排序方式: 共有33条查询结果,搜索用时 93 毫秒
1.
Jo E Sanna MG Gonzalez-Cabrera PJ Thangada S Tigyi G Osborne DA Hla T Parrill AL Rosen H 《Chemistry & biology》2005,12(6):703-715
The essential role of the sphingosine 1-phosphate (S1P) receptor S1P(1) in regulating lymphocyte trafficking was demonstrated with the S1P(1)-selective nanomolar agonist, SEW2871. Despite its lack of charged headgroup, the tetraaromatic compound SEW2871 binds and activates S1P(1) through a combination of hydrophobic and ion-dipole interactions. Both S1P and SEW2871 activated ERK, Akt, and Rac signaling pathways and induced S1P(1) internalization and recycling, unlike FTY720-phosphate, which induces receptor degradation. Agonism with receptor recycling is sufficient for alteration of lymphocyte trafficking by S1P and SEW2871. S1P(1) modeling and mutagenesis studies revealed that residues binding the S1P headgroup are required for kinase activation by both S1P and SEW2871. Therefore, SEW2871 recapitulates the action of S1P in all the signaling pathways examined and overlaps in interactions with key headgroup binding receptor residues, presumably replacing salt-bridge interactions with ion-dipole interactions. 相似文献
2.
Bonini BF Comes-Franchini M Mazzanti G Ricci A Sala M 《The Journal of organic chemistry》1996,61(21):7242-7243
3.
Alvisi D Blart E Bonini BF Mazzanti G Ricci A Zani P 《The Journal of organic chemistry》1996,61(20):7139-7146
The palladium-catalyzed desilylation-arylation of substituted vinylsilanes by p-iodoanisole in the presence of bidentate phosphine ligands is described. Apart from enhancing the rate of the reaction considerably, heteroatom-based functional groups in the vinylsilane moiety have a profound influence on the regiochemistry. A catalytic cycle for the chelation-controlled desilylation-arylation reaction involving five- and six-membered chelate rings is proposed. 相似文献
4.
Bianca F. Bonini Mauro Comes-Franchini Mariafrancesca Fochi Germana Mazzanti 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):451-452
α-Silyl Vinylsulfides, obtained in a stereoselective manner through enethiolizable silyl thioketones, can be used for the synthesis of vinylsulfides and vinylsilane with a specific geometry, and for the preraration of bicyclic and open chain thiofunzionalized enones. 相似文献
5.
Cecília L. Siqueira Edilson F. Arruda Laura Bahiense Germana L. Bahr Geraldo R. Motta 《European Journal of Operational Research》2018,264(3):870-883
This paper proposes an integrated approach for the long-term planning and surgery allocation problem with downstream constraints. It is motivated by a case study in the Brazilian National Institute of Traumatology and Orthopedics, which provides elective high complexity surgeries for patients from the Brazilian public health system. We introduce an optimization problem that designs a periodic surgery allocation schedule as well as a recovery ward utilization plan, with a view at balancing patient arrivals and releases in the long term, in such a way that all surgeries are performed in a timely manner. 相似文献
6.
Angelo Albert Francesco Paolo Colonna Maurizio Guerra Bianca F. Bonini Germana Mazzanti Zoltàn Dinya Gian Franco Pedulli 《Journal of organometallic chemistry》1981,221(1):47-55
The radical adducts resulting from the reaction between group IVB organometallic radicals MR3 (M = Si, Ge, Sn; R = alkyl or aryl) and a number of thioketones of the chromone and flavone series have been investigated by ESR spectroscopy. The spectral parameters obtained for these species have been compared with those of similar adducts of the corresponding ketones. Both classes of radicals adopt an orthogonal conformation, and the differences between the former and the latter paramagnetic species can be accounted for by the different electronegativity of oxygen and sulphur. the effects of substitution of the heterocyclic oxygen with a sulphur or selenium atom on the spin density distribution are likewise explained. INDO calculations have been carried out on the model systems CH2XSiH3 (X = O, S). 相似文献
7.
The aim of this work is to propose design criteria, based on rheological characterisation for improving drill-in fluids performance.
In particular, it reports an example in which rheological approaches helped improve drill-in fluids resistance to temperature.
As a starting system a commercial drill-in fluid containing xanthan gum and calcium carbonate was chosen and evaluated. Different
samples were then prepared by changing the initial formulation in order to increase the system's stability to temperature.
Drill-in fluids' performance have been compared by considering their “damaging potential”, filtration properties and, “cakes”.
All drill-in fluids have been tested before and after aging at a given temperature with “hot rolling tests”. The systems'
gel structure was characterized by measuring dynamic moduli (G′ and G′′) in the linear viscoelastic range and all samples
were compared by evaluating their “melting” temperature and gel network strength during time cure tests. The results obtained
from this work suggest that the rheological tests carried out on the whole drill-in fluid can provide insights into fluids'
damaging potential and “cake” structure. In particular, rheology proved to be able to provide quantitative information about
gel strength and temperature stability that permitted one to improve drill-in fluids' formulation in order to preclude formation
damage and to meet industrial requirements.
Received: 6 February 2000 Accepted: 15 November 2000 相似文献
8.
9.
Bardelli F Barone G Crupi V Longo F Majolino D Mazzoleni P Venuti V 《Analytical and bioanalytical chemistry》2011,399(9):3147-3153
We report on a non-destructive study of Sicilian ceramic fragments of cultural heritage interest, classified as “proto-majolica”
pottery and dating back to the twelfth to thirteen centuries AD. The analytical approach used is based on the employment of
two totally non-invasive spectroscopic techniques: X-ray fluorescence (XRF), using a portable energy-dispersive XRF analyser,
and X-ray absorption spectroscopy, using synchrotron radiation as a probe (SR-XAS). XRF measurements allowed us to collect
elemental and spatially resolved information on major and minor constituents of the decorated coating of archaeological pottery
fragments, so providing preliminary results on the main components characterizing the surface. In particular, we assigned
to Fe and Mn the role of key elements of the colouring agent. With the aim of obtaining more detailed information, we performed
SR-XAS measurements at the Fe and Mn K-edges at the Italian BM08 beamline at the European Synchrotron Radiation Facility (Grenoble,
France). The experimental data were analysed by applying principal component analysis and least-squares fitting to the near-edge
part of the spectra (X-ray absorption near-edge structure) to determine the samples’ speciation. From the overall results,
umber, a class of brownish pigments characterized by a mixture of hydrated iron and manganese oxides, has been ascribed as
a pigmenting agent. 相似文献
10.
Giovanni Barbera Germana Barone Vincenza Crupi Francesca Longo Domenico Majolino Paolo Mazzoleni Valentina Venuti 《X射线光谱测定》2013,42(1):8-15
The preciousness of historical artifacts leads to the performance of nondestructive and/or microdestructive analyses, especially when the archeological finds are stored in museums. The PXRF spectrometry represents a powerful technique for the chemometric study of the materials, in alternative to the more usual destructive X‐ray‐based methods. A large set of limestones belonging to several formations cropping out in the Hyblean area (south‐eastern Sicily, Italy) was analyzed by means of a PXRF instrument. The main goal was to test the PXRF potentiality for the discrimination of rocks with similar features and to create a chemical database of carbonate rocks, which were commonly used in the past in the manufacturing of sculptures and stone artifacts. Fluorescence data were processed by means of multivariate statistical analysis. In particular, principal components analysis and linear discriminant analysis were applied. The results allowed us to classify the samples belonging to different formations and to distinguish different rock typologies within each formation. Finally, the investigation showed that the analytical PXRF data can be suitable for a substantial characterization of stone materials and this could be extended to museum materials belonging to cultural heritage. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献