Quantum Speed Limits across the Quantum-to-Classical Transition

Quantum speed limits set an upper bound to the rate at which a quantum system can evolve. Adopting a phase-space approach, we explore quantum speed limits across the quantum-to-classical transition and identify equivalent bounds in the classical world. As a result, and contrary to common belief, we show that speed limits exist for both quantum and classical systems. As in the quantum domain, classical speed limits are set by a given norm of the generator of time evolution.National Institute of General Medical Sciences (U.S.) (Grant R25GM076321

The effects of non-uniform drive on plasma filaments

Wendelstein 7-X core fueling is primarily achieved through pellet injection. The trajectory of plasmoids from an ablating pellet is an ongoing research question, which is complicated by the complex magnetic geometry of W7-X; curvature drive varies significantly toroidally, including a change in the drift drive direction. Here we use the Hermes model in BOUT++ to simulate cold plasma filaments in slab geometries where the magnetic drift drive is non-uniform along the field line. It is shown that if the field-line-averaged curvature drive is non-zero, a filament will propagate coherently in the direction of average drive. It is also shown that a non-uniform drive will provide a non-uniform propagation; an effect which is reduced at higher temperatures due to an increased sound speed along the field line. Finally, simulations with curvature similar to that found in Wendelstein 7-X are performed which indicate a slow radial propagation of plasma filaments despite a highly non-uniform drive profile

A Positioning Theory Analysis of Interaction Surrounding Design Failures in an Elementary Engineering Club

This qualitative study applies Positioning Theory to identify positions that mediate the experiences of design failure within the context of an afterschool engineering club (EC) with elementary students diverse in language, race, ethnicity, gender, and academic abilities. We ask: (1) What kinds of structural design failure and failure responses did participants in EC experience? and (2) What are students’ and teachers’ positions in relation to responses to design failure? Types of positions (e.g., builder, tinkerer, idea-elicitor, director, observer) were identified in relation to children’s and teachers’ actions and speech in response to structural design failure during EC. Participants included 12 third-grade students and four teachers involved in EC for eight weeks. Data sources include audio transcripts, video, and field notes. Twenty-four design failure episodes were identified and transcribed multimodally from video, followed by coding of episodes using a multimodal Positioning Theory analytical framework. Findings discuss the kinds of engineering design actions and associated positionings unfolding in response to failure as well as the positions mediating teacher and student responses to design. We highlight the importance of student and teacher mediation as well as how Positioning Theory can be used to expand our understanding of (re)positionings that can occur within responses to design failure. Specifically, elementary engineering curricular materials must create the context to support the range of positions taken up in response to design failure. This includes explicit modeling of discursive actions surrounding design failure, multiple opportunities for students to experience and respond to design failure with time to improve beyond the design–build–test model, and support for teachers to address the range of students’ responses to design failures knowledgeably and flexibly

Cost-effectiveness analysis of the New South Wales adult drug court program

In New South Wales, Australia, a cost-effectiveness evaluation was conducted of an adult drug court (ADC) program as an alternative to jail for criminal offenders addicted to illicit drugs. This article describes the program, the cost-effectiveness analysis, and the results. The results of this study reveal that, for the 23-month period of the evaluation, the ADC was as cost-effective as were conventional sanctions in delaying the time to the first offense and more cost-effective in reducing the frequency of offending for those outcome measures selected. Although the evaluation was conducted using the traditional steps of a cost-effectiveness analysis, because of the complexity of the program and data limitations it was not always possible to adhere to textbook procedures. As such, each step involved in undertaking the cost-effectiveness analysis is discussed, highlighting the key issues faced in the evaluation. © 2004 Sage Publications

Stringy K-theory and the Chern character

For a finite group G acting on a smooth projective variety X, we construct two new G-equivariant rings: first the stringy K-theory of X, and second the stringy cohomology of X. For a smooth Deligne-Mumford stack Y we also construct a new ring called the full orbifold K-theory of Y. For a global quotient Y=[X/G], the ring of G-invariants of the stringy K-theory of X is a subalgebra of the full orbifold K-theory of the the stack Y and is linearly isomorphic to the ``orbifold K-theory'' of Adem-Ruan (and hence Atiyah-Segal), but carries a different, ``quantum,'' product, which respects the natural group grading. We prove there is a ring isomorphism, the stringy Chern character, from stringy K-theory to stringy cohomology, and a ring homomorphism from full orbifold K-theory to Chen-Ruan orbifold cohomology. These Chern characters satisfy Grothendieck-Riemann-Roch for etale maps. We prove that stringy cohomology is isomorphic to Fantechi and Goettsche's construction. Since our constructions do not use complex curves, stable maps, admissible covers, or moduli spaces, our results simplify the definitions of Fantechi-Goettsche's ring, of Chen-Ruan's orbifold cohomology, and of Abramovich-Graber-Vistoli's orbifold Chow. We conclude by showing that a K-theoretic version of Ruan's Hyper-Kaehler Resolution Conjecture holds for symmetric products. Our results hold both in the algebro-geometric category and in the topological category for equivariant almost complex manifolds.Comment: Exposition improved and additional details provided. To appear in Inventiones Mathematica

Polysubstance Use in Early Adulthood: Patterns and Developmental Precursors in an Urban Cohort

Polysubstance use (i.e., simultaneous or sequential use of different psychoactive substances) is associated with increases in the risk of severe health problems and social impairments. The present study leverages community-representative, long-term longitudinal data from an urban cohort to assess: (a) the prevalence and continuation of polysubstance use between adolescence and early adulthood; (b) different patterns of polysubstance use (i.e., combinations of substances) in early adulthood; and (c) childhood risk factors for polysubstance use in early adulthood. At age 20 (n = 1,180), respondents provided comprehensive self-reported information on past-year substance use, including use of legal and illicit substances (e.g., cannabinoids, stimulants, and hallucinogens), and nonmedical use of prescription drugs (e.g., opioids, tranquilizers). In adolescence (ages 13–17), limited versions of this questionnaire were administered. In childhood (ages 7–11), potential risk factors, including individual-level factors (e.g., sensation-seeking, low self-control, aggression, and internalizing symptoms) and social-environmental factors (e.g., social stressors, exposure to others’ substance use), were assessed. We fitted latent class models to identify classes of participants with different substance use profiles in early adulthood. The results show that polysubstance use increased between early adolescence and early adulthood. The continuation of polysubstance use was common (stability between all adjacent assessments: odds ratio >7). At age 20, more than one-third of participants reported polysubstance use (involving illicit substances, nonmedical use of prescription drugs, and cannabidiol). Four latent classes with polysubstance use were identified: (1) broad spectrum of substances; (2) cannabis and club drugs; (3) cannabis and the nonmedical use of prescription drugs; and (4) different cannabinoids. Risk factors for any polysubstance use included childhood sensation-seeking and exposure to others’ substance use; some childhood risk factors were differentially associated with the four classes (e.g., low self-control in childhood was associated with an increased likelihood of being in the broad spectrum class). The classes also differed with regard to socio-demographic factors. This study revealed that polysubstance use is a widespread and multifaceted phenomenon that typically emerges during adolescence. To facilitate the design of tailored prevention mechanisms, the heterogeneity of polysubstance use and respective socio-demographic and developmental precursors need to be considered