Cavity Development During Creep Deformation in Alumina with a Bimodal Grain Size Distribution

An alumina sample, codoped with equimolar proportions of magnesia and zirconia, exhibited a bimodal grain size distribution after hot-pressing. Flexural creep experiments were performed on this material at temperatures of 1673 and 1773 K in air. Inspection of the deformed specimens revealed extensive creep cavitation, with cavities developing preferentially in the coarse-grained regions. The nucleation, growth, and interlinkage of the cavities led to the formation of cracks. Crack growth occurred in the coarse-grained regions by the linkage of cavities with the crack tip. However, several cracks were observed to terminate after extending up to a fine-grained region of a specimen. A model has been developed to rationalize the observation that preferential cavitation occurs in the coarse-grained regions of a specimen undergoing creep deformation.     

Ultraviolet sensing properties of polyvinyl alcohol-coated aluminium-doped zinc oxide nanorods

Undoped and aluminium (Al)-doped zinc oxide (ZnO) nanorods have been synthesized by electrochemical route. The synthesized materials have been characterized by X-ray diffraction, UV–visible spectrometer and scanning electron microscope. The Al-doped ZnO nanorods have been coated with polyvinyl alcohol. Current–voltage characteristics have been investigated in dark and under UV-light illumination. Aluminium doping in ZnO increase its electrical conductivity and further polyvinyl alcohol coating on Al-doped ZnO increase UV sensitivity of the material. Response and recovery time of Al-doped ZnO and PVA-coated Al-doped ZnO nanorods have been recorded. PVA-coated Al-doped ZnO nanorods shows very fast response and recovery time of 10 s in comparison to uncoated ZnO (20 min) nanorods.     

Isolation and identification of proteolytic psychrotrophic sporeforming bacteria from raw milk supplies at an experimental dairy in India

Of 51 samples of raw milk produced at the National Dairy Research Institute, 65% were found to contain proteolytic psychrotrophic sporeforming bacilli. The protease activity of 50 isolates selected ranged from 20 to 480 units/ml. Twenty/four per cent (12) of the total isolates exhibited enzyme activity in the range 51–100 units/ml, while 20% (10) had protease activity of more than 300 units/ml. Of the 50 isolates, 36% were Bacillus cereus, 20% B. polymyxa, 14% each B. laterosporus and B. circulans. 10% B. pumilus. 4% B. subtilis and 2% were identified as B. coagulans.     

Isolation and identification of protease-producing psychrotrophic bacteria from dairy products in India

Of the 259 proteolytic psychrotrophic bacterial cultures isolated from different dairy products produced at the National Dairy Research Institute, 39 cultures exhibited more than 150 units/ml protease activity. These isolates were identified and grouped into five genera, viz ., Pseudomonas spp ., Flavobacterium spp ., Alcaligenes spp ., Micrococcus spp., and Staphylococcus spp. The culture supernatants from six isolates retained more than 50% enzyme activity after heating at 50° C for 10 min, protease of Pseudomonas sp. 8–25 having maximum heat resistance.     

Effect of capping agents on optical and antibacterial properties of cadmium selenide quantum dots

Cadmium selenide quantum dots (CdSe QDs) were synthesized in aqueous phase by the freezing temperature injection technique using different capping agents (viz. thioglycolic acid, 1-thioglycerol, L-cysteine). Absorption spectra of CdSe QDs exhibited a blue shift as compared to its bulk counterpart, which is an indication of quantum confinement effect. The photoluminescence spectra of CdSe QDs confirmed that the particles are poly-dispersed and possess enhanced luminescent property, depending upon the chemical nature of capping agents. The QDs have been characterized by Fourier-transform infrared spectroscopy, atomic absorption spectroscopy and transmission electron microscopy. Further, antimicrobial activity of as-prepared QDs has also been investigated using the disk diffusion method.     

Calcium supplementation in colorectal cancer prevention: A systematic meta-analysis of adverse events

Despite the multiple systematic reviews and meta-analyses accumulating evidence on the preventive effect of calcium supplementation for colorectal cancer, most of the associated adverse effects are not systematically analyzed. The aim of the study is evaluating adverse events associated with calcium supplementation for colorectal cancer prevention through a systematic meta-analysis. We searched Medline, PubMed Central, EMBASE (Excerpta Medica database), Scopus, Cochrane Central Register of Controlled Trials, and Web of Science published in English from database inception up to 31 July 2019. In the current systematic meta-analysis, we included human studies (including cohort studies, clinical trials, case-control studies) on supplementation of calcium in patients with or at risk of colorectal cancer. Assessment of the quality of included studies was performed by Jadad score. Information on the patient population, number of enrolled subjects in each group, dose of calcium supplementation, duration of calcium supplementation, and reported adverse events were gathered. The data were pooled for incidence rates for any adverse event during the study period regardless of causality association. We identified 6 studies, comprising 4583 participants that met the inclusion criteria. Meta-analysis on pooled incidence rates for adverse event during study period showed no statistically significant increased risk for cancer (OR = 0.92, 95% CI: 0.70–1.21, P = 0.577; I² = 0.0%, P = 0.731), coronary revascularization (OR = 1.12, 95% CI: 0.79–1.59, P = 0.492; I² = 0.0%, P = 0.957), myocardial infarction (OR = 0.81, 95% CI: 0.34–1.91, P = 0.634; I² = 67.9%, P = 0.047), stroke (OR = 0.75, 95% CI: 0.42–1.33, P = 0.332, I² = 0.00%, P = 0.717), Transient Ischemic Attack (TIA) (OR = 1.37, 95% CI: 0.28–6.51, P = 0.692, I² = 81.9%, P = 0.002), urolithiasis (OR = 1.23, 95% CI: 0.75–2.01, P = 0.410; I² = 0.0%, P = 0.851), fracture (OR = 0.98, 95% CI: 0.70–1.37, P = 0.938; I² = 37.8%, P = 0.152) and death (OR = 1.05, 95% CI: 0.71–1.56, P = 0.786, I² = 12.2%, P = 0.317) in patients receiving calcium supplementation for colorectal cancer prevention compared to control. Based on the results of Egger test, publication bias was not observed among the studies (P = 0.262). The current result of the meta-analysis on human studies reporting adverse events associated with calcium supplementation for the prevention of colorectal cancer demonstrated no statistically significant increased risk for the development of adverse events compared to control groups.     

FORCED OSCILLATIONS IN A TUBULAR LINEAR INDUCTION MOTOR

ABSTRACT

A method of obtaining forced sustained oscillations in a tubular linear induction motor (TLIM) is presented. Equations of motion of the motor/controller system are formulated and solved for various operating conditions. The performance of the system is thus evaluated. Results obtained from the analysis are compared with the experimental results     

A ROLLING HORIZON HEURISTIC FOR REACTIVE SCHEDULING OF BATCH PROCESS OPERATIONS

Batch chemical plants are dynamic processing facilities where static production schedules can rarely be adhered to due to market and operating uncertainties. On-line schedule modification of a prior; timing assignments and resource allocations in response to unantipicated disruptions is done through a decomposition heuristic that uses a rolling horizon implementation policy. An attempt is made to minimize the impact of the disruptions on the original schedule near the point of each deviation while exploiting the combinatorial flexibility of task and resource reassignments in future scheduling time windows. The problem is addressed as a multiobjective optimization problem involving completion time criteria, relative customer importance, and production cost considerations.

A rigorous analysis of problem sensitive parameters, including penalty weights and subhorizon length, is conducted. A model plant case study is performed. Variations on storage availability and task flexibility are investigated in an attempt to characterize dominant effects of the weighting parameters. Results indicate that user preference can serve as a strong guide for obtaining near optimal reactive scheduling solutions. It is shown that the combinatories can be controlled and that costly and inefficient full scale rescheduling of multipurpose production facilities can be avoided.