886 research outputs found

    Neutrino-Deuteron Scattering in Effective Field Theory at Next-to-Next-to Leading Order

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    We study the four channels associated with neutrino-deuteron breakup reactions at next-to-next to leading order in effective field theory. We find that the total cross-section is indeed converging for neutrino energies up to 20 MeV, and thus our calculations can provide constraints on theoretical uncertainties for the Sudbury Neutrino Observatory. We stress the importance of a direct experimental measurement to high precision in at least one channel, in order to fix an axial two-body counterterm.Comment: 32 pages, 14 figures (eps

    Compton Scattering and the Spin Structure of the Nucleon at Low Energies

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    We analyze polarized Compton scattering which provides information on the spin-structure of the nucleon. For scattering processes with photon energies up to 100 MeV the spin-structure dependence can be encoded into four independent parameters-the so-called spin-polarizabilities γi,i=1...4\gamma_i, i=1...4 of the nucleon, which we calculate within the framework of the "small scale expansion" in SU(2) baryon chiral perturbation theory. Specific application is made to "forward" and "backward" spin- polarizabilities.Comment: 8 pages revtex file, separation between pion-pole and regular contributions detailed + minor wording changes, results and conclusions unchange

    Chiral Analysis of Quenched Baryon Masses

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    We extend to quenched QCD an earlier investigation of the chiral structure of the masses of the nucleon and the delta in lattice simulations of full QCD. Even after including the meson-loop self-energies which give rise to the leading and next-to-leading non-analytic behaviour (and hence the most rapid variation in the region of light quark mass), we find surprisingly little curvature in the quenched case. Replacing these meson-loop self-energies by the corresponding terms in full QCD yields a remarkable level of agreement with the results of the full QCD simulations. This comparison leads to a very good understanding of the origins of the mass splitting between these baryons.Comment: 23 pages, 6 figure

    Characterization of halogen-bridged binuclear metal complexes as hybridized two-band materials

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    We study the electronic structure of halogen-bridged binuclear metal (MMX) complexes with a two-band Peierls-Hubbard model. Based on a symmetry argument, various density-wave states are derived and characterized. The ground-state phase diagram is drawn within the Hartree-Fock approximation, while the thermal behavior is investigated using a quantum Monte Carlo method. All the calculations conclude that a typical MMX compound Pt_2(CH_3CS_2)_4I should indeed be regarded as a d-p-hybridized two-band material, where the oxidation of the halogen ions must be observed even in the ground state, whereas another MMX family (NH_4)_4[Pt_2(P_2O_5H_2)_4X] may be treated as single-band materials.Comment: 16 pages, 11 figures embedded, to be published in Phys. Rev.

    A Seat at the Table: Strategic Engagement in Service Activities for Early-Career Faculty From Underrepresented Groups in the Academy

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    Many academic institutions strive to promote more diverse and inclusive campuses for faculty, staff, and students. As part of this effort, these institutions seek to include individuals from historically underrepresented groups (URGs)-such as women, people from racial/ethnic minority populations, persons with disabilities-on committees and in other service activities. However, given the low number of faculty members from URGs at many institutions, these faculty members tend to receive more requests to provide service to the institution or department (e.g., serving on committees, mentoring) than their counterparts from majority groups. Faculty members from URGs, especially early-career faculty, thus risk becoming overburdened with providing service at the expense of working on other scholarly activities required for promotion and tenure (i.e., conducting research, publishing). Although many scholars and others have written about this "minority tax" and its implications for early-career faculty from underrepresented racial/ethnic minority groups, fewer have published about how this tax extends beyond racial/ethnic minorities to women and persons with disabilities. Further, the literature provides scant practical advice on how to avoid overburdening early-career faculty from URGs. Here, a group of multidisciplinary early- and mid-career faculty members from URGs seek to provide their peers from URGs with practical strategies for both evaluating the appropriateness of service requests and declining those that are not a good fit. The authors also provide institutional leaders with actionable recommendations to prevent early-career faculty from URGs from becoming overburdened with service

    Affective Man-Machine Interface: Unveiling human emotions through biosignals

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    As is known for centuries, humans exhibit an electrical profile. This profile is altered through various psychological and physiological processes, which can be measured through biosignals; e.g., electromyography (EMG) and electrodermal activity (EDA). These biosignals can reveal our emotions and, as such, can serve as an advanced man-machine interface (MMI) for empathic consumer products. However, such a MMI requires the correct classification of biosignals to emotion classes. This chapter starts with an introduction on biosignals for emotion detection. Next, a state-of-the-art review is presented on automatic emotion classification. Moreover, guidelines are presented for affective MMI. Subsequently, a research is presented that explores the use of EDA and three facial EMG signals to determine neutral, positive, negative, and mixed emotions, using recordings of 21 people. A range of techniques is tested, which resulted in a generic framework for automated emotion classification with up to 61.31% correct classification of the four emotion classes, without the need of personal profiles. Among various other directives for future research, the results emphasize the need for parallel processing of multiple biosignals

    Cardiovascular Dysfunction and Frailty among Older Adults in the Community: The ARIC Study

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    Background: The contribution of cardiovascular dysfunction to frailty in older adults is uncertain. This study aimed to define the relationship between frailty and cardiovascular structure and function, and determine whether these associations are independent of coexisting abnormalities in other organ systems. Methods: We studied 3,991 older adults (mean age 75.6 - 5.0 years; 59% female) from the Atherosclerosis Risk in Communities (ARIC) Study in whom the following six organ systems were uniformly assessed: cardiac (by echocardiography), vascular (by ankle-brachial-index and pulse-wave-velocity), pulmonary (by spirometry), renal (by estimated glomerular filtration rate), hematologic (by hemoglobin), and adipose (by body mass index and bioimpedance). Frailty was defined by the presence of ?3 of the following: low strength, low energy, slowed motor performance, low physical activity, or unintentional weight loss. Results: Two hundred eleven (5.3%) participants were frail. In multivariable analyses adjusted for demographics, diabetes, hypertension, and measures of other organ system function, frailty was independently and additively associated with left ventricular hypertrophy (odds ratio [OR] = 1.72; 95% confidence interval [CI] = 1.30-2.40), reduced global longitudinal strain (reflecting systolic function; OR = 1.68; 95% CI = 1.16-2.44), and greater left atrial volume index (reflecting diastolic function; OR = 1.60; 95% CI = 1.13-2.27), which together demonstrated the greatest association with frailty (OR = 2.10; 95% CI = 1.57-2.82) of the systems studied. Lower magnitude associations were observed for vascular and pulmonary abnormalities, anemia, and impaired renal function. Cardiovascular abnormalities remained associated with frailty after excluding participants with prevalent cardiovascular disease. Conclusions: Abnormalities of cardiac structure and function are independently associated with frailty, and together show the greatest association with frailty among the organ systems studied
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