Showing papers by "Braunschweig University of Technology published in 2001"
TL;DR: In this paper, the authors present an overview of the instrumentation used to measure the magnetic field on the four Cluster spacecraft and an overview the performance of the operational modes used in flight.
Abstract: . The accurate measurement of the magnetic field along the orbits of the four Cluster spacecraft is a primary objective of the mission. The magnetic field is a key constituent of the plasma in and around the magnetosphere, and it plays an active role in all physical processes that define the structure and dynamics of magnetospheric phenomena on all scales. With the four-point measurements on Cluster, it has become possible to study the three-dimensional aspects of space plasma phenomena on scales commeasurable with the size of the spacecraft constellation, and to distinguish temporal and spatial dependences of small-scale processes. We present an overview of the instrumentation used to measure the magnetic field on the four Cluster spacecraft and an overview the performance of the operational modes used in flight. We also report on the results of the preliminary in-orbit calibration of the magnetometers; these results show that all components of the magnetic field are measured with an accuracy approaching 0.1 nT. Further data analysis is expected to bring an even more accurate determination of the calibration parameters. Several examples of the capabilities of the investigation are presented from the commissioning phase of the mission, and from the different regions visited by the spacecraft to date: the tail current sheet, the dusk side magnetopause and magnetosheath, the bow shock and the cusp. We also describe the data processing flow and the implementation of data distribution to other Cluster investigations and to the scientific community in general. Key words. Interplanetary physics (instruments and techniques) – magnetospheric physics (magnetospheric configuration and dynamics) – space plasma physics (shock waves)
1,218 citations
TL;DR: In this article, a general method for the investigation and quantification of delocalization in molecules is proposed based on the anisotropy of the current-induced density (ACID), which is a scalar field invariant with respect to the relative orientation of the magnetic field and the molecule.
Abstract: We report a general method for the investigation and quantification of delocalization in molecules. The method is based on the anisotropy of the current-induced density (ACID). Compared to the current density, which has been frequently used to investigate delocalization, the ACID approach has several advantages: it is a scalar field which is invariant with respect to the relative orientation of the magnetic field and the molecule, it is not a simple function of the overall electron density, it has the same symmetry as the wave function, and it can be plotted as an isosurface. Several selected examples demonstrate the predictive power and the general applicability of this method.
528 citations
TL;DR: In this paper, a general upper bound on the quantum capacity of a one-mode Gaussian channel with attenuation or amplification and classical noise was derived. But the bounds were not explicitly evaluated for the case of a single-mode channel.
Abstract: We show how to compute or at least to estimate various capacity-related quantities for bosonic Gaussian channels. Among these are the coherent information, the entanglement-assisted classical capacity, the one-shot classical capacity, and a quantity involving the transpose operation, shown to be a general upper bound on the quantum capacity, even allowing for finite errors. All bounds are explicitly evaluated for the case of a one-mode channel with attenuation or amplification and classical noise.
476 citations
TL;DR: In this paper, a set of independent Bell-correlation inequalities for n-partite systems with two dichotomic observables each were constructed, which are complete in the sense that the inequalities are satisfied if and only if the correlations considered allow a local classical model.
Abstract: We construct a set of ${2}^{{2}^{n}}$ independent Bell-correlation inequalities for n-partite systems with two dichotomic observables each, which is complete in the sense that the inequalities are satisfied if and only if the correlations considered allow a local classical model. All these inequalities can be summarized in a single, albeit nonlinear inequality. We show that quantum correlations satisfy this condition provided the state has positive partial transpose with respect to any grouping of the n systems into two subsystems. We also provide an efficient algorithm for finding the maximal quantum-mechanical violation of each inequality, and show that the maximum is always attained for the generalized GHZ state.
464 citations
TL;DR: In this article, the authors show how to simplify the computation of the entanglement of formation and the relative entropy for states, which are invariant under a group of local symmetries.
Abstract: We show how to simplify the computation of the entanglement of formation and the relative entropy of entanglement for states, which are invariant under a group of local symmetries. For several examples of groups we characterize the state spaces, which are invariant under these groups. For specific examples we calculate the entanglement measures. In particular, we derive an explicit formula for the entanglement of formation for $(U\ensuremath{\bigotimes}U)$-invariant states, and we find a counterexample of the additivity conjecture for the relative entropy of entanglement.
456 citations
TL;DR: In this paper, the authors established a one-to-one correspondence between quantum teleportation, dense coding, orthonormal bases of maximally entangled vectors, and unitary operators with respect to the Hilbert-Schmidt scalar product.
Abstract: We establish a one-to-one correspondence between (1) quantum teleportation schemes, (2) dense coding schemes, (3) orthonormal bases of maximally entangled vectors, (4) orthonormal bases of unitary operators with respect to the Hilbert–Schmidt scalar product and (5) depolarizing operations, whose Kraus operators can be chosen to be unitary. The teleportation and dense coding schemes are assumed to be `tight' in the sense that all Hilbert spaces involved have the same finite dimension d, and the classical channel involved distinguishes d 2 signals. A general construction procedure for orthonormal bases of unitaries, involving Latin squares and complex Hadamard matrices is also presented.
390 citations
TL;DR: It is proved necessary and sufficient conditions for the graph such that the resulting code corrects a certain number of errors, which allows a simple verification of the one-error correcting property of codes of length 5 in any dimension.
Abstract: We present a construction for quantum error correcting codes. The basic ingredients are a graph and a finite Abelian group, from which the code can explicitly be obtained. We prove necessary and sufficient conditions for the graph such that the resulting code corrects a certain number of errors. This allows a simple verification of the one-error correcting property of codes of length 5 in any dimension. As examples, we construct a large class of maximum distance separable codes, i.e. codes saturating the Singleton bound, as well as a code of length 10 detecting three errors.
383 citations
TL;DR: It is shown that, for systems composed of a single oscillator for Alice and an arbitrary number for Bob, positivity of the partial transpose implies separability, but this implication fails with two oscillators on each side, as it is shown by constructing a five parameter family of bound entangled Gaussian states.
Abstract: We discuss the entanglement properties of bipartite states with Gaussian Wigner functions. For the separability, and the positivity of the partial transpose, we establish explicit necessary and sufficient criteria in terms of the covariance matrix of the state. It is shown that, for systems composed of a single oscillator for Alice and an arbitrary number for Bob, positivity of the partial transpose implies separability. However, this implication fails with two oscillators on each side, as we show by constructing a five parameter family of bound entangled Gaussian states.
377 citations
TL;DR: A German Riesling wine has been fractionated with the aid of countercurrent chromatography and the structures of 101 compounds were established by mass spectrometry and NMR spectroscopy, finding forty-four compounds exhibited a phenolic or benzylic structure.
Abstract: A German Riesling wine has been fractionated with the aid of countercurrent chromatography. After purification by HPLC, the structures of 101 compounds were established by mass spectrometry and NMR spectroscopy. Seventy-three of the isolated compounds exhibited a phenolic or benzylic structure. Fifty-four compounds were reported for the first time as Riesling wine constituents. New compounds identified in this work included twelve benzoic and cinnamic acid derivatives. In addition to two isomeric (E)-caffeoyl ethyl tartrates, the glucose esters of (E)-cinnamic, (E)-p-coumaric, and (E)-ferulic acid, as well as the 4-O-glucosides of (E)- and (Z)-ferulic acid, have been identified for the first time in Riesling wine. The structures of two additional phenylpropanoids were elucidated as 3-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-propan-1-one and 2,3-dihydroxy-1-(4-hydroxy-3-methoxyphenyl)-propan-1-one. Moreover, two ethyl esters, i.e., ethyl protocatechuate and ethyl gallate, as well as the glucose ester of vanil...
313 citations
TL;DR: It is shown that blocking engulfment enhances cell survival when cells are subjected to weak pro-apoptotic signals, indicating that genes that mediate corpse removal can also function to actively kill cells.
Abstract: Genetic studies have identified over a dozen genes that function in programmed cell death (apoptosis) in the nematode Caenorhabditis elegans. Although the ultimate effects on cell survival or engulfment of mutations in each cell death gene have been extensively described, much less is known about how these mutations affect the kinetics of death and engulfment, or the interactions between these two processes. We have used four-dimensional-Nomarski time-lapse video microscopy to follow in detail how cell death genes regulate the extent and kinetics of apoptotic cell death and removal in the early C. elegans embryo. Here we show that blocking engulfment enhances cell survival when cells are subjected to weak pro-apoptotic signals. Thus, genes that mediate corpse removal can also function to actively kill cells.
301 citations
TL;DR: The cloning of the aba3 gene from Arabidopsis thaliana is reported and the biochemical characterization of the purified protein shows a transsulfuration reaction similar to bacterial NifS.
TL;DR: Evidence is provided that actin plays an important functional role in nuclear export not only of retroviral RNAs but also of host proteins such as protein kinase inhibitor (PKI).
Abstract: Nuclear export of proteins containing leucine-rich nuclear export signals (NESs) is mediated by the export receptor CRM1/exportin1. However, additional protein factors interacting with leucine-rich NESs have been described. Here, we investigate human immunodeficiency virus type 1 (HIV-1) Rev-mediated nuclear export and Mason-Pfizer monkey virus (MPMV) constitutive transport element (CTE)–mediated nuclear export in microinjected Xenopus laevis oocytes. We show that eukaryotic initiation factor 5A (eIF-5A) is essential for Rev and Rev-mediated viral RNA export, but not for nuclear export of CTE RNA. In vitro binding studies demonstrate that eIF-5A is required for efficient interaction of Rev–NES with CRM1/exportin1 and that eIF-5A interacts with the nucleoporins CAN/nup214, nup153, nup98, and nup62. Quite unexpectedly, nuclear actin was also identified as an eIF-5A binding protein. We show that actin is associated with the nucleoplasmic filaments of nuclear pore complexes and is critically involved in export processes. Finally, actin- and energy-dependent nuclear export of HIV-1 Rev is reconstituted by using a novel in vitro egg extract system. In summary, our data provide evidence that actin plays an important functional role in nuclear export not only of retroviral RNAs but also of host proteins such as protein kinase inhibitor (PKI).
Book•
01 Jun 2001TL;DR: Readings in Hardware/Software Co-Design presents the papers that have shaped the hardware/software co-design field since its inception in the early 1990s to provide professionals, researchers, and graduate students with a single reference source for this critical aspect of computing design.
Abstract: Readings in Hardware/Software Co-Design presents the papers that have shaped the hardware/software co-design field since its inception in the early 1990s Field experts Giovanni De Micheli, Rolf Ernst, and Wayne Wolf introduce sections of the book and provide context for the papers that follow This collection provides professionals, researchers, and graduate students with a single reference source for this critical aspect of computing design
TL;DR: In this article, the authors discuss general Bell inequalities for bipartite and multipartite systems, emphasizing the connection with convex geometry on the mathematical side, and the communication aspects on the physical side.
Abstract: We discuss general Bell inequalities for bipartite and multipartite systems, emphasizing the connection with convex geometry on the mathematical side, and the communication aspects on the physical side. Known results on families of generalized Bell inequalities are summarized. We investigate maximal violations of Bell inequalities as well as states not violating (certain) Bell inequalities. Finally, we discuss the relation between Bell inequality violations and entanglement properties currently discussed in quantum information theory.
Posted Content•
TL;DR: The relation between Bell inequality violations and entanglement properties currently discussed in quantum information theory is discussed and maximal violations of Bell inequalities as well as states not violating (certain) Bell inequalities are investigated.
Abstract: We discuss general Bell inequalities for bipartite and multipartite systems, emphasizing the connection with convex geometry on the mathematical side, and the communication aspects on the physical side. Known results on families of generalized Bell inequalities are summarized. We investigate maximal violations of Bell inequalities as well as states not violating (certain) Bell inequalities. Finally, we discuss the relation between Bell inequality violations and entanglement properties currently discussed in quantum information theory.
TL;DR: In this paper, the authors proposed a measurement on the N-fold system that approximately yields the spectrum of the density operator, and showed that the probability for errors decreases exponentially with a rate computed explicitly.
Abstract: Given N quantum systems prepared according to the same density operator $\ensuremath{\rho},$ we propose a measurement on the N-fold system that approximately yields the spectrum of $\ensuremath{\rho}.$ The projections of the proposed observable decompose the Hilbert space according to the irreducible representations of the permutations on N points, and are labeled by Young frames, whose relative row lengths estimate the eigenvalues of $\ensuremath{\rho}$ in decreasing order. We show convergence of these estimates in the limit $\stackrel{\ensuremath{\rightarrow}}{N}\ensuremath{\infty},$ and that the probability for errors decreases exponentially with a rate we compute explicitly.
TL;DR: The cloning of a plant sulfite oxidase gene from Arabidopsis thaliana and the biochemical characterization of the encoded protein (At-SO) are reported and it is shown that a cross-reacting protein of similar size occurs in a wide range of plant species, including both herbacious and woody plants.
TL;DR: An overview of the applications of wet disintegration in wastewater and sludge treatment is provided and thermal, freeze/thaw and biological treatments can be realized at low costs if the conditions are appropriate.
TL;DR: In this paper, the authors describe the implementation of analytical Hartree-Fock gradients for periodic systems in the code CRYSTAL, emphasizing the technical aspects of this task.
TL;DR: In this paper, the first THz imaging spectrometer based on continuous-wave THz radiation is presented, which uses a two-colour external-cavity laser diode.
Abstract: The first THz imaging spectrometer based on continuous-wave THz radiation is presented. The new setup is less expensive than conventional time-domain imaging systems that comprise femtosecond lasers. The system uses a two-colour external-cavity laser diode. Hence it is much more compact as compared to systems based on optically pumped solid-state lasers. As an example we investigate a human liver with metastasis.
TL;DR: A simple generic approach for obtaining new fast lower bounds for the bin packing problem based on dual feasible functions is presented, which proves an asymptotic worst-case performance of 3/4 for a bound that can be computed in linear time for items sorted by size.
Abstract: The bin packing problem is one of the classical NP-hard optimization problems. In this paper, we present a simple generic approach for obtaining new fast lower bounds, based on dual feasible functions. Worst-case analysis as well as computational results show that one of our classes clearly outperforms the previous best “economical” lower bound for the bin packing problem by Martello and Toth, which can be understood as a special case. In particular, we prove an asymptotic worst-case performance of 3/4 for a bound that can be computed in linear time for items sorted by size. In addition, our approach provides a general framework for establishing new bounds.
TL;DR: In this paper, the chip formation of Ti6Al4V was described in the cutting speed range between 300 m/min and 6000m/min, where the specific cutting forces were measured.
TL;DR: In this article, the thermal heat conductivity of doped and undoped spin ladders is analyzed theoretically using a simple kinetic model, and the spin gap and the temperature-dependent mean free path of the magnons, which measures about several thousand angstrom at low temperature.
Abstract: We have measured the thermal heat conductivity $\ensuremath{\kappa}$ of the compounds ${\mathrm{Sr}}_{14}{\mathrm{Cu}}_{24}{\mathrm{O}}_{41}$ and ${\mathrm{Ca}}_{9}{\mathrm{La}}_{5}{\mathrm{Cu}}_{24}{\mathrm{O}}_{41}$ containing doped and undoped spin ladders, respectively. We find a huge anisotropy of both, the size and the temperature dependence of $\ensuremath{\kappa}$ that we interpret in terms of a very large heat conductivity due to the magnetic excitations of the one-dimensional spin ladders. This magnon heat conductivity decreases with increasing hole doping of the ladders. Magnon heat transport is analyzed theoretically using a simple kinetic model. From this analysis we determine the spin gap and the temperature-dependent mean free path of the magnons, which measures about several thousand angstrom at low temperature. The relevance of several scattering channels for the magnon transport is discussed.
TL;DR: The newly discovered enzymatic function of the plasmodial gene product suggests a reconsideration of its presumed role in parasitic antioxidant defense.
01 Jan 2001
TL;DR: The SteinLib is presented, a library of data sets for the Steiner tree problem in graphs that extends former libraries on Steiners tree problems by many new interesting and difficult instances, most of them arising from real-world applications.
Abstract: In this paper we present the SteinLib, a library of data sets for the Steiner tree problem in graphs. This library extends former libraries on Steiner tree problems by many new interesting and difficult instances, most of them arising from real-world applications. We give a survey on the difficulty of these problem instances by stating references to state-of-the-art software packages that were the first or are currently among the best to solve these instances.
TL;DR: The evidence for an association between childhood leukaemia and magnetic field eposure in this study comes from a measure of exposure during the night, and the effect on a population level in Germany would be small.
Abstract: Our objective was to investigate whether exposure to residential power-frequency (50 Hz) magnetic fields above 0.2 μT increases a child's risk of leukaemia and to confirm or reject a finding from a previous German study on this topic, which reported increased leukaemia risk with exposure to stronger magnetic fields during the night. A population-based case-control study was used, covering the whole of the former West Germany. Residential magnetic fields were measured over 24 hr for 514 children with acute leukaemia identified by the German Childhood Cancer Registry and 1,301 control children taken from population registration files. Magnetic fields above 0.2 μT were relatively rare in Germany (only 1.5% of the study population). Childhood leukaemia and 24 hr median magnetic fields were only weakly related (OR = 1.55, 95% CI 0.65–3.67). A significant association was seen between childhood leukaemia and magnetic field exposure during the night (OR = 3.21, 95% CI 1.33–7.80). A dose-response-relationship was observed after combining the data of all German studies on magnetic fields and childhood leukaemia. The evidence for an association between childhood leukaemia and magnetic field eposure in our study comes from a measure of exposure during the night. Despite the large size of our study, the results are based on small numbers of exposed children. If the observed association stands, the effect on a population level in Germany would be small. © 2001 Wiley-Liss, Inc.
TL;DR: In this article, a feed-batch and two-stage continuous process for the production of sophorolipids with the yeast Candida bombicola ATCC 22214.1.
TL;DR: In this article, the authors study separability properties in a five-dimensional set of states of quantum systems composed of three subsystems of equal but arbitrary finite Hilbert space dimension, and they compute explicitly the following subsets and their extreme points: (1) triseparable states, which are convex combinations of triple tensor products, (2) biseparably states which are separable for a twofold partition of the system, and (3) states with positive partial transpose with respect to such a partition.
Abstract: We study separability properties in a five-dimensional set of states of quantum systems composed of three subsystems of equal but arbitrary finite Hilbert space dimension. These are the states that can be written as linear combinations of permutation operators, or equivalently, commute with unitaries of the form $U\ensuremath{\bigotimes}U\ensuremath{\bigotimes}U.$ We compute explicitly the following subsets and their extreme points: (1) triseparable states, which are convex combinations of triple tensor products, (2) biseparable states, which are separable for a twofold partition of the system, and (3) states with positive partial transpose with respect to such a partition. Tripartite entanglement is investigated in terms of the relative entropy of tripartite entanglement and of the trace norm.
TL;DR: In this article, the mechanical loading of the thermal barrier coating (TBC)/thermally grown oxide (TGO)/bond coat interface region is calculated for a TBC coated superalloy specimen using a finite element model.
TL;DR: In this article, the authors present a derivation of the linear heating Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation for a constant nucleation rate and diffusion-controlled growth, in the hard impingement approximation.