79 research outputs found
Matter collineations of Spacetime Homogeneous G\"odel-type Metrics
The spacetime homogeneous G\"odel-type spacetimes which have four classes of
metrics are studied according to their matter collineations. The obtained
results are compared with Killing vectors and Ricci collineations. It is found
that these spacetimes have infinite number of matter collineations in
degenerate case, i.e. det, and do not admit proper matter
collineations in non-degenerate case, i.e. det. The degenerate
case has the new constraints on the parameters and which characterize
the causality features of the G\"odel-type spacetimes.Comment: 12 pages, LaTex, no figures, Class. Quantum.Grav.20 (2003) 216
On a stationary spinning string spacetime
The properties of a stationary massless string endowed with intrinsic spin
are discussed. The spacetime is Minkowskian geometrically but the topology is
nontrivial due to the horizon located on the surface , similar with
Rindler's case. For less than the Planck length , has the
same sign as and closed timelike curves are possible.
We assume an elementary particles' spin originates in the frame dragging
effect produced by the rotation of the source. The Sagnac time delay is
calculated and proves to be constant.Comment: revised version of hep-th/0602014 v1, 7 pages, title changed, sec.5
removed, talk given at "Recent Developments in Gravity" (NEB XII), Nafplio,
Greece, 29 June 200
The astrometric Gaia-FUN-SSO observation campaign of 99 942 Apophis
Astrometric observations performed by the Gaia Follow-Up Network for Solar
System Objects (Gaia-FUN-SSO) play a key role in ensuring that moving objects
first detected by ESA's Gaia mission remain recoverable after their discovery.
An observation campaign on the potentially hazardous asteroid (99 942) Apophis
was conducted during the asteroid's latest period of visibility, from
12/21/2012 to 5/2/2013, to test the coordination and evaluate the overall
performance of the Gaia-FUN-SSO . The 2732 high quality astrometric
observations acquired during the Gaia-FUN-SSO campaign were reduced with the
Platform for Reduction of Astronomical Images Automatically (PRAIA), using the
USNO CCD Astrograph Catalogue 4 (UCAC4) as a reference. The astrometric
reduction process and the precision of the newly obtained measurements are
discussed. We compare the residuals of astrometric observations that we
obtained using this reduction process to data sets that were individually
reduced by observers and accepted by the Minor Planet Center. We obtained 2103
previously unpublished astrometric positions and provide these to the
scientific community. Using these data we show that our reduction of this
astrometric campaign with a reliable stellar catalog substantially improves the
quality of the astrometric results. We present evidence that the new data will
help to reduce the orbit uncertainty of Apophis during its close approach in
2029. We show that uncertainties due to geolocations of observing stations, as
well as rounding of astrometric data can introduce an unnecessary degradation
in the quality of the resulting astrometric positions. Finally, we discuss the
impact of our campaign reduction on the recovery process of newly discovered
asteroids.Comment: Accepted for publication in A&
Stationary Cylindrical Anisotropic Fluid
We present the whole set of equations with regularity and matching conditions
required for the description of physically meaningful stationary cylindrically
symmmetric distributions of matter, smoothly matched to Lewis vacuum spacetime.
A specific example is given. The electric and magnetic parts of the Weyl tensor
are calculated, and it is shown that purely electric solutions are necessarily
static. Then, it is shown that no conformally flat stationary cylindrical fluid
exits, satisfying regularity and matching conditions.Comment: 17 pages Latex. To appear in Gen.Rel.Gra
Does rotation generate a massive string ?
The properties of a stationary massive string endowed with intrinsic angular
momentum are investigated. The spacetime is generated by an "improper" time
translation combined with uniform rotation. The mass per unit length of the
string is proportional to the angular velocity . The spacetime is
Minkowskian geometrically but the topology is nontrivial thanks to the event
horizon located on the surface (similar with Rindler's spacetime) and
to the deficit angle generated by rotation. The Sagnac time delay is
calculated. It proves to be nonvanishing even when due to the
intrinsic spin of the string.Comment: 4 pages, minor changes, talk given at the XXIXth Spanish Relativity
Meeting (ERE 2006), Palma de Mallorca, Spain, Sept. 4 - 8, 2006, appeared in
Jour. Phys. : Conf. Ser. 66 (2007) 01205
TRP genes family expression in colorectal cancer
Colorectal cancer (CRC) is the most common cancer of the gastrointestinal tract. Different factors are responsible for the development of CRC. Transient Receptor Potential (TRP) which is an important component of calcium channel is associated with several pathological conditions like cancer, neurodegenerative and cardiovascular diseases. Thirty members of the family of TRP ion channel in mammals have been determined till now. The aim of this study is to investigate TRPM, TRPV and TRPC gene expression levels in tumor tissues of CRC patients and to analyze the relationship of expression in tumor tissue of CRC with other known prognostic factors. Material and Methods: In this study, 93 CRC patients were included. The level of TRP gene expression in paraffin blocks of normal and cancerous colorectal tissue samples were studied at the level of mRNA with Real-time PCR. Results: The mRNA expression level of TRPV3, TRPV4, TRPV5, TRPM4 and TRPC6 genes in 37 female and 56 male patients diagnosed with CRC was revealed lower in tumor tissue as compared to normal tissue (p < 0.05). No statistically significant differences of mRNA expression levels of other TRP genes were found. Conclusions: TRP gene family like TRPV3, TRPV4, TRPV5, TRPM4 and TRPC6 may be thought as potential genes contributing to tumorigenesis as their expression decreases in CRC as compared to normal tissues. Key Words: colorectal cancer, TRP genes family: TRPV3, TRPV4, TRPV5, TRPM4, TRPC6, mRNA expression
Tako-tsubo cardiomyopathy after administration of ergometrine following elective caesarean delivery: a case report
<p>Abstract</p> <p>Introduction</p> <p>Tako-tsubo cardiomyopathy (stress-induced cardiomyopathy or transient left ventricular ballooning) is characterized by clinical suspicion of an acute myocardial infarction with transient apical or midventricular dyskinesia of the left ventricle without significant coronary stenosis on angiography. The etiology of this disease remains obscure. One of the possible causes is myocardial ischemia induced by coronary vasospasm due to sympathetic activation. It has been hypothesized that the application of ergometrine could induce tako-tsubo cardiomyopathy.</p> <p>Case presentation</p> <p>We report the case of a 28-year-old Turkish woman who developed tako-tsubo cardiomyopathy after administration of ergometrine for release of placenta and prevention of bleeding during the post-partum phase in the course of an elective caesarean delivery. Tako-tsubo cardiomyopathy was diagnosed by echocardiography and urgent cardiac magnetic resonance imaging. A coronary angiography was not performed because of the absence of myocardial necrosis or ischemia and signs of myocarditis on cardiac magnetic resonance imaging.</p> <p>Conclusion</p> <p>This life-threatening disease should be excluded in the differential diagnosis by comparing the symptoms with those of typical heart failure, particularly after use of ergometrine.</p
LRS Bianchi type I universes exhibiting Noether symmetry in the scalar-tensor Brans-Dicke theory
Following up on hints of anisotropy in the cosmic microwave background
radiation (CMB) data, we investigate locally rotational symmetric (LRS) Bianchi
type I spacetimes with non-minimally coupled scalar fields. To single out
potentially more interesting solutions, we search for Noether symmetry in this
system. We then specialize to the Brans-Dicke (BD) field in such a way that the
Lagrangian becomes degenerate (nontrivial) and solve the equations for Noether
symmetry and the potential that allows it. Then we find the exact solutions of
the equations of motion in terms of three parameters and an arbitrary function.
We illustrate with families of examples designed to be generalizations of the
well-known power-expansion, exponential expansion and Big Rip models in the
Friedmann-Robertson-Walker (FRW) framework. The solutions display surprising
variation, a large subset of which features late-time acceleration as is
usually ascribed to dark energy (phantom or quintensence), and is consistent
with observational data.Comment: 25 pages, no figure, to appear in General Relativity and Gravitatio
Adult Cardiac Progenitor Cell Aggregates Exhibit Survival Benefit Both In Vitro and In Vivo
Background: A major hurdle in the use of exogenous stems cells for therapeutic regeneration of injured myocardium remains the poor survival of implanted cells. To date, the delivery of stem cells into myocardium has largely focused on implantation of cell suspensions. Methodology and Principal Findings: We hypothesize that delivering progenitor cells in an aggregate form would serve to mimic the endogenous state with proper cell-cell contact, and may aid the survival of implanted cells. Microwell methodologies allow for the culture of homogenous 3D cell aggregates, thereby allowing cell-cell contact. In this study, we find that the culture of cardiac progenitor cells in a 3D cell aggregate augments cell survival and protects against cellular toxins and stressors, including hydrogen peroxide and anoxia/reoxygenation induced cell death. Moreover, using a murine model of cardiac ischemia-reperfusion injury, we find that delivery of cardiac progenitor cells in the form of 3D aggregates improved in vivo survival of implanted cells. Conclusion: Collectively, our data support the notion that growth in 3D cellular systems and maintenance of cell-cell contact improves exogenous cell survival following delivery into myocardium. These approaches may serve as a strategy to improve cardiovascular cell-based therapies
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