Determination of Optimum Machining Parameters for Face Milling Process of Ti6A14V Metal Matrix Composite

This paper shows the novel approach of Taguchi-Based Grey Relational Analysis of Ti6Al4V Machining parameter. Ti6Al4V metal matrix composite has been fabricated using the powder metallurgy route. Here, all the components of TI6Al4V machining forces, including longitudinal force (F_x), radial force (F_y), tangential force (F_z), surface roughness and material removal rate (MRR) are measured during the facing operation. The effect of three process parameters, cutting speed, tool feed and cutting depth, is being studied on the matching responses. Orthogonal design of experiment (Taguchi L9) has been adopted to execute the process parameters in each level. To validate the process output parameters, the Grey Relational Analysis (GRA) optimization approach was applied. The percentage contribution of machining parameters to the parameter of response performance was interpreted through variance analysis (ANOVA). Through the GRA process, the emphasis was on the fact that for TI6Al4V metal matrix composite among all machining parameters, tool feed serves as the highest contribution to the output responses accompanied by the cutting depth with the cutting speed in addition. From optimal testing, it is found that for minimization of machining forces, maximization of MRR and minimization of Ra, the best combinations of input parameters are the 2nd stage of cutting speed (175 m/min), the 3rd stage of feed (0.25 mm/edge) as well as the 2nd stage of cutting depth (1.2 mm). It is also found that hardness of Ti6Al4V MMC is 59.4 HRA and composition of that material remain the same after milling operation.     

Seven-year trends in cataract surgery indications and quality of outcomes at Aravind Eye Hospitals,India

PurposeTo report trends in cataract surgery indications, visual acuity outcomes, complication rates and reoperation rates at ten Aravind Eye Hospitals in Tamil Nadu, India.MethodsIn this retrospective database study we analyzed seven years of data of cataract surgeries at Aravind during January 1, 2012 to December 31, 2018. Our main outcome measures were preoperative and 1-month postoperative uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA); and rates of intraoperative complications and reoperations. We performed Cochran–Armitage trend tests.ResultsIn 1.86 million eyes that underwent cataract surgery, the percentage of eyes undergoing phacoemulsification (PE) showed an increasing trend (p < 0.0001), from 26.8% in 2012 to 33.5% in 2018. The percentage of eyes undergoing manual small incision cataract surgery (SICS) showed a decreasing trend (p < 0.0001), from 70.0% in 2012 to 65.1% in 2018. For SICS, the percentages of eyes with good postoperative UCVA and BCVA showed increasing trends (p < 0.0001 for each), and the percentages of eyes with poor postoperative UCVA and BCVA showed decreasing trends (p < 0.0001 for each). Results for PE surgeries were mixed. For both PE and SICS rates of intraoperative complications showed a declining trend (p < 0.0001 for each) and a slight increasing trend for reoperations (PE p < 0.02; SICS p < 0.0001).ConclusionsDuring this seven-year period there were noticeable trends in cataract surgeries performed at Aravind in terms of the mix of surgical procedures, preoperative vision, and cataract surgical outcomes.Subject terms: Risk factors, Lens diseases     

Temozolomide resistance in glioblastoma occurs by miRNA-9-targeted PTCH1, independent of sonic hedgehog level

Glioblastoma Multiforme (GBM), the most common and lethal adult primary tumor of the brain, showed a link between Sonic Hedgehog (SHH) pathway in the resistance to temozolomide (TMZ). PTCH1, the SHH receptor, can tonically represses signaling by endocytosis. We asked how the decrease in PTCH1 in GBM cells could lead to TMZ-resistance. TMZ resistant GBM cells have increased PTCH1 mRNA and reduced protein. Knockdown of Dicer, a Type III RNAase, indicated that miRNAs can explain the decreased PTCH1 in TMZ resistant cells. Computational studies, real-time PCR, reporter gene studies, western blots, target protector oligos and ectopic expression identified miR-9 as the target of PTCH1 in resistant GBM cells with concomitant activation of SHH signaling. MiR-9 mediated increases in the drug efflux transporters, MDR1 and ABCG2. MiR-9 was increased in the tissues from GBM patients and in an early passage GBM cell line from a patient with recurrent GBM but not from a naïve patient. Pharmacological inhibition of SHH signaling sensitized the GBM cells to TMZ. Taken together, miR-9 targets PTCH1 in GBM cells by a SHH-independent method in GBM cells for TMZ resistance. The identified pathways could lead to new strategies to target GBM with combinations of drugs.     

Multidrug resistance of Pseudomonas aeruginosa as known from surveillance of nosocomial and community infections in an Indian teaching hospital

Aim

The aim of the present study was to record nosocomial and community-acquired accounts of antibiotic resistance in Pseudomonas aeruginosa strains, isolated from clinical samples of a hospital by surveillance, over a period of 18?months (November 2009–April 2011).

Subject and Methods

Clinical samples from nosocomial sources, i.e. wards and cabins and intensive care unit (ICU) and neonatal intensive care unit (NICU) sources, and community (outpatient department, OPD) sources of a hospital were used for isolating strains of P. aeruginosa.

Results

Of 368 isolated strains of P. aeruginosa, a total of 201 (54.62%) strains were from nosocomial and 167 (45.38%) strains were from community samples. There were 42 (25.14%) extended spectrum β-lactamase (ESβL) strains among the 167 isolates from the community samples. And from wards and cabins, there were 29 (23%) ESβL strains among the 126 isolates. Of the 75 isolates from ICU and NICU, there were 25 (33.33%) ESβL strains; the total of nosocomial ESβL strains was 54 (26.86%) in this study from the total of 201 P. aeruginosa isolates. In a computation of the χ² test of independence for assessing incidences of ESβL strains among all multidrug-resistant (MDR) strains, it was inferred that ESβL strains were equally distributed in wards and cabins, ICU and NICU or community, similar to the rest of the other MDR P. aeruginosa strains. Fifteen antibiotics were used for assessing antibiotic sensitivity of all isolated P. aeruginosa strains and a progressive increase of percent values of drug resistance was recorded.

Conclusion

This study on surveillance of a hospital revealed the daunting state of occurrence of MDR P. aeruginosa. A progressive increase of percent values of drug resistance to 15 antibiotics used for antibiotic sensitivity of P. aeruginosa strains was recorded.     

Some pharmacological actions of the essential oil of Blumea membranacea

The essential oil obtained from the plant Blumea membranacea produced a marked and long lasting fall in blood pressure in anaesthetized dogs. The oil exerted a direct depressant action on frog heart and spasmolytic effect on rabbit ileum. It also depressed the conditioned avoidance response, adversely affected rotarod performance and potentiated the pentobarbitone induced hypnosis in rats.     

Influence of testosterone and dihydrotestosterone on bone-matrix induced endochondral bone formation

Summary A bone matrix-induced endochondral bone development model has been used to study the effects of androgens on different stages of bone development in castrated young adult rats. Androgen treatment, especially with dihydrotestosterone (DHT) for 7 days, inhibited³⁵SO₄ incorporation by the developing cartilage in the induced plaques. Castrated control animals maintained for 11 days after implantation of bone matrix showed significantly lower calcium levels in the induced implant than was observed earlier in the unoperated controls. DHT treatment for 11 days caused dramatic increases in levels of calcium in the implants. Testosterone had little effect. When androgen treatment was continued for 21 days, while levels of alkaline phosphatase in the implants were unaffected, levels of calcium in the implants were significantly higher than on day 11 for both castrated control and androgen-treated animals. Peak alkaline phosphatase activity (day 10) is known to precede peak calcium mineralizing activity (day 12) in this model and it is also known that calcium levels remain high thereafter. Evaluation of calcium and alkaline phosphatase levels in the proximal tibial metaphyses of castrated control and androgen-treated groups of animals showed no changes after 11 days treatment. Prolonged treatment (21 days) elevated the levels of alkaline phosphatase whereas no change was observed in calcium levels in the tibial metaphyses. These findings demonstate that androgens stimulate mineralization and that DHT is more active when used for short periods of time and in early stages of bone development in matrix-induced implants.