cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Quasar Selection Based on Photometric Variability
Creators: name: MacLeod, C. L.
name: Brooks, K.
name: Ivezic, Z.
name: Kochanek, C. S.
name: Gibson, R.
name: Meisner, A.
name: Kozlowski, S.
name: Sesar, B.
name: Becker, A. C.
name: de Vries, W.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We develop a method for separating quasars from other variable point sources using SDSS Stripe 82 light curve data for ~10,000 variable objects. To statistically describe quasar variability, we use a damped random walk model parametrized by a damping time scale, tau, and an asymptotic amplitude (structure function), SF_inf. With the aid of an SDSS spectroscopically confirmed quasar sample, we demonstrate that variability selection in typical extragalactic fields with low stellar density can deliver complete samples with reasonable purity (or efficiency, E). Compared to a selection method based solely on the slope of the structure function, the inclusion of the tau information boosts E from 60% to 75% while maintaining a highly complete sample (98%) even in the absence of color information. For a completeness of C=90%, E is boosted from 80% to 85%. Conversely, C improves from 90% to 97% while maintaining E=80% when imposing a lower limit on tau. With the aid of color selection, the purity can be further boosted to 96%, with C= 93%. Hence, selection methods based on variability will play an important role in the selection of quasars with data provided by upcoming large sky surveys, such as Pan-STARRS and the Large Synoptic Survey Telescope (LSST). For a typical (simulated) LSST cadence over 10 years and a photometric accuracy of 0.03 mag (achieved at i~22), C is expected to be 88% for a simple sample selection criterion of tau>100 days. In summary, given an adequate survey cadence, photometric variability provides an even better method than color selection for separating quasars from stars.
description: (v2) 50 pages, accepted to ApJ
Das Bis(ferrocenyl)phosphenium-Ion im neuen Licht betrachtet
Creators: name: Olaru, Marian
name: Mischin, Alexandra
name: Malaspina, Lorraine A.
name: Mebs, Stefan
name: Beckmann, Jens
Publisher: name: FID GEO
Year: 2019

description: Abstract Das Bis(ferrocenyl)phosphenium-Ion, [Fc2P]+, wurde von Cowley et al. (J. Am. Chem. Soc. 1981, 103, 714–715) als Donor-freies, divalentes Phosphenium-Ion beschrieben. Unsere Untersuchung der molekularen und elektronischen Struktur zeigt, dass [Fc2P]+ bedeutende intramolekulare Fe⋅⋅⋅P-Kontakte aufweist, die hauptsächlich elektrostatischer Natur sind und welche die Lewis-Azidität reduzieren. Nichtsdestotrotz bildet [Fc2P]+ mit den Lewis-Basen PPh3 und IPr die Donor-Akzeptor-Komplexe [Fc2P(PPh3)]+ und [Fc2P(IPr)]+ (IPr=1,3-Bis(2,6-di-i-propylphenyl)imidazole-2-yliden).
Iron Loss and Parameter Measurement of Permanent Magnet Synchronous Machines
Creators: name: Richter, Jan
name: Dollinger, Andreas
name: Doppelbauer, Martin
Publisher: name: Karlsruhe
Year: 2014
Subjects: electric machines
electric resistance
friction
loss measurement
magnetic loss
measurement techniques
nonlinear magnetics
parameter extraction
permanent magnet motors
system identification

description: In this paper a measurement technique for synchronous machines is presented that allows the experimental identification of stator flux linkage as well as iron and friction losses in each operation point. The technique can be applied to all kinds of synchronous electric machines, even to machines showing magnetic anisotropy, iron saturation and cross-coupling. Influences of spatial harmonics, inverter switching and temperature transients are considered. The method uses steady-state measurements at constant motor speed. It is based on a combined evaluation of two operation points with corresponding magnetic states, one being in the motor and the other in the generator mode. The method is demonstrated by characterization of an automotive permanent magnet synchronous traction motor.
Predictive Current Control of Saturated Cross-Coupled Permanent Magnet Synchronous Machines
Creators: name: Richter, Jan
name: Gemaßmer, Tobias
name: Doppelbauer, Martin
Publisher: name: Karlsruhe
Year: 2014
Subjects: control design
cross-coupling
current control
machine vector control
nonlinear control systems
permanent magnet machines
predictive control
saturation magnetization

description: Highly utilized permanent magnet synchronous machines show magnetic saturation and cross-coupling effects. These phenomena are described by nonlinear differential equations and make feedback current control of the machine challenging. State of the art current control methods usually ignore these effects and hence do not produce optimal results in transient operation or in operation at the inverter voltage limit. Therefore, this paper presents a method to design a current controller taking into account saturation and dynamic cross-coupling. Feed forward calculation of transient quantities in realtime enables complete decoupling and dead-beat behavior which is experimentally validated by test bench measurements. With this approach, strongly nonlinear, highly utilized synchronous machines can be successfully controlled achieving best control quality in all operational conditions.
Moving walls accelerate mixing
Creators: name: Thiffeault, Jean-Luc
name: Gouillart, Emmanuelle
name: Dauchot, Olivier
Publisher: name: arXiv
Year: 2011
Subjects: subject: Fluid Dynamics (physics.flu-dyn)
subject: Soft Condensed Matter (cond-mat.soft)
subject: Chaotic Dynamics (nlin.CD)
subject: FOS: Physical sciences

description: Mixing in viscous fluids is challenging, but chaotic advection in principle allows efficient mixing. In the best possible scenario,the decay rate of the concentration profile of a passive scalar should be exponential in time. In practice, several authors have found that the no-slip boundary condition at the walls of a vessel can slow down mixing considerably, turning an exponential decay into a power law. This slowdown affects the whole mixing region, and not just the vicinity of the wall. The reason is that when the chaotic mixing region extends to the wall, a separatrix connects to it. The approach to the wall along that separatrix is polynomial in time and dominates the long-time decay. However, if the walls are moved or rotated, closed orbits appear, separated from the central mixing region by a hyperbolic fixed point with a homoclinic orbit. The long-time approach to the fixed point is exponential, so an overall exponential decay is recovered, albeit with a thin unmixed region near the wall.
description: 17 pages, 13 figures. PDFLaTeX with RevTeX 4-1 style
Classical skyrmions in SU(N)/SO(N) cosets
Creators: name: Gillioz, Marc
Publisher: name: arXiv
Year: 2011
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We construct the skyrmion solutions appearing in the coset spaces SU(N)/SO(N) for N > 2 and compute their classical mass. For N = 3, the third homotopy group pi_3(SU(3)/SO(3)) = Z_4 implies the existence of two distinct solutions: the skyrmion of winding number two has spherical symmetry and is found to be the lightest non-trivial field configuration; the skyrmion and antiskyrmion of winding number plus and minus one are slightly heavier and of toroidal shape. For N >= 4, there is only one skyrmion since the third homotopy group is Z_2. It is found to have spherical symmetry and is significantly lighter than the N = 3 solutions.
description: 14 pages, 3 figures; v2: discussion improved
Determination of the Static Potential with Dynamical Fermions
Creators: name: Donnellan, Michael
name: Knechtli, Francesco
name: Leder, Björn
name: Sommer, Rainer
Publisher: name: arXiv
Year: 2010
Subjects: subject: High Energy Physics - Lattice (hep-lat)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We present in detail a technique to extract the potential between a static quark and anti-quark pair from Wilson loops measured on dynamical configurations. This technique is based on HYP smearing and leads to an exponential improvement of the noise-to-signal ratio of Wilson loops. We explain why the correct continuum potential is obtained and show numerical evidence that the cut-off effects are small. We present precise results for the non-perturbative potential. As applications, we determine the scale r_0/a and study the shape of the static potential in the range of distances around r_0, where it can be compared with phenomenological potential models.
description: 26 pages, 8 figures, 2 tables; new figure 2, update of figure 7, published version
Drainage structures and transit-time distributions in conduit-dominated and fissured karst aquifer systems
Creators: name: Lauber, Ute
Publisher: name: Karlsruhe
Year: 2014
Subjects: karst hydrogeology
tracer test
stable isotopes
transit-time

description: Karst aquifers are important groundwater resources. Solutionally-enlarged conduits embedded in a fissured rock matrix result in a highly heterogeneous underground drainage pattern that makes karst aquifers difficult to characterize. This thesis emphasizes the identification of drainage structures and the quantification of related transit-time distributions of diverse karst aquifer systems. Applied methods include artificial tracer tests, natural tracer analysis, and discharge analysis.
Theory of spin waves in ferromagnetic (Ga,Mn)As
Creators: name: Werpachowska, Agnieszka
name: Dietl, Tomasz
Publisher: name: arXiv
Year: 2010
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: The collective behavior of spins in a dilute magnetic semiconductor is determined by their mutual interactions and influenced by the underlying crystal structure. Hence, we begin with the atomic quantum-mechanical description of this system using the proposed variational-perturbation calculus, and then turn to the emerging macroscopic picture employing phenomenological constants. Within this framework we study spin waves and exchange stiffness in the p-d Zener model of (Ga,Mn)As, its thin layers and bulk crystals described by the spds* tight-binding approximation. Analyzing the anisotropic part of exchange, we find that the Dzyaloshinskii-Moriya interaction may lead to the cycloidal spin arrangement and uniaxial in-plane anisotropy in thin layers, resulting in a surface-like anisotropy in thicker films. We also derive and discuss the spin-wave contribution to magnetization and Curie temperature. Our theory reconstructs the values of stiffness determined from the temperature dependence of magnetization, but reproduces only partly those obtained from analyzing precession modes in (Ga,Mn)As thin films.
description: 17 pages, 12 figures (added Eq. 36, replaced Fig. 10)
Subgrid-scale heat flux modeling for large eddy simulation of turbulent mixed convection
Creators: name: Morar, Dejan
Publisher: name: Karlsruhe
Year: 2014
Subjects: LES
dynamic model
heat flux

description: In the present work, new subgrid-scale (SGS) heat flux model for large eddy simulation (LES) of turbulent mixed convection is developed. The new model explicitly includes the buoyancy production term. It is based on the algebraic equations and dynamic procedure is applied to calculate model coefficients. An experiment on turbulent mixed convection to water in a vertical duct is used for validation of the model.
Pros and Cons: Magnetic versus Optical Microrobots
Creators: name: Sitti, Metin
name: Wiersma, Diederik S.
Publisher: name: FID GEO
Year: 2020

description: Abstract Mobile microrobotics has emerged as a new robotics field within the last decade to create untethered tiny robots that can access and operate in unprecedented, dangerous, or hard-to-reach small spaces noninvasively toward disruptive medical, biotechnology, desktop manufacturing, environmental remediation, and other potential applications. Magnetic and optical actuation methods are the most widely used actuation methods in mobile microrobotics currently, in addition to acoustic and biological (cell-driven) actuation approaches. The pros and cons of these actuation methods are reported here, depending on the given context. They can both enable long-range, fast, and precise actuation of single or a large number of microrobots in diverse environments. Magnetic actuation has unique potential for medical applications of microrobots inside nontransparent tissues at high penetration depths, while optical actuation is suitable for more biotechnology, lab-/organ-on-a-chip, and desktop manufacturing types of applications with much less surface penetration depth requirements or with transparent environments. Combining both methods in new robot designs can have a strong potential of combining the pros of both methods. There is still much progress needed in both actuation methods to realize the potential disruptive applications of mobile microrobots in real-world conditions.
Nonconventional odd denominator fractional quantum Hall states in the second Landau level
Creators: name: Kumar, A.
name: Manfra, M. J.
name: Csáthy, G. A.
name: Pfeiffer, L. N.
name: West, K. W.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We report the observation of a new fractional quantum Hall state in the second Landau level of a two-dimensional electron gas at the Landau level filling factor $ν=2+6/13$. We find that the model of noninteracting composite fermions can explain the magnitude of gaps of the prominent 2+1/3 and 2+2/3 states. The same model fails, however, to account for the gaps of the 2+2/5 and the newly observed 2+6/13 states suggesting that these two states are of exotic origin.omposite fermion model. However, the weaker 2+2/5 and 2+6/13 states deviate significantly suggesting that these states are of exotic origin.
175: Defending against the scientific dark arts
Creators: name: Quintana, Daniel
name: Heathers, James
Publisher: name: OSF
Year: 2019

description: We chat about a recent blogpost from Dorothy Bishop, in which she proposes a Master course that will provide training in fraud detection—what should such a course specifically teach and where would these people work to apply their training? We also discuss whether open science is a cult that has trouble seeing outward.
A note on the realignment criterion
Creators: name: Li, Chi-Kwong
name: Poon, Yiu-Tung
name: Sze, Nung-Sing
Publisher: name: arXiv
Year: 2011
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: For a quantum state in a bipartite system represented as a density matrix, researchers used the realignment matrix and functions on its singular values to study the separability of the quantum state. We obtain bounds for elementary symmetric functions of singular values of realignment matrices. This answers some open problems proposed by Lupo, Aniello, and Scardicchio. As a consequence, we show that the proposed scheme by these authors for testing separability would not work if the two subsystems of the bipartite system have the same dimension.
description: 11 pages, to appear in Journal of Physics A: Mathematical and Theoretical
Glassy aspects of melting dynamics (On melting dynamics and the glass transition, Part I)
Creators: name: Krzakala, Florent
name: Zdeborová, Lenka
Publisher: name: arXiv
Year: 2010
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Disordered Systems and Neural Networks (cond-mat.dis-nn)
subject: FOS: Physical sciences

description: The following properties are in the present literature associated with the behavior of super-cooled glass-forming liquids: faster than exponential growth of the relaxation time, dynamical heterogeneities, growing point-to-set correlation length, crossover from mean field behavior to activated dynamics. In this paper we argue that these properties are also present in a much simpler situation, namely the melting of the bulk of an ordered phase beyond a first order phase transition point. This is a promising path towards a better theoretical, numerical and experimental understanding of the above phenomena and of the physics of super-cooled liquids. We discuss in detail the analogies and the differences between the glass and the bulk melting transitions.
description: 12 pages, 6 figures, first part of two papers on melting dynamics and the glass transition
Bioinspired Liposomes for Oral Delivery of Colistin to Combat Intracellular Infections by Salmonella enterica
Creators: name: Menina, Sara
name: Eisenbeis, Janina
name: Kamal, Mohamed Ashraf M.
name: Koch, Marcus
name: Bischoff, Markus
name: Gordon, Sarah
name: Loretz, Brigitta
name: Lehr, Claus-Michael
Publisher: name: FID GEO
Year: 2019

description: Abstract Bacterial invasion into eukaryotic cells and the establishment of intracellular infection has proven to be an effective means of resisting antibiotic action, as anti-infective agents commonly exhibit a poor permeability across the host cell membrane. Encapsulation of anti-infectives into nanoscaled delivery systems, such as liposomes, is shown to result in an enhancement of intracellular delivery. The aim of the current work is, therefore, to formulate colistin, a poorly permeable anti-infective, into liposomes suitable for oral delivery, and to functionalize these carriers with a bacteria-derived invasive moiety to enhance their intracellular delivery. Different combinations of phospholipids and cholesterol are explored to optimize liposomal drug encapsulation and stability in biorelevant media. These liposomes are then surface-functionalized with extracellular adherence protein (Eap), derived from Staphylococcus aureus. Treatment of HEp-2 and Caco-2 cells infected with Salmonella enterica using colistin-containing, Eap-functionalized liposomes resulted in a significant reduction of intracellular bacteria, in comparison to treatment with nonfunctionalized liposomes as well as colistin alone. This indicates that such bio-invasive carriers are able to facilitate intracellular delivery of colistin, as necessary for intracellular anti-infective activity. The developed Eap-functionalized liposomes, therefore, present a promising strategy for improving the therapy of intracellular infections.
Error probability analysis in quantum tomography: a tool for evaluating experiments
Creators: name: Sugiyama, Takanori
name: Turner, Peter S.
name: Murao, Mio
Publisher: name: arXiv
Year: 2010
Subjects: subject: Quantum Physics (quant-ph)
subject: Statistics Theory (math.ST)
subject: FOS: Physical sciences
subject: FOS: Mathematics

description: We expand the scope of the statistical notion of error probability, i.e., how often large deviations are observed in an experiment, in order to make it directly applicable to quantum tomography. We verify that the error probability can decrease at most exponentially in the number of trials, derive the explicit rate that bounds this decrease, and show that a maximum likelihood estimator achieves this bound. We also show that the statistical notion of identifiability coincides with the tomographic notion of informational completeness. Our result implies that two quantum tomographic apparatuses that have the same risk function, (e.g. variance), can have different error probability, and we give an example in one qubit state tomography. Thus by combining these two approaches we can evaluate, in a reconstruction independent way, the performance of such experiments more discerningly.
description: 14pages, 2 figures (an analysis of an example is added, and the proof of Lemma 2 is corrected)
Photobodies: Light-Activatable Single-Domain Antibody Fragments
Creators: name: Jedlitzke, Benedikt
name: Yilmaz, Zahide
name: Dörner, Wolfgang
name: Mootz, Henning D.
Publisher: name: FID GEO
Year: 2019

description: Abstract Photocaged antibody fragments, termed photobodies, have been developed that are impaired in their antigen-binding capacity and can be activated by irradiation with UV light (365 nm). This rational design concept builds on the selective photocaging of a single tyrosine in a nanobody (a single-domain antibody fragment). Tyrosine is a frequently occurring residue in central positions of the paratope region. o-Nitrobenzyl-protected tyrosine variants were incorporated into four nanobodies, including examples directed against EGFR and HER2, and photodeprotection restores the native sequence. An anti-GFP photobody exhibited an at least 10 000-fold impaired binding affinity before photodeprotection compared with the parent nanobody. A bispecific nanobody–photobody fusion protein was generated to trigger protein heterodimerization by light. Photoactivatable antibodies are expected to become versatile protein reagents and to enable novel approaches in diagnostic and therapeutic applications.
Effective and Reversible Carbon Dioxide Insertion into Cerium Pyrazolates
Creators: name: Bayer, Uwe
name: Werner, Daniel
name: Maichle-Mössmer, Cäcilia
name: Anwander, Reiner
Publisher: name: FID GEO
Year: 2020

description: Abstract The homoleptic pyrazolate complexes [CeIII4(Me2pz)12] and [CeIV(Me2pz)4]2 quantitatively insert CO2 to give [CeIII4(Me2pz⋅CO2)12] and [CeIV(Me2pz⋅CO2)4], respectively (Me2pz=3,5-dimethylpyrazolato). This process is reversible for both complexes, as observed by in situ IR and NMR spectroscopy in solution and by TGA in the solid state. By adjusting the molar ratio, one molecule of CO2 per [CeIV(Me2pz)4] complex could be inserted to give trimetallic [Ce3(Me2pz)9(Me2pz⋅CO2)3(thf)]. Both the cerous and ceric insertion products catalyze the formation of cyclic carbonates from epoxides and CO2 under mild conditions. In the absence of epoxide, the ceric catalyst is prone to reduction by the co-catalyst tetra-n-butylammonium bromide (TBAB).
Correlation between balance energy and transition energy for symmetric colliding nuclei
Creators: name: Rajni
name: Kumar, Suneel
name: Puri, Rajeev K.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: We study the correlation between balance energy and transition energy of fragment in heavy-ion collisions for different systems at incident energies between 40 and 1200 MeV/nucleon using an isospin-dependent quantum molecular dynamics model. With increasing incident energy, the elliptic flow shows a transition from positive (in-plane) to negative (out-of-plane) flow. This transition energy is found to depend on the size of fragments, composite mass of reacting system, and the impact parameter of reaction. It has been observed that reduced cross-section can explain the experimental data. There is a correlation between transition energy and balance energy as their difference decreases with increase in the total mass of colliding nuclei.
Individual and joint performance of DNA methylation profiles, genetic risk score and environmental risk scores for predicting breast cancer risk
Creators: name: Guan, Zhong
name: Raut, Janhavi R.
name: Weigl, Korbinian
name: Schöttker, Ben
name: Holleczek, Bernd
name: Zhang, Yan
name: Brenner, Hermann
Publisher: name: FID GEO
Year: 2019

description: DNA methylation patterns in the blood, genetic risk scores (GRSs), and environmental risk factors can potentially improve breast cancer (BC) risk prediction. We assessed the individual and joint predictive performance of methylation, GRS, and environmental risk factors for BC incidence in a prospective cohort study. In a cohort of 5462 women aged 50–75 from Germany, 101 BC cases were identified during 14 years of follow-up and were compared to 263 BC-free controls in a nested case–control design. Three previously suggested methylation risk scores (MRSs) based on methylation of 423, 248, and 131 cytosine-phosphate-guanine (CpG) loci, and a GRS based on the risk alleles from 269 recently identified single nucleotide polymorphisms were constructed. Additionally, multiple previously proposed environmental risk scores (ERSs) were built based on environmental variables. Areas under the receiver operating characteristic curves (AUCs) were estimated for evaluating BC risk prediction performance. MRS and ERS showed limited accuracy in predicting BC incidence, with AUCs ranging from 0.52 to 0.56 and from 0.52 to 0.59, respectively. The GRS predicted BC incidence with a higher accuracy (AUC = 0.61). Adjusted odds ratios per standard deviation increase (95% confidence interval) were 1.07 (0.84–1.36) and 1.40 (1.09–1.80) for the best performing MRS and ERS, respectively, and 1.48 (1.16–1.90) for the GRS. A full risk model combining the MRS, GRS, and ERS predicted BC incidence with the highest accuracy (AUC = 0.64) and might be useful for identifying high-risk populations for BC screening.
Lipid-dependent coupling of secretory cargo sorting and trafficking at the trans-Golgi network
Creators: name: Von Blume, Julia
name: Hausser, Angelika
Publisher: name: FID GEO
Year: 2019

description: In eukaryotic cells, the trans-Golgi network (TGN) serves as a platform for secretory cargo sorting and trafficking. In recent years, it has become evident that a complex network of lipid–lipid and lipid–protein interactions contributes to these key functions. This review addresses the role of lipids at the TGN with a particular emphasis on sphingolipids and diacylglycerol. We further highlight how these lipids couple secretory cargo sorting and trafficking for spatiotemporal coordination of protein transport to the plasma membrane.
Pseudo-Killing Spinors, Pseudo-supersymmetric p-branes, Bubbling and Less-bubbling AdS Spaces
Creators: name: Lu, H.
name: Wang, Zhao-Long
Publisher: name: arXiv
Year: 2011
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: We consider Einstein gravity coupled to an n-form field strength in D dimensions. Such a theory cannot be supersymmetrized in general, we nevertheless propose a pseudo-Killing spinor equation and show that the AdS X Sphere vacua have the maximum number of pseudo-Killing spinors, and hence are fully pseudo-supersymmetric. We show that extremal p-branes and their intersecting configurations preserve fractions of the pseudo-supersymmetry. We study the integrability condition for general (D,n) and obtain the additional constraints that are required so that the existence of the pseudo-Killing spinors implies the Einstein equations of motion. We obtain new pseudo-supersymmetric bubbling AdS_5 X S^5 spaces that are supported by a non-self-dual 5-form. This demonstrates that non-supersymmegtric conformal field theories may also have bubbling states of arbitrary droplets of free fermions in the phase space. We also obtain an example of less-bubbling AdS geometry in D=8, whose bubbling effects are severely restricted by the additional constraint arising from the integrability condition.
description: typos corrected, extra comments and references added, version appeared in JHEP
Will the tachyonic Universe survive the Big Brake?
Creators: name: Keresztes, Zoltán
name: Gergely, László Á.
name: Kamenshchik, Alexander Yu.
name: Gorini, Vittorio
name: Polarski, David
Publisher: name: arXiv
Year: 2010
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We investigate a Friedmann universe filled with a tachyon scalar field, which behaves as dustlike matter in the past, while it is able to accelerate the expansion rate of the universe at late times. The comparison with type Ia supernovae (SNIa) data allows for evolutions driving the universe into a Big Brake. Some of the evolutions leading to a Big Brake exhibit a large variation of the equation of state parameter at low redshifts which is potentially observable with future data though hardly detectable with present SNIa data. The soft Big Brake singularity occurs at finite values of the scale factor, vanishing energy density and Hubble parameter, but diverging deceleration and infinite pressure. We show that the geodesics can be continued through the Big Brake and that our model universe will recollapse eventually in a Big Crunch. Although the time to the Big Brake strongly depends on the present values of the tachyonic field and of its time derivative, the time from the Big Brake to the Big Crunch represents a kind of invariant timescale for all field parameters allowed by SNIa.
description: v2: slightly expanded, 14 pages, 5 figures, 3 tables; version to be published in Phys.Rev.D
Local Leukocyte Invasion during Hyperacute Human Ischemic Stroke
Creators: name: Kollikowski, Alexander M.
name: Schuhmann, Michael K.
name: Nieswandt, Bernhard
name: Müllges, Wolfgang
name: Stoll, Guido
name: Pham, Mirko
Publisher: name: FID GEO
Year: 2020

description: Objective Bridging the gap between experimental stroke and patients by ischemic blood probing during the hyperacute stage of vascular occlusion is crucial to assess the role of inflammation in human stroke and for the development of adjunct treatments beyond recanalization. Methods We prospectively observed 151 consecutive ischemic stroke patients with embolic large vessel occlusion of the anterior circulation who underwent mechanical thrombectomy. In all these patients, we attempted microcatheter aspiration of 3 different arterial blood samples: (1) within the core of the occluded vascular compartment and controlled by (2) carotid and (3) femoral samples obtained under physiological flow conditions. Subsequent laboratory analyses comprised leukocyte counting and differentiation, platelet counting, and the quantification of 13 proinflammatory human chemokines/cytokines. Results Forty patients meeting all clinical, imaging, interventional, and laboratory inclusion criteria could be analyzed, showing that the total number of leukocytes significantly increased under the occlusion condition. This increase was predominantly driven by neutrophils. Significant increases were also apparent for lymphocytes and monocytes, accompanied by locally elevated plasma levels of the T-cell chemoattractant CXCL-11. Finally, we found evidence that short-term clinical outcome (National Institute of Health Stroke Scale at 72 hours) was negatively associated with neutrophil accumulation. Interpretation We provide the first direct human evidence that neutrophils, lymphocytes, and monocytes, accompanied by specific chemokine upregulation, accumulate in the ischemic vasculature during hyperacute stroke and may affect outcome. These findings strongly support experimental evidence that immune cells contribute to acute ischemic brain damage and indicate that ischemic inflammation initiates already during vascular occlusion. Ann Neurol 2020;87:466–479
Efficient OER Catalyst with Low Ir Volume Density Obtained by Homogeneous Deposition of Iridium Oxide Nanoparticles on Macroporous Antimony-Doped Tin Oxide Support
Creators: name: Böhm, Daniel
name: Beetz, Michael
name: Schuster, Maximilian
name: Peters, Kristina
name: Hufnagel, Alexander G.
name: Döblinger, Markus
name: Böller, Bernhard
name: Bein, Thomas
name: Fattakhova-Rohlfing, Dina
Publisher: name: FID GEO
Year: 2019

description: Abstract A multistep synthesis procedure for the homogeneous coating of a complex porous conductive oxide with small Ir nanoparticles is introduced to obtain a highly active electrocatalyst for water oxidation. At first, inverse opal macroporous Sb doped SnO2 (ATO) microparticles with defined pore size, composition, and open-porous morphology are synthesized that reach a conductivity of ≈3.6 S cm−1 and are further used as catalyst support. ATO-supported iridium catalysts with a controlled amount of active material are prepared by solvothermal reduction of an IrOx colloid in the presence of the porous ATO particles, whereby homogeneous coating of the complete outer and inner surface of the particles with nanodispersed metallic Ir is achieved. Thermal oxidation leads to the formation of ATO-supported IrO2 nanoparticles with a void volume fraction of ≈89% calculated for catalyst thin films based on scanning transmission electron microscope tomography data and microparticle size distribution. A remarkably low Ir bulk density of ≈0.08 g cm−3 for this supported oxide catalyst architecture with 25 wt% Ir is determined. This highly efficient oxygen evolution reaction catalyst reaches a current density of 63 A gIr−1 at an overpotential of 300 mV versus reversible hydrogen electrode, significantly exceeding a commercial TiO2-supported IrO2 reference catalyst under the same measurement conditions.
Solvate-Induced Semiconductor to Metal Transition: Flat 1∞ [Bi1−] Zigzag Chains in Metallic KBi⋅NH3 versus 1∞ [Bi1−] Helices in Semiconducting KBi
Creators: name: Mayer, Kerstin
name: Dums, Jasmin V.
name: Benda, Christian B.
name: Klein, Wilhelm
name: Fässler, Thomas F.
Publisher: name: FID GEO
Year: 2020

description: Abstract Polymeric 1∞ [Bi]− in KBi⋅NH3 has planar zigzag chains with two-connected Bi atoms and metallic properties, whereas KBi, which has helical chains of Bi atoms, is semiconducting. The isomerization of the Bi chain is induced by solvate molecules. In the novel layered solvate structure uncharged 2∞ [KBi] layers are separated by intercalated NH3 molecules. These layers are a structural excerpt of the iso(valence)electronic CaSi, whose metallic properties arise from the planarity of the zigzag chain of Si atoms. Computational studies support this view, they show an anisotropic metallic behavior along the Bi chain. Electron delocalization is also found in the new cyclic anion [Bi6]4− isolated in K2[K(18-crown-6)]2[Bi6]⋅9 NH3. Although [Bi6]4− should exhibit one localized double bond, electron delocalization is observed in analogy to the lighter homologues [P6]4− and [As6]4−. Both compounds were characterized by single-crystal X-ray structure determination.
Heating of solar chromosphere by electromagnetic wave absorption in a plasma slab model
Creators: name: Tsiklauri, D.
name: Pechhacker, R.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Plasma Physics (physics.plasm-ph)
subject: FOS: Physical sciences

description: The heating of solar chromospheric inter-network regions by means of the absorption of electromagnetic (EM) waves that originate from the photospheric blackbody radiation is studied in the framework of a plasma slab model. The absorption is provided by the electron-neutral collisions in which electrons oscillate in the EM wave field and electron-neutral collisions damp the EM wave. Given the uncertain nature of the collision cross-section due to the plasma micro-turbulence, it is shown that for plausible physical parameters, the heating flux produced by the absorption of EM waves in the chromosphere is between $20 - 45$ % of the chromospheric radiative loss flux requirement. It is also established that there is an optimal value for the collision cross-section, $5 \times 10^{-18}$ m$^{2}$, that produces the maximal heating flux of 1990 W m$^{-2}$.
description: Physics of Plasmas, in press, April 2011 issue (final printed version, typos in proofs corrected)
Activated Carbon in the Third Dimension—3D Printing of a Tuned Porous Carbon
Creators: name: Steldinger, Hendryk
name: Esposito, Alessandro
name: Brunnengräber, Kai
name: Gläsel, Jan
name: Etzold, Bastian J. M.
Publisher: name: FID GEO
Year: 2019

description: Abstract A method for obtaining hierarchically structured porous carbons, employing 3D printing to control the structure down to the lower µm scale, is presented. To successfully 3D print a polymer precursor and transfer it to a highly stable and structurally conformal carbon material, stereolithography 3D printing and photoinduced copolymerization of pentaerythritol tetraacrylate and divinylbenzene are employed. Mechanically stable structures result and a resolution of ≈15 µm is demonstrated. This approach can be combined with liquid porogen templating to control the amount and size (up to ≈100 nm) of transport pores in the final carbonaceous material. Additional CO2 activation enables high surface area materials (up to 2200 m2 g-1) that show the 3D printing controlled µm structure and nm sized transport pores. This unique flexibility holds promise for the identification of optimal carbonaceous structures for energy application, catalysis, and adsorption.
Atomic Layer Deposition of ZnO on InP Quantum Dot Films for Charge Separation, Stabilization, and Solar Cell Formation
Creators: name: Crisp, Ryan W.
name: Hashemi, Fatemeh S. M.
name: Alkemade, Jordi
name: Kirkwood, Nicholas
name: Grimaldi, Gianluca
name: Kinge, Sachin
name: Siebbeles, Laurens D. A.
name: Van Ommen, J. Ruud
name: Houtepen, Arjan J.
Publisher: name: FID GEO
Year: 2020

description: Abstract To improve the stability and carrier mobility of quantum dot (QD) optoelectronic devices, encapsulation or pore infilling processes are advantageous. Atomic layer deposition (ALD) is an ideal technique to infill and overcoat QD films, as it provides excellent control over film growth at the sub-nanometer scale and results in conformal coatings with mild processing conditions. Different thicknesses of crystalline ZnO films deposited on InP QD films are studied with spectrophotometry and time-resolved microwave conductivity measurements. High carrier mobilities of 4 cm2 (V s)−1 and charge separation between the QDs and ZnO are observed. Furthermore, the results confirm that the stability of QD thin films is strongly improved when the inorganic ALD coating is applied. Finally, proof-of-concept photovoltaic devices of InP QD films are demonstrated with an ALD-grown ZnO electron extraction layer.
Nuclear Envelope Permeability Barrier as a Fast-Response Intracellular Mechanostat
Creators: name: Shahin, Victor
name: Kouzel, Ivan U.
name: Rosso, Gonzalo
name: Liashkovich, Ivan
Publisher: name: FID GEO
Year: 2019

description: Abstract The nuclear envelope is an undisputed component of the intracellular mechanotransduction cascades which collect, process, and respond to mechanical stimuli from the environment. At the same time, the nuclear envelope performs the function of a selective barrier between the nuclear and cytoplasmic compartments. Although the mechanosensing and the barrier functions of the nuclear envelope have both been subjects of intense research, a possible reciprocal relationship between them is only beginning to emerge. In this report, the role of the nucleocytoplasmic permeability barrier is evaluated in nuclear mechanics. Using a combination of atomic force and confocal microscopy, the functional state of the nucleocytoplasmic permeability barrier and the nuclear mechanics is monitored. By modulating the stringency of the barrier and simulating the active transport imbalance across the nuclear envelope, the decisive impact of these parameters on nuclear mechanics is demonstrated. It is concluded that the nucleocytoplasmic barrier is the second essential component of the intracellular mechanostat function performed by the nuclear envelope.
Glassy dynamics as a melting process (On melting dynamics and the glass transition, Part II)
Creators: name: Krzakala, Florent
name: Zdeborová, Lenka
Publisher: name: arXiv
Year: 2010
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Disordered Systems and Neural Networks (cond-mat.dis-nn)
subject: FOS: Physical sciences

description: There are deep analogies between the melting dynamics in systems with a first order phase transition and the dynamics from equilibrium in super-cooled liquids. For a class of Ising spin models undergoing a first order transition - namely p-spin models on the so-called Nishimori line - it can be shown that the melting dynamics can be exactly mapped to the equilibrium dynamics. In this mapping the dynamical -or mode-coupling- glass transition corresponds to the spinodal point, while the Kauzmann transition corresponds to the first order phase transition itself. Both in mean field and finite dimensional models this mapping provides an exact realization of the random first order theory scenario for the glass transition. The corresponding glassy phenomenology can then be understood in the framework of a standard first order phase transition.
description: 14 pages, 7 figures, second part of two papers on melting dynamics and the glass transition
Electrocatalytic Hydrogen Production with a Molecular Cobalt Complex in Aqueous Solution
Creators: name: Wilken, Mona
name: Siewert, Inke
Publisher: name: FID GEO
Year: 2020

description: Abstract Herein, we present the synthesis of a cobalt complex with a pentadentate ligand platform and its application in the electrochemical hydrogen evolution reaction (LCF3=2,6-bis(methoxybis(4-trifluormethyl-1H-imidazol-2-yl)methyl)pyridine). The complex is active in neutral to acidic solvent mixtures containing 50 % water. Electronic tuning in the ligand backbone, that is introduction of electron-withdrawing CF3-groups, shifts the onset potential of the catalytic wave to less negative potentials. NMR and UV/Vis studies indicate that the CoIII complex is deprotonated twice in the ligand backbone under neutral conditions. Reduction is accompanied by protonation, as indicated by pH-dependent CV measurements, and the CoI state initiates catalysis. The result suggests that the pentadentate ligand is an ideal platform for cobalt catalysts in the oxidative and reductive water splitting reaction.
Axial beanspruchte K-Knoten aus dünnwandigen Rechteckhohlprofilen
Creators: name: Fleischer, Oliver
Publisher: name: Karlsruhe
Year: 2014
Subjects: Rechteckhohlprofile
K-Konten
Traglasten
Bemessung
Spaltweite

description: Aufgrund des eingeschränkten Anwendungsbereichs von Rechteckhohlprofilknoten (DIN EN 1993-1-8) sind viele in den technischen Lieferbedingungen enthaltene Querschnitte nur durch eine Zustimmung im Einzelfall (ZiE) einsetzbar. Die Verwendung dieser Querschnitte wird daher im Allgemeinen vermieden. Mit dem vorgestellten Bemessungskonzept ist die Bemessung von K-Knoten mit dünnwandigen Gurten möglich, so dass diese Querschnitte der Bemessung von Hohlprofilknoten zugänglich gemacht werden.
Higgs Spin Determination and Unitarity of Vector-boson Scattering at the LHC
Creators: name: Frank, Jessica
Publisher: name: Karlsruhe
Year: 2014

description: After the discovery of a new particle at the LHC, it is crucial to verify or disprove whether it is the SM Higgs boson. Thus, its features, including its spin, have to be determined. In order to distinguish between spin-0 and spin-2, light spin-2 resonances are studied. Since the SM Higgs boson ensures the unitarity of vector-boson scattering, another topic is to investigate if other particles are able to perform the same task. Furthermore, heavy spin-2 resonances at the LHC are studied.
Resolving the dynamical mass of a z~1.3 QSO host galaxy using SINFONI and Laser Guide Star assisted Adaptive Optics
Creators: name: Inskip, Katherine J.
name: Jahnke, Knud
name: Rix, Hans-Walter
name: van de Ven, Glenn
Publisher: name: arXiv
Year: 2011
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: Recent studies of the tight scaling relations between the masses of supermassive black holes and their host galaxies have suggested that in the past black holes constituted a larger fraction of their host galaxies' mass. However, these arguments are limited by selection effects and difficulties in determining robust host galaxy masses at high redshifts. Here we report the first results of a new, complementary diagnostic route: we directly determine a dynamical host galaxy mass for the z=1.3 luminous quasar J090543.56+043347.3 through high-spatial-resolution (0.47", 4kpc FWHM) observations of the host galaxy gas kinematics over 30x40 kpc using ESO/VLT/SINFONI with LGS/AO. Combining our result of M_dyn = 2.05+1.68_0.74 x 10^11 M_sun (within a radius 5.25 +- 1.05 kpc) with M_BH,MgII = 9.02 \pm 1.43 x 10^8 M_sun, M_BH,Halpha = 2.83 +1.93-1.13 x 10^8 M_sun, we find that the ratio of black hole mass to host galaxy dynamical mass for J090543.56+043347.3 matches the present-day relation for M_BH vs. M_Bulge,Dyn, well within the IR scatter, deviating at most a factor of two from the mean. J090543.56+043347.3 displays clear signs of an ongoing tidal interaction and of spatially extended star formation at a rate of 50-100 M_sun/yr, above the cosmic average for a galaxy of this mass and redshift. We argue that its subsequent evolution may move J090543.56+043347.3 even closer to the z=0 relation for M_BH vs. M_Bulge,Dyn. Our results support the picture where any substantive evolution in these relations must occur prior to z~1.3. Having demonstrated the power of this modelling approach we are currently analyzing similar data on seven further objects to better constrain such evolution.
description: Accepted for publication in ApJ, 14 pages, 10 Figures
Signatures of a Charge Density Wave Phase and the Chiral Anomaly in the Fermionic Material Cobalt Monosilicide CoSi
Creators: name: Schnatmann, Lauritz
name: Geishendorf, Kevin
name: Lammel, Michaela
name: Damm, Christine
name: Novikov, Sergey
name: Thomas, Andy
name: Burkov, Alexander
name: Reith, Heiko
name: Nielsch, Kornelius
name: Schierning, Gabi
Publisher: name: FID GEO
Year: 2019

description: Abstract Materials with topological electronic states have emerged as one of the most exciting discoveries of condensed quantum matter, hosting quasiparticles with extremely low effective mass and high mobility. Weyl materials contain such topological states in the bulk and additionally have a non-trivial chiral charge. However, despite known quantum effects caused by these chiral states, the interplay between chiral states, and a charge density wave phase, an ordering of the electrons to a correlated phase is not experimentally explored. Indications for the formation of a charge density wave phase in the Weyl material cobalt monosilicide CoSi are observed. Furthermore, the typical signatures of the charge density wave phase together with typical signatures of Weyl fermions in magnetic field dependent electrical transport characterization are investigated. The charge density wave and the chiral contribution to the electrical magneto-transport are separated as well as a suppression of the charge density wave phase is observed in magnetic fields.