2,794 research outputs found
Strong uniqueness for stochastic evolution equations with unbounded measurable drift term
We consider stochastic evolution equations in Hilbert spaces with merely
measurable and locally bounded drift term and cylindrical Wiener noise. We
prove pathwise (hence strong) uniqueness in the class of global solutions. This
paper extends our previous paper (Da Prato, Flandoli, Priola and M. Rockner,
Annals of Prob., published online in 2012) which generalized Veretennikov's
fundamental result to infinite dimensions assuming boundedness of the drift
term. As in our previous paper pathwise uniqueness holds for a large class, but
not for every initial condition. We also include an application of our result
to prove existence of strong solutions when the drift is only measurable,
locally bounded and grows more than linearly.Comment: The paper will be published in Journal of Theoretical Probability.
arXiv admin note: text overlap with arXiv:1109.036
Analysis of ghrelin concentrations in serum samples processed at one, two, and three hours after collection
Obesity is becoming an epidemic of modern society. While the health-related consequences of obesity have been well studied, scientists continue to search for biological risk factors associated with this disease. Since the 1999 discovery of an appetite-stimulating hormone, ghrelin, researchers have further questioned the physiological interactions that lead to obesity. The fundus of the stomach, as well as the intestines and kidneys produce ghrelin before it circulates throughout the body and attaches to its receptor sites located within the section of the brain responsible for appetite-regulation. The hormone increases and decreases in a circadian rhythm that may dictate the routine human eating patterns of breakfast, lunch and dinner.
While the field of ghrelin research continues to grow as evidenced by the increasing number of published articles, the majority of the ghrelin research occurs in the laboratory setting. This environment has provided researchers with the preservation and storage techniques necessary to analyze ghrelin. For example, the current Millipore Human Ghrelin (Total) ELISA kit protocol for measuring ghrelin requires the collected blood be centrifuged thirty minutes after collection and immediately placed in a freezer. This limitation alone may impede researchers wishing to conduct clinical research because these requirements are frequently not possible.
The objectives of this study were to determine the optimal storage time before processing blood samples collected in the clinical setting to ensure the preservation of ghrelin and to conclude whether a change in the manufacturer\u27s protocol was warranted.
By comparing blood samples processed according to the Millipore ELISA kit protocol to samples stored for one, two, and three hours, it was determined that mean ghrelin concentrations at thirty minutes, one hour and two hour were not significantly different, suggesting that the current Millipore ELISA protocol of thirty minutes can be extended for a period of up to two hours.
When the crude model was adjusted to include the variables time, waist circumference and exercise, the statistically significant variables in previous ANOVA models, the presence or absence of an exercise routine was found to have the strongest association to mean ghrelin concentrations. These findings will facilitate the experimental design of research aimed at studying ghrelin levels in individuals outside of the laboratory setting, and can also support new research analyzing the effect of exercise on ghrelin levels
Bulk Mediated Surface Diffusion: The Infinite System Case
An analytical soluble model based on a Continuous Time Random Walk (CTRW)
scheme for the adsorption-desorption processes at interfaces, called
bulk-mediated surface diffusion, is presented. The time evolution of the
effective probability distribution width on the surface is calculated and
analyzed within an anomalous diffusion framework. The asymptotic behavior for
large times shows a sub-diffusive regime for the effective surface diffusion
but, depending on the observed range of time, other regimes may be obtained.
Montecarlo simulations show excellent agreement with analytical results. As an
important byproduct of the indicated approach, we present the evaluation of the
time for the first visit to the surface.Comment: 15 pages, 7 figure
Bulk Mediated Surface Diffusion: Finite System Case
We address the dynamics of adsorbed molecules (a fundamental issue in surface
physics) within the framework of a Master Equation scheme, and study the
diffusion of particles in a finite cubic lattice whose boundaries are at the
and the planes where , while the and
directions are unbounded. As we are interested in the effective diffusion
process at the interface , we calculate analytically the conditional
probability for finding the system on the plane as well as the surface
dispersion as a function of time and compare these results with Monte Carlo
simulations finding an excellent agreement.Comment: 19 pages, 8 figure
Seasonal changes in population of the Amphipod Gammarus aequicauda (Martynov, 1931)
Monthly collections were made for one year (March 2001 to February 2002) in Mar Piccolo of Taranto (Ionian sea, Italy), in order to establish the seasonal fluctuations of a population of Gammarus aequicauda (Crustacea, Amphipoda). Variations in the population structure, sex ratio and fecundity were studied. The population comprised all stages of the life cycle all year round, thus showing continuous reproduction. Size differences between males and females occurred throughout the year with males being larger than females. The recruitment of juveniles into the population occurred particularly in autumn-winter. Females consistently predominated in numbers over males during winter months. Female cephalic length was positively correlated with eggs number
The Symplectic Penrose Kite
The purpose of this article is to view the Penrose kite from the perspective
of symplectic geometry.Comment: 24 pages, 7 figures, minor changes in last version, to appear in
Comm. Math. Phys
Dynamical Masses of Low Mass Stars in the Taurus and Ophiuchus Star Forming Regions
We report new dynamical masses for 5 pre-main sequence (PMS) stars in the
L1495 region of the Taurus star-forming region (SFR) and 6 in the L1688 region
of the Ophiuchus SFR. Since these regions have VLBA parallaxes these are
absolute measurements of the stars' masses and are independent of their
effective temperatures and luminosities. Seven of the stars have masses
solar masses, thus providing data in a mass range with little data, and of
these, 6 are measured to precision . We find 8 stars with masses in the
range 0.09 to 1.1 solar mass that agree well with the current generation of PMS
evolutionary models. The ages of the stars we measured in the Taurus SFR are in
the range 1-3 MY, and MY for those in L1688. We also measured the
dynamical masses of 14 stars in the ALMA archival data for Akeson~\&~Jensen's
Cycle 0 project on binaries in the Taurus SFR. We find that the masses of 7 of
the targets are so large that they cannot be reconciled with reported values of
their luminosity and effective temperature. We suggest that these targets are
themselves binaries or triples.Comment: 20 page
Electron-Electron Bremsstrahlung Emission and the Inference of Electron Flux Spectra in Solar Flares
Although both electron-ion and electron-electron bremsstrahlung contribute to
the hard X-ray emission from solar flares, the latter is normally ignored. Such
an omission is not justified at electron (and photon) energies above
keV, and inclusion of the additional electron-electron bremsstrahlung in
general makes the electron spectrum required to produce a given hard X-ray
spectrum steeper at high energies.
Unlike electron-ion bremsstrahlung, electron-electron bremsstrahlung cannot
produce photons of all energies up to the maximum electron energy involved. The
maximum possible photon energy depends on the angle between the direction of
the emitting electron and the emitted photon, and this suggests a diagnostic
for an upper cutoff energy and/or for the degree of beaming of the accelerated
electrons.
We analyze the large event of January 17, 2005 observed by RHESSI and show
that the upward break around 400 keV in the observed hard X-ray spectrum is
naturally accounted for by the inclusion of electron-electron bremsstrahlung.
Indeed, the mean source electron spectrum recovered through a regularized
inversion of the hard X-ray spectrum, using a cross-section that includes both
electron-ion and electron-electron terms, has a relatively constant spectral
index over the range from electron kinetic energy keV to MeV. However, the level of detail discernible in the recovered electron
spectrum is not sufficient to determine whether or not any upper cutoff energy
exists.Comment: 7 pages, 5 figures, submitted to Astrophysical Journa
Wolf-like or dog-like? A comparison of gazing behaviour across three dog breeds tested in their familiar environments
Human-directed gazing, a keystone in dog\u2013human communication, has been suggested to derive from both domestication and breed selection. The influence of genetic similarity to wolves and selective pressures on human-directed gazing is still under debate. Here, we used the \u2018unsolvable task\u2019 to compare Czechoslovakian Wolfdogs (CWDs, a close-to-wolf breed), German Shepherd Dogs (GSDs) and Labrador Retrievers (LRs). In the \u2018solvable task\u2019, all dogs learned to obtain the reward; however, differently from GSDs and LRs, CWDs rarely gazed at humans. In the \u2018unsolvable task\u2019, CWDs gazed significantly less towards humans compared to LRs but not to GSDs. Although all dogs were similarly motivated to explore the apparatus, CWDs and GSDs spent a larger amount of time in manipulating it compared to LRs. A clear difference emerged in gazing at the experimenter versus owner. CWDs gazed preferentially towards the experimenter (the unfamiliar subject manipulating the food), GSDs towards their owners and LRs gazed at humans independently from their level of familiarity. In conclusion, it emerges that the artificial selection operated on CWDs produced a breed more similar to ancient breeds (more wolf-like due to a less-intense artificial selection) and not very human-oriented. The next step is to clarify GSDs\u2019 behaviour and better understand the genetic role of this breed in shaping CWDs\u2019 heterospecific behaviour
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