Resonator-induced dissipation of transverse nuclear-spin signals in cold nanoscale samples

The back action of typical macroscopic resonators used for detecting nuclear magnetic resonance can cause a reversible decay of the signal, known as radiation damping. A mechanical resonator that is strongly coupled to a microscopic sample can in addition induce an irreversible dissipation of the nuclear-spin signal, distinct from radiation damping. We provide a theoretical description of resonator-induced transverse relaxation that is valid for samples of a few nuclear spins in the low-temperature regime, where quantum fluctuations play a significant role in the relaxation process, as well as for larger samples and at higher temperatures. Transverse relaxation during free evolution and during spin locking are analyzed, and simulations of relaxation in example systems are presented. In the case where an isolated spin 1/2 interacts with the resonator, transverse relaxation is exponential during free evolution, and the time constant for the relaxation is T_2=2/R_h, where R_h is the rate constant governing the exchange of quanta between the resonator and the spin. For a system of multiple spins, the time scale of transverse relaxation during free evolution depends on the spin Hamiltonian, which can modify the relaxation process through the following effects: (1) changes in the structure of the spin-spin correlations present in the energy eigenstates, which affect the rates at which these states emit and absorb energy, (2) frequency shifts that modify emission and absorption rates within a degenerate manifold by splitting the energy degeneracy and thus suppressing the development of resonator-induced correlations within the manifold, and (3) frequency shifts that introduce a difference between the oscillation frequencies of single-quantum coherences ρ_(ab) and ρ_(cd) and average to zero the transfers between them. This averaging guarantees that the spin transitions responsible for the coupling between ρ_(ab) and ρ_(cd) cause irreversible loss of order rather than a reversible interconversion of the coherences. In systems of a few spins, transverse relaxation is accelerated by a dipolar Hamiltonian that is either the dominant term in the internal spin Hamiltonian or a weak perturbation to the chemical-shift Hamiltonian. A pure chemical-shift Hamiltonian yields exponential relaxation with T_2=2/R_h in the case where the Larmor frequencies of the spins are distinct and sufficiently widely spaced. During spin locking with a nutation frequency fast enough to average the evolution under the internal spin Hamiltonian but not the interactions occurring during the correlation time of the resonator, relaxation of the spin-locked component is exponential with time constant T_(1ρ)=2/R_h

Polarization of nuclear spins by a cold nanoscale resonator

A cold nanoscale resonator coupled to a system of nuclear spins can induce spin relaxation. In the low-temperature limit where spin-lattice interactions are “frozen out,” spontaneous emission by nuclear spins into a resonant mechanical mode can become the dominant mechanism for cooling the spins to thermal equilibrium with their environment. We provide a theoretical framework for the study of resonator-induced cooling of nuclear spins in this low-temperature regime. Relaxation equations are derived from first principles, in the limit where energy donated by the spins to the resonator is quickly dissipated into the cold bath that damps it. A physical interpretation of the processes contributing to spin polarization is given. For a system of spins that have identical couplings to the resonator, the interaction Hamiltonian conserves spin angular momentum, and the resonator cannot relax the spins to thermal equilibrium unless this symmetry is broken by the spin Hamiltonian. The mechanism by which such a spin system becomes “trapped” away from thermal equilibrium can be visualized using a semiclassical model, which shows how an indirect spin-spin interaction arises from the coupling of multiple spins to one resonator. The internal spin Hamiltonian can affect the polarization process in two ways: (1) By modifying the structure of the spin-spin correlations in the energy eigenstates, and (2) by splitting the degeneracy within a manifold of energy eigenstates, so that zero-frequency off-diagonal terms in the density matrix are converted to oscillating coherences. Shifting the frequencies of these coherences sufficiently far from zero suppresses the development of resonator-induced correlations within the manifold during polarization from a totally disordered state. Modification of the spin-spin correlations by means of either mechanism affects the strength of the fluctuating spin dipole that drives the resonator. In the case where product states can be chosen as energy eigenstates, spontaneous emission from eigenstate populations into the resonant mode can be interpreted as independent emission by individual spins, and the spins relax exponentially to thermal equilibrium if the development of resonator-induced correlations is suppressed. When the spin Hamiltonian includes a significant contribution from the homonuclear dipolar coupling, the energy eigenstates entail a correlation specific to the coupling network. Simulations of dipole-dipole coupled systems of up to five spins suggest that these systems contain weakly emitting eigenstates that can trap a fraction of the population for time periods ≫100/R_0, where R_0 is the rate constant for resonator-enhanced spontaneous emission by a single spin 1/2. Much of the polarization, however, relaxes with rates comparable to R_0. A distribution of characteristic high-field chemical shifts tends to increase the relaxation rates of weakly emitting states, enabling transitions to states that can quickly relax to thermal equilibrium. The theoretical framework presented in this paper is illustrated with discussions of spin polarization in the contexts of force-detected nuclear-magnetic-resonance spectroscopy and magnetic-resonance force microscopy

The Stories Behind the Story (Foreword and Introduction to Introducing Evangelical Ecotheology: Foundations in Scripture, Theology, History, and Praxis)

Excerpt: Nathan and I (Dan) pulled into the Mbanhela community in the Gaza province of Mozambique and were greeted by the high-spirited singing of six women who form the livestock association of that small community. A Christian relief and development organization, of which Nathan is the country director, provided funds for a large chicken coop, feed, supplies, and 300 chickens for the Mbanhela community. In addition, it furnished training in basic animal husbandry and marketing. Every two months the community starts a new cycle with 320 chicks. Raising chickens for income empowers that community and helps it toward health and sustainability. But the goal of raising livestock is not just for community development. The Mbanhela community decided that God had called them to provide a home for twenty-nine orphans and other vulnerable children. (One woman, Pastor Ramira, said to us matter-of-factly, “God tells us to care for the orphans and widows, and so we do.”) Profits from the sale of the chickens help those children attend school and buy books and school supplies

The Early Evolution of Rhynchosaurs

The rhynchosaurian archosauromorphs are an important and diverse group of fossil tetrapods that first appeared during the Early Triassic and probably became extinct during the early Late Triassic (early Norian). Here, the early evolution of rhynchosaurs during the Early and early Middle Triassic (Induan-Anisian: 252.2-242 Mya) is reviewed based on new anatomical observations and their implications for the taxonomy, phylogenetic relationships and macroevolutionary history of the group. A quantitative phylogenetic analysis recovered a paraphyletic genus Rhynchosaurus, with “Rhynchosaurus” brodiei more closely related to hyperodapedontines than to Rhynchosaurus articeps. Therefore, a new genus is erected, resulting in the new combination Langeronyx brodiei. A body size analysis found two independent increases in size in the evolutionary history of rhynchosaurs, one among stenaulorhynchines and the other in the hyperodapedontine lineage. Maximum likelihood fitting of phenotypic evolution models to body size data found ambiguous results, with body size evolution potentially interpreted as fitting either a non-directional Brownian motion model or a stasis model. A Dispersal-ExtinctionCladogenesis analysis reconstructed the areas that are now South Africa and Europe as the ancestral areas of Rhynchosauria and Rhynchosauridae, respectively. The reconstruction of dispersal events between geographic areas that are broadly separated paleolatitudinally implies that barriers to the dispersal of rhynchosaurs from either side of the paleo-Equator during the Middle Triassic were either absent or permeable.Fil: Ezcurra, Martin Daniel. University of Birmingham; Reino Unido. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Montefeltro, Felipe C.. University of Birmingham; Reino Unido. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Butler, Richard J.. University of Birmingham; Reino Unid

Nanoscale Torsional Resonator for Polarization and Spectroscopy of Nuclear Spins

We propose a torsional resonator that couples to the transverse spin dipole of an attached sample. The absence of relative motion eliminates a source of friction that would otherwise hinder nanoscale implementation. Enhanced spontaneous emission induced by the resonator relaxes the longitudinal spin dipole at a rate of ~1  s^(-1) in the low-temperature limit. With signal averaging, single-proton magnetic resonance spectroscopy appears feasible at ~10  mK and a high magnetic field, while single-shot sensitivity is practical for samples with at least tens of protons in a volume of ~5  nm^3

State Super-Maximum Security Policies: An Examination of Admission Characteristics, Classification Reviews, Mental Health Amenities, and Inmate Privileges

Super-maximum security prisons have flourished within a political environment that endorses tougher criminal sanctions. This punitive evolution has created new problems for correctional agencies attempting to control the “worst of the worst” inmates. Federal courts and researchers have examined the detrimental effects supermax isolation has on inmates’ mental health. This analysis examines forty-two state supermax policies to determine how states admit inmates to supermax custody, the classification review process, the management of inmates with mental illnesses, and the availability of privileges for supermax inmates. Drawing on the concept of the McDonaldization of Justice (Ritzer, 1993), particular attention is given to understanding the role of official policy and procedures on managing problematic inmates. Guided by previous research on supermax penitentiaries, the correctional policies have been aggregated regionally to provide insight into geographical differences for the operation of supermax units. Policy implications for establishing more inclusive and thorough rules and regulations for the admission, review, and management of supermax units are discussed

A Strategy to Enfold Korean Students of Cerritos Community College Into the International Pentecostal Church

This study presents an attractional and incarnational strategy to help members of International Pentecostal Church (hereafter, IPC) to reach out and enfold some of the local Korean population into its congregation. The strategy focuses upon the church working together with students of the Cerritos Community College (hereafter, CCC) Christian Student club to influence Korean students into fellowship, Bible study, and Pentecostal worship gatherings. Ultimately the goal of this study includes Korean students experiencing their personal new birth experience. In three parts, this paper addresses the IPC ministry context, theological foundation, and strategies to enfold some Korean students from CCC into its congregation. Upon describing the need and challenges of IPC to reach into the Korean community, the first part of this paper discusses the Bellflower and surrounding area’s demographics, with special attention given to the Korean community. A discovery of IPC’s strengths and weaknesses provides insights and potential modifications. A subsequent section discusses the CCC, its characteristics and demographics with particular focus given to the Korean student population that builds the basis for the strategies described later in the paper. The second part of this paper examines the theological basis for the focused thrust to reach and enfold students of the Korean community. It evaluates the biblical and theological considerations for the project. The paper then addresses the missiological and ecclesiological backdrops for the endeavor. The third part of this paper discusses the strategy for accomplishing the goals. After clearly defining the goals, the paper presents the project’s strategic overview that includes the pastor’s responsibility, IPC’s responsibility, CCC’s roles, as well as defines what the church should expect to see when a student is enfolded into IPC’s worshipping community. Subsequently, the specific strategy is addressed and an assessment section helps to evaluate the success of the focused ministry project. Theological Mentor: Kurt Fredrickson, Ph

The REVERE project:Experiments with the application of probabilistic NLP to systems engineering

Despite natural language’s well-documented shortcomings as a medium for precise technical description, its use in software-intensive systems engineering remains inescapable. This poses many problems for engineers who must derive problem understanding and synthesise precise solution descriptions from free text. This is true both for the largely unstructured textual descriptions from which system requirements are derived, and for more formal documents, such as standards, which impose requirements on system development processes. This paper describes experiments that we have carried out in the REVERE1 project to investigate the use of probabilistic natural language processing techniques to provide systems engineering support

How to make better mistakes in public policy

We all make mistakes, a tendency which also extends to those who work in public policy. Despite this seemingly universal tendency, we often only hear about successes. Bucking this trend, Kevin Arceneaux and Daniel Butler describe a recent pilot program aimed at boosting civic engagement in a Midwestern town, based on Get Out the Vote literature. Rather than increasing the number of people who volunteered for town committees as intended, the three tactics they tested actually had no effect or reduced the chances that people would volunteer

Bilingual, digital, audio-visual training modules improve technical knowledge of feedlot and dairy workers

Two studies were conducted to determine the effectiveness of digital multimedia modules as training tools for animal care workers. Employees at a commercial feedlot (n = 17) and a commercial dairy (n = 10) were asked to independently complete a 10-question quiz prior to and following viewing of training modules. Module topics in the feedlot were proper handling of non-ambulatory animals and humane methods of euthanasia; modules were administered to the workers, as a group, in either English (n = 7) or Spanish (N = 10), depending on previously indicated worker preference. Modules addressing dairy cattle health practices and dairy cattle handling were presented to the dairy care workers who had a preference for learning in either English (n = 7) or Spanish (n = 3). For feedlot workers, post-test scores were improved by 28% after viewing the modules compared to pre-test scores (74% vs. 58%; P 0.30) between language, topic, and between-test variation, indicating that the modules were equally effective at information delivery to both audiences in both languages. For the dairy workers, test scores improved by 27% from pre-viewing to post-viewing (73% vs. 92%; P < 0.01); there was an interaction between the effect of module and language preference (P < 0.01) indicating that although scores increased for both of the topic areas for the English-speaking workers, only the score for the animal health topic increased for the Spanish-speaking workers. Regardless of nationality, level of formal education, topic, or preferred language, digital media are effective at improving knowledge transfer to animal care professionals