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Institution

Leibniz University of Hanover

EducationHanover, Niedersachsen, Germany
About: Leibniz University of Hanover is a education organization based out in Hanover, Niedersachsen, Germany. It is known for research contribution in the topics: Finite element method & Population. The organization has 14283 authors who have published 29845 publications receiving 682152 citations.


Papers
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Journal ArticleDOI
TL;DR: It is demonstrated that hot particles can be ideally used inside a microfluidic fixed-bed reactor for performing chemical syntheses including catalytic transformations, and magnetic induction in an electromagnetic field is a third way to introduce thermal energy to a reactor.
Abstract: Interest in magnetic nanoparticles has increased considerably lately, with diverse applications as magnetic liquids, in catalysis, in biotechnology and biomedicine, and in magnetic resonance spectroscopy. A principal problem associated with naked metallic nanoparticles is their high chemical reactivity, in particular oxidation by air. This drawback can be overcome by coating the nanoparticles with SiO2, metal oxides, gold, or carbon. Several applications of these nanoparticles for quasi-homogeneous catalysis have been disclosed. These particles are typically removed after the reaction by exploiting their magnetic properties. An unexploited and very important feature of magnetic materials is the possibility of heating them in an electromagnetic field. It has been demonstrated that isolated magnetic nanoparticles show magnetic behavior different from that in the bulk. These magnetic nanoparticles when coated with a silica shell can show superparamagnetic behavior. The silica coating prevents the magnetic cores from coupling, thereby preserving their superparamagnetic properties. These composites do not have a residual magnetization and their magnetization curves are anhysteretic. However, the susceptibility of a superparamagnetic material is almost as high as that of a ferromagnetic material. The concept of magnetically induced hyperthermia is based on specific properties of the magnetic nanoparticles upon exposure to a constantly changing magnetic field. Surprisingly, this property of magnetic nanoparticles has so far not been applied in chemical synthesis, although organic chemists are constantly testing new technologies such as microwave irradiation, solid-phase synthesis, and new reactor designs in their work with the goal of performing syntheses and workups more efficiently. Herein we disclose the first application of heating magnetic silica-coated nanoparticles in an electromagnetic field. We demonstrate that these hot particles can be ideally used inside a microfluidic fixed-bed reactor for performing chemical syntheses including catalytic transformations. Thus, besides conventional and microwave heating, magnetic induction in an electromagnetic field is a third way to introduce thermal energy to a reactor. Superparamagnetic materials like nanoparticles 1 can be heated in mediumor high-frequency fields. As the technical setup for the middle-frequency field (25 kHz) is simpler (see Figure 1b,c), we investigated the electromagnetic induction of heat in magnetic nanoparticles in this frequency range. In principal, the processes can be operated in a cyclic or a continuous mode. The inductor can accommodate a flowthrough reactor (glass; 14 cm length, 9 mm internal diameter), which is filled with superparamagnetic material 1. The reactor can be operated up to a backup

169 citations

Journal ArticleDOI
B. P. Abbott1, Richard J. Abbott1, Rana X. Adhikari2, A. Ageev3  +220 moreInstitutions (30)
TL;DR: In this paper, the authors report on a search for gravitational waves from coalescing compact binary systems in the Milky Way and the Magellanic Clouds using data taken by two of the three LIGO interferometers.
Abstract: We report on a search for gravitational waves from coalescing compact binary systems in the Milky Way and the Magellanic Clouds. The analysis uses data taken by two of the three LIGO interferometers during the first LIGO science run and illustrates a method of setting upper limits on inspiral event rates using interferometer data. The analysis pipeline is described with particular attention to data selection and coincidence between the two interferometers. We establish an observational upper limit of R<1.7x10^(2) per year per Milky Way Equivalent Galaxy (MWEG), with 90% confidence, on the coalescence rate of binary systems in which each component has a mass in the range 1-3 M☉.

169 citations

Journal ArticleDOI
TL;DR: Putative in vivo functions of the Arabidopsisd‐CDes protein are discussed, and plants grown under low sulfate concentration showed an accumulation of d‐cysteine RNA and increased protein levels, suggesting post‐translational regulation.
Abstract: In several organisms d-cysteine desulfhydrase (d-CDes) activity (EC 4.1.99.4) was measured; this enzyme decomposes d-cysteine into pyruvate, H2S, and NH3. A gene encoding a putative d-CDes protein was identified in Arabidopsis thaliana (L) Heynh. based on high homology to an Escherichia coli protein called YedO that has d-CDes activity. The deduced Arabidopsis protein consists of 401 amino acids and has a molecular mass of 43.9 kDa. It contains a pyridoxal-5′-phosphate binding site. The purified recombinant mature protein had a Km for d-cysteine of 0.25 mm. Only d-cysteine but not l-cysteine was converted by d-CDes to pyruvate, H2S, and NH3. The activity was inhibited by aminooxy acetic acid and hydroxylamine, inhibitors specific for pyridoxal-5′-phosphate dependent proteins, at low micromolar concentrations. The protein did not exhibit 1-aminocyclopropane-1-carboxylate deaminase activity (EC 3.5.99.7) as homologous bacterial proteins. Western blot analysis of isolated organelles and localization studies using fusion constructs with the green fluorescent protein indicated an intracellular localization of the nuclear encoded d-CDes protein in the mitochondria. d-CDes RNA levels increased with proceeding development of Arabidopsis but decreased in senescent plants; d-CDes protein levels remained almost unchanged in the same plants whereas specific d-CDes activity was highest in senescent plants. In plants grown in a 12-h light/12-h dark rhythm d-CDes RNA levels were highest in the dark, whereas protein levels and enzyme activity were lower in the dark period than in the light indicating post-translational regulation. Plants grown under low sulfate concentration showed an accumulation of d-CDes RNA and increased protein levels, the d-CDes activity was almost unchanged. Putative in vivo functions of the Arabidopsisd-CDes protein are discussed.

169 citations

01 Jan 2006
TL;DR: This paper focuses on the design of a generic system architecture which allows for self-organisation but at the same time enables adequate reactions to control the – sometimes completely unexpected – emerging global behaviour of these self- Organised technical systems.
Abstract: Technical scenarios in areas like automotive or production systems will increasingly consist of a large number of components cooperating in potentially unlimited and dynamically changing networks to satisfy the functional requirements of their execution environment. Due to the high complexity it will be impossible to explicitly design the behaviour of the components for every potentially arising situation. Therefore, it will be necessary to leave an adequate degree of freedom allowing for a self-organised behaviour. Organic Computing (OC) has developed the vision of selforganising systems adapting robustly to dynamically changing environments without running out of control. This paper focuses on the design of a generic system architecture which allows for self-organisation but at the same time enables adequate reactions to control the – sometimes completely unexpected – emerging global behaviour of these self-organised technical systems.

169 citations

Journal ArticleDOI
TL;DR: In this paper, a single-step synthesis of magnesium ferrite (MgFe2O4) nanoparticles with an average crystallite size of about 8.5 nm synthesized via mechanochemical processing of binary oxide precursors at room temperature is reported.
Abstract: A single-step synthesis of magnesium ferrite (MgFe2O4) nanoparticles with an average crystallite size of about 8.5 nm synthesized via mechanochemical processing of binary oxide precursors at room temperature is reported. The study highlights the nature of the cation disorder and of the spin arrangement in mechanosynthesized MgFe2O4 as well as its response to changes in temperature. An unusual property of the magnetization enhancement in nanoscale mechanosynthesized MgFe2O4 is reported. Whereas the inner core of a MgFe2O4 nanoparticle exhibits a partly inverse spinel structure with a Neel type collinear spin alignment, the major features of the ionic and spin configurations in the grain boundary (surface) region are a nonequilibrium cation distribution and a canted spin arrangement. Although the spin-canting effect tends to reduce the magnetic moment, the magnetization enhancement exhibited by mechanosynthesized MgFe2O4 is attributed to the nearly random distribution of magnetic cations in the surface regi...

168 citations


Authors

Showing all 14621 results

NameH-indexPapersCitations
Hyun-Chul Kim1764076183227
Peter Zoller13473476093
J. R. Smith1341335107641
Chao Zhang127311984711
Benjamin William Allen12480787750
J. F. J. van den Brand12377793070
J. H. Hough11790489697
Hans-Peter Seidel112121351080
Karsten Danzmann11275480032
Bruce D. Hammock111140957401
Benno Willke10950874673
Roman Schnabel10858971938
Jan Harms10844776132
Hartmut Grote10843472781
Ik Siong Heng10742371830
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
2023221
2022520
20212,280
20202,210
20192,105
20181,959