THz Aperture Near-Field Spectroscopy of Dirac Plasmons in Topological Insulator Bi2Se3

We map the dispersion relation in ribbon gratings of topological insulator Bi2Se3 using both far-field and aperture-type near-field THz spectroscopy methods. The results are consistent with theoretical predictions of coupling between the optical phonon and massless Dirac plasmons

Designing an efficient hybrid optical cavity

We present an efficient terahertz (THz) detector based on an optically thin hybrid cavity. We use experimental and numerical methods to design efficient detectors, finding a hybrid cavity structure with a photoconductive (PC) layer as thin as 50 nm which absorbs almost 80% of light at the operation wavelength. These optically thin detectors are well suited to near-field microscopy and terahertz component integration

LT-GaAs metasurfaces as continuous-wave THz detectors operating in the telecommunications band

We present a novel approach for efficient continuous-wave (CW) detection of terahertz (THz) radiation using low-temperature-grown gallium arsenide (LT-GaAs) meta-surfaces. While typical THz CW detectors require complex material growth, annealing, and device architectures, our approach demonstrates that LT-GaAs, despite its low absorption at infrared wavelengths, can be used for low-noise THz detection by nanostructuring it into a metasurface

Off-limb EUV observations of the solar corona and transients with the CORONAS-F/SPIRIT telescope-coronagraph

The SPIRIT telescope aboard the CORONAS-F satellite (in orbit from 26 July 2001 to 5 December 2005), observed the off-limb solar corona in the 175 Å (Fe IX, X and XI lines) and 304 Å (He II and Si XI lines) bands. In the coronagraphic mode the mirror was tilted to image the corona at the distance of 1.1...5 <I>R</I><sub>sun</sub> from the solar center, the outer occulter blocked the disk radiation and the detector sensitivity was enhanced. This intermediate region between the fields of view of ordinary extreme-ultraviolet (EUV) telescopes and most of the white-light (WL) coronagraphs is responsible for forming the streamer belt, acceleration of ejected matter and emergence of slow and fast solar wind. We present here the results of continuous coronagraphic EUV observations of the solar corona carried out during two weeks in June and December 2002. The images showed a "diffuse" (unresolved) component of the corona seen in both bands, and non-radial, ray-like structures seen only in the 175 Å band, which can be associated with a streamer base. The correlations between latitudinal distributions of the EUV brightness in the corona and at the limb were found to be high in 304 Å at all distances and in 175 Å only below 1.5 <I>R</I><sub>sun</sub>. The temporal correlation of the coronal brightness along the west radial line, with the brightness at the underlying limb region was significant in both bands, independent of the distance. On 2 February 2003 SPIRIT observed an expansion of a transient associated with a prominence eruption seen only in the 304 Å band. The SPIRIT data have been compared with the corresponding data of the SOHO LASCO, EIT and UVCS instruments

Dipolar resonances in conductive carbon micro-fibers probed by near-field terahertz spectroscopy

We observe dipole resonances in thin conductive carbon micro-fibers by detecting an enhanced electric field in the near-field of a single fiber at terahertz (THz) frequencies. Time-domain analysis of the electric field shows that each fiber sustains resonant current oscillations at the frequency defined by the fiber's length. Strong dependence of the observed resonance frequency and degree of field enhancement on the fibers' conductive properties enable direct non-contact probing of the THz conductivity in single carbon micro-fibers. We find the conductivity of the fibers to be within the range of 1– 5×104 S/m. This approach is suitable for experimental characterization of individual doped semiconductor resonators for THz metamaterials and devices

Prostaglandin H synthase kinetics in the two-phase aqueous-micellar system

AbstractReaction mixture for PGHS (prostaglandin-H-synthase) is a two-phase system including micellar hydrophobic phase and hydrophilic aqueous phase. Reagents added to the mixture are distributed between phases, thus concentrations of reagents dissolved in phases can differ significantly from their overall contents.Using dynamic light scattering we found that the hydrophobic phase produced by tween-20 consists of micelles, which radius (4–5nm) does not depend on either tween-20 overall content (0.1%–1% v/v) or arachidonic acid (AA) addition (10–1000μM) or PGHS addition (1μM).Tween-20 overall content changing from 0.1% to 2% v/v dramatically affected COX kinetic, but accounting AA distribution between phases allowed us to estimate “true” parameters, independent of the tween-20 overall content and the concentration of another substrate: KMOx equals 9.8μM O2 in the aqueous phase or 0.0074bar in the gaseous phase, KMAA equals 5400μM AA in the phase of tween-20 micelles and 5400/PμM AA in the aqueous phase (P is the distribution ratio for the AA between the aqueous phase and the hydrophobic phase (P≫1000)). This approach allowed to evaluate PS, the distribution ratio for the AA between the hydrophobic phase and the PGHS active center (PS ~310). This coefficient indicates the AA selectivity toward the cyclooxygenase active center

The Current Performance of the Third Interplanetary Network

The 3rd Interplanetary Network (IPN) has been operating since April 2001 with two distant spacecraft, Ulysses and Mars Odyssey, and numerous near-Earth spacecraft, such as BeppoSAX, Wind, and HETE-II. Mars Odyssey is presently in orbit about Mars, and the network has detected approximately 30 cosmic, SGR, and solar bursts. We discuss the results obtained to date and use them to predict the future performance of the network.Comment: To appear in the proceedings of the conference on Gamma-Ray Bursts and Afterglow Astronomy 2001: A Workshop Celebrating the First Year of the HETE Mission, to be published by AI