Semiclassical theory of Fermi resonance between stretching and bending modes in polyatomic molecules

Approximate semiclassical solutions are developed for a system of a Morse oscillator coupled to a harmonic oscillator via a nonlinear perturbation. This system serves as a model for the interaction of an excited stretching mode with a bending mode in a polyatomic molecule. Three semiclassical methods are used to treat this model. In particular, a matrix diagonalization, a two‐state model, and a uniform semiclassical approximation (USC) based on Mathieu functions are each used to determine the splittings and state mixing involved in these stretch–bend Fermi resonances. For small perturbations, approximate analytic semiclassical expressions are obtained for the system treated. These analytic expressions are given for the splittings using a two‐state or USC method and for the overlaps of the zeroth order states with the eigenstates of the molecule using a USC method

The highly excited C-H stretching states of CHD_3, CHT_3, and CH_3D

Unlike many other molecules having local modes, the highly excited C-H stretching states of CHD_3 show well resolved experimental spectra and simple Fermi resonance behavior. In this paper the local mode features in this prototype molecule are examined using a curvilinear coordinate approach. Theory and experiment are used to identify the vibrational state coupling. Both kinetic and potential terms are employed in order to characterize the coupling of the C-H stretch to various other vibrational modes, notably those including D-C-H bending. Predictions are also made for CHT_3 and the role of dynamical coupling on the vibrational states of CH_3D explored. Implications of these findings for mode-specific and other couplings are discussed

Modifiable predictors of ventricular ectopy in the community

Background Premature ventricular contractions (PVCs) predict heart failure and death. Data regarding modifiable risk factors for PVCs are scarce. Methods and Results We studied 1424 Cardiovascular Health Study participants randomly assigned to 24-hour Holter monitoring. Demographics, comorbidities, habits, and echocardiographic measurements were examined as predictors of PVC frequency and, among 845 participants, change in PVC frequency 5 years later. Participants exhibited a median of 0.6 (interquartile range, 0.1-7.1) PVCs per hour. Of the more directly modifiable characteristics and after multivariable adjustment, every SD increase in systolic blood pressure was associated with 9% more PVCs (95% confidence interval [CI], 2%-17%; P=0.01), regularly performing no or low-intensity exercise compared with more physical activity was associated with ≈15% more PVCs (95% CI, 3-25%; P=0.02), and those with a history of smoking exhibited an average of 18% more PVCs (95% CI, 3-36%; P=0.02) than did never smokers. After 5 years, PVC frequency increased from a median of 0.5 (IQR, 0.1-4.7) to 1.2 (IQR, 0.1-13.8) per hour ( P<0.0001). Directly modifiable predictors of 5-year increase in PVCs, described as the odds per each quintile increase in PVCs, included increased diastolic blood pressure (odds ratio per SD increase, 1.16; 95% CI, 1.02-1.31; P=0.02) and a history of smoking (OR, 1.31; 95% CI, 1.02-1.68; P=0.04). Conclusions Enhancing physical activity, smoking cessation, and aggressive control of blood pressure may represent fruitful strategies to mitigate PVC frequency and PVC-associated adverse outcomes

A Bakry-\'Emery Almost Splitting Result With Applications to the Topology of Black Holes

The almost splitting theorem of Cheeger-Colding is established in the setting of almost nonnegative generalized $m$-Bakry-\'{E}mery Ricci curvature, in which $m$ is positive and the associated vector field is not necessarily required to be the gradient of a function. In this context it is shown that with a diameter upper bound and volume lower bound the fundamental group of such manifolds is almost abelian. Furthermore, extensions of well-known results concerning Ricci curvature lower bounds are given for generalized $m$-Bakry-\'{E}mery Ricci curvature. These include: the first Betti number bound of Gromov and Gallot, Anderson's finiteness of fundamental group isomorphism types, volume comparison, the Abresch-Gromoll inequality, and a Cheng-Yau gradient estimate. Finally, this analysis is applied to stationary vacuum black holes in higher dimensions to find that low temperature horizons must have limited topology, similar to the restrictions exhibited by (extreme) horizons of zero temperature.Comment: Comm. Math. Phys., to appea

Isolation of GCN5 and ADA5 in a selection for transcriptional adaptors

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 1997.Includes bibliographical references.by Gregora A. Marcus.Ph.D

ADA1, a novel component of the ADA/GCN5 complex, has broader effects than GCN5, ADA2, or ADA3

9 pages, 5 figures, 3 tables.-- PMID: 9154821 [PubMed].-- PMCID: PMC232175.The ADA genes encode factors which are proposed to function as transcriptional coactivators. Here we describe the cloning, sequencing, and initial characterization of a novel ADA gene, ADA1. Similar to the previously isolated ada mutants, ada1 mutants display decreases in transcription from various reporters. Furthermore, ADA1 interacts with the other ADAs in the ADA/GCN5 complex as demonstrated by partial purification of the complex and immunoprecipitation experiments. We estimate that the complex has a molecular mass of approximately 2 MDa. Previously, it had been demonstrated that ada5 mutants displayed more severe phenotypic defects than the other ada mutants (G. A. Marcus, J. Horiuchi, N. Silverman, and L. Guarente, Mol. Cell. Biol. 16:3197-3205, 1996; S. M. Roberts and F. Winston, Mol. Cell. Biol. 16:3206-3213, 1996). ada1 mutants display defects similar to those of ada5 mutants and different from those of the other mutants with respect to promoters affected, inositol auxotrophy, and Spt- phenotypes. Thus, the ADAs can be separated into two classes, suggesting that the ADA/GCN5 complex may have two separate functions. We present a speculative model on the possible roles of the ADA/GCN5 complex.We thank A. Koleske, D. Chao, C. Wilson, C. Hengartner, and R. Young for sharing antibodies and for technical assistance. We also thank A. Greenleaf and C. Peterson for sharing antisera and K. Kaplan for assistance with the Sprint BIOCAD apparatus. We are grateful to S. Roberts and F. Winston for strains, T. D. Fox and D. Allis for sharing unpublished results, and D. McNabb for critical comments on the manuscript. G.M. thanks C. Armstrong and S. Treadway for help with the GCN5 antibody. J.H. was an HHMI predoctoral fellow. This work was supported by grant GM50207 from NIH to L.G.Peer reviewe

Adiabatically reduced coupled equations for intramolecular dynamics calculations

"Adiabatically reduced" coupled equations are derived to obtain an approximate quantum mechanical solution for the dynamics of nonstationary states in isolated polyatomic molecules. Under suitable conditions, the number of such equations is considerably less than the number of coupled equations needed in practice for the exact calculation. The relationship of the present technique to several other methods, including the partitioning method, is discussed, and specific applications of the present treatment are given

Validation of a consumer-grade activity monitor for continuous daily activity monitoring in individuals with multiple sclerosis.

Background:Technological advancements of remote-monitoring used in clinical-care and research require validation of model updates. Objectives:To compare the output of a newer consumer-grade accelerometer to a previous model in people with multiple sclerosis (MS) and to the ActiGraph, a waist-worn device widely used in MS research. Methods:Thirty-one individuals with MS participated in a 7-day validation by the Fitbit Flex (Flex), Fitbit Flex-2 (Flex2) and ActiGraph GT3X. Primary outcome was step count. Valid epochs of 5-min block increments, where there was overlap of ≥1 step/min for both devices were compared and summed to give a daily total for analysis. Results:Bland-Altman plots showed no systematic difference between the Flex and Flex2; mean step-count difference of 25 more steps-per-day more recorded by Flex2 (95% confidence intervals (CI) = 2, 48; p = 0.04),interclass correlation coefficient (ICC) = 1.00. Compared to the ActiGraph, Flex2 (and Flex) tended to record more steps (808 steps-per-day more than the ActiGraph (95% CI= -2380, 765; p < 0.01), although the ICC was high (0.98) indicating that the devices were likely measuring the same kind of activity. Conclusions:Steps from Flex and Flex2 can be used interchangeably. Differences in total step count between ActiGraph and Flex devices can make cross-device comparisons of numerical step-counts challenging particularly for faster walkers

elicit: A system for detecting insiders who violate need-to-know

Abstract. Malicious insiders do great harm and avoid detection by using their legitimate privileges to steal information that is often outside the scope of their duties. Based on information from public cases, consultation with domain experts, and analysis of a massive collection of information-use events and contextual information, we developed an approach for detecting insiders who operate outside the scope of their duties and thus violate need-to-know. Based on the approach, we built and evaluated elicit, a system designed to help analysts investigate insider threats. Empirical results suggest that, for a specified decision threshold of .5, elicit achieves a detection rate of .84 and a false-positive rate of .015, flagging per day only 23 users of 1, 548 for further scrutiny. It achieved an area under an roc curve of .92