Pulsating radio emission at decametre wavelengths from the sun     

Ch. V. Sastry  V. Krishan  K. R. Subramanian 《Journal of Astrophysics and Astronomy》1981,2(1):59-65

Observations on the pulsation pattern in the time profile of short duration solar radio bursts at decametre wavelengths are presented. The pulsations are found to be present predominantly in the saturation phase of the burst. A tentative physical model based on the non-linear development of the waves interacting in a turbulent medium is invoked to explain the origin of the pulsations.  相似文献   

Primordial magnetic fields and formation of molecular hydrogen     

Shiv K. Sethi  Biman B. Nath  Kandaswamy Subramanian 《Monthly notices of the Royal Astronomical Society》2008,387(4):1589-1596

We study the implications of primordial magnetic fields for the thermal and ionization history of the post-recombination era. In particular, we compute the effects of dissipation of primordial magnetic fields owing to ambipolar diffusion and decaying turbulence in the intergalactic medium (IGM) and the collapsing haloes, and compute the effects of the altered thermal and ionization history on the formation of molecular hydrogen. We show that, for magnetic field strengths in the range  2 × 10⁻¹⁰≲ B ₀≲ 2 × 10⁻⁹ G  , the molecular hydrogen fraction in IGM and collapsing halo can increase by a factor of 5 to 1000 over the case with no magnetic fields. We discuss the implication of the increased molecular hydrogen fraction on the radiative transfer of ultraviolet photons and the formation of first structures in the universe.  相似文献   

Socioeconomic effect of dust storms in Kuwait     

Ali Al-Hemoud  Mane Al-Sudairawi  Subramanian Neelamanai  Adel Naseeb  Weam Behbehani 《Arabian Journal of Geosciences》2017,10(1):18

Kuwait is an arid country with an annual average rainfall of about 110 to 120 mm. Hence, dust storms have become a common environmental crisis. Although the dry summer months commonly have more dust storms, in recent years, dust storms occur more frequently in the spring season as well. Accumulated data of dust storms in Kuwait for the past 14 years (2001–2014) showed that the month of March had the highest number of dust storms (total 19), which is rather unusual, with an average of 8 dust storms per year (year 2008 had the highest dust storms of total 22). This study explored four socioeconomic effects of dust storms in Kuwait, specifically traffic accident rates, oil export loss due to close out of marine terminals, airline delays due to airport operation shutdown, and agriculture degradation. Statistical analysis using t test and Pearson correlation showed no apparent relationship between dust storms and traffic accident rates or agricultural production; however, loss of oil export and flight delay cost were affected by dust storms. There has been very few published research on the socioeconomic impact of dust storms; this is the first paper that explores the detailed socioeconomic effect of dust storms in Kuwait.  相似文献   

Source and distribution of trace metals and nutrients in Narmada and Tapti river basins,India   总被引：2，自引：1，他引：1  

Sanjay Kumar Sharma  V. Subramanian 《Environmental Earth Sciences》2010,61(7):1337-1352

The study was designed to establish the distributions of trace metals, dissolved organic carbon, and inorganic nutrients as well as to assess the extent of anthropogenic inputs into the Narmada and Tapti rivers. Water and sediment qualities are variable in the rivers, and there are major pollution problems at certain locations, mainly associated with urban and industrial centers. The metal concentrations of samples of the aquatic compartments investigated were close to the maximum permissible concentration for the survival of aquatic life, except for higher values of Cu (5–763 μg l⁻¹), Pb (24–376 μg l⁻¹), Zn (24–730 μg l⁻¹), and Cr (70–740 μg l⁻¹) and for drinking water except for elevated concentrations of metals such as Pb, Fe (850–2,060 μg l⁻¹), Cr, and Ni (20–120 μg l⁻¹). In general, the concentrations of trace metals in the rivers vary down stream which may affect the “health” of the aquatic ecosystem and may also affect the health of the rural community that depends on the untreated river water directly for domestic use. The assessment of EF, I _geo, and PLI in the sediments reveals overall moderate pollution in the river basins.  相似文献   

High energy observations of June 1980 solar flares     

B. Lokanadham  P. K. Subramanian  Allan L. Kiplinger  B. R. Dennis 《Astrophysics and Space Science》1986,119(1):5-8

The paper presents a detailed study of the high energy X-ray observation of the most unusual solar events observed on 4 and 7 June, 1980 with the Hard X-Ray Burst Spectrometer (HXRBS) on Solar Maximum Mission (SMM) satellite. The hard X-ray data of the events are also compared with the radio microwave fluxes.The X-ray time profiles of these flares are characterized by the occurrence of impulsive phase superposed with a number of narrow spikes before the occurrence of the main energetic events. Studies of the temporal and spectral properties of these events indicated a quasi-oscillatory nature of the sources. Various models for explaining the evolution of the events are considered and the sequential firing loop model seems to be consistent with the observations of the events.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.  相似文献   

Heavy metal contamination in mangrove habitats of Singapore   总被引：1，自引：0，他引：1  

Cuong DT  Bayen S  Wurl O  Subramanian K  Wong KK  Sivasothi N  Obbard JP 《Marine pollution bulletin》2005,50(12):1732-1738

  相似文献   

Phosphorus,silicon, and some trace contaminants in the Ganges Estuary     

V. Subramanian 《Estuaries and Coasts》1993,16(3):453-458

Dissolved silica and phosphorous show a highly nonconservative behavior in the Ganges Estuary. In addition, phosphorous also shows seasonal variations, with winter levels higher than the levels in the monsoon. Mineral composition inducates enrichment of coarse quartz grains due to selective removal of finer clays in the estuary, either due to flocculation or due to dredging effects of the Port of Calcutta. Particulate P and Si show strong opposite trends, possibly indicating the presence of P in predominently nondetrial fractions in the sediments. Certain trace contaminants, such as Fe, Mn, Cu, Pb and Zn, show seasonal variability as well as enrichment in suspended particulate material relative to bed sediments. Levels of all these contaminents are still well below those reported for rivers such as the Rhine and other highly man-influenced systems.  相似文献   

Geochemistry of the Cauvery Estuary,East Coast of India     

A. L. Ramanathan  P. Vaithiyanathan  V. Subramanian  B. K. Das 《Estuaries and Coasts》1993,16(3):459-474

Major ion chemistry of water and elemental geochemistry of suspended and surficial sediments collected from the Cauvery Estuary were studied to understand the geochemical processes in this tropical estuarine system. Specific conductance (EC), total dissolved solids (TDS), and total suspended matter (TSM) increased conservatively with increasing chlorinity. In general, SO₄ ^2?, Na, K, Ca, and Mg showed an increasing trend while H₄SiO₄ and PO₄ ^3? showed a decreasing trend toward the sea. Additional removal mechanisms operating for these ions in the Cauvery Estuary have been identified based on observed concentrations. Factor analysis pointed out the sources contributing to the observed trends in estuarine water chemistry. POC and PON decreased toward the high chlorinity zone. TSM in the Cauvery Estuary were mostly of inorganic nature. Stable carbon isotope values showed that the carbon was equally of marine and terrestrial origin and helped to delineate the contribution of river water and seawater. The ? mean size (a logarithmic grain size scale commonly used by sedimentologists) indicated that the surficial sediments were primarily comprised of coarse and silt, whereas suspended sediments were principally silt and clay. Suspended sediments were enriched in clays compared to surficial sediments. Quartz and feldspar were abundant among detritals while chlorite, kaolinite, and montmorillonite were dominant among clays. Silicon was the most abundant element in the sediments followed by Al, Ca, Na, K, Fe, Mn, and P. Heavy metals were enriched in the suspended sediments compared to the surficial bottom sediments as follows: Fe = 3.5, Mn = 7.4, Pb = 1.1, Zn = 15.2, Cu = 7.4, and Cr = 4.0. The levels of Cd, Cr, Zn, and Fe increased up the middle reaches and then decreased toward the sea due to urban effluent and fertilizer input. Size fractionation studies indicated that the metal concentration in the finer fraction was 50% higher by mass than the coarse silt and fine silt fractions. Chemical fractionation studies showed that the abundance of metals were in the order of residual > organic/sulfide > carbonate > Fe/Mn oxide > exchangeable fractions.  相似文献   

Persistent organochlorine residues in green mussels from coastal waters of South India     

A. Ramesh  S. Tanabe  A. N. Subramanian  D. Mohan  V. K. Venugopalan  R. Tatsukawa 《Marine pollution bulletin》1990,21(12):587-590

Green mussels (Perna viridis) collected from nine locations along the South Indian coast were used as bioindicator to assess the organochlorine contamination (HCHs, DDTs, and PCBs) in the coastal environment of South India. Concentrations of ΣHCH and ΣDDT were found to be similar, ranging from 3 to 39 ng g⁻¹ on wet wt basis. On the other hand, PCB levels were apparently lower, varying from <1.0 to 7.1 ng g⁻¹ wet wt. The residue pattern of organochlorines in mussels are principally similar to those in Indian human samples, reported earlier. The coastal marine pollution by HCH in India ranks among the highly contaminated areas in the world.  相似文献   

Coastal geomorphology and sediment distribution mapping using Landsat—TM digital data —A study in Coastal area of parts of Orissa,India     

S. K. Subramanian  K. Keshavasamy  K. Hanumantha Rao  S. K. Bhan 《Journal of the Indian Society of Remote Sensing》1988,16(3):1-6

An area of about 1100 sq.km forming a part of east coast of India was taken for digital analysis using the VAX 11/780 image analysis computer system. The data used for the analysis is Thematic mapper data of Landsat 5. By using the maximum likelihood algorithm and the existing ground truth, the area was classified geomorphologicall.. In addition a qualitative mapping of suspended sediments of coastal waters in Bay of Bengal around the estuary of Dhamra river in Orissa has been carried out. In seventeen classes, eleven correspond to geomorphic units and six belongs to different categories of sediments concentration in Coastal waters.  相似文献