2,357 research outputs found
Graying of the Professoriate Reconsidered: The Impact of Demographics on Criminal Justice Education
The demographic composition, especially the age structure of criminal justice faculty, is of interest to students in criminal justice education for a number of reasons. First, an overall assessment provides some gauge of the relative age of the faculty in the field. Second, observations of changes in the composition of the age structure over time provide insight into the aging process and attendant developmental process of the field itself. Third, age composition has a major impact on the job market for criminal justice faculty. This of course, in turn, partially determines career possibilities for neophytes in the field. It also serves as a major factor in setting the limits of both vertical and horizontal faculty career mobility. Fourth, age composition has a direct bearing on potential for improving the quality of criminal justice education
Improved Fast Randomized Iteration Approach to Full Configuration Interaction
We present three modifications to our recently introduced fast randomized
iteration method for full configuration interaction (FCI-FRI) and investigate
their effects on the method's performance for Ne, HO, and N. The
initiator approximation, originally developed for full configuration
interaction quantum Monte Carlo, significantly reduces statistical error in
FCI-FRI when few samples are used in compression operations, enabling its
application to larger chemical systems. The semi-stochastic extension, which
involves exactly preserving a fixed subset of elements in each compression,
improves statistical efficiency in some cases but reduces it in others. We also
developed a new approach to sampling excitations that yields consistent
improvements in statistical efficiency and reductions in computational cost. We
discuss possible strategies based on our findings for improving the performance
of stochastic quantum chemistry methods more generally.Comment: 13 pages, 5 figure
Approximating matrix eigenvalues by subspace iteration with repeated random sparsification
Traditional numerical methods for calculating matrix eigenvalues are
prohibitively expensive for high-dimensional problems. Iterative random
sparsification methods allow for the estimation of a single dominant eigenvalue
at reduced cost by leveraging repeated random sampling and averaging. We
present a general approach to extending such methods for the estimation of
multiple eigenvalues and demonstrate its performance for several benchmark
problems in quantum chemistry.Comment: 31 pages, 7 figure
Beyond Walkers in Stochastic Quantum Chemistry: Reducing Error using Fast Randomized Iteration
We introduce a family of methods for the full configuration interaction
problem in quantum chemistry, based on the fast randomized iteration (FRI)
framework [L.-H. Lim and J. Weare, SIAM Rev. 59, 547 (2017)]. These methods,
which we term "FCI-FRI," stochastically impose sparsity during iterations of
the power method and can be viewed as a generalization of full configuration
interaction quantum Monte Carlo (FCIQMC) without walkers. In addition to the
multinomial scheme commonly used to sample excitations in FCIQMC, we present a
systematic scheme where excitations are not sampled independently. Performing
ground-state calculations on five small molecules at fixed cost, we find that
the systematic FCI-FRI scheme is 11 to 45 times more statistically efficient
than the multinomial FCI-FRI scheme, which is in turn 1.4 to 178 times more
statistically efficient than the original FCIQMC algorithm.Comment: 19 pages, 7 figure
Use of partial-wave decomposition to identify resonant interference effects in the photoionizationâexcitation of argon
We have studied simultaneous photoionization and excitation of Ar in the range of incident photon energies between 36.00 and 36.36 eV, where the resonant production of doubly excited neutral Ar states imbedded in the ionization continuum is dominant. By measuring the relative Stokes parameters of the fluorescence from residual Ar+â (3p4 [3P] 4p) ions (2P1/2, 465.8 nm transition; 2P3/2, 476.5 nm; 2D3/2, 472.7 nm; 2D5/2, 488.0 nm; 4P5/2, 480.6 nm; 4D5/2, 514.5 nm) we demonstrate a technique for determining individual partial-wave cross sections in photoionizing collisions. This procedure is shown to be important in sorting out competing dynamical ionization mechanisms, particularly with regard to resonant production of intermediate doubly excited autoionizing states. Comparison with theoretical photoionization cross sections demonstrates that spinâorbit coupling between different states of Ar II needs to be accounted for in the calculations
Developmental changes in the organization of functional connections between the basal ganglia and cerebral cortex
The basal ganglia (BG) comprise a set of subcortical nuclei with sensorimotor, cognitive, and limbic subdivisions, indicative of functional organization. BG dysfunction in several developmental disorders suggests the importance of the healthy maturation of these structures. However, few studies have investigated the development of BG functional organization. Using resting-state functional connectivity MRI (rs-fcMRI), we compared human child and adult functional connectivity of the BG with rs-fcMRI-defined cortical systems. Because children move more than adults, customized preprocessing, including volume censoring, was used to minimize motion-induced rsfcMRI artifact. Our results demonstrated functional organization in the adult BG consistent with subdivisions previously identified in anatomical tracing studies. Group comparisons revealed a developmental shift in bilateral posterior putamen/pallidum clusters from preferential connectivity with the somatomotor âfaceâ system in childhood to preferential connectivity with control/attention systems (frontoparietal, ventral attention) in adulthood. This shift was due to a decline in the functional connectivity of these clusters with the somatomotor face system over development, and no change with control/attention systems. Applying multivariate pattern analysis, we were able to reliably classify individuals as children or adults based on BGâcortical system functional connectivity. Interrogation of the features driving this classification revealed, in addition to the somatomotor face system, contributions by the orbitofrontal, auditory, and somatomotor hand systems. These results demonstrate that BGâcortical functional connectivity evolves over development, and may lend insight into developmental disorders that involve BG dysfunction, particularly those involving motor systems (e.g., Tourette syndrome)
Developmental Changes in the Organization of Functional Connections between the Basal Ganglia and Cerebral Cortex
The basal ganglia (BG) comprise a set of subcortical nuclei with sensorimotor, cognitive, and limbic subdivisions, indicative of functional organization. BG dysfunction in several developmental disorders suggests the importance of the healthy maturation of these structures. However, few studies have investigated the development of BG functional organization. Using resting-state functional connectivity MRI (rs-fcMRI), we compared human child and adult functional connectivity of the BG with rs-fcMRI-defined cortical systems. Because children move more than adults, customized preprocessing, including volume censoring, was used to minimize motion-induced rsfcMRI artifact. Our results demonstrated functional organization in the adult BG consistent with subdivisions previously identified in anatomical tracing studies. Group comparisons revealed a developmental shift in bilateral posterior putamen/pallidum clusters from preferential connectivity with the somatomotor âfaceâ system in childhood to preferential connectivity with control/attention systems (frontoparietal, ventral attention) in adulthood. This shift was due to a decline in the functional connectivity of these clusters with the somatomotor face system over development, and no change with control/attention systems. Applying multivariate pattern analysis, we were able to reliably classify individuals as children or adults based on BGâcortical system functional connectivity. Interrogation of the features driving this classification revealed, in addition to the somatomotor face system, contributions by the orbitofrontal, auditory, and somatomotor hand systems. These results demonstrate that BGâcortical functional connectivity evolves over development, and may lend insight into developmental disorders that involve BG dysfunction, particularly those involving motor systems (e.g., Tourette syndrome)
The MASSIVE Survey. VI. The spatial sistribution and kinematics of warm ionized gas in the most massive local early-type galaxies
We present the first systematic investigation of the existence, spatial distribution, and kinematics of warm ionized gas as traced by the [O ii] 3727 Ă
emission line in 74 of the most massive galaxies in the local universe. All of our galaxies have deep integral-field spectroscopy from the volume- and magnitude-limited MASSIVE survey of early-type galaxies with stellar mass (M K < â25.3 mag) and distance D < 108 Mpc. Of the 74 galaxies in our sample, we detect warm ionized gas in 28, which yields a global detection fraction of 38 ± 6% down to a typical [O ii] equivalent width limit of 2 Ă
. MASSIVE fast rotators are more likely to have gas than MASSIVE slow rotators with detection fractions of 80 ± 10% and 28 ± 6%, respectively. The spatial extents span a wide range of radii (0.6â18.2 kpc; 0.1â4R e ), and the gas morphologies are diverse, with 17/28 â 61 ± 9% being centrally concentrated, 8/28 â 29 ± 9% exhibiting clear rotation out to several kiloparsecs, and 3/28 â 11 ± 6% being extended but patchy. Three out of four fast rotators show kinematic alignment between the stars and gas, whereas the two slow rotators with robust kinematic measurements available exhibit kinematic misalignment. Our inferred warm ionized gas masses are roughly ~105 M â. The emission line ratios and radial equivalent width profiles are generally consistent with excitation of the gas by the old underlying stellar population. We explore different gas origin scenarios for MASSIVE galaxies and find that a variety of physical processes are likely at play, including internal gas recycling, cooling out of the hot gaseous halo, and gas acquired via mergers
Scaling up community-based goat breeding programmes via multi-stakeholder collaboration
Community-based livestock breeding programmes (CBBPs) have emerged as a potential approach to implement sustainable livestock breeding in smallholder systems. In Malawi and Uganda, goat CBBPs were introduced to improve production and productivity of indigenous goats through selective breeding. Scaling up CBBPs have recently received support due to evidence-based results from current implementation and results of CBBPs implemented in other regions of the world. This paper explores strategies for scaling up goat CBBPs in Malawi and Uganda, and documents experiences and lessons learned during implementation of the programme. A number of stakeholders supporting goat-based interventions for improving smallholdersâ livelihoods exists. This offers an opportunity for different actors to work together by pooling financial resources and technical expertise for establishment and sustainability of goat CBBPs. Scaling up strategies should be an integral part of the pilot design hence dissemination partners need to be engaged during the design and inception stages of the pilot CBBPs. Creation of self-sustaining CBBPs requires early collaborative programme planning, meaningful investment and long-term concerted and coordinated efforts by collaborating partners. Permanently established actors, like government agencies and research and training institutions, are better placed to coordinate such efforts. The overall goal of the scaling up programme should be creation of a financially sustainable system, in which smallholders are able, on their own, to transact and sustain operations of their local breeding institutions using locally generated revenue/ resources. Since CBBP scaling up is a âlearning by doing processâ, an effective monitoring and evaluation system should be an integral part of the process
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