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221.
Selection effects are a major source of error in statistical studies of pulsar data since the observed sample is a biased
subset of the full galactic pulsar population. It is important to identify all selection effects and make a reasonable model
before attempting to determine pulsar properties. Here we discuss a hitherto neglected selection effect which is a function
of the periodP of the pulsar. We find that short-P pulsars are more difficult to detect, particularly if their dispersion measures are high. We also discuss a declination-dependent
selection effect in the II Molonglo Survey (II MS), and find some evidence for the existence of both selection effects in
the pulsar data from this survey. We discuss the implications of these additional selection effects for the recently proposed
‘injection’ of pulsars whereby pulsars seem to switch on only at longerP. Using the II MS data we calculate that the observability of pulsars withP between 0.0 s and 0.5 s is about 18 per cent less with the new selection effects than hitherto believed; the mean correction
is 6 per cent forP between 0.5 s and 1.0 s. We conclude that injection is not qualitatively affected by these corrections. 相似文献
222.
Loreta Fernandes Fraddry D’Souza S. G. P. Matondkar Narayan B. Bhosle 《Journal of Earth System Science》2006,115(3):363-370
Amino sugars (AS) are important constituents of organic matter. However, very little is known about their cycling in marine
waters. In this research, we assessed the distribution and cycling of these compounds in waters of the Bay of Bengal. For
this purpose, samples of suspended particu late matter (SPM) were collected from 8 depths (surface to 1000 m) at 6 locations
during the 166th cruise of the ORV Sagar Kanya in the Bay of Bengal in July/August 2001. The SPM samples were analysed for
particulate organic carbon (POC), particulate nitrogen (PN) and AS concentrations and composition. The AS varied between 0.4
and 17.5 nmol/l. Concentrations were high in the surface waters and generally decreased with increasing depth. AS concentration
decreased from the south to north. AS accounted for 0.01 to 0.71% and 0.05 to 2.37% of POC and PN, respectively. Rapid decrease
in AS-C% and AS-N% with depth indicates that these compounds were preferentially degraded relative to bulk POC and PN. The
composition of AS suggests that glucosamine (GLU-N) and galactosamine (GAL-N) were present in the surface SPM samples, and
their abundance decreased from surface downwards. Relatively, low values of GLU-N/GAL-N ratio indicate that the organic matter
was mostly derived from the detritus of micro-organisms. Our data suggest that chitin, a polymer of the glucosamine produced
by many marine organisms was not the major source of AS in the Bay. Rapid cycling of these compounds indicates their importance
in the cycling of nitrogen in marine waters 相似文献
223.
224.
Uday Narayan Ghosh Prasanta Chatterjee Sanjib Kumar Kundu 《Astrophysics and Space Science》2012,339(2):255-260
The head-on collision of dust acoustic solitary waves are studied in a dusty plasma composed of dust and nonextensive distributed
ions by using the extended version of Poincaré-Lighthill-Kuo (PLK) method. The effect of the nonextensivity on the phase shift
is studied. It is found that the presence of nonextensive distributed ions plays a significant role on the collision of dust
acoustic solitary waves. 相似文献
225.
This work investigates the validity of the generalized second law of thermodynamics in modified f(R) Horava–Lifshitz gravity proposed by Chaichian et al. (Class. Quantum Grav. 27: 185021, 2010), which is invariant under foliation-preserving diffeomorphisms. It has been observed that the equation of state parameter behaves like quintessence (w>−1). We study the thermodynamics of the apparent, event and particle horizons in this modified gravity. We observe that under this gravity, the time derivative of total entropy stays at positive level and hence the generalized second law is validated. 相似文献
226.
Uday Narayan Ghosh Deb Kumar Ghosh Prasanta Chatterjee Mustapha Bacha Mouloud Tribeche 《Astrophysics and Space Science》2013,343(1):265-272
The properties of nonplanar (cylindrical and spherical) ion-acoustic solitary waves (IA SWs) in an unmagnetized, collisionless electron-positron-ion (e-p-i) plasma, whose constituents are q-distributed electrons and positrons and inertial ions, are investigated by deriving the modified Gardner (MG) equation. The well known reductive perturbation method is employed to derive the MG equation. The basic features of nonplanar IA Gardner solitons (GSs) are discussed. It is found that the properties of nonplanar IA GSs (rarefactive and compressive) are significantly affected by the particle nonextensivity. 相似文献
227.
Distribution of dissolved carbohydrates and uronic acids in a tropical estuary,India 总被引:2,自引:0,他引:2
Vishwas B. Khodse Narayan B. Bhosle S. G. Prabhu Matondkar 《Journal of Earth System Science》2010,119(4):519-530
Carbohydrates including uronic acids are among the active components of dissolved organic carbon, and play an important role
in biogeochemical cycling of organic carbon in marine environments. In order to understand their distribution, concentrations
of total dissolved carbohydrate (TCHO), dissolved polysaccharide (PCHO), dissolved monosaccharide (MCHO), and dissolved uronic
acid (URA) were measured in the Mandovi estuary, west coast of India during the monsoon and premonsoon seasons. The estuary
experienced nearly fresh water condition during the monsoon season and marine condition during the pre-monsoon season. Concentrations
of TCHO, MCHO and URA ranged from 17.7 to 67.3 μM C, 4.1 to 15.5 μM C and 2.3 to 10.8 μM C, and their contribution to dissolved
organic carbon (DOC) varied from ∼11 to 60%, 2.5 to 9.7%, and 1.8 to 5.3%, respectively. PCHO accounted for ∼52 to 92% of
the TCHO. Generally, concentrations and yields of TCHO species were greater during the monsoon season. Phytoplankton abundance
and bacterial cell numbers influenced the distribution of TCHO in the pre-monsoon season but not during the monsoon season.
Transport of TCHO rich (11 to 60%) dissolved organic matter from the Mandovi estuary to the coastal waters during the monsoon
season may affect ecosystem function by fueling biological activity of heterotrophic micro-organisms. 相似文献
228.
The present investigation attempts to quantify the temporal variation of Solar Flare Index(SFI)with other activity indices during solar cycles 21-24 by using different techniques such as linear regression,correlation,cross-correlation with phase lag-lead,etc.Different Solar Activity Indices(SAI)considered in this present study are Sunspot Number(SSN),10.7 cm Solar Radio Flux(F10.7),Coronal Index(CI)and MgⅡCore-to-Wing Ratio(MgⅡ).The maximum cycle amplitude of SFI and considered SAI has a decreasing trend from solar cycle 22,and cycle 24 is the weakest solar cycle among all other cycles.The SFI with SSN,F10.7,CI and MgⅡshows hysteresis during all cycles except for solar cycle 22 where both paths for ascending and descending phases are intercepting each other,thereby representing a phase reversal.A positive hysteresis circulation exists between SFI and considered SAI during solar cycles 22 and 23,whereas a negative circulation exists in cycles 21 and 24.SFI has a high positive correlation with coefficient values of 0.92,0.94,0.84 and 0.81 for SSN,F10.7,CI and MgⅡrespectively.According to crosscorrelation analysis,SFI has a phase lag with considered SAI during an odd-number solar cycle(solar cycles21 and 23)but no phase lag/lead during an even-numbered solar cycle(solar cycles 22 and 24).However,the entire smoothed monthly average SFI data indicate an in-phase relationship with SSN,F10.7 and MgⅡ,and a one-month phase lag with CI.The presence of those above characteristics strongly confirms the outcomes of different research work with various solar indices and the highest correlation exists between SFI and SSN as well as F10.7 which establishes that SFI may be considered as one of the prime activity indices to interpret the characteristics of the Sun’s active region as well as for more accurate short-range or long-range forecasting of solar events. 相似文献
229.
Different measurements of the Hubble constant(H0)are not consistent,and a tension between the CMB based methods and cosmic distance ladder based methods has been observed.Measurements from various distance based methods are also inconsistent.To aggravate the problem,the same cosmological probe(TypeⅠa SNe for instance)calibrated through different methods also provides different values of H0.We compare various distance ladder based methods through the already available unique data obtained from the Hubble Space Telescope(HST).Our analysis is based on parametric(t-test)as well as non-parametric statistical methods such as the Mann-Whitney U test and Kolmogorov-Smirnov test.Our results show that different methods provide different values of H0 and the differences are statistically significant.The biases in the calibration would not account for these differences as the data have been taken from a single telescope with a common calibration scheme.The unknown physical effects or issues with the empirical relations of distance measurement from different probes could give rise to these differences. 相似文献
230.
Kinwat crystalline inlier exposes Palaeoproterozoic granitoids belonging to the northern extensions of younger phase of Peninsular
gneissic complex (PGC) within Deccan Trap country in Eastern Dharwar Craton (EDC) and bounded in south by a major NW-SE trending
lineament (Kaddam fault). Geochemically, the Kinwat granitoids are similar to high-K, calc-alkaline to shoshonite magnesian
granitoids and subdivided into two major groups, i.e. felsic group (pink and grey granites) and intermediate to felsic group
(hybrid granitoids). The felsic group (∼67–74% SiO2) shares many features with Neoarchaean to Palaeoproterozoic high potassic granites of PGC such as higher LILE and LREE content
and marked depletion in Eu, P and HFSE, especially Nb, Ti, relative to LILE and LREE. The hybrid granitoids (∼58–67% SiO2) have comparatively higher Ca, Mg and Na contents and slightly lower REE content than the granitoids of felsic group. Both,
felsic and hybrid granitoids are metaluminous to weakly peraluminous and belong to highly fractionated I-type suite as evidenced
by negative correlation of SiO2 with MgO, FeOt, CaO, Na2O, Al2O3, whereas K2O, Rb and Ba show sympathetic relationship with SiO2. Moderate to strong fractionated REE patterns (Ce/YbN: ∼54–387) and strong negative Eu anomalies (Eu/Eu*: 0.13–0.41) are quite apparent in these granitoids. The geochemical characteristics
together with mineralogical features such as presence of biotite±hornblende as the dominant ferromagnesian mineral phases
point towards intracrustal magma source, i.e. derivation of magma by partial melting of probably tonalitic igneous protolith
at moderate crustal levels for felsic granites, whereas hybrid granitoids appear to be products of juvenile mantle-crust interaction,
in an active continental margin setting. 相似文献