cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Macroscopic conductivity of aqueous electrolyte solutions scales with ultrafast microscopic ion motions
Creators: name: Balos, Vasileios
name: Imoto, Sho
name: Netz, Roland R.
name: Bonn, Mischa
name: Bonthuis, Douwe Jan
name: Nagata, Yuki
name: Hunger, Johannes
Publisher: name: Freie Universität Berlin
Year: 2020
Subjects: subject: dielectric-relaxation
subject: temperature-dependence
subject: water dynamics
subject: spectroscopy
subject: solvation
subject: exchange
subject: shell
subject: 500 Naturwissenschaften und Mathematik::530 Physik::530 Physik

description: Despite the widespread use of aqueous electrolytes as conductors, the molecular mechanism of ionic conductivity at moderate to high electrolyte concentrations remains largely unresolved. Using a combination of dielectric spectroscopy and molecular dynamics simulations, we show that the absorption of electrolytes at similar to 0.3 THz sensitively reports on the local environment of ions. The magnitude of these high-frequency ionic motions scales linearly with conductivity for a wide range of ions and concentrations. This scaling is rationalized within a harmonic oscillator model based on the potential of mean force extracted from simulations. Our results thus suggest that long-ranged ionic transport is intimately related to the local energy landscape and to the friction for short-ranged ion dynamics: a high macroscopic electrolyte conductivity is thereby shown to be related to large-amplitude motions at a molecular scale.
Compact Binary Progenitors of Short Gamma-Ray Bursts
Creators: name: Giacomazzo, Bruno
name: Perna, Rosalba
name: Rezzolla, Luciano
name: Troja, Eleonora
name: Lazzati, Davide
Publisher: name: arXiv
Year: 2012
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: In recent years, detailed observations and accurate numerical simulations have provided support to the idea that mergers of compact binaries containing either two neutron stars (NSs) or an NS and a black hole (BH) may constitute the central engine of short gamma-ray bursts (SGRBs). The merger of such compact binaries is expected to lead to the production of a spinning BH surrounded by an accreting torus. Several mechanisms can extract energy from this system and power the SGRBs. Here we connect observations and numerical simulations of compact binary mergers, and use the current sample of SGRBs with measured energies to constrain the mass of their powering tori. By comparing the masses of the tori with the results of fully general-relativistic simulations, we are able to infer the properties of the binary progenitors which yield SGRBs. By assuming a constant efficiency in converting torus mass into jet energy, epsilon_{jet}=10%, we find that most of the tori have masses smaller than 0.01M_{sun}, favoring "high-mass" binary NSs mergers, i.e., binaries with total masses >~1.5 the maximum mass of an isolated NS. This has important consequences for the gravitational-wave signals that may be detected in association with SGRBs, since "high-mass" systems do not form a long-lived hypermassive NS after the merger. While NS-BH systems cannot be excluded to be the engine of at least some of the SGRBs, the BH would need to have an initial spin of ~0.9, or higher.
description: 6 pages, 3 figures. Extended the discussion on jet efficiency. Accepted for publication on The Astrophysical Journal Letters
Root‐derived trans‐zeatin cytokinin protects Arabidopsis plants against photoperiod stress
Creators: name: Frank, Manuel
name: Cortleven, Anne
name: Novak, Ondrej
name: Schmülling, Thomas
Publisher: name: Freie Universität Berlin
Year: 2020
Subjects: subject: Arabidopsis thaliana
subject: cytokinin signalling
subject: photoperiod
subject: root-to-shoot signalling
subject: trans-zeatin
subject: 500 Naturwissenschaften und Mathematik::570 Biowissenschaften; Biologie::570 Biowissenschaften; Biologie

description: Recently, a novel type of abiotic stress caused by a prolongation of the light period - coined photoperiod stress - has been described in Arabidopsis. During the night after the prolongation of the light period, stress and cell death marker genes are induced. The next day, strongly stressed plants display a reduced photosynthetic efficiency and leaf cells eventually enter programmed cell death. The phytohormone cytokinin (CK) acts as a negative regulator of this photoperiod stress syndrome. In this study, we show that Arabidopsis wild‐type plants increase the CK concentration in response to photoperiod stress. Analysis of cytokinin synthesis and transport mutants revealed that root‐derived trans‐zeatin (tZ)‐type CKs protect against photoperiod stress. The CK signalling proteins ARABIDOPSIS HISTIDINE PHOSPHOTRANSFER PROTEIN 2 (AHP2), AHP3 and AHP5 and transcription factors ARABIDOPSIS RESPONSE REGULATOR 2 (ARR2), ARR10 and ARR12 are required for the protective activity of CK. Analysis of higher order B‐type arr mutants suggested that a complex regulatory circuit exists in which the loss of ARR10 or ARR12 can rescue the arr2 phenotype. Together the results revealed the role of root‐derived CK acting in the shoot through the two‐component signalling system to protect from the negative consequences of strong photoperiod stress.
Electrical and thermoelectrical transport in Dirac fermions through a quantum dot
Creators: name: Aono, Tomosuke
Publisher: name: arXiv
Year: 2012
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We investigate the conductance and thermopower of massless Dirac fermions through a quantum dot using a pseudogap Anderson model in the non-crossing approximation. When the Fermi level is at the Dirac point, the conductance has a cusp where the thermopower changes its sign. When the Fermi level is away from the Dirac point, the Kondo temperature illustrates a quantum impurity transition between an asymmetric strong coupling Kondo state and a localized moment state. The conductance shows a peak near this transition and reaches the unitary limit at low temperatures. The magnitude of the thermopower exceeds $k_B/e$, and the thermoelectric figure of merit exceeds unity.
description: 5 pages, 4 figures
Arbitrary quantum control of qubits in the presence of universal noise
Creators: name: Green, Todd J.
name: Sastrawan, Jarrah
name: Uys, Hermann
name: Biercuk, Michael J.
Publisher: name: arXiv
Year: 2012
Subjects: subject: Quantum Physics (quant-ph)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Atomic Physics (physics.atom-ph)
subject: FOS: Physical sciences

description: In this manuscript we address the problem of deriving \emph{analytic} expressions for calculating universal decoherence-induced errors in qubits undergoing arbitrary, unitary, time-dependent quantum-control protocols. For a qubit undergoing unitary decoherence the evolution of a qubit state in the presence of time-varying semiclassical fields may be treated geometrically. We show that the fidelity of an arbitrary control operation may then be expressed to arbitrary order in terms of experimentally relevant spectral characteristics of the noise and the control over all Cartesian directions and accounting for noise cross-correlations. We formulate \emph{control matrices} in the time domain to capture the effects of piecewise-constant control, and convert them to generalized Fourier-domain filter functions. Such generalized filter functions may therefore be derived for complex temporally modulated control protocols, accounting for susceptibility to rotations of the qubit state vector in three dimensions. Taken together, this framework provides a computationally efficient means to calculate the effects of universal noise on arbitrary quantum control protocols without the need for time-consuming simulations of Bloch vector evolution. As a concrete example, we apply our method to treating the problem of dynamical decoupling incorporating realistic control pulses of arbitrary duration or form, including the replacement of simple $π$-pulses with complex dynamically corrected gates.
description: To appear in New J. Phys. Expanded to include discussions of limits of analytic approximation, comparison of filter-function with full numerical simulation, and incorporation of explicit forms of higher-order filter functions. Related references at http://www.physics.usyd.edu.au/~mbiercuk
Momentum-resolved radio-frequency spectroscopy of a spin-orbit coupled atomic Fermi gas near a Feshbach resonance in harmonic traps
Creators: name: Peng, Shi-Guo
name: Liu, Xia-Ji
name: Hu, Hui
name: Jiang, Kaijun
Publisher: name: arXiv
Year: 2012
Subjects: subject: Quantum Gases (cond-mat.quant-gas)
subject: FOS: Physical sciences

description: We theoretically investigate the momentum-resolved radio-frequency spectroscopy of a harmonically trapped atomic Fermi gas near a Feshbach resonance in the presence of equal Rashba and Dresselhaus spin-orbit coupling. The system is qualitatively modeled as an ideal gas mixture of atoms and molecules, in which the properties of molecules, such as the wavefunction, binding energy and effective mass, are determined from the two-particle solution of two-interacting atoms. We calculate separately the radio-frequency response from atoms and molecules at finite temperatures by using the standard Fermi golden rule, and take into account the effect of harmonic traps within local density approximation. The total radio-frequency spectroscopy is discussed, as functions of temperature and spin-orbit coupling strength. Our results give a qualitative picture of radio-frequency spectroscopy of a resonantly interacting spin-orbit coupled Fermi gas and can be directly tested in atomic Fermi gases of K40 atoms at Shanxi University and of Li6 atoms at MIT.
description: 11 pages, 9 Figures
ENVELHECER A CONSTITUIÇÃO OU REJUVENECER MENTES: eis a questão
Creators: name: Santana, José Cláudio Pavão
Publisher: name: Zenodo - Cadernos da Pena do Pavao
Year: 2023

description: Ano 04 – n. 01/2016
Com objetivo pontual e sintético, mas, sobretudo, pedagógico, vei-me à mente esta reflexão.
Falo da reiterada prática de Tribunais de alardear decisões cujas ementas parecem inimigas mortais do conteúdo silogístico contido no julgado. Isso quando os intérpretes não mergulham em enigmas herméticos!
Spherical agglomeration of superconducting and normal microparticles with and without applied electric field
Creators: name: Ghosh, R. S. B.
name: Hirsch, J. E.
Publisher: name: arXiv
Year: 2012
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: It was reported by R. Tao and coworkers that in the presence of a strong electric field superconducting microparticles assemble into balls of macroscopic dimensions. Such a finding has potentially important implications for the understanding of the fundamental physics of superconductors. However, we report here the results of experimental studies showing that (i) ball formation also occurs in the absence of an applied electric field, (ii) the phenomenon also occurs at temperatures above the superconducting transition temperature, and (iii) it can also occur for non-superconducting materials. Possible origins of the phenomenon are discussed.
description: Small changes in response to referee's comments. To be published in Phys. Rev. B
Working Together: Integrating Computational Modeling Approaches to Investigate Complex Phenomena
Creators: name: Bielik, Tom
name: Fonio, Ehud
name: Feinerman, Ofer
name: Duncan, Ravit Golan
name: Levy, Sharona T.
Publisher: name: Freie Universität Berlin
Year: 2021
Subjects: subject: science
subject: students
subject: inquiry
subject: conceptions
subject: framework
subject: thinking
subject: 500 Naturwissenschaften und Mathematik::570 Biowissenschaften; Biologie::570 Biowissenschaften; Biologie

description: Complex systems are made up of many entities, whose interactions emerge into distinct collective patterns. Computational modeling platforms can provide a powerful means to investigate emergent phenomena in complex systems. Some research has been carried out in recent years about promoting students' modeling practices, specifically using technologically advanced tools and approaches that allow students to create, manipulate, and test computational models. However, not much research had been carried out on the integration of several modeling approaches when investigating complex phenomena. In this paper, we describe the design principles used to develop a middle school unit about ants' collective behavior that integrates three modeling approaches: conceptual drawn models, agent-based models, and system dynamics models. We provide results from an initial implementation of an 8th grade curricular unit, indicating that students engaged with several aspects of the modeling practice. Students' conceptual knowledge about ant pheromone communication increased following learning the unit. We also found gains in students' metamodeling knowledge about models as tools for investigating phenomena. We discuss the affordances and challenges of engaging students with several modeling approaches in science classroom.
Combining radial and continuous flow synthesis to optimize and scale-up the production of medicines
Creators: name: Guidi, Mara
name: Moon, Sooyeon
name: Anghileri, Lucia
name: Cambié, Dario
name: Seeberger, Peter H.
name: Gilmore, Kerry
Publisher: name: Freie Universität Berlin
Year: 2021
Subjects: subject: drug
subject: production
subject: medicines
subject: 500 Naturwissenschaften und Mathematik::540 Chemie::540 Chemie und zugeordnete Wissenschaften

description: Current drug production in batch cannot adapt rapidly to market demands, evidenced by recent shortages in many markets globally of essential medicines. Flow chemistry is a valuable tool for on-demand production of active pharmaceutical ingredients (APIs). Here, we reveal a new concept to develop and produce APIs, where an automated synthesizer that works with discrete volumes of solutions is employed at the discovery stage to identify the optimal synthetic route and conditions before a commercially available continuous flow system is used for scale-up. This concept is illustrated by the synthesis of nifedipine and paracetamol, in short supply in Germany during the COVID-19 pandemic, and the local anesthetic lidocaine.
A Snu114-GTP-Prp8 module forms a relay station for efficient splicing in yeast
Creators: name: Jia, Junqiao
name: Ganichkin, Oleg M.
name: Preussner, Marco
name: Absmeier, Eva
name: Alings, Claudia
name: Loll, Bernhard
name: Heyd, Florian
name: Wahl, Markus C.
Publisher: name: Freie Universität Berlin
Year: 2020
Subjects: subject: elongation-factor G
subject: cryoEM structure
subject: conformational-changes
subject: crystal-structure
subject: structural basis
subject: Prp8 protein
subject: spliceosome
subject: snRNP
subject: 500 Naturwissenschaften und Mathematik::540 Chemie::540 Chemie und zugeordnete Wissenschaften

description: The single G protein of the spliceosome, Snu114, has been proposed to facilitate splicing as a molecular motor or as a regulatory G protein. However, available structures of spliceosomal complexes show Snu114 in the same GTP-bound state, and presently no Snu114 GTPase-regulatory protein is known. We determined a crystal structure of Snu114 with a Snu114-binding region of the Prp8 protein, in which Snu114 again adopts the same GTP-bound conformation seen in spliceosomes. Snu114 and the Snu114-Prp8 complex co-purified with endogenous GTP. Snu114 exhibited weak, intrinsic GTPase activity that was abolished by the Prp8 Snu114-binding region. Exchange of GTP-contacting residues in Snu114, or of Prp8 residues lining the Snu114 GTP-binding pocket, led to temperature-sensitive yeast growth and affected the same set of splicing events in vivo. Consistent with dynamic Snu114-mediated protein interactions during splicing, our results suggest that the Snu114-GTP-Prp8 module serves as a relay station during spliceosome activation and disassembly, but that GTPase activity may be dispensable for splicing.
Food and Governmentality in the Green City: The Case of German Food Policy Councils
Creators: name: Birnbaum, Alena
name: Lütke, Petra
Publisher: name: Universität Kassel
Year: 2023
Subjects: subject: food
subject: German Food Policy Councils
subject: governmentality
subject: green city
subject: transformation
subject: 300
subject: 710
subject: Deutschland
subject: Ernährungspolitik
subject: Transformation

description: Gefördert durch den Publikationsfonds der Universität Kassel
Strong-coupling effects in dissipatively coupled optomechanical systems
Creators: name: Weiss, Talitha
name: Bruder, Christoph
name: Nunnenkamp, Andreas
Publisher: name: arXiv
Year: 2012
Subjects: subject: Quantum Physics (quant-ph)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: In this paper we study cavity optomechanical systems in which the position of a mechanical oscillator modulates both the resonance frequency (dispersive coupling) and the linewidth (dissipative coupling) of a cavity mode. Using a quantum noise approach we calculate the optical damping and the optically-induced frequency shift. We find that dissipatively coupled systems feature two parameter regions providing amplification and two parameter regions providing cooling. To investigate the strong-coupling regime, we solve the linearized equations of motion exactly and calculate the mechanical and optical spectra. In addition to signatures of normal-mode splitting that are similar to the case of purely dispersive coupling, the spectra contain a striking feature that we trace back to the Fano line shape of the force spectrum. Finally, we show that purely dissipative coupling can lead to optomechanically-induced transparency which will provide an experimentally convenient way to observe normal-mode splitting.
description: 21 pages, 7 figures
"INVENCIONICES" DO SENADO
Creators: name: Santana, José Cláudio Pavão
Publisher: name: Zenodo - Cadernos da Pena do Pavao
Year: 2023

description: Ano 04 – n.. 10/2016Hoje vivemos uma das páginas mais negras da história constitucional deste país.
Já se teve notícia de fechamento do Congresso Nacional, de cassação de direitos políticos, de banimento de cidadãos fatos esses todos que tinham a exceção como fonte.
Galactic Chemical Evolution and the Oxygen Isotopic Composition of the Solar System
Creators: name: Nittler, Larry R.
name: Gaidos, Eric
Publisher: name: arXiv
Year: 2012
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We review current observational and theoretical constraints on the Galactic chemical evolution (GCE) of oxygen isotopes in order to explore whether GCE plays a role in explaining the lower 17O/18O ratio of the Sun, relative to the present-day interstellar medium, or the existence of distinct 16O-rich and 16O-poor reservoirs in the Solar System. Although the production of both 17O and 18O are related to the metallicity of progenitor stars, 17O is most likely produced in stars that evolve on longer timescales than those that produce 18O. Therefore the 17O/18O ratio need not have remained constant over time, contrary to preconceptions and the simplest models of GCE. An apparent linear, slope-one correlation between delta17O and delta18O in the ISM need not necessarily reflect an O isotopic gradient, and any slope-one galactocentric gradient need not correspond to evolution in time. Instead, increasing 17O/18O is consistent both with observational data from molecular clouds and with modeling of the compositions of presolar grains. Models in which the rate of star formation has decelerated over the past few Gyr or in which an enhanced period of star formation occurred shortly before solar birth ("starburst") can explain the solar-ISM O-isotopic difference without requiring a local input of supernova ejecta into the protosolar cloud. "Cosmic chemical memory" models in which interstellar dust is on average older than interstellar gas predict that primordial Solar System solids should be 16O-rich, relative to the Sun, in conflict with observations. However, scenarios in which the 16O-rich contribution of very massive stars could lead to 16O-poor solids and a 16O-rich bulk Sun, if the Solar System formed shortly after a starburst, independent of the popular scenario of photochemical self-shielding of CO.
description: 36 pages, 12 figures, Accepted for publication in Meteoritics and Planetary Science
Modular detergents tailor the purification and structural analysis of membrane proteins including G-protein coupled receptors
Creators: name: Urner, Leonhard H.
name: Liko, Idlir
name: Yen, Hsin-Yung
name: Hoi, Kin-Kuan
name: Bolla, Jani Reddy
name: Gault, Joseph
name: Schweder, Marc-Philip
name: Ehrmann, Svenja
name: Haag, Rainer
name: Pagel, Kevin
Publisher: name: Freie Universität Berlin
Year: 2020
Subjects: subject: dendritic amphiphiles
subject: mass-spectrometry
subject: lipid-binding
subject: dynamics
subject: complexes
subject: micelles
subject: trends
subject: family
subject: 500 Naturwissenschaften und Mathematik::570 Biowissenschaften; Biologie::570 Biowissenschaften; Biologie

description: Detergents enable the purification of membrane proteins and are indispensable reagents in structural biology. Even though a large variety of detergents have been developed in the last century, the challenge remains to identify guidelines that allow fine-tuning of detergents for individual applications in membrane protein research. Addressing this challenge, here we introduce the family of oligoglycerol detergents (OGDs). Native mass spectrometry (MS) reveals that the modular OGD architecture offers the ability to control protein purification and to preserve interactions with native membrane lipids during purification. In addition to a broad range of bacterial membrane proteins, OGDs also enable the purification and analysis of a functional G-protein coupled receptor (GPCR). Moreover, given the modular design of these detergents, we anticipate fine-tuning of their properties for specific applications in structural biology. Seen from a broader perspective, this represents a significant advance for the investigation of membrane proteins and their interactions with lipids.
LEI E (DES) HUMANIDADE
Creators: name: Santana, José Cláudio Pavão
Publisher: name: Zenodo - Cadernos da Pena do Pavao
Year: 2023

description: Ano 04 – n. 08/2016
Quando o fetichismo legal ganhou sua expressão mais enfática os juízes franceses propalavam: "Eu não conheço o Direito Civil. Eu conheço o Código de Napoleão"!
Fato ou lenda, em verdade o que se extrai disso é o contronto eterno entre a estática legal e a dinâmica do intérprete.
Protecting conditional quantum gates by robust dynamical decoupling
Creators: name: Piltz, Ch.
name: Scharfenberger, B.
name: Khromova, A.
name: Varón, A. F.
name: Wunderlich, Ch.
Publisher: name: arXiv
Year: 2012
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Dephasing -- phase randomization of a quantum superposition state -- is a major obstacle for the realization of high fidelity quantum logic operations. Here, we implement a two-qubit Controlled-NOT gate using dynamical decoupling (DD), despite the gate time being more than one order of magnitude longer than the intrinsic coherence time of the system. For realizing this universal conditional quantum gate, we have devised a concatenated DD sequence that ensures robustness against imperfections of DD pulses that otherwise may destroy quantum information or interfere with gate dynamics. We compare its performance with three other types of DD sequences. These experiments are carried out using a well-controlled prototype quantum system -- trapped atomic ions coupled by an effective spin-spin interaction. The scheme for protecting conditional quantum gates demonstrated here is applicable to other physical systems, such as nitrogen vacancy centers, solid state nuclear magnetic resonance, and circuit quantum electrodynamics.
description: 6 pages, 5 figures. Replaced with published version (wording changed in some places, added references)
The glyphosate formulation Roundup® LB plus influences the global metabolome of pig gut microbiota in vitro
Creators: name: Krause, Jannike L.
name: Haange, Sven-Bastiaan
name: Schape, Stephanie S.
name: Engelmann, Beatrice
name: Rolle-Kampczyk, Ulrike
name: Fritz-Wallace, Katarina
name: Wang, Zhipeng
name: Pöppe, Judith
name: Bote, Katrin
name: Rösler, Uwe
Publisher: name: Freie Universität Berlin
Year: 2020
Subjects: subject: 16S
subject: Metaproteome
subject: Meta-metabolome
subject: Continuous in vitro culture
subject: Bioreactor
subject: Microbiome
subject: 600 Technik, Medizin, angewandte Wissenschaften::630 Landwirtschaft::630 Landwirtschaft und verwandte Bereiche

description: Glyphosate is the world's most widely used herbicide, and its potential side effects on the intestinal microbiota of various animals, from honeybees to livestock and humans, are currently under discussion. Pigs are among the most abundant livestock animals worldwide and an impact of glyphosate on their intestinal microbiota function can have serious consequences on their health, not to mention the economic effects. Recent studies that addressed microbiota-disrupting effects focused on microbial taxonomy but lacked functional information. Therefore, we chose an experimental design with a short incubation time in which effects on the community structure are not expected, but functional effects can be detected. We cultivated intestinal microbiota derived from pig colon in chemostats and investigated the acute effect of 228 mg/d glyphosate acid equivalents from Roundup® LB plus, a frequently applied glyphosate formulation. The applied glyphosate concentration resembles a worst-case scenario for an 8–9 week-old pig and relates to the maximum residue levels of glyphosate on animal fodder. The effects were determined on the functional level by metaproteomics, targeted and untargeted meta-metabolomics, while variations in community structure were analyzed by 16S rRNA gene profiling and on the single cell level by microbiota flow cytometry. Roundup® LB plus did not affect the community taxonomy or the enzymatic repertoire of the cultivated microbiota in general or on the expression of the glyphosate target enzyme 5-enolpyruvylshikimate-3-phosphate synthase in detail. On the functional level, targeted metabolite analysis of short chain fatty acids (SCFAs), free amino acids and bile acids did not reveal significant changes, whereas untargeted meta-metabolomics did identify some effects on the functional level. This multi-omics approach provides evidence for subtle metabolic effects of Roundup® LB plus under the conditions applied.
Triconnected Planar Graphs of Maximum Degree Five are Subhamiltonian
Creators: name: Hoffmann, Michael
name: Klemz, Boris
Publisher: name: Freie Universität Berlin
Year: 2020
Subjects: subject: Graph drawing
subject: book embedding
subject: Hamiltonian graph
subject: planar graph
subject: bounded degree graph
subject: graph augmentation
subject: computational geometry
subject: SPQR decomposition
subject: 000 Informatik, Informationswissenschaft, allgemeine Werke::000 Informatik, Wissen, Systeme::000 Informatik, Informationswissenschaft, allgemeine Werke

description: We show that every triconnected planar graph of maximum degree five is subhamiltonian planar. A graph is subhamiltonian planar if it is a subgraph of a Hamiltonian planar graph or, equivalently, if it admits a 2-page book embedding. In fact, our result is stronger because we only require vertices of a separating triangle to have degree at most five, all other vertices may have arbitrary degree. This degree bound is tight: We describe a family of triconnected planar graphs that are not subhamiltonian planar and where every vertex of a separating triangle has degree at most six. Our results improve earlier work by Heath and by Bauernoppel and, independently, Bekos, Gronemann, and Raftopoulou, who showed that planar graphs of maximum degree three and four, respectively, are subhamiltonian planar. The proof is constructive and yields a quadratic time algorithm to obtain a subhamiltonian plane cycle for a given graph. As one of our main tools, which might be of independent interest, we devise an algorithm that, in a given 3-connected plane graph satisfying the above degree bounds, collapses each maximal separating triangle into a single edge such that the resulting graph is biconnected, contains no separating triangle, and no separation pair whose vertices are adjacent.
Supermassive Seeds for Supermassive Black Holes
Creators: name: Johnson, Jarrett L.
name: Whalen, Daniel J.
name: Li, Hui
name: Holz, Daniel E.
Publisher: name: arXiv
Year: 2012
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: Recent observations of quasars powered by supermassive black holes (SMBHs) out to z > 7 constrain both the initial seed masses and the growth of the most massive black holes (BHs) in the early universe. Here we elucidate the implications of the radiative feedback from early generations of stars and from BH accretion for popular models for the formation and growth of seed BHs. We show that by properly accounting for (1) the limited role of mergers in growing seed BHs as inferred from cosmological simulations of early star formation and radiative feedback, (2) the sub-Eddington accretion rates of BHs expected at the earliest times, and (3) the large radiative efficiencies (e_rad) of the most massive BHs inferred from observations of active galactic nuclei at high redshift (e_rad > 0.1), we are led to the conclusion that the initial BH seeds may have been as massive as > 10^5 M_Sun. This presents a strong challenge to the Population III seed model, which calls for seed masses of ~ 100 M_Sun and, even with constant Eddington-limited accretion, requires e_rad < 0.09 to explain the highest-z SMBHs in today's standard LambdaCDM cosmological model. It is, however, consistent with the prediction of the direct collapse scenario of SMBH seed formation, in which a supermassive primordial star forms in a region of the universe with a high molecule-dissociating background radiation field, and collapses directly into a 10^4--10^6 M_Sun seed BH. These results corroborate recent cosmological simulations and observational campaigns which suggest that these massive BHs were the seeds of a large fraction of the SMBHs residing in the centers of galaxies today.
description: 9 pages, 2 figures; accepted for publication in ApJ
Triangles and Girth in Disk Graphs and Transmission Graphs
Creators: name: Kaplan, Haim
name: Klost, Katharina
name: Mulzer, Wolfgang
name: Roditty, Liam
name: Seiferth, Paul
name: Sharir, Micha
Publisher: name: Freie Universität Berlin
Year: 2020
Subjects: subject: disk graph
subject: transmission graph
subject: triangle
subject: girth
subject: 000 Informatik, Informationswissenschaft, allgemeine Werke::000 Informatik, Wissen, Systeme::000 Informatik, Informationswissenschaft, allgemeine Werke

description: Let S subset of R-2 be a set of n sites, where each s is an element of S has an associated radius r(s) > 0. The disk graph D(S) is the undirected graph with vertex set S and an undirected edge between two sites s, t is an element of S if and only if vertical bar st vertical bar <= r(s) + r(t), i.e., if the disks with centers s and t and respective radii r(s) and r(t) intersect. Disk graphs are used to model sensor networks. Similarly, the transmission graph T(S) is the directed graph with vertex set S and a directed edge from a site s to a site t if and only if vertical bar st vertical bar <= r(s), i.e., if t lies in the disk with center s and radius r(s). We provide algorithms for detecting (directed) triangles and, more generally, computing the length of a shortest cycle (the girth) in D(S) and in T(S). These problems are notoriously hard in general, but better solutions exist for special graph classes such as planar graphs. We obtain similarly efficient results for disk graphs and for transmission graphs. More precisely, we show that a shortest (Euclidean) triangle in D(S) and in T(S) can be found in O(n log n) expected time, and that the (weighted) girth of D(S) can be found in O(n log n) expected time. For this, we develop new tools for batched range searching that may be of independent interest.
Counter-propagating frequency mixing with Terahertz waves in diamond
Creators: name: Clerici, Matteo
name: Caspani, Lucia
name: Rubino, Eleonora
name: Peccianti, Marco
name: Cassataro, Marco
name: Busacca, Alessandro
name: Ozaki, Tsuneyuki
name: Faccio, Daniele
name: Morandotti, Roberto
Publisher: name: arXiv
Year: 2012
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: Frequency conversion by means of Kerr-nonlinearity is one of the most common and exploited nonlinear optical processes in the UV, visible, IR and Mid-IR spectral regions. Here we show that wave mixing of an optical field and a Terahertz wave can be achieved in diamond, resulting in the frequency conversion of the THz radiation either by sum- or difference-frequency generation. In the latter case, we show that this process is phase-matched and most efficient in a counter-propagating geometry.
Point defects, compositional fluctuations, and secondary phases in non-stoichiometric kesterites
Creators: name: Schorr, Susan
name: Gurieva, Galina
name: Guc, Maxim
name: Dimitrievska, Mirjana
name: Pérez-Rodríguez, Alejandro
name: Izquierdo-Roca, Victor
name: Schnohr, Claudia S.
name: Kim, Juran
name: Jo, William
name: Manuel Merino, José
Publisher: name: Freie Universität Berlin
Year: 2020
Subjects: subject: kesterites
subject: point defects
subject: stoichiometry deviations
subject: secondary phases
subject: diffraction
subject: Raman spectroscopy
subject: Kelvin probe force
subject: 500 Naturwissenschaften und Mathematik::550 Geowissenschaften, Geologie::550 Geowissenschaften

description: The efficiency of kesterite-based solar cells is limited by various non-ideal recombination paths, amongst others by a high density of defect states and by the presence of binary or ternary secondary phases within the absorber layer. Pronounced compositional variations and secondary phase segregation are indeed typical features of non-stoichiometric kesterite materials. Certainly kesterite-based thin film solar cells with an off-stoichiometric absorber layer composition, especially Cu-poor/Zn-rich, achieved the highest efficiencies, but deviations from the stoichiometric composition lead to the formation of intrinsic point defects (vacancies, anti-sites, and interstitials) in the kesterite-type material. In addition, a non-stoichiometric composition is usually associated with the formation of an undesirable side phase (secondary phases). Thus the correlation between off-stoichiometry and intrinsic point defects as well as the identification and quantification of secondary phases and compositional fluctuations in non-stoichiometric kesterite materials is of great importance for the understanding and rational design of solar cell devices. This paper summarizes the latest achievements in the investigation of identification and quantification of intrinsic point defects, compositional fluctuations, and secondary phases in non-stoichiometric kesterite-type materials.
High transient stress in the lower crust: Evidence from dry pseudotachylytes in granulites, Lofoten Archipelago, northern Norway
Creators: name: Dunkel, Kristina G.
name: Zhong, Xin
name: Arnestad, Paal Ferdinand
name: Valen, Lars Vesterager
name: Jamtveit, Bjørn
Publisher: name: Freie Universität Berlin
Year: 2021
Subjects: subject: intermediate-depth earthquakes
subject: facies pseudotachylytes
subject: musgrave ranges
subject: shear zones
subject: constraints
subject: equilibria
subject: transition
subject: mylonites
subject: 500 Naturwissenschaften und Mathematik::550 Geowissenschaften, Geologie::551 Geologie, Hydrologie, Meteorologie

description: Seismic activity below the standard seismogenic zone is difficult to investigate because the geological records of such earthquakes, pseudotachylytes, are typically reacted and/or deformed. Here, we describe unusually pristine pseudotachylytes in lower-crustal granulites from the Lofoten Archipelago, northern Norway. The pseudotachylytes have essentially the same mineralogical composition as their host (mainly plagioclase, alkali feldspar, orthopyroxene) and contain microstructures indicative of rapid cooling, i.e., feldspar microlites and spherulites and "cauliflower" garnets. Mylonites are absent, both in the wall rocks and among the pseudotachylyte clasts. The absence of features recording precursory ductile deformation rules out several commonly invoked mechanisms for triggering earthquakes in the lower crust, including thermal runaway, plastic instabilities, and downward propagation of seismic slip from the brittle to the ductile part of a fault. The anhydrous mineralogy of host and pseudotachylytes excludes dehydration-induced embrittlement. In the absence of such weakening mechanisms, stress levels in the lower crust must have been transiently high.
Facilitated crystal handling using a simple device for evaporation reduction in microtiter plates
Creators: name: Barthel, Tatjana
name: Huschmann, Franziska U.
name: Wallacher, Dirk
name: Feiler, Christian G.
name: Klebe, Gerhard
name: Weiss, Manfred S.
name: Wollenhaupt, Jan
Publisher: name: Freie Universität Berlin
Year: 2021
Subjects: subject: evaporation reduction
subject: crystal handling
subject: crystal harvesting
subject: crystallographic fragment screening
subject: 500 Naturwissenschaften und Mathematik::540 Chemie::548 Kristallografie

description: In the past two decades, most of the steps in a macromolecular crystallography experiment have undergone tremendous development with respect to speed, feasibility and increase of throughput. The part of the experimental workflow that is still a bottleneck, despite significant efforts, involves the manipulation and harvesting of the crystals for the diffraction experiment. Here, a novel low-cost device is presented that functions as a cover for 96-well crystallization plates. This device enables access to the individual experiments one at a time by its movable parts, while minimizing evaporation of all other experiments of the plate. In initial tests, drops of many typically used crystallization cocktails could be successfully protected for up to 6 h. Therefore, the manipulation and harvesting of crystals is straightforward for the experimenter, enabling significantly higher throughput. This is useful for many macromolecular crystallography experiments, especially multi-crystal screening campaigns.
CFD modelling of an animal occupied zone using an anisotropic porous medium model with velocity depended resistance parameters
Creators: name: Doumbia, E. Moustapha
name: Janke, David
name: Yi, Qianying
name: Amon, Thomas
name: Kriegel, Martin
name: Hempel, Sabrina
Publisher: name: Freie Universität Berlin
Year: 2021
Subjects: subject: Pressure drop
subject: Heat transfer
subject: Computational fluid dynamics
subject: Richardson number
subject: 600 Technik, Medizin, angewandte Wissenschaften::630 Landwirtschaft::630 Landwirtschaft und verwandte Bereiche

description: The airflow in dairy barns is affected by many factors, such as the barn's geometry, weather conditions, configurations of the openings, cows acting as heat sources, flow obstacles, etc. Computational fluids dynamics (CFD) has the advantages of providing detailed airflow information and allowing fully-controlled boundary conditions, and therefore is widely used in livestock building research. However, due to the limited computing power, numerous animals are difficult to be designed in detail. Consequently, there is the need to develop and use smart numerical models in order to reduce the computing power needed while at the same time keeping a comparable level of accuracy. In this work the porous medium modeling is considered to solve this problem using Ansys Fluent. A comparison between an animal occupied zone (AOZ) filled with randomly arranged 22 simplified cows' geometry model (CM) and the porous medium model (PMM) of it, was made. Anisotropic behavior of the PMM was implemented in the porous modeling to account for turbulence influences. The velocity at the inlet of the domain has been varied from 0.1 m s(-1) to 3 in s(-1) and the temperature difference between the animals and the incoming air was set at 20 K. Leading to Richardson numbers Ri corresponding to the three types of heat transfer convection, i.e. natural, mixed and forced convection. It has been found that the difference between two models (the cow geometry model and the PMM) was around 2% for the pressure drop and less than 6% for the convective heat transfer. Further the usefulness of parametrized PMM with a velocity adaptive pressure drop and heat transfer coefficient is shown by velocity field validation of an on-farm measurement.
Qualitative aspects of the phase diagram of J1-J2 model on the cubic lattice
Creators: name: Salmon, Octavio D. R.
name: Crokidakis, Nuno
name: Neto, Minos A.
name: Padilha, Igor T.
name: Viana, J. Roberto
name: de Sousa, J. Ricardo
Publisher: name: arXiv
Year: 2012
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: The qualitative aspects of the phase diagram of the Ising model on the cubic lattice, with ferromagnetic nearest-neighbor interactions ($J_{1}$) and antiferromagnetic next-nearest-neighbor couplings ($J_{2}$) are analyzed in the plane temperature versus $α$, where $α=J_{2}/|J_{1}|$ is the frustration parameter. We used the original Wang-Landau sampling and the standard Metropolis algorithm to confront past results of this model obtained by the effective-field theory (EFT) for the cubic lattice. Our numerical results suggest that the predictions of the EFT are in general qualitatively correct, but the low-temperature reentrant behavior, observed in the frontier separating the ferromagnetic and the colinear order, is an artifact of the EFT approach and should disappear when we consider Monte Carlo simulations of the model. In addition, our results indicate that the continuous phase transition between the Ferromagnetic and the Paramagnetic phases, that occurs for $0.0 \leq α< 0.25$, belongs to the universality class of the three-dimensional pure Ising Model.
description: 16 pages, 11 figures, to appear in IJMPB
Attempts to Synthesize a Thiirane, Selenirane, and Thiirene by Dealkylation of Chalcogeniranium and Thiirenium Salts
Creators: name: Poleschner, Helmut
name: Seppelt, Konrad
Publisher: name: Freie Universität Berlin
Year: 2021
Subjects: subject: ab-initio calculations
subject: NMR spectroscopy
subject: selenium
subject: sulfur
subject: X-ray diffraction
subject: 500 Naturwissenschaften und Mathematik::540 Chemie::546 Anorganische Chemie

description: Thiiranium salts [Ad(2)SR]X-+(-)(5,8,9,11,12; X-=Tf2N-(Tf=CF3SO2), SbCl6-) and seleniranium salts [Ad(2)SeR]X-+(-)(14,16,17,23-25; X-=Tf2N-, BF4-, CHB11Cl11-, SbCl6-) are synthesized from strained alkene bis(adamantylidene) (1). The disulfides and the diselenides (Me3SiCH2CH2E)(2)(4,13), (tBuMe(2)SiCH(2)CH(2)E)(2)(7,22), and (NCCH2CH2E)(2)(10,15; E=S, Se) have been used. The thiirenium salts [tBu(2)C(2)SR]X-+(-)(34) and [Ad(2)C(2)SR]X-+(-)(35,36) are prepared from the bis-tert-butylacetylene (2) and bis-adamantyl-acetylene (3) with R=Me(3)SiCH(2)CH(2)andtBuMe(2)SiCH(2)CH(2). Attempts to cleave off the groups Me3SiCH2CH2,tBuMe(2)SiCH(2)CH(2), and NCCH(2)CH(2)resulted in thiiranes27,30. No selenirane Ad(2)Se (33) is formed from seleniranium salts, instead cleavage to the alkene (1) and diselenide (13,15) occurs. The thiirenium salt [Ad(2)C(2)SCH(2)CH(2)SiMe(3)]+Tf2N-(35) does not yield the thiirene Ad(2)C(2)S (37), the three-membered ring is cleaved, forming the alkyne (3) and disulfide (4). All compounds are characterized by ESI mass spectra, NMR spectra, and by quantum chemical calculations. Crystal structures of the salts8,12,25,17,26,36and the thiiranes27,30are presented.
C\ast-geometric phase for mixed states: entanglement, decoherence and spin system
Creators: name: Viennot, David
name: Lages, José
Publisher: name: arXiv
Year: 2012
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We study a kind of geometric phases for entangled quantum systems, and particularly a spin driven by a magnetic field and entangled with another spin. The new kind of geometric phase is based on an analogy between open quantum systems and dissipative quantum systems which uses a C\ast-module structure. We show that the system presents from the viewpoint of their geometric phases, two behaviours. The first one is identical to the behaviour of an isolated spin driven by a magnetic field, as the problem originally treated by Berry. The second one is specific to the decoherence process. The gauge structures induced by these geometric phases are then similar to a magnetic monopole gauge structure for the first case, and can be viewed as a kind of instanton gauge structure for the second case. We study the role of these geometric phases in the evolution of a mixed state, particularly by focusing on the evolution of the density matrix coherence. We investigate also the relation between the geometric phase of the mixed state of one of the entangled systems and the geometric phase of the bipartite system.
Characterization of defined sulfated heparin-like oligosaccharides by electrospray ionization ion trap mass spectrometry
Creators: name: Lemmnitzer, Katharina
name: Köhling, Sebastian
name: Freyse, Joanna
name: Rademann, Jörg
name: Schiller, Jürgen
Publisher: name: Freie Universität Berlin
Year: 2021
Subjects: subject: (over)sulfation
subject: desalination
subject: ESI (IT) MS
subject: fondaparinux
subject: glycosaminoglycans
subject: sulfate loss
subject: 500 Naturwissenschaften und Mathematik::570 Biowissenschaften; Biologie::570 Biowissenschaften; Biologie

description: Glycosaminoglycans (GAG) as long, unbranched polysaccharides are major components of the extracellular matrix. Many studies provided additional evidence of a specific binding between mediators and sulfated GAG, at which the sulfation code-which means the number and positions of sulfate groups along the polysaccharide chain-plays an important role. GAG from natural sources are very inhomogeneous regarding their sulfation patterns and molecular weight. Additionally, there is a high risk of contamination. This results in a growing interest in the careful characterization of native GAG and the synthesis of artificial GAG. Additionally, chemically oversulfated GAG analogues show many favorable properties. However, the structural characterization of these carbohydrates by mass spectrometry remains challenging. One significant problem is the sulfate loss during the ionization, which increases with the number of sulfate residues. We used the sulfated pentasaccharide fondaparinux as model substance to optimize sample preparation and measurement conditions, compared different established desalination methods and already existing protocols for sulfated oligosaccharides, and investigated their impact on the quality of the mass spectra. After optimization of the measurement conditions, we could establish a gentle and fast protocol for the mass spectrometry characterization of (fully) sulfated, artificial GAG-like oligosaccharides with minimized sulfate loss in the positive and negative ion mode. Here, the negative ion mode was more sensitive in comparison with the positive one, and fondaparinux species with sulfate loss were not detectable under the optimized conditions in the positive ion mode.