IR Region (ir + region)

Distribution by Scientific Domains


Selected Abstracts


Crystal growth, crystal structure and physical properties of polar orthorhombic tris(glycine) zinc chloride

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 2 2008
M. Fleck
Abstract Large single crystals of the polar (point group mm 2) compound tris(glycine) zinc chloride, (NH3CH2COO)3 · ZnCl2, were grown from aqueous solutions. The refractive indices were measured in the wavelength region from 365 nm to 1083 nm and an unpolarised absorption spectrum was recorded (transparency range from 260 to 1550nm). The phase matching conditions for second harmonic generation were analysed: both, type I (ss-f) and type II (sf-f) are possible in the red and near IR region. All five components of the piezoelectric tensor [dijk ] were determined; the maximum values of longitudinal and transverse piezoelectric effects are less than one half of d111 of ,-quartz. In addition, a redetermination of the crystal structure (including location of H atoms) is presented. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Melatonin modulates the action of near infrared radiation on cell adhesion

JOURNAL OF PINEAL RESEARCH, Issue 3 2003
Tiina I. Karu
Abstract: The adhesion of human cervical cancer (HeLa) cells to a glass matrix is evaluated following their irradiation in a suspension with a pulsed near-infrared (IR) light-emitting diode (wavelength 820 nm, pulse repetition frequency 10 Hz, irradiation dose 16,120 J/m2) when melatonin (4 × 10,11 to 4 × 10,5 m) is added to cell suspension immediately before or after the irradiation. Also, the dependence of visible-to-near-IR radiation (600,840 nm, 52 J/m2) on cell adhesion (action spectrum) is recorded in absence and presence of melatonin (4 × 10,6 m). It is found that melatonin in pharmacological concentrations (but not in physiological range) inhibited cell adherence. Irradiation of cells before or after melatonin treatment normalizes cell adhesion to control level. Melatonin in pharmacological concentrations eliminates stimulation of cell attachment induced by irradiation. Pre-treatment (but not post-treatment) with melatonin in the physiological concentration eliminates cell adhesion stimulation induced by irradiation. Melatonin modifies the light action spectrum significantly in near IR region (760,840 nm only). Thus, the peak at 820,830 nm characteristic for the light action spectrum is fully reduced. [source]


FEMO modelling of optical properties of natural biopolymers chitin and chitosan

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2008
G. Luna-Bárcenas
Abstract Chitin and its derivative chitosan are widely used in the food, cosmetic, agricultural and biomedical industries because of their physicochemical and biocompatible properties. In this work, we studied thin films of both materials prepared by a solvent-cast method. The optical properties were investigated in the UV-VIS and infrared (IR) spectral regions; both biopolymers exhibit similar absorption bands characterized by two regions at 250,500 nm and at 850,1300 nm. Chitin and chitosan have practically the same parameters of a crystalline structure. We assume that these features (similarity of the structure and of the optical properties) are not just the coincidence but reflect the essential relation between the crystalline structure symmetry and the electronic transitions. The later was modeled on the basis of the quantum mechanical Free Electron Molecular Orbital approximation, using the new type, mirror-like boundary conditions. The calculations made on the basis of the known parameters of crystalline structure give reasonable agreement with the experimental spectra without any adjustable parameters. The difference between the optical properties of the two materials in the IR region reflects the difference in their molecular structure and composition. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Electroactive composite systems containing high conductive polymer layers on poly(ethylene) porous films,

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9-10 2006
G. K. Elyashevich
Abstract New composite electroactive materials containing conducting polymers were elaborated by oxidative polymerization of aniline and pyrrole onto porous poly(ethylene) films. The morphology of the conducting phase on the surface of the composites was investigated by scanning electron microscopy. The influence of preparation method and porous support structure on electric and mechanical properties of the composite materials was studied. The correlation between the composites electroconductivity and the absorbance of electromagnetic radiation in the IR region was observed. It was found that gas separation and ion-exchange membrane properties of the composites strongly depend on their conductivity and content of conducting component. Copyright © 2006 John Wiley & Sons, Ltd. [source]