Search

A well-known squaramide-cinchonine organocatalyst was immobilized in a controlled way onto three types of commercial porous glass beads EziG™ (EziG OPAL, EziG Amber, and EziG Coral) and applied in asymmetric Michael reactions. The performance of the immobilized catalysts was evaluated under batch and continuous-flow conditions, showing promising results in both approaches. In batch reactions, 0.8 and 1.6 mol% of the immobilized cinchonine-squaramide provided the products with excellent yields (up to 99%) and enantioselectivities (up to 99% ee). These excellent results were also verified in the case of continuous-flow reactions, where also 0.8 and 1.6 mol% of the catalyst immobilized onto the glass beads afforded the product with extraordinary yields (up to 99%) and very high enantioselectivities (up to 97% ee). The immobilized catalysts could be recycled (up to seven cycles) using both approaches. [ABSTRACT FROM AUTHOR]

The purpose of the study was to understand the mechanisms of biochar-induced changes in the available content of aluminum (Al), cadmium (Cd), zinc (Zn), copper (Cu), and manganese (Mn) in a wide range of soils. Five soils from different regions of the Czech Republic were incubated for 12 weeks with four rates of biochar (0.5%, 2%, 4%, and 8% w/w). The available concentrations of Al, Cd, Zn, Cu, and Mn were determined on the 7th and 84th day of incubation. There was a significant decline in the available content of Al, Zn, Cu, Mn, and Cd except in the available content of Al in one soil, which is characterized by very low Al content, higher cation exchange capacity (CEC), and neutral pH = 7.0. The decline in the mobile contents of Al, Zn, Cu, Mn, and Cd was significant in all cases of 8% biochar rate. The decline in the content of Al, Zn, Cu, Mn, and Cd was mainly due to the increment in soil pH and increment in CEC, decline in dissolved organic carbon (DOC), and the release of exchangeable Ca2+ and K+ from biochar. The application of high amounts of biochar to soil could increase the available content of some metals like Al. On the other hand, biochar could efficiently reduce the mobility of Al, Zn, Cu, Mn, and Cd in soil, while the decline is mainly caused by biochar-induced changes in soil pH, CEC, DOC, and exchangeable Ca2+ and K+ content of treated soils.

Phenolic compounds are hazardous pollutants known to be toxic at low concentration. Removal of phenols from industrial wastewater streams before their discharge into receiving water bodies is thus obligatory. Numerous phenol-degrading nonhalophilic bacterial isolates have been described, but detailed information regarding phenol degradation by halophiles is rather sparse. The present study aims at evaluating the capacity of phenol degradation by new species of Bacillus. Halophilic bacteria were isolated from mangrove region on the western coast of the Red Sea of Egypt. Bacterial isolate showed the highest potentiality of phenol degradation was identified using 16S rRNA sequencing method as Bacillus sp. 2BSG-PDA-16. The optimum conditions for achieving high phenol degradation were 300 mg/l phenol concentration, 1% glucose, peptone, 5% NaCl, pH7, 30°C and 6% (v/v) inoculum size. Upon applied all these conditions, the phenol degradation reached 85.6 % removal. Calcium alginate was employed to immobilize the cells. Compared to free cells, the immobilized cells were not only able to tolerate high concentration of phenol but also are able to degrade it completely in a shorter time. Free cells degrade 600 mg/l in 10 days, whereas the immobilized cells could completely degrade 800 mg/l in 8 days. It could be concluded that this moderately halophilic Bacillus sp. 2BSG-PDA-16 might be useful for the degradation of phenol, particularly in saline environments. [ABSTRACT FROM AUTHOR]

This article addresses the similarities between the experiences of life as a banlieue youth, as a prisoner and as an undocumented migrant, from the perspectives of foreign-national youths who grew up in French suburbs but were ordered to be deported as a consequence of a criminal sentence. The article draws on ethnographic fieldwork and interviews with such ‘illegalized’ and deportable inmates at different stages of their trajectories and their way through the criminal justice and immigration enforcement systems in the Paris region. [ABSTRACT FROM AUTHOR]

The aim of this article is to collect the results published from the beginning (2000) on asymmetric direct aldol reactions taking place in the presence of immobilized chiral organocatalysts. The seven groups of organocatalysts discussed are: asymmetric direct aldol reactions catalyzed by: (1) covalently bonded immobilized hydroxyproline organocatalysts; (2) covalently bonded immobilized prolinamide organocatalysts; (3) covalently bonded immobilized peptide organocatalysts; (4) other covalently bonded immobilized chiral organocatalysts; (5) chiral organocatalysts bonded by ionic groups; (6) chiral organocatalysts with adsorptive bonding; and (7) other types of immobilized chiral organocatalysts. The main objective of this article based on results obtained by using about 360 immobilized organocatalysts, to bring to the focus of catalyst systems in which the aldol reactions yield beta-hydroxyketones of maximal optical purity, while keeping catalyst concentrations and reaction times as low and as short as possible. Trends recognized in data obtained in this field of investigation may mark out further tasks for the purpose of practical application. [ABSTRACT FROM AUTHOR]

Within the present phase, we emphasize a series of important elements as concerns theevaluation of SME. The evaluating methods to be applied to large companies are usually valid to smallenterprises, also. But, thanks to certain characteristic features, specific methods that carry out to viewsconsidered to be more approached towards the circulation value were elaborated, methods that are ordinarilyeasier to approach and more direct.

Supersonic jets emit shock waves to the outside called 'Mach waves' which are long, straight and have about equal angles. Experiments done by Oertel Sen. clearly visualized these Mach waves and he showed, moreover, that such Mach waves also exist inside the jet. Measuring the Mach wave angles from many shock tube experiments revealed the existence of three wave families. They move with different speeds, denoted as w, w′ and w″, which only depend on the jet Mach number M and the ratio a/ a of the sound speed a outside and a inside the jet. For illuminating theoretically the experimental outcomes, a brand-new assumption is made which explains the three found speeds w, w′ and w″. Its central point is the production of Mach waves by two rows of vortices moving downstream inside of the jet mixing layer in two separate vortex trains. The inner vortex train creates the w′-Mach waves outside the jet and the outer vortex chain is accompanied by the w″-Mach waves towards inside the jet. Both chains form a contact surface which moves with speed w. For validating the results of the new theory the shock tube experiments are the only ones worldwide by which these three wave families have been visualized using differential interferometry: by frame series, by immobilization images and by streak records. They show density differences by light intensity variations on the image. By the immobilizations and the streak records the flow is observed through a slit on a rotating drum camera. Immobilizations use a wide opened slit and the camera turns with the speed of the Mach waves to be observed. With a narrow adjusted slit, streak records show the Mach wave traces clearly. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

α-Amylase was immobilized on Dowex MAC-3 with 88 % yield and amyloglucosidase on Amberlite IRA-400 ion-exchange resin beads with 54 % yield by adsorption process. Immobilized enzymes were characterized to measure the kinetic parameters and optimal operational parameters. Optimum substrate concentration and temperature were higher for immobilized enzymes. The thermal stability of the enzymes enhanced after the immobilization. Immobilized enzymes were used in the hydrolysis of the natural starch at high concentration (35 % w/v). The time required for liquefaction of starch to 10 dextrose equivalent (DE) and saccharification of liquefied starch to 96 DE increased. Immobilized enzymes showed the potential for use in starch hydrolysis as done in industry. [ABSTRACT FROM AUTHOR]

Abstract: Ureases are enzymes highly desirable in immobilized form for a number of applications that exploit urea cleavage and an increase in pH, inherent to the reaction. Major among them are medical and analytical applications, but there have emerged new biotechnological and engineering areas, proving that there exists a growing demand for robust reliable immobilized urease preparations with defined properties. These can be assured by immobilizing the enzymes. By creating disturbance in the original state of enzymes, immobilizations inevitably change enzyme properties, enabling them to be customized for specific applications. In this context, this article offers a review of reports on immobilizations of ureases covering the last two decades. It surveys the immobilization techniques and support materials applied, in addition to the resulting properties of the enzymes. In this manner it attempts to provide useful guidance through the wealth of available immobilization data in the literature, but more importantly, to develop an integrated perspective on how to customize ureases for their applications, which may help establish rational immobilization procedures in place of tedious experimental optimization. [Copyright &y& Elsevier]

Soil nitrogen mineralization patterns were investigated under field conditions in the presence of five leaf litters of different qualities, Faidherbia albida , Azadirachta indica , Andropogon gayanus , Casuarina equisetifolia , and Eragrostis tremula . The experimentation was conducted in a tropical sandy soil in central Senegal over 12 months. No relationship could be drawn between litter quality (N content, cellulose, hemicellulose, lignin) and N mineralization during this field experimentation. By contrast, the presence of the litter modified the soil N cycle. At all sampling dates, the patterns of N mineralization were most high in litter amendment. The content of mineral N was highest in Casuarina equisetifolia amendment (17.03 µg N g -1 soil in November 2000, and 28.53 µg N g -1 soil in March 2001). Soil incubated in the absence of the different litters exhibited a different pattern of N mineralization. Net mineralization was observed when the soil had been previously submitted to the influence of Casuarina equisetifolia (4.87 µg N g -1 soil), while net immobilization was observed in the case of Azadirachta indica (8.13 µg N g -1 soil). [ABSTRACT FROM AUTHOR]

Information from theoretical models of redox enzyme linked biosensors highlights the importance of membrane thickness and enzyme loading on signal response in regard to both sensitivity and reproducibility. The conclusions are substantiated by examination of practical examples in the literature and, with a view to the importance of the character of the enzyme layer and overlayers, immobilization techniques are assessed which are in current use. [ABSTRACT FROM AUTHOR]

The purpose of the study was to understand the mechanisms of biochar-induced changes in the available content of aluminum (Al), cadmium (Cd), zinc (Zn), copper (Cu), and manganese (Mn) in a wide range of soils. Five soils from different regions of the Czech Republic were incubated for 12 weeks with four rates of biochar (0.5%, 2%, 4%, and 8% w/w). The available concentrations of Al, Cd, Zn, Cu, and Mn were determined on the 7th and 84th day of incubation. There was a significant decline in the available content of Al, Zn, Cu, Mn, and Cd except in the available content of Al in one soil, which is characterized by very low Al content, higher cation exchange capacity (CEC), and neutral pH = 7.0. The decline in the mobile contents of Al, Zn, Cu, Mn, and Cd was significant in all cases of 8% biochar rate. The decline in the content of Al, Zn, Cu, Mn, and Cd was mainly due to the increment in soil pH and increment in CEC, decline in dissolved organic carbon (DOC), and the release of exchangeable Ca2+ and K+ from biochar. The application of high amounts of biochar to soil could increase the available content of some metals like Al. On the other hand, biochar could efficiently reduce the mobility of Al, Zn, Cu, Mn, and Cd in soil, while the decline is mainly caused by biochar-induced changes in soil pH, CEC, DOC, and exchangeable Ca2+ and K+ content of treated soils. [ABSTRACT FROM AUTHOR]

A new type of heterogeneous, polystyrene-bound catalyst is introduced: A cross-linking, dendritic ligand, the TADDOL 1, is copolymerized with styrene, loaded with titanate, and used for the enantioselective catalysis of the addition of Et 2 Zn to PhCHO. The polymer-bound catalyst has an unprecedented efficiency and stability in multiple applications., (© 1999 WILEY‐VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.)