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901.
A method for the decolourization of coloured cotton fabric dyed with vat dyes, based on exposure to infrared laser light,
has been tested. Pulsed CO2 laser has been used for all experiments. To detect changes in colour shade, reflection data of original and dyed cotton irradiated
at various fluency of infrared laser light were measured on a UV–VIS spectrophotometer, and then colour intensity was calculated
for each vat dye. To observe changes in chemical composition and morphology of fiber surfaces, an analysis was performed by
X-ray photoelectron spectroscopy and scanning electron microscopy due to thermal effects. Thermal stability of vat dyes and
cotton fabric was determined with differential scanning calorimetry method to simulate the heating process during exposure
of samples to the infrared laser irradiation. 相似文献
902.
Kinga Stefanowska Dr. Adrian Franczyk Jakub Szyling Mikołaj Pyziak Dr. Piotr Pawluć Dr. Jędrzej Walkowiak 《化学:亚洲杂志》2018,13(16):2101-2108
Comprehensive studies on platinum‐catalyzed hydrosilylation of a wide range of terminal and internal alkynes with spherosilicate (HSiMe2O)8Si8O12 ( 1 a ) were performed. The influence of the reaction parameters and the types of reagents and catalysts on the efficiency of the process, which enabled the creation of a versatile and selective method to synthesize olefin octafunctionalized octaspherosilicates, was studied in detail. Within this work, twenty novel 1,2‐(E)‐disubstituted and 1,1,2‐(E)‐trisubstituted alkenyl‐octaspherosilicates ( 3 a – m , 6 n – t ) were selectively obtained with high yields, and fully characterized (1H, 13C, 29Si NMR, FTIR, MALDI TOF or TOF MS ES+ analysis). Moreover, the molecular structure of the compound (Me3Si(H)C=C(H)SiMe2O)8Si8O12 ( 3 a ) was determined by X‐ray crystallography for the first time. The developed procedures are the first that allow selective hydrosilylation of terminal silyl, germyl, aryl, and alkyl alkynes with 1 a , as well as the direct introduction of sixteen functional groups into the 1 a structure by the hydrosilylation of internal alkynes. This method constituted a powerful tool for the synthesis of hyperbranched compounds with a Si?O based cubic core. The resulting products, owing to their unique structure and physicochemical properties, are considered novel, multifunctional, hybrid, and nanometric building blocks, intended for the synthesis of star‐shaped molecules or macromolecules, as well as nanofillers and polymer modifiers. In the presented syntheses, commercially available reagents and catalysts were used, so these methods can be easily repeated, rapidly scaled up, and widely applied. 相似文献
903.
Gierczyk B Nowak-Wydra B Grajewski J Zalas M 《Magnetic resonance in chemistry : MRC》2007,45(2):123-127
Substituted 2-(phenylamino)-5-phenyl-1,3,4-oxadiazoles were studied by 15N NMR spectroscopy. All signals were assigned on the basis of HMQC and HMBC experiments. Chemical shifts values were correlated with empirical Hammett parameters as well as with calculated electron densities and chemical shieldings. 相似文献
904.
Dr. Jakub Šebera Prof. Jaroslav Burda Dr. Michal Straka Prof. Akira Ono Prof. Chojiro Kojima Prof. Yoshiyuki Tanaka Dr. Vladimír Sychrovský 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(30):9884-9894
A reaction mechanism that describes the substitution of two imino protons in a thymine:thymine (T:T) mismatched DNA base pair with a HgII ion, which results in the formation of a (T)N3‐HgII‐N3(T) metal‐mediated base pair was proposed and calculated. The mechanism assumes two key steps: The formation of the first HgII? N3(T) bond is triggered by deprotonation of the imino N3 atom in thymine with a hydroxo ligand on the HgII ion. The formation of the second HgII? N3(T) bond proceeds through water‐assisted tautomerization of the remaining, metal‐nonbonded thymine base or through thymine deprotonation with a hydroxo ligand of the HgII ion already coordinated to the thymine base. The thermodynamic parameters ΔGR=?9.5 kcal mol?1, ΔHR=?4.7 kcal mol?1, and ΔSR=16.0 cal mol?1 K?1 calculated with the ONIOM (B3LYP:BP86) method for the reaction agreed well with the isothermal titration calorimetric (ITC) measurements by Torigoe et al. [H. Torigoe, A. Ono, T. Kozasa, Chem. Eur. J. 2010 , 16, 13218–13225]. The peculiar positive reaction entropy measured previously was due to both dehydration of the metal and the change in chemical bonding. The mercury reactant in the theoretical model contained one hydroxo ligand in accord with the experimental pKa value of 3.6 known for an aqua ligand of a HgII center. The chemical modification of T:T mismatched to the T‐HgII‐T metal‐mediated base pair was modeled for the middle base pair within a trinucleotide B‐DNA duplex, which ensured complete dehydration of the HgII ion during the reaction. 相似文献
905.
Cannizzo A Blanco-Rodríguez AM El Nahhas A Sebera J Zális S Vlcek A Chergui M 《Journal of the American Chemical Society》2008,130(28):8967-8974
Ultrafast electronic-vibrational relaxation upon excitation of the singlet charge-transfer b (1)A' state of [Re(L)(CO) 3(bpy)] ( n ) (L = Cl, Br, I, n = 0; L = 4-Et-pyridine, n = 1+) in acetonitrile was investigated using the femtosecond fluorescence up-conversion technique with polychromatic detection. In addition, energies, characters, and molecular structures of the emitting states were calculated by TD-DFT. The luminescence is characterized by a broad fluorescence band at very short times, and evolves to the steady-state phosphorescence spectrum from the a (3)A" state at longer times. The analysis of the data allows us to identify three spectral components. The first two are characterized by decay times tau 1 = 85-150 fs and tau 2 = 340-1200 fs, depending on L, and are identified as fluorescence from the initially excited singlet state and phosphorescence from a higher triplet state (b (3)A"), respectively. The third component corresponds to the long-lived phosphorescence from the lowest a (3)A" state. In addition, it is found that the fluorescence decay time (tau 1) corresponds to the intersystem crossing (ISC) time to the two emissive triplet states. tau 2 corresponds to internal conversion among triplet states. DFT results show that ISC involves electron exchange in orthogonal, largely Re-localized, molecular orbitals, whereby the total electron momentum is conserved. Surprisingly, the measured ISC rates scale inversely with the spin-orbit coupling constant of the ligand L, but we find a clear correlation between the ISC times and the vibrational periods of the Re-L mode, suggesting that the latter may mediate the ISC in a strongly nonadiabatic regime. 相似文献
906.
Quantum chemistry beyond Born–Oppenheimer approximation on a quantum computer: A simulated phase estimation study 下载免费PDF全文
Libor Veis Jakub Višňák Hiroaki Nishizawa Hiromi Nakai Jiří Pittner 《International journal of quantum chemistry》2016,116(18):1328-1336
We present an efficient quantum algorithm for beyond‐Born–Oppenheimer molecular energy computations. Our approach combines the quantum full configuration interaction method with the nuclear orbital plus molecular orbital method. We give the details of the algorithm and demonstrate its performance by classical simulations. Two isotopomers of the hydrogen molecule (H2, HT) were chosen as representative examples and calculations of the lowest rotationless vibrational transition energies were simulated. © 2016 Wiley Periodicals, Inc. 相似文献
907.
Evelyne Flandrin Antoni Marczyk Jakub Przybyło Jean-François Saclé Mariusz Woźniak 《Graphs and Combinatorics》2013,29(5):1329-1336
We consider proper edge colorings of a graph G using colors of the set {1, . . . , k}. Such a coloring is called neighbor sum distinguishing if for any pair of adjacent vertices x and y the sum of colors taken on the edges incident to x is different from the sum of colors taken on the edges incident to y. The smallest value of k in such a coloring of G is denoted by ndiΣ(G). In the paper we conjecture that for any connected graph G ≠ C 5 of order n ≥ 3 we have ndiΣ(G) ≤ Δ(G) + 2. We prove this conjecture for several classes of graphs. We also show that ndiΣ(G) ≤ 7Δ(G)/2 for any graph G with Δ(G) ≥ 2 and ndiΣ(G) ≤ 8 if G is cubic. 相似文献
908.
909.
Simple iron gall inks composed of gallic acid, ferrous sulfate, and gum arabic and in some cases also of copper(II) sulfate
were prepared. The process of iron ion complex formation with gallic acid was investigated using UV-VIS spectroscopy, pH measurements,
and by monitoring the concentration changes of Fe(II) ions. The admixture of Fe(II) ions to gallic acid induced a bathochromic
shift of absorption bands at 215 nm and 265 nm in the UV-VIS spectra. Formation of a new absorbance band in the visible area
was also observed and used to calculate the initial rate of complex formation. Concurrently, the pH values and the concentration
of Fe(II) ions in the solution decreased. Gum arabic significantly enhanced the complex formation and its stability. On the
contrary, the addition of Cu(II) ions to the solution decelerated the complex formation considerably.
Dedicated to Professor L’ubomír Lapčík, DrSc., in honor of his 70th birthday 相似文献
910.
Comparison of potentials stability of different types of solid contact lead selective electrodes is presented. Conducting polymer based sensors (hydrophilic and conducting - poly(3,4-ethylenedioxythiophene) or hydrophobic and semiconducting-polyoctylthiophene) were studied in parallel with coated wire and hydrogel (poly(hydroxyethylmethacrylate)) contact electrodes. The within day and between days potential stability was compared, highlighting the effect of sensor storing conditions. The obtained results clearly demonstrate that different conclusions on stability of sensors’ potential can be drawn depending on experimental protocol applied. Polyoctylthiophene based contacts show superior within day stability with no influence of dry storage. On the other hand, a chronopotentiometric method of stability evaluation clearly prefers poly(3,4-ethylenedioxythiophene) based sensors, pointing to smallest resistance and polarizability. It is clearly shown that the choice of experimental conditions applied to test stability can favor particular type of contact used.The inductively coupled plasma mass spectrometry with laser ablation (LA-ICP-MS) experiments conducted for different arrangements tested has shown that for poly(3,4-ethylenedioxythiophene) and poly(hydroxyethylmethacrylate) type contacts longer contact time with lead(II) solution results in changes in the elemental composition of the transducer layer. On the other hand, in line with high stability observed under potentiometric conditions, no changes were seen for polyoctylthiophene based transducer. 相似文献