Dark and Dairy

notes: Extended version with footnotes available here: http://www.rajesh.io/street-metaphysics/?tag=Dharmapolispublication-status: PublishedCopyright © 2014 The HinduNewspaper - Opinio

A study of the seasonal changes in the dissolved oxygen of the surface waters of the sea on the Malabar Coast

There is wide recognition at the present day of the importance of hydrographical investigations, particularly in association with biological studies of the marine environment. A knowledge of the physics and chemistry of sea-water is essential for a scientific approach to the fundamental problem of organic production in the sea and, in certain instances, greatly helps in the solution of specific problems connected with fisheries. Investigations on the distribution and seasonal variations of temperature, salinity, dissolved oxygen, pH and of various inorganic compounds of phosphorus, nitrogen and silicon, —usually referred to as " nutrient salts,"—have been carried out in many countries abroad largely in temperate latitudes (Harvey, 1945). Work in tropical waters has not been on the same scale and most of it is of recent date. Studies carried out in India and Australia would be found in the publications of Sewell (1925-32), Orr (1933), Dakin and Colefax (1935), Thompson and Gilson (1937), Bal et al., (1951), Chidambaram et al. (1951, 1954), Jayaraman (1951, 1954), Prasad (1952) and Ramamurthy (1953, 1953 a). In regard particularly to dissolved oxygen, mention may be made of the attempts of Cooper (1933) and others to derive an index of organic productivity of an area from values of oxygen production and consumption. " In nature, the oxygen accumulates in the layers of organic production and thus its fluctuations in time and space give a measure of the intensity of phytoplankton outbursts. It can provide only minimal values because the exact quantity of oyxgen produced is obscured by the respiratory activity of animals and bacteria, and in case of surface supersaturation some oxygen is given off" to the atmosphere" (Sverdrup et al, 1942, p. 934). The above quotation makes evident the usefulness of oxygen values when they are available in required detail. A simple series of values derived from analysis of surface samples such as is presented below, has interest from another angle revealing as it does the broad features of the changes in composition of the sea-water from season to season and year to year

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Search for optical bursts from the gamma ray burst source GBS 0526-66

Attempts were made to detect optical bursts from the gamma-ray burst source GBS 0526-66 during Dec. 31, 1984 to Jan. 2, 1985 and Feb. 23 to Feb. 24, 1985, using the one meter reflector of the Kavalur Observatory. Jan. 1, 1985 coincided with the zero phase of the predicted 164 day period of burst activity from the source (Rothschild and Lingenfelter, 1984). A new optical burst photon counting system with adjustable trigger threshold was used in parallel with a high speed photometer for the observations. The best time resolution was 1 ms and maximum count rate capability was 255,000 counts s(-1). Details of the instrumentation and observational results are presented

Facility location on terrains

Given a terrain defined as a piecewise-linear function with n triangles, and m point sites on it, we would like to identify the location on the terrain that minimizes the maximum distance to the sites. The distance is measured as the length of the Euclidean shortest path along the terrain. To simplify the problem somewhat, we extend the terrain to (the surface of) a polyhedron. To compute the optimum placement, we compute the furthest-site Voronoi diagram of the sites on the polyhedron. The diagram has maximum combinatorial complexity Q(mn2), and the algorithm runs in O(mn² log²m log n) time

Detection of a Series of X-ray Dips Associated with a Radio Flare in GRS 1915+105

We report the detection of a series of X-ray dips in the Galactic black hole candidate GRS 1915+105 during 1999 June 6-17 from observations carried out with the Pointed Proportional Counters of the Indian X-ray Astronomy Experiment on board the Indian satellite IRS-P3. The observations were made after the source made a transition from a steady low-hard state to a chaotic state which occuered within a few hours. Dips of about 20-160 seconds duration are observed on most of the days. The X-ray emission outside the dips shows a QPO at ~ 4 Hz which has characteristics similar to the ubiquitous 0.5 - 10 Hz QPO seen during the low-hard state of the source. During the onset of dips this QPO is absent and also the energy spectrum is soft and the variability is low compared to the non-dip periods. These features gradually re-appear as the dip recovers. The onset of the occurrence of a large number of such dips followed the start of a huge radio flare of strength 0.48 Jy (at 2.25 GHz). We interpret these dips as the cause for mass ejection due to the evacuation of matter from an accretion disk around the black hole. We propose that a super-position of a large number of such dip events produces a huge radio jet in GRS 1915+105.Comment: 18 pages, 7 figures, Accepted for publication in Ap

Observation of X-ray transient XTE J1748-288 by the Indian X-ray astronomy experiment

The observations of a newly discovered X-ray transient source XTE J1748-288 were made in the energy band 2 - 18 keV with the Indian X-ray Astronomy Experiment(IXAE) on the IRS-P3 satellite during 1998, June 14-25. The source count rate declined gradually with an exponential decay time of 19 ± 1.6 days. The X-ray light curves showed no significant intensity variations on short time scales (≤ 10s). The power density spectrum obtained from timing analysis of the data shows no quasi-periodic oscillations in the frequency range of 0.002 Hz to 5 Hz. From the observed X-ray and radio characteristics, it is suggested that the X-ray source in XTE J1748-288 is more likely to be a black hole rather than a neutron star

Different types of X-ray bursts from GRS 1915+105 and their origin

We report the X-ray observations of the Galactic X-ray transient source GRS 1915+105 with the PPCs of the Indian X-ray Astronomy Experiment(IXAE) onboard the Indian satellite IRS-P3 during 1997 June - August, which have revealed the presence of four types of intense X-ray bursts. All the observed bursts have a slow exponential rise, a sharp linear decay, and they can broadly be put in two classes: irregular and quasi-regular bursts in one class, and regular bursts in another class. The regular bursts are found to have two distinct time scales and they persist over extended durations. There is a strong correlation between the preceding quiescent time and the burst duration for the quasi-regular and irregular bursts. No such correlation is found for the regular bursts. The ratio of average flux during the burst time to the average flux during the quiescent phase is high and variable for the quasi- regular and irregular bursts while it is low and constant for the regular bursts. We suggest that the peculiar bursts that we have seen are charact- eristic of the change of state of the source. The source can switch back and forth between the low-hard state and the high-soft state near critical accretion rates in a very short time scale. A test of the model is presented using the publicly available 13-60 keV RXTE/PCA data for irregular and regular bursts concurrent with our observations.Comment: 13 pages, 12 figures, Accepted in APJ, emulateapj style use

IXAE observations of the X-ray pulsar XTE J1946+274

We report results from two observations of the transient binary X-ray pulsar XTE J1946+274 with the Indian X-ray Astronomy Experiment (IXAE) made in September 18-30 1999 and June 28-July 7 2000. The pulsar has a ~80 days orbital period during which the X-ray intensity varies almost sinusoidally between intensity levels of 5 and 50 mCrab. The mid-time of the two observations with the IXAE are separated by an orbital phase of 0.56 and were in the decaying and rising parts of its orbital modulation, respectively. During both the observations, strong pulsations with 15.8 s period are detected in the 2-6 and 6-18 keV energy bands of IXAE. The pulse profiles in both the observations are double peaked and identical with a similar pulse fractions of ~30% in the two energy bands. The pulse periods and its local derivatives are obtained from the IXAE observations. The known pulse period history shows small deviations from an otherwise nearly constant spin-up trend of the pulsar since its discovery. If the measured local period derivatives are a sum of a nearly constant spin-up of the pulsar and effect of its orbital motion, it suggests that the orbit of this Be X-ray binary is eccentric. The RXTE-ASM light curve shows a continuous detection of 10 orbital modulation of the source since its discovery

X-ray observation of XTE J2012+381 during the 1998 outburst

The outburst of X-ray transient source XTE J2012+381 was detected by the RXTE All-Sky Monitor on 1998 May 24th. Following the outburst, X-ray observations of the source were made in the 2–18 keV energy band with the Pointed Proportional Counters of the Indian X-ray Astronomy Experiment (IXAE) on-board the Indian satellite IRS-P3 during 1998 June 2nd–10th. The X-ray flux of the source in the main outburst decreased exponentially during the period of observation. No large amplitude short-term variability in the intensity is detected from the source. The power density spectrum obtained from the timing analysis of the data shows no indication of any quasi-periodic oscillations in 0.002–0.5 Hz band. The hardness ratio i.e. the ratio of counts in 6–18 keV to 2–6 keV band, indicates that the X-ray spectrum is soft with spectral index >2. From the similarities of the X-ray properties with those of other black hole transients, we conclude that the X-ray transient XTE J2012+381 is likely to be a black hole