2,005 research outputs found
Fluctuation theorems for excess and housekeeping heats for underdamped systems
We present a simple derivation of the integral fluctuation theorems for
excess housekeeping heat for an underdamped Langevin system, without using the
concept of dual dynamics. In conformity with the earlier results, we find that
the fluctuation theorem for housekeeping heat holds when the steady state
distributions are symmetric in velocity, whereas there is no such requirement
for the excess heat. We first prove the integral fluctuation theorem for the
excess heat, and then show that it naturally leads to the integral fluctuation
theorem for housekeeping heat. We also derive the modified detailed fluctuation
theorems for the excess and housekeeping heats.Comment: 10 pages. Section 3 contains further generalization
Fluctuation theorems in presence of information gain and feedback
In this study, we rederive the fluctuation theorems in presence of feedback,
by assuming the known Jarzynski equality and detailed fluctuation theorems. We
first reproduce the already known work theorems for a classical system, and
then extend the treatment to the other classical theorems. For deriving the
extended quantum fluctuation theorems, we have considered open systems. No
assumption is made on the nature of environment and the strength of system-bath
coupling. However, it is assumed that the measurement process involves
classical errors.Comment: 8 pages, 1 figur
Entropy production theorems and some consequences
The total entropy production fluctuations are studied in some exactly
solvable models. For these systems, the detailed fluctuation theorem holds even
in the transient state, provided initially the system is prepared in thermal
equilibrium. The nature of entropy production during the relaxation of a system
to equilibrium is analyzed. The averaged entropy production over a finite time
interval gives a better bound for the average work performed on the system than
that obtained from the well known Jarzynski equality. Moreover, the average
entropy production as a quantifier for information theoretic nature of
irreversibility for finite time nonequilibrium processes is discussed.Comment: 12 pages, 3 figure
Testing general relativity with the reflection spectrum of the supermassive black hole in 1H0707495
Recently, we have extended the X-ray reflection model relxill to test the
spacetime metric in the strong gravitational field of astrophysical black
holes. In the present Letter, we employ this extended model to analyze
XMM-Newton, NuSTAR, and Swift data of the supermassive black hole in 1H0707-495
and test deviations from a Kerr metric parametrized by the Johannsen
deformation parameter . Our results are consistent with the
hypothesis that the spacetime metric around the black hole in 1H0707-495 is
described by the Kerr solution.Comment: 10 pages, 7 figures. v2: refereed versio
Public Release of RELXILL_NK: A Relativistic Reflection Model for Testing Einstein's Gravity
We present the public release version of relxill_nk, an X-ray reflection
model for testing the Kerr hypothesis and general relativity. This model
extends the relxill model that assumes the black hole spacetime is described by
the Kerr metric. We also present relxilllp_nk, the first non-Kerr X-ray
reflection model with a lamppost corona configuration, as well as all other
models available in the full relxill_nk package. In all models the relevant
relativistic effects are calculated through a general relativistic ray-tracing
code that can be applied to any well-behaved, stationary, axisymmetric, and
asymptotically flat black hole spacetime. We show that the numerical error
introduced by using a ray-tracing code is not significant as compared with the
observational error present in current X-ray reflection spectrum observations.
In addition, we present the reflection spectrum for the Johannsen metric as
calculated by relxill_nk.Comment: 15 pages, 8 figures. v2: refereed version. Code and documentation
available at
http://www.physics.fudan.edu.cn/tps/people/bambi/Site/RELXILL_NK.html and at
http://www.tat.physik.uni-tuebingen.de/~nampalliwar/relxill_nk
Regulation of Sterol Biosynthesis in the Human Fungal Pathogen Aspergillus Fumigatus: Opportunities for Therapeutic Development
Sterols are a major component of eukaryotic cell membranes. For human fungal infections caused by the filamentous fungus Aspergillus fumigatus, antifungal drugs that target sterol biosynthesis and/or function remain the standard of care. Yet, an understanding of A. fumigatus sterol biosynthesis regulatory mechanisms remains an under developed therapeutic target. The critical role of sterol biosynthesis regulation and its interactions with clinically relevant azole drugs is highlighted by the basic helix loop helix (bHLH) class of transcription factors known as Sterol Regulatory Element Binding Proteins (SREBPs). SREBPs regulate transcription of key ergosterol biosynthesis genes in fungi including A. fumigatus. In addition, other emerging regulatory pathways and target genes involved in sterol biosynthesis and drug interactions provide additional opportunities including the unfolded protein response, iron responsive transcriptional networks, and chaperone proteins such as Hsp90. Thus, targeting molecular pathways critical for sterol biosynthesis regulation presents an opportunity to improve therapeutic options for the collection of diseases termed aspergillosis. This mini-review summarizes our current understanding of sterol biosynthesis regulation with a focus on mechanisms of transcriptional regulation by the SREBP family of transcription factors
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