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A new operating mode in experiments searching for free neutron-antineutron oscillations based on coherent neutron and antineutron mirror reflections
No full textAn observation of neutron-antineutron oscillations ( - ), which violate both and by 2 units, would constitute a fundamental discovery and contribute to our understanding of the baryon asymmetry of the universe. A sufficiently stringent upper constraint on this process would also make a major contribution by ruling out the possibility of post-sphaleron baryogenesis (PSB) involving first-generation quarks, which would mean that sphaleron transitions at the electroweak scale are essential for baryogenesis within the Sakharov paradigm. We show that one can design an experiment with free n using existing or projected neutron sources that can reach the sensitivity needed to rule out PSB if one allows the and , with sufficiently small tangential velocity, to coherently reflect from mirrors composed of certain nuclei. We show that the sensitivity of a future experiment can be greatly improved, and a more compact and less expensive apparatus can be realized. A sensitivity gain of ~ in the oscillation probability relative to the existing free- limit can be reached if one is willing to adopt a long flight path with a horizontal guide viewing a cold neutron source, or a significantly shorter flight path with a vertical guide viewing a very cold neutron source
Calculations of neutron reflectivity in the eV energy range from mirrors made of heavy nuclei with neutron-nucleus resonances
No full textWe evaluate the reflectivity of neutron mirrors composed of certain heavy nuclei which possess strong neutron-nucleus resonances in the eV energy range. We consider possible corrections to the usual formulas of neutron optics for this case and find that dispersion and multiple scattering effects are negligible but one must take Doppler broadening into account. Effects from surface roughness and phonon scattering are small compared to the Doppler corrections and are either the same as or smaller than those for mirror reflection with meV neutrons. We show that the reflectivity of such a mirror for some nuclei can in principle be high enough near energies corresponding to compound neutron-nucleus resonances to be of interest for certain scientific applications in nondestructive evaluation of subsurface material composition
Resting state network modularity along the prodromal late onset Alzheimer's disease continuum
No full textAlzheimer's disease is considered a disconnection syndrome, motivating the use of brain network measures to detect changes in whole-brain resting state functional connectivity (FC). We investigated changes in FC within and among resting state networks (RSN) across four different stages in the Alzheimer's disease continuum. FC changes were examined in two independent cohorts of individuals (84 and 58 individuals, respectively) each comprising control, subjective cognitive decline, mild cognitive impairment and Alzheimer's dementia groups. For each participant, FC was computed as a matrix of Pearson correlations between pairs of time series from 278 gray matter brain regions. We determined significant differences in FC modular organization with two distinct approaches, network contingency analysis and multiresolution consensus clustering. Network contingency analysis identified RSN sub-blocks that differed significantly across clinical groups. Multiresolution consensus clustering identified differences in the stability of modules across multiple spatial scales. Significant modules were further tested for statistical association with memory and executive function cognitive domain scores. Across both analytic approaches and in both participant cohorts, the findings converged on a pattern of FC that varied systematically with diagnosis within the frontoparietal network (FP) and between the FP network and default mode network (DMN). Disturbances of modular organization were manifest as greater internal coherence of the FP network and stronger coupling between FP and DMN, resulting in less segregation of these two networks. Our findings suggest that the pattern of interactions within and between specific RSNs offers new insight into the functional disruption that occurs across the Alzheimer's disease spectrum
Brain-Derived Neurotrophic Factor Genotype-Specific Differences in Cortical Activation in Chronic Aphasia
No full textPurpose: The brain-derived neurotrophic factor (BDNF) gene has been shown to be important for synaptic plasticity in animal models. Human research has suggested that BDNF genotype may influence stroke recovery. Some studies have suggested a genotype-specific motor-related brain activation in stroke recovery. However, recovery from aphasia in relation to BDNF genotype and language-related brain activation has received limited attention. We aimed to explore functional brain activation by BDNF genotype in individuals with chronic aphasia. Consistent with findings in healthy individuals and individuals with poststroke motor impairment, we hypothesized that, among individuals with aphasia, the presence of the Met allele of the BDNF gene is associated with reduced functional brain activation compared to noncarriers of the Met allele. Method: Eighty-seven individuals with chronic stroke-induced aphasia performed a naming task during functional magnetic resonance imaging scanning and submitted blood or saliva samples for BDNF genotyping. The mean number of activated voxels was compared between groups, and group-based activation maps were directly compared. Neuropsychological testing was conducted to compare language impairment between BDNF genotype groups. The Western Aphasia Battery Aphasia Quotient (Kertesz, 2007) was included as a covariate in all analyses. Results: While lesion size was comparable between groups, the amount of activation, quantified as the number of activated voxels, was significantly greater in noncarriers of the Met allele (whole brain: 98,500 vs. 28,630, p < .001; left hemisphere only: 37,209 vs. 7,000, p < .001; right hemisphere only: 74,830 vs. 30,630, p < .001). This difference was most strongly expressed in the right hemisphere posterior temporal area, pre- and postcentral gyrus, and frontal lobe, extending into the white matter. Correspondingly, the atypical BDNF genotype group was found to have significantly less severe aphasia (Western Aphasia Battery Aphasia Quotient of 64.2 vs. 54.3, p = .033) and performed better on a naming task (Philadelphia Naming Test [Roach, Schwartz, Martin, Grewal, & Brecher, 1996] score of 74.7 vs. 52.8, p = .047). A region of interest analysis of intensity of activation revealed no group differences, and a direct comparison of average activation maps across groups similarly yielded null results. Conclusion: BDNF genotype mediates cortical brain activation in individuals with chronic aphasia. Correspondingly, individuals carrying the Met allele present with more severe aphasia compared to noncarriers. These findings warrant further study into the effects of BDNF genotype in aphasia
Genetic Screen in Chlamydia muridarum Reveals Role for an Interferon-Induced Host Cell Death Program in Antimicrobial Inclusion Rupture
No full textInterferon-regulated immune defenses protect mammals from pathogenically diverse obligate intracellular bacterial pathogens of the genus Chlamydia. Interferon gamma (IFN-γ) is especially important in controlling the virulence of Chlamydia species and thus impacts the modeling of human chlamydial infection and disease in mice. How IFN-γ contributes to cell-autonomous defenses against Chlamydia species and how these pathogens evade IFN-γ-mediated immunity in their natural hosts are not well understood. We conducted a genetic screen which identified 31 IFN-γ-sensitive (Igs) mutants of the mouse model pathogen Chlamydia muridarum. Genetic suppressor analysis and lateral gene transfer were used to map the phenotype of one of these mutants, Igs4, to a missense mutation in a putative chlamydial inclusion membrane protein, TC0574. We observed the lytic destruction of Igs4-occupied inclusions and accompanying host cell death in response to IFN-γ priming or various proapoptotic stimuli. However, Igs4 was insensitive to IFN-γ-regulated cell-autonomous defenses previously implicated in anti-Chlamydia trachomatis host defense in mice. Igs4 inclusion integrity was restored by caspase inhibitors, indicating that the IFN-γ-mediated destruction of Igs4 inclusions is dependent upon the function of caspases or related prodeath cysteine proteases. We further demonstrated that the Igs4 mutant is immune restricted in an IFN-γ-dependent manner in a mouse infection model, thereby implicating IFN-γ-mediated inclusion destruction and host cell death as potent in vivo host defense mechanisms to which wild-type C. muridarum is resistant. Overall, our results suggest that C. muridarum evolved resistance mechanisms to counter IFN-γ-elicited programmed cell death and the associated destruction of intravacuolar pathogens
A Qualitative Investigation of Music Use among Amateur and Semi-Professional Golfers
No full textMusic use in golf receives minimal attention from both applied and empirical perspectives. Golfers, coaches, and sport psychology practitioners alike may benefit from understanding and utilizing music within their work. Since music use in golf has become an increasingly common practice, the purpose of the current study was to investigate current music use among golfers using a qualitative approach. Researchers aimed to identify potential psychological and physiological effects derived from music use during golf practice and pre-performance, given the limited empirical research in this area to date. Semi-structured interviews were conducted with ten amateur and semi-professional golfers (five male, five female, Mage = 22.9 years, SD = 5.04 years). Consensual qualitative research (CQR) methodology was used to analyze the interview data. Six domains emerged from the CQR analysis regarding participants’ self-reported music use in golf: tempo, attention, physiological regulation, psychological regulation, effects of music on performance perceptions, and context (to use or not to use). Given the capacity of carefully selected music to elicit profound affective, neurophysiological, and behavioral responses, there is clear potential for mental performance consultants to utilize music in working with golfers in training contexts. Implications, caveats, and future research recommendations are provided
The diverse niches of megajournals: Specialism within generalism
No full textOver the past decade, megajournals have expanded in popularity and established a legitimate niche in academic publishing. Leveraging advantages of digital publishing, megajournals are characterized by large publication volume, broad interdisciplinary scope, and peer‐review filters that select primarily for scientific soundness as opposed to novelty or originality. These publishing innovations are complementary and competitive vis‐à‐vis traditional journals. We analyze how megajournals (PLOS One, Scientific Reports) are represented in different fields relative to prominent generalist journals (Nature, PNAS, Science) and “quasi‐megajournals” (Nature Communications, PeerJ). Our results show that both megajournals and prominent traditional journals have distinctive niches, despite the similar interdisciplinary scopes of such journals. These niches—defined by publishing volume and disciplinary diversity—are dynamic and varied over the relatively brief histories of the analyzed megajournals. Although the life sciences are the predominant contributor to megajournals, there is variation in the disciplinary composition of different megajournals. The growth trajectories and disciplinary composition of generalist journals—including megajournals—reflect changing knowledge dissemination and reward structures in science
Resonances in forward photoproduction on hydrogen
No full textWe show that the cross section of the production in the reaction at forward angles and with unpolarized photons can be described in terms of gauge invariant one pion t-channel exchange amplitudes. Proper description of the polarized cross sections requires, however, the inclusion of contributions from the baryon exchanges
First-Order Definable Counting-Only Queries
No full textFor several practical queries on bags of sets of objects, the answer does not depend on the precise composition of these sets, but only on the number of sets to which each object belongs. This is the case = 1 for the more general situation where the query answer only depends on the number of sets to which each group of at most objects belongs. We call such queries k-counting-only. Here, we focus on -SyCALC, -counting-only queries that are first-order definable. As -SyCALC is semantically defined, however, it is not surprising that it is already undecidable whether a first-order query is in 1-SyCALC. Therefore, we introduce SimpleCALC-, a syntactically defined (strict) fragment of -SyCALC. It turns out that many practical queries in -SyCALC can already be expressed in SimpleCALC-. We prove that the -counting-only queries form a non-collapsing hierarchy: for every , there exist (+1)-counting-only queries that are not -counting-only. This result specializes to both SimpleCALC- and -SyCALC. Finally, we establish a strong dichotomy between 1-SyCALC and SimpleCALC- on the one hand and 2-SyCALC on the other hand by showing that satisfiability, validity, query containment, and query equivalence are decidable for the former two languages, but not for the latter one
Co-located contemporaneous mapping of morphological, hydrological, chemical, and biological conditions in a 5th-order mountain stream network, Oregon, USA
No full textA comprehensive set of measurements and calculated metrics describing physical, chemical, and biological conditions in the river corridor is presented. These data were collected in a catchment-wide, synoptic campaign in the H. J. Andrews Experimental Forest (Cascade Mountains, Oregon, USA) in summer 2016 during low-discharge conditions. Extensive characterization of 62 sites including surface water, hyporheic water, and streambed sediment was conducted spanning 1st- through 5th-order reaches in the river network. The objective of the sample design and data acquisition was to generate a novel data set to support scaling of river corridor processes across varying flows and morphologic forms present in a river network