Novel Synthesis of SrBi2Nb2O9 Powders From Hydroxide Precursors

Simple hydroxide precursors were used for the first time for the synthesis of a typical Aurivillius compound (SrBi₂Nb₂O₉ (SBN)) at a low temperature. This method is very advantageous because it circumvents the use of SrCO₃ in the case of conventional ceramics as well in the coprecipitation methods, thereby lowering the formation of the product phase. Commercially purchased strontium hydroxide is mixed thoroughly with freshly precipitated bismuth and niobium hydroxides in a stoichiometric ratio and heated at different temperatures ranging from 100°C to 750°C for 12 h. The sequence of the reaction and evolution of the product phase was monitored by X-ray diffraction (XRD) studies by recording the XRD for samples calcined at different temperatures. The incipient SBN phase begins to form at temperatures as low as 400°C, and phase formation was complete only at 650°C as revealed by the XRD observations. The differential thermal/thermogravimetric analyses) also corroborate this result. The morphology and average particle size of these powders were investigated by transmission electron microscopy studies.     

Dextran-coated gold nanoparticles for the assessment of antimicrobial susceptibility

Bacteria rapidly evolve mechanisms to become resistant to antibiotics. Therefore, identifying an effective antibiotic or antibacterial agent and administering it at concentrations that will successfully prevent bacterial growth (antimicrobial susceptibility) is critical for health care decision making and vital for the battle against multi-drug-resistant bacteria. Currently, the determination of antimicrobial susceptibility requires at least 24 h. Herein, we describe a nanoparticle-based antimicrobial susceptibility assay based on the concanavalin A-induced clustering of dextran-coated gold nanoparticles, which sense the presence of available complex carbohydrates in bacterial suspension. Under conditions of bacterial growth inhibition, addition of concanavalin A results in the formation of extensive dextran gold nanoassemblies, which are facilitated by the presence of free carbohydrates in solution and result in large shifts in the surface plasmon band of the nanoparticles. Meanwhile, at conditions of increased bacterial growth, a decrease in the amount of free carbohydrates in solution will occur due to an increased carbohydrate uptake by the proliferating bacteria. This will result in a decrease in the size of the gold nanoparticle clusters and an increase in the number of nanoparticles that bind to bacterial surface carbohydrates, causing lower shifts in the plasmonic band. The gold nanoparticle-based assessment of antimicrobial susceptibility yields results within 3 h and can be used for the high-throughput screening of samples during epidemics and identification of potential antimicrobial agents to expedite clinical decision-making in point-of-care diagnostics.     

Consumption of brown rice: a potential pathway for arsenic exposure in rural Bengal

This study assesses the arsenic (As) accumulation in different varieties of rice grain, that people in rural Bengal mostly prefer for daily consumption, to estimate the potential risk of dietary As exposure through rice intake. The rice samples have been classified according to their average length (L) and L to breadth (B) ratio into four categories, such as short-bold (SB), medium-slender (MS), long-slender (LS), and extra-long slender (ELS). The brown colored rice samples fall into the SB, MS, or LS categories; while all Indian Basmati (white colored) are classified as ELS. The study indicates that the average accumulation of As in rice grain increases with a decrease of grain size (ELS: 0.04; LS: 0.10; MS: 0.16; and SB: 0.33 mg kg(-1)), however people living in the rural villages mostly prefer brown colored SB type of rice because of its lower cost. For the participants consuming SB type of brown rice, the total daily intake of inorganic As (TDI-iAs) in 29% of the cases exceeds the previous WHO recommended provisional tolerable daily intake value (2.1 μg day(-1) kg(-1) BW), and in more than 90% of cases, the As content in the drinking water equivalent to the inorganic As intake from rice consumption (C(W,eqv)) exceeds the WHO drinking water guideline of 10 μg L(-1). This study further demonstrates that participants in age groups 18-30 and 51-65 yrs are the most vulnerable to the potential health threat of dietary As exposure compared to participants of age group 31-50 yrs, because of higher amounts of brown rice consumption patterns and lower BMI.     

Testing tubewell platform color as a rapid screening tool for arsenic and manganese in drinking water wells

A low-cost rapid screening tool for arsenic (As) and manganese (Mn) in groundwater is urgently needed to formulate mitigation policies for sustainable drinking water supply. This study attempts to make statistical comparison between tubewell (TW) platform color and the level of As and Mn concentration in groundwater extracted from the respective TW (n = 423), to validate platform color as a screening tool for As and Mn in groundwater. The result shows that a black colored platform with 73% certainty indicates that well water is safe from As, while with 84% certainty a red colored platform indicates that well water is enriched with As, compared to WHO drinking water guideline of 10 μg/L. With this guideline the efficiency, sensitivity, and specificity of the tool are 79%, 77%, and 81%, respectively. However, the certainty values become 93% and 38%, respectively, for black and red colored platforms at 50 μg/L, the drinking water standards for India and Bangladesh. The respective efficiency, sensitivity, and specificity are 65%, 85%, and 59%. Similarly for Mn, black and red colored platform with 78% and 64% certainty, respectively, indicates that well water is either enriched or free from Mn at the Indian national drinking water standard of 300 μg/L. With this guideline the efficiency, sensitivity, and specificity of the tool are 71%, 67%, and 76%, respectively. Thus, this study demonstrates that TW platform color can be potentially used as an initial screening tool for identifying TWs with elevated dissolved As and Mn, to make further rigorous groundwater testing more intensive and implement mitigation options for safe drinking water supplies.     

Electro-Fenton treatment of synthetic organic dyes: Influence of operational parameters and kinetic study

This work investigates oxidative decolorization of two different dyes, Methylene blue and Titan yellow in aqueous solution using an environmentally friendly advanced electro-chemical oxidation (electro-Fenton) process. The effect of operating conditions like H₂O₂ concentration, current density, initial dye concentration was studied in a batch stirred cell. Individual decolorization decay kinetics for both dyes was investigated. The second-order absolute rate constants (L mol^?1 s^?1) between hydroxyl radical and dye have been calculated from experimental data by fitting it to the decolorization model. The apparent kinetic constants, k _app (s^?1) for Methylene blue and Titan yellow dye decolorization were also determined. The experimental data showed a good fit to the theoretical model, which can predict data in a wide range of % dye decolorization. This process also reduces COD of the dye solution, and the unit energy demand (UED) in kWh/kg COD removed for different electrical current has been reported.     

High-Dose Phosphorus-Implanted 4H-SiC: Microwave and Conventional Post-Implantation Annealing at Temperatures ≥1700°C

Semi-insulating 4H-SiC ⟨0001⟩ wafers have been phosphorus ion implanted at 500°C to obtain phosphorus box depth profiles with dopant concentration from 5 × 10¹⁹ cm⁻³ to 8 × 10²⁰ cm⁻³. These samples have been annealed by microwave and conventional inductively heated systems in the temperature range 1700°C to 2050°C. Resistivity, Hall electron density, and Hall mobility of the phosphorus-implanted and annealed 4H-SiC layers have been measured in the temperature range from room temperature to 450°C. The high-resolution x-ray diffraction and rocking curve of both virgin and processed 4H-SiC samples have been analyzed to obtain the sample crystal quality up to about 3 μm depth from the wafer surface. For both increasing implanted phosphorus concentration and increasing post-implantation annealing temperature the implanted material resistivity decreases to an asymptotic value of about 1.5 × 10⁻³ Ω cm. Increasing the implanted phosphorus concentration and post-implantation annealing temperature beyond 4 × 10²⁰ cm⁻³ and 2000°C, respectively, does not bring any apparent benefit with respect to the minimum obtainable resistivity. Sheet resistance and sheet electron density increase with increasing measurement temperature. Electron density saturates at 1.5 × 10²⁰ cm⁻³ for implanted phosphorus plateau values ≥4 × 10²⁰ cm⁻³, irrespective of the post-implantation annealing method. Implantation produces an increase of the lattice parameter in the bulk 4H-SiC underneath the phosphorus-implanted layer. Microwave and conventional annealing produce a further increase of the lattice parameter in such a depth region and an equivalent recovered lattice in the phosphorus-implanted layers.     

Prospection of the use of encapsulation in food packaging

Food safety and extended shelf life linked to convenience were the major reasons for the development of the packaging field. However, advances in material science and the widespread encapsulation technologies are allowing the establishment of new concepts for packages, such as intelligent and active packages. Particulate systems have been developed in recent years for the most diverse area with several purposes that can be employed to improve packaging performance mainly focusing on the modification of barrier properties. This review analyzes the recent developments using encapsulation in food packaging and the main concepts about mass transfer evolved in the functionality of these packages, as well as discusses the research challenges faced by the food packaging sector.     

Application of non-dominated sorting genetic algorithm for multi-objective optimization of electrical discharge diamond face grinding process

Hybrid machining processes (HMPs), having potential for machining of difficult to machine materials but the complexity and high manufacturing cost, always need to optimize the process parameters. Our objective was to optimize the process parameters of electrical discharge diamond face grinding (EDDFG), considering the simultaneous effect of wheel speed, pulse current, pulse on-time and duty factor on material removal rate (MRR) and average surface roughness (Ra). The experiments were performed on a high speed steel (HSS) workpiece at a self developed face grinding setup on an EDM machine. All the experimental results were used to develop the mathematical model using response surface methodology (RSM). The developed model was used to generate the initial population for a genetic algorithm (GA) during optimization, non-dominated sorting genetic algorithm (NSGA-II) was used to optimize the process parameters of EDDFG process. Finally, optimal solutions obtained from pareto front are presented and compared with experimental data.     

Fabrication and characterization of vertically aligned long ZnO nanorods on transparent substrate

Vertically aligned long ZnO nanorods (NRs) were grown by metal organic chemical vapor deposition (MOCVD) technique. Prior to the NRs growth Ga-doped ZnO (GZO) film was deposited by DC sputtering technique on glass substrates. The length and width of the NRs were 25 microm and 450-500 nm, respectively. Structural and optical properties of the NRs were investigated after the growth. The NRs were single crystalline in nature with the preferred growth along c-axis. The diffusion of Ga atoms in the bottom of the NRs during the growth is detected. A prominent near band edge emission of NRs was observed from room-temperature photoluminescence study. Electrical characteristics across the NRs-thin film hybrid structure were measured with UV exposure, where the rise and fall of the photocurrent was exponential in nature due to the desorption and adsorption of oxygen in the surface.     

Single-domain antibody bioconjugated near-IR quantum dots for targeted cellular imaging of pancreatic cancer

Successful targeted imaging of BxPC3 human pancreatic cancer cells is feasible with near-IR CdTeSe/CdS quantum dots (QDs) functionalized with single-domain antibody (sdAb) 2A3. For specific targeting, sdAbs are superior to conventional antibodies, especially in terms of stability, aggregation, and production cost. The bright CdTeSe/CdS QDs were synthesized to emit in the diagnostic window of 650-900 nm with a narrow emission band. 2A3 was derived from llama and is small in size of 13 kDa, but with fully-functional recognition to the target carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6), a possible biomarker as a therapeutic target of pancreatic cancer. For compelling imaging, optical may be the most sensible among the various imaging modalities, regarding the sensitivity and cost. This first report on sdAb-conjugated near-IR QDs with high signal to background sensitivity for targeted cellular imaging brings insights into the development of optical molecular imaging for early stage cancer diagnosis.