Search results for "Homogeneous"
showing 10 items of 718 documents
The vegetation of a historic road system in the suburban area of Monte Pellegrino (Palermo, Sicily)
2020
Knowledge of the processes by which plants colonize old structures is a key element for nature-based design both in urban and suburban contexts. This paper analyses the natural vegetation on walls and in other microhabitats of the roadway structures of Monte Pellegrino (606 m a.s.l.) near Palermo (Sicily), built in the first half of the 1900s. The historical road has particular construction and architectural features, and its characteristics have been maintained to this day. The route, approximately 16 kilometers long, is well integrated within a site of high naturalistic value which has been designated as a Special Area of Conservation (ITA020014) of the Natura 2000 network, and it is also…
ChemInform Abstract: Bubble Fractionation of Enantiomers from Solution Using Molecularly Imprinted Polymers as Collectors.
2010
Adsorptive bubble separation methods have been used to enrich components from both heterogeneous and homogeneous solutions. These methods are particularly effective for processing large solution volumes at low cost. Previous work demonstrated that chiral, surface-active collectors could be used to enrich enantiomers from homogeneous solution in a foam fractionation process. In a significant extension of this work, the use of highly selective molecularly imprinted polymers (MIPs) and heterogeneous solutions for the bubble flotation of enantiomers was evaluated. The high selectivity and ease of recycling of the MIP make this a potentially powerful approach for process-scale separations from l…
Chemie an starren Grenzflächen, 12. Reduktionsstudien von an Aerosil kovalent Grenzflächen-gebundenen Azo- und Disulfid-Gruppen
1988
Aerosile mit kovalent verknupften, endstandigen Azo- und Disulfid-Gruppen wurden mit dem Ziele hergestellt, Information uber eine Elektronenubergangs-Abstands-Beziehung bei Elektroreduktionen (und bei anderen Reduktionsvorgangen) zu erhalten. Die Grenzflachen-modifizierten Aerosile A–H, J und N wurden hergestellt. Die modifizierten Aerosile A–H und J mit einer ausreichend hohen Belegungsdichte wurden polarographisch untersucht und die erhaltenen Werte mit den Halbstufenpotentialen der homogen gelosten Analogverbindungen verglichen (Tab. 3). Mit einigem Vorbehalt sprechen die Ergebnisse dafur, das Elektronen Abstande von 10–15 A uberwinden konnen. Chemistry on Rigid Interfaces, 12. — Reducti…
Diffusion Control in Single-Site Zinc Reticular Amination Catalysts.
2020
Zn-containing metal-organic frameworks have been used for the first time as heterogeneous catalysts in the amination of C-Cl bonds. The use of extended bis(pyrazolate) linkers can generate highly porous architectures, which favor the diffusion of amines to the confined spaces with respect to other imidazolate frameworks with narrower pore windows. The N4Zn nodes of the Zn-reticular framework show comparable activity to state-of-the-art homogeneous Zn amination catalysts, avoiding the use of basic conditions, precious metals, or other additives. This is combined with long-term activity and stability upon several reaction cycles, without contamination of the reaction product. ispartof: INORGA…
Dalton communication. Crystal structure and oxo-transfer properties of [NH4]2[WVIO2{O2CC(S)Ph2}2]
1994
The complex [NH4]2[WVIO2{O2CC(S)Ph2}2] is the first example of a non-dithiolene tungsten complex capable of oxidising benzoin to benzil in methanol; the reduced complex product formed, presumably a monomeric WVIO species, was reoxidised with nitrate ions, regenerating the starting WVIO2 complex which then acts as a true homogeneous catalyst.
A Liquid-Liquid Biphasic Homogeneous Organocatalytic Aldol Protocol Based on the Use of a Silica Gel Bound Multilayered Ionic Liquid Phase
2012
An innovative two stage liquid–liquid biphasic homogeneous protocol for the asymmetric organocatalytic aldol reaction is proposed, based on the use of the cis-ion-tagged proline 8 dissolved in the liquid film of a multilayered ionic liquid covalently bonded to silica gel 4. The resulting catalytically active material 9 is first soaked with cyclohexanone in the presence of water, resulting in a semi-transparent gel, then the aldehyde is added and the mixture stirred at RT. In the first stage, 4 acts as a catalyst reservoir that delivers 8 to the cyclohexanone phase allowing the reaction to take place homogeneously. In the second stage, cyclohexanone is removed under vacuum and the resulting …
Heterogeneous vs Homogeneous Palladium Catalysts for Cross-Coupling Reactions
2012
A large number of immobilized-Pd-catalysts for cross-coupling reactions have been introduced in the last decade. Are the observed catalyzed reactions truly heterogeneous or are they homogeneous due to leached palladium? This account critically addresses the leaching issue by selectively referring to some of the newly developed catalytic systems in an attempt to evaluate said systems based on uniform criteria. The report is concluded by identifying the relevant chemical and structural challenges in the field.
Chiral expansion of the nucleon mass to order q^6
2006
We present the results of a complete two-loop calculation at order q^6 of the nucleon mass in manifestly Lorentz-invariant chiral perturbation theory. The renormalization is performed using the reformulated infrared renormalization, which allows for the treatment of two-loop integrals while preserving all relevant symmetries, in particular chiral symmetry.
Über die Verwendung von homogenen azeotropen Gemischen in der Dünnschichtchromatographie 8. Mitt.: Gaschromatographische Untersuchung einiger Fließmi…
1970
Homogene azeotrope Gemische wurden vor und nach ihrer Benutzung als Fliesmittel in der DC gaschromatographisch untersucht. Hierbei zeigte sich, das bei hohem Anteil an polaren Komponenten (> 15%) keine veranderung in der Zusammensetzung der Fliesmittel eintrat. Eine gewisse Abreicherung der polaren Komponenten war jedoch festzustellen, wenn deren Anteil klein sowie der Polaritatsunterschied der Einzelkomponenten gros war und die DC-Platten eine grosere Schichtdicke als 0,1 mm besasen. Homogeneous Azeotropic Mixtures in Thin-layer Chromatography Homogeneous azeotropic mixtures have been analyzed by gas chromatography before and after they were used as solvents in TLC. If polar components wer…
Miniature diamond-anvil cells for FTIR-microspectroscopy of small quantities of biosamples.
2018
Fourier transform infrared (FTIR) spectroscopy techniques and data analyses have become widely available, are easy to use, and are convenient for studies of various biosamples, especially in biomedical science. Yet, cultivation of cells and purification of cell components are costly, often methodically challenging, and time and labor consuming. Therefore, reduction of the sample amount is of high value. Here we propose a novel method for the analysis of small quantities of biosamples by FTIR-microscopy of dry films using a diamond-anvil cell (DAC). This approach allows us to decrease the sample volume at least a hundred times compared to that for a high-throughput screening device (HTS-XT, …