3,037 research outputs found
A QUALITATIVE ANALYSIS OF THE HIGH RACQUET POSITION BACKHAND DRIVE OF AN ELITE RACQUETBALL PLAYER
Since 1950, when Joe Sobek put strings on his paddleball
paddle, the sport of racquetball has grown to the point where it has
attained international status. Today, racquetball is played in 57
countries. It has been granted representation on the United States
Olympic Committee (USOC) and is under consideration as a future
Olympic sport, possible as early as the 1992 games. In spite of its rapid and international growth, racquetball remains a relatively new sport,on which very little research has been reported
Limiting Behaviour of the Mean Residual Life
In survival or reliability studies, the mean residual life or life expectancy
is an important characteristic of the model. Here, we study the limiting
behaviour of the mean residual life, and derive an asymptotic expansion which
can be used to obtain a good approximation for large values of the time
variable. The asymptotic expansion is valid for a quite general class of
failure rate distributions--perhaps the largest class that can be expected
given that the terms depend only on the failure rate and its derivatives.Comment: 19 page
Quantum state estimation and large deviations
In this paper we propose a method to estimate the density matrix \rho of a
d-level quantum system by measurements on the N-fold system. The scheme is
based on covariant observables and representation theory of unitary groups and
it extends previous results concerning the estimation of the spectrum of \rho.
We show that it is consistent (i.e. the original input state \rho is recovered
with certainty if N \to \infty), analyze its large deviation behavior, and
calculate explicitly the corresponding rate function which describes the
exponential decrease of error probabilities in the limit N \to \infty. Finally
we discuss the question whether the proposed scheme provides the fastest
possible decay of error probabilities.Comment: LaTex2e, 40 pages, 2 figures. Substantial changes in Section 4: one
new subsection (4.1) and another (4.2 was 4.1 in the previous version)
completely rewritten. Minor changes in Sect. 2 and 3. Typos corrected.
References added. Accepted for publication in Rev. Math. Phy
Kinetics of Radioiodinated Heptadecanoic Acid and Metabolites in the Normal and Ischaemic Canine Heart
This study was undertaken to elucidate if the myocardial elimination rate of the radioactivity after administration of radioiodinated heptadecanoic acid was related to beta-oxidation of the fatty acid or related to washout of free radioiodide. In samples of normal and ischaemic myocardium the distribution of the radioactivity over free radioiodide, heptadecanoic acid and lipids was determined. In normal myocardium the major component was free radioiodide, only a small percentage being heptadecanoic acid. In ischaemic myocardium more radiolabelled lipids were present and less free iodide when compared with normal myocardium. The percentage heptadecanoic acid was slightly increased. It is concluded that radioiodinated heptadecanoic acid behaves like the natural analogues regarding uptake and distribution. However, washout of free radioiodide determines the elimination rate as observed during a scintigraphic stud
The 1+1-dimensional Kardar-Parisi-Zhang equation and its universality class
We explain the exact solution of the 1+1 dimensional Kardar-Parisi-Zhang
equation with sharp wedge initial conditions. Thereby it is confirmed that the
continuum model belongs to the KPZ universality class, not only as regards to
scaling exponents but also as regards to the full probability distribution of
the height in the long time limit.Comment: Proceedings StatPhys 2
Mutation, selection, and ancestry in branching models: a variational approach
We consider the evolution of populations under the joint action of mutation
and differential reproduction, or selection. The population is modelled as a
finite-type Markov branching process in continuous time, and the associated
genealogical tree is viewed both in the forward and the backward direction of
time. The stationary type distribution of the reversed process, the so-called
ancestral distribution, turns out as a key for the study of mutation-selection
balance. This balance can be expressed in the form of a variational principle
that quantifies the respective roles of reproduction and mutation for any
possible type distribution. It shows that the mean growth rate of the
population results from a competition for a maximal long-term growth rate, as
given by the difference between the current mean reproduction rate, and an
asymptotic decay rate related to the mutation process; this tradeoff is won by
the ancestral distribution.
Our main application is the quasispecies model of sequence evolution with
mutation coupled to reproduction but independent across sites, and a fitness
function that is invariant under permutation of sites. Here, the variational
principle is worked out in detail and yields a simple, explicit result.Comment: 45 pages,8 figure
Decreased exposure to sunitinib due to concomitant administration of ifosfamide: results of a phase I and pharmacokinetic study on the combination of sunitinib and ifosfamide in patients with advanced solid malignancies
Background:This study aimed to define the maximally tolerated dose (MTD) of sunitinib combined with two different infusion schedules of ifosfamide. Methods:Patients with advanced solid tumours, good performance score, good organ function, and no standard therapy available were eligible. Continuous once daily sunitinib, in escalating doses per cohort, was combined with ifosfamide, 9 g m-2 for 3 days or 6 g m-2 for 5 days, administered every 3 weeks. Pharmacokinetic (PK) and pharmacodynamic (PD) assessments were performed. Results:With growth-factor support, the MTD of sunitinib combined with either ifosfamide schedule was 12.5 mg in 32 patients enrolled. Neutropenia-related adverse events were dose-limiting toxicities. Sunitinib did not affect ifosfamide PK. Ifosfamide significantly decreased exposure to sunitinib and increased exposure to its metabolite, SU12662. No consistent changes in PD parameters were observed. Conclusion:With growth-factor support, the MTD of sunitinib with both ifosfamide schedules was 12.5 mg. Ifosfamide produced decreased sunitinib blood levels because of CYP3A induction. As PK interactions cannot explain the relatively low sunitinib doses that can be combined with ifosfamide, synergy in toxicity is likely. Whether this also holds true for anti-tumour activity needs to be further explored.British Journal of Cancer advance online publication, 18 May 2010; doi:10.1038/sj.bjc.6605696 www.bjcancer.com
Opportunistic screening versus usual care for diagnosing atrial fibrillation in general practice:a cluster randomised controlled trial
BackgroundAtrial fibrillation [AF] increases the risk of stroke, heart failure, and all-cause mortality. AF may be asymptomatic and therefore remain undiagnosed. Devices such as single-lead electrocardiographs [ECGs] may help GPs to diagnose AF.AimTo investigate the yield of opportunistic screening for AF in usual primary care using a single-lead ECG device.Design and settingA clustered, randomised controlled trial among patients aged >= 65 years with no recorded AF status in the Netherlands from October 2014 to March 2016.MethodFifteen intervention general practices used a single-lead ECG device at their discretion and 16 control practices offered usual care. The follow-up period was 1 year, and the primary outcome was the proportion of newly diagnosed cases of AF.ResultsIn total. 17 107 older people with no recorded AF status were eligible to participate in the study. In the intervention arm. 10.7% of eligible patients [n = 919] were screened over the duration of the study year. The rate of newly diagnosed AF was similar in the intervention and control practices [1.43% versus 1.37%, P= 0.73]. Screened patients were more likely to have comorbidities, such as hypertension [60.0% versus 48.7%], type 2 diabetes [24.3% versus 18.6%], and chronic obstructive pulmonary disease [11.3% versus 7.4%], than eligible patients not screened in the intervention arm. Among patients with newly diagnosed AF in intervention practices. 27% were detected by screening, 23% by usual primary care. and 50% by a medical specialist or after stroke/transient ischaemic attack.ConclusionOpportunistic screening with a single-lead ECG at the discretion of the GP did not result in a higher yield of newly detected cases of AF in patients aged >= 65 years in the community than usual care. For higher participation rates in future studies, more rigorous screening methods are needed.</p
Colligative properties of solutions: I. Fixed concentrations
Using the formalism of rigorous statistical mechanics, we study the phenomena
of phase separation and freezing-point depression upon freezing of solutions.
Specifically, we devise an Ising-based model of a solvent-solute system and
show that, in the ensemble with a fixed amount of solute, a macroscopic phase
separation occurs in an interval of values of the chemical potential of the
solvent. The boundaries of the phase separation domain in the phase diagram are
characterized and shown to asymptotically agree with the formulas used in
heuristic analyses of freezing point depression. The limit of infinitesimal
concentrations is described in a subsequent paper.Comment: 28 pages, 1 fig; see also math-ph/0407035 (both to appear in JSP
- …