Variational study of the Holstein polaron

The paper deals with the ground and the first excited state of the polaron in the one dimensional Holstein model. Various variational methods are used to investigate both the weak coupling and strong coupling case, as well as the crossover regime between them. Two of the methods, which are presented here for the first time, introduce interesting elements to the understanding of the nature of the polaron. Reliable numerical evidence is found that, in the strong coupling regime, the ground and the first excited state of the self-trapped polaron are well described within the adiabatic limit. The lattice vibration modes associated with the self-trapped polarons are analyzed in detail, and the frequency softening of the vibration mode at the central site of the small polaron is estimated. It is shown that the first excited state of the system in the strong coupling regime corresponds to the excitation of the soft phonon mode within the polaron. In the crossover regime, the ground and the first excited state of the system can be approximated by the anticrossing of the self-trapped and the delocalized polaron state. In this way, the connection between the behavior of the ground and the first excited state is qualitatively explained.Comment: 11 pages, 4 figures, PRB 65, 14430

The Clinical and Classroom Utility of the Inventory of Reading Occupations: An Assessment Tool of Children’s Reading Participation

Background: The aim of this study was to determine the initial clinical and classroom utility of the Inventory of Reading Occupations (IRO), a new tool to assess children’s reading participation. Method: The study used phenomenological qualitative and descriptive methods. The participants included 38 occupational therapists, speech-language pathologists, classroom teachers, and parents who completed or reviewed responses of children on the IRO. To provide triangulation, 20 of the children who completed the IRO were interviewed. Data were thematically analyzed and then categorized using a central Strengths-Weaknesses-Opportunities-Threats premise. Results: The majority of the participants indicated favorable response to the clinical and classroom utility of the tool. Common themes were (a) the IRO is a user-friendly and engaging assessment that allows students to reflect on their reading participation; (b) the IRO is more suitable for children who engage in more structured reading; (c) the IRO can be adapted for older children; and (d) there is a need to identify whether the IRO is better as a screening or a full assessment tool. Conclusion: The study provided useful perspectives on how the tool can be further improved as a measure of the reading participation of school-aged children

Determining the Internal Validity of the Inventory of Reading Occupations: An Assessment Tool of Children’s Reading Participation

The Inventory of Reading Occupations (IRO) is an assessment tool of children’s reading participation. In this study, we used Rasch methods to determine the internal validity of the IRO. Participants included 192 typical and struggling readers from kindergarten to third grade from five different states in the United States. We analyzed the fit of each of the items in the 17 reading categories, the test items in the three dimensions of reading participation, and the contexts of reading in the IRO. Analysis indicated that the IRO items support the Rasch model of unidimensionality. Analysis also indicated that 1 of the 30 test items can be revised to strengthen test validity. Moreover, the analysis also suggested that the IRO is more useful for first- to third-grade students. This study provides evidence of internal validity of a useful tool to assess children’s reading participation

Validation of Afterbody Aeroheating Predictions for Planetary Probes: Status and Future Work

A review of the relevant flight conditions and physical models for planetary probe afterbody aeroheating calculations is given. Readily available sources of afterbody flight data and published attempts to computationally simulate those flights are summarized. A current status of the application of turbulence models to afterbody flows is presented. Finally, recommendations for additional analysis and testing that would reduce our uncertainties in our ability to accurately predict base heating levels are given

Electromagnetic Reduction of Plasma Density During Atmospheric Reentry and Hypersonic Flights

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76341/1/AIAA-32147-259.pd

Transition Within a Hypervelocity Boundary Layer on a 5-Degree Half-Angle Cone in Air/CO_2 Mixtures

Laminar to turbulent transition on a smooth 5-degree half angle cone at zero angle of attack is investigated computationally and experimentally in hypervelocity flows of air, carbon dioxide, and a mixture of 50% air and carbon dioxide by mass. Transition N factors above 10 are observed for air flows. At comparable reservoir enthalpy and pressure, flows containing carbon dioxide are found to transition up to 30% further downstream on the cone than flows in pure air in terms of x-displacement, and up to 38% and 140%, respectively, in terms of the Reynolds numbers calculated at edge and reference conditions

Vascular responses of the extremities to transdermal application of vasoactive agents in Caucasian and African descent individuals

This is an accepted manuscript of an article published by Springer in European Journal of Applied Physiology on 04/04/2015, available online: https://doi.org/10.1007/s00421-015-3164-2 The accepted version of the publication may differ from the final published version.© 2015, Springer-Verlag Berlin Heidelberg. Purpose: Individuals of African descent (AFD) are more susceptible to non-freezing cold injury than Caucasians (CAU) which may be due, in part, to differences in the control of skin blood flow. We investigated the skin blood flow responses to transdermal application of vasoactive agents. Methods: Twenty-four young males (12 CAU and 12 AFD) undertook three tests in which iontophoresis was used to apply acetylcholine (ACh 1 w/v %), sodium nitroprusside (SNP 0.01 w/v %) and noradrenaline (NA 0.5 mM) to the skin. The skin sites tested were: volar forearm, non-glabrous finger and toe, and glabrous finger (pad) and toe (pad). Results: In response to SNP on the forearm, AFD had less vasodilatation for a given current application than CAU (P = 0.027–0.004). ACh evoked less vasodilatation in AFD for a given application current in the non-glabrous finger and toe compared with CAU (P = 0.043–0.014) with a lower maximum vasodilatation in the non-glabrous finger (median [interquartile], AFD n = 11, 41[234] %, CAU n = 12, 351[451] %, P = 0.011) and non-glabrous toe (median [interquartile], AFD n = 9, 116[318] %, CAU n = 12, 484[720] %, P = 0.018). ACh and SNP did not elicit vasodilatation in the glabrous skin sites of either group. There were no ethnic differences in response to NA. Conclusion: AFD have an attenuated endothelium-dependent vasodilatation in non-glabrous sites of the fingers and toes compared with CAU. This may contribute to lower skin temperature following cold exposure and the increased risk of cold injuries experienced by AFD.Published versio

Spectroscopic Measurements in the Shock Relaxation Region of a Hypervelocity Mach Reflection

We examine the spatial temperature profile in the non-equilibrium relaxation region behind a stationary shock wave. The normal shock wave is established through a Mach reflection configuration from an opposing wedge arrangement for a hypervelocity air Mach 7.42 freestream. Schlieren images confirm that the shock configuration is steady and the location is repeatable. Emission spectroscopy is used to identify dissociated species and to obtain vibrational temperature measurements using the NO and OH A-X band sequences. Temperature measurements are presented at selected locations behind the normal shock. LIFBASE is used as the simulation spectrum software for OH temperature-fitting, however the need to access higher vibrational and rotational levels for NO leads to the use of an in-house developed algorithm. For NO, results demonstrate the contribution of higher vibrational and rotational levels to the spectra at the conditions of this study. Very good agreement is achieved between the experimentally measured NO vibrational temperatures and calculations performed using a state-resolved, one-dimensional forced harmonic oscillator thermochemical model

Simulation of Ablating Hypersonic Vehicles with Finite-Rate Surface Chemistry

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140434/1/6.2014-2124.pd