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R Mittal

Publications and source records attributed to R Mittal.

At least 19 recordsLinked to original sources
PubMed2001

Origin of negative thermal expansion in cubic ZrW2O8 revealed by high pressure inelastic neutron scattering.

Isotropic negative thermal expansion has been reported in cubic ZrW2O8 over a wide range of temperatures (0-1050 K). Here we report the direct experimental determination of the Grüneisen parameters of phonon modes as a function of their energy, averaged over the whole Brillouin zone, by means of high pressure inelastic neutron scattering measurements. We observe a pronounced softening of the phonon spectrum at P = 1.7 kbar compared to that at ambient pressure by about 0.1-0.2 meV for phonons of energy below 8 meV. This unusual phonon softening on compression, corresponding to large negative Grüneisen parameters, is able to account for the observed large negative thermal expansion.

Journal Article↗
PubMed2001

Matrix effects during potassium and calcium determinations in rice saplings using X-ray spectrometery.

For selectively excited calcium K X-rays in rice saplings, the relations alpha = N(KR)[1 + A gamma + B beta/(1 + alpha)] and 1/N(Ca) = alpha/beta + b + c beta are found to support the enhancement of potassium K X-rays and N(Ca) calcium K X-ray counts during potassium and calcium determinations, respectively. Here alpha, beta and gamma are weight fractions of potassium, calcium and the matrix substrate, respectively, N(KR) is the relative potassium K X-ray counts of the sample to that of pure potassium and A, B, a, b and c are constants. Tests of these relations, using eight known mixtures of CaCO3, KNO3 and Na2B4O7 10H2O (borax), have further supported the findings.

Calcium↗
PubMed2001

Application of large-eddy simulation to the study of pulsatile flow in a modeled arterial stenosis.

The technique of large-eddy simulation (LES) has been applied to the study of pulsatile flow through a modeled arterial stenosis. A simple stenosis model has been used that consists of a one-sided 50 percent semicircular constriction in a planar channel. The inlet volume flux is varied sinusoidally in time in a manner similar to the laminar flow simulations of Tutty (1992). LES is used to compute flow at a peak Reynolds number of 2000 and a Strouhal number of 0.024. At this Reynolds number, the flow downstream of the stenosis transitions to turbulence and exhibits all the classic features of post-stenotic flow as described by Khalifa and Giddens (1981) and Lieber and Giddens (1990). These include the periodic shedding of shear layer vortices and transition to turbulence downstream of the stenosis. Computed frequency spectra indicate that the vortex shedding occurs at a distinct high frequency, and the potential implication of this for noninvasive diagnosis of arterial stenoses is discussed. A variety of statistics have been also extracted and a number of other physical features of the flow are described in order to demonstrate the usefulness of LES for the study of post-stenotic flows.

Arterial Occlusive Diseases↗
PubMed2000

Studies of ion-exchange resin complex of chloroquine phosphate.

High-potency adsorbates of chloroquine phosphate (CQP) were prepared by the batch method using a polyacrylic acid ion-exchange resin. Taste evaluation of the adsorbates shows significant masking of the bitterness of the drug. The complex formation was complete at pH 6.0. Stability studies at 37 degrees C, 45 degrees C, and 60 degrees C indicated that the complex was stable at all conditions for 1 month. In vitro release studies revealed complete drug elution from the complex at pH 1.2 and 2.0.

Acrylic Resins↗
PubMed2000

In vitro antioxidant activity of piperine.

Oxygen radical injury and lipid peroxidation have been suggested as major causes of atherosclerosis, cancer, liver disease and the aging process. Piperine, having an antiinflammatory effect, has been demonstrated in in vitro experiments to protect against oxidative damage by inhibiting or quenching free radicals and reactive oxygen species and hydroxyl radicals. The effect on lipid peroxidation was also examined and IC50 values were calculated. Piperine was found to act as a hydroxyl radical scavenger at low concentrations, but at higher concentrations, it activated the fenton reaction resulting in increased generation of hydroxyl radicals. Whereas it acts as a powerful superoxide scavenger and IC50 is 1.82 mM, a 52% inhibition of lipid peroxidation was observed at a dose of 1400 microM with an IC50 of 1.23 mM. The results depict that piperine possesses direct antioxidant activity against various free radicals. This study also opens newer views on the potential efficacy of piperine in protecting tissues from peroxidative damage.

Alkaloids↗
PubMed2000

Wilson's disease--early onset and lessons from a pediatric cohort in India.

OBJECTIVE: To study the clinical profile at presentation and on follow up in cases of Wilson's disease presenting at this hospital. METHODS: Case records of children diagnosed as Wilson's disease (WD) admitted in the hospital or attending the Pediatric outpatient department were retrospectively studied with regard to clinical features, investigations, and family screening at the time of presentation. Note was made of the treatment received by the patients. Clinical profile on follow up was recorded with respect to side effects of treatment, and whether patient improved, deteriorated or remained the same, either from the records or by calling the patient for a follow up, if possible. RESULTS: Analysis of 25 children with Wilson's disease comprising 19 index cases and 6 siblings detected on family screening, revealed mean age of onset for the hepatic presentation was 6.8 years versus 8 years for the neurologic patient. A quarter of index cases has a family history strongly suspicious for Wilson disease which has been earlier overlooked. Clinical presentation was hepatic in 5 patients, purely neurologic in 5, mixed hepatic and neurologic in 9, hemolytic anemia in 1 and polyarthritis in 1. Patients received treatment with D penicillamine, zinc, pyridoxine and low copper diet. Follow upon 18 patients revealed improvement in majority, residual dysarthria in seven,prolonged persistence of KF rings in 15 and complications like renal tubular acidosis with osteopenia in one. CONCLUSION: The early age of onset of symptoms, prolonged KF rings persistence and progression of symptoms among sibs despite therapy is of interest as it may be related to a high copper intake, which may be due to the practice of using brass or copper utensils for cooking Since a large number of children has either a past history of jaundice or sibling deaths due to jaundice or cirrhosis, a high index of suspicion and screening for KF rings is emphasized as a simple and cost effective way of detecting a curable disease at an early stage and family screening of all index cases is imperative. Progression of symptoms among sibs on oral zinc and low dose pencillamine suggests inadequacy of zinc alone for prophylaxis.

Adolescent↗
PubMed1999

Tuberculosis of the foot.

In 44 patients with tuberculosis of the foot we identified five radiological patterns of lesions; cystic, rheumatoid, subperiosteal, kissing and spina ventosa. Cystic destruction had the best outcome and rheumatoid the poorest. All the patients were cured after antituberculous treatment for 18 months, and none required surgery.

Adolescent↗
PubMed1998

Trapezius transfer for deltoid paralysis.

We have reviewed 26 patients treated by trapezius transfer for deltoid paralysis due to brachial plexus injury or old poliomyelitis. We assessed the power of shoulder abduction and the tendency for subluxation. There were good results in 16 patients (60%); five were fair and five poor. Trapezius transfer appears to give reasonable results in the salvage of abductor paralysis of the shoulder.

Adolescent↗