Exchange bias on epitaxial Ni films due to ultrathin NiO layer

Exchange anisotropy refers to the effect that an antiferromagnetic (AF) layer grown in contact with a ferromagnetic (FM) layer has on the magnetic response of the FM layer. The most notable changes in the FM hysteresis loop due to the surface exchange coupling are a coercivity enhanced over the value typically observed in films grown on a nonmagnetic substrate, and a shift in the hysteresis loop of the ferromagnet away from the zero field axis. A typical observation is that the thickness of the antiferromagnet needs to exceed a critical value before exchange bias is observed. Here we report on the exchange bias properties observed in an epitaxial Ni/NiO system where a thin NiO layer forms spontaneously and is observed after annealing epitaxial Ni films MBE grown on MgO substrates.     

Crystal and molecular structures of two polymorphs of 4-methyl-2-nitroacetanilide (MNA)

Journal of Chemical Crystallography - The crystal and molecular structure of white (MNA-1) and yellow (MNA-3) forms of 4-methyl-2-nitroacetanilide have been determined by X-ray diffraction...     

Arbitrary single primer amplification of trace DNA substrates yields sequence content profiles that are discriminatory and reproducible

Single primer amplification is shown to yield a DNA profile that is reproducible when based on the sequence content of the amplicons rather than on the pattern of length polymorphism. The sequence-based profile increases in reliability with increasing numbers of cycles of amplification. This process uses an arbitrarily chosen primer and a low initial annealing temperature in order to amplify sequences from the whole metagenome present in a sample that may contain only trace DNA, and a large number of cycles to select subsets of sequences based on variable amplification efficiency. Using arrays, we demonstrate the utility and limitations of this approach for profiling the large metagenomes typical of soils and the trace DNA present in drug seizures. We suggest that this type of profiling will be most effective once next-generation sequencing and advanced sequence analysis becomes routine.     

New high-energy luminescence bands from Co2+ in ZnSe

Three sharp absorption features in the energy range 2.36–2.55 eV have been detected in the transmission spectrum of Co-diffused ZnSe, and a number of luminescence transitions originating from the lowest of these states at 2.361 eV have been observed. Photoluminescence excitation spectra prove that these are high energy excited states of the Co²⁺_Zn impurity, a conclusion confirmed by comparison of measured and predicted luminescence energies. This represents the first identification of luminescence branching from a higher excited state of a transition metal ion in any semiconductor. The sharp, weakly phonon-coupled transitions involve either intra-impurity excitation or transitions from the impurity to localised states split off from a minimum in the conduction band. The implications of these observations for the mechanism of host-impurity energy transfer and for the nature of the excited state wavefunctions are discussed.     

Simultaneous attainment of high electron and ion temperatures in discharges with internal transport barriers in ASDEX upgrade

Internal transport barriers have been demonstrated to exist also under conditions with T(e) approximately T(i) approximately 10 keV and predominant electron heating of the tokamak core region. Central electron cyclotron heating was added to neutral beam injection-heated ASDEX Upgrade discharges with a preexisting internal transport barrier, established through programmed current ramping leading to shear reversal. Compared to a reference internal transport barrier discharge without electron cyclotron resonance heating, the electron heat conductivity in the barrier region was found not to increase, in spite of a fivefold increase in electron heat flux, and also angular momentum and ion energy transport did not deteriorate.