Synthesis and photochemical properties of 3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-9<Emphasis Type="Italic">H</Emphasis>-carbazole derivatives

Method of synthesis has been developed for a series of 3,6-di-tert-butyl-9H-carbazole derivatives and their photochemical properties have been investigated. The dependence of the Steglich esterification reaction on the nature of the catalyst was studied. The synthesized compounds show fluorescent emission in the range 400–600 nm with a high quantum yield.     

Fe3O4@Nico@Ag纳米催化剂催化硝基芳烃加氢（英文）

We report the fabrication and characterization of a magnetically recyclable Fe3O4@Nico@Ag catalyst for reduction reactions in the liquid phase. Fe3O4 is a magnetic core and nicotinic acid was used as the linker for Ag. The characterization was done with X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, vibrating sample magnetometry (VSM), and ultraviolet-visible spectroscopy. VSM measurements proved the super-paramagnetic property of the catalyst.     

Catalytic Synthesis of N‐Unprotected Piperazines,Morpholines, and Thiomorpholines from Aldehydes and SnAP Reagents

Commercially available SnAP (stannyl amine protocol) reagents allow the transformation of aldehydes and ketones into a variety of N‐unprotected heterocycles. By identifying new ligands and reaction conditions, a robust catalytic variant that expands the substrate scope to previously inaccessible heteroaromatic substrates and new substitution patterns was realized. It also establishes the basis for a catalytic enantioselective process through the use of chiral ligands.     

Shear modulus of single wood pulp fibers from torsion tests

Cellulose - The shear modulus of pulp fibers is difficult to measure and only very little literature is available on this topic. In this work we are introducing a method to measure this fiber...     

New eco-friendly low-cost binders for Li-ion anodes

In the production of commercial Li-ion batteries, the active materials slurries are generally prepared using polyvinylidene fluoride (PVdF) as binder because of its good adhesion properties and electrochemical stability. Unfortunately, there are some disadvantages related to the use of PVdF: the most important is the use of toxic and environmentally unfriendly solvents, such as N-methyl-pyrrolidone (NMP), and the second is the high costs. In the light of these considerations, it seemed straightforward to investigate the suitability of some water-soluble, inexpensive, and eco-friendly materials to test as alternative binders (sodium alginate, chitosan tragacanth gum, gelatin). The rheological properties of these materials have been investigated in addition to the electrochemical characterization. Furthermore, graphite electrodes with PVdF, carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) binders have been considered for sake of comparison. We found that some of these water-soluble binders, besides good electrochemical performances, showed a high adhesion to the current collector and a good electrochemical stability under the experimental conditions employed, which makes them interesting for the next generation of Li-ion batteries.     

Zirconium oxide films: deposition techniques and their applications in dye-sensitized solar cells

Zirconium oxide (ZrO₂) is acquiring considerable attention of most of the research groups and leading to a large number of publications due to its unique properties, especially in the context of emerging trends in the third generation of solar cell research. ZrO₂ films offer magnificent aspects related to physicochemical properties, and the properties are found to be dependent on synthesis methods. In the present review, various deposition techniques used to grow zirconium oxide thin films and their application to enhance the quantum efficiency of titanium oxide (TiO₂) based dye-sensitized solar cells (DSSCs) are discussed. Also, the modulated performances of DSSCs fabricated by growing the conformal ZrO₂ insulating films to retard interfacial recombination dynamics on preformed TiO₂ films are discussed.

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Online hyphenation of size-exclusion chromatography and gas-phase electrophoresis facilitates the characterization of protein aggregates

Gas-phase electrophoresis yields size distributions of polydisperse, aerosolized analytes based on electrophoretic principles. Nanometer-sized, surface-dry, single-charged particles are separated in a high laminar sheath flow of particle-free air and an orthogonal tunable electric field. Additionally, nano Electrospray Gas-Phase Electrophoretic Mobility Molecular Analyzer (nES GEMMA) data are particle-number based. Therefore, small particles can be detected next to larger ones without a bias, for example, native proteins next to their aggregates. Analyte transition from the liquid to the gas phase is a method inherent prerequisite. In this context, nonvolatile sample buffers influence results. In the worst case, the (bio-)nanoparticle signal is lost due to an increased baseline and unspecific clustering of nonvolatile components. We present a novel online hyphenation of liquid chromatography and gas-phase electrophoresis, coupling a size-exclusion chromatography (SEC) column to an advanced nES GEMMA. Via this novel approach, it is possible to (i) separate analyte multimers already present in liquid phase from aggregates formed during the nES process, (ii) differentiate liquid phase and spray-induced multimers, and (iii) to remove nonvolatile buffer components online before SEC–nES GEMMA analysis. Due to these findings, SEC–nES GEMMA has the high potential to help to understand aggregation processes in biological buffers adding the benefit of actual size determination for noncovalent assemblies formed in solution. As detection and characterization of protein aggregation in large-scale pharmaceutical production or sizing of noncovalently bound proteins are findings directly related to technologically and biologically relevant situations, we proposed the presented method to be a valuable addition to LC-MS approaches.     

Mikroskopische Untersuchung der Tropfenkondensation

The heat transfer during dropwise condensation can be calculated from the distribution function of the drop sizes and the growth function of single drops. Both functions are obtained from motion pictures with high magnification. The motion pictures are taken during condensation of steam of about 25 °C on vertical copper and brass surfaces. A simple approximation for the growth function is given which agrees with the exact solution ofUmur andGriffith [8] within the limits of about 1%.     

Die scheinbare Wärmedurchgangszahl von Plattenwärmeaustauschern

Zusammenfassung Um bei Platten-Wärmeaustauschern die übertragene Wärme richtig zu erhalten, muß das Produkt aus der Wärmedurchgangszahl k=1/(1/a ₁ + / + 1/a ₂), der gesamten Heizfläche A und der mittleren logarithmischen Temperatur differenz _m im allgemeinen noch mit einem Korrekturfaktor Z multipliziert werden, der von der Fließweganzahl n und der dimensionslosen Größe =(k A₀)/(M c) abhängt: Q=Z (kA_m) =k_sA_m (k_s=scheinbare Wärmedurchgangszahl). Unter der Voraussetzung, daß Gegenstrom herrscht und das Umwälzverhältnis U=M₁c₁/M₂c₂=1 ist, konnte diese Funktion Z=Z (n, )=k_s/k jetzt im Anschluß an eine frühere Rechnung für die reine Hintereinanderschaltung beliebig vieler Fließwege bestimmt werden. Die gefundenen Formeln weisen für gerade und ungerade Fließweganzahlen kleine Unterschiede auf. Doch verlaufen beide Kurvenscharen so gleichartig, daß sie sich gegenseitig ergänzend sehr gut ineinander fügen. — Eine wichtige Folgerung aus den Rechnungsergebnissen ist, daß die scheinbare Wärmedurchgangszahl k_s bei einem gegebenem Austauscher für jeden Massenstrom einen absoluten Höchstwert hat.

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The apparent overall heat transfer coefficient of plate heat exchangers

In order to get the correct value of the transfered heat Q of plate heat exchangers one must multiply the product of the overall heat transfer coefficient k=(1/a ₁ + / + 1/a ₂), the total heating area A and the logarithmic mean temperature difference _m with a correction factor Z: Q=Z · k · A · _m =k_s · A_m, where k_s means the so called apparent overall heat transfer coefficient. Z is, as was shown in a previous paper, a function of the numbers of flow channels and the dimensionless quantity =(k · A₀)/M · c. In this paper, assuming counter flow and the validity of the relation U=M₁c₁/M₂c₂=1, the correction factor Z is determined for the pure series con nexion of any desired number of flow channels. — An important conclusion drawn from our results is, that for a given heat exanger, k_s has an absolute maximum value for every mass flow rate.

     

Optimal control of free-stream turbulence intensity by means of honeycombs

The characteristics of honeycombs of different shapes and sizes used for reducing free-stream turbulence in wind tunnels have been experimentally investigated. The optimum geometric dimensions of the honeycomb and its optimum location in the wind tunnel necessary to ensure a minimum level of turbulence in the working section have been determined.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 163–174, May–June, 1994.