Source: https://www.niscair.res.in/ScienceCommunication/ResearchJournals/rejour/ijms/ijms2k7/ijms_march07.asp
Timestamp: 2019-04-26 06:12:13+00:00

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An attempt to improve wind wave short-term forecasts based on artificial neural networks is reported. The novelty of the study consists in the use of relatively short time series of wave observations collected over 2 consecutive months to accomplish the tasks of wave predictions and data assimilation. Separate neural networks were developed to predict five wind wave parameters, namely, the significant wave height, zero-up-crossing wave period, peak wave period, mean direction at the peak period and directional spreading over intervals of 3, 6, 12 and 24 hours, and to correct these predictions. Data from a directional buoy were used to train and validate the networks. The results of the simulations carried out without and with the proposed methodology were favourably compared to time series of wave parameters estimated in the field. Moreover, time series plots and scatterplots of the wave characteristics as well as statistics show an improvement of the results achieved due to data merging.
An experimental investigation was carried out to study the motion characteristics of a data buoy under regular as well as uni-modal and bimodal sea states. For the present study, the 2.2 m diameter discus shaped data buoy of India’s National Data Buoy Programme (NDBP) was scale modeled and, its heave and pitch motions were measured by two methods using potentiometers and motion capturing non contact infra-red cameras. The response amplitude operators obtained through the present experiment are proved to be predicting the different ranges of sea states well. The details of the model, instrumentation, testing conditions and the response amplitude operators for heave and pitch as a function of excitation frequency are presented and discussed in this paper.
The dynamic behavior of a 1:100 scale model of 140000 DWT turret moored FPSO system for three operating conditions, i.e., 40 % DWT, 70 % DWT and 100 % DWT with three hawser lengths, i.e., 15 %, 20 % and 25 % of the length of FPSO is discussed in this paper. The model tests were conducted in the 2 m wide wave flume under regular waves for the wave frequencies ranging from 0.55 Hz to 1.25 Hz in steps of 0.04 Hz at a water depth of 1 m for head sea condition. The motion response was measured using rotary type potentiometers. The mooring and hawser line forces were measured using specially fabricated ring type load cells. The test results of the forces and motion response were analyzed for the three hawser lengths at three operating conditions. From the analysis of the results, it is found that the tension in the forward mooring line is more than the tension in the aft mooring line for all loading conditions and hawser lengths. It is also observed that the tension of the forward mooring line decreases with increase in hawser length. The mooring tension is maximum for all hawser lengths at the full load condition.
To ascertain whether severe Indian Ocean tsunami of 26 December 2004 along the coast of India generated a change in diversity of foraminifera, inter-tidal post- tsunami samples were collected between 3rd and 4th January 2005 and compared with shore samples prior to tsunami, collected during an ongoing survey between 11th and 12th December 2004. A total of 24 sediment samples from different sites were analysed for foraminiferal diversity and also for sediment characteristics. Total foraminiferal number, organic matter and calcium carbonate showed considerable increase in post-tsunami samples. Significant changes in diversity were observed as indicated by Shannon Diversity and Morisita-Horn Similarity indices. As many as 41 species belonging to 20 genera, 14 families and 3 sub-orders were identified from pre-tsunami samples, while 71 species belonging to 34 genera, 17 families and 3 sub-orders were recorded from post-tsunami samples. A marked increase in foraminiferal relicts was observed in post-tsunami samples, suggesting a large-scale transportation of deeper water, offshore sediment to intertidal zone. Thus, geological events may cause abrupt changes in foraminiferal abundance and diversity of sediments.
Vibriosis is a commonly encountered disease in cultured shrimps. Vibrio spp. are the natural inhabitants of marine and brackish water ecosystems, which act as opportunistic pathogens in shrimp farms and shrimp hatcheries. Since the pathogenicity of Vibrio harveyi and V. alginolyticus is highly variable, a study was conducted to collect isolates of these two species from shrimp farming systems to analyse their strain variability. The above two bacteria were isolated from shrimp-farm water, sediment, shrimp larvae and hatchery water samples and subjected to polymerase chain reaction (PCR) fingerprinting using insertion sequence (IS) targeted primers. The IS primers were able to differentiate the intraspecies variability existing in both V. alginolyticus and V. harveyi strains efficiently. Twenty strains of V. alginolyticus tested differentiated into nine fingerprint patterns and 14 strains of V. harveyi also differentiated into 8 fingerprint groups. Dendrogram analysis of the two species tested was not able to associate the virulence factors studied, viz. production of amylase, gelatinase and lipase genetically. However, it has been found that all the amylase lacking V. alginolyticus strains except one belonged to a single genogroup. Dendrogram analysis confirmed the source independent genetic variability present within the same species of Vibrio tested.
0.15-37.21 ´ 104 CFU g-1 (dry wt) to the bottom section (6-9 cm; 0.10-36.92 ´ 104 CFU g-1 (dry wt). The total heterotrophic bacterial population correlated significantly with sediment water (P<0.02), total organic carbon (P<0.02) and clay fraction (P<0.01). Vertical distribution of bacterial population showed regular trend of decreasing with increasing sediment depth and the higher population was observed in the northern transects. Lower counts of bacterial population may be attributed to the small-scale patchiness and presence of dormant or slow growing bacteria in the sediments of Bay of Bengal.
The feeding physiology of Mnemiopsis leidyi fed on Artemia salina were investigated under laboratory conditions. Multifactorial experimental designs were used to study the factors affecting gastrovascular emptying in M. leidyi. A high correlation was found between number of prey ingested and digestion time. Modelling of gastric emptying time (GET,h.) of M. leidyi fed on A.salina was attempted to describe the effect of animal size, prey number, container volume and temperature on the digestion time. GET= 3.42- 0.00636 W + 0.0121 pN - 0.155 V - 0.00983 T. The clearance-rate was significantly affected by container volume and the feeding time. Multiple regression was attemped to model clearance rate: CR = 0.366 + 0.377 V - 0.197 H. Studying the feeding periodicity over a 24 h period, it was found that under laboratory condition and with readily available prey, M. leidyi feeds continuously except for the early hours of the day. Under such conditions medium size Mnemiompsis (11.36±0.38 g) consumed between 1286 and 2741 artemia daily. With the models of gastric emptying time (GET) and clearance rate (CR) presented in this study, quantitative assessment of the predatory impact of the ctenophore Mnemiopsis leidyi on the Black Sea ecosystem can be faciliated.
‘Ridge back shrimp’, Solenocera choprai, caught from a depth of 70 to 100 m off Mangalore, has been contributing substantially to the commercial fishery of the coast from 1993 onwards. During 2002, the species formed > 50% of the total shrimp landing of Mangalore fisheries harbour (2746 t). Since it is a non-conventional species to commercial fishery, the detailed information about the biology and population characteristics of the species is reported for the first time. The present paper deals with the morphometric relationship like length-weight relationship and carapace length-total length relationship of the species which will be useful in studying the population dynamics of the species. The life span of S. choprai is about 30 months and males and females attain a total length of 66 mm and 83 mm at the end of 12 months, 88 mm and 109 mm at the end of 24 months respectively. The results of the study will help in formulation of strategies for the management of this resource in terms of regulation of mesh size and fishing pressure.
A rapid single extraction procedure using dithiocarbamate complexing agent in methyl-isobutyl ketone (MIBK) organic phase and acid exchange back-extraction is described for the simultaneous quantitative preconcentration of Fe, Mn, V, Cr, Ni, Co, Cu, Zn, As, Mo, Cd, Pb and U in seawater followed by its determination by inductively coupled plasma mass spectrometry (ICP-MS). This method gives quantitative recoveries for all above metals at pH 4.1-6.4. A matrix matching seawater certified reference material (CRM), NASS-5, was used for calibration so as to minimize the matrix and other associated effects. Blanks and detection limits were in ng/l range. The method gives a recovery of 94-100% for 100 ml sample, facilitating the rapid and interference-free analysis of seawater samples. Excellent agreement was obtained with the certified values of another seawater CRM, CASS-4, when it was analyzed as an unknown. The major advantage of this procedure is that rapid analysis can be performed for a wide range of metals from relatively small samples.
Accidental spillage of petroleum in marine environment provokes serious damage to marine ecosystem. Microbial degradation of petroleum hydrocarbons is one of the major practice in the natural decontamination process. Out of 130 crude oil degrading bacteria isolated from Bhavnagar (Alang) coast, NW India, 12 isolates designated as TV 1 – TV 12 that formed maximum clearing zone on mineral medium were examined for their hydrocarbon degradation potential in temporal sequence of events. Among these, isolate TV 11 showed maximum growth (0.70 mg/ml) and degradation (22.8 %) on 34th day, followed by TV 4 that showed maximum growth (0.60 mg/ml) and degradation (17.0 %) and TV 3 that showed maximum growth (0.59 mg/ml) and degradation (16.2 %) on 28th day of incubation. Isolate TV 11 was identified as Marinococcus albus, TV 3 as Methylobacterium mesophilicum and TV 4 as Nocardia otitidiscaviarum. Effect of various crude oil concentrations (2 - 6 g/l), temperature (20 – 37 ºC) and pH (6 - 9) on growth and degradation revealed that 5 g/l of crude oil concentration, 30 ºC temperature for M. albus and 25 ºC for M. mesophilicum and N. otitidiscaviarum and pH 7 were optimum for both growth and degradation. Enhanced bacterial growth and degradation achieved with optimized concentrations of crude oil, temperature and pH can make their use suitable in devising an appropriate bioremediation strategy for oil contaminated sites.

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