Modeling of the solubility of alumina in the NaF-AlF<Subscript>3</Subscript> system at 1300 K

The experimentally well-known alumina solubility in the range of acidic to neutral cryolite-base melts has been modeled thermodynamically in terms of several oxyfluoride solutes. For an acidic melt, cryolite ratio r=1.5, the dominant solute is monoxygen Na₂Al₂OF₆. In a less acidic regime, dioxygen Na₂Al₂O₂F₄ is dominant, whereas for neutral compositions (r=3), Na₄Al₂O₂F₆ starts to gain importance. The fit of the model to the experimental solubility data is virtually perfect. The values of the equilibrium constants for the formation of the individual solutes are reported. The formation and conversion of these oxyfluoride complexes serve as an effective buffer opposing change in the melt basicity.     

Studies on structural,dielectric and charge transport properties of PVA:LiBr solid polymer electrolyte films

In the present study, solid polymer electrolytes (SPEs) based on poly (vinyl alcohol) (PVA) doped with lithium bromide (LiBr) were prepared by solution casting method. Fourier transform infrared spectroscopy results affirm the complexation of LiBr with PVA. X-ray diffraction results exhibit the increase of amorphous nature of the polymer electrolytes, which is also observed in scanning electron microscopy images and atomic force microscopy topographs. Thermogravimetric analysis thermographs endorse the increase of thermal stability of the polymer due to doping. Dielectric studies exhibit non-Debye nature of the polymer electrolytes. Conductivity spectra reveal the maximum ionic conductivity (1.15 × 10⁻⁴ S/cm) for 20 wt% LiBr/PVA electrolyte at ambient temperature. Impedance analysis reveals the decrease of ionic relaxation in the polymer electrolytes and the studied transport properties of the electrolyte show that the major contribution to the conduction in this polymer electrolyte is ions.     

LHAP: A lightweight network access control protocol for ad hoc networks

Most ad hoc networks do not implement any network access control, leaving these networks vulnerable to resource consumption attacks where a malicious node injects packets into the network with the goal of depleting the resources of the nodes relaying the packets. To thwart or prevent such attacks, it is necessary to employ authentication mechanisms to ensure that only authorized nodes can inject traffic into the network. We propose LHAP, a hop-by-hop authentication protocol for ad hoc networks. LHAP resides in between the network layer and the data link layer, thus providing a layer of protection that can prevent or thwart many attacks from happening, including outsider attacks and insider impersonation attacks. Our detailed performance evaluation shows that LHAP incurs small performance overhead and it also allows a tradeoff between security and performance.     

Melting treatment of waste asbestos using mixture of hydrogen and oxygen produced from water electrolysis

In this study, we melted four types of waste asbestos containing material such as spread asbestos, plasterboard asbestos, slate asbestos and asbestos 99 wt%, in a melting furnace at 1,450–1,550 that uses a mixture of hydrogen and oxygen (Brown’s gas) as a fuel. More volatile components (CaO, K₂O) are enriched in spread asbestos, plasterboard asbestos, and slate asbestos, while less volatile compounds (SiO₂, Fe₂O₃, MgO) remain in asbestos 99%. Through basicity of raw materials, spread asbestos, plasterboard asbestos, and slate asbestos were found to have more alkalinity, and asbestos 99% was found more acidic. SEM and EDX results revealed that all raw materials had various kinds of asbestos fiber. Spread asbestos, plasterboard asbestos, and slate asbestos were considered as tremolite asbestos, whereas asbestos 99% was considered as chrysotile asbestos. It was further confirmed by SEM and XRD studies that all waste materials contained some crystalline structures which transformed into amorphous glassy structure on melting. Also, in case of added glass cullet during the melting of spread asbestos, it transformed the raw material into a perfect vitrified product having more glassy surface and amorphous in nature     

Prevalence of thermoduric bacteria and spores on 10 Midwest dairy farms

Thermoduric bacteria (TDB), including sporeformers and their spores, can be present in milk and dairy products even after pasteurization. They have the potential to adversely affect the quality and shelf life of products. The objectives of this study were to identify the origin and common species of heat-resistant bacteria occurring during summer and winter on Midwest dairy farms. Bulk tank milk samples were taken from 10 dairy farms located along the South Dakota section of Interstate 29, with herd sizes ranging from 650 to 3,500 lactating dairy cows. Milk samples were profiled for the prevalence of TDB and spore counts (SC). Corn silage samples and swabs of the milking clusters were also taken at the dairies to further profile the potential sources of TDB and SC. The samples were taken 3 times during 2 seasons [winter (January–March) and summer (June–August)] to track seasonal changes in the farm bacterial flora. During winter, the average TDB counts in bulk tank milk were 2.61 log compared with 2.76 log TDB counts in the summer. The SC was 1.08 log in the winter, which was half the 2.06 log SC present in the summer season. Corn silage sampled in winter contained a 7.57 log TDB count compared with an increased 10.77 log TDB count during summer sampling. Concentrations of SC in corn silage reached an average of 6.3 log in winter compared with 11.81 log for summer. The seasonal effect was evident with an increase in summer counts across the board for TDB and SC, both in the feed and bulk tank milk samples. Bacillus licheniformis was the predominant species identified in 62.4% of winter (85 total) and 49.4% of summer (83 total) samples. Bacillus subtilis made up 9.4% of the remaining winter isolates, followed by Bacillus sonorensis at 8.2%. Conversely, B. sonorensis made up 12% of the summer isolates followed by Bacillus pumilus at 10.8%. Bacillus licheniformis is a ubiquitous microbe and was isolated from both TDB and sporeformer categories in all 3 sample types. There were larger increases in SC than TDB, indicating that summer temperatures and conditions may favor proliferation of sporeforming bacteria over that of TDB. In conclusion, samples from bulk tank milk, milking cluster swabs, and corn silage samples at each of the 10 sites indicated that B. licheniformis was the major contaminant species, regardless of season. In this experiment, corn silage was the major environmental source of both TDB and SC with higher concentrations in summer when compared with winter.     

Adsorption isotherms for red chilli (Capsicum annum L.)

The adsorption equilibrium moisture contents for red chilli were determined experimentally in relative humidity range of 11–97% at the temperatures of 20, 30, 40, and 50°C. Six equilibrium moisture content models were fitted to the experimental data. The modified Oswin model was the best fitted equation for relative humidity range of 11–97% for the adsorption data of red chilli.     

Short communication: A competitive exclusion study reveals the emergence of Bacillus subtilis as a predominant constitutive microorganism of a whey reverse osmosis membrane biofilm matrix

Microbial attachment and colonization on separation membranes lead to biofilm formation. Some isolates within the biofilm microflora acquire greater resistance to the chemical cleaning protocols on prolonged use of membranes. It is thus likely that the constitutive microflora might compete with each other and result in certain species emerging as predominant, especially within older biofilms. To understand the microbial interactions within biofilms, the emergence of predominance was studied in the current investigation. An 18-mo-old reverse osmosis membrane was procured from a whey processing plant. The membrane pieces (2.54 × 2.54 cm²) were neutralized by dipping in Letheen broth. The resuscitation step was done in tryptic soy broth (TSB) at 37°C, followed by plating on tryptic soy agar (TSA) to recover the constitutive microflora. Distinct colonies of isolates were further identified using MALDI-TOF as Bacillus licheniformis, Exiguobacterium aurantiacum, Acinetobacter radioresistens, Bacillus subtilis (rpoB sequencing), and 1 unidentified species each of Exiguobacterium and Bacillus. Further, the competitive exclusion study helped establish the emergence of predominance using a co-culturing technique. Fifteen combinations (of 2 isolates each) were prepared from the isolates. Pure cultures of the respective isolates were spiked in a ratio of 1:1 in TSB and incubated at 37°C for 24 h, followed by plating on TSA. The enumerated colonies were distinguished based on colony morphology, Gram staining, and MALDI-TOF to identify the type of the isolate. Plate counts of B. subtilis emerged as predominant with mean log counts of 7.22 ± 0.22 cfu/mL. The predominance of B. subtilis was also validated using the process of natural selection in a multispecies growth environment. In this instance, the TSB culture with overnight-incubated membrane piece (with mixed-species biofilm) at 37°C for 12 h was inoculated in fresh TSB and incubated for the second cycle. Overall, 5 such sequential broth-culture incubation cycles were carried out, followed by pour plating on TSA plates, at the end of each cycle. The isolates obtained were identified using a similar methodology as mentioned above. The fifth subsequent transfer depicted the presence of only 1 B. subtilis isolate on plating, thereby validating its predominance under the conditions of the experiment.     

Short communication: Evaluating the recovery potential of injured cells of Listeria innocua under product temperature-abuse conditions and passage through simulated gastrointestinal fluids

Ice cream handling and serving conditions on the consumer side may result in temperature abuse before consumption. Under some extreme conditions, even the sporadic presence of injured bacterial cells might pose a health risk due to the possibility of recovery of those cells. We conducted this investigation to evaluate the potential of injured cells of Listeria innocua to recover under ice cream temperature abuse conditions and on exposure to simulated gastrointestinal (GI) fluids. Ice cream mix samples (42% total solids), spiked with 4 log₁₀ cfu/g of Listeria innocua, were thermally treated at 69°C for 30 min. Potential heat-injured cells were recovered in buffered Listeria broth (BLEB), followed by isolation on Listeria-specific modified Oxford agar (MOX). The ice cream mix samples, containing potentially injured cells of Listeria innocua, were followed through overnight aging (7°C), freezing (?3.3°C), and overnight hardening (?40°C) steps to obtain the final ice cream samples. To simulate temperature abuse conditions, the samples were held for 12 h at 4.4°C, followed by 30 min at room temperature (22°C); this treatment was considered the first cycle of temperature abuse. To generate a worst-case scenario, the samples were exposed to 3 such consecutive temperature abuse cycles. At the end of each cycle, direct plating was done on MOX to recover viable cells, and BLEB enrichment verified the presence of potential injured cells. In addition, the ice cream samples, containing potential injured cells, were passed through simulated GI fluids. As a first step, samples were mixed (1:1) with simulated gastric fluids (pH 1.0 and 2.0 before mixing) and held at 37°C in a shaker incubator. Samples drawn at 15, 30, and 60 min were analyzed for viable and potential injured cells. To study the effect of sequential transit through simulated intestinal fluid, a mixture of ice cream and gastric fluid (1:1) from the gastric fluid experiment above was added to simulated intestinal fluid (pH 6.8) and held at 37°C. Samples were analyzed at 30 and 360 min for viable and potential injured cells. Three trials were conducted and the samples collected in duplicates. The temperature abuse or GI fluid exposure studies did not result in the recovery of potential injured cells of Listeria innocua in the ice cream samples under the conditions tested. Exposure to gastric fluids, however, did not eliminate the potential injured cells. Further studies are necessary to understand the exact risk implications of these findings.     

Wave scattering through an orthotropic thermoelastic slab sandwiched between two isotropic elastic half-spaces

Abstract

Present study deals with the scattering of a plane wave through an orthotropic thermoelastic slab sandwiched between two elastic half-spaces. Unlike the classical theory of thermoelasticity, we have employed non-classical thermoelastic theories (LS-theory and GL-theory) to analyze the scattering of plane waves. The amplitude ratios for different waves have been computed numerically for the considered generalized theories of thermoelasticity. The effect of the slab thickness on the amplitude ratios has been shown graphically. Moreover, the amplitude ratios of different waves (i.e., reflected, transmitted, forward and backward waves) are compared for different values of slab thickness under both the LS-theory and GL-theory.     

Nanostructured MIEC Ba0.5Sr0.5Co0.6Fe0.4O3−δ (BSCF5564) cathode for IT-SOFC by nitric acid aided EDTA–citric acid complexing process (NECC)

Ba_0.5Sr_0.5Co_0.6Fe_0.4O_3−δ(BSCF5564) was synthesized by nitric acid aided EDTA–citric acid complexing sol-gel method (NECC). Both, the phase formation temperature and time of BSCF5564 synthesized NECC were found to be low i.e. single perovskite phase formation temperature is 200 °C less as compared to the conventional method of synthesis. The orthorhombic perovskite structure has been formed after calcination at 800 °C for 5 h. Scanning electron microscopy reveals the formation of porous material constituting nano-sized and irregularly shaped rod-like structure with particle size approximately ranges from 90 to 160 nm. The total weight loss of the BSCF5564 sample comes out to be 6.6%, indicating that quadrivalence state Co⁴⁺ and Fe⁴⁺ in the sample have been completely reduced to the trivalent state Co³⁺ and Fe³⁺ due to thermal analysis. The value of E_a for BSCF5564 prepared by NECC was 0.2288 eV. The electrical conductivity of BSCF5564 synthesized by NECC is observed to be steady at high temperature (above 700 °C).