1,527 research outputs found
Anomalous Hall effect in the noncollinear antiferromagnet Mn5Si3
Metallic antiferromagnets with noncollinear orientation of magnetic moments
provide a playground for investigating spin-dependent transport properties by
analysis of the anomalous Hall effect. The intermetallic compound Mn5Si3 is an
intinerant antiferromagnet with collinear and noncollinear magnetic structures
due to Mn atoms on two inequivalent lattice sites. Here, magnetotransport
measurements on polycrystalline thin films and a single crystal are reported.
In all samples, an additional contribution to the anomalous Hall effect
attributed to the noncollinear arrangment of magnetic moments is observed.
Furthermore, an additional magnetic phase between the noncollinear and
collinear regimes above a metamagnetic transition is resolved in the single
crystal by the anomalous Hall effect.Comment: 7 pages, 4 figure
Competing magnetic correlations across the ferromagnetic quantum critical point in the Kondo system CeTiVGe: V NMR as a local probe
V nuclear magnetic resonance (NMR) and magnetization studies on
CeTiVGe have been performed to explore the evolution from the
ferromagnetic () to the antiferromagnetic Kondo lattice state (), with focus on the emergence of a possible ferromagnetic quantum critical
point (FMQCP) at . From the temperature dependence of the
nuclear spin-lattice relaxation rate, , and the Knight shift,
\textit{K}, for and a considerable competition between ferro-
and antiferromagnetic correlations is found. Around the critical concentration
() quantum-critical spin fluctuations entail weak
antiferromagnetic spin fluctuations admixed with ferromagnetic spin
fluctuations. The FMQCP in CeTiVGe therefore is not purely
ferromagnetic in nature.Comment: 9 pages and 12 figures, accepted at PR
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On the electronic properties of a single dislocation
A detailed knowledge of the electronic properties of individual dislocations is necessary for next generation nanodevices. Dislocations are fundamental crystal defects controlling the growth of different nanostructures (nanowires) or appear during device processing. We present a method to record electric properties of single dislocations in thin silicon layers. Results of measurements on single screw dislocations are shown for the first time. Assuming a cross-section area of the dislocation core of about 1 nm2, the current density through a single dislocation is J = 3.8 × 1012 A/cm2 corresponding to a resistivity of ρ ≅ 1 × 10-8 Ω cm. This is about eight orders of magnitude lower than the surrounding silicon matrix. The reason of the supermetallic behavior is the high strain in the cores of the dissociated dislocations modifying the local band structure resulting in high conductive carrier channels along defect cores
Revealing the molecular signatures of host-pathogen interactions.
Advances in sequencing technology and genome-wide association studies are now revealing the complex interactions between hosts and pathogen through genomic variation signatures, which arise from evolutionary co-existence
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Single-electron transitions in one-dimensional native nanostructures
Low-temperature measurements proved the existence of a two-dimensional electron gas at defined dislocation arrays in silicon. As a consequence, single-electron transitions (Coulomb blockades) are observed. It is shown that the high strain at dislocation cores modifies the band structure and results in the formation of quantum wells along dislocation lines. This causes quantization of energy levels inducing the formation of Coulomb blockades
Mitochondrial Ca²⁺ Uniporter haploinsufficiency enhances long-term potentiation at hippocampal mossy fibre synapses
Long-term changes in synaptic strength form the basis of learning and memory. These changes rely upon energy demanding mechanisms which are regulated by local Ca2+ signaling. Mitochondria are optimised for providing energy and buffering Ca2+. However, our understanding of the role of mitochondria in regulating synaptic plasticity is incomplete. Here we have used optical and electrophysiological techniques in cultured hippocampal neurons and ex vivo hippocampal slices from mice with haploinsufficiency of the mitochondrial Ca2+ uniporter (MCU+/-) to address whether reducing mitochondrial Ca2+ uptake alters synaptic transmission and plasticity. We found that cultured MCU+/- hippocampal neurons have impaired Ca2+ clearance, and consequently enhanced synaptic vesicle fusion at presynapses occupied by mitochondria. Furthermore, long-term potentiation (LTP) at mossy fibre (MF) synapses, a process which is dependent on presynaptic Ca2+ accumulation, is enhanced in MCU+/- slices. Our results reveal a previously unrecognized role for mitochondria in regulating presynaptic plasticity of a major excitatory pathway involved in learning and memory
Segmentation of Skin Lesions Using Level Set Method
Diagnosis of skin cancers with dermoscopy has been widely accepted as a clinical routine. However, the diagnostic accuracy using dermoscopy relies on the subjective judgment of the dermatologist. To solve this problem, a computer-aided diagnosis system is demanded. Here, we propose a level set method to fulfill the segmentation of skin lesions presented in dermoscopic images. The differences between normal skin and skin lesions in the color channels are combined to define the speed function, with which the evolving curve can be guided to reach the boundary of skin lesions. The proposed algorithm is robust against the influences of noise, hair, and skin textures, and provides a flexible way for segmentation. Numerical experiments demonstrated the effectiveness of the novel algorithm
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