Magnetotransport in graphene on silicon side of SiC

We have studied the transport properties of graphene grown on silicon side of SiC. Samples under study have been prepared by two different growth methods in two different laboratories. Magnetoresistance and Hall resistance have been measured at temperatures between 4 and 100 K in resistive magnet in magnetic fields up to 22 T. In spite of differences in sample preparation, the field dependence of resistances measured on both sets of samples exhibits two periods of magneto-oscillations indicating two different parallel conducting channels with different concentrations of carriers. The semi-quantitative agreement with the model calculation allows for conclusion that channels are formed by high-density and low-density Dirac carriers. The coexistence of two different groups of carriers on the silicon side of SiC was not reported before.Comment: 5 pages, 6 figures, accepted for publication in the "IOP Journal of Physics: Conference series" as a contribution to the proceedings of the 20th International Conference on "High Magnetic Fields in Semiconductor Physics", HMF 2

Free carrier effects in gallium nitride epilayers: the valence band dispersion

The dispersion of the A-valence-band in GaN has been deduced from the observation of high-index magneto-excitonic states in polarised interband magneto-reflectivity and is found to be strongly non-parabolic with a mass in the range 1.2-1.8 m_{e}. It matches the theory of Kim et al. [Phys. Rev. B 56, 7363 (1997)] extremely well, which also gives a strong k-dependent A-valence-band mass. A strong phonon coupling leads to quenching of the observed transitions at an LO-phonon energy above the band gap and a strong non-parabolicity. The valence band was deduced from subtracting from the reduced dispersion the electron contribution with a model that includes a full treatment of the electron-phonon interaction.Comment: Revtex, 4 pages, 5 figure

Flight of the dragonflies and damselflies

This work is a synthesis of our current understanding of the mechanics, aerodynamics and visually mediated control of dragonfly and damselfly flight, with the addition of new experimental and computational data in several key areas. These are: the diversity of dragonfly wing morphologies, the aerodynamics of gliding flight, force generation in flapping flight, aerodynamic efficiency, comparative flight performance and pursuit strategies during predatory and territorial flights. New data are set in context by brief reviews covering anatomy at several scales, insect aerodynamics, neuromechanics and behaviour. We achieve a new perspective by means of a diverse range of techniques, including laser-line mapping of wing topographies, computational fluid dynamics simulations of finely detailed wing geometries, quantitative imaging using particle image velocimetry of on-wing and wake flow patterns, classical aerodynamic theory, photography in the field, infrared motion capture and multi-camera optical tracking of free flight trajectories in laboratory environments. Our comprehensive approach enables a novel synthesis of datasets and subfields that integrates many aspects of flight from the neurobiology of the compound eye, through the aeromechanical interface with the surrounding fluid, to flight performance under cruising and higher-energy behavioural modes

Temporal fine structure of all-normal dispersion fiber supercontinuum

Experimental characterization of spectro-temporal structure of octave-spanning, coherent fiber supercontinuum pulses is performed and full-field information is retrieved using time-domain ptychography. Fast femtosecond oscillations are observed and traced back to imperfections of the pump pulses

Increased levels of VEGF-C and macrophage infiltration in lipedema patients without changes in lymphatic vascular morphology

Lipedema is a chronic adipose tissue disorder characterized by the disproportional subcutaneous deposition of fat and is commonly misdiagnosed as lymphedema or obesity. The molecular determinants of the lipedema remain largely unknown and only speculations exist regarding the lymphatic system involvement. The aim of the present study is to characterize the lymphatic vascular involvement in established lipedema. The histological and molecular characterization was conducted on anatomically-matched skin and fat biopsies as well as serum samples from eleven lipedema and ten BMI-matched healthy patients. Increased systemic levels of vascular endothelial growth factor (VEGF)-C (P=0.02) were identified in the serum of lipedema patients. Surprisingly, despite the increased VEGF-C levels no morphological changes of the lymphatic vessels were observed. Importantly, expression analysis of lymphatic and blood vessel-related genes revealed a marked downregulation of Tie2 (P<0.0001) and FLT4 (VEGFR-3) (P=0.02) consistent with an increased macrophage infiltration (P=0.009), without changes in the expression of other lymphatic markers. Interestingly, a distinct local cytokine milieu, with decreased VEGF-A (P=0.04) and VEGF-D (P=0.02) expression was identified. No apparent lymphatic anomaly underlies lipedema, providing evidence for the different disease nature in comparison to lymphedema. The changes in the lymphatic-related cytokine milieu might be related to a modified vascular permeability developed secondarily to lipedema progression

Design and modeling of dispersion-engineered all-chalcogenide triangular-core fiber for mid-infrared-region supercontinuum generation

An ultrabroadband mid-infrared supercontinuum (SC) source has been designed and modeled using a 10-mm-long all-chalcogenide triangular-core fiber (TCF). The TCF structure can be fabricated from Ge11.5As24Se64.5 chalcogenide glass as a core and Ge11.5As24S64.5 chalcogenide glass for its cladding running along the length of the fiber instead of air holes. Assuming the pump operates at 4 μm, the TCF is optimized by varying its side length using both anomalous-dispersion and all-normal-dispersion SC generation. Mid-infrared-region SC spectral broadening spanning beyond 15 μm could be generated with a low peak power of 3 kW by the proposed TCF structure optimized with varying its side length between 7 and 8 μm in anomalous-dispersion pumping. On the other hand, the TCF side length has to be decreased to 5.5 μm and below to optimize it for pumping in all-normal-dispersion-region SC generation. A coherent flat-top SC evolution in the mid-infrared region of up to 7 μm could be observed by this design with the same pump peak power and pulse duration applied before. The ultrawide optical bandwidth obtained by the proposed TCF design can be an effective tool for mid-infrared-region applications such as optical coherence tomography, molecular fingerprint spectroscopy, and biomedical imaging