cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Arbeitsintegration – Implementierung eines Learning Management Systems bei der arbeitsmarktlichen Massnahme Berner Stellennetz (AMM BEST). Eine qualitative Analyse aus der Sicht von internen und externen Expertinnen und Experten
Creators: name: Stähli, Tatjana
Publisher: name: Hochschule für Angewandte Psychologie FHNW
Year: 2023
Subjects: subject: Learning Management System
subject: Akzeptanz
subject: Reaktanz
subject: Zielpsychologie
subject: Technologieakzeptanzmodell
subject: Selbstwirksamkeit
subject: Blended Learning
subject: 150 - Psychologie
subject: 003 - Systeme

description: Eine Lernplattform soll gemäss neuem Leistungsauftrag in die Bewerbungskurse bei der arbeitsmarktlichen Massnahme Berner Stellennetz integriert werden. Dabei soll ein Produkt entstehen, welches von den Teilnehmenden akzeptiert und genutzt wird sowie Erkenntnisse aus der Psychologie berücksichtigt. In der Vorliegenden Arbeit wird anhand von qualitativer Forschung in Form von internen und externen Experteninterviews eine Gesamtübersicht geschaffen und Hinweise zur Konzeption und Implementierung der Lernplattform zusammengetragen. Dabei fliessen Erkenntnisse zu den Konstrukten Akzeptanz und Reaktanz ein. Ebenfalls werden Determinanten der modernen Zielpsychologie ermittelt und Handlungsempfehlungen für Inhalte und Gestaltung abgeleitet. Die Determinanten der Machbarkeit und Wünschbarkeit, konkretes vs. abstraktes Denken, Ideal-Selbst vs. Soll-Selbst, implizite Theorien der Fähigkeit und Zielhierarchien können bei der Gestaltung der Lernplattform berücksichtigt werden. Auf der Lernplattform lassen sie sich mittels Erfolgsgeschichten, verschiedener Hilfestellungen für die Zielformulierung, positiver Formulierungen mit Fokus auf Fortschritte und der Abbildung von Lernzielen und Beispielen zu Zielhierarchien abbilden. Zugleich gelten Selbstwirksamkeit und Optimismus als auf die Machbarkeits-Determinante einwirkende Grössen. Selbstwirksamkeit kann mit Erfolgserlebnissen auf der Lernplattform gestärkt werden. Optimismus unterstützt dabei, Ziele zu formulieren und umzusetzen. Die Fachkräfte können mit ihrer Haltung einen Beitrag zur optimistischen Stimmung leisten. Ebenso zentral für eine zielführende Umsetzung sind die Wahrnehmung des Nutzens sowie der Bedienbarkeit der Lernplattform. Diese soll einen hohen Unterhaltungs- sowie Informationswert bieten. Integration von Humor und Referenzpersonen auf der Lernplattform und Partizipation wirken sich positiv auf Widerstände aus. Stets zu berücksichtigen ist die heterogene Zielgruppe. Eine individuelle Auseinandersetzung mit der Lernplattform soll dabei möglich sein und wirkt reaktanzmindernd.
Remote Sensing D/H Ratios in Methane Ice: Temperature-Dependent Absorption Coefficients of CH3D in Methane Ice and in Nitrogen Ice
Creators: name: Grundy, W. M.
name: Morrison, S. J.
name: Bovyn, M. J.
name: Tegler, S. C.
name: Cornelison, D. M.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences

description: The existence of strong absorption bands of singly deuterated methane (CH3D) at wavelengths where normal methane (CH4) absorbs comparatively weakly could enable remote measurement of D/H ratios in methane ice on outer solar system bodies. We performed laboratory transmission spectroscopy experiments, recording spectra at wavelengths from 1 to 6 \mum to study CH3D bands at 2.47, 2.87, and 4.56 \mum, wavelengths where ordinary methane absorption is weak. We report temperature-dependent absorption coefficients of these bands when the CH3D is diluted in CH4 ice and also when it is dissolved in N2 ice, and describe how these absorption coefficients can be combined with data from the literature to simulate arbitrary D/H ratio absorption coefficients for CH4 ice and for CH4 in N2 ice. We anticipate these results motivating new telescopic observations to measure D/H ratios in CH4 ice on Triton, Pluto, Eris, and Makemake.
description: 17 pages, 7 figures
Entwicklung und Evaluation eines Feedbackkonzeptes für Online-Self-Assessments
Creators: name: Pässler, Katja
name: Mitrovic, Tanja
Publisher: name: Fachhochschule Nordwestschweiz FHNW
Year: 2023
Subjects: subject: 150 - Psychologie

description: Dieser Beitrag präsentiert ein Feedbackkonzept, das entwickelt wurde, um psychologisch-diagnostische Informationen für Studieninteressierte möglichst zielgruppengerecht darzustellen. Online-Self-Assessments (OSAs) sind als Selbsttests zur Studienorientierung konzipiert, die von Studieninteressierten meist ohne fachliche Begleitung oder Einbettung in eine Beratungssituation genutzt werden. Allerdings zeigt sich, dass das Feedback für Ratsuchende häufig zu komplex formuliert und dargestellt wird und nur mit Erläuterungen durch Dritte vollumfänglich verständlich ist, gerade dann, wenn psychologisch-diagnostische Informationen vermittelt werden. Dies kann bei Studieninteressierten zu Fehlinterpretationen und Demotivation führen z.B. wenn aufgrund von Fehlannahmen eine fehlende Passung zum Studiengang geschlussfolgert wird. Der Beitrag stellt ein Feedbackkonzept vor, das in einem mehrstufigen Iterationsprozess mit Studieninteressierten entwickelt und evaluiert wurde. Zunächst wurde eine umfassende Analyse bestehender Feedbackformate und ihrer Einschränkungen durchgeführt. Basierend auf dieser Analyse wurden verschiedene Prototypen des Feedbackkonzepts entworfen und in zwei Fokusgruppendiskussionen mit Studieninteressierten erprobt. Hauptaugenmerk lag dabei auf der Verständlichkeit der Ergebnisinterpretation und der Frage, wie diese durch die grafische Gestaltung des Feedbacks und die inhaltliche Ausrichtung der Feedbacktexte verbessert werden kann. Anschliessend wurde das Feedbackkonzept umgesetzt und mit mehreren Nutzer*innen einem Usability-Test unterzogen. Aufbauend auf den Ergebnissen des Usability-Tests wurde die Umsetzung des Feedbacks nochmals angepasst und verbessert. In einem letzten Schritt wurde der Fragebogen mit individualisiertem Feedback nochmals in einer quantitativen Befragung mit Studieninteressierten erprobt. Der iterative Prozess gewährleistete, dass das Feedbackkonzept auf die spezifischen Bedürfnisse und Anforderungen der Studieninteressierten abgestimmt wurde. Die Ergebnisse der Evaluation verdeutlichen die Wirksamkeit des entwickelten Feedbackkonzepts. Die Nutzer*innen schätzen die Verständlichkeit der Ergebnisdarstellung als sehr hoch ein und erkennen deren Relevanz für die Bewertung ihrer individuellen Passung zu den Anforderungen des Studiengangs. Das vorgeschlagene Feedbackkonzept verdeutlicht, wie verschiedene Schwierigkeiten herkömmlicher komplexer Feedbackformate durch bestimmte grafische und inhaltliche Anpassung überwunden werden können. Die Studie zeigt außerdem die Bedeutung der Einbindung der Zielgruppe, um die Verständlichkeit und Benutzerfreundlichkeit des Feedbacks sicherzustellen, wenn psychologisch-diagnostische Informationen ohne fachliche Begleitung interpretiert werden.
Telescopes don't make catalogues!
Creators: name: Hogg, David W.
name: Lang, Dustin
Publisher: name: arXiv
Year: 2010
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Data Analysis, Statistics and Probability (physics.data-an)
subject: FOS: Physical sciences

description: Astronomical instruments make intensity measurements; any precise astronomical experiment ought to involve modeling those measurements. People make catalogues, but because a catalogue requires hard decisions about calibration and detection, no catalogue can contain all of the information in the raw pixels relevant to most scientific investigations. Here we advocate making catalogue-like data outputs that permit investigators to test hypotheses with almost the power of the original image pixels. The key is to provide users with approximations to likelihood tests against the raw image pixels. We advocate three options, in order of increasing difficulty: The first is to define catalogue entries and associated uncertainties such that the catalogue contains the parameters of an approximate description of the image-level likelihood function. The second is to produce a K-catalogue sampling in "catalogue space" that samples a posterior probability distribution of catalogues given the data. The third is to expose a web service or equivalent that can re-compute on demand the full image-level likelihood for any user-supplied catalogue.
description: presented at ELSA 2010: Gaia, at the frontiers of astrometry
SWAP-SECCHI Observations of a Mass-Loading Type Solar Eruption
Creators: name: Seaton, Daniel B.
name: Mierla, Marilena
name: Berghmans, David
name: Zhukov, Andrei N.
name: Dolla, Laurent
Publisher: name: arXiv
Year: 2010
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Space Physics (physics.space-ph)
subject: FOS: Physical sciences

description: We present a three-dimensional reconstruction of an eruption that occurred on 3 April 2010 using observations from SWAP onboard PROBA2 and SECCHI onboard STEREO. The event unfolded in two parts: an initial flow of cooler material confined to low in the corona, followed by a flux rope eruption higher in the corona. We conclude that mass off-loading from the first part triggered a rise, and, subsequently, catastrophic loss of equilibrium of the flux rope.
description: 3 figures
Spatially highly resolved study of AFM scanning tip–quantum dot local interaction
Creators: name: Kičin, S.
name: Pioda, A.
name: Ihn, Thomas
name: Sigrist, Martin
name: Fuhrer, A.
name: Ensslin, Klaus
name: Reinwald, Matthias
name: Wegscheider, Werner
Publisher: name: Universität Regensburg
Year: 2005
Subjects: subject: 530 Physik

description: Scanning-gate imaging of semiconductor quantum dots (QDs) promises access to probability distributions of quantum states. It could therefore be a novel tool for designing and optimizing tailored quantum states in such systems. A detailed study of a lithographically defined semiconductor QD in the Coulomb-blockade regime is presented, making use of the scanning-gate technique at a base temperature of 300 mK. The method allows a one-by-one manipulation of electrons in the structure. The obtained images interpreted with a suitable QD model guide the way to a local investigation of the electronic interior of the QD. Future perspectives of scanning-gate experiments on QDs are discussed.
Development and Application of Transmission Electron Microscopy for Colossal Magnetoresistance Materials
Creators: name: CHAO, WEI
Publisher: name: Monash University
Year: 2022
Subjects: subject: 100712 Nanoscale Characterisation
subject: FOS: Nanotechnology

description: Colossal magnetoresistance (CMR) materials are promising for spintronics, which uses spins instead of charges to transfer information. However, the application is currently limited by the low transition temperature and large magnetic field required. In this thesis, we use high-energy electrons as a probe to directly observe these materials on the atomic scale. The short wavelength and strong interaction of electrons with atoms allow us to look at the materials with high spatial resolution and high sensitivity. Our developed experimental and analysis techniques provide new insights into the structure-properties relationships of such CMR materials.
Non-equilibrium phase transition in a sheared granular mixture
Creators: name: Garzo, V.
name: Trizac, E.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: The dynamics of an impurity (or tracer particle) immersed in a dilute granular gas under uniform shear flow is investigated. A non-equilibrium phase transition is identified from an exact solution of the inelastic Boltzmann equation for a granular binary mixture in the tracer limit, where the impurity carries either a vanishing (disordered phase) or a finite (ordered phase) fraction of the total kinetic energy of the system. In the disordered phase, the granular temperature ratio (impurity "temperature" over that of the host fluid) is finite, while it diverges in the ordered phase. To correctly capture this extreme violation of energy equipartition, we show that the picture of an impurity enslaved to the host fluid is insufficient.
Magneto-gyrotropic photogalvanic effects in semiconductor quantum wells
Creators: name: Belkov, Vassilij
name: Ganichev, Sergey
name: Ivchenko, Eougenious
name: Tarasenko, Sergey
name: Weber, Wolfgang
name: Giglberger, Stephan
name: Olteanu, M.
name: Tranitz, Hans-Peter
name: Danilov, Sergey
name: Schneider, Petra
name: Wegscheider, Werner
name: Weiss, Dieter
name: Prettl, Wilhelm
Publisher: name: Universität Regensburg
Year: 2005
Subjects: subject: 530 Physik

description: We show that free-carrier (Drude) absorption of both polarized and unpolarized terahertz radiation in quantum well (QW) structures causes an electric photocurrent in the presence of an in-plane magnetic field. Experimental and theoretical analysis evidences that the observed photocurrents are spin dependent and related to the gyrotropy of the QWs. Microscopic models for the photogalvanic effects in QWs based on asymmetry of photoexcitation and relaxation processes are proposed. In most of the investigated structures the observed magneto-induced photocurrents are caused by spin-dependent relaxation of non-equilibrium carriers.
Notes on "quantum gravity" and non-commutative geometry
Creators: name: Gracia-Bondia, Jose M.
Publisher: name: arXiv
Year: 2010
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: I hesitated for a long time before giving shape to these notes, originally intended for preliminary reading by the attendees to the Summer School "New paths towards quantum gravity" (Holbaek Bay, Denmark, May 2008). At the end, I decide against just selling my mathematical wares, and for a survey, necessarily very selective, but taking a global phenomenological approach to its subject matter. After all, non-commutative geometry does not purport yet to solve the riddle of quantum gravity; it is more of an insurance policy against the probable failure of the other approaches. The plan is as follows: the introduction invites students to the fruitful doubts and conundrums besetting the application of even classical gravity. Next, the first experiments detecting quantum gravitational states inoculate us a healthy dose of skepticism on some of the current ideologies. In Section 3 we look at the action for general relativity as a consequence of gauge theory for quantum tensor fields. Section 4 briefly deals with the unimodular variants. Section 5 arrives at non-commutative geometry. I am convinced that, if this is to play a role in quantum gravity, commutative and non-commutative manifolds must be treated on the same footing; which justifies the place granted to the reconstruction theorem. Together with Section 3, this part constitutes the main body of the notes. Only very summarily at the end of this section we point to some approaches to gravity within the non-commutative realm. The last section delivers a last dose of skepticism. My efforts will have been rewarded if someone from the young generation learns to mistrust current mindsets.
description: 54 pages. Proceedings of the Summer School "New paths towards quantum gravity", Holbaek, Denmark; B. Booss-Bavnbek, G. Esposito and M. Lesch, eds. Springer, Berlin, 2010; pp. 3-58
Study of the localization-delocalization transition for phonons via transfer matrix method techniques
Creators: name: Pinski, Sebastian D.
name: Roemer, Rudolf A.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Disordered Systems and Neural Networks (cond-mat.dis-nn)
subject: FOS: Physical sciences

description: We use a transfer-matrix method to study the localization properties of vibrations in a `mass and spring' model with simple cubic lattice structure. Disorder is applied as a box-distribution to the force-constants $k$ of the springs. We obtain the reduced localization lengths $Λ_M$ from calculated Lyapunov exponents for different system widths to roughly locate the squared critical transition frequency $ω_{\text{c}}^2$. The data is finite-size scaled to acquire the squared critical transition frequency of $ω_{\text{c}}^2 = 12.54 \pm 0.03$ and a critical exponent of $ν= 1.55 \pm 0.002$.
description: 6 pages, 3 figures, 1 table, conference proceedings
Excitonic signature in gain and carrier induced change of refractive index spectra of (In,Al)GaN quantum well lasers
Creators: name: Schwarz, Ulrich
name: Sturm, Evi
name: Wegscheider, Werner
name: Kümmler, V.
name: Lell, Alfred
name: Härle, Volker
Publisher: name: Universität Regensburg
Year: 2004
Subjects: subject: indium compounds, aluminium compounds, gallium compounds, III-V semiconductors, wide band gap semiconductors, quantum well lasers, excitons, refractive index, spectral line shift, electroluminescence, quantum confined Stark effect, semiconductor plasma, carrier density
subject: 530 Physik
subject: 42.55.Px; 85.35.Be; 71.35.Ee; 72.30.+q; 78.20.Ci; 78.67.De; 78.60.Fi

description: The exciton is observed in (In,Al)GaN laser diodes as resonance in the optical gain spectra and in the spectra of the carrier induced change of the refractive index. The observed instability of the exciton with respect to the free electron-hole plasma with increasing carrier densities is accompanied by a blueshift of the exciton resonance due to the quantum confined Stark shift. The experiments confirm central points of many-body simulations of InGaN/GaN quantum wells. The exciton becomes unstable near threshold and so lasing occurs from the electron–hole plasma.
Spin relaxation due to electron-electron magnetic interaction in high Lande g-factor semiconductors
Creators: name: Kamra, Akashdeep
name: Ghosh, Bahniman
name: Ghosh, Tarun K.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: We investigate spin transport in InSb/InAlSb heterostructure using the Monte Carlo approach, generalized by including density matrix description of spin for taking spin dynamics into account. In addition to the dominant Dyakonov-Perel (DP) mechanism for spin control and relaxation, we consider magnetic interaction between electrons which assumes importance due to high electronic Lande g-factor in the material. It is found that while the effect of magnetic interaction is not important at low densities, it reduces the spin relaxation length by as much as 50% at higher densities. We also present a calculation which elucidates the suppression of decoherence attributed to wave vector dependent magnetic field in the DP relaxation mechanism. We note that magnetic interaction is a general relaxation mechanism which may assume importance in materials with high electronic Lande g-factor.
description: accepted for publication in Journal of Applied Physics
WSR Maximized Resource Allocation in Multiple DF Relays Aided OFDMA Downlink Transmission
Creators: name: Wang, Tao
name: Vandendorpe, Luc
Publisher: name: arXiv
Year: 2011
Subjects: subject: Information Theory (cs.IT)
subject: Systems and Control (eess.SY)
subject: Optimization and Control (math.OC)
subject: FOS: Computer and information sciences
subject: FOS: Electrical engineering, electronic engineering, information engineering
subject: FOS: Mathematics

description: This paper considers the weighted sum rate (WSR) maximized resource allocation (RA) constrained by a system sum power in an orthogonal frequency division multiple access (OFDMA) downlink transmission system assisted by multiple decode-and-forward (DF) relays. In particular, multiple relays may cooperate with the source for every relay-aided transmission. A two-step algorithm is proposed to find the globally optimum RA. In the first step, the optimum source/relay power and assisting relays that maximize the rate is found for every combination of subcarrier and destination, assuming a sum power is allocated to the transmission at that subcarrier to that destination in the relay-aided transmission mode and the direct mode, respectively. In the second step, a convex-optimization based algorithm is designed to find the globally optimum assignment of destination, transmission mode, and sum power for each subcarrier to maximize the WSR. Combining the RAs found in the two steps, the globally optimum RA can be found. In addition, we show that the optimum RA in the second step can readily be derived when the system sum power is very high. The effectiveness of the proposed algorithm is illustrated by numerical experiments.
description: 13 pages and 14 figures, to appear in IEEE Transactions Signal Processing
title: Universität Kassel, Vorlesungsverzeichnis WiSe 2015 / 2016
Creators: name: (:Unkn) Unknown
Publisher: name: Universität Kassel
Year: 2015
Subjects: subject: 350
subject: 370
subject: Universität Kassel
subject: Vorlesungsverzeichnis

description: PDF zum Online-Vorlesungsverzeichnis
Stochastic dynamic programming optimization model for operations planning of a multireservoir hydroelectric system
Creators: name: Ayad, Amr
Publisher: name: University of British Columbia
Year: 2018

description: This thesis presents a Stochastic Dynamic Programming (SDP) modeling algorithm to model six hydropower plants in British Columbia (BC), Canada. The main output of the algorithm is the water value function for the two biggest reservoirs in BC, Williston and Kinbasket reservoirs. The AMPL programming language was used to implement the algorithm. Extensive testing has shown that the program is able to solve the problem producing acceptable water value and marginal value functions up to a problem size of ~ 164 million states per time step using the computing resources available on one of the BC Hydro’s servers. The objective of the work presented here was to assess the sensitivity of solution efficiency and precision for several storage state and decision space discretizations. The impact of introducing a storage state-space corridor, as an alternative of the traditional fixed storage state-space, was investigated. In addition, the sensitivity of the modeling results to different spill penalty values was analyzed. It was found that finer state-space increments give more precise results but the granularity was limited to the computing resources available. Introducing the storage state-space corridor provided several advantages; nevertheless, care should be taken in the design of such corridors so that the solution efficiency and accuracy are not jeopardized. Also, recommendations on the use of suitable spill penalty value are provided. Flexibility is one important feature of the modeling algorithm. This flexibility is a result of optimizing the algorithm and the organization of the code, which provided control over the increment of the state-spaces and the storage corridor, the ability to run the problem for one storage reservoir while fixing the state of the other storage reservoir and the ability of the user to run the model either directly on a personal computer/server using the command prompt or by using a scheduling program to optimize the use and sharing of computing assets. Further enhancements of the algorithm will enable the model developed in this thesis to handle much larger problems but will likely still suffer from the limitations due to the inherent curse of dimensionality in modeling using the SDP algorithm.
The Double-Peaked 2008 Outburst of the Accreting Milli-Second X-ray Pulsar, IGR J00291+5934
Creators: name: Lewis, F.
name: Russell, D. M.
name: Jonker, P. G.
name: Linares, M.
name: Tudose, V.
name: Roche, P.
name: Clark, J. S.
name: Torres, M. A. P.
name: Maitra, D.
name: Bassa, C. G.
name: Steeghs, D.
name: Patruno, A.
name: Migliari, S.
name: Wijnands, R.
name: Nelemans, G.
name: Kewley, L. J.
name: Stroud, V. E.
name: Modjaz, M.
name: Bloom, J. S.
name: Blake, C. H.
name: Starr, D.
Publisher: name: arXiv
Year: 2010
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: In August 2008, the accreting milli-second X-ray pulsar (AMXP), IGR J00291+5934, underwent an outburst lasting ~ 100 days, the first since its discovery in 2004. We present data from the double-peaked outburst from Faulkes Telescope North, the INT, the Keck Telescope, PAIRITEL, the Westerbork Synthesis Radio Telescope and the Swift, XMM-Newton and RXTE X-ray missions. We study the outburst's evolution at various wavelengths. We study the light curve morphology, presenting the first radio-X-ray Spectral Energy Distributions (SEDs) for this source and the most detailed UV-IR SEDs for any outbursting AMXP. We show simple models that attempt to identify the emission mechanisms responsible. We analyse short-timescale optical variability, and compare a medium resolution optical spectrum with those from 2004. The outburst morphology is unusual for an AMXP, comprising two peaks, the second containing a 'plateau' of ~ 10 days at maximum brightness within 30 days of the initial activity. This has implications on duty cycles of short-period X-ray transients. The X-ray spectrum can be fitted by a single, hard power-law. We detect optical variability of ~ 0.05 magnitudes, on timescales of minutes, but find no periodic modulation. In the optical, the SEDs contain a blue component, indicative of an irradiated disc, and a transient near-infrared (NIR) excess. This excess is consistent with a simple model of an optically thick synchrotron jet (as seen in other outbursting AMXPs). The optical spectrum shows a double-peaked H alpha profile, a diagnostic of an accretion disc, but we do not clearly see other lines (e.g. He I, II) reported in 2004. Optical/IR observations of AMXPs are excellent for studying the evolution of both the outer accretion disc and the inner jet, and may eventually provide us with tight constraints to model disc-jet coupling in accreting neutron stars.
description: 15 pages, 10 figures, accepted for publication in A&A
Carbon-doped high-mobility two-dimensional hole gases on (110) faced GaAs
Creators: name: Schmult, Stefan
name: Gerl, Christian
name: Wurstbauer, Ursula
name: Mitzkus, Christian
name: Wegscheider, Werner
Publisher: name: Universität Regensburg
Year: 2005
Subjects: subject: gallium arsenide, aluminium compounds, carbon, III-V semiconductors, semiconductor heterojunctions, hole mobility, semiconductor doping
subject: 530 Physik
subject: 81.05.Ea; 73.40.Kp;73.61.Ey; 72.20.Fr; 61.72.Vv;

description: Carbon-doped high-mobility two-dimensional hole gases grown on (110) oriented GaAs substrates have been grown with hole mobilities exceeding 106 cm2/Vs in single heterojunction GaAs/AlGaAs structures. At these high mobilities, a pronounced mobility anisotropy has been observed. Rashba induced spin-splitting in these asymmetric structures has been found to be independent on the transport direction.
Large deviations for disordered bosons and multiple orthogonal polynomial ensembles
Creators: name: Eichelsbacher, Peter
name: Sommerauer, Jens
name: Stolz, Michael
Publisher: name: arXiv
Year: 2011
Subjects: subject: Mathematical Physics (math-ph)
subject: FOS: Physical sciences
subject: 60F10, 15B52, 33C45, 60B20

description: We prove a large deviations principle for the empirical measures of a class of biorthogonal and multiple orthogonal polynomial ensembles that includes biorthogonal Laguerre, Jacobi and Hermite ensembles, the matrix model of Lueck, Sommers and Zirnbauer for disordered bosons, the Stieltjes-Wigert matrix model of Chern-Simons theory, and Angelesco ensembles.
description: 20 pages
Study of two dimensional materials graphene and FeSe
Creators: name: Yang, Rui
Publisher: name: University of British Columbia
Year: 2018

description: The properties of several two-dimensional (2d) materials are studied. The main content is the study of magnetic impurities in graphene through phase coherent transport phenomena, including weak localization (WL) and universal conductance fluctuations (UCF). Magnetic impurities manifest themselves in the in-plane magnetic field and temperature dependence of the dephasing (phase breaking) rate. Our experiments unambiguously reveal the existence of magnetic impurities through the in-plane magnetic field dependence of WL and UCF. The properties of the magnetic impurities are further studied through the dephasing rate as a function of magnetic field and temperature. The WL dephasing rate as a function of in-plane magnetic field shows a non-monotonic behaviour, which is rooted in the existence of magnetic impurities with a Landé g factor different from that of the free electron. The collapse of the dephasing rate as a function of temperature is a sign of the quenching of magnetic impurities, which could come from Kondo coupling between magnetic impurities and conduction electrons or Ruderman-Kittel-Kasuya-Yosida (RKKY) coupling between magnetic impurities. The implications of our graphene experiments are two-fold: on the one hand, they provide new knowledge about the interplay among magnetic moments and electrons in graphene; on the other hand, they also established an effective tool to reveal the existence of magnetic impurities in 2d systems. In addition to graphene, we also studied the exfoliation and stability of thin sheets of FeSe -- a member of the Fe-based superconductors family. Our Raman Spectroscopy, Atomic Force Microscopy, Optical Microscopy and Time-of-Flight-Secondary-Ion-Mass-Spectroscopy experiments show that FeSe nanosheets decay in air, precipitation of Se and oxidation likely occurring during the decay process. Our transport measurements show that FeSe nanosheets exposed briefly to air can still retain superconductivity.
Complex-Valued Random Vectors and Channels: Entropy, Divergence, and Capacity
Creators: name: Tauboeck, Georg
Publisher: name: arXiv
Year: 2011
Subjects: subject: Information Theory (cs.IT)
subject: FOS: Computer and information sciences

description: Recent research has demonstrated significant achievable performance gains by exploiting circularity/non-circularity or propeness/improperness of complex-valued signals. In this paper, we investigate the influence of these properties on important information theoretic quantities such as entropy, divergence, and capacity. We prove two maximum entropy theorems that strengthen previously known results. The proof of the former theorem is based on the so-called circular analog of a given complex-valued random vector. Its introduction is supported by a characterization theorem that employs a minimum Kullback-Leibler divergence criterion. In the proof of latter theorem, on the other hand, results about the second-order structure of complex-valued random vectors are exploited. Furthermore, we address the capacity of multiple-input multiple-output (MIMO) channels. Regardless of the specific distribution of the channel parameters (noise vector and channel matrix, if modeled as random), we show that the capacity-achieving input vector is circular for a broad range of MIMO channels (including coherent and noncoherent scenarios). Finally, we investigate the situation of an improper and Gaussian distributed noise vector. We compute both capacity and capacity-achieving input vector and show that improperness increases capacity, provided that the complementary covariance matrix is exploited. Otherwise, a capacity loss occurs, for which we derive an explicit expression.
description: 33 pages, 1 figure, slightly modified version of first paper revision submitted to IEEE Trans. Inf. Theory on October 31, 2010
Influence of manganese contamination on high-mobility GaAs/AlGaAs heterostructures
Creators: name: Wagenhuber, Klaus
name: Tranitz, H.-P.
name: Reinwald, Matthias
name: Wegscheider, Werner
Publisher: name: Universität Regensburg
Year: 2004
Subjects: subject: gallium arsenide, aluminium compounds, III-V semiconductors, semiconductor heterojunctions, photoluminescence, molecular beam epitaxial growth, semiconductor growth, semiconductor epitaxial layers, electron mobility, galvanomagnetic effects, manganese
subject: 530 Physik
subject: 73.61.Ey; 78.66.Fd; 81.05.Ea; 81.15.Hi; 78.55.Cr; 73.40.Kp; 73.50.Dn; 73.50.Jt

description: Photoluminescence and magnetotransport measurements have been performed to assess the quality of modulation-doped GaAs/AlGaAs heterostructures. The temporal evolution of the low-temperature electron mobility of samples prepared in a molecular-beam-epitaxy chamber containing manganese as a source material was studied. Mn contamination was identified to be responsible for the reduction of the electron mobility to 1×106 cm2/V s and the appearance of a distinct photoluminescence band. In contrast, structures in which this signal is absent reach mobility values of 5.4×106 cm2/V s. This directly proves that the epitaxy of high-mobility electron systems and structures containing GaMnAs layers, in principle, can be combined in one growth chamber.
Universal, additive effect of temperature on the rheology of amorphous solids
Creators: name: Chattoraj, Joyjit
name: Caroli, Christiane
name: Lemaître, Anaël
Publisher: name: arXiv
Year: 2010
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: Extensive measurements of macroscopic stress in a 2D LJ glass, over a broad range of temperatures ($T$) and strain rates ($\dotγ$), demonstrate a very significant decrease of the flowing stress with $T$, even much below the glass transition. A detailed analysis of the interplay between loading, thermal activation, and mechanical noise leads us to propose that over a broad ($\dotγ,T$) region, the effect of temperature amounts to a mere lowering of the strains at which plastic events occur, while the athermal avalanche dynamics remains essentially unperturbed. Temperature is then shown to correct the athermal stress by a (negative) additive contribution which presents a universal form, thus bringing support to and extending an expression proposed by Johnson and Samwer [1]. Our prediction is shown to match strikingly well numerical data up to the vicinity of $T_g$.
Using the Check-All-That-Apply (CATA) methodology to evaluate the flavour of foreign global and domestic Chinese coffee products
Creators: name: Chen, Yan Ping
name: Julaiti, Xiayidan
name: Guo, Chenyang
name: Blank, Imre
name: Zhou, Disheng
name: Yu, Lingxiao
name: Liu, Yuan
Publisher: name: Zenodo
Year: 2022
Subjects: Chinese coffee
check-all-that-apply (CATA)
consumer preference
principal coordinate analysis

description: The Chinese coffee consumption is growing with the domestic market mainly dominated by imported coffee beans and coffee brands. In this study, the check-all-that-apply (CATA) method was used to evaluate two groups of coffee products. One group was consisting of commercial samples containing four foreign and four domestic brands. The other group comprised lab-roasted samples using raw coffee beans grown in China, in the Yunnan province. The hedonic scores of each sample were collected to present subjects’ liking intensities. The results showed that Chinese young subjects participating in this study preferred coffee with cocoa, caramel, nutty aroma, and a distinct mouthfeel. They also prefer coffee with milder bitter and less sour taste. Over-roasting Yunnan coffee beans may cause undesired musty sensation, while mild thermal processing tend to result in lower roasted notes. This study provided an efficient way to obtain sensory profiles of coffee samples using CATA. Different from the traditional consumer survey, this method presents clues for the coffee industry to optimise their products, which resonate with Chinese consumers’ sensory preference.
Nanometre spaced electrodes on a cleaved AlGaAs surface
Creators: name: Luber, Sebastian M.
name: Strobel, Sebastian
name: Tranitz, Hans-Peter
name: Wegscheider, Werner
name: Schuh, Dieter
name: Tornow, Marc
Publisher: name: Universität Regensburg
Year: 2005
Subjects: subject: 530 Physik

description: We present a novel technique for fabricating nanometre spaced metal electrodes on a smooth crystal cleavage plane with precisely predetermined spacing. Our method does not require any high-resolution nanolithography tools, all lateral patterning being based on conventional optical lithography. Using molecular beam epitaxy we embedded a thin gallium arsenide (GaAs) layer in between two aluminium gallium arsenide (AlGaAs) layers with monolayer precision. By cleaving the substrate an atomically flat surface is obtained exposing the AlGaAs–GaAs sandwich structure. After selectively etching the GaAs layer, the remaining AlGaAs layers are used as a support for deposited thin film metal electrodes. We characterized these coplanar electrodes by atomic force microscopy and scanning electron microscopy; this revealed clean, symmetric and macroscopically flat surfaces with a maximum corrugation of less than 1.2 nm. In the case of a device with a 20 nm thick GaAs layer the measured electrode distance was 22.5 nm with a maximum deviation of less than 2.1 nm. To demonstrate the electrical functionality of our device we positioned single colloidal gold nanoparticles between the electrodes by an alternating voltage trapping method; this resulted in a drop of electrical resistance from ~11 G Ω to ~1.5 k Ω at 4.2 K. The device structure has large potential for the manipulation of nanosized objects like molecules or more complex aggregates on flat surfaces and the investigation of their electrical properties in a freely suspended configuration.
Strong coupling treatment of the polaronic system consisting of an impurity in a condensate
Creators: name: Casteels, W.
name: Van Cauteren, T.
name: Tempere, J.
name: Devreese, J. T.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Quantum Gases (cond-mat.quant-gas)
subject: FOS: Physical sciences

description: The strong coupling treatment of the Fröhlich-type polaronic system, based on a canonical transformation and a standard Landau-Pekar type variational wave function, is applied to the polaronic system consisting of an impurity in a condensate. Within this approach the Relaxed Excited States are retrieved as a typical polaronic feature in the energy spectrum. For these states we calculate the corresponding effective mass and the minimal coupling constant required for them to occur. The present approach allows to derive approximate expressions for the transition energies between different Relaxed Excited States in a much simpler way than with the full Mori-Zwanzig approach, and with a good accuracy, which improves with increasing coupling. The transition energies obtained here can be used as the spectroscopic fingerprint for the experimental observation of Relaxed Excited States of impurities in a condensate.
Spin effects in a quantum ring
Creators: name: Ihn, Thomas
name: Fuhrer, A.
name: Ensslin, Klaus
name: Wegscheider, Werner
name: Bichler, Max
Publisher: name: Universität Regensburg
Year: 2005
Subjects: subject: Quantum dots; Quantum computing; Exchange effects; Zeeman splitting
subject: 530 Physik
subject: 73.23.−b; 03.67.Lx

description: Recent experiments that are reviewed explore the spin states of a ring-shaped many-electron quantum dot. Coulomb-blockade spectroscopy is used to access the spin degree of freedom. The Zeeman effect observed for states with successive electron number allows to select possible sequences of spin ground states of the ring. Spin-paired orbital levels can be identified by probing their response to magnetic fields normal to the plane of the ring and electric fields caused by suitable gate voltages. This narrows down the choice of ground-state spin sequences. A gate-controlled singlet–triplet transition is identified and the size of the exchange interaction matrix element is determined.
Coupling symmetry of quantum dot states
Creators: name: Rogge, M. C.
name: Harke, B.
name: Fricke, C.
name: Hohls, F.
name: Reinwald, Matthias
name: Wegscheider, Werner
name: Haug, R. J.
Publisher: name: Universität Regensburg
Year: 2005
Subjects: subject: 530 Physik
subject: 73.63.Kv, 73.23.Hk, 73.21.La

description: With noninvasive methods, we investigate ground and excited states of a lateral quantum dot. Charge detection via a quantum point contact is used to map the dot dynamics in a regime where the current through the dot is too low for transport measurements. In this way we investigate and compare the tunneling rates from the dot to source and drain. We find a symmetry line on which the tunneling rates to both leads are equal. In this situation ground states as well as excited states influence the mean charge of the dot. A detailed study in this regime reveals that the coupling symmetry depends on the number of states contributing to transport and on the spatial distribution of individual states.
Strong impact of light induced conical intersections on the spectrum of diatomic molecules
Creators: name: Sindelka, Milan
name: Moiseyev, Nimrod
name: Cederbaum, Lorenz S.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Atomic Physics (physics.atom-ph)
subject: Chemical Physics (physics.chem-ph)
subject: FOS: Physical sciences

description: We show that dressing of diatomic molecules by running laser waves gives rise to conical intersections (CIs). Due to presence of such CIs, the rovibronic molecular motions are strongly coupled. A pronounced impact of the CI on the spectrum of $Na_2$ molecule is demonstrated via numerical calculation for weak and moderate laser intensity, and an experiment is suggested on this basis. The position of the light induced CI and the strength of its non-adiabatic couplings can be chosen by changing the frequency and intensity of the used running laser wave. This offers new possibilities to control the photo-induced rovibronic molecular dynamics.
description: 4 pages, 7 figures
Probing coherent electronic states in double quantum dots
Creators: name: Qin, H.
name: Holleitner, A. W.
name: Wegscheider, Werner
name: Hüttel, Andreas K.
name: Blick, Robert H.
name: Bichler, Max
name: Eberl, Karl
name: Kotthaus, Jörg P.
Publisher: name: Universität Regensburg
Year: 2004
Subjects: subject: 530 Physik
subject: 03.65.Ud; 03.67.-a; 73.21.La; 73.23.Hk

description: Experimental results on both serial and parallel double quantum dots are presented. The quantum dots are realized in the two-dimensional electron gas of an AlGaAs/GaAs heterostructure. By varying the inter-dot tunnel barriers, double quantum dots are tuned from the weak coupling limit to the strong coupling case. In serial double quantum dots, bonding and anti-bonding molecular states are probed by both direct tunneling and photon-assisted tunneling spectroscopy. In parallel double quantum dots, a coherent transport through the whole structure is verified through Aharonov-Bohm oscillations in the magnetotransport data. Furthermore, coherent molecular states are read out by a cotunneling current. Finally, a scheme for preparing and measuring a solid-state quantum bit is discussed.
New Vector Boson Near the Z-pole and the Puzzle in Precision Electroweak Data
Creators: name: Dermisek, Radovan
name: Kim, Sung-Gi
name: Raval, Aditi
Publisher: name: arXiv
Year: 2011
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Experiment (hep-ex)
subject: FOS: Physical sciences

description: We show that a Z' with suppressed couplings to the electron compared to the Z-boson, with couplings to the b-quark, and with a mass close to the mass of the Z-boson, provides an excellent fit to forward-backward asymmetry of the b-quark and R_b measured on the Z-pole and $\pm 2$ GeV off the Z-pole, and to A_e obtained from the measurement of left-right asymmetry for hadronic final states. It also leads to a significant improvement in the total hadronic cross section on the Z-pole and R_b measured at energies above the Z-pole. In addition, with a proper mass, it can explain the excess of $Zb\bar b$ events at LEP in the 90-105 GeV region of the $b\bar b$ invariant mass.
description: 10 pages, 1 figure
Sustained-release solid dispersion of pelubiprofen using the blended mixture of aminoclay and pH independent polymers: preparation and in vitro/in vivo characterization
Creators: name: Lee, Yeo-Song
name: Song, Jae Guen
name: Lee, Sang Hoon
name: Han, Hyo-Kyung
Publisher: name: Taylor & Francis
Year: 2017
Subjects: subject: Biophysics
subject: Biochemistry
subject: Space Science
subject: Medicine
subject: Physiology
subject: FOS: Biological sciences
subject: Pharmacology
subject: 39999 Chemical Sciences not elsewhere classified
subject: FOS: Chemical sciences
subject: 69999 Biological Sciences not elsewhere classified
subject: Cancer
subject: Hematology
subject: Computational Biology

description: The present study aimed to develop the sustained-release oral dosage form of pelubiprofen (PEL) by using the blended mixture of 3-aminopropyl functionalized-magnesium phyllosilicate (aminoclay) and pH-independent polymers. The sustained-release solid dispersion (SRSD) was prepared by the solvent evaporation method and the optimal composition of SRSD was determined as the weight ratio of drug: Eudragit® RL PO: Eudragit® RS PO of 1:1:2 in the presence of 1% of aminoclay (SRSD(F6)). The dissolution profiles of SRSD(F6) were examined at different pHs and in the simulated intestinal fluids. The drug release from SRSD(F6) was limited at pH 1.2 and gradually increased at pH 6.8, resulting in the best fit to Higuchi equation. The sustained drug release from SRSD(F6) was also maintained in simulated intestinal fluid at fasted-state (FaSSIF) and fed-state (FeSSIF). The structural characteristics of SRSD(F6) were examined by using powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR), indicating the change of drug crystallinity to an amorphous form. After oral administration in rats, SRSD(F6) exhibited the prolonged drug exposure in plasma. For both PEL and PEL-transOH (active metabolite), once a day dosing of SRSD(F6) achieved oral exposure (AUC) comparable to those from the multiple dosing (3 times a day) of untreated drug. In addition, the in vivo absorption of SRSD(F6) was well-correlated with the in vitro dissolution data, establishing a good level A in vitro/in vivo correlation. These results suggest that SRSD(F6) should be promising for the sustained-release of PEL, thereby reducing the dosing frequency.