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Notes: A microinterferometric backscatter detector (MIBD) has been developed to perform subnanoliter volume refractive index measurements using a simple, folded optical train based on the interaction of a laser beam and a fused silica capillary tube. Positional changes of the interference pattern extrema (fringes) allow for the determination of Δn at the 10−7 level, corresponding to 5.3 pmole or 0.48 ng of solute, when thermal noise is controlled at 8×10−3 °C. MIBD is relatively path-length insensitive for capillaries ranging in inner diameter from 75 to 775 μm, allowing a large range of detection volumes, from 350 pL to 40 nL, to be produced. A theoretical model of the microinterferometric backscatter detector has also been developed and evaluated and has been found to be in agreement with experimental data. This model indicates increased sensitivity of the instrument as the wavelength of the probe beam and the wall thickness of the capillary tube are reduced. © 2000 American Institute of Physics.

Notes: A double-resonance spectrometer, suitable for the investigation of low lying intermolecular vibrational modes and of tunneling transitions of van der Waals complexes, is described. The instrument utilizes a pulsed molecular beam Fourier transform microwave spectrometer (frequency range 4–26 GHz) for signal detection, and a high frequency, phase stabilized, backward wave oscillator (258–375 GHz), as well as a millimeter wave synthesizer (78–118 GHz), as pump radiation sources. A brief description of the Fourier transform microwave spectrometer and of the phase stabilization system of the backward wave oscillator is given. The experimental arrangement is such that the molecular ensemble travels through the submillimeter radiation field prior to the pulsed excitation microwave experiment, in which the resulting population changes are detected. The sensitivity and the resolution capabilities of the new technique are illustrated with double resonance spectra of the van der Waals complexes Ar–CO and CO–N2. © 1998 American Institute of Physics.

Notes: We study the propagation of elastic waves that are generated in a fluid-filled borehole surrounded by a cracked transversely isotropic medium. In the model studied the anisotropy and borehole axes coincide. To obtain the effective elastic moduli of a cracked medium we have applied Hudson's theory that enables the determination of the overall properties as a function of the crack orientation in relation to the symmetry axis of the anisotropic medium. This theory takes into account the hydrodynamic mechanism of the elastic-wave attenuation caused by fluid filtration from the cracks into a porous matrix.We have simulated the full waveforms generated by an impulse source of finite length placed on the borehole axis. The kinematic and dynamic parameters of the compressional, shear and Stoneley waves as functions of the matrix permeability, crack orientation and porosity were studied. The modelling results demonstrated the influence of the crack-system parameters (orientation and porosity) on the velocities and amplitudes of all wave types. The horizontally orientated cracks result in maximal decrease of the elastic-wave parameters (velocities and amplitudes).Based on the fact that the shear- and Stoneley-wave velocities in a transversely isotropic medium are determined by different shear moduli, we demonstrate the feasibility of the acoustic log to identify formations with close to horizontal crack orientations.

Notes: An approach to determining the effective elastic moduli of rocks with double porosity is presented. The double-porosity medium is considered to be a heterogeneous material composed of a homogeneous matrix with primary pores and inclusions that represent secondary pores. Fluid flows in the primary-pore system and between primary and secondary pores are neglected because of the low permeability of the primary porosity. The prediction of the effective elastic moduli consists of two steps. Firstly, we calculate the effective elastic properties of the matrix with the primary small-scale pores (matrix homogenization). The porous matrix is then treated as a homogeneous isotropic host in which the large-scale secondary pores are embedded. To calculate the effective elastic moduli at each step, we use the differential effective medium (DEM) approach. The constituents of this composite medium – primary pores and secondary pores – are approximated by ellipsoidal or spheroidal inclusions with corresponding aspect ratios.We have applied this technique in order to compute the effective elastic properties for a model with randomly orientated inclusions (an isotropic medium) and aligned inclusions (a transversely isotropic medium). Using the special tensor basis, the solution of the one-particle problem with transversely isotropic host was obtained in explicit form.The direct application of the DEM method for fluid-saturated pores does not account for fluid displacement in pore systems, and corresponds to a model with isolated pores or the high-frequency range of acoustic waves. For the interconnected secondary pores, we have calculated the elastic moduli for the dry inclusions and then applied Gassmann's tensor relationships. The simulation of the effective elastic characteristic demonstrated that the fluid flow between the connected secondary pores has a significant influence only in porous rocks containing cracks (flattened ellipsoids). For pore shapes that are close to spherical, the relative difference between the elastic velocities determined by the DEM method and by the DEM method with Gassmann's corrections does not exceed 2%. Examples of the calculation of elastic moduli for water-saturated dolomite with both isolated and interconnected secondary pores are presented. The simulations were verified by comparison with published experimental data.

Notes: High photosensitivity increasing with decreasing incident light intensity and switching are observed in ZnSe/GaAs heterostructures. A model based on the possibility of conduction induced by carriers hopping between deep defect centers located in the bulk of ZnSe is presented. © 1995 American Institute of Physics.

Notes: 1. The aim of the present study was to examine the effects of isoteoline (IST), a new tetrahydroaporphine derivative, on the blood pressure and some of the components of renin-angiotensin-aldosterone system (RAAS) in spontaneously hypertensive rats (SHR).2. After long-term treatment (14 days, 3 times daily) in a dose of 1 mg/kg orally and intraperitoneally, IST induced a significant decrease of the systolic blood pressure (SBP) in SHR (from 192 ± 2 to 155 ± 5 mgHg).3. At the same time, IST induced a significant decrease of the levels of plasma renin activity (PRA) and aldosterone (ALD) and manifested a trend to increase the sodium plasma level.4. These results indicate that IST after chronic long-term treatment induced a marked antihypertensive effect and inhibited the components of RAAS in SHR. Apparently, the long-lasting antihypertensive effect of IST in SHR was mediated and realized in part by inhibition of the components of RAAS.

Notes: 1. The effect of environmental temperature on the indirect measurement of rat blood pressure and heart rate was investigated with special reference to the tail arterial blood flow in both strains of SHRSP and WKY.2. Very good correlations (r 〉 0.82, P 〈 0.05; t-test, 10 d.f.) were observed between the two values of systolic blood pressure or heart rate measured by a direct and an indirect method at environmental temperatures between 26 and 38°C in SHRSP, and 34 and 38°C in WKY, respectively.3. When the temperature was elevated by 10°C from 25°C to 35°C, the regional blood flow in the tail artery increased by 52–69%, sufficient to detect a blood flow increase by the indirect method.4. These data showed that the best way to measure the accurate blood pressure and heart rate in both strains of SHRSP and WKY by the indirect volume-oscillometric method was to hold the rats at 34–36°C for 5 min.

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