Dynamical tunneling in molecules: Quantum routes to energy flow

Dynamical tunneling, introduced in the molecular context, is more than two decades old and refers to phenomena that are classically forbidden but allowed by quantum mechanics. On the other hand the phenomenon of intramolecular vibrational energy redistribution (IVR) has occupied a central place in the field of chemical physics for a much longer period of time. Although the two phenomena seem to be unrelated several studies indicate that dynamical tunneling, in terms of its mechanism and timescales, can have important implications for IVR. Examples include the observation of local mode doublets, clustering of rotational energy levels, and extremely narrow vibrational features in high resolution molecular spectra. Both the phenomena are strongly influenced by the nature of the underlying classical phase space. This work reviews the current state of understanding of dynamical tunneling from the phase space perspective and the consequences for intramolecular vibrational energy flow in polyatomic molecules.Comment: 37 pages and 23 figures (low resolution); Int. Rev. Phys. Chem. (Review to appear in Oct. 2007

Weak capture of protons by protons

The cross section for the proton weak capture reaction $^1H(p,e^+\nu_e)^2H$ is calculated with wave functions obtained from a number of modern, realistic high-precision interactions. To minimize the uncertainty in the axial two-body current operator, its matrix element has been adjusted to reproduce the measured Gamow-Teller matrix element of tritium $\beta$ decay in model calculations using trinucleon wave functions from these interactions. A thorough analysis of the ambiguities that this procedure introduces in evaluating the two-body current contribution to the pp capture is given. Its inherent model dependence is in fact found to be very weak. The overlap integral $\Lambda^2(E=0)$ for the pp capture is predicted to be in the range 7.05--7.06, including the axial two-body current contribution, for all interactions considered.Comment: 17 pages RevTeX (twocolumn), 5 postscript figure

Factors influencing the participation of gastroenterologists and hepatologists in clinical research

<p>Abstract</p> <p>Background</p> <p>Although clinical research is integral to the advancement of medical knowledge, physicians face a variety of obstacles to their participation as investigators in clinical trials. We examined factors that influence the participation of gastroenterologists and hepatologists in clinical research.</p> <p>Methods</p> <p>We surveyed 1050 members of the American Association for the Study of Liver Diseases regarding their participation in clinical research. We compared the survey responses by specialty and level of clinical trial experience.</p> <p>Results</p> <p>A majority of the respondents (71.6%) reported involvement in research activities. Factors most influential in clinical trial participation included funding and compensation (88.3%) and intellectual pursuit (87.8%). Barriers to participation were similar between gastroenterologists (n = 160) and hepatologists (n = 189) and between highly experienced (n = 62) and less experienced (n = 159) clinical researchers. These barriers included uncompensated research costs and lack of specialized support. Industry marketing was a greater influence among respondents with less trial experience, compared to those with extensive experience (15.7% vs 1.6%; <it>P </it>< .01). Hepatologists and respondents with extensive clinical trial experience tended to be more interested in phase 1 and 2 studies, whereas gastroenterologists and less experienced investigators were more interested in phase 4 studies.</p> <p>Conclusion</p> <p>This study suggests that the greatest barrier to participation in clinical research is lack of adequate resources. Respondents also favored industry-sponsored research with less complex trial protocols and studies of relatively short duration.</p

Empirical Tests for Evaluation of Multirate Filter Bank Parameters

Empirical tests have been developed for evaluating the numerical properties of multirate M-band filter banks represented as N matrices of filter coe#cients. Each test returns a numerically observed estimate ofa1 M vector parameter in which the m element corresponds to the m filter band. These vector valued parameters can be readily converted to scalar valued parameters for comparison of filter bank performance or optimization of filter bank design. However, they are intended primarily for the characterization and verification of filter banks. By characterizing the numerical performance of analytic or algorithmic designs, these tests facilitate the experimental verification of theoretical specifications

Intermolecular vibrational energy redistribution in DCO (X^2A'): Classical-Quantum correspondence, dynamical assignments of highly excited states, and phase space transport

Intermolecular dynamics of highly excited DCO (X^2A') is studied from a classical-quantum perspective using the effective spectroscopic Hamiltonian proposed recently by Trollch and Temps (Z. Phy. Chem. 215, 207 (2001)). This work focuses on the polyads P = 3 and P = 4 corresponding to excitation energies E_v ~ 5100 cm^-1 and 7000 cm^-1 respectively. The majority of states belonging to these polyads are dynamically assigned, despite extensive stochasticity in the classical phase space, using the recently proposed technique of level velocities. A wavelet based time-frequency analysis is used to reveal the nature of phase space transport and the relevant dynamical bottlenecks. The local frequency analysis clearly illustrates the existence of mode-specific IVR dynamics i.e., differing nature of the IVR dynamics ensuing from CO stretch and the DCO bend bright states. In addition the role of the weak Fermi resonance involving the CO stretch and DCO bend modes is investigated. A key feature of the present work is that the techniques utilized for the analysis i.e., parametric variations and local frequency analysis are not limited by the dimensionality of the system. This study, thus, explores the potential for understanding IVR in large molecules from both time domain and frequency domain perspectives.Comment: 15 pages, 8 low resolution figures (including 2 color figures). submitted to PCC

Who Benefits From Teams? Comparing Workers, Supervisors, and Managers

This paper offers a political explanation for the diffusion and sustainability of team-based work systems by examining the differential outcomes of team structures for 1200 workers, supervisors, and middle managers in a large unionized telecommunications company. Regression analyses show that participation in self-managed teams is associated with significantly higher levels of perceived discretion, employment security, and satisfaction for workers and the opposite for supervisors. Middle managers who initiate team innovations report higher employment security, but otherwise are not significantly different from their counterparts who are not involved in innovations. By contrast, there are no significant outcomes for employees associated with their participation in offline problem-solving teams

The Schwinger Variational Method

Variational methods have proven invaluable in theoretical physics and chemistry, both for bound state problems and for the study of collision phenomena. For collisional problems they can be grouped into two types: those based on the Schroedinger equation and those based on the Lippmann-Schwinger equation. The application of the Schwinger variational (SV) method to e-molecule collisions and photoionization has been reviewed previously. The present chapter discusses the implementation of the SV method as applied to e-molecule collisions

Progressive dementia associated with ataxia or obesity in patients with Tropheryma whipplei encephalitis

<p>Abstract</p> <p>Background</p> <p><it>Tropheryma whipplei</it>, the agent of Whipple's disease, causes localised infections in the absence of histological digestive involvement. Our objective is to describe <it>T. whipplei </it>encephalitis.</p> <p>Methods</p> <p>We first diagnosed a patient presenting dementia and obesity whose brain biopsy and cerebrospinal fluid specimens contained <it>T. whipplei </it>DNA and who responded dramatically to antibiotic treatment. We subsequently tested cerebrospinal fluid specimens and brain biopsies sent to our laboratory using <it>T. whipplei </it>PCR assays. PAS-staining and <it>T. whipplei </it>immunohistochemistry were also performed on brain biopsies. Analysis was conducted for 824 cerebrospinal fluid specimens and 16 brain biopsies.</p> <p>Results</p> <p>We diagnosed seven patients with <it>T. whipplei </it>encephalitis who demonstrated no digestive involvement. Detailed clinical histories were available for 5 of them. Regular PCR that targeted a monocopy sequence, PAS-staining and immunohistochemistry were negative; however, several highly sensitive and specific PCR assays targeting a repeated sequence were positive. Cognitive impairments and ataxia were the most common neurologic manifestations. Weight gain was paradoxically observed for 2 patients. The patients' responses to the antibiotic treatment were dramatic and included weight loss in the obese patients.</p> <p>Conclusions</p> <p>We describe a new clinical condition in patients with dementia and obesity or ataxia linked to <it>T. whipplei </it>that may be cured with antibiotics.</p