftosis, following by swollen legs of lower limbs or lymphedema among women. In Greater Recife, northeastern, Brazil, a bancroftian filariasis endemic area, a pioneering, prospective surgical study proposes a new mechanism for filarial-induced hydrocele and presents evidence that the filarial hydrocele fluid may damage the testis. Thus, based on the findings presented, the authors propose that in bancroftian filariasis endemic areas hydrocele patients should be operated on using a specific surgical technique in order to avoid recurrence of the disease, and consequently, additional damage to the testicle
The GALEX Arecibo SDSS Survey. VI. Second Data Release and Updated Gas Fraction Scaling Relations
We present the second data release from the GALEX Arecibo SDSS Survey (GASS),
an ongoing large Arecibo program to measure the HI properties for an unbiased
sample of ~1000 galaxies with stellar masses greater than 10^10 Msun and
redshifts 0.025<z<0.05. GASS targets are selected from the Sloan Digital Sky
Survey (SDSS) spectroscopic and Galaxy Evolution Explorer (GALEX) imaging
surveys, and are observed until detected or until a gas mass fraction limit of
a few per cent is reached. This second data installment includes new Arecibo
observations of 240 galaxies, and marks the 50% of the complete survey. We
present catalogs of the HI, optical and ultraviolet parameters for these
galaxies, and their HI-line profiles. Having more than doubled the size of the
sample since the first data release, we also revisit the main scaling relations
of the HI mass fraction with galaxy stellar mass, stellar mass surface density,
concentration index, and NUV-r color, as well as the gas fraction plane
introduced in our earlier work.Comment: 30 pages, 12 figures. Accepted for publication in A&A. Version with
complete Appendix A available at http://www.mpa-garching.mpg.de/GASS/pubs.php
. GASS released data can be found at
http://www.mpa-garching.mpg.de/GASS/data.ph
Black hole entropy calculations based on symmetries
Symmetry based approaches to the black hole entropy problem have a number of
attractive features; in particular they are very general and do not depend on
the details of the quantization method. However we point out that, of the two
available approaches, one faces conceptual problems (also emphasized by
others), while the second contains certain technical flaws. We correct these
errors and, within the new, improved scheme, calculate the entropy of
3-dimensional black holes. We find that, while the new symmetry vector fields
are well-defined on the ``stretched horizon,'' and lead to well-defined
Hamiltonians satisfying the expected Lie algebra, they fail to admit a
well-defined limit to the horizon. This suggests that, although the formal
calculation can be carried out at the classical level, its real, conceptual
origin probably lies in the quantum theory.Comment: 14 pages, Latex, CGPG-01/1-
Chandra Observations of Extended X-ray Emission in Arp 220
We resolve the extended X-ray emission from the prototypical ultraluminous
infrared galaxy Arp 220. Extended, faint edge-brightened, soft X-ray lobes
outside the optical galaxy are observed to a distance of 10 to 15 kpc on each
side of the nuclear region. Bright plumes inside the optical isophotes coincide
with the optical line emission and extend 11 kpc from end to end across the
nucleus. The data for the plumes cannot be fit by a single temperature plasma,
and display a range of temperatures from 0.2 to 1 keV. The plumes emerge from
bright, diffuse circumnuclear emission in the inner 3 kpc centered on the
Halpha peak, which is displaced from the radio nuclei. There is a close
morphological correspondence between the Halpha and soft X-ray emission on all
spatial scales. We interpret the plumes as a starburst-driven superwind, and
discuss two interpretations of the emission from the lobes in the context of
simulations of the merger dynamics of Arp 220.Comment: Accepted for publication in ApJ; see also astro-ph/0208477 (Paper 1
Symmetries at stationary Killing horizons
It has often been suggested (especially by Carlip) that spacetime symmetries
in the neighborhood of a black hole horizon may be relevant to a statistical
understanding of the Bekenstein-Hawking entropy. A prime candidate for this
type of symmetry is that which is exhibited by the Einstein tensor. More
precisely, it is now known that this tensor takes on a strongly constrained
(block-diagonal) form as it approaches any stationary, non-extremal Killing
horizon. Presently, exploiting the geometrical properties of such horizons, we
provide a particularly elegant argument that substantiates this highly
symmetric form for the Einstein tensor. It is, however, duly noted that, on
account of a "loophole", the argument does fall just short of attaining the
status of a rigorous proof.Comment: 11 pages, Revte
On the emergence of Lorentzian signature and scalar gravity
In recent years, a growing momentum has been gained by the emergent gravity
framework. Within the latter, the very concepts of geometry and gravitational
interaction are not seen as elementary aspects of Nature but rather as
collective phenomena associated to the dynamics of more fundamental objects. In
this paper we want to further explore this possibility by proposing a model of
emergent Lorentzian signature and scalar gravity. Assuming that the dynamics of
the fundamental objects can give rise in first place to a Riemannian manifold
and a set of scalar fields we show how time (in the sense of hyperbolic
equations) can emerge as a property of perturbations dynamics around some
specific class of solutions of the field equations. Moreover, we show that
these perturbations can give rise to a spin-0 gravity via a suitable
redefinition of the fields that identifies the relevant degrees of freedom. In
particular, we find that our model gives rise to Nordstrom gravity. Since this
theory is invariant under general coordinate transformations, this also shows
how diffeomorphism invariance (albeit of a weaker form than the one of general
relativity) can emerge from much simpler systems.Comment: 10 pages, revtex4. Replaced with the published versio
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