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121.
Skwarczynski M Sohma Y Noguchi M Kimura T Hayashi Y Kiso Y 《The Journal of organic chemistry》2006,71(6):2542-2545
O-N Intramolecular alkoxycarbonyl (carbonate-carbamate) migration was found to occur as a common reaction of hydroxyamino acids under mild basic aqueous conditions with no formation of side products. Carbonate protective groups migrate to produce amino-protected carbamate derivatives of hydroxyamino acids with high efficiency and purity. 相似文献
122.
Karel Procházka Pavel Matějíček Mariusz Uchman Miroslav Štěpánek Jana Humpolíčková Martin Hof Milena Špírková 《Macromolecular Symposia》2008,273(1):95-102
Summary: The self-assembled core-shell nanoparticles based on fluorescently double-tagged high-molar-mass polystyrene-block-poly(methacrylic acid), PS-PMA, were prepared in aqueous buffers by dialysis from 1,4-dioxane – water mixtures. The conformations of shell-forming PMA chains were studied using nonradiative excitation energy transfer measurements. The study shows that two populations of distinctly different conformations (collapsed and stretched) coexist in the shell and their ratio depends on pH. 相似文献
123.
We extend a new method to measure possible variation of the speed of light by using Baryon Acoustic Oscillations and the Hubble function onto an inhomogeneous pressure model of the universe. The method relies on the fact that there is a simple relation between the angular diameter distance maximum and the Hubble function (H) evaluated at the same maximum‐condition redshift, which includes the speed of light c. One limit of such a method was the assumption of the vanishing of spatial curvature (though, as it has been shown, a non‐zero curvature has negligible effect). In this paper, apart from taking into account an inhomogeneity, we consider non‐zero spatial curvature and calculate an exact relation between and H. Our main result is the evaluation if current or future missions such as Square Kilometer Array (SKA) can be sensitive enough to detect any spatial variation of c which can in principle be related to the recently observed spatial variation of the fine structure constant (an effect known as α‐dipole). 相似文献
124.
Mariusz Kubus H.-Jürgen Meyer Lorenz Kienle Andrzej M. Kłonkowski 《Journal of Non》2009,355(24-27):1333-1337
The luminescence behavior of composite materials consisting of nanocrystals of Y3?xAl5O12:Tb (YAG:Tb3+) embedded into silica xerogel has been studied. Blue and green luminescence of the materials is due to a cross-relaxation effect in Tb3+ ions doped into a YAG lattice. The materials with YAG:Tb3+ nanocrystals immobilized in silica exhibit enhancement of Tb3+ luminescence in comparison with the macrocrystalline YAG:Tb3+ powder. The Tb3+ luminescence intensity of a composite material dried at room temperature can be improved when higher aliphatic alcohols are applied in a one-pot procedure during a sol–gel synthesis. On the other hand, the Tb3+ luminescence is quenched in the presence of Ag nanoparticles in the material. The composite material (YAG:Tb3+ in silica) exhibits thermal stability at higher temperatures and achieves the highest emission intensity after having been annealed at 700 °C. 相似文献
125.
Mariusz P. Mitoraj Goran V. Janjić Vesna B. Medaković Dušan Ž. Veljković Artur Michalak Snežana D. Zarić Miloš K. Milčić 《Journal of computational chemistry》2015,36(3):171-180
The water/aromatic parallel alignment interactions are interactions where the water molecule or one of its O? H bonds is parallel to the aromatic ring plane. The calculated energies of the interactions are significant, up to ΔECCSD(T)(limit) = ?2.45 kcal mol?1 at large horizontal displacement, out of benzene ring and CH bond region. These interactions are stronger than CH···O water/benzene interactions, but weaker than OH···π interactions. To investigate the nature of water/aromatic parallel alignment interactions, energy decomposition methods, symmetry‐adapted perturbation theory, and extended transition state‐natural orbitals for chemical valence (NOCV), were used. The calculations have shown that, for the complexes at large horizontal displacements, major contribution to interaction energy comes from electrostatic interactions between monomers, and for the complexes at small horizontal displacements, dispersion interactions are dominant binding force. The NOCV‐based analysis has shown that in structures with strong interaction energies charge transfer of the type π → σ*(O? H) between the monomers also exists. © 2014 Wiley Periodicals, Inc. 相似文献
126.
Dr. Mariusz Tasior Vincent Hugues Dr. Mireille Blanchard‐Desce Prof. Daniel T. Gryko 《化学:亚洲杂志》2012,7(11):2656-2661
New, strongly fluorescent benzo[1,2‐d:4,5‐d′]bisimidazoles have been prepared by the reaction of Bandrowski′s base with various aldehydes. Their structures were carefully designed to achieve efficient excited‐state intramolecular proton transfer and good two‐photon‐absorption (2PA) cross‐sections. Functional dyes that possessed both high fluorescence quantum yields and large Stokes shifts were prepared. A π‐expanded D‐A‐D derivative that possessed Φfl=50 % and σ2=230 GM in the spectroscopic area of interest for biological imaging is an excellent candidate as a fluorescent probe. Thanks to the presence of two reactive amino groups, such compounds can be easily transformed into probes for bioconjugation. All of these benzo[1,2‐d:4,5‐d′]bisimidazoles were also strongly fluorescent in the solid state. 相似文献
127.
Marcin Koba Mariusz Belka Tomasz Ciesielski Tomasz B?czek 《Central European Journal of Chemistry》2012,10(1):216-223
The lipophilicity values of selected acridinone (imidazoacridinone and triazoloacridinone) derivatives were measured by gradient
reversed-phase high-performance liquid chromatography (RP-HPLC) using a C18 stationary phase with a water/acetonitrile mixture
as a mobile phase. The retention times obtained served as input data and appropriate log kw values (i.e., the retention factor log kw extrapolated to 0% organic modifier) as an alternative to log P were calculated using the DryLab program. The relationships
between the lipophilicity (log kw) and the chemical structure of the studied compounds, as well as correlation between experimentally determined lipophilicities
(log kw) and log P data calculated using some commonly available software, are discussed. 相似文献
128.
129.
Ceborska M Zimnicka M Pietrzak M Troć A Koźbiał M Lipkowski J 《Organic & biomolecular chemistry》2012,10(27):5186-5188
The formation of different complexes of folic acid depending on the size of the host cyclodextrin resulting in either an exclusion compound (with the smallest α-cyclodextrin) or 2-rotaxane, where cyclodextrin is threaded over folic acid (with β- and γ-cyclodextrins), is presented. The formation is carried out in water which allows both possible application in pharmaceutical sciences and usage of environmentally friendly "green chemistry". The obtained compounds are thoroughly characterized using one and two dimensional NMR, mass spectrometry, differential scanning calorimetry and thermogravimetric analysis. 相似文献
130.
An identity of the form x 1?x n ??x 1?? x 2?? ?x n?? where ?? is a non-trivial permutation on the set {1,??,n} is called a permutation identity. If u??v is a permutation identity, then ?(u??v) [respectively r(u??v)] is the maximal length of the common prefix [suffix] of the words u and v. A variety that satisfies a permutation identity is called permutative. If $\mathcal{V}$ is a permutative variety, then $\ell=\ell(\mathcal{V})$ [respectively $r=r(\mathcal{V})$ ] is the least ? [respectively r] such that $\mathcal{V}$ satisfies a permutation identity ?? with ?(??)=? [respectively r(??)=r]. A?variety that consists of nil-semigroups is called a nil-variety. If ?? is a set of identities, then $\operatorname {var}\varSigma$ denotes the variety of semigroups defined by ??. If $\mathcal{V}$ is a variety, then $L (\mathcal{V})$ denotes the lattice of all subvarieties of $\mathcal{V}$ . For ?,r??0 and n>1 let $\mathfrak{B}_{\ell,r,n}$ denote the set that consists of n! identities of the form $$t_1\cdots t_\ell x_1x_2 \cdots x_n z_{1}\cdots z_{r}\approx t_1\cdots t_\ell x_{1\pi}x_{2\pi} \cdots x_{n\pi}z_{1}\cdots z_{r}, $$ where ?? is a permutation on the set {1,??,n}. We prove that for each permutative nil-variety $\mathcal{V}$ and each $\ell\ge\ell(\mathcal{V})$ and $r\ge r(\mathcal{V})$ there exists n>1 such that $\mathcal{V}$ is definable by a first-order formula in $L(\operatorname{var}{\mathfrak{B}}_{l,r,n})$ if ???r or $\mathcal{V}$ is definable up to duality in $L(\operatorname{var}{\mathfrak{B}}_{\ell,r,n})$ if ?=r. 相似文献