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1.
B. Szafran P. S
p J. Adamowski S. Bednarek 《Physica E: Low-dimensional Systems and Nanostructures》2003,18(4):523-529
We present a theoretical study of the charging spectra in natural and artificial atoms. We apply a model electrostatic potential created by a homogenously charged sphere. This model potential allows for a continuous passage from the Coulomb potential of the nucleus to parabolic confinement potential of quantum dots. We consider electron systems with N=1,…,10 electrons with the use of the Hartree–Fock method. We discuss the qualitative similarities and differences between the chemical potential spectrum of electron systems bound to nucleus and confined in quantum dots. 相似文献
2.
TERESA HŁADOŃ JAN Pawlaczyk BARBARA Szafran 《Journal of inclusion phenomena and macrocyclic chemistry》2000,36(1):1-8
The ibuprofen--cyclodextrin inclusion complex was prepared by theco-precipitation method. The identity of the obtained product was verified by X-ray and thermogravimetric techniques. The effect of -cyclodextrin on the stability of ibuprofen was analysed. 相似文献
3.
Barbara Szafran Jan Pawlaczyk 《Journal of inclusion phenomena and macrocyclic chemistry》1995,23(4):277-288
The 1 : 1 inclusion complex involving sulfafurazole (SF) and-cyclodextrin (-CD) is prepared by the freeze-drying method and characterized on the basis of its chemical analysis, thermal behavior, infrared spectrum, X-ray powder pattern and13C NMR spectrum in DMSO-d6 solution. The stability constant of the inclusion complex was determined by the solubility method. The effect of cyclodextrin on the UV absorption spectrum of sulfafurazole was also observed. 相似文献
4.
The rate constants have been measured for deprotonation reaction of substituted N-phenacyl-pyridinium bromides, in the pyridine ring, with 1,4-diazabicyclo[2,2,2]octane in water and DMSO, and some with 1,8-diazabicyclo[5,4,0]undec-7-ene. The dependence of the rate constant, k, on pKa of substituted pyridines is made of two distinct linear branches obtained for the salts with electron-withdrawing and electron-donating substituents, respectively. The structures of four salts have been determined by the B3LYP/6-31G(d,p) level of theory and compared with the available X-ray structure. The effect of the substituent and solvent on k values has been discussed. 相似文献
5.
Rate constants for the deprotonation reaction of N-phenacyl-4-R-pyridinium bromides (R=H, CH3, CN) with 1,4-diazabicyclo[2.2.2]octane were measured in three silicon polypodands, Me2Si24, EtSi34 and PhSi34. Silicon polypodands as open molecular capsules lower the deprotonation rates but increase the stability of the formed ylides in comparison to DMSO and water. 相似文献
6.
Mati Karelson Toomas Tamm Alan R. Katritzky Miroslaw Szafran Michael C. Zerner 《International journal of quantum chemistry》1990,37(1):1-13
We examine solvent effects on carbon radical and ionic centers of HCXY by including a self-consistent reaction-field into the AM 1 and MNDO electronic structure models to mimic dielectric effects. We find that such concepts as merostability are principally solvent effects, and that, as expected, molecules with large dipoles or with charge assymmetry are stabilized more by solvent than those with atoms that are more electrically neutral. Of some importance in this study is the finding that conformation is also dependent on solvation and that change in geometry must be considered if an accurate estimate is to be made of energy differences such as those examined in the calculations of merostabilization. 相似文献
7.
B. Szafran F.M. Peeters S. Bednarek J. Adamowski 《Physica E: Low-dimensional Systems and Nanostructures》2005,26(1-4):252
Wigner molecules formed at high magnetic fields in circular and elliptic quantum dots are studied by exact diagonalization (ED) and unrestricted Hartree–Fock (UHF) methods with multicenter basis of displaced lowest Landau level wave functions. The broken symmetry states with semi-classical charge density constructed from superpositions of the ED solutions are compared to the UHF results. UHF overlooks the dependence of the few-electron wave functions on the actual relative positions of electrons localized in different charge puddles and partially compensates for this neglect by an exaggerated separation of charge islands which are more strongly localized than in the exact broken-symmetry states. 相似文献
8.
Osmotic coefficients measured by vapour pressure osmometry are reported for benzene solutions of complexes of pyridine with trifluoroacetic, dichloroacetic and chloroacetic acids at 25°C. Solute activities decrease with increasing concentration due to formation of self-associates. It is suggested that dipole-dipole interactions contribute substantially to the stability of the associates. 相似文献
9.
1,4-Dimethylpiperazine mono-betaine (1-carboxymethyl-1,4-dimethylpiperazinium inner salt, MBPZ) crystallizes as monohydrate. The crystals are orthorhombic, space group Pccn. Two MBPZ molecules and two water molecules form a cyclic oligomer, (MBPZ·H2O)2. The O–H···O and O–H···N hydrogen bonds are of 2.769(1) and 2.902(1) Å, respectively. The dimers interact with the neighboring molecules through the C–H···O hydrogen bonds of 3.234(1) Å. The piperazine ring assumes a chair conformation with the N(4)–CH3 and N+(1)–CH2COO− groups in the equatorial position and the N+(1)–CH3 group in the axial one. The FTIR spectrum is compared with that calculated by the B3LYP/6-31G(d,p) level of theory. 相似文献
10.
In this study, we thoroughly analyzed molecular gradient generation, its stability over time, and linearity in our high-throughput drug screening microfluidic assay (HTS). These parameters greatly affect the precision and accuracy of the device’s analytical protocol. As part of the research, we developed a mathematical model of dependence of the concentration profile on the initial concentrations of active substances in reservoirs and the number of tilts, as well as the dependence of the active substance concentration profiles in the culture chambers on the concentration profile of the reference dye in the indicator chamber. The mean concentration prediction error of the proposed equations ranged from 1.4% to 2.4% for the optimized parameters of the procedure and did not increase with the incubation time. The concentration profile linearity index, Pearson’s correlation coefficient reached −0.997 for 25 device tilts. The observed time stability of the profiles was very good. The mean difference between the concentration profile after 5 days of incubation and the baseline profile was only 7.0%. The newly created mathematical relationships became part of the new HTS biochip operating protocols, which are detailed in the article. 相似文献