Endothelium and valvular diseases of the heart

It has become increasingly evident that the endothelium plays a critical role in the pathogenesis of valvular heart disease. The endothelium helps regulate vascular tone, inflammation, thrombosis, and vascular remodeling. Dysfunction of the endothelial cells has been linked to many vascular disorders including atherosclerosis. Common valvular diseases such as senile degenerative valve disease, myxomatous (or floppy) valves, rheumatic valves, and infective endocarditis valves show changes in the synthetic, morphologic, and metabolic functions of the valvular endothelial cells. These diseases are active processes related to endothelial cell dysfunction. Endothelial cell dysfunction is caused by mechanical forces, bacterial infection, autoantibodies, and circulating modulators of endothelial cell function. This study reviews the role of endothelial cell dysfunction in the more common valvular diseases. Continued research on endothelial cell dysfunction is crucial to our understanding of valvular heart diseases and may elucidate novel treatment and prevention strategies.     

Effect of steady magnetic field on laser-induced breakdown spectroscopy

Effects of a steady magnetic field on the laser-induced breakdown spectroscopy of certain elements (Mn, Mg, Cr, and Ti) in aqueous solution were studied, in which the plasma plume expanded across an external steady magnetic field (approximately 6 kilogauss). Nearly 1.6 times enhancement in the line emission intensity was observed in the presence of the magnetic field. The temporal evolution of the line emission showed a significant enhancement in plasma emission between 2- and 7- micro(s) gate delays for Mg in the presence of the magnetic field (5-30 micro(s) for Mn). This enhancement in the emission is attributed to an increase in the rate of recombination because of an increase in plasma density due to a magnetic confinement after cooling the plasma. The increase in the optical line emission due to magnetic confinement was absent when the plasma was hot with a dominant background (continuum) emission. The limits of detection of Mg and Mn were reduced by a factor of two in the presence of a steady magnetic field of 5 kilogauss.     

Which dreams come true? Endogeneity, industry structure and forecasting accuracy

Forecasts are plentiful. Accurate long-range forecasts are rare.But some forecasts are more accurate than others are and a feware very accurate. In this paper, we first explore the caseof Moore's Law, a forecast that has proven quite accurate foralmost 40 years. We illustrate how expectations that Moore'sLaw will continue to be accurate actually make it accurate.Based on the insights of this case, we hypothesize that twofactors facilitate such self-fulfilling forecasts and so makeaccuracy more possible. We test these hypotheses on a set of3142 forecasts about US manufacturing industries during the1970s. We find that high industry concentration and high controlover the predicted variable tend to increase the accuracy offorecasts.     

A biomechanical analysis of loads on x-ray technologists: a field study

The aim of the study was to determine the biomechanical loads on radiographers in their occupation. Seven x-ray technologists (one male and six females with combined mean age 32.5 years, mean height 164.6 cm and mean weight 68.3 kg) volunteered to be videotaped while doing their jobs (same as normal and others in a simulated manner). X-ray technologists perform all these tasks regularly every day as part of their assignments. The magnitude of the load handled was measured on weighing scale and recorded. The videotape was played back in the laboratory and the initial and final frames of the tasks investigated were frozen for analysis. The joint angles, the height and weight of the technologist, and the load on their hands (weighed before the task was performed) were input into the 3-D Michigan static strength model for calculation of the lumbosacral load and loads on the joints of the extremities. The lumbosacral compression and shear loads were calculated for 16 tasks commonly performed by all x-ray technologists. The x-ray technologists' work was found to be biomechanically quite demanding. Tasks such as repositioning patients horizontally and lifting a patient from a wheelchair caused lumbosacral compression loads of 7,936N and 8,335N respectively, in which exceeded the maximum permissible limit set by NIOSH in 1981. The action limit defined by NIOSH was exceeded by other tasks. It is also of interest that the majority of the x-ray technologists were female.     

Oral immunization of macaques with attenuated vaccine virus induces protection against vaginally transmitted AIDS

The chimeric simian-human immunodeficiency virus SHIVKU-1, bearing the envelope of human immunodeficiency virus type 1 (HIV-1), causes fulminant infection with subtotal loss of CD4(+) T cells followed by development of AIDS in intravaginally inoculated macaques and thus provides a highly relevant model of sexually transmitted disease caused by HIV-1 in human beings. Previous studies using this SHIV model had shown that the vpu and nef genes were important in pathogenesis of the infection, and so we deleted portions of these genes to create two vaccines, DeltavpuDeltanefSHIV-4 (vaccine 1) and DeltavpuSHIVPPc (vaccine 2). Six adult macaques were immunized subcutaneously with vaccine 1, and six were immunized orally with vaccine 2. Both viruses caused infection in all inoculated animals, but whereas vaccine 1 virus caused only a nonproductive type of infection, vaccine 2 virus replicated productively but transiently for a 6- to 10-week period. Both groups were challenged 6 to 7 months later with pathogenic SHIVKU-1 by the intravaginal route. All four unvaccinated controls developed low CD4(+) T-cell counts (<200/microliter) and AIDS. The 12 vaccinated animals all became infected with SHIVKU-1, and two in group 1 developed a persistent productive infection followed by development of AIDS in one. The other 10 have maintained almost complete control over virus replication even though spliced viral RNA was detected in lymph nodes. This suppression of virus replication correlated with robust antiviral cell-mediated immune responses. This is the first demonstration of protection against virulent SHIV administered by the intravaginal route. This study supports the concept that sexually transmitted HIV disease can be prevented by parenteral or oral immunization.     

Subspace based estimation of the signal to interference ratio for TDMA cellular systems

The Signal‐to‐Interference Ratio (SIR) has been highlighted in the literature to be a most efficient criterion for several methods aiming at reducing the effects of cochannel interference, e.g., diversity reception, dynamic channel allocation and power control. In this paper we address the problem of how to obtain fast and accurate measurements of this parameter in a practical context. We develop a general SIR estimation technique for narrow‐band cellular systems that is based on a signal subspace approach using the sample covariance matrix of the received signal. Simulation results using the frame structure in the GSM system show that the SIR can be estimated to within an error of 0.3 dB after only 200 ms, or within an error of 0.1 dB after only 0.6 seconds. This revised version was published online in July 2006 with corrections to the Cover Date.     

Nucleation of a 60° glide dislocation in two-dimensional or three-dimensional growth of epilayers

The nucleation of a 60° glide dislocation in epitaxial thin films is analyzed. Nucleation from either a free surface or from a threading dislocation is considered. In this work, the presence of either infinitely long steps in a two-dimensional film or finite size steps in a two-dimensional or a three-dimensional film is proposed to reduce the activation energy associated with dislocation nucleation. The activation energy is reduced below 40 kT, a value predicted by standard nucleation theory for favorable nucleation, if the step is partially eliminated upon nucleation of a dislocation. However, when the coherency stress is small due to smaller lattice mismatch parameter, the activation energy can not be reduced below 40 kT. In addition, the activation energy is found to be a function of the size of the step but not that of the epilayer. Bowing of a threading dislocation by nucleation of kinks and propagation of the kinks along the dislocation is also analyzed using small angle approximation of the bow out. The activation energy associated with the bow out is again found to be independent of the size of the epilayer thickness. The critical size of the epilayer can be defined if the coherency strain energy remaining in the film is released in the form of thermal energy that helps to overcome the activation energy for nucleation of a dislocation.     

CORRELATION OF GLUCOSE (DEXTROSE) DEGRADATION AT 90 TO 190°C IN 0.4 TO 20% ACID

Decomposition of glucose is described over a wide range of acid concentrations and temperatures by a correlation based on an Arrhenius type model combined with a modified Debye-Huckel equation. Degradation depends on temperature and acid concentration, represented by hydrogen ion activity. Kinetic data from our laboratory for 4 and 12 wt% glucose were combined with literature data to establish this model. Alternative non-linear mechanisms were compared by regression analysis of the published data as well as data developed in this study. Values of the degradation constant vary from 0.109 hr^-1 (at 20 wt% acid and 190°C) to 4.18 × 10^-7 (at 0.4 wt% acid and 100°C). This result will be useful to model glucose degradation in acid hydrolysis of celluloses, sterilization of fermentor feeds, and stripping of fermentation ethanol.     

Protein engineering of a novel constitutively active hormone-receptor complex

Human chorionic gonadotropin (hCG) is a heterodimeric glycoprotein hormone consisting of an alpha and a beta subunit that stimulates intracellular levels of cAMP via a G protein-coupled receptor. Herein we report the engineering and characterization of a novel molecule in which the receptor and its heterodimeric ligand were covalently linked in a single polypeptide chain. The hormone-receptor complex was expressed in cells transfected with this construct, but the cells were unable to bind significant amounts of exogenous hCG. However, cleavage of the hormone with a site-specific protease rendered the receptor accessible to exogenously added hormone. Cells transfected with the hCG-receptor construct contained elevated basal levels of cAMP; moreover, addition of hormone had no significant effect. These results are consistent with a strong and stable interaction between the single-chain hormone and its covalently linked receptor that results in a constitutively active complex.