There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

The Design and Analysis of Experiments

In this review, we highlight the use of organic photoredox catalysts in a myriad of synthetic transformations with a range of applications. This overview is arranged by catalyst class where the photophysics and electrochemical characteristics of each is discussed to underscore the differences and advantages to each type of single electron redox agent. We highlight both net reductive and oxidative as well as redox neutral transformations that can be accomplished using purely organic photoredox-active catalysts. An overview of the basic photophysics and electron transfer theory is presented in order to provide a comprehensive guide for employing this class of catalysts in photoredox manifolds.

Organic Photoredox Catalysis

介绍了Kirk—Othmer Encyclopedia of Chemical Technology（化工技术百科全书）（第五版）电子图书网络版数据库，并对该数据库使用方法和检索途径作出了说明，且结合实例简单地介绍了该数据库的检索方法。

Kirk-Othmer Encyclopedia of Chemical Technology数据库介绍及实例

A flow-focusing geometry is integrated into a microfluidic device and used to study drop formation in liquid–liquid systems. A phase diagram illustrating the drop size as a function of flow rates and flow rate ratios of the two liquids includes one regime where drop size is comparable to orifice width and a second regime where drop size is dictated by the diameter of a thin “focused” thread, so drops much smaller than the orifice are formed. Both monodisperse and polydisperse emulsions can be produced.

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Formation of dispersions using “flow focusing” in microchannels

An interdigital mixer-redispersion capillary assembly was applied to prevent the liquid-liquid bubbly flow coalescence in microreactors. The redispersion capillary consisted of 1-mm-long 0.25 mm inner-diameter constrictions, placed every 0.50 m along the channel length. The system was tested on the phase transfer-catalyzed esterification to produce benzyl benzoate. The application of constrictions to prevent coalescence resulted in a better reproducibility and higher conversion compared to a capillary without constrictions. The bubbly flow generated by the interdigital mixer-redispersion capillary assembly was found to be independent of the redispersion capillary inner diameters (0.50 and 0.75 mm) while being highly dependent on the flow rates. By controlling the total flow rate and the aqueous-to-organic ratio, the bubbly flow surface-to-volume ratio could be increased up to 230 700 m2m–3. Compared to the conventional phase transfer-catalyzed esterification, the continuous operation in the interdigital mixer-redispersion capillary assembly eliminated the use of solvents and bases, removing an energy-intensive step of distillation while increasing process safety.

Redispersion Microreactor System for Phase Transfer‐Catalyzed Esterification

Microreactors as a novel concept in chemical technology enable the introduction of new reaction procedures in chemistry, pharmaceutical industry, and molecular biology. Miniaturized reaction systems offer many exceptional technical advantages for a large num- ber of applications. The large surface-to-volume ratio of miniaturized fluid components allows for significantly enhanced process control and heat management. Moreover, the unique possibilities of microchemical systems pave the way to a distributed point-of-use and on-demand production of extremely harmful and toxic substances. On the other side of the coin, miniaturization of complete set-ups for chemical synthe- ses to a suitcase or even to a shoe-box size opens several possibilities to possibly use them as tools for terrorist attacks and to facilitate the clandestine manufacture of chemical agents. Microfabrication techniques are common and allow the machining of special materials (e.g., high-alloyed steel, titanium, ceramics, or glass). Meanwhile, micromachining techniques are available anywhere in the world. Therefore, these techniques are no longer unique nor pro- prietary and they cannot prevent construction or distribution of microreaction systems by people with allegiance to a terrorist organization.

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Microreactors. Prospects already achieved and possible misuse

State of the Art of Microreaction Technology

Hydroquinone and phloroglucinol were used as substrates for the aqueous Kolbe-Schmitt synthesis, using a novel processing methodology, termed high-p,T processing, recently demonstrated for the carboxylation of resorcinol. By the high-p,T approach, the temperature limitations of classical batch synthesis, e.g., set by reflux conditions (solvent boiling point), can be overcome by simple technical expenditure, e.g., the use of a few microstructured components, a capillary, and a needle valve at very low internal holdup. In this way, favorable speed-up of chemical reaction is achieved at temperatures normally outside the useful range for organic synthesis. While the hydroquinone synthesis gave only very low yields, phloroglucinol was converted to the corresponding carboxylic acid at a high yield of 50 %, which is about 20 % higher than for a laboratory batch synthesis. Process intensification was achieved by reducing the reaction time from 2 h for the batch synthesis to 50 s for the micro processing. However, the most favorable temperature is limited to ca. 130 °C, since at higher temperatures, decarboxylation of the product back to phloroglucinol outpaces the speed-up of the reaction, while at lower temperatures, the reaction rate and conversion are insufficient.

Microreactor processing for the aqueous Kolbe-Schmitt synthesis of hydroquinone and phloroglucinol

An atmospheric pressure microplasma technique is demonstrated for the gas phase synthesis of Ni nanoparticles by plasma-assisted nickelocene dissociation at different conditions. The dissociation process and the products are characterized by complementary analytical methods to establish the relationship between operational conditions and product properties. The innovation is to show proof-of-principle of a new synthesis route which offers access to less costly and less poisonous reactant, a higher quality product, and a simple, continuous and pre/post treatment-free manner with chance for fine-tuning “in-flight”. Results show that Ni nanoparticles with controllable magnetic properties are obtained, in which flexible adjustment of product properties can be achieved by tuning operational parameters. At the optimized condition only fcc Ni nanoparticles are formed, with saturation magnetization value of 44.4 mAm2/g. The upper limit of production rate for Ni nanoparticles is calculated as 4.65 × 10−3 g/h using a single plasma jet, but the process can be scaled-up through a microplasma array design. In addition, possible mechanisms for plasma-assisted nickelocene dissociation process are discussed.

Volker Hessel

Papers

Redispersion Microreactor System for Phase Transfer‐Catalyzed Esterification

Microreactors. Prospects already achieved and possible misuse

State of the Art of Microreaction Technology

Microreactor processing for the aqueous Kolbe-Schmitt synthesis of hydroquinone and phloroglucinol

Synthesis of Ni nanoparticles with controllable magnetic properties by atmospheric pressure microplasma assisted process