6,312 research outputs found
An Extension of the Fluctuation Theorem
Heat fluctuations are studied in a dissipative system with both mechanical
and stochastic components for a simple model: a Brownian particle dragged
through water by a moving potential. An extended stationary state fluctuation
theorem is derived. For infinite time, this reduces to the conventional
fluctuation theorem only for small fluctuations; for large fluctuations, it
gives a much larger ratio of the probabilities of the particle to absorb rather
than supply heat. This persists for finite times and should be observable in
experiments similar to a recent one of Wang et al.Comment: 12 pages, 1 eps figure in color (though intelligible in black and
white
Regulation of sonic hedgehog-GLI1 downstream target genes PTCH1, Cyclin D2, Plakoglobin, PAX6 and NKX2.2 and their epigenetic status in medulloblastoma and astrocytoma
Abstract Background The Sonic hedgehog (Shh) signaling pathway is critical for cell growth and differentiation. Impairment of this pathway can result in both birth defects and cancer. Despite its importance in cancer development, the Shh pathway has not been thoroughly investigated in tumorigenesis of brain tumors. In this study, we sought to understand the regulatory roles of GLI1, the immediate downstream activator of the Shh signaling pathway on its downstream target genes PTCH1, Cyclin D2, Plakoglobin, NKX2.2 and PAX6 in medulloblastoma and astrocytic tumors. Methods We silenced GLI1 expression in medulloblastoma and astrocytic cell lines by transfection of siRNA against GLI1. Subsequently, we performed RT-PCR and quantitative real time RT-PCR (qRT-PCR) to assay the expression of downstream target genes PTCH1, Cyclin D2, Plakoglobin, NKX2.2 and PAX6. We also attempted to correlate the pattern of expression of GLI1 and its regulated genes in 14 cell lines and 41 primary medulloblastoma and astrocytoma tumor samples. We also assessed the methylation status of the Cyclin D2 and PTCH1 promoters in these 14 cell lines and 58 primary tumor samples. Results Silencing expression of GLI1 resulted up-regulation of all target genes in the medulloblastoma cell line, while only PTCH1 was up-regulated in astrocytoma. We also observed methylation of the cyclin D2 promoter in a significant number of astrocytoma cell lines (63%) and primary astrocytoma tumor samples (32%), but not at all in any medulloblastoma samples. PTCH1 promoter methylation was less frequently observed than Cyclin D2 promoter methylation in astrocytomas, and not at all in medulloblastomas. Conclusions Our results demonstrate different regulatory mechanisms of Shh-GLI1 signaling. These differences vary according to the downstream target gene affected, the origin of the tissue, as well as epigenetic regulation of some of these genes.http://deepblue.lib.umich.edu/bitstream/2027.42/78313/1/1471-2407-10-614.xmlhttp://deepblue.lib.umich.edu/bitstream/2027.42/78313/2/1471-2407-10-614.pdfPeer Reviewe
p-Brane cosmology and phases of Brans-Dicke theory with matter
We study the effect of the solitonic degrees of freedom in string cosmology
following the line of Rama. The gas of solitonic p-brane is treated as a
perfect fluid in a Brans-Dicke type theory. In this paper, we find exact
cosmological solutions for any Brans-Dicke parameter and for general
parameter of equation of state and classify the cosmology of the
solutions on a parameter space of and .Comment: 26 pages, 5 figures, Contents and references added; published in
Phys. Rev. D57(1998) 462
Functional Approach to Stochastic Inflation
We propose functional approach to the stochastic inflationary universe
dynamics. It is based on path integral representation of the solution to the
differential equation for the scalar field probability distribution. In the
saddle-point approximation scalar field probability distributions of various
type are derived and the statistics of the inflationary-history-dependent
functionals is developed.Comment: 20 pages, Preprint BROWN-HET-960, uses phyzz
Oblique projection for scalable rank-adaptive reduced-order modeling of nonlinear stochastic PDEs with time-dependent bases
Time-dependent basis reduced order models (TDB ROMs) have successfully been
used for approximating the solution to nonlinear stochastic partial
differential equations (PDEs). For many practical problems of interest,
discretizing these PDEs results in massive matrix differential equations (MDEs)
that are too expensive to solve using conventional methods. While TDB ROMs have
the potential to significantly reduce this computational burden, they still
suffer from the following challenges: (i) inefficient for general
nonlinearities, (ii) intrusive implementation, (iii) ill-conditioned in the
presence of small singular values, and (iv) error accumulation due to fixed
rank. To this end, we present a scalable method based on oblique projections
for solving TDB ROMs that is computationally efficient, minimally intrusive,
robust in the presence of small singular values, rank-adaptive, and highly
parallelizable. These favorable properties are achieved via low-rank
approximation of the time discrete MDE. Using the discrete empirical
interpolation method (DEIM), a low-rank decomposition is computed at each
iteration of the time stepping scheme, enabling a near-optimal approximation at
a fraction of the cost. We coin the new approach TDB-CUR since it is equivalent
to a CUR decomposition based on sparse row and column samples of the MDE. We
also propose a rank-adaptive procedure to control the error on-the-fly.
Numerical results demonstrate the accuracy, efficiency, and robustness of the
new method for a diverse set of problems
Pure Luminosity Evolution Hypothesis for QSOs: From Luminosity Functions to Synthetic Catalogues
This paper describes the simulation of realistic Monte-Carlo extragalactic
catalogues, aimed at comparing the behaviour of cosmological tests versus input
parameters. QSO catalogues are built on a Luminosity Function derived from data
through suitable computation of individual maximum volumes in complete (but
magnitude- and redshift-limited) samples requiring neither of redshift nor of
apparent magnitude histogram. The values of the evolution parameter are derived
for various cosmologies, corresponding to =1/2 in the sample of 400
Ultra-Violet Excess (UVX) QSOs (Boyle et al 1990). The various luminosity
functions are compared, both for the whole sample and in redshift bins. An
evolution characteristic time is defined and computed, depending strongly on
the cosmology, but practically constant when expressed in terms of the age of
the Universe. Algorithms are given for producing unbiased or biased catalogues
based on the null hypothesis that the objects are uniformly distributed in
volume but suffer Pure Luminosity Evolution.Comment: uuencode compressed tar file of Latex and macros files. Tar
compressed poscript files of the papers and figures are also available by
anonymous ftp at ftp://summer.obs-mip.fr/pub/OUTGOING/paper2 or upon request
at [email protected]
The effects of buserelin microparticles on ovarian function in healthy women
Objective. To investigate the tolerance, pharmacokinetics and pharmacodynamJcs of the microparticle fonnulation of buserelin, when it wasaaministered subcutaneously.Design. A single-blind, randomised, parallel-group design was used to investigate the duration of suppression of ovarian function associated with doses of 1,8, 3,6 and 7,2 mg buserelin administered subcutaneously as microparticles.Setting. The study was carried out at the Hoechst Research Centre for Clinical Pharmacology, Department of Pharmacology, University of the Orange Free State, Bloemfontein.Patients. Thirty-two healthy premenopausal female volunteers aged between 19 and 39 years and weighing between 52 and 85 kg completed the study.Outcome measures. Serum progesterone and oestradiol concentrations were measured twice weekly until normal ovarian function resumed, i.e. when serum progesterone concentrations increased to at least 8 nmoVI (a sign of ovulation) and oestradiol concentrations increased to values above 300 pmol/l. Serum and urinary concentrations of buserelin were measured at the same times as those of progesterone and oestradiol.Results. Doses of 1,8,3,6 and 7,2 mg elicited anovulation for mean periods of 52, 77 and 113 days and suppressed ovarian production of oestrogen for 19, 38 and 69 days. Resumption of normal ovarian function occurred when serum buserelin concentrations decreased to between 0,03 and 0,05 lJg/ml. The correlation coefficient between dose and duration of anovulation was 0,75; the correlation coefficient between dose and duration of suppression of oestrogen production was 0,76.Conclusion. Apart from minor side-effects such as hot flushes, vaginal spotting and acne, the compound was tolerated well. We conclude that a good relationship exists between dose and duration of suppression of ovarian function. Doses of 3,6 - 7,2 mg buserelin should suppress oestrogen production for approximately 6 - 9 weeks and ovulation for 11 - 16 weeks
Global AdS Picture of 1/2 BPS Wilson Loops
We study the holographic dual string configuration of 1/2 BPS circular Wilson
loops in N=4 super Yang-Mills theory by using the global coordinate of AdS. The
dual string worldsheet is given by the Poincare disk AdS_2 sitting at a
constant global time slice of AdS_5. We also analyze the correlator of two
concentric circular Wilson loops from the global AdS perspective and study the
phase transition associated with the instability of annulus worldsheet
connecting the two Wilson loops.Comment: 14 pages, 3 figures, v2: discussion on two branches corrected, v3:
reference adde
Stationary shapes of deformable particles moving at low Reynolds numbers
Lecture Notes of the Summer School ``Microswimmers -- From Single Particle
Motion to Collective Behaviour'', organised by the DFG Priority Programme SPP
1726 (Forschungszentrum J{\"{u}}lich, 2015).Comment: Pages C7.1-16 of G. Gompper et al. (ed.), Microswimmers - From Single
Particle Motion to Collective Behaviour, Lecture Notes of the DFG SPP 1726
Summer School 2015, Forschungszentrum J\"ulich GmbH, Schriften des
Forschungszentrums J\"ulich, Reihe Key Technologies, Vol 110, ISBN
978-3-95806-083-
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