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showing 10 items of 1967 documents
Kinetische Untersuchungen zu Diels‐Alder‐Reaktionen des Cyclooctins mit anschließender Aromatisierung
1984
Aus Cyclooctin (1) und den cyclischen Dienen 2a – g entstehen die Tricyclen 3a – g, die ganz unterschiedliche Stabilitat aufweisen. 3a, b, f und g zerfallen spontan. Unter Abspaltung von CO2, SO2, CO und N2 entstehen die aromatischen Verbindungen 4a – c. 3c eliminiert beim Erhitzen C2H4. 3e wird thermisch kaum mehr gespalten, aber ganz effizient bei der Photolyse, und 3d ist schlieslich gegenuber einer Aromatisierung stabil. Die thermische Ethylenabspaltung und die doppelte Photodecarbonylierung werden kinetisch untersucht. Kinetic Investigations of Diels-Alder-Reactions of Cyclooctyne with Consecutive Aromatization The tricyclic compounds 3a – g, generated from cyclooctyne (1) and the cycl…
Cycloadditionen von Benzothiet und aromatischen Nitroso‐Verbindungen
1993
Cycloaddition Reactions of Benzothiete and Aromatic Nitroso Compounds The new heterocyclic ring systems 4H-3,1,2-benzoxathiazines 4 and 2,3-dihydro-1,2-benzothiazol 1-oxides 6 can be synthesized by cycloaddition of benzothiete (1) and aromatic nitroso compounds 3. The regioselectivity of the primary step and the secondary thermal or acid-catalyzed rearrangements are discussed.
Implant insertion torque value in immediate loading : a retrospective study
2019
Background The aim of this study is to verify if the Insertion Torque Value (ITV) of 32 Ncm for immediate loading protocol (ILP), as indicated by literature, is still, with the advance in implant research, a real significant cut-off for long-term implant survival. Material and Methods In this retrospective study, data from 224 patients that during three years of clinical practice, were submitted to the insertion of 322 implants with immediate loading protocol, have been recorded, pooled and analyzed. Data were organized based on Insertion Torque Value (ITV): > 32 Ncm (CG) and 32 Ncm are still characterized by a lower crestal bone resorption, there are no statistically significant difference…
On the development of a communication-aware task mapping technique
2004
Clusters have become a very cost-effective platform for high-performance computing. In these systems, although currently existing networks actually provide enough bandwidth for the existing applications and workstations, the trend is towards the interconnection network becoming the system bottleneck. Therefore, in the future, scheduling strategies will have to take into account the communication requirements of the applications and the communication bandwidth that the network can offer. One of the key issues in these strategies is the task mapping technique used when the network becomes the system bottleneck.In this paper, we propose a communication-aware mapping technique that tries to mat…
Cohesive-frictional interface model with oligocyclic degradation of surfaces roughness
2008
The present work is devoted to the constitutive modelling, through the classical interface kinematical formulation, of the mechanical behaviour of the internal adhesive layers, connecting different bodies. The proposed interface constitutive model couples a cohesive behaviour with a frictional one and it is able to follow the transition from the sound condition to the fully cracked one by means of a specific interpretation of the damage variable. In the fully cracked condition, the dilatancy exhaustion and the frictional strength degradation are also modelled.
An Interface Mechanical Model with a Cohesive to Frictional Transition
2009
A thermodynamically consistent mechanical interface model is presented. The model is based on the interface damage mechanic theory applied in a special fashion such that the interface damage variable is also used as a parameter which drives the continuous and smooth transition from the sound initial cohesive state to the final fully fractured frictional state. Interface damage activation and fictional sliding are promoted by a damage activation function and a Coulomb frictional yielding function. The main features of the model are discussed in details and some numerical results for the material response are shown in monotonic and cyclic loading regimes.
Moving multi-loads problem in layered cracked beams with interlayer slip
2017
This contribution concerns the vibration response of layered cracked uniform beams with interlayer slip under moving multiple loads. Considering a linear constitutive relation between the horizontal slip and the interlaminar shear force, the Euler-Bernoulli hypothesis is assumed to hold for each layer separately. Modeling cracks as internal elastic rotational joints, related discontinuities of the response variables are treated by the theory of generalized functions. In this manner, exact eigenfunctions are derived from a characteristic equation built as determinant of 6x6 matrix, for any number of cracks. Building pertinent orthogonality conditions for the deflection eigenfunctions, the re…
Multifunctional CD4(+) T cells correlate with active Mycobacterium tuberculosis infection.
2010
Th1 CD4(+) T cells and their derived cytokines are crucial for protection against Mycobacterium tuberculosis. Using multiparametic flow cytometry, we have evaluated the distribution of seven distinct functional states (IFN-gamma/IL-2/TNF-alpha triple expressors, IFN-gamma/IL-2, IFN-gamma/TNF-alpha or TNF-alpha/IL-2 double expressors or IFN-gamma, IL-2 or TNF-alpha single expressors) of CD4(+) T cells in individuals with latent M. tuberculosis infection (LTBI) and active tuberculosis (TB). We found that triple expressors, while detectable in 85-90%TB patients, were only present in 10-15% of LTBI subjects. On the contrary, LTBI subjects had significantly higher (12- to 15-fold) proportions of…
Diels-Alder Reactions of (1H-Indol-3-yl)-enacetamides and -endiacetamides: A Selective Access to Acetylamino-Functionalized [b]Annelated Indoles and …
1991
Diels-Alder reactions of the (1H-indol-3-yl)-enacetamides and -endiacetamides 1a–d with some carbodieno-philes and 4-phenyl-3H-1,2,4-triazole-3,5(4H)-dione give rise to the novel amino-functionalized carbazole; 4–6 and 8 (Scheme 3). Ethenetetracarbonitrile reacts with 1b to furnish the Michael-type adduct 7 (Scheme 3). Structural aspects of the starting materials 1, which exhibit above all 3-vinyl-1H-indole reactivity, are discussed with regard to the prediction of a Diels-Alder process.
A Synthetic Model for the [4+2] Cycloaddition in the Biosynthesis of the Brevianamides, Paraherquamides, and Related Compounds
2000
Abstract The reactivity of model systems for the proposed [4+2] cycloaddition in the biosynthesis of the brevianamides, paraherquamides, and marcfortines is explored. The model for the intermolecular reaction reveals that the cycloaddition takes place under mild conditions only if activated, very reactive dienophiles are used. When relatively unreactive dienophiles such as cyclopentene and cyclohexene are used, harsh reaction conditions and/or a Lewis acid catalyst are necessary for the reaction. In contrast, the model for the intramolecular reaction demonstrates that the cycloaddition takes place within a few hours at room temperature, even in the absence of a Lewis acid catalyst. Conclusi…