Feasibility studies for the measurement of time-like proton electromagnetic form factors from p¯ p→ μ+μ- at P ¯ ANDA at FAIR

This paper reports on Monte Carlo simulation results for future measurements of the moduli of time-like proton electromagnetic form factors, | GE| and | GM| , using the p¯ p→ μ+μ- reaction at P ¯ ANDA (FAIR). The electromagnetic form factors are fundamental quantities parameterizing the electric and magnetic structure of hadrons. This work estimates the statistical and total accuracy with which the form factors can be measured at P ¯ ANDA , using an analysis of simulated data within the PandaRoot software framework. The most crucial background channel is p¯ p→ π+π-, due to the very similar behavior of muons and pions in the detector. The suppression factors are evaluated for this and all other relevant background channels at different values of antiproton beam momentum. The signal/background separation is based on a multivariate analysis, using the Boosted Decision Trees method. An expected background subtraction is included in this study, based on realistic angular distributions of the background contribution. Systematic uncertainties are considered and the relative total uncertainties of the form factor measurements are presented

Beam spin asymmetry measurements of deeply virtual π0 production with CLAS12

The new experimental measurements of beam spin asymmetry were performed for the deeply virtual exclusive pi0 production in a wide kinematic region with the photon virtualities Q2 up to 6.6 GeV2 and the Bjorken scaling variable xB in the valence regime. The data were collected by the CEBAF Large Acceptance Spectrometer (CLAS12) at Jefferson Lab with longitudinally polarized 10.6 GeV electrons scattered on an unpolarized liquid-hydrogen target. Sizable asymmetry values indicate a substantial contribution from transverse virtual photon amplitudes to the polarized structure functions. The interpretation of these measurements in terms of the Generalized Parton Distributions (GPDs) demonstrates their sensitivity to the chiral-odd GPD ET, which contains information on quark transverse spin densities in unpolarized and polarized nucleons and provides access to the nucleon's transverse anomalous magnetic moment. Additionally, the data were compared to a theoretical model based on a Regge formalism that was extended to the high photon virtualities

Entwicklung einer Methodik zur Unterschuchung der Ausfallrate von aktiven implantierten Medizingeräten auf Reiseflughöhen

Einleitung: In unserer immer älter werdenden Gesellschaft wächst die Anzahl der Menschen mit aktiven implantierten Medizingeräten (AIMD) wie Herzschrittmachern und Defibrillatoren. Im Zusammenhang mit der Strahlenexposition durch kosmische Strahlung auf Flugreisen gibt es klinische Berichte über Fehlfunktionen der AIMD. Dazu gehören veränderte Stimulationsparameter, die zu einer Verschlechterung der Symptomatik der Betroffenen bis hin zum Ausfall und Austausch der Geräte führen können. Aus Beobachtungen in der Strahlentherapie ist bekannt, dass dicht-ionisierende Teilchen wie Neutronen den Speicher der Geräte durch Single Event Upsets verändern können. Neutronen sind ein wesentlicher Bestandteil der kosmischen Strahlung auf Reiseflughöhen, deren Rate während starker Weltraumwetterereignissen um einige Größenordnungen ansteigen kann. Daher sind gerade diese Szenarien von besonderem Interesse für die Untersuchung von Fehlfunktionen in AIMD. Fragestellung: Wie kann die Rate bestimmt werden, mit der ein aktives implantiertes Medizingerät während einer Flugreise oder bei einem schweren Weltraumwetterereignis ausfällt? Methodik: Möglich wird dies durch Bestrahlungen der Geräte mit Neutronen und Protonen mit bekannten Energien und Flüssen und der Aufzeichnung und Analyse von Fehlfunktionen. Die Ergebnisse können anschlie- ßend auf verschiedene bekannte Strahlungsumgebungen wie auf Reiseflughöhen oder während schwerer Weltraumwetterereignisse übertragen und eine jeweilige Ausfallrate bestimmt werden. Ergebnis: Bei vorbereitenden Untersuchungen in einfachen Speicherchips konnten Single Event Upsets mit Neutronen und Protonen verschiedener Energien ausgelöst werden. Es konnten Wahrscheinlichkeiten für diese Ereignisse berechnet und eine Rate für Single Event Upsets auf Reiseflughöhen abgeschätzt werden. Schlussfolgerung: Die Untersuchungsmethodik war bereits bei Speicherchips erfolgreich und kann im nächsten Schritt auf aktive implantierte Medizingeräte übertragen werden. Es sollen damit die Ausfallwahrscheinlichkeiten der Geräte bei Neutronen- und Protonenbestrahlung erfasst werden, um anschließend die Ausfallraten in verschiedenen Strahlungsumgebungen abschätzen zu können

Anregungsenergien primaerer Fragmente aus quasielastischen Reaktionen von 8.AMeV "1"1"6Sn mit "4"8Ti

SIGLEAvailable from TIB Hannover: DW 4253 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

In vivo measurements and numerical analysis of the biomechanical characteristics of the human periodontal ligament.

The periodontal ligament is a complex tissue with respect to its biomechanical behaviour. It is important to understand the mechanical behaviour of the periodontal ligament during physiological loading in healthy patients as well as during the movement of the tooth in orthodontic treatment or in patients with periodontal disease, as these might affect the mechanical properties of the periodontal ligament (PDL). Up to now, only a limited amount of in vivo data is available concerning this issue. The aim of this study has been to determine the time dependent material properties of the PDL in an experimental in vivo study, using a novel device that is able to measure tooth displacement intraorally. Using the intraoral loading device, tooth deflections at various velocities were realised in vivo on human teeth. The in vivo investigations were performed on the upper left central incisors of five volunteers aged 21-33 years with healthy periodontal tissue. A deflection, applied at the centre of the crown, was linearly increased from 0 to 0.15mm in a loading period of between 0.1 and 5.0s. Individual numerical models were developed based on the experimental results to simulate the relationship between the applied force and tooth displacement. The numerical force/displacement curves were fitted to the experimental ones to obtain the material properties of the human PDL. For the shortest loading time of 0.1s, the experimentally determined forces were between 7.0 and 16.2N. The numerically calculated Young's modulus varied between 0.9MPa (5.0s) and 1.2MPa (0.1s). By considering the experimentally and numerically obtained force curves, forces decreased with increasing loading time. The experimental data gained in this study can be used for the further development and verification of a multiphasic constitutive law of the PDL

A Situated Model of Creative Learning

This article puts forward a situated model of creative learning. Most educational studies on creativity tend to concentrate on explaining the relation between teaching and creativity while keeping learning as a secondary concept. However, it has been stated that it is likely that teaching creatively leads to creative learning, suggesting that there is a need to describe the concept of creative learning and to analyse its possible constituents. Accordingly, this presentation introduces an empirically based and theoretically informed model of a creative learning community. The model is based on three key concepts or learning principles which can take different forms in particular settings and social practices. These are respectively: (1) Immersion in the topic of interest, in traditions and in the subject matter, (2) Experimentation and inquiry learning and (3) Resistance from the material of interest. As a theoretical point of departure, this presentation will outline a situated model of creativity and learning, and following this, will introduce a model of creative learning. This presentation will include several empirical examples. In the final part, the model will be discussed in relation to the concept of creative teaching