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1.
The sub-iron-iron flux ratio in cosmic rays at an atmospheric depth of 9.8 g cm–2 has been estimated using a balloon-borne CR-39 (HCB) stack launched from Alice Springs for 32 hours. The recovered and chemically etched plates were analysed optically and the measured etch pit diameters yielded the sub-iron-iron flux ratio at the flight altitude. The sub-iron-iron flux ratio has been corrected for the top of the atmosphere by considering the loss of heavy ions due to nuclear interaction and fragmentation. The present result has been compared with the result expected from the source composition derived by Protheroeet al. as well as other authors. 相似文献
2.
Solar neutrino in relation to solar activity 总被引:2,自引:0,他引:2
D. Basu 《Solar physics》1992,142(1):205-208
Here we have carried out a power-spectrum analysis of solar nuclear gamma-ray (NGR) flares observed by SMM and HINOTORI satellites. The solar NGR flares show a periodicity of 152 days, confirming the existence of a 152–158 days periodicity in the occurrence of solar activity phenomena and also indicating that the NGR flares are a separate class of solar flares. The power-spectrum analysis of the daily sunspot areas on the Sun for the period 1980–1982 shows a peak around 159 days while sunspot number data do not show any periodicity (Verma and Joshi, 1987). Therefore, only sunspot area data should be treated as an indicator of solar activity and not the daily sunspot number data. 相似文献
3.
D. Basu 《Journal of Astrophysics and Astronomy》2003,24(1-2):11-21
A correlation between redshifts (z) and apparent magnitudes (V) (Hubble relation) of Quasi Stellar Objects (QSOs) has long been sought. Such a correlation exists for galaxies whose redshifts are of cosmological origin. However, a plot of the two quantities representing the Hubble diagram for QSOs exhibits, in general, a wild scatter. This raises the question whether redshifts of QSOs are cosmological. On the other hand, most luminous QSOs in groups, and subsamples with particular properties, have been reported to show the Hubble relation. In the present paper, we analyse all optically non-variable QSOs in a comprehensive sample. In our analysis we grouped the objects into certain intervals of apparent magnitudes. Correlations obtained between redshifts and magnitudes are all statistically robust. Also, the Hubble relation in the usual formV = 5 logz +C is obeyed very convincingly for QSOs withV < 19.5. 相似文献
4.
This article describes the impact of satellite altimeter data on the simulations of sea level variability (SLV) by a nonlinear reduced gravity model of the entire Indian Ocean. The model has been forced by 6-hourly analyzed wind stress data containing SSM/I observations and has been able to produce realistic circulation features. However, SLV values observed by Topex/Poseidon altimeter do not fit these simulations because of imperfect initial data. Hence an attempt has been made to initialize the model using altimeter data. The initialized model-generated SLVvalues have been compared with SLV derived by altimeter for monsoon as well as nonmonsoon months of 1996. Experimental runs have been performed for 10 days, 20 days, and one month. It has been found that the initialized model results on the final day of these experiments are in very good agreement with altimeter data of the same day. It is thus possible, in principle, to hindcast and forecast sea level variations in the time scale of 10 days to one month with the availability of good quality wind data for forcing the model and altimeter observations of sea level for initializing it. 相似文献
5.
Jerome Métral Laurent Charlet Sara Bureau Sukumar Basu Mallik Sudipta Chakraborty Kazi M Ahmed MW Rahman Zhongqi Cheng Alexander van Geen 《Geochemical transactions》2008,9(1):1
Background
The origin of the spatial variability of dissolved As concentrations in shallow aquifers of the Bengal Basin remains poorly understood. To address this, we compare here transects of simultaneously-collected groundwater and aquifer solids perpendicular to the banks of the Hooghly River in Chakdaha, India, and the Old Brahmaputra River in Araihazar, Bangladesh. 相似文献6.
Biswajit Mukhopadhyay Michael J. Holdaway 《Contributions to Mineralogy and Petrology》1994,116(4):462-472
The equilibrium in which hydrous Fe-cordierite breaks down to almandine, sillimanite, quartz, and water was previously experimentally determined by Richardson (1968) and Holdaway and Lee (1977) using QMF buffer and by Weisbrod (1973) using QIF buffer. All these studies yielded similar results — a negative dP/dT slope for the equilibrium curve. However, based on theoretical arguments, Martignole and Sisi (1981), and based on Fe-Mg partitioning experiments on coexisting cordierite and garnet in equilibrium with sillimanite and quartz, Aranovich and Podlesskii (1983) suggested that this equilibrium curve has a positive dP/dT slope and its position depends on the water content of the equilibrium cordierite. We have redetermined this equilibrium using a much improved tecnique of detecting reaction direction, and cordierite starting material that contained virtually no hercynite. Hercynite was present as a contaminant in the cordierites of previous experimental studies and possibly reacted with quartz during the experimental runs to expand the apparent stability field of Fe-cordierite. We synthesized Fe-cordierite from reagent grade oxides at 710°C and 2 kbar (using QMF buffer) with two intermediate stages of grinding and mixing. The cordierite has a unit cell volume of 1574.60 Å3 (molar volume=23.706 J/bar) and no Fe3+ as indicated by X-ray diffraction and room temperature Mössbauer studies respectively. Reaction direction was concluded by noting20% change of the ratios of intensities of two key X-ray diffraction peaks of cordierite and almandine. Our results show that the four-phase equilibrium curve passes through the points 2.1 kbar, 650°C and 2.5 kbar, 750°C. This disagrees with all previous experimental studies. H2O in the Fe-cordierite, equilibrated at 2.2 kbar and 700°C and determined by H-extraction line in the stable isotope laboratory, is 1.13 wt% (n=0.41 moles). H2O content of pure Mg-cordierite equilibrated under identical conditions and determined by thermogravimentric conditions and determined by thermogravimetric analysis is 1.22 wt% (n=0.40). Similar determinations on Fe-cordierite and Mg-cordierite equilibrated at 2.0 kbar and 650°C show 1.27 wt% (n=0.46) and 1.47 wt% (n=0.48) of H2O respectively. Thus, H2O content appears to be independent of Fe/Mg ratio in cordierite, a conclusion which supports previous experimental determinations. The experimentally determined equilibrium curve represents conditions of PH2O=Ptotal. From this we calculated the anhydrous curve representing equilibrium under conditions of X
H2O
V
=0.0. A family of calculated equilibrium curves of constant n
H2O
Cord
cut the experimentally determined curve at a very small angle indicating a slight variation in n
H2O
Cord
in cordierite in equilibrium with almandine, sillimanite, and quartz under the conditions of constant X
H2O
V
. Ancther set of calculated equilibrium curves, each representing constant a
H2O
V
demonstrate that the slopes of the curves vary with X
H2O
V
, and are all positive in the full range of 0.0X
H2O
V
1.0. 相似文献
7.
D. Basu 《Astrophysics and Space Science》1992,191(1):43-48
Absorption features shown by QSOs may be identified and measured as reported absorption redshift systems, or may remain unidentified and not measured. The features are believed to be observed in objects with high emission redshifts (z
em), although no quantitative analysis exists to examine any such preferential trend, except that by Basu (1982). However, redshift data have since increased enormously both in range of the redshift spectrum and in number. Furthermore, the earlier analysis was based on only the reported absorption redshifts while unidentified absorption features were not dealt with. The present paper analyses the updated data, both identified and unidentified features. It is found that absorption features may be expressed as exponential function ofz
em, and upper limits are set for the percentage of QSOs showing absorption features. Finally, an entirely new method of analysis confirms the earlier conclusion of Basu (1982) that the appearance of absorbing clouds is closely associated with the creation of the QSOs, the two may be having a common cause. It is suggested that absorption QSOs may be a separate class of QSOs whose birth is accompanied with creation of absorbing clouds. 相似文献
8.
Helium isotopes have been measured in samples of two ferromanganese crusts (VA13/2 and CD29-2) from the central Pacific Ocean. With the exception of the deepest part of crust CD29-2 the data can be explained by a mixture of implanted solar- and galactic cosmic ray-produced (GCR) He, in extraterrestrial grains, and radiogenic He in wind-borne continental dust grains. 4He concentrations are invariant and require retention of less than 12% of the in situ He produced since crust formation. Loss has occurred by recoil and diffusion. High 4He in CD29-2 samples older than 42 Ma are correlated with phosphatization and can be explained by retention of up to 12% of the in situ-produced 4He. 3He/4He of VA13/2 samples varies from 18.5 to 1852 Ra due almost entirely to variation in the extraterrestrial He contribution. The highest 3He/4He is comparable to the highest values measured in interplanetary dust particles (IDPs) and micrometeorites (MMs). Helium concentrations are orders of magnitude lower than in oceanic sediments reflecting the low trapping efficiency for in-falling terrestrial and extraterrestrial grains of Fe-Mn crusts. The extraterrestrial 3He concentration of the crusts rules out whole, undegassed 4-40 μm diameter IDPs as the host. Instead it requires that the extraterrestrial He inventory is carried by numerous particles with significantly lower He concentrations, and occasional high concentration GCR-He-bearing particles. 相似文献
9.
The damping‐solvent extraction method for the analysis of unbounded visco‐elastic media is evaluated numerically in the frequency domain in order to investigate the influence of the computational parameters—domain size, amount of artificial damping, and mesh density—on the accuracy of results. An analytical estimate of this influence is presented, and specific questions regarding the influence of the parameters on the results are answered using the analytical estimate and numerical results for two classical problems: the rigid strip and rigid disc footings on a visco‐elastic half‐space with constant hysteretic material damping. As the domain size is increased, the results become more accurate only at lower frequencies, but are essentially unaffected at higher frequencies. Choosing the domain size to ensure that the static stiffness is computed accurately leads to an unnecessarily large domain for analysis at higher frequencies. The results improve by increasing artificial damping but at a slower rate as the total (material plus artificial) damping ratio ζt gets closer to 0.866. However, the results do not deteriorate significantly for the larger amounts of artificial damping, suggesting that ζt≈0.6 is appropriate; a larger value is not likely to influence the accuracy of results. Presented results do not support the earlier suggestion that similar accuracy can be achieved by a large bounded domain with small damping or by a small domain with larger damping. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
10.
The Banded Hematite Jasper Formation within the Iron Ore Supergroup of the Singhbhum Craton in eastern India comprises fine alternating layers of jasper and specularite. It was deposited at 3000 Ma and deformed by a mobile episode at 2700 Ma. Hematite pigment (<1 μm) mixed with cryptocrystalline silica and specularite (> 10 μm) is chiefly responsible for red to brown rhythmic bands in the hematite jasper facies although thermomagnetic study also shows that minor amounts (1–2%) of magnetite are present. Palaeomagnetic study identifies a dual polarity remanence resident in hematite (D/I = 283/60°, α95 = 12°) which predates deformation. Studies of the fabric of magnetic susceptibility and rock magnetic results suggest a diagenetic origin for this magnetisation with the hematite formed from oxidation of primary magnetite. The palaeopole (32°E, 24°N, dp/dm = 14/18°) records the earliest post-metamorphic magnetisation event in the Orissa Craton. A minimum apparent polar wander motion of the Orissa-Singhbhum craton of through 80° is identified during Late Archaean times (2900-2600 Ma). 相似文献