5,856 research outputs found
Transverse energy distributions and production in Pb+Pb collisions
We have analyzed the latest NA50 data on transverse energy distributions and
suppression in Pb+Pb collisions. The transverse energy distribution
was analysed in the geometric model of AA collisions. In the geometric model,
fluctuations in the number of NN collisions at fixed impact parameter are taken
into account. Analysis suggests that in Pb+Pb collisions, individual NN
collisions produces less , than in other AA collisions. The nucleons are
more transparent in Pb+Pb collisions. The transverse energy dependence of the
suppression was obtained following the model of Blaizot et al, where
charmonium suppression is assumed to be 100% effective above a threshold
density. With fluctuations in number of NN collisions taken into account, good
fit to the data is obtained, with a single parameter, the threshold density.Comment: Revised version with better E_T fit. 4 pages, 2 figure
Differentially Private Model Selection with Penalized and Constrained Likelihood
In statistical disclosure control, the goal of data analysis is twofold: The
released information must provide accurate and useful statistics about the
underlying population of interest, while minimizing the potential for an
individual record to be identified. In recent years, the notion of differential
privacy has received much attention in theoretical computer science, machine
learning, and statistics. It provides a rigorous and strong notion of
protection for individuals' sensitive information. A fundamental question is
how to incorporate differential privacy into traditional statistical inference
procedures. In this paper we study model selection in multivariate linear
regression under the constraint of differential privacy. We show that model
selection procedures based on penalized least squares or likelihood can be made
differentially private by a combination of regularization and randomization,
and propose two algorithms to do so. We show that our private procedures are
consistent under essentially the same conditions as the corresponding
non-private procedures. We also find that under differential privacy, the
procedure becomes more sensitive to the tuning parameters. We illustrate and
evaluate our method using simulation studies and two real data examples
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Oxidative stress specifically downregulates survivin to promote breast tumour formation.
BackgroundBreast cancer, a heterogeneous disease has been broadly classified into oestrogen receptor positive (ER+) or oestrogen receptor negative (ER-) tumour types. Each of these tumours is dependent on specific signalling pathways for their progression. While high levels of survivin, an anti-apoptotic protein, increases aggressive behaviour in ER- breast tumours, oxidative stress (OS) promotes the progression of ER+ breast tumours. Mechanisms and molecular targets by which OS promotes tumourigenesis remain poorly understood.ResultsDETA-NONOate, a nitric oxide (NO)-donor induces OS in breast cancer cell lines by early re-localisation and downregulation of cellular survivin. Using in vivo models of HMLE(HRAS) xenografts and E2-induced breast tumours in ACI rats, we demonstrate that high OS downregulates survivin during initiation of tumourigenesis. Overexpression of survivin in HMLE(HRAS) cells led to a significant delay in tumour initiation and tumour volume in nude mice. This inverse relationship between survivin and OS was also observed in ER+ human breast tumours. We also demonstrate an upregulation of NADPH oxidase-1 (NOX1) and its activating protein p67, which are novel markers of OS in E2-induced tumours in ACI rats and as well as in ER+ human breast tumours.ConclusionOur data, therefore, suggest that downregulation of survivin could be an important early event by which OS initiates breast tumour formation
Study on Noncommutative Representations of Galilean Generators
The representations of Galilean generators are constructed on a space where
both position and momentum coordinates are noncommutating operators. A
dynamical model invariant under noncommutative phase space transformations is
constructed. The Dirac brackets of this model reproduce the original
noncommutative algebra. Also, the generators in terms of noncommutative phase
space variables are abstracted from this model in a consistent manner. Finally,
the role of Jacobi identities is emphasised to produce the noncommuting
structure that occurs when an electron is subjected to a constant magnetic
field and Berry curvature.Comment: Title changed, new references added, published in Int. J. Mod. Phys.
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Barriers to reporting non-motor symptoms to health-care providers in people with Parkinson's
Background: Non-motor symptoms (NMS) are common in Parkinson's disease (PD) and cause significant distress. A high rate of non-declaration of NMS by patients to healthcare providers (HCP) means that many NMS remain untreated. Current understanding of the factors preventing disclosure of NMS to HCPs is limited. The present study aimed to i) further assess the prevalence of NMS and associated distress, ii) establish current rates of NMS reporting across a range of sources, and iii) explore overall and any symptom specific barriers to help-seeking for NMS.
Methods: 358 PD patients completed a cross-sectional survey of NMS severity, reporting and barriers to help-seeking. A series of Generalised Estimating Equations were used to determine whether barriers were symptom specific.
Results: A mean of 10.5 NMS were reported by each patient. Rates of non-reporting of NMS ranged from 15 to 72% of those experiencing distressing symptoms. The most commonly reported barriers to help-seeking were acceptance of symptoms; lack of awareness that a symptom was associated with PD, and belief that no effective treatments were available. Symptom specific barriers were found for sexual dysfunction (embarrassment), unexplained pain and urinary problems (belief about lack of treatment availability).
Conclusion: A diverse range of barriers prevent PD patients reporting NMS to HCPs and these barriers differ between NMS. The study provides the foundations for developing interventions to increase reporting by targeting individual NMS. Increasing rates of help-seeking for NMS by patients to their Parkinson's healthcare providers will increase appropriate clinical care which may improve quality of life and well-being
Near-linear Time Algorithm for Approximate Minimum Degree Spanning Trees
Given a graph , we wish to compute a spanning tree whose maximum
vertex degree, i.e. tree degree, is as small as possible. Computing the exact
optimal solution is known to be NP-hard, since it generalizes the Hamiltonian
path problem. For the approximation version of this problem, a
time algorithm that computes a spanning tree of degree at most is
previously known [F\"urer \& Raghavachari 1994]; here denotes the
minimum tree degree of all the spanning trees. In this paper we give the first
near-linear time approximation algorithm for this problem. Specifically
speaking, we propose an time algorithm that
computes a spanning tree with tree degree for any constant .
Thus, when , we can achieve approximate solutions with
constant approximate ratio arbitrarily close to 1 in near-linear time.Comment: 17 page
A Model for Phase Transition based on Statistical Disassembly of Nuclei at Intermediate Energies
Consider a model of particles (nucleons) which has a two-body interaction
which leads to bound composites with saturation properties. These properties
are : all composites have the same density and the ground state energies of
composites with k nucleons are given by -kW+\sigma k^{2/3} where W and \sigma
are positive constants. W represents a volume term and \sigma a surface tension
term. These values are taken from nuclear physics. We show that in the large N
limit where N is the number of particles such an assembly in a large enclosure
at finite temperature shows properties of liquid-gas phase transition. We do
not use the two-body interaction but the gross properties of the composites
only. We show that (a) the p-\rho isotherms show a region where pressure does
not change as changes just as in Maxwell construction of a Van der Waals
gas, (b) in this region the chemical potential does not change and (c) the
model obeys the celebrated Clausius-Clapeyron relations. A scaling law for the
yields of composites emerges. For a finite number of particles N (upto some
thousands) the problem can be easily solved on a computer. This allows us to
study finite particle number effects which modify phase transition effects. The
model is calculationally simple. Monte-Carlo simulations are not needed.Comment: RevTex file, 21 pages, 5 figure
Deconfinement and the Hagedorn Transition in String Theory
Superseded and extended in hep-th/0105110 and hep-th/0208112.Comment: Superseded and extended in hep-th/0105110 and hep-th/020811
Stochastic pump of interacting particles
We consider the overdamped motion of Brownian particles, interacting via
particle exclusion, in an external potential that varies with time and space.
We show that periodic potentials that maintain specific position-dependent
phase relations generate time-averaged directed current of particles. We obtain
analytic results for a lattice version of the model using a recently developed
perturbative approach. Many interesting features like particle-hole symmetry,
current reversal with changing density, and system-size dependence of current
are obtained. We propose possible experiments to test our predictions.Comment: 4 pages, 2 figure
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