118 research outputs found
Collapsing and static thin massive charged dust shells in a Reissner-Nordstr\"om black hole background in higher dimensions
The problem of a spherically symmetric charged thin shell of dust collapsing
gravitationally into a charged Reissner-Nordstr\"om black hole in spacetime
dimensions is studied within the theory of general relativity. Static charged
shells in such a background are also analyzed. First a derivation of the
equation of motion of such a shell in a -dimensional spacetime is given.
Then a proof of the cosmic censorship conjecture in a charged collapsing
framework is presented, and a useful constraint which leads to an upper bound
for the rest mass of a charged shell with an empty interior is derived. It is
also proved that a shell with total mass equal to charge, i.e., an extremal
shell, in an empty interior, can only stay in neutral equilibrium outside its
gravitational radius. This implies that it is not possible to generate a
regular extremal black hole by placing an extremal dust thin shell within its
own gravitational radius. Moreover, it is shown, for an empty interior, that
the rest mass of the shell is limited from above. Then several types of
behavior of oscillatory charged shells are studied. In the presence of a
horizon, it is shown that an oscillatory shell always enters the horizon and
reemerges in a new asymptotically flat region of the extended
Reissner-Nordstr\"om spacetime. On the other hand, for an overcharged interior,
i.e., a shell with no horizons, an example showing that the shell can achieve a
stable equilibrium position is presented. The results presented have
applications in brane scenarios with extra large dimensions, where the creation
of tiny higher dimensional charged black holes in current particle accelerators
might be a real possibility, and generalize to higher dimensions previous
calculations on the dynamics of charged shells in four dimensions.Comment: 21 pages, 2 figure
The Tolman-Bondi--Vaidya Spacetime: matching timelike dust to null dust
The Tolman-Bondi and Vaidya solutions are two solutions to Einstein equations
which describe dust particles and null fluid, respectively. We show that it is
possible to match the two solutions in one single spacetime, the
Tolman-Bondi--Vaidya spacetime. The new spacetime is divided by a null surface
with Tolman-Bondi dust on one side and Vaidya fluid on the other side. The
differentiability of the spacetime is discussed. By constructing a specific
solution, we show that the metric across the null surface can be at least
and the stress-energy tensor is continuous.Comment: 5 pages, no figur
Laser-assisted microchanneling on PMMA substrate utilizing two-pass fabrication method
Microchannel is widely used in microfluidic devices for mixing, chemical reaction, detection, particle separation and etc. CO2 laser-based microchanneling of PMMA as a low cost, rapid, noncontact fabrication method has attracted the attention of industry. However, the typical V-shape grooves fabricated by CO2 laser microchanneling have limitations since the V-shape grooves will affect the flow behavior and heat transfer of the fluid, which are important to the performance of microfluidic devices. A two-pass fabrication method is proposed and investigated in this paper to improve the quality of the PMMA microchannel fabricated by CO2 laser. It was found that by using this method, a trapezoidal shape groove can be formed. Such a microchannel is of higher quality compared with the V-shape groove microchannel
Charged shells in Lovelock gravity: Hamiltonian treatment and physical implications
Using a Hamiltonian treatment, charged thin shells in spherically symmetric
spacetimes in d dimensional Lovelock-Maxwell theory are studied. The
coefficients of the theory are chosen to obtain a sensible theory, with a
negative cosmological constant appearing naturally. After writing the action
and the Lagrangian for a spacetime comprised of an interior and an exterior
regions, with a thin shell as a boundary in between, one finds the Hamiltonian
using an ADM description. For spherically symmetric spacetimes, one reduces the
relevant constraints. The dynamic and constraint equations are obtained. The
vacuum solutions yield a division of the theory into two branches, d-2k-1>0
(which includes general relativity, Born-Infeld type theories) and d-2k-1=0
(which includes Chern-Simons type theories), where k gives the highest power of
the curvature in the Lagrangian. An additional parameter, chi, gives the
character of the vacuum solutions. For chi=1 the solutions have a black hole
character. For chi=-1 the solutions have a totally naked singularity character.
The integration through the thin shell takes care of the smooth junction. The
subsequent analysis is divided into two cases: static charged thin shell
configurations, and gravitationally collapsing charged dust shells. Physical
implications are drawn: if such a large extra dimension scenario is correct,
one can extract enough information from the outcome of those collapses as to
know, not only the actual dimension of spacetime, but also which particular
Lovelock gravity, is the correct one.Comment: 25 pages, 9 figure
Harnessing Geometric Frustration to Form Band Gaps in Acoustic Channel Lattices
We demonstrate both numerically and experimentally that geometric frustration
in two-dimensional periodic acoustic networks consisting of arrays of narrow
air channels can be harnessed to form band gaps (ranges of frequency in which
the waves cannot propagate in any direction through the system). While resonant
standing wave modes and interferences are ubiquitous in all the analyzed
network geometries, we show that they give rise to band gaps only in the
geometrically frustrated ones (i.e. those comprising of triangles and
pentagons). Our results not only reveal a new mechanism based on geometric
frustration to suppress the propagation of pressure waves in specific frequency
ranges, but also opens avenues for the design of a new generation of smart
systems that control and manipulate sound and vibrations
Clinical practice guidelines of remote ischemic conditioning for the management of cerebrovascular diseases
Remote ischemic conditioning (RIC) using transient limb ischemia and reperfusion has been shown in small clinical studies to reduce myocardial injury and infarction in cardiac patients, although larger clinical outcome studies have been neutral. Experimental and emerging clinical studies have also reported beneficial effects of limb RIC in a number of different settings of cerebrovascular disease including stroke (ischemic and hemorrhagic), carotid artery stenosis, intracranial artery stenosis, aneurysms, small vessel disease, and vascular cognitive impairment. Although limb RIC has many advantages, in that it is non-invasive, easy to administer, relatively innocuous, cost-effective, has few or no contraindications, and may be deployed under various circumstances (e.g., home, ambulance, and hospital), several questions remain regarding its clinical application for cerebrovascular disease. Therefore, in this document, we aim to provide practicing clinicians with a coherent synthesis of the latest scientific evidence, and we propose several recommendations to help facilitate the clinical application of limb RIC for the management of cerebrovascular disease
Meta-analysis of genome-wide association studies identifies 8 novel loci involved in shape variation of human head hair
Shape variation of human head hair shows striking variation within and between human populations, while its genetic basis is far from being understood. We performed a series of genome-wide association studies (GWASs) and replication studies in a total of 28 964 subjects from 9 cohorts from multiple geographic origins. A meta-analysis of three European GWASs identified 8 novel loci (1p36.23
A Novel T-Cell Engaging Bi-specific Antibody Targeting the Leukemia Antigen PR1/HLA-A2
Despite substantial advances in the treatment of acute myeloid leukemia (AML), only 30% of patients survive more than 5 years. Therefore, new therapeutics are much needed. Here, we present a novel therapeutic strategy targeting PR1, an HLA-A2 restricted myeloid leukemia antigen. Previously, we have developed and characterized a novel T-cell receptor-like monoclonal antibody (8F4) that targets PR1/HLA-A2 and eliminates AML xenografts by antibody-dependent cellular cytotoxicity (ADCC). To improve the potency of 8F4, we adopted a strategy to link T-cell cytotoxicity with a bi-specific T-cell-engaging antibody that binds PR1/HLA-A2 on leukemia and CD3 on neighboring T-cells. The 8F4 bi-specific antibody maintained high affinity and specific binding to PR1/HLA-A2 comparable to parent 8F4 antibody, shown by flow cytometry and Bio-Layer Interferometry. In addition, 8F4 bi-specific antibody activated donor T-cells in the presence of HLA-A2+ primary AML blasts and cell lines in a dose dependent manner. Importantly, activated T-cells lysed HLA-A2+ primary AML blasts and cell lines after addition of 8F4 bi-specific antibody. In conclusion, our studies demonstrate the therapeutic potential of a novel bi-specific antibody targeting the PR1/HLA-A2 leukemia-associated antigen, justifying further clinical development of this strategy
Fully automatic landmarking of 2D photographs identifies novel genetic loci influencing facial features
We report a genome-wide association study for facial features in > 6,000 Latin Americans. We placed 106 landmarks on 2D frontal photographs using the cloud service platform Face++. After Procrustes superposition, genome-wide association testing was performed for 301 inter-landmark distances. We detected nominally significant association (P-value < 5×10− 8) for 42 genome regions. Of these, 9 regions have been previously reported in GWAS of facial features. In follow-up analyses, we replicated 26 of the 33 novel regions (in East Asians or Europeans). The replicated regions include 1q32.3, 3q21.1, 8p11.21, 10p11.1, and 22q12.1, all comprising strong candidate genes involved in craniofacial development. Furthermore, the 1q32.3 region shows evidence of introgression from archaic humans. These results provide novel biological insights into facial variation and establish that automatic landmarking of standard 2D photographs is a simple and informative approach for the genetic analysis of facial variation, suitable for the rapid analysis of large population samples.- Introduction - Results And Discussion -- Study sample and phenotyping -- Trait/covariate correlation and heritability -- Overview of GWAS results and integration with the literature -- Follow-up of genomic regions newly associated with facial features: Replication in two human cohorts -- Follow-up of genomic regions newly associated with facial features: effects in the mouse -- Genome annotations at associated loci - Conclusion - Methods -- Study subjects -- Genotype data -- Phenotyping -- Statistical genetic analysis -- Interaction of EDAR with other genes -- Expression analysis for significant SNPs -- Detection of archaic introgression near ATF3 and association with facial features -- Annotation of SNPs in FUMA -- Shape GWAS in outbred mic
Intestinal toxicity to CTLA-4 blockade driven by IL-6 and myeloid infiltration
View full abstracthttps://openworks.mdanderson.org/leading-edge/1055/thumbnail.jp
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