Phase analysis and dielectric properties of ceramics in PbO-MgO-ZnO-Nb<SUB>2</SUB>O<SUB>5</SUB> system: a comparative study of materials obtained by ceramic and molten salt synthesis routes

Compositions of the type 3PbO-MgO/ZnO-Nb2O5 were synthesized by the ceramic route at 1000&#176;C and sintered at 1200&#176;C. Powder X-ray diffraction studies of the 1000&#176;C heated products show the presence of the cubic pyrochlore and the columbite (Mg/ZnNb2O6) type phase in the ratio of 3 : 1 for all possible combinations of MgO and ZnO. Further heating at 1200&#176;C led to a decrease in the cubic pyrochlore phase and an increase in the columbite phase by around 10%. Compacted pellets sintered further showed the appearance of the perovskite phase. Similar compositions synthesized using the KCl-NaCl molten salt method at 900&#176;C for 6 h gave a significant amount of the cubic perovskite related phase of the type Pb(Mg/Zn)1/3Nb2/3O3 for all compositions containing MgO. The amount of the perovskite phase was nearly 55% for the Mg rich compositions and decreased with increase in Zn content, the pure Zn composition yielding mainly the cubic pyrochlore phase. On sintering these phases at 1000&#176;C the perovskite phase content decreased. The dielectric constant of the composite materials formed by the ceramic route was in the region of 14 to 20 and varied little with frequency. The composites obtained by the molten salt method, however, showed much larger dielectric constants in the region 40-150 at 500 kHz for various compositions. The dielectric loss tangent of these composites were lower by an order (0.005-0.03 at 500 kHz) compared to the ceramic route

Ba\u3csub\u3e8\u3c/sub\u3eZnTa\u3csub\u3e6\u3c/sub\u3eO\u3csub\u3e24\u3c/sub\u3e: A New High Q Dielectric Perovskite

The hexagonal perovskite, Ba8ZnTa6O24, was prepared in single-phase form and was found to be a stable secondary phase, formed as a result of the loss of ZnO from Ba(Zn1/3Ta2/3)O3 microwave dielectrics. The experimental and calculated X-ray patterns of Ba8ZnTa6O24 indicate it is isostructural with Ba8Ta6NiO24 with an 8H (cchc)2 close-packed BaO3 stacking sequence and the lattice parameters, a=10.0825(14), c=19.0587 (38)Å . High-density ceramics of Ba8ZnTa6O24 could be prepared at temperatures considerably lower (1400ºC) than those used to sinter pure Ba(Zn1/3Ta2/3)O3, and exhibit very good microwave dielectric properties with ε=30.5, Qf=62300, and τf=+36 ppm/ºC at 8.9 GHz

Influence of strontium on the cubic to ordered hexagonal phase transformation in barium magnesium niobate

Oxides of the type Ba3−xSrxMgNb2O9 were synthesized by the solid state route. The x=0 composition (Ba3MgNb2O9) was found to crystallize in a disordered (cubic) perovskite structure when sintered at 1000C. For higher Sr doping (x ≥ 0.5), there was clearly the presence of an ordered hexagonal phase indicated by the growth of superstructure reflections in the powder X-ray diffraction patterns. In all the compositions there was the presence of a minor amount of Ba5−xSrxNb4O15 phase which increased with Sr substitution up to x =1 and then it remained nearly constant at about 5%. Samples sintered at 1300C showed the hexagonally ordered phase for the entire range of composition (0 ≤x ≤ 3). The degree of ordering being considerably greater than in the 1000C heated samples as evidenced by several superstructure reflections

Synthesis of Ba<SUB>3</SUB>ZnNb<SUB>2</SUB>O<SUB>9</SUB>-Sr<SUB>3</SUB>ZnNb<SUB>2</SUB>O<SUB>9</SUB> solid solution and their dielectric properties

Oxides of the type, Ba3−xSrxZnNb2O9 (0 ≤ x ≤ 3), were synthesized by the solid state route. Oxides calcined at 1000°C show single cubic phase for all the compositions. The cubic lattice parameter (a) decreases with increase in Sr concentration from 4·0938(2) forx = 0 to 4·0067(2) for x = 3. Scanning electron micrographs show maximum grain size for thex = 1 composition (~ 2 μm) at 1200°C. Disks sintered at 1200°C show dielectric constant variation between 28 and 40 (at 500 kHz) for different values of x with the maximum dielectric constant at x = 1

A Qualitative Analysis of Indoor Air Quality Pollutants inside a Private Car Cabin Using Response Surface Methodology

Indoor air quality (IAQ) plays a significant role in our daily life. IAQ is not only important in interior buildings but is also essential to the low volume space of automobile compartments. This study investigates the three critical IAQ pollutants of CO2, PM2.5, and PM10 in an air-conditioned private car cabin. Three qualitative input factors of human load, route, and air conditioning (ON and OFF) were considered to evaluate the effect of in-cabin car pollutants. Analysis of variance (ANOVA) was applied to determine the effect of the input parameters that affect IAQ in the car cabin. A mathematical modelling of response factors (pollutants) was determined using response surface methodology (RSM) in connection with the Taguchi orthogonal test design. It was found that indoor car cabin CO2, PM2.5, and PM10 concentrations were 3.32, 1.35, and 1.33 times higher than the on-road concentrations, respectively. The air-conditioning input factor has more effects for in-cabin pollutants compared with the other two input factors of human load and route. The R2 values obtained were greater than 95% for all the response factors. According to the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) standard limit, the air supply flow rate of 7.64 l/s per human (maximum 4 human load) was not enough to keep CO2 concentrations below 1000 ppm in the currently tested car cabin

Substantial Impact of Precipitants and Dispersant on the Structural and Optical Properties of CeO2 Nanoparticles

Cerium oxide nanoparticles are prepared by simple precipitation method with various precipitants. The prepared samples are analyzed by XRD, FT-IR and PL. XRD confirms the occurrence of single-phase polycrystalline cubic fluorite structure with dominant orientation along (111) direction. The sharp band at 1415 cm-1 originated from –CH3 deformation and –CH2 scissoring vibrations of PVP, also A strong band at 848 and 400 cm-1 due to the envelope of the phonon band of the metal oxide (Ce-O) network obtained from FT-IR spectra. PL spectra exhibit the presence of strong blue and weak blue-green emission in the visible region. Additions of PVP strongly distress the peaks intensity of the samples

POTENTIAL OF URAI MATHIRAI (PEDIATRIC SIDDHA FORMULATION) FOR THE PROPHYLAXIS AND MANAGEMENT OF COVID-19 IN CHILDREN

The World Health Organization (WHO) data proposes that 8.5% of reported COVID-19 cases belong to pediatric population who are aged less than 18 years. Supportive care alone is recommended in asymptomatic, mild, or moderate pediatric COVID-19 patients by the panel of pediatric infectious diseases physicians and pharmacists from 20 geographically diverse North American institutions. This review article focuses on the prophylactic and therapeutic potential of Urai mathirai in the management of pediatric COVID-19 patients. The literature was looked, in databases such as Medline/PubMed Central/PubMed, Google Scholar, Science Direct, Web of science, Directory of open access journals (DOAJ), and reference lists to distinguish published manuscripts relevant to the use of Urai mathirai to prevent or treat COVID-19 in children. The herbs found in Urai Mathirai and their bioactive phytoconstituents possess antiviral, anti-inflammatory, antioxidant, immunomodulatory, bronchodilatory and other pharmacological effects relevant to the management of signs and manifestations of COVID-19. The viability of Urai Mathirai in the prophylaxis and management of pediatric COVID-19 patients could further be established by future clinical studies

High-density Cultivation in the Production of Microbial Products

Microbial fermentation processes are of great importance for the production of many bioproducts. Even for established processes, improvements in product yield, productivity, and quality are always continually demanded. This is particularly true as the products mature from being novelty to high demand, even bulk, substances, as has been witnessed for several antimicrobial compounds. High-density cultivations have been found very useful in producing a large number of modern bioproducts. Selection of the mode of fermentation, operating conditions, and optimized media are important characteristic features for high cell density, productivity, as well as the commercial success of any microbial product. This contribution reviews some of the challenges and technologies investigated for high-density cultivation. Important aspects such as medium composition, reactor conditions, oxygen transfer, temperature, agitation, pH, modes of operation, and feeding strategies for high-density cultivation are summarized in this review

Comparison of four dental pulp-capping agents by cone-beam computed tomography and histological techniques—a split-mouth design ex vivo study

Dental pulp-capping is done to preserve vital teeth when the pulp is exposed due to caries, trauma or instrumentation. Various materials are used as pulp-capping agents. The introduction of newer materials requires scientific studies to assess their clinical efficacy. The study was designed as a split-mouth randomized analysis of four pulp-capping agents (calcium hydroxide, mineral trioxide aggregate (MTA), Biodentine and EndoSequence root repair material (ERRM)). Based on selection criteria, 15 orthodontic patients requiring the extraction of four premolars (60 teeth total) were included in the study. After pulp-capping, the teeth were extracted after 8 weeks. We analyzed the extracted teeth using cone-beam computed tomography (CBCT) and histological sections to determine the quality of the dentinal bridge and the pulpal response. Ordinal scores were given based on the completeness of the dentinal bridge, the type of bridge and the degree of pulpal inflammation. Results were analyzed using a Kruskal–Wallis test (p &lt; 0.05) with post hoc Conover values being used when applicable. All four pulp-capping materials elicited dentinal bridge formation (60/60). MTA had the highest scores (10/15) in dentinal bridge formation followed by ERRM (8/15). Both materials showed more samples with complete dentinal bridges (9/15 each) and a favorable pulpal response (15/15). Teeth capped with calcium hydroxide showed more cases of incomplete bridge formation (9/15) and pulpal inflammation. These differences in dentinal bridge formation and pulpal inflammation were statistically significant (p 0.001 and p 0.00005, respectively), with post hoc tests revealing no significant differences between MTA and ERRM (p 0.49 and p 0.71, respectively). MTA and ERRM performed better than the other pulp-capping materials but did not differ significantly from each other. The individual preference for a pulp-capping material may be based on clinical efficacy and handling characteristics

Effect of Developed Low Cost Minimal Medium on Lipid and Exopolysaccharide Production by Lipomyces starkeyi Under Repeated Fed-batch and Continuous Cultivation

The main objective of this study was to investigate the effects of a low cost minimal medium, developed by the UL Bioprocessing Lab, on the cultivation of Lipomyces starkeyi NRRL Y-11557 using repeated fed-batch and continuous fermentation strategies. The highest cell and lipid concentrations obtained were 22.7 g L–1 and 11.67 g L–1 under repeated fed-batch cultivation, respectively. Continuous cultivation with the dilution rate of 0.06 h–1 presented the highest cell (0.401 g g–1) and lipid yields (0.177g g–1). Exopolysaccharide production was observed when L. starkeyi was cultivated in the minimal media supplemented with 90 g L–1 glucose under repeated fed-batch fermentation. The produced exopolysaccharide is likely composed of 4–5 repeating sugar units, incorporating mannose and galactose and their respective uronic acids. This work is licensed under a Creative Commons Attribution 4.0 International License