Electronic structure methods: Augmented Waves, Pseudopotentials and the Projector Augmented Wave Method

The main goal of electronic structure methods is to solve the Schroedinger equation for the electrons in a molecule or solid, to evaluate the resulting total energies, forces, response functions and other quantities of interest. In this paper we describe the basic ideas behind the main electronic structure methods such as the pseudopotential and the augmented wave methods and provide selected pointers to contributions that are relevant for a beginner. We give particular emphasis to the Projector Augmented Wave (PAW) method developed by one of us, an electronic structure method for ab-initio molecular dynamics with full wavefunctions. We feel that it allows best to show the common conceptional basis of the most widespread electronic structure methods in materials science.Comment: to appear in: Handbook of Materials Modeling; Volume 1: Methods and Models, Sidney Yip (Ed.); Kluwer Academic Publisher

International comparative study of systems for the government advancement of research and development

The reorganization, structure and instruments of government advancement of research in three countries was compared: France, Sweden and the USA. In France the powers are centralized; in Sweden and the USA, decentralized. Assistance to projects is provided with grants and contracts in all three countries. France and Sweden also give loans with conditional waiving of reimbursement in case of failure. In all three countries indirect assistance is provided only with small tax breaks

Minimalinvasive Mitralklappenchirurgie : Ergebnisse einer Studie an 331 Patienten

Die minimalinvasive Herzchirurgie ist an der Universität Frankfurt seit Ende der 90er Jahre ein etabliertes Verfahren zur Therapie von Mitralklappenvitien. Dabei kommen die rechtslaterale Minithorakotomie und die partielle oberer Sternotomie mit Verwendung der Herz-Lungen-Maschine zum Einsatz. In der Klinik für Thorax-, Herz- und thorakale Gefäßchirurgie in Frankfurt wurde von Januar 1998 bis Dezember 2005 bei 331 Patienten die Mitralklappe rekonstruiert bzw. ersetzt, und zwar über die rechtsseitige Minithorakotomie in 231 Fällen, über die partielle Sternotomie bei 100 Patienten. Ziel der vorliegenden Studie war die Evaluierung perioperativer und postoperativer Komplikationen. Perioperativ starben lediglich in der Chitwood-Gruppe 3 Patienten. Das Langzeitüberleben beider Gruppen nähert sich dem der Normalbevölkerung. Hinsichtlich des Zieles dieser Operationen, die Wiederherstellung der Funktion der Mitralklappe, wurden an der Universität Frankfurt, im Vergleich mit bereits vorliegenden Studien, ähnlich gute Ergebnisse erzielt. Früh- und Spätkomplikationen traten bei beiden Operationsverfahren selten auf. Dies wird vor allem an der geringen Reoperationsrate deutlich. Bei der Nachuntersuchung zeigten sich im Vergleich zum präoperativen Zustand der Patienten hochsignifikante Verbesserungen hinsichtlich NYHA-Klassifikation, also der allgemeinen Leistungsfähigkeit. Die erfassten Patienten konnten auch von der Verbesserung der Ventrikelfunktionsparameter profitieren, worin sich die beiden Gruppen nicht unterschieden. Obwohl die postoperativen Ergebnisse gut waren, gilt doch hervorzuheben, dass es zu einigen Problemen gekommen ist: 6 Patienten der Chitwood-Gruppe, deren Mitralklappe mit Hilfe einer Fraterplastik rekonstruiert wurde, mussten reoperiert werden. Daher wurde die Technik der Fraterplastik seit März 2003 nicht mehr eingesetzt. Die dargestellten Ergebnisse aus der Literatur belegen die Effektivität der beiden minimalinvasiven Therapieformen im Hinblick auf Überleben, spätere Leistungsfähigkeit sowie peri- und postoperativer Komplikationen. Beide Methoden haben bewiesen, für ausgewählte Patienten eine sichere Alternative zur medianen Sternotomie zu sein. Durch die Komplexität des Verfahrens nach Chitwood werden heute die meisten minimalinvasiven Eingriffe über die partielle obere Sternotomie durchgeführt. Inzwischen wurde ihre Anwendbarkeit auf Notfallpatienten und Kombinationseingriffe an den Herzklappen ausgeweitet.At the University of Frankfurt, minimally invasive heart surgery is a well-established procedure for the treatment of mitral valve disease. Two approaches, the right lateral minithoracotomy, and the partial upper sternotomy (using cardiopulmonary bypass), are applied. Between January 1998 and December 2005, the mitral valve of 331 patients have been reconstructed or replaced at the Department of Thoracic and Cardiovascular Surgery in Frankfurt. In 231 patients, the approach was performed through right lateral minithoracotomy, and in 100 through partial upper sternotomy. The aim of this study was the evaluation of perioperative and postoperative complications. There was one perioperative death in the Chitwood-group. Long-term survival rates of both groups converged to that of a normal population. Referring to the objective of the operation, the restoration of the mitral valve function, the University of Frankfurt achieved similar positive results compared to already existing studies. In both procedures short and long-term complications appeared rarely, which becomes particularly apparent due to the low rate of re-operation. The results of the follow-ups showed a significant improvement of the NYHA classification compared to the preoperative values. Patients of both groups also benefitted from improvement in their left ventricular function. In spite of the good postoperative results, we see appearance of some problems: six patients in the Chitwood-group, whose mitral valve had been reconstructed using the technique of mural annulus shortening suture annuloplasty (first described by Frater), had to be re-operated. Thus, this technique has not been used since March 2003. The results of former studies, document the effectiveness of both procedures through survival rates, postoperative mobility, quality of life, and peri-/postoperative complications. Both procedures demonstrated beeing a safe alternative to standard median sternotomy for selected patients. Nowadays, due to the complexity of the Chitwood-procedure, the majority of minimally invasive interventions are performed using the upper partial sternotomy. Meanwhile, its application has been extended to emergencies and combined heart valve surgery

Encouraging engagement: mentoring students with chronic absenteeism

For students across the United States, chronic absenteeism is a significant problem that can lead to poor academic performance, dropping out of school, and lack of success in college and/or the workplace. Although schools implement a wide range of interventions to promote school attendance, some students continue to be absent from school. This paper examines the national problem of chronic absenteeism and the problem at two schools (one middle and one secondary) in the western region of North Carolina. We recommend the implementation of evidence-based mentoring practices adapted from the mentoring program Check & Connect™, including personalized academic interventions and relationship-building between students and adults to increase student engagement. Analyses suggest that the applied mentoring program may, indeed, improve attendance for students considered chronically absent and, in addition, may improve their academic performance and reduce discipline referrals

A Simple μ-PTV Setup to Estimate Single-Particle Charge of Triboelectrically Charged Particles

Triboelectric separation is a useful phenomenon that can be used to separate fine powders. To design technical devices or evaluate the potential of powders to be triboelectrically separated, knowledge about the charge distribution on a single-particle level has to be obtained. To estimate the single-particle charge distribution in an application-oriented way, a simple μ-PTV system was developed. The designed setup consists of a dispersing and a charging unit using a Venturi nozzle and a tube, respectively, followed by a separation chamber. In the separation chamber, a homogenous electrical field leads to a deflection of the particles according to their individual charge. The trajectories of the particles are captured on single frames using microscope optics and a high-speed camera with a defined exposure time. The particles are illuminated using a laser beam combined with a cylindrical lens. The captured images enable simultaneous measurement of positively and negatively charged particles. The charge is calculated assuming a mean particle mass derived from the mean particle size. Initial experiments were carried out using starch of different botanical origins and protein powder. Single-component experiments with starch powders show very different charge distributions for positively and negatively charged particles, whereas protein powder shows bipolar charging. Different starch-protein mixtures show similar patterns for positive and negative charge distributions

Исследование датчиков рН и удельной электрической проводимости фирмы WTW в системе автоматизированного контроля качества очистки сточных вод

We demonstrate the suitability of microcavities based on circular grating resonators (CGRs) as fast switches. This type of optical resonator is characterized by a high quality factor and very small mode volume. The waveguide-coupled CGRs are fabricated with silicon-on-insulator technology compatible with standard complementary metal-oxide semiconductor (CMOS) processing. The linear optical properties of the CGRs are investigated by transmission spectroscopy. From 3D finite-difference time-domain simulations of isolated CGRs, we identify the measured resonances. We probe the spatial distribution and the parasitic losses of a resonant optical mode with scanning near-field optical microscopy. We observe fast all-optical switching within a few picoseconds by optically generating free charge carriers within the cavity. (C) 2009 Optical Society of Americ

Experimental investigation on pore size distribution and drying kinetics during lyophilization of sugar solutions

[EN] The pore structure is a decisive factor for the process efficiency and product quality of freeze dried products. In this work the two-dimensional ice crystal structure was investigated for maltodextrin solutions with different concentrations by a freeze drying microscope. The resulting drying kinetics was investigated for different pore structures. Additionally the three-dimensional pore structure of the freeze dried samples was measured by µ-computed tomography and the pore size distribution was quantified by image analysis techniques. The two- and three-dimensional pore size distributions were compared and linked to the drying kinetics.Foerst, P.; Lechner, M.; Vorhauer, N.; Schuchmann, H.; Tsotsas, E. (2018). Experimental investigation on pore size distribution and drying kinetics during lyophilization of sugar solutions. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 1415-1422. https://doi.org/10.4995/IDS2018.2018.7310OCS1415142

Field-driven femtosecond magnetization dynamics induced by ultrastrong coupling to THz transients

Controlling ultrafast magnetization dynamics by a femtosecond laser is attracting interest both in fundamental science and industry because of the potential to achieve magnetic domain switching at ever advanced speed. Here we report experiments illustrating the ultrastrong and fully coherent light-matter coupling of a high-field single-cycle THz transient to the magnetization vector in a ferromagnetic thin film. We could visualize magnetization dynamics which occur on a timescale of the THz laser cycle and two orders of magnitude faster than the natural precession response of electrons to an external magnetic field, given by the Larmor frequency. We show that for one particular scattering geometry the strong coherent optical coupling can be described within the framework of a renormalized Landau Lifshitz equation. In addition to fundamentally new insights to ultrafast magnetization dynamics the coherent interaction allows for retrieving the complex time-frequency magnetic properties and points out new opportunities in data storage technology towards significantly higher storage speed.Comment: 25 page