Quaternary 2D Transition Metal Dichalcogenides (TMDs) with Tunable Bandgap

Alloying/doping in 2D material is important due to wide range bandgap tunability. Increasing the number of components would increase the degree of freedom which can provide more flexibility in tuning the bandgap and also reduces the growth temperature. Here, synthesis of quaternary alloys Mo_x W_1?x S_2y Se_{2(1?y )} is reported using chemical vapor deposition. The composition of alloys is tuned by changing the growth temperatures. As a result, the bandgap can be tuned which varies from 1.61 to 1.85 eV. The detailed theoretical calculation supports the experimental observation and shows a possibility of wide tunability of bandgap.     

Biological phenol removal using immobilized cells in a pulsed plate bioreactor: effect of dilution rate and influent phenol concentration

The continuous aerobic biodegradation of phenol in synthetic wastewater was carried out using Nocardia hydrocarbonoxydans immobilized over glass beads packed between the plates in a pulsed plate bioreactor at a frequency of pulsation of 0.5s(-1) and amplitude of 4.7 cm. The influence of dilution rate and influent phenol concentration on start up and steady state performance of the bioreactor was studied. The time taken to reach steady state has increased with increase in dilution rate and influent phenol concentration. It was found that, as the dilution rate is increased, the percentage degradation has decreased. Steady state percentage degradation was also reduced with increased influent phenol concentration. Almost 100% degradation of 300 and 500 ppm influent phenol could be achieved at a dilution rate of 0.4094 h(-1) and more than 99% degradation could be achieved with higher dilution rates. At a higher dilution rate of 1.0235 h(-1) and at concentrations of 800 and 900 ppm the percentage degradation has reduced to around 94% and 93%, respectively. The attached biomass dry weight, biofilm thickness and biofilm density at steady state were influenced by influent phenol concentration and dilution rate.     

Raft-forming agents: antireflux formulations

Gastroesophageal reflux disease (GERD) is caused by excessive reflux of gastric content and duodenal bile into the esophagus, and impaired clearance of refluxate from the esophagus. In this perspective, raft-forming antireflux formulations offer better alternatives to the conventional therapies for treatment of uncomplicated GERD. In addition to the alginate-based systems, various natural polysaccharides have generated interest as raft-forming agents because of their bioadhesive/mucoprotective nature. Inclination of current therapy is towards natural products for healing of the disease, which also underlines the market potential of this class, demanding for thorough investigation and development of evaluation methods with better in vitro-in vivo correlation.     

Environmental radioactivity studies in the proposed Lambapur and Peddagattu uranium mining areas of Andhra Pradesh, India

The present work was aimed at the establishment of baseline radioactive data in the proposed Lambapur and Peddagattu uranium mining areas in the Andhra Pradesh state, India. The background concentrations of naturally occurring radioactivity in the near-surface soils of the study areas were estimated and the results were analysed. The (238)U concentration in the near-surface soil of the study area was found to vary from 100 to 176 Bq kg(-1), with a mean of 138±24 Bq kg(-1). (232)Th in the study area soils was found to vary between 64 and 116 Bq kg(-1), with a mean of 83±15 Bq kg(-1). The (40)K concentration was found to vary between 309 and 373 Bq kg(-1), with a mean of 343±20 Bq kg(-1). The mean natural background radiation levels were also measured with thermoluminescence (TL) dosimetry technique and with a μR-survey meter, in the villages of the study area. Dose rates measured by TL are found to vary from 1287 to 3363 μGy y(-1), with a mean of 2509 ± 424 μGy y(-1). The dose rates measured in the same villages with a μR-survey meter were found to be in the range of 1211-3255 μGy y(-1), with a mean of 2524 ± 395 μGy y(-1). The mean radiation levels in the study area are found to be relatively high when compared with (Indian) national and international averages. Correlations among radon, thoron and gamma dose rates were found to be poor. The pre-operational data produced in this work will be useful for comparison with future radiation levels during the proposed uranium mining operations.     

Study of different approaches for management of contaminated emulsified aqueous secondary waste

The underlying objective governing the management of radioactive waste is protection of human being and the environment, now as well as in the future. As a waste management philosophy, utmost emphasis is given to waste volume minimization at all stages of design, operation and maintenance [1]. The development of innovative treatment processes for low and intermediate level wastes (LLW and ILW) in recent times has focused on volume reduction as one of the main objectives [2]. During reprocessing of spent fuel, an optimized mixture of tri-n-butyl phosphate (TBP) and dodecane is used as an extracting agent for actinides. During their repeated use, solvent undergoes chemical/radiolytic degradation, loosing its efficiency and hence to be discarded as spent organic solvent waste. This waste is presently being treated by alkaline hydrolysis process where spent solvent is refluxed with concentrated sodium hydroxide solution at 110°C [3]. TBP component of the spent solvent waste gets hydrolyzed and is converted into sodium salt of di-butyl phosphate (DBP). The other products obtained during hydrolysis include sodium salt of mono-butyl phosphate (MBP), butanol and phosphoric acid. Dodecane component of the spent solvent waste does not take part in the hydrolysis reaction and appears as a clear phase. The dodecane waste thus separated is subjected for thermal destruction by incineration. The emulsified aqueous layer thus obtained retains most of the activity present in the spent solvent waste. The present paper describes experimental studies performed to look for various approaches for management of this type of waste.     

Geographic variation in the flavour volatiles of Alphonso mango

Alphonso, one of the most popular cultivars of mango in India is known to exhibit geographic variation in the flavour of ripe fruits. To get chemical insight into this difference, volatiles were studied in the ripening fruits of Alphonso mangoes from three cultivation locations in India. Ripe fruits from Deogad had lower content of mono- and sesquiterpenes and higher content of lactones and furanones as compared to the fruits from Dapoli; whereas fruits from Vengurle had average quantities of these chemicals in comparison with Deogad and Dapoli fruits. This variation was clearly reflected as separate clustering of the localities in the Principal Component Analysis. The localities were indistinguishable from each other in terms of raw fruit volatiles. This study exemplifies a case of phenotypic plasticity; since the plants chosen were clonally propagated, such geographic variation in the volatiles can be attributed to varied abiotic conditions at these three localities.     

An experimental study on cracking evolution in concrete and cement mortar by the b-value analysis of acoustic emission technique

Notched three point bend (TPB) specimens made with plain concrete and cement mortar were tested under crack mouth opening displacement (CMOD) control at a rate of 0.0004 mm/s and simultaneously acoustic emissions (AE) released were recorded during the experiments. Amplitude distribution analysis of AE released during concrete was carried out to study the development of fracture process in concrete and mortar specimens. The slope of the log-linear frequency–amplitude distribution of AE is known as the AE based b-value. The AE based b-value was computed in terms of physical process of time varying applied load using cumulative frequency distribution (Gutenberg–Richter relationship) and discrete frequency distribution (Aki's method) of AE released during concrete fracture. AE characteristics of plain concrete and cement mortar were studied and discussed and it was observed that the AE based b-value analysis serves as a tool to identify the damage in concrete structural members.     

Characteristics of U.S. waterpipe users: a preliminary report.

Waterpipe smoking, a traditional method of tobacco use, has experienced a resurgence in the Middle East and Indian subcontinent in recent years. Despite growing evidence of its dependence potential and health-damaging effects, waterpipe use has spread beyond these regions to many other countries, including the United States. Because little is known about waterpipe use in the United States, we surveyed convenience samples of users from two U.S. cities, Richmond, Virginia (n = 109), and Memphis, Tennessee (n = 34). Respondents in both cities were primarily young adults, a majority (75%) were men, and most were college students or had a college degree. Initial and current use usually occurred in a social context, with a group of friends in a cafe or restaurant or at home. Most respondents had smoked waterpipe for 2 or fewer years, and 67% currently smoked at least once a month (22% smoked at least once per week and 10% smoked daily). Most believed waterpipe use to be less addictive and harmful than cigarette smoking, believed they could quit use at any time, but had no plans or desire to quit. A majority of respondents used other tobacco products such as cigarettes, and 35% of those who did not smoke cigarettes said they would "probably" or "definitely" smoke one in the next year. Multivariate correlates of greater frequency of use included younger age at first use, ownership of a waterpipe, use occurring primarily with groups of friends, and the perception of being "hooked." Waterpipe users in these two convenience samples from the United States were young and educated, tended to experiment with multiple forms of tobacco, were unaware of the potentially harmful and addictive properties of waterpipe use, and planned to continue use in the future. Educational efforts are needed to increase awareness of the potential hazards of this increasingly popular form of tobacco use.     

DATA ACQUISITION SYSTEM FOR ARC-DRIVEN HF/DF CHEMICAL LASERS

The article focuses on the development of a data acquisition system (DAS) working in a noisy and hostile environment for an arc-operated hydrogen fluoride/deuterium fluoride (HF/DF) chemical laser. PC-based DAS has been configured using Advantech plug and play modules with fiber link connectivity. This article also focuses on implementation of an orifice-based precise gas flow control system. The plasma arc discharge in an arc heater/generator is essentially employed for inducing thermal dissociation of sulfur hexafluoride SF₆ for production of fluorine atoms, and DAS has been used for performance optimization of the composition of the lasing mixture by independently varying the flow rate, pressure, and temperature of its constituents. Since arc load is complex with high voltage transients and electromagnetic noise, an optical fiber link has been implemented for data transmission. This article also discusses digital output interface circuitry for various electro-pneumatic actuators/solenoid valves. The developed DAS has been used for monitoring and performance evaluation of parameters for 50 kW arc tunnel.