419 research outputs found
A simplistic pedagogical formulation of a thermal speed distribution using a relativistic framework
A novel pedagogical technique is presented that can be used in the
undergraduate (UG) class to formulate a relativistically extended Kinetic
Theory of Gases and thermal speed distribution, while assuming the basic
thermal symmetry arguments of the famous Maxwell-Boltzmann distribution as
presented at the UG level. The adopted framework can be used by students to
understand the physics in a thermally governed system at high temperature and
speeds, without having to indulge in high level tensor based mathematics, as
has been done by the previous works in the subject. Our approach, a logical
extension of that proposed by Maxwell, will first recapitulate what is taught
and known in the UG class and then present a methodology inspired from the
Maxwell-Boltzmann framework that will help students to understand and derive
the physics of relativistic thermal systems. The methodology uses simple tools
well known to undergraduates and involves a component of computational
techniques that can be used to involve students in this exercise. We have tried
to place the current work in a larger perspective in regard to the earlier
works done and emphasize on it's simplicity and accessibility to students.
Towards the end, interesting implications of the relativistically extended
distribution are presented and compared with the Maxwell-Boltzmann results at
various temperatures.Comment: 13 pages, 5 figures, Publication accepted in Pramana - Journal of
Physics (Indian Academy of Sciences). Revised version has an additional
section, discussing previous work on relativistic Kinetic Theory in section
2.1 and comparison with these in section 6. Arguments for formulating a
relativistic thermal speed distributions have been enriched and made more
clear and categorical in section
Towards the “ultimate earthquake-proof” building: Development of an integrated low-damage system
The 2010–2011 Canterbury earthquake sequence has highlighted the
severe mismatch between societal expectations over the reality of seismic performance
of modern buildings. A paradigm shift in performance-based design criteria
and objectives towards damage-control or low-damage design philosophy and
technologies is urgently required. The increased awareness by the general public,
tenants, building owners, territorial authorities as well as (re)insurers, of the severe
socio-economic impacts of moderate-strong earthquakes in terms of damage/dollars/
downtime, has indeed stimulated and facilitated the wider acceptance and
implementation of cost-efficient damage-control (or low-damage) technologies.
The ‘bar’ has been raised significantly with the request to fast-track the development
of what the wider general public would hope, and somehow expect, to live
in, i.e. an “earthquake-proof” building system, capable of sustaining the shaking of
a severe earthquake basically unscathed.
The paper provides an overview of recent advances through extensive research,
carried out at the University of Canterbury in the past decade towards the development
of a low-damage building system as a whole, within an integrated
performance-based framework, including the skeleton of the superstructure, the
non-structural components and the interaction with the soil/foundation system.
Examples of real on site-applications of such technology in New Zealand, using
concrete, timber (engineered wood), steel or a combination of these materials, and
featuring some of the latest innovative technical solutions developed in the laboratory
are presented as examples of successful transfer of performance-based seismic
design approach and advanced technology from theory to practice
On BCFW shifts of integrands and integrals
In this article a first step is made towards the extension of
Britto-Cachazo-Feng-Witten (BCFW) tree level on-shell recursion relations to
integrands and integrals of scattering amplitudes to arbitrary loop order.
Surprisingly, it is shown that the large BCFW shift limit of the integrands has
the same structure as the corresponding tree level amplitude in any minimally
coupled Yang-Mills theory in four or more dimensions. This implies that these
integrands can be reconstructed from a subset of their `single cuts'. The main
tool is powercounting Feynman graphs in a special lightcone gauge choice
employed earlier at tree level by Arkani-Hamed and Kaplan. The relation between
shifts of integrands and shifts of its integrals is investigated explicitly at
one loop. Two particular sources of discrepancy between the integral and
integrand are identified related to UV and IR divergences. This is
cross-checked with known results for helicity equal amplitudes at one loop. The
nature of the on-shell residue at each of the single-cut singularities of the
integrand is commented upon. Several natural conjectures and opportunities for
further research present themselves.Comment: 43 pages, 6 figures, v2: minor improvement in exposition, typos
fixed, bibliography update
Genome Majority Vote Improves Gene Predictions
Recent studies have noted extensive inconsistencies in gene start sites among orthologous genes in related microbial genomes. Here we provide the first documented evidence that imposing gene start consistency improves the accuracy of gene start-site prediction. We applied an algorithm using a genome majority vote (GMV) scheme to increase the consistency of gene starts among orthologs. We used a set of validated Escherichia coli genes as a standard to quantify accuracy. Results showed that the GMV algorithm can correct hundreds of gene prediction errors in sets of five or ten genomes while introducing few errors. Using a conservative calculation, we project that GMV would resolve many inconsistencies and errors in publicly available microbial gene maps. Our simple and logical solution provides a notable advance toward accurate gene maps
Key stages of mammary gland development: Molecular mechanisms involved in the formation of the embryonic mammary gland
The development of the embryonic mammary gland involves communication between the epidermis and mesenchyme and is coordinated temporally and spatially by various signaling pathways. Although many more genes are likely to control mammary gland development, functional roles have been identified for Wnt, fibroblast growth factor, and parathyroid hormone-related protein signaling. This review describes what is known about the molecular mechanisms that regulate embryonic mammary gland development
A primary care, multi-disciplinary disease management program for opioid-treated patients with chronic non-cancer pain and a high burden of psychiatric comorbidity
BACKGROUND: Chronic non-cancer pain is a common problem that is often accompanied by psychiatric comorbidity and disability. The effectiveness of a multi-disciplinary pain management program was tested in a 3 month before and after trial. METHODS: Providers in an academic general medicine clinic referred patients with chronic non-cancer pain for participation in a program that combined the skills of internists, clinical pharmacists, and a psychiatrist. Patients were either receiving opioids or being considered for opioid therapy. The intervention consisted of structured clinical assessments, monthly follow-up, pain contracts, medication titration, and psychiatric consultation. Pain, mood, and function were assessed at baseline and 3 months using the Brief Pain Inventory (BPI), the Center for Epidemiological Studies-Depression Scale scale (CESD) and the Pain Disability Index (PDI). Patients were monitored for substance misuse. RESULTS: Eighty-five patients were enrolled. Mean age was 51 years, 60% were male, 78% were Caucasian, and 93% were receiving opioids. Baseline average pain was 6.5 on an 11 point scale. The average CESD score was 24.0, and the mean PDI score was 47.0. Sixty-three patients (73%) completed 3 month follow-up. Fifteen withdrew from the program after identification of substance misuse. Among those completing 3 month follow-up, the average pain score improved to 5.5 (p = 0.003). The mean PDI score improved to 39.3 (p < 0.001). Mean CESD score was reduced to 18.0 (p < 0.001), and the proportion of depressed patients fell from 79% to 54% (p = 0.003). Substance misuse was identified in 27 patients (32%). CONCLUSIONS: A primary care disease management program improved pain, depression, and disability scores over three months in a cohort of opioid-treated patients with chronic non-cancer pain. Substance misuse and depression were common, and many patients who had substance misuse identified left the program when they were no longer prescribed opioids. Effective care of patients with chronic pain should include rigorous assessment and treatment of these comorbid disorders and intensive efforts to insure follow up
Patterns of Pacific decadal variability recorded by Indian Ocean corals
We investigate Pacific Decadal Oscillation (PDO) signals recorded by two bimonthly resolved coral δ18O series from La Réunion and Ifaty (West Madagascar), Indian Ocean from 1882 to 1993. To isolate the main PDO frequencies, we apply a band pass filter to the time series passing only periodicities from 16 to 28 years. We investigate the covariance patterns of the coral time series with sea surface temperature (SST) and sea level pressure (SLP) of the Indian and Pacific Oceans. In addition, the empirical orthogonal functions of the filtered SST and SLP fields (single and coupled) are related to the filtered coral times series. The covariance maps show the typical PDO pattern for SST and SLP, confirming the coupling between the Indian and Pacific Oceans. Both corals show the strongest signal in boreal summer. The La Réunion (Ifaty) coral better records SST (SLP) than SLP (SST) pattern variability. We suggest that the filtered La Réunion coral δ18O represents δ18O of seawater that varies with the South Equatorial Current, which, in turn, is linked with the SST PDO. The filtered Ifaty coral δ18O represents SST and is remotely linked with the SLP PDO variability. A combined coral record of the Ifaty and La Réunion boreal summer δ18O series explains about 64% of the variance of the coupled SST/SLP PDO time series
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