438 research outputs found
Is Quantum Mechanics Compatible with an Entirely Deterministic Universe?
A b s t r a c t It will be argued that 1) the Bell inequalities are not
equivalent with those inequalities derived by Pitowsky and others that indicate
the Kolmogorovity of a probability model, 2) the original Bell inequalities are
irrelevant to both the question of whether or not quantum mechanics is a
Kolmogorovian theory as well as the problem of determinism, whereas 3) the
Pitowsky type inequalities are not violated by quantum mechanics, hence 4)
quantum mechanics is a Kolmogorovian probability theory, therefore, 5) it is
compatible with an entirely deterministic universe.Comment: 15 pages, (compressed and uuencoded) Postscript (188 kb), preprint
94/0
The Jurassic pleurotomarioidean gastropod Laevitomaria and its palaeobiogeographical history
The genus Laevitomaria is reviewed and its palaeobiogeographical history is reconstructed based on the re-examination of its type species L. problematica, the study of material stored at the National Natural History Museum of Luxembourg, and an extensive review of the literature. The systematic study allows ascribing to Laevitomaria a number of Jurassic species from the western European region formerly included in other pleurotomariid genera. The following new combinations are proposed: Laevitomaria allionta, Laevitomaria amyntas, Laevitomaria angulba, Laevitomaria asurai, Laevitomaria daityai, Laevitomaria fasciata, Laevitomaria gyroplata, Laevitomaria isarensis, Laevitomaria joannis, Laevitomaria repeliniana, Laevitomaria stoddarti, Laevitomaria subplatyspira, and Laevitomaria zonata. The genus, which was once considered as endemic of the central part of the western Tethys, shows an evolutionary and palaeogeographical history considerably more complex than previously assumed. It first appeared in the Late Sinemurian in the northern belt of the central western Tethys involved in the Neotethyan rifting, where it experienced a first radiation followed by an abrupt decline of diversity in the Toarcian. Species diversity increased again during Toarcian\u2013Aalenian times in the southernmost part of western European shelf and a major radiation occurred during the Middle Aalenian to Early Bajocian in the northern Paris Basin and southern England. After a latest Bajocian collapse of diversity, Laevitomaria disappeared from both the central part of western Tethys and the European shelf. In the Bathonian, the genus appeared in the south-eastern margin of the Tethys where it lasted until the Oxfordian
Detection of the evolutionary stages of variables in M3
The large number of variables in M3 provides a unique opportunity to study an
extensive sample of variables with the same apparent distance modulus. Recent,
high accuracy CCD time series of the variables show that according to their
mean magnitudes and light curve shapes, the variables belong to four separate
groups. Comparing the properties of these groups (magnitudes and periods) with
horizontal branch evolutionary models, we conclude that these samples can be
unambiguously identified with different stages of the horizontal branch stellar
evolution. Stars close to the zero age horizontal branch (ZAHB) show Oosterhoff
I type properties, while the brightest stars have Oosterhoff II type statistics
regarding their mean periods and RRab/RRc number ratios. This finding
strengthens the earlier suggestion of Lee et al. (1990) connecting the
Oosterhoff dichotomy to evolutionary effects, however, it is unexpected to find
large samples of both of the Oosterhoff type within a single cluster, which is,
moreover, the prototype of the Oosterhoff I class globular clusters. The very
slight difference between the Fourier parameters of the stars (at a given
period) in the three fainter samples spanning over about 0.15 mag range in M_V
points to the limitations of any empirical methods which aim to determine
accurate absolute magnitudes of RR Lyrae stars solely from the Fourier
parameters of the light curves.Comment: 4 pages, 4 figures. Submitted to Astrophys. J. Letter
Large size and slow rotation of the trans-Neptunian object (225088) 2007 OR10 discovered from Herschel and K2 observations
We present the first comprehensive thermal and rotational analysis of the
second most distant trans-Neptunian object (225088) 2007 OR10. We combined
optical light curves provided by the Kepler space telescope -- K2 extended
mission and thermal infrared data provided by the Herschel Space Observatory.
We found that (225088) 2007 OR10 is likely to be larger and darker than derived
by earlier studies: we obtained a diameter of d=1535^{+75}_{-225} km which
places (225088) 2007 OR10 in the biggest top three trans-Neptunian objects. The
corresponding visual geometric albedo is p_V=0.089^{+0.031}_{-0.009}. The light
curve analysis revealed a slow rotation rate of P_rot=44.81+/-0.37 h,
superseded by a very few objects only. The most likely light-curve solution is
double-peaked with a slight asymmetry, however, we cannot safely rule out the
possibility of having a rotation period of P_rot=22.40+/-0.18 h which
corresponds to a single-peaked solution. Due to the size and slow rotation, the
shape of the object should be a MacLaurin ellipsoid, so the light variation
should be caused by surface inhomogeneities. Its newly derived larger diameter
also implies larger surface gravity and a more likely retention of volatiles --
CH_4, CO and N_2 -- on the surface.Comment: Accepted for publication in AJ, 8 pages in emulateapj styl
Serotonin-mediated tuning of human helper T cell responsiveness to the chemokine CXCL12
In addition to its role as neurotransmitter, serotonin (5-HT) is an important modulator of inflammation and immunity. Here, we report novel findings suggesting a 5-HT involvement in T cell migration. In particular, we show that 5-HT tunes the responsiveness of human T lymphocytes to the broadly expressed chemokine CXCL12 in transwell migration assays. By real-time PCR, western blot analysis and electrophysiological patch clamp experiments, we demonstrate that the type 3 5-HT receptor (5-HT 3) is functionally expressed in human primary T cells. In addition, specific 5-HT 3 receptor agonists selectively decrease T cell migration towards gradients of CXCL12 but not of inflammatory chemokines, such as CCL2 and CCL5. In transmigration experiments, 5-HT 3 receptor stimulation reverts the inhibitory effect of endothelial-bound CXCL12 on T cell migration. Our data suggest that the reduced T cell responsiveness to CXCL12 induced by 5-HT may occur to facilitate T cell extravasation and migration into inflamed tissues
Evolutionary game dynamics in phenotype space
Evolutionary dynamics can be studied in well-mixed or structured populations.
Population structure typically arises from the heterogeneous distribution of
individuals in physical space or on social networks. Here we introduce a new
type of space to evolutionary game dynamics: phenotype space. The population is
well-mixed in the sense that everyone is equally likely to interact with
everyone else, but the behavioral strategies depend on distance in phenotype
space. Individuals might behave differently towards those who look similar or
dissimilar. Individuals mutate to nearby phenotypes. We study the `phenotypic
space walk' of populations. We present analytic calculations that bring
together ideas from coalescence theory and evolutionary game dynamics. As a
particular example, we investigate the evolution of cooperation in phenotype
space. We obtain a precise condition for natural selection to favor cooperators
over defectors: for a one-dimensional phenotype space and large population size
the critical benefit-to-cost ratio is given by b/c=1+2/sqrt{3}. We derive the
fundamental condition for any evolutionary game and explore higher dimensional
phenotype spaces.Comment: version 2: minor changes; equivalent to final published versio
On the detectability of habitable exomoons with Kepler-class photometry
In this paper we investigate the detectability of a habitable-zone exomoon
around various configurations of exoplanetary systems with the Kepler Mission
or photometry of approximately equal quality. We calculate both the predicted
transit timing signal amplitudes and the estimated uncertainty on such
measurements in order to calculate the confidence in detecting such bodies
across a broad spectrum of orbital arrangements. The effects of stellar
variability, instrument noise and photon noise are all accounted for in the
analysis. We validate our methodology by simulating synthetic lightcurves and
performing a Monte Carlo analysis for several cases of interest.
We find that habitable-zone exomoons down to 0.2 Earth masses may be detected
and ~25,000 stars could be surveyed for habitable-zone exomoons within Kepler's
field-of-view. A Galactic Plane survey with Kepler-class photometry could
potentially survey over one million stars for habitable-zone exomoons. In
conclusion, we propose that habitable exomoons will be detectable should they
exist in the local part of the galaxy.Comment: Accepted for publication in the Monthly Notices of the Royal
Astronomical Societ
Channel formation by yeast F-ATP synthase and the role of dimerization in the mitochondrial permeability transition
Purified F-ATP synthase dimers of yeast mitochondria display Ca(2+)-dependent channel activity with properties resembling those of the permeability transition pore (PTP) of mammals. After treatment with the Ca(2+) ionophore ETH129, which allows electrophoretic Ca(2+) uptake, isolated yeast mitochondria undergo inner membrane permeabilization due to PTP opening. Yeast mutant strains \u394TIM11 and \u394ATP20 (lacking the e and g F-ATP synthase subunits, respectively, which are necessary for dimer formation) display a striking resistance to PTP opening. These results show that the yeast PTP originates from F-ATP synthase and indicate that dimerization is required for pore formation in situ
- …