194 research outputs found
Shape of the 8B Alpha and Neutrino Spectra
The beta-delayed alpha spectrum from the decay of 8B has been measured with a
setup that minimized systematic uncertainties that affected previous
measurements. Consequently the deduced neutrino spectrum presents much smaller
uncertainties than the previous recommendation. The 8B neutrino spectrum is
found to be harder than previously recommended with about (10-20)% more
neutrinos at energies between 12-14 MeV. The efficiencies of the 37Cl, 71Ga,
40Ar, and SuperKamiokande detectors are respectively, 3.6%, 1.4%, 5.7% and 1.8%
larger than previously thought.Comment: 4 pages, 5 figure
Status of the UCNτ experiment
The neutron is the simplest nuclear system that can be used to probe the structure of the weak interaction and search for physics beyond the standard model. Measurements of neutron lifetime and β-decay correlation coefficients with precisions of 0.02% and 0.1%, respectively, would allow for stringent constraints on new physics. The UCNτ experiment uses an asymmetric magneto-gravitational UCN trap with in situ counting of surviving neutrons to measure the neutron lifetime, τ_n = 877.7s (0.7s)_(stat) (+0.4/−0.2s)_(sys). We discuss the recent result from UCNτ, the status of ongoing data collection and analysis, and the path toward a 0.25 s measurement of the neutron lifetime with UCNτ
Measurement of the neutron lifetime using an asymmetric magneto- gravitational trap and in situ detection
The precise value of the mean neutron lifetime, , plays an important
role in nuclear and particle physics and cosmology. It is a key input for
predicting the ratio of protons to helium atoms in the primordial universe and
is used to search for new physics beyond the Standard Model of particle
physics. There is a 3.9 standard deviation discrepancy between
measured by counting the decay rate of free neutrons in a beam (887.7 2.2
s) and by counting surviving ultracold neutrons stored for different storage
times in a material trap (878.50.8 s). The experiment described here
eliminates loss mechanisms present in previous trap experiments by levitating
polarized ultracold neutrons above the surface of an asymmetric storage trap
using a repulsive magnetic field gradient so that the stored neutrons do not
interact with material trap walls and neutrons in quasi-stable orbits rapidly
exit the trap. As a result of this approach and the use of a new in situ
neutron detector, the lifetime reported here (877.7 0.7 (stat) +0.4/-0.2
(sys) s) is the first modern measurement of that does not require
corrections larger than the quoted uncertainties.Comment: 9 pages, 3 figures, 2 table
Post-Construction Support and Sustainability in Community-Managed Rural Water Supply
Executive Summary This volume reports the main findings from a multi-country research project that was designed to develop a better understanding of how rural water supply systems are performing in developing countries. We began the research in 2004 to investigate how the provision of support to communities after the construction of a rural water supply project affected project performance in the medium term. We collected information from households, village water committees, focus groups of village residents, system operators, and key informants in 400 rural communities in Bolivia, Ghana, and Peru; in total, we discussed community water supply issues with approximately 10,000 individuals in these communities. To our surprise, we found the great majority of the village water systems were performing well. Our findings on the factors influencing their sustainability will, we hope, be of use to policy makers, investors, and managers in rural water supply
Teaching Domestic Violence in the New Millennium: Intersectionality as a Framework for Social Change
This article describes an intersectional approach to teaching about domestic violence (DV), which aims to empower students as critical thinkers and agents of change by merging theory, service learning, self-reflection, and activism. Three intersectional strategies and techniques for teaching about DV are discussed: promoting difference-consciousness, complicating gender-only power frameworks, and organizing for change. The author argues that to empower future generations to end violence, educators should put intersectionality into action through their use of scholarship, teaching methods, and pedagogical authority. Finally, the benefits and challenges of intersectional pedagogy for social justice education are considered
Prediction of native-state hydrogen exchange from perfectly funneled energy landscapes
Simulations based on perfectly funneled energy landscapes often capture many of the kinetic features of protein folding. We examined whether simulations based on funneled energy functions can also describe fluctuations in native-state protein ensembles. We quantitatively compared the site-specific local stability determined from structure-based folding simulations, with hydrogen exchange protection factors measured experimentally for ubiquitin, chymotrypsin inhibitor 2, and staphylococcal nuclease. Different structural definitions for the open and closed states based on the number of native contacts for each residue, as well as the hydrogen-bonding state, or a combination of both criteria were evaluated. The predicted exchange patterns agree with the experiments under native conditions, indicating that protein topology indeed has a dominant effect on the exchange kinetics. Insights into the simplest mechanistic interpretation of the amide exchange process were thus obtained.Fil: Craig, Patricio Oliver. Fundación Instituto Leloir; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquimicas de Buenos Aires; Argentina. University of California San Diego. Department of Chemistry and Biochemistry; Estados UnidosFil: Lätzer, Joachim. Rutgers University. BioMaPS Institute; Estados UnidosFil: Weinkam, Patrick. University of California at San Francisco. Department of Bioengineering and Therapeutic Sciences; Estados UnidosFil: Hoffman, Ryan M. B.. University Of California At San Diego; Estados UnidosFil: Ferreiro, Diego. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Komives, Elizabeth A.. University Of California At San Diego; Estados UnidosFil: Wolynes, Peter G.. University Of California At San Diego; Estados Unido
Discrete Kinetic Models from Funneled Energy Landscape Simulations
A general method for facilitating the interpretation of computer simulations of protein folding with minimally frustrated energy landscapes is detailed and applied to a designed ankyrin repeat protein (4ANK). In the method, groups of residues are assigned to foldons and these foldons are used to map the conformational space of the protein onto a set of discrete macrobasins. The free energies of the individual macrobasins are then calculated, informing practical kinetic analysis. Two simple assumptions about the universality of the rate for downhill transitions between macrobasins and the natural local connectivity between macrobasins lead to a scheme for predicting overall folding and unfolding rates, generating chevron plots under varying thermodynamic conditions, and inferring dominant kinetic folding pathways. To illustrate the approach, free energies of macrobasins were calculated from biased simulations of a non-additive structure-based model using two structurally motivated foldon definitions at the full and half ankyrin repeat resolutions. The calculated chevrons have features consistent with those measured in stopped flow chemical denaturation experiments. The dominant inferred folding pathway has an “inside-out”, nucleation-propagation like character
Fundamental Neutron Physics: a White Paper on Progress and Prospects in the US
Fundamental neutron physics, combining precision measurements and theory,
probes particle physics at short range with reach well beyond the highest
energies probed by the LHC. Significant US efforts are underway that will probe
BSM CP violation with orders of magnitude more sensitivity, provide new data on
the Cabibbo anomaly, more precisely measure the neutron lifetime and decay, and
explore hadronic parity violation. World-leading results from the US
Fundamental Neutron Physics community since the last Long Range Plan, include
the world's most precise measurement of the neutron lifetime from UCN,
the final results on the beta-asymmetry from UCNA and new results on hadronic
parity violation from the NPDGamma and n-He runs at the FNPB (Fundamental
Neutron Physics Beamline), precision measurement of the radiative neutron decay
mode and n-He at NIST. US leadership and discovery potential are ensured
by the development of new high-impact experiments including BL3, Nab, LANL nEDM
and nEDM@SNS. On the theory side, the last few years have seen results for the
neutron EDM from the QCD term, a factor of two reduction in the
uncertainty for inner radiative corrections in beta-decay which impacts CKM
unitarity, and progress on {\it ab initio} calculations of nuclear structure
for medium-mass and heavy nuclei which can eventually improve the connection
between nuclear and nucleon EDMs. In order to maintain this exciting program
and capitalize on past investments while also pursuing new ideas and building
US leadership in new areas, the Fundamental Neutron Physics community has
identified a number of priorities and opportunities for our sub-field covering
the time-frame of the last Long Range Plan (LRP) under development. This white
paper elaborates on these priorities.Comment: arXiv admin note: text overlap with arXiv:2304.0345
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