Showing papers by "Annamalai University published in 2010"

The Loss of Species: Mangrove Extinction Risk and Geographic Areas of Global Concern

Abstract: Mangrove species are uniquely adapted to tropical and subtropical coasts, and although relatively low in number of species, mangrove forests provide at least US $1.6 billion each year in ecosystem services and support coastal livelihoods worldwide. Globally, mangrove areas are declining rapidly as they are cleared for coastal development and aquaculture and logged for timber and fuel production. Little is known about the effects of mangrove area loss on individual mangrove species and local or regional populations. To address this gap, species-specific information on global distribution, population status, life history traits, and major threats were compiled for each of the 70 known species of mangroves. Each species' probability of extinction was assessed under the Categories and Criteria of the IUCN Red List of Threatened Species. Eleven of the 70 mangrove species (16%) are at elevated threat of extinction. Particular areas of geographical concern include the Atlantic and Pacific coasts of Central America, where as many as 40% of mangroves species present are threatened with extinction. Across the globe, mangrove species found primarily in the high intertidal and upstream estuarine zones, which often have specific freshwater requirements and patchy distributions, are the most threatened because they are often the first cleared for development of aquaculture and agriculture. The loss of mangrove species will have devastating economic and environmental consequences for coastal communities, especially in those areas with low mangrove diversity and high mangrove area or species loss. Several species at high risk of extinction may disappear well before the next decade if existing protective measures are not enforced.

Application of water quality index for groundwater quality assessment: Thirumanimuttar sub-basin, Tamilnadu, India

Abstract: An attempt has been made to understand the hydrogeochemical parameters to develop water quality index in Thirumanimuttar sub-basin. A total of 148 groundwater samples were collected and analyzed for major cations and anions. The domination of cations and anions was in the order of Na>Mg>Ca>K for cations and Cl>HCO(3) >SO(4) in anions. The hydrogeochemical facies indicate alkalis (Na and K) exceed alkaline earths (Ca and Mg) and strong acids (Cl and SO(4)) exceed weak acid (HCO(3)). Water quality index rating was calculated to quantify overall water quality for human consumption. The PRM samples exhibit poor quality in greater percentage when compared with POM due to effective leaching of ions, over exploitation of groundwater, direct discharge of effluents and agricultural impact. The overlay of WQI with chloride and EC correspond to the same locations indicating the poor quality of groundwater in the study area. SAR, Na%, and TH were noted higher during both the seasons indicating most of the groundwater locations not suitable for irrigation purposes.

Anticancer Drugs from Marine Flora: An Overview

Abstract: Marine floras, such as bacteria, actinobacteria, cyanobacteria, fungi, microalgae, seaweeds, mangroves, and other halophytes are extremely important oceanic resources, constituting over 90% of the oceanic biomass. They are taxonomically diverse, largely productive, biologically active, and chemically unique offering a great scope for discovery of new anticancer drugs. The marine floras are rich in medicinally potent chemicals predominantly belonging to polyphenols and sulphated polysaccharides. The chemicals have displayed an array of pharmacological properties especially antioxidant, immunostimulatory, and antitumour activities. The phytochemicals possibly activate macrophages, induce apoptosis, and prevent oxidative damage of DNA, thereby controlling carcinogenesis. In spite of vast resources enriched with chemicals, the marine floras are largely unexplored for anticancer lead compounds. Hence, this paper reviews the works so far conducted on this aspect with a view to provide a baseline information for promoting the marine flora-based anticancer research in the present context of increasing cancer incidence, deprived of the cheaper, safer, and potent medicines to challenge the dreadful human disease.

Geochemical and geo-statistical assessment of heavy metal concentration in the sediments of different coastal ecosystems of Andaman Islands, India

Abstract: Spatial distribution of metal concentrations in the surface sediment samples collected from 16 marine locations covering different coastal ecosystems such as mangroves, seagrasses, dead coral and sandy beaches of the Andaman islands, India was studied. pH, EC, sediment grain size and heavy metal (Al, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb and Zn) concentrations were determined and contamination factor (CF) and geo-accumulation index (Igeo) were calculated to understand the pollution status of the study area based on the background values. CF of different heavy metals has revealed that different metals have different levels of accumulation viz. Al: 0.01–0.22, Mg: 0.38–1.85, Fe: 0.06–0.74, Mn: 0.04–1.18, Cu: 0.18–2.93, Cr: 0.52–12.6, Zn: 0.3–1.39, Ni: 0.06–0.89, Pb: BDL–0.74, Co: 0.1–0.35 and Cd: 2.3–12.9. In general the metal concentration was less in these ecosystems when compared to similar ecosystems of mainland of India. Concentration of some metals like Cr and Cd was comparatively higher than the background values which is an important issue of concern to the coastal managers of the region. Spatial data on heavy metals, collected now, would help the coastal zone managers to identify the vulnerable sites and take remedial actions.

Therapeutic potential of Phyllanthus emblica (amla): the ayurvedic wonder

Abstract: Medicinal plants are nature's gift to human beings to promote a disease free healthy life. Many medicinal plants are present in a group of herbal preparations of the Indian traditional health care system (Ayurveda) named Rasayana proposed for their interesting antioxidant activities. Phyllanthus emblica Linn. (syn. Emblica officinalis), commonly known as Indian gooseberry or amla, family Euphorbiaceae, is an important herbal drug used in unani (Graceo - arab) and ayurvedic systems of medicine. The plant is used both as a medicine and as a tonic to build up lost vitality and vigor. Phyllanthus emblica is highly nutritious and could be an important dietary source of vitamin C, amino acids, and minerals. The plant also contains phenolic compounds, tannins, phyllembelic acid, phyllembelin, rutin, curcum-inoids, and emblicol. All parts of the plant are used for medicinal purposes, especially the fruit, which has been used in Ayurveda as a potent rasayana and in traditional medicine for the treatment of diarrhea, jaundice, and inflammation. Various plant parts show antidiabetic, hypolipidemic, antibacterial, antioxidant, antiulcerogenic, hepatoprotective, gastroprotective, and chemopreventive properties. Here we discuss its historical, etymological, morphological and pharmacological aspects.

Study on tool wear and surface roughness in machining of particulate aluminum metal matrix composite-response surface methodology approach

Abstract: Metal matrix composites (MMC) have become a leading material among composite materials, and in particular, particle reinforced aluminum MMCs have received considerable attention due to their excellent engineering properties. These materials are known as the difficult-to-machine materials because of the hardness and abrasive nature of reinforcement element-like silicon carbide particles (SiCp). In this study, an attempt has been made to model the machinability evaluation through the response surface methodology in machining of homogenized 20% SiCp LM25 Al MMC manufactured through stir cast route. The combined effects of four machining parameters including cutting speed (s), feed rate (f), depth of cut (d), and machining time (t) on the basis of two performance characteristics of flank wear (VBmax) and surface roughness (Ra) were investigated. The contour plots were generated to study the effect of process parameters as well as their interactions. The process parameters are optimized using desirability-based approach response surface methodology.

Chemopreventive efficacy of gallic acid, an antioxidant and anticarcinogenic polyphenol, against 1,2-dimethyl hydrazine induced rat colon carcinogenesis.

Abstract: Colon cancer is a major cause of morbidity and mortality in developed and developing countries and its etiology is known to be a combination of hereditary, environmental, dietary factors and lack of physical activity. Chemoprevention offers a novel approach to control the incidence of colon cancer. Gallic acid (GA) is a polyphenol widely present in tea and other plants which is popularly used in the traditional medicine of China. The present study was to evaluate the efficacy of GA supplementation on tissue lipid peroxidation and antioxidant defense system in 1,2-dimethyhydrazine (DMH) induced colon carcinogenesis in male Wistar rats. The rats were assorted into six groups, viz., group1 control rats received modified pellet diet; group 2 rats received GA (50 mg/kg body weight) orally along with modified pellet diet; group 3 rats received DMH (20 mg/kg body weight) subcutaneously once a week for the first 15 weeks; groups 4, 5 and 6 rats received GA along with DMH during the initiation, post- initiation stages and the entire period of study respectively. All the rats were sacrificed at the end of 30 weeks and the tissues were evaluated biochemically. We observed decreased lipid peroxidation (LPO) products such as thiobarbituric acid reactive substances (TBARS), lipid hydroperoxides (LOOH) and conjugated dienes (CD) and diminished levels of antioxidants such as superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH), glutathione reductase (GR) and glutathione peroxidase (GPx) in the tissues of DMH treated rats, which were elevated significantly on GA supplementation. Moreover, enhanced activity of ascorbic acid and α-tocopherol levels were also observed in DMH alone treated rats which were significantly reduced on GA supplementation. Our results suggest that GA could exert a significant chemopreventive effect on DMH induced colon carcinogenesis.

Antioxidant defense system, lipid peroxidation, proline-metabolizing enzymes, and biochemical activities in two Morus alba genotypes subjected to NaCl stress.

Abstract: Salt stress-induced changes in antioxidant enzymes, lipid peroxidation, proline and glycine betaine contents, and proline-metabolizing enzymes were examined in the leaves of two mulberry cultivars (Local and Sujanpuri). With increasing salinity up to 150 mM NaCl, superoxide dismutase, catalase, ascor-bate peroxidase, guaiacol peroxidase, glutathione reductase, and monodehydroascorbate reductase activities were increased in both cultivars as compared to control, but more pronounced increase was observed in cv. Local. Salt stress enhanced the rate of lipid peroxidation (as indicated by increasing MDA content) in both cultivars. Under NaCl stress, cv. Local showed less change in the MDA content than cv. Sujanpuri. Salt stress resulted in a significant accumulation of free proline in mulberry leaves, and more accumulation was detected in cv. Local than cv. Sujanpuri. The leaves of cv. Local showed 9-fold accumulation of glycine betaine in comparision with cv. Sujanpuri after 20 days at 150 mM NaCl. A decrease in proline oxidase activity and an increase in γ-glutamyl kinase activity were observed with increasing NaClconcentration. The relative water content and electrolyte leakage also decreased after increasing the NaCl concentration, but a decrease was more pronounced in cv. Sujanpuri than in cv. Local. The results indicate that oxidative stress may play an important role in salt-stressed mulberry plants and cv. Local have more efficient antioxidant characteristics, which could provide for a better protection against oxidative stress.

Volvulus of the sigmoid colon

Abstract: Aims The current status of sigmoid volvulus (SV) was reviewed to assess trends in management and to assess the literature. Method The literature on SV was retrieved using PubMed, Embase, Scopus, Pakmedinet, African Journals online (AJOL), Indmed and Google scholar. These databases were searched for text words including ‘sigmoid’, ‘colon’ and ‘volvulus’. Relevant nonindexed surgical journals published from endemic countries were also manually searched. We focused on original articles published within the last 10 years; but classical references prior to this period were also included. Seminal papers published in non-English languages were also included. Results Sigmoid volvulus is a leading cause of acute colonic obstruction in South America, Africa, Eastern Europe and Asia. It is rare in developed countries such as USA, UK, Japan and Australia. Characteristic geographic variations in the incidence, clinical features, prognosis and comorbidity of SV justify recognition of endemic and sporadic subtypes. Controversy on aetiologic agents can be minimized by classifying them into ‘predisposing’ and ‘precipitating’ factors. Modern imaging systems, although more effective than plain radiographs, are yet to gain popularity. Emergency endoscopic reduction is the treatment of choice in uncomplicated patients. But it is only a temporizing procedure, and it should be followed in most cases by elective definitive surgery. Resection of the redundant sigmoid colon is the gold standard operation. The role of newer nonresective alternatives is yet to be ascertained. Although emergency resection with primary anastomosis (ERPA) has been controversial in the past, it is now increasingly accepted as a safe option with superior results. Management in elderly debilitated patients is extremely difficult. Paediatric SV significantly differs from that in adults. SV is frequently associated with neuropsychiatric diseases, diabetes mellitus and Chagas disease. The overall mortality in recent studies is < 5%. Conclusion There are almost no randomised controlled studies. According to the grading system of Oxford Center for Evidence Based Medicine (CEVM), available published evidence is at level 4. The recommendations resulting form this review are of ‘C’ grade.

Optimization of the friction-stir-welding process and tool parameters to attain a maximum tensile strength of AA7075–T6 aluminium alloy:

Abstract: High-strength, precipitation-hardening AA7075 alloy is used extensively in aircraft primary structures. The friction-stir-welding (FSW) process is an emerging solid-state joining process in which the material that is being welded does not melt and recast. The FSW process and tool parameters play a major role in deciding the joint strength. In this paper an attempt has been made to establish an empirical relationship between the FSW process and tool parameters (tool rotational speed, welding speed, axial force, shoulder diameter, pin diameter, and tool material hardness) and the tensile strength of the joint. Statistical tools such as design of experiments, analysis of variance, and regression analysis are used to develop the relationships. The developed empirical relationship can be effectively used to predict the tensile strength of FSW joints at the 95 per cent confidence level. A sensitivity analysis is also carried out and compared with the relative impact of input parameters on tensile streng...

Predictions of the optimized friction stir spot welding process parameters for joining AA2024 aluminum alloy using RSM

Abstract: The friction stir spot welding process (FSSW) is a variant of the linear friction stir welding process in which the material is being welded without bulk melting. The FSSW parameters such as tool rotational speed, plunge rate, plunge depth, and dwell time play a major role in determining the strength of the joints. A central composite rotatable design with four factors and five levels was chosen to minimize the number of experimental conditions. An empirical relationship was established to predict the tensile shear fracture load of friction stir spot-welded AA2024 aluminum alloy by incorporating independently controllable FSSW process parameters. Response surface methodology (RSM) was applied to optimize the FSSW parameters to attain maximum lap shear strength of the spot weld.

Antihyperglycaemic and antioxidant effect of hyponidd, an ayurvedic herbomineral formulation in streptozotocin-induced diabetic rats

Abstract: Hyponidd is a herbomineral formulation composed of the extracts of ten medicinal plants ( Momordica charantia, Melia azadirachta, Pterocarpus marsupium, Tinospora cordifolia , Gymnema sylvestre, Enicostemma littorale, Emblica officinalis, Eugenia jambolana, Cassia auriculata and Curcuma longa). We have investigated hyponidd for its possible antihyperglycaemic and antioxidant effect in diabetic rats. Rats were rendered diabetic by streptozotocin (STZ) (45 mg kg(-1) body weight). Oral administration of hyponidd (100 mg kg(-1) and 200 mg kg(-1)) for 45 days resulted in significant lowered levels of blood glucose and significant increased levels of hepatic glycogen and total haemoglobin. An oral glucose tolerance test was also performed in experimental diabetic rats in which there was a significant improvement in blood glucose tolerance in the rats treated with hyponidd. Hyponidd administration also decreased levels of glycosylated haemoglobin, plasma thiobarbituric acid reactive substances, hydroperoxides, ceruloplasmin and alpha-tocopherol in diabetic rats. Plasma reduced glutathione and vitamin C were significantly elevated by oral administration of hyponidd. The effect of hyponidd at a dose of 200 mg kg(-1) was more effective than glibenclamide (600 microg kg(-1)) in restoring the values to near normal. The results showed that hyponidd exhibits antihyperglycaemic and antioxidant activity in STZ-induced diabetic rats.

Study of evaluation of groundwater in Gadilam basin using hydrogeochemical and isotope data

Abstract: Gadilam river basin has gained its importance due to the presence of Neyveli Lignite open cast mines and other industrial complexes. It is also due to extensive depressurization of Cuddalore aquifer, and bore wells for New Veeranam Scheme are constructed downstream of the basin. Geochemical indicators of groundwater were used to identify the chemical processes that control hydrogeochemistry. Chemical parameters of groundwater such as pH, electrical conductivity, total dissolved solids, sodium (Na + ), potassium (K + ), calcium (Ca + ), magnesium (Mg + ), bicarbonate \(({\rm HCO}_{3}^{-})\), sulfate \(({\rm SO}_{4}^{-})\), phosphate \(({\rm PO}_{4}^{-})\), and silica (H4SiO4) were determined. Interpretation of hydrogeochemical data suggests that leaching of ions followed by weathering and anthropogenic impact controls the chemistry of the groundwater. Isotopic study reveals that recharge from meteoric source in sedimentary terrain and rock–water interaction with significant evaporation prevails in hard rock region.