1,265 research outputs found
Su(3) Algebraic Structure of the Cuprate Superconductors Model based on the Analogy with Atomic Nuclei
A cuprate superconductor model based on the analogy with atomic nuclei was
shown by Iachello to have an structure. The mean-field approximation
Hamiltonian can be written as a linear function of the generators of
algebra. Using algebraic method, we derive the eigenvalues of the reduced
Hamiltonian beyond the subalgebras and of
algebra. In particular, by considering the coherence between s- and d-wave
pairs as perturbation, the effects of coherent term upon the energy spectrum
are investigated
Classical Effective Field Theory for Weak Ultra Relativistic Scattering
Inspired by the problem of Planckian scattering we describe a classical
effective field theory for weak ultra relativistic scattering in which field
propagation is instantaneous and transverse and the particles' equations of
motion localize to the instant of passing. An analogy with the non-relativistic
(post-Newtonian) approximation is stressed. The small parameter is identified
and power counting rules are established. The theory is applied to reproduce
the leading scattering angle for either a scalar interaction field or
electro-magnetic or gravitational; to compute some subleading corrections,
including the interaction duration; and to allow for non-zero masses. For the
gravitational case we present an appropriate decomposition of the gravitational
field onto the transverse plane together with its whole non-linear action. On
the way we touch upon the relation with the eikonal approximation, some
evidence for censorship of quantum gravity, and an algebraic ring structure on
2d Minkowski spacetime.Comment: 29 pages, 2 figures. v4: Duration of interaction is determined in Sec
4 and detailed in App C. Version accepted for publication in JHE
The Age of the Galactic Disk
I review different methods devised to derive the age of the Galactic Disk,
namely the Radio-active Decay (RD), the Cool White Dwarf Luminosity Function
(CWDLF), old opne clusters (OOC) and the Color Magnitude Diagram (CMD) of the
stars in the solar vicinity. I argue that the disk is likely to be 8-10 Gyr
old. Since the bulk of globulars has an age around 13 Gyr, the possibility
emerges that the Galaxy experienced a minimum of Star Formation at the end of
the halo/bulge formation. This minimum might reflect the time at which the
Galaxy started to acquire material to form the disk inside-out.Comment: 10 pages, 4 figure, invited review, in "The chemical evolution of the
Milky Way : Stars vs Clusters, Vulcano (Italy), 20-24 September 199
Spectral quantification of nonlinear behaviour of the nearshore seabed and correlations with potential forcings at Duck, N.C., U.S.A
Local bathymetric quasi-periodic patterns of oscillation are identified from
monthly profile surveys taken at two shore-perpendicular transects at the USACE
field research facility in Duck, North Carolina, USA, spanning 24.5 years and
covering the swash and surf zones. The chosen transects are the two furthest
(north and south) from the pier located at the study site. Research at Duck has
traditionally focused on one or more of these transects as the effects of the
pier are least at these locations. The patterns are identified using singular
spectrum analysis (SSA). Possible correlations with potential forcing
mechanisms are discussed by 1) doing an SSA with same parameter settings to
independently identify the quasi-periodic cycles embedded within three
potentially linked sequences: monthly wave heights (MWH), monthly mean water
levels (MWL) and the large scale atmospheric index known as the North Atlantic
Oscillation (NAO) and 2) comparing the patterns within MWH, MWL and NAO to the
local bathymetric patterns. The results agree well with previous patterns
identified using wavelets and confirm the highly nonstationary behaviour of
beach levels at Duck; the discussion of potential correlations with
hydrodynamic and atmospheric phenomena is a new contribution. The study is then
extended to all measured bathymetric profiles, covering an area of 1100m
(alongshore) by 440m (cross-shore), to 1) analyse linear correlations between
the bathymetry and the potential forcings using multivariate empirical
orthogonal functions (MEOF) and linear correlation analysis and 2) identify
which collective quasi-periodic bathymetric patterns are correlated with those
within MWH, MWL or NAO, based on a (nonlinear) multichannel singular spectrum
analysis (MSSA). (...continued in submitted paper)Comment: 50 pages, 3 tables, 8 figure
Reconfiguration of Cliques in a Graph
We study reconfiguration problems for cliques in a graph, which determine
whether there exists a sequence of cliques that transforms a given clique into
another one in a step-by-step fashion. As one step of a transformation, we
consider three different types of rules, which are defined and studied in
reconfiguration problems for independent sets. We first prove that all the
three rules are equivalent in cliques. We then show that the problems are
PSPACE-complete for perfect graphs, while we give polynomial-time algorithms
for several classes of graphs, such as even-hole-free graphs and cographs. In
particular, the shortest variant, which computes the shortest length of a
desired sequence, can be solved in polynomial time for chordal graphs,
bipartite graphs, planar graphs, and bounded treewidth graphs
Developmental programming: State-of-the-science and future directions-Summary from a Pennington Biomedical symposium.
OBJECTIVE: On December 8-9, 2014, the Pennington Biomedical Research Center convened a scientific symposium to review the state-of-the-science and future directions for the study of developmental programming of obesity and chronic disease. The objectives of the symposium were to discuss: (i) past and current scientific advances in animal models, population-based cohort studies, and human clinical trials, (ii) the state-of-the-science of epigenetic-based research, and (iii) considerations for future studies. RESULTS: This symposium provided a comprehensive assessment of the state of the scientific field and identified research gaps and opportunities for future research in order to understand the mechanisms contributing to the developmental programming of health and disease. CONCLUSIONS: Identifying the mechanisms which cause or contribute to developmental programming of future generations will be invaluable to the scientific and medical community. The ability to intervene during critical periods of prenatal and early postnatal life to promote lifelong health is the ultimate goal. Considerations for future research including the use of animal models, the study design in human cohorts with considerations about the timing of the intrauterine exposure, and the resulting tissue-specific epigenetic signature were extensively discussed and are presented in this meeting summary.The symposium was funded by NORC Center Grant P30DK072476 from the NIDDK. LAG is supported by T32DK064584 from the NIDDK. Work in MS Laboratory was supported by MOP‐42411 from the Canadian Institute of Health Research. Work in JAM Laboratory was supported by the Center for Nutrition Research at the University of Navarra in Pamplona, Spain. RAW is supported by a grant from the U.S. Department of Agriculture (USDA) [CRIS 3092‐5‐001‐059]. Work in BTH Laboratory was supported by the National Institutes of Health (R01AG042190) and the European Union's Seventh Framework Program IDEAL (FP7/2007‐2011; grant agreement No. 259679). Work in CL Laboratory was funded by The Swedish Research Council and The Novo Nordisk Foundation. SEO is a member of the University of Cambridge MRC Metabolic Diseases Unit. MFH is the recipient of an American Diabetes Association (ADA) Pathways To Stop Diabetes Award. Work in ER and LMR Laboratories was partially funded by a NORC grant titled “Nutritional Programming: Environmental and Molecular Interactions” to ER (P30DK072476)
An exploratory randomised controlled trial of a premises-level intervention to reduce alcohol-related harm including violence in the United Kingdom
<b>Background</b><p></p>
To assess the feasibility of a randomised controlled trial of a licensed premises intervention to reduce severe intoxication and disorder; to establish effect sizes and identify appropriate approaches to the development and maintenance of a rigorous research design and intervention implementation.<p></p>
<b>Methods</b><p></p>
An exploratory two-armed parallel randomised controlled trial with a nested process evaluation. An audit of risk factors and a tailored action plan for high risk premises, with three month follow up audit and feedback. Thirty-two premises that had experienced at least one assault in the year prior to the intervention were recruited, match paired and randomly allocated to control or intervention group. Police violence data and data from a street survey of study premises’ customers, including measures of breath alcohol concentration and surveyor rated customer intoxication, were used to assess effect sizes for a future definitive trial. A nested process evaluation explored implementation barriers and the fidelity of the intervention with key stakeholders and senior staff in intervention premises using semi-structured interviews.<p></p>
<b>Results</b><p></p>
The process evaluation indicated implementation barriers and low fidelity, with a reluctance to implement the intervention and to submit to a formal risk audit. Power calculations suggest the intervention effect on violence and subjective intoxication would be raised to significance with a study size of 517 premises.<p></p>
<b>Conclusions</b><p></p>
It is methodologically feasible to conduct randomised controlled trials where licensed premises are the unit of allocation. However, lack of enthusiasm in senior premises staff indicates the need for intervention enforcement, rather than voluntary agreements, and on-going strategies to promote sustainability
Maximum-Entropy Weighting of Multi-Component Earth Climate Models
A maximum entropy-based framework is presented for the synthesis of
projections from multiple Earth climate models. This identifies the most
representative (most probable) model from a set of climate models -- as defined
by specified constraints -- eliminating the need to calculate the entire set.
Two approaches are developed, based on individual climate models or ensembles
of models, subject to a single cost (energy) constraint or competing
cost-benefit constraints. A finite-time limit on the minimum cost of modifying
a model synthesis framework, at finite rates of change, is also reported.Comment: Inspired by discussions at the Mathematical and Statistical
Approaches to Climate Modelling and Prediction workshop, Isaac Newton
Institute for Mathematical Sciences, Cambridge, UK, 11 Aug. to 22 Dec. 2010.
Accepted for publication in Climate Dynamics, 8 August 201
A new durophagous scincomorphan lizard genus from the Late Cretaceous Iharkút locality (Hungary, Bakony Mts)
Dot Display Affects Approximate Number System Acuity and Relationships with Mathematical Achievement and Inhibitory Control
Much research has investigated the relationship between the Approximate Number System (ANS) and mathematical achievement, with continued debate surrounding the existence of such a link. The use of different stimulus displays may account for discrepancies in the findings. Indeed, closer scrutiny of the literature suggests that studies supporting a link between ANS acuity and mathematical achievement in adults have mostly measured the ANS using spatially intermixed displays (e.g. of blue and yellow dots), whereas those failing to replicate a link have primarily used spatially separated dot displays. The current study directly compared ANS acuity when using intermixed or separate dots, investigating how such methodological variation mediated the relationship between ANS acuity and mathematical achievement. ANS acuity was poorer and less reliable when measured with intermixed displays, with performance during both conditions related to inhibitory control. Crucially, mathematical achievement was significantly related to ANS accuracy difference (accuracy on congruent trials minus accuracy on incongruent trials) when measured with intermixed displays, but not with separate displays. The findings indicate that methodological variation affects ANS acuity outcomes, as well as the apparent relationship between the ANS and mathematical achievement. Moreover, the current study highlights the problem of low reliabilities of ANS measures. Further research is required to construct ANS measures with improved reliability, and to understand which processes may be responsible for the increased likelihood of finding a correlation between the ANS and mathematical achievement when using intermixed displays
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