Theory of controlled quantum dynamics

We introduce a general formalism, based on the stochastic formulation of quantum mechanics, to obtain localized quasi-classical wave packets as dynamically controlled systems, for arbitrary anharmonic potentials. The control is in general linear, and it amounts to introduce additional quadratic and linear time-dependent terms to the given potential. In this way one can construct for general systems either coherent packets moving with constant dispersion, or dynamically squeezed packets whose spreading remains bounded for all times. In the standard operatorial framework our scheme corresponds to a suitable generalization of the displacement and scaling operators that generate the coherent and squeezed states of the harmonic oscillator.Comment: LaTeX, A4wide, 28 pages, no figures. To appear in J. Phys. A: Math. Gen., April 199

On characters of Chevalley groups vanishing at the non-semisimple elements

Let G be a finite simple group of Lie type. In this paper we study characters of G that vanish at the non-semisimple elements and whose degree is equal to the order of a maximal unipotent subgroup of G. Such characters can be viewed as a natural generalization of the Steinberg character. For groups G of small rank we also determine the characters of this degree vanishing only at the non-identity unipotent elements.Comment: Dedicated to Lino Di Martino on the occasion of his 65th birthda

Conjugacy and cocycle conjugacy of automorphisms of O2 are not Borel

Abstrac

Occupational Therapy Students’ Perceptions of OSCE: A Qualitative Descriptive Analysis

Objective Structured Clinical Examinations (OSCE) are commonly used across health professions educational programs to evaluate student clinical competencies. OSCE are multiple, brief stations representing common practice scenarios. The purpose of the study was to evaluate student perceptions of OSCE. The researchers implemented 17 OSCE stations with 40 second year occupational therapy students to assess clinical competencies prior to fieldwork. Applying a qualitative descriptive methodologic approach, researchers analyzed station rating data, Qualtrics survey Likert-type items, and Qualtrics survey open-ended responses. Number of station rating responses varied widely, due to perceived time press. Station rating responses confirmed the more robust 80% response to Qualtrics survey. Analysis of Likert-type items revealed perceptions of OSCE as comprehensive, mixed eustress and distress, confirming of competence, and supportive of growth. Four dimensions of learning emerged from analysis of open-ended items: temporal, real world, bottlenecks to learning, and being open to the process. Findings affirmed student perceptions of OSCE to be valuable as summative and formative assessment of clinical competence. Existing literature supports three of the four dimensions of learning. The researchers advocate additional research to examine bottlenecks to learning, psychometrics of OSCE, the use of OSCE in program evaluation, and longitudinal study of student performance related to OSCE

Fixing Conditions in the Freeze Substitution Technique for Light Microscopy Observation of Frozen Beef Tissue

The freeze substitution histological technique allows the indirect light microscopicobservation and the quantitative evaluation of ice crystal size in frozen tissues. Theuseofchemical fixatives in substitu ting fluids improves morphological and histochemical preservation of the tissue. Fixation conditions become important since this step can introduce modifications in crystal sizes . Effects of temperature on: a) diffusion rate of fixing solution in tissue, b) recrystallization rate of ice in frozen beef and c) variations of the froze~ water fraction were ana lyzed, establishing that 1sothermal freeze fixation constitutes an appropriate method for histological observation. Fixing at temperatures lower than that of the sample, in an attempt to reduce recrystallization effects , involves an increase of the frozen water fraction i.n the tissue leading to modifications in size of ice crystals and to changes in the histological structure

NICS-TNG infrared spectroscopy of trans-neptunian objects 2000 EB173 and 2000 WR106

We report complete near-infrared (0.9-2.4 $\mu$m) spectral observations of trans-neptunian objects (TNOs) 2000 EB173 and 2000 WR106 collected using the new Near Infrared Camera Spectrometer (NICS) attached to the 3.56m Telescopio Nazionale Galileo (TNG). Both spectra are very red and with a quite strong and broad drop extending throughout the K band. However, while 2000 EB173 does not show any evidence of narrow absorption features, the spectrum of 2000 WR106 has quite deep water ice absorption at 1.5 and 2.0 $\mu$m. Moreover, the latter object is significantly less red than the former indicating, therefore, that the surface of 2000 WR106 is ``cleaner'' (i.e. less processed by particle irradiation) than that of 2000 EB173

A yield-cost tradeoff governs Escherichia coli’s decision between fermentation and respiration in carbon-limited growth

Living cells react to changes in growth conditions by re-shaping their proteome. This accounts for different stress-response strategies, both specific (i.e., aimed at increasing the availability of stress-mitigating proteins) and systemic (such as large-scale changes in the use of metabolic pathways aimed at a more efficient exploitation of resources). Proteome re-allocation can, however, imply significant biosynthetic costs. Whether and how such costs impact the growth performance are largely open problems. Focusing on carbon-limited E. coli growth, we integrate genome-scale modeling and proteomic data to address these questions at quantitative level. After deriving a simple formula linking growth rate, carbon intake, and biosynthetic costs, we show that optimal growth results from the tradeoff between yield maximization and protein burden minimization. Empirical data confirm that E. coli growth is indeed close to Pareto-optimal over a broad range of growth rates. Moreover, we establish that, while most of the intaken carbon is diverted into biomass precursors, the efficiency of ATP synthesis is the key driver of the yield-cost tradeoff. These findings provide a quantitative perspective on carbon overflow, the origin of growth laws and the multidimensional optimality of E. coli metabolism