An independent single surgeon's 7-year experience with Birmingham hip resurfacing is presented. T... more An independent single surgeon's 7-year experience with Birmingham hip resurfacing is presented. The study also involved investigation of the significance of pedestal sign in patients requiring revision. A consecutive 117 hips in 101 patients (59 male and 42 female patients) operated on by the senior author (VGJ) were assessed at a mean follow-up of 7 years (range, 5-9.4 years). Mean age at surgery was 54 years (range, 20-74 years). Seventy-three hips had a preoperative diagnosis of primary osteoarthritis, and secondary osteoarthritis was seen in 44 hips. Failure was defined as revision for any reason. Revision of the femoral component alone was undertaken in 8 hips (6.8%): 5 within first year for periprosthetic fracture neck of femur and in 3 hips after 5 years of follow-up. In 2 patients who were known to have osteonecrosis of the femoral head preoperatively, the femoral component progressively collapsed into varus after 5 years of follow-up. Pedestal sign was the earliest radiologic sign noted in these 2 patients and progressed rapidly within 1 year on serial radiographs well before the onset of clinical symptoms. Kaplan-Meier survival with revision as end point at 7 years was 91.5% (95% confidence interval, 97.6%-85.4%). Keywords: birmingham hip resurfacing, osteonecrosis, pedestal sign.
Assessing the quality of image segmentation algorithms is an essential step towards the quantitat... more Assessing the quality of image segmentation algorithms is an essential step towards the quantitative analysis of biological microscopy images. Given the limited accuracy of segmentation algorithms in all but trivial cases, it is particularly important to define an index to grade the quality of segmentations. Such an index can help guide the choice of algorithms for a particular application, assist in optimizing algorithm parameters, and provide a measure of quality when evaluating scientific conclusions drawn from the results of the segmentation. Motivated by the problem of segmenting microscopy images of thick tissue sections, we propose an approach to evaluate segmentation quality for images that contain a large number of objects (e.g., nuclei). The evaluation of such images is rendered difficult for two reasons, (i) the correspondence of components between two segmentations of the same image is often ambiguous, and (ii) the number of components in the image is typically too large to generate complete ground truth for. Existing evaluation techniques of segmentation algorithms are inadequate to be applied under these constraints. Our proposed evaluation strategy addresses both these constraints by suitably modifying a commonly accepted evaluation index. We demonstrate the efficacy of our proposed strategy towards the evaluation of typical segmentations of fluorescence microscopy images of cell nuclei.
The present article describes the failure of a primary reformer tube in an ammonia plant. The fai... more The present article describes the failure of a primary reformer tube in an ammonia plant. The failure took place at the stub end of the reformer tube where a SS 321 flange was joined to a HK 40 catalyst tube by welding. Detailed metallurgical examinations indicated that the failure was due to stress corrosion cracking. Both longitudinal and transverse cracks were observed at the region of fracture. The cracks originated at the interface of the weld and HAZ at the inner surface and progressed to the outside of the tube in the transverse (thickness) direction. Microstructural study revealed chromium carbides precipitation at the grain boundaries in the heat affected zones on either sides of the weld. The results clearly indicated that the steel had undergone sensitisation which subsequently led to failure of the reformer tube by stress corrosion cracking. #
A micro/hairline crack was noticed on a low speed, hollow shaft of a single stage helical gearbox... more A micro/hairline crack was noticed on a low speed, hollow shaft of a single stage helical gearbox during service. Though this had not resulted in a catastrophic failure, the shaft was withdrawn from service because of leakage of oil. Subsequent investigation revealed that the crack had initiated by fatigue at one of the keyway edges and progressed about 3/4 of the shaft periphery in a helical manner but had not given rise to final fracture of the shaft. The fatigue crack initiation was due to stress concentration arising from a depression mark at the keyway end surface. The problem was further aggravated due to inadequate radius at the keyway edges and rough machining marks. An analysis of the failure, together with recommendations for failure prevention, is presented in this paper. #
Cracks were observed at the trailing edge of the blades of a turbine rotor blisk of a gas turbine... more Cracks were observed at the trailing edge of the blades of a turbine rotor blisk of a gas turbine engine during inspection following an endurance test. The integrally bladed disk was made of Mar-M-247 alloy, cast and hipped. Visual inspection, micro and macro fractography, and metallography of the failed blades indicated that the failure was caused by stress rupture at
A reverse phase high performance liquid chromatography method was developed for the simultaneous ... more A reverse phase high performance liquid chromatography method was developed for the simultaneous estimation of aspirin and clopidogrel bisulphate in formulation. The separation was achieved by octadecyl column (C 18 ) and acetonitrile:methanol:20 mM phosphate buffer at pH 3 (50:7:43 v/v) as eluent, at a fl ow rate of 1 ml/min. Detection was carried out at 240 nm. Quantitation was done by external standard calibration method. The retention time of aspirin and clopidogrel bisulphate was found to be 2.40 and 9.27 min, respectively. The method has been validated for linearity, accuracy and precision. Linearity for aspirin and clopidogrel bisulphate were in the range of 10-50 µg/ml for both the drugs. The mean recoveries obtained for aspirin and clopidogrel bisulphate were 100.86% and 100.20%, respectively. The developed method was found to be accurate, precise, selective and rapid for the simultaneous estimation of aspirin and clopidogrel bisulphate in capsules.
To elucidate the association between macular pigment optical density (MPOD) and various types of ... more To elucidate the association between macular pigment optical density (MPOD) and various types of obesity in the South-Indian population. In total, 300 eyes of 161 healthy volunteers of South-Indian origin were studied. MPOD was measured psychophysically at 0.25°, 0.50°, 1.00°, and 1.75° eccentricities from fovea. Anthropometric measurements included waist circumference (WC) and waist-to-hip ratio (WHR) and body mass index (BMI). Using the WHO Expert Consultation guidelines, obesity was defined based on BMI alone (BMI ≥ 23 kg/m(2)), based on WC alone (WC ≥ 90 cm for men and ≥ 80 cm for women), and based on WHR alone (≥ 0.90 for men and ≥ 0.85 for women). Isolated generalized obesity was defined as increased BMI and normal WC. Isolated abdominal obesity was defined as increased WC and normal BMI. Combined obesity was defined as increased BMI and increased WC. Mean MPOD at all eccentricities was not significantly different between men and women. Mean MPOD values did not significantly differ in various types of obesity, when compared with the normal subjects. On subgroup analysis, in age group ≥ 60 years, mean MPOD values were significantly higher in subjects with obesity based on BMI (0.61 vs 0.41, P=0.036), obesity based on WHR (0.67 vs 0.41, P=0.007), and isolated generalized obesity (0.66 vs 0.41, P=0.045) in comparison with normal subjects at 0.25° eccentricity. We found lack of an association between MPOD and obesity in the South-Indian population. A similar finding was also noted on age group- and gender-wise analyses.
In order to study the effects of vitamin D (calciferol) and its inter-relationship to adrenocorti... more In order to study the effects of vitamin D (calciferol) and its inter-relationship to adrenocortical hormone (prednisolone) metabolic balance studies were performed in 10 normal children and 10 children with vitamin D deficiency rickets. An increase in the intestinal absorption of calcium and phosphorus due to administration of vitamin D was observed in all the children with rickets. The initial negative calcium and phosphorus balances became positive in all the cases following the administration of vitamin D (10,000 I.U. orally/day). Vitamin D raised the serum calcium and phosphorus levels, increased urinary calcium excretion and promoted the renal retention of phosphorus in rickets. Vitamin D exerted similar actions when given to normal children but the effects were much less pronounced. All had positive calcium and phosphorus balances. The concurrent administration of prednisolone (10 mg orally/day) and vitamin D caused significant inhibition of the intestinal absorption of calcium and phosphorus in all children with rickets. Similar inhibitory effects of prednisolone, though of minor degree, were observed in normal children. The results of our short term balance experiments suggested that prednisolone had a blocking or antagonising effect on the metabolic actions of vitamin D on intestine. Prednisolone, however, is not the complete antimetabolite of vitamin D and further work is needed to discover the metabolic process where it competes with vitamin D, particularly with its newly discovered metabolites, 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol.
This Business Project is the result of a hard work developed by four entrepreneurial engineers du... more This Business Project is the result of a hard work developed by four entrepreneurial engineers during the last six months. This has been possible thank to the strong knowledge acquired within the Business Administration Master.
An independent single surgeon's 7-year experience with Birmingham hip resurfacing is presented. T... more An independent single surgeon's 7-year experience with Birmingham hip resurfacing is presented. The study also involved investigation of the significance of pedestal sign in patients requiring revision. A consecutive 117 hips in 101 patients (59 male and 42 female patients) operated on by the senior author (VGJ) were assessed at a mean follow-up of 7 years (range, 5-9.4 years). Mean age at surgery was 54 years (range, 20-74 years). Seventy-three hips had a preoperative diagnosis of primary osteoarthritis, and secondary osteoarthritis was seen in 44 hips. Failure was defined as revision for any reason. Revision of the femoral component alone was undertaken in 8 hips (6.8%): 5 within first year for periprosthetic fracture neck of femur and in 3 hips after 5 years of follow-up. In 2 patients who were known to have osteonecrosis of the femoral head preoperatively, the femoral component progressively collapsed into varus after 5 years of follow-up. Pedestal sign was the earliest radiologic sign noted in these 2 patients and progressed rapidly within 1 year on serial radiographs well before the onset of clinical symptoms. Kaplan-Meier survival with revision as end point at 7 years was 91.5% (95% confidence interval, 97.6%-85.4%). Keywords: birmingham hip resurfacing, osteonecrosis, pedestal sign.
Assessing the quality of image segmentation algorithms is an essential step towards the quantitat... more Assessing the quality of image segmentation algorithms is an essential step towards the quantitative analysis of biological microscopy images. Given the limited accuracy of segmentation algorithms in all but trivial cases, it is particularly important to define an index to grade the quality of segmentations. Such an index can help guide the choice of algorithms for a particular application, assist in optimizing algorithm parameters, and provide a measure of quality when evaluating scientific conclusions drawn from the results of the segmentation. Motivated by the problem of segmenting microscopy images of thick tissue sections, we propose an approach to evaluate segmentation quality for images that contain a large number of objects (e.g., nuclei). The evaluation of such images is rendered difficult for two reasons, (i) the correspondence of components between two segmentations of the same image is often ambiguous, and (ii) the number of components in the image is typically too large to generate complete ground truth for. Existing evaluation techniques of segmentation algorithms are inadequate to be applied under these constraints. Our proposed evaluation strategy addresses both these constraints by suitably modifying a commonly accepted evaluation index. We demonstrate the efficacy of our proposed strategy towards the evaluation of typical segmentations of fluorescence microscopy images of cell nuclei.
The present article describes the failure of a primary reformer tube in an ammonia plant. The fai... more The present article describes the failure of a primary reformer tube in an ammonia plant. The failure took place at the stub end of the reformer tube where a SS 321 flange was joined to a HK 40 catalyst tube by welding. Detailed metallurgical examinations indicated that the failure was due to stress corrosion cracking. Both longitudinal and transverse cracks were observed at the region of fracture. The cracks originated at the interface of the weld and HAZ at the inner surface and progressed to the outside of the tube in the transverse (thickness) direction. Microstructural study revealed chromium carbides precipitation at the grain boundaries in the heat affected zones on either sides of the weld. The results clearly indicated that the steel had undergone sensitisation which subsequently led to failure of the reformer tube by stress corrosion cracking. #
A micro/hairline crack was noticed on a low speed, hollow shaft of a single stage helical gearbox... more A micro/hairline crack was noticed on a low speed, hollow shaft of a single stage helical gearbox during service. Though this had not resulted in a catastrophic failure, the shaft was withdrawn from service because of leakage of oil. Subsequent investigation revealed that the crack had initiated by fatigue at one of the keyway edges and progressed about 3/4 of the shaft periphery in a helical manner but had not given rise to final fracture of the shaft. The fatigue crack initiation was due to stress concentration arising from a depression mark at the keyway end surface. The problem was further aggravated due to inadequate radius at the keyway edges and rough machining marks. An analysis of the failure, together with recommendations for failure prevention, is presented in this paper. #
Cracks were observed at the trailing edge of the blades of a turbine rotor blisk of a gas turbine... more Cracks were observed at the trailing edge of the blades of a turbine rotor blisk of a gas turbine engine during inspection following an endurance test. The integrally bladed disk was made of Mar-M-247 alloy, cast and hipped. Visual inspection, micro and macro fractography, and metallography of the failed blades indicated that the failure was caused by stress rupture at
A reverse phase high performance liquid chromatography method was developed for the simultaneous ... more A reverse phase high performance liquid chromatography method was developed for the simultaneous estimation of aspirin and clopidogrel bisulphate in formulation. The separation was achieved by octadecyl column (C 18 ) and acetonitrile:methanol:20 mM phosphate buffer at pH 3 (50:7:43 v/v) as eluent, at a fl ow rate of 1 ml/min. Detection was carried out at 240 nm. Quantitation was done by external standard calibration method. The retention time of aspirin and clopidogrel bisulphate was found to be 2.40 and 9.27 min, respectively. The method has been validated for linearity, accuracy and precision. Linearity for aspirin and clopidogrel bisulphate were in the range of 10-50 µg/ml for both the drugs. The mean recoveries obtained for aspirin and clopidogrel bisulphate were 100.86% and 100.20%, respectively. The developed method was found to be accurate, precise, selective and rapid for the simultaneous estimation of aspirin and clopidogrel bisulphate in capsules.
To elucidate the association between macular pigment optical density (MPOD) and various types of ... more To elucidate the association between macular pigment optical density (MPOD) and various types of obesity in the South-Indian population. In total, 300 eyes of 161 healthy volunteers of South-Indian origin were studied. MPOD was measured psychophysically at 0.25°, 0.50°, 1.00°, and 1.75° eccentricities from fovea. Anthropometric measurements included waist circumference (WC) and waist-to-hip ratio (WHR) and body mass index (BMI). Using the WHO Expert Consultation guidelines, obesity was defined based on BMI alone (BMI ≥ 23 kg/m(2)), based on WC alone (WC ≥ 90 cm for men and ≥ 80 cm for women), and based on WHR alone (≥ 0.90 for men and ≥ 0.85 for women). Isolated generalized obesity was defined as increased BMI and normal WC. Isolated abdominal obesity was defined as increased WC and normal BMI. Combined obesity was defined as increased BMI and increased WC. Mean MPOD at all eccentricities was not significantly different between men and women. Mean MPOD values did not significantly differ in various types of obesity, when compared with the normal subjects. On subgroup analysis, in age group ≥ 60 years, mean MPOD values were significantly higher in subjects with obesity based on BMI (0.61 vs 0.41, P=0.036), obesity based on WHR (0.67 vs 0.41, P=0.007), and isolated generalized obesity (0.66 vs 0.41, P=0.045) in comparison with normal subjects at 0.25° eccentricity. We found lack of an association between MPOD and obesity in the South-Indian population. A similar finding was also noted on age group- and gender-wise analyses.
In order to study the effects of vitamin D (calciferol) and its inter-relationship to adrenocorti... more In order to study the effects of vitamin D (calciferol) and its inter-relationship to adrenocortical hormone (prednisolone) metabolic balance studies were performed in 10 normal children and 10 children with vitamin D deficiency rickets. An increase in the intestinal absorption of calcium and phosphorus due to administration of vitamin D was observed in all the children with rickets. The initial negative calcium and phosphorus balances became positive in all the cases following the administration of vitamin D (10,000 I.U. orally/day). Vitamin D raised the serum calcium and phosphorus levels, increased urinary calcium excretion and promoted the renal retention of phosphorus in rickets. Vitamin D exerted similar actions when given to normal children but the effects were much less pronounced. All had positive calcium and phosphorus balances. The concurrent administration of prednisolone (10 mg orally/day) and vitamin D caused significant inhibition of the intestinal absorption of calcium and phosphorus in all children with rickets. Similar inhibitory effects of prednisolone, though of minor degree, were observed in normal children. The results of our short term balance experiments suggested that prednisolone had a blocking or antagonising effect on the metabolic actions of vitamin D on intestine. Prednisolone, however, is not the complete antimetabolite of vitamin D and further work is needed to discover the metabolic process where it competes with vitamin D, particularly with its newly discovered metabolites, 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol.
This Business Project is the result of a hard work developed by four entrepreneurial engineers du... more This Business Project is the result of a hard work developed by four entrepreneurial engineers during the last six months. This has been possible thank to the strong knowledge acquired within the Business Administration Master.
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