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141.
Halina M. Ratajczak John A. Ladd W.J. Orville-Thomas Henryk Ratajczak 《Molecular physics》2013,111(4):1019-1025
The 14N quadrupolar relaxation time for pyrrole as the pure liquid and in solution in 1,4-dioxan, pyridine, 3,5-lutidine and 2-fluoropyridine has been determined from the line-shape analysis of the imido proton magnetic resonance signal. The dependence of the line shape on solute concentration and temperature was studied and the activation parameters for molecular reorientation determined. 相似文献
142.
Michael Quentin Dirk Blondin Janina Klasen Rotem Shlomo Lanzman Falk-Roland Miese Christian Arsov Peter Albers Gerald Antoch Hans-Jörg Wittsack 《Magnetic resonance imaging》2012
Purpose
To evaluate which mathematical model (monoexponential, biexponential, statistical, kurtosis) fits best to the diffusion-weighted signal in prostate magnetic resonance imaging (MRI).Materials and Methods
24 prostate 3-T MRI examinations of young volunteers (YV, n= 8), patients with biopsy proven prostate cancer (PC, n= 8) and an aged matched control group (AC, n= 8) were included. Diffusion-weighted imaging was performed using 11 b-values ranging from 0 to 800 s/mm2.Results
Monoexponential apparent diffusion coefficient (ADC) values were significantly (P<.001) lower in the peripheral (PZ) zone (1.18±0.16 mm2/s) and the central (CZ) zone (0.73±0.13 mm2/s) of YV compared to AC (PZ 1.92±0.17 mm2/s; CZ 1.35±0.21 mm2/s). In PC ADCmono values (0.61±0.06 mm2/s) were significantly (P<.001) lower than in the peripheral of central zone of AC. Using the statistical analysis (Akaike information criteria) in YV most pixels were best described by the biexponential model (82%), the statistical model, respectively kurtosis (93%) each compared to the monoexponential model. In PC the majority of pixels was best described by the monoexponential model (57%) compared to the biexponential model.Conclusion
Although a more complex model might provide a better fitting when multiple b-values are used, the monoexponential analyses for ADC calculation in prostate MRI is sufficient to discriminate prostate cancer from normal tissue using b-values ranging from 0 to 800 s/mm2. 相似文献143.
Mariusz Pluska Andrzej CzerwinskiJacek Ratajczak Anna SzerlingJerzy Kątcki 《Physica B: Condensed Matter》2012,407(15):2854-2857
Cathodoluminescence (CL) in scanning electron microscopy (SEM) is commonly accepted as revealing local properties of a specimen region illuminated by an electron beam. CL is widely used to visualize defects in semiconductor structures. However, the presence of a strong electric field in, for example, heterojunctions or p–n junctions causes a separation of generated electron–hole (e–h) pairs and suppresses recombination in the specimen region excited by the beam. As a result CL – a radiative recombination – becomes quenched. At the same time, electron beam-induced current (EBIC) flows throughout the structure, which may produce secondary electroluminescence that is registered by the CL detector. Consequently, the CL measurement is distorted and if there are defects in the structure, they remain unrevealed. The current study shows that registration of the CL signal for different values of electron beam current (including high ones) enables true defect detection in semiconductor layers with built-in electric field. Results for a special test structure prepared with focused ion beam on AlGaAs/GaAs laser heterostructures with an 8 nm InGaAs quantum well are presented. 相似文献
144.
Steady-state spectroscopic studies of two ortho (-OCH3 and -OH) derivatives of methyl p-dimethylaminobenzoate have been performed. The absorption spectra of molecules under study are analyzed taking into consideration results of quantum chemical semiempirical calculations. The fluorescence spectra of these molecules possess in polar solvents two bands, i.e., the locally excited and intramolecular charge transfer (ICT) fluorescence band. Their intensity ratio as well as the fluorescence/phosphorescence intensity ratio determined at 77 K depends on the solvent polarity. Theoretical studies of the TICT phenomenon have been made in order to explain the dual emission of molecules under study. Calculated electric dipole moments of these molecules in the ground, S0, and excited, S1(LE) and S1(ICT) states, have been compared with experimentally determined data. Theoretically determined transition energies, ΔEi, oscillator strengths, fi, and electric dipole moments μS0, μS1(LE) and μS1(ICT) of the planar donor-acceptor (D/A) conformer agree with experimental data. According to Marcus theory inner- and outer-solvatation sphere reorganization energies (λout, λin) are calculated using the determined spectroscopic properties of molecules under study. 相似文献
145.
Płuska M Czerwinski A Ratajczak J Katcki J Oskwarek L Rak R 《Micron (Oxford, England : 1993)》2009,40(1):46-50
The electron-microscope image distortion generated by electromagnetic interference (EMI) is an important problem for accurate imaging in scanning electron microscopy (SEM). Available commercial solutions to this problem utilize sophisticated hardware for EMI detection and compensation. Their efficiency depends on the complexity of distortions influence on SEM system. Selection of a proper method for reduction of the distortions is crucial. The current investigations allowed for a separation of the distortions impact on several components of SEM system. A sum of signals from distortion sources causes wavy deformations of specimen shapes in SEM images. The separation of various reasons of the distortion is based on measurements of the periodic deformations of the images for different electron beam energies and working distances between the microscope final aperture and the specimen. Using the SEM images, a direct influence of alternating magnetic field on the electron beam was distinguished. Distortions of electric signals in the scanning block of SEM were also separated. The presented method separates the direct magnetic field influence on the electron beam below the SEM final aperture (in the chamber) from its influence above this aperture (in the electron column). It also allows for the measurement of magnetic field present inside the SEM chamber. The current investigations gave practical guidelines for selecting the most efficient solution for reduction of the distortions. 相似文献
146.
N.A. Atamas A.M. Yaremko T. Seeger A. Leipertz A. Bienko Z. Latajka H. Ratajczak A.J. Barnes 《Journal of Molecular Structure》2004,708(1-3):189-195
The experimental and theoretically predicted Raman spectra for the first few alkanes in the homologous series: methane, ethane, propane and butane are presented for the region 2700–3100 cm−1. The structure of the spectra is rather complex. Analysis of the results obtained shows that Fermi resonance occurs between the CH stretching vibrations in the 3000 cm−1 region and the 2ν overtones of deformation vibrations in the low frequency (1450–1500 cm−1) region. 相似文献
147.
Z. Latajka H. Ratajczak K. Romanowska Z. Tomczak 《Journal of organometallic chemistry》1977,139(2):129-133
A systematic CNDO/2 study has been carried out on the molecular complexes formed between dimethylberyllium and aliphatic amines. It has shown that the calculated molecular properties of these complexes, viz. the interaction energy, amount of charge transferred and the enhancement of the dipole moment are related to the ionization potential of the amine. The results are discussed in terms of the Mulliken's charge transfer theory. 相似文献
148.
Phenyltin compounds are known to be biologically active. Their chemical structure suggests that they are likely to interact with the lipid fraction of cell membranes. Using fluorescence and NMR techniques, the effect of phenyltin compounds on selected regions of model lipid bilayers formed from phosphatidylcholine was studied. The polarization of N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) dipalmitoyl-L -phosphatidylethanolamine and desorption of praseodymium ions was used to probe the polar region, whereas the polarization of 1 - (4 - trimethylammoniumphenyl) - 6 - phenyl - 1,3,5-hexatriene p-toluenesulfonate measured the hydrophobic core of the membrane. In addition, changes in the N-(5-fluoresceinthiocarbanoly)dipalmitoyl - L - α - phosphatidyl - ethanolamine fluorescence intensity indicated the amount of charge introduced by organotin compounds to the membrane surface. There were no relevant changes of measured parameters when tetraphenyltin was introduced to the vesicle suspension. Diphenyltin chloride causes changes of the hydrophobic region, whereas the triphenyltin chloride seems to adsorb in the headgroup region of the lipid bilayer. When the hemolytic activity of phenyltin compounds was measured, triphenyltin chloride was the most effective whereas diphenyltin chloride was much less effective. Tetraphenyltin causes little damage. Based on the presented data, a correlation between activity of those compounds to hemolysis (and toxicity) and the location of the compound within the lipid bilayer could be proposed. In order to inflict damage on the plasma membrane, the compound has to penetrate the lipid bilayer. Tetraphenyltin does not partition into the lipid fraction; therefore its destructive effect is negligible. The partition of the compound into the lipid phase is not sufficient enough, by itself, to change the structure of the lipid bilayer to a biologically relevant degree. The hemolytic potency seems to be dependent on the location of the compound within the lipid bilayer. Triphenyltin chloride which adsorbs on the surface of the membrane, causes a high level of hemolysis, whereas diphenyltin chloride, which penetrates much deeper, seems to have only limited potency. © 1998 John Wiley & Sons, Ltd. 相似文献
149.
Zdzisław Latajka Henryk Ratajczak W.J. Orville-Thomas Emil Ratajczak 《Journal of Molecular Structure》1975,28(2):323-328
CNDO/2 molecular orbital calculations have been carried out on the Dewar structures of pyrazine, pyrimidine and pyridazine in order to determine the configurations of minimum energy. 相似文献
150.
Marek J. Potrzebowski Jarosaw Baszczyk Wiesaw R. Majzner Micha W. Wieczorek Janina Baraniak Wojciech J. Stec 《Solid state nuclear magnetic resonance》1998,11(3-4):215-224
high resolution solid state NMR spectroscopy was employed to study structural properties of bis(diisopropoxyphosphorothioyl) diselenide 1 and bis(dineopentoxyphosphorothioyl) diselenide 2. The principal elements Tii of
effective dipolar/chemical shift tensor were calculated from spinning sideband intensities employing the WIN-MAS program. The values of anisotropy and asymmetry parameters reflect the distortion of the selenium environment. It was found that the T33 component mostly contributes to changes in the isotropic chemical shifts.
CP/MAS experiments were used to decide the assignment of space group by counting the number of crystallographically unique selenium centers in the unit cell. Crystals of diselenide 1 are triclinic, space group P
with a=8.485(3) Å, b=8.508(1) Å, c=8.511(2) Å, =98.835(15)°, β=111.653(24)°, γ=93.524(21)°, V=559.5(3) Å3, Dc=1.544(2) g/cm3 and Z=1. Refinement using 2222 reflections for 157 variables gives R=0.037. Crystals of diselenide 2 are triclinic, space group P1 with a=9.1418(8) Å, b=9.1465(8) Å, c=9.9200(9) Å, =74.751(8)°, β=74.629(7)°, γ=82.216(7)°, V=769.7(1) Å3, Dc=1.365(2) g/cm3 and Z=1. Refinement using 3316 reflections for 297 variables gives R=0.0272. 相似文献