289 research outputs found
Synthesizing attractors of Hindmarsh-Rose neuronal systems
In this paper a periodic parameter switching scheme is applied to the
Hindmarsh-Rose neuronal system to synthesize certain attractors. Results show
numerically, via computer graphic simulations, that the obtained synthesized
attractor belongs to the class of all admissible attractors for the
Hindmarsh-Rose neuronal system and matches the averaged attractor obtained with
the control parameter replaced with the averaged switched parameter values.
This feature allows us to imagine that living beings are able to maintain vital
behavior while the control parameter switches so that their dynamical behavior
is suitable for the given environment.Comment: published in Nonlinear Dynamic
Quantum oscillations from Fermi arcs
When a metal is subjected to strong magnetic field B nearly all measurable
quantities exhibit oscillations periodic in 1/B. Such quantum oscillations
represent a canonical probe of the defining aspect of a metal, its Fermi
surface (FS). In this study we establish a new mechanism for quantum
oscillations which requires only finite segments of a FS to exist. Oscillations
periodic in 1/B occur if the FS segments are terminated by a pairing gap. Our
results reconcile the recent breakthrough experiments showing quantum
oscillations in a cuprate superconductor YBCO, with a well-established result
of many angle resolved photoemission (ARPES) studies which consistently
indicate "Fermi arcs" -- truncated segments of a Fermi surface -- in the normal
state of the cuprates.Comment: 8 pages, 5 figure
Promoting menstrual health among persian adolescent girls from low socioeconomic backgrounds: a quasi-experimental study
<p>Abstract</p> <p>Background</p> <p>Research in the past decade has revealed average to poor menstrual health among many Iranian girls. The present study investigated the effectiveness of a health promotion project on improving menstrual health in adolescent girls in Iran.</p> <p>Methods</p> <p>A quasi-experimental study was conducted to evaluate the effectiveness of the health intervention program. A total of 698 students (study participants and controls) in several schools in Mazandaran province, Iran were included. The project comprised 10 two-hour educational sessions. Educational topics included the significance of adolescence, physical and emotional changes during adolescence, pubertal and menstruation health and premenstrual syndrome. A self-administered questionnaire measuring demographic characteristics, behaviors during menstruation, menstrual patterns, sources of information about menstruation and personal health data was administered. The questionnaire was administered to all participating students after the experimental group received the training.</p> <p>Results</p> <p>Among the most significant results was the impact of educational sessions on bathing and genital hygiene. A total of 61.6% in the experimental group compared with 49.3% in the control group engaged in usual bathing during menstruation (p = 0.002). Individual health status was significantly statistically correlated with menstrual health. Attitude towards menstruation was also significantly related to menstrual health.</p> <p>Conclusions</p> <p>The present study confirms that educational interventions, such as the health promotion project in this study, can be quite effective in promoting menstrual health.</p
Nodal quasiparticle meltdown in ultra-high resolution pump-probe angle-resolved photoemission
High- cuprate superconductors are characterized by a strong
momentum-dependent anisotropy between the low energy excitations along the
Brillouin zone diagonal (nodal direction) and those along the Brillouin zone
face (antinodal direction). Most obvious is the d-wave superconducting gap,
with the largest magnitude found in the antinodal direction and no gap in the
nodal direction. Additionally, while antinodal quasiparticle excitations appear
only below , superconductivity is thought to be indifferent to nodal
excitations as they are regarded robust and insensitive to . Here we
reveal an unexpected tie between nodal quasiparticles and superconductivity
using high resolution time- and angle-resolved photoemission on optimally doped
BiSrCaCuO. We observe a suppression of the nodal
quasiparticle spectral weight following pump laser excitation and measure its
recovery dynamics. This suppression is dramatically enhanced in the
superconducting state. These results reduce the nodal-antinodal dichotomy and
challenge the conventional view of nodal excitation neutrality in
superconductivity.Comment: 7 pages, 3 figure. To be published in Nature Physic
Tibet, the Himalaya, Asian monsoons and biodiversity - In what ways are they related?
Prevailing dogma asserts that the uplift of Tibet, the onset of the Asian monsoon system and high biodiversity in southern Asia are linked, and that all occurred after 23 million years ago in the Neogene. Here, spanning the last 60 million years of Earth history, the geological, climatological and palaeontological evidence for this linkage is reviewed. The principal conclusions are that: 1) A proto-Tibetan highland existed well before the Neogene and that an Andean type topography with surface elevations of at least 4.5Â km existed at the start of the Eocene, before final closure of the Tethys Ocean that separated India from Eurasia. 2) The Himalaya were formed not at the start of the India-Eurasia collision, but after much of Tibet had achieved its present elevation. The Himalaya built against a pre-existing proto-Tibetan highland and only projected above the average height of the plateau after approximately 15Â Ma. 3) Monsoon climates have existed across southern Asia for the whole of the Cenozoic, and probably for a lot longer, but that they were of the kind generated by seasonal migrations of the Inter-tropical Convergence Zone. 4) The projection of the High Himalaya above the Tibetan Plateau at about 15Â Ma coincides with the development of the modern South Asia Monsoon. 5) The East Asia monsoon became established in its present form about the same time as a consequence of topographic changes in northern Tibet and elsewhere in Asia, the loss of moisture sources in the Asian interior and the development of a strong winter Siberian high as global temperatures declined. 6) New radiometric dates of palaeontological finds point to southern Asia's high biodiversity originating in the Paleogene, not the Neogene
Fractal superconductivity near localization threshold
We develop a semi-quantitative theory of electron pairing and resulting
superconductivity in bulk "poor conductors" in which Fermi energy is
located in the region of localized states not so far from the Anderson mobility
edge . We review the existing theories and experimental data and argue
that a large class of disordered films is described by this model.
Our theoretical analysis is based on the analytical treatment of pairing
correlations, described in the basis of the exact single-particle eigenstates
of the 3D Anderson model, which we combine with numerical data on eigenfunction
correlations. Fractal nature of critical wavefunction's correlations is shown
to be crucial for the physics of these systems.
We identify three distinct phases: 'critical' superconductive state formed at
, superconducting state with a strong pseudogap, realized due to
pairing of weakly localized electrons and insulating state realized at
still deeper inside localized band. The 'critical' superconducting phase is
characterized by the enhancement of the transition temperature with respect to
BCS result, by the inhomogeneous spatial distribution of superconductive order
parameter and local density of states. The major new feature of the
pseudo-gaped state is the presence of two independent energy scales:
superconducting gap , that is due to many-body correlations and a new
"pseudogap" energy scale which characterizes typical binding energy
of localized electron pairs and leads to the insulating behavior of the
resistivity as a function of temperature above superconductive . Two gap
nature of the "pseudo-gaped superconductor" is shown to lead to a number of
unusual physical properties.Comment: 110 pages, 39 figures. The revised version corrects a number of
typos, adds references and discussion of recent result
Targeted hepatitis C antibody testing interventions: a systematic review and meta-analysis
Testing for hepatitis C virus (HCV) infection may reduce the risk of liver-related morbidity, by facilitating earlier access to treatment and care. This review investigated the effectiveness of targeted testing interventions on HCV case detection, treatment uptake, and prevention of liver-related morbidity. A literature search identified studies published up to 2013 that compared a targeted HCV testing intervention (targeting individuals or groups at increased risk of HCV) with no targeted intervention, and results were synthesised using meta-analysis. Exposure to a targeted testing intervention, compared to no targeted intervention, was associated with increased cases detected [number of studies (n) = 14; pooled relative risk (RR) 1.7, 95 % CI 1.3, 2.2] and patients commencing therapy (n = 4; RR 3.3, 95 % CI 1.1, 10.0). Practitioner-based interventions increased test uptake and cases detected (n = 12; RR 3.5, 95 % CI 2.5, 4.8; and n = 10; RR 2.2, 95 % CI 1.4, 3.5, respectively), whereas media/information-based interventions were less effective (n = 4; RR 1.5, 95 % CI 0.7, 3.0; and n = 4; RR 1.3, 95 % CI 1.0, 1.6, respectively). This meta-analysis provides for the first time a quantitative assessment of targeted HCV testing interventions, demonstrating that these strategies were effective in diagnosing cases and increasing treatment uptake. Strategies involving practitioner-based interventions yielded the most favourable outcomes. It is recommended that testing should be targeted at and offered to individuals who are part of a population with high HCV prevalence, or who have a history of HCV risk behaviour
Using molecular data for epidemiological inference: assessing the prevalence of Trypanosoma brucei rhodesiense in Tsetse in Serengeti, Tanzania
Background: Measuring the prevalence of transmissible Trypanosoma brucei rhodesiense in tsetse populations is essential for understanding transmission dynamics, assessing human disease risk and monitoring spatio-temporal trends and the impact of control interventions. Although an important epidemiological variable, identifying flies which carry transmissible infections is difficult, with challenges including low prevalence, presence of other trypanosome species in the same fly, and concurrent detection of immature non-transmissible infections. Diagnostic tests to measure the prevalence of T. b. rhodesiense in tsetse are applied and interpreted inconsistently, and discrepancies between studies suggest this value is not consistently estimated even to within an order of magnitude.
Methodology/Principal Findings: Three approaches were used to estimate the prevalence of transmissible Trypanosoma brucei s.l. and T. b. rhodesiense in Glossina swynnertoni and G. pallidipes in Serengeti National Park, Tanzania: (i) dissection/microscopy; (ii) PCR on infected tsetse midguts; and (iii) inference from a mathematical model. Using dissection/microscopy the prevalence of transmissible T. brucei s.l. was 0% (95% CI 0–0.085) for G. swynnertoni and 0% (0–0.18) G. pallidipes; using PCR the prevalence of transmissible T. b. rhodesiense was 0.010% (0–0.054) and 0.0089% (0–0.059) respectively, and by model inference 0.0064% and 0.00085% respectively.
Conclusions/Significance: The zero prevalence result by dissection/microscopy (likely really greater than zero given the results of other approaches) is not unusual by this technique, often ascribed to poor sensitivity. The application of additional techniques confirmed the very low prevalence of T. brucei suggesting the zero prevalence result was attributable to insufficient sample size (despite examination of 6000 tsetse). Given the prohibitively high sample sizes required to obtain meaningful results by dissection/microscopy, PCR-based approaches offer the current best option for assessing trypanosome prevalence in tsetse but inconsistencies in relating PCR results to transmissibility highlight the need for a consensus approach to generate meaningful and comparable data
Disparities in self-reported postpartum depression among Asian, Hawaiian, and Pacific Islander women in Hawai‘i: Pregnancy, Risk, Assessment, and Monitoring System (PRAMS), 2004-2007
Postpartum depression affects 10–20% of women and causes significant morbidity and mortality among mothers, children, families, and society, but little is known about postpartum depression among the individual Asian and Pacific Islander racial/ethnic groups. This study sought to identify the prevalence of postpartum depression among common Asian and Pacific Islander racial/ethnic groups. Data from the Hawaii Pregnancy Risk Assessment and Monitoring System (PRAMS), a population-based surveillance system on maternal behaviors and experiences before, during, and after the birth of a live infant, were analyzed from 2004 through 2007 and included 7,154 women. Questions on mood and interest in activities since giving birth were combined to create a measure of Self-reported Postpartum Depressive Symptoms (SRPDS). A series of generalized logit models with maternal race or ethnicity adjusted for other sociodemographic characteristics evaluated associations between SRPDS and an intermediate level of symptoms as possible indicators of possible SRPDS. Of all women in Hawaii with a recent live birth, 14.5% had SRPDS, and 30.1% had possible SRPDS. The following Asian and Pacific Islander racial or ethnic groups were studied and found to have higher odds of SRPDS compared with white women: Korean (adjusted odds ratio [AOR] = 2.8;95% confidence interval [CI]: 2.0–4.0), Filipino (AOR = 2.2;95% CI: 1.7–2.8), Chinese (AOR = 2.0;95% CI: 1.5–2.7), Samoan (AOR = 1.9;95% CI: 1.2–3.2), Japanese (AOR = 1.6;95% CI: 1.2–2.2), Hawaiian (AOR = 1.7;95% CI: 1.3–2.1), other Asian (AOR = 3.3;95% CI: 1.9–5.9), other Pacific Islander (AOR = 2.2;95% CI: 1.5–3.4), and Hispanic (AOR = 1.9;95% CI: 1.1–3.4). Women who had unintended pregnancies (AOR = 1.4;95% CI: 1.2–1.6), experienced intimate partner violence (AOR = 3.7;95% CI: 2.6–5.5), smoked (AOR = 1.5;95% CI: 1.2–2.0), used illicit drugs (AOR = 1.9;95% CI: 1.3–3.9), or received Women, Infant, and Children (WIC) benefits during pregnancy (AOR = 1.4;95% CI: 1.2–2.6) were more likely to have SRPDS. Several groups also were at increased risk for possible SRPDS, although this risk was not as prominent as seen with the risk for SRPDS. One in seven women reported SRPDS, and close to a third reported possible SRPDS. Messages about postpartum depression should be incorporated into current programs to improve screening, treatment, and prevention of SRPDS for women at risk
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