Study of Titanium based Composite Coatings for Resistance against Molten Aluminium Soldering on H13 Tool Steel

The service life of industrial components is limited predominantly by chemical corrosion, mechanical failure or mechanical wear. In the aluminium high pressure die casting industry, liquid aluminium is extremely reactive with the constituents of H13 die steel and has a tendency to form intermetallic layers. This chemical interaction results in sticking of molten metal to the die surface which produces defective castings and also damages the die surface. The use of thermal spray coatings provides protection to the surfaces operating in severe environments. An HVOF thermally sprayed coating has the advantage of having excellent bond strength and very low porosity levels (< 1%). This research work is concerned with producing and evaluating the performance of titanium/alumina based composite coatings to improve the service life of tool steel (H13) used for dies in aluminium high pressure die casting and dummy blocks used in Al extrusion. In this research work, the powder feedstocks for making the composite coatings were produced by high energy mechanical milling of a mixture of Al and TiO₂ powders in two different molar ratios followed by a thermal reaction process. The feedstock powder was then thermally sprayed using a high velocity oxygen fuel (HVOF) technique on H13 steel substrates to produce Ti(Al,O)/Al₂O₃ and TiAl/Al₂O₃ composite coatings. The performance of the coatings was assessed in terms of Al soldering, liquid metal corrosion resistance, thermal shock resistance and wear resistance. In an immersion test, the coated specimens were dipped into molten Al at a temperature of 700 ± 10 °C for different intervals of time. The performance of the coatings was tested in terms of liquid metal corrosion resistance and propensity to Al soldering. The dissolution behaviour of the coatings was evaluated by measuring weight loss after dipping the samples in to molten aluminium. The immersion test results showed that the coated samples have relatively few locations where aluminium soldering (reactive/chemical) occurred, however, an H13 steel surface showed more tendency for aluminium soldering. It was found that composite coatings changed the molten Al attack on H13 tool steel from a generalized to a localized one. No reaction between molten aluminium and a Ti(Al,O)/Al₂O₃ composite coating was identified. The TiAl/Al2O₃ composite coating was found to be attacked by molten aluminium as a result of a reaction between the coating and molten aluminium. The metallic phase TiAl in the composite coating is believed to be attacked by the molten Al. A Ti(Al,O)/Al₂O₃ composite coating was found to be a better protective coating than the TiAl/Al₂O₃ composite coating due its stability against molten aluminium attack. The thermal shock behaviour of the composite coatings was investigated by subjecting the coated coupons to a number of cycles, each cycle consisting of a holding time of 30 seconds in molten aluminium at 700 ± 10 °C followed by quenching into water. The surfaces of the coupons were examined for Al soldering and an evaluation of surface spallation. Any cracks found in the coatings were studied to explain their thermal shock behaviour. A Ti(Al,O)/Al₂O₃ composite coating on H13 tool steel produced from a fine feedstock has better thermal shock resistance than the Ti(Al,O)/Al₂O₃ TiAl/Al₂O₃ composite coatings produced from the agglomerated feedstocks. The study also describes and compares the tribological properties such as friction and sliding wear rate of the composite coatings both at room and high temperature (700.°C) under dry and lubricating conditions. The wear resistance of the coatings was investigated by a tribometer using a spherical ended alumina, flat ended high speed steel and spherical ended hardened steel pins as counter bodies. The experimental results show that the composite coatings look promising for high temperature applications due to their low wear rate at high temperature. However room temperature applications of the composite coatings can be improved under lubricated conditions. Successful trials of a Ti(Al,O)/Al₂O₃ composite coated dummy block revealed that the coating has potential as an industrial coating

Use of Amplatz Sheath in Percutaneous Nephrolithotomy and effect of its various sizes: Randomized Controlled Trial

Background: Nephrostomy tract itself is the most common source of hemorrhage during percutaneous nephrolithotomy, which can be avoided by puncturing through the calyx with minimal angulation between calyceal system and the nephroscope shaft. Smaller the sheath diameter, lesser would be the bleeding. Our objective was to compare mean change in hemoglobin (HB) level in patients undergoing percutaneous nephrolithotomy (PCNL) with 24 versus 30 French Amplatz sheath. Methods: In this study, 142 patients were randomly divided into Group A undergoing procedure with 24 French Amplatz sheath; and Group B with 30 French sheath. At the end of procedure in both groups, nephrostomy tube was kept for 24 hours. On first post-operative day, patients’ HB was checked and compared with pre-operative data, along with blood transfusion rates. SPSS 20 was used for data analysis and p-value < 0.05 was considered significant. Results: Median age and interquartile range of Group-A and Group-B patients was (40; 18) and (41; 21) years respectively. While stone size of Group-A and Group-B patients reported as (2.0; 0.60) and (2.1; 0.70) cm. The operative time and interquartile ratio of Group-A and Group-B patients was (75; 45) and (85; 45) minutes and we found significant change in HB of Group-A (0.90; 0.80) with Group-B patients (1.90; 0.70) gm/dl respectively [p = 0.000]. Conclusion: It was observed that use of 24 French Amplatz sheath lead to less renal hemorrhage and less hemoglobin drop compared to standard 30 French Amplatz sheath. Thus, small size Amplatz sheath in percutaneous nephrolithotomy may be considered effective and safe option for treatment of renal stones

Supine PCNL is the Way Forward, with Reduced Anesthesia and Operative Times As Compared to Prone PCNL, Along with Comparable Blood Loss and Stone Free Rates

Objective:The aim of this study is to compare safety and efficacy of supine versus prone percutaneous nephrolithotomy (PCNL) in terms of stonefree rate, operative time, anesthesia time and blood loss in a retrospective case-control trial.Materials and Methods:Fifty patients underwent supine PCNL during the study period (group A). Equal number of patients, who underwent prone PCNL during same period with similar demographic and clinical attributes, were taken as controls (group B). Demographic details, such as gender and age, and body mass index, stone size, stone location and stone laterality were comparable between the two groups. Pre- and post-operative hemoglobin (Hb) levels in patients in both groups were tabulated. Variables analyzed to compare the groups included operative time, anesthesia time, fall in Hb, blood transfusion, stone clearance and need for auxiliary procedure.Results:The median operative time (minutes) in patients of group A [35; interquartile ratio (IQR): 25], was significantly different from group B (70; IQR: 40) (p=0.000). The median anesthesia time (minutes) in patients in group A (50; IQR: 25) was significantly different from group B (85; 45) (p=0.000). The median fall in Hb (g/dL) in patients in group A (1.700; IQR: 1.2) was significantly different from group B (1.200; IQR: 2.4) (p=0.967). Two patients in group A and 7 in group B needed blood transfusion (p=0.080). Thirty two patient in group A and 34 in group B achieved stonefree status (p=0.833). Eleven patients in group A and 6 in group B needed auxiliary procedure in the form of extracorporeal shockwave lithotripsy (p=0.287).Conclusion:Supine PCNL is as safe and effective as conventionally performed prone PCNL, with an added benefit of decreased operative and anesthesia time

Is Routine Measurement of Post-operative Hemoglobin and Electrolytes Necessary in Every Patient After Transurethral Resection of the Prostate?

Objective: To evaluate the importance of post-operative hemoglobin and electrolyte monitoring after transurethral resection of the prostate (TURP) and establish the parameters to be considered for monitoring.Materials and Methods:Data of patients who underwent TURP between 2007 and 2017 were reviewed. Data regarding prostate size, irrigation fluid volume, resection time, pre- and post-operative electrolytes, hemoglobin levels taken within 48 hours before and after surgery, and blood transfusion information were collected. In order to establish parameters for post-operative laboratory monitoring, we categorized prostate size, resection time, and irrigation fluid into groups i.e. (80 g), (60 min) and (40 L) respectively.Results:A total of 1.000 patients were included. The median age was 66 years with the minimum of 46 years and maximum of 98 years. The median prostate size was 54.26 g. Among all pre- and post-operative laboratory parameters, only hemoglobin and sodium showed a significant change, which were analyzed further. Drop in hemoglobin was significantly associated with increasing prostate size and volume of irrigation fluid. Patients with a prostate size of >80 g had 27.3 times higher chance of significant (>2 g) drop in hemoglobin while 5.1 times higher when irrigation volume exceeded 40 liters. Low levels of sodium were strongly associated with prostate size, irrigation fluid volume, and resection time. However, all these factors become insignificant (p≥0.05) for their effect on low sodium, when these variables were adjusted with each other. Blood transfusion was performed in 27 patients. All these patients belonged to a group of patients with prostate size of more than 80 g with high resection time and irrigation fluid volume. Three patients had TUR syndrome. Post-operative hemoglobin and electrolytes monitoring contributed to a change in the management of only 14% of patients.Conclusion:Routine post-operative hemoglobin and electrolyte measurement is not required in every patient undergoing TURP. Use of risk stratification approach will help us to decide which patient needs post-operative lab testing

Comparing Holmium (Ho): YAG Laser with Pneumatic Lithoclast for Treatment Efficacy of Ureteric Stones

Background: Holmium YAG (yttrium-aluminum-garnet) laser, a comparatively new technique, can clear all types and sizes of stones and is only being used in two institutes of Karachi, Pakistan. The study aimed to compare pneumatic lithoclast and holmium YAG laser, to evaluate stone-free rate (SFR), postoperative complications, operative duration, and effectiveness. Methods: This cross-sectional research included 60 patients with age 16-65 years having ureteric stones, reporting to kidney center, Urology Department, Karachi, Pakistan. CT Scan of Kidneys, Ureter, and Bladder (KUB) were used to record stone size, laterality, and location within the ureter. Patients were divided into two clusters of 30 each, group A (Ho: YAG laser) and group B (pneumatic Lithoclast) having 0.5 to 02 cm of size ureteric stones. An Independent two-sample “t” test was used to assess the difference for the continuous variables. A p-value of ≤0.05 was considered statistically significant. Results: Stone sizes distribution was 1.3±0.3cms and 1.4±0.3cms for A and B groups respectively (p=0.8). The insignificance of the p-value demonstrated no substantial divergence between both groups and stone sizes. Clearance from the proximal ureter was noted 26(84.6%) in group A and 41.7% in group B with (p<0.05). A reduced lithotripsy activation period of 30.8±3.7mins was associated with stone size (p<0.05). Conclusion: Holmium: YAG Laser had better stone-free rate (SFR), with 84% clearance than pneumatic. Improved and effective clearance reduces the risk of residual stones within a lesser time, required for getting back to normal life routines. Keywords: Lasers; Ureteric Stones; Ho: YAG Laser; Pneumatic Lithoclast; Kidney Stones

OUTCOME OF PERCUTANEOUS NEPHROLITHOTOMY IN RENAL ANOMALIES: SINGLE CENTER EXPERIENCE

Background: PCNL is standard surgical treatment for renal stone > 2.0 cm and stone resistant to Extracorporeal Shock Wave Lithotripsy. This study was conducted to evaluate the outcome of percutaneous nephrolithotomy in renal anomalies. Methods: This cross sectional study was conducted at The Kidney Center postgraduate training institute Karachi from January 2010 to June 2017, comprised of 60 patients of stone size (median, IQR) 2.75,1.2. Percutaneous nephrolithotomy was done under general anesthesia; intra operative flouroscopy was done for stone clearance. Post-operative x-ray KUB was done to verify the clearance of stone. Results: Out of the 60 patients, most patients had horseshoe kidney 35 (58.3%) with right sided renal stone and majority of the stones are located in pelvis 37 (61.7%). 48 (80.0%) patients required nephrostomy while only 24 (40%) required Double J Stent insertion. In 42 (70%) patients 100% clearance was achieved and only 20 (33.3%) patients needed secondary procedures. Double J Stent insertion was done in both types of renal abnormality. In case of 100% clearance Double J Stent was inserted in 3 (33.3%) patients with malrotation while 7 (46.7%) horseshoe kidneys required Double J Stent insertion. Conclusion: Percutaneous nephrolithotomy is a safe treatment option in renal anomalies patients with renal stones

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy

Effects of antiplatelet therapy after stroke due to intracerebral haemorrhage (RESTART): a randomised, open-label trial

Background: Antiplatelet therapy reduces the risk of major vascular events for people with occlusive vascular disease, although it might increase the risk of intracranial haemorrhage. Patients surviving the commonest subtype of intracranial haemorrhage, intracerebral haemorrhage, are at risk of both haemorrhagic and occlusive vascular events, but whether antiplatelet therapy can be used safely is unclear. We aimed to estimate the relative and absolute effects of antiplatelet therapy on recurrent intracerebral haemorrhage and whether this risk might exceed any reduction of occlusive vascular events. Methods: The REstart or STop Antithrombotics Randomised Trial (RESTART) was a prospective, randomised, open-label, blinded endpoint, parallel-group trial at 122 hospitals in the UK. We recruited adults (≥18 years) who were taking antithrombotic (antiplatelet or anticoagulant) therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage, discontinued antithrombotic therapy, and survived for 24 h. Computerised randomisation incorporating minimisation allocated participants (1:1) to start or avoid antiplatelet therapy. We followed participants for the primary outcome (recurrent symptomatic intracerebral haemorrhage) for up to 5 years. We analysed data from all randomised participants using Cox proportional hazards regression, adjusted for minimisation covariates. This trial is registered with ISRCTN (number ISRCTN71907627). Findings: Between May 22, 2013, and May 31, 2018, 537 participants were recruited a median of 76 days (IQR 29–146) after intracerebral haemorrhage onset: 268 were assigned to start and 269 (one withdrew) to avoid antiplatelet therapy. Participants were followed for a median of 2·0 years (IQR [1·0– 3·0]; completeness 99·3%). 12 (4%) of 268 participants allocated to antiplatelet therapy had recurrence of intracerebral haemorrhage compared with 23 (9%) of 268 participants allocated to avoid antiplatelet therapy (adjusted hazard ratio 0·51 [95% CI 0·25–1·03]; p=0·060). 18 (7%) participants allocated to antiplatelet therapy experienced major haemorrhagic events compared with 25 (9%) participants allocated to avoid antiplatelet therapy (0·71 [0·39–1·30]; p=0·27), and 39 [15%] participants allocated to antiplatelet therapy had major occlusive vascular events compared with 38 [14%] allocated to avoid antiplatelet therapy (1·02 [0·65–1·60]; p=0·92). Interpretation: These results exclude all but a very modest increase in the risk of recurrent intracerebral haemorrhage with antiplatelet therapy for patients on antithrombotic therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage. The risk of recurrent intracerebral haemorrhage is probably too small to exceed the established benefits of antiplatelet therapy for secondary prevention

Effects of antiplatelet therapy after stroke due to intracerebral haemorrhage (RESTART): a randomised, open-label trial

Background: Antiplatelet therapy reduces the risk of major vascular events for people with occlusive vascular disease, although it might increase the risk of intracranial haemorrhage. Patients surviving the commonest subtype of intracranial haemorrhage, intracerebral haemorrhage, are at risk of both haemorrhagic and occlusive vascular events, but whether antiplatelet therapy can be used safely is unclear. We aimed to estimate the relative and absolute effects of antiplatelet therapy on recurrent intracerebral haemorrhage and whether this risk might exceed any reduction of occlusive vascular events. Methods: The REstart or STop Antithrombotics Randomised Trial (RESTART) was a prospective, randomised, open-label, blinded endpoint, parallel-group trial at 122 hospitals in the UK. We recruited adults (≥18 years) who were taking antithrombotic (antiplatelet or anticoagulant) therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage, discontinued antithrombotic therapy, and survived for 24 h. Computerised randomisation incorporating minimisation allocated participants (1:1) to start or avoid antiplatelet therapy. We followed participants for the primary outcome (recurrent symptomatic intracerebral haemorrhage) for up to 5 years. We analysed data from all randomised participants using Cox proportional hazards regression, adjusted for minimisation covariates. This trial is registered with ISRCTN (number ISRCTN71907627). Findings: Between May 22, 2013, and May 31, 2018, 537 participants were recruited a median of 76 days (IQR 29–146) after intracerebral haemorrhage onset: 268 were assigned to start and 269 (one withdrew) to avoid antiplatelet therapy. Participants were followed for a median of 2·0 years (IQR [1·0– 3·0]; completeness 99·3%). 12 (4%) of 268 participants allocated to antiplatelet therapy had recurrence of intracerebral haemorrhage compared with 23 (9%) of 268 participants allocated to avoid antiplatelet therapy (adjusted hazard ratio 0·51 [95% CI 0·25–1·03]; p=0·060). 18 (7%) participants allocated to antiplatelet therapy experienced major haemorrhagic events compared with 25 (9%) participants allocated to avoid antiplatelet therapy (0·71 [0·39–1·30]; p=0·27), and 39 [15%] participants allocated to antiplatelet therapy had major occlusive vascular events compared with 38 [14%] allocated to avoid antiplatelet therapy (1·02 [0·65–1·60]; p=0·92). Interpretation: These results exclude all but a very modest increase in the risk of recurrent intracerebral haemorrhage with antiplatelet therapy for patients on antithrombotic therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage. The risk of recurrent intracerebral haemorrhage is probably too small to exceed the established benefits of antiplatelet therapy for secondary prevention

Effects of antiplatelet therapy after stroke due to intracerebral haemorrhage (RESTART): a randomised, open-label trial

BACKGROUND: Antiplatelet therapy reduces the risk of major vascular events for people with occlusive vascular disease, although it might increase the risk of intracranial haemorrhage. Patients surviving the commonest subtype of intracranial haemorrhage, intracerebral haemorrhage, are at risk of both haemorrhagic and occlusive vascular events, but whether antiplatelet therapy can be used safely is unclear. We aimed to estimate the relative and absolute effects of antiplatelet therapy on recurrent intracerebral haemorrhage and whether this risk might exceed any reduction of occlusive vascular events. METHODS: The REstart or STop Antithrombotics Randomised Trial (RESTART) was a prospective, randomised, open-label, blinded endpoint, parallel-group trial at 122 hospitals in the UK. We recruited adults (≥18 years) who were taking antithrombotic (antiplatelet or anticoagulant) therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage, discontinued antithrombotic therapy, and survived for 24 h. Computerised randomisation incorporating minimisation allocated participants (1:1) to start or avoid antiplatelet therapy. We followed participants for the primary outcome (recurrent symptomatic intracerebral haemorrhage) for up to 5 years. We analysed data from all randomised participants using Cox proportional hazards regression, adjusted for minimisation covariates. This trial is registered with ISRCTN (number ISRCTN71907627). FINDINGS: Between May 22, 2013, and May 31, 2018, 537 participants were recruited a median of 76 days (IQR 29-146) after intracerebral haemorrhage onset: 268 were assigned to start and 269 (one withdrew) to avoid antiplatelet therapy. Participants were followed for a median of 2·0 years (IQR [1·0- 3·0]; completeness 99·3%). 12 (4%) of 268 participants allocated to antiplatelet therapy had recurrence of intracerebral haemorrhage compared with 23 (9%) of 268 participants allocated to avoid antiplatelet therapy (adjusted hazard ratio 0·51 [95% CI 0·25-1·03]; p=0·060). 18 (7%) participants allocated to antiplatelet therapy experienced major haemorrhagic events compared with 25 (9%) participants allocated to avoid antiplatelet therapy (0·71 [0·39-1·30]; p=0·27), and 39 [15%] participants allocated to antiplatelet therapy had major occlusive vascular events compared with 38 [14%] allocated to avoid antiplatelet therapy (1·02 [0·65-1·60]; p=0·92). INTERPRETATION: These results exclude all but a very modest increase in the risk of recurrent intracerebral haemorrhage with antiplatelet therapy for patients on antithrombotic therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage. The risk of recurrent intracerebral haemorrhage is probably too small to exceed the established benefits of antiplatelet therapy for secondary prevention. FUNDING: British Heart Foundation