355 research outputs found
Post-Einsteinian tests of gravitation
Einstein gravitation theory can be extended by preserving its geometrical
nature but changing the relation between curvature and energy-momentum tensors.
This change accounts for radiative corrections, replacing the Newton
gravitation constant by two running couplings which depend on scale and differ
in the two sectors of traceless and traced tensors. The metric and curvature
tensors in the field of the Sun, which were obtained in previous papers within
a linearized approximation, are then calculated without this restriction.
Modifications of gravitational effects on geodesics are then studied, allowing
one to explore phenomenological consequences of extensions lying in the
vicinity of general relativity. Some of these extended theories are able to
account for the Pioneer anomaly while remaining compatible with tests involving
the motion of planets. The PPN Ansatz corresponds to peculiar extensions of
general relativity which do not have the ability to meet this compatibility
challenge.Comment: 19 pages Corrected typo
The Behaviour Of Cosmological Models With Varying-G
We provide a detailed analysis of Friedmann-Robertson-Walker universes in a
wide range of scalar-tensor theories of gravity. We apply solution-generating
methods to three parametrised classes of scalar-tensor theory which lead
naturally to general relativity in the weak-field limit. We restrict the
parameters which specify these theories by the requirements imposed by the
weak-field tests of gravitation theories in the solar system and by the
requirement that viable cosmological solutions be obtained. We construct a
range of exact solutions for open, closed, and flat isotropic universes
containing matter with equation of state and in vacuum.
We study the range of early and late-time behaviours displayed, examine when
there is a `bounce' at early times, and expansion maxima in closed models.Comment: 58 pages LaTeX, 6 postscript figures, uses eps
Can the Pioneer anomaly be of gravitational origin? A phenomenological answer
In order to satisfy the equivalence principle, any non-conventional mechanism
proposed to gravitationally explain the Pioneer anomaly, in the form in which
it is presently known from the so-far analyzed Pioneer 10/11 data, cannot leave
out of consideration its impact on the motion of the planets of the Solar
System as well, especially those orbiting in the regions in which the anomalous
behavior of the Pioneer probes manifested itself. In this paper we, first,
discuss the residuals of the right ascension \alpha and declination \delta of
Uranus, Neptune and Pluto obtained by processing various data sets with
different, well established dynamical theories (JPL DE, IAA EPM, VSOP). Second,
we use the latest determinations of the perihelion secular advances of some
planets in order to put on the test two gravitational mechanisms recently
proposed to accommodate the Pioneer anomaly based on two models of modified
gravity. Finally, we adopt the ranging data to Voyager 2 when it encountered
Uranus and Neptune to perform a further, independent test of the hypothesis
that a Pioneer-like acceleration can also affect the motion of the outer
planets of the Solar System. The obtained answers are negative.Comment: Latex2e, 26 pages, 6 tables, 2 figure, 47 references. It is the
merging of gr-qc/0608127, gr-qc/0608068, gr-qc/0608101 and gr-qc/0611081.
Final version to appear in Foundations of Physic
Anorgasmia in women
This article reports on the etiology and treatment of anorgasmia. Etiological factors include childhood and adolescent experiences, current individual attitudes, and lifestyle factors, as well as the quality and dynamics of past and present committed relationships. It is important to assess the nature of each of the previously mentioned factors in determining the nature of the orgasmic dysfunction as well as assisting in the development of a treatment plan. Treatment approaches for anorgasmia need to address individual factors (e.g., performance anxiety, poor body image) as well as interpersonal problems. A systemic treatment framework would appear to be the most useful approach to treat this sexual dysfunction, as this type of strategy identifies and treats the difficulties experienced by the anorgasmic woman within the total context of her life. Of course, this approach necessitates the involvement of the partner in therapy, and treatment is unlikely to be effective unless the problems experienced by both the woman and her partner are addressed. Limitations of past research in terms of inadequate evaluation of treatment, low sample sizes, and poorly defined interventions are discussed. Finally, directions for future research to advance our understanding of the most effective treatments for anorgasmia are considered. <br /
Post-Einsteinian tests of linearized gravitation
The general relativistic treatment of gravitation can be extended by
preserving the geometrical nature of the theory but modifying the form of the
coupling between curvature and stress tensors. The gravitation constant is thus
replaced by two running coupling constants which depend on scale and differ in
the sectors of traceless and traced tensors. When calculated in the solar
system in a linearized approximation, the metric is described by two
gravitation potentials. This extends the parametrized post-Newtonian (PPN)
phenomenological framework while allowing one to preserve compatibility with
gravity tests performed in the solar system. Consequences of this extension are
drawn here for phenomena correctly treated in the linear approximation. We
obtain a Pioneer-like anomaly for probes with an eccentric motion as well as a
range dependence of Eddington parameter to be seen in light deflection
experiments.Comment: 15 pages. Accepted version, to appear in Classical and Quantum
Gravit
An approach for the identification of targets specific to bone metastasis using cancer genes interactome and gene ontology analysis
Metastasis is one of the most enigmatic aspects of cancer pathogenesis and is
a major cause of cancer-associated mortality. Secondary bone cancer (SBC) is a
complex disease caused by metastasis of tumor cells from their primary site and
is characterized by intricate interplay of molecular interactions.
Identification of targets for multifactorial diseases such as SBC, the most
frequent complication of breast and prostate cancers, is a challenge. Towards
achieving our aim of identification of targets specific to SBC, we constructed
a 'Cancer Genes Network', a representative protein interactome of cancer genes.
Using graph theoretical methods, we obtained a set of key genes that are
relevant for generic mechanisms of cancers and have a role in biological
essentiality. We also compiled a curated dataset of 391 SBC genes from
published literature which serves as a basis of ontological correlates of
secondary bone cancer. Building on these results, we implement a strategy based
on generic cancer genes, SBC genes and gene ontology enrichment method, to
obtain a set of targets that are specific to bone metastasis. Through this
study, we present an approach for probing one of the major complications in
cancers, namely, metastasis. The results on genes that play generic roles in
cancer phenotype, obtained by network analysis of 'Cancer Genes Network', have
broader implications in understanding the role of molecular regulators in
mechanisms of cancers. Specifically, our study provides a set of potential
targets that are of ontological and regulatory relevance to secondary bone
cancer.Comment: 54 pages (19 pages main text; 11 Figures; 26 pages of supplementary
information). Revised after critical reviews. Accepted for Publication in
PLoS ON
First results from the multichannel interferometer system on HSX
This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder
Fast and Slow Effects of Medial Olivocochlear Efferent Activity in Humans
Background: The medial olivocochlear (MOC) pathway modulates basilar membrane motion and auditory nerve activity on both a fast (10–100 ms) and a slow (10–100 s) time scale in guinea pigs. The slow MOC modulation of cochlear activity is postulated to aide in protection against acoustic trauma. However in humans, the existence and functional roles of slow MOC effects remain unexplored. Methodology/Principal Findings: By employing contralateral noise at moderate to high levels (68 and 83 dB SPL) as an MOC reflex elicitor, and spontaneous otoacoustic emissions (SOAEs) as a non-invasive probe of the cochlea, we demonstrated MOC modulation of human cochlear output both on a fast and a slow time scale, analogous to the fast and slow MOC efferent effects observed on basilar membrane vibration and auditory nerve activity in guinea pigs. The magnitude of slow effects was minimal compared with that of fast effects. Consistent with basilar membrane and auditory nerve activity data, SOAE level was reduced by both fast and slow MOC effects, whereas SOAE frequency was elevated by fast and reduced by slow MOC effects. The magnitudes of fast and slow effects on SOAE level were positively correlated. Conclusions/Significance: Contralateral noise up to 83 dB SPL elicited minimal yet significant changes in both SOAE leve
Mifamurtide for the treatment of nonmetastatic osteosarcoma
International audienceINTRODUCTION: The standard treatment for osteosarcoma requires both macroscopic surgical wide resection and postoperative multi-drug chemotherapy in neoadjuvant and adjuvant settings. However, the 5-year event-free survival has remained at a plateau of 60-70% of patients with nonmetastatic osteosarcoma for more than 30 years. AREAS COVERED: Mifamurtide (liposomal muramyl tripeptide phosphatidylethanolamine; L-MTP-PE) is a new agent. L-MTP-PE is a nonspecific immunomodulator, which is a synthetic analog of a component of bacterial cell walls. L-MTP-PE activates macrophages and monocytes as a potent activator of immune response in addition to standard chemotherapy. It also improves the overall survival from 70 to 78% and results in a one-third reduction in the risk of death from osteosarcoma. This review summarizes the most recent findings about L-MTP-PE and its therapeutic application for nonmetastatic osteosarcoma. EXPERT OPINION: Recently, L-MTP-PE has been approved in Europe for the treatment of nonmetastatic osteosarcoma with chemotherapy. L-MTP-PE in combination with traditional treatment is expected to go mainstream and to be beneficial for patients with osteosarcoma. Information about potential benefit regarding mifamurtide use in the neoadjuvant setting (i.e., before surgery) and/or usefulness of L-MTP-PE in metastatic in relapsed and metastatic osteosarcoma requires analysis of expanded access and/or future clinical trials of L-MTP-PE in high-burden and low-burden situations
- …