Optimum Design for External Seismic Stability of Geosynthetic Reinforced Soil Walls: Reliability Based Approach

In this paper, an analytical study considering the effect of uncertainties in the seismic analysis of geosynthetic-reinforced soil (GRS) walls is presented. Using limit equilibrium method and assuming sliding wedge failure mechanism, analysis is conducted to evaluate the external stability of GRS walls when subjected to earthquake loads. Target reliability based approach is used to estimate the probability of failure in three modes of failure, viz., sliding, bearing, and eccentricity failure. The properties of reinforced backfill, retained backfill, foundation soil, and geosynthetic reinforcement are treated as random variables. In addition, the uncertainties associated with horizontal seismic acceleration and surcharge load acting on the wall are considered. The optimum length of reinforcement needed to maintain the stability against three modes of failure by targeting various component and system reliability indices is obtained. Studies have also been made to study the influence of various parameters on the seismic stability in three failure modes. The results are compared with those given by first-order second moment method and Monte Carlo simulation methods. In the illustrative example, external stability of the two walls, Gould and Valencia walls, subjected to Northridge earthquake is reexamined.

Optimum Design for External Seismic Stability of Geosynthetic Reinforced Soil Walls: Reliability Based Approach

In this paper, an analytical study considering the effect of uncertainties in the seismic analysis of geosynthetic-reinforced soil (GRS) walls is presented. Using limit equilibrium method and assuming sliding wedge failure mechanism, analysis is conducted to evaluate the external stability of GRS walls when subjected to earthquake loads. Target reliability based approach is used to estimate the probability of failure in three modes of failure, viz., sliding, bearing, and eccentricity failure. The properties of reinforced backfill, retained backfill, foundation soil, and geosynthetic reinforcement are treated as random variables. In addition, the uncertainties associated with horizontal seismic acceleration and surcharge load acting on the wall are considered. The optimum length of reinforcement needed to maintain the stability against three modes of failure by targeting various component and system reliability indices is obtained. Studies have also been made to study the influence of various parameters on the seismic stability in three failure modes. The results are compared with those given by first-order second moment method and Monte Carlo simulation methods. In the illustrative example, external stability of the two walls, Gould and Valencia walls, subjected to Northridge earthquake is reexamined.

Probabilistic evaluation of seismic soil liquefaction potential based on SPT data

The performance-based liquefaction potential analysis was carried out in the present study to estimate the liquefaction return period for Bangalore, India, through a probabilistic approach. In this approach, the entire range of peak ground acceleration (PGA) and earthquake magnitudes was used in the evaluation of liquefaction return period. The seismic hazard analysis for the study area was done using probabilistic approach to evaluate the peak horizontal acceleration at bed rock level. Based on the results of the multichannel analysis of surface wave, it was found that the study area belonged to site class D. The PGA values for the study area were evaluated for site class D by considering the local site effects. The soil resistance for the study area was characterized using the standard penetration test (SPT) values obtained from 450 boreholes. These SPT data along with the PGA values obtained from the probabilistic seismic hazard analysis were used to evaluate the liquefaction return period for the study area. The contour plot showing the spatial variation of factor of safety against liquefaction and the corrected SPT values required for preventing liquefaction for a return period of 475 years at depths of 3 and 6 m are presented in this paper. The entire process of liquefaction potential evaluation, starting from collection of earthquake data, identifying the seismic sources, evaluation of seismic hazard and the assessment of liquefaction return period were carried out, and the entire analysis was done based on the probabilistic approach.

Pt2+ Dispersed in Ce0.83Ti0.15O2-delta: Significant Improvement in PROX Activity by Ti Substitution in CeO2 in Hydrogen Rich Stream

Pt2+ ion dispersed in CeO2, Ce1-xTixO2-delta and TiO2 have been tested for preferential oxidation of carbon monoxide (PROX) in hydrogen rich stream. It is found that Pt2+ substituted CeO2 and Ce(1-x)TixO(2-delta) in the form of solid solution Ce0.98Pt0.02O2-delta and Ce0.83Ti0.15Pt0.02O2-delta are highly CO selective low temperature PROX catalysts in hydrogen rich stream. Just 15% of Ti substitution in CeO2 improves the overall PROX activity.

Photocatalytic activity of tin-substituted TiO2 in visible light

Ultrafine powders of (Ti1-xSnx)O2, 0activity (after platinization) in the visible light region (420-550 nm) for H2 production from aqueous solutions containing sacrificial donors such as hypophosphite. The spectral sensitization is shown to be due to peroxotitanium species present in the lattice.

Oligosaccharides modulate the apoptotic activity of glycodelin

GlycodelinA (GdA), a multifunctional glycoprotein secreted at high concentrations by the uterine endometrium during the early phases of pregnancy, carries glycan chains on asparagines at positions N28 and N63. GdA purified from amniotic fluid is known to be a suppressor of T-cell proliferation, an inducer of T-cell apoptosis, and an inhibitorof sperm-zona binding in contrast to its glycoform, glycodelinS (GdS), which is secreted by the seminal vesicles into the seminal plasma. The oligosaccharide chains of GdA terminate in sialic acid residues, whereas those of GdS are not sialylated but are heavily fucosylated. Our previous work has shown that the apoptogenic activity of GdA resides in the protein backbone, and we have also demonstrated the importance of sialylation for the manifestation of GdA-induced apoptosis. Recombinant glycodelin (Gd) expressed in the Sf21 insec cell line yielded an apoptotically active Gd; however, the same geneexpressed in the insect cell line Tni produced apoptotically inactive Gd, as observed with the gene expressed in the Chinese hamster ovary(CHO) cell line and earlier in Pichia pastoris. Glycan analysis of the Tni and Sf21 cell line-expressed Gd proteins reveals differences in their glycan structures, which modulate the manifestation of apoptogenic activity of Gd. Through apoptotic assays carried out with the wild-type (WT) and glycosylation mutants of Gd expressed in Sf21 and Tni cells before and after mannosidase digestion, we conclude that the accessibility to the apoptogenic region of Gd is influenced by the size of the glycans.

Photocatalytic Activity of Microwave Plasma-Synthesized TiO2 Nanopowder

Nanocrystalline TiO2 was synthesized using the microwave plasma technique and characterized using X-ray diffraction, transmission electron microscopy, scanning electron microscopy, laser particle size analyzer, UV-vis spectroscopy and BET surface area analyzer. The synthesized TiO2 powder crystallized in anatase phase and the crystallite sizes were in nanometers. The photocatalytic activity of the compound was determined and compared against the activity of the commercial Degussa P-25 TiO2 catalyst. The degradation rates of the dyes were found to be higher over the synthesized TiO2 as compared to that over commercial Degussa P-25 TiO2.

Synthesis and Antileukemic Activity of 1-((S)-2-Amino-4,5,6,7-tetrahydrobenzo[d]thiazol-6-yl)-3-(substituted phenyl)urea Derivatives

Heterocyclic urea derivatives play an important role as anticancer agents because of their good inhibitory activity against receptor tyrosine kinases (RTKs), raf kinases, protein tyrosine kinases (PTKs), and NADH oxidase, which play critical roles in many aspects of tumorigenesis. Benzothiazole moiety constitutes an important scaffold of drugs, possessing several pharmacological functions, mainly the anticancer activity. Based on these interesting properties of benzothiazoles and urea moiety to obtain new biologically active agents, we synthesized a series of novel 1-((S)-2-amino-4,5,6.7-tetrahydrobenzo[d]thiazol-6-yl)-3-(substituted phenyl)urea derivatives and evaluated for their efficacy as antileukemic agents against two human leukemic cell lines (K562 and Reh). These compounds showed good and moderate cytotoxic effect to cancer cell lines tested. Compounds with electron-withdrawing chloro and fluoro substituents on phenyl ring showed good activity and compounds with electron-donating methoxy group showed moderate activity. Compound with electron-withdrawing dichloro substitution on phenyl ring of aryl urea showed good activity. Further, lactate dehydrogenase (LDH) assay, flow cytometric analysis of annexin V-FITC/propidium iodide (PI) double staining and DNA fragmentation studies showed that compound with dichloro substitution on phenyl ring of aryl urea can induce apoptosis.

Synthesis, X-ray structure and catalytic properties of a copper(II) Schiff base complex modeling the activity of the Cu-B site of dopamine beta-hydroxylase

The copper(II) complex [Cu(salgly) (bpy)] . 4H(2)O (1), where salgly is a tridentate glycinatosalicylaldimine Schiffbase Ligand, is prepared and structurally characterized. The complex is found to be catalytically active in the oxidation of ascorbic acid by dioxygen and the process is also effective in the presence of benzylamine giving benzaldehyde as a product, thus modeling the activity of the Cu-B site of dopamine beta-hydroxylase. (C) 2000 Elsevier Science S.A. All rights reserved.

Photocytotoxicity and DNA cleavage activity of L-arg and L-lys Schiff base oxovanadium(IV) complexes having phenanthroline bases

Oxovanadium(IV) complexes [VO(sal-argH)(B)] Cl (1-3) and [VO(sal-lysH)(B)] Cl (4-6), where sal-argH2 and sal-lysH(2) are N-salicylidene-L-arginine and N-salicylidene-L-lysine Schiff bases and B is a phenanthroline base, viz. 1,10-phenanthroline (phen in 1 and 4); dipyrido[3,2-d: 2', 3'-f] quinoxaline (dpq in 2 and 5) and dipyrido[3,2-a: 2', 3'-c] phenazine (dppz in 3 and 6), have been prepared, characterized and their DNA photocleavage activity studied. Complex 1, characterized by X-ray crystallography, shows the presence of a vanadyl group in VIVO3N3 coordination geometry with a tridentate Schiff base having a pendant guanidinium moiety and bidentate phen ligand. The complexes exhibit a d-d band at similar to 715 nm in 20% DMF-Tris-HCl buffer. The complexes are redox active showing cathodic and anodic responses near -1.0 V and 0.85 V (vs. SCE) for the V(IV)-V(III) and V(V)-V(IV) couples, respectively, in DMF-Tris-HCl buffer. The complexes bind to calf thymus DNA giving Kb values in the range of 3.8 x 10(4) to 1.6 x 10(5) M-1. Thermal denaturation and viscosity data suggest DNA groove binding nature of the complexes. The complexes do not show any `chemical nuclease'' activity in dark in the presence of 3-mercaptopropionic acid or H2O2. The dpq and dppz complexes are efficient photocleavers of plasmid DNA in UV-A (365 nm) and red light (676 nm) via singlet oxygen pathway. The dppz complexes exhibit photocytotoxicity in HeLa cancer cells giving IC50 values of 15.4 mu M for 3 and 17.5 mu M for 6 in visible light while being non-toxic in dark giving IC50 values of > 100 mu M.

Studies on follicular atresia: role of gonadotropins and gonadal steroids in regulating cathepsin-D activity of preovulatory follicles in the rat

Preovulatory follicular atresia was studied using pregnant mare serum gonadotropin (PMSG)-primed rats (15 IU/rat) which were deprived of hormonal support either by allowing the metabolic clearance of the PMSG or by injecting a specific PMSG antiserum (PMSG a/s). Atresia was monitored by an increase in lysosomal cathepsin-D activity and a decrease in the receptor activity of the granulosa cells (GC) isolated from the preovulatory follicles. It was shown that the increase in lysosomal activity and the decrease in receptor activity seen at 96 h after PMSG (or PMSG plus PMSG a/s) could be arrested both by follicle stimulating hormone (FSH) and luteinizing hormone (LH). Injection of cyanoketone or clomiphene citrate together with FSH/LH prevented this 'rescue' suggesting a role for estrogens in the regulation of atresia. Although the administration of estradiol-17 beta (20 micrograms/rat) together with PMSG a/s could show a 'rescue effect' in terms of reduction in cathepsin-D activity the gonadotropin receptor activities of these granulosa cells were not restored. The injection of dihydrotestosterone (DHT) to 48 h PMSG-primed rats induced atresia as noted by an increase in cathepsin-D activity. However, the exogenous administration of FSH along with DHT prevented this atretic effect suggesting that DHT is not having a direct effect on atresia. Determination of androgen: estrogen content of the granulosa cells and an analysis of the individual profile of androgen and estrogen revealed that the increase in cathepsin-D activity could be correlated only with the decrease in GC estrogen content. This along with the observation that GC showed a loss of estrogen synthesis well before the increase in cathepsin-D activity strongly points out that the lack of estrogen rather than an increase in androgen is the principle factor responsible for the atresia of preovulatory follicles in the rat.

Growth of and trehalase activity in the thermophilic fungusThermomyces lanuginosus

The thermophilic fungus,Thermomyces lanuginosus, was grown in a glucose-asparagine liquid medium. Optimal mycelial growth occurred at 50°C. The conditions for sporulation were different from those required for vegetative growth. the former being favoured by lower nitrogen level and temperature. Trehalase (α, α-glu coside-l-glucohydrolase, EC 3.2.1.28) was one of the most active glycosidases at 50°C. Non-sporulating mycelium had higher levels of this enzyme than the sporulating mycelium. Trehalase was synthesized constitutively and its activity appears to be controlled by catabolite repression.