Long-term evolution of massive star explosions

We examine simulations of core-collapse supernovae in spherical symmetry. Our model is based on general relativistic radiation hydrodynamics with three-flavor Boltzmann neutrino transport. We discuss the different supernova phases, including the long-term evolution up to 20 seconds after the onset of explosion during which the neutrino fluxes and mean energies decrease continuously. In addition, the spectra of all flavors become increasingly similar, indicating the change from charged- to neutral-current dominance. Furthermore, it has been shown recently by several groups independently, based on sophisticated supernova models, that collective neutrino flavor oscillations are suppressed during the early mass-accretion dominated post-bounce evolution. Here we focus on the possibility of collective flavor flips between electron and non-electron flavors during the later, on the order of seconds, evolution after the onset of an explosion with possible application for the nucleosynthesis of heavy elements.Comment: 12 pages, 7 figures, conference proceeding, HANSE 2011 worksho

Toward Realistic Altruism: A Community-Based Field Experience

This is a study of the perceptions of preservice teachers engaged in a human services field experience and the college instructors responsible for teaching the Human Development course attached to the field experience. Student data came from semistructured focus group interviews and student journals maintained throughout the experience, faculty data from onc-onone semi-structured interviews. Using the constant comparative method, data for students and faculty were grouped as follows: a) what students do during their placements, b) benefits and challenges of the experience, c) connections built between their experiences in the field and in the classroom. Analysis indicated that while the experience is generally perceived as valuable, there are gaps between what students actually do and faculty perceptions. Also, certain types of placements are much more powerful than others in yielding desired results of empathy, awareness of diversity and teaching skills. Recommendations for increasing the benefits and minimizing knowledge gaps are discussed

Die operative Versorgung der sekundären Coxarthrose bei kongenitaler Hüftluxation (Crowe TypIV)

Zusammenfassung: Operationsziel: Ziel der Therapie ist die mechanische und funktionelle Stabilisation einer hohen Hüftluxation bei dysplasiebedingter Coxarthrose mittels endoprothetischem Ersatz. Indikationen: Hüftdysplasie im Erwachsenenalter. Fortgeschrittene symptomatische Coxarthrose. Hohe Hüftluxation gemäß CroweIII/IV. Symptomatische Beinlängendifferenz. Kontraindikationen: Zerebrospinale Dysfunktionen. Muskeldystrophien. Manifeste Störung des Knochenmetabolismus. Infektion. Immunsupprimierte Patienten. Operationstechnik: Seitenlage (variabel). Gerade laterale Inzision über dem Trochanter major und Eingehen zwischen dem Vorderrand des M.gluteus maximus und dem Hinterrand des M.gluteus medius, dem sog. Gibson-Intervall. Darstellen des N.ischiadicus und permanente Kontrolle desselben, um hier bei jeglichen Manipulationen, vor allem bei der Reposition des Femurs, einen Traktionsschaden aufgrund erhöhter Spannung zu vermeiden. Trochanter-Flip-Osteotomie und Darstellen der Gelenkkapsel zwischen M.piriformis und M.gluteus minimus. Aufgrund des Hochstands des Femurs kann hier die Identifikation der anatomischen Landmarken erschwert sein. Schrittweise Z-förmige Kapsulektomie der elongierten Kapsel und Darstellen der Primärpfanne, die häufig aufgrund der langzeitigen Luxation des Femurkopfs nur rudimentär ausgebildet ist. Lokalisation des Pfannengrunds bzw. der Tränenfigur. Aufraspeln der Pfanne und Implantation der mit der Pfannengröße konformen Hakendachschale. Fixation der Pfanne je nach Halt und Knochenqualität mit 3-5Schrauben. Resektion des proximalen Femurs je nach Spannung der Weichteile bis auf Höhe oder sogar unter das Niveau des Trochanter minor. Anschließend Aufraspeln des Femurs und unter steter Spannungskontrolle des N.ischiadicus Reposition des Femurs in die Hüftpfanne; je nach Spannung des N.ischiadicus und der umgebenden Weichteile erfolgt eine Nachresektion des proximalen Femurs. Anfrischen des proximalen Femurs mit dem Meißel zur besseren Konsolidation des Trochanter-major-Fragments. Refixation des Trochanters mittels Cerclage, wobei die Muskulatur des M.gluteus medius an seinem Ursprung am Os ilium oder am muskulotendinösen Übergang am Trochanterfragment etwas mobilisiert werden muss, um den Trochanter major wieder distal am proximalen Femur refixieren zu können. Weiterbehandlung: Während der Hospitalisierung regelmäßige Behandlung auf der passiven Bewegungsschiene mit maximal 70° Flexion. Keine aktive Abduktion, keine passive Adduktion über die Mittellinie, kein Heben des gestreckten Beins, 10-15kg Teilbelastung an zwei Unterarmgehstöcken während 8Wochen. Je nach Compliance des Patienten und intraoperativer Stabilität der Prothese trägt der Patient eine Antiluxationsbandage (in Bern Hohmann-Bandage) für die ersten 6-8Wochen postoperativ. Anschließend erste klinische und radiologische Nachkontrolle und je nach Konsolidation des Trochanter major schrittweiser Übergang zur Vollbelastung. Thromboseprophylaxe bis zur Vollbelastung. Ergebnisse: Im beobachteten Zeitraum von 1998-2012 erfolgten insgesamt 28Hüftprothesenimplantationen bei hoher Hüftluxation im Erwachsenenalter im Stadium CroweIV, die mit einer Hakendachschale und einer femoralen Verkürzungsosteotomie behandelt wurden. Aktuell liegen von 14Patienten nach 8 ± 1,2Jahren (3,5-12Jahren) klinische Nachuntersuchungen vor. In diesem mittleren Beobachtungszeitraum zeigten sich gemäß Merle-d'Aubigné-Score bei 86 % der operierten Patienten Verbesserungen. Gute bis exzellente Resultate wurden in 71 % der Fälle erreicht. Langzeitergebnisse (< 10Jahre) stehen bis dato noch au

Adsorption of Multi-block and Random Copolymer on a Solid Surface: Critical Behavior and Phase Diagram

The adsorption of a single multi-block $AB$-copolymer on a solid planar substrate is investigated by means of computer simulations and scaling analysis. It is shown that the problem can be mapped onto an effective homopolymer adsorption problem. In particular we discuss how the critical adsorption energy and the fraction of adsorbed monomers depend on the block length $M$ of sticking monomers $A$, and on the total length $N$ of the polymer chains. Also the adsorption of the random copolymers is considered and found to be well described within the framework of the annealed approximation. For a better test of our theoretical prediction, two different Monte Carlo (MC) simulation methods were employed: a) off-lattice dynamic bead-spring model, based on the standard Metropolis algorithm (MA), and b) coarse-grained lattice model using the Pruned-enriched Rosenbluth method (PERM) which enables tests for very long chains. The findings of both methods are fully consistent and in good agreement with theoretical predictions.Comment: 27 pages, 12 figure

On the stability of very massive primordial stars

The stability of metal-free very massive stars ($Z$ = 0; M = 120 - 500 \msol) is analyzed and compared with metal-enriched stars. Such zero-metal stars are unstable to nuclear-powered radial pulsations on the main sequence, but the growth time scale for these instabilities is much longer than for their metal-rich counterparts. Since they stabilize quickly after evolving off the ZAMS, the pulsation may not have sufficient time to drive appreciable mass loss in Z = 0 stars. For reasonable assumptions regarding the efficiency of converting pulsational energy into mass loss, we find that, even for the larger masses considered, the star may die without losing a large fraction of its mass. We find a transition between the $\epsilon$- and $\kappa$-mechanisms for pulsational instability at Z\sim 2\E{-4} - 2\E{-3}. For the most metal-rich stars, the $\kappa$-mechanism yields much shorter $e$-folding times, indicating the presence of a strong instability. We thus stress the fundamental difference of the stability and late stages of evolution between very massive stars born in the early universe and those that might be born today.Comment: 7 pages, 5 figures. Minor changes, more results given in Table 1, accepted for publication in Ap

LED technology breaks performance barrier

Light-emitting diodes made from perovskite semiconductors have reached a milestone in the efficiency with which they emit light — potentially ushering in a new platform for lighting and display technology

Measurements of branching fraction ratios and CP-asymmetries in suppressed B^- -> D(-> K^+ pi^-)K^- and B^- -> D(-> K^+ pi^-)pi^- decays

We report the first reconstruction in hadron collisions of the suppressed decays B^- -> D(-> K^+ pi^-)K^- and B^- -> D(-> K^+ pi^-)pi^-, sensitive to the CKM phase gamma, using data from 7 fb^-1 of integrated luminosity collected by the CDF II detector at the Tevatron collider. We reconstruct a signal for the B^- -> D(-> K^+ pi^-)K^- suppressed mode with a significance of 3.2 standard deviations, and measure the ratios of the suppressed to favored branching fractions R(K) = [22.0 \pm 8.6(stat)\pm 2.6(syst)]\times 10^-3, R^+(K) = [42.6\pm 13.7(stat)\pm 2.8(syst)]\times 10^-3, R^-(K)= [3.8\pm 10.3(stat)\pm 2.7(syst]\times 10^-3, as well as the direct CP-violating asymmetry A(K) = -0.82\pm 0.44(stat)\pm 0.09(syst) of this mode. Corresponding quantities for B^- -> D(-> K^+ pi^-)pi^- decay are also reported.Comment: 8 pages, 1 figure, accepted by Phys.Rev.D Rapid Communications for Publicatio

Effect of collective neutrino flavor oscillations on vp-process nucleosynthesis

The vp process is a primary nucleosynthesis process which occurs in core collapse supernovae. An essential role in this process is being played by electron antineutrinos. They generate, by absorption on protons, a supply of neutrons which, by (n,p) reactions, allow to overcome waiting point nuclei with rather long beta-decay and proton-capture lifetimes. The synthesis of heavy elements by the vp process depends sensitively on the \bar{\nu}_e luminosity and spectrum. As has been shown recently, the latter are affected by collective neutrino flavor oscillations which can swap the \bar{\nu}_e and \bar{\nu}_{\mu,\tau} spectra above a certain split energy. Assuming such a swap scenario, we have studied the impact of collective neutrino flavor oscillations on the vp-process nucleosynthesis. Our results show that the production of light p-nuclei up to mass number A=108 is very sensitive to collective neutrino oscillations.Comment: 4 pages, 3 figures, submitted to Physics Letters