Numerical inversion of rational Laplace transforms

Effective methods for numerical inversion of any rational Laplace transform are described. The methods are based on a stable algorithm for the numerical solution of a homogeneous system of 1st-order differential equations.     

Sympathetic influence on ventricular compliance

Intracisternal injections of veratrine in the anesthetized dog were used to study the effects of extreme sympathetic stimulation on left ventricular diastolic compliance. The results obtained were compared with those seen during volume expansion with whole blood, and after removal of both stellate ganglia. The injection of veratrine into the cisterna magna caused an increase in left ventricular end-diastolic pressure (LVEDP) which was considerably larger than that which occurred in left ventricular end-diastolic circumferential (LVEDC) segment length suggesting a reduction in diastolic compliance. There were also increases in left ventricular systolic pressure (LVSP) as well as its first derivative (LV dp/dt). Bilateral stellectomy during the veratrine response abruptly reduced LVEDP with a lesser decrease in LVEDC. Thus, the left ventricular compliance change was reversed. Both LVSP and LV dp/dt were decreased by stellectomy but remained above control levels. During transfusion, the pressure-length curve of the ventricle was located downward and to the right in comparison with the curve observed with intracisternal veratrine.     

Osteoid resorption by mononuclear cells in vitro

For the first time, mononuclear cell-mediated ingestion of osteoid in cultures of long bones of fetal rats is described and characterized. The mononuclear cells, located at sites of osteoid deposition, ingest collagen fibrils and clumps of mineral crystals which are segregated within cytoplasmic vacuoles or multivesicular bodies. The ingestion of osteoid continues in cultures treated with agents that normally inhibit osteoclastic bone resorption. Morphologically, the osteoid-containing cells are characterized by a moderate number of mitochondria and short-stranded rough endoplasmic reticulum, a modest Golgi apparatus and variable numbers of vesicles, vacuoles, and multivesicular bodies. The morphologic appearance of the mononuclear cell is consistent with that of a macrophage.     

Application of infra-red digital subtraction techniques to the microstructure of polychloroprenes: 1. Accentuation and assignment of bands due to structural irregularities

Infra-red digital subtraction techniques have been employed to accentuate and assign the bands associated with the structural irregularities present in predominantly trans-1,4- polychloroprenes. The spectral contribution of the trans-1,4- configuration was removed from the spectra of polychloroprenes synthesized at different temperatures revealing contributions due to cis-1,4-, 1,2- and 3,4- structural irregularities. In addition bands associated with end-groups were also observed. The results demonstrate the potential of infra-red digital subtraction techniques to determine, both qualitatively and quantitatively, relatively small concentrations of structural irregularities in polychloroprenes.     

Non-denaturing assay for the determination of the potency of recombinant bovine somatotropin by high-performance size-exclusion chromatography

A non-denaturing high-performance size-exclusion chromatographic method has been developed for the determination of the potency of recombinant bovine somatotropin (rbST) in bulk materials. A Spherogel TSK 3000 PW column containing a polymer base packing material with very hydrophilic bonded surface was used in this method. Ammonium hydrogencarbonate buffer pH 9.0, was used as the mobile phase. This method was shown to be non-denaturing by rat mass-gain assay and radioreceptor assay. The optimization for the separation and determination of rbST has been investigated. The method was validated for the determination of rbST in bulk materials. In addition, rbST soluble aggregates formed in the production process due to protein association, used to be found in bulk materials. The behavior of rbST soluble aggregates in ammonium hydrogencarbonate solutions have been studied. The bio-inactive aggregates can be separated by the method developed in this study. The high-low chromatographic technique has been used to estimate rbST soluble aggregates in bulk materials.     

A self-consistent model of a nonplanar quantum-well periodic laserarray

An analysis of a nonplanar semiconductor periodic laser array is carried out using a self-consistent model that successfully explains the experimentally observed efficiencies and output optical patterns. This model takes into account the two-dimensional injected current distribution coupled with the optical intensity profile and gain variation from the mesa to the groove. The optical field distribution of the nonplanar laser array is treated as a linear combination of the optical modes in the mesas, grooves, and bends using the effective index method. Numerical results show the multimode operation due to spatial hole burning, the near-field patterns affected by the nonuniform current injection, and the competition of available carriers among the modes of neighboring waveguides     

Carrier recombination rates in strained-layer InGaAs-GaAs quantumwells

The carrier recombination rates in semiconductor quantum wells are found to be structure dependent. Under high levels of excitation they generally do not follow the recombination rule of the bulk material. Through a differential carrier-lifetime measurement in the strained-layer InGaAs/GaAs quantum wells, it is shown that in quantum wells with lower potential barrier or thinner well width, the recombination rates are smaller due to a larger portion of the injected carriers populating the confinement layers where the carriers recombine more slowly owing to dilute carrier volume density     

Corrosion behaviour of aluminium-based metal matrix composites

The corrosion characteristics, in 3.5 wt% NaCl solution, of aluminium alloy composites containing a range of reinforcements have been investigated using potentiostatic measurements and simple immersion tests. Complementary microstructural studies carried out on corroded surfaces and sections through corroded material have identified a number of preferential corrosion sites; these include the fiber/matrix interface, especially where it contains chemical reaction products resulting from composite fabrication, as well as second phases and pores in the metal matrix. The effect on corrosion behaviour of the different reinforcements, with particular reference to their chemistry and geometry, is discussed, as is the influence of composite manufacturing route.