Modelling the atomic structure of very high-density amorphous ice

The structure of very high-density amorphous (VHDA) ice has been modelled by positionally disordering three crystalline phases, namely ice IV, VI and XII. These phases were chosen because only they are stable or metastable in the region of the ice phase diagram where VHDA ice is formed, and their densities are comparable to that of VHDA ice. An excellent fit to the medium range of the experimentally observed pair-correlation function g(r) of VHDA ice was obtained by introducing disorder into the positions of the H2O molecules, as well as small amounts of molecular rotational disorder, disorder in the O--H bond lengths and disorder in the H--O--H bond angles. The low-k behaviour of the experimental structure factor, S(k), is also very well reproduced by this disordered-crystal model. The fraction of each phase present in the best-fit disordered model is very close to that observed in the probable crystallization products of VHDA ice. In particular, only negligible amounts of ice IV are predicted, in accordance with experimental observation.Comment: 4 pages, 3 figures, 1 table, v2: changes made in response to referees' comments, the justification for using certain ice phases is improved, and ice IV is now disordered as wel

Real-time monitoring of solid-phase peptide synthesis using a variable bed glow reactor

On-resin aggregation and incomplete amide bond formation are major challenges for solid-phase peptide synthesis that are difficult to be monitored in real-time. Incorporation of a pressure-based variable bed flow reactor into an automated solid-phase peptide synthesizer permitted real-time monitoring of resin swelling to determine amino acid coupling efficiency and on-resin aggregation

Fast two-dimensional model

A two dimensional (altitude and latitude) model of the atmosphere is used to investigate problems relating to the variability of the dynamics and temperature of the atmosphere on the ozone distribution, solar cycle variations of atmospheric constituents, the sensitivity of model results to tropospheric trace gas sources, and assessment computations of changes in ozone related to manmade influences. In a comparison between two dimensional model results in which the odd nitrogen family was transported together and model results in which the odd nitrogen species was transported separately, it was found that the family approximations are adequate for perturbation scenario calculations

Relationships Between Physical Measurements and Calving Difficulty in Two-Year-Old Santa Gertrudis Heifers

Last updated: 6/1/200

The Impact of a Change in Antibacterial Prophylaxis from Ceftazidime to Levofloxacin in Allogeneic Hematopoietic Cell Transplantation

Antibiotic prophylaxis has been used during the initial phases of myeloablative hematopoietic cell transplantation (HCT) for more than two decades. However, the optimal regimen in terms of both cost and clinical effectiveness is unclear. We retrospectively compared the clinical and microbiological impact of a change in antibiotic prophylaxis practice from ceftazidime (n=216 patients with HCT in 2000–2002) to levofloxacin (n=219 patients, August 2002–2005) in patients receiving myeloablative conditioning. Levofloxacin prophylaxis was associated with fever and a change in antibiotics during neutropenia, but this strategy was not associated with any adverse outcomes. Patients receiving levofloxacin had lower rates of significant bacteremia than did those receiving ceftazidime (day 100, 19.2 vs 29.6%, P=0.02). The use of levofloxacin was associated with lower antibiotic acquisition costs. There was no deleterious impact caused by levofloxacin prophylaxis on survival, emergence of antibiotic resistance, detection of Clostridium difficile Ag in stool specimens, incidence of viridans group streptococcal bacteremia or Pseudomonas infections. There was a trend toward lower rates of bacteriuria, wound and bacterial respiratory infections in the levofloxacin than in the ceftazidime group, but these differences were not statistically significant. These data support the use of levofloxacin as prophylaxis in myeloablative allogeneic HCT when prophylaxis is used