Hasil untuk "Chemical industries"

Keisuke Makino, Naoto Tanibata, Hayami Takeda et al.

Na-ion batteries are anticipated for large-scale energy-storage applications due to their resource advantages over Li-ion batteries. Chloride-based cathode materials exhibiting high voltage, offers the possibility to achieve high energy density. While chloride electrodes suffer from leaching into liquid electrolytes, employing all-solid-state batteries with solid electrolytes can mitigate this issue. A sodium chloride cathode material NaFeCl₄ has been reported to operate at a high voltage derived from chloride (3.45 V vs. Na/Na+) and demonstrates a high energy density of 281 Wh (kg-cathode)−1. However, the ionic conductivity of NaFeCl4 is relatively low (5.9 × 10−6S cm−1 at 30 ºC). In this study, we conducted anion substitution to improve the ionic conductivity of NaFeCl4 and found that substituting the chloride ion Cl− with the nitrite ion NO₂−, which has the same valence and a similar ionic radius, increased the ionic conductivity by approximately fourfold (2.7 × 10−5S cm−1 at 30 ºC). Raman spectroscopy and XRD measurements confirmed the incorporation of nitrite ion (NO₂−) units into the lattice, leading to lattice expansion. These findings demonstrate that the substitution of polyatomic anions is a promising approach for expanding the compositional space of chloride-based solid solutions and enhancing their ionic conductivity.

Jonathan C. Denman, Xinyu Zhao, Jennifer Colborn et al.

Large eddy simulations (LES) are conducted in this study to understand the convective and radiative heat transfer characteristics within a backward-facing step combustor. The Penn State backward-facing step combustor is modeled and the experimental signals are directly compared with computational results to validate physical models and numerical procedures. The baseline simulation features a wall-resolved LES of the full-combustor geometry for a lean methane/air mixture at an equivalence ratio of 0.55. A 16-species skeletal mechanism is employed with a dynamic thickened flame model to capture turbulence-chemistry interactions. A dynamic Smagorinsky model is employed to capture the subgrid-scale stress. A Monte-Carlo ray tracing based radiation solver is employed with a highly accurate line-by-line spectral database to post-process LES solutions to obtain the radiative heat fluxes. Comparison between the baseline results after accounting for experimental facility constraints show excellent agreement in radiative heat fluxes at four sensor locations. The total heat fluxes consisting of both radiation and convection is under-predicted by approximately 30%. Further parametric studies that use different spanwise dimensions, chemical kinetic models, molecular transport models, and thickening factors show that the better prediction of the temperature and flame speed of GRI-mech 3.0 can increase the prediction of convective heat transfer, while maintaining a similar comparison in the prediction of radiative heat transfer. The molecular transport model is also critical for the well-resolved LES to correctly capture the flame brush angles. The turbulence-chemistry interaction effects seem to be well-captured by the grid and have a negligible impact on the results. Compared to the reduced-span geometry that is frequently employed in backward-facing step configuration simulations, the full-span geometry is shown to be significant for capturing flame stabilization and heat transfer characteristics. Finally, limitation of this model validation study is discussed.

W.M. Alkanj, A. Kynast, M. Töpfer et al.

The fabrication of piezoelectric multilayer actuators (MLA) with lead-free piezoceramic materials and excellent performance represents a great challenge in the process of replacing the current family of lead-based actuators. Sintering under low pO2 allows co-firing with base metal electrodes, which is an important step towards competitive multilayer actuator fabrication technologies. We prepared sodium potassium niobate (KNNLT) piezoelectric multilayer actuators with Ni electrodes by sintering at low pO2 of 10−11 atm at 950 °C, followed by reoxidation at 850 °C in 10−6 atm. We demonstrate the impact of the sintering protocol, i.e., sintering temperature Ts and pO2, on the phase composition and continuity of Ni electrodes, and on the actuator performance. We discuss the subtle interplay between sintering conditions, microstructure, reoxidation kinetics and piezoelectric performance. The Ni-MLA exhibits a unipolar strain of 0.74 ‰ at 3 kV/mm, a normalized strain coefficient d33* = 247 p.m./V and a loss of tanδ = 0.041.

Anil Kumar Adukadukkam, Rachna Pillai, Mamatha Puthiyathara Kanakamma

Abstract Limestone is one of the essential raw materials in the cement, paint, steel, ceramic, glass, chemical, pharmaceutical, paper, and fertilizer industries. In India, only 8% of the limestone resources are placed under the reserve category, of which 97% is of cement grade. Thus, India depends on imports to bridge the demand‐supply gap of steel, blast furnace, and chemical‐grade limestone. Efforts of Geological Survey of India (GSI) to locate alternate sources for limestone led to the discovery of enormous quantities of carbonate minerals called limemud from the continental shelf margin of the west coast of India. GSI carried out systematic studies to explore the nature of the disposition, quality, quantity, and suitability of the offshore limemud for various industrial applications. A preliminary estimate of resources using high‐resolution subbottom profiling and sediment core sample studies established the occurrence of more than 172 billion tonnes of high‐grade (The content of CaCO3 is greater than 80 wt%) limemud in 0.4–28.0 m thick stratified sediment layers spread over an area of 18 000 km2. Chemical, physical, mineralogical, beneficiation, and agglomeration studies found the offshore limemud as a potential replacement for limestone in the cement, filler, blast furnace, steel melting shop, lime production, paint, and Grade‐I steel industries. An assessment of mining and transportation costs indicates that the offshore limemud (USD 5–6/ton) is more cost‐effective than that imported from other countries (USD16‐18/ton). With several advantageous factors like low impurity, mode of occurrence in overburden‐free stratified form, fine‐grained slurry nature, and shallow water depth, sustainable mining of offshore limemud could be a future reality with controllable technological, economic, and environmental challenges.

Van Hong Thi Pham, Jaisoo Kim, Soonwoong Chang et al.

The emission of methylene blue (MB) from common industries causes risks to human health by making clean drinking water unavailable and hampering environmental safety. A biological approach offering a more cost-efficient and sustainable alternative solution has been studied and demonstrated to be significantly effective for the removal of MB using promising microbial isolates. Therefore, this study targeted bacterial candidates, namely <i>Bacillus</i> sp. React3, isolated from soil with the potential to decolorize MB. The phenogenic identification of strain React3 was performed by 16S rRNA sequencing, showing a similarity of 98.86% to <i>Bacillus velezensis</i> CR-502T. The ability of this bacterial strain to decolorize MB was proven through both the lignin peroxidase efficiency and accumulation in the biomass of the living cells. MB removal was determined by the reduction in the maximum absorption at a wavelength of 665 nm, which was observed to be up to 99.5% after 48 h of incubation. The optimal conditions for the MB degradation of strain React3 were pH 7, 35 °C, static, 4% inoculum, and 1000 mg/L of MB, with tryptone as a carbon source and yeast extract as a nitrogen source.

Yao Sun, Shiyu Liu, Zhe Zhan et al.

<i>Pseudomonas fluorescens (P. fluorescens)</i> and <i>Pseudomonas fragi (P. fragi)</i>, two kinds of psychrotrophic <i>Pseudomonas</i> species with pathogenicity, are likely to contaminate foods and cause diseases even in fairly cold environments, an outcome which should be suppressed. This paper investigates the antibacterial mechanisms of <i>Dellaglioa algida (D. algida)</i>, a new type of low-temperature-resistant <i>Lactobacillus</i>, on two such <i>Pseudomonas</i>. By the enzyme treatment approach, the antibacterial substance existing in the cell-free supernatant (CFS) of <i>D. algida</i> is preliminarily determined as organic acid or protein; then, its inhibition effects are assessed under various culture environments, including pH value, salinity, and culture time, where the best antibacterial performance is achieved at pH = 6.00, S = 0%, and culture time = 48 h. A series of experiments on biofilms indicate that <i>D. algida</i> is not only able to inhibit the generation or damage the integrality of the biofilm of the two mentioned <i>Pseudomonas</i>, but also can reduce the motility, including swarming and swimming, of <i>P. fragi</i> and restrain the swarming of <i>P. fluorescens</i>. The aformentioned developed antibacterial mechanisms show the possibility of using <i>D. algida</i> in applications as an inhibitor for psychrotrophic <i>Pseudomonas</i> in the food industry, by virtue of its strong suppression capability, especially in cold environments.

Singh Sathya Prakash, Kanas Nikola, Einarsrud Mari-Ann et al.

The thermoelectric properties of ceramics with composition A0.98La0.02MnO3-δ are anticipated to vary with the basicity and atomic portion of the alkaline earth metal, A. In the present investigation ceramic powder precursors with composition A0.98La0.02MnO3-δ (A = Ca, Ba) were synthesized by the solid-state method and sintered in air at 1400°C. Seebeck coefficient, electrical and thermal conductivities were characterized for both materials from 100 to 900°C in air. The highest zT of 0.10 at 900°C was reached for Ca0.98La0.02MnO3-δ. The high zT is attributed to the enhanced electronic conductivity (∼90 S/cm at 900°C) due to La doping. zT for Ba0.98La0.02MnO3-δ reached its highest value (0.02) at 800°C corresponding to a low electronic conductivity (∼2 S/cm), while the thermal conductivity was significantly reduced compared to Ca0.98La0.02MnO3-δ reaching ∼1W/(m•K) combined with a high Seebeck coefficient, −290 μV/K. The present data represent a valuable basis for further development of these materials with respect to applications in thermoelectric devices.

Mostafa Soleimani Shadvar, Shirin Moradkhani

Background: Falcaria vulgaris and Echinophora platyloba, two members of Apiaceae family, are native flora of Iran and have numerous ethnobotanical applications. Objectives: The present study focuses on the chemical composition of the essential oils and the evaluation of the antioxidant capacity of F. vulgaris and E. platyloba growing in Hamadan province. Methods: Hydrodistillated essential oil from aerial parts of F. vulgaris and E. platyloba were obtained using clevenger apparatus. The chemical composition of the essential oils was determined using GC-MS analysis. Methanol extracts from aerial parts and seeds of F. vulgaris and E. platyloba were obtained by Soxhlet extractor. The antioxidant properties of the extracts were determined through use of several antioxidant assays (DPPH, FRAP, β-carotene-linoleic acid and iron-chelating test). Results: GC-MS analysis revealed that the major components of F. vulgaris essential oil were spathulenol, and palmitic acid. The main components of E. platyloba were γ-decalactone and (E)-sesquilavandulol. The extract from aerial parts of F. vulgaris consistently exhibited more antioxidative power than the rest of the extracts, followed by the extracts from aerial parts of E. platyloba. The results of DPPH, FRAP and β-carotene-linoleic tests were well correlated with each other, but they were somewhat different from the results of the iron-chelating test. Conclusion: The results of this research showed that F. vulgaris and E. platyloba contain significant antioxidant properties; therefore, their use in food and pharmaceutical industries as preservatives will be fruitful.

Mariana Muniz da Silva, Angélica Cristina de Souza, Emanuel Roberto Faria et al.

Kombucha is a beverage obtained from fermentation of <i>Camellia sinensis</i> tea using a symbiotic culture of bacteria and yeast (SCOBY). This association of bacteria and yeasts can be an interesting source of microorganisms for developing fermented beverages, including beer. The objective of this study was to evaluate kombucha SCOBY and commercial brewing yeast as a starter culture for the elaboration of beer. Three assays were performed to develop the beverage (C = control, KL = kombucha + yeast, K = kombucha). The pH, density, carbohydrates, organic acids and ethanol were evaluated during fermentation. Microbial counts (yeasts and mesophilic bacteria) and volatile compounds were recorded at the initial and final fermentation times. The content of total phenolic compounds, antioxidant capacity, color and bitterness (IBU) of the beers were determined. The results showed that kombucha-fermented wort produces a beer with differentiated characteristics. Increased lactic acid (0.73 g/L) and low alcohol content (1.3%) were observed in the K assay. Further, desired volatile compounds, such as ethyl octanoate, phenethyl acetate and 2-phenylethanol, were also found in this beer. The combination of kombucha and commercial yeast for beer production showed carbohydrate consumption and contents of organic acids similar to those of control beer, producing beers with an alcohol content of 5.9%. From the results, it was possible to observe a tendency for the content of total phenolic compounds (37.57, 33.00 and 31.64 mg/100 mL for K, KY and C assays, respectively) to increase when the wort was inoculated with kombucha. There was no difference in the antioxidant activity of the produced beers. All produced beers showed a yellowish color and a bitterness value (IBU) of 27%. The present study showed that adding kombucha as a starter culture produced beer with differentiated properties, such as high antioxidant activity, low alcohol content and sour characteristics.

Nawal A. Alshehri, Abid A. Memon, M. Asif Memon et al.

The chemical reactions widely operate in industries to enhance the heat transfer rate among the chosen domain. In the current article, we are going to observe an exothermic reaction of calcium oxide and water in a backward step tubular reactor with a cooled surrounded surface. The tubular reactor will be considered axisymmetric with an aspect ratio of 0.5, 0.6, and 0.7 from half radius to the length of the reactor. The governing partial differential equations of mass, momentum, and energy and diffusion equations are solved using the commercial package of finite element method of COMSOL Multiphysics 5.6. A parametric study is done by using the Reynolds number in the range and activation energy E in a range from 71,000 J/mol to 75,000 J/mol. The initial concentration of calcium oxide is tested from 1% to 3%. The computational results will be displayed for the upstream and downstream of the channel. It was concluded that the temperature difference is increasing linearly against the concentration of calcium hydroxide upstream and nonfunctional downstream. The average Sherwood and Nusselt numbers give a positive response with increasing the aspect ratio as well as the Reynolds number. The rotation rate at the middle of the downstream was also concluded using the Reynolds number and aspect ratio.

Lu Wang, Xu Yang, Zhuoting Li et al.

In this work, the hydrothermal extract of spent coffee grounds (SCG) was used to make alcoholic beverages with commercial <i>S. cerevisiae</i> strain D254. The sensory characteristics of the SCG alcoholic beverages were analyzed using sensory description, electronic nose, electronic tongue, and gas chromatography-mass spectrometry (GC-MS). The results suggested that the supplement of 0.20% (NH₄)₂HPO₄ was effective at improving growth and alcohol fermentation of <i>Saccharomyces cerevisiae</i> D254 in SCG extract. SCG fermented beverages (SFB) and SCG distilled spirits (SDS) produced at the optimized fermentation conditions had appropriate physicochemical properties and different sensory characteristics. Fermentation aromas, especially esters, were produced in SFB, increasing the complexity of aroma and lowing the irritating aroma. The combination of original and fermentation components might balance the outstanding sourness, astringency, and saltiness tastes of SFB. The fermentation aroma was partially lost and the sourness, bitterness, astringency, and saltiness tastes were relieved in distillation, leading to the relatively more prominent aroma typicality of coffee and a soft taste. These findings lay a foundation for producing new high-quality coffee-flavored alcoholic beverages or flavoring liquors.

Jonny Ariel Fajardo Daza, Frank Carlos Herrera Ruales, Carol Andrea Ibarra Cabrera et al.

Background: The determination of polyphenols in cocoa beans allows the establishing of antioxidant properties of great benefit to this product. Objectives: Optimization of the ultrasound-assisted extraction method to determine the content of polyphenols in cocoa beans. Methods: Two experiments design stages were carried out to optimize the ultrasound-assisted extraction process of polyphenols from the cocoa bean. In the first experiment design stage, the adequate extraction solvent was determined; for this purpose, five types of solvents were evaluated through a completely random design unrestricted (CRD). In the second experiment stage, a central composite design 22 + star point (with two central points) was used, which was evaluated using the response surface methodology to determine the influence of the temperature, time, and solute / solvent ratio. Results: The experiment found that acetone: water: acetic acid (70: 29.5: 0.5) mixture, leads to a greater amount of total extracted phenols measured for the Folin-Ciocalteu method. Analysis of variance (ANOVA) found that six significant effects that influence the response variable (total phenols extracted). The main effects were of the three factors and three of their interactions. Conclusions: After the optimizing said factors, an optimal point was found: 39.3 °C oftemperature, 74.5 minutes, and 22.8 mL of solvent per gram of cocoa sample.

Zhengjuan Wang, Guohong Zhou, Danyu Jiang et al.

Abstract A2B2O7 system compounds, which usually present three phase structures mainly based on the ionic radius ratios of r A and r B (r A/r B), have been studied for potential applications in many fields, such as thermal barrier coatings, luminescence powders, fast-ion conductors, photocatalysts, and matrices for immobilization of highly active radionuclides. Since 2005, La2Hf2O7 was fabricated into transparent ceramics and much more attentions were paid on A2B2O7 transparent ceramics for new applications. In this review, the development of A2B2O7 system transparent ceramics was described. The structure characteristics, powder synthesis method, and sintering techniques of the final A2B2O7 transparent ceramics were summarized. After that, the mostly reported A2Hf2O7, A2Zr2O7, and A2Ti2O7 system transparent ceramics were systematically introduced. The potential application fields and future development trends were also discussed, focusing on scintillators, optical elements, and other luminescent materials

Bev Dahlby, Mukesh Khanal

The counterpart to the economic cycle is the policy cycle. Whenever there is a downturn in the Alberta economy because of slumping oil and gas prices, politicians of all persuasions, from Peter Lougheed to Rachel Notley, have called for policies to diversify the economy, on the assumption that expanding other sectors of the economy will insulate Alberta’s economy against volatile oil and gas prices. However, just because a sector is not directly part of the oil and gas extraction sector, does not necessarily make it counter-cyclical. In fact, the sectors that have been promoted in the name of diversification are often linked to the oil and gas extraction sector and follow the same boom-bust cycle.In other words, the government’s attempts to subsidize certain sectors in the name of “diversification” do not insulate the provincial economy from fluctuations in oil and gas prices and may even exacerbate the economic cycle. Missing in the discussion is an appreciation of how changes in the structure of the Alberta economy have affected output and income volatility. In the last 20 years, sectoral output shares have become more diversified in Alberta, and this has contributed to a 21 per cent reduction in aggregate output volatility over that period. Successive governments have tried promoting manufacturing as a way to diversify the economy, but manufacturing is the third most volatile sector, and its volatility is linked closely with the boom-bust cycles of the oil and gas extraction sector. So, increasing manufacturing, including petrochemical manufacturing, will actually make output volatility worse, not better. In fact, a one standard deviation increase in average per capita output in the oil and gas extraction sector is associated with in a 9.45-per cent increase in average per capita output in the chemical manufacturing subsector, suggesting the same boom-and-bust relationship between the two sectors. It is not the only sector like that: 16 other sectors in Alberta are linked to the same boom-bust cycle as the oil and gas sector. The more important diversification issue in the province is not output volatility, but the volatility of labour income. In the last 20 years, labour income has become increasingly concentrated in Alberta’s two most volatile sectors, oil and gas extraction and construction. As a result, volatility of aggregate labour income in Alberta increased by 40 per cent during that period. Rather than trying to change Alberta’s industrial mix by subsidizing industries that may only contribute to more volatility of economic output, a more sensible government approach would be to adopt policies that address the problem of labourincome volatility. That would include finding ways to expand unemployment insurance for Alberta workers, as the current federal government policy actually provides fewer supports to unemployed Albertans than it does to residents of other regions. Average weekly earnings of Albertans were 20 per cent higher than national average weekly earnings over the 2012 to 2016 period. However, maximum annual insurable earnings under EI are determined based on national average weekly earnings. Higherwage earners should have the opportunity to enrol in a voluntary supplemental EI program, and if the federal government does not want to provide it, the provincial government could. Additionally, the government can promote self-insurance among workers by expanding tax-sheltered savings products, like tax-free savings accounts, so workers can accumulate back-up funds when labour incomes are high, to help sustain them during downturns. Finally, the provincial government needs to abandon its procyclical spending patterns. That means spending less money when oil revenues are high, to avoid exacerbating labour and material shortages, and maintaining spending, rather than forced cutbacks, during downturns in the economy. That, of course, would require a great deal more political discipline than the easier and more fashionable attempts to subsidize output diversification.

Lifen Su, Lei Miao, Jibin Miao et al.

Zinc aluminate spinel cryogels with various molar ratio of Al/Zn are synthesized by sol–gel technology followed by vacuum freeze drying. The structures and optical properties are both found to be affected by the molar ratios of Al/Zn and annealed temperatures. The peaks of zinc oxide (ZnO) and zinc dialuminum oxide (ZnAl2O4) are both obtained for the samples with more Zn content annealed at 750 °C or upward. The composites have a large surface area (137 m2/g) with mesoporous structure after annealing at 750 °C. The SEM images reveal that the ZnAl2O4 crystals formed a multilayer structure with redundant ZnO particles which deposited on it. Furthermore, the maximum infrared reflectance is about 80% with an improvement of 35% in the infrared region after annealing at 950 °C compared with that of 450 °C, which indicates that these porous cryogels have a potential application as thermal insulating materials at a high temperature.

S.A., Mediclinics

Not available<br><br>No disponible

Gabriela Carrillo Zeledón, Mauricio Redondo Solano, María Laura Arias Echandi

Listeria monocytogenes, además de ser un género capaz de producir una enfermedad infecciosa grave en el hombre, puede formar biopelículas en distintas superficies relacionadas con el ambiente de producción alimentario. Éstas constituyen un serio problema debido a que son una fuente importante y constante de contaminación para los alimentos y el ambiente de producción, además de que las bacterias presentes en ellas poseen una aumentada resistencia hacia agentes físicos y químicos de uso frecuente. En el presente trabajo se estudió la capacidad de formación de biopelícula de cepas de L. monocytogenes previamente aisladas a partir de queso tierno bajo diferentes condiciones de temperatura y cultivo. Se utilizó una técnica de microplaca con diferentes medios de cultivo (CICC, CTS 1:20 y suero de queso) a diferentes temperaturas de incubación (refrigeración, ambiente y 35ºC). La capacidad de formación de biopelícula fue clasificada según la densidad óptica obtenida a 620 nm. Ninguna de las cepas evaluadas fue clasificada como formadora fuerte de biopelicula bajo ninguna de las variables estudiadas, sí se detectaron formadoras débiles y moderadas. Los resultados obtenidos ponen de manifiesto la influencia del contenido de nutrientes en el medio de cultivo sobre la formación de biopelícula, no obstante, el CICC fue el único medio que permitió la expresión de formadores moderados. Por el contrario, el suero de queso resultó poco favorecedor. La formación de biopelícula es un proceso multifactorial, donde el nivel de adsorción depende de gran cantidad de variables y cuyo estudio debe fomentarse, de manera que se desarrollen metodologías que permitan su reducción o eliminación, de manera que las industrias alimentarias aseguren productos inocuos y de buena calidad microbiológica.<br>Listeria monocytogenes is a bacteria associated with the production of severe infectious disease in human being, but also with the formation of biofilms in different surfaces related to the food production environment. Biofilm represents a serious problem in food industry, since it is a constant and important contamination source and also, bacteria present in it have an increased resistance towards physical and chemical agents of common use. The capacity of biofilm formation of L. monocytogenes strains previously isolated from soft cheese samples from Costa Rica was studied under different temperature and culture conditions. The microplate technique was performed using different culture media (BHIB, TSB 1:20 and cheese serum) and at different incubation temperatures (refrigeration, environmental and 35ºC). Biofilm formation capacity was classified according to the optical density obtained at 620nm. None of the strains evaluated was classified as strong biofilm former under any of the variables studied, nevertheless, weak and moderate formers were detected. The results obtained show the influence of the nutrient content of the culture media used over biofilm formation; BHIB was the only culture media that allowed the expression of moderate biofilm forms, contrary to cheese serum that did not promote biofilm production. Biofilm formation is a multifactorial process, where adsorption level depends on several variables and its study must be promoted in order to develop methodologies that allow its reduction or elimination, so food industries may offer safe food products to consumers.

Ester Lucía Gutiérrez E., Gladys Ramírez López

Mohammad Reza Hadjmohammadi, Mohammad Javad Chaichi, Maryam Yousefpour

The solvatochromism of fluoresceine and its derivatives was studied in solvents of different Hydrogen Bond Donor (HBD), Hydrogen Bond Acceptor (HBA), Donor Number (DN) and Acceptor Number (AN) by their UV-Vis spectra. Results showed that position, intensity and shape of absorption bands change with type of solvent. These changes can be rationalized by solvatochromic parameters such as α, β, ET (30), DN and AN using multiple linear regression (MLR) technique. Correlation coefficients of obtained equations were 0.965-0.999.

Lothar Reh