Short Wavelength Range Research Articles

Wavelength-dependent effects of evening light exposure on sleep architecture and sleep EEG power density in men

Light strongly influences the circadian timing system in humans via non-image-forming photoreceptors in the retinal ganglion cells. Their spectral sensitivity is highest in the short-wavelength range of the visible light spectrum as demonstrated by melatonin suppression, circadian phase shifting, acute physiological responses, and subjective alertness. We tested the impact of short wavelength light (460 nm) on sleep EEG power spectra and sleep architecture. We hypothesized that its acute action on sleep is similar in magnitude to reported effects for polychromatic light at higher intensities and stronger than longer wavelength light (550 nm). The sleep EEGs of eight young men were analyzed after 2-h evening exposure to blue (460 nm) and green (550 nm) light of equal photon densities (2.8 x 10(13) photons x cm(-2) x s(-1)) and to dark (0 lux) under constant posture conditions. The time course of EEG slow-wave activity (SWA; 0.75-4.5 Hz) across sleep cycles after blue light at 460 nm was changed such that SWA was slightly reduced in the first and significantly increased during the third sleep cycle in parietal and occipital brain regions. Moreover, blue light significantly shortened rapid eye movement (REM) sleep duration during these two sleep cycles. Thus the light effects on the dynamics of SWA and REM sleep durations were blue shifted relative to the three-cone visual photopic system probably mediated by the circadian, non-image-forming visual system. Our results can be interpreted in terms of an induction of a circadian phase delay and/or repercussions of a stronger alerting effect after blue light, persisting into the sleep episode.

Direct milling and casting of polymer-based optical waveguides for improved transparency in the visible range

Polymer waveguides fabricated from photoresist have an inherent high propagation loss in the short visible wavelength range caused by absorption due to the added photosensitizers. We have addressed this problem by development of two novel methods for the fabrication of microfluidic systems with integrated optical waveguides. Polymethylmethacrylate (PMMA) is dissolved in anisole and ‘doped’ with styrene-arcylonitrile copolymer to vary the refractive index. The doped PMMA with a higher refractive index is then spin coated onto a PMMA substrate with a lower refractive index to provide waveguide properties. Direct micromilling enabled us to fabricate 100 µm wide optical waveguides. Propagation losses of less than 1 dB cm−1 could be achieved throughout the entire visual range down to a wavelength of 400 nm. A casting process amenable to high number production of such devices was furthermore developed.

Measurement of nitrous acid and retrieval of aerosol parameters with differential optical absorption spectroscopy

Differential optical absorption spectroscopy (DOAS) is a spectroscopic technique which can be used to monitor many kinds of air pollutants simultaneously. In th is paper, in situ measurement of nitrous acid and retrieval of aerosol parameter s in a fixed wavelength range (307 nm—380 nm) were performed with DOAS system d eveloped by our laboratory. The measurements of HONO concentration were more acc urate using the NO2 standard absorption cross section measured by our selves a nd aerosol parameters were retrieved successfully in a shorter wavelength range.

Inviscid instability of an unbounded shear layer: effect of surface tension, density and velocity profile

The inviscid temporal stability analysis of an unbounded shear layer of two fluids of different density is investigated. Two background velocity profiles are considered: the piecewise-linear profile and the more realistic error-function profile. The disturbance kinetic energy is analyzed to physically understand the mechanism that causes instability. The surface-tension effect is investigated extensively. Surface tension is found to destabilize the neutrally stable waves that exist when surface tension is absent. This surface-tension-induced unstable mode is generally weaker than the dominant mode and extremely less evident when the density and/or viscosity difference increases. Short-wavelength instability is observed with a background viscosity jump at the interface. A comparison between the two velocity profiles is presented. The piecewise-linear profile does not match the more realistic results obtained with the error-function profile in the short wavelength range, especially in nonhomogeneous shear-layer flows; however, the phase-speed results are in a good agreement with those of the error-function profile.

Generation of strong coherent extreme ultraviolet radiation from the laser plasma produced on the surface of solid targets

We demonstrate the generation of high harmonics (up to the 65th order, λ=12.24 nm) of a Ti:sapphire laser radiation after the propagation of femtosecond laser pulses through the low-excited plasma produced by a picosecond prepulse radiation on the surface of different targets. High-order harmonics generated from the surface plasma of most targets showed a plateau pattern. It is assumed that the harmonic generation in these conditions occurs due to the interaction of the femtosecond pulses with the ions. The conversion efficiencies at the plateau region were varied between 1×10-7 to 8×10-6, depending on the target. The main contribution to the limitation of harmonic generation efficiency and cutoff energy was attributed to the self-defocusing of main pulse. A considerable restriction of the 27th harmonic generation was observed at different focusing conditions in the case of chromium plasma. Our observation of the resonance-induced enhancement of a single harmonic (λ=61.2 nm) at a plateau region with the efficiency of 8×10-5 in the case of In plasma can offer some expectation that analogous processes can be realized in other plasma samples in the shorter wavelength range where the highest harmonics were achieved.

Investigation into the Growth Kinetics of CdTe Nanocrystals in Germanophosphate Glasses by Optical Spectroscopy

The evolution of the absorption, photoluminescence, and Raman spectra of germanophosphate glasses containing CdTe semiconductor nanocrystals is investigated. It is shown that two stages can be distinguished in the evolution of the absorption spectra during isothermal annealing. At the first stage, the annealing is accompanied by the appearance of the absorption peak. At the second stage, an increase in the heat treatment time leads to a shift in the absorption peak toward the short-wavelength range. The dependence of the mean size of nanocrystals is calculated within the tight-binding model. It is revealed that, at the second stage, the dependence of the mean size of CdTe nanocrystals formed in the germanophosphate matrix can be described by the relationship R ∼ t0.12−0.16. This dependence is confirmed by the photoluminescence and Raman spectroscopic data (on the position of the Lamb mode).

Discovery and origin of a Palaeogene smectite-bearing clay deposit in the SE Gobi (Mongolia)

AbstractThe smectite-bearing red bed series of the Palaeogene Ergeliin zoo Formation in Mongolia is part of an alluvial-fluvial fan prograding over prodelta/mudflat deposits. The series was investigated in the field (mapping and portable infrared (IR) spectrometry in the short wavelength (SW) range) and samples were analysed in the laboratory using thin sections, X-ray diffraction, X-ray fluorescence, cation exchange capacity and Fourier transform infrared spectrometry in the mid-IR range. Two reference sections are treated in more detail as to the environment of deposition and concentration of smectite. The deposits at Ulaan uul are representative of a distal fan section with prevalent mudflats, whereas Ulaan buur offers insight into a braided river drainage system. Metabasic rocks in the hinterland delivered mica and chlorite from which smectite originated during diagenesis under semi-arid climatic and surface-near conditions. Towards the basin edge, smectite is replaced by kaolinite. The prime area in which we were interested in the smectite is the most distal part of the alluvial-fluvial fan, which was the subject of a field-based IR survey. This exploration method is a valuable tool to obtain a quick overview of the mineral composition and reduce the number of samples in the field for follow-up analyses. Its weak and strong points are discussed.

UVBLUE: A New High‐Resolution Theoretical Library of Ultraviolet Stellar Spectra

We present an extended ultraviolet-blue (850-4700 AA) library of theoretical stellar spectral energy distributions (SEDs) computed at high resolution, R= 50,000. The UVBLUE grid, as we named the library, is based on LTE calculations carried out with ATLAS9 and SYNTHE codes developed by R. L. Kurucz and consists of nearly 1800 entries that cover a large volume of the parameter space. It spans a range in effective temperature from 3000 to 50,000 K, the surface gravity ranges from log g= 0.0 to 5.0 with a step of 0.5 dex, while seven chemical compositions are considered: [Fe/H]= -2.0, -1.5, -1.0, -0.5, +0.0, +0.3 and +0.5 dex. For its coverage across the H-R diagram, this library is the most comprehensive one ever computed at high resolution in the short-wavelength spectral range, and useful application can be foreseen both for the study of single stars and in population synthesis models of galaxies and other stellar systems.

Cu(In,Al)S2 Thin Film Solar Cell

A Cu(In,Al)S2 thin film solar cell has exhibited good adhesion to Mo-coated glass and comparatively high efficiency. The sputter-deposited metallic precursor was sulfurized and then treated in a KCN solution to remove a CuxS impurity phase and an excessive Al compound from the film surface. When the precursor layer was Cu-rich, the treated sulfide film could be used as an efficient absorber material. It had the same band gap as CuInS2. The spectral response of the cell was increased in a short wavelength range. The bottom region of the film was considered to consist of a Cu(In,Al)S2 alloy that enhanced the film adhesion to the Mo back contact. The film was analyzed using X-ray diffraction, electron probe microanalysis, scanning electron microscopy and field ion microscopy combined with focused ion beam technique.

High-frequency response of isotropic-laminated cylindrical shells modeled by a layer-wise theory

In this paper, the high-frequency response of isotropic-laminated cylindrical shells is investigated using a layer-wise theory. The cylindrical shell is discretized in an arbitrary number of layers in the radial direction, and a three-dimensional stress state is assumed in each layer. Approximate numerical results obtained by the layer-wise theory are compared with the exact wave-dispersion analytical results. The very good agreement between approximate and exact results indicates that the layer-wise theory can accurately describe of the dynamic response of cylindrical shells in the high-frequency (short-wavelength) range.

Acoustostimulated expansion of the short-wavelength sensitivity range of AlGaAs/GaAs Solar cells

The effect of ultrasonic waves on the spectral sensitivity of solar energy converters based on AlGaAs/GaAs heterostructures has been studied. Ultrasonic treatment of a zinc-doped graded-gap AlxGa1−xAs film leads to the formation of a surface layer sensitive to electromagnetic radiation in the wavelength range λ < 0.551 μm. It is established that this layer is formed as a result of the acoustostimulated inward diffusion of zinc from the surface to the bulk of the graded-gap layer. The observed expansion of the short-wavelength sensitivity range and an increase in the efficiency of nonequilibrium charge carrier collection in AlGaAs/GaAs solar cells are due to improvement of the crystal defect structure and the dopant redistribution under the action of ultrasound.

Interpretation of Broadband Emission from a Gas-Discharge Krypton–Xenon Plasma

The broadband continuum emission that was previously observed in a gas-discharge plasma of a krypton-xenon mixture is interpreted as an emission of KrXe* and Xe2 molecules due to the bound-free transition 0+(3P1) → 0+(1S0). For the vibrational levels v = 0–5 of the 0+(3P1), 0+(1S0) state of the KrXe* molecule, the relative intensities I v (λ) of the transitions v, 0+(3P1) → e, 0+(1S0) are calculated as functions of the wavelength λ using data from the literature on the internuclear potentials 0+(3P1) and 0+(1S0) and the dipole moment functions. From comparison with the experimental spectra, the population distribution over the vibrational levels of the 0+(3P1) state of the KrXe* and Xe2 molecules is obtained and the vibrational temperature is determined for different methods of excitation of the spectra. It is noted that the internuclear potentials used ensure a satisfactory description of the contribution of the radiation from the Xe2 molecule to the experimental spectrum. At the same time, the modeled continuum emission of the KrXe* molecule turned out to be shifted toward the short-wavelength range by 5–7 nm, while its width (5–6 nm) proved to be half as broad as the experimental width.

Widely wavelength-tunable 40 GHz femtosecond pulse source based on compression of externally-modulated pulse using 1.4 km comb-like profiled fibre

Wide tunability over the entire C-band of the generation of 40 GHz high-quality 500 fs pulse train is shown by compressing an externally-modulated pulse train using 1.4 km comb-like profiled fibre. The use of the comb-like profiled fibre is essential for the features of short fibre and wide operating wavelength range.

Second-Order Optical Nonlinearity and Magnetic Order in Disordered Oxides

Recent research activities of the author's group concerning second-order optical nonlinearity induced in amorphous oxides and magnetic order in a disordered crystalline lattice are described. For the second-order optical nonlinearity, an attention is paid to second-harmonic generation (SHG) in thermally or optically poled tellurite glasses. Some tellurite glasses which exhibit interesting properties such as very stable second-order nonlinearity and large second-order nonlinear susceptibility are presented. The former is realized in ZnO-TeO2 glass, and the latter is attained for Na+-doped WO3-TeO2 glass. Also, the mechanism for SHG in optically poled Nb2O5-TeO2 glasses doped with vanadium ions is argued. A model including two-step absorption at a wavelength of 532 nm and the presence of photo-induced electrons and positive holes trapped at localized states is proposed. On the other hand, magnetic and magnetooptical properties of disordered ZnFe2O4 thin film prepared by a sputtering method are reported as an interesting example of magnetic order in a disordered lattice. The resultant disordered thin film shows high magnetization even at room temperature and a spin-freezing temperature higher than room temperature. The temperature dependence of magnetization under the conditions of field cooling and zero-field cooling, the dependence of spin-freezing temperature on frequency of ac magnetic field, and temperature variation of ac nonlinear susceptibility suggest that the spin-freezing or magnetic transition of the disordered ZnFe2O4 thin film is explainable in terms of the superparamagnetism with strong intercluster interactions. It is also demonstrated that large Faraday effect is observed in a short wavelength range for the disordered ZnFe2O4 thin film.

Phase transition in ZnS thin film phosphor

The effect of an original non-vacuum annealing of thin ZnS films according to the annealing conditions and type of substrate on the film's crystalline structure and surface morphology in relation with photoluminescent (PL) properties was investigated. ZnS thin films were deposited by electron-beam evaporation (EBE) on ceramic (BaTiO 3) and glass substrates heated to 150–200 °C. Three types of the targets such as ZnS, ZnS:Cu and ZnS:Cu, Al were used. The film thickness varied from 0.6 to 1 μm. As-deposited films were annealed at the atmospheric pressure in S 2-rich ambient atmosphere at 600–950 °C for 1 h. The ZnS:Cu films were Ga co-doped by annealing in the same atmosphere and temperature with additional Ga vapor. The ZnS films were doped with Cu, Cl using the thermal diffusion method by embedding the samples in ZnS:Cu, Cl powder. X-ray diffraction (XRD) technique, atomic force microscopy (AFM) and the measurements of PL parameters were used for investigation. The temperature of the ZnS phase transition from the sphalerite to wurtzite structure depends on the presence, type and ratio of additional impurities. It was revealed that Ga and Cl act not only as co-dopant to improve the luminescent properties, but also as activators of recrystallization processes. The transition of ZnS film's sphalerite lattice to wurtzite leads to the displacement of the blue emission band position towards the short-wavelength range by 10 nm.

Study on Spectral Response of GaAlAs/GaAs Staircase Band Gap Photodiodes

Three structures of a GaAlAs/GaAs staircase band gap photodiode have been fabricated and their spectral responses have been measured. The experimental results are almost consistent with the theoretical results except that the short-wavelength range expands more due to the electron diffusion current. Moreover, the spectral response of the three structures can be resolved into several peaks corresponding to the band gap of each GaAlAs active layer.

Silver and copper clusters and small particles stabilized within nanoporous silicate-based materials

Silver and copper ions were incorporated into mordenites with variable SiO2/Al2O3 molar ratio (MR) and silica xerogels. Heat treatment of the samples in hydrogen flow leads to the formation of reduced silver and copper species (nanoparticles and clusters). Their properties, influenced by variation of matrix structure, MR in mordenite and reduction conditions were studied by UV–vis optical spectroscopy. Investigation into optical spectra allows to follow the variation of electronic properties of reduced copper and silver small metal clusters and nanoparticles supported in zeolites and porous silica xerogel matrices. Metal nanoparticles exhibiting the plasmon resonance band are formed under the higher reduction temperatures. Their appearance has the complicated dependence on MR in mordenites, but similarity is observed for conditions leading to the formation of Cu and Ag nanoparticles. Small metal clusters were proposed to be responsible for the absorption bands in the short-wavelength range both for mordenites and silica xerogels. The more pronounced peaks for silver are assigned to Ag8 in mordenite and Ag19–Ag20 in silica xerogels. Structure and composition of matrix dominate over temperature dependence of metal ions reduction; similar reduced species appears at different temperatures for mordenite and xerogels. In the case of mordenites their chemical composition, that is, the SiO2/Al2O3 molar ratio, is the main parameter that permits to vary obtained metal species under the same condition of reduction.

A Two-Temperature Model for LBVs

The continuum energy distributions of R127 and R110 in the outburst phase are fitted by use of a optically envelope model. Both stars show two peaks in the continuum energy distributions in which one lies in the short-wavelength range (near 1250Å) and the other in the optical band. We suggest that the fluxes in the UV and optical bands may have different origins: the UV flux comes from the central star and the optical flux comes from the expanded optically envelope. We construct such a model for LBVs with the use of two LTE atmosphere models with different temperatures, and find it to be in satisfactory agreement with the observed spectral energy distributions of R127 and R110.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Sensitivity of ex situ and in situ spectral surface plasmon resonance sensors in the analysis of protein arrays

We have investigated the sensitivity of ex situ (analysis under air condition) and in situ (analysis under liquid condition) spectral SPR sensors, which were self-constructed with fiber optic spectrometers. The sensitivity of SPR sensors was analyzed in the wavelength range of 550-780 nm by the interactions of streptavidin and biotinylated IgG, and the sensitivity was dependent on the wavelength of measurements. The sensitivity of an ex situ SPR sensor operated at the long wavelength range from 712 nm was approximately 2.6 times higher than that at the short wavelength range from 571 nm. In addition, the sensitivity of an ex situ spectral SPR sensor was about twice as high as that of an in situ spectral SPR sensor for the same resonance wavelength range. This was interpreted in that the difference in sensitivity between two SPR sensors was significantly caused by the evanescent field intensity at the metal/dielectric interface. Thus, it was suggested that ex situ spectral SPR sensors operated at the long wavelength range are sensitive biosensors for the high-throughput analysis of protein interactions on protein arrays.

On the brightness of diluted photon source in synchrotron light facilities

The undulator radiation spectral brightness in storage ring is studied taking into account the effects of the electron beam oscillating trajectory and the beam transverse size variation along the undulator. The modified optimal beta function at the source point to reach maximum brightness is obtained that is in direct relation with the emitted photons wavelength. It is shown that the maximum spectral brightness in long wavelength range is achieved with low beta lattice, while in short wavelength range with larger beta.