Bielefeld University

About: Bielefeld University is a education organization based out in Bielefeld, Nordrhein-Westfalen, Germany. It is known for research contribution in the topics: Population & Quantum chromodynamics. The organization has 10123 authors who have published 26576 publications receiving 728250 citations. The organization is also known as: University of Bielefeld & UNIVERSITAET BIELEFELD.

Combustion at the focus: laser diagnostics and control

Abstract: Fifty years after the foundation of the Combustion Institute and almost 150 years after Michael Faraday's famous lectures on the combustion of a candle, combustion diagnostics have come a long way from visual inspection of a flame to detailed analysis of a combustion process with a multitude of sophisticated techniques, often using lasers. The extended knowledge on combustion phenomena gained by application of these diagnostic techniques, combined with equally advanced numerical simulation of the process, has been instrumental in designing modern combustion devices with efficient performance and reduced pollutant emission. Also, similar diagnostic techniques are now employed to develop sensors for process control in combustion. This article intends to give a perspective on the potential of combustion diagnostics by highlighting selected application examples and by guiding the reader to recent literature. In particular, techniques are emphasized, which permit measurement of important features of the chemical composition, sometimes in conjunction with flow field parameters. Although a complete image of present research and applications in combustion diagnostics and control is beyond the scope of this article, this overview may be a starting place where ideas may be found to solve specific combustion problems with the aid of diagnostics. (Less)

Quenching of hadron spectra in media

Abstract: We determine how the yield of large transverse momentum hadrons is modified due toinduced gluon radiation off a hard parton traversing a QCD medium. The quenching factoris formally a collinear- and infrared-safe quantity and can be treated perturbatively. In spiteof that, in the p ⊥ region of practical interest, its value turns out to be extremely sensitive tolarge distances and can be used to unravel the properties of dense quark-gluon final statesproduced in heavy ion collisions. We also find that the standard modelling of quenching byshifting p ⊥ in the hard parton cross section by the mean energy loss is inadequate. 1 Introduction The so-called jet quenching [1–6] is considered an important signal of the production of a newstate of dense matter (quark-gluon plasma) in ultrarelativistic heavy ion collisions. This isunderstood as the suppression of the yield of large transverse momentum jets or particles withrespect to proton-proton collisions.In this paper we concentrate on the quenching effect in inclusive particle spectra, due to theenergy loss by medium induced gluon radiation [7–24].

Quantum oscillations in a molecular magnet

Abstract: Molecular magnets are a type of molecule containing multiple magnetic ions whose spins are tightly coupled to give a single 'collective' spin. The quantum mechanical properties of this collective spin are attracting attention as a possible basis for the functional unit of a quantum computer. Until now it has not been clear whether the quantum spin states of these molecular entities are sufficiently long-lived to permit useful computation, but new work suggests that they are. Bertaina et al. observed pronounced quantum oscillations between the spin states of one such molecular magnet, consistent with long-lived quantum coherence, in this system at least. They also outline a scheme by which, through careful material design, these properties could be harnessed in a practical context. Molecular magnets are a class of molecule containing multiple magnetic ions whose spins are tightly coupled to give a single 'collective' spin. But it has remained an open question whether the quantum spin states of these molecular entities are sufficiently long-lived to permit useful computation. Pronounced quantum oscillations between the spin states of one such molecular magnet have been observed, indicating that quantum coherence is long-lived. The term ‘molecular magnet’ generally refers to a molecular entity containing several magnetic ions whose coupled spins generate a collective spin, S (ref. 1). Such complex multi-spin systems provide attractive targets for the study of quantum effects at the mesoscopic scale. In these molecules, the large energy barriers between collective spin states can be crossed by thermal activation or quantum tunnelling, depending on the temperature or an applied magnetic field2,3,4. There is the hope that these mesoscopic spin states can be harnessed for the realization of quantum bits—‘qubits’, the basic building blocks of a quantum computer—based on molecular magnets5,6,7,8. But strong decoherence9 must be overcome if the envisaged applications are to become practical. Here we report the observation and analysis of Rabi oscillations (quantum oscillations resulting from the coherent absorption and emission of photons driven by an electromagnetic wave10) of a molecular magnet in a hybrid system, in which discrete and well-separated magnetic clusters are embedded in a self-organized non-magnetic environment. Each cluster contains 15 antiferromagnetically coupled S = 1/2 spins, leading to an S = 1/2 collective ground state11,12,13. When this system is placed into a resonant cavity, the microwave field induces oscillatory transitions between the ground and excited collective spin states, indicative of long-lived quantum coherence. The present observation of quantum oscillations suggests that low-dimension self-organized qubit networks having coherence times of the order of 100 μs (at liquid helium temperatures) are a realistic prospect.

Phylogenetic classification of short environmental DNA fragments

Abstract: Metagenomics is providing striking insights into the ecology of microbial communities. The recently developed massively parallel 454 pyrosequencing technique gives the opportunity to rapidly obtain metagenomic sequences at a low cost and without cloning bias. However, the phylogenetic analysis of the short reads produced represents a significant computational challenge. The phylogenetic algorithm CARMA for predicting the source organisms of environmental 454 reads is described. The algorithm searches for conserved Pfam domain and protein families in the unassembled reads of a sample. These gene fragments (environmental gene tags, EGTs), are classified into a higher-order taxonomy based on the reconstruction of a phylogenetic tree of each matching Pfam family. The method exhibits high accuracy for a wide range of taxonomic groups, and EGTs as short as 27 amino acids can be phylogenetically classified up to the rank of genus. The algorithm was applied in a comparative study of three aquatic microbial samples obtained by 454 pyrosequencing. Profound differences in the taxonomic composition of these samples could be clearly revealed.

European Perspectives on Men and Masculinities: National and Transnational Approaches

Abstract: The social relations of home and work represent some of the most fundamental aspects of gender relations in society, and thus some of the most important elements in the construction of men and masculinities. The separation of home and work is both a very real one and an ideological construction. It is at the root of much liberal social science, as well as figuring, in more or less sophisticated ways, in non-feminist (Habermas, 1984, 1987) and feminist (Fraser, 1989) critical theory. In some ways it refers to the distinction between production and reproduction; but an over-simple division into dual spheres has been shown to be theoretically flawed, historically inaccurate (Bose, 1987; Hearn, 1992) and contrary to the experience of some people and some social categories, for example, women of colour (Collins, 1990).