Chloride transport and the resulting corrosion of steel bars in alkali activated slag concretes

As the relative performance of alkali activated slag (AAS) concretes in comparison to portland cement (PC) counterparts for chloride transport and resulting corrosion of steel bars is not clear, an investigation was carried out and the results are reported in this paper. The effect of alkali concentration and modulus of sodium silicate solution used in AAS was studied. Chloride transport and corrosion properties were assessed with the help of electrical resistivity, non-steady state chloride diffusivity, onset of corrosion, rate of corrosion and pore solution chemistry. It was found that: (i) although chloride content at surface was higher for the AAS concretes, they had lower chloride diffusivity than PC concrete; (ii) pore structure, ionic exchange and interaction effect of hydrates strongly influenced the chloride transport in the AAS concretes; (iii) steel corrosion resistance of the AAS concretes was comparable to that of PC concrete under intermittent chloride ponding regime, with the exception of 6 % Na2O and Ms of 1.5; (iv) the corrosion behaviour of the AAS concretes was significantly influenced by ionic exchange, carbonation and sulphide concentration; (v) the increase of alkali concentration of the activator generally increased the resistance of AAS concretes to chloride transport and reduced its resulting corrosion, and a value of 1.5 was found to be an optimum modulus for the activator for improving the chloride transport and the corrosion resistance

Tri-iodothyronine alters superoxide dismutase expression in a teleost Anabas testudineus

393-398The effect of tri-iodothyronine (T₃) on superoxide dismutase (SOD) expression was evaluated in a teleost Anabas testudineus (euthyroid fish) by native gel electrophoresis and Western blot analysis. SOD is an essential enzyme for the survival of oxygen-utilizing organisms. Its expression is altered by the stress, presumably due to the increase in concentration of superoxide radical in cells. Variations of thyroid hormone levels are the major physiological modulators of cellular oxidative stress. T₃ administration generates an oxidative stress, which to some extent is neutralized by the changed activity of enzymes like SOD. T₃ treatment decreased CuZn SOD density in liver and brain of A. testudineus. The activity of CuZn SOD in liver and brain was confirmed by native gel analysis. The different physiological states of thyroid influenced the CuZn SOD activity. Western blot analysis further confirmed that liver and brain CuZn SOD decreased after T₃ treatment. From these findings, it was clear that T₃ treatment in euthyroid fish created an oxidative stress condition and thyroid hormone effectively maintained antioxidant status to overcome this situation in teleosts

Rapid regulatory effect of tri-iodothyronine (T₃) on antioxidant enzyme activities in a fish Anabas testudineus (Bloch): Short-term in vivo and in vitro study

119-122The short-term action of thyroid hormone tri-iodothyronine (T₃) was studied in vivo and in vitro on antioxidant enzyme activities in a teleost Anabas testudineus (Bloch). T₃ injection in vivo (200 ng) in normal fish decreased the lipid peroxidation products and increased superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx) activities after 30 min. T₃ in vitro (10⁻⁶ M) increased the antioxidant activities of catalase, glutathione reductase (GR), GPx and glutathione level after 15/30 min, except SOD, substantiating in vivo effects in normal fish. The results suggest a rapid regulatory effect of thyroid hormone in vivo and in vitro, in the removal of reactive oxygen species in A. testudineus

An evaluation of satellite and in situ based sea surface temperature datasets in the North Indian Ocean region

Satellite based daily fields of Pathfinder SST (PFSST) and blended-analysed fields like National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) and Reynolds weekly SST data were compared with the in situ measurements obtained from several drifting buoys and a moored buoy in the north Indian Ocean. The mean differences (bias) and scatter (root mean square deviation (RMSD)) were higher than the ideally expected values of < 0.01° C and 0.5° C for all three datasets. There was very little difference in the error statistics from one region to another. The error statistics differed significantly from year to year. The PFSST fields reported cooler SSTs ~0.5° C, during August 1991 to April 1992, due to the increased input of aerosols in the atmosphere caused by the eruption of Mount Pinatubo. Being a high resolution dataset, the PFSST is best able to mimic the sudden changes in the in situ SSTs that happen over a couple of days to a couple of weeks. Neither NCEP/NCAR data nor the Reynolds data were able to mimic the changes in SST that occur over a period of a few days. All three datasets are useful for the analysis of low frequency oscillations like annual and semi-annual cycles. PFSST and NCEP/NCAR SSTs are also useful for the analysis of higher frequency oscillations in the SST fields such as the 26-day period oscillations in the equatorial Indian Ocean

Daily SST fields produced by blending infrared and microwave radiometer estimates

Measurement of Sea Surface Temperature (SST) using satellite based sensors have matured during the last decade. The infrared measurements, using the AVHRR sensor, flown onboard the NOAA satellites, have been used for the generation of high resolution operational products on daily basis, since 1982. However, the intrinsic problem of the infrared radiation prevents the retrieval of SST in the presence of clouds. This causes heavy loss of SST data over the north Indian Ocean especially during the summer monsoon (June-September). The recent advances in the microwave remote sensing of SST provides an alternative for the retrieval of SSTs in the presence of clouds. The microwaves, though they can measure the SSTs in the presence of clouds, their spatial resolution is poorer than that of infrared measurements. Near land boundaries the retrievals of the SSTs using microwaves are inferior due to the contamination from the emissions from land. In this study we take the advantage of the SST retrievals from infrared (NOAA/AVHRR) and microwave (TRMM/TMI) sensors and produce a new SST filed. An objective analysis scheme is used to combine the SSTs retrieved using AVHRR (9 km daily ascending and descending passes) and TMI (25 km ascending and descending passes) sensors to produce a daily field at a spatial resolution of 18 km. The new SST fields when compared with in situ measurements (drifting buoy SSTs) showed improvement (Root Mean Square Error of 0.659 ° C). The corresponding root mean square error of the SSTs derived from AVHRR and TMI were 0.642 ° C, and 0.783 ° C respectively

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Thyroid status alters gill ionic metabolism and chloride cell morphology as evidenced by scanning electron microscopy in a teleost <i style="">Anabas testudineus</i> (Bloch): Short and long term <i style="">in vivo</i> study

1015-1021Gill is the main organ of osmotic regulation in teleosts and chloride cells are the sites of ion transport across gill epithelium. Thyroid hormones are implicated in the regulation of osmotic balance in teleosts also. Treatment with 6-propyl thiouracil (6-PTU) inhibited the membrane bound enzyme Na+K+ ATPase in the gill while triiodothyronine (T3) injection stimulated it in a short-term in vivo study in the teleost Anabas testudineus. Na+, K+ and Ca2+ ions were also decreased in the 6-PTU treated fish and the T3 treatment increased their concentrations in the gill lamellae. The gill morphology also changed according to the thyroid status in the long term study. 6-PTU treatment altered the typical serrated morphology of the gill lamellae, while the T3 treatment reversed it. T3 injection increased the density of pavement and chloride cells as evidenced by scanning electron microscopy. The results demonstrate that physiological status of the thyroid influences gill Na+ pump activity and chloride cell morphological changes. Further, the study suggests a regulatory role of T3 on gill ions (Na+, K+ and Ca2+), Na+K+ and Ca2+ ATPase activity and the different gill cell types in A. testudineus

Insulin regulates ionic metabolism in a fresh water teleost, <i>Anabas testudineus </i>(Bloch)

702-709Short term effects of insulin on total brain and branchial Na+K+ATPase, Ca2+ATPase and Na+, K+ and Ca2+ ions were investigated in A. testudineus. The increase in brain Ca2+ ATPase after alloxan treatment may account for an increased amount of intracellular calcium required for biochemical events taking place inside the cells. Branchial Na+K+ATPase was significantly stimulated while Ca2+ ATPase significantly inhibited after alloxan treatment. This suggests that alloxan exerts its inhibitory effect on the ATP-driven Ca2+ transport via; its action on the Ca2+ pump protein rather than the membrane permeability to Ca2+. The increased activity of brain Na+K+ ATPase at 3 and 24 hr by insulin to alloxan pretreated fish may account for the stimulated co-transport of glucose and its utilization for energy requirements and the excitatory action on neurons in the brain. The elevated brain Ca2+ ATPase may be due to the role of calcium as a second messenger in hormone action. At 24 hr, the activity of branchial Na+K+ ATPase and Ca2+ ATPase in alloxan pretreated specimens was significantly stimulated by insulin. This may be due to increased synthesis of these enzyme units. Administration of insulin (1U/fish) in normal fish significantly inhibited the activity of brain and branchial Na+K+ ATPase while brain Ca2+ATPase showed a stimulatory effect at 3 and 24 hr compared to control. Inhibition of total branchial Ca2+ ATPase activity by insulin may be due to increased Ca2+ concentration. Higher plasma glucose level in alloxan treated groups confirms the diabetic effect of alloxan. Insulin reverses this effect. The possible mechanism by which insulin controls Na+K+ ATPase activity appears to be tissue specific. The results seem to be the first report on the effect of insulin on ATPase activity in a teleost. These data are consistent with the hypothesis that insulin performs a role in hydro mineral regulation in freshwater teleosts

Tri-iodo thyronine regulates antioxidant enzyme activities in different cell fractions through a mechanism sensitive to actinomycin D in a teleost, <i style="">Anabas testudineus</i> (Bloch)

640-646The present study evaluated the effects of hyperthyroid state on lipid peroxidation and antioxidant enzymes in the crude (CF), post nuclear (PNF) and mitochondrial fractions (MF) of the fish liver. The in vivo injection of T3 (200ng) did not change the lipid peroxidation products, malondialdehyde (MDA) and conjugated dienes (CD), while actinomycin D (10mg), a potent mRNA inhibitor when administered with T3 increased them. The antioxidant enzymes like superoxide dismutase (SOD) and catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) had an increased activity in CF and MF of hyperthyroid group to compete the increased oxidative stress, but actinomycin D partially inhibited the T3‑ &nbsp;induced activity. SOD and CAT activities in PNF of hyperthyroid group had no change, the glutathione concentration varied depending on the GPx and GR activity. Hyperthyroidism decreased the protein content, while simultaneous administration of actinomycin D inhibited the T3 action of elevating the protein content. The results suggest that the antioxidant defense status in A. testudineus is modulated by thyroid hormone, through an action sensitive to actinomycin D