3,169 research outputs found
On Tunnelling Through the Black Hole Horizon
It is shown here that there is no way for particle creation to occur by
quantum tunneling through an infinitesimal neighborhood of the black hole
horizon. This result is a trivial consequence of the regularity of the horizon,
the equivalence principle and the general covariance of the relativistic theory
of gravity. Moreover, we also confirm the less trivial statement that no
particle creation by quantum tunneling through the black hole horizon is
possible independent of the size of the presupposed tunneling domain.Comment: 21 pages, new section is adde
On the evolution of decoys in plant immune systems
The Guard-Guardee model for plant immunity describes how resistance proteins
(guards) in host cells monitor host target proteins (guardees) that are
manipulated by pathogen effector proteins. A recently suggested extension of
this model includes decoys, which are duplicated copies of guardee proteins,
and which have the sole function to attract the effector and, when modified by
the effector, trigger the plant immune response. Here we present a
proof-of-principle model for the functioning of decoys in plant immunity,
quantitatively developing this experimentally-derived concept. Our model links
the basic cellular chemistry to the outcomes of pathogen infection and
resulting fitness costs for the host. In particular, the model allows
identification of conditions under which it is optimal for decoys to act as
triggers for the plant immune response, and of conditions under which it is
optimal for decoys to act as sinks that bind the pathogen effectors but do not
trigger an immune response.Comment: 15 pages, 6 figure
Bosonic D-branes at finite temperature with an external field
Bosonic boundary states at finite temperature are constructed as solutions of
boundary conditions at for bosonic open strings with a constant gauge
field coupled to the boundary. The construction is done in the
framework of thermo field dynamics where a thermal Bogoliubov transformation
maps states and operators to finite temperature. Boundary states are given in
terms of states from the direct product space between the Fock space of the
closed string and another identical copy of it. By analogy with zero
temperature, the boundary states heve the interpretation of -brane at
finite temperature. The boundary conditions admit two different solutions. The
entropy of the closed string in a -brane state is computed and analysed. It
is interpreted as the entropy of the -brane at finite temperature.Comment: 21 pages, Latex, revised version with minor corrections and
references added, to be published in Phys. Rev.
Rapid and concomitant gut microbiota and endocannabinoidome response to diet-induced obesity in mice
The intestinal microbiota and the expanded endocannabinoid (eCB) system, or endocannabinoidome (eCBome), have both been implicated in diet-induced obesity and dysmetabolism. These systems were recently suggested to interact during the development of obesity. We aimed at identifying the potential interactions between gut microbiota composition and the eCBome during the establishment of diet-induced obesity and metabolic complications. Male mice were fed a high-fat, high-sucrose (HFHS) diet for 56âdays to assess jejunum, ileum, and cecum microbiomes by 16S rRNA gene metataxonomics as well as ileum and plasma eCBome by targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS). The HFHS diet induced early (3âdays) and persistent glucose intolerance followed by weight gain and hyperinsulinemia. Concomitantly, it induced the elevation of the two eCBs, anandamide, in both ileum and plasma, and 2-arachidonoyl-glycerol, in plasma, as well as alterations in several other N-acylethanolamines and 2-acylglycerols. It also promoted segment-specific changes in the relative abundance of several genera in intestinal microbiota, some of which were observed as early as 3âdays following HFHS diet. Weight-independent correlations were found between the relative abundances of, among others, Barnesiella, Eubacterium, Adlercreutzia, Parasutterella, Propionibacterium, Enterococcus, and Methylobacterium and the concentrations of anandamide and the anti-inflammatory eCBome mediator N-docosahexaenoyl-ethanolamine. This study highlights for the first time the existence of potential interactions between the eCBome, an endogenous system of multifunctional signaling lipids, and several intestinal genera during early and late HFHS-induced dysmetabolic events, with potential impact on the host capability of adapting to increased intake of fat and sucrose
Charge Induced Vortex Lattice Instability
It has been predicted that superconducting vortices should be electrically
charged and that this effect is particularly enhanced for, high temperature
superconductors.\cite{kho95,bla96} Hall effect\cite{hag91} and nuclear magnetic
resonance (NMR) experiments\cite{kum01} suggest the existence of vortex
charging, but the effects are small and the interpretation controversial. Here
we show that the Abrikosov vortex lattice, characteristic of the mixed state of
superconductors, will become unstable at sufficiently high magnetic field if
there is charge trapped on the vortex core. Our NMR measurements of the
magnetic fields generated by vortices in BiSrCaCuO
single crystals\cite{che07} provide evidence for an electrostatically driven
vortex lattice reconstruction with the magnitude of charge on each vortex
pancake of x, depending on doping, in line
with theoretical estimates.\cite{kho95,kna05}Comment: to appear in Nature Physics; 6 pages, 7 figure
Sedentary Time and Central Adiposity in Children
There is currently a global epidemic of obesity, with a recent pooled analysis indicating that over the last forty yrs, the number of obese people worldwide has risen from 105 million to 641 million (1). The global economic and clinical burden is substantial, with pressures not only for treating obesity per se but also for treating the associated myriad of noncommunicable diseases such as type 2 diabetes, fatty liver disease, cardiovascular disease, osteoarthritis, and cancer. Importantly, childhood obesity is a strong predictor of adult obesity (2)
On the SU(1,1) Thermal Group of Bosonic Strings and D-Branes
All possible Bogoliubov operators that generate the thermal transformations
in the Thermo Field Dynamics (TFD) form a SU(1,1) group. We discuss this
contruction in the bosonic string theory. In particular, the transformation of
the Fock space and string operators generated by the most general SU(1,1)
unitary Bogoliubov transformation and the entropy of the corresponding thermal
string are computed. Also, we construct the thermal -brane solution
generated by the SU(1,1) transformation in a constant Kalb-Ramond field and
compute its entropy.Comment: misprints correcte
Quantum Aspects of Supersymmetric Maxwell Chern-Simons Solitons
We study the various quantum aspects of the supersymmetric Maxwell
Chern-Simons vortex systems. The fermion zero modes around the vortices will
give rise the degenerate states of vortices. We analyze the angular momentum of
these zero modes and apply the result to get the supermultiplet structures of
the vortex. The leading quantum correction to the mass of the vortex coming
from the mode fluctuations is also calculated using various methods depending
on the value of the coefficient of the Chern-Simons term to be zero,
infinite and finite, separately. The mass correction is shown to vanish for all
cases. Fermion numbers of vortices are also discussed.Comment: 40 pages, ReVTeX, HYUPT-94/04 SNUTP 94-6
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