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191.
We construct spectral triples and, in particular, Dirac operators, for the algebra of continuous functions on certain compact metric spaces. The triples are countable sums of triples where each summand is based on a curve in the space. Several fractals, like a finitely summable infinite tree and the Sierpinski gasket, fit naturally within our framework. In these cases, we show that our spectral triples do describe the geodesic distance and the Minkowski dimension as well as, more generally, the complex fractal dimensions of the space. Furthermore, in the case of the Sierpinski gasket, the associated Dixmier-type trace coincides with the normalized Hausdorff measure of dimension log3/log2. 相似文献
192.
193.
Gustavo Nicolodelli Cristina KurachiVanderlei Salvador Bagnato 《Applied Surface Science》2011,257(7):2419-2422
Femtosecond laser ablation of materials is turning to be an important tool for micromachining as well as for selective removal of biological tissues. In a great number of applications, laser ablation has to process through interfaces separating media of different properties. The investigation of the ablation behavior within materials and passing through interfaces is the main aim of this study. Especially, the analysis of the discontinuity in the ablation profile close to interfaces between distinct materials can reveal some of the phenomena involved in the formation of an ablated microcavity geometry. We have used a method that correlates the ablation cross sectional area with the local laser intensity. The effective intensity ablation properties were obtained from surface ablation data of distinct materials. The application of this method allows the prediction of the occurrence of a size discontinuity in the ablation geometry at the interface of distinct media, a fact which becomes important when planning applications in different media. 相似文献
194.
Catalina Gómez Jean-Luc Putaux Iñaki Mondragon Cristina Castro Piedad Gañán 《Composite Interfaces》2013,20(1):29-37
Cellulose microfibrils extracted by various alkaline treatments of vascular bundles from banana rachis were used to elaborate films. The films were comparatively studied to determine changes in polarity induced by various treatments. Atomic force microscopy was used to characterize the surface morphology of the films and transmission electron microscopy was employed to characterize the microfibrils used to elaborate the films. Contact angles were measured to determine surface free energy (SFE) and thermogravimetric analyses were carried out to determine changes in composition of the films. The results showed that the films of cellulose microfibrils prepared by the peroxide alkaline (PA) and peroxide alkaline-hydrochloric acid (PA-HCl) treatments had lower content of non-cellulosic constituents like xylose and had lower SFE than films of microfibrils treated with KOH-5. Furthermore, specimens treated with the most concentrated KOH solution (18 wt%) and sodium chloride presented the highest SFE and polar component. 相似文献
195.
Cristina Di Bari Tomonari Suzuki Calogero Vetro 《Nonlinear Analysis: Theory, Methods & Applications》2008
We introduce a notion of cyclic Meir–Keeler contractions and prove a theorem which assures the existence and uniqueness of a best proximity point for cyclic Meir–Keeler contractions. This theorem is a generalization of a recent result due to Eldred and Veeramani. 相似文献
196.
Barbara La Ferla Laura Russo Cristina Airoldi Francesco Nicotra 《Tetrahedron: Asymmetry》2009,20(6-8):744-745
A C-glycoside mimetic of l-galactose 1-diphosphate, a potential ligand of GDP-l-galactose hydrolase, an enzyme involved in the biosynthesis of vitamin C, has been designed, stereoselectively synthesised by C-allylation of tribenzylated l-fucose, by periodate-osmium tetroxide degradation of the double bond, by condensation of the obtained aldehydes with benzylacetate and by deprotection. The obtained mimetic was linked to a sepharose resin. 相似文献
197.
Cristina Pinedo-Rivilla Mariana Carrara Cafêu Josefina Aleu Casatejada Ângela Regina Araujo Isidro G. Collado 《Tetrahedron: Asymmetry》2009,20(23):2666-2672
A set of five fungal species, Botrytis cinerea, Trichoderma viride and Eutypa lata, and the endophytic fungi Colletotrichum crassipes and Xylaria sp., was used in screening for microbial biocatalysts to detect monooxygenase and alcohol dehydrogenase activities (for the stereoselective reduction of carbonyl compounds). 4-Ethylcyclohexanone and acetophenone were biotransformed by the fungal set. The main reaction pathways involved reduction and hydroxylations at several positions including tertiary carbons. B. cinerea was very effective in the bioreduction of both substrates leading to the chiral alcohol (S)-1-phenylethanol in up to 90% enantiomeric excess, and the cis–trans ratio for 4-ethylcyclohexanol was 0:100. trans-4-Ethyl-1-(1S-hydroxyethyl)cyclohexanol, obtained from biotransformation by means of an acyloin-type reaction, is reported here for the first time. The absolute configurations of the compounds trans-4-ethyl-1-(1S-hydroxyethyl)cyclohexanol and 4-(1S- and 4-(1R-hydroxyethyl)cyclohexanone were determined by NMR analysis of the corresponding Mosher’s esters. 相似文献
198.
Cristina Santamaría Beln García-Mora Gregorio Rubio Enrique Navarro 《Mathematical and Computer Modelling》2009,50(5-6):726
A Markovian approach to analyze different states of the superficial vesical carcinoma is considered, taking into account up to two recurrences and the possibility of progression. So, three transient states are considered: free of disease, first, and second recurrence; and an absorbent state, the progression. A methodology based in phase-type distributions is also used, that allows the usual quantities of interest in survival studies to be expressed in a well-structured form. This type of distribution has shown its utility in queue theory, and has the advantage that mathematical expressions can be presented in a closed form that allows algebraic treatment. 相似文献
199.
Pavel Bělík Bob Jennings Mikhail M. Shvartsman Cristina U. Thomas 《Journal of Elasticity》2009,95(1-2):57-77
We describe an asymptotic model for the behavior of PET-like heat-shrinkable thin films that includes both membrane and bending energies when the thickness of the film is positive. We compare the model to Koiter’s shell model and to models in which a membrane energy or a bending energy are obtained by Γ-convergence techniques. We also provide computational results for various temperature distributions applied to the films. 相似文献
200.
Cristina R. Dias Rodica Zãvoianu M. Farinha Portela 《Reaction Kinetics and Catalysis Letters》2002,77(2):317-324
The acid-base properties of several NiMoO4 catalysts supported on two silicas and prepared by different methods have been studied by temperature-programmed desorption of NH3. The catalytic behavior in the oxidative dehydrogenation of isobutane for two NiMoO4 catalysts with different acid-base properties are compared. 相似文献