5,760 research outputs found
A non-autonomous stochastic discrete time system with uniform disturbances
The main objective of this article is to present Bayesian optimal control
over a class of non-autonomous linear stochastic discrete time systems with
disturbances belonging to a family of the one parameter uniform distributions.
It is proved that the Bayes control for the Pareto priors is the solution of a
linear system of algebraic equations. For the case that this linear system is
singular, we apply optimization techniques to gain the Bayesian optimal
control. These results are extended to generalized linear stochastic systems of
difference equations and provide the Bayesian optimal control for the case
where the coefficients of these type of systems are non-square matrices. The
paper extends the results of the authors developed for system with disturbances
belonging to the exponential family
Damagnetization cooling of a gas
We demonstrate demagnetization cooling of a gas of ultracold Cr atoms.
Demagnetization is driven by inelastic dipolar collisions which couple the
motional degrees of freedom to the spin degree. By that kinetic energy is
converted into magnetic work with a consequent temperature reduction of the
gas. Optical pumping is used to magnetize the system and drive continuous
demagnetization cooling. Applying this technique, we can increase the phase
space density of our sample by one order of magnitude, with nearly no atom
loss. This method can be in principle extended to every dipolar system and
could be used to achieve quantum degeneracy via optical means.Comment: 10 pages, 5 figure
AlN/CrN multilayer structures with increased thermal stability
CrAlYN nanolayered coatings of greatly enhanced thermal stability have been developed by doping with levels of Y up to 9 at.%. This prevented the complete dissolution of the layered structure after annealing at 1100 °C in Ar for 1 h, commonly observed in coatings with little or no Y content, although the bilayer period increased from ~ 5 nm to ~ 10 nm. The improved thermal stability is attributed to the formation of a continuous YN layer between the CrN and AlN layers, reducing the rate of interdiffusion
Topics in Quantum Computers
I provide an introduction to quantum computers, describing how they might be
realized using language accessible to a solid state physicist. A listing of the
minimal requirements for creating a quantum computer is given. I also discuss
several recent developments in the area of quantum error correction, a subject
of importance not only to quantum computation, but also to some aspects of the
foundations of quantum theory.Comment: 22 pages, Latex, 1 eps figure, Paper to be published in "Mesoscopic
Electron Transport", edited by L. Kowenhoven, G. Schoen and L. Sohn, NATO ASI
Series E, Kluwer Ac. Publ., Dordrecht. v2: typos in refrences fixe
Supernatants from lymphocytes stimulated with Bacillus Calmette-Guerin can modify the antigenicity of tumours and stimulate allogeneic T-cell responses
BACKGROUND: Reduced expression of class 1 human leucocyte antigens (HLA1) is often a mechanism by which tumours evade surveillance by the host immune system. This is often associated with an immune function that is unable to mount appropriate responses against disease, which can result in a state that favours carcinogenesis. METHODS: In the current study, we have explored the effects of Bacillus Calmette-Guerin (BCG) on the cytokine output of leucocytes, which is a key determinant in generating antitumour action, and have also assessed the effect of these cytokine cocktails on HLA1 expression in solid tumour cell lines. RESULTS: BCG potently activated a broad range of leucocytes, and also enhanced the production of cytokines that were Th(1)-predominant. Supernatants from BCG-treated leucocytes significantly increased the expression of HLA1 on the surface of cancer cell lines, which correlated with increased cytolytic T-cell activity. We also showed that the increased HLA1 expression was associated with activation of intracellular signalling pathways, which was triggered by the increases in the Th(1)-cytokines interferon-γ and tumour necrosis factor-α, as counteracting their effects negated the enhancement. CONCLUSION: These studies reaffirm the role of BCG as a putative immunotherapy through their cytokine-modifying effects on leucocytes and their capacity to enhance tumour visibility
Specific involvement of atypical PKCζ/PKMζ in spinal persistent nociceptive processing following peripheral inflammation in rat.
BACKGROUND: Central sensitization requires the activation of various intracellular signalling pathways within spinal dorsal horn neurons, leading to a lowering of activation threshold and enhanced responsiveness of these cells. Such plasticity contributes to the manifestation of chronic pain states and displays a number of features of long-term potentiation (LTP), a ubiquitous neuronal mechanism of increased synaptic strength. Here we describe the role of a novel pathway involving atypical PKCζ/PKMζ in persistent spinal nociceptive processing, previously implicated in the maintenance of late-phase LTP. RESULTS: Using both behavioral tests and in vivo electrophysiology in rats, we show that inhibition of this pathway, via spinal delivery of a myristoylated protein kinase C-ζ pseudo-substrate inhibitor, reduces both pain-related behaviors and the activity of deep dorsal horn wide dynamic range neurons (WDRs) following formalin administration. In addition, Complete Freund's Adjuvant (CFA)-induced mechanical and thermal hypersensitivity was also reduced by inhibition of PKCζ/PKMζ activity. Importantly, this inhibition did not affect acute pain or locomotor behavior in normal rats and interestingly, did not inhibited mechanical allodynia and hyperalgesia in neuropathic rats. Pain-related behaviors in both inflammatory models coincided with increased phosphorylation of PKCζ/PKMζ in dorsal horn neurons, specifically PKMζ phosphorylation in formalin rats. Finally, inhibition of PKCζ/PKMζ activity decreased the expression of Fos in response to formalin and CFA in both superficial and deep laminae of the dorsal horn. CONCLUSIONS: These results suggest that PKCζ, especially PKMζ isoform, is a significant factor involved in spinal persistent nociceptive processing, specifically, the manifestation of chronic pain states following peripheral inflammation
Secular Evolution of Galaxy Morphologies
Today we have numerous evidences that spirals evolve dynamically through
various secular or episodic processes, such as bar formation and destruction,
bulge growth and mergers, sometimes over much shorter periods than the standard
galaxy age of 10-15 Gyr. This, coupled to the known properties of the Hubble
sequence, leads to a unique sense of evolution: from Sm to Sa. Linking this to
the known mass components provides new indications on the nature of dark matter
in galaxies. The existence of large amounts of yet undetected dark gas appears
as the most natural option. Bounds on the amount of dark stars can be given
since their formation is mostly irreversible and requires obviously a same
amount of gas.Comment: 8 pages, Latex2e, crckapb.sty macros, 1 Postscript figure, replaced
with TeX source; To be published in the proceeedings of the "Dust-Morphology"
conference, Johannesburg, 22-26 January, 1996, D. Block (ed.), (Kluwer
Dordrecht
Interpreting 16S metagenomic data without clustering to achieve sub-OTU resolution
The standard approach to analyzing 16S tag sequence data, which relies on
clustering reads by sequence similarity into Operational Taxonomic Units
(OTUs), underexploits the accuracy of modern sequencing technology. We present
a clustering-free approach to multi-sample Illumina datasets that can identify
independent bacterial subpopulations regardless of the similarity of their 16S
tag sequences. Using published data from a longitudinal time-series study of
human tongue microbiota, we are able to resolve within standard 97% similarity
OTUs up to 20 distinct subpopulations, all ecologically distinct but with 16S
tags differing by as little as 1 nucleotide (99.2% similarity). A comparative
analysis of oral communities of two cohabiting individuals reveals that most
such subpopulations are shared between the two communities at 100% sequence
identity, and that dynamical similarity between subpopulations in one host is
strongly predictive of dynamical similarity between the same subpopulations in
the other host. Our method can also be applied to samples collected in
cross-sectional studies and can be used with the 454 sequencing platform. We
discuss how the sub-OTU resolution of our approach can provide new insight into
factors shaping community assembly.Comment: Updated to match the published version. 12 pages, 5 figures +
supplement. Significantly revised for clarity, references added, results not
change
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