Aspen Wood Anatomy and Fluid Transport

Measurements of vinyl monomer impregnation, air permeability, moisture diffusion, and extractives content were made on the wood of two aspen trees from northern New Brunswick. The anatomy of the same wood was studied using the scanning electron microscope. There was high extractives content in the core, and tyloses were present in the core and heartwood. These caused the fluids to move with progressively greater difficulty from sapwood to heartwood to core

Photogenerated Carriers in SrTiO3 Probed by Mid-Infrared Absorption

Infrared absorption spectra of SrTiO$_3$ have been measured under above-band-gap photoexcitations to study the properties of photogenerated carriers, which should play important roles in previously reported photoinduced phenomena in SrTiO$_3$. A broad absorption band appears over the entire mid-infrared region under photoexcitation. Detailed energy, temperature, and excitation power dependences of the photoinduced absorption are reported. This photo-induced absorption is attributed to the intragap excitations of the photogenerated carriers. The data show the existence of a high density of in-gap states for the photocarriers, which extends over a wide energy range starting from the conduction and valence band edges.Comment: 5 pages, 5 figures, submitted to J. Phys. Soc. Jp

Reaction Time of a Group of Physics Students

The reaction time of a group of students majoring in Physics is reported here. Strong co-relation between fatigue, reaction time and performance have been seen and may be useful for academicians and administrators responsible of working out time-tables, course structures, students counsellings etc.Comment: 10 pages, 4 figure

Ion implantation induced photosensitivity in Ge-doped silica : E ect of induced defects on refractive index changes

Planar germanosilicate thin film glasses grown by flame hydrolysis technique on silica substrate have been implanted at 5 MeV with silicon ions to a dose of 1014 ions/cm2. Samples were subsequently exposed to a series of KrF (5 eV) and ArF (6.4 eV) excimer laser irradiation. Optical absorption and electron spin resonance were measured before and after each series of irradiation. We report an important refractive index change that can be correlated with the photobleaching of the ion implantation induced absorption bands

Difference in the behavior of oxygen deficient defects in Ge-doped silica optical fiber preforms under ArF and KrF excimer laser irradiation

Photobleaching of optical absorption bands in the 5 eV region and the creation of others at higher and lower energy have been examined in the case of ArF (6.4 eV) and KrF (5 eV) excimer laserirradiation of 3GeO2:97SiO2glasses. We report a difference in the transformation process of the neutral oxygen monovacancy and also of the germanium lone pair center (GLPC) into electron trap centers associated with fourfold coordinated Ge ions and Ge-E′ centers when we use one or the other laser. Correlations between absorption bands and electron spin resonance signals were made after different steps of laser irradiation. It was found that the KrF laser generates twice as many Ge-E′ centers as the ArF laser for the same dose of energy delivered. The main reason for this difference is found to be the more efficient bleaching of the GLPC (5.14 eV) by the KrF laser compared to that by the ArF laser

Bumble bees strategically use ground level linear features in navigation

Extended ground level structures like roads or field edges can be important cues for navigating animals,seen for example in road-following pigeons. In a landscape devoid of skyline cues but with a rectangular grid of pathways and roads, we used harmonic radar to track free-flying bumble bees,Bombus terrestris. Individual bees consistently used ground level linear features for navigation in a wide range of behavioural contexts. Bee exploration flights, search behaviour and foraging routes were shaped by linear features, with bees frequently flying along and parallel to pathways and roads. Comparisons off light trajectories across these behavioural contexts show that individuals modulated their use of linear features strategically with respect to their individual goals and experience. Bees searching for a feeder used linear features to target their search, while foragers often followed pathways to return to their hive without overshooting. These findings on a major pollinator have important implications for the placements of bee colonies for agriculture and floral resources for conservation

The OH Masers Towards IRAS 19092+0841

Context. Maser emission is a strong tool for studying high mass star forming regions and their evolutionary stages. OH masers in particular can trace the circumstellar material around protostars and determine their magnetic field strengths at milliarcsecond resolution. Aims. Imaging OH maser mission towards high mass protostellar objects to determine their evolutionary stages and to locate the detected maser emission in the process of high mass star formation. Methods. In 2007, we surveyed OH maser towards 217 high mass protostellar objects to study its presence. In this paper, we present a follow up MERLIN observations of a ground state OH maser emission towards one of these objects, IRAS 19092+0841. Results. Emission from the two OH main spectral lines, 1665 and 1667 MHz, were detected close to the central object. The positions and velocities of the OH maser features have been determined. The masers are distributed over a region of ~ 500 corresponding to 22400 AU (or ~ 0.1 pc) at a distance of 4.48 kpc. The polarization properties of the OH maser features were determined as well. We identify three Zeeman pairs from which we inferred a magnetic field strength of ~ 4:4mG pointing towards the observer. Conclusions. The relatively small velocity spread and the relatively wide spacial distribution of the OH maser features support the suggestion that this object could be in an early evolutionary state before the presence of disk and/or jet/outfows.Comment: 6 pages, 2 figures and 3 table

Formation and bleaching of strong ultraviolet absorption bands in germanium implanted synthetic fused silica

Germanium ions have been implanted in fused silica using ion beams having energies of 3 and 5 MeV and doses ranging from 1×1012 to 5×1014 ions/cm2. For wavelengths shorter than 400 nm, the optical absorption increases strongly with two absorption bands appearing at 244 and 212 nm. The ion-induced optical absorption can be bleached almost completely by irradiation with 249 nm excimer laser light. Ion implantation also increases the refractive index of silica near the substrate surface. At 632.8 nm a refractive index increase of more than 10-2 has been measured. This decreases by 4×10-3 upon bleaching with 249 nm light