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R S Rao

Publications and source records attributed to R S Rao.

At least 19 recordsLinked to original sources
PubMed2005

High-pressure study of adamantane: variable shape simulations up to 26 GPa.

We report simulations of adamantane by carefully combining ab initio and empirical approaches to enable simulations with internal degrees of freedom on crystalline adamantane up to a pressure of 26 GPa. Two sets of simulations, assuming the adamantane molecule as a rigid (RB) and flexible body (FB), have been carried out as a function of pressure up to 26 GPa to understand changes in the crystal structure as well as molecular structure. The flexible body simulations have been performed by including 6 lowest frequency internal modes (obtained from DFT calculations performed with Gaussian98) out of the total of 72. The calculated variation in c/a and V/V(0) from the RB and FB calculations as a function of pressure have been compared with the experimental curve. Other relevant thermodynamic and structural properties reported are the radial distribution functions, deviation in the position of a given type of atom with respect to its position at standard pressure, delta(s), cell parameters, volume, and energy. With an increase in pressure, three additional peaks are seen to develop gradually at three different pressures in the center of mass (com)-com radial distribution function (rdf). We attribute these changes to structural transformations (probably second-order phase transitions) which is consistent with the three phase transitions reported by Vijayakumar et al. for adamantane in the pressure range of 1 atm-15 GPa. Our simulations also show that these additional peaks in the rdf's are associated with the differences between opposite and parallel spin neighbors of Greig and Pawley as well as the crystallographic directional dependence of intermolecular distances in the first three shells of the neighbors. Also, the structural quantities from the RB calculation show considerable deviation from the FB calculation for pressures greater than 5 GPa, which suggests that the rigid body assumption for molecules may not be valid above this pressure.

Journal Article↗
PubMed2002

Evidence-based protocols for the management of well-differentiated carcinomas of the thyroid.

OBJECTIVES: In recent years, well-differentiated carcinomas of the thyroid have been stratified into low-risk and high-risk groups. The pattern of thyroid cancer in India is different from that seen in the West. Moreover, patients present with more advanced stages of the disease. Our aim was to develop protocols for the management of well-differentiated thyroid cancer, based on the analysis of our data and our experience. METHODS: Cases of thyroid carcinoma, which were surgically treated at the Tata Memorial Hospital during 1970-5, were studied. The survival curves were plotted according to the Kaplan-Meier method. Univariate analysis was done using the log rank test. The prognostic factors analyzed were age, sex, tumour size, extra-thyroid extension, distant metastases and lymph node metastases. Multivariate analysis using the Cox regression model was performed. Analyses were separate for follicular and papillary carcinomas. RESULTS: Four hundred and seventeen cases were entered in the study, of which 198 were follicular and 219 were papillary. Based on the evidence derived from this study, we stratified our cases into low- and high-risk groups. The low-risk group consisted of patients below 40 years of age, nodules smaller than 5 cm, absence of extra-thyroidal spread and absence of distant metastases. For follicular carcinoma, the low-risk group had 100% survival at 15 years, compared with 40% for the high-risk group. (p < 0.001). For papillary carcinomas, the survival at 15 years was 95% for the low-risk group and 40% for the high-risk group (p < 0.001). CONCLUSIONS: We recommend lobectomy for the low-risk group, and total thyroidectomy for the high-risk group and for cases with lymph node metastases. In the latter, total thyroidectomy facilitates the use of 131I.

Adenocarcinoma, Follicular↗
PubMed2001

Infertility among women exposed prenatally to diethylstilbestrol.

Although it is well established that women exposed to diethylstilbestrol in utero have an increased risk of spontaneous abortion, ectopic pregnancy, and preterm delivery, it is not known whether they also have an increased risk of infertility. The authors assessed this question in data from a collaborative follow-up study of the offspring of women who took diethylstilbestrol during pregnancy. In 1994, 1,753 diethylstilbestrol-exposed and 1,050 unexposed women from an ongoing cohort study (National Cooperative Diethylstilbestrol Adenosis Study and Dieckmann cohorts) provided data on difficulties in conceiving and reasons for the difficulty. Age-adjusted relative risks were computed for the association of diethylstilbestrol exposure with specific types of infertility. A greater proportion of exposed than unexposed women were nulligravid (relative risk (RR) = 1.3, 95% confidence interval (CI): 1.1, 1.5), and a greater proportion had tried to become pregnant for at least 12 months without success (RR = 1.8, 95% CI: 1.6, 2.1). Diethylstilbestrol exposure was significantly associated with infertility due to uterine and tubal problems, with relative risks of 7.7 (95% CI: 2.3, 25) and 2.4 (95% CI: 1.2, 4.6), respectively. The present findings indicate that diethylstilbestrol-exposed women have a higher risk of infertility than do unexposed women and that the increased risk of infertility is primarily due to uterine or tubal problems.

Adult↗
PubMed2001

Low-dose oral contraceptive use and the risk of myocardial infarction.

BACKGROUND: Studies of oral contraceptives (OCs) containing 50 microg or more of estrogen suggest an increased risk of myocardial infarction (MI) among current users, particularly if they smoke heavily. OBJECTIVE: To assess whether use of the newer lower-dose OCs increases the risk of MI. METHODS: A case-control study was conducted from January 1985 through March 1999 in 75 hospitals in the greater-Boston and greater-Philadelphia areas. Data on OC use and MI risk factors were obtained by interview from 627 women with a nonfatal first MI (cases) and 2947 female hospital controls younger than 45 years. RESULTS: The overall odds ratio (OR) for current OC use relative to never used was 1.3 (95% confidence interval [CI], 0.8-2. 2). The OR was elevated, 2.5 (95% CI, 0.9-7.5), among heavy smokers (>/=25 cigarettes per day) but close to 1.0 among lighter smokers (OR = 0.8) and nonsmokers (OR = 1.3). For current OC use together with heavy smoking relative to nonuse and nonsmoking, the OR was 32 (95 % CI, 12-81), considerably greater than that for heavy smoking alone, 12 (95% CI, 8.6-16). The ORs did not vary according to the type of formulation or the dose of estrogen; there were too few users to assess the new 20-microg preparations. Past OC use was unrelated to risk. CONCLUSION: Current use of low-dose OCs in the United States is unrelated to an increased risk of MI among nonsmokers and light smokers, but users who smoke heavily may be at greatly increased risk.

Adult↗
PubMed2001

Height and breast cancer risk: results from the Black Women's Health Study (United States).

OBJECTIVES: Numerous studies, but not all, have yielded positive associations between adult height and risk of breast cancer. There are few data on black women. We evaluated adult height in relation to breast cancer in data from the Black Women's Health Study, a prospective cohort study of 64,530 African-American women aged 18-69 years at baseline in 1995. METHODS: A total of 910 cases of breast cancer were analyzed: 700 prevalent cases reported at baseline and 210 incident cases that occurred during the first 2 years of follow-up. A comparison group of controls frequency-matched on 5-year category of birth year was chosen from among participants who had not developed breast cancer. Odds ratios (OR) were calculated for various categories of adult height compared to a reference category of height less than or equal to 61 inches (155 cm), with control for current age, age at menarche, and years of education. RESULTS: Increased height was associated with an increased risk of breast cancer overall (p trend = 0.001); the OR for the highest category of height, > 69 inches (175 cm), was 1.6 (95% confidence interval 1.1-2.3). The association was stronger among premenopausal women and women who had less than 16 years of education. Results were similar for prevalent and incident cases. CONCLUSION: The present findings indicate that height is associated with breast cancer risk in African-American women.

Adolescent↗
PubMed2001

Evaluation of Lp[a] and other independent risk factors for CHD in Asian Indians and their USA counterparts.

Conventional risk factors for coronary heart disease (CHD) do not completely account for the observed increase in premature CHD in people from the Indian subcontinent or for Asian Indians who have immigrated to the USA. The objective of this study was to determine the effect of immigration to the USA on plasma levels of lipoprotein [a] (Lp[a]) and other independent risk factors for CHD in Asian Indians. Three subject groups were studied: group 1, 57 subjects living in India and diagnosed with CHD (CHD patients); group 2, 46 subjects living in India and showing no symptoms of CHD (control subjects); group 3, 206 Asian Indians living in the USA. Fasting blood samples were drawn to determine plasma levels of triglyceride (TG), total cholesterol (TC), low density lipoprotein [LDL cholesterol (LDL-Chol)], high density lipoprotein [HDL cholesterol (HDL-Chol)], apolipoprotein B-100 (apoB-100), and Lp[a]. Apolipoprotein [a] (apo[a]) size polymorphism was determined by immunoblotting. Plasma TG, apoB-100, and Lp[a] concentrations were higher in CHD patients than in control and USA groups. CHD patients had higher levels of TC and LDL-Chol and lower HDL-Chol than control subjects. However, the USA population had higher levels of TC, LDL-Chol, and apoB-100 and lower HDL-Chol than control subjects. Plasma Lp[a] levels were inversely correlated with the relative molecular weight of the more abundant of each subject's two apo[a] isoforms (MAI), and CHD patients showed higher frequencies of lower relative molecular weights among MAI. Our observed changes in lipid profiles suggest that immigrating to the USA may place Asian Indians at increased risk for CHD. This study suggests that elevated plasma Lp[a] confers genetic predisposition to CHD in Asian Indians, and nutritional and environmental factors further increase the risk of CHD. This is the first report implicating MAI size as a predictor for development of premature CHD in Asian Indians. Including plasma Lp[a] concentration and apo[a] phenotype in screening procedures may permit early detection and preventive treatment of CHD in this population.

Adult↗
PubMed2001

Survey for tuberculosis in a tribal population in North Arcot District.

SETTING: Tribal villages in the jungles of the Jawadhu hills, South India. OBJECTIVE: To estimate the prevalence of tuberculosis (TB) infection and disease in a remote tribal population. DESIGN: A cross-sectional survey with two-stage screening for identification of cases. A stratified probability proportional sample with the hamlet as the unit. METHODS: Among 56 revenue divisions with a population of about 66,000, 24 revenue divisions were selected. Among 26,320 persons registered, children < 10 years were tuberculin tested and reactions were read after 72 hours. Those over 15 were X-rayed, and tuberculosis symptoms were investigated. Sputum was collected from those with abnormal X-ray or symptoms and examined for smear and culture positivity and sensitivity. RESULTS: Of the 6952 children tested and read, 5% had BCG scars and the prevalence of infection was 5%. The annual risk of infection was 1.1. Among adults, the prevalence of bacillary cases was 8/1000 and X-ray cases 29/1000. The prevalence of bacillary disease was higher among males, particularly with increasing age. Thirty symptomatic cases had normal X-rays and 63 X-ray cases had no symptoms. Thus prevalence would have been underestimated if either method had been used alone for screening. Isoniazid resistance was seen in 12% of patients, two of whom also had rifampicin resistance (2.6%). CONCLUSIONS: The prevalence and pattern of tuberculosis in this tribal group is similar to that observed in non-tribal areas.

Adolescent↗
PubMed2000

Descriptive epidemiology of physical activity in African-American women.

OBJECTIVES: We assessed walking for exercise and moderate and strenuous physical activity in relation to both demographic and health-related characteristics among African-American women from various parts of the United States who participate in the Black Women's Health Study. METHODS: The data were collected in 1995 by mail questionnaire from 64,524 U.S. black women aged 21 to 69 years. The 64,101 women who provided data on physical activity are the subjects of the present report. RESULTS: The present study revealed low levels of physical activity among the African-American women: 57% reported an hour or less per week walking for exercise, 18% reported moderate activity, and 61% reported strenuous physical activity. Strenuous physical activity increased with education. Higher levels of walking for exercise and moderate and strenuous activity were associated with higher levels of participation in strenuous exercise in high school. CONCLUSION: Physical activity levels are low in African-American women. Based on the findings of the present study it may be suggested that educational efforts to increase levels of physical activity should start at an early age.

Adult↗
PubMed2000

Socio-demographic and maternal determinants of low birth weight: a multivariate approach.

A community based study was conducted in the rural areas of Udupi taluk, Karnataka state of South India to identify the socio-demographic, maternal and obstetric determinants of low birth weight. All singleton live births that occurred in the study area during a one year period (October 1991 to September 1992) were included. A total of 2919 singleton child-mother pairs formed the basis of the analysis. Information about social, demographic and economic conditions of the families; maternal factors such as age, parity, quality of antenatal care and previous obstetric history were collected by interviewing the mothers and family members and verifying the available medical records through the field investigators especially recruited and trained for this purpose. Data was analyzed using multiple logistic regression model. Primis, elderly mothers and mothers who had not received good quality antenatal care were found to be more at risk of having low birth weight babies. Other significant determinants were family custom, socio-economic status and environmental sanitation.

Female↗
PubMed2000

Evaluation of an isometric and a position joystick in a target acquisition task for individuals with cerebral palsy.

Individuals with cerebral palsy (CP) with upper limb disability have difficulty operating standard computer input devices such as, a mouse and a keyboard. The present study evaluated the performance of unimpaired individuals and those with CP in the use of a zero-order spring-centered position joystick and a zero-order isometric joystick when interacting with the computer. We hypothesize that the isometric device due to its stiff resistance would provide better control on cursor movement than the position joystick. The subjects acquired differently sized targets at different distances by positioning a cursor on the target. Performance with the position joystick was superior to that of the isometric joystick. The time to acquire the target was directly proportional to the cursor-target distance A, and indirectly proportional to the target size W. Subjects chose to move more slowly toward the smaller and closer targets and they increased speed for larger and more distant targets. The phase-plane diagram that plots values of the velocity profile of the cursor over its displacement revealed the presence of one large amplitude movement that accounts for the peak velocity of the cursor, and several submovements. Fitts' index of difficulty, log(e)(2W/A) was found to be a good predictor of the movement time in a cursor positioning task for both, unimpaired individuals and those with CP.

Adult↗
PubMed2000

Comparison of alternative survey methods for sensitive self-reported behaviours in a follow-up study of isotretinoin.

BACKGROUND: Responses to questions on sensitive behaviours can be affected by when and how questions are asked. METHODS: Using data from an ongoing survey of women taking isotretinoin (a teratogenic drug used to treat acne), we compared answers to questions on contraceptive use during therapy among 126966 women who had begun treatment in 1990-93. 20503 were randomly assigned to a group which was surveyed by telephone at the start of treatment, during treatment and 6 months after treatment ended (DAT group). 106463 received a mail survey 6 months after treatment ended (AT group). Women who could not be contacted during treatment, along with the non-respondents in the AT group, received follow-up surveys by US mail, air courier and, if necessary, were called by telephone. RESULTS: The response rate was higher in the DAT group (96.4%) than in the AT group (84.8%). Among respondents, the odds of reported contraceptive use in the AT group compared with the DAT group (asked at 6 months after treatment) was 1.41 [95% confidence interval (CI): 1.36-1.46]. However, rates of oral contraceptive (OC) use were virtually identical in the two groups. In both groups, women surveyed by telephone reported lower rates of contraceptive use than women surveyed by mail. In the AT group, a late response was associated with a significantly lower rate of contraceptive use. CONCLUSIONS: Both mode of data collection (phone versus mail) and time to response affected reported rates of contraceptive use. Reasonable assumptions about the effect of non-response could not account for the difference between the AT and DAT groups. We found that contacting women during their treatment did not increase their reported use of contraceptives.

Acne Vulgaris↗
PubMed2000

A case-control study of analgesic use and ovarian cancer.

A recent case-control study raised the hypothesis that acetaminophen use 1 day or more per week for at least 6 months reduces the risk of epithelial ovarian cancer. We assessed analgesic use in relation to epithelial ovarian cancer risk using data from our case-control surveillance study of medication use and cancer. Patients were interviewed in hospitals in Baltimore, Boston, New York, and Philadelphia during 1976-1998. We compared 780 women with epithelial ovarian cancer to 2053 cancer controls and 2570 noncancer controls. For acetaminophen use 1 day or more per week for at least 6 months, the odds ratio estimate was 0.9 (95% confidence interval, 0.6-1.4) derived with cancer controls and 1.0 (0.6-1.5) with noncancer controls. Estimates for more frequent and longer term use were also compatible with 1.0. The odds ratios among patients with metastatic ovarian cancer were reduced but not statistically significant. The odds ratio for use of nonsteroidal anti-inflammatory drugs 4 or more days per week for at least 5 years, 0.5, was statistically significant. The present results provide only weak support for a reduction in the risk of epithelial ovarian cancer among acetaminophen users. They raise the possibility of an inverse association with long-term nonsteroidal anti-inflammatory drug use.

Acetaminophen↗
PubMed1999

Correlates of hysterectomy among African-American women.

Hysterectomy is the second most common surgery performed on US women. Baseline data from a large study of African-American women were used to examine correlates of premenopausal hysterectomy. Analyses were conducted on participants aged 30-49 years; 5,163 had had a hysterectomy and 29,787 were still menstruating. Multiple logistic regression was used to compute prevalence odds ratios for the association of hysterectomy with various factors. Hysterectomy was associated with region of residence: Odds ratios for living in the South, Midwest, and West relative to the Northeast were 2.63 (95% confidence interval (CI): 2.38, 2.91), 2.02 (95% CI: 1.81, 2.25), and 1.89 (95% CI: 1.68, 2.12), respectively. Hysterectomy was inversely associated with years of education and age at first birth: Odds ratios were 1.96 (95% CI: 1.74, 2.21) for < or =12 years of education relative to >16 years and 4.33 (95% CI: 3.60, 5.22) for first birth before age 20 relative to age 30 or older. Differences in the prevalence of major indications for hysterectomy did not explain the associations. This study indicates that the correlates of hysterectomy among African-American women are similar to those for White US women. The associations with geographic region and educational attainment suggest that there may be modifiable factors which could lead to reduced hysterectomy rates.

Adult↗
PubMed1999

Risk factors for coronary heart disease in African American women.

There have been few studies of risk factors for coronary heart disease in African American women. The authors investigated factors associated with prevalent coronary heart disease in data provided by participants in the Black Women's Health Study. In 1995, 64,530 US Black women aged 21-69 years completed postal health questionnaires. The 352 women who reported having had a heart attack (cases) were frequency matched 5:1 on age with 1,760 women who had not (controls); medical record review for 35 cases indicated that two-thirds had had a heart attack and the remainder had other coronary heart disease. Odds ratios, obtained from multiple logistic regression analyses, were significantly elevated for cigarette smoking, drug-treated hypertension, drug-treated diabetes mellitus, elevated cholesterol level, and history of heart attack in a parent. High body mass index (kg/m2) was associated with coronary heart disease in the absence of control for hypertension, diabetes mellitus, and elevated cholesterol but not when they were controlled, suggesting that obesity may influence risk as a result of its effects on blood pressure, glucose tolerance, and cholesterol levels. Odds ratios increased with increasing parity and with decreasing age at first birth. These data suggest that important risk factors for coronary heart disease are similar in Black women and White women.

Adult↗
PubMed1999

Risk of breast cancer according to use of antidepressants, phenothiazines, and antihistamines.

In laboratory studies, some antidepressants caused increased growth of mammary tumors. The relation of use of these drugs to the development of breast cancer was examined in a hospital-based case-control study. Information, including lifetime medication history, was collected by interview from 5,814 women with primary breast cancer diagnosed within the previous year, 5,095 women with primary malignancies of other sites, and 5,814 women with other conditions. Relative risks were estimated by using unconditional multiple logistic regression for regular use (> or =4 days per week for > or =4 weeks beginning > or =1 year before admission) of antidepressants and structurally similar drugs. With reference to never use of each drug, relative risks were statistically compatible with 1.0 for selective serotonin reuptake inhibitors (SSRI), tricyclics, other antidepressants, phenothiazines, and antihistamines; results were very similar using both control groups. There were no significant increases in risk for any category of regular use, stratified according to cumulative duration of use or time interval since the most recent use or for any individual drug within the broader classes. However, the estimate for regular SSRI use in the previous year, 1.8, was of borderline statistical significance (95% confidence interval: 1.0, 3.3). The findings do not support an overall association between the use of antidepressants, phenothiazines, or antihistamines and breast cancer. However, the results for SSRIs are not entirely reassuring.

Adult↗
PubMed1999

Oral contraceptive use and risk of gestational trophoblastic tumors.

BACKGROUND: Gestational trophoblastic disease refers to a spectrum of rare benign and malignant gynecologic disorders whose pathogenesis is not well understood. Recent studies from China and the United States have raised the hypothesis that long-term use of oral contraceptives before conception may increase the risk of gestational trophoblastic tumors. A multicenter case-control study of gestational trophoblastic tumors was undertaken to test this hypothesis. METHODS: Telephone interviews were conducted with 235 case patients, including 50 with gestational choriocarcinoma, and 413 control subjects matched on recentness of pregnancy, age at pregnancy, and area of residence. Relative risks (odds ratios) were computed by conditional logistic regression. Reported P values are two-sided. RESULTS: The relative risk estimate for ever having used oral contraceptives before the index pregnancy was 1.9 (95% confidence interval [CI] = 1.2-3.0), and the risk increased with duration of use (P for trend = .05). The estimate was highest for women who used oral contraceptives during the cycle in which they became pregnant (relative risk = 4.0; 95% CI=1.6-10), but there was no consistent pattern according to the time interval since last use. Separate analyses of choriocarcinoma and persistent mole yielded similar results, i.e., the relative risk estimates for oral contraceptive use were 2.2 (95% CI=0.8-6.4) and 1.8 (95% CI=1.0-3.0), respectively. Control for the number of sexual partners, which was independently associated with risk (P for trend = .05), did not materially change the results. CONCLUSIONS: This study, the largest to date, indicates that long duration of oral contraceptive use before conception increases the risk of gestational trophoblastic tumors. These findings may provide clues to the pathogenesis of this rare disease. Changes in use of oral contraceptives are not warranted, however, because the incidence attributable to oral contraceptive use is very low.

Adult↗