The surface radiation budget (SRB) project is an important part of the Global Energy and Water Cy... more The surface radiation budget (SRB) project is an important part of the Global Energy and Water Cycle Experiment (GEWEX) under the World Climate Research Program (WCRP). The earlier Version 1.1 of WCRP SRB was a 4-year shortwave dataset. It has since been upgraded, and the new version, Release 2, has a 1-degree latitudinal and longitudinal resolution and covers the period from July 1983 to October 1995. The variables include, among others, all-sky surface shortwave/longwave downward/upward fluxes, cloud fraction, cloud optical depth, aerosol optical depth. The shortwave flux data have been compared with ground-based observations from the Baseline Surface Radiation Network (BSRN), the Global Energy Balance Archive (GEBA), the Climate Monitoring and Diagnostics Laboratory (CMDL), and the monthly mean comparisons show generally good agreement. The Global Precipitation Climatology Project (GPCP) under WCRP is aimed to quantify the spatial and temporal distribution of precipitation on global scale and over many years. Up till present, GPCP has released Version 2 of global monthly precipitation with a 2.5-degree latitudinal and longitudinal resolution and time coverage from January 1979 to May 2003. Preliminary comparisons of these data with ground observations from the Global Daily Climatology Network at selected sites are very encouraging. Earlier we have applied the empirical orthogonal functions (EOFs) to the analysis of the shortwave/longwave radiation and cloud fields. The predominant annual cycles, semi-annual cycles, and distinctive interannual oscillations in synchrony with the El Nino/Southern Oscillations have been identified. In this study, we apply the canonical correlation analysis (CCA) to different pairs of the above variables. Although visual inspection of the above variables and EOFs thereof can detect correlations at various levels, to quantify the correlations of different variables we need to apply CCA, an eigen technique, to the datasets. This analysis will give us insight into the dynamics of the global climate system and contribute to statistical predictions of such parameters as solar energy availability and precipitation for industrial and agricultural purposes.
We present a framework for high-level synthesis that enables the designer to explore the best cho... more We present a framework for high-level synthesis that enables the designer to explore the best choice of source level and low level parallelizing transformations for improved synthesis. Within this framework, we have implemented a methodology that applies a set of parallelizing code transformations, both at the source level and during scheduling. Using these transformations, the designer can optimize high-level synthesis results and reduce the impact of control flow constructs on the quality of results. In our methodology, we first apply a set of source level pre-synthesis transformations that include common sub-expression elimination (CSE), copy propagation, dead code elimination and loop-invariant code motion, along with more coarse level code restructuring transformations such as loop unrolling. We then explore scheduling techniques that use a set of aggressive speculative code motions to maximally parallelize the design by re-ordering, speculating and sometimes even duplicating operations in the design. In particular, we present a new technique called "Dynamic CSE" that dynamically coordinates CSE and code motions such as speculation and conditional speculation during scheduling. We also show how operation chaining across conditional boundaries can be used to optimize control flow. We have built the Spark high-level synthesis framework that takes a behavioral description in ANSI-C as input and generates synthesizable register-transfer level VHDL. Our results from three moderately complex design targets, namely, MPEG-1, MPEG-2 and the GIMP image processing tool validate the utility of our approach to the behavioral synthesis of designs with complex control flows.
An industrial semibatch nylon 6 reactor has been optimized using a one-variable (at a time) searc... more An industrial semibatch nylon 6 reactor has been optimized using a one-variable (at a time) search technique. The vapor release rate from the reactor and the final monomer conversion have been constrained to lie very close to the values currently present. The degree of polymerization of the product is, similarly, constrained to lie at a value of 152.
The monitoring of satellite visible calibration has become an important issue as the data collect... more The monitoring of satellite visible calibration has become an important issue as the data collected from the satellites is used to study climate. Most of the work in this area focuses upon using earth targets in clear-skies. Spectral dependencies of various satellite instruments and surface properties along with atmospheric constituents like aerosols affect these calibrations. Here, we present a methodology that uses the the coldest-brightest pixels from deep tropical convective cirrus anvil clouds. These clouds are ideally suited for this calibration check because they are relatively homogeneous and are dominated by multiple-scattering processes at the optically thick limit. The height of the clouds are such that spectrally dependent atmospheric scattering processing are minimized. The frequency of occurrence and microphysical properties of these clouds may change in time without affecting the cloud reflectivity characteristics. This technique was first developed to verify CERES broadband SW channel calibration. Here, we adapt the method to evaluate its usefulness for AVHRR and geosynchronous observations from the International Satellite Cloud Climatology Project (ISCCP) inter-calibrated data set. The procedure uses a brightness temperature threshold to find the coldest pixels in tropical convective areas. The visible radiances are then binned in terms of solar zenith, satellite viewing and relative azimuth angles. Statistical analysis of the bins provides information regarding the reflectivity of these clouds which are compared to theoretical radiative transfer calculations. Anisotropic models are applied to the bin averaged reflectances to compute albedos. These statistical properties will be computed for multiple months within a time period, to check how the properties change over time. This will provide information regarding ISCCP calibration stability which can be compared to other instrument calibrations such as VIRS and eventually MODIS observations. After accounting for spectral responsivities, these targets may also be used to intercompare instruments and possibly to link new EOS era measurements with past satellite observations relevant to the construction of long-term climatologies. Preliminary results from one month of data show that ratio of mean visible channel albedo to broadband CERES albedo gives 1.08 for combined ISCCP satellites and 1.16 for VIRS. The spread of albedo averages for the solar zenith angle bins between satellites are within the stated ISCCP relative uncertainty of 5%.
ABSTRACT Small, zwitterionic peptides (2-6 residues) are flexible molecules that occur in solutio... more ABSTRACT Small, zwitterionic peptides (2-6 residues) are flexible molecules that occur in solution as an ensemble of conformational forms in dynamic equilibrium. They occur widely in Nature as components of the peptide pool produced by protein hydrolysis. Molecular modelling provides information on the conformations they adopt in aqueous solution. Contrary to expectations, they exist in a limited range of conformational forms that arise from particular combinations of backbone torsions. From the computed energies of the conformers, those with similar conformations can be aggregated and a profile of the conformer population displayed using a 3D pseudo- Ramachandran plot. Several different generic peptide transporters have evolved with complementary substrate specificities in response to these varied conformational forms. Molecular recognition templates (MRTs) define the stereo-electronic features of particular conformations that determine peptide recognition and binding by these transporters. The binding and transport of any peptide correlates with the proportion of its conformers that occur in a particular MRT. Specific conformer binding appears generally to involve little or no ligand rearrangement, which minimises conformational entropy loss. Conformational analysis of peptide analogues, evaluation of their similarities to normal peptides and comparison of their conformer profiles with MRTs, allows estimates of their molecular recognition as putative bioactive ligands for such proteins, this is illustrated for a variety of pseudopeptides, isosteres and conformationally-constrained analogues. For peptide therapeutics, such as -lactam antibiotics, inhibitors of angiotensin-converting enzyme, antiviral and chemotherapeutic agents, this approach can be used to evaluate in silico virtual libraries of drug analogues to estimate their potential for targeted delivery and oral availability.
Ieee Transactions on Computer Aided Design of Integrated Circuits and Systems, Nov 1, 2006
The quality of synthesis results for most high-level synthesis approaches is strongly affected by... more The quality of synthesis results for most high-level synthesis approaches is strongly affected by the choice of control flow (through conditions and loops) in the input description. This leads to a need for high-level and compiler transformations that overcome the effects of programming style on the quality of generated circuits. To address this issue, we have developed a set of speculative code-motion transformations that enable movement of operations through, beyond, and into conditionals with the objective of maximizing performance. We have implemented these code transformations, along with supporting code-motion techniques and variable renaming techniques, in a high-level synthesis research framework called Spark. Spark takes a behavioral description in ANSI-C as input and generates synthesizable register-transfer level VHDL. We present results for experiments on designs derived from three real-life multimedia and image processing applications, namely, the MPEG-1 and -2 and GNU image manipulation program applications. We find that the speculative-code motions lead to reductions between 36% and 59% in the number of states in the finite-state machine (controller complexity) and the cycles on the longest path (performance) compared with the case when only nonspeculative code motions are employed. Also, logic synthesis results show fairly constant critical path lengths (clock period) and a marginal increase in area.
The effect of pause time on VLF spectra radiated by stepped leaders (SLs) of lightning discharge ... more The effect of pause time on VLF spectra radiated by stepped leaders (SLs) of lightning discharge is studied. It is assumed that all the individual leader pulsers are identical in all aspects except that successive pulses occur at different times. Analysis of about 100 atmospheric recordings due to leader pulses reveals that the VLF spectra of SLs are of two types: in one type the spectra show a narrow bandwidth or a tendency to generate harmonics, in the other type the VLF spectra exhibit broad maxima. The experimental results fully support the theory of Arnold and Pierce (1964), according to which the VLF amplitude spectrum of a series of leader pulses will be broad when the mean pause time between successive leader pulses is of the same order as its own standard deviation; if the standard deviation is very small compared to the mean pause time of stepping, the spectrum would have a pronounced maxima at its repetition frequency and its harmonics. No deep nulls are observed in the spectra.
A Fully Automatic Question-Answering System for Intelligent Search in E-Learning Documents PRAVEE... more A Fully Automatic Question-Answering System for Intelligent Search in E-Learning Documents PRAVEEN KUMAR, SHRIKANT KASHYAP, ANKUSH MITTAL, AND SUMIT GUPTA Indian Institute of Technology, India pkmaxuec@ iitr. ernet. in shrikuec@ iitr. ernet. in ankumfec@ iitr. ...
Clinical signs and symptoms that might predict atlantoaxial subluxation were studied prospectivel... more Clinical signs and symptoms that might predict atlantoaxial subluxation were studied prospectively in 135 of 180 children with Down's syndrome aged 6-14 years who form the Hester Adrian Research Centre cohort. Lateral radiographs of the cervical spine were taken in flexed, extended, and neutral positions, and the percentage of abnormalities in each view was 14, 10, and 10%, respectively. Gait was the only significant clinical predictor. The relative risk of having an abnormal neck radiograph with an abnormal gait was 2-91 (95% confidence interval (CI) 1 to 8). The sensitivity was 50% and the specificity 81%. Nineteen children had repeat radiographs to assess the reliability of radiological diagnosis. Six had abnormalities; five of 19 (26%) had an abnormality on the first radiograph, and four of 19 (21%) had an abnormality on a second radiograph, but only three (15%) had an abnormality on both occasions in any view (95% CI 0 to 25).
The dissolution of lameUar precipitates by cell boundary migration has been studied in a Cu-15 wt... more The dissolution of lameUar precipitates by cell boundary migration has been studied in a Cu-15 wt.%In alloy in the temperature range 778-853 K, primarily by optical microscopy. Microstructural observations indicated that the process of dissolution in this alloy is a cellular mode of transformation. By approximating the tip radius at the ~-5 interface as equal to half the width of a 6 lamella, the interface composition during dissolution was determined using the Gibbs-Thomson relation. The boundary diffusivities were calculated using the theories of Tu and Turnbull and of Petermann and Hornbogen modified for dissolution and a formulation applying balance of fluxes at the edge of a receding cell boundary similar to the formulation of Aaronson and Liu for the cellular precipitation reaction. The diffusivity values calculated from the experimental data fall within a range of two orders of magnitude for these theories but in all cases are four to five orders of magnitude higher than the volume diffusivity. For this alloy, there exists a critical temperature at which the driving forces for cellular precipitation and dissolution are equal. The value lies approximately 23 K below the equilibrium solvus temperature. An activation energy in the range 148-159 kJ tool -I for different models has been obtained which agrees well with the Q values reported for cellular precipitation in Cu-In alloys.
We report a colossal resistance drop around insulator–metal transition temperature (TMI) in Sm0.5... more We report a colossal resistance drop around insulator–metal transition temperature (TMI) in Sm0.55Sr0.45MnO3 induced by direct current. Polycrystalline samples of Sm0.55Sr0.45MnO3 were synthesized through solid state reaction method. They have been investigated by X-ray diffraction for phase evaluation, scanning electron microscopy for grain morphology and dc resistivity measurement techniques for resistivity–temperature behavior. The resistivity–temperature behavior has been measured with different biasing currents (1 mA, 2.5 mA, 5 mA, 10 mA and 50 mA). With increasing biasing current, the resistivity of the samples decreased drastically. The change in the resistivity of the samples for bias currents 1 mA and 50 mA at TMI was found to be ∼2560%. This phenomenon of electroresistance is discussed in view of strong interaction between carrier spins and localized spins in Mn ions and percolative mechanism of phase-separation.▶ A colossal resistance drop around insulator-metal transition temperature (TMI) in polycrystalline samples of Sm0.55Sr0.45MnO3 has been observed by applying different direct currents in pulsed mode. ▶ The change in the resistivity of the samples for bias currents 1 mA and 50 mA at TMI was found to be ∼2560%. ▶ The observed phenomenon can be useful for the potential applications of the electroresistance (ER) such as nonvolatile memory elements.
The surface radiation budget (SRB) project is an important part of the Global Energy and Water Cy... more The surface radiation budget (SRB) project is an important part of the Global Energy and Water Cycle Experiment (GEWEX) under the World Climate Research Program (WCRP). The earlier Version 1.1 of WCRP SRB was a 4-year shortwave dataset. It has since been upgraded, and the new version, Release 2, has a 1-degree latitudinal and longitudinal resolution and covers the period from July 1983 to October 1995. The variables include, among others, all-sky surface shortwave/longwave downward/upward fluxes, cloud fraction, cloud optical depth, aerosol optical depth. The shortwave flux data have been compared with ground-based observations from the Baseline Surface Radiation Network (BSRN), the Global Energy Balance Archive (GEBA), the Climate Monitoring and Diagnostics Laboratory (CMDL), and the monthly mean comparisons show generally good agreement. The Global Precipitation Climatology Project (GPCP) under WCRP is aimed to quantify the spatial and temporal distribution of precipitation on global scale and over many years. Up till present, GPCP has released Version 2 of global monthly precipitation with a 2.5-degree latitudinal and longitudinal resolution and time coverage from January 1979 to May 2003. Preliminary comparisons of these data with ground observations from the Global Daily Climatology Network at selected sites are very encouraging. Earlier we have applied the empirical orthogonal functions (EOFs) to the analysis of the shortwave/longwave radiation and cloud fields. The predominant annual cycles, semi-annual cycles, and distinctive interannual oscillations in synchrony with the El Nino/Southern Oscillations have been identified. In this study, we apply the canonical correlation analysis (CCA) to different pairs of the above variables. Although visual inspection of the above variables and EOFs thereof can detect correlations at various levels, to quantify the correlations of different variables we need to apply CCA, an eigen technique, to the datasets. This analysis will give us insight into the dynamics of the global climate system and contribute to statistical predictions of such parameters as solar energy availability and precipitation for industrial and agricultural purposes.
We present a framework for high-level synthesis that enables the designer to explore the best cho... more We present a framework for high-level synthesis that enables the designer to explore the best choice of source level and low level parallelizing transformations for improved synthesis. Within this framework, we have implemented a methodology that applies a set of parallelizing code transformations, both at the source level and during scheduling. Using these transformations, the designer can optimize high-level synthesis results and reduce the impact of control flow constructs on the quality of results. In our methodology, we first apply a set of source level pre-synthesis transformations that include common sub-expression elimination (CSE), copy propagation, dead code elimination and loop-invariant code motion, along with more coarse level code restructuring transformations such as loop unrolling. We then explore scheduling techniques that use a set of aggressive speculative code motions to maximally parallelize the design by re-ordering, speculating and sometimes even duplicating operations in the design. In particular, we present a new technique called "Dynamic CSE" that dynamically coordinates CSE and code motions such as speculation and conditional speculation during scheduling. We also show how operation chaining across conditional boundaries can be used to optimize control flow. We have built the Spark high-level synthesis framework that takes a behavioral description in ANSI-C as input and generates synthesizable register-transfer level VHDL. Our results from three moderately complex design targets, namely, MPEG-1, MPEG-2 and the GIMP image processing tool validate the utility of our approach to the behavioral synthesis of designs with complex control flows.
An industrial semibatch nylon 6 reactor has been optimized using a one-variable (at a time) searc... more An industrial semibatch nylon 6 reactor has been optimized using a one-variable (at a time) search technique. The vapor release rate from the reactor and the final monomer conversion have been constrained to lie very close to the values currently present. The degree of polymerization of the product is, similarly, constrained to lie at a value of 152.
The monitoring of satellite visible calibration has become an important issue as the data collect... more The monitoring of satellite visible calibration has become an important issue as the data collected from the satellites is used to study climate. Most of the work in this area focuses upon using earth targets in clear-skies. Spectral dependencies of various satellite instruments and surface properties along with atmospheric constituents like aerosols affect these calibrations. Here, we present a methodology that uses the the coldest-brightest pixels from deep tropical convective cirrus anvil clouds. These clouds are ideally suited for this calibration check because they are relatively homogeneous and are dominated by multiple-scattering processes at the optically thick limit. The height of the clouds are such that spectrally dependent atmospheric scattering processing are minimized. The frequency of occurrence and microphysical properties of these clouds may change in time without affecting the cloud reflectivity characteristics. This technique was first developed to verify CERES broadband SW channel calibration. Here, we adapt the method to evaluate its usefulness for AVHRR and geosynchronous observations from the International Satellite Cloud Climatology Project (ISCCP) inter-calibrated data set. The procedure uses a brightness temperature threshold to find the coldest pixels in tropical convective areas. The visible radiances are then binned in terms of solar zenith, satellite viewing and relative azimuth angles. Statistical analysis of the bins provides information regarding the reflectivity of these clouds which are compared to theoretical radiative transfer calculations. Anisotropic models are applied to the bin averaged reflectances to compute albedos. These statistical properties will be computed for multiple months within a time period, to check how the properties change over time. This will provide information regarding ISCCP calibration stability which can be compared to other instrument calibrations such as VIRS and eventually MODIS observations. After accounting for spectral responsivities, these targets may also be used to intercompare instruments and possibly to link new EOS era measurements with past satellite observations relevant to the construction of long-term climatologies. Preliminary results from one month of data show that ratio of mean visible channel albedo to broadband CERES albedo gives 1.08 for combined ISCCP satellites and 1.16 for VIRS. The spread of albedo averages for the solar zenith angle bins between satellites are within the stated ISCCP relative uncertainty of 5%.
ABSTRACT Small, zwitterionic peptides (2-6 residues) are flexible molecules that occur in solutio... more ABSTRACT Small, zwitterionic peptides (2-6 residues) are flexible molecules that occur in solution as an ensemble of conformational forms in dynamic equilibrium. They occur widely in Nature as components of the peptide pool produced by protein hydrolysis. Molecular modelling provides information on the conformations they adopt in aqueous solution. Contrary to expectations, they exist in a limited range of conformational forms that arise from particular combinations of backbone torsions. From the computed energies of the conformers, those with similar conformations can be aggregated and a profile of the conformer population displayed using a 3D pseudo- Ramachandran plot. Several different generic peptide transporters have evolved with complementary substrate specificities in response to these varied conformational forms. Molecular recognition templates (MRTs) define the stereo-electronic features of particular conformations that determine peptide recognition and binding by these transporters. The binding and transport of any peptide correlates with the proportion of its conformers that occur in a particular MRT. Specific conformer binding appears generally to involve little or no ligand rearrangement, which minimises conformational entropy loss. Conformational analysis of peptide analogues, evaluation of their similarities to normal peptides and comparison of their conformer profiles with MRTs, allows estimates of their molecular recognition as putative bioactive ligands for such proteins, this is illustrated for a variety of pseudopeptides, isosteres and conformationally-constrained analogues. For peptide therapeutics, such as -lactam antibiotics, inhibitors of angiotensin-converting enzyme, antiviral and chemotherapeutic agents, this approach can be used to evaluate in silico virtual libraries of drug analogues to estimate their potential for targeted delivery and oral availability.
Ieee Transactions on Computer Aided Design of Integrated Circuits and Systems, Nov 1, 2006
The quality of synthesis results for most high-level synthesis approaches is strongly affected by... more The quality of synthesis results for most high-level synthesis approaches is strongly affected by the choice of control flow (through conditions and loops) in the input description. This leads to a need for high-level and compiler transformations that overcome the effects of programming style on the quality of generated circuits. To address this issue, we have developed a set of speculative code-motion transformations that enable movement of operations through, beyond, and into conditionals with the objective of maximizing performance. We have implemented these code transformations, along with supporting code-motion techniques and variable renaming techniques, in a high-level synthesis research framework called Spark. Spark takes a behavioral description in ANSI-C as input and generates synthesizable register-transfer level VHDL. We present results for experiments on designs derived from three real-life multimedia and image processing applications, namely, the MPEG-1 and -2 and GNU image manipulation program applications. We find that the speculative-code motions lead to reductions between 36% and 59% in the number of states in the finite-state machine (controller complexity) and the cycles on the longest path (performance) compared with the case when only nonspeculative code motions are employed. Also, logic synthesis results show fairly constant critical path lengths (clock period) and a marginal increase in area.
The effect of pause time on VLF spectra radiated by stepped leaders (SLs) of lightning discharge ... more The effect of pause time on VLF spectra radiated by stepped leaders (SLs) of lightning discharge is studied. It is assumed that all the individual leader pulsers are identical in all aspects except that successive pulses occur at different times. Analysis of about 100 atmospheric recordings due to leader pulses reveals that the VLF spectra of SLs are of two types: in one type the spectra show a narrow bandwidth or a tendency to generate harmonics, in the other type the VLF spectra exhibit broad maxima. The experimental results fully support the theory of Arnold and Pierce (1964), according to which the VLF amplitude spectrum of a series of leader pulses will be broad when the mean pause time between successive leader pulses is of the same order as its own standard deviation; if the standard deviation is very small compared to the mean pause time of stepping, the spectrum would have a pronounced maxima at its repetition frequency and its harmonics. No deep nulls are observed in the spectra.
A Fully Automatic Question-Answering System for Intelligent Search in E-Learning Documents PRAVEE... more A Fully Automatic Question-Answering System for Intelligent Search in E-Learning Documents PRAVEEN KUMAR, SHRIKANT KASHYAP, ANKUSH MITTAL, AND SUMIT GUPTA Indian Institute of Technology, India pkmaxuec@ iitr. ernet. in shrikuec@ iitr. ernet. in ankumfec@ iitr. ...
Clinical signs and symptoms that might predict atlantoaxial subluxation were studied prospectivel... more Clinical signs and symptoms that might predict atlantoaxial subluxation were studied prospectively in 135 of 180 children with Down's syndrome aged 6-14 years who form the Hester Adrian Research Centre cohort. Lateral radiographs of the cervical spine were taken in flexed, extended, and neutral positions, and the percentage of abnormalities in each view was 14, 10, and 10%, respectively. Gait was the only significant clinical predictor. The relative risk of having an abnormal neck radiograph with an abnormal gait was 2-91 (95% confidence interval (CI) 1 to 8). The sensitivity was 50% and the specificity 81%. Nineteen children had repeat radiographs to assess the reliability of radiological diagnosis. Six had abnormalities; five of 19 (26%) had an abnormality on the first radiograph, and four of 19 (21%) had an abnormality on a second radiograph, but only three (15%) had an abnormality on both occasions in any view (95% CI 0 to 25).
The dissolution of lameUar precipitates by cell boundary migration has been studied in a Cu-15 wt... more The dissolution of lameUar precipitates by cell boundary migration has been studied in a Cu-15 wt.%In alloy in the temperature range 778-853 K, primarily by optical microscopy. Microstructural observations indicated that the process of dissolution in this alloy is a cellular mode of transformation. By approximating the tip radius at the ~-5 interface as equal to half the width of a 6 lamella, the interface composition during dissolution was determined using the Gibbs-Thomson relation. The boundary diffusivities were calculated using the theories of Tu and Turnbull and of Petermann and Hornbogen modified for dissolution and a formulation applying balance of fluxes at the edge of a receding cell boundary similar to the formulation of Aaronson and Liu for the cellular precipitation reaction. The diffusivity values calculated from the experimental data fall within a range of two orders of magnitude for these theories but in all cases are four to five orders of magnitude higher than the volume diffusivity. For this alloy, there exists a critical temperature at which the driving forces for cellular precipitation and dissolution are equal. The value lies approximately 23 K below the equilibrium solvus temperature. An activation energy in the range 148-159 kJ tool -I for different models has been obtained which agrees well with the Q values reported for cellular precipitation in Cu-In alloys.
We report a colossal resistance drop around insulator–metal transition temperature (TMI) in Sm0.5... more We report a colossal resistance drop around insulator–metal transition temperature (TMI) in Sm0.55Sr0.45MnO3 induced by direct current. Polycrystalline samples of Sm0.55Sr0.45MnO3 were synthesized through solid state reaction method. They have been investigated by X-ray diffraction for phase evaluation, scanning electron microscopy for grain morphology and dc resistivity measurement techniques for resistivity–temperature behavior. The resistivity–temperature behavior has been measured with different biasing currents (1 mA, 2.5 mA, 5 mA, 10 mA and 50 mA). With increasing biasing current, the resistivity of the samples decreased drastically. The change in the resistivity of the samples for bias currents 1 mA and 50 mA at TMI was found to be ∼2560%. This phenomenon of electroresistance is discussed in view of strong interaction between carrier spins and localized spins in Mn ions and percolative mechanism of phase-separation.▶ A colossal resistance drop around insulator-metal transition temperature (TMI) in polycrystalline samples of Sm0.55Sr0.45MnO3 has been observed by applying different direct currents in pulsed mode. ▶ The change in the resistivity of the samples for bias currents 1 mA and 50 mA at TMI was found to be ∼2560%. ▶ The observed phenomenon can be useful for the potential applications of the electroresistance (ER) such as nonvolatile memory elements.
American Journal of Respiratory and Critical Care Medicine, Sep 15, 2013
The relationship between airway inflammation and obesity in severe asthma is poorly understood. W... more The relationship between airway inflammation and obesity in severe asthma is poorly understood. We sought to determine the relationship between sputum mediator profiles and the distribution of eosinophilic inflammation and obesity in people with severe asthma. Clinical parameters and eight mediators in sputum were assessed in 131 subjects with severe asthma from a single center categorized into lean, overweight, and obese groups defined by their body mass index. In an independent group of people with severe asthma (n = 45) and healthy control subjects (n = 19) eosinophilic inflammation was enumerated in bronchial submucosa, blood, and sputum and related to their body mass index. Sputum IL-5 geometric mean (95% confidence interval) (pg/ml) was elevated in the obese (1.8 [1.2-2.6]) compared with overweight (1.1 [0.8-1.3]; P = 0.025) and lean (0.9 [0.6-1.2]; P = 0.018) subjects with asthma and was correlated with body mass index (r = 0.29; P < 0.001). There was no relationship among body mass index, the sputum cell count, or other sputum mediators. In the bronchoscopy group the submucosal eosinophil number in the subjects with asthma was correlated with body mass index (Spearman rank correlation, rs = 0.38; P = 0.013) and the median (interquartile range) number of submucosal eosinophils was increased in obese (19.4 [11.8-31.2]) (cells per square millimeter) versus lean subjects (8.2 [5.4-14.6]) (P = 0.006). There was no significant association between sputum or peripheral blood eosinophil counts and body mass index. Sputum IL-5 and submucosal eosinophils, but not sputum eosinophils, are elevated in obese people with severe asthma. Whether specific antieosinophilic therapy is beneficial, or improved diet and lifestyle in obese asthma has antiinflammatory effects beyond weight reduction, requires further study.
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