Removal of terrain effects from SAR satellite imagery of Arctictundra

Synthetic aperture radar (SAR) images of the Earth's terrestrial surface contain geometric and radiometric image effects which are caused by varying terrain elevation and slope. The radiometric effects tend to mask signal variations caused by other physical variables such as soil moisture and surface vegetation type, which are known to influence SAR backscatter signals. As a result, raw SAR images are of limited use in classifying surface vegetation type or quantifying the spatial distribution of soil moisture in regions of terrain relief, The authors present a technique for removing radiometric terrain effects from SAR images. Image correction was carried out in two steps. First, an existing modeling package was used in combination with digital elevation data in order to map the raw image pixels onto a geodetic coordinate system, thereby removing the geometric portion of the image distortion. Radiometric effects were then removed with the aid of a backscatter model which treats the reflected radiation as a combination of diffuse-Lambertian and specular components. Parameters in the backscatter model were determined by comparing two C-band SAR images of a test area in a region of Arctic tundra which were taken from ascending and descending orbit tracks of the ERS-1 satellite. The ascending and descending images displayed reductions in pixel value variance of 30% and 13%, respectively, after processing. Direct comparison of the two test area images reveals a dramatic improvement in image similarity after processing     

Site-directed mutagenesis of the yeast V-ATPase B subunit (Vma2p)

The B subunit of the vacuolar (H+)-ATPase (V-ATPase) has previously been shown to participate in nucleotide binding and to possess significant sequence homology with the alpha subunit of the mitochondrial F-ATPase, which forms the major portion of the noncatalytic nucleotide binding sites and contributes several residues to the catalytic sites of this complex. Based upon the recent x-ray structure of the mitochondrial F1 ATPase (Abrahams, J.P., Leslie, A.G., Lutter, R., and Walker, J.E. (1994) Nature 370,621-628), site-directed mutagenesis of the yeast VMA2 gene has been carried out in a strain containing a deletion of this gene. VMA2 encodes the yeast V-ATPase B subunit (Vma2p). Mutations at two residues postulated to be contributed by Vma2p to the catalytic site (R381S and Y352S) resulted in a complete loss of ATPase activity and proton transport, with the former having a partial effect on V-ATPase assembly. Interestingly, substitution of Phe for Tyr-352 had only minor effects on activity (15-30% inhibition), suggesting the requirement for an aromatic ring at this position. Alteration of Tyr-370, which is postulated to be near the adenine binding pocket at the noncatalytic sites, to Arg, Phe, or Ser caused a 30-50% inhibition of proton transport and ATPase activity, suggesting that an aromatic ring is not essential at this position. Finally, mutagenesis of residues in the region corresponding to the P-loop of the alpha subunit (H180K, H180G, H180D, N181V) also inhibited proton transport and ATPase activity by approximately 30-50%. None of the mutations in either the putative adenine binding pocket nor the P-loop region had any effect on the ability of Vma2p to correctly fold nor on the V-ATPase to correctly assemble. The significance of these results for the structure and function of the nucleotide binding sites on the B subunit is discussed.     

A search for a short term test to assess the machinability of stainless steels

The paper describes four short term tests that were used to assess the machinability of stainless steels. Three of the tests, such as power bandsaw, slot milling, and turning, involved metal removal, while the fourth was based on the criterion of critical accumulated damage (CAD). Only the latter (CAD test) ranked the machinability of stainless steels consistently with the results of a long term automatic screw machining test. The critical accumulated damage can be assessed very easily from a compression test and this seems to be a short term test that could be used to assess the machinability of stainless steels.     

Defensin stimulates the binding of lipoprotein (a) to human vascular endothelial and smooth muscle cells

There is evidence to suggest that elevated plasma levels of lipoprotein (a) [Lp(a)] represent a risk factor for the development of atherosclerotic vascular disease, but the mechanism by which this lipoprotein localizes to involved vessels is only partially understood. In view of studies suggesting a link between inflammation and atherosclerosis and our previous finding that leukocyte defensin modulates the interaction of plasminogen and tissue-type plasminogen activator with cultured human endothelial cells, we examined the effect of this peptide on the binding of Lp(a) to cultured vascular endothelium and vascular smooth muscle cells. Defensin increased the binding of Lp(a) to endothelial cells approximately fourfold and to smooth muscle cells approximately sixfold. Defensin caused a comparable increase in the amount of Lp(a) internalized by each cell type, but Lp(a) internalized as a consequence of defensin being present was not degraded, resulting in a marked increase in the total amount of cell-associated lipoprotein. Abundant defensin was found in endothelium and in intimal smooth muscle cells of atherosclerotic human cerebral arteries, regions also invested with Lp(a). These studies suggest that defensin released from activated or senescent neutrophils may contribute to the localization and persistence of Lp(a) in human vessels and thereby predispose to the development of atherosclerosis.     

Comparison of Neoral and Sandimmun cyclosporin A pharmacokinetic profiles in young renal transplant recipients

A major factor influencing whole blood cyclosporin A levels in young children with renal transplants is the variable absorption of Sandimmun (SIM). Neoral (NEO) is a new microemulsion of cyclosporin A (CYA) that has been reported to have better absorption characteristics. We compared the pharmacokinetics of SIM and NEO in nine renal transplant recipients aged less than 11 years (range 4.8-10.9 years) and observed clinical parameters during 6 months of NEO therapy. Median CYA dosage was 149 mg/m2 per day (range 98-226). We observed an increase in the maximum CYA concentration (Cmax) of 114%, an increase in area under the curve (AUC) of 71% and the time to reach Cmax was reduced from 1.75 h to 1.25 h with NEO, while 12-h trough levels (C12 h) did not change significantly. AUC correlated with C12 h for SIM (r2 = 0.833) and NEO (r2 = 0.699) and also C1.5 h for NEO (r2 = 0.775). During 24 weeks' follow-up, the coefficient of variation of CYA levels was lower for NEO (13%) than for SIM (20%). Although CYA dosages at the start and the end of 6 months on NEO were similar, only one patient was maintained on a constant dose. Four patients had acute reversible rises in plasma creatinine which responded to a 11% reduction in NEO dose; their increase in AUC was greater than those patients not showing a rise in plasma creatinine. Overall, median plasma creatinine was unchanged at the end of the study. NEO was well tolerated by the patients; temporary nausea and headache were experienced by three patients and one of them stopped NEO after 20 days. Other biochemical parameters were not significantly different on NEO.     

An autosomal dominant, qualitative platelet disorder associated with multimerin deficiency, abnormalities in platelet factor V, thrombospondin, von Willebrand factor, and fibrinogen and an epinephrine aggregation defect

Multimerin is a massive soluble, multimeric protein found in platelets and endothelial cells. Recent studies identified multimerin as a specific coagulation factor V binding protein, complexed with platelet, but not plasma, factor V. These findings led us to investigate individuals with inherited factor V deficiencies for possible multimerin abnormalities. Platelet proteins were evaluated using immunoassays, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoblotting, immunoprecipitation, and direct binding studies. Patients with factor V Quebec, a disorder with abnormal platelet factor V, had a quantitative deficiency in multimerin (n = 11 tested; mean, 12.5%; range, 5% to 27% of the normal pool; normal range, 45% to 214%) with a normal multimer pattern. Quantitative and qualitative abnormalities were detected in their platelet factor V. An unrelated patient who was deficient in platelet and plasma factor V had normal platelet multimerin. The levels of platelet beta-thromboglobulin, von Willebrand factor, thrombospondin, and fibrinogen antigen were normal in the factor V Quebec patients. However, proteins with abnormal mobility were detected in their platelet lysate and releasate, and their platelet thrombospondin, von Willebrand factor, and fibrinogen showed evidence of proteolytic degradation. Platelet counts of the factor V Quebec patients ranged from mildly thrombocytopenic to low normal (mean, 159 x 10(9)/L; range, 104 to 198 x 10(9)/L). In addition, their platelets failed to aggregate in response to 6 to 10 micromol/L epinephrine despite normal numbers of platelet alpha 2-adrenergic receptors. These data indicate that patients with factor V Quebec have an inherited bleeding disorder distinct from other platelet disorders and associated with multiple abnormalities, including multimerin deficiency, abnormal platelet factor V, thrombospondin, von Willebrand factor, and fibrinogen, and an epinephrine aggregation defect.     

Rupture of a sinus of Valsalva aneurysm into the right ventricle. A case report in the cardiology clinic at the University Hospital Center of Dakar]

Human cytolytic T lymphocytes specific for autologous Burkitt's lymphoma express the gamma, delta T cell receptor and recognize immunoglobulin idiotype in an MHC-unrestricted manner. Antibodies against a member of the heat shock protein 70 family inhibit this specific cytotoxicity, implicating these molecules in tumor recognition and antigen presentation. Such data is relevant to the design of novel immunotherapies for cancer and provides new insights into target recognition by gamma, delta T cells.     

Optoelectronic winner-take-all VLSI shunting neural network

In this paper we present an analog winner-take-all MOS VLSI (metal-oxide semiconductor/very large scale integration) optoelectronic network. By varying either the input current or circuit parameters, the circuit can evidence several different behaviors such as contrast enhancement, strict winner-take-all, or winner-take-all with hysteresis. Simulation and experimental results from the prototype circuit are also discussed.