301 research outputs found

    Two-body electrodisintegration of the three-nucleon bound state with Δ-isobar excitation

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    Electrodisintegration of the three-nucleon bound state with two-body final states is described. The description uses nucleon degrees of freedom extended to include the excitation of a single nucleon to a Δ isobar. The baryonic interaction and the electromagnetic current couple nucleonic states and states with a Δ isobar. Exact solutions of three-particle scattering equations are employed for the initial and final states of the reactions; due to the excitation of the Δ isobar an effective three-nucleon force is included. The current has one-baryon and two-baryon contributions. Theoretical predictions for the reactions with selected kinematic specifications are given. The role of the Δ isobar in the description of the considered processes is discussed and its effect on observables is quantitatively isolated

    Factors influencing the development of school bonding among middle school students

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    The goal of this research is to examine the trajectory of school bonding over the middle school period and how factors such as gender, substance use, antisocial peers, delinquent behavior, and academic achievement affect this developmental process. Data from four waves of measurement of 2,902 adolescents are analyzed using hierarchical growth curve modeling. Results suggest that school bonding decreases in a nonlinear fashion from Grades 6 to 8. However, school bonding development varies based on interindividual differences. Boys have lower initial levels and greater decreases in school bonding than girls. Student deviant behavior, having antisocial peers, and low academic achievement are associated with lower levels of school bonding at Grade 6. Low grades and an increase in substance use are associated with a steeper decrease of school bonding over time. Increases in substance use and being male are also associated with a curvilinear pattern of school bonding. Implications for interventions are discussed

    The political import of deconstruction—Derrida’s limits?: a forum on Jacques Derrida’s specters of Marx after 25 Years, part I

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    Jacques Derrida delivered the basis of The Specters of Marx: The State of the Debt, the Work of Mourning, & the New International as a plenary address at the conference ‘Whither Marxism?’ hosted by the University of California, Riverside, in 1993. The longer book version was published in French the same year and appeared in English and Portuguese the following year. In the decade after the publication of Specters, Derrida’s analyses provoked a large critical literature and invited both consternation and celebration by figures such as Antonio Negri, Wendy Brown and Frederic Jameson. This forum seeks to stimulate new reflections on Derrida, deconstruction and Specters of Marx by considering how the futures past announced by the book have fared after an eventful quarter century. Maja Zehfuss, Antonio Vázquez-Arroyo and Dan Bulley and Bal Sokhi-Bulley offer sharp, occasionally exasperated, meditations on the political import of deconstruction and the limits of Derrida’s diagnoses in Specters of Marx but also identify possible paths forward for a global politics taking inspiration in Derrida’s work of the 1990s

    Time- and momentum-resolved photoemission studies using time-of-flight momentum microscopy at a free-electron laser

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    Time-resolved photoemission with ultrafast pump and probe pulses is an emerging technique with wide application potential. Real-time recording of nonequilibrium electronic processes, transient states in chemical reactions, or the interplay of electronic and structural dynamics offers fascinating opportunities for future research. Combining valence-band and core-level spectroscopy with photoelectron diffraction for electronic, chemical, and structural analyses requires few 10 fs soft X-ray pulses with some 10 meV spectral resolution, which are currently available at high repetition rate free-electron lasers. We have constructed and optimized a versatile setup commissioned at FLASH/PG2 that combines free-electron laser capabilities together with a multidimensional recording scheme for photoemission studies. We use a full-field imaging momentum microscope with time-of-flight energy recording as the detector for mapping of 3D band structures in (kx, ky, E) parameter space with unprecedented efficiency. Our instrument can image full surface Brillouin zones with up to 7 Å−1 diameter in a binding-energy range of several eV, resolving about 2.5 × 105 data voxels simultaneously. Using the ultrafast excited state dynamics in the van der Waals semiconductor WSe2 measured at photon energies of 36.5 eV and 109.5 eV, we demonstrate an experimental energy resolution of 130 meV, a momentum resolution of 0.06 Å−1, and a system response function of 150 fs

    Reflection-enhanced gain in traveling-wave parametric amplifiers

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    The operating principle of traveling-wave parametric amplifiers is typically understood in terms of the standard coupled mode theory, which describes the evolution of forward propagating waves without any reflections, i.e., for perfect impedance matching. However, in practice, superconducting microwave amplifiers are unmatched nonlinear finite-length devices, where the reflecting waves undergo complex parametric processes, not described by the standard coupled mode theory. Here, we present an analytical solution for the TWPA gain, which includes the interaction of reflected waves. These reflections result in corrections to the well-known results of the standard coupled mode theory, which are obtained for both three-wave and four-wave mixing processes. Due to these reflections, the gain is enhanced and unwanted nonlinear phase modulations are suppressed. Predictions of the model are experimentally demonstrated on two types of unmatched TWPA, based on coplanar waveguides with a central wire consisting of (i) a high kinetic inductance superconductor, and (ii) an array of 2000 Josephson junctions

    Examples of superconducting technology application: sensing and interfacing

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    Technological processes for the fabrication of low- and high- Tc Josephson junctions, aimed for certain applications, are described. On the one hand, the integration of low- Tc superconductor digital electronics with superconducting sensor arrays enables input signal processing with quantum limited resolution at millikelvin temperatures. We describe this mixed signal superconductor technology for analogue sensor readout and signal multiplexing for operating temperatures down to 300 mK. On the other hand, by making use of modern high- Tc Josephson junction technology, sensitive magnetometers, which require a modest cooling power, can be developed. Examples of the application of the mentioned processes are shown

    Centrilobular emphysema and coronary artery calcification: mediation analysis in the SPIROMICS cohort

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    Abstract Background Chronic obstructive pulmonary disease (COPD) is associated with a two-to-five fold increase in the risk of coronary artery disease independent of shared risk factors. This association is hypothesized to be mediated by systemic inflammation but this link has not been established. Methods We included 300 participants enrolled in the SPIROMICS cohort, 75 each of lifetime non-smokers, smokers without airflow obstruction, mild-moderate COPD, and severe-very severe COPD. We quantified emphysema and airway disease on computed tomography, characterized visual emphysema subtypes (centrilobular and paraseptal) and airway disease, and used the Weston visual score to quantify coronary artery calcification (CAC). We used the Sobel test to determine whether markers of systemic inflammation mediated a link between spirometric and radiographic features of COPD and CAC. Results FEV1/FVC but not quantitative emphysema or airway wall thickening was associated with CAC (p = 0.036), after adjustment for demographics, diabetes mellitus, hypertension, statin use, and CT scanner type. To explain this discordance, we examined visual subtypes of emphysema and airway disease, and found that centrilobular emphysema but not paraseptal emphysema or bronchial thickening was independently associated with CAC (p = 0.019). MMP3, VCAM1, CXCL5 and CXCL9 mediated 8, 8, 7 and 16% of the association between FEV1/FVC and CAC, respectively. Similar biomarkers partially mediated the association between centrilobular emphysema and CAC. Conclusions The association between airflow obstruction and coronary calcification is driven primarily by the centrilobular subtype of emphysema, and is linked through bioactive molecules implicated in the pathogenesis of atherosclerosis. Trial Registration ClinicalTrials.gov: Identifier: NCT01969344 .https://deepblue.lib.umich.edu/bitstream/2027.42/146749/1/12931_2018_Article_946.pd
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