Electron-Phonon Interaction Contribution to the Total Energy of Group IV Semiconductor Polymorphs: Evaluation and Implications.

In density functional theory (DFT)-based total energy studies, the van der Waals (vdW) and zero-point vibrational energy (ZPVE) correction terms are included to obtain energy differences between polymorphs. We propose and compute a new correction term to the total energy, due to electron-phonon interactions (EPI). We rely on Allen's general formalism, which goes beyond the quasi-harmonic approximation (QHA), to include the free energy contributions due to quasiparticle interactions. We show that, for semiconductors and insulators, the EPI contributions to the free energies of electrons and phonons are the corresponding zero-point energy contributions. Using an approximate version of Allen's formalism in combination with the Allen-Heine theory for EPI corrections, we calculate the zero-point EPI corrections to the total energy for cubic and hexagonal polytypes of carbon, silicon and silicon carbide. The EPI corrections alter the energy differences between polytypes. In SiC polytypes, the EPI correction term is more sensitive to crystal structure than the vdW and ZPVE terms and is thus essential in determining their energy differences. It clearly establishes that the cubic SiC-3C is metastable and hexagonal SiC-4H is the stable polytype. Our results are consistent with the experimental results of Kleykamp. Our study enables the inclusion of EPI corrections as a separate term in the free energy expression. This opens the way to go beyond the QHA by including the contribution of EPI on all thermodynamic properties.

Value of pharmacist medication interviews on optimizing the electronic medication reconciliation process.

PURPOSE: Few studies have explored the impact of using different methods for obtaining accurate medication histories on medication safety. This study was conducted to compare the accuracy and clinical impact of pharmacist medication histories obtained by electronic medical record review (EMRR) alone with those obtained by direct interviews combined with EMRR. METHOD: This 18-week prospective study included patients who were admitted to the Inpatient Medicine Service at the study institution and who had a pharmacist-conducted medication reconciliation EMRR within 48 hours of hospital admission. A chart review was performed to collect data to determine whether differences existed in the number of discrepancies, recommendations, and medication errors between the EMRR alone group compared to the EMRR combined with the patient interview group. RESULTS: Five hundred thirteen discrepancies were identified with the EMRR group compared to 986 from the combined EMRR and patient interview group (P < .001). Significantly more recommendations were made in the combination interview group compared to the EMRR alone group (260 vs 97; P < .001). Fewer medication errors were identified for the EMRR alone group compared to the combination interview group (55 vs 134; P < .001). The most common errors were omitted medications followed by extra dose/failure to discontinue therapy and wrong dose/frequency errors. CONCLUSION: Pharmacist-conducted admission medication interviews combined with EMRR can potentially identify harmful medication discrepancies and prevent medication errors.

Comparison of the ELISPOT and cytokine flow cytometry assays for the enumeration of antigen-specific T cells.

The enumeration of antigen-specific T cell responses has been greatly facilitated in recent years by the development of methods based on the detection of cytokines. In particular, the enzyme-linked immunospot (ELISPOT) and cytokine flow cytometry (CFC) assays have become popular. Since both assays are likely to continue to be in widespread use, it is important to evaluate whether their results are comparable. In the current study, we compared the results obtained in the ELISPOT and CFC assays using peptide pools corresponding to CMV and HIV-1 proteins in chronically HIV-1-infected individuals. Analysis of T cell responses to peptide pools indicated that the CMV pp65 and HIV-1 Gag CFC and ELISPOT-derived results were statistically correlated. However, the results obtained with each assay differed in important ways: the magnitude of the response was consistently higher in the CFC assay while the CFC assay was less likely than the ELISPOT assay to detect low-level responses. Furthermore, there was a lack of numeric agreement between ELISPOT and CFC results. For studies that require the detection of low-level responses, or definition of responses as positive or negative, the ELISPOT assay may be preferable. In contrast, the CFC has a greater dynamic range and allows for phenotypic discrimination of responding cells, making it the assay of choice for most other applications.