The Arecibo Methanol Maser Galactic Plane Survey - III: Distances and Luminosities

We derive kinematic distances to the 86 6.7 GHz methanol masers discovered in the Arecibo Methanol Maser Galactic Plane Survey. The systemic velocities of the sources were derived from 13CO (J=2-1), CS (J=5-4), and NH3 observations made with the ARO Submillimeter Telescope, the APEX telescope, and the Effelsberg 100 m telescope, respectively. Kinematic distance ambiguities were resolved using HI self-absorption with HI data from the VLA Galactic Plane Survey. We observe roughly three times as many sources at the far distance compared to the near distance. The vertical distribution of the sources has a scale height of ~ 30 pc, and is much lower than that of the Galactic thin disk. We use the distances derived in this work to determine the luminosity function of 6.7 GHz maser emission. The luminosity function has a peak at approximately 10^{-6} L_sun. Assuming that this luminosity function applies, the methanol maser population in the Large Magellanic Cloud and M33 is at least 4 and 14 times smaller, respectively, than in our Galaxy.Comment: Accepted by Ap

Prediction of assimilation efficiency of lepidopterans

From 206 values reported for over 60 lepidopteran species, it was found that nitrogen content of food shows a significant (P<0.001) and a positive correlation (r=0.704) to assimilation efficiency with standard error of 10·33. Unlike in aquatic animals, water content of food influences assimilation efficiency in these terrestrial lepidopterans; however, the relation between leaf water and assimilation efficiency is also correlated, but the correlation is lower than that (r=0·529; SE=11·8) obtained for leaf nitrogen. Considering the individual effect of water on assimilation efficiency as well as its covarying relation with nitrogen, leaf water was included as a co-predictor. The inclusion of leaf water as a co-predictor of leaf nitrogen content improves the precision of prediction (r=0·868; SE=9·7). The role of digestive reducing substances (e.g. Tannins) on assimilation efficiency was considered as a second co-predictor. Realising the difficulties of considering the digestive reducing substances as a second co-predictor, and observing the closeness of the observed and predicted values in the present study, nitrogen and water contents of leaf are considered as adequate explanatory variables for the prediction of assimilation efficiency

Rhythms in the biting behaviour of a mosquito Armigeres subalbatus

The biting cycle of Armigeres subalbatus is distinctly crepuscular, exhibiting two peaks of activity, a smaller one at dawn and a larger one at dusk. The biting cycle is entrained to natural light-dark cycles and the time interval from dawn to dawn or dusk to dusk peaks is exactly 24 h and from dawn to dusk or dusk to dawn is about 12 h measured at 50% level. This rhythm manifests itself day after day without any marked qualitative change. The rate of change of light intensity may determine the onset of crepuscular biting. The sudden increase (up to ca. 17 lx) or decrease (down to ca. 4 lx) in the intensity of ambient light at the time of sunrise or sunset coincides with the peak of the biting activity. The density of the population of the host-seeking females fluctuates in relation to the phases of the moon, increasing with the full moon phase and decreasing with the new moon phase. Even though the density of the population is greater outdoors than indoors both at ground levels and in the first floor, the peak of activity occurs at the same time in all the places. A vertical stratification of biting activity was also noticed

Polarity-dependent reversible resistance switching in Ge–Sb–Te phase-change thin films

In this paper, we demonstrate reversible resistance switching in a capacitorlike cell using a Ge–Sb–Te film that does not rely on amorphous-crystalline phase change. The polarity of the applied electric field switches the cell resistance between lower- and higher-resistance states, as was observed in current-voltage characteristics. Moreover, voltage pulses less than 1.25 V showed this switching within time scales of microseconds with more than 40% contrast between the resistance states. The latter are found to be nonvolatile for months. The switching could also be achieved at nanoscales with atomic force microscopy with a better resistance contrast of three orders of magnitude.

Prediction of absorption efficiency from food nitrogen in amphibians

Gravimetric estimation of absorption efficiency in amphibians is a time consuming process and still subject to technical errors. The need for the application of indirect methods requiring no quantitative recovery of feces is indicated. From 41 values reported for 11 amphibian species, it is observed that nitrogen content of food is significantly (P<0·001) and positively correlated (>0·9) with absorption efficiency. From the obtained regression equation (absorption efficiency=49·615+4·596 nitrogen), the per cent efficiency can be predicted with 3·748 standard error

Production and utilization of frogs: an ecological view

The frog producing area in India has been doubled (23–51 million ha) during the last 30 years, while the frog harvest has also been consistently increased by the biology education (3–18 million frogs) and export (17–60 million frogs) sectors. The carrying capacity of the irrigated land is in the range of 28 frogs/ha and a 7% harvest of the population may represent the optimal utilization. Frogs do control agricultural pests but not vectors like mosquitoes. A ban on the frog export from India would mean the loss of not only a revenue of 10 million US dollars/annum but also the jobs for 0–16 million villagers. The need for development of mass culturing techniques of tadpoles, juvenile frogs and ranching of frogs is emphasized

Spectral Energy Distributions of 6.7 GHz methanol masers

The 6.7 GHz maser transition of methanol has been found exclusively towards massive star forming regions. A majority of the masers have been found to lack the presence of any associated radio continuum. This could be due to the maser emission originating prior to the formation of an HII region around the central star, or from the central object being too cool to produce a HII region. One way to distinguish between the two scenarios is to determine and model the spectral energy distributions (SEDs) of the masers. We observed a sample of 20 6.7 GHz methanol masers selected from the blind Arecibo survey, from centimeter to submillimeter wavelengths. We combined our observations with existing data from various Galactic plane surveys to determine SEDs from centimeter to near-infrared wavelengths. We find that 70% of the masers do not have any associated radio continuum, with the rest of the sources being associated with hypercompact and ultracompact HII regions. Modeling the SEDs shows them to be consistent with rapidly accreting massive stars, with accretion rates well above 10^{-3} M_sun/yr. The upper limits on the radio continuum are also consistent with any ionized region being confined close to the stellar surface. This confirms the paradigm of 6.7 GHz methanol masers being signposts of early phases of massive star formation, mostly prior to the formation of a hypercompact HII region.Comment: 15 pages, 4 figures; Accepted by A&

Effect of NaCl on in vitro plant regeneration from embryogenic callus cultures of 'cv IR 64' indica rice (Oryza sativa L.)

In vitro experiments were conducted to assess the effect of salt stress on callus induction, survival, fresh weight, regeneration, proline level and total protein content in salt sensitive indica rice cv. IR 64. For callus induction and regeneration, seeds and calli were subjected to 25, 50, 75 and 100 mM NaCl mediated salt stress which caused significant reduction in proliferation when compared to the control. Gradual reduction in regeneration was observed with increasing salt concentrations (25 to 100 mM). The relative regeneration was maximum at 50 mM. Similarly, a significant increase in proline content (6.5 fold in callus culture and 9.2 fold in the leaves) was observed at 50 mM NaCl after 30 days. However, the adverse effect of salt was more pronounced on total protein content, except at 50 mM. These results suggest that proline accumulation is an index of salinity tolerance and this important international variety can be genetically manipulated to develop salinity tolerant crop.Key words: Abiotic stress, callus proliferation, proline assay, salinity, total protein