cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Quantifying Molecular Stiffness and Interaction with Lateral Force Microscopy
Creators: name: Weymouth, Alfred J.
name: Hofmann, Thomas
name: Giessibl, Franz J.
Publisher: name: Universität Regensburg
Year: 2014
Subjects: subject: 530 Physik

description: The spatial resolution of atomic force microscopy (AFM) can be drastically increased by terminating the tip with a single CO molecule. However, the CO molecule is not stiff, and lateral forces, such as those around the sides of molecules, distort images. This issue begs a larger question of how AFM can probe structures that are laterally weak. Lateral force microscopy (LFM) can probe lateral stiffnesses that are not accessible to normal-force AFM, resulting in higher spatial resolution. With LFM, we determined the torsional spring constant of a CO-terminated tip molecule to be 0.24 N/m. This value is less than that of a surface molecule, and an example of a system whose stiffness is a product not only of bonding partners but also local environment.
Minimal supersolutions of convex BSDEs
Creators: name: Drapeau, Samuel
name: Heyne, Gregor
name: Kupper, Michael
Publisher: name: arXiv
Year: 2011
Subjects: subject: Probability (math.PR)
subject: FOS: Mathematics

description: We study the nonlinear operator of mapping the terminal value $ξ$ to the corresponding minimal supersolution of a backward stochastic differential equation with the generator being monotone in $y$, convex in $z$, jointly lower semicontinuous and bounded below by an affine function of the control variable $z$. We show existence, uniqueness, monotone convergence, Fatou's lemma and lower semicontinuity of this operator. We provide a comparison principle for minimal supersolutions of BSDEs.
description: Published in at http://dx.doi.org/10.1214/13-AOP834 the Annals of Probability (http://www.imstat.org/aop/) by the Institute of Mathematical Statistics (http://www.imstat.org)
Phase stabilities at a glance: Stability diagrams of nickel dipnictides
Creators: name: Bachhuber, Frederik
name: Rothballer, Jan
name: Söhnel, Th.
name: Weihrich, Richard
Publisher: name: Universität Regensburg
Year: 2013
Subjects: subject: 540 Chemie

description: In the course of the recent advances in chemical structure prediction, a straightforward type of diagram to evaluate phase stabilities is presented based on an expedient example. Crystal structures and energetic stabilities of dipnictides Ni Pn 2 (Pn = N, P, As, Sb, Bi) are systematically investigated by first principles calculations within the framework of density functional theory using the generalized gradient approximation to treat exchange and correlation. These dipnictides show remarkable polymorphism that is not yet understood systematically and offers room for the discovery of new phases. Relationships between the concerned structures including the marcasite, the pyrite, the arsenopyrite/CoSb2, and the NiAs2 types are highlighted by means of common structural fragments. Electronic stabilities of experimentally known and related AB2 structure types are presented graphically in so-called stability diagrams. Additionally, competing binary phases are taken into consideration in the diagrams to evaluate the stabilities of the title compounds with respect to decomposition. The main purpose of the stability diagrams is the introduction of an image that enables the estimation of phase stabilities at a single glance. Beyond that, some of the energetically favored structure types can be identified as potential new phases.
Temperature dependence of ion-beam mixing in crystalline and amorphous germanium isotope multilayer structures
Creators: name: Radek, M.
name: Bracht, H.
name: Posselt, M.
name: Schmidt, B.
name: Bougeard, Dominique
Publisher: name: Universität Regensburg
Year: 2014
Subjects: subject: 530 Physik

description: Self-atom mixing induced by 310 keV gallium (Ga) ion implantation in crystalline and preamorphized germanium (Ge) at temperatures between 164 K and 623 K and a dose of 1 × 1015 cm−2 is investigated using isotopic multilayer structures of alternating 70 Ge and nat Ge layers grown by molecular beam epitaxy. The distribution of the implanted Ga atoms and the ion-beam induced depth-dependent self-atom mixing was determined by means of secondary ion mass spectrometry. Three different temperature regimes of self-atom mixing, i.e., low-, intermediate-, and high-temperature regimes are observed. At temperatures up to 423 K, the mixing is independent of the initial structure, whereas at 523 K, the intermixing of the preamorphized Ge structure is about twice as high as that of crystalline Ge. At 623 K, the intermixing of the initially amorphous Ge structure is strongly reduced and approaches the mixing of the crystalline material. The temperature dependence of ion-beam mixing is described by competitive amorphization and recrystallization processes.
Asymmetric Neutrino Emission from Magnetized Proto-Neutron Star Matter including Hyperons in Relativistic Mean Field Theory
Creators: name: Maruyama, Tomoyuki
name: Kajino, Toshitaka
name: Yasutake, Nobutoshi
name: Cheoun, Myung-Ki
name: Ryu, Chung-Yeol
Publisher: name: arXiv
Year: 2010
Subjects: subject: Nuclear Theory (nucl-th)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We calculate asymmetric neutrino absorption and scattering cross sections on hot and dense magnetized neutron-star matter including hyperons in fully relativistic mean field theory. The absorption/scattering cross sections are suppressed/enhanced incoherently in the direction of the magnetic fielld, B. The asymmetry is 2-4% at the matter density ρ_0 < ρ_B < 3ρ_0 and temperature T < 40 MeV for B=2 X 10^{17} G. This asymmetry is comparable to the effects owing to parity violation or asymmetric magnetic field topology proposed for the origin of pulsar kicks.
description: 9 pages, 3 figure
Automated lumbar vertebral level identification using ultrasound
Creators: name: Hetherington, Jorden Hicklin
Publisher: name: University of British Columbia
Year: 2018

description: Spinal needle procedures require identification of the vertebral level for effectiveness and safety. E.g. in obstetric epidurals, the preferred target is between the third and fourth lumbar vertebra. The current clinical standard involves "blind" identification of the level through manual palpation, which only has a 30% reported accuracy. Therefore, there is a need for better anatomical identification prior to needle insertion. Ultrasound provides anatomical information to physicians, which is not obtainable via manual palpation. However, due to artifacts and the complex anatomy of the spine, ultrasound is not commonly used for pre-puncture planning. This thesis describes two machine learning based systems that can aid physicians to utilize ultrasound for lumbar level identification. The first system, LIT, is proposed to identify vertebrae, assigning them to their respective levels and tracking them in a sequence of ultrasound images in the paramedian plane. A deep sparse auto-encoder network learns to extract anatomical features from pre-processed ultrasound images. A feasibility study (n=15) evaluated performance. The second system, SLIDE, identifies vertebral levels from a sequence of ultrasound images in the transverse plane. The system uses a deep convolutional neural network (CNN) to classify transverse planes of the lower spine. In conjunction, a novel state-machine is developed to automatically identify vertebral levels as the transducer moves. A feasibility study (n=20) evaluated performance. The CNN achieves 88% accuracy in discriminating images from three planes of the spine. As a system, SLIDE successfully identifies all lumbar levels in 17 of 20 test scans, processed at real-time speed. A clinical study with 76 parturient patients was performed. The study compares level identification accuracy between manual palpation, versus SLIDE, with both compared to freehand ultrasound. SLIDE's level identification outperformed palpation with an odds ratio of nearly 3. A subset of recorded ultrasound (n=60) was labeled and used to retrain the CNN, improving classification accuracy to 93%. The systems showcase the utility of machine learning in spinal ultrasound analysis, with varied approaches to automatically identifying vertebral levels. The systems can be used to improve the accuracy of vertebral level identification compared to manual palpation alone.
Temporal predictability facilitates action, not perception
Creators: name: Thomaschke, Roland
name: Dreisbach, Gesine
Publisher: name: Universität Regensburg
Year: 2013
Subjects: subject: temporal cognition; time estimation, time perception, motor processes, attention, temporal frequency
subject: 150 Psychologie

description: Expectancy for upcoming action requirements is a fundamental prerequisite for human control of action. In the research reported here, we investigated which part of cognitive processing benefits from temporal predictability. In a binary forced-choice paradigm, visual targets were preceded by different intervals. In one condition, targets could be predicted by the length of the intervals. In other conditions, response goals or response effectors could be predicted by the length of the intervals. Behavioral advantages were observed when response effectors were temporally predictable, whereas temporal predictability of response goals and target stimuli was not sufficient. The findings thus show that temporal expectancy in speeded choice-reaction tasks facilitates late, effector-specific motor processing. These findings are of importance not only for our basic understanding of action control but also for any human-machine interaction that involves system delays.
Experimental investigation of the optical spin-selection rules in bulk Si and Ge/Si quantum dots
Creators: name: Sircar, N.
name: Bougeard, Dominique
Publisher: name: Universität Regensburg
Year: 2014
Subjects: subject: 530 Physik

description: We study the relationship between the circular polarization of photoluminescence and the magnetic-field-induced spin polarization of the recombining charge carriers in bulk Si and Ge/Si quantum dots. First, we quantitatively compare experimental results on the degree of circular polarization of photons resulting from phonon-assisted radiative transitions in intrinsic and doped bulk Si with calculations which we adapt from recently predicted spin-dependent phonon-assisted transition probabilities in Si. The excellent agreement of our experiments and calculations quantitatively verifies these spin-dependent transition probabilities and extends their validity to weak magnetic fields. Such magnetic fields can induce a luminescence polarization of up to 3%/T. We then investigate phononless transitions in Ge/Si quantum dots as well as in degenerately doped Si. Our experiments systematically show that the sign of the degree of circular polarization of luminescence resulting from phononless transitions is opposite to the one associated with phonon-assisted transitions in Si and with phononless transitions in direct-band-gap semiconductors. This observation implies qualitatively different spin-dependent selection rules for phononless transitions, which seem to be related to the confined character of the electron wave function.
An indispensable classification of monomial curves in $\mathbb{A}^4(\mathbbmss{k}) $
Creators: name: Katsabekis, Anargyros
name: Ojeda, Ignacio
Publisher: name: arXiv
Year: 2011
Subjects: subject: Commutative Algebra (math.AC)
subject: FOS: Mathematics
subject: 13F20 (Primary) 16W50, 13F55 (Secondary)

description: In this paper a new classification of monomial curves in $\mathbb{A}^4(\mathbbmss{k})$ is given. Our classification relies on the detection of those binomials and monomials that have to appear in every system of binomial generators of the defining ideal of the monomial curve; these special binomials and monomials are called indispensable in the literature. This way to proceed has the advantage of producing a natural necessary and sufficient condition for the definining ideal of a monomial curve in $\mathbb{A}^4(\mathbbmss{k})$ to have a unique minimal system of binomial generators. Furthermore, some other interesting results on more general classes of binomial ideals with unique minimal system of binomial generators are obtained.
description: 17 pages; fixed typos, added some clarifying remarks, minor corrections to the original version. Accepted for publication in Pacific Journal of Mathematics
Geologic Hazards in Kentucky
Creators: name: Carey, Daniel I.
name: Hounshell, Terry D.
name: Kiefer, John D.
Publisher: name: Kentucky Geological Survey, University of Kentucky
Year: 2008

description: Abstract:
Geologic data were derived from the Kentucky Geological Survey-U.S. Geological Survey areal geologic mapping project. Nearly 190 geologists mapped the geology of Kentucky from 1960 to 1978. KGS geologists converted the resulting 707 geologic quadrangle maps into digital format at part of the STATEMAP component of the National Cooperative Geologic Mapping Program of the United States Geological Survey.
Holder Shadowing on Finite Intervals
Creators: name: Tikhomirov, Sergey
Publisher: name: arXiv
Year: 2011
Subjects: subject: Dynamical Systems (math.DS)
subject: FOS: Mathematics
subject: 37C50, 37D20

description: For any $θ, ω> 1/2$ we prove that, if any $d$-pseudotrajectory of length $\sim 1/d^ω$ of a diffeomorphism $f\in C^2$ can be $d^θ$-shadowed by an exact trajectory, then $f$ is structurally stable. Previously it was conjectured by Hammel-Grebogi-Yorke that for $θ= ω= 1/2$ this property holds for a wide class of non-uniformly hyperbolic diffeomorphisms. In the proof we introduce the notion of sublinear growth property for inhomogenious linear equations and prove that it implies exponential dichotomy.
description: 19 pages. Minor changes
The transcript elongation factor SPT4/SPT5 is involved in auxin-related gene expression in Arabidopsis
Creators: name: Dürr, Julius
name: Lolas, Ihab B.
name: Sørensen, Brian B.
name: Schubert, Veit
name: Houben, Andreas
name: Melzer, Michael
name: Deutzmann, Rainer
name: Grasser, Marion
name: Grasser, Klaus D.
Publisher: name: Universität Regensburg
Year: 2014
Subjects: subject: 580 Pflanzen (Botanik)

description: The heterodimeric complex SPT4/SPT5 is a transcript elongation factor (TEF) that directly interacts with RNA polymerase II (RNAPII) to regulate messenger RNA synthesis in the chromatin context. We provide biochemical evidence that in Arabidopsis, SPT4 occurs in a complex with SPT5, demonstrating that the SPT4/SPT5 complex is conserved in plants. Each subunit is encoded by two genes SPT4-1/2 and SPT5-1/2. A mutant affected in the tissue-specifically expressed SPT5-1 is viable, whereas inactivation of the generally expressed SPT5-2 is homozygous lethal. RNAi-mediated downregulation of SPT4 decreases cell proliferation and causes growth reduction and developmental defects. These plants display especially auxin signalling phenotypes. Consistently, auxin-related genes, most strikingly AUX/IAA genes, are downregulated in SPT4–RNAi plants that exhibit an enhanced auxin response. In Arabidopsis nuclei, SPT5 clearly localizes to the transcriptionally active euchromatin, and essentially co-localizes with transcribing RNAPII. Typical for TEFs, SPT5 is found over the entire transcription unit of RNAPII-transcribed genes. In SPT4–RNAi plants, elevated levels of RNAPII and SPT5 are detected within transcribed regions (including those of downregulated genes), indicating transcript elongation defects in these plants. Therefore, SPT4/SPT5 acts as a TEF in Arabidopsis, regulating transcription during the elongation stage with particular impact on the expression of certain auxin-related genes.
Decomposition of Unitary Matrices for Finding Quantum Circuits: Application to Molecular Hamiltonians
Creators: name: Daskin, Anmer
name: Kais, Sabre
Publisher: name: arXiv
Year: 2010
Subjects: subject: Quantum Physics (quant-ph)
subject: Information Theory (cs.IT)
subject: FOS: Physical sciences
subject: FOS: Computer and information sciences

description: Constructing appropriate unitary matrix operators for new quantum algorithms and finding the minimum cost gate sequences for the implementation of these unitary operators is of fundamental importance in the field of quantum information and quantum computation. Evolution of quantum circuits faces two major challenges: complex and huge search space and the high costs of simulating quantum circuits on classical computers. Here, we use the group leaders optimization algorithm to decompose a given unitary matrix into a proper-minimum cost quantum gate sequence. We test the method on the known decompositions of Toffoli gate, the amplification step of the Grover search algorithm, the quantum Fourier transform, and the sender part of the quantum teleportation. Using this procedure, we present the circuit designs for the simulation of the unitary propagators of the Hamiltonians for the hydrogen and the water molecules. The approach is general and can be applied to generate the sequence of quantum gates for larger molecular systems.
The RNA polymerase trigger loop functions in all three phases of the transcription cycle
Creators: name: Fouqueau, Thomas
name: Zeller, Mirijam Elisabeth
name: Cheung, Alan C.
name: Cramer, Patrick
name: Thomm, Michael
Publisher: name: Universität Regensburg
Year: 2013
Subjects: subject: 570 Biowissenschaften, Biologie

description: The trigger loop (TL) forms a conserved element in the RNA polymerase active centre that functions in the elongation phase of transcription. Here, we show that the TL also functions in transcription initiation and termination. Using recombinant variants of RNA polymerase from Pyrococcus furiosus and a reconstituted transcription system, we demonstrate that the TL is essential for initial RNA synthesis until a complete DNA–RNA hybrid is formed. The archaeal TL is further important for transcription fidelity during nucleotide incorporation, but not for RNA cleavage during proofreading. A conserved glutamine residue in the TL binds the 2’-OH group of the nucleoside triphosphate (NTP) to discriminate NTPs from dNTPs. The TL also prevents aberrant transcription termination at non-terminator sites.
On hyperbolic Bessel processes and beyond
Creators: name: Jakubowski, Jacek
name: Wiśniewolski, Maciej
Publisher: name: arXiv
Year: 2011
Subjects: subject: Probability (math.PR)
subject: Statistics Theory (math.ST)
subject: FOS: Mathematics

description: We investigate distributions of hyperbolic Bessel processes. We find links between the hyperbolic cosine of hyperbolic Bessel processes and functionals of geometric Brownian motion. We present an explicit formula for the Laplace transform of the hyperbolic cosine of a hyperbolic Bessel process and some other interesting probabilistic representations of this Laplace transform. We express the one-dimensional distribution of a hyperbolic Bessel process in terms of other, known and independent processes. We present some applications including a new proof of Bougerol's identity and its generalization. We characterize the distribution of the process which is the hyperbolic sine of hyperbolic Bessel process.
description: Published in at http://dx.doi.org/10.3150/12-BEJ458 the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm)
Chemical and Crystallographic Characterization of the Tip Apex in Scanning Probe Microscopy
Creators: name: Hofmann, Thomas
name: Pielmeier, Florian
name: Giessibl, Franz J.
Publisher: name: Universität Regensburg
Year: 2014
Subjects: subject: Atomic force microscopy (AFM), Scanning tunneling microscopy (including chemistry induced with STM), Structure of nanoscale materials
subject: 530 Physik
subject: 68.37.Ps
subject: 61.46.-w
subject: 68.37.Ef

description: The apex atom of a W scanning probe tip reveals a nonspherical charge distribution as probed by a CO molecule bonded to a Cu(111) surface [Welker et al., Science 336, 444 (2012).]. Three high-symmetry images were observed and related to three low-index crystallographic directions of the W bcc crystal. Open questions remained, such as the detectability of a contamination of W tips by sample material (here Cu), and the applicability of the method to distinguish other atomic species. In this work, we investigate bulk Cu and Fe tips. In both cases, we can associate our data with the fcc (Cu) and bcc (Fe) crystal structures using a simple electrostatic model that is based on the partial filling of d orbitals.
The final candidate from the JVAS/CLASS search for 6 arcsec to 15 arcsec image separation lensing
Creators: name: McKean, J. P.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: A search for 6 arcsec to 15 arcsec image separation lensing in the Jodrell Bank-Very Large Array Astrometric Survey (JVAS) and the Cosmic Lens All-Sky Survey (CLASS) by Phillips et al. found thirteen group and cluster gravitational lens candidates. Through radio and optical imaging and spectroscopy, Phillips et al. ruled out the lensing hypothesis for twelve of the candidates. In this paper, new optical imaging and spectroscopy of J0122+427, the final lens candidate from the JVAS/CLASS 6 arcsec to 15 arcsec image separation lens search, are presented. This system is found not to be a gravitational lens, but is just two radio-loud active galactic nuclei that are separated by ~10 arcsec on the sky and are at different redshifts. Therefore, it is concluded that there are no gravitational lenses in the JVAS and CLASS surveys with image separations between 6 arcsec to 15 arcsec. This result is consistent with the expectation that group- and cluster-scale dark matter haloes are inefficient lenses due to their relatively flat inner density profiles.
description: 5 pages, 3 figures, 2 tables, accepted for publication in MNRAS
Nested Sampling with Constrained Hamiltonian Monte Carlo
Creators: name: Betancourt, M. J.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Data Analysis, Statistics and Probability (physics.data-an)
subject: FOS: Physical sciences

description: Nested sampling is a powerful approach to Bayesian inference ultimately limited by the computationally demanding task of sampling from a heavily constrained probability distribution. An effective algorithm in its own right, Hamiltonian Monte Carlo is readily adapted to efficiently sample from any smooth, constrained distribution. Utilizing this constrained Hamiltonian Monte Carlo, I introduce a general implementation of the nested sampling algorithm.
description: 15 pages, 4 figures
Optimal stopping in a general framework
Creators: name: Kobylanski, Magdalena
name: Quenez, Marie-Claire
Publisher: name: arXiv
Year: 2010
Subjects: subject: Probability (math.PR)
subject: FOS: Mathematics

description: We study the optimal stopping time problem $v(S)={\rm ess}\sup_{θ\geq S} E[ϕ(θ)|\mathcal {F}_S]$, for any stopping time $S$, where the reward is given by a family $(ϕ(θ),θ\in\mathcal{T}_0)$ \emph{of non negative random variables} indexed by stopping times. We solve the problem under weak assumptions in terms of integrability and regularity of the reward family. More precisely, we only suppose $v(0) < + \infty$ and $ (ϕ(θ),θ\in \mathcal{T}_0)$ upper semicontinuous along stopping times in expectation. We show the existence of an optimal stopping time and obtain a characterization of the minimal and the maximal optimal stopping times. We also provide some local properties of the value function family. All the results are written in terms of families of random variables and are proven by only using classical results of the Probability Theory.
Multi-objective Gaussian process approach for robust optimization and prediction of carbonization process
Creators: name: Ramezankhani, Milad
Publisher: name: University of British Columbia
Year: 2017

description: Carbon fibers are high-performance and high-strength reinforcement materials in advanced industries such as aerospace, automotive and energy sector. This class of materials is often derived from polyacrylonitrile (PAN) fiber precursor. The conversion of polyacrylonitrile precursor to carbon fibers is essentially comprised of two major stages; namely, stabilization and carbonization. The carbonization is a very energy-consuming and expensive step due to its high temperature requirements. In order to achieve desirable physical and mechanical properties of carbon fibers through this step, a large amount of energy is required. A cost-effective approach to optimize energy consumption of this process, however, is the use of predictive modelling techniques. In that goal, herein, a Gaussian Process (GP) approach is proposed to firstly, predict multiple mechanical properties of carbon fibers in the presence of manufacturing noise and secondly, optimize them under a minimum energy consumption criterion and a range of process constraints and bounds. The resulting model for each property of carbon fibers consists of two Gaussian Process models. The first model describes the mean value of the property and the second one predicts its standard deviation. The proposed Gaussian Process approach is compared to a traditional regression approach using the measurements obtained from the Carbon Nexus pilot plant in Australia. The Gaussian Process approach clearly proved to be more effective in terms of both prediction accuracy and robustness. Through employing Gaussian Process models, the modulus and tensile strength mean values of carbon fibers along with their standard deviations (STD) were successfully predicted under different process conditions. Squared exponential covariance and linear mean functions were proven to be most suitable in constructing the Gaussian Process in the performed case study. It was found that the modulus and tensile strength responses do not have an evident correlation with respect to each other, hence a multi-objective optimization approach was developed to acquire overall optimum process conditions. To estimate the trade-off between fiber material properties under the multi-objective optimization problem, a standard as well as an adaptive weighted sum method was applied under various constraints and bounds, including the energy consumed during carbonization.
Egg-layiyng "intermorphs" in the ant Crematogaster smithi neither affect sexual production nor male parentage
Creators: name: Oettler, Jan
name: Dijkstra, Michiel B.
name: Heinze, Jürgen
Publisher: name: Universität Regensburg
Year: 2013
Subjects: subject: 570 Biowissenschaften, Biologie

description: We study male parentage and between-colony variation in sex allocation and sexual production in the desert ant Crematogaster smithi, which usually has only one singly-mated queen per nest. Colonies of this species are known to temporarily store nutrients in the large fat body of intermorphs, a specialized female caste intermediate in morphology between queens and workers. Intermorphs repackage at least part of this fat into consumable but viable male-destined eggs. If these eggs sometimes develop instead of being eaten, intermorphs will be reproductive competitors of the queen but—due to relatedness asymmetries—allies of their sister worker. Using genetic markers we found a considerable proportion of non-queen sons in some, but not all, colonies. Even though intermorphs produce ~1.7× more eggs than workers, their share in the parentage of adult males is estimated to be negligible due to their small number compared to workers. Furthermore, neither colony-level sex allocation nor overall sexual production was correlated with intermorph occurrence or number. We conclude that intermorph-laid eggs typically do not survive and that the storage of nutrients and their redistribution as eggs by intermorphs is effectively altruistic.
Relativistic point-form approach to hadron properties
Creators: name: Plessas, W.
Publisher: name: arXiv
Year: 2010
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: We present a review of the description of hadron properties along an invariant mass operator in the point form of Poincaré-invariant relativistic dynamics. The quark-quark interaction is furnished by a linear confinement, consistent with the QCD string tension, and a hyperfine interaction derived from Goldstone-boson exchange. The main advantage of the point-form approach is the possibility of calculating manifestly covariant observables, since the generators of Lorentz transformations remain interaction-free. We discuss the static properties of the mass-operator eigenstates, such as the invariant mass spectra of light- and heavy-flavor baryons, the characteristics of the eigenstates in terms of their spin, flavor, and spatial dependences as well as their classification into spin-flavor multiplets. Regarding dynamical observables we address the electroweak structures of the nucleon and hyperon ground states, including their electric radii, magnetic moments as well as axial charges, and in addition a recently derived microscopic description of the $πNN$ as well as $πNΔ$ interaction vertices. Except for hadronic resonance decays, which are not addressed here due to space limitations, all of these observables are obtained in good agreement with existing phenomenology. Relativistic (boost) effects are generally sizable. We conclude that low-energy hadrons can be well described by an effective theory with a finite number of degrees of freedom, as long as the symmetries of low-energy quantum chromodynamics (spontaneously broken chiral symmetry) as well as special relativity (Poincaré invariance) are properly taken into account. The latter requirement is particularly well and efficiently met in the point-form approach.
description: 10 pages, 8 figures, 3 tables Contribution to the LC2010 Conference, Valencia, Spain, June 14-18,2010
Pheromone Diversification and Age-Dependent Behavioural Plasticity Decrease Interspecific Mating Costs in Nasonia
Creators: name: Ruther, Joachim
name: McCaw, Jennifer
name: Böcher, Lisa
name: Pothmann, Daniela
name: Putz, Irina
Publisher: name: Universität Regensburg
Year: 2014
Subjects: subject: 590 Tiere (Zoologie)

description: Interspecific mating can cause severe fitness costs due to the fact that hybrids are often non-viable or less fit. Thus, theory predicts the selection of traits that lessen reproductive interactions between closely related sympatric species. Males of the parasitic wasp Nasonia vitripennis differ from all other Nasonia species by an additional sex pheromone component, but the ecological selective forces underlying this pheromone diversification are unknown. Here we present data from lab experiments suggesting that costly interspecific sexual interactions with the sympatric species N. giraulti might have been responsible for the pheromone evolution and some courtship-related behavioural adaptations in N. vitripennis. Most N. giraulti females are inseminated already within the host, but N. giraulti males still invest in costly sex pheromones after emergence. Furthermore, they do not discriminate between N. vitripennis females and conspecifics during courtship. Therefore, N. vitripennis females, most of which emerge as virgins, face the risk of mating with N. giraulti resulting in costly all-male broods due to Wolbachia-induced cytoplasmic incompatibility. As a counter adaptation, young N. vitripennis females discriminate against N. giraulti males using the more complex conspecific sex pheromone and reject most of them during courtship. With increasing age, however, N. vitripennis females become less choosy, but often compensate mating errors by re-mating with a conspecific. By doing so, they can principally avoid suboptimal offspring sex ratios, but a microcosm experiment suggests that under more natural conditions N. vitripennis females cannot completely avoid fitness costs due to heterospecific mating. Our study provides support for the hypothesis that communication interference of closely related sympatric species using similar sexual signals can generate selective pressures that lead to their divergence.
On the Chromatic Thresholds of Hypergraphs
Creators: name: Balogh, József
name: Butterfield, Jane
name: Hu, Ping
name: Lenz, John
name: Mubayi, Dhruv
Publisher: name: arXiv
Year: 2011
Subjects: subject: Combinatorics (math.CO)
subject: FOS: Mathematics

description: Let F be a family of r-uniform hypergraphs. The chromatic threshold of F is the infimum of all non-negative reals c such that the subfamily of F comprising hypergraphs H with minimum degree at least $c \binom{|V(H)|}{r-1}$ has bounded chromatic number. This parameter has a long history for graphs (r=2), and in this paper we begin its systematic study for hypergraphs. Łuczak and Thomassé recently proved that the chromatic threshold of the so-called near bipartite graphs is zero, and our main contribution is to generalize this result to r-uniform hypergraphs. For this class of hypergraphs, we also show that the exact Turán number is achieved uniquely by the complete (r+1)-partite hypergraph with nearly equal part sizes. This is one of very few infinite families of nondegenerate hypergraphs whose Turán number is determined exactly. In an attempt to generalize Thomassen's result that the chromatic threshold of triangle-free graphs is 1/3, we prove bounds for the chromatic threshold of the family of 3-uniform hypergraphs not containing {abc, abd, cde}, the so-called generalized triangle. In order to prove upper bounds we introduce the concept of fiber bundles, which can be thought of as a hypergraph analogue of directed graphs. This leads to the notion of fiber bundle dimension, a structural property of fiber bundles that is based on the idea of Vapnik-Chervonenkis dimension in hypergraphs. Our lower bounds follow from explicit constructions, many of which use a hypergraph analogue of the Kneser graph. Using methods from extremal set theory, we prove that these Kneser hypergraphs have unbounded chromatic number. This generalizes a result of Szemerédi for graphs and might be of independent interest. Many open problems remain.
description: 37 pages, 4 figures
Non-perturbative renormalization of quark mass in Nf=2+1 QCD with the Schroedinger functional scheme
Creators: name: Taniguchi, Yusuke
Publisher: name: arXiv
Year: 2010
Subjects: subject: High Energy Physics - Lattice (hep-lat)
subject: FOS: Physical sciences

description: We present an evaluation of the quark mass renormalization factor for Nf=2+1 QCD. The Schroedinger functional scheme is employed as the intermediate scheme to carry out non-perturbative running from the low energy to deep in the high energy perturbative region. The regularization independent step scaling function of the quark mass is obtained in the continuum limit. Renormalization factors for the pseudo scalar density and the axial vector current are also evaluated for the same action and the bare couplings as two recent large scale Nf=2+1 simulations; previous work of the CP-PACS/JLQCD collaboration, which covered the up-down quark mass range heavier than m_pi=500 MeV and that of PACS-CS collaboration on the physical point using the reweighting technique.
description: 7 pages, talk given at the XXVIII International Symposium on Lattice Filed Theory, June 14-19,2010, Villasimius, Sardinia Italy
Quantum Graphs Whose Spectra Mimic the Zeros of the Riemann Zeta Function
Creators: name: Kuipers, Jack
name: Hummel, Quirin
name: Richter, Klaus
Publisher: name: Universität Regensburg
Year: 2014
Subjects: subject: 530 Physik
subject: 03.65.Sq,
subject: 02.10.De
subject: 05.45.Mt

description: One of the most famous problems in mathematics is the Riemann hypothesis: that the nontrivial zeros of the Riemann zeta function lie on a line in the complex plane. One way to prove the hypothesis would be to identify the zeros as eigenvalues of a Hermitian operator, many of whose properties can be derived through the analogy to quantum chaos. Using this, we construct a set of quantum graphs that have the same oscillating part of the density of states as the Riemann zeros, offering an explanation of the overall minus sign. The smooth part is completely different, and hence also the spectrum, but the graphs pick out the low-lying zeros.
Morphology, Chemistry and Function of the Postpharyngeal Gland in the South American Digger Wasps Trachypus boharti and Trachypus elongatus
Creators: name: Herzner, Gudrun
name: Kaltenpoth, Martin
name: Poettinger, T.
name: Weiss, Katharina
name: Koedam, Dirk
name: Kroiss, Johannes
name: Strohm, Erhard
Publisher: name: Universität Regensburg
Year: 2013
Subjects: subject: 590 Tiere (Zoologie)

description: Microbes pose severe threats to animals as competitors or pathogens and strongly affect the evolution of life history traits like parental care. Females of the European beewolf Philanthus triangulum, a solitary digger wasp, provision their offspring with paralyzed honeybees and embalm them with the secretion from large postpharyngeal glands (PPG) that contain mainly unsaturated hydrocarbons. This coating changes the physico-chemical properties of the prey surface, causes a reduction of water condensation and retards growth of mold fungi. Here we examined the closely related South American genus Trachypus, which shows a life-history similar to Philanthus. We investigated whether Trachypus spp. also possess PPGs and embalm larval provisions. Using histological methods and 3D reconstructions we show that Trachypus boharti and T. elongatus possess PPGs that are similar to P. triangulum but somewhat smaller. The ultrastructure of the gland epithelium suggests that the gland content is at least partly sequestered from the hemolymph. Chemical analyses using gas chromatography / mass spectrometry revealed that both the cuticle and PPGs of Trachypus contain mainly unsaturated long-chain hydrocarbons. The gland of T. boharti additionally contains long-chain ketones. The hydrocarbons from the PPG of T. elongatus occurred on prey bees excavated from nests in the field but not on conspecific control bees. While the embalming only slightly elevated the amount of hydrocarbons on prey bees, the proportion of unsaturated hydrocarbons, which is crucial for the antifungal effect, was significantly increased. The Trachypus species under study possess PPGs that are very similar to the PPG of P. triangulum with regard to morphology, ultrastructure and chemistry. Moreover, we provide clear evidence that T. elongatus females embalm their prey, presumably as a means of prey preservation. The observed differences among Trachypus and Philanthus in gland size and prey embalming may have evolved in response to divergent ecological conditions.
Activation of a chimeric Rpb5/RpoH subunit using library selection
Creators: name: Sommer, Bettina
name: Waege, Ingrid
name: Pöllmann, David
name: Seitz, Tobias
name: Thomm, Michael
name: Sterner, Reinhard
name: Hausner, Winfried
Publisher: name: Universität Regensburg
Year: 2014
Subjects: subject: 570 Biowissenschaften, Biologie

description: Rpb5 is a general subunit of all eukaryotic RNA polymerases which consists of a N-terminal and a C-terminal domain. The corresponding archaeal subunit RpoH contains only the conserved C-terminal domain without any N-terminal extensions. A chimeric construct, termed rp5H, which encodes the N-terminal yeast domain and the C-terminal domain from Pyrococcus furiosus is unable to complement the lethal phenotype of a yeast rpb5 deletion strain (Δrpb5). By applying a random mutagenesis approach we found that the amino acid exchange E197K in the C-terminal domain of the chimeric Rp5H, either alone or with additional exchanges in the N-terminal domain, leads to heterospecific complementation of the growth deficiency of Δrpb5. Moreover, using a recently described genetic system for Pyrococcus we could demonstrate that the corresponding exchange E62K in the archaeal RpoH subunit alone without the eukaryotic N-terminal extension was stable, and growth experiments indicated no obvious impairment in vivo. In vitro transcription experiments with purified RNA polymerases showed an identical activity of the wild type and the mutant Pyrococcus RNA polymerase. A multiple alignment of RpoH sequences demonstrated that E62 is present in only a few archaeal species, whereas the great majority of sequences within archaea and eukarya contain a positively charged amino acid at this position. The crystal structures of the Sulfolobus and yeast RNA polymerases show that the positively charged arginine residues in subunits RpoH and Rpb5 most likely form salt bridges with negatively charged residues from subunit RpoK and Rpb1, respectively. A similar salt bridge might stabilize the interaction of Rp5H-E197K with a neighboring subunit of yeast RNA polymerase and thus lead to complementation of Δrpb5.
Amenability of low-grade ore stockpiles to sensor-based ore sorting technology
Creators: name: Mazhary, Arvin
Publisher: name: University of British Columbia
Year: 2017

description: With sensor-based ore sorting attracting more attention among the industry leaders, and in an effort to show the potential for sensor-based ore sorting technology, this research takes a particle sorting approach and looks at sorting low-grade and waste rock stockpiles to concentrate the misplaced mineralized rocks and generate value. The results from the optical sensor showed that where there was a visual distinction between the mineralized and gangue material, this sensor managed to identify each group well. Despite using a multivariate linear regression (MLR) analysis, the electromagnetic sensor did not predict the grades effectively. The X-Ray Transmission (XRT) sensor performed quite well for both base metal and gold samples. One recurring problem was the presence of iron minerals such as pyrite that, due to their relatively high atomic density, tarnished the sorting results. With elemental distinguishing capabilities, the X-Ray Fluorescence (XRF) sensor boasts great potential for ore sorting. Both single and multivariate linear regression analysis were used to analyse the results from the XRF sensor. Although, while overall satisfactory results were obtained from the XRF sensor, sensor capabilities in actual dynamic sorting cases need to be assessed. Recommendations for future work can be on different aspects of this work. One would be to try to improve the static, bench-top testing facilities so they represent dynamic sorting scenarios better, such as use of a conveyor-type platform where rocks can pass under a sensor. If a similar study is to be performed, it is highly suggested to focus the efforts on one mine, one size fraction (preferably -50 mm +37.5 mm) with a larger number of particles. In terms of continuation of this work, it would be best to take these tests to the next level and perform bulk sorting tests to determine how these bench-scale tests correlate with bulk dynamic sorting results. Also, a detailed economic analysis based on these results would yield valuable results.
Perspectives on MADS-box expression during orchid flower evolution and development
Creators: name: Mondragon-Palomino, Mariana
Publisher: name: Universität Regensburg
Year: 2013
Subjects: subject: 570 Biowissenschaften, Biologie

description: The diverse morphology of orchid flowers and their complex, often deceptive strategies to become pollinated have fascinated researchers for a long time. However, it was not until the 20th century that the ontogeny of orchid flowers, the genetic basis of their morphology and the complex phylogeny of Orchidaceae were investigated. In parallel, the improvement of techniques for in vitro seed germination and tissue culture, together with studies on biochemistry, physiology, and cytology supported the progress of what is now a highly productive industry of orchid breeding and propagation. In the present century both basic research in orchid flower evo-devo and the interest for generating novel horticultural varieties have driven the characterization of many members of the MADS-box family encoding key regulators of flower development. This perspective summarizes the picture emerging from these studies and discusses the advantages and limitations of the comparative strategy employed so far. I address the growing role of natural and horticultural mutants in these studies and the emergence of several model species in orchid evo-devo and genomics. In this context, I make a plea for an increasingly integrative approach. Keywords: Orchidaceae, evo-devo, MADS-box gene, peloric mutant, gene family, transcriptome, model species
Constraints from Type IA Supernovae on λ-CDM Model in Randers-Finsler Space
Creators: name: Chang, Zhe
name: Li, Ming-Hua
name: Li, Xin
Publisher: name: arXiv
Year: 2010
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: Gravitational field equations in Randers-Finsler space of approximate Berwald type are investigated. A modified Friedmann equation and a new luminosity distance-redshift relation is proposed. A best-fit to the Type Ia supernovae (SNe) observations yields that the $Ω_Λ$ in the $Λ$-CDM model is suppressed to almost zero. This fact indicates that the astronomical observations on the Type Ia SNe can be described well without invoking any form of dark energy. The best-fit age of the universe is given. It is in agreement with the age of our galaxy.
description: 14 pages, 3 figures
Optical Rotatory Dispersion Measurement of D-Glucose with Fixed Polarizer Analyzer Accessory in Conventional Spectrophotometer
Creators: name: Penzkofer, Alfons
Publisher: name: Universität Regensburg
Year: 2013
Subjects: subject: 530 Physik

description: ABSTRACT In the sample compartment of a conventional spectrophotometer, mounting of a polarizer before sample and an analyzer behind sample allows the determination of the optical rotatory dispersion of optical active media by measurement of the transmission ratio of crossed and parallel arranged polarizer and analyzer. A formula for the determination of the angle of rotation is derived from the transmission ratio. The arrangement is applied to determine the molar optical rotation of D-glucose in water in the wavelength range from 220 nm to 820 nm. KEYWORDS Optical Activity; Optical Rotatory Dispersion; Specific Optical Rotation; Molar Optical Rotation; Polarimeter; Spectropolarimeter; Grape Sugar; D-Glucose
Zeta functions of regular arithmetic schemes at s=0
Creators: name: Morin, Baptiste
Publisher: name: arXiv
Year: 2011
Subjects: subject: Number Theory (math.NT)
subject: Algebraic Geometry (math.AG)
subject: FOS: Mathematics
subject: 14F20, 14G10, 11S40, 11G40, 19F27

description: Lichtenbaum conjectured the existence of a Weil-étale cohomology in order to describe the vanishing order and the special value of the Zeta function of an arithmetic scheme $\mathcal{X}$ at $s=0$ in terms of Euler-Poincaré characteristics. Assuming the (conjectured) finite generation of some étale motivic cohomology groups we construct such a cohomology theory for regular schemes proper over $\mathrm{Spec}(\mathbb{Z})$. In particular, we obtain (unconditionally) the right Weil-étale cohomology for geometrically cellular schemes over number rings. We state a conjecture expressing the vanishing order and the special value up to sign of the Zeta function $ζ(\mathcal{X},s)$ at $s=0$ in terms of a perfect complex of abelian groups $RΓ_{W,c}(\mathcal{X},\mathbb{Z})$. Then we relate this conjecture to Soulé's conjecture and to the Tamagawa number conjecture of Bloch-Kato, and deduce its validity in simple cases.
description: 53 pages. To appear in Duke Math. J