cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Stochastic Structural Stability Theory applied to roll/streak formation in boundary layer shear flow
Creators: name: Farrell, Brian F.
name: Ioannou, Petros J.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Fluid Dynamics (physics.flu-dyn)
subject: Atmospheric and Oceanic Physics (physics.ao-ph)
subject: FOS: Physical sciences

description: Stochastic Structural Stability Theory (SSST) provides an autonomous, deterministic, nonlinear dynamical system for evolving the statistical mean state of a turbulent system. In this work SSST is applied to the problem of understanding the formation of the roll/streak structures that arise from free-stream turbulence (FST) and are associated with bypass transition in boundary layers. Roll structures in the cross-stream/spanwise plane and associated streamwise streaks are shown to arise as a linear instability of interaction between the FST and the mean flow. In this interaction incoherent Reynolds stresses arising from FST are organized by perturbation streamwise streaks to coherently force perturbation rolls giving rise to an amplification of the streamwise streak perturbation and through this feedback to an instability of the combined roll/streak/turbulence complex. The dominant turbulent perturbation structures involved in supporting the roll/streak/turbulence complex instability are non-normal optimal perturbations with the form of oblique waves. The cooperative linear instability giving rise to the roll/streak structure arises at a bifurcation in the parameter of STM excitation parameter. This structural instability eventually equilibrates nonlinearly at finite amplitude and although the resulting statistical equilibrium streamwise streaks are inflectional the associated flows are stable. Formation and equilibration of the roll/streak structure by this mechanism can be traced to the non-normality which underlies interaction between perturbations and mean flows in modally stable systems.
description: 16 pages, 24 figures, has been submitted for publication to Physics of Fluids
Sustainability of GEPs and Networks in Research Funding Organisations
Creators: name: Dvořáčková, Jana
Publisher: name: Zenodo
Year: 2022
Subjects: gender equality
superah2020
gender equality plan

description: Presentation held by Jana Dvořáčková (Technology Agency of the Czech Republic) during the Supera Final Conference, organised by SUPERA on 25 March 2022.
Spectroscopic ages and metallicities of galaxies
Creators: name: Koleva, M.
name: Bedregal, A.
name: Prugniel, Ph.
name: De Rijcke, S.
name: Zeilinger, W. W.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: Dwarf galaxies are generally faint. To derive their age and metallicity distributions, it is critical to optimize the use of any collected photon. Koleva et al., using full spectrum fitting, have found strong population gradients in some dwarf elliptical galaxies. Here, we show that the population profiles derived with this method are consistent and more precise than those obtained with spectrophotometric indices. This allows studying fainter objects in less telescope time.
description: 2 pages, 1 figure, to appear in the proceedings of the CRAL conference, Lyon, June 2010, "A Universe of Dwarf Galaxies", eds. M. Koleva, Ph. Prugniel and I. Vauglin; EDP Sciences in the European Astronomical Society
An extensive grid of mass fluxes for Galactic O stars
Creators: name: Lucy, L. B.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: A previously-described code for constructing moving reversing layers (MRL) is improved by replacing a two-parameter model for the radiative acceleration due to lines with a flexible non-parametric description, thus allowing a greater degree of dynamical consistency to be achieved in modelling turbulent transonic flow in the outer atmospheric layers of O stars. With this new code, mass fluxes J are computed at fifty-seven points in (T_eff, g)-space. Specifically, J's are computed for all Lanz-Hubeny (2003) NLTE atmospheres with T_eff (kK) \in (27.5, 55) and log g \leq 4.5. Differences with widely-used mass-loss formulae are emphasized, and opportunities for differential spectroscopic tests identified.
description: 8 pages, 9 figure. Revised version submitted to Astronomy and Astrophysics
Size matters : local government sustainability planning in British Columbia
Creators: name: Littley, Kenneth James
Publisher: name: University of British Columbia
Year: 2018

description: The purpose of this research is to understand the application of sustainability principles at the level of local governments of different sizes in the Province of British Columbia. Sustainability principles in the study area are integrated into all other community planning processes through the development of an Integrated Community Sustainability Plan (ICSP). However, the process for developing an ICSP, including the definition of what sustainability means and how it is applied, is left up to the individual community, leading to conceptual confusion. Through a literature review, the study identifies pillars, principles, and ecological and anthropocentric ideologies of sustainability, which are then used to assess local government sustainability frameworks. When local governments develop their ICSPs, a fundamental challenge is the misunderstanding of concepts and principles of sustainability. A tension also exists because the application of sustainability theory is done in local government through the use of urban planning principles, known as “Smart Growth.” Principles of Smart Growth theory, identified in the literature as the way to apply sustainability in the local context, are also explored in communities in four size categories. These urban–centric Smart Growth principles are often grafted onto smaller local governments where they are not scalable for a number of reasons. To identify size–related variables and other variables which affect a community’s understanding of the concept of sustainability, a grounded theory approach, complimented by cross–case study analysis, and a defined coding procedure was used. 16 local government sustainability plans from across the province were reviewed to identify where the plans diverge from the theory as outlined in the literature. To support, validate and extend the findings, semi–structured interviews were conducted with local government planning managers and other senior staff. These expert interviews were then used to identify how size plays a role in a local government’s understanding of sustainability and to identify what other factors also play a role. These complimentary methods lead to the findings for the research question: 1. How does the size of local government affect how sustainability is understood and applied to policy as reflected in ICSPs in British Columbia?
Broadband electrical detection of spin excitations in Ga0.98Mn0.02As using a photovoltage technique
Creators: name: Wirthmann, André
name: Hui, Xiong
name: Mecking, N.
name: Gui, Y. S.
name: Chakraborty, T.
name: Hu, C. M.
name: Reinwald, Matthias
name: Schüller, Christian
name: Wegscheider, Werner
Publisher: name: Universität Regensburg
Year: 2008
Subjects: subject: 530 Physik

description: We report on microwave photovoltage and simultaneous magnetotransport measurements in a Ga, Mn As film oriented normal to the magnetic field. We detect the ferromagnetic resonance over a broad frequency range of 2–18.5 GHz and determine the spectroscopic g-factor and separate the Gilbert from the inhomogeneous contribution to magnetization relaxation. Temperature dependent measurements below the saturation magnetization indicate that the photovoltage signal can serve as a sensitive tool to study the crystal anisotropy. We demonstrate that the combination of spin dynamics with charge transport is a promising tool to study microstructured ferromagnetic semiconductor samples.
Towards enabling human-robot handovers : exploring nonverbal cues for fluent human-robot handovers
Creators: name: Pan, Matthew Keith Xi-Jie
Publisher: name: University of British Columbia
Year: 2018

description: Fundamental human to human interactions - sharing spaces, tools, handing over objects, carrying objects together - are part of the everyday experience; for most people, the task of handing over an object to another person is a natural and seemingly effortless task. However, in the context of human-robot interaction, smooth and seamless interaction is an open problem of fundamental interest for robotics designers, integrators and users alike. This thesis explores how nonverbal cues exhibited during robot giving and receiving behaviours change how users perceive the robot, and affect the handover task. Additionally, the work also investigates how robots can recognize and interpret expressions conveyed by a human giver to infer handover intent. Over the course of several user studies examining human-human and human-robot handovers, the role of nonverbal cues such as gaze and object orientation and how they may play a part in establishing fluency and efficiency of robot-to-human handovers are investigated. These studies provide insights into how robots can be trained through observation of human-to-human handovers. Furthermore, this thesis examines the role of nonverbal cues in the less-studied human-to-robot handover interaction. In this exploration, kinematic features from motion-captured skeleton models of a giver are used to establish the intent to handover, thereby enabling a robot to appropriately react and receive the object. Additionally, changing user perceptions, geometry and dynamics of human-to-robot handovers are explored through variation of initial pose, grasp type during, and retraction speed after handover of the robot receiver. Findings from this thesis demonstrate that nonverbal cues such as gaze and object orientation in the case of robot-to-human handovers, and kinodynamics during human-to-robot handovers, can significantly affect multiple aspects of the interaction including user perception, fluency, legibility, efficiency, geometry and fluidity of the handover. Using a machine learning approach, recognizing handover intent from nonverbal kinematics of the giver's pose could also be performed effectively. Thus, the work presented in this thesis indicates that nonverbal cues can serve as a powerful medium by which details of a handover can be subtly communicated to the human partner, resulting in a more natural experience in this ubiquitous, collaborative activity.
Efficient Beam Converter for the Generation of Femtosecond Vortices
Creators: name: Shvedov, Vladlen G.
name: Hnatovsky, Cyril
name: Krolikowski, Wieslaw
name: Rode, Andrei V.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: We describe an optical beam converter for an efficient transformation of Gaussian femtosecond laser beams to single- or double-charge vortex beams showing no spatial or topological charge dispersion. The device achieves a conversion efficiency of 75% for single- and 50% for double-charge vortex beams and can operate with high energy broad bandwidth pulses. We also show that the topological charge of a femtosecond vortex beam can be determined by analyzing its intensity distribution in the focal area of a cylindrical lens.
description: 9 pages, 4 figures, submitted to Optics Letters 10 March 2010
New Double-Mode and Other RR Lyrae Stars from WASP Data
Creators: name: Wils, Patrick
Publisher: name: arXiv
Year: 2010
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: 42 RRab, 46 RRc and 7 previously unidentified double-mode RR Lyrae stars were found in the publicly available data of the WASP archive. The Galactic double-mode RR Lyrae stars appear to show a bimodal period distribution.
description: Published as IBVS 5955
Soil Carbon fractioning in Chestnut tree forests
Creators: name: Mosquera-Losada MR
name: Ferreiro-Domínguez N
name: Silva-Pando FJ
name: Rodriguez-Rigueiro J
name: Arias-Martínez D
name: Santiago-Freijanes JJ
name: Rigueiro-Rodríguez, A.
Publisher: name: Zenodo
Year: 2019
Subjects: C fractioning
macroagregates
microagregates

description: Nowadays, the lack of profitability of some chestnut stands linked to the high amount of man
power needed to harvest the chestnut fruits in high step mountain areas. A good option to increase
profitability of these areas is to rare animals to use fruit as feeds. Most of the mountain
chestnut stands are associated to less favored areas where autochthonous breeds are able
to survive and even procreate due to the adaptation they have to these difficult environments.
An INIA National Project was funded by the Spanish Ministry of Agriculture to evaluate two
stocking rates in four different scenarios located in the Galicia, Asturias and Vasque Country.
An initial sampling was done to evaluate the soil capacity of storing Carbon in the different
conditions. Carbon fractioning was conducted in order to evaluate the persistence of carbon
in the soil linked to macro and micro (lime plus silt) fractions. A good relationship between
the C stored in soil and the C in each fraction was highly correlated with the exception to that
linked to microagregates, which can indicate the difficulty of C to be stored in long term stock
particles
Spectrophotometry of the Huygens Region of the Orion Nebula, the Extended Orion Nebula, and M~43; Scattered Light Systematically Distorts Conditions Derived from Emission-Lines
Creators: name: O'Dell, C. R.
name: Harris, Jessica A.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We report on medium resolution spectrophotometry of the Orion Nebula region, including for the first time the Extended Orion Nebula and the nearby M~43. The 49 long slit observations were divided into 99 smaller samples, which have allowed determinations of the amount of extinction, extinction corrected \Hbeta\ surface brightness, electron temperatures (from [S~II], [N~II], and [O~III]), and electron densities (from [S~II] and [Cl~III]) throughout much of this complex region. We verify an earlier conclusion from a radio/optical study that beyond about 5\arcmin\ from \ori\ local emission begins to be contaminated by scattering of light from the much brighter central Huygens Region of M~42 and this scattered light component becomes dominant at large distances. This contamination means that the derived properties for the outer regions are not accurate. From comparison of the light from the dominant star in M~43 with the continuum of that nebula (which is almost entirely scattered star light) it is determined that scattered light is enhanced in the blue, which can lead to observed Balmer line ratios that are theoretically impossible and erroneous electron temperatures. This blue scattering of emission-lines is important even in the Huygens Region because it means that at anything except very high spectroscopic resolution the observed lines are a blend of the original and scattered light, with shorter wavelength lines being artificially enhanced. This can lead to over-estimates of the electron temperatures derived from the nebular and auroral line ratios of forbidden lines. This phenomenon is probably applicable to many other H~II regions.
Broadband emission and low absorption in microdisks with AlGaAs quantum wells
Creators: name: Kipp, T.
name: Petter, K.
name: Heyn, Christian
name: Heitmann, Detlef
name: Schüller, Christian
Publisher: name: Universität Regensburg
Year: 2008
Subjects: subject: 530 Physik

description: In microphotoluminescence measurements at room temperature on Al0.2Ga0.8As/Al0.4Ga0.6As multiple quantum well microdisks, we observe a large number of whispering gallery modes in a remarkably broad energy range of about 250 meV. This is in contrast to microdisks containing InGaAs or GaAs quantum wells, where typically only one or two whispering gallery modes are observed, but similar to the behavior of microdisks containing self-organized InAs quantum dots. We conclude that impurity levels below the recombination energy of free electron-hole pairs inside the alloy quantum wells lead to an efficient internal broadband emitter with low absorption.
Herschel photometry of brightest cluster galaxies in cooling flow clusters
Creators: name: Edge, A. C.
name: Oonk, J. B. R.
name: Mittal, R.
name: Allen, S. W.
name: Baum, S. A.
name: Boehringer, H.
name: Bregman, J. N.
name: Bremer, M. N.
name: Combes, F.
name: Crawford, C. S.
name: Donahue, M.
name: Egami, E.
name: Fabian, A. C.
name: Ferland, G. J.
name: Hamer, S. L.
name: Hatch, N. A.
name: Jaffe, W.
name: Johnstone, R. M.
name: McNamara, B. R.
name: O'Dea, C. P.
name: Popesso, P.
name: Quillen, A. C.
name: Salome, P.
name: Sarazin, C. L.
name: Voit, G. M.
name: Wilman, R. J.
name: Wise, M. W.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: The dust destruction timescales in the cores of clusters of galaxies are relatively short given their high central gas densities. However, substantial mid-infrared and sub-mm emission has been detected in many brightest cluster galaxies. In this letter we present Herschel PACS and SPIRE photometry of the brightest cluster galaxy in three strong cooling flow clusters, A1068, A2597 and Zw3146. This photometry indicates that a substantial mass of cold dust is present (>3 x 10^7 Mo) at temperatures significantly lower (20-28K) than previously thought based on limited MIR and/or sub-mm results. The mass and temperature of the dust appear to match those of the cold gas traced by CO with a gas-to-dust ratio of 80-120.
description: Accepted for A&A Herschel Special Issue, 7 pages, 3 figures
Fabrication of large periodic arrays of AlGaAs microdisks by laser-interference lithography and selective etching
Creators: name: Petter, K.
name: Kipp, T.
name: Heitmann, Detlef
name: Heyn, Ch.
name: Schüller, Christian
Publisher: name: Universität Regensburg
Year: 2002
Subjects: subject: 530 Physik

description: By laser-interference lithography, reactive-ion etching, and selective wet-chemical etching using a citric acid-based solution, we have fabricated large periodic arrays of AlGaAs microdisks with periods of 4 µm and disk diameters between 1.5 and 2 µm. The arrays are characterized by temperature-dependent photoluminescence spectroscopy. Taking into account the below-threshold absorption of the quantum wells inside the disks, we get disk quality factors close to the theoretical maximum value. We demonstrate that our technique allows one also to produce one-dimensionally or two-dimensionally coupled arrays of microdisks.
On Form Factors of the conjugated field in the non-linear Schröodinger model
Creators: name: Kozlowski, K. K.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Mathematical Physics (math-ph)
subject: High Energy Physics - Theory (hep-th)
subject: Exactly Solvable and Integrable Systems (nlin.SI)
subject: FOS: Physical sciences

description: Izergin-Korepin's lattice discretization of the non-linear Schrödinger model along with Oota's inverse problem provides one with determinant representations for the form factors of the lattice discretized conjugated field operator. We prove that these form factors converge, in the zero lattice spacing limit, to those of the conjugated field operator in the continuous model. We also compute the large-volume asymptotic behavior of such form factors in the continuous model. These are in particular characterized by Fredholm determinants of operators acting on closed contours. We provide a way of defining these Fredholm determinants in the case of generic parameters.
description: 23 pages
Identification of Overlapping Communities by Locally Calculating Community-Changing Resolution Levels
Creators: name: Havemann, Frank
name: Heinz, Michael
name: Struck, Alexander
name: Gläser, Jochen
Publisher: name: arXiv
Year: 2010
Subjects: subject: Data Analysis, Statistics and Probability (physics.data-an)
subject: Physics and Society (physics.soc-ph)
subject: FOS: Physical sciences
subject: H.2.8

description: An algorithm for the detection of overlapping natural communities in networks was proposed by Lancichinetti, Fortunato, and Kertesz (LFK) last year. The LFK algorithm constructs natural communities of (in principle) all nodes of a graph by maximising the local fitness of communities. The resulting modules can overlap. The generation of communities can easily be repeated for many values of resolution; thus allowing different views on the network at different resolutions. We implemented the main idea of the LFK algorithm---to generate natural communities of each node of a network---in a different way. We start with a value of the resolution parameter that is high enough for each node to be its own natural community. As soon as the resolution is reduced, each node acquires other nodes as members of its community, i.e. natural communities grow. For each community found at a certain resolution level we calculate the next lower resolution where a node is added. After adding a node to a community of a seed node we check whether it is also the natural community of a node that we have already analysed. In this case, we can stop expanding the seed node's community. We tested our algorithm on a small benchmark graph and on a network of about 500 papers in information science (weighted with the Salton index of bibliographic coupling). In our tests, this approach results in characteristic ranges of resolution where a large resolution change does not lead to a growth of the natural community. Such stable modules were also obtained by applying the LFK algorithm but since we determine communities for all resolution values in one run, our approach is faster than the LFK reference. And our algorithm reveals the hierarchical structure of the graph more easily.
description: 10 pages, 12 figures, also presented as "A local algorithm to get overlapping communities at all resolution levels in one run" in a poster session at ASONAM conference, Odense, Denmark, August 2010
Quasiatomic Fine Structure and Selection Rules in Quantum Dots
Creators: name: Schüller, Christian
name: Keller, K.
name: Biese, G.
name: Ulrichs, E.
name: Rolf, L.
name: Steinebach, C.
name: Heitmann, Detlef
name: Eberl, K.
Publisher: name: Universität Regensburg
Year: 1998
Subjects: subject: 530 Physik

description: We probe the electronic shell structure of quasiatomic systems, realized in GaAs-AlGaAs quantum dots, by resonant Raman spectroscopy. We observe a series of discrete spin-density excitations, whose energies are very close to single-particle level spacings in a quantum dot. The combined information from experiments at different wave vectors in the lateral direction and from investigations with applied magnetic fields reveals a distinct set of Raman allowed transitions (Δn,Δm), where changes Δn and Δm are changes in radial and angular momentum quantum numbers, respectively.
Herschel observations of FIR emission lines in brightest cluster galaxies
Creators: name: Edge, A. C.
name: Oonk, J. B. R.
name: Mittal, R.
name: Allen, S. W.
name: Baum, S. A.
name: Boehringer, H.
name: Bregman, J. N.
name: Bremer, M. N.
name: Combes, F.
name: Crawford, C. S.
name: Donahue, M.
name: Egami, E.
name: Fabian, A. C.
name: Ferland, G. J.
name: Hamer, S. L.
name: Hatch, N. A.
name: Jaffe, W.
name: Johnstone, R. M.
name: McNamara, B. R.
name: O'Dea, C. P.
name: Popesso, P.
name: Quillen, A. C.
name: Salome, P.
name: Sarazin, C. L.
name: Voit, G. M.
name: Wilman, R. J.
name: Wise, M. W.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: The question of how much gas cools in the cores of clusters of galaxies has been the focus of many, multiwavelength studies in the past 30 years. In this letter we present the first detections of the strongest atomic cooling lines, [C II], [O I] and [N I] in two strong cooling flow clusters, A1068 and A2597, using Herschel PACS. These spectra indicate that the substantial mass of cold molecular gas (>10^9 Mo) known to be present in these systems is being irradiated by intense UV radiation, most probably from young stars. The line widths of these FIR lines indicate that they share dynamics similar but not identical to other ionised and molecular gas traced by optical, near-infrared and CO lines. The relative brightness of the FIR lines compared to CO and FIR luminosity is consistent with other star-forming galaxies indicating that the properties of the molecular gas clouds in cluster cores and the stars they form are not unusual. These results provide additional evidence for a reservoir of cold gas that is fed by the cooling of gas in the cores of the most compact clusters and provide important diagnostics of the temperature and density of the dense clouds this gas resides in.
description: Accepted for the A&A Herschel Special Issue, 5 pages, 2 figures
Work distribution for the driven harmonic oscillator with time-dependent strength: Exact solution and slow driving
Creators: name: Speck, Thomas
Publisher: name: arXiv
Year: 2011
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: We study the work distribution of a single particle moving in a harmonic oscillator with time-dependent strength. This simple system has a non-Gaussian work distribution with exponential tails. The time evolution of the corresponding moment generating function is given by two coupled ordinary differential equations that are solved numerically. Based on this result we study the behavior of the work distribution in the limit of slow but finite driving and show that it approaches a Gaussian distribution arbitrarily well.
Hybrid density functional theory calculations on phonons in LaCoO3
Creators: name: Gryaznov, Denis
name: Evarestov, Robert A.
name: Maier, Joachim
Publisher: name: arXiv
Year: 2010
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: Phonon frequencies at Gamma-point in non-magnetic rhombohedral phase of LaCoO3 were calculated using density functional theory (DFT) with hybrid exchange correlation functional PBE0. The calculations involved a comparison of results for two types of basis functions commonly used in ab intiio calculations, namely the plane wave (PW) approach and linear combination of atomic orbitals (LCAO), as implemented in VASP and CRYSTAL computer codes, respectively. A good qualitative, but also within an error margin of less than 30%, a quantitative agreement was observed not only between the two formalisms but also between theoretical and experimental phonon frequency predictions. It is concluded that the hybrid PBE0 functional is able to predict correctly the phonon properties in LaCoO3.
description: 4 pages, 3 tables
Common Fermi Surface Topology and Nodeless Superconducting Gap in K0.68Fe1.79Se2 and (Tl0.45K0.34)Fe1.84Se2 Superconductors Revealed from Angle-Resolved Photoemission Spectroscopy
Creators: name: Zhao, Lin
name: Mou, Daixiang
name: Liu, Shanyu
name: Jia, Xiaowen
name: He, Junfeng
name: Peng, Yingying
name: Yu, Li
name: Liu, Xu
name: Liu, Guodong
name: He, Shaolong
name: Dong, Xiaoli
name: Zhang, Jun
name: He, J. B.
name: Wang, D. M.
name: Chen, G. F.
name: Guo, J. G.
name: Chen, X. L.
name: Wang, Xiaoyang
name: Peng, Qinjun
name: Wang, Zhimin
name: Zhang, Shenjin
name: Yang, Feng
name: Xu, Zuyan
name: Chen, Chuangtian
name: Zhou, X. J.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We carried out high resolution angle-resolved photoemission measurements on the electronic structure and superconducting gap of K_0.68Fe_1.79Se_2 (T_c=32 K) and (Tl_0.45K_0.34)Fe_1.84Se_2 (T_c=28 K) superconductors. In addition to the electron-like Fermi surface near M(π,π), two electron-like Fermi pockets are revealed around the zone center Γ(0,0) in K0.68Fe1.79Se_2. This observation makes the Fermi surface topology of K_0.68Fe_1.79Se_2 consistent with that of (Tl,Rb)_xFe_{2-y}Se_2 and (Tl,K)_xFe_{2-y}Se_2 compounds. A nearly isotropic superconducting gap (Δ) is observed along the electron-like Fermi pocket near the M point in K_0.68Fe_1.79Se_2 (Δ\sim 9 meV) and (Tl_0.45K_0.34)Fe_1.84Se_2 (Δ\sim 8 meV). The establishment of a universal picture on the Fermi surface topology and superconducting gap in the A_xFe_2-ySe_2 (A=K, Tl, Cs, Rb and etc.) superconductors will provide important information in understanding the superconductivity mechanism of the iron-based superconductors.
description: 4 pages, 4 figures
Optical Probing of a Fractionally Charged Quasihole in an Incompressible Liquid
Creators: name: Schüller, Christian
name: Broocks, K.-B.
name: Schröter, P.
name: Heyn, Ch.
name: Heitmann, Detlef
name: Bichler, Max
name: Wegscheider, Werner
name: Chakraborty, Tapash
name: Apalkov, V. M.
Publisher: name: Universität Regensburg
Year: 2003
Subjects: subject: two-dimensional electron gas, photoluminescence, excitons, electric charge, quasiparticles, magnetic field effects, localised states, energy gap
subject: 530 Physik

description: In photoluminescence spectroscopy of a low-mobility two-dimensional electron gas subjected to a quantizing magnetic field, we observe an anomaly around nu= (1/3) at a very low temperature (0.1 K) and an intermediate electron density (0.9×1011 cm–2). The anomaly is explained as due to perturbation of the incompressible liquid at the Laughlin state due to close proximity of a localized charged exciton which creates a fractionally charged quasihole in the liquid. The anomaly of ~2 meV can be destroyed by applying a small thermal energy of ~0.2 meV that is enough to close the quasihole energy gap.
Risk management of downy mildew in soybean
Creators: name: Rittler, Leopold
name: Dima, Dragos
name: Petrović, Kristina
name: Hackl, Gerald
Publisher: name: Zenodo
Year: 2021
Subjects: soybeans
legumes
crop management
plant pathogens

description: Downy mildew is caused by the plant pathogen Peronospora manshurica. Downy mildew is a common fungal disease of soybean, found worldwide. It is soil and seed-borne and infection may result in yield losses of 5 to up to 10% in severe cases. So far, in Central Europe the damage caused is observed to be low. This practice note provides information on the pathogen`s biology and control of the disease presenting a foundation for effective management.
Electronic Dephasing in the Quantum Hall Regime
Creators: name: Fromer, N. A.
name: Schüller, Christian
name: Chemla, D. S.
name: Shahbazyan, T. V.
name: Perakis, I. E.
name: Maranowski, K.
name: Gossard, A. C.
Publisher: name: Universität Regensburg
Year: 1999
Subjects: subject: 530 Physik

description: By means of degenerate four-wave mixing (FWM), we investigate the quantum coherence of electron-hole pairs in the presence of a two-dimensional electron gas in modulation-doped GaAs-AlGaAs quantum wells in the quantum Hall effect regime. With increasing magnetic field, we observe a crossover from Markovian to non-Markovian behavior, as well as large jumps in the decay time of the FWM signal at even Landau level filling factors. The main observations can be qualitatively reproduced by a model which takes into account scattering by the collective excitations of the two-dimensional electron gas.
The interaction of repetitive mild traumatic brain injury, Alzheimer disease and ageing
Creators: name: Cheng, Wai Hang
Publisher: name: University of British Columbia
Year: 2018

description: Traumatic brain injury (TBI) is an important public health issue worldwide. It is strongly linked to neurodegenerative conditions such as Alzheimer’s Disease (AD) and Chronic Traumatic Encephalopathy. Despite numerous promising pre-clinical studies, there is no effective clinical treatment for TBI, indicating inefficiency in translation of scientific research from bench to bedside. This thesis thus attempts to address the issue through two approaches. Firstly, we reviewed the commonly-used pre-clinical TBI models, and found that many lack thorough biomechanical considerations. We thus developed a new mouse TBI model, Closed-Head Impact Model of Engineered Rotational Acceleration (CHIMERA). CHIMERA reproducibly induces clinically-relevant TBI, both in terms of biomechanics and neuropathology. CHIMERA mild TBI (mTBI) induces behavioural (e.g. neurological, motor, and cognitive), histological and biochemical changes (e.g. diffuse axonal injury, white matter microgliosis, and brain cytokine induction). We further demonstrated that CHIMERA mTBI outcomes are scalable by varying the mechanical inputs. These observations demonstrate that CHIMERA is a novel and valuable platform for TBI research. Next, we induced CHIMERA mTBI in APP/PS1 mice, a transgenic model of AD amyloidosis, and characterised both acute and long-term consequences. Here we included two age groups of animals, as TBI occur in both the young and the old populations. In the acute phase, mTBI led to subtle and transient age-dependent changes in A-beta deposits. Age-at-injury and genotype showed complex interactions in determining microglial and cytokine outcomes, such that neuroinflammation was increased in old wildtype mice and young APP/PS1 mice. Age-at-injury also markedly affected neurofilament response, as neurofilament-positive axonal bulbs and plasma neurofilament-light levels were elevated in young mice, but not old mice, of both genotypes. In the chronic phase, mTBI led to prolonged white matter microgliosis and axonal injury up to 8-mo post-injury. MTBI also intensified long-term fear memory in APP/PS1 mice, reminiscent of post-traumatic stress disorder phenotypes. In summary, we have developed a reproducible and clinically-relevant TBI model. We showed that genetic predisposition to AD and age-at-injury are both significant modifiers of acute and long-term mTBI outcomes. These findings may provide insights for future attempts in understanding the mechanistic pathways of TBI pathogenesis.
On rational solutions of multicomponent and matrix KP hierarchies
Creators: name: Tacchella, Alberto
Publisher: name: arXiv
Year: 2010
Subjects: subject: Exactly Solvable and Integrable Systems (nlin.SI)
subject: Mathematical Physics (math-ph)
subject: FOS: Physical sciences

description: We derive some rational solutions for the multicomponent and matrix KP hierarchies generalising an approach by Wilson. Connections with the multicomponent version of the KP/CM correspondence are discussed.
description: 15 pages, no figures
Oscillator strengths of dark charged excitons at low electron filling factors
Creators: name: Schüller, Christian
name: Broocks, K.-B.
name: Heyn, Ch.
name: Heitmann, Detlef
Publisher: name: Universität Regensburg
Year: 2002
Subjects: subject: aluminium compounds, gallium arsenide, semiconductor quantum wells, III-V semiconductors, oscillator strengths, excitons, photoluminescence, light absorption, two-dimensional electron gas, quantum Hall effect, triplet state
subject: 530 Physik

description: By direct absorption spectroscopy and comparison to photoluminescence (PL), we investigate negatively charged excitons in dilute two-dimensional electron systems at temperatures down to T = 40 mK in the regime of the fractional quantum Hall effect. At very low temperatures, for filling factor nu<1/3, an additional excitation appears in the PL spectrum, between the well-known singlet and triplet excitons. The observation of a similar excitation by PL was reported very recently [G. Yusa et al., Phys. Rev. Lett. 87, 216402 (2001)], and the excitation was assigned, in spite of the PL intensity similar to that of the neutral exciton, to be due to a dark triplet exciton. By comparing PL and direct absorption spectra in optically thin samples at T<100 mK, we can identify the new excitation indeed as a "dark" mode, since we find that the oscillator strength is much smaller than those of the "bright" modes.
PEP: first Herschel probe of dusty galaxy evolution up to z~3
Creators: name: Gruppioni, C.
name: Pozzi, F.
name: Andreani, P.
name: Rodighiero, G.
name: Cimatti, A.
name: Altieri, B.
name: Aussel, H.
name: Berta, S.
name: Bongiovanni, A.
name: Brisbin, D.
name: Cava, A.
name: Cepa, J.
name: Daddi, E.
name: Dominguez-Sanchez, H.
name: Elbaz, D.
name: Schreiber, N. Forster
name: Genzel, R.
name: Floc'h, E. Le
name: Lutz, D.
name: Magdis, G.
name: Magliocchetti, M.
name: Magnelli, B.
name: Maiolino, R.
name: Nordon, R.
name: Per'ez-García, A. M.
name: Poglitsch, A.
name: Popesso, P.
name: Riguccini, L.
name: Saintonge, A.
name: Sanchez-Portal, M.
name: Santini, P.
name: Shao, L.
name: Sturm, E.
name: Tacconi, L.
name: Valtchanov, I.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We exploit the deepest existing far-infrared (FIR) data obtained so far by Herschel at 100 and 160 um in the GOODS-N, as part of the PACS Evolutionary Probe (PEP) survey, to derive for the first time the evolution of the rest-frame 60-um, 90-um, and total IR luminosity functions (LFs) of galaxies and AGNs from z=0 to unprecedented high redshifts (z~2-3). The PEP LFs were computed using the 1/Vmax method. The FIR sources were classified by means of a detailed broad- band SED-fitting analysis and spectral characterisation. Based on the best-fit model results, k-correction and total IR (8-1000 um) luminosity were obtained for each source. LFs (monochromatic and total) were then derived for various IR populations separately in different redshift bins and compared to backward evolution model predictions. We detect strong evolution in the LF to at least z~2. Objects with SEDs similar to local spiral galaxies are the major contributors to the star formation density (SFD) at z< 0.3, then, as redshift increases, moderate SF galaxies - most likely containing a low-luminosity AGN - start dominating up to z ~= 1.5. At >1.5 the SFD is dominated by the contributions of starburst galaxies. In agreement with previous findings, the comoving IR LD derived from our data evolves approximately as (1 + z)^(3.8+/-0.3) up to z~1, there being some evidence of flattening up to z~2.
description: Accepted for publication in the A&A Herschel first results Special Issue
Anomalous dispersion of charged excitons in dilute two-dimensional electron systems at low temperatures
Creators: name: Broocks, K.-B.
name: Schröter, P.
name: Heitmann, Detlef
name: Heyn, Ch.
name: Schüller, Christian
name: Bichler, Max
name: Wegscheider, Werner
Publisher: name: Universität Regensburg
Year: 2002
Subjects: subject: excitons, two-dimensional electron gas, quantum Hall effect, photoluminescence, absorption
subject: 530 Physik

description: We report the observation of a strong anomaly in the magnetic-field dispersion of negatively charged excitons in dilute two-dimensional electron systems. The anomaly exists in an intermediate density range around 1×1011 cm–2, and at temperatures T<1 K, only. The strength of the anomaly at T = 0.1 K is about 2.5 meV, and the most striking feature is that it can be completely destroyed by a small thermal energy of about 0.2 meV (2 K). Furthermore, the anomaly is observed both in photoluminescence and direct absorption measurements, which gives a strong indication that it is of intrinsic origin.
title: Land - atmosphere coupling in climate models over North America; understanding inter-model differences
Creators: name: García García, Almudena
Publisher: name: Memorial University of Newfoundland
Year: 2020

description: The interactions between the lower atmosphere and the land surface are associated with weather and climate phenomena such as the duration, frequency and intensity of extreme temperature and precipitation events. Thus, the representation of land- atmosphere interactions in climate model simulations is crucial for projecting future changes in the statistics of extreme events as realistically as possible. Given the importance of the land-atmosphere interaction, the purpose of the thesis is to evaluate climate simulations performed by General Circulation Models (GCMs) and Regional Climate Models (RCMs) and examine the role of the Land Surface Model (LSM) component and the horizontal resolution over North America. For this purpose, I analyze a large set of simulations from GCMs and RCMs used by the fifth assessment report of the Intergovernmental Panel on Climate Change (IPCC) as well as my own simulations performed by the Weather Research and Forecasting (WRF) model. Results show that GCM simulations present large uncertainties in the representation of land-atmosphere interactions in comparison with observations. This work also reveals a dependence of the simulated land-atmosphere interactions on the LSM components used in regional and global simulations. Additionally, the LSM component is identified as an important source of uncertainty in the simulation of extreme temperature and precipitation events. Increasing the horizontal resolution also affects the simulation of land-atmosphere interactions, which lead to the intensification of precipitation, evapotranspiration and soil moisture at low latitudes; that is increased latent heat flux, soil moisture, and precipitation. The impact of both factors, horizontal resolution and the LSM, is larger in summer in agreement with the summer intensification of land-atmosphere interactions reported in the literature. The comparison of model simulations and observations indicates that the use of the most comprehensive LSM component available in WRF, the Community Land Model version 4 (CLM4), leads to a better representation of temperature climatologies. In contrast, finer horizontal resolutions are associated with larger biases in the WRF simulation of precipitation climatology, due to the overestimation of precipitation in the WRF model. Due to the large effect of the LSM component on the simulation of near-surface conditions shown in this dissertation, the use of simple version of LSM component in GCMs, RCMs or reanalyses can be an important limitation in climate simulations and reanalysis products.
Spectroscopy of Few-Electron Collective Excitations in Charge-Tunable Artificial Atoms
Creators: name: Brocke, T.
name: Bootsmann, M.-T.
name: Tews, M.
name: Wunsch, B.
name: Pfannkuche, D.
name: Heyn, Ch.
name: Hansen, W.
name: Heitmann, Detlef
name: Schüller, Christian
Publisher: name: Universität Regensburg
Year: 2003
Subjects: subject: indium compounds, gallium arsenide, semiconductor quantum dots, light scattering, III-V semiconductors, spectral line broadening, red shift
subject: 530 Physik

description: We report the investigation of electronic excitations in InGaAs self-assembled quantum dots using resonant inelastic light scattering. The dots can be charged via a gate by N = 1,[ellipsis (horizontal)],6 electrons. We observe excitations, which are identified as transitions of electrons, predominantly from the s to the p shell (s–p transitions) of the quasiatoms. We find that the s–p transition energy decreases and the observed band broadens, when the p shell is filled with 1 to 4 electrons. By a theoretical model, which takes into account the full Coulomb interaction in the few-electron artificial atom, we can confirm the experimental results to be an effect of the Coulomb interaction in the quantum dot.
Acoustic plasmons and indirect intersubband excitations in tunneling-coupled GaAs-AlxGa1ÀxAs double quantum wells
Creators: name: Bootsmann, M.-T.
name: Hu, C. M.
name: Heyn, Ch.
name: Heitmann, Detlef
name: Schüller, Christian
Publisher: name: Universität Regensburg
Year: 2003
Subjects: subject: gallium arsenide, aluminium compounds, III-V semiconductors, semiconductor quantum wells, plasmons, light scattering, carrier density, RPA calculations
subject: 530 Physik

description: In photoluminescence spectroscopy of a low-mobility two-dimensional electron gas subjected to a quantizing magnetic field, we observe an anomaly around nu= (1/3) at a very low temperature (0.1 K) and an intermediate electron density (0.9×1011 cm–2). The anomaly is explained as due to perturbation of the incompressible liquid at the Laughlin state due to close proximity of a localized charged exciton which creates a fractionally charged quasihole in the liquid. The anomaly of ~2 meV can be destroyed by applying a small thermal energy of ~0.2 meV that is enough to close the quasihole energy gap.
Fermi edge singularities in the mesoscopic regime: Anderson orthogonality catastrophe
Creators: name: Hentschel, Martina
name: Ullmo, Denis
name: Baranger, Harold U.
Publisher: name: Universität Regensburg
Year: 2005
Subjects: subject: mesoscopic systems, Fermi level, catastrophe theory, photoexcitation, fluctuations, ground states, bound states, random processes, chaos, perturbation theory
subject: 530 Physik

description: For generic mesoscopic systems, such as quantum dots or nanoparticles, we study the Anderson orthogonality catastrophe (AOC) and Fermi-edge singularities in photoabsorption spectra in a series of two papers. In the present paper we focus on AOC for a finite number of particles in discrete energy levels where, in contrast to the bulk situation, AOC is not complete. Moreover, fluctuations characteristic for mesoscopic systems lead to a broad distribution of AOC ground-state overlaps. The fluctuations originate dominantly in the levels around the Fermi energy, and we derive an analytic expression for the probability distribution of AOC overlaps in the limit of strong perturbations. We address the formation of a bound state and its importance for symmetries between the overlap distributions for attractive and repulsive potentials. Our results are based on a random matrix model for the chaotic conduction electrons that are subject to a rank-one perturbation corresponding, for example, to the localized core hole generated in the photoabsorption process.
Loss and revival of phase coherence in a Bose–Einstein condensate moving through an optical lattice
Creators: name: Nesi, Francesco
name: Modugno, Michele
Publisher: name: Universität Regensburg
Year: 2004
Subjects: subject: 530 Physik

description: We investigate the phase coherence of a trapped Bose–Einstein condensate that undergoes a dynamical superfluid–insulator transition in the presence of a one-dimensional optical lattice. We study the evolution of the condensate after a sudden displacement of the harmonic trapping potential by solving the Gross–Pitaevskii equation, and comparing the results with the prediction of two effective 1D models. We show that, owing to the 3D nature of the system, the breakdown of the superfluid current above a critical displacement is not associated with a sharp transition, but there exists a range of displacements for which the condensate can recover a certain degree of coherence. We also discuss the implications on the interference pattern after the ballistic expansion as measured in recent experiments at LENS.
Fermi-Edge Singularities in the Mesoscopic X-Ray Edge Problem
Creators: name: Hentschel, Martina
name: Ullmo, Denis
name: Baranger, Harold U.
Publisher: name: Universität Regensburg
Year: 2005
Subjects: subject: XANES, Fermi level, quantum dots, nanoparticles, chaos, fluctuations, two-dimensional electron gas
subject: 530 Physik

description: We study the x-ray edge problem for a chaotic quantum dot or nanoparticle displaying mesoscopic fluctuations. In the bulk, x-ray physics is known to produce Fermi-edge singularities—deviations from the naively expected photoabsorption cross section in the form of a peaked or rounded edge. For a coherent system with chaotic dynamics, we find substantial changes; in particular, a photoabsorption cross section showing a rounded edge in the bulk will change to a slightly peaked edge on average as the system size is reduced to a mesoscopic (coherent) scale.