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51.
[reaction: see text] Deoxymannojirimycin (2) and swainsonine (4) have been synthesized from each enantiomer of the same bicyclic carbamate precursor 7. The key intermediate was prepared by a simple and efficient three-step synthesis involving RCM of the diene 8, which in turn is easily accessible in any configuration from enantiomerically enriched 2,3-epoxy-4-penten-1-ol 9. 相似文献
52.
Coluccio ML Ciardelli G Bertoni F Silvestri D Cristallini C Giusti P Barbani N 《Macromolecular bioscience》2006,6(6):403-411
The preparation of an enzymatic controlled drug release system from blends of PVA/starch/alphaA, in the form of films, is described. It was shown that alphaA hydrolyses the starch within these films, resulting in a time-dependent change of the porosity in the matrix. Films were characterized by calorimetric analysis to study the interactions between the enzyme and the polymeric constituents at the molecular level. The presence of alphaA, in fact, influenced the PVA crystallization in the blends. Release tests and permeability experiments were carried out to evaluate the transport properties of the films. An increase in porosity and permeability was observed by increasing alphaA content (16-28 wt.-%). Films loaded with theophylline and caffeine were also prepared to analyze drug release properties of the matrix. Drug release kinetics were coherent with the measured changes in porosity: at higher alphaA concentrations the amount of released drug increased under the influence of diffusion and erosion processes. The results obtained are promising for the realization of drug delivery devices for a rapid release or for the release of poorly soluble drugs which usually remain entrapped in the matrix.SEM images of a PVA/starch/alphaA film before (A) and after (B) the erosion. 相似文献
53.
Caterina Rinaudo Mario Allegrina Elisa Fornero Maya Musa Alessandro Croce Donata Bellis 《Journal of Raman spectroscopy : JRS》2010,41(1):27-32
Histological sections of a patient affected by an important respiratory disease were analysed firstly by optical microscope(OM)—crossed polarisers—to identify the presence of incorporated inorganic particles, with particular attention to the fibrous ones. Then, the particles/fibres that were found were studied both with micro‐Raman spectroscopy and variable‐pressure scanning electron microscopy with energy‐dispersive spectroscopy (VP‐SEM/EDS). The two techniques allowed the in situ characterisation of the inorganic phases without disintegration of the organic matter. Micro‐Raman spectroscopy was able to identify the vibrating chemical groups of the mineral phase associated with the inorganic grain while the crystalline structure was preserved by the biological system. The VP‐SEM/EDS characterisation, defining the elemental chemical composition of the analysed particle/fibre, allowed confirmation of the mineral phase deducible from spectroscopic data or its identification with certainty when the spectroscopic data were not exhaustive. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
54.
Let A and B be two points of \(\mathop {\mathrm{PG}}(d,q^n)\) and let \(\Phi \) be a collineation between the stars of lines with vertices A and B, that does not map the line AB into itself. In this paper we prove that if \(d=2\) or \(d\ge 3\) and the lines \(\Phi ^{-1}(AB), AB, \Phi (AB) \) are not in a common plane, then the set \(\mathcal{C}\) of points of intersection of corresponding lines under \(\Phi \) is the union of \(q-1\) scattered \({\mathbb {F}}_{q}\)-linear sets of rank n together with \(\{A,B\}\). As an application we will construct, starting from the set \(\mathcal{C}\), infinite families of non-linear \((d+1, n, q;d-1)\)-MRD codes, \(d\le n-1\), generalizing those recently constructed in Cossidente et al. (Des Codes Cryptogr 79:597–609, 2016) and Durante and Siciliano (Electron J Comb, 2017). 相似文献
55.
Carlo Bianca Caterina Mogno 《Mathematical and Computer Modelling of Dynamical Systems: Methods, Tools and Applications in Engineering and Related Sciences》2018,24(2):207-235
This paper deals with the modelling of pedestrian dynamics at the entry of a metro station by means of the thermostatted kinetic theory framework. Specifically, the model depicts the time evolution of the pedestrian dynamics at the turnstiles under no panic conditions. The modelling of the microscopic interactions is based on the stochastic game theory and reflects the decision dynamics of the turnstiles pursued by pedestrians. A qualitative analysis is addressed to the equilibrium solutions by means of the classical stability theory of perturbations. Numerical simulations aim at showing the emerging behaviours captured by the model. In particular the model validation is obtained by performing a sensitivity analysis on the parameters and on the initial conditions. Further refinements and research perspective, including the modelling under panic conditions, are discussed in the last section of the paper. 相似文献
56.
Multivariate Hierarchical Copulas with Shocks 总被引:2,自引:0,他引:2
Fabrizio Durante Marius Hofert Matthias Scherer 《Methodology and Computing in Applied Probability》2010,12(4):681-694
A transformation to obtain new multivariate hierarchical copulas, starting with an arbitrary copula, is introduced. In addition
to the hierarchical structure, the presented construction principle explicitly supports singular components. These may be
interpreted as the effect of local or global shocks to the underlying random variables. A large spectrum of dependence patterns
can be achieved by the presented transformation, which seems promising for practical applications. Moreover, copulas arising
from this construction are similarly admissible with respect to analytical tractability and sampling routines as the original
copula. Finally, several well-known families of copulas may be interpreted as special cases. 相似文献
57.
58.
A unital in PG(2, q2) is a set of points such that each line meets in 1 or points. The well‐known example is the classical unital consisting of all absolute points of a unitary polarity of PG(2, q2). Unitals other than the classical one also exist in PG(2, q2) for every . Actually, all known unitals are of Buekenhout–Metz type [see F. Buekenhout, Geom Dedicata 5 (1976), 189–194, R. Metz, Geom Dedicata 8 (1979), 125–126.], and they can be obtained by a construction due to F. Buekenhout, (Geom Dedicata 5 (1976), 189–194).. The unitals constructed by R. D. Baker and G. L. Ebert (J Combin Theory Ser A 60 (1992), 67–84), and independently by J. W. P. Hirschfeld and T. Sz?nyi (Discrete Math 97 (1991), 229–242), are the union of q conics. Our Theorem 1.1 shows that this geometric property characterizes the Baker–Ebert–Hirschfeld–Sz?nyi unitals. © 2012 Wiley Periodicals, Inc. J. Combin. Designs 21: 101–111, 2013 相似文献
59.
Caterina Fraschetti Antonello Filippi Luisa Mannina Anatoly P. Sobolev Maurizio Speranza 《Journal of mass spectrometry : JMS》2014,49(7):608-612
The effects of methanol (M) and acetonitrile (A) on the stability of cycloserine (1) have been studied. InfraRed Multiphoton PhotoDissociation (IRMPD) spectroscopy of the ionic species from electrospray ionization tandem mass spectrometry (ESI‐MS) of 1/M and 1/A solutions points to extensive dimerization of 1 to cis‐3,6‐bis(aminooxymethyl)‐2,5‐piperidinedione (2), while the same process is not observed in the ESI‐MS of 1/M solutions. 1D and 2D nuclear magnetic resonance experiments confirmed these findings by showing that partial dimerization of 1 actually takes place at room temperature in acetonitrile even before ESI‐MS analysis. Comparison of nuclear magnetic resonance and IRMPD spectroscopic data from the same 1/A solution suggests that dimerization of cycloserine is enhanced in the ESI source. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
60.
Ferroxidase Activity in Eukaryotic Ferritin is Controlled by Accessory‐Iron‐Binding Sites in the Catalytic Cavity
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Dr. Caterina Bernacchioni Dr. Cecilia Pozzi Flavio Di Pisa Prof. Stefano Mangani Prof. Paola Turano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(45):16213-16219
Ferritins are iron‐storage nanocage proteins that catalyze the oxidation of Fe2+ to Fe3+ at ferroxidase sites. By a combination of structural and spectroscopic techniques, Asp140, together with previously identified Glu57 and Glu136, is demonstrated to be an essential residue to promote the iron oxidation at the ferroxidase site. However, the presence of these three carboxylate moieties in close proximity to the catalytic centers is not essential to achieve binding of the Fe2+ substrate to the diferric ferroxidase sites with the same coordination geometries as in the wild‐type cages. 相似文献