菱沸石-粘土复合物在沥青精制中的应用

阿尔伯塔的油砂资源日益成为北美重要的战略性能源供给.本实验室通过采用碱性条件下在高岭土表面上组装菱沸石的方法,合成了新型的菱沸石-粘土复合材料,并证明此复合材料是比菱沸石更好的油砂沥青精制剂.XRD,SEM,TEM,N2物理吸附和XPS表面元素分析结果表明,菱沸石-粘土复合材料具有大体积烃类分子可及的独特的外表面,该复合材料不仅可降低油砂沥青的裂解反应温度,同时还可大幅度脱除沥青中的硫、氮、镍和钒等杂质.     

Minimal length of two intersecting simple closed geodesics

On a hyperbolic Riemann surface, given two simple closed geodesics that intersect n times, we address the question of a sharp lower bound L _n on the length attained by the longest of the two geodesics. We show the existence of a surface S _n on which there exists two simple closed geodesics of length L _n intersecting n times and explicitly find L _n for . The first author was supported in part by SNFS grant number 2100-065270, the second author was supported by SNFS grant number PBEL2-106180.     

Sorption of n‐hexane in amorphous polystyrene

Sorption properties of pure n‐hexane vapor in amorphous polystyrene (PS) were studied at 298 K by thermogravimetry under controlled vapor pressure. Two sorption–desorption cycles were performed by varying the relative pressure between 0 and 0.91. Mixing of PS with n‐hexane resulted in a strong plasticization, which was evidenced by quite significant depression in the glass transition temperature of the polymer as shown by differential scanning calorimetry. Maximum quantity of n‐hexane sorbed in the PS at 298 K and at a pressure close to saturation was about 12.4 wt %. The thermogravimetry yielded an isotherm with a strong hysteresis loop, explanation of which was hypothesized with the help of (a) Flory–Huggins sorption model extended by Vrentas, (b) analysis in terms of modification in the glass transition temperature of the n‐hexane/PS system as a function of sorbed quantity, and (c) change in total volume of the system. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1252–1258     

The FIGARO II experiment: a general outline of the mission and the principal scientific results

Summary The FIGARO II (French Italian Gamma-Ray Observatory) experiment has been launched successfully three times: in July 1986 from Milo (Trapani), in November 1988 from Charleville (Australia) and in July 1990 again from Milo. In the first flight the observational program was limited to the Crab pulsar PSR0531+21 only because of a telemetry failure: the high sensitivity of FIGARO II allowed an accurate study of the pulse shape as well as a phase-resolved spectroscopy. It was also possible to evaluate the dispersion measure of the Crab pulsar at the flight date from the time delay between gamma-ray and radio pulses. The major results of the second flight were a stringent upper limit to the low-energy gamma-ray flux from PSR 0833-45 (Vela pulsar)—well below the detection claimed by the UCR group —and the observation of a strong emission in the 0.511 MeV annihilation line from the inner region of our Galaxy. The data acquired in the third flight are still under analysis, but preliminary results suggest changes in the shape of the pulse profile. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.     

Wirkungsweise polymerer Vergrauungsinhibitoren in Waschmitteln

Zusammenfassung Im Waschprozeß werden ölige Anschmutzungen von textilen Oberflächen abgelöst und dispergiert. Die Flotte soll darüber hinaus das Wideraufziehen (Redeposition) frei schwebender Schmutzanteile auf Textilfasern vermindern.Bei empfohlener Solldosierung eines Waschmittels entfalten Tenside, Komplexbildner, Builder und Zeolithe den größten Teil der erforderlichen Stabilisierungswirkung. Polymere Vergrauungsinhibitoren bewirken nur graduelle zusätzliche Verbesserungen. Mit fortschreitender Unterdosierung nimmt die stabilisierende Tensid-und Builder-Wirkung schnell ab und die Bedeutung polymerer Vergrauungsinhibitoren steigt.Der Wirkungsmechanismus weist ein hohes Maß an Selektivität gegenüber textilen Substraten auf. Auf polarem Gut (z. B. Baumwolle) wird oft mit Erfolg Carboxymethylcellulose eingesetzt. Die Wirkungsweise beruht in diesem Falle weitgehend auf der sterischen Polymerschutzwirkung adsorbierter Schichten.Auf hydrophoberen Polyesterfasern zeigen Celluloseether mit hydrophoben Seitenketten (z. B. Hydroxypropylcellulose) sehr gute Effekte. Dabei wird die sterische Komponente der Polymerschutzwirkung durch Erniedrigung der treibenden Kraft der Heterokoagulation (Hydrophilierung sämtlicher hydrophober Grenzflächen) verstärkt. An Mischgeweben werden daher oft Kombinationen mehrerer Vergrauungsinhibitoren genutzt.Die vergrauungsinhibierende Wirksamkeit polymerer Substanzen für Polyester kann durch deren Fähigkeit, ungeachtet der Konkurrenz mit restlichen Inhaltsstoffen des Waschmittels möglichst starke effektiv irreversible Hydrophilierungseffekte hervorzurufen, charakterisiert werden.

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In laundering, oily soils are detached from textile surfaces and dispersed. In addition, the washing solution should reduce the redeposition of free suspended soil particles onto the textile fibres.In the case of a recommended predetermined dosage of a detergent the main part of the required stabilizing effect is due to the surfactants, complexing agents, builders and zeolites. Polymeric antiredeposition agents cause only gradual additional improvements. In the case of a weak dosage the stabilizing effects of the surfactants and builders rapidly decrease and the effects of the polymeric antiredeposition agents increase.The mechanism of these effects is characterized by high selectivity of the textile substrates. In the case of polar textiles (for instance cotton) carboxy methyl cellulose is often successfully used. In this case the mode of action is mostly due to steric repulsion of the adsorbed layer.In the case of hydrophobic polyester fibres cellulose ethers with hydrophobic sidechains (for instance hydroxy propyl cellulose) show very good effects. In this case the steric component of the polymeric repulsion is supported by the decrease of the driving force of the heterocoagulation (hydrophilization of all hydrophobic interfaces). For this reason combinations of several antiredeposition agents are often used for mixed fabrics.The performenace of the polymeric agents for polyesters can be characterized by their ability to cause strong effective irreversible hydrophilization effects despite the competitive influences of the residual detergent ingrediences.

Vortrag anläßlich der Hauptversammlung der Kolloid-Gesellschaft in Berlin vom 2. bis 4. Oktober 1985.     

One pot synthesis of nitrogen-containing polycyclic delta-lactones by double nucleophilic addition of bis(trimethylsilyl)ketene acetals to pyridines

Pyridine and bis(TMS)ketene acetals (TMS = trimethylsilyl) react successively with methylchloroformate and iodine (or peracids) to give, via functionalized dihydropyridines, bicyclic nitrogen-containing lactones which have been characterized by X-ray crystallography.     

Lactonizations of carboxylic acid-substituted 3-fluorodihydropyridines with electrophiles: peculiar behaviour of F(+)

Whereas for 3-fluorodihydropyridine-substituted carboxylic acids electrophiles such as HCl, iodine, bromine and peracids discriminate the double bond lacking and that bearing fluorine, no such differentiation took place in the case of electrophilic fluorine since the formation of both mono and gem-difluorolactones took place.     

Applications of a theorem of Singerman about Fuchsian groups

Assume that we have a (compact) Riemann surface S, of genus greater than 2, with , where is the complex unit disc and Γ is a surface Fuchsian group. Let us further consider that S has an automorphism group G in such a way that the orbifold S/G is isomorphic to where is a Fuchsian group such that and has signature σ appearing in the list of non-finitely maximal signatures of Fuchsian groups of Theorems 1 and 2 in [6]. We establish an algebraic condition for G such that if G satisfies such a condition then the group of automorphisms of S is strictly greater than G, i.e., the surface S is more symmetric that we are supposing. In these cases, we establish analytic information on S from topological and algebraic conditions. Received: 4 April 2008     

Capturing the multivariate extremal index: bounds and interconnections

The multivariate extremal index function is a direction specific extension of the well-known univariate extremal index. Since statistical inference on this function is difficult it is desirable to have a broad characterization of its attributes. We extend the set of common properties of the multivariate extremal index function and derive sharp bounds for the entire function given only marginal dependence. Our results correspond to certain restrictions on the two dependence functions defining the multivariate extremal index, which are opposed to Smith and Weissman’s (1996) conjecture on arbitrary dependence functions. We show further how another popular dependence measure, the extremal coefficient, is closely related to the multivariate extremal index. Thus, given the value of the former it turns out that the above bounds may be improved substantially. Conversely, we specify improved bounds for the extremal coefficient itself that capitalize on marginal dependence, thereby approximating two views of dependence that have frequently been treated separately. Our results are completed with example processes.