An ab-initio converse NMR approach for pseudopotentials

We extend the recently developed converse NMR approach [T. Thonhauser, D. Ceresoli, A. Mostofi, N. Marzari, R. Resta, and D. Vanderbilt, J. Chem. Phys. \textbf{131}, 101101 (2009)] such that it can be used in conjunction with norm-conserving, non-local pseudopotentials. This extension permits the efficient ab-initio calculation of NMR chemical shifts for elements other than hydrogen within the convenience of a plane-wave pseudopotential approach. We have tested our approach on several finite and periodic systems, finding very good agreement with established methods and experimental results.Comment: 11 pages, 2 figures, 4 tables; references expande

Physics of Solid and Liquid Alkali Halide Surfaces Near the Melting Point

This paper presents a broad theoretical and simulation study of the high temperature behavior of crystalline alkali halide surfaces typified by NaCl(100), of the liquid NaCl surface near freezing, and of the very unusual partial wetting of the solid surface by the melt. Simulations are conducted using two-body rigid ion BMHFT potentials, with full treatment of long-range Coulomb forces. After a preliminary check of the description of bulk NaCl provided by these potentials, which seems generally good even at the melting point, we carry out a new investigation of solid and liquid surfaces. Solid NaCl(100) is found in this model to be very anharmonic and yet exceptionally stable when hot. It is predicted by a thermodynamic integration calculation of the surface free energy that NaCl(100) should be a well ordered, non-melting surface, metastable even well above the melting point. By contrast, the simulated liquid NaCl surface is found to exhibit large thermal fluctuations and no layering order. In spite of that, it is shown to possess a relatively large surface free energy. The latter is traced to a surface entropy deficit, reflecting some kind of surface short range order. Finally, the solid-liquid interface free energy is derived through Young's equation from direct simulation of partial wetting of NaCl(100) by a liquid droplet. It is concluded that three elements, namely the exceptional anharmonic stability of the solid (100) surface, the molecular short range order at the liquid surface, and the costly solid liquid interface, all conspire to cause the anomalously poor wetting of the (100) surface by its own melt in the BMHFT model of NaCl -- and most likely also in real alkali halide surfaces.Comment: modified version of JCP 123, 164701 15 pages, 25 figure

HCD-SIM: Healthcare Clinic Design Simulator With Application to a Bone Marrow Transplant Clinic

The treatment of patients in outpatient healthcare clinics is continually growing as technology improves and recovery benefits are recognized. In this thesis, a simulation framework is developed to model the operational aspects of clinics with the goal of providing a method to understand the impact of clinic design decisions relative to productivity, efficiency, and quality of patient care. The healthcare clinic design simulator (HCD-Sim) is designed to study the dynamic system behavior of clinics and to analyze alternative outpatient healthcare clinic designs. Additionally, the simulation framework is created using a data-driven structure that can represent a large class of outpatient healthcare clinics through the specification of clinic data relative to patient flows, work flows, and resource requirements. To demonstrate capability, the framework is applied to a representative general clinic to analyze capacity and investigate important resources that impact the clinic’s performance. Lastly, the framework is applied to a Bone Marrow Transplant (BMT) clinic application to examine the system and provide design recommendations

Orbital magnetization in crystalline solids: Multi-band insulators, Chern insulators, and metals

We derive a multi-band formulation of the orbital magnetization in a normal periodic insulator (i.e., one in which the Chern invariant, or in 2d the Chern number, vanishes). Following the approach used recently to develop the single-band formalism [T. Thonhauser, D. Ceresoli, D. Vanderbilt, and R. Resta, Phys. Rev. Lett. {\bf 95}, 137205 (2005)], we work in the Wannier representation and find that the magnetization is comprised of two contributions, an obvious one associated with the internal circulation of bulk-like Wannier functions in the interior and an unexpected one arising from net currents carried by Wannier functions near the surface. Unlike the single-band case, where each of these contributions is separately gauge-invariant, in the multi-band formulation only the \emph{sum} of both terms is gauge-invariant. Our final expression for the orbital magnetization can be rewritten as a bulk property in terms of Bloch functions, making it simple to implement in modern code packages. The reciprocal-space expression is evaluated for 2d model systems and the results are verified by comparing to the magnetization computed for finite samples cut from the bulk. Finally, while our formal proof is limited to normal insulators, we also present a heuristic extension to Chern insulators (having nonzero Chern invariant) and to metals. The validity of this extension is again tested by comparing to the magnetization of finite samples cut from the bulk for 2d model systems. We find excellent agreement, thus providing strong empirical evidence in favor of the validity of the heuristic formula.Comment: 14 pages, 8 figures. Fixed a typo in appendix

Orbital magnetization in periodic insulators

Working in the Wannier representation, we derive an expression for the orbital magnetization of a periodic insulator. The magnetization is shown to be comprised of two contributions, an obvious one associated with the internal circulation of bulk-like Wannier functions in the interior, and an unexpected one arising from net currents carried by Wannier functions near the surface. Each contribution can be expressed as a bulk property in terms of Bloch functions in a gauge-invariant way. Our expression is verified by comparing numerical tight-binding calculations for finite and periodic samples.Comment: submitted to PRL; signs corrected in Eqs. (11), (12), (19), and (20

Why Are Alkali Halide Solid Surfaces Not Wetted By Their Own Melt?

Alkali halide (100) crystal surfaces are anomalous, being very poorly wetted by their own melt at the triple point. We present extensive simulations for NaCl, followed by calculations of the solid-vapor, solid-liquid, and liquid-vapor free energies showing that solid NaCl(100) is a nonmelting surface, and that its full behavior can quantitatively be accounted for within a simple Born-Meyer-Huggins-Fumi-Tosi model potential. The incomplete wetting is traced to the conspiracy of three factors: surface anharmonicities stabilizing the solid surface; a large density jump causing bad liquid-solid adhesion; incipient NaCl molecular correlations destabilizing the liquid surface. The latter is pursued in detail, and it is shown that surface short-range charge order acts to raise the surface tension because incipient NaCl molecular formation anomalously reduces the surface entropy of liquid NaCl much below that of solid NaCl(100).Comment: 4 pages, 3 figure

Erlotinib in patients with previously irradiated, recurrent brain metastases from non-small cell lung cancer: Two case reports

Background: With the current improvements in primary lung care, the long-term control of brain metastases becomes a clinical challenge. No established therapeutic approaches exist for cranial relapse after response to previous radiotherapy and systemic therapy. Tyrosine kinase inhibitors like erlotinib with its proven activity in non-small cell lung cancer may provide clinical benefits in such patients. Patients and Methods: Two case reports are presented illustrating the efficacy of erlotinib in patients with recurrent brain metastases and parallel thoracic progression. Results: Both patients showed lasting partial remissions in the brain and lung, and clinical symptom improvement. Conclusion: The observed survival times of above 18 and 15 months, respectively, since occurrence of cranial disease manifestation in line with the achieved progression-free survival times of 9 and 6 months by the erlotinib third-line therapy are remarkable. The use of targeted therapies after whole-brain irradiation should be investigated more systematically in prospective clinical trials