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1

Modification influence on the structural parameters of polymer ophthalmic materials

Chamerski K., Korzekwa W., Miedzinski R., Filipecki J.

Optica Applicata

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2016

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Vol. 46, nr 1

47--55

EN

Studies on polymer materials used in ophthalmological surgery as intraocular implants are presented in this paper. The material under investigation were brand new lenses provided by Alcon. The first lens, model SA60AT, was the basis structure, whereas the other one, model SN60AT, was a structure with an added modification in the form of a blue light chromophore. Results obtained with the use of the positron annihilation lifetime spectroscopy, as well as UV-vis-NIR methods, showed that the structure modified by the chromophore becomes more packed, while the results obtained by means of the UV-vis-NIR methods showed that the modification restricts the blue light transmission.

2

Analysis of free volumes and light transmission in hydrogel and silicone-hydrogel polymer contact lenses

Kocela A., Miedzinski R., Filipecka K., Filipecki J.

Optica Applicata

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2016

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Vol. 46, nr 1

35--45

EN

The free volume holes and light transmission of hydrogel and silicone-hydrogel polymer contact lenses were investigated. As the material, the Proclear family (omafilcon A) of hydrogel contact lenses and the Biofinity family (comfilcon A) of silicone-hydrogel contact lenses were used. Positron annihilation lifetime spectroscopy was used to characterize geometrical sizes and fractions of the free volume holes in the investigated samples. There was a clear difference in the size of free volume holes and the fractional free volume between silicone-hydrogel and hydrogel polymer contact lenses. These changes are shown by a thorough analysis of the long-lived component of lifetime of ortho-positronium. At the same time, UV-vis-NIR in the spectral range 200-1000 nm studies were performed on the same samples of contact lenses spectrometry.

3

Analiza porównawcza struktury wewnętrznej implantów hydrofilowych oraz hydrofobowych stosowanych w chirurgii okulistycznej metodą spektroskopii czasów życia pozytonów

Chamerski K.

Technical Issues

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2015

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nr 3

3--10

EN

In presented work internal structures of intraocular lenses were analyzed in terms of defectiveness degree. Studies were conducted by means of positron annihilation lifetime spectroscopy method PALS. The aim of the work was determination of basic parameters describing annihilation centers in research materials, such as positron lifetime in bulk material, mean positron lifetime in the internal structure, positron trapping rate by trapping centers as well as free volumes dimensions. In obtained results differences in free volumes and positron traps concentrations between hydrophilic and hydrophobic materials were noted. Furthermore, comparison of materials with and without blue light chromophores revealed differences in positron trapping rate by multivacancy-like free spaces. Achieved results were referenced for mechanical properties of the studied materials.

4

Understanding electron-positron momentum densities in solids : effect of the positron distribution

Rubaszek A.

Nukleonika

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2015

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Vol. 60, No. 4, part 1

759--763

EN

The influence of the positron distribution on the electron-positron (e-p) momentum densities (MDs) is studied in terms of the l (l = s, p, d, f) character of the initial electronic state. The effect of the positron is discussed for momenta in the extended and reduced zone scheme on the example of Al (simple metal), Cu (metal with almost filled d shell), and Cr (transition metal). Present result indicates a weak sensitivity of the e-p MD inside the central Fermi surface to the positron charge density for the delocalized s and p electrons. In the case of d states, the effect of the positron on the relevant contribution to the e-p MD directly reflects the degree of localization of d electrons in the electron density of states.

5

Studies of unicellular microorganisms Saccharomyces cerevisiae by means of positron annihilation lifetime spectroscopy

Kubicz E., Jasińska B., Zgardzińska B., Bednarski T., Białas P., Czerwiński E., Gajos A., Gorgol M., Kamińska D., Kapłon Ł., Kochanowski A., Korcyl G., Kowalski P., Kozik T., Krzemień W., Niedźwiecki S., Pałka M., Raczyński L., Rajfur Z., Rudy Z., Rundel O., Sharma N. G., Silarski M., Słomski A., Strzelecki A., Wieczorek A., Wiślicki W., Zieliński M., Moskal P.

Nukleonika

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2015

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Vol. 60, No. 4, part 1

749--753

EN

Results of positron annihilation lifetime spectroscopy (PALS) and microscopic studies on simple microorganisms, brewing yeasts, are presented. Lifetime of ortho-positronium (o-Ps) were found to change from 2.4 to 2.9 ns (longer-lived component) for lyophilized and aqueous yeasts, respectively. Also hygroscopicity of yeasts in time was examined, allowing to check how water – the main component of the cell – affects PALS parameters, thus lifetime of o-Ps were found to change from 1.2 to 1.4 ns (shorter-lived component) for the dried yeasts. The time sufficient to hydrate the cells was found below 10 hours. In the presence of liquid water, an indication of reorganization of yeast in the molecular scale was observed. Microscopic images of the lyophilized, dried, and wet yeasts with best possible resolution were obtained using inverted microscopy (IM) and environmental scanning electron microscopy (ESEM) methods. As a result, visible changes to the surface of the cell me mbrane were observed in ESEM images.

6

Positron annihilation studies of high-manganese steel deformed by rolling

Dryzek E., Sarnek M., Wróbel M.

Nukleonika

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2015

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Vol. 60, No. 4, part 1

709--712

EN

Positron annihilation spectroscopy (PAS) has been used to study the annealing behavior of cold rolled Fe – 21 wt% Mn steel with 0.05 wt% C. After the initial annealing of defects shown by Doppler broadening of the annihilation line, a slight increase in the annihilation line shape parameter, i.e., the so-called S parameter and then its decrease in the temperature range between 225◦C and 450◦C indicates generation of new defects and their subsequent annealing. This temperature range coincides with X-ray diffraction measurements, which indicate reversion of deformation-induced ε-martensite. However, for annealing in this temperature range with slow cooling of the sample, the formation of ferrite already starts. The results are compared with our previous results for deformed austenitic stainless steel 1.4301 (EN) where only reversion of deformation-induced α'-martensite was detected.

7

Positron annihilation in liquid crystals

Dryzek E., Juszyńska-Gałązka E.

Nukleonika

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2015

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Vol. 60, No. 4, part 1

703--708

EN

Positron annihilation studies of liquid crystals are reviewed with particular reference to thermotropic liquid crystals with rod-like molecules. The studies of compounds exhibiting smectic A or smectic E phases indicate that local arrangement of dipole molecules play an important role because high electron density at the end group of molecules can influence substantially formation and annihilation of positronium. The obtained ortho-positronium lifetimes in these phases can be explained by antiparallel pairing of molecules in case of the smectic A phase or a structure with a nanosegregation of alkyl chains and others parts of molecules into sublayers and liquid-like state of alkyl chains in case of the smectic E phase.

8

PALS investigations of free volumes thermal expansion of J-PET plastic scintillator synthesized in polystyrene matrix

Wieczorek A., Zgardzińska B., Jasińska B., Gorgol M., Bednarski T., Białas P., Czerwiński E., Gajos A., Kamińska D., Kapłon Ł., Kochanowski A., Korcyl G., Kowalski P., Kozik T., Krzemień W., Kubicz E., Niedźwiecki S., Pałka M., Raczyński L., Rudy Z., Rundel O., Sharma N. G., Silarski M., Silarski A., Strzelecki A., Wiślicki W., Zieliński M., Moskal P.

Nukleonika

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2015

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Vol. 60, No. 4, part 1

777--781

EN

The polystyrene doped with 2,5-diphenyloxazole as a primary fluor and 2-(4-styrylphenyl)benzoxazole as a wavelength shifter prepared as a plastic scintillator was investigated using positronium probe in wide range of temperatures from 123 to 423 K. Three structural transitions at 260, 283, and 370 K were found in the material. In the o-Ps intensity dependence on temperature, the significant hysteresis is observed. Heated to 370 K, the material exhibits the o-Ps intensity variations in time.

9

Comparison of the free volume sizes and shapes determined from crystallographic and PALS data

Tydda M., Jasińska B.

Nukleonika

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2015

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Vol. 60, No. 4, part 1

771--775

EN

Two different classes of molecular crystals were investigated. The first group was benzenediols, which are characterized by the same chemical composition but a different organization of their crystallographic structures; all of the compounds from this group have only one kind of free volumes. The second class was represented by olanzapine, which has more complex chemical composition and two kinds of free volumes in the structure. The o-Ps lifetime values determined from positron annihilation lifetime spectroscopy (PALS) measurements agree quite well with those calculated for sizes found from crystallographic data for benzenediols (agreement within 10% of the lifetime values). For olanzapine, a good agreement is observed in the case of cuboidal free volumes, while for the other kind of void, the agreement is less satisfactory. Positronium diffusion coefficient determined from o-Ps redistribution in olanzapine agrees with these found for polymers.

10

Studies of CdI2-Bi3 microstructures with optical methods, atomic force microscopy and positron annihilation spectroscopy

Karbovnyk I., Bolesta I., Rovetskii I, Velgosh S, Klym H.

Materials Science Poland

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2014

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Vol. 32, No. 3

391--395

EN

Results of the comprehensive morphological study of CdI2–BiI3 layered crystals are presented. Direct AFM observations of micro- and nanostructures formed in the volume of the crystals confirm the predictions made on the basis of positron annihilation spectroscopy studies. The model explaining the possible pores formation mechanism is proposed and validated by the results of luminescence measurements at 8 K.

11

Nieniszczące badania warstwy wierzchniej stali metodą wykorzystującą anihilację pozytonów

Zaleski K., Zaleski R.

Przegląd Mechaniczny

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2013

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nr 2

37--40

PL

Właściwości warstwy wierzchniej są bardzo ważną cechą elementów maszyn. W pracy przedstawiono wyniki badań doświadczalnych warstwy wierzchniej stali C45 i 100Cr6 metodami wykorzystującymi anihilację pozytonów Badane próbki były obrabiane metodą nagniatania wibracyjnego. Obróbka nagniataniem powodowała powstawanie ściskających naprężeń własnych w warstwie wierzchniej próbek. Badania anihilacji pozytonów były prowadzone metodą rozkładu kątowego promieniowania pochodzącego z anihilacji dwufotonowej pozytonów oraz spektroskopii czasów życia pozytonów Na podstawie wyników badań stwierdzono, że naprężenia własne w warstwie wierzchniej badanych stali mają wpływ na parametry anihilacji pozytonów.

EN

Properties of the surface layer are very important feature of machine elements. In the paper the results of the surface layer study by positron annihilation methods have been presented for 45C and 100Cr6 steels. Tested samples were treated by vibratory shot peening. The shot peening treatment created compressive residual stresses in the surface layer of the samples. Angular distribution of the two-quanta annihilation radiation and positron annihilation lifetime spectroscopy were used in the study. Results of the experiment revealed, that various residual stresses in the surface layer of the tested steels reflect in different positron annihilation parameters.

12

Uniqueness of studies on electron densities in the extended momentum space

Kontrym-Sznajd G.

Nukleonika

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2013

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Vol. 58, No. 1

203-206

EN

This work draws attention to the fact that by measuring electronic structure via angular correlation of positron radiation (ACAR) and Compton scattering experiments one probes electron densities in the extended momentum space, directly related to the electron Bloch wave functions. Presenting some examples of electron densities in the extended and reduced momentum spaces, it is demonstrated what kind of information concerning the electronic structure can be obtained depending on the considered space. It is also shown how the knowledge of the symmetry selection rules allows to separate various Fermi surfaces and establish Fermi momenta.

13

Positron annihilation studies of mesoporous iron modified MCM-41 silica

Wiertel M., Surowiec Z., Budzyński M., Gac W.

Nukleonika

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2013

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Vol. 58, No. 1

245-250

EN

MCM-41 silica materials modified by iron incorporation in the stage of its synthesis were investigated. The aim of the studies was determination of the nature of iron species and the influence of its content on the structural changes of materials and following the changes of their properties. For this purpose, the N2 sorption/desorption method and positron annihilation lifetime spectroscopy (PALS) were used. Disappearance of the longest-lived ortho-positronium (o-Ps) component (tau5) present in the PALS spectra of the initial MCM-41 material in the spectra of Fe-modified MCM-41 measured in vacuum is a result of a strong chemical o-Ps quenching and/or the Ps inhibition mechanism. Filling of pores by air or N2 at ambient pressure causes reappearance of the (tau5) component with lifetime shortened in comparison to that observed in vacuum for pure MCM-41 to the extent which can be explained by usual paramagnetic quenching in air. In contrary to the tendency observed for (tau5) lifetime which is practically independent of Fe content, the relevant intensity I5 monotonically decreases. This fact suggests that only inhibition of Ps formation occurs for the samples in air. Observed anti-quenching effect of air seems to be a result of competition of two processes : neutralization of surface active centres acting as inhibitors and considerably weaker paramagnetic quenching by O2 molecules.

14

Positron annihilation in precious and common opals

Chojcan J., Sachanbiński M., Idczak R., Konieczny R.

Nukleonika

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2013

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Vol. 58, No. 1

225-228

EN

The nano-porosity structure of several non-crystalline opal samples of different origin was investigated with positronium atoms. The obtained data show that the structure depends on both the kind of opal (precious, common or hyalite) as well as the place of its creation (sedimentary or volcanic rocks). The sizes of the pores "seen" by positronium atoms are relatively small, not greater than about 1 nm for all studied samples which may suggest that the pores are located inside the silica matter from which the samples are made. Moreover, the pores detected in the "sedimentary" precious opals are smaller and have less diverse sizes than those found in 'sedimentary" common opals and "volcanic' precious opals.

15

Momentum distributions in positron annihilation with tightly bound electrons in Al

Boroński E.

Nukleonika

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2013

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Vol. 58, No. 1

211-214

EN

An approach based on Carbotte, Salvadori and Chiba two-body schemes for calculation of electron-positron (e-p) momentum densities ro(p) for core electrons in solids is developed. The approach allows to avoid such common approximations as the local density approximation (LDA) etc. in determination of ro(p) of deeper atomic shells and reduces the contribution to ro(p) for higher momenta. Thus, the final calculations of the Doppler spectra of annihilation radiation yield lower values for greater momenta than those obtained within the LDA scheme. The exemplary calculations for Al are presented.

16

Influence of neoplastic therapy on the investigated blood using positron annihilation lifetime spectroscopy

Pietrzak R., Borbulak S., Szatanik R.

Nukleonika

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2013

|

Vol. 58, No. 1

199-202

EN

The influence of neoplastic radiotherapy and chemotherapy was investigated using annihilation lifetime spectroscopy in blood types 0 Rh+ -AB Rh+. Changes in the parameters of the longest lived component of the spectrum were analyzed depending on the time between the moment of taking the blood sample from a patient and that of taking measurements, and also the time passing from the cessation of radio- and chemotherapy.

17

Gas filling of SBA - 15 silica micropores probed by positron annihilation lifetime spectroscopy (PALS)

Gorgol M., Zaleski R., Kierys A.

Nukleonika

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2013

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Vol. 58, No. 1

229-233

EN

Positron annihilation lifetime measurements were conducted in situ while two gasses (nitrogen and oxygen, respectively) were introduced into the SBA-15 porous silica sample. Slow changes in lifetime spectra were observed during a long lasting gas interaction with the sample. Introduced gases slowly filled the free volumes, starting from the smallest ones, especially small micropores. In the presence of a gas, the rate of change of ortho-positronium (o-Ps) and unbound positron intensity was larger than the rate of change of lifetime. This suggests the existence of an additional process, which reduces the number of ortho-positronium atoms due to the interaction with the gas. Moreover, the process of filling pores with gas was slower than the process of emptying them while the gas was pumped out.

18

Annealing behaviour of plastically deformed stainless steel 1.4307 studied by positron annihilation methods

Dryzek E., Sarnek M., Siemek K.

Nukleonika

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2013

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Vol. 58, No. 1

215-219

EN

Isochronal and isothermal annealing of stainless steel 1.4307 samples deformed by compression were investigated using Doppler broadening measurements of the annihilation line. We made an attempt to describe the obtained dependencies in terms of vacancy migration and sinking to the grain boundaries. The model assumed spherical grains with a homogeneous initial distribution of vacancies. The model was capable of following the isochronal annealing data quite accurately. However, the obtained activation energy of vacancy migration equal to 0.44 plus or minus 0.05 eV seemed too low. The isothermal annealing dependency was reproduced less precisely. The reason for this may be the presence of the alfa'-martensite particles in the samples, which can introduce additional defects seen by positrons in the temperature range in which the martensite reversion takes place.

19

Zastosowanie metody PALS do oceny stopnia zdefektowania struktury szkieł tlenkowych ołowiowo-bizmutowo-galowych

Golis E., Filipecki J., Reben M., Wasylak J.

Szkło i Ceramika

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2012

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R. 63, nr 3

26-28

PL

W pracy zaprezentowano badania struktury szkieł tlenkowych ołowiowo-bizmutowo-galowych z wykorzystaniem metody spektrometrii czasów życia anihilujących pozytonów PAL. Obliczone parametry wychwytu pozytonów w badanych szkłach pozwalają wyciągać wnioski dotyczące stopnia i charakteru zdefektowania struktury szkieł. Korelacja otrzymanych wyników z własnościami magnetooptycznymi pozwala na formułowanie hipotez dotyczących wpływu defektów struktury szkieł na ich własności magnetooptyczne. Otrzymane wyniki badań wskazują na postawienie hipotezy, że na własności magnetooptyczne badanych szkieł ma wpływ nie ilość a wielkość defektów oraz istnienie swobodnych objętości w strukturze szkła.

EN

Positron lifetime spectroscopy PALS has been applied to the investigation of lead-bismuth-gallium glass structure. The calculated parameters of positrons trapping in the studied glasses allow to draw conclusions about the defect degree and nature of glass structure. The correlation of obtained results with magneto-optic properties allows to formulate hypotheses concerning the influence of defects in the structure onto their magneto-optical properties. The obtained results of studied glasses suggest that size of defects and the existence of free volume in the glass have significant influence on magneto-optical properties.

20

Spektroskopia czasów życia pozytonów jako narzędzie badań stopnia zdefektowania materiałów o strukturze nieuporządkowanej

Golis E., Filipecki J., Kocela A.

Materiały Ceramiczne

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2012

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T. 64, nr 2

177-180

PL

W pracy przedstawiono wykorzystanie spektroskopii czasów życia pozytonów PALS do badania stopnia zdefektowania materiałów o strukturze nieuporządkowanej. Jako materiałów badawczych użyto następujących próbek: szkło tlenkowe, szkło chalkogenidkowe i polimer. Metoda PALS jest szczególnie czuła na wykrywanie w materiałach o strukturze nieuporządkowanej defektów strukturalnych, w których pułapkowany może być zarówno pozyton (defekty liniowe), jak i pozyt (luki, wolne objętości). W wyniku przeprowadzonych pomiarów otrzymano krzywe opisujące zależność liczby zliczeń aktów anihilacyjnych w funkcji czasu. Rozkład widma czasu życia pozytonów był przeprowadzony na trzy składowe t1, t2 i t3. Składowa t1 jest odpowiedzialna za anihilację swobodną pozytonów i anihilację z elektronami defektów punktowych typu wakans. Składowa t2 związana jest z występowaniem defektów objętościowych powstających na granicach międzyziarnowych, dyslokacji lub skupisk wakansów. Składowa t3 przypisywana jest do anihilacji pick-off oznaczającej pułapkowanie orto-pozytu, o-Ps, przez wolne objętości i daje informację o geometrycznych parametrach tych wolnych objętości. Obliczone parametry wychwytu pozytonów i pozytu w badanych, nieuporządkowanych strukturalnie materiałach pozwalają wyciągnąć wnioski dotyczące stopnia i charakteru zdefektowania badanych materiałów.

EN

The paper presents the use of positron lifetime spectroscopy PALS to study the defect degree of structures of disordered materials. Oxide glass, chalcogenide glass and polymer were used in the study. The PALS method is particularly sensitive to detect the structure of disordered materials with structural defects that can trap both the positron (linear defects) and positronium (the free volume). As a result of the measurements, curves describing the dependence of the number of counts of annihilation acts as a function of time were obtained. The positron lifetime spectra were resolved into three components t1, t2 and t3. The component t1 is responsible for the free positron annihilation and the annihilation with electrons of vacancy-type point defects. The component t2 is related to the presence of bulk defects that arise at the grain boundaries, dislocations or clusters of vacancies. The component t3 is assigned to the pick-off annihilation of ortho-positronium (o-Ps) by the free volume, and gives information on the geometric parameters of the free volume. The calculated parameters of uptake of the positron and positronium in the structurally disordered materials under consideration allowed us to draw conclusions about the degree and nature of their defects.