Microscopic theory of reversible pressure broadening in hole‐burning spectra of impurities in glasses

This is the publisher's version, also available electronically from http://scitation.aip.org/content/aip/journal/jcp/90/6/10.1063/1.455881.Recently, Sesselmann e t a l. [Phys. Rev. B 3 6, 7601 (1987)] have examined the effect of pressure changes on hole‐burning spectra of dye molecules in polymerglasses, finding that the hole shift and broadening are linear in the pressure change and its magnitude, respectively. We develop a statistical, microscopic theory of this effect, and of the inhomogeneous line shape itself. In the limit that the density of solvent perturbers becomes large, the general theory predicts that both the inhomogeneous line shape and the hole shape after a pressure change will be Gaussian, in qualitative agreement with experiment. By considering a specific model for the solute–solvent interaction, we then provide a quantitative analysis of the experiments that shows that the pressure broadening is due to changes in the local environment of each chromophore. As a further test of the theory, we make a prediction as to the frequency dependence of the pressure‐dependent hole shift, which can be easily tested by experiment

On the microscopic nature of inhomogeneously broadened spectra of chromophores in glasses and crystals

This is the publisher's version, also available electronically from http://scitation.aip.org/content/aip/journal/jcp/90/7/10.1063/1.455796

T 2 can be greater than 2T 1 even at finite temperature

This is the publisher's version also available electronically from http://scitation.aip.org/content/aip/journal/jcp/94/6/10.1063/1.460627.The relaxation of a nondegenerate two‐level quantum system linearly and off‐diagonally coupled to a thermal bath of quantum‐mechanical harmonic oscillators is studied. The population and phase relaxation times,T 1 and T 2, are calculated to fourth order in the system/bath interaction. Focus is on a specific model of the bath spectral density that is both Ohmic (proportional to frequency at low frequency) and Lorentzian, and which has the property that, in the semiclassical or high‐temperature limit, it reproduces the stochastic model studied previously by Budimir and Skinner [J. Stat. Phys. 4 9, 1029 (1987)]. For this fully quantum‐mechanical model, it is found that under certain conditions the standard inequality,T 2≤2T 1, is violated, demonstrating that this unusual result, which was originally derived from the (infinite‐temperature) stochastic model, is valid at finite temperature as well

Telephone-based MAGDA in postpartum women with a prior history of gestational diabetes: A change in microsystem level

The research reported in this paper is a project of the Australian Primary Health Care Research Institute which is supported by a grant from the Australian Government Department of Health and Ageing under the Primary Health Care Research Evaluation and Development Strategy

On the ratio T2/T1 for non‐Ohmic spectral densities

This is the publisher's version, also available electronically from http://scitation.aip.org/content/aip/journal/jcp/101/1/10.1063/1.468089.Defining T 1 and T 2 to be the population and phase relaxation times, respectively, for a two‐level system coupled to a bath, previous work for Ohmic spectral densities has shown, surprisingly, that in some instances T 2≳2T 1. This note shows that this inequality can also be realized for non‐Ohmic spectral densities

Modeling peer effect modification by network strength: The diffusion of implantable cardioverter defibrillators in the US hospital network

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154422/1/sim8466.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154422/2/sim8466_am.pd

Structure and triclustering in Ba-Al-O glass

Glass-forming ability in the (BaO) x(Al 2O 3) 1-x system (0≤x≤1) was investigated by using the containerless aerodynamic levitation and laser-heating method. The main glass-forming region was found to occur for 0.40(2) ≤x≤ 0.48(2), where there is insufficient oxygen to form an ideal network of corner-sharing AlO 4 tetrahedra in which the oxygen atoms are twofold coordinated, with another narrow glass-forming region at x = 0.62(2) around the eutectic composition. The glass corresponding to x = 0.4 was chosen for further investigation by using both neutron and x-ray diffraction, and a detailed atomistic model was built by applying a combination of molecular dynamics and reverse Monte Carlo methods. The results show a network structure based predominantly on corner-sharing tetrahedral AlO 4 motifs in which triclusters (OAl 3 units formed by three tetrahedral Al atoms sharing a common vertex) play an integral part, with as many as 21% of the oxygen atoms involved in these configurations. The barium ions bind to an average of 7.4 O atoms, most of which are twofold-coordinated bridging oxygen atoms. The larger size of barium compared to calcium narrows the range of glass-forming compositions in alkaline-earth aluminates such that the main glass-forming range corresponds to a regime in which an oxygen-deficient Al-O network is stabilized by the formation of triclusters

Quantum‐mechanical derivation of the Bloch equations: Beyond the weak‐coupling limit

This is the publisher's version, also available electronically from http://scitation.aip.org/content/aip/journal/jcp/94/6/10.1063/1.460626Two nondegenerate quantum levels coupled off‐diagonally and linearly to a bath of quantum‐mechanical harmonic oscillators are considered. In the weak‐coupling limit one finds that the equations of motion for the reduced density‐matrix elements separate naturally into two uncoupled pairs of linear equations for the diagonal and off‐diagonal elements, which are known as the Bloch equations. The equations for the populations form the simplest two‐component master equation, and the rate constant for the relaxation of nonequilibrium population distributions is 1/T 1, defined as the sum of the ‘‘up’’ and ‘‘down’’ rate constants in the master equation. Detailed balance is satisfied for this master equation in that the ratio of these rate constants is equal to the ratio of the equilibrium populations. The relaxation rate constant for the off‐diagonal density‐matrix elements is known as 1/T 2. One finds that this satisfies the well‐known relation 1/T 2=1/2T 1. In this paper the weak‐coupling limit is transcended by deriving the Bloch equations to fourth order in the coupling. The equations have the same form as in the weak‐coupling limit, but the rate constants are calculated to fourth order. For the population‐relaxation rate constants this results in an extension to fourth order of Fermi’s golden rule. We find that these higher‐order rate constants do indeed satisfy detailed balance. Comparing the dephasing and population‐relaxation rate constants, we find that in fourth order 1/T 2≠1/2T 1

Hyperstrong Radio-Wave Scattering in the Galactic Center. II. A Likelihood Analysis of Free Electrons in the Galactic Center

The scattering diameters of Sgr A* and several nearby OH masers (~ 1" at 1 GHz) indicate that a region of enhanced scattering is along the line of sight to the Galactic center. We combine radio-wave scattering data and free-free emission and absorption measurements in a likelihood analysis that constrains the following parameters of the GC scattering region: The GC-scattering region separation, d; the angular extent of the region, \psi_l; the outer scale on which density fluctuations occur, l_0; and the gas temperature, T. The maximum likelihood estimates of these parameters are d = 133_{-80}^{+200} pc, 0.5 degrees <= \psi_l <~ 1 degrees, and (l_0/1 pc)^{2/3}T^{-1/2} = 10^{-7 +/- 0.8}. As host media for the scattering, we consider the photoionized surface layers of molecular clouds and the interfaces between molecular clouds and the 10^7 K ambient gas. We are unable to make an unambiguous determination, but we favor an interface model in which the scattering medium is hot (T ~ 10^6 K) and dense (n_e ~ 10 cm^{-3}). The GC scattering region produces a 1 GHz scattering diameter for an extragalactic source of 90", if the region is a single screen, or 180", if the region wraps around the GC, as appears probable. We modify the Taylor-Cordes model for the Galactic distribution of free electrons in order to include an explicit GC component. Pulsars seen through this region will have a dispersion measure of approximately 2000 pc cm^{-3}, of which 75% arises from the GC component. We stress the uniqueness of the GC scattering region, probably resulting from the high-pressure environment in the GC.Comment: 39 pages with 9 PostScript figures; LaTeX2e with AASTeX macro aaspp4, to be published in Ap

Benefits beyond cardiometabolic health: the potential of frequent high intensity ‘exercise snacks’ to improve outcomes for those living with and beyond cancer

High intensity interval training (HIIT) has been shown to consistently elicit rapid and significant adaptations in a number of physiological systems, across many different healthy and clinical populations. In addition, there is increasing interest in how some acute, yet transient responses to high intensity exercise potentially reduce the risks of particular diseases. Recent work has shown that discrete, brief bouts of high intensity exercise (termed ‘exercise snacks’) can improve glucose control and vascular health and thus counter the negative cardiometabolic consequences of prolonged, uninterrupted periods of inactivity. In this brief review, we advance the case, using evidence available from pre‐clinical studies in the exercise oncology literature, that brief, frequently completed bouts of high intensity exercise embedded within an individual's overall daily and weekly physical activity schedule, may transiently impact the tumour microenvironment and improve the health outcomes for those who have been diagnosed and treated for cancer. imag