The University of Hannover, officially the Gottfried Wilhelm Leibniz Universität Hannover, short Leibniz Universität Hannover, is a public university located in Hannover, Germany. Founded in 1831, it is one of the largest and oldest science and technology universities in Germany. In the 2014/15 school year it enrolled 25,688 students, of which 2,121 were from foreign countries. It has nine faculties which offer 190 full and part degree programs in 38 fields of study. The University is named after Gottfried Wilhelm Leibniz, the 18th century mathematician and philosopher.Leibniz Universität Hannover is a member of TU9, an association of the nine leading Institutes of Technology in Germany. It is also a member of the Conference of European Schools for Advanced Engineering Education and Research , a non-profit association of leading engineering universities in Europe. The university sponsors the German National Library of Science and Technology , the largest science and technology library in the world. Wikipedia.
Morgenstern K.,Leibniz University of Hanover
Progress in Surface Science | Year: 2011
Molecular electronics offers a promising way for constructing nano-electronic devices in future with faster performance and smaller dimensions. For this aim, electronic switches are essential as basic components for storage and logical operations. The main requirements for a molecular switch are reversibility and bistability. This necessitates the existence of at least two different thermally stable forms of a molecule that may be changed repeatedly from one state to the other one through an external stimulus. The transition should then be connected to a measurable change in molecular properties. The development of such molecular switches on the single molecule level is a major challenge on the path towards incorporating molecules as building units into nanoelectronic circuits. Since isomers may differ significantly in physical and chemical properties, isomerisation opens a way for a molecular switch. In this article, an overview is provided over those isomerisation reactions of single molecules adsorbed on surfaces that are investigated with a scanning tunnelling microscope and that have a potential as a molecular switch in future molecular electronics. These are mainly, but not exclusively, constitutional, configurational, and geometric isomerisation reactions. The external stimulus is either light or the possible interaction with the tip of a scanning tunnelling microscope, i.e. electrons, electric field, or mechanical force. Some reactions are similar to those observed for the molecule in the liquid phase, but some are observed or even possible only on a surface. The detailed investigation of the isomerisation yield dependence on several parameters gives insight into the underlying processes of the reaction. © 2011 Elsevier Ltd. All rights reserved.
Caro J.,Leibniz University of Hanover
Current Opinion in Chemical Engineering | Year: 2011
Despite much progress in the development of zeolite molecular sieve membranes, there is so far no industrial gas separation by zeolite membranes, with the exception of the de-watering of bio-ethanol by steam permeation using LTA membranes. During the last 5 years, metal-organic framework (MOF) membranes have been developed and tested in gas separation. The complete tool box of techniques originally developed for the preparation of zeolite membranes could be applied for the preparation of MOF membranes, such as the use of macroporous ceramic or metal supports, seeding, intergrowth-supporting additives, and microwave heating. There are some structure-related properties of MOFs which recommend them as suitable material for molecular sieve membranes. On the other hand, the structural flexibility of MOFs apparently prevents a sharp molecular sieving with a pore size estimated from the 'rigid' crystallographic structure by size exclusion. An application of MOFs is predicted in so-called mixed matrix membranes which show improved performance in comparison with the pure polymer membranes. Different from zeolites as organic-inorganic material, the MOF nanoparticles can be easily embedded into organic polymers, and standard shaping technologies to hollow fibers or spiral wound geometries can be applied. © 2011 Elsevier Ltd. All rights reserved.
Busch P.,University of York |
Lahti P.,University of Turku |
Werner R.F.,Leibniz University of Hanover
Reviews of Modern Physics | Year: 2014
Recent years have witnessed a controversy over Heisenberg's famous error-disturbance relation. Here the conflict is resolved by way of an analysis of the possible conceptualizations of measurement error and disturbance in quantum mechanics. Two approaches to adapting the classic notion of root-mean-square error to quantum measurements are discussed. One is based on the concept of a noise operator; its natural operational content is that of a mean deviation of the values of two observables measured jointly, and thus its applicability is limited to cases where such joint measurements are available. The second error measure quantifies the differences between two probability distributions obtained in separate runs of measurements and is of unrestricted applicability. We show that there are no nontrivial unconditional joint-measurement bounds for state-dependent errors in the conceptual framework discussed here, while Heisenberg-type measurement uncertainty relations for state-independent errors have been proven. © 2014 American Physical Society.
Walther C.,Leibniz University of Hanover |
Denecke M.A.,Karlsruhe Institute of Technology
Chemical Reviews | Year: 2013
A study was conducted to investigate actinide colloids and particles of environmental concern. Sources of actinide particles in the environment other than nuclear explosions and nuclear power plant accidents were naturally occurring radioactive matter or particle contaminants released from other military activities related to nuclear power production and from minor occurrences, such as nuclear powered satellites. These particles containing actinide element contaminants were found in the environment in a wide variety of forms or morphologies and compositions, exhibiting varying chemistries and stabilities. The morphology, elemental, and isotopic composition of actinide particles were obtained by a variety of experimental techniques, such as electron microscopy, mass spectrometry (MS), and some other techniques.
Scherer G.F.E.,Leibniz University of Hanover
Journal of Experimental Botany | Year: 2011
Since we are living in the 'age of transcription', awareness of aspects other than transcription in auxin signal transduction seems to have faded. One purpose of this review is to recall these other aspects. The focus will also be on the time scales of auxin responses and their potential or known dependence on either AUXIN BINDING PROTEIN 1 (ABP1) or on TRANSPORT-INHIBITOR-RESISTANT1 (TIR1) as a receptor. Furthermore, both direct and indirect evidence for the function of ABP1 as a receptor will be reviewed. Finally, the potential functions of a two-receptor system for auxin and similarities to other two-receptor signalling systems in plants will be discussed. It is suggested that such a functional arrangement is a property of plants which strengthens tissue autonomy and overcomes the lack of nerves or blood circulation which are responsible for rapid signal transport in animals. © 2011 The Author(s).