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91.
92.
Elena Molteni Giovanni Onida Giancarlo Cappellini 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(4):98
We study the electronic properties of the Si(001):Uracil, Si(001):Thymine, andSi(001):5-Fluorouracil systems, focusing on the Si dimer-bridging configuration withadsorption governed by carbonyl groups. While the overall structural and electronicproperties are similar, with small differences due to chemical substitutions, much largereffects on the surface band dispersion and bandgap show up as a function of the molecularorientation with respect to the surface. An off-normal orientation of the molecular planesis favored, showing larger bandgap and lower total energy than the upright position. Wealso analyze the localization of gap-edge occupied and unoccupied surface states. 相似文献
93.
94.
In presence of tin(II) bromide, noble metals give coloured products which are suitable for spcctrophotometric determinations. The colours are red (platinum), yellow-orange (rhodium), yellow-brown (palladium), yellow (iridium) and violet (gold) They are extracted, except for gold, with isoamyl alcohol Platinum, rhodium and palladium can be separated from irdium, and rhodium and platinum from palladium. Rhodium and platinum can be determined simultaneously. 相似文献
95.
Placido Giannetto Giovanni Sindona Nicola Uccella 《Journal of heterocyclic chemistry》1978,15(1):49-52
The unimolecular processes of some methylenoxazolidinones bombarded in the gas phase by electrons have been investigated by MIKE analysis, precise mass measurements and isotopic labelling studies. The overall delocalisation effect of the substitution on the nitrogen contained has been ascertained through the study of the reaction mechanism and of the possible reacting ionic structures. 相似文献
96.
Kinga Suwińska Giovanni Dario Andreetti 《Journal of inclusion phenomena and macrocyclic chemistry》1983,1(1):71-78
C28H36O10. KSCN is monoclinic, space groupP21 withZ=2,a=10.390(3),b=8.959(7),c=16.377(7) Å, =92.49(5)°. FinalR=0.053 for 1437 reflections measured at room temperature. The K– ion lies on the least-squares plane formed by the six oxygen atoms in the macrocyclic ring. The SCN– ion was found on the same face of the macrocycle as the chiral glucopyranoside moiety.Methyl-4,6-O-benzylidene-2,3-O-(1,2-bis(ethoxyethoxy)benzenediyl)--d-glucopyranoside. 相似文献
97.
This investigation represents a first attempt to gain a quantitative estimate of the effects of the anions sulfate, citrate, acetate, chloride and thiocyanate on the thermodynamic stability (DeltaG degrees) of a model globular protein in ice at -15 degrees C. The method, based on guanidinium chloride denaturation of the azurin mutant C112S from Pseudomonas aeruginosa, distinguishes between the effects of cooling to subfreezing temperatures from those induced specifically by the formation of a solid ice phase. The results confirm that, both in liquid and frozen states, kosmotropes (sulfate, citrate and acetate) increase significantly protein stability, relative to chloride, whereas the chaotrope thiocyanate decreases it. Throughout, their stabilizing efficacy was found to rank according to the Hofmeister series, sulfate>citrate>acetate>chloride>thiocyanate, although the magnitude of Delta(DeltaG degrees) exhibited a distinct sensitivity among the anions to low temperature and to ice formation. In the liquid state, lowering the temperature from +20 to -15 degreesC weakens considerably the stabilizing efficacy of the organic anions citrate and acetate. Among the anions sulfate stands out as the only strong stabilizer at subfreezing temperatures while SCN- becomes an even stronger denaturant. Freezing of the solution in the presence the "neutral" salt NaCl destabilizes the protein, DeltaG degrees progressively decreasing up to 3-4 kcal/mol as the fraction of liquid water in equilibrium with ice (VL) is reduced to less than 1%. Kosmotropes do attenuate the decrease in protein stability in ice although in the case of citrate and acetate, their efficacy diminishes sharply as the liquid fraction shrinks to below 2.7%. On the contrary, sulfate is remarkable for it maintains constantly high the stability of azurin in liquid and frozen solutions, down to the smallest VL (0.5%) examined. Throughout, the reduction in DeltaG degrees caused by the solidification of water correlates with the decrease in the denaturant m value, an indirect indication that protein-ice interactions generally lead to partial unfolding of the native state. It is proposed that binding of the kosmotropes to the ice interface may inhibit protein adsorption to the solid phase and thereby counter the ice perturbation. 相似文献
98.
Giovanni Buffa Dr. Luca Dore Prof. Francesca Tinti Dr. Markus Meuwly Prof. 《Chemphyschem》2008,9(15):2237-2244
An experimental and theoretical study of pressure broadening and pressure shift of HCO+ rotational lines perturbed by collisions with He is presented. Results are reported from measurements at 88 K for the lines j=4←3, 5←4 and 6←5 with frequencies ranging from 0.35 to 0.54 THz. Using a new CCSD(T)/aug‐cc‐pVQZ potential energy surface for the He–HCO+ interaction, the collisional line shape parameters are studied from fully quantum and semiclassical calculations. Results from the quantum treatment are in satisfactory agreement with experiments whereas the semiclassical approach can lead to appreciable differences. A study of the dependence of line width Γ and shift s as a function of the translational energy shows the presence of quantum oscillations. Calculations on a previous Hartree–Fock‐based potential energy surface lead to quite similar results for the collisional line shape parameters. Using a simplified version of the potential morphing method it is found that the line width Γ is particularly sensitive to the long‐range part of the potential energy surface. This also explains the success of the first line‐broadening calculations which date back to the 1950s. 相似文献
99.
Giovanni C. Petrucelli Mauricio A. Meirinho Thais R. Macedo Claudio Airoldi 《Thermochimica Acta》2006,450(1-2):16-21
Synthesized hydrated lamellar acidic crystalline magadiite (H2Si14O29·2H2O) nanocompound was used as host for intercalation of polar n-alkylmonoamine molecules of the general formula H3C(CH2)nNH2 (n = 1–6) in aqueous solution. The original interlayer distance (d) of 1500 pm, determined by X-ray powder diffraction patterns, increases after intercalation. The values correlated with the number of aliphatic amine carbon (nc) atoms: d = [(1312 ± 11) + (21 ± 2)]nc. The amount of intercalated amines (Ns), decreased as nc increased: Ns = [(5.82 ± 0.04) − (0.45 ± 0.01)]nc. The acidic layered nanocompound was calorimetrically titrated with the amines and the thermodynamic data gave exothermic values for all guest molecules, as shown by the correlation: ΔintH = −[(24.45 ± 0.49) − (1.91 ± 0.10)]nc and d = [(1576 ± 16) − (10.8 ± 1.0)]ΔintH. The negative values of the Gibbs energies and the positive entropies also presented the correlations: ΔintG = −[(22.8 ± 0.2) − (0.2 ± 0.1)]nc and ΔintS = [(6 ± 1) + (5 ± 1)]nc, respectively. 相似文献
100.
Dattilo D Armelao L Maggini M Fois G Mistura G 《Langmuir : the ACS journal of surfaces and colloids》2006,22(21):8764-8769
We report the immobilization of a fulleropyrrolidine, bearing a dec-9-ynyl functionality, on silicon surfaces through a thermal hydrosilylation protocol. Contact angle measurements on porous silicon (PS) surfaces reveal an unusual dependence of the angle with the PS roughness that apparently contradicts Wenzel's formula. This result has been explained by an extension of Wenzel's model in which the critical angle, which discriminates between the hydrophilic/hydrophobic character of a solid material, is substantially reduced below 90 degrees by surface roughness. 相似文献