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41.
Levels of organochlorine pesticide residues (p,p′ DDT, DDD, DDE, Aldrin, Dieldrin, Lindane, Heptachlor and BHC) were analysed in the dry and wet seasons in four organs (muscle, liver, gut and egg samples) of Ganges Perch, Lates calcarifer, collected during October–November–December, 1996 and May–June–July, 1997 from the Ganges–Brahmaputtra–Meghna estuary. The residues were analysed by using gas-chromatography (GC) in electron capture detector (ECD) mode and were verified by thin layer chromatography (TLC). Among the four organs analysed, the residues were found in the order egg > gut > muscle > liver. The pesticide residues were found in the order ∑DDT > Heptachlor >Dieldrin > Aldrin. Higher levels of residues were found during the dry season due to high lipid content in fishes. A positive correlation was observed between the pesticide residues (∑DDT and ∑OCs) and lipid contents of fish, and the correlation was found to be linear. The concentrations of pesticide residues in muscle, liver and gut were below the FAO/WHO (1993) recommended permissible limit except in eggs. 相似文献
42.
Variation in growth, physiology and ionic relations patterns of Allenrolfea occidentalis, a perennial halophyte of dry habitats, was studied under field conditions from May 1996 to November 1997. An A. occidentalis community has a characteristic soil pH of 7·3–8·3. During the two years, the population was exposed to great variations in soil salinity, from 29 to 146 dS m−1, and soil moisture, ranging from drought (9·2%) to wet (19%). The salt concentrations were significantly higher in the surface soil layers than in the subsurface layers. Seasonal changes in dry weight are directly related to soil salinity stress. Allenrolfea occidentalis had greater growth and biomass production under saline conditions. Na+and Cl−ions were accumulated in plant tissues in much greater amounts than K+, Ca2+, and Mg2+. Soil salinities were significantly reduced at the end of the growing season. Water potentials of the shoots decreased significantly with increasing salinity. The plant (Fv/Fmratio) was more affected by salinity and irradiation levels during the summer period. 相似文献
43.
Summary The dielectric tensor of a time-varying anisotropic electron-plasma has been studied with the consideration of the effect of collision. The tripple splitting of the electromagnetic waves is obtained from the dispersion relation which gives the two usual magnetoionic modes in the limiting case. The randomness of electron number density has been evaluated by the help of field variables and also by the nature of fluctuation of dielectric tensor. 相似文献
44.
Mohammad Asadullah Khan 《Journal of Geodesy》1973,47(3):227-235
An intrresting variation on the familiar method of determining the earth's equatorial radius ae, from a knowledge of the earth's equatorial gravity is suggested. The value of equatorial radius thus found is 6378,142±5
meters. The associated parameters are GM=3.986005±.000004 × 1020 cm3 sec-−2 which excludes the relative mass of atmosphere ≅10−6 ξ GM, the equatorial gravity γe 978,030.9 milligals (constrained in this solution by the Potsdam Correction of 13.67 milligals as the Potsdam Correction
is more directly, orless indirectly, measurable than the equatorial gravity) and an ellipsoidal flattening of f=1/298.255. 相似文献
45.
46.
Mouradian Z. Soru-Escaut I. Hiei E. McALLISTER A. H. Shibasaki K. Ohyama M. Khan J. I. Uchida Y. 《Solar physics》1998,180(1-2):313-329
The 7 May 1992 filament disappearance in the low corona is analyzed. The cool and hot components of this event are studied, using H, soft X-ray and radio data. We first show the general effect of the disparition brusque (DB) on the life of the filament, which was a quiescent filament in the vicinity of an active region, and then give the history of the development of the 7 May event. The main stages of the event are: (i) the formation of hot arches spanning the cool filament; (ii) rise of the filament, with plasma ejection into the corona, in which we note some spreading of loops from the main body, with two distinct rising velocity phases of the H filament; (iii) formation of X-ray arches below the filament, the foot points of the arcades being two-ribbon H flare patches. The dynamics of H and X-rays features are given. 相似文献
47.
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49.
Macrobenthic faunal composition was studied at six different depth ranges (30–50, 51–75, 76–100, 101–150, 151–175 and >176 m) in five transects (off Karaikkal, Parangipettai, Cuddalore‐SIPCOT, Cheyyur and Chennai) in the continental shelf of southeast coast of India. Eleven diverse taxa were found, comprising 113 species of polychaetes, 14 species of bivalves, 10 species of amphipods and ‘others’ (five tanaids, five crabs, four isopods, three echinoderms, two shrimps, two cnidarians, two fishes and one cephalochordate). Polychaetes were the dominant taxa, constituting 88.5% of the total abundance and 30.7% of the total biomass. The number of species (seven per 0.2 m2 at >176 m depth range in Chennai to 46 per 0.2 m2 at 30–50 m in Cheyyur), abundance (216 per 0.2 m2 at >176 m in Karaikkal to 353 per 0.2 m2 at 30–50 m in Cheyyur) and biomass (0.09 g per 0.2 m2 at 151–175 m in Karaikkal and 4.6 g per 0.2 m2 at 30–50 m in Cheyyur) of macrobenthos decreased with increase in depth. DO decreased gradually from 30 m depth; beyond 150 m, the decrease was pronounced due to the presence of the oxygen minimum zone. Using the distance based linear model (DISTLM), it was found that the environmental variables explained about 73.3% of the total variability in macrofaunal distribution. The heavy metals cobalt and mercury, as well as water pressure (proxy for depth), showed a significant relationship with macrofauna, explaining respectively 9, 7.3 and 7% of the total variability. The contribution of other variables was smaller. 相似文献
50.
Evaluation of the intermediate-term periodicities in solar and cosmic ray activities during cycle 23
In this paper we investigate the presence and temporal evolution of galactic cosmic rays (GCRs) time-series and three solar
parameters, namely the daily sunspot number, the coronal green line and the 10.7 cm solar radio flux over the period 1996–2003
by the wavelet technique. A number of short- and intermediate-term quasi-periodicities were also detected in both GCR and
solar parameters. For the short-term range, we have identified quasi-periods of 16–30 days, 40–55 days, 60–70 days, 80–90 days
and 80–100 days. In the case of intermediate range, the significant periods were 120–140 days, 150–170 days, 190–210 days,
240–260 days, ≈1.09 yr. and ≈1.23 yr. The wavelet power spectra show that all the above-mentioned periods are intermittent
in nature and occurred in different time-series in different intervals. The result exhibits that the well-known “Rieger period”
of (150–160 days) was prominent in both GCR and solar data sets during the ascending phase of cycle 23. Possible reasons behind
the observed periods were discussed with the help of previous results and existing numerical models. 相似文献