Three-colour photometry of GH pegasi

The geometrical elements of the system GH Pegasi and a slightly improved period of 2 _. ^d 556136 have been given.     

An analysis of the light changes of the eclipsing binary XY ceti in the frequency-domain

The photoelectric observations of the eclipsing binary XY Ceti presented by us (see Srivastava and Padalia, 1975) have been analysed by Okazaki (1978) and Ramellaet al. (1980). They presented different sets of elements from the same set of our observations. This necessitated us to obtain the elements of XY Ceti again employing recent method of determination of elements.The revised geometrical elements of the eclipsing binary XY Ceti have been obtained by the method of Fourier analysis of the light changes in the frequency-domain, which was developed by Kopal (1979). These have been compared with our earlier (Srivastava and Padalia, 1975) results obtained by employing Russell and Merrill's (1952) method. The revised absolute dimensions of XY Ceti have been obtained using the spectroscopic elements given by Popper (1971), and the newly derived geometrical elements. The Roche radii have been derived to discuss the evolution of the system. The secondary component lies reasonably near to the Main Sequence, while the primary component falls above it. The evolutionary discussion indicates that the system is a detached one.     

An exact similarity solution in radiation magneto-gas-dynamics for the flows behind a spherical shock wave

An exact similarity solution for a spherical magnetogasdynamic shock is obtained in the case when radiation energy, radiation pressure and radiative heat flux are important. The total energy of the shock wave increase with time. We have shown that due to the magnetic field the flow variables are considerably changed. Also, due to increases in radiation pressure number the radiation flux is increased.     

Propagation of exponential shock waves in magnetogasdynamics

Self-similar flows of a perfect gas behind the cylindrical shock wave propagating exponentially in an atmosphere whose density varies inversely as the fourth power of shock radius are investigated. The effects of radiation flux has also been taken into consideration. The total energy of the wave is constant.     

Spectral-luminosity classification,colour variations and suspected beta canis Majoris-type variability in IZ Persei

The colour indices and the spectrum-luminosity classification of the eclipsing binary system IZ Persei have been presented for the first time. The colour indices of the system appear reddened. Applying the interstellar reddening corrections, the spectral-luminosity classes of the primary and the secondary components of IZ Per come out to be B2.5III-V and B5III-V, respectively. The averageB-V andU-B colour excesses come out to be 0 ^m .4 and 0 ^m .2, respectively. The colour indices show continuous variation throughout the cycle, and indicate the presence of intrinsic variability. Tentative analysis suggests that the primary component of IZ Per is a Beta Canis Majoris-type variable. The possibility of a shell has also been discussed.     

CU Eridani — A suspected variable

Photometric observations of CU Eridani, recently classified as non-variable, indicate it to be a variable star.     

Luminescence chronology of incision and channel pattern changes in the River Ganga, India

The River Ganga in the central Gangetic plain shows the incision of 20 m of Late Quaternary sediments that form a vast upland terrace (T₂). The incised Ganga River Valley shows two terraces, namely the river valley (terrace-T₁) and the present-day flood plain (terrace-T₀). Terrace-T₁ shows the presence of meander scars, oxbow lakes, scroll plains, which suggests that a meandering river system prevailed in the past. The present-day river channel flows on terrace-T₀ and is braided, sensu stricto. It is thus inferred that the River Ganga experienced at least two phases of tectonic adjustments: (1) incision and (2) channel metamorphosis from meandering to braided.Optical dating of samples from three different terraces has bracketed the phase of incision to be <6 and 4 ka. Different ages of the top of terrace-T₂ show that this surface experienced differential erosion due to tectonic upwarping in the region, which also caused the river incision. River metamorphosis occurred some time during 4 and 0.5 ka.     

Mycorrhizal Colonization Affects the Survival of Vetiveria zizanioides (L.) Nash Grown in Water Containing As(III)

The presence of arsenic (As) in water is of great public concern. Arsenic exists in three common valence states viz., As(0) metalloid arsenic, As(III) (arsenite) and As(V) (arsenate). Arsenite [As(III)] is the most toxic form among arsenicals which, predominates in anaerobic conditions, generally in flooded soils and in the water with high BOD. Experiments were conducted to investigate the effect of As(III) on the mycorrhization in vetiver (Vetiveria zizanioides (L.) Nash) grass in hydroponics. Studies showed significant alteration in the mycorrhizal colonization in the roots of vetiver exposed to higher concentrations of As(III) starting from 1.0, 2.0, 3.0, 4.0 to 5.0 mg/L prepared in 5% Hoagland nutrient solution without addition of phosphate ions. Considerable reduction in the mycorrhizal intensity (M) was observed in all the treatment sets as compared to the control suggesting a negative impact of the As(III) on the mycorrhizal association. Simultaneously, the study also showed that, As(III) is toxic to the vetiver plants having mycorrhizal association however plants with non‐mycorrhizal (cleansed) roots were found to be able to survive for a longer period exposed to As(III).     

Eclipsing binary UW Bootis

Photometric observations of primary minimum inU, B, andV filters have been discussed. The amplitude of variation in all the three filters is 0 ^m .66. We do not find variations in the period and its revised value is 1^d.0047115.