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By observing experimentally obtained photoelastic fringe patterns and applying classical solutions for an infinite plate containing a circular hole under remote tension and the modified Hertz contact theory, a replaced superposition method is proposed. In this paper we use this method to investigate the state of stress around a near-surface circular hole in a semi-infinite plate under a concentrated load. The well-matched conditions between the reconstructed and experimental photoelastic fringe patterns indicate the applicability of the proposed method.

Xenotransplantation of pig organs and tissues to humans involves a risk of infection by porcine endogenous retrovirus (PERV). This investigation examined potential transmission of PERV by using an in vitro culture system and the in vivo nude-mouse model to assess the safety of a bioartificial skin composed of porcine matrix. Polymerase chain reactions for the DNA and RNA of PERV gag and pol sequences were used to survey PERV infection. An in vitro culture system, artificial skin composed of porcine matrix, was incubated in DKSF medium for 32 days, and the presence of PERV was determined by sampling every other day. The blood of 12 nude mice was screened on days 3, 14, and 21 for PERV, after the mice had received three different skin grafts. Tissue biopsy did not yield evidence of PERV DNA integration or mRNA expression in the nude-mouse model. These results suggest that porcine dermal matrix (PDM), living dermal equivalent (LDE), and living skin equivalent (LSE) do not produce infectious PERV in in vitro culture assays. Which supports evidence showing no PERV virus transmission in in vivo nude-mouse recipients.

195Pt-,139La- and11B-NMR have been investigated in quaternary RM2B2C (R=Y, La, Th and M=Ni, Pd, Pt). The electric quadrupole frequency of139La changes more than 5 times in magnitude from M=Ni to Pt, indicating that the hybridization of La-5d and d-electrons of M-element changes largely. The analysis of11B and139La spectra shows also the large change of the magnetic anisotropy with R and M element, i.e., χII c>χII ab in LaNi2B2C, but χII c>χII ab YNi2B2C.The data of T1T and K of195Pt and11B are consistent with the band effects and with no evidence of strong antiferromagnetic correlation effects.

Tl-201 myocardial scintigraphy (Tl study) tends to be attenuated by soft tissues (such as the diaphragm) due to its low energy emission. 99mTc-sestamibi (2-methoxy isobutyl isonitrile) is a relatively new agent with a higher energy emission and this characteristic accounts for the higher quality of 99mTc-sestamibi images. The purpose of this study is to evaluate the ability of 99mTc-sestamibi in alleviating the inferior attenuation of Tl studies. 99mTc-sestamibi SPECT myocardial scintigraphy was performed on 13 patients with inferior wall perfusion defects as determined by Tl study (but with normal coronary artery as evidenced by cardiac catheterization). All patients underwent Tl SPECT study using a standard procedure. Same-day protocol (rest-stress sequence) was used for 99mTc-sestamibi SPECT imaging. All images were analyzed by two independent observers. The results of our study reveal that 99mTc-sestamibi produced better images. The inferior wall perfusion defects in the T1 study were noted in one case only (1/13) in the 99mTc-sestamibi study. Our study suggests that 99mTc-sestamibi can remarkably reduce the inferior attenuation of Tl study.

The chemical kinetics of laser pyrolysis of Si(CH3)2Cl2 was studied. Besides Si/C deposited on substrate as a needle the main gaseous products were H2 and HCI. The decomposition rate constants of Si(CH3)2Cl2 and the formation rate constants of H2 and HCl were measured. The chemical and physical properties of the Si/C needles were studied by various methods, such as their outer features, elemental analysis, Auger depth profile spectra, X-ray diffraction. Other useful properties, such as electric resistivity, photovoltaic effect and hardness, were also reported. A model for the pyrolysis and the growth process of this Si/C needles was proposed. It should be emphasized that the samples with desired physical properties could be grown by controlling the growth conditions properly -- the laser power and the pressure of Si(CH3)2Cl2.

The optical absorption and fluorescence characteristics of 4′-6-diamidino-2-phenylindole (DAPI) with DNA and chromosomes were studied. There is a decrease in extinction coefficient and shift in the absorption spectra to a higher wavelength when the dye binds to DNA. The fluorescence of DAPI is enhanced by both A-T and G-C base-pairs. The enhancement by A-T rich is significantly greater than by G-C rich DNA. The dye produces a localized bright fluorescence in centromeric regions of mouse chromosomes and the constrictions of human chromosomes 1 and 16; these regions are known to contain A-T rich DNA and show dull fluorescence when treated with quinacrine. This dye may be useful for identifying A-T rich region in chromosomes. The fluorescence of DAPI bound to polynucleotides or chromosomes is partially quenched by the introduction of BrdU. This suppression of dye fluorescence allows optical detection of sister chromatid exchanges and chromosome region containing DNA with an unequal distribution of thymidine between polynucleotide chains after BrdU incorporation.

The relative frequencies of sister chromatid exchanges (SCE) and chromatid breaks in BrdU (5-bromodeoxyuridine) - sensitive site (lq22 leads to lq23) in Chinese hamster cells after BrdU incorporation were studied. The results show that chromatid breaks do not follow the "exchange hypothesis" and provide evidence that chromatid breaks and SCEs are two independent events despite some common features.

Previous studies on intravenous hydralazine kinetics have been performed using nonselective analytical techniques that measure not only hydralazine but also certain hydralazine metabolites such as hydralazine pyruvic acid hydrazone (HPH). We studied the time course of hydralazine and HPH in eight hypertensive patients after 0.3 mg/kg intravenous with selective high-pressure liquid chromatographic assays. "Apparent" hydralazine concentrations were also determined using a nonselective gas-liquid chromatographic procedure. Total plasma clearance, CLT[72.9 +/- 4.9 (SEM) ml . min-1 . kg-1], apparent volume of distribution, Vd area (5.83 +/- 0.30 1 . kg-1), steady-state volume of distribution, Vd ss (1.83 +/- 0.17 . kg-1), and terminal half-life, t1/2 (53.7 min, harmonic mean) were independent of acetylator phenotype. The high ClT is compatible with rapid intravascular conversion of hydralazine to HPH and a high hepatic extraction ratio. Peak HPH concentrations occurred 10 to 60 min after dose; mean HPH t1/2 was 239 min. "Apparent" hydralazine concentrations were usually highest in the 2-min plasma sample and declined with a mean t1/2 of 296 min. Reports based on nonselective assay methods have underestimated CLT, Vd ss, and Vd area and have overestimated the t1/2 of hydralazine.

Hybrid cell clones between mouse cells deficient in hypoxanthine phosphoribosyltransferase and human diploid cells were analyzed for the expression of human uridine diphosphate galactose-4-epimerase (UDPGal-4-epimerase, EC 5.1.3.2) and for the segregation of human chromosomes. Ten of the 18 independent hybrid clones analyzed were found to express human UDPGal-4-epimerase. Karyotype analysis of these hybrids showed concordant segregation of human UDPGal-4-epimerase with chromosome 1. Human UDPGal-4-epimerase is expressed as a dimeric structure demonstrated by the formation of an intermediate heterodimer migrating between the human and mouse forms in the cell hybrids. The gene specifying this enzyme was also observed to be syntenic with enolase-1. These results indicate that the structural gene for human UDPGal-4-epimerase is located on chromosome 1.

An experimental investigation was carried out to determine the critical buckling loads of several shallow spherical sandwich shells. A cold-forming process simultaneously using pressure and vacuum was employed to manufacture the nearly perfect spherical facing layers from 5052 aluminum-alloy sheets of 0.006 and of 0.008-in. thicknesses. Eight shallow spherical-shell specimens of 20-in. base diameter and of 20 and 30-in. radii with 1/8 and 1/4-in. thickness of “Flexcore” have been tested in a 300-psi autoclave specifically designed for these experiments. The pressure on shells was developed by the differential pressure between the inner and the outer chambers separated by the shell being tested. When the inner chamber was maintained at atmospheric pressure and gas pressure was applied in the outer chamber, the testing procedure was termed “soft.” Alternatively, the inner chamber would be filled with fluid with the outer chamber remaining filled with gas. By initially pressurizing both chambers equally, a load on the shell could be developed by the differential pressure due to controlled bleeding of the fluid inside the inner chamber, while the gas in the outer chamber was maintained at the initial pressure. This is an accurate volume-control experiment and this testing procedure was termed “hard.” In the latter case, it was possible to monitor the displacements of the shell for each load increment with a nest of clip gages of an unique design. It was found that there is no substantial difference in the buckling loads between the hard and “soft” systems. All shells buckled in the plastic range. A reasonably good correlation is obtained with a linear theory using the double modulus for the sandwich segments.