cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Effective AdS/renormalized CFT
Creators: name: Fan, JiJi
Publisher: name: arXiv
Year: 2011
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: For an effective AdS theory, we present a simple prescription to compute the renormalization of its dual boundary field theory. In particular, we define anomalous dimension holographically as the dependence of the wave-function renormalization factor on the radial cutoff in the Poincare patch of AdS. With this definition, the anomalous dimensions of both single- and double- trace operators are calculated. Three different dualities are considered with the field theory being CFT, CFT with a double-trace deformation and spontaneously broken CFT. For the second dual pair, we compute scaling corrections at the UV and IR fixed points of the RG flow triggered by the double-trace deformation. For the last case, we discuss whether our prescription is sensitive to the AdS interior or equivalently, the IR physics of the dual field theory.
description: 20 pages, 3 figures
Surfactant mediated growth of Ti/Ni multilayers
Creators: name: Gupta, Mukul
name: Amir, S. M.
name: Gupta, Ajay
name: Stahn, Jochen
Publisher: name: arXiv
Year: 2011
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: The surfactant mediated growth of Ti/Ni multilayers is studied. They were prepared using ion beam sputtering at different adatom energies. It was found that the interface roughness decreased significantly when the multilayers were sputtered with Ag as surfactant at an ion energy of 0.75 keV. On the other hand, when the ion energy was increased to 1 keV, it resulted in enhanced intermixing at the interfaces and no appreciable effect of Ag surfactant could be observed. On the basis of the obtained results, the influence of adatom energy on the surfactant mediated growth mechanism is discussed.
description: 3 Pages, 3 Figures
Generic nondegeneracy in convex optimization
Creators: name: Drusvyatskiy, Dmitriy
name: Lewis, Adrian S.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Optimization and Control (math.OC)
subject: FOS: Mathematics
subject: 49J53 (Primary), 32F32, 47H05 (Secondary)

description: We show that minimizers of convex functions subject to almost all linear perturbations are nondegenerate. An analogous result holds more generally, for lower-C^2 functions.
description: 13 pages
Radiolysis of H2O:CO2 ices by heavy energetic cosmic ray analogs
Creators: name: Pilling, S.
name: Duarte, E. Seperuelo
name: Domaracka, A.
name: Rothard, H.
name: Boduch, P.
name: da Silveira, E. F.
Publisher: name: arXiv
Year: 2010
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: An experimental study on the interaction of heavy, highly charged, and energetic ions (52 MeV Ni^13+) with pure H2O, pure CO2 and mixed H2O:CO2 astrophysical ice analogs is presented. This analysis aims to simulate the chemical and the physicochemical interactions induced by heavy cosmic rays inside dense and cold astrophysical environments such as molecular clouds or protostellar clouds. The measurements were performed at the heavy ion accelerator GANIL (Grand Accelerateur National d'Ions Lourds in Caen, France). The gas samples were deposited onto a CsI substrate at 13 K. In-situ analysis was performed by a Fourier transform infrared (FTIR) spectrometer at different fluences. Radiolysis yields of the produced species were quantified. The dissociation cross sections of pure H2O and CO2 ices are 1.1 and 1.9E-13 cm^2, respectively. In the case of mixed H2O:CO2 (10:1) the dissociation cross sections of both species are about 1E-13 cm^2. The measured sputtering yield of pure CO2 ice is 2.2E4 molec/ion. After a fluence of 2-3E12 ions/cm^2 the CO2/CO ratio becomes roughly constant (~0.1), independent of the of initial CO2/H2O ratio. A similar behavior is observed for the H2O2/H2O ratio which stabilizes at 0.01, independent of the initial H2O column density or relative abundance.
description: 13 pages, 9 figures, 4 tables. Accepted to be published in Astronomy and Astrophysics
Formation history, structure and dynamics of discs and spheroids in simulated Milky Way mass galaxies
Creators: name: Scannapieco, Cecilia
name: White, Simon D. M
name: Springel, Volker
name: Tissera, Patricia B.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We study the stellar discs and spheroids in eight simulations of galaxy formation within Milky Way-mass haloes in a Lambda Cold Dark Matter cosmology. A first paper in this series concentrated on disc properties. Here, we extend this analysis to study how the formation history, structure and dynamics of discs and spheroids relate to the assembly history and structure of their haloes. We find that discs are generally young, with stars spanning a wide range in stellar age: the youngest stars define thin discs and have near-circular orbits, while the oldest stars form thicker discs which rotate ~2 times slower than the thin components, and have 2-3 times larger velocity dispersions. Unlike the discs, spheroids form early and on short time-scales, and are dominated by velocity dispersion. We find great variety in their structure. The inner regions are bar- or bulge-like, while the extended outer haloes are rich in complex non-equilibrium structures such as stellar streams, shells and clumps. Our discs have very high in-situ fractions, i.e. most of their stars formed in the disc itself. Nevertheless, there is a non-negligible contribution (~15 percent) from satellites that are accreted on nearly coplanar orbits. The inner regions of spheroids also have relatively high in-situ fractions, but 65-85 percent of their outer stellar population is accreted. We analyse the circular velocities, rotation velocities and velocity dispersions of our discs and spheroids, both for gas and stars, showing that the dynamical structure is complex as a result of the non-trivial interplay between cooling and SN heating.
description: Submitted to MNRAS. 20 pages, 18 figures
A Computational Literature Analysis of Conversational AI and Chat-bots With a Focus on Coaching
Creators: name: Pande, Charuta
Publisher: name: Zenodo
Year: 2022

description: Conversational AI is an interdisciplinary field of research that involves studies on conversational agents, commonly called as chatbots. This master thesis provides quantitative evidence of an increasing interest in this research field. The thesis identifies the top venues where Conversational AI research has been published between 2016 and 2020. Additionally, this research presents the results of computational literature analysis of research publications on conversational agents from two scientific databases. Through the computational technique of topic modeling using the Latent Dirichlet Allocation algorithm, nine prominent topics in Conversational AI publications were identified, two of which are related to the domain of coaching. By performing author analysis, key contributors to the field of Conversational AI and more specifically in the domain of coaching were identified. From the affiliations, it was observed that authors from Europe have a prominent contribution in this research area. Based on the findings from the literature, a research agenda has been proposed to continue future research in Conversational AI and the domain of coaching.
Dynamics of massive stellar black holes in young star clusters and the displacement of ultra-luminous X-ray sources
Creators: name: Mapelli, M.
name: Ripamonti, E.
name: Zampieri, L.
name: Colpi, M.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: In low-metallicity environments, massive stars might avoid supernova explosion and directly collapse, forming massive (~25-80 solar masses) stellar black holes (MSBHs), at the end of their life. MSBHs, when hosted in young massive clusters, are expected to form binaries and to strongly interact with stars, mainly via three-body encounters. We simulate various realizations of young star clusters hosting MSBHs in hard binaries with massive stars. We show that a large fraction (~44 per cent) of MSBH binaries are ejected on a short timescale (<=10 Myr). The offset of the ejected MSBHs with respect to the parent cluster is consistent with observations of X-ray binaries and ultra-luminous X-ray sources. Furthermore, three-body encounters change the properties of MSBH binaries: the semi-major axis changes by <=50 per cent and the eccentricity of the system generally increases. We shortly discuss the implications of our simulations on the formation of high-mass X-ray binaries hosting MSBHs.
description: 10 pages, 9 figures, accepted for publication in MNRAS
The cell cycle regulates mouse and human pancreas development
Creators: name: Krentz, Nicole Angela Jane
Publisher: name: University of British Columbia
Year: 2018

description: Diabetes is caused by a loss or dysfunction of insulin-producing pancreatic beta-cells. A potential treatment for diabetes is to replace these cells through transplantation. As there is a shortage of donor tissue, efforts to generate an unlimited source of functional insulin-producing beta-cells from human embryonic stem cells (hESCs) are ongoing. During pancreas development, proliferating pancreatic progenitors activate Neurog3, exit the cell cycle, and differentiate. The overarching goal of this thesis was to understand the role of the cell cycle in regulating Neurog3 expression and endocrine cell fate. First, the length of each cell cycle phase of pancreatic progenitors was measured using cumulative EdU labelling, determining an increase in G1 length in Pdx1+ progenitors from 4.5±0.4 to 7.2±0.8 hours between embryonic day (E)11.5 and E13.5. Next, two mouse models were used to show that cell cycle lengthening within pancreatic progenitors stimulates endocrine differentiation. Kras heterozygous loss-of-function mice have increased endocrine cell genesis that was correlated with an increase in progenitor cell cycle length. Ectopic expression of the cyclin-dependent kinase inhibitor Cdkn1b in Sox9+ progenitor cells resulted in a 2.7-fold increase in the number of Neurog3+ cells. As Cdkn1b is an inhibitor of G1-S cyclin-dependent kinases (Cdks), the effect of directly inhibiting Cdk2, Cdk4 and Cdk6 on endocrine differentiation was investigated. Treating embryonic pancreata, ex vivo, for 24 hours with Cdk inhibitors resulted in a 3-fold increase in the number of Neurog3+ cells. To investigate the consequences of CDK inhibition on human endocrine differentiation, a NEUROG3-2A-eGFP (N5-5) knock-in reporter CyT49 hESC line was generated using CRISPR-Cas9. CDK inhibition increased the number of GFP+ endocrine progenitor cells 1.7-fold. These findings suggest that G1 lengthening is required for normal mouse and human organogenesis and that cyclin-dependent kinases act directly to reduce Neurog3 protein. In the final chapter, single-cell transcriptomics was used to profile the gene expression and cell populations present during mouse and human endocrine development. In conclusion, these studies show that progenitor cell-cycle G1 lengthening, through its actions on stabilization of Neurog3, is an essential determinant of normal endocrine cell genesis.
Conformal anomaly around the sudden singularity
Creators: name: Houndjo, M. J. S.
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: Quantum effects due to particle creation on a classical sudden singularity have been investigated in a previous work. The conclusion was that quantum effects do not lead to the avoidance nor the modification of the sudden future singularity. In this paper, we investigate quantum corrections coming from conformal anomaly near the sudden future singularity. We conclude that when the equation of state is chosen to be $p=-ρ-Aρ^α$, the conformal anomaly can transform the sudden singularity in the singularity of type III for any $α> 1/2$ and in the singularity of the type I (the big rip) or the big crunch for $1/2
description: Latex file, 10 pages
Plane wave stability of some conservative schemes for the cubic Schrödinger equation
Creators: name: Dahlby, Morten
name: Owren, Brynjulf
Publisher: name: arXiv
Year: 2010
Subjects: subject: Numerical Analysis (math.NA)
subject: FOS: Mathematics
subject: 65M06 (Primary) 35Q41, 35Q55 (Secondary)

description: The plane wave stability properties of the conservative schemes of Besse and Fei et al. for the cubic Schrödinger equation are analysed. Although the two methods possess many of the same conservation properties, we show that their stability behaviour is very different. An energy preserving generalisation of the Fei method with improved stability is presented.
description: 12 pages, 6 figures
Absence of exponentially localized solitons for the Novikov--Veselov equation at negative energy
Creators: name: Kazeykina, Anna
name: Novikov, Roman
Publisher: name: arXiv
Year: 2011
Subjects: subject: Mathematical Physics (math-ph)
subject: Analysis of PDEs (math.AP)
subject: FOS: Physical sciences
subject: FOS: Mathematics

description: We show that Novikov--Veselov equation (an analog of KdV in dimension 2 + 1) does not have exponentially localized solitons at negative energy.
Implications of Electronics Constraints for Solid-State Quantum Error Correction and Quantum Circuit Failure Probability
Creators: name: Levy, James E.
name: Carroll, Malcolm S.
name: Ganti, Anand
name: Phillips, Cynthia A.
name: Landahl, Andrew J.
name: Gurrieri, Thomas M.
name: Carr, Robert D.
name: Stalford, Harold L.
name: Nielsen, Erik
Publisher: name: arXiv
Year: 2011
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: In this paper we present the impact of classical electronics constraints on a solid-state quantum dot logical qubit architecture. Constraints due to routing density, bandwidth allocation, signal timing, and thermally aware placement of classical supporting electronics significantly affect the quantum error correction circuit's error rate. We analyze one level of a quantum error correction circuit using nine data qubits in a Bacon-Shor code configured as a quantum memory. A hypothetical silicon double quantum dot quantum bit (qubit) is used as the fundamental element. A pessimistic estimate of the error probability of the quantum circuit is calculated using the total number of gates and idle time using a provably optimal schedule for the circuit operations obtained with an integer program methodology. The micro-architecture analysis provides insight about the different ways the electronics impact the circuit performance (e.g., extra idle time in the schedule), which can significantly limit the ultimate performance of any quantum circuit and therefore is a critical foundation for any future larger scale architecture analysis.
description: 10 pages, 7 figures, 3 tables
title: Universität Kassel, Vorlesungsverzeichnis WiSe 2014 / 2015
Creators: name: (:Unkn) Unknown
Publisher: name: Universität Kassel
Year: 2014
Subjects: subject: 350
subject: 370
subject: Universität Kassel
subject: Vorlesungsverzeichnis

description: PDF zum Online-Vorlesungsverzeichnis
Logarithmic corrections to $\mathbf{a^2}$ scaling in lattice QCD with Wilson and Ginsparg-Wilson quarks
Creators: name: Husung, Nikolai Andre
name: Marquard, Peter
name: Sommer, Rainer
Publisher: name: Deutsches Elektronen-Synchrotron, DESY, Hamburg
Year: 2021
Subjects: subject: 530
subject: sigma model, nonlinear
subject: quark
subject: scaling
subject: Ginsparg-Wilson relation
subject: quantum chromodynamics
subject: lattice field theory
subject: anomalous dimension
subject: lattice

description: The 38th International Symposium on Lattice Field Theory, LATTICE2021 26th-30th July, 2021 Zoom/Gather@Massachusetts Institute of Technology, Lattice 2021, Online, United States, 26 Jul 2021 - 30 Jul 2021; Proceedings of Science / International School for Advanced Studies (LATTICE2021), (2021).
description: We analyse the leading logarithmic corrections to the $a^2$ scaling of lattice artefacts in QCD, following the seminal work of Balog, Niedermayer and Weisz in the O(n) non-linear sigma model. Limiting the discussion to contributions from the action, the leading logarithmic corrections can be determined by the anomalous dimensions of mass-dimension 6 operators. These operators form a minimal on-shell basis of the Symanzik Effective Theory. We present results for non-perturbatively O($a$) improved Wilson and Ginsparg-Wilson quarks.
description: Published by SISSA, Trieste
A study on a privacy measure for social networks : computational complexity and properties on random graphs
Creators: name: Zhang, Congsong
Publisher: name: University of British Columbia
Year: 2018

description: As the booming of social networks, network analysis has benefited greatly from released network data. Meanwhile, the leakage of users' information is becoming more and more serious. The users' personal information may be compromised even if the data are anonymized before being released. Adversaries can uniquely re-identify a user in an anonymized social network by the quasi-identifiers as their background knowledge. To measure the resistance against privacy attacks in anonymized social networks where the background knowledge of adversaries is the metric representation, R. Trujillo-Rasua and I.G. Yero introduced a new measure: (k,l)-anonymity based on the notions k-antiresolving set and k-metric antidimension in 2016. In this thesis, we prove that the problem of computing k-metric antidimension is NP-hard by a polynomial-time reduction from a well-known NP-complete problem, the exact cover by the 3-sets problem (X3C problem), to a decision version of the problem of computing k-metric antidimension. With this conclusion, we prove that the (k,l)-anonymity problem is NP-complete. Also, in the hope to get a general relation between k and l in the (k,l)-anonymity problem, we study the behaviors of k-antiresolving sets in Erdos-Renyi random graphs. We establish three bounds on the size of k-antiresolving sets in Erdos-Renyi random graphs leading to a range of k-metric antidimension where k is constant.
A biophysical model of cell adhesion mediated by immunoadhesin drugs and antibodies
Creators: name: Gutenkunst, Ryan N.
name: Coombs, Daniel
name: Star, Toby
name: Dustin, Michael L.
name: Goldstein, Byron
Publisher: name: arXiv
Year: 2010
Subjects: subject: Cell Behavior (q-bio.CB)
subject: FOS: Biological sciences

description: A promising direction in drug development is to exploit the ability of natural killer cells to kill antibody-labeled target cells. Monoclonal antibodies and drugs designed to elicit this effect typically bind cell-surface epitopes that are overexpressed on target cells but also present on other cells. Thus it is important to understand adhesion of cells by antibodies and similar molecules. We present an equilibrium model of such adhesion, incorporating heterogeneity in target cell epitope density and epitope immobility. We compare with experiments on the adhesion of Jurkat T cells to bilayers containing the relevant natural killer cell receptor, with adhesion mediated by the drug alefacept. We show that a model in which all target cell epitopes are mobile and available is inconsistent with the data, suggesting that more complex mechanisms are at work. We hypothesize that the immobile epitope fraction may change with cell adhesion, and we find that such a model is more consistent with the data. We also quantitatively describe the parameter space in which binding occurs. Our results point toward mechanisms relating epitope immobility to cell adhesion and offer insight into the activity of an important class of drugs.
description: 13 pages, 5 figures
Mixing in Supersonic Turbulence
Creators: name: Pan, Liubin
name: Scannapieco, Evan
Publisher: name: arXiv
Year: 2010
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: In many astrophysical environments, mixing of heavy elements occurs in the presence of a supersonic turbulent velocity field. Here we carry out the first systematic numerical study of such passive scalar mixing in isothermal supersonic turbulence. Our simulations show that the ratio of the scalar mixing timescale, $τ_{\rm c}$, to the flow dynamical time, $τ_{\rm dyn}$ (defined as the flow driving scale divided by the rms velocity), increases with the Mach number, $M$, for $M \lsim3$, and becomes essentially constant for $M \gsim3.$ This trend suggests that compressible modes are less efficient in enhancing mixing than solenoidal modes. However, since the majority of kinetic energy is contained in solenoidal modes at all Mach numbers, the overall change in $τ_{\rm c}/τ_{\rm dyn}$ is less than 20\% over the range $1 \lsim M \lsim 6$. At all Mach numbers, if pollutants are injected at around the flow driving scale, $τ_{\rm c}$ is close to $τ_{\rm dyn}.$ This suggests that scalar mixing is driven by a cascade process similar to that of the velocity field. The dependence of $τ_{\rm c}$ on the length scale at which pollutants are injected into flow is also consistent with this cascade picture. Similar behavior is found for the variance decay timescales for scalars without continuing sources. Extension of the scalar cascade picture to the supersonic regime predicts a relation between the scaling exponents of the velocity and the scalar structure functions, with the scalar structure function becoming flatter as the velocity scaling steepens with Mach number. Our measurements of the volume-weighted velocity and scalar structure functions confirm this relation for $M\lsim 2,$ but show discrepancies at $M \gsim 3$.
description: Accepted by ApJ
Calculation of $ρ$ meson decay width from the PACS-CS configurations
Creators: name: CS Collaboration
name: Aoki, S.
name: ~Ishikawa, K. I.
name: Ishizuka, N.
name: Kanaya, K.
name: Kuramashi, Y.
name: Namekawa, Y.
name: Okawa, M.
name: Taniguchi, Y.
name: Ukawa, A.
name: Ukita, N.
name: Yamazaki, T.
name: Yoshié, T.
Publisher: name: arXiv
Year: 2010
Subjects: subject: High Energy Physics - Lattice (hep-lat)
subject: FOS: Physical sciences

description: We present preliminary results on the $ρ$ meson decay width from $N_f=2+1$ full QCD configurations generated by PACS-CS Collaboration. The decay width is estimated from the $P$-wave scattering phase shift for the isospin $I=1$ two-pion system. The finite size formula presented by Lüscher in the center of mass frame and its extension to non-zero total momentum frame by Rummukainen and Gottlieb are employed for the calculations of the phase shift. Our calculations are carried out at $m_π=410\ {\rm MeV}$ ($m_π/m_ρ=0.46$) and $a=0.091\ {\rm fm}$ on a $32^3\times 64$ ($La=2.9 {\rm fm}$) lattice.
description: 7 pages, 4 figures, talk given at the XXVIII International Symposium on Lattice Filed Theory, June 14-19,2010, Villasimius, Sardinia Italy
Bridging the gap between theory and practice of green building water system at the University of British Columbia, Canada
Creators: name: Badiei, Sahar
Publisher: name: University of British Columbia
Year: 2018

description: The sustainability of the built environment involves efficient performance of all related systems, including the water system. The way water is consumed in urban areas is proven to be inefficient and unsustainable. Although the green building industry has taken profound steps to reduce water footprints in the built environment, a significant gap is observed in predicted and actual performance of water systems in some green awarded projects. Therefore, this thesis aims to review, question and redefine water systems on paper and in practice of green building in the University of British Columbia (UBC) Vancouver campus. Water strategies within current green building practice are studied to find the performance gaps. The Center for Interactive Research of Sustainability (CIRS) building was researched as a case study through different lenses of academics, planners, designers, builders and operators, who were involved with this project. This research finds a number of successes and areas for improvement in water strategies of the CIRS project. The performance gaps are due to a lack of a comprehensive water plan for UBC, policies and incentives for water pricing, and not engaging all stakeholders in early stages of the process. Finally, this research recommends improving campus-wide water policies and plans and enhancing collaboration and integration throughout all phases of building projects. These strategies can bridge the gap between theory and practice of water systems in future green building projects at UBC.
Alfven Wave Amplification and Self-Containment of Cosmic-Rays Escaping from a Supernova Remnant
Creators: name: Fujita, Yutaka
name: Takahara, Fumio
name: Ohira, Yutaka
name: Iwasaki, Kazunari
Publisher: name: arXiv
Year: 2011
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: We study the escape of cosmic-ray (CR) protons accelerated at a supernova remnant (SNR) by numerically solving a diffusion-convection equation from the vicinity of the shock front to the region far away from the front. We consider the amplifications of Alfven waves generated by the escaping CR particles and their effects on CR escape into interstellar medium (ISM). We find that the amplification of the waves significantly delays the escape of the particles even far away from the shock front (on a scale of the SNR). This means that the energy spectrum of CR particles measured through gamma-ray observations at molecular clouds around SNRs is seriously affected by the particle scattering by the waves.
description: Accepted for publication in MNRAS
The first Herschel view of the mass-SFR link in high-z galaxies
Creators: name: Rodighiero, G.
name: Cimatti, A.
name: Gruppioni, C.
name: Popesso, P.
name: Andreani, P.
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: Fontana, A.
name: Schreiber, N. Forster
name: Franceschini, A.
name: Genzel, R.
name: Grazian, A.
name: Lutz, D.
name: Magdis, G.
name: Magliocchetti, M.
name: Magnelli, B.
name: Maiolino, R.
name: Mancini, C.
name: Nordon, R.
name: Garcia, A. M. Perez
name: Poglitsch, A.
name: Santini, P.
name: Sanchez-Portal, M.
name: Pozzi, F.
name: Riguccini, L.
name: Saintonge, A.
name: Shao, L.
name: Sturm, E.
name: Tacconi, L.
name: Valtchanov, I.
name: Wetzstein, M.
name: Wieprecht, E.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We exploit deep observations of the GOODS-N field taken with PACS, on board of Herschel, as part of the PEP guaranteed time, to study the link between star formation and stellar mass in galaxies to z~2. Starting from a stellar mass-selected sample of ~4500 galaxies with mag[4.5mu]<23 (AB), we identify ~350 objects with a PACS detection at 100 or 160mu and ~1500 with only Spitzer 24 mu counterpart. Stellar masses and total IR luminosities (LIR) are estimated by fitting the SEDs. Consistently with other Herschel results, we find that LIR based only on 24 mu data is overestimated by a median factor ~1.8 at z~2, whereas it is underestimated (with our approach) up to a factor ~1.6 at 0.510^(11) (M_sun) galaxies from z=0 to z=2, and seems to flatten at z>1.5 in this mass range. Moreover, the most massive galaxies have the lowest SSFR at any z, implying that they have formed their stars earlier and more rapidly than their low mass counterparts.
description: Accepted for publication in the A&A Herschel Special issue
Optical Properties of T-Shaped Quantum Wire Lasers
Creators: name: Sorba, L.
name: Schedelbeck, Gert
name: Wegscheider, Werner
name: Bichler, Max
name: Abstreiter, Gerhard
Publisher: name: Universität Regensburg
Year: 2000
Subjects: subject: 530 Physik

description: The optical properties of GaAs/AlGaAs T-shaped quantum wire (QWR) lasers have been investigated. In particular, we have studied the dependence of the stimulated emission intensity from the pump laser wavelength. We found that for an excitation power above the threshold for stimulated emission of the QWR, only for an excitation energy (= 782 nm) smaller than the absorption band of the multiple quantum well (MQW) lasing condition was achieved. For larger values of the excitation energy ( = 738 nm), only spontaneous emission of the QWR is observed. Furthermore, we have investigated the temperature stability of the QWR laser. We found a constant behavior of the QWR emission intensity in a temperature range from 4 to 40 K indicating a high stability of one-dimensional excitons up to 40 K, while an intensity decrease was measured for higher temperatures.
Jacobian deformation ellipsoid and Lyapunov stability analysis revisited
Creators: name: Waldner, Franz
name: Klages, Rainer
Publisher: name: arXiv
Year: 2010
Subjects: subject: Chaotic Dynamics (nlin.CD)
subject: FOS: Physical sciences

description: The stability analysis introduced by Lyapunov and extended by Oseledec is an excellent tool to describe the character of nonlinear n-dimensional flows by n global exponents if these flows are stable in time. However, there are two main shortcomings: (a) The local exponents fail to indicate the origin of instability where trajectories start to diverge. Instead, their time evolution contains a much stronger chaos than the trajectories, which is only eliminated by integrating over a long time. Therefore, shorter time intervals cannot be characterized correctly, which would be essential to analyse changes of chaotic character as in transients. (b) Moreover, although Oseledec uses an n dimensional sphere around a point x to be transformed into an n dimensional ellipse in first order, this local ellipse has yet not been evaluated. The aim of this contribution is to eliminate these two shortcomings. Problem (a) disappears if the Oseledec method is replaced by a frame with a 'constraint' as performed by Rateitschak and Klages (RK) [Phys. Rev. E 65 036209 (2002)]. The reasons why this method is better will be illustrated by comparing different systems. In order to analyze shorter time intervals, integrals between consecutive Poincare points will be evaluated. The local problems (b) will be solved analytically by introducing the symmetric 'Jacobian deformation ellipsoid' and its orthogonal submatrix, which enable to search in the full phase space for extreme local separation exponents. These are close to the RK exponents but need no time integration of the RK frame. Finally, four sets of local exponents are compared: Oseledec frame, RK frame, Jacobian deformation ellipsoid and its orthogonal submatrix.
description: 24 pages, 21 figures, submitted for publication
Survey of O VI absorption in the Large Magellanic Cloud
Creators: name: Pathak, A.
name: Pradhan, A. C.
name: Sujatha, N. V.
name: Murthy, Jayant
Publisher: name: arXiv
Year: 2010
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We present a survey of interstellar O VI absorption in the Large Magellanic Cloud (LMC) towards 70 lines of sight based on Far Ultraviolet Spectroscopic Explorer (FUSE) observations. The survey covers O VI absorption in a large number of objects in different environmental conditions of the LMC. Overall, a high abundance of O VI is present in active and inactive regions of the LMC with mean log[N(O VI)] = 14.23 atoms cm$^{-2}$. There is no correlation observed between O VI absorption and emissions from the hot gas (X-ray surface brightness) or the warm gas (H$_α$ surface brightness). O VI absorption in the LMC is patchy and the properties are similar to that of the Milky Way (MW). In comparison to the Small Magellanic Cloud (SMC), O VI is lower in abundance even though SMC has a lower metallicity compared to the LMC and the MW. We present observations in 10 superbubbles of the LMC of which we detect O VI absorption in 5 superbubbles for the first time and the superbubbles show an excess O VI absorption of about 40% compared to non-superbubble lines of sight. We have also studied the properties of O VI absorption in the 30 Doradus region. Even though O VI does not show any correlation with X-ray emission for the LMC, a good correlation between log[N(O VI)] and X-ray surface brightness for 30 Doradus region is present. We also find that O VI abundance decreases with increasing distance from the star cluster R136.
description: 25 pages, 9 figures. Accepted for publication in MNRAS
title: Altern in Gemeinde und Region
Creators: name: :None
Publisher: name: Wissenschaftliche Verlagsgesellschaft Stuttgart
Year: 2009
Subjects: subject: Lebensbedingungen
subject: Stadtentwicklung
subject: Regionalentwicklung
subject: Alter
subject: 300

description: Im Mittelpunkt des Bandes steht die Frage, in welcher Weise der Ort das Altern beeinflusst, welche Bedingungen schrumpfende und wachsende, ländliche und städtische, zentrennahe und periphere Gebiete für die Lebensqualität und die Chancen des Alterns bieten. Entwickelt wird eine Gesamtperspektive auf Themen, die die Alternsforschung und Stadt- bzw. Regionalforschung gegenseitig befruchten und einen interessanten Schnittpunkt politischer Aktivitäten bilden. Ausführlich dargestellt werden Handlungsfelder auf der lokalen und regionalen Ebene (Arbeit, Bildung, Gesundheit, Partizipation, Umwelt). Die Ergebnisse werden durch umfangreiches graphisches Material und zahlreiche Beispiele unterstützt, so dass vielfältige Anregungen für eine alternssensible Politik gegeben werden.
description: Nova Acta Leopoldina: NAL ; Abhandlungen der Deutschen Akademie der Naturforscher Leopoldina, vol. 103, Nummer 367
A Gibbs approach to Chargaff's second parity rule
Creators: name: Hart, Andrew
name: Martínez, Servet
name: Olmos, Felipe
Publisher: name: arXiv
Year: 2011
Subjects: subject: Probability (math.PR)
subject: Dynamical Systems (math.DS)
subject: Applications (stat.AP)
subject: FOS: Mathematics
subject: FOS: Computer and information sciences
subject: 62G10, 62M07, 62P10, 92D20

description: Chargaff's second parity rule (CSPR) asserts that the frequencies of short polynucleotide chains are the same as those of the complementary reversed chains. Up to now, this hypothesis has only been observed empirically and there is currently no explanation for its presence in DNA strands. Here we argue that CSPR is a probabilistic consequence of the reverse complementarity between paired strands, because the Gibbs distribution associated with the chemical energy between the bonds satisfies CSPR. We develop a statistical test to study the validity of CSPR under the Gibbsian assumption and we apply it to a large set of bacterial genomes taken from the GenBank repository.
description: 16 pages
Bursting SN 1996cr's Bubble: Hydrodynamic and X-ray Modeling of its Circumstellar Medium
Creators: name: Dwarkadas, Vikram V.
name: Dewey, Daniel
name: Bauer, Franz
Publisher: name: arXiv
Year: 2010
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: SN1996cr is one of the five closest SNe to explode in the past 30 years. Due to its fortuitous location in the Circinus Galaxy at ~ 3.7 Mpc, there is a wealth of recently acquired and serendipitous archival data available to piece together its evolution over the past decade, including a recent 485 ks Chandra HETG spectrum. In order to interpret this data, we have explored hydrodynamic simulations, followed by computations of simulated spectra and light curves under non-equilibrium ionization conditions, and directly compared them to the observations. Our simulated spectra manage to fit both the X-ray continuum and lines at 4 epochs satisfactorily, while our computed light curves are in good agreement with additional flux-monitoring data sets. These calculations allow us to infer the nature and structure of the circumstellar medium, the evolution of the SN shock wave, and the abundances of the ejecta and surrounding medium. The data imply that SN 1996cr exploded in a low-density medium before interacting with a dense shell of material about 0.03pc away from the progenitor star. We speculate that the shell could be due to the interaction of a blue supergiant or Wolf-Rayet wind with a previously existing red supergiant (RSG) wind. The shock wave has now exited the shell and is expanding in the medium exterior to it, possibly the undisturbed continuation of the dense RSG wind. The narrow lines that earned SN 1996cr its IIn designation possibly arise from dense, shocked clumps in the CSM. Although the possibility for an LBV progenitor for this Type IIn SN cannot be completely excluded, it is inconsistent with much of the data. These calculations allow us to probe the stellar mass loss in the very last phases ($ < 10^4$ years) of a massive star's life ($> 10^6$ years), and provide another means to deducing the progenitor of the SN.
description: Accepted to MNRAS. 21 pages, 8 Figures, 6 in color. For a version with higher resolution colour figures see http://astro.uchicago.edu/~vikram/1996cr/
Virtual Scanning Tunneling Microscopy: A Local Spectroscopic Probe of 2D Electron Systems
Creators: name: Sciambi, Adam
name: Pelliccione, Matthew
name: Bank, Seth R.
name: Gossard, Arthur C.
name: Goldhaber-Gordon, David
Publisher: name: arXiv
Year: 2010
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: We propose a novel probe technique capable of performing local low-temperature spectroscopy on a 2D electron system (2DES) in a semiconductor heterostructure. Motivated by predicted spatially-structured electron phases, the probe uses a charged metal tip to induce electrons to tunnel locally, directly below the tip, from a "probe" 2DES to a "subject" 2DES of interest. We test this concept with large-area (non-scanning) tunneling measurements, and predict a high spatial resolution and spectroscopic capability, with minimal influence on the physics in the subject 2DES.
title: Systemmodell für Selbstoptimierende Produktionssysteme
Creators: name: Mayer, Marcel Ph.
name: Schlick, Christopher M.
name: Müller, Simon
name: Freudenberg, Reinhard
name: Schmitt, Robert
Publisher: name: DuEPublico: Duisburg-Essen Publications Online, University of Duisburg-Essen, Germany
Year: 2013

description: Im Rahmen des Beitrages wird ein systematisches Modell für selbstoptimierende Produktionssysteme vorgestellt. Das Modell unterscheidet in Anlehnung an die kaskadierenden Qualitätsregelkreise nach SCHMITT et al. (2011) die folgenden Ebenen: 1) Segment, 2) Zelle, 3) Maschine und 4) Prozess. Die grundlegende Anforderung an das Modell ist dabei, dass jede Ebene für sich über selbstoptimierende Funktionen verfügen soll. Somit ergeben sich gekoppelte Teilsysteme, die „Fähigkeiten der Autonomie, der Wandlungsfähigkeit und der Kognition“ (SCHMITT et al. 2011, S.750) besitzen. Darüber hinaus kann jede untergeordnete Ebene als Regelstrecke der nächsthöheren betrachtet werden. Aufbauend auf den Arbeiten von LITOIU et al. (2005) im Bereich der hierarchischen Kontrolle von Softwaresystemen ergibt sich so ein kaskadierendes Regelkreismodell, welches eine selbstähnliche Struktur aufweist.
Slow quench dynamics of periodically driven quantum gases
Creators: name: Poletti, Dario
name: Kollath, Corinna
Publisher: name: arXiv
Year: 2011
Subjects: subject: Quantum Gases (cond-mat.quant-gas)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We study the evolution of bosons in a periodically driven optical lattice during a slow change of the driving amplitude. Both the regime of high frequency and low frequency driving are investigated. In the low frequency regime, resonant absorption of energy is observed. In the high frequency regime, the dynamics is compared to a system with an effective Hamiltonian in which the atoms are `dressed' by the driving field. This `dressing' can dramatically change the amplitude and sign of the effective tunneling. A particular focus of this study is the investigation of the time-scales necessary for the evolving quantum state to follow almost adiabatically to the ground-state of the effective many body system.
description: 10 pages, 8 figures
Disentangling the social net : examining the links between social capital, empowerment and social difference in two ecotourism villages in Ghana
Creators: name: Ramón Hidalgo, Ana Elia
Publisher: name: University of British Columbia
Year: 2018

description: Reconciling conservation of natural resources with rural community empowerment is a much-needed goal, and a global challenge. Community-based natural resource management (CBNRM) is one attempt to reconcile such endeavours. Attracted by its promises, social capital has become a focus for policy and research in CBNRM and community development in recent years. However, social capital has been approached as a catchall and a decontextualized concept, rendering the term close to unusable for effective management. Furthermore, the tendency to treat communities as homogenous units has created further confusion when examining the role of social capital and devising appropriate actions. In this context, the goal of this doctoral dissertation was to critically investigate social capital as it relates to empowerment and equity impacts to offer new insights for effective and contextually-driven practices, in particular within the context of community-based ecotourism (CBE). As such, this research borrows from the fields of sociology, feminist political ecology and community development, to investigate if and how social capital plays a role in community empowerment in two CBE projects in rural villages in the Volta Region of Ghana by employing a multimethod and multilevel approach. To avoid confounding terms and to navigate the complexity, I separately analyze different social capital and empowerment components. Employing both qualitative and quantitative data sources and analyses (including social network analysis) and incorporating a feminist perspective, I provide a novel, re-politicized and structured approach for the exploration, in the Ghanaian CBE context, of well-established social capital hypotheses that to date, have been primarily applied in Western societies. Overall, research findings show that social capital, social exclusions and empowerment opportunities are all interdependent phenomena occurring concurrently at different ecological scales and in different participatory spaces. I argue that a comprehensive understanding of the merits of social capital in the context of CBE requires a multilevel and multidimensional analytical approach and an interdisciplinary perspective to develop successful community projects that do not further social inequities but rather, enable collective action in, and shared benefits from, natural resource management.
Phase Space Engineering in Optical Microcavities I: Preserving near-field uniformity while inducing far-field directionality
Creators: name: Painchaud-April, Guillaume
name: Poirier, Julien
name: Gagnon, Denis
name: Dubé, Louis J.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: Optical microcavities have received much attention over the last decade from different research fields ranging from fundamental issues of cavity QED to specific applications such as microlasers and bio-sensors. A major issue in the latter applications is the difficulty to obtain directional emission of light in the far-field while keeping high energy densities inside the cavity (i.e. high quality factor). To improve our understanding of these systems, we have studied the annular cavity (a dielectric disk with a circular hole), where the distance cavity-hole centers, d, is used as a parameter to alter the properties of cavity resonances. We present results showing how one can affect the directionality of the far-field while preserving the uniformity (hence the quality factor) of the near-field simply by increasing the value of d. Interestingly, the transition between a uniform near- and far-field to a uniform near- and directional far-field is rather abrupt. We can explain this behavior quite nicely with a simple model, supported by full numerical calculations, and we predict that the effect will also be found in a large class of eigenmodes of the cavity.
description: 12th International Conference on Transparent Optical Networks
Evaluating uncertainty in tropical forest loss between 1990 and 2010 : an inter-comparison of different data sets
Creators: name: Ferretti-Gallon, Kalifi
Publisher: name: University of British Columbia
Year: 2018

description: Tropical forests are a lynchpin for environmental and social services, but are undergoing rapid deforestation. Despite the urgency of this issue, and despite rapid technological advances in monitoring tropical deforestation, and the existence of multiple studies of tropical forest loss over the last two decades, there is little certainty on the rates of tropical forest loss. We intercompared available pan-tropical forest change studies over the 1990-2010 period to examine: 1) differences in tropical forest loss during the 1990s, 2) differences in tropical forest loss in the 2000s, 3) differences in the rate of change of tropical forest loss from the 1990s to the 2000s, and 4) how these pan-tropical estimates compare to independent country/regional-level estimates of tropical forest loss. On balance, we conclude that tropical forest loss is decelerating between those decades. We also find that country reports from the Forest Resources Assessment of the Food and Agriculture Organization appear to be the least reliable; that satellite-based data appear the most reliable despite some persistent differences; and that there is higher agreement between forest loss estimates in Latin America. Our study improves current understanding of tropical forest loss in order to better inform policies to reduce deforestation, and in order to improve future tropical forest change analyses.
Quantum dots formed in a GaAs/AlGaAs quantum ring
Creators: name: Mühle, A.
name: Wegscheider, Werner
name: Haug, Rolf J.
Publisher: name: Universität Regensburg
Year: 2008
Subjects: subject: Aharonov-Bohm effect, aluminium compounds, Coulomb blockade, gallium arsenide, III-V semiconductors, quantum point contacts, semiconductor quantum dots
subject: 530 Physik
subject: 73.21.La; 73.63.Kv; 73.23.Hk

description: We demonstrate the tunability of a GaAs/AlGaAs quantum ring showing coherent Aharonov-Bohm oscillations up to a gate voltage regime where the ring splits into three quantum dots. This is explained based on the structure's special confinement potential. We characterized the dots by analyzing the corresponding sets of Coulomb blockade lines. Additionally, the spatial configuration of the dots was confirmed by charge measurements using an adjacent quantum point contact.