Full-text resources of PSJD and other databases are now available in the new Library of Science.
Visit https://bibliotekanauki.pl
Preferences help
Polish version English version Language
enabled [disable] Abstract
Number of results

Results found: 7

Number of results on page
first rewind previous Page / 1 next fast forward last

Search results

help Sort By:

help Limit search:
first rewind previous Page / 1 next fast forward last
1
Content available remote

Absolute Structure Determination in Absence of Heavy Scatterers

100%
Grochowski J.
Acta Physica Polonica A
|
1997
|
vol. 91
|
issue 4
745-756
EN
Methods of absolute structure determination for molecules containing only light atoms (C, H, N, O) are discussed in the paper. This experimentally difficult problem has a direct application in the structure determination of naturally originated compounds and modern chiral drugs. Several experimental methods of absolute structure determination like electron diffraction, multiple X-ray diffraction and X-ray anomalous scattering techniques are briefly discussed and compared. An application of dedicated azimuthal scan method for the case of hexamethylenetetramine is given as an illustration of this technique.
2
Content available remote

Resonant Scattering of Light Atoms - Measuring Methods and Applications

63%
Grochowski J., Serda P.
Acta Physica Polonica A
|
1992
|
vol. 82
|
issue 1
147-156
EN
The paper describes measuring methods of weak resonant scattering signals occurring in X-ray diffraction pattern of a crystal containing light atoms (C, N, O, F) in its unit cell. Difficulties resulting from the large distance on the energy scale between the K-absorption edges of light atoms and contemporary available energy range of X-ray sources for diffraction experiments may be overcome using mixed synchrotron radiation and sealed tube measurements. Techniques such as high resolution synchrotron radiation diffraction experiment, low resolution azimuthal scan, top reflection azimuthal scan are discussed and their applications are presented. Several enantiomer correctness indicators, evaluating the confidence level of absolute structure determination, are applied for crystals containing oxygen or nitrogen as anomalous scatterers. Resonant scattering of light atoms, which are fundamental constituents of organic molecules and polymers, carries the information about the absolute structure. Growing importance of stereospecific drugs which follows recent recognition of drug-receptor interaction mechanism increases the demand for determination of drug molecule handedness. Investigation of absolute structure for molecules in their original shape (without the introduction of heavy anomalous scatterers) is potentially a vast application field of the described methodology.
3
Content available remote

Optimization of Azimuthal Scan Procedure for Absolute Structure Determination

63%
Grochowski J., Serda P.
Acta Physica Polonica A
|
1997
|
vol. 91
|
issue 5
961-968
EN
The paper describes the application of the azimuthal scan technique for absolute structure determination using X-ray anomalous dispersion. A diffraction pattern with rotation around the scattering vector provides information about various anisotropic effects: absorption, extinction and multi-beam interaction. Recording of azimuthal scans for Friedel pairs is proposed as an alternative to single reflection measurement. Several factors affecting the smoothness of the azimuthal scan curves are discussed and a procedure for eliminating various sources of errors, involving a Fourier filtering, is proposed in order to increase feasibility of chiral discrimination.
4
Content available remote

Temperature Cross-Sensitivity for Highly Refractive Index Sensitive Nanocoated Long-Period Gratings

45%
Grochowski J., Myśliwiec M., Mikulic P., Bock W., Śmietana M.
|
EN
There is a demand for highly refractive index sensitive devices simultaneously insensitive to temperature (T) changes. We investigate both T and refractive index sensitivity of long-period gratings coated with 100 nm thin high refractive index (n ≈ 1.9 at λ = 1550 nm) silicon nitride (SiN_{x}) film. The long-period gratings with period of 500 μm were induced in standard Corning SMF28 fibre using electric arc and nanocoated with SiN_{x} by radio frequency plasma enhanced chemical vapour deposition method. As a sensorial effect we investigated resonance shift with temperature variations (from 30 to 70°C) for measurement in deionized water (n_{D} = 1.33) and glycerine (n_{D} = 1.46). In case of measurements in water for resonance observed at λ = 1510 nm, refractive index sensitivity of - 85 nm/RIU and temperature sensitivity of 0.09 nm/C (H_2O) were obtained which gives refractive index-T sensitivity ratio (RI/T) of - 944°C/RIU. Refractive index and T sensitivity of sensor covered with SiN_{x} film increased to - 618 nm/RIU and 0.22 nm/°C, respectively. Thanks to nanocoating deposition, refractive index-T sensitivity ratio was improved by factor of 3. In case of measurements in glycerine significant influence of glycerine's thermo-optic coefficient on obtained results was observed. It is worth noticing that SiN_{x} coating stabilizes sensing behaviour of the sensor.
5
Publication available in full text mode
Content available

Structural Characterization of Carane Derivative Stereoisomers - Potent Local Anesthetics

39%
Grochowski J., Serda P., Pasenkiewicz-Gierula M., Czarnecki R., Librowski T., Lochyński S., Frąckowiak B.
Acta Physica Polonica A
|
2002
|
vol. 101
|
issue 5
665-674
EN
The paper reports on structural investigation and phase analysis of a newly synthesized potent local anesthetic with chiral molecular structure. Absolute structure and absolute configuration on four chiral centres was determined using microcrystalline single-crystal diffraction with anomalous scattering of X-ray radiation azimuthal scan technique. Phase analysis for new compound (KP23SS) and its epimer (KP23RS) was carried out using classical and synchrotron radiation powder diffraction. Enantiopurity of the bulk material was verified for both isomers by comparison of experimental and simulated high-resolution powder diffraction diagrams. The presence of two new polymorphic phases of KP23RS was documented. Comparative conformational analysis was carried out using differential Fourier synthesis and least-squares molecule overlap technique. A model of epimeric disorder was discussed for the homochiral phase.
6
Content available remote

Effect of Wet Etching of Arc-Induced Long-Period Gratings on Their Refractive Index Sensitivity

39%
Myśliwiec M., Grochowski J., Krogulski K., Mikulic P., Bock W., Śmietana M.
Acta Physica Polonica A
|
2013
|
vol. 124
|
issue 3
521-524
EN
The paper presents highly refractive index sensitive operation of long-period gratings enhanced by wet etching of the fiber cladding. Long-period gratings with period of 283 μm were induced in Corning SMF28 optical fibre using electric arc technique. Then etching in hydrofluoric (HF) acid solution has been applied to improve operation of the sensor. Sensitivity improvement effect induced by fiber cladding reduction has been numerically simulated. The developed numerical model enables quick estimation of cladding thickness reduction essential to achieve dispersion turning point. At this point long-period gratings reaches maximum sensitivity to external medium refractive index. Simulation showed that dispersion turning point for this long-period grating is achieved by cladding thickness reduction of 1.7 μm. We obtained good simulation match with experimental results, where approximately the same thickness was etched. The refractive index sensitivity of the long-period grating-based sensor has been improved by factor of 5. Since long-period grating period is limited when using electric arc fabrication method, this physical limitation makes difficult achievement of dispersion turning point and reaching maximum sensitivity of the long-period grating. We show that sensitivity of electric arc induced long-period grating can be significantly improved by post processing techniques such as wet etching.
7
Content available remote

Capability of Semiconducting NiO Films in Gamma Radiation Dosimetry

27%
Guziewicz M., Jung W., Grochowski J., Borysiewicz M., Golaszewska K., Kruszka R., Baranska A., Piotrowska A., Witkowski B., Domagala J., Gryzinski M., Tyminska K., Stonert A.
Acta Physica Polonica A
|
2011
|
vol. 120
|
issue 6A
A-69-A-72
EN
Electrical properties of RF magnetron sputtered p-NiO films were characterized after fabrication and after gamma irradiations using ^{137}Cs and ^{60}Co sources. Electrical parameters are obtained from the Hall measurements, impedance spectroscopy and C-V measurement of n-Si/p-NiO junction diodes. The results show that resistivity of the NiO film is gradually increased following after sequential irradiation processes because of the decrease in holes' concentration. Hole concentration of a NiO film decreases from the original value of 4.36 × 10^{16} cm^{-3} to 2.86 × 10^{16} cm^{-3} after ^{137}Cs γ irradiation with doses of 10 Gy. In the case of γ irradiation from ^{60}Co source, hole concentration of the film decreases from 6.3 × 10^{16}/cm^3 to 4.1 × 10^{16}/cm^3 and to 2.9 × 10^{16}/cm^3 after successive expositions with a dose of 20 Gy.
first rewind previous Page / 1 next fast forward last
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.