Directed evolution: Past,present, and future

Directed evolution, the laboratory process by which biological entities with desired traits are created through iterative rounds of genetic diversification and library screening or selection, has become one of the most useful and widespread tools in basic and applied biology. From its roots in classical strain engineering and adaptive evolution, modern directed evolution came of age 20 years ago with the demonstration of repeated rounds of polymerase chain reaction (PCR)‐driven random mutagenesis and activity screening to improve protein properties. Since then, numerous techniques have been developed that have enabled the evolution of virtually any protein, pathway, network, or entire organism of interest. Here, we recount some of the major milestones in the history of directed evolution, highlight the most promising recent developments in the field, and discuss the future challenges and opportunities that lie ahead. © 2013 American Institute of Chemical Engineers AIChE J, 59: 1432–1440, 2013     

Organoclay rheological additives: Past,present and future

Rheological or flow properties have important implications in many and diverse applications. Often, an additive is used to impart the desired flow behavior. Among these, organoclay products, formed by the reaction of organic cations with smectite clays, are the most widely used additives for solvent-based coatings. The cation— usually a quaternary ammonium salt—used will influence the performance of the resultant organoclay. Criteria to consider in the choice of a cation are molecular size, compatibility with the fluid in which the organoclay is to be used, stability and reactivity. To form a stable organoclay product, the organic cation must contain at least one long-chain alkyl group. Othr groups attached to the cation may be divided into two categories: “filler” groups serve to complete the tetrahedron around the nitrogen, whereas “active” groups contribute beneficially to the performance of the organoclay. Our study of the structure/property relationships has led to the development of new additives described here. These are superior, particularly in terms of use, while providing the same excellent rheological control offered by earlier additives.     

氯氟烃替代物的过去、现在和未来

该文对氯氟烃（CFCs）替代物的开发方法、发展现状进行了介绍。目前，开发出的CFCs替代物包括氢氯氟碳（HCFCs）、氢氟烃（HFCs）和氢氟烯烃（HFOs）。其中，HFOs环境性能优异，可在制冷和发泡领域实现对HFCs的替代。总结了HFOs的主要合成路线，并指出最佳的产业化路线。展望了CFCs替代物的未来发展趋势，由于HFOs的核心专利被国外发达国家所垄断，而且HFOs存在二次污染和易燃的风险，同时HFOs类物质的性能难以满足精密清洗、高端芯片先进制造、高压电器绝缘等领域的使用要求，因此，今后的研究重点在于，开发满足国家重大战略需求的新一代替代物，实现诸多领域CFCs的精准替代。     

化学反应工程的前世、今生与未来

回顾了化学反应工程学科和相关工业重要贡献的发展历史,提出以"物质的传递与转化"、"能量的传递与转化"和"信息的传递与转化"所组成的"三传三转"作为化学工程学科范式的新解读模式;强调了多尺度研究对于理解反应工程复杂问题的重要意义,计算技术的发展大大促进了反应工程理论的进步;从学科交叉和化工前沿角度探讨了反应工程新的发展方向,尤其展望了大型化煤化工、大规模天然气(页岩气)利用等将为中国的反应工程发展带来更为优越的国际领先契机,也是未来反应工程的任务和挑战。     

SHS in the UK: Past, present, and future directions

The United Kingdom has played a small but significant role in the development of SHS. Parkin and Kuznetsov have studied the formation of complex oxides in external fields. Wood and Christanthou have studied the formation of intermetallic compounds and refractory materials by SHS. Perry, Thompson, and Green have made contributions to the synthesis of materials by solution phase auto-combustion reactions. The UK has also made contributions to the theory of SHS and the monitoring of SHS reactions by time resolved X-ray, neutron, and thermal imaging studies. The UK has been at the forefront in the development of a sub-class of SHS reactions termed solid state metathesis. Presented at the International Conference on Historical Aspects of SHS in Different Countries, October 22–27, 2007, Chernogolovka, Moscow, Russia.     

Imitation dairy products—Past,present and future

The history of substitute dairy products and their impact on the market is reviewed. The present status of filled and imitation milk products is discussed from the flavor acceptance, economic, legal and nutritional standpoints. Comments on some factors which will affect the future growth potential of these products, such as Consumer acceptance, economics, proposed legislation with respect to compositional, nutritional and labeling requirements and industry attitude toward marketing of these products are given. Presented at a meeting of North Central Section of the American Oil Chemists’ Society, September 18, 1968.     

Past, present, and future of periodic mesoporous organosilicas-the PMOs

Periodic mesoporous organosilicas (PMOs) represent an exciting new class of organic-inorganic nanocomposites targeted for a broad range of applications such as catalysis and sensing, separations, and microelectronics. Their hallmark is the presence of organic bridging groups incorporated into the channel walls of an ordered nanoporous structure, which represents a useful tool to finely tune the chemical and physical properties of the materials. We discuss the history of the discovery and development of the PMOs emphasizing the most important recent advancements regarding compositions and structures, morphologies, and properties. Furthermore, we present an outlook about the promising future perspectives of PMOs that result from the latest developments in this field.     

Enzyme immobilization onto renewable polymeric matrixes: Past,present, and future trends

In this review, we present an overview of the different renewable polymers that are currently being used as matrixes for enzyme immobilization and their properties and of new developments in biocatalysts preparation and applications. Polymers obtained from renewable resources have attracted much attention in recent years because they are environmentally friendly and available in large quantities from natural sources. Different methods for the immobilization of enzymes with these matrixes are reviewed, in particular: (1) binding to a prefabricated biopolymer, (2) entrapment, and (3) crosslinking of enzyme molecules. Emphasis is given to relatively recent developments, such as the use of novel supports, novel entrapment methods and protocols of polymer derivatization, and the crosslinking of enzymes. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42125.     

Hybrid semi-parametric modeling in process systems engineering: Past,present and future

Hybrid semi-parametric models consist of model structures that combine parametric and nonparametric submodels based on different knowledge sources. The development of a hybrid semi-parametric model can offer several advantages over traditional mechanistic or data-driven modeling, as reviewed in this paper. These advantages, such as broader knowledge base, transparency of the modeling approach and cost-effective model development, have been widely recognized, not only in academia but also in the industry.In this paper, the most common hybrid semi-parametric modeling and parameter identification techniques are revisited. Applications in the areas of (bio)chemical engineering for process monitoring, control, optimization, scale-up and model-reduction are reviewed. It is outlined that the application of hybrid semi-parametric techniques does not automatically lead into better results but that rational knowledge integration has potential to significantly improve model-based process operation and design.     

Evolution of polymeric hollow fibers as sustainable technologies: Past, present, and future

Energy, water, affordable healthcare and global warming are four major global concerns resulting from resource depletion, record high oil prices, clean water shortages, high costs of pharmaceuticals, and changing climate conditions. Among many potential solutions, advances in membrane technology afford direct, effective and feasible approaches to solve these sophisticated issues. Membrane technology encompasses numerous technology areas including materials science and engineering, chemistry and chemical engineering, separation and purification phenomena, molecular simulation, as well as process and product design. Currently, polymeric hollow fiber membranes made using a non-solvent-induced phase inversion process are the dominant products because polymers offer a broad spectrum of materials chemistry and result in membranes with desirable physicochemical properties for diverse applications. Their low cost and ease of fabrication make polymeric membranes superior to inorganic membranes. Therefore, this review focuses on state-of-the-art polymeric hollow fiber membranes made from non-solvent-induced phase inversion and the potential of membrane processes for sustainable water and energy production. The specific topics include: (i) basic principles of hollow fiber membrane formation and the phase inversion process; (ii) membranes for energy (natural gas, H₂, and biofuel) production; (iii) membranes for CO₂ capture; and (iv) emerging desalination technologies (forward osmosis and membrane distillation) for water production. Finally, future opportunities and challenges for the development of advanced membrane structures are discussed.     

Formulations for vinyl house siding: History,present, future

In the early 1960s, vinyl house siding was first commercialized. The colors were pastels and included white, green, yellow, and gray. All siding tended to bleach and fade (oxidize) to an extent where medium and dark colors were unacceptable, since the fading is more noticeable in deeper colors. All the early siding was made from cubes on single-screw extruders. Powder compounds were first introduced in the late 1960s, as was twin-screw extrusion. At the same time higher processing temperatures were used on, both twin- and single-screw extruders. That led to a well-fused and tougher product. Formulation changes reduced bleaching and fading and permitted such medium-depth colors as tan, gold, beige, blue, and olive. This technology allowed rapid growth in the vinyl siding industry in the late 1970s. Surface distortion (oil canning) was recognized as a potential problem with the early gray color and recognized as a major problem with dark colors; it was resolved only by understanding the fundamental principles involved. Another major problem was the fading in dark colors and here again extensive research into the principles of weathering led to the use of a thin, highly weatherable capping as a cost-effective solution. For the future, many technical developments can be expected in this rapidly growing market. However, judging by the occasional withdrawal of a formulation from the market, and by an occasional homeowner complaint, present performance in several properties must be judged as just adequate. For this market to continue its rapid growth, future performance should be better than today's. This can be accomplished without hurting economics by careful understanding of all parameters involved. Formulation changes will allow better performance. Standards must be raised to control product performance, especially surface distortion and color stability in darker colors, and to insure retention of physical properties after long-term weathering.     

Electrocatalysis: present and future

The development of electrocatalytic materials and our knowledge of the factors which determine catalytic activity are reviewed. To the present, the main aim has been to produce electrocatalysts which minimize overpotentials, particularly for gas evolving or consuming electrode reactions. In the future, however, materials which optimize the selectivity of more complex reactions may increase in importance. It must be recognized that the development of electrocatalysts has been essentially empirical and there remains a gulf between those who develop electrode materials and those who seek to understand the physical chemistry of electrocatalysis.     

Model predictive control: past,present and future

More than 15 years after model predictive control (MPC) appeared in industry as an effective means to deal with multivariable constrained control problems, a theoretical basis for this technique has started to emerge. The issues of feasibility of the on-line optimization, stability and performance are largely understood for systems described by linear models. Much progress has been made on these issues for non-linear systems but for practical applications many questions remain, including the reliability and efficiency of the on-line computation scheme. To deal with model uncertainty ‘rigorously’ an involved dynamic programming problem must be solved. The approximation techniques proposed for this purpose are largely at a conceptual stage. Among the broader research needs the following areas are identified: multivariable system identification, performance monitoring and diagnostics, non-linear state estimation, and batch system control. Many practical problems like control objective prioritization and symptom-aided diagnosis can be integrated systematically and effectively into the MPC framework by expanding the problem formulation to include integer variables yielding a mixed-integer quadratic or linear program. Efficient techniques for solving these problems are becoming available.     

Food colorants: their past,present and future

Whether we are purchasing fresh vegetables from a market stall, ready meals from the supermarket, eating at home or in a five‐star restaurant, we use colour to tell us what to expect in terms of taste, nutrition and safety. This review considers the techniques that have, over the years, been employed to modify the colour of our food, and the interactions of these techniques with issues of safety and nutrition. The demand for brightly coloured food resulted in the incorporation of some questionable inorganic and organic chemistry being used in food products. A limited number of synthetic dyes are still used in food today, but health concerns and the consumer‐driven demand for natural colorants has brought about a change in the way food is coloured. The proliferation of products with labels that state they contain “No artificial colours” on supermarket shelves suggests that the future of azo dyes and their various derivatives is strictly limited. Nature produces an abundance of colours and many of these are extracted and used as natural food colorants; however, they are subject to application limitations and stability problems. Significant research by academia and industry into methods to stabilise and expand the application possibilities for the various approved natural food colorants is ongoing, but most developments that food colour manufacturers proclaim are enhanced vehicles for delivering established natural pigments into food products.     

Epoxide resins as adhesives: Past and present

Epoxide resins were introduced commercially thirty-three years ago. One of the first formulations was an adhesive. There has been continuous development of the systems since then based on an increasing range of materials used in their constitution and an increasing knowledge of their chemistry and cured properties. This paper examines some of the scientific topics that contribute to the present day knowledge of these high strength adhesives and that are now used when advances are sought in the technology.