Drag coefficients of irregularly shaped particles

The steady-state free-fall conditions of isolated groups of ordered packed spheres moving through Newtonian fluids have been studied experimentally. Measurements of the drag coefficients are reported in this paper for six different geometrical shapes, including isometric, axisymmetric, orthotropic, plane and elongated conglomerates of spheres. From these measurements, a new and accurate empirical correlation for the drag coefficient, C_D, of variously shaped particles has been developed. This correlation has been formulated in terms of the Reynolds number based on the particle nominal diameter, Re, the ratio of the surface-equivalent-sphere to the nominal diameters, d_A/d_n, and the particle circularity, c. The predictions have been tested against both the experimental data for C_D collected in this study and the ones reported in previous works for cubes, rectangular parallelepipeds, tetrahedrons, cylinders and other shapes. A good agreement has been observed for the variously shaped agglomerates of spheres as well as for the regularly shape particles, over the ranges 0.15<Re<1500, 0.80<d_A/d_n<1.50 and 0.4<c<1.0.     

NO x reduction over CeO2–ZrO2 supported iridium catalyst in the presence of propanol

This article describes the catalytic routes that are available for converting unsaturated fatty acid esters and related compounds, obtained from renewable resources, into useful chemical products via the olefin metathesis reaction. These routes offer new possibilities for the oleochemical industry as a contribution to a sustainable chemical industry. Highly selective homogeneous as well as heterogeneous catalyst systems have been developed for these metathetical conversions. Supported rhenium oxide catalysts are already active at room temperature, can be easily separated from the reaction mixture, and can be regenerated many times. New well-defined homogeneous ruthenium complexes are very effective catalysts, showing high turnover numbers. The present knowledge about the catalyst systems and the possibilities for practical applications for the metathetical conversion of unsaturated fatty acid esters and oils will be discussed.     

Estimating net N mineralization under unfertilized winter wheat using simulations with NET N and a balance approach

Eliminating uncertainty in soil N supply could reduce fertilizer input, but the amount of N mineralized during plant growth is usually still unknown. We aimed to test the relatively simple two-pool net N mineralization model NET N that uses site-specific temperature and soil water functions as well as pedotransfer functions for deriving the pool sizes and was developed for NW Germany. The objectives were to (1) evaluate, if field net N mineralization under unfertilized winter wheat could be satisfactorily simulated, and to (2) examine the variation in time patterns of net N mineralization within years and sites and from two functional N pools: a rather small, fast mineralizable N pool (N_fast) and a much greater, slowly mineralizable N pool (N_slow). NET N simulations for 36 site-year-combinations and up to five dates within the growing season were evaluated with detailed N balance approaches (calculated from: soil mineral N contents, plant N uptake using estimates of green area index, simulated N leaching). Simulated net N mineralization was highly significantly correlated (r² = 0.58; root mean square error = 24.2 kg N ha^?1) to estimations from the most detailed balance approach, with total simulated net N mineralization until mid August ranging from 62.1 to 196.5 kg N ha^?1. It also became evident that N mineralization from pool N_slow—in contrast to pool N_fast—was considerably higher for loess soils than for sandy or loamy soils. The results suggest that NET N was adequate for simulations in unfertilized winter wheat. However, further field studies are necessary for proving its applicability under fertilized conditions.     

Across-task conflict regulation: A replication failure.

Fernandez-Duque and Knight (2008, Experiment 4) described an across-task effect of endogenously generated, anticipatory control: A cue that predicted conflict in an upcoming Eriksen flanker task modulated conflict regulation in a subsequent number Stroop task. In 3 experiments, 1 of which included an exact replication condition, we failed to observe the expected across-task effect. However, a reanalysis of our data revealed a conflict adaptation effect: Number task processing on incongruent trials was influenced by random fluctuations in flanker task performance. Our findings, alongside reports of reactive across-task conflict regulation (Freitas, Bahar, Yang, & Banai, 2007), challenge Fernandez-Duque and Knight’s claim that across-task effects are a distinctive feature of anticipatory cognitive control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ethische und rechtliche Aspekte im Umgang mit genetischen Zufallsbefunden – Herausforderungen und Lösungsansätze

Definition of the problem With an increasing number of genetic results obtained in whole genome analyses, the problem of incidental findings arises, i.e., findings that are discovered beyond the aims of the original investigation but have potential health or reproductive importance for patients or research participants. Since national or international guidelines have not been established, the authors discuss for Germany the current opinions about the management of incidental findings in clinical care and research. Arguments Following the German genetic diagnosis act (?Gendiagnostikgesetz“, GenDG), it is mandatory to inform about the possibility of incidental findings. It is part of the informed consent which findings are communicated to the patient, taking the right not to know and the protection of minors into account. In the research context, the GenDG is not valid; however, the disclosure of possible incidental findings should be also included in the consent documents. There is agreement that results of high clinical utility should be returned to participants, even if there is no obligation to do so. The following aspects have to be considered when dealing with incidental findings: (1) information given in the consent documents, (2) interpretation of genetic results according to high, moderate, possible, questionable or unknown clinical meaning, (3) processing of returning results at the present and in the future, and (4) decision about resources to evaluate the clinical utility, to communicate results and to transfer them into clinical practice. Conclusion There is urgent need for empirical research and policy development in the context of incidental genetic results. In addition, it is important to study how patients and participants understand and utilize incidental findings and to develop educative and communicative strategies.     

Modified Mo/V/W‐Mixed Oxides for Catalytic Tar Removal from Biosyngas via Oxidation

In view of the growing energy demand and the current climate problems, renewable energy sources are becoming increasingly popular. The so‐called biosyngas obtained from the gasification of dry biomass can be used to synthesize fuels and basic chemicals. Besides gaseous by‐products and salts, this gas contains tar which needs to be removed before downstream processing. Catalysts like Mo/V/W‐oxides were found to be inert towards the oxidation of CO and H₂ but are able to activate the tar model compound naphthalene highly selective. Unfortunately, besides the total oxidation, the partial oxidation to the undesired intermediates phthalic acid anhydride and maleic acid anhydride takes place. Modification of the catalyst with bases leads to synergetic effects on the catalyst surface, the total oxidation is promoted, and the formation of intermediates decreases.     

Efficient production of uniform nanometer‐sized polymer vesicles in stirred‐tank reactors

Polymer vesicles, so‐called polymersomes, gain more and more attention as potential carriers for medical and biotechnological applications. To put the production of these nanocompartments into action at an industrial scale, an efficient and scalable process has to be established. Moreover, being able to control the resulting particle size distribution (PSD) is vital. In this work, the amphiphilic triblock copolymer poly(2‐methyloxazoline)₁₅–poly(dimethylsiloxane)₆₈–poly(2‐methyloxazoline)₁₅ is formed into polymersomes in miniaturized stirred‐tank reactors. Varying flow conditions have a huge impact on the resulting PSD. Dynamic light scattering measurements show that driving a S‐shaped stirrer at 4000 rpm in unbaffled reactors leads to a monomodal PSD with a low polydispersity index (PDI<0.2). Vesicles with a mean diameter of 200 nm are achieved within less than 1 h in a single production step. The robustness of the established process is shown by producing uniform polymersomes at different temperatures and varying pH and buffer molarities. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43274.     

Production of sugar fatty acid estrs by enzymatic esterification in a stirred-tank membrane reactor: Optimization of parameters by response surface methodology

6-O-β-D(+)-Glucose stearate serving as a model product of glucose fatty acid monoesters was synthesized using lipase B from Candiada antarctica (Chirazyme^® L-2) in a mainly solid-phase system in a stirred-tank membrane reactor. Esterification was performed in the presence of a small amount of ethyl methylketone (EMK), maintaining a catalytic liquid phase as well as forming an azeotrope with the reaction water. The azeotrope was evaporated and broken by membrane vapor permeation, then the dried EMK was returned to the reaction medium. The process was optimized by response surface methodology based on five major reaction parameters [time (T), substrate ratio (acyl donor to glucose, S _r, temperature (R _t), amount of solvent [solvent to substrates, [w/w], S _a), and enzyme load (E _l)] varied at three levels, resulting in higher yields. Thus, under optimized conditions [T _r=58 h; S _r=2.7; E _l=8.9% (w/w); R _t=78°C; S _a=1.9], up to 93% yields of glucose stearate were achieved.