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排序方式: 共有802条查询结果,搜索用时 15 毫秒
61.
62.
Antonino Mazzaglia Luigi Monsu' Scolaro Raphael Darcy Ruth Donohue Bart Jan Ravoo 《Journal of inclusion phenomena and macrocyclic chemistry》2002,44(1-4):127-132
The entanglement process between porphyrins and some amphiphiliccyclodextrins and the occurrence of different species have been proved by the combination of UV-Visabsorption, fluorescence anisotropy, resonance light scattering and 1H NMR spectroscopy. 相似文献
63.
Clostridium thermocellum, an anaerobic thermophilic cellulolytic bacterium, produces an extremely cohesive, very high-molecular-mass multicellulase-containing complex termed thecellulosome. One of its components, the S1 subunit, is a nonenzymatic, 210 kDa glycopolypeptide. Upon preconditioning of the intact cellulosome with lowionic-strength or low-pH solutions, the S1 subunit separates in hot sodium dodecyl sulfate (SDS) solutions into a series of defined lowermolecular-mass subcomponents. Under the same conditions, the purified S1 subunit demonstrated the same behavior. Higher levels of glycosylation associated with the larger S1 subcomponents. The data support alterations in the conformational state of the S1 structure that lead to its disintegration induced by combined treatments with SDS and heating. Evidence is provided that this phenomenon may reflect a physiological response of the cellulosome, since similar alterations in S1 appear to accompany its binding to cellulose. 相似文献
64.
Dr. Hans‐Georg Stammler M. Sc. Sebastian Blomeyer Priv.‐Doz. Dr. Raphael J. F. Berger Prof. Dr. Norbert W. Mitzel 《Angewandte Chemie (International ed. in English)》2015,54(46):13816-13820
The charge density distribution of the trimethylaluminum dimer was determined by high‐angle X‐ray diffraction of a single crystal and quantum‐chemical methods and analyzed using the quantum theory of atoms in molecules. The data can be interpreted as Al2Me6 being predominantly ionically bonded, with clear indications of topological asymmetry for the bridging Al? C bonds owing to delocalized multicenter bonding. This interpretation is supported by the calculated magnetic response currents. The data shed new light on the bonding situation in this basic organometallic molecule, which was previously described by contradicting interpretations of bonding. 相似文献
65.
To allow for a reliable examination of the interaction between velocity fluctuations, acoustics and combustion, a novel numerical procedure is discussed in which a spectral solution of the Navier–Stokes equations is directly associated to a high-order finite difference fully compressible DNS solver (sixth order PADE). Using this combination of high-order solvers with accurate boundary conditions, simulations have been performed where a turbulent premixed V-shape flame develops in grid turbulence. In the light of the DNS results, a sub-model for premixed turbulent combustion is analyzed. To cite this article: R. Hauguel et al., C. R. Mecanique 333 (2005). 相似文献
66.
Amir H. Bahrami Michael Raatz Jaime Agudo-Canalejo Raphael Michel Emily M. Curtis Carol K. Hall Michael Gradzielski Reinhard Lipowsky Thomas R. Weikl 《Advances in colloid and interface science》2014
How nanoparticles interact with biomembranes is central for understanding their bioactivity. Biomembranes wrap around nanoparticles if the adhesive interaction between the nanoparticles and membranes is sufficiently strong to compensate for the cost of membrane bending. In this article, we review recent results from theory and simulations that provide new insights on the interplay of bending and adhesion energies during the wrapping of nanoparticles by membranes. These results indicate that the interplay of bending and adhesion during wrapping is strongly affected by the interaction range of the particle–membrane adhesion potential, by the shape of the nanoparticles, and by shape changes of membrane vesicles during wrapping. The interaction range of the particle–membrane adhesion potential is crucial both for the wrapping process of single nanoparticles and the cooperative wrapping of nanoparticles by membrane tubules. 相似文献
67.
Lucimara Mendonça CostaEmerson Schwingel Ribeiro Mariana Gava SegatelliDanielle Raphael do Nascimento Fernanda Midori de OliveiraCésar Ricardo Teixeira Tarley 《Spectrochimica Acta Part B: Atomic Spectroscopy》2011,66(5):329-337
The present study describes the adsorption characteristic of Cd(II) onto Nb2O5/Al2O3 mixed oxide dispersed on silica matrix. The characterization of the adsorbent has been carried out by infrared spectroscopy (IR), scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), energy dispersive X-ray fluorescence analysis (EDXRF) and specific surface area (SBET). From batch experiments, adsorption kinetic of Cd(II) was described by a pseudo-second-order kinetic model. The Langmuir linear isotherm fitted to the experimental adsorption isotherm very well, and the maximum adsorption capacity was found to be 17.88 mg g−1. Using the effective material, a method for Cd(II) preconcentration at trace level was developed. The method was based on on-line adsorption of Cd(II) onto SiO2/Al2O3/Nb2O5 at pH 8.64, in which the quantitative desorption occurs with 1.0 mol L−1 hydrochloric acid towards FAAS detector. The experimental parameters related to the system were studied by means of multivariate analysis, using 24 full factorial design and Doehlert matrix. The effect of SO42−, Cu2+, Zn2+ and Ni2+ foreign ions showed no interference at 1:100 analyte:interferent proportion. Under the most favorable experimental conditions, the preconcentration system provided a preconcentration factor of 18.4 times, consumption index of 1.08 mL, sample throughput of 14 h−1, concentration efficiency of 4.35 min−1, linear range from 5.0 up to 35.0 μg L−1 and limits of detection and quantification of 0.19 and 0.65 μg L−1 respectively. The feasibility of the proposed method for Cd(II) determination was assessed by analysis of water samples, cigarette sample and certified reference materials TORT-2 (Lobster hepatopancreas) and DOLT-4 (Dogfish liver). 相似文献
68.
Hirtenlehner C Krims C Hölbling J List M Zabel M Fleck M Berger RJ Schoefberger W Monkowius U 《Dalton transactions (Cambridge, England : 2003)》2011,40(38):9899-9910
Gold(I) complexes bearing N-heterocyclic carbenes (NHC) of the type (NHC)AuBr (3a/3b) [NHC = 1-methyl-3-benzylimidazol-2-ylidene (= MeBnIm), and 1,3-dibenzylimidazol-2-ylidene (= Bn(2)Im)] are prepared by transmetallation reactions of (tht)AuBr (tht = tetrahydrothiophene) and (NHC)AgBr (2a/2b). The homoleptic, ionic complexes [(NHC)(2)Au]Br (6a/6b) are synthesized by the reaction with free carbene. Successive oxidation of 3a/3b and 6a/6b with bromine gave the respective (NHC)AuBr(3) (4a/4b) and [(NHC)(2)AuBr(2)]Br (7a/7b) in good overall yields as yellow powders. All complexes were characterized by NMR spectroscopy, mass spectrometry, elemental analysis and single crystal X-ray diffraction. Reactions of the Au(III) complexes towards anionic ligands like carboxylates, phenolates and thiophenolates were investigated and result in a complete or partial reduction to a Au(I) complex. Irradiation of the Au(III) complexes with UV light yield the Au(I) congeners in a clean photo-reaction. 相似文献
69.
Jongsung Kim Jaechul Sung Ermaliza Razali Raphael C.-W. Phan Marc Joye 《Designs, Codes and Cryptography》2011,60(1):15-35
The theory of designing block ciphers is mature, having seen significant progress since the early 1990s for over two decades,
especially during the AES development effort. Nevertheless, interesting directions exist, in particular in the study of the
provable security of block ciphers along similar veins as public-key primitives, i.e. the notion of pseudorandomness (PRP)
and indistinguishability (IND). Furthermore, recent cryptanalytic progress has shown that block ciphers well designed against
known cryptanalysis techniques including related-key attacks (RKA) may turn out to be less secure against RKA than expected.
The notion of provable security of block ciphers against RKA was initiated by Bellare and Kohno, and subsequently treated
by Lucks. Concrete block cipher constructions were proposed therein with provable security guarantees. In this paper, we are
interested in the security notions for RKA-secure block ciphers. In the first part of the paper, we show that secure tweakable
permutation families in the sense of strong pseudorandom permutation (SPRP) can be transformed into secure permutation families
in the sense of SPRP against some classes of RKA (SPRP–RKA). This fact allows us to construct a secure SPRP–RKA cipher which
is faster than the Bellare–Kohno PRP–RKA cipher. We also show that function families of a certain form secure in the sense
of a pseudorandom function (PRF) can be transformed into secure permutation families in the sense of PRP against some classes
of RKA (PRP–RKA). We can exploit it to get various constructions secure against some classes of RKA from known MAC algorithms.
Furthermore, we discuss how the key recovery (KR) security of the Bellare–Kohno PRP–RKA, the Lucks PRP–RKA and our SPRP–RKA
ciphers relates to existing types of attacks on block ciphers like meet-in-the-middle and slide attacks. In the second part
of the paper, we define other security notions for RKA-secure block ciphers, namely in the sense of indistinguishability (IND) and non-malleability, and show the relations between these security notions. In particular, we show that secure tweakable permutation families
in the sense of IND (resp. non-malleability) can be transformed into RKA-secure permutation families in the sense of IND (resp.
non-malleability). 相似文献
70.
Synthesis, performance, and modeling of immobilized nano-sized magnetite layer for phosphate removal 总被引:2,自引:0,他引:2
A homogeneous layer of nano-sized magnetite particles (<4 nm) was synthesized by impregnation of modified granular activated carbon (GAC) with ferric chloride, for effective removal of phosphate. A proposed mechanism for the modification and formation of magnetite onto the GAC is specified. BET results showed a significant increase in the surface area of the matrix following iron loading, implying that a porous nanomagnetite layer was formed. Batch adsorption experiments revealed high efficiency of phosphate removal, by the newly developed adsorbent, attaining maximum adsorption capacity of 435 mg PO(4)/g Fe (corresponding to 1.1 mol PO(4)/mol Fe(3)O(4)). It was concluded that initially phosphate was adsorbed by the active sites on the magnetite surface, and then it diffused into the interior pores of the nanomagnetite layer. It was demonstrated that the latter is the rate-determining step for the process. Innovative correlation of the diffusion mechanism with the unique adsorption properties of the synthesized adsorbent is presented. 相似文献