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R K Saini

Publications and source records attributed to R K Saini.

At least 19 recordsLinked to original sources
PubMed2003

Thermoelectric power of p-doped single-wall carbon nanotubes and the role of phonon drag.

We measured thermoelectric power S of bulk single-wall carbon nanotube materials p doped with acids. In contrast to oxygen-exposed or degassed samples, S is very small at the lowest temperatures, increases superlinearly above a characteristic and sample-dependent T, and then levels off. We attribute this unusual behavior to 1D phonon drag, in which the depression of the Fermi energy cuts off electron-phonon scattering at temperatures below a characteristic T0. This idea is supported by a model calculation in which the low temperature behavior of phonon drag is specifically related to the one-dimensional character of the electronic spectrum.

Journal Article↗
PubMed2001

Formation, isolation, spectroscopic properties, and calculated properties of some isomers of C(60)H(36).

Isomers of C(60)H(36) and He@C(60)H(36) have been synthesized by the Birch or dihydroanthracene reduction of C(60) and isolated by preparative high-pressure liquid chromatography. (3)He, (13)C, and (1)H NMR spectroscopic properties were then determined. A comparison of experimental chemical shifts against those computed using density functional theory (B3LYP) with polarized triple- and double-zeta basis sets for He and C,H, respectively, allowed provisional assignment of structure for several isomers to be made. Theoretical calculations have also been carried out to identify low-energy structures. The transfer hydrogenation method using dihydroanthracene gives a major C(60)H(36) isomer and a minor C(60)H(36) isomer with C(3) symmetry as determined by the (13)C NMR spectrum of C(60)H(36) and the (3)He NMR spectrum of the corresponding sample of (3)He@C(60)H(36). In view of the HPLC retention times and the (3)He chemical shifts observed for the Birch and dihydroanthracene reduction products, the two isomers generated by the latter procedure can be only minor isomers of the Birch reduction. A significant energy barrier apparently exists in the dihydroanthracene reduction of C(60) for the conversion of the C(3) and C(1) symmetry isomers of C(60)H(36) to the T symmetry isomer previously predicted by many calculations to be among the most stable C(60)H(36) isomers. Many of the (1)H NMR signals exhibited by C(60)H(36) (and C(60)H(18), previously reported) are unusually deshielded compared to "ordinary" organic compounds, presumably because the unusual structures of C(60)H(36) and C(60)H(18) result in chemical shift tensors with one or more unusual principal values. Calculations clearly show a relationship between exceptionally deshielded protons beta to a benzene ring in C(60)H(18) and C(60)H(36) and relatively long C-C bonds associated with these protons. The additional information obtained from 1D and 2D (1)H NMR spectra obtained at ultrahigh field strengths (up to 900 MHz) will serve as a critical test of chemical shifts to be obtained from future calculations on different C(60)H(36) isomers.

Journal Article↗
PubMed2001

Reactions of cycloproparenes with metal carbenes.

[figure: see text] Benzocyclopropene and cyclopropa[b]naphthalene react with dichloro-bis(tricyclohexylphosphine)methylideneruthenium, incorporating the metallacarbene to form unstable 3-ruthenacyclopentenes, which decompose to give o-xylylenes that can be trapped as Diels-Alder adducts by dimethyl acetylenedicarboxylate. In contrast, bis(eta 5-cyclopentadienyl)methylidenetitanium forms moderately stable 2- and 3-titanacyclopentene complexes.

Journal Article↗
PubMed2000

Behaviour of Glossina morsitans morsitans Westwood (Diptera: Glossinidae) on waterbuck Kobus defassa Ruppel and feeding membranes smeared with waterbuck sebum indicates the presence of allomones.

The behavioural responses of caged individual teneral Glossina morsitans morsitans on waterbuck and ox and on feeding membranes with and without smears of different doses of waterbuck sebum were compared. No significant difference was found in the initial landing behaviour on the two animals, nor on treated and control parts of the membrane. However, the subsequent behaviours of the flies were significantly different. Whereas none of the flies that landed on the ox showed any escape behaviour, more than a third of those that initially landed on waterbuck departed before probing. Similar results were obtained on feeding membranes treated in part with 1.0 or 1.4 mg cm(-2) of waterbuck sebum. Moreover, flies that landed on waterbuck or its sebum changed probing sites more often and probed significantly longer. The proportions that initiated feeding during the 10 min observation period were also significantly less. Our results suggest the presence of both volatile and non-volatile allomones on waterbuck which would account for low numbers of flies found attracted to and feeding on waterbuck in the wild.

Animals↗
PubMed1998

Effects of fly abundance on catch index of traps for Glossina fuscipes fuscipes (Diptera: Glossinidae).

The effect of fly abundance on the catch index of traps and that of rain as a source of variation in fly abundance were investigated for Glossina fuscipes fuscipes Newstead around Lake Victoria, western Kenya, using odor-baited and color-improved traps. There was a significant inverse relationship between the catch index of experimental traps and abundance of flies; the catch index being the ratio of catch in the experimental trap per catch in a reference trap. At low tsetse abundance (< 10 flies per trap per day) there was a 3-fold increase of the catch of females in the experimental trap compared with the control. Rainfall alone explained 22-87% of the total variation of fly abundance. It is suggested that fly abundance should be considered in evaluating baits for G. f. fuscipes or when using traps for monitoring. The relative depression of the catch index at high abundance may be related to avoidance of conspecifics. Flies entered standard traps in an inverse proportion to the number observed at the trap. Females approached traps in greater numbers when fewer decoys (dead flies) were placed on traps.

Animals↗
PubMed1997

Use of the factorial design and quadratic response surface models to evaluate the fosinopril and hydrochlorothiazide combination therapy in hypertension.

The combination of angiotensin converting enzyme (ACE) inhibitor and thiazide diuretic has advantages over monotherapy for the treatment of hypertension. Previous study designs have often been inadequate to demonstrate the details of interactions between these antihypertensive agents. This study used a modified 4 x 4 factorial randomized, double-blind, placebo-controlled, parallel group design to study the efficacy of 17 different doses of fosinopril (Fos), a phosphinic acid derived ACE inhibitor, and hydrochlorothiazide (HCTZ) in 550 patients with mild to moderate hypertension. Data from these variables were fit to quadratic response surface models (QRSM) using polynomial functions in the doses of the two components. Using QRSM, seated systolic (SeSBP) and diastolic blood pressure (SeDBP) responses at 8 weeks were predicted for actual doses and interpolated for intermediate doses not studied. Fos and HCTZ alone and in combination produced a dose-related reduction in SeSBP and SeDBP. Using 10 mg Fos + 12.5 mg HCTZ reduced the adjusted mean SeDBP 6.3 mm Hg and 20 mg Fos + 12.5 mg HCTZ lowered the same measure 9.1 mm Hg. Coadministration of Fos and HCTZ produced an additive antihypertensive effect. This study of combination agents for hypertension using a factorial design with QRSM accurately predicts dose responses and is a valuable clinical trial methodology.

Adult↗
PubMed1996

Efficacy and safety of fosinopril/hydrochlorothiazide combinations on ambulatory blood pressure profiles in hypertension. Fosinopril/Hydrochlorothiazide Investigators.

Twenty-four-hour ambulatory blood pressure monitoring (ABPM) was used to assess the antihypertensive efficacy and safety of the angiotensin converting enzyme (ACE) inhibitor fosinopril (Fos) in combination with hydrochlorothiazide (HCTZ) in doses of 10/12.5 mg and 20/12.5 mg taken once daily versus placebo in patients with mild-to-moderate hypertension. In two methodologically identical studies, the antihypertensive effects were evaluated by 24-h ABPM and by seated office diastolic (DBP) and systolic (SBP) blood pressures. After a 4- or 5-week placebo washout, 79 patients received randomized, double-blind treatment for 8 weeks with either the Fos/HCTZ 10/12.5-mg dose combination (n = 41) or placebo (n = 38), and in the second study, 62 patients were treated with either the Fos/HCTZ 20/12.5-mg dose combination (n = 30) or placebo (n = 32). Changes from baseline in mean 24-h systolic and diastolic ABPM were significantly different from placebo for both doses (SBP/DBP with 10/12.5 mg, -18.2/ -10.1 mm Hg, P <or= .001; SBP/DBP with 20/12.5 mg, -22.9/ -11.2 mm Hg, P <or= .001); whereas ambulatory SBP and DBP in the placebo group were virtually unchanged. Although the antihypertensive effect of the higher Fos/HCTZ dose combination (20/12.5 mg) appeared greater than the lower dose (10/12.5 mg), no attempt was made to make a comparison between the two doses over these two independent studies. This difference in blood pressure lowering was not reproduced by the office blood pressure readings. Both dose combinations of Fos/HCTZ produced significantly greater reductions in the office seated DBP than placebo at all time points tested with a maximum treatment effect (drug effect - placebo effect) of -7.3 mm Hg for the 10/12.5-mg dose and -8.2 mm Hg for the 20/12.5-mg dose after 8 weeks of therapy (P <or= .01). Based on the results obtained in these trials, both dose combinations of Fos/HCTZ taken once daily were safe and effective in the management of patients with mild-to-moderate hypertension. Twenty-four-hour ABPM detected what appears to be an enhanced blood pressure reduction with the higher Fos/HCTZ dose combination (20/12.5 mg) at peak and trough, which was not reproduced by trough office blood pressure measurements, suggesting greater sensitivity of 24-h ABPM for evaluating antihypertensive effects.

Adolescent↗
PubMed1987

A behavioural bioassay to identify attractive odours for Glossinidae.

1. A behavioural bioassay, based on antennal movement responses, was developed using Glossina morsitans morsitans Westwood for screening chemical attractancy to tsetse. 2. Chemicals found to be attractive to male tsetse were acetone, formaldehyde, methylethylketone, methylvinylketone, 1-octen-3-ol and pentanal but not acetophenone, hexanal, lactic acid or urea. 3. Female tsetse also responded to all these chemicals in a similar fashion. Overall responses of females were, however, less than those of males. 4. These laboratory bioassay findings agree with field observations on tsetse responses to certain chemical odours. Therefore this behavioural bioassay should be a useful laboratory test procedure for screening attractants.

Animals↗
PubMed1986

Effects of SQ 26,533 on reperfusion arrhythmias, ST-segment elevation and on infarct size in anesthetized dogs.

The antiarrhythmic, antifibrillatory activities and the ability of SQ 26,533 to reduce infarct size were investigated in the canine models of reperfusion arrhythmias. In model 1, halothane-anesthetized dogs were subjected to acute occlusion of left circumflex coronary artery (LCX) for 30 min followed by reperfusion. SQ 26,533 infused at 50 micrograms/kg/min for 45 min significantly reduced (78%) the incidence of ventricular ectopic beats during the 30-min ligation of LCX. In addition, four of seven dogs (57%) survived after reperfusion, in contrast to 100% mortality observed in untreated animals. In model 2, left anterior descending artery under pentobarbital anesthesia was occluded for 20 min and released. SQ 26,533 (2.5 mg/kg i.v.) given 1 hr before occlusion significantly reduced (81%) ventricular ectopic beats during acute occlusion and four of five animals (80%) survived left anterior descending artery reperfusion, unlike saline controls (100% mortality). Similar efficacy was seen in a feline model of reperfusion arrhythmias. The model 3 animals under pentobarbital anesthesia were occluded for 60 min followed by reperfusion of the LCX in the presence of critical stenosis. SQ 26,533 (2.5 mg/kg every 90 min) given 50 min after LCX occlusion not only resulted in a significant reduction (91%) of postreperfusion ventricular ectopic beats for the entire 5-hr observation period but also significantly reduced (42%) the infarct size at 24 hr. Antiarrhythmic doses of SQ 26,533 caused minimal hemodynamic changes, except for a marked decrease in heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗