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Yields Only (yield + only)
Selected AbstractsAssessment of balsam of Peru patch testsCONTACT DERMATITIS, Issue 6 2000Bolli Bjarnason To find an ideal test technique for as low a dose of balsam of Peru (Myroxylon Pereirae) as possible, subjects testing positive to balsam of Peru are re-tested with a 25% concentration of balsam of Peru in petrolatum. Applications are with Finn Chambers® for 6 different application times, and directly by foils for 96 h (4 days (D)). The goals are to confirm which subjects are positive and which are not, and, using that information, to see if it is possible to distinguish between these 2 groups, tested concomitantly at much lower serial dose levels, in terms of perfusion or by visual assessments. 5 different serial doses are applied with strips for 3,96 h (4D) and with foils for 96 h (4D). The Finn Chamber® tests allow a distinction between visually positive and negative subjects supported by perfusion assessments. With the foils, a 24× lower serial dose level than with the 25% test substance is sufficient to distinguish between positive and negative subjects in terms of perfusion values. This approach requires readings up to 9 days. With this test, the visual approach yields only 3 of 10 positive subjects. This study demonstrates that a lower test dose is possible with perfusion assessments compared to visual ones. [source] Silica-Immobilized NHC,CuI Complex: An Efficient and Reusable Catalyst for A3 -Coupling (Aldehyde,Alkyne,Amine) under Solventless Reaction ConditionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 13 2008Min Wang Abstract A novel silica-immobilized NHC,CuI complex was developed and used as a highly efficient catalyst in the three-component coupling reactions of aldehydes, alkynes and amines (A3 -coupling). The reactions were applicable to aromatic and aliphatic aldehydes, alkynes and amines, and generated the corresponding propargylamines in good yields only in the presence of SiO2,NHC,CuI (2 mol-%) at room temp. under solvent-free reaction conditions. Moreover, the catalyst was quantitatively recovered from the reaction mixture by a simple filtration and reused for ten cycles with almost consistent activity.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] A new parallelization strategy for solving time-dependent 3D Maxwell equations using a high-order accurate compact implicit scheme,INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 5 2006Eugene Kashdan Abstract With progress in computer technology there has been renewed interest in a time-dependent approach to solving Maxwell equations. The commonly used Yee algorithm (an explicit central difference scheme for approximation of spatial derivatives coupled with the Leapfrog scheme for approximation of temporal derivatives) yields only a second-order of accuracy. On the other hand, an increasing number of industrial applications, especially in optic and microwave technology, demands high-order accurate numerical modelling. The standard way to increase accuracy of the finite difference scheme without increasing the differential stencil is to replace a 2nd-order accurate explicit scheme for approximation of spatial derivatives with the 4th-order accurate compact implicit scheme. In general, such a replacement requires additional memory resources and slows the computations. However, the curl-based form of Maxwell equations allows us to construct an effective parallel algorithm with the alternating domain decomposition (ADD) minimizing the communication time. We present a new parallel approach to the solution of three-dimensional time-dependent Maxwell equations and provide a theoretical and experimental analysis of its performance. Copyright © 2006 John Wiley & Sons, Ltd. [source] Site-specific synthesis of Amadori-modified peptides on solid phaseJOURNAL OF PEPTIDE SCIENCE, Issue 6 2006Andrej Frolov Abstract Glycation of peptides and proteins is a slow chemical reaction of reducing sugars modifying the amino groups. The first intermediates of this nonenzymatic glycosylation are the Amadori products that can undergo further chemical reactions, finally leading to advanced glycation end products (AGEs). The formation of AGEs was not only linked to aging of tissues and organs in general but also to several diseases such as diabetes mellitus and Alzheimer's disease. Because of the importance of these modifications and their potential use as diagnostic markers, a global postsynthetic approach on solid phase was developed. The peptides were synthesized by Fmoc/tBu-chemistry, with the lysine residue to be modified being protected with the very acid-labile methyltrityl group. Incubation of the peptides with D -glucose in DMF at elevated temperatures resulted in product yields of 35%. Neighboring residues with bulky protecting groups reduced the yields only slightly. The major by-products were the unmodified peptide and an oxidation product. Whereas the unmodified peptide eluted before the glycated peptide, all other by-products eluted later in RP-HPLC, allowing simple purification. Copyright © 2005 European Peptide Society and John Wiley & Sons, Ltd. [source] Artificial polymerases and molecular chaperonesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2009Akira Harada Abstract Cyclodextrins (CDs) were found to initiate polymerization of lactone to give polyesters with a CD ring at the end of the polymer chain in high yields only by mixing and heating with monomer without cocatalysts or solvents. CD-tethered polyester propagates with the formation of poly-pseudorotaxane, which is necessary to initiate further polymerization. CDs threaded onto the polymer chain are also essential for maintaining the propagating state of the polyester. By polymerizing with CD, switching the activity of the polymerization by photoisomerization was demonstrated. This polymerization system showed specific substrate recognition, releasing the products from the active site. By using the above polymerization system, ,-CD nanospheres which initiates the oligomerization of lactone were constructed. It was found that the formation of poly-pseudorotaxane on the nanosphere enabled further polymerization activity for lactone. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4469,4481, 2009 [source] Bauteiloberfläche und Schwingfestigkeit , Untersuchungen zum Einfluss der Randschicht auf die Dauerschwingfestigkeit von Bauteilen aus StahlMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 5 2006U. Kleemann Dipl.-Ing. surface; surface layer; fatigue strength; surface stress-concentration factor Abstract Die Berechnung der Schwingfestigkeit hat in den letzten Jahren für die Bauteilentwicklung an Bedeutung gewonnen. Aus Zeit- und Kostengründen wird angestrebt, den experimentellen Festigkeitsnachweis auf die Freigabe von Sicherheitsteilen zu beschränken. Die Schwingfestigkeit von glatten, polierten Werkstoffproben (Spannungs- und Dehnungswöhlerlinie) kann heute mit guter Treffsicherheit abgeschätzt bzw. entsprechenden Katalogen entnommen werden. Die Übertragbarkeit der Schwingfestigkeit von Werkstoffproben auf reale Bauteile ist jedoch mit erheblichen Schwierigkeiten verbunden, da eine Reihe von Einflussgrößen zu berücksichtigen sind wie Geometrie und Größe, Mittelspannung, Beanspruchungsart, Mehrachsigkeit, Randschicht (Oberflächentopographie, Eigenspannungen, Gefüge, Härte), Temperatur, korrosive Medien u.,a.. Der Einfluss dieser Größen ist komplex und lässt sich nur sehr grob durch eine Multiplikation von Einflussfaktoren beschreiben. Der heutige Stand im Technischen Regelwerk zum Oberflächeneinfluss, z.,B. FKM-Richtlinie ,Rechnerischer Festigkeitsnachweis für Maschinenbauteile", basiert auf einem Kenntnisstand, der 50 Jahre zurückliegt. Der Ausgang für das Forschungsvorhaben war die Forderung der Industrie nach einer verbesserten rechnerischen Erfassung des Einflusses der Oberflächenbearbeitung bei Zerspanung. Hierzu wurde auf einen Vorschlag von Liu zurückgegriffen, der die Oberflächentopographie neben der Rauheit durch eine Oberflächenformzahl kennzeichnet. Zur Erfassung des Werkstoffes wird eine charakteristische Strukturlänge eingeführt, die sich aus der Werkstoffwechselfestigkeit und dem Schwellenwert für makroskopischen Rissfortschritt berechnet. Weiterhin wurde überprüft, welche Festigkeitshypothesen in der Lage sind, den biaxialen Eigenspannungszustand an der zerspanten Oberfläche realistisch zu erfassen. Damit kann ein Konzept vorgeschlagen werden, mit dem die Dauerfestigkeit zutreffend berechnet werden kann, wenn die statische Festigkeit, die Oberflächentopographie und die Eigenspannungen bekannt sind. Zur Validierung werden Schwingversuche an drei Stählen und zwei Sphärogusslegierungen bei unterschiedlichen Randschichteigenschaften durchgeführt. Structural component surface and fatigue strength , Investigations on the effect of the surface layer on the fatigue strength of structural steel components For the development of structural components, the importance of calculating the fatigue strength has steadily increased during recent years. In order to save time and cost, efforts are in progress for limiting experimental strength testing to the release of safety components. The fatigue strength of smooth, polished material specimens (stress and strain S-N curve) can now be estimated with high accuracy, or can be obtained from the corresponding catalogs. However, the results of fatigue strength determinations on material specimens cannot be applied to real components without considerable difficulty, since a number of decisive parameters must be taken into account. These factors include the geometry and size, mean stress, type of load, multiaxiality, surface layer (surface topography, residual stresses, structure, hardness), temperature, corrosive media, etc. The effect of these parameters is complex, and a multiplication of the various decisive factors yields only a very rough description. The current state of the art in the catalog of technical rules on surface effects, such as the FKM guideline, "Computational Demonstration of Strength for Machine Components", is based on results which were obtained 50 years ago. The original incentive for the research project was the industrial demand for an improved computational method for determining the effect of surface machining by cutting processes. For this purpose, recourse was made to a proposal by Liu, who characterises the surface topography, besides the roughness, with the use of a surface stress-concentration factor. A characteristic structural length is introduced for describing the material; this length is calculated from the fatigue strength of the material and the threshold value for macroscopic crack propagation. Moreover, a check was made to determine which strength hypotheses are capable of realistically describing the biaxial residual stress state on the machined surface. Thus, a concept can be proposed for accurately calculating the fatigue strength, provided that the static strength, the surface topography, and the residual stresses are known. For validation, alternating-load tests are to be performed on three types of steel and two nodular cast alloys with different surface layer properties. [source] | |||||||||||||