Nitrogen isotopes in chondrules: signatures of precursors and formation processes

Nitrogen isotope abundance of 68 individual chondrules separated from six ordinary, two carbonaceous and two enstatite chondrites has been analysed. N composition of chondrules from ordinary and carbonaceous chondrites generally shows large variation and differs from that of their host. This large range of N composition suggests the presence of different N components in their precursors. Chondrules from the enstatite chondrites on the other hand show N isotopic composition similar to that of their host, suggesting precursors with similar N components for both chondrules and their host meteorites. Nitrogen isotopic systematics therefore distinguishes chondrules in enstatite chondrites from those in ordinary and carbonaceous chondrites. Chondrules in ordinary and carbonaceous chondrites require precursors that are different from those of their parent meteorites and formation in nebular environment, whereas chondrules in enstatite chondrites are formed from the same precursors as those of their host chondrites and presumably in the same region

Water characteristics, mixing and circulation in the Bay of Bengal during southwest monsoon

Influence of the freshwater influx, the wind forcing and the Indian Ocean monsoon drift current on the property distributions and the circulation in the Bay of Bengal during southwest monsoon has been quantified. At the head of the Bay, waters of low salinity, affected by the freshwater influx, occupy the upper 90 m water column. The isohaline 34.0 × 10−3 separating these waters from those of underlying saline waters shoals southward gradually and outcrops around 14N, 10N and 6N in the western, central and southeastern regions of the Bay respectively. The wind-stress-curl-induced upwelling effect is confined to depth limits of 50–100 m as is supported by a band of cold (24°–19°C) water in the central Bay. In the southern and central regions of the Bay, the monsoon drift current feeds the large scale cyclonic gyre apart from maintaining the northward flowing boundary current in the eastern Bay. A warm (27°–23°C), saline (35.0–35.2 × 10−3) watermass is advected northeastward along with the monsoon drift current into the Bay up to 14N at the depth limits of 50–100 m. Below this depth, in the western Bay a well-defined southward flow in the form of a boundary current is documented. Intense vertical mixing is inferred at the zones of salinity fronts in the depth limits of 40–100 m and also at deeper depths (\u3e 2200 m) and elsewhere lateral mixing is predominant

Kinetics of Oxidation of Methyl Orange & Methyl Red by V(V)*

16-1

Nitrogen in stone meteorites and terrestrial standards

Nitrogen contents have been determined by neutron activation method in stone meteorites and silicate standards. Leaching and sieving experiments on standards indicate that contamination from atmospheric nitrogen is negligible. For BCR-1 nitrogen contents show a range from 15 to 62ppm. The study includes 32 chondrites belonging to various classes and six achondrites. Nitrogen is high in C1 and C2 chondrites (500 to 1,000ppm) and in E chondrites (100 - 500ppm). C3 group shows variable amounts of nitrogen. Ordinary chondrites have similar nitrogen contents (~30pm) irrespective of their petrologic group. For all classes of meteorites, chondrules have lower nitrogen compared to the matrix. Dark phases of some gas- rich meteorites are enriched in nitrogen as compared to their light counterparts. Non-magnetic portions have slightly excess N compared to the magnetic portions. Correlation of N with C, In, Bi, Tl, Zn and Cd indicates the presence of two host phases for N

Studies of upwelling along the West Coast of India using geopotential anomaly

As summer is the season of mixing: and winter the season of stratification in the Arabian Sea along the west coast of India, summer minus winter dynamic depth. which takes into account the integrated effects of temperature, salinity and pressure is considered to reveal regional differences of the intensity of upwelling: relative to winter situation. The areas of intensive upwelling a r e thus identified. Stabilities of water layers during summer are examined with respect to those during winter

Live-bait resources and development

The success of the pole and line fishery of Lakshadweep depends, among other factors, directly on the availability in sufficient quantities of suitable live-bait fishes around the islands. Information on the live-bait resources of Lakshadweep is limited to a few reports from Minicoy- Jones (1958, 1964) described the fishing method, storage and utilisation of bait fish and Iisted the various species of live-bait fishes of Lakshadweep. Jones (1961 a, 1961 b) has predicted the potentialities of Spratelloides delicatulus and S. japonicus as live-bait for pole and line fishery for skipjack much earlier than mechanised fishing was introduced in the northern islands of Lakshadweep. Thomas (1964) made some observations on the fluctuations in the live-bait fishes at Minicoy. Fluctuations in the seasonal availability of live-baits at Minicoy during the years 1981-85 has been presented by Pillai et al. (1986). However, details of exploited bait fish resources and seasonal abundance of different bait species around the various islands is still lacking

Simulation of Deep Water Wave Climate for the Indian Seas

The ocean wave climate has a variety of applications in Naval defence. However, a long-term and reliable wave climate for the Indian Seas (The Arabian Sea and The Bay of Bengal) over a desired grid resolution could not be established so far due to several constraints. In this study, an attempt was made for the simulation of wave climate for the Indian Seas using the third-generation wave model (3g-WAM) developed by WAMDI group. The 3g-WAM as such was implemented at NPOL for research applications. The specific importance of this investigation was that, the model utilized a “mean climatic year of winds” estimated using historical wind measurements following statistical and probabilistic approaches as the winds which were considered for this purpose were widely scattered in space and time. Model computations were carried out only for the deep waters with current refraction. The gridded outputs of various wave parameters were stored at each grid point and the spectral outputs were stored at selected locations. Monthly, seasonal and annual distributions of significant wave parameters were obtained by post-processing some of the model outputs. A qualitative validation of simulated wave height and period parameters were also carried out by comparing with the observed data. The study revealed that the results of the wave climate simulation were quite promising and they can be utilized for various operational and ocean engineering applications.Therefore, this study will be a useful reference/demonstration for conducting such experiments in the areas where wind as well as wave measurements are insufficient

Measurement of Orbital Decay in the Double Neutron Star Binary PSR B2127+11C

We report the direct measurement of orbital period decay in the double neutron star pulsar system PSR B2127+11C in the globular cluster M15 at the rate of $(-3.95 \pm 0.13) \times 10^{-12}$, consistent with the prediction of general relativity at the $\sim 3$ level. We find the pulsar mass to be $m_p = (1.358 \pm 0.010) M_\odot$ and the companion mass $m_c = (1.354 \pm 0.010) M_\odot$. We also report long-term pulse timing results for the pulsars PSR B2127+11A and PSR B2127+11B, including confirmation of the cluster proper motion.Comment: 12 pages, 4 figures, accepted for publication in ApJ

Modelling and development of a horizontal vibratory rod mill for mechanical alloying: a first report

The present work deals with the development of a horizontal vibratory rod mill for mechanical alloying and synthesis of nanostructured materials. A simplistic model for optimization of milling efficiency has been developed, and the optimal operating parameters have been theoretically identified. The significance of developing such a mill lies in the possibility of high temperature mechanical alloying, which can open up new vistas for synthesis of nanoscale alloys

Salinity changes in the estuary and the coastal sea adjacent to the portmouth at Cochin

The article deals with the details of salinity changes in the Cochin estuary and its influence and interrelations with the Vembanad lake