Reduced frequency-independent models for seismic analysis of concrete gravity dams

A methodology is presented to allow a consistent and rational transition from linear frequency-domain model of concrete gravity dam-foundation-reservoir systems to time-domain models suitable for nonlinear seismic analysis. Two types of reservoir models are considered. These are an added mass approach based on the Westergaard method, and a finite element formulation using displacements as nodal variables to represent the reservoir. Coordinate reduction techniques are used to reduce the number of degrees-of-freedom needed to represent properly the reservoir and the foundation. A simplified time-domain model of energy dissipation in the reservoir and the foundation is developed by providing boundary dampers at the interface of the different media along with added stiffness and mass matrices. The added system matrices are calibrated to provide low level (elastic) time-domain response compatible to that obtained by using frequency-dependent system properties. The application to a typical gravity dam shows that the seismic response in time-domain can be properly predicted using the proposed methodology to develop frequency-independent system properties.     

Effect of plating time for electroless nickel coating on rebar surface: An option for application in concrete structure

The ternary Ni-P-Fe alloy coating was developed by an electroless process using a citrate bath. During the steel sample dip in bath, Fe will first get dissolved from the rebar surface and would subsequently get introduced in the bath as Fe²⁺. This, in turn, would activate the surface and Ni, P and Fe are co-deposited on the activated rebar surface. The first deposition layer would act as catalyst for subsequent metal deposition. The coating was characterised using SEM, EDS and XRD techniques. The bath pH was found to play a strong role on process kinetics as well as composition of the coating but not on coating structure. The weight percentage of Ni, P and Fe in the coating was found to have a relationship with the bath pH. The Tafel and salt spray test were conducted to find out corrosion resistance performance of the coatings. Electrochemical behavior of the coated rebars in simulated concrete environment was influenced by the pH of the concrete pore solution and the ‘P’ content in the coating. Corrosion potential and the corrosion rate of the coating increased with increase in ‘P’ content in the coating and pH of the pore solution, whereas the resistance against chloride attack of the coating increased with increase in ‘P’ content. The marginal drop in the bond strength of the coated rebar with the concrete structure may be due to the higher ‘P’ content which is expected to provide improved surface smoothness.     

Abnormally expressed low-voltage-activated calcium channels in beta-cells from NOD mice and a related clonal cell line

A macroscopic low-voltage-activated (LVA) inward current was found in pancreatic beta-cells isolated from NOD mice. However, this current was not present in nondiabetic prone mouse (e.g., Swiss-Webster) pancreatic beta-cells. We performed pharmacological analyses on this current in NOD insulinoma tumor cells (NIT-1). This cell line was developed from pancreatic beta-cells of a transgenic NOD mouse. The sodium-channel blocker, tetrodotoxin (TTX; 2 micromol/l) had no effect on this LVA current. The amplitudes of currents elicited by a -20 mV test pulse retained similarity when the extracellular sodium concentration was increased from 0 to 115 mmol/l; when the extracellular calcium concentration was decreased from 10 to 2 mmol/l, there was an approximate 50% reduction of this current elicited by a -30 mV test pulse. Neither the L-type calcium-channel blocker, nifedipine (3 micromol/l), nor the N-type calcium-channel blocker, omega-CgTx-GVIA (1 micromol/l), at -30 mV produced an appreciable effect. The T-type calcium-channel blockers, nickel (3 micromol/l) and amiloride (250 micromol/l), effectively reduced the peak of this current. In 2 mmol/l calcium external solution, the threshold of voltage-dependent activation of this calcium current was approximately -65 mV, and the peak current occurred at -20 mV. Half-maximum steady-state inactivation was around -43 mV. The mean time constant of slow deactivating tail currents generated by a preceding 20 mV pulse was 2.53 ms. The intracellular free calcium concentration was two- to threefold higher in NOD mouse pancreatic beta-cells compared with Swiss-Webster pancreatic beta-cells. We concluded that there are LVA calcium channels abnormally expressed in NOD mouse beta-cells. This LVA calcium channel may be factorial to the high cytosolic free calcium concentration observed in these cells, and thereby may contribute to the pathogenesis of NOD mouse beta-cells.     

Primary malignant rhabdoid tumor of the central nervous system

Luteinizing hormone (LH) induces progesterone production in hen ovarian granulosa cells, and this induction is inhibited when chloride ions are removed from the culture medium. This suggests that chloride channels may be involved in the signal transduction pathway responsible for the LH-induced progesterone production. In this report, we examined effects of LH on plasma membrane ion currents in single granulosa cells isolated from the largest preovulatory follicle (Fl) of the hen (Gallus domesticus). Using the perforated patch whole cell voltage clamp technique, we found that addition of LH rapidly activated a chloride current in these cells. This chloride current was present at all voltages tested (-90 to +50 mV), showed outward rectification and showed no obvious time or voltage dependence. Its magnitude was 3.5-fold that of the total resting membrane current measured before LH treatment. LH is known to elevate cyclic AMP in these cells. We found that addition of the cAMP analog Sp-cAMPS mimicked LH in inducing chloride currents in these cells. We conclude that LH can activate a chloride conductance in granulosa cells, and that this action may be mediated by cAMP.     

Recombinant human interleukin-11 in experimental Pseudomonas aeruginosa sepsis in immunocompromised animals

The therapeutic potential of recombinant human interleukin-11 (rhIL-11) was tested in a neutropenic rat model that mimics the clinical consequences of myelosuppressive chemotherapy complicated by Pseudomonas aeruginosa sepsis. rhIL-11-treated animals (150 micrograms/kg intravenously every 24 h for 3 days) had reduced endotoxin levels (P < .05) and less pulmonary edema fluid (P < .001) and were protected (P < .01) against thinning and necrosis of the intestinal mucosa compared with the control group. The survival rate in rhIL-11-treated animals was 40% (19/47), whereas it was 0 (0 of 19) in the control group (P < .01). The addition of ciprofloxacin (10 mg/kg every 12 h) resulted in a survival rate of 9 (60%) of 15, while the combination of rhIL-11 and ciprofloxacin resulted in 100% survival (15/15; P < .05). These results indicate that rhIL-11 supports mucous membrane integrity of the alimentary tract and decreases the systemic inflammatory response to experimental gram-negative infection in immunocompromised animals.     

Puffing characteristics of some processed rice stored in different packaging systems

Varietal differences in the puffing characteristics of parboiled rice (PABR), parboiled milled rice (PAMR) and milled rice (MR) after storage in polyethylene bags (PLY), polyethylene impregnated jute bags and jute bags (JUB) for varying times up to 120 days were studied. Monthly observations covering changes in physicochemical properties considered to have bearings on the puffing characteristics of rice were made and the factors responsible for puffing of rice have been tentatively identified. Better puffing followed increased ageing of rice samples. PABR was a better puffer than PAMR while MR yielded charred rice and hence was unsuitable for puffed rice production. Alkali degradation and grain hardness had some regulatory effect on the quality of puffing of rice. PLY emerged as the best packaging material for storing rice for later puffing. In JUB rapid damage of rice samples occurred owing to insect infestation and it was the poorest packaging unit.     

Effects of mechanical pressure on charge transport in ferrocene in the presence of adsorbed vapours

The change in the adsorption-induced electrical conductivity of ferrocene as a function of temperature has been studied under moderate pressure. At constant temperature, the logarithm of conductivity has been observed to be proportional to the applied pressure. A drastic change in the electrical conductivity behaviour of ferrocene, at the adsorbed state, as a function of temperature under mechanical pressure has been observed. The results are discussed in the light of different existing theories. Our results suggest that ferrocene in the vapour-adsorbed state undergoes phase transition which is modified by both temperature and pressure, and the effect of such phase transition is reflected in the unusual variation of conductivity with temperature under different pressures.