8,279 research outputs found

    Zone leveling and solution growth of complex compound semiconductors in space

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    A research program on complex semiconducting compounds and alloys was completed that addressed the growth of single crystals of CdSe(y)Te(1-y), Zn(x)Cd(1-x)Te, Mn(x)Cd(1-x)Te, InP(y)As(1-y) and CuInSe2 and the measurement of fundamental physico-chemical properties characterizing the above materials. The purpose of this ground based research program was to lay the foundations for further research concerning the growth of complex ternary compound semiconductors in a microgravity environment

    Just war and military morale: a brief reflection on the correlation between the legality of war and the moral repercussions for members of US and UK forces arising from the questionable legality of the campaign Iraqi Freedom of March 2003

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    Does it matter to a member of the military whether the military campaign in which he is taking part is lawful or not? Despite the observation that the crime of aggression (post Kampala 2010) constitutes a ‘leadership crime par excellence,’ which limits any (future) criminal responsibility accordingly, the legality or illegality of any military action under international law can create moral implications for the common foot soldier and mid-level officer and also have a tangible impact on the national legal frameworks under which these forces operate. This short article uses the example of Operation Iraqi Freedom (2003) to discuss the repercussions of a—most likely—illegal military campaign for individual members of democratic armed forces before the background of the present discussion of NATO led action in Libya

    Conformational Mechanics of Polymer Adsorption Transitions at Attractive Substrates

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    Conformational phases of a semiflexible off-lattice homopolymer model near an attractive substrate are investigated by means of multicanonical computer simulations. In our polymer-substrate model, nonbonded pairs of monomers as well as monomers and the substrate interact via attractive van der Waals forces. To characterize conformational phases of this hybrid system, we analyze thermal fluctuations of energetic and structural quantities, as well as adequate docking parameters. Introducing a solvent parameter related to the strength of the surface attraction, we construct and discuss the solubility-temperature phase diagram. Apart from the main phases of adsorbed and desorbed conformations, we identify several other phase transitions such as the freezing transition between energy-dominated crystalline low-temperature structures and globular entropy-dominated conformations.Comment: 13 pages, 15 figure

    Quantum limit transport and destruction of the Weyl nodes in TaAs

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    Weyl fermions are a new ingredient for correlated states of electronic matter. A key difficulty has been that real materials also contain non-Weyl quasiparticles, and disentangling the experimental signatures has proven challenging. We use magnetic fields up to 95 tesla to drive the Weyl semimetal TaAs far into its quantum limit (QL), where only the purely chiral 0th Landau levels (LLs) of the Weyl fermions are occupied. We find the electrical resistivity to be nearly independent of magnetic field up to 50 tesla: unusual for conventional metals but consistent with the chiral anomaly for Weyl fermions. Above 50 tesla we observe a two-order-of-magnitude increase in resistivity, indicating that a gap opens in the chiral LLs. Above 80 tesla we observe strong ultrasonic attenuation below 2 kelvin, suggesting a mesoscopically-textured state of matter. These results point the way to inducing new correlated states of matter in the QL of Weyl semimetals

    Review of the Neotropical millipede genus Pycnotropis CARL, 1914 (Diplopoda, Polydesmida, Aphelidesmidae)

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    A review of Pycnotropis is presented, with the description of 14 new species: P. goeldii n.sp., P. madeira n.sp., P. sigma n.sp. and P. urucu n.sp., all from Brazil, P. carli n.sp. from Ecuador, P. curvata n.sp., P. falcata n.sp., P. jeekeli n.sp., P. pallidicornis n.sp., P. similis n.sp., P. subfalcata n. sp., P. unapi n.sp., P. torresi n.sp. and P. zumbii n.sp., all from Peru. P. acuticollis (ATTEMS, 1899), is redescribed upon the holotype from Brazil. Based on abundant strictly topotypic material, P. tida (CHAMBERLIN, l94l), is considered as a subjective senior synonym of P. epiclysmus HOFFMAN, 1995 (syn.n.). A key has been compiled to all 26 species of this diverse genus, with notes on its distribution

    Electronic in-plane symmetry breaking at field-tuned quantum criticality in CeRhIn5

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    Electronic nematics are exotic states of matter where electronic interactions break a rotational symmetry of the underlying lattice, in analogy to the directional alignment without translational order in nematic liquid crystals. Intriguingly such phases appear in the copper- and iron-based superconductors, and their role in establishing high-temperature superconductivity remains an open question. Nematicity may take an active part, cooperating or competing with superconductivity, or may appear accidentally in such systems. Here we present experimental evidence for a phase of nematic character in the heavy fermion superconductor CeRhIn5. We observe a field-induced breaking of the electronic tetragonal symmetry of in the vicinity of an antiferromagnetic (AFM) quantum phase transition at Hc~50T. This phase appears in out-of-plane fields of H*~28T and is characterized by substantial in-plane resistivity anisotropy. The anisotropy can be aligned by a small in-plane field component, with no apparent connection to the underlying crystal structure. Furthermore no anomalies are observed in the magnetic torque, suggesting the absence of metamagnetic transitions in this field range. These observations are indicative of an electronic nematic character of the high field state in CeRhIn5. The appearance of nematic behavior in a phenotypical heavy fermion superconductor highlights the interrelation of nematicity and unconventional superconductivity, suggesting nematicity to be a commonality in such materials
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