270 research outputs found

    High energy emission from microquasars

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    The microquasar phenomenon is associated with the production of jets by X-ray binaries and, as such, may be associated with the majority of such systems. In this chapter we briefly outline the associations, definite, probable, possible, and speculative, between such jets and X-ray, gamma-ray and particle emission.Comment: Contributing chapter to the book Cosmic Gamma-Ray Sources, K.S. Cheng and G.E. Romero (eds.), to be published by Kluwer Academic Publishers, Dordrecht, 2004. (19 pages

    Two-dimensional NMR lineshape analysis

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    NMR titration experiments are a rich source of structural, mechanistic, thermodynamic and kinetic information on biomolecular interactions, which can be extracted through the quantitative analysis of resonance lineshapes. However, applications of such analyses are frequently limited by peak overlap inherent to complex biomolecular systems. Moreover, systematic errors may arise due to the analysis of two-dimensional data using theoretical frameworks developed for one-dimensional experiments. Here we introduce a more accurate and convenient method for the analysis of such data, based on the direct quantum mechanical simulation and fitting of entire two-dimensional experiments, which we implement in a new software tool, TITAN (TITration ANalysis). We expect the approach, which we demonstrate for a variety of protein-protein and protein-ligand interactions, to be particularly useful in providing information on multi-step or multi-component interactions

    Intra-colony channels in E. coli function as a nutrient uptake system

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    The ability of microorganisms to grow as aggregated assemblages has been known for many years, however their structure has remained largely unexplored across multiple spatial scales. The development of the Mesolens, an optical system which uniquely allows simultaneous imaging of individual bacteria over a 36 mm2 field of view, has enabled the study of mature Escherichia coli macro-colony biofilm architecture like never before. The Mesolens enabled the discovery of intra-colony channels on the order of 10 μm in diameter, that are integral to E. coli macro-colony biofilms and form as an emergent property of biofilm growth. These channels have a characteristic structure and re-form after total mechanical disaggregation of the colony. We demonstrate that the channels are able to transport particles and play a role in the acquisition of and distribution of nutrients through the biofilm. These channels potentially offer a new route for the delivery of dispersal agents for antimicrobial drugs to biofilms, ultimately lowering their impact on public health and industry

    Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set

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    We report a measurement of the bottom-strange meson mixing phase \beta_s using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays in which the quark-flavor content of the bottom-strange meson is identified at production. This measurement uses the full data set of proton-antiproton collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity. We report confidence regions in the two-dimensional space of \beta_s and the B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2, -1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in agreement with the standard model expectation. Assuming the standard model value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +- 0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +- 0.009 (syst) ps, which are consistent and competitive with determinations by other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012

    Schizophrenia and psychotic symptoms in families of two American Indian tribes

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    Abstract Background The risk of schizophrenia is thought to be higher in population isolates that have recently been exposed to major and accelerated cultural change, accompanied by ensuing socio-environmental stressors/triggers, than in dominant, mainstream societies. We investigated the prevalence and phenomenology of schizophrenia in 329 females and 253 males of a Southwestern American Indian tribe, and in 194 females and 137 males of a Plains American Indian tribe. These tribal groups were evaluated as part of a broader program of gene-environment investigations of alcoholism and other psychiatric disorders. Methods Semi-structured psychiatric interviews were conducted to allow diagnoses utilizing standardized psychiatric diagnostic criteria, and to limit cultural biases. Study participants were recruited from the community on the basis of membership in pedigrees, and not by convenience. After independent raters evaluated the interviews blindly, DSM-III-R diagnoses were assigned by a consensus of experts well-versed in the local cultures. Results Five of the 582 Southwestern American Indian respondents (prevalence = 8.6 per 1000), and one of the 331 interviewed Plains American Indians (prevalence = 3.02 per 1000) had a lifetime diagnosis of schizophrenia. The lifetime prevalence rates of schizophrenia within these two distinct American Indian tribal groups is consistent with lifetime expectancy rates reported for the general United States population and most isolate and homogeneous populations for which prevalence rates of schizophrenia are available. While we were unable to factor in the potential modifying effect that mortality rates of schizophrenia-suffering tribal members may have had on the overall tribal rates, the incidence of schizophrenia among the living was well within the normative range. Conclusion The occurrence of schizophrenia among members of these two tribal population groups is consistent with prevalence rates reported for population isolates and in the general population. Vulnerabilities to early onset alcohol and drug use disorders do not lend convincing support to a diathesis-stressor model with these stressors, commonly reported with these tribes. Nearly one-fifth of the respondents reported experiencing psychotic-like symptoms, reaffirming the need to examine sociocultural factors actively before making positive diagnoses of psychosis or schizophrenia.</p

    Stab Injury to the Preauricular Region With Laceration of the External Carotid Artery Without Involvement of the Facial Nerve: a Case Report

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    BACKGROUND: Open injuries to the face involving the external carotid artery are uncommon. These injuries are normally associated with laceration of the facial nerve because this nerve is more superficial than the external carotid artery. Hence, external carotid artery lesions are usually associated with facial nerve dysfunction. We present an unusual case report in which the patient had an injury to this artery with no facial nerve compromise. CASE PRESENTATION: A 25-year-old Portuguese man sustained a stab wound injury to his right preauricular region with a broken glass. Immediate profuse bleeding ensued. Provisory tamponade of the wound was achieved at the place of aggression by two off-duty doctors. He was initially transferred to a district hospital, where a large arterial bleeding was observed and a temporary compressive dressing was applied. Subsequently, the patient was transferred to a tertiary hospital. At admission in the emergency room, he presented a pulsating lesion in the right preauricular region and slight weakness in the territory of the inferior buccal branch of the facial nerve. The physical examination suggested an arterial lesion superficial to the facial nerve. However, in the operating theater, a section of the posterior and lateral flanks of the external carotid artery inside the parotid gland was identified. No lesion of the facial nerve was observed, and the external carotid artery was repaired. To better understand the anatomical rationale of this uncommon clinical case, we dissected the preauricular region of six cadavers previously injected with colored latex solutions in the vascular system. A small triangular space between the two main branches of division of the facial nerve in which the external carotid artery was not covered by the facial nerve was observed bilaterally in all cases. CONCLUSIONS: This clinical case illustrates that, in a preauricular wound, the external carotid artery can be injured without facial nerve damage. However, no similar description was found in the reviewed literature, which suggests that this must be a very rare occurrence. According to the dissection study performed, this is due to the existence of a triangular space between the cervicofacial and temporofacial nerve trunks in which the external carotid artery is not covered by the facial nerve or its branches.info:eu-repo/semantics/publishedVersio

    Financial wellbeing of Asian Americans

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    The Asian American population in the United States has been increasing. Research on the economic wellbeing of this minority group is far from being adequate. It is generally found that Asian Americans are more highly educated and have more wealth. Although the homeownership rate of this population is lower than the national average rate, the gap is gradually narrowing. Asian Americans are found to have more confidence in their financial future and have better management in their financial lives. In addition, Asian-owned businesses have been an important part of the U.S. economy and, as such, the self-employment status of Asian Americans has stimulated great interest for research. Large differences in financial behaviors exist among different groups in Asian Americans. This chapter serves the purpose to summarize past research on Asian American consumer finances and provide directions for future research.Includes bibliographical references

    Challenges in multidisciplinary cancer care among general surgeons in Canada

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    <p>Abstract</p> <p>Background</p> <p>While many factors can influence the way that cancer care is delivered, including the way that evidence is packaged and disseminated, little research has evaluated how health care professionals who manage cancer patients seek and use this information to identify whether and how this could be supported. Through interviews we identified that general surgeons experience challenges in coordinating care for complex cancer patients whose management is not easily addressed by guidelines, and conducted a population-based survey of general surgeon information needs and information seeking practices to extend these findings.</p> <p>Methods</p> <p>General surgeons with privileges at acute care hospitals in Ontario, Canada were mailed a questionnaire to solicit information needs (task, importance), information seeking (source, frequency of and reasons for use), key challenges and suggested solutions. Non-responders received up to three reminder packages. Significant differences among sub-groups (age, setting) were examined statistically (Kruskal Wallis, Mann Whitney, Chi Square). Standard qualitative methods were used to thematically analyze open-ended responses.</p> <p>Results</p> <p>The response rate was 44.2% (170/385) representing all 14 health regions. System resource constraints (60.4%), comorbidities (56.4%) and physiologic factors (51.8%) were top-ranked issues creating information needs. Local surgical colleagues (84.6%), other local colleagues (82.2%) and the Internet (81.1%) were top-ranked sources of information, primarily due to familiarity and speed of access. No resources were considered to be highly applicable to patient care. Challenges were related to limitations in diagnostics and staging, operative resources, and systems to support multidisciplinary care, together accounting for 76.0% of all reported issues. Findings did not differ significantly by surgeon age or setting of care.</p> <p>Conclusion</p> <p>General surgeons appear to use a wide range of information resources but they may not address the complex needs of many cancer patients. Decision-making is challenged by informational and logistical issues related to the coordination of multidisciplinary care. This suggests that limitations in system capacity may, in part, contribute to variable guideline compliance. Further research is required to evaluate the appropriateness of information seeking, and both concurrent and consecutive mechanisms by which to achieve multidisciplinary care.</p

    Is Cortisol Excretion Independent of Menstrual Cycle Day? A Longitudinal Evaluation of First Morning Urinary Specimens

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    Background Cortisol is frequently used as a marker of physiologic stress levels. Using cortisol for that purpose, however, requires a thorough understanding of its normal longitudinal variability. The current understanding of longitudinal variability of basal cortisol secretion in women is very limited. It is often assumed, for example, that basal cortisol profiles do not vary across the menstrual cycle. This is a critical assumption: if cortisol were to follow a time dependent pattern during the menstrual cycle, then ignoring this cyclic variation could lead to erroneous imputation of physiologic stress. Yet, the assumption that basal cortisol levels are stable across the menstrual cycle rests on partial and contradictory evidence. Here we conduct a thorough test of that assumption using data collected for up to a year from 25 women living in rural Guatemala. Methodology We apply a linear mixed model to describe longitudinal first morning urinary cortisol profiles, accounting for differences in both mean and standard deviation of cortisol among women. To that aim we evaluate the fit of two alternative models. The first model assumes that cortisol does not vary with menstrual cycle day. The second assumes that cortisol mean varies across the menstrual cycle. Menstrual cycles are aligned on ovulation day (day 0). Follicular days are assigned negative numbers and luteal days positive numbers. When we compared Models 1 and 2 restricting our analysis to days between −14 (follicular) and day 14 (luteal) then day of the menstrual cycle did not emerge as a predictor of urinary cortisol levels (p-value &gt;0.05). Yet, when we extended our analyses beyond that central 28-day-period then day of the menstrual cycle become a statistically significant predictor of cortisol levels. Significance The observed trend suggests that studies including cycling women should account for day dependent variation in cortisol in cycles with long follicular and luteal phases
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