25 research outputs found
Bianchi Type-II String Cosmological Models in Normal Gauge for Lyra's Manifold with Constant Deceleration Parameter
Full text linkThe present study deals with a spatially homogeneous and anisotropic
Bianchi-II cosmological models representing massive strings in normal gauge for
Lyra's manifold by applying the variation law for generalized Hubble's
parameter that yields a constant value of deceleration parameter. The variation
law for Hubble's parameter generates two types of solutions for the average
scale factor, one is of power-law type and other is of the exponential form.
Using these two forms, Einstein's modified field equations are solved
separately that correspond to expanding singular and non-singular models of the
universe respectively. The energy-momentum tensor for such string as formulated
by Letelier (1983) is used to construct massive string cosmological models for
which we assume that the expansion () in the model is proportional to
the component of the shear tensor . This
condition leads to , where A, B and C are the metric coefficients
and m is proportionality constant. Our models are in accelerating phase which
is consistent to the recent observations. It has been found that the
displacement vector behaves like cosmological term in the
normal gauge treatment and the solutions are consistent with recent
observations of SNe Ia. It has been found that massive strings dominate in the
decelerating universe whereas strings dominate in the accelerating universe.
Some physical and geometric behaviour of these models are also discussed.Comment: 24 pages, 10 figure
Assessing Aphid Infestation in Indian Mustard (Brassica juncea L.) under Present and Future Climate Scenarios
Full text linkMustard (Brassica juncea L.) production in India suffers from aphid, Lipaphis erysimi (Kaltenbach), infestation considerably. Role of weather on the incidence and development of mustard aphids was assessed from experimental data from six north Indian locations. Aphid appearance and population build up was found to be regulated by temperature and time to attain peak population was relatively short in warm humid climates than in cool climates. Aphids appeared generally when the accumulated thermal time ranged between 810-847 and diurnal temperature range had a key role on the pest build up. Functional relations developed from the present study between aphid incidence and peak population using previous weeks weather and pest data for majority of the locations could be used for taking of any prophylactic/control measures. Projections on aphid population in future climates using generated weather variables indicated that warming may not increase aphid population at all locations uniformly. DOI: http://dx.doi.org/10.3329/bjar.v38i3.16924 Bangladesh J. Agril. Res. 38(3): 373-387, September 2013</jats:p
Trend analysis of climatic variables in Pigeonpea growing regions in India
No full textTrend analysis of the climate variables at different locations (Kanpur, Hyderabad, Bangalore, Pusa, Pantnagar, Parbhani, Varanasi and Pune) in India were studied. These locations are very important for growing of pulses especially pigeonpea. Trend in these locations were analyzed for the maximum temperature (MaxT), minimum temperature (MinT), rainfall (RF) and bright sunshine hours (BSH) on seasonal (summer, kharif or rainy season and rabi or post-rainy season), monthly (January to December), and weekly (1-52 standard meteorological week) time scales for the period 1970-2010. Significant trends were identified using the Mann-Kendall test and the Sen’s slope estimator. Maximum and minimum temperature series showed a rising trend at most of the stations. Some stations located in the north and northeastern India showed a falling trend in temperature. At most of the stations in the south, central and western parts of India a rising trend was found in various climatic variables except rainfall. Most of the data used in trend analysis pertained to the stations located in urban areas considered as heat islands.</jats:p
Not Available
No full textNot AvailableChanges in climate and weather could profoundly affect the population dynamics and status of insect pests of
crops. Aphids are ubiquitous insect herbivores whose behavior could be influenced by climate change. We
studied the impact of elevated CO2 (eCO2) on Aphis craccivora Koch on cowpea (Vigna unguiculata L.).
Cowpea plants were grown under ambient (380 ppm) and elevated (550 and 700 ppm) CO2 conditions in open
top chambers (OTCs). Feeding trials were conducted using ‘cut leaf’ technique and the aphids were cultured
individually in the laboratory. Results showed that the host plant and aphid species were significantly and
positively influenced by eCO2. The mean fecundity (number of nymphs per day, 80%), Mean relative growth
rate (MRGR, 8%) and adult weight (22%) of aphids increased but the longevity (5 %) and development time
(5%) decreased significantly at eCO2 conditions over ambient CO2. Bio chemical analysis of cowpea foliage
indicated an increased C:N ratio (8%) and decreased nitrogen content (7%) and non-significant variation of
carbon and phenol content at eCO2 conditions.Not Availabl
Possible future climate for rice growing regions in India: Visualising 2050 and pest-related impact thereof
No full textChanges in climatic variables may affect phenological phases of crops and affect plant growth and development, these changes also lead to emergence of new pests and diseases. Therefore, there is need to relate the trends of climatic parameters with rice productivity vis-á-vis the pest dynamics in the crop at different sites apart from projecting a future scenario for the crop in the country. For this long-term seasonal, monthly and weekly trends in climatic data, viz. temperature (maximum and minimum), relative humidity (morning and afternoon), rainfall and bright sunshine hours on seasonal (kharif or rainy season, rabi or post-rainy season and summer), monthly (January to December) and weekly (1-52 standard meteorological week or SMW) time scales for the period 1970–2010 at 14 different agroclimatic centers situated in rice growing regions of India were investigated. Mann–Kendall and Sen’s slope estimator, non-parametric test were used for studying the magnitute as well as statistical significance of trend in climatic data. Trend analyses of the climatic variables in rice growing regions of different locations (Palampur, Chiplima, Jagdalpur, Kaul, Cuttack, Kanpur, Hyderabad, Bengaluru, Samastipur, Pantnagar, Parbhani, Varanasi, Pune and Coimbatore) in India were studied. Positive trend for maximum temperature [for kharif season varied from 0.006°C/yr (Pune) to 0.045°C/yr (Chiplima)] were observed at five locations, negative trends [maximum for Jagdalpur (0.047°C/yr) and minimum for Bengaluru (0.011°C / yr)] were observed at eight locations while one location showed no change in maximum temperature. Minimum temperature showed increasing trend at most of the locations in kharif seasons. Relative humidity in the morning and afternoon also showed increasing trend at most of the locations in kharif. Increase in rainfall for kharif season varied from 8.990 mm/yr (Chiplima) to 0.008 mm/yr (Parbhani); the decrease was highest for Jagdalpur (5.329 mm/yr) followed by Coimbatore (4.485 mm/yr) and least for Varanasi (0.213 mm/yr). Positive and negative trends for total rainfall were observed at seven locations each. In kharif season (23-39 SMW), weekly maximum temperature showed a rising trend except at Cuttack, Kaul, Bengaluru, Pantnagar, Parbhani and Coimbatore while minimum temperature showed the increasing trend except at Palampur, Kanpur and Parbhani. Rainfall pattern showed a falling trend except at Cuttack, Hyderabad, Chiplima, Pune and Coimbatore. Monthly analysis of maximum temperature indicates that the trends are increasing in months of February, March, April, July, August and November while the trends are decreasing in months of January, May, June, September, October and December at most of the locations. Mimimum temperature showed an increasing trend in all months except January. Rainfall showed negative trends in monthly total rainfall during June-September. In June, seven locations showed negative trends which varied from 0.246 mm/yr (Kanpur) to 3.703 mm/yr (Jagdalpur); in July, 10 locations indicated negative trends that varied from 0.231 mm/yr (Samastipur) to 2.144 mm/yr (Chiplima); in August and September eight locations had negative trends. Coimbatore showed negative trends in monthly rainfall from May to December, the decrease was highest for November (4.854 mm/yr) and least in June (0.246 mm/yr). Based on these trends in climatic variables, monthly projected mean and seasonal change till 2050 were also obtained. The changes in climatic variable can be utilised for identification of the hotspot zones of important pest of rice based on the physiological aspect of pest. These changes may lead to possible rise in blast disease of rice at Kaul, Hyderabad and Pune. There looks a possible trend in reduction of the yellow stem borer insect-pest on rice crop in Central and Peninsular India with rise in the Northern latitudes of the country. There is need to relate the trends of climatic parameters with rice productivity vis-á-vis the pest dynamics in the crop at different sites apart from projecting a future scenario for the crop in the country.</jats:p
Possible future climate for rice growing regions of India: Visualising 2050 and pest-related impact thereof.
Get PDFChanges in climatic variables may affect phenological phases of crops and affect plant growth and development,
these changes also lead to emergence of new pests and diseases. Therefore, there is need to relate the trends of climatic
parameters with rice productivity vis-á-vis the pest dynamics in the crop at different sites apart from projecting a
future scenario for the crop in the country. For this long-term seasonal, monthly and weekly trends in climatic data,
viz. temperature (maximum and minimum), relative humidity (morning and afternoon), rainfall and bright sunshine
hours on seasonal (kharif or rainy season, rabi or post-rainy season and summer), monthly (January to December)
and weekly (1-52 standard meteorological week or SMW) time scales for the period 1970–2010 at 14 different agroclimatic
centers situated in rice growing regions of India were investigated. Mann–Kendall and Sen’s slope estimator,
non-parametric test were used for studying the magnitute as well as statistical significance of trend in climatic data.
Trend analyses of the climatic variables in rice growing regions of different locations (Palampur, Chiplima, Jagdalpur,
Kaul, Cuttack, Kanpur, Hyderabad, Bengaluru, Samastipur, Pantnagar, Parbhani, Varanasi, Pune and Coimbatore)
in India were studied. Positive trend for maximum temperature [for kharif season varied from 0.006°C/yr (Pune) to
0.045°C/yr (Chiplima)] were observed at five locations, negative trends [maximum for Jagdalpur (0.047°C/yr) and
minimum for Bengaluru (0.011°C / yr)] were observed at eight locations while one location showed no change in
maximum temperature. Minimum temperature showed increasing trend at most of the locations in kharif seasons.
Relative humidity in the morning and afternoon also showed increasing trend at most of the locations in kharif. Increase
in rainfall for kharif season varied from 8.990 mm/yr (Chiplima) to 0.008 mm/yr (Parbhani); the decrease was highest
for Jagdalpur (5.329 mm/yr) followed by Coimbatore (4.485 mm/yr) and least for Varanasi (0.213 mm/yr). Positive
and negative trends for total rainfall were observed at seven locations each. In kharif season (23-39 SMW), weekly
maximum temperature showed a rising trend except at Cuttack, Kaul, Bengaluru, Pantnagar, Parbhani and Coimbatore
while minimum temperature showed the increasing trend except at Palampur, Kanpur and Parbhani. Rainfall pattern
showed a falling trend except at Cuttack, Hyderabad, Chiplima, Pune and Coimbatore. Monthly analysis of maximum
temperature indicates that the trends are increasing in months of February, March, April, July, August and November
while the trends are decreasing in months of January, May, June, September, October and December at most of the
locations. Mimimum temperature showed an increasing trend in all months except January. Rainfall showed negative
trends in monthly total rainfall during June-September. In June, seven locations showed negative trends which varied
from 0.246 mm/yr (Kanpur) to 3.703 mm/yr (Jagdalpur); in July, 10 locations indicated negative trends that varied
from 0.231 mm/yr (Samastipur) to 2.144 mm/yr (Chiplima); in August and September eight locations had negative
trends. Coimbatore showed negative trends in monthly rainfall from May to December, the decrease was highest
for November (4.854 mm/yr) and least in June (0.246 mm/yr). Based on these trends in climatic variables, monthly
projected mean and seasonal change till 2050 were also obtained. The changes in climatic variable can be utilised for
identification of the hotspot zones of important pest of rice based on the physiological aspect of pest. These changes
may lead to possible rise in blast disease of rice at Kaul, Hyderabad and Pune. There looks a possible trend in reduction
of the yellow stem borer insect-pest on rice crop in Central and Peninsular India with rise in the Northern latitudes of
the country. There is need to relate the trends of climatic parameters with rice productivity vis-á-vis the pest dynamics
in the crop at different sites apart from projecting a future scenario for the crop in the country.
Key words: Climate variability, Mann–Kendall test
