Non-collinear spin-spiral phase for the uniform electron gas within Reduced-Density-Matrix-Functional Theory

The non-collinear spin-spiral density wave of the uniform electron gas is studied in the framework of Reduced-Density-Matrix-Functional Theory. For the Hartree-Fock approximation, which can be obtained as a limiting case of Reduced-Density-Matrix-Functional Theory, Overhauser showed a long time ago that the paramagnetic state of the electron gas is unstable with respect to the formation of charge or spin density waves. Here we not only present a detailed numerical investigation of the spin-spiral density wave in the Hartree-Fock approximation but also investigate the effects of correlations on the spin-spiral density wave instability by means of a recently proposed density-matrix functional.Comment: 9 pages, 10 figure

Intraossäre Infusion: Eine wichtige Technik auch für die Kinderanästhesie

Zusammenfassung: Die zeitgerechte Etablierung eines venösen Zugangs kann insbesondere bei Säuglingen und Kleinkindern eine große Herausforderung sein. Hier hat sich die intraossäre Infusionstechnik seit den 1940er Jahren als schnelle, effiziente und sichere Alternativmethode zur Schaffung eines Gefäßzugangs bewährt, um einem vitalgefährdeten Kind dringend benötigte Medikamente und Flüssigkeiten zu applizieren. Während in den internationalen Leitlinien zur pädiatrischen Notfallmedizin der intraossären Infusion eine hohe Priorität eingeräumt wird, greifen die meisten Anästhesisten nur sehr zögerlich auf diese langjährig bewährte Punktionstechnik zurück. Die vorliegende Arbeit beschreibt die intraossäre Infusionstechnik, stellt zwei unterschiedliche Kanülierungssysteme vor und diskutiert, basierend auf den aktuellen notfallmedizinischen Leitlinien sowie anhand von eigenen Fallbeispielen, potenzielle Indikationen für die Kinderanästhesie. Demnach sollten insbesondere akut vital-gefährdete Kinder mit Kreislaufstillstand, Laryngospasmus, akuter Atemwegsblutung, hypovolämischem Schock oder Hypothermie bei ausgedehnten Verbrennungen ohne liegenden bzw. rasch anzulegenden venösen Zugang mit einer intraossären Kanüle versorgt werden. Inwieweit die intraossäre Infusion auch beim nichtakut vital-gefährdeten Kind mit schwierigem oder unmöglichem peripheren Venenzugang in der Anästhesie überbrückend und zeitlich begrenzt eingesetzt werden sollte, wird die zukünftige Diskussion zeigen. Die erfolgreiche Anwendung der intraossären Infusionstechnik in der Kinderanästhesie verlangt die unmittelbare Verfügbarkeit der entsprechenden Ausrüstung, die umfassende Schulung und das regelmäßige Training sowie eine klare Regelung für ihre Anwendung innerhalb der Anästhesieabteilun

Excited states in bilayer graphene quantum dots

We report on ground- and excited state transport through an electrostatically defined few-hole quantum dot in bilayer graphene in both parallel and perpendicular applied magnetic fields. A remarkably clear level scheme for the two-particle spectra is found by analyzing finite bias spectroscopy data within a two-particle model including spin and valley degrees of freedom. We identify the two-hole ground-state to be a spin-triplet and valley-singlet state. This spin alignment can be seen as Hund's rule for a valley-degenerate system, which is fundamentally different to quantum dots in carbon nano tubes and GaAs-based quantum dots. The spin-singlet excited states are found to be valley-triplet states by tilting the magnetic field with respect to the sample plane. We quantify the exchange energy to be 0.35meV and measure a valley and spin g-factor of 36 and 2, respectively

Kinetic-Energy Density-Functional Theory on a Lattice

We present a kinetic-energy density-functional theory and the corresponding kinetic-energy Kohn-Sham (keKS) scheme on a lattice and show that by including more observables explicitly in a density-functional approach already simple approximation strategies lead to very accurate results. Here we promote the kinetic-energy density to a fundamental variable along side the density and show for specific cases (analytically and numerically) that there is a one-to-one correspondence between the external pair of on-site potential and site-dependent hopping and the internal pair of density and kinetic-energy density. Based on this mapping we establish two unknown effective fields, the mean-field exchange-correlation potential and the mean-field exchange-correlation hopping, that force the keKS system to generate the same kinetic-energy density and density as the fully interacting one. We show, by a decomposition based on the equations of motions for the density and the kinetic-energy density, that we can construct simple orbital-dependent functionals that outperform the corresponding exact-exchange Kohn-Sham (KS) approximation of standard density-functional theory. We do so by considering the exact KS and keKS systems and compare the unknown correlation contributions as well as by comparing self-consistent calculations based on the mean-field exchange for the keKS and the exact-exchange for the KS system, respectively

Effect of resonant magnetic perturbations on low collisionality discharges in MAST and a comparison with ASDEX Upgrade

Sustained ELM mitigation has been achieved on MAST and AUG using RMPs with a range of toroidal mode numbers over a wide region of low to medium collisionality discharges. The ELM energy loss and peak heat loads at the divertor targets have been reduced. The ELM mitigation phase is typically associated with a drop in plasma density and overall stored energy. In one particular scenario on MAST, by carefully adjusting the fuelling it has been possible to counteract the drop in density and to produce plasmas with mitigated ELMs, reduced peak divertor heat flux and with minimal degradation in pedestal height and confined energy. While the applied resonant magnetic perturbation field can be a good indicator for the onset of ELM mitigation on MAST and AUG there are some cases where this is not the case and which clearly emphasise the need to take into account the plasma response to the applied perturbations. The plasma response calculations show that the increase in ELM frequency is correlated with the size of the edge peeling-tearing like response of the plasma and the distortions of the plasma boundary in the X-point region.Comment: 31 pages, 28 figures. This is an author-created, un-copyedited version of an article submitted for publication in Nuclear Fusion. IoP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from i

Airway complications after lung transplantation: risk factors, prevention and outcome

PURPOSE: Anastomotic complications following lung transplantation (LuTx) have been described in up to 15% of patients. Challenging to treat, they are associated with high morbidity and a mortality rate of 2-5%. The aim of this study was to analyze the incidence of complications in a consecutive series of bronchial anastomosis after LuTx at our center and to delineate the potential risk factors. METHODS: Between 1992 and 2007, 441 bronchial anastomoses were performed in 235 patients. Indications for transplantation were cystic fibrosis (35.7%) emphysema (28.1%) pulmonary fibrosis (12.8%) and pulmonary hypertension (7.7%). There were 206 sequential bilateral and 28 single transplants including lobar engraftments in 20 cases. The donor bronchus was shortened to the plane of the lobar carina including the medial wall of the intermediate bronchus. Peribronchial tissue was left untouched. Anastomosis was carried out using a continuous absorbable running suture (PDS 4/0) at the membranous and interrupted sutures at the cartilaginous part. Six elective surveillance bronchoscopies were done monthly during the first half-year post-LuTx, with detailed assessment of the pre- and post-anastomotic airways. RESULTS: One-year survival since 2000 was 90.5%. In all 441 anastomoses performed, no significant dehiscence was observed. In one patient, a small fistula was detected and closed surgically on postoperative day five. Fungal membranes were found in 50% of the anastomoses at 1 month and in 14% at 6 months. Discrete narrowing of the anastomotic lumen without need for intervention was found in 4.9% of patients at 1 month and in 2.4% at 6 months. Age, cytomegalovirus status, induction therapy, immunosuppressive regimen, ischemic time, and ventilation time had no influence on bronchial healing. CONCLUSIONS: Clinically relevant bronchial anastomotic complications after LuTx can be avoided by use of a simple standardized surgical technique. Aggressive antibiotic and antifungal therapy might play an important supportive rol

Kindersimulation heute und morgen: Perspektiven und Konzepte

Zusammenfassung: Die Konfrontation mit kritisch kranken Neugeborenen, Säuglingen und Kleinkindern ist selten und stellt ein Behandlungsteam vor besondere Herausforderungen. Für eine erfolgreiche Notfallbehandlung sind sichere technische und nichttechnische Fertigkeiten essenziell. Kindersimulatoren ermöglichen die Schaffung einer didaktischen Infrastruktur zur Vernetzung von Lehrbuchtheorie mit erfahrungsaktiver Praxis. Zur Erfassung des aktuellen Status der Kindersimulation in Deutschland, Österreich und der Schweiz wurde eine Onlinebefragung aller entsprechend aktiven Zentren durchgeführt. Derzeit wird Kindersimulation in 24Zentren betrieben. Diese verfügen über 39 pädiatrische Simulatoren: 8 für Neugeborene, 26 für Säuglinge und 5 für Kinder. Eine gewisse Kongruenz im Standard ist unter den Zentren feststellbar. Die meisten Instruktoren verfügen über eine spezialisierte Instruktorenausbildung. Von den Instruktoren sind 26% Pflegefachkräfte und 67% Ärzte, davon haben Pädiater und Anästhesisten den größten Anteil. Viele Zentren (38%) funktionieren lediglich durch das spezielle Engagement ihrer Mitarbeiter, die diverse Aktivitäten in ihrer Freizeit organisieren. Videogestützte Nachbesprechungen gelten als Grundlage für ein effektives Training. Einen besonderen inhaltlichen Schwerpunkt legen fast alle Zentren (92%) auf die Vermittlung von nichttechnischen Fertigkeiten (interpersonelle Aspekte des Zwischenfallmanagements). Im Rahmen des kürzlich etablierten PaedSim-Projekts sollen die Curricula von Kindersimulationskursen noch klarer strukturiert sowie international standardisiert werden, um dadurch Trainingseffektivität und -nachhaltigkeit zu erhöhe

Photoinduced 3D orientational order in side chain liquid crystalline azopolymers

We apply experimental technique based on the combination of methods dealing with principal refractive indices and absorption coefficients to study the photoinduced 3D orientational order in the films of liquid crystalline (LC) azopolymers. The technique is used to identify 3D orientational configurations of trans azobenzene chromophores and to characterize the degree of ordering in terms of order parameters. We study two types of LC azopolymers which form structures with preferred in-plane and out-of-plane alignment of azochromophores, correspondingly. Using irradiation with the polarized light of two different wavelengths we find that the kinetics of photoinduced anisotropy can be dominated by either photo-reorientation or photoselection mechanisms depending on the wavelength. We formulate the phenomenological model describing the kinetics of photoinduced anisotropy in terms of the isomer concentrations and the order parameter tensor. We present the numerical results for absorption coefficients that are found to be in good agreement with the experimental data. The model is also used to interpret the effect of changing the mechanism with the wavelength of the pumping light.Comment: uses revtex4 28 pages, 10 figure

Self-amplified photo-induced gap quenching in a correlated electron material.

Capturing the dynamic electronic band structure of a correlated material presents a powerful capability for uncovering the complex couplings between the electronic and structural degrees of freedom. When combined with ultrafast laser excitation, new phases of matter can result, since far-from-equilibrium excited states are instantaneously populated. Here, we elucidate a general relation between ultrafast non-equilibrium electron dynamics and the size of the characteristic energy gap in a correlated electron material. We show that carrier multiplication via impact ionization can be one of the most important processes in a gapped material, and that the speed of carrier multiplication critically depends on the size of the energy gap. In the case of the charge-density wave material 1T-TiSe2, our data indicate that carrier multiplication and gap dynamics mutually amplify each other, which explains-on a microscopic level-the extremely fast response of this material to ultrafast optical excitation