Density-functional-based predictions of Raman and IR spectra for small Si clusters

We have used a density-functional-based approach to study the response of silicon clusters to applied electric fields. For the dynamical response, we have calculated the Raman activities and infrared (IR) intensities for all of the vibrational modes of several clusters (SiN with N=3-8, 10, 13, 20, and 21) using the local density approximation (LDA). For the smaller clusters (N=3-8) our results are in good agreement with previous quantum-chemical calculations and experimental measurements, establishing that LDA-based IR and Raman data can be used in conjunction with measured spectra to determine the structure of clusters observed in experiment. To illustrate the potential of the method for larger clusters, we present calculated IR and Raman data for two low-energy isomers of Si10 and for the lowest-energy structure of Si13 found to date. For the static response, we compare our calculated polarizabilities for N=10, 13, 20, and 21 to recent experimental measurements. The calculated results are in rough agreement with experiment, but show less variation with cluster size than the measurements. Taken together, our results show that LDA calculations can offer a powerful means for establishing the structures of experimentally fabricated clusters and nanoscale systems

Electronic Structure of Superconducting Ba6c60

We report the results of first-principles electronic-structure calculations for superconducting Ba6C60. Unlike the A3C60 superconductors, this new compound shows strong Ba-C hybridization in the valence and conduction regions, mixed covalent/ionic bonding character, partial charge transfer, and insulating zero-gap band structure.Comment: 11 pages + 4 figures (1 appended, others on request), LaTeX with REVTE

A Non-invasive Method of Measuring Respiration while Providing Wireless Power for Rodents with Implantable Devices

Respiratory measurements can be used as diagnostic and research tools. Spirometry is the gold standard for gaining these measurements, but is difficult to use in rodents as it requires an invasive procedure. Total Body Plethysmograpy (TBP) is a non-invasive way to measure respiration rates that does not cause stress to the rodent. In this system, the subject is encased in a solid, constant volume chamber with measurements determining the subject’s respiration. When using TBP in medical or research settings, challenges occur in powering devices within the TBP chamber as wires and other recording equipment compromise the airtightness of the chamber. Therefore, it is imperative to create a TBP chamber that provides wireless power for these purposes. To do so, subjects were placed in a cubic or cylindrical airtight chamber with one inflow and exhaust nozzle to control chamber pressure and provide a steady stream of fresh oxygen. Pressure readings from the inside of the chamber were taken at a rate of four samples per second. Tests were run from two minutes to three hours to encompass rodent activity. Tests were inconclusive for measuring respiration with the specific sensors used, and further research and testing is needed to perfect this method. Once the method is proven to work with the pressure sensors, it will be able to be paired with the MRC chasm and therefore implemented in other studies

The Effects of a High Fat Meal on Blood Flow Regulation during Arm Exercise

A diet high in saturated fats results in endothelial dysfunction and can lead to atherosclerosis, a precursor to cardiovascular disease. Exercise training is a potent stimulus though to mitigate the negative effects of a high saturated fat diet; however, it is unclear how high-saturated fat meal (HSFM) consumption impacts blood flow regulation during a single exercise session. PURPOSE: This study sought to examine the impact of a single HSFM on peripheral vascular function during an acute upper limb exercise bout. METHODS: Ten young healthy individuals completed two sessions of progressive handgrip exercise. Subjects either consumed a HSFM (0.84 g of fat/kg of body weight) 4 hours prior or remained fasted before the exercise bout. Progressive rhythmic handgrip exercise (6kg, 12kg, 18kg) was performed for 3 minutes per stage at rate of 1 Hz. The brachial artery (BA) diameter and blood velocity was obtained using Doppler Ultrasound (GE Logiq e) and BA blood flow was calculated with these values. RESULTS: BA blood flow and flow mediated dilation (normalized for shear rate) during the handgrip exercise significant increased from baseline in all workloads, but no differences were revealed in response to the HSFM consumption. CONCLUSION: Progressive handgrip exercise augmented BA blood flow and flow mediated dilation in both testing days; however, there was no significant differences following the HSFM consumption. This suggests that upper limb blood flow regulation during exercise is unaltered by a high fat meal in young healthy individuals.https://scholarscompass.vcu.edu/gradposters/1060/thumbnail.jp

Molecular structures and vibrations of neutral and anionic CuOx (x = 1-3,6) clusters

We report equilibrium geometric structures of CuO2, CuO3, CuO6, and CuO clusters obtained by an all-electron linear combination of atomic orbitals scheme within the density-functional theory with generalized gradient approximation to describe the exchange-correlation effects. The vibrational stability of all clusters is examined on the basis of the vibrational frequencies. A structure with Cs symmetry is found to be the lowest-energy structure for CuO2, while a -shaped structure with C2v symmetry is the most stable structure for CuO3. For the larger CuO6 and CuO clusters, several competitive structures exist with structures containing ozonide units being higher in energy than those with O2 units. The infrared and Raman spectra are calculated for the stable optimal geometries. ~Comment: Uses Revtex4, (Better quality figures can be obtained from authors

Beyond Sensitivity: Patterns of Maternal Interaction in Secure vs. Non-Secure Attachment Relationships

Attachment theory proposes that the sensitivity of a mother’s interactions with her child is the main developmental determinant of the quality of their attachment relationship (Ainsworth et al., 1978; De Wolff & van Ijzendoorn, 1997). Empirical findings have generally supported this assertion; however, the strength of this association remains a matter of debate as the results of empirical findings have been highly variable (Atkinson et al., 2000; DeWolff & van IJzendoorn, 1997). Several researchers have suggested that assessing maternal behaviour as a single global dimension may fail to capture important variation in the quality of interactions that influence the developing attachment relationship (van IJzendoorn, 1995; Pederson et al., 1998). Consequently, assessing distinct aspects of maternal interactive behaviour may provide additional insight into the maternal contribution to the quality of the attachment relationship

Hydrogen adsorption and magnetic behavior of Fen and Con clusters: Controlling the magnetic moment and anisotropy one atom at a time

Theoretical studies to investigate the effect of H absorption on the magnetic moment of small Fen and Con clusters have been carried out using gradient corrected density-functional approach. Our studies on clusters containing up to four transition metal and 2 H atoms show that the successive addition of H atoms can lead to monotonic or oscillatory change from the free cluster magnetic moment. A detailed analysis of the density of electronic states shows that the variations in the magnetic moment can be related to the location of the lowest unoccupied molecular orbital in the parent cluster. It is shown that the addition of hydrogen can substantially change the magnetic anisotropy. In particular Co3H2is shown to exhibit magnetic anisotropy that is higher than any of the known anisotropies in the molecular nanomagnets