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181.
Valeria Ambrogi Luana Perioli Morena Nocchetti Loredana Latterini Cinzia Pagano Elena Massetti Carlo Rossi 《Journal of Physics and Chemistry of Solids》2012,73(1):94-98
Kojic acid (KOJ) is a melanin synthesis inhibitor widely used as skin lightening agent in topical preparations. Unfortunately it is easily susceptible to photo-oxidation, phenomenon responsible for chemical and organoleptic modifications. The aim of this work was the intercalation of KOJ in hydrotalcite-like compounds (HTlc) in order to stabilize KOJ and to reduce its photolability. Hydrotalcite containing Zn and Al (ZnAl-HTlc) was used as host to obtain the final compound ZnAl-HTlc-KOJ. The intercalation was carried out, after many attempts, by ionic exchange mechanism by means of the strong base EtO? in anhydrous ethanol/dimethylsulfoxide (DMSO) mixture as solvent in order to generate KOJ? anions. The final product was characterized by the X-ray powder diffraction (XRPD), FT-IR spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and elemental analysis. The intercalated compound was formulated in a siliconic water free self-emulsifying ointment and the in vitro release profile was evaluated. All samples (intercalation compound and its formulation) were submitted also to spectrophotometric assays in order to evaluate the matrix protective effect towards ultraviolet rays. 相似文献
182.
Ren Q Reedy CG Terrell EA Wieting JM Wagie RW Asplin JP Doyle LM Long SJ Everard MT Sauer JS Baumgart CE D'Acchioli JS Bowling NP 《The Journal of organic chemistry》2012,77(5):2571-2577
The effective conjugation of ortho and ortho-alt-para-arylene ethynylenes, with appropriately positioned pyridine and pyrazine heterocycles, increases upon binding to Ag(I) and Pd(II) cations. Significant bathochromic shifts in the electronic spectra, witnessed upon introduction of these metal bridges, are consistent with enhanced electron delocalization in the unsaturated backbone. Control studies suggest that this electronic behavior is attributable exclusively (in the case of Ag(I)) or partially (in the case of Pd(II)) to conformational restrictions of the conjugated backbones. 相似文献
183.
Perez-Delgado Y Barroso JZ Garofalo LA Manzanares CE 《The journal of physical chemistry. A》2012,116(9):2071-2079
The vibrational overtone spectra of the acetylenic (Δυ = 4, 5) and methyl (Δυ = 5, 6) C-H stretch transitions of tert-butyl acetylene [(CH(3))(3)C-C≡C-H] were obtained using the phase shift cavity ring down (PS-CRD) technique at 295 K. The C-H stretch fundamental and overtone absorptions of the acetylenic (Δυ = 2 and 3) and methyl (Δυ = 2-4) C-H bonds have been obtained using a Fourier transform infrared and near-infrared spectrophotometer. Harmonic frequency ω(ν(1)) and anharmonicities x(ν(1)) and x(ν(1), ν(24)) are reported for the acetylenic C-H bond. Molecular orbital calculations of geometry and vibrational frequencies were performed. A harmonically coupled anharmonic oscillator (HCAO) model was used to determine the overtone energy levels and assign the absorption bands to vibrational transitions of methyl C-H bonds. Band strength values were obtained experimentally and compared with intensities calculated in terms of the HCAO model where only the C-H modes are considered. No adjustable parameters were used to get order of magnitude agreement with experimental intensities for all pure local mode C-H transitions. 相似文献
184.
L. N. Coelho B. Diaz R. Magalhães-Paniago A. Malachias 《The European physical journal. Special topics》2012,208(1):217-229
In this work we depict schematically the use of resonant (anomalous) X-ray diffraction as a tool to directly probe strain
and composition of self-assembled semiconductor islands. By employing a direct analysis at the Eu L3 edge its composition gradient is quantified for EuTe:SnTe capped islands. Projection maps are proposed to visualize the results,
providing an alternative capability to infer quantum dot properties. A more complex methodology is applied to the study of
InP:GaAs islands, in which complementary anomalous measurements are performed. For this system the number of samples analyzed
allows us to extract the activation energy for Ga adatoms diffusion from the substrate to the islands. 相似文献
185.
de Carvalho Benini Kelly Cristina Coelho Ornaghi Heitor L. Pereira Paulo Henrique Fernandes Maschio Leandro José Voorwald Herman Jacobus Cornelis Cioffi Maria Odila Hilário 《Journal of Thermal Analysis and Calorimetry》2021,143(1):73-85
Journal of Thermal Analysis and Calorimetry - The effects of chemical treatment sequences on the chemical, physical, and mainly the thermal properties of Imperata Brasiliensis grass in the process... 相似文献
186.
187.
In the spirit of Göllnitz’s “big” partition theorem of 1967, we present a new mod-6 partition identity. Alladi et al. provided a four-parameter refinement of Göllnitz’s big theorem in 1995 via a key identity of generating functions and the method of weighted words. By means of this technique, two similar mod-6 identities of this type were discovered—one by Alladi in 1999 and one by Alladi and Andrews in 2015. We finish the picture by presenting and proving the fourth and final possible mod-6 identity in this spirit. Furthermore, we provide a complete generalization of mod-n identities of this type. Finally, we apply a similar argument to generalize an identity of Alladi et al. from 2003.
相似文献188.
Andreia S. R. Oliveira Patrícia V. Mendonça Arménio C. Serra Jorge F. J. Coelho 《Journal of polymer science. Part A, Polymer chemistry》2020,58(1):145-153
The supplemental activator and reducing agent (SARA) atom transfer radical polymerization (ATRP) mediated by Na2S2O4 in the presence of air, without external deoxygenation or additional oxygen scavengers, is reported for several vinyl monomers: methyl acrylate (MA), n-butyl acrylate (n-BA), methyl methacrylate (MMA), 2-(dimethylamino)ethyl methacrylate (DMAEMA), poly(ethylene glycol) methyl ether acrylate (OEOA), and styrene (Sty). The polymerizations can be conducted in aqueous medium or using organic/water mixtures as solvent, with low concentration of copper, near room temperature. In the absence of any external deoxygenation, several well-defined homopolymers and block copolymers were obtained (Ð < 1.3). The evolution of the oxygen concentration during the polymerizations was monitored with an optical oxygen sensor. The consumption of oxygen prior polymerization in ethanol/water mixtures was attributed to the combined presence of Na2S2O4 and alkyl halide initiator, which led to a lower initiation efficiency (Ieff). This could be overcome by decreasing the headspace volume of the reaction. The system reported exhibited the potential to be scalable, which is very relevant from an industrial standpoint. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 145–153 相似文献
189.
da Trindade L. G. Christinelli W. A. Zanchet L. Coelho D. Trench A. B. Martini Emilse M. A. Correa Daniel S. Mattoso Luiz H. C. Pereira E. C. 《Journal of Solid State Electrochemistry》2019,23(4):1109-1119
Journal of Solid State Electrochemistry - New materials can be developed using a known compound with enhanced properties modifying and controlling its microstructure, morphology, and density of... 相似文献
190.
N.V. Vugman R.A. Giannoni J.A.Coelho Neto 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1997,124(2):352-354
The hyperfine interaction with13C in nonenriched [Rh(CN)6]4−, in a KCl host lattice at 7 K, is measured by continuous-wave X- and Q-band electron paramagnetic resonance, allowing, for the first time, a comparative study of spin densities on the carbon of the axial cyanide in this complex and in the similar [Co(CN)6]4−complex. From the experimental data corrected for dipolar interactions,Aiso= 79.80 × 10−4cm−1andAanis= 0.76 × 10−4cm−1. 相似文献