347 research outputs found
Upper tropospheric circulation and thermal anomalies over central Asia associated with major droughts and floods in India
No full textThe composite upper tropospheric (200 hPa) circulation and thermal anomalies during April to June were examined in respect of seven drought years (1965, 1966, 1968, 1972, 1974, 1979 and 1982), three flood years (1961, 1970 and 1975) and twelve normal years (1962, 1963, 1964, 1967, 1969, 1971, 1973, 1976, 1977, 1978, 1980 and 1981) using the upper air data of 21 stations of 22 years (1961-1982), There were significant differences between the anomalies during drought and flood years. The anomaly patterns during the normal years were similar to those of flood years but the anomalies were weaker. It has found that a cyclonic (anticyclonic) anomalous circulation with cold (warm) temperature developed over central Asia near Caspian sea during April of drought (flood) years. These anomalies persisted and strengthened during the later months. The cold cyclonic anomalous circulation adversely affects monsoon performance due to excess Eurasian snow cover and the large-scale intrusion of dry westerlies into Indian region
Clouds and cloud radiative forcing over tropical Indian Ocean and their relationship with sea surface temperature
No full textEarth radiation budget experiment (ERBE) radiative fluxes and International Satellite Cloud Climatology Project (ISCCP) C-2 cloud parameters for the four representative months of January, April, July and October and for the period 1985-1988 are used to study the cloud-radiation interaction over the tropical Indian Ocean (20° S-20° N, 50° E-100° E), and its relationship with sea surface temperature (SST). Some important results are compared with those over tropical west Pacific Ocean (20° S-20° N, 130° E-180° E). Over Indian Ocean, both the shortwave cloud radiative forcing (SWCRF) and longwave cloud radiative forcing (LWCRF) are found to be correlated most with high cloud amounts (HCA) among the various cloud types. HCA and cloud radiative forcings in turn show a positive relationship with SST above 26.4°C. During July and October, after reaching a maximum value at 29°C, the relationship is found to be negative. In the rising portion of the HCA-SST relationship, at certain SST threshold value (27.4°C for July) the probability of occurrence of high convective clouds suddenly rises above 50. During January and July above this SST threshold value the SWCRF is found to be significantly larger than LWCRF, thus causing large negative net cloud radiative forcing. This is found to be associated with the sudden rise in the spatial extent (cloud amount) and the optical depth of the high clouds above the SST threshold values
High bandwidth interchip communication for regular networks dc by Rajeevan Amirtharajah.
No full textThesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1994.Includes bibliographical references (leaves 48-49).M.Eng
Defect-tolerant N2-transistor structure for reliable nanoelectronic designs
No full textNanodevices based circuit design will be based on the acceptance that a high percentage of devices in the design will be defective. In this work, we investigate a defect tolerant technique that adds redundancy at the transistor level and provides built-in immunity to permanent defects (stuck-open, stuck-short and bridges). The proposed technique is based on replacing each transistor by N2-transistor structure (N≥2) that guarantees defect tolerance of all N-1 defects as validated by theoretical analysis and simulation. As demonstrated by extensive simulation results using ISCAS 85 and 89 benchmark circuits, the investigated technique achieves significantly higher defect tolerance than recently reported nanoelectronics defect-tolerant techniques (even with up to 4 to 5 times more transistor defect probability) and at reduced area overhead. For example, the quadded-transistor structure technique requires nearly half the area of the quadded logic technique
A gene signature for post-infectious chronic fatigue syndrome
No full textBackground: At present, there are no clinically reliable disease markers for chronic fatigue syndrome. DNA chip microarray technology provides a method for examining the differential expression of mRNA from a large number of genes. Our hypothesis was that a gene expression signature, generated by microarray assays, could help identify genes which are dysregulated in patients with post-infectious CFS and so help identify biomarkers for the condition. Methods: Human genome-wide Affymetrix GeneChip arrays (39,000 transcripts derived from 33,000 gene sequences) were used to compare the levels of gene expression in the peripheral blood mononuclear cells of male patients with post-infectious chronic fatigue (n = 8) and male healthy control subjects (n = 7). Results: Patients and healthy subjects differed significantly in the level of expression of 366 genes. Analysis of the differentially expressed genes indicated functional implications in immune modulation, oxidative stress and apoptosis. Prototype biomarkers were identified on the basis of differential levels of gene expression and possible biological significance Conclusion: Differential expression of key genes identified in this study offer an insight into the possible mechanism of chronic fatigue following infection. The representative biomarkers identified in this research appear promising as potential biomarkers for diagnosis and treatment
Winter surface pressure anomalies over Eurasia and Indian summer monsoon
No full textIn this study, the spatial relationships between the monthly mean sea level pressure (MSLP) anomalies and Indian summer monsoon rainfall (ISMR) have been examined using the gridded MSLP data (GMSLP2) for 46 years (1949-1994). Winter MSLP anomalies over NW Europe (south Europe) are negatively (positively) correlated with ISMR. During the strong (deficient) monsoon years, there is enhanced (weakened) poleward pressure gradient over Eurasia. The Europe pressure gradient index, which is an indicator of the winter poleward pressure gradient, is significantly and positively correlated with ISMR. This relationship also suggests a link between the North Atlantic Oscillation and ISMR on inter-annual time scale. The winter pressure gradient over Eurasia has physical linkage with Indian summer monsoon rainfall, through winter snow cover anomalies and springtime mid latitude activities like upper tropospheric blocking highs and stationary wave anomalies
Net Cloud Radiative Forcing at the Top of the Atmosphere in the Asian Monsoon Region
No full textBased on the data from Earth Radiation Budget Experiment (ERBE), many investigators have concluded that the net cloud radiative forcing at the top of the atmosphere is small in the deep convective region of the Tropics. This conclusion has been shown to be invalid for the Asian monsoon region during the period June–September. The ERBE data have been used to show that in the Asian monsoon region the net cloud radiative forcing at the top of the atmosphere is negative and its magnitude exceeds in 25% of the grids in this region. The large negative net cloud radiative forcing in the Asian monsoon region during June–September has been shown to be on account of the presence of large amount of high clouds and the large optical depth of these clouds. This combination of high cloud amount and high optical depth occurs in the Asian monsoon region only. In the other deep convective regions of the Tropics, high clouds with large optical depths are present, but they do not cover a large area
Prediction of Indian summer monsoon: Status, problems and prospects
No full textIn this article, we review the present status and problems and future prospects of long-range forecasts of Indian summer monsoon. Since 1988, the India Meteorological Department has been issuing forecasts based on 16-parameter power regression and parametric models. All these forecasts are proved to be reasonably correct. However, in some years, forecast error was larger than the model error of ± 4. In 2000, four new promising predictors were introduced in the operational models. Using an empirical model with 100 years of data (1901-2000), we show that Indian summer monsoon predictability exhibits epochal variations. During the recent years the model is showing poor forecast skill due to weakened coupling between the boundary forcing and Indian monsoon. In spite of serious efforts by the modelling groups, there are still problems in the dynamical predictions of Indian monsoon. Prediction of Indian monsoon variability is found to be sensitive to the initial conditions, suggesting that chaotic internal dynamics may ultimately limit the predictability of Indian summer monsoon
Prediction of Indian summer monsoon: status, problems and prospects
No full textIn this article, we review the present status and problems and future prospects of long-range forecasts of Indian summer monsoon. Since 1988, the India Meteorological Department has been issuing forecasts based on 16-parameter power regression and parametric models. All these forecasts are proved to be reasonably correct. However, in some years, forecast error was larger than the model error of ± 4%. In 2000, four new promising predictors were introduced in the operational models. Using an empirical model with 100 years of data (1901-2000), we show that Indian summer monsoon predictability exhibits epochal variations. During the recent years the model is showing poor forecast skill due to weakened coupling between the boundary forcing and Indian monsoon. In spite of serious efforts by the modelling groups, there are still problems in the dynamical predictions of Indian monsoon. Prediction of Indian monsoon variability is found to be sensitive to the initial conditions, suggesting that chaotic internal dynamics may ultimately limit the predictability of Indian summer monsoon
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