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Search Results: 1 - 10 of 9522 matches for " Sandra Gruenewald "
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Resistance, reinhabitation, and regime change
Gruenewald, D.
Journal of Research in Rural Education , 2006,
Abstract: This article was initially delivered as the lead keynote address at the Third Research Symposium of the Appalachian Collaborative Center for Learning, Assessment, and Instruction in Mathematics (Newark, Ohio: May 18, 2006).
Computing Humbert Surfaces
David Gruenewald
Mathematics , 2007,
Abstract: We describe an algorithm which computes components of Humbert surfaces in terms of Rosenhain invariants, based on Runge's method
Pointing Calibration for the Cherenkov Telescope Array Medium Size Telescope Prototype
Louise Oakes,Bagmeet Behera,Juergen Baehr,Sandra Gruenewald,Tobias Raeck,Stefan Schlenstedt,Anja Schubert,Ullrich Schwanke,for the CTA Consortium
Physics , 2013,
Abstract: Pointing calibration is an offline correction applied in order to obtain the true pointing direction of a telescope. The Cherenkov Telescope Array (CTA) aims to have the precision to determine the position of point-like as well as slightly extended sources, with the goal of systematic errors less than 7 arc seconds in space angle. This poster describes the pointing calibration concept being developed for the CTA Medium Size Telescope (MST) prototype at Berlin-Adlershof, showing test results and preliminary measurements. The MST pointing calibration method uses two CCD cameras, mounted on the telescope dish, to determine the true pointing of the telescope. The "Lid CCD" is aligned to the optical axis of the telescope, calibrated with LEDs on the dummy gamma-camera lid; the "Sky CCD" is pre-aligned to the Lid CCD and the transformation between the Sky and Lid CCD camera fields of view is precisely modelled with images from special pointing runs which are also used to determine the pointing model. During source tracking, the CCD cameras record images which are analysed offline using software tools including Astrometry.net to determine the true pointing coordinates.
Heuristics on pairing-friendly abelian varieties
John Boxall,David Gruenewald
Mathematics , 2012, DOI: 10.1112/S1461157015000091
Abstract: We discuss heuristic asymptotic formulae for the number of pairing-friendly abelian varieties over prime fields, generalizing previous work of one of the authors arXiv:math1107.0307
Measuring WWZ and WWgamma coupling constants with Z-pole data
Peter Molnar,Martin W. Gruenewald
Physics , 1999, DOI: 10.1016/S0370-2693(99)00815-1
Abstract: Triple gauge boson couplings between Z, gamma and the W boson are determined by exploiting their impact on radiative corrections to fermion-pair production in e+e- interactions at centre-of-mass energies near the Z-pole. Recent values of observables in the electroweak part of the Standard model are used to determine the four parameters epsilon_1, epsilon_2, epsilon_3 and epsilon_b. In a second step the results on the four epsilon parameters are used to determine the couplings Delta-g^1_Z and Delta-kappa_gamma. For a wide range of scales, these indirect coupling measurements are more precise than recent direct measurements at LEP 2 and at the TEVATRON. The Standard model predictions agree well with these measurements.
[Book review] Reclaiming the Local in Language Policy and Practice (A. Suresh Canagarajah, Ed.)
Gruenewald, D. A.,Salsbury, T. L.
Journal of Research in Rural Education , 2006,
Explicit CM-theory for level 2-structures on abelian surfaces
Reinier Broker,David Gruenewald,Kristin Lauter
Mathematics , 2009,
Abstract: For a complex abelian variety $A$ with endomorphism ring isomorphic to the maximal order in a quartic CM-field $K$, the Igusa invariants $j_1(A), j_2(A),j_3(A)$ generate an abelian extension of the reflex field of $K$. In this paper we give an explicit description of the Galois action of the class group of this reflex field on $j_1(A),j_2(A),j_3(A)$. We give a geometric description which can be expressed by maps between various Siegel modular varieties. We can explicitly compute this action for ideals of small norm, and this allows us to improve the CRT method for computing Igusa class polynomials. Furthermore, we find cycles in isogeny graphs for abelian surfaces, thereby implying that the `isogeny volcano' algorithm to compute endomorphism rings of ordinary elliptic curves over finite fields does not have a straightforward generalization to computing endomorphism rings of abelian surfaces over finite fields.
Pulsed laser deposition with simultaneous in situ real-time monitoring of optical spectroscopic ellipsometry and reflection high-energy electron diffraction
J. H. Gruenewald,J. Nichols,S. S. A. Seo
Physics , 2013, DOI: 10.1063/1.4798621
Abstract: We present a pulsed laser deposition (PLD) system that can monitor growth by simultaneously using in situ optical spectroscopic ellipsometry (SE) and reflection high-energy electron diffraction (RHEED). The RHEED precisely monitors the number of thin-film layers and surface structure during the deposition and the SE measures the optical spectra of the samples simultaneously. The thin-film thickness information obtained from RHEED facilitates the SE modeling process, which allows extracting the in situ optical spectra, i.e. the dielectric functions, of thin-films during growth. The in situ dielectric functions contain indispensable information about the electronic structure of thin-films. We demonstrate the performance of this system by growing LaMnO3+{\delta} (LMO) thin-films on SrTiO3 (001) substrates. By using in situ SE and RHEED simultaneously, we show that real-time thickness and dielectric functions of the LMO thin-films can be effectively extracted. The simultaneous monitoring of both optical SE and RHEED offers important clues to understand the growth mechanism of atomic-scale thin-films.
Reliability of continuous cardiac output measurement during intra-abdominal hypertension relies on repeated calibrations: an experimental animal study
Matthias Gruenewald, Jochen Renner, Patrick Meybohm, Jan H?cker, Jens Scholz, Berthold Bein
Critical Care , 2008, DOI: 10.1186/cc7102
Abstract: Ten pigs were anaesthetised and instrumented for haemodynamic measurements. Cardiac output was obtained using CCO by pulse power analysis (PulseCO; LiDCO monitor), using CCO by pulse contour analysis (PCCO; PiCCO monitor) and using CCO by pulmonary artery catheter thermodilution (CCOPAC), and was compared with bolus transcardiopulmonary thermodilution CO (COTCP) at baseline, after fluid loading, at IAH and after an additional fluid loading at IAH. Whereas PulseCO was only calibrated at baseline, PCCO was calibrated at each experimental step.PulseCO and PCCO underestimated CO, as the overall bias ± standard deviation was 1.0 ± 1.5 l/min and 1.0 ± 1.1 l/min compared with COTCP. A clinically accepted agreement between all of the CCO methods and COTCP was observed only at baseline. Whereas IAH did not influence the CO, increased CO following fluid loading at IAH was only reflected by CCOPAC and COTCP, not by uncalibrated PulseCO and PCCO. After recalibration, PCCO was comparable with COTCP.The CO obtained by uncalibrated PulseCO and PCCO failed to agree with COTCP during IAH and fluid loading. In the critically ill patient, recalibration of continuous arterial waveform CO methods should be performed after fluid loading or before a major change in therapy is initiated.Monitoring cardiac output (CO) allows early detection of haemodynamic instability and may be used to guide intensive care, aiming to reduce morbidity and mortality in high-risk patients [1]. In the past decade, continuous cardiac output (CCO) was commonly obtained by pulmonary artery catheter (PAC) with integrated heating filaments. The risk–benefit ratio of right heart catheterisation simply for CO determination has been questioned due to associated complications and the availability of less invasive alternatives [2]. Various monitor devices have been recently introduced into clinical practise that use the arterial pressure waveform to calculate CO on a beat-to-beat basis, such as the LiDCO?plus system usi
Optical Constants of - and -Zinc(II)-Phthalocyanine Films
Michael Kozlik,S?ren Paulke,Marco Gruenewald,Roman Forker,Torsten Fritz
Dataset Papers in Science , 2013, DOI: 10.1155/2013/926470
Abstract: We present a dataset of the optical constants of α- and β-zinc(II)-phthalocyanine (ZnPc). They were determined accurately from transmission and differential reflectance spectra, with the surface roughness taken into account. For this purpose, thin films were prepared on quartz glass substrates via physical vapor deposition and characterized by ultraviolet-visible (UV-Vis) spectroscopy before as well as after a well-defined annealing process. Kramers-Kronig consistency of the optical constants obtained was checked by means of a numerical algorithm. 1. Introduction Zinc(II)-phthalocyanine (ZnPc) is a promising material for organic electronics, especially photovoltaic devices. It has already been applied in prototypes of solar cells [1–4]. Furthermore, it is already known that phthalocyanines (including ZnPc) can exist in multiple types of crystalline phases [5]; in particular, the metastable -ZnPc (higher electrical conductivity) and the stable -ZnPc (lower electrical conductivity) [6] need to be distinguished. Structural analysis of both phases and detailed information about the phase transition as shown in [7] are needed to set suitable constraints for a numerical model to determine the optical constants of - and -ZnPc. Once the optical constants are known, they can be used for modeling layer systems or even photovoltaic devices, or vice versa, for a nondestructive optical analysis of the crystallinity of ZnPc layers. Here, we present a reliable method for the determination of optical constants of organic thin films, where the surface roughness is taken into account. Finally, we present a detailed dataset of optical constants for polycrystalline - and -ZnPc covering an energy interval from 1.2?eV to 5.0?eV. 2. Methodology Thin films of ZnPc were prepared via physical vapor deposition on quartz glass. Quartz glass was used as substrate due to the low absorbance in a broad spectral range ( between 300?nm and 850?nm). After thorough in situ degassing, the ZnPc powder obtained from Sigma-Aldrich with 97% chemical purity was thermally evaporated from a ceramic crucible in a tungsten boat and deposited at a rate of 0.6??/s under high vacuum conditions (pressure: ?mbar). To realize the growth of the phase, ZnPc was deposited on substrates kept at room temperature [8]. A phase transition from -ZnPc to -ZnPc upon annealing has been demonstrated in the literature [7, 9, 10]. Here, the stable -ZnPc phase was obtained from the metastable -ZnPc samples via annealing under ambient conditions for 3?h at 240°C and above. Films of both phases with different thicknesses
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