4,997 research outputs found
Viewing the efficiency of chaos control
This paper aims to cast some new light on controlling chaos using the OGY-
and the Zero-Spectral-Radius methods. In deriving those methods we use a
generalized procedure differing from the usual ones. This procedure allows us
to conveniently treat maps to be controlled bringing the orbit to both various
saddles and to sources with both real and complex eigenvalues. We demonstrate
the procedure and the subsequent control on a variety of maps. We evaluate the
control by examining the basins of attraction of the relevant controlled
systems graphically and in some cases analytically
Preliminary tests of the electrostatic plasma accelerator
This report describes the results of a program to verify an electrostatic plasma acceleration concept and to identify those parameters most important in optimizing an Electrostatic Plasma Accelerator (EPA) thruster based upon this thrust mechanism. Preliminary performance measurements of thrust, specific impulse and efficiency were obtained using a unique plasma exhaust momentum probe. Reliable EPA thruster operation was achieved using one power supply
Strong Decays of Strange Quarkonia
In this paper we evaluate strong decay amplitudes and partial widths of
strange mesons (strangeonia and kaonia) in the 3P0 decay model. We give
numerical results for all energetically allowed open-flavor two-body decay
modes of all nsbar and ssbar strange mesons in the 1S, 2S, 3S, 1P, 2P, 1D and
1F multiplets, comprising strong decays of a total of 43 resonances into 525
two-body modes, with 891 numerically evaluated amplitudes. This set of
resonances includes all strange qqbar states with allowed strong decays
expected in the quark model up to ca. 2.2 GeV. We use standard nonrelativistic
quark model SHO wavefunctions to evaluate these amplitudes, and quote numerical
results for all amplitudes present in each decay mode. We also discuss the
status of the associated experimental candidates, and note which states and
decay modes would be especially interesting for future experimental study at
hadronic, e+e- and photoproduction facilities. These results should also be
useful in distinguishing conventional quark model mesons from exotica such as
glueballs and hybrids through their strong decays.Comment: 69 pages, 5 figures, 39 table
Coating selection program - Theory
Heat balance equations for optimizing optical coating patterns for spacecraft temperature control syste
Evaluation of 172 candidate polymorphisms for association with oligozoospermia or azoospermia in a large cohort of men of European descent
Monotonicity of Fitness Landscapes and Mutation Rate Control
A common view in evolutionary biology is that mutation rates are minimised.
However, studies in combinatorial optimisation and search have shown a clear
advantage of using variable mutation rates as a control parameter to optimise
the performance of evolutionary algorithms. Much biological theory in this area
is based on Ronald Fisher's work, who used Euclidean geometry to study the
relation between mutation size and expected fitness of the offspring in
infinite phenotypic spaces. Here we reconsider this theory based on the
alternative geometry of discrete and finite spaces of DNA sequences. First, we
consider the geometric case of fitness being isomorphic to distance from an
optimum, and show how problems of optimal mutation rate control can be solved
exactly or approximately depending on additional constraints of the problem.
Then we consider the general case of fitness communicating only partial
information about the distance. We define weak monotonicity of fitness
landscapes and prove that this property holds in all landscapes that are
continuous and open at the optimum. This theoretical result motivates our
hypothesis that optimal mutation rate functions in such landscapes will
increase when fitness decreases in some neighbourhood of an optimum, resembling
the control functions derived in the geometric case. We test this hypothesis
experimentally by analysing approximately optimal mutation rate control
functions in 115 complete landscapes of binding scores between DNA sequences
and transcription factors. Our findings support the hypothesis and find that
the increase of mutation rate is more rapid in landscapes that are less
monotonic (more rugged). We discuss the relevance of these findings to living
organisms
Discovery of the Cobalt Isotopes
Twenty-six cobalt isotopes have so far been observed; the discovery of these
isotopes is discussed. For each isotope a brief summary of the first refereed
publication, including the production and identification method, is presented.Comment: to be published in Atomic Data and Nuclear Data Table
Who uses NHS health checks? Investigating the impact of ethnicity and gender and method of invitation on uptake of NHS health checks
Background
NHS Health Checks is a national risk assessment prevention programme for all individuals aged 40-74 that reside in England. Through the systematic assessment of an individualâs ten year disease risk, this programme aims to provide early identification and subsequent management of this risk. However, there is limited evidence on how socio-demographic factors impact on uptake and what influence the invitation method has on uptake to this programme.
Methods
NHS Health Check data from April 2013 to March 2014 was analysed (Nâ=â50,485) for all 30 GP Practices in Luton, a culturally diverse town in England, UK. Data was collected for age, ethnicity, uptake (attendance and non attendance) and invitation method (letter written, verbal face-to-face, telephone). Actual usage of NHS Health Checks was determined for each ethnic group of the population and compared using Chi-square analysis.
Results
The overall uptake rate for Luton was 44 %, markedly lower that the set target of 50â75 %. The findings revealed a variation of uptake in relation to age, gender, level of deprivation. Ethnicity and gender variations were also found, with âWhite Britishâ âBlack Caribbeanâ and âIndianâ patients most likely to take up a NHS Health Check.
However, patients from âAny Other White Backgroundâ and âBlack Africanâ were significantly less likely to uptake an NHS Health Check compared to all other ethnic groups. Ethnicity and gender differences were also noted in relation to invitation method.
Conclusions
The findings revealed that different invitation methods were effective for different ethnic and gender groups. Therefore, it is suggested that established protocols of invitation are specifically designed for maximizing the response rate for each population group. Future research should now focus on uncovering the barriers to uptake in particular culturally diverse population groups to determine how public health teams can better engage with these communities
Observation of Pseudoscalar and Axial Vector Resonances in pi- p -> K+ K- pi0 n at 18 GeV
A new measurement of the reaction pi- p -> K+ K- pi0 n has been made at a
beam energy of 18 GeV. A partial wave analysis of the K+ K- pi0 system shows
evidence for three pseudoscalar resonances, eta(1295), eta(1416), and
eta(1485), as well as two axial vectors, f1(1285), and f1(1420). Their observed
masses, widths and decay properties are reported. No signal was observed for
C(1480), an IG J{PC} = 1+ 1{--} state previously reported in phi pi0 decay.Comment: 7 pages, 6 figs, to be submitted to Phys. Let
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