An improved set of electron-THFA cross sections refined through a neural network-based analysis of swarm data.

We review experimental and theoretical cross sections for electron transport in α-tetrahydrofurfuryl alcohol (THFA) and, in doing so, propose a plausible complete set. To assess the accuracy and self-consistency of our proposed set, we use the pulsed-Townsend technique to measure drift velocities, longitudinal diffusion coefficients, and effective Townsend first ionization coefficients for electron swarms in admixtures of THFA in argon, across a range of density-reduced electric fields from 1 to 450 Td. These measurements are then compared to simulated values derived from our proposed set using a multi-term solution of Boltzmann's equation. We observe discrepancies between the simulation and experiment, which we attempt to address by employing a neural network model that is trained to solve the inverse swarm problem of unfolding the cross sections underpinning our experimental swarm measurements. What results from our neural network-based analysis is a refined set of electron-THFA cross sections, which we confirm is of higher consistency with our swarm measurements than that which we initially proposed. We also use our database to calculate electron transport coefficients in pure THFA across a range of reduced electric fields from 0.001 to 10 000 Td.

Self-consistency of electron-THF cross sections using electron swarm techniques.

The drift velocity and first Townsend ionization coefficient of electrons in gaseous tetrahydrofuran are measured over the range of reduced electric fields 4-1000 Td using a pulsed-Townsend technique. The measured drift velocities and Townsend ionization coefficients are subsequently used, in conjunction with a multi-term Boltzmann equation analysis, as a further discriminative assessment on the accuracy and completeness of a recently proposed set of electron-THF vapor cross sections. In addition, the sensitivity of the transport coefficients to uncertainties in the existing cross sections is presented. As a result of that analysis, a refinement of the momentum transfer cross section for electron-THF scattering is presented, along with modifications to the neutral dissociation and dissociative electron attachment cross sections. With these changes to the cross section database, we find relatively good self-consistency between the measured and simulated drift velocities and Townsend coefficients.

Monte Carlo study of coherent scattering effects of low-energy charged particle transport in Percus-Yevick liquids.

We generalize a simple Monte Carlo (MC) model for dilute gases to consider the transport behavior of positrons and electrons in Percus-Yevick model liquids under highly nonequilibrium conditions, accounting rigorously for coherent scattering processes. The procedure extends an existing technique [Wojcik and Tachiya, Chem. Phys. Lett. 363, 381 (2002)], using the static structure factor to account for the altered anisotropy of coherent scattering in structured material. We identify the effects of the approximation used in the original method, and we develop a modified method that does not require that approximation. We also present an enhanced MC technique that has been designed to improve the accuracy and flexibility of simulations in spatially varying electric fields. All of the results are found to be in excellent agreement with an independent multiterm Boltzmann equation solution, providing benchmarks for future transport models in liquids and structured systems.

Electron scattering and transport in liquid argon.

The transport of excess electrons in liquid argon driven out of equilibrium by an applied electric field is revisited using a multi-term solution of Boltzmann's equation together with ab initio liquid phase cross-sections calculated using the Dirac-Fock scattering equations. The calculation of liquid phase cross-sections extends previous treatments to consider multipole polarisabilities and a non-local treatment of exchange, while the accuracy of the electron-argon potential is validated through comparison of the calculated gas phase cross-sections with experiment. The results presented highlight the inadequacy of local treatments of exchange that are commonly used in liquid and cluster phase cross-section calculations. The multi-term Boltzmann equation framework accounting for coherent scattering enables the inclusion of the full anisotropy in the differential cross-section arising from the interaction and the structure factor, without an a priori assumption of quasi-isotropy in the velocity distribution function. The model, which contains no free parameters and accounts for both coherent scattering and liquid phase screening effects, was found to reproduce well the experimental drift velocities and characteristic energies.

Emulating solid-state physics with a hybrid system of ultracold ions and atoms.

We propose and theoretically investigate a hybrid system composed of a crystal of trapped ions coupled to a cloud of ultracold fermions. The ions form a periodic lattice and induce a band structure in the atoms. This system combines the advantages of high fidelity operations and detection offered by trapped ion systems with ultracold atomic systems. It also features close analogies to natural solid-state systems, as the atomic degrees of freedom couple to phonons of the ion lattice, thereby emulating a solid-state system. Starting from the microscopic many-body Hamiltonian, we derive the low energy Hamiltonian, including the atomic band structure, and give an expression for the atom-phonon coupling. We discuss possible experimental implementations such as a Peierls-like transition into a period-doubled dimerized state.

The relationship between mucosal cyclooxygenase-2 (COX-2) expression and experimental radiation-induced mucositis.

Although cycloooxygenase-2 (COX-2) is upregulated by factors associated with oral mucositis, its role in the pathogenesis of mucositis has not been studied. We investigated the kinetics of mucosal COX-2 expression following radiation exposure, and assessed its relationship to the development of oral mucositis in an established animal model using immunohistochemical endpoints. While little or no COX-2 expression was observed in unirradiated mucosa or in tissue taken 2 days after radiation, COX-2 expression was dramatic on days 10 and 16, especially in submucosal fibroblasts and endothelium. The kinetics of COX-2 expression paralleled mucositis severity. A burst of angiogenic activity was seen on day 21 following peak COX-2 expression. The kinetics of COX-2 expression relative to mucositis progression suggests that COX-2 is not a primary driver of radiation injury, but instead plays an amplifying role.

Abciximab provides cost-effective survival advantage in high-volume interventional practice.

BACKGROUND: Placebo-controlled randomized trials of platelet glycoprotein (GP) IIb/IIIa blockade during percutaneous coronary intervention have demonstrated efficacy of these agents for reducing the risk of periprocedural ischemic events. However, cost-effectiveness of this adjunctive pharmacotherapy has been scrutinized. Extrapolation of cost-efficacy observations from clinical trials to "real world" interventional practice is problematic. METHODS: Consecutive percutaneous coronary interventions (n = 1472) performed by Ohio Heart Health Center operators at The Christ Hospital, Cincinnati, Ohio, in 1997 were analyzed for procedural and long-term (6-month) outcomes and charges. Observations on cost and efficacy (survival) were adjusted for nonrandomized abciximab allocation by means of "propensity scoring" methods. RESULTS: Abciximab therapy was associated with a survival advantage to 6 months after percutaneous coronary intervention. The average reduction in mortality rate at 6 months was 3.4% (unadjusted) and 4.9% when adjusted for nonrandomization. The average charge increment to 6 months was $1512 (unadjusted) and $950 when adjusted for nonrandomization. Patients deriving the greatest reduction in mortality rates also had a reduction in total cardiovascular charges to 6 months. Distinguishing demographics of this population included multivessel coronary intervention, coronary stent deployment, intervention within 1 week of myocardial infarction, and lower left ventricular ejection fraction. The average cost per life-year gained in this study was $2875 for all patients (unadjusted) and $1243 when adjusted for nonrandomization. CONCLUSIONS: Abciximab provides a cost-effective survival advantage in high-volume interventional practice that compares favorably with currently accepted standards. Clinical and procedural demographics associated with increased cost-effectiveness included multivessel coronary intervention, stent deployment, recent (<1 week) myocardial infarction, and impaired left ventricular function.

Hospital drug formularies and use of hospital services.

Many hospitals have introduced formularies to reduce hospital pharmacy expense, among other reasons. This study provides empirical evidence of the influence of hospital formulary restrictions on pharmacy charges, all other hospital charges, and on length of stay, using a survey of hospital drug policies and hospital discharge data from Washington State in 1989. Limiting the number of drugs in particular therapeutic categories reduced total charges incurred for gastrointestinal disease and asthma patients, increased total charges for cardiovascular disease patients, and had no effect on charges for infectious diseases patients. Restricting availability of drugs reduced pharmacy charges, but these savings tended to be offset by increases in other charges. Combining the categories, we found that restricting availability of drugs did not affect charges. We conclude that across-the-board restrictions do not result in cost savings, although savings may be realized for particular drug categories.

Control of epilepsy with a single daily dose of phenytoin sodium.

Fifty-three patients in an epileptic centre have been studied. All were receiving phenytoin and many were also receiving other antoconvulsant drugs. 2. Thirty-six patients took part in a three month cross over study. There was no significant change in the frequency of epileptic seizures or in the late morning serum concentration of phenytoin when the treatemtn was changed from two to three spaced doses of phenytoin sodium/day to a single dose at 12.00 hours. 3. Seventeen patients acted as a control group. They received phenytoin sodium as two or three spaced doses/day throughout the study. There was no significant change in the frequency of epileptic seizures or in the late morning serum concentration of phenytoin between the first and second three month periods of observation. 4. It is concluded that the total daily dose of phenytoin sodium may be given once daily without reduction of the anticonvulsant effect.