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S R Kulkarni

Publications and source records attributed to S R Kulkarni.

At least 19 recordsLinked to original sources
PubMed2007

The Ulcerated Leg Severity Assessment score for prediction of venous leg ulcer healing.

BACKGROUND: The aim of the study was to create a reliable scoring system for the prediction of venous ulcer healing in patients treated with compression. METHODS: A prospective baseline study to identify risk factors for venous ulcer healing was undertaken between March 1999 and August 2001. All patients were treated with multilayer compression. A number of variables were related to 24-week healing rates. A Cox regression model was used to identify risk factors that predicted ulcer healing, from which a scoring system was developed and validated prospectively between February 2004 and March 2005. RESULTS: In the baseline study of 229 patients, patient age, ulcer chronicity and venous refill time (VRT) of 20 s or less were identified as risk factors. Using these factors and hazard ratios from the Cox regression analysis, the following formula was devised: Ulcerated Leg Severity Assessment (ULSA) score=age+chronicity-50 (when VRT is greater than 20 s). Patients with an ULSA score of 50 or less had higher 24-week ulcer healing rates than those with higher scores in both the baseline study (P<0.001, log rank test) and the validation study performed in 86 patients (P=0.007, log rank test). CONCLUSION: The ULSA score may help to identify patients with venous ulcers unlikely to respond to conventional treatment who could be offered alternative therapy.

Adult↗
PubMed2006

A novel explosive process is required for the gamma-ray burst GRB 060614.

Over the past decade, our physical understanding of gamma-ray bursts (GRBs) has progressed rapidly, thanks to the discovery and observation of their long-lived afterglow emission. Long-duration (> 2 s) GRBs are associated with the explosive deaths of massive stars ('collapsars', ref. 1), which produce accompanying supernovae; the short-duration (< or = 2 s) GRBs have a different origin, which has been argued to be the merger of two compact objects. Here we report optical observations of GRB 060614 (duration approximately 100 s, ref. 10) that rule out the presence of an associated supernova. This would seem to require a new explosive process: either a massive collapsar that powers a GRB without any associated supernova, or a new type of 'engine', as long-lived as the collapsar but without a massive star. We also show that the properties of the host galaxy (redshift z = 0.125) distinguish it from other long-duration GRB hosts and suggest that an entirely new type of GRB progenitor may be required.

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PubMed2006

Common variants in the TCF7L2 gene are strongly associated with type 2 diabetes mellitus in the Indian population.

AIMS AND HYPOTHESIS: India has the greatest number of diabetic subjects in any one country, but the genetic basis of type 2 diabetes mellitus in India is poorly understood. Common non-coding variants in the transcription factor 7-like 2 gene (TCF7L2) have recently been strongly associated with increased risk of type 2 diabetes in European populations. We investigated whether TCF7L2 variants are also associated with type 2 diabetes mellitus in the Indian population. MATERIALS AND METHODS: We genotyped type 2 diabetes patients (n = 955) and ethnically matched control subjects (n = 399) by sequencing three single nucleotide polymorphisms (SNPs) (rs7903146, rs12255372 and rs4506565) in TCF7L2. RESULTS: We observed a strong association with all the polymorphisms, including rs12255372 (odds ratio [OR] 1.50 [95% CI = 1.24-1.82], p = 4.0 x 10(-5)), rs4506565 (OR 1.48 [95% CI = 1.24-1.77], p = 2.0 x 10(-5)) and rs7903146 (OR 1.46 [95% CI = 1.22-1.75], p = 3.0 x 10(-5)). All three variants showed increased relative risk when homozygous rather than heterozygous, with the strongest risk for rs12255372 (OR 2.28 [95% CI = 1.40-3.72] vs OR 1.43 [95% CI = 1.11-1.83]). We found no association of the TCF7L2 genotypes with age at diagnosis, BMI or WHR, but the risk genotype at rs12255372 was associated with higher fasting plasma glucose (p = 0.001), higher 2-h plasma glucose (p = 0.0002) and higher homeostasis model assessment of insulin resistance (HOMA-R; p = 0.012) in non-diabetic subjects. CONCLUSIONS: Our study in Indian subjects replicates the strong association of TCF7L2 variants with type 2 diabetes in other populations. It also provides evidence that variations in TCF7L2 may play a crucial role in the pathogenesis of type 2 diabetes by influencing both insulin secretion and insulin resistance. TCF7L2 is an important gene for determining susceptibility to type 2 diabetes mellitus and it transgresses the boundaries of ethnicity.

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PubMed2006

Relativistic ejecta from X-ray flash XRF 060218 and the rate of cosmic explosions.

Over the past decade, long-duration gamma-ray bursts (GRBs)--including the subclass of X-ray flashes (XRFs)--have been revealed to be a rare variety of type Ibc supernova. Although all these events result from the death of massive stars, the electromagnetic luminosities of GRBs and XRFs exceed those of ordinary type Ibc supernovae by many orders of magnitude. The essential physical process that causes a dying star to produce a GRB or XRF, and not just a supernova, is still unknown. Here we report radio and X-ray observations of XRF 060218 (associated with supernova SN 2006aj), the second-nearest GRB identified until now. We show that this event is a hundred times less energetic but ten times more common than cosmological GRBs. Moreover, it is distinguished from ordinary type Ibc supernovae by the presence of 10(48) erg coupled to mildly relativistic ejecta, along with a central engine (an accretion-fed, rapidly rotating compact source) that produces X-rays for weeks after the explosion. This suggests that the production of relativistic ejecta is the key physical distinction between GRBs or XRFs and ordinary supernovae, while the nature of the central engine (black hole or magnetar) may distinguish typical bursts from low-luminosity, spherical events like XRF 060218.

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PubMed2006

A photometric redshift of z = 6.39 +/- 0.12 for GRB 050904.

Gamma-ray bursts (GRBs) and their afterglows are the most brilliant transient events in the Universe. Both the bursts themselves and their afterglows have been predicted to be visible out to redshifts of z approximately 20, and therefore to be powerful probes of the early Universe. The burst GRB 000131, at z = 4.50, was hitherto the most distant such event identified. Here we report the discovery of the bright near-infrared afterglow of GRB 050904 (ref. 4). From our measurements of the near-infrared afterglow, and our failure to detect the optical afterglow, we determine the photometric redshift of the burst to be z = 6.39 - 0.12 + 0.11 (refs 5-7). Subsequently, it was measured spectroscopically to be z = 6.29 +/- 0.01, in agreement with our photometric estimate. These results demonstrate that GRBs can be used to trace the star formation, metallicity, and reionization histories of the early Universe.

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PubMed2005

The afterglow and elliptical host galaxy of the short gamma-ray burst GRB 050724.

Despite a rich phenomenology, gamma-ray bursts (GRBs) are divided into two classes based on their duration and spectral hardness--the long-soft and the short-hard bursts. The discovery of afterglow emission from long GRBs was a watershed event, pinpointing their origin to star-forming galaxies, and hence the death of massive stars, and indicating an energy release of about 10(51) erg. While theoretical arguments suggest that short GRBs are produced in the coalescence of binary compact objects (neutron stars or black holes), the progenitors, energetics and environments of these events remain elusive despite recent localizations. Here we report the discovery of the first radio afterglow from the short burst GRB 050724, which unambiguously associates it with an elliptical galaxy at a redshift z = 0.257. We show that the burst is powered by the same relativistic fireball mechanism as long GRBs, with the ejecta possibly collimated in jets, but that the total energy release is 10-1,000 times smaller. More importantly, the nature of the host galaxy demonstrates that short GRBs arise from an old (> 1 Gyr) stellar population, strengthening earlier suggestions and providing support for coalescing compact object binaries as the progenitors.

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PubMed2005

The afterglow of GRB 050709 and the nature of the short-hard gamma-ray bursts.

The final chapter in the long-standing mystery of the gamma-ray bursts (GRBs) centres on the origin of the short-hard class of bursts, which are suspected on theoretical grounds to result from the coalescence of neutron-star or black-hole binary systems. Numerous searches for the afterglows of short-hard bursts have been made, galvanized by the revolution in our understanding of long-duration GRBs that followed the discovery in 1997 of their broadband (X-ray, optical and radio) afterglow emission. Here we present the discovery of the X-ray afterglow of a short-hard burst, GRB 050709, whose accurate position allows us to associate it unambiguously with a star-forming galaxy at redshift z = 0.160, and whose optical lightcurve definitively excludes a supernova association. Together with results from three other recent short-hard bursts, this suggests that short-hard bursts release much less energy than the long-duration GRBs. Models requiring young stellar populations, such as magnetars and collapsars, are ruled out, while coalescing degenerate binaries remain the most promising progenitor candidates.

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PubMed2005

Detection of a radio counterpart to the 27 December 2004 giant flare from SGR 1806-20.

It was established over a decade ago that the remarkable high-energy transients known as soft gamma-ray repeaters (SGRs) are located in our Galaxy and originate from neutron stars with intense (< or = 10(15)G) magnetic fields-so-called 'magnetars'. On 27 December 2004, a giant flare with a fluence exceeding 0.3 erg cm(-2) was detected from SGR 1806-20. Here we report the detection of a fading radio counterpart to this event. We began a monitoring programme from 0.2 to 250 GHz and obtained a high-resolution 21-cm radio spectrum that traces the intervening interstellar neutral hydrogen clouds. Analysis of the spectrum yields the first direct distance measurement of SGR 1806-20: the source is located at a distance greater than 6.4 kpc and we argue that it is nearer than 9.8 kpc. If correct, our distance estimate lowers the total energy of the explosion and relaxes the demands on theoretical models. The energetics and the rapid decay of the radio source are not compatible with the afterglow model that is usually invoked for gamma-ray bursts. Instead, we suggest that the rapidly decaying radio emission arises from the debris ejected during the explosion.

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PubMed2005

Characteristics of gestational diabetic mothers and their babies in an Indian diabetes clinic.

AIMS AND OBJECTIVES: To compare clinical and metabolic features of mothers with gestational diabetes (GDM) and their offspring with those in non-diabetic pregnancies at the King Edward Memorial Hospital, Pune, India. MATERIALS AND METHODS: Antenatal information was obtained from hospital records. GDM was diagnosed by 75 g OGTT (Oral Glucose Tolerance Test) in clinically high-risk women. Anthropometric measurements of mother and the babies were recorded within 24h of delivery and a maternal blood sample collected for hematological and biochemical measurements. RESULTS: Between the period Jan 1998 to December 2003,265 women with gestational diabetes were treated in our Unit. Forty nine percent had first-degree relatives with diabetes. Compared to non-diabetic mothers (n=215) GDM mothers were older (29.0 vs. 26.0y, p<0.001), more obese (body mass index- BMI 26.0 vs. 22.0 kg/m2, p<0.001), centrally obese (Waist hip ratio-WHR 0.89 vs 0.86, p<0.001), adipose (sum of 4 skinfolds 98.4 vs. 61.4 mm, p<0.001) and had higher blood pressure (127/80 vs. 122/70 mmHg, p<0.001). GDM mothers had higher concentrations of plasma triglycerides (195.0 vs. 153.0 mg/dl, p<0.01); blood hemoglobin (11.7 vs 10.9 g/dl, p<0.001) and higher platelet count but lower concentration of HDL cholesterol and albumin. Sixty percent GDM mothers and 34% of non-diabetic mothers were delivered by caesarean-section, 23% of GDM mothers delivered pre term (<37 wk). Despite the smaller gestation, babies of GDM mothers were heavier (BW 2950.0 vs. 2824.0g, p<0.001, adjusted for gender), longer (48.9 vs. 48.0 cm, p<0.01) and more adipose (sum of 2 skinfolds 10.5 vs. 8.5 mm). Only 5% of babies born to GDM mothers weighed > 4000 g but 30% were >90th centile of birth weight of babies born to non-diabetic mothers. Babies of GDM mothers suffered higher neonatal morbidity. CONCLUSIONS: GDM mothers in urban India are more obese and more adipose than non-diabetic mothers, frequently have a family history of diabetes and show metabolic features of insulin resistance syndrome, suggesting high cardiovascular risk. Neonates of GDM mothers are heavier, longer and more adipose than those born to non-diabetic mothers, and suffer higher neonatal morbidity.

Adult↗
PubMed2004

The sub-energetic gamma-ray burst GRB 031203 as a cosmic analogue to the nearby GRB 980425.

Over the six years since the discovery of the gamma-ray burst GRB 980425, which was associated with the nearby (distance approximately 40 Mpc) supernova 1998bw, astronomers have debated fiercely the nature of this event. Relative to bursts located at cosmological distance (redshift z approximately 1), GRB 980425 was under-luminous in gamma-rays by three orders of magnitude. Radio calorimetry showed that the explosion was sub-energetic by a factor of 10. Here we report observations of the radio and X-ray afterglow of the recent GRB 031203 (refs 5-7), which has a redshift of z = 0.105. We demonstrate that it too is sub-energetic which, when taken together with the low gamma-ray luminosity, suggests that GRB 031203 is the first cosmic analogue to GRB 980425. We find no evidence that this event was a highly collimated explosion viewed off-axis. Like GRB 980425, GRB 031203 appears to be an intrinsically sub-energetic gamma-ray burst. Such sub-energetic events have faint afterglows. We expect intensive follow-up of faint bursts with smooth gamma-ray light curves (common to both GRB 031203 and 980425) to reveal a large population of such events.

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PubMed2004

A distance of 133-137 parsecs to the Pleiades star cluster.

Nearby 'open' clusters of stars (those that are not gravitationally bound) have played a crucial role in the development of stellar astronomy because, as a consequence of the stars having a common age, they provide excellent natural laboratories to test theoretical stellar models. Clusters also play a fundamental part in determining distance scales. The satellite Hipparcos surprisingly found that an extensively studied open cluster--the Pleiades (also known as the Seven Sisters)--had a distance of D = 118 +/- 4 pc (refs 2, 3), about ten per cent smaller than the accepted value. The discrepancy generated a spirited debate because the implication was that either current stellar models were incorrect by a surprising amount or Hipparcos was giving incorrect distances. Here we report the orbital parameters of the bright double star Atlas in the Pleiades, using long-baseline optical/infrared interferometry. From the data we derive a firm lower bound of D > 127 pc, with the most likely range being 133 < D < 137 pc. Our result reaffirms the fidelity of current stellar models.

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PubMed2003

A common origin for cosmic explosions inferred from calorimetry of GRB030329.

Past studies have suggested that long-duration gamma-ray bursts have a 'standard' energy of E(gamma) approximately 10(51) erg in the ultra-relativistic ejecta, after correcting for asymmetries in the explosion ('jets'). But a group of sub-energetic bursts, including the peculiar GRB980425 associated with the supernova SN1998bw (E(gamma) approximately 10(48) erg), has recently been identified. Here we report radio observations of GRB030329 that allow us to undertake calorimetry of the explosion. Our data require a two-component explosion: a narrow (5 degrees opening angle) ultra-relativistic component responsible for the gamma-rays and early afterglow, and a wide, mildly relativistic component that produces the radio and optical afterglow more than 1.5 days after the explosion. The total energy release, which is dominated by the wide component, is similar to that of other gamma-ray bursts, but the contribution of the gamma-rays is energetically minor. Given the firm link of GRB030329 with SN2003dh, our result indicates a common origin for cosmic explosions in which, for reasons not yet understood, the energy in the highest-velocity ejecta is extremely variable.

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PubMed2003

The bright optical afterglow of the nearby gamma-ray burst of 29 March 2003.

Past studies of cosmological gamma-ray bursts (GRBs) have been hampered by their extreme distances, resulting in faint afterglows. A nearby GRB could potentially shed much light on the origin of these events, but GRBs with a redshift z <or= 0.2 have been estimated to occur only rarely, about once per decade. Here we report the discovery of the bright optical afterglow emission from the burst of 29 March 2003 (GRB030329; ref. 2). The brightness of the afterglow and the prompt report of its position resulted in extensive follow-up observations at many wavelengths, along with the measurement of the redshift, z = 0.169 (ref. 4). The gamma-ray and afterglow properties of GRB030329 are similar to those of GRBs at cosmological redshifts. Observations have already identified the progenitor as a massive star that exploded as a supernova.

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PubMed2003

Early optical emission from the gamma-ray burst of 4 October 2002.

Observations of the long-lived emission--or 'afterglow'--of long-duration gamma-ray bursts place them at cosmological distances, but the origin of these energetic explosions remains a mystery. Observations of optical emission contemporaneous with the burst of gamma-rays should provide insight into the details of the explosion, as well as into the structure of the surrounding environment. One bright optical flash was detected during a burst, but other efforts have produced negative results. Here we report the discovery of the optical counterpart of GRB021004 only 193 seconds after the event. The initial decline is unexpectedly slow and requires varying energy content in the gamma-ray burst blastwave over the course of the first hour. Further analysis of the X-ray and optical afterglow suggests additional energy variations over the first few days.

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PubMed2003

Extracapsular cataract surgery compared with manual small incision cataract surgery in community eye care setting in western India: a randomised controlled trial.

AIM: To study "manual small incision cataract surgery (MSICS)" for the rehabilitation of cataract visually impaired and blind patients in community based, high volume, eye hospital setting; to compare the safety and effectiveness of MSICS with conventional extracapsular cataract surgery (ECCE). METHODS: In a single masked randomised controlled clinical trial, 741 patients, aged 40-90 years, with operable cataract were randomly assigned to receive either MSICS or ECCE and operated upon by one of eight participating surgeons. Intraoperative and postoperative complications were graded and scored according to the Oxford Cataract Treatment and Evaluation Team recommendations. The patients were followed up at 1 week, 6 weeks, and 1 year after surgery and their visual acuity recorded. RESULTS: This paper reports outcomes at 1 and 6 weeks. 706 of the 741(95.3%) patients completed the 6 week follow up. 135 of 362 (37.3%) of ECCE group and 165 of 344 (47.9%) of MSICS group had uncorrected visual acuity of 6/18 or better after 6 weeks of follow up. 314 of 362 (86.7%) of ECCE group and 309 of 344 (89.8%) of MSICS group had corrected postoperative vision of 6/18 or better. Four of 362 (1.1%) of ECCE group and six of 344 (1.7%) of MSICS group had corrected postoperative visual acuity less than 6/60. There were no significant differences between the two groups for intraoperative and severe postoperative complications. CONCLUSION: MSICS and ECCE are both safe and effective techniques for treatment of cataract patients in community eye care settings. MSICS needs similar equipment to ECCE, but gives better uncorrected vision.

Adult↗
PubMed2001

A test of general relativity from the three-dimensional orbital geometry of a binary pulsar.

Binary pulsars provide an excellent system for testing general relativity because of their intrinsic rotational stability and the precision with which radio observations can be used to determine their orbital dynamics. Measurements of the rate of orbital decay of two pulsars have been shown to be consistent with the emission of gravitational waves as predicted by general relativity, but independent verification was not possible. Such verification can in principle be obtained by determining the orbital inclination in a binary pulsar system using only classical geometrical constraints. This would permit a measurement of the expected retardation of the pulse signal arising from the general relativistic curvature of space-time in the vicinity of the companion object (the 'Shapiro delay'). Here we report high-precision radio observations of the binary millisecond pulsar PSR J0437-4715, which establish the three-dimensional structure of its orbit. We see the Shapiro delay predicted by general relativity, and we determine the mass of the neutron star and its white dwarf companion. The determination of such masses is necessary in order to understand the origin and evolution of neutron stars.

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