342 research outputs found
Evolution and Earth's Entropy
Entropy decreases on the Earth due to day/night temperature differences. This
decrease exceeds the decrease in entropy on the Earth related to evolution by
many orders of magnitude. Claims by creationists that science is somehow
inconsistent with regard to evolution are thus show to be baseless.Comment: 2 page
Reference frames and rigid motions in relativity: Applications
The concept of rigid reference frame and of constricted spatial metric, given
in the previous work [\emph{Class. Quantum Grav.} {\bf 21}, 3067,(2004)] are
here applied to some specific space-times: In particular, the rigid rotating
disc with constant angular velocity in Minkowski space-time is analyzed, a new
approach to the Ehrenfest paradox is given as well as a new explanation of the
Sagnac effect. Finally the anisotropy of the speed of light and its measurable
consequences in a reference frame co-moving with the Earth are discussed.Comment: 13 pages, 1 figur
The Relative Space: Space Measurements on a Rotating Platform
We introduce here the concept of relative space, an extended 3-space which is
recognized as the only space having an operational meaning in the study of the
space geometry of a rotating disk. Accordingly, we illustrate how space
measurements are performed in the relative space, and we show that an old-aged
puzzling problem, that is the Ehrenfest's paradox, is explained in this purely
relativistic context. Furthermore, we illustrate the kinematical origin of the
tangential dilation which is responsible for the solution of the Ehrenfest's
paradox.Comment: 14 pages, 2 EPS figures, LaTeX, to appear in the European Journal of
Physic
Relativistic contraction and related effects in noninertial frames
Although there is no relative motion among different points on a rotating
disc, each point belongs to a different noninertial frame. This fact, not
recognized in previous approaches to the Ehrenfest paradox and related
problems, is exploited to give a correct treatment of a rotating ring and a
rotating disc. Tensile stresses are recovered, but, contrary to the prediction
of the standard approach, it is found that an observer on the rim of the disc
will see equal lengths of other differently moving objects as an inertial
observer whose instantaneous position and velocity are equal to that of the
observer on the rim. The rate of clocks at various positions, as seen by
various observers, is also discussed. Some results are generalized for
observers arbitrarily moving in a flat or a curved spacetime. The generally
accepted formula for the space line element in a non-time-orthogonal frame is
found inappropriate in some cases. Use of Fermi coordinates leads to the result
that for any observer the velocity of light is isotropic and is equal to ,
providing that it is measured by propagating a light beam in a small
neighborhood of the observer.Comment: 15 pages, significantly revised version, title changed, to appear in
Phys. Rev.
On the experimental determination of the one-way speed of light
In this contribution the question of the isotropy of the one-way speed of
light from an experimental perspective is addressed. In particular, we analyze
two experimental methods commonly used in its determination. The analysis is
aimed at clarifying the view that the one-way speed of light cannot be
determined by techniques in which physical entities close paths. The procedure
employed here will provide epistemological tools such that physicists
understand that a direct measurement of the speed not only of light but of any
physical entity is by no means trivial. Our results shed light on the physics
behind the experiments which may be of interest for both physicists with an
elemental knowledge in special relativity and philosophers of science.Comment: 8 pages, 5 figures. To appear in the European Journal of Physic
Enantioselective Synthesis of Sealutomicin C
The sealutomicins are a family of anthraquinone antibiotics featuring an enediyne (sealutomicin A) or Bergman-cyclized aromatic ring (sealutomicins B–D). Herein we report the development of an enantioselective organocatalytic method for the synthesis of dihydroquinolines and the use of the developed method in the total synthesis of sealutomicin C which features a transannular cyclization of an aryllithium onto a γ-lactone as a second key step
Simultaneity and generalized connections in general relativity
Stationary extended frames in general relativity are considered. The
requirement of stationarity allows to treat the spacetime as a principal fiber
bundle over the one-dimensional group of time translations. Over this bundle a
connection form establishes the simultaneity between neighboring events
accordingly with the Einstein synchronization convention. The mathematics
involved is that of gauge theories where a gauge choice is interpreted as a
global simultaneity convention. Then simultaneity in non-stationary frames is
investigated: it turns to be described by a gauge theory in a fiber bundle
without structure group, the curvature being given by the Fr\"olicher-Nijenhuis
bracket of the connection. The Bianchi identity of this gauge theory is a
differential relation between the vorticity field and the acceleration field.
In order for the simultaneity connection to be principal, a necessary and
sufficient condition on the 4-velocity of the observers is given.Comment: RevTeX, 9 pages, 2 figures, 1 table. Previous title "The gauge nature
of simultaneity". Classical and Quantum Gravity
http://www.iop.org/EJ/journal/CQ
The relativistic Sagnac Effect: two derivations
The phase shift due to the Sagnac Effect, for relativistic matter and
electromagnetic beams, counter-propagating in a rotating interferometer, is
deduced using two different approaches. From one hand, we show that the
relativistic law of velocity addition leads to the well known Sagnac time
difference, which is the same independently of the physical nature of the
interfering beams, evidencing in this way the universality of the effect.
Another derivation is based on a formal analogy with the phase shift induced by
the magnetic potential for charged particles travelling in a region where a
constant vector potential is present: this is the so called Aharonov-Bohm
effect. Both derivations are carried out in a fully relativistic context, using
a suitable 1+3 splitting that allows us to recognize and define the space where
electromagnetic and matter waves propagate: this is an extended 3-space, which
we call "relative space". It is recognized as the only space having an actual
physical meaning from an operational point of view, and it is identified as the
'physical space of the rotating platform': the geometry of this space turns out
to be non Euclidean, according to Einstein's early intuition.Comment: 49 pages, LaTeX, 3 EPS figures. Revised (final) version, minor
corrections; to appear in "Relativity in Rotating Frames", ed. G. Rizzi and
M.L. Ruggiero, Kluwer Academic Publishers, Dordrecht, (2003). See also
http://digilander.libero.it/solciclo
An early peak of relapse after surgery for breast cancer
There is great interest among oncologists concerning what we might learn by examining the pattern of relapse after breast cancer surgery. What you see depends upon how hard you look. Up to now, investigators have examined the hazard ratio for relapse every 6–12 months. In a research paper, published in this issue of Breast Cancer Research, the Milan group have looked at the hazard ratio every three months and have found, for the first time, a distinct, very early peak of relapse in a group of premenopausal, node-positive patients not given chemotherapy or hormone therapy. What is now needed is for other groups to repeat this observation and, if found, to examine the characteristics of the tumours producing this phenomenon in order to develop hypotheses about its cause and possible treatments
Genetic Variants of VEGFA and FLT4 Are Determinants of Survival in Renal Cell Carcinoma Patients Treated with Sorafenib
Molecular markers of sorafenib efficacy in patients with metastatic renal cell carcinoma (mRCC) are not available. The purpose of this study was to discover genetic markers of survival in patients with mRCC treated with sorafenib. Germline variants from 56 genes were genotyped in 295 patients with mRCC. Variant-overall survival (OS) associations were tested in multivariate regression models. Mechanistic studies were conducted to validate clinical associations. VEGFA rs1885657, ITGAV rs3816375, and WWOX rs8047917 (sorafenib arm), and FLT4 rs307826 and VEGFA rs3024987 (sorafenib and placebo arms combined) were associated with shorter OS. FLT4 rs307826 increased VEGFR-3 phosphorylation, membrane trafficking, and receptor activation. VEGFA rs1885657 and rs58159269 increased transcriptional activity of the constructs containing these variants in endothelial and RCC cell lines, and VEGFA rs58159269 increased endothelial cell proliferation and tube formation. FLT4 rs307826 and VEGFA rs58159269 led to reduced sorafenib cytotoxicity. Genetic variation in VEGFA and FLT4 could affect survival in sorafenib-treated patients with mRCC. These markers should be examined in additional malignancies treated with sorafenib and in other angiogenesis inhibitors used in mRCC. Significance: Clinical and mechanistic data identify germline genetic variants in VEGFA and FLT4 as markers of survival in patients with metastatic renal cell carcinoma.Peer reviewe
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