Microorganism preservation by convective air-drying—A review

At present, microorganisms are mainly preserved by freeze-drying. There is, however, lack of studies conducted on various cheaper yet promising convective air-drying alternatives. Convective air-drying has been proven to produce dried culture with comparable cell survival and final moisture content to that of freeze-drying. This paper aims to draw an understanding to application and suitability of convective air-drying which includes spray, oven, heat pump, fluidized bed, conveyor, and rotary drying to preserve microorganisms. The paper concludes that drying near ambient temperature and the addition of dehydration protectants are important to obtain satisfactory drying quality.     

Manufacturing porous ceramic materials by tape casting—A review

Tape casting is a well-established technique to fabricate ceramic tapes. This technique has been usually applied to produce dense substrates for electronic applications, but recently there are increasing efforts regarding the production of porous cast tapes. The aim of this paper is to present the latest strategies and achievements to manufacture porous ceramic materials by tape casting. The pores morphology can be manipulated by adjusting particle size, sacrificial pore formers, sintering conditions, and combined techniques (phase inversion and freeze casting). Moreover, tape casting enables adjusting the thickness of the product, which is a key property in separation applications using membranes and/or support materials with tailorable structure.     

Flavor components of olive oil—A review

The unique and delicate flavor of olive oil is attributed to a number of volatile components. Aldehydes, alcohols, esters, hydrocarbons, ketones, furans, and other compounds have been quantitated and identified by gas chromatography-mass spectrometry in good-quality olive oil. The presence of flavor compounds in olive oil is closely related to its sensory quality. Hexanal, trans-2-hexenal, 1-hexanol, and 3-methylbutan-1-ol are the major volatile compounds of olive oil. Volatile flavor compounds are formed in the olive fruit through an enzymatic process. Olive cultivar, origin, maturity stage of fruit, storage conditions of fruit, and olive fruit processing influence the flavor components of olive oil and therefore its taste and aroma. The components octanal, nonala, and 2-hexenal, as well as the volatile alcohols propanol, amyl alcohols, 2-hexenol, 2-hexanol, and heptanol, characterize the olive cultivar. There are some slight changes in the flavor components in olive oil obtained from the same oil cultivar grown in different areas. The highest concentration of volatile components appears at the optimal maturity stage of fruit. During storage of olive fruit, volatile flavor components, such as aldehydes and esters, decrease. Phenolic compounds also have a significant effect on olive oil flavor. There is a good correlation between aroma and flavor of olive oil and its polyphenol content. Hydroxytyrosol, tyrosol, caffeic acid, coumaric acid, and p-hydroxybenzoic acid influence mostly the sensory characteristics of olive oil. Hydroxytyrosol is present in good-quality olive oil, while tyrosol and some phenolic acids are found in olive oil of poor quality. Various off-flavor compounds are formed by oxidation, which may be initiated in the olive fruit. Pentanal, hexanal, octanal, and nonanal are the major compounds formed in oxidized olive oil, but 2-pentenal and 2-heptenal are mainly responsible for the off-flavor.     

Laser drilling of structural ceramics—A review

Structural ceramics are becoming widely popular in numerous fields because of high mechanical and physical properties. It is of great difficulty for conventional techniques to machine brittle and hard materials. As one of nontraditional machining methods, laser beam machining has emerged as an effective technique for drilling of ceramics. This paper reviews the research work on laser drilling of structural ceramics from its different pulse width. Lasers have been discussed to understand effects of critical experimental parameters on the quality characteristics and physical mechanisms involved in drilling ceramics. In addition, it is held that heat and liquid-assisted laser processing serves as a useful method to improve processing quality. Computational approaches of ANSYS and COMSOL are used to predict laser input parameters’ effects on quality of hole and describe the physical phenomena during processing. Comments on laser drilling of ceramics developments and future directions are provided at the end.     

Drying of biofuels from the forest—A review

The literature during 2000–2016 about drying of biofuels from the forest has been reviewed. Biofuels constitute a low-cost energy resource that is likely to continue to increase and the dryers for such products should be simple, robust, and easy to operate. In 1970s and 1980s, rotary dryers and flash dryers were the most common types, and in 1990s, superheated steam (SHS) dryers became common. Maintenance costs and use of medium pressure steam for the SHS dryers are important topics to consider and one drawback for the rotary dryers is that high-temperature heat sources are used. The development during the last 15 years has moved toward moving bed dryers because of the possibility to use cheap low-temperature energy sources, robust design, and direct capacity control that is achieved by controlling the air temperature in the dryer. A price for the dry biofuel of 15–20 Euro/MWh has been indicated to make a dryer installation profitable based on no cost for the thermal energy and 40 Euro/MWh as the cost for the electrical energy. Shrinkage and the internal transport of moisture and heat in large particles of biofuels will need more considerations in the future. Fractionation of the biofuels, codrying with other products, the total cost for the drying process, environmental issues, and development of drying processes operating at high dew points are the other things to consider.     

Immobilization of multi-enzyme in porous solid supports—a theoretical study

A theoretical study is presented dealing with the immobilization of two enzymes into a porous solid support. The developed model basically takes into account the interplay between restricted diffusions of two enzymes within intraparticle void space and their competitive adsorptions onto available functional sites on the interior surfaces. Simulations have shown that parameters such as binding rates of enzymes, initial bulk concentration ratio, pellet size and impregnating time have significant influence on the eventual distribution of two enzymes within the porous solid supports.     

Going against the flow—A review of non-additive means of drag reduction

The conventional mainstream method of polymer additives for reducing drag in pipes is disadvantageous from certain environmental perspectives. This paper aims to go against the flow by challenging the widespread preference for using polymeric and surfactant-based drag reducers and discusses the performance of five alternative methods that do not involve polymer additives: riblets, dimples, oscillating walls, compliant surfaces, and microbubbles. The hypothetical mechanisms involved, success of each approach, relevant stages of development, important findings, and possible avenue for future research are discussed. The results obtained in this paper have exposed the potentials of new drag reduction technologies.     

Thermoset/graphene polymer composites—A review of processing and properties

Polymer-carbon nanocomposites incorporate the exceptional properties of both the polymer matrices, such as low cost and simple processing, with the distinctive features of the carbon-based fillers, such as high electrical and thermal conductivities, and excellent mechanical properties. Various fillers like carbon black (CB), graphite, expanded graphite (EG), and carbon nanotubes (CNTs) are being used to produce materials with advanced properties. However, at high filler loading, these filler materials have some major challenges such as filler agglomeration. Recently, graphene has gained increased interest as an alternative filler to produce polymer nanocomposites with advanced characteristics. Thermosetting polymer composites with graphene fillers are being considered for multiple applications and are a subject of interest for researchers because of enhanced properties like excellent corrosion resistance and low density. This review outlines studies to improve the mechanical, electrical, and thermal properties of thermoset/graphene composites.     

Lipids and endothelium-dependent vasodilation—A review

Studies using both in vitro and in vivo techniques have repeatedly shown that endothelium-dependent vasodilation (EDV) is impaired in different forms of experimental as well as human hypercholesterolemia. Clearly this impaired EDV can be reversed by lowering cholesterol levels by diet or medical therapy. Competitive blocking of l-arginine, changes in nitric oxide synthase acitivity, increased release of endothelin-1, and inactivation of nitric oxide due to superoxide ions all contribute to the impairment in EDV during dyslipidemia. The oxidation of low density lipoprotein, with its compound lysophosphatidylcholine, plays a critical role in these events. However, data on the role of triglycerides and fat-rich meals regarding EDV are not so consistent as data for cholesterol, although a view that the compositions of individual fatty acids and antioxidants are of major importance is emerging. Thus, this review shows that while impaired FDV is a general feature of hypercholesterolemia, the mechanisms involved and the therapeutic opportunities available still have to be investigated. Furthermore, discrepancies regarding the role of triglycerides and fat content in food may be explained by divergent effects of different fatty acids on the endothelium.     

The use of environmentally sustainable bio-derived solvents in solvent extraction applications——A review

Replacement of volatile organic compounds (VOCs) by greener or more environmental y sustainable solvents is becoming increasingly important due to the increasing health and environmental concerns as wel as economic pressures associated with VOCs. Solvents that are derived from biomass, namely bio-derived solvents, are a type of green solvent that have attracted intensive investigations in recent years because of their advantages over con-ventional VOCs, such as low toxicity, biodegradability and renewability. This review aims to summarize the use of bio-derived solvents in solvent extraction applications, with special emphasis given to utilization of biodiesels and terpenes. Compared with the conventional VOCs, the overall performance of these bio-derived solvents is comparable in terms of extraction yields and selectivity for natural product extraction and no difference was found for metal extraction. To date most researchers have focused on laboratory scale thermodynamics studies. Future work is required to develop and test new bio-derived solvents and understand the kinetic performance as well as solvent extraction pilot plant studies.     

Oxidation of alkylbenzenes catalyzed by polymer-bound 2,2′-bipyridine-iron complexes

Polymer-bound 2,2′-bipyridine-iron complexes were synthesized and found to be novel catalysts for the oxidation of saturated hydrocarbons. Toluene, p-xylene, ethylbenzene, n-propylbenzene and n-butylbenzene were oxidized under an atmosphere of air or oxygen in the absence of solvent at 110°C in the presence of the iron complexes chemically immobillized on polymers, affording corresponding ketones and alcohols in most cases. Except for toluene, the conversion of alkylbenzene was 20% to 35% with the different iron complexes: The selectivity in producing ketone and alcohol in the oxidation of PhR (where R = Et, n-propyl and n-butyl was ∼100%.     

Food processing wastewater purification by microalgae cultivation associated with high value-added compounds production — A review

Microalgae have been considered as an efficient microorganism for wastewater treatment with simultaneously bioenergy and high value-added compounds production. However, the high energy cost associated with complicated biorefinery (e.g. microalgae cultivation, harvesting, drying, extraction, conversion, and purification) is a critical challenge that inhibits its large-scale application. Among different nutrition (e.g. carbon, nitrogen and phosphorous) sources, food processing wastewater is a relative safe and suitable one for microalgae cultivation due to its high organic content and low toxicity. In this review, the characteristic of different food wastewater is summarized and compared. The potential routes of value-added products (i.e. biofuel, pigment, polysaccharide, and amino acid) production along with wastewater purification are introduced. The existing challenges (e.g. biorefinery cost, efficiency and mechanism) of microalgal-based wastewater treatment are also discussed. The prospective of microalgae-based food processing wastewater treatment strategies (such as microalgae-bacteria consortium, poly-generation of bioenergy and value-added products) is forecasted. It can be observed that food wastewater treatment by microalgae could be a promising strategy to commercially realize waste source reduce, conversion and reutilization.     

Separation of Binary Liquid Systems by Sorption—A Comparison with Pervaporation

Abstract

Studies were carried out on the separation of the ethanol-water and the methanol-acetone systems by sorption using different commercially available molecular sieves (m.s.) as adsorbents. The separation factor (α) is found to be around 100 for m.s. 3A/ethanol-water system and is around 85 for m.s. 4A/ methanol-acetone system at respective azeotropic compositions. These separation factors appear to be better than the results reported by many workers using membrane process “pervaporation.” A comparison is made between the selectivity of pervaporation and sorption with respect to the systems studied.     

Waste glass in civil engineering applications—A review

Each year, hundreds of thousands of tons of industrial wastes are being stockpiled, landfilled, and disposed of in storages occupying large areas of land that would otherwise be available for productive use. Recycling of such wastes is now becoming of urgent global interest due to an increasing population, the rise in anthropogenic activities, and the need for more efficient resource and waste management systems. Among many wastes, the generation of glass is dramatically increasing, particularly in the municipal, industrial, and construction sectors. In civil engineering, in general, crushed waste glass has been mainly investigated as a substitute for sand and fine-grained aggregate in concrete production. In geotechnical engineering, in particular, the application of glass wastes is mainly limited to road pavements or as an additive to different soils for subgrade improvement. While glass wastes are relatively inert and potentially offer several opportunities for recycling as a substitute for diminishing and increasingly expensive sand supplies, their potential use yet remains relatively under-researched. This paper systematically reviews the current status of knowledge on the use of glass wastes in various civil engineering applications and discusses the suitability assessment of waste glass for use as a sustainable alternative to traditional civil engineering materials.     

Nanocellulose-based polymer composites for energy applications—A review

With rapid fossil fuel consumption and ecological concerns, alternative options of green energy development and its efficient storage technology is an emergent area of research. Nanocellulose is observed to be a very-promising sustainable and environmentally friendly nanomaterial for green and renewable electronics for advanced electrochemical energy conversion/conservation devices. This review begins with a basic introduction on the sources and properties of nanocellulose. It provides an overview of the recent advancements made by researchers in integrating nanocellulose with active materials to form a flexible film/aerogel/3D structures as a substrate for powering portable electronics, electric vehicles, etc. The review highlights the use of nanocellulose-based composites in energy conversion devices such as solar cells, piezoelectric materials, and lithium ion batteries. Recent research shows that the power conversion efficiency of solar cells and the piezoelectric performance of piezoelectric materials can be increased when the matrix is reinforced with nanocellulose. The review also focuses on the updates of nanocellulose-based composites in separators, binders, and electrodes of energy conservation devices such as supercapacitors, and energy capture devices such as CO₂ separators. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48959.     

Isothermal reaction calorimeters—I. A literature review

Most chemical and physical processes are accompanied by heat effects. These heat effects may contain significant information concerning the mechanism of the process, and a safe scale up of the process often requires a quantitative knowledge of the heat generated or consumed. In the present review one particular laboratory equipment for measurement of heat effects—the isothermal reaction calorimeter—will be described. Part I is a literature study of the available calorimeter equipment. Isothermal reaction calorimeters are described and classified according to the measurement principle of the particular design. Part II describes different techniques for numerical treatment of calorimeter data. It is argued that modern filtering methods and careful mathematical modeling can be used to obtain a significant improvement in the determination of physical and chemical parameters from calorimeter experiments. Finally, as an example a new data treatment system for a commercial bench scale isothermal calorimeter will be discussed.