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Wyszukujesz frazę "positron lifetime spectroscopy" wg kryterium: Wszystkie pola


Tytuł:
A new approach to the presentation of the positron annihilation lifetime spectroscopy results, n-alkanes
Autorzy:
Zgardzińska, B.
Standzikowski, K.
Powiązania:
https://bibliotekanauki.pl/articles/1057935.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
36.10.Dr
78.70.Bj
82.30.Gg
Opis:
The standard form of the positron annihilation lifetime spectroscopy results presentation are two plots of o-Ps lifetime and intensity as a function of external factor, e.g. temperature, pressure. Both o-Ps parameters change (stepwise) when in the medium phase transitions occur. For a more complete picture of the structural changes occurring in the matter we suggest to use an additional plot, in the coordinates, (τ₃, I₃). The hydrocarbons are selected to show the advantages following from the presentation of the results in the intensity-lifetime (INTI) plot.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1496-1500
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analiza porównawcza struktury wewnętrznej implantów hydrofilowych oraz hydrofobowych stosowanych w chirurgii okulistycznej metodą spektroskopii czasów życia pozytonów
Comparative analysis of internal structures of hydrophilic and hydrophobic implants applied in ophthalmology by means of positron annihilation lifetime spectroscopy
Autorzy:
Chamerski, K.
Powiązania:
https://bibliotekanauki.pl/articles/134780.pdf
Data publikacji:
2015
Wydawca:
ADVSEO
Tematy:
soczewki wewnątrzgałkowe
anihilacja pozytonów
wolna objętość
wielozadaniowość
hydrofilowość
hydrofobowość
chromofory
intraocular lenses
positron annihilation
free volume
multivacancies
hydrophilicity
hydrophobicity
chromophores
Opis:
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.
Źródło:
Technical Issues; 2015, 3; 3-10
2392-3954
Pojawia się w:
Technical Issues
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Badanie wpływu domieszki Gd na stopień zdefektowania struktury szkła tellurowego
Studying influence of element Gd on voids degree of structure the tellurite glass
Autorzy:
Filipecki, J.
Golis, E.
Kotynia, K.
Chamerski, K.
Powiązania:
https://bibliotekanauki.pl/articles/168534.pdf
Data publikacji:
2015
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Ceramiki i Materiałów Budowlanych
Tematy:
szkła tellurowe
defekty
anihilacja
spektroskopia czasów życia pozytonu
tellurite glasses
defects
annihilation
positron lifetime spectroscopy
Opis:
Materiałem badawczym było szkło tellurowe. Badaniom poddano szkło bazowe TeO2-P2O3-ZnO-LiNbO3 oraz szkło domieszkowane gadolinem (TeO2-P2O3-ZnO-LiNbO3)(Gd2O3). W celu dokonania analizy własności strukturalnych wykorzystano metodę pomiarów czasów życia pozytonów PALS (Positron Annihilation Lifetime Spectroscopy). W proponowanej metodzie możliwa jest identyfikacja defektów strukturalnych trudnych do wychwycenia innymi tradycyjnymi metodami pomiarowymi. Przeprowadzone badania wykazały istnienie dwóch składowych czasów życia pozytonów τ1 i τ2. W oparciu o model dwustanowy obliczono parametry wychwytu pozytonów, które pozwalają wyciągnąć wnioski o charakterze i stopniu zdefektowania badanych szkieł tellurowych.
The tellurite glass such as: TeO2-P2O3-ZnOLiNbO3 as a reference glass and (TeO2-P2O3-ZnO-LiNbO3)(Gd2O3) has been studied. The positron lifetime PALS (Positron Annihilation Lifetime Spectroscopy) was used to analyze the structural properties of tellurite glasses. The proposed method, can identify structural defects which are difficult to capture by other traditional methods. The study showed the existence of two components τ1 and ττ. The basis of the two-state model parameters were calculated capture of positrons, which allow you to draw conclusions about the nature and degree of defect studied tellurite glasses.
Źródło:
Szkło i Ceramika; 2015, R. 66, nr 1, 1; 17-19
0039-8144
Pojawia się w:
Szkło i Ceramika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Free Volume of PVA/SSA Proton Exchange Membrane Studied by Positron Annihilation Lifetime Spectroscopy
Autorzy:
Gomaa, M.
Hugenschmidt, C.
Dickmann, M.
Abdel-Hamed, M.
Abdel-Hady, E.
Mohamed, H.
Powiązania:
https://bibliotekanauki.pl/articles/1033241.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
82.47.Gh
78.70.Bj
Opis:
Humidity control and water management in polymer electrolyte membranes for fuel cells are still of high importance to improve the fuel cells' efficiencies. In this study, poly (vinyl alcohol) (PVA)was crosslinked using 15 wt% sulfosuccinic acid (SSA) by a solution casting method and additionally thermally crosslinked at 100°C. Positron annihilation lifetime spectroscopy was used to study the mean free volume size and the distribution at different humidity. A slight decrease in the free volume was found up to a relative humidity of 30% whereas it increases strongly for a relative humidity of more than 30%. The volume of the voids duplicates from 0.036 to 0.078 nm³ by changing the relative humidity from 30 to 80%. Thermogravimetric analyzer was used to determine the thermal stability of the membrane. From thermogravimetric analyzer data, it was found that the PVA with 15 wt% SSA membrane are chemically stable up to 200°C.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1519-1522
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Free-Volume Studies in Polycaprolactone/Poly(propylene oxide) Urethane/Urea Membranes by Positron Lifetime Spectroscopy
Autorzy:
Ferreira Marques, M.
Gordo, P.
de Lima, A.
Queiroz, D.
Norberta de Pinho, M.
Major, P.
Kajcsos, Zs.
Powiązania:
https://bibliotekanauki.pl/articles/1812490.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.41.+e
78.70.Bj
82.30.Gg
Opis:
Positron annihilation lifetime spectroscopy was used to study the free volume parameters in polypropylene oxide-based tri-isocyanate terminated prepolymer/polycaprolactone diol bi-soft urethane/urea membranes (PU/PCL) with PCL content from 5 up to 25 wt%. Positron annihilation lifetime spectroscopy measurements carried out in the temperature range 298-324 K mirrored the phase separation of the various soft and hard segments present in the membranes. The size and amount of free volume holes determined by positron annihilation lifetime spectroscopy appear to be correlated with the $CO_2$ gas permeability through the membranes.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1359-1364
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Gas filling of SBA - 15 silica micropores probed by positron annihilation lifetime spectroscopy (PALS)
Autorzy:
Gorgol, M.
Zaleski, R.
Kierys, A.
Powiązania:
https://bibliotekanauki.pl/articles/147961.pdf
Data publikacji:
2013
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
SBA-15 porous silica
positron annihilation
Opis:
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.
Źródło:
Nukleonika; 2013, 58, 1; 229-233
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hydrolytic Degradation of Poly(L-Lactide-co-Glycolide) Studied by Positron Annihilation Lifetime Spectroscopy and Other Techniques
Autorzy:
Pamuła, E.
Dryzek, E.
Dobrzyński, P.
Powiązania:
https://bibliotekanauki.pl/articles/2047148.pdf
Data publikacji:
2006-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
82.35.-x
82.35.Lr
78.70.Bj
61.18.Fs
82.56.Ub
83.85.Jn
68.37.Ps
Opis:
Changes of the poly(L-lactide-co-glycolide) structure as a function of degradation time in phosphate-buffered saline for 7 weeks were investigated by gel permeation chromatography, differential scanning calorimetry, nuclear magnetic resonance ($\text{}^{1}$H NMR), and positron annihilation lifetime spectroscopy. Surface properties as wettability by sessile drop and topography by atomic force microscopy were also characterized. Chain-scission of polyester bonds in hydrolysis reaction causes a quite uniform decrease in molecular weight, and finally results in an increase in semicrystallinity. Molecular composition of the copolymer and water contact angle do not change considerably during degradation time. Atomic force microscopy studies suggest that the copolymer degrades by "in bulk" mechanism. The average size of the molecular-level free volume holes declines considerably after one week of degradation and remains constant till the sixth week of degradation. The free volume fraction decreases as a function of degradation time.
Źródło:
Acta Physica Polonica A; 2006, 110, 5; 631-640
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of neoplastic therapy on the investigated blood using positron annihilation lifetime spectroscopy
Autorzy:
Pietrzak, R.
Borbulak, S.
Szatanik, R.
Powiązania:
https://bibliotekanauki.pl/articles/147997.pdf
Data publikacji:
2013
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
blood
positron annihilation
Opis:
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.
Źródło:
Nukleonika; 2013, 58, 1; 199-202
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of PCM Microcapsules with Paraffin Filling by Positron Lifetime Spectroscopy
Autorzy:
Zgardzińska, B.
Powiązania:
https://bibliotekanauki.pl/articles/1402636.pdf
Data publikacji:
2015-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
62.23.Pq
61.80.Fe
61.72.-y
61.46.-w
81.07.Nb
64.70.Nd
82.35.Pq
Opis:
Positron annihilation lifetime spectroscopy was applied to investigate the microcapsules composed of n-eicosane (filling material) and polysiloxane polymer (shell) in the range of temperatures 123-333 K. Pure components of microcapsules were also investigated as a base for interpretation of the measurement results. The temperature of phase transitions in microcapsules was determined. It showed the appearance of a rotary phase, which is not present in pure n-eicosane. In the considered material, two types of free volume have been identified. The sizes of free volumes able to accommodate Ps were estimated using standard models. On the basis of the o-Ps intensities, the content of polysiloxane in microcapsules was estimated as about 40%. Internal structure of the microcapsules (morphology) was observed by scanning electron microscopy.
Źródło:
Acta Physica Polonica A; 2015, 127, 5; 1536-1539
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ortho-positronium migration in mesopores of MCM-41, MSF and SBA-3
Autorzy:
Zaleski, R.
Błażewicz, A.
Kierys, A.
Powiązania:
https://bibliotekanauki.pl/articles/147955.pdf
Data publikacji:
2013
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
nitrogen adsorption/desorption
porous materials
positron annihilation lifetime spectroscopy (PALS)
positronium migration
Opis:
Three materials: MCM-41, MSF and SBA-3 with a very similar pore diameter but different lengths of cylindrical pores were investigated using the nitrogen sorption method and positron annihilation lifetime spectroscopy. The size of primary pores and interparticle spaces obtained by both methods is similar. However, volume ratios between the discussed kinds of pores found by the above-mentioned methods differ significantly. Such discrepancy is the result of both ortho-positronium migration and the inaccessibility of the pores for nitrogen. Comparing the results of nitrogen sorption and positron annihilation lifetime spectroscopy allows us to estimate that connectivity between the primary pores and the interparticle spaces is the highest in MCM-41 and lowest in SBA-3.
Źródło:
Nukleonika; 2013, 58, 1; 235-240
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
PALS investigation of resorcinol under high pressure
Autorzy:
Tydda, M.
Jasińska, B.
Pieniążek, A.
Powiązania:
https://bibliotekanauki.pl/articles/147999.pdf
Data publikacji:
2013
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
free volume
ortho-positronium (o-Ps)
pressure
positron annihilation lifetime spectroscopy (PALS)
Opis:
Two kinds of measurements were conducted with resorcinol at high pressure : the first one with the use of a mechanical press and the second one with the use of a gaseous compressor. In the second case, due to some gas penetrating the material structure, the lifetime spectra obtained were difficult to analyze. The free volumes in resorcinol were influenced both by high pressure and the gas coming into the crystallographic structure.
Źródło:
Nukleonika; 2013, 58, 1; 195-198
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
PALS investigations of matrix Vycor glass doped with molecules of luminescent dye and silver nanoparticles. Discrepancies from the ETE model
Autorzy:
Gorgol, M.
Jasińska, B.
Reisfeld, R.
Powiązania:
https://bibliotekanauki.pl/articles/147152.pdf
Data publikacji:
2015
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
positron annihilation lifetime spectroscopy (PALS)
porous glass
lumogen dye ROT-305
silver nanoparticles
Vycor glass
Opis:
A thermal stability of three materials: undoped reference Vycor glass, glass filled with ROT-305 red dye, and silver nanoparticles was investigated by positron annihilation lifetime spectroscopy (PALS) in a broad temperature range (from 93 to 473 K). The attempt of pore size calculations from the ortho-positronium lifetime data was performed using the extended Tao-Eldrup (ETE) model. Below room temperature, a significant decrease in lifetime values of the longest-lived component was found for all the samples. This effect could not be explained by thermal shrinkage of the material and is probably caused by interaction of -Ps with a Vycor glass matrix. The greatest discrepancy from the ETE model predictions was observed for the reference glass. Doping the base material with dye molecules and silver nanoparticles resulted in similar small decrease in this discrepancy. After reheating the samples to the room temperature, the PALS components returned to the initial values. In the temperature range of 293–473 K, quite good agreement between PALS results and the ETE model predictions was observed for the reference glass and the glass incorporated with dye molecules. The observed small discrepancy in this range could possibly be partly explained by thermal expansion of the material. For the glass doped with silver nanoparticles, a significant change in PALS parameters was observed in the temperature range from 403 to 473 K.
Źródło:
Nukleonika; 2015, 60, No. 4, part 1; 717-720
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Photoluminescence and positron annihilation lifetime studies on pellets of ZnO nanocrystals
Autorzy:
Karbowski, A.
Fedus, K.
Patyk, J.
Bujak, Ł.
Służewski, K.
Karwasz, G.
Powiązania:
https://bibliotekanauki.pl/articles/148001.pdf
Data publikacji:
2013
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
photoluminescence (PL)
positron annihilation lifetime spectroscopy (PALS)
X-ray diffraction (XRD)
ZnO nanocrystals
Opis:
We explore the interrelationships between the X-ray diffraction patterns, the photoluminescence spectra and the positron lifetimes obtained from circular pellets composed of commercial ZnO nanoparticles. The experimental results are studied as a function of thermal treatment at different temperatures. X-ray diffractograms reveal the temperature- independent wurtzite phase structure of nanocrystals and show huge enlargement of ZnO grains after annealing at temperatures higher than 700 centigrade. Photoluminescence measurements exhibit two emission bands : a near band edge emission in UV (small tilde 378 nm) and a defect-related broad visible peak with a maximum in the green region ( small tilde 502 nm). The significant enhancement of the green emission at the expense of UV luminescence is observed after sample sintering at 800 and 1000 centigrade. The positron annihilation lifetime spectroscopy (PALS) is applied in order to study the thermally induced evolution of defects. The lifetime components show a step-like dependence on the thermal treatment, but do not follow exactly the variation in crystallographic phases and only vaguely follow differences in photoluminescence. The positron data indicate therefore some additional structural and/or defect changes. The possible origin of green luminescence from ZnO pellets is discussed.
Źródło:
Nukleonika; 2013, 58, 1; 189-194
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Polypropylene/polyhedral oligomeric silsesquioxane nanocomposites – study of free volumes, crystallinity degree and mass flow rate
Nanokompozyty polipropylen/poliedryczne oligomeryczne silseskwioksany – badania objętości swobodnych, stopnia krystaliczności oraz masowego wskaźnika szybkości płynięcia
Autorzy:
Niemczyk, A.
Dziubek, K.
Czaja, K.
Szatanik, R.
Szołyga, M.
Dutkiewicz, M.
Marciniec, B.
Powiązania:
https://bibliotekanauki.pl/articles/947285.pdf
Data publikacji:
2016
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Chemii Przemysłowej
Tematy:
nanocomposites
polypropylene
polyhedral oligomeric silsesquioxanes (POSS)
positron annihilation lifetime spectroscopy (PALS)
crystallinity degree
mass flow rate
polipropylen
poliedryczne oligomeryczne silseskwioksany (POSS)
spektroskopia czasów życia pozytonów (PALS)
stopień krystaliczności
masowy wskaźnik szybkości płynięcia
nanokompozyty
Opis:
Polypropylene/polyhedral oligomeric silsesquioxane (PP/POSS) nanocomposites were prepared by the melt blending method. Positron Annihilation Lifetime Spectroscopy (PALS) was used to study the effects of the structure and of the amount of POSS on the free volumes in PP. The PALS parameters: o-Ps lifetime and its intensity, were compared to the crystallinity degree and to the mass flow rate (MFR) of nanocomposites. The presence of POSS nanofillers affected the PP microstructure and the size and number of free volumes in the polymer. The crystallinity degree was decreased and the intensity of o-Ps component was increased by increasing POSS contents. The MFR values increased for nanocomposites, thus POSS nanoparticles can act as plasticizers and generate more free volumes in PP.
Nanokompozyty polipropylen/poliedryczne oligomeryczne silseskwioksany (PP/POSS) przygotowano metodą mieszania w stanie stopionym polimeru. Wpływ struktury oraz ilości zastosowanych nanonapełniaczy POSS na objętości swobodne w polipropylenie określono z zastosowaniem spektroskopii czasów życia pozytonów (PALS). Ustalono zależności pomiędzy parametrami PALS: czasem życia o-Ps (τ3) inatężeniem (I3) składowej o-Ps oraz wartościami stopnia krystaliczności (Xc) i masowego wskaźnika szybkości płynięcia (MFR) badanych materiałów. Obecność nanonapełniaczy POSS wpłynęła na liczbę i rozmiary objętości swobodnych w polimerze, co spowodowało zmianę mikrostruktury osnowy polipropylenowej. Wraz ze zwiększaniem zawartości napełniaczy POSS zmniejszał się stopień krystaliczności kompozytów, zwiększało natężenie składowej o-Ps, adodatkowo wzrastała wartość MFR – nanocząstki POSS pełniły w układzie rolę plastyfikatorów.
Źródło:
Polimery; 2016, 61, 9; 610-615
0032-2725
Pojawia się w:
Polimery
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Porosity of Silica Monoliths with Tailored Mesopores of Ink-Bottle Shape Determined by Nitrogen Adsorption and Positron Annihilation Lifetime Spectroscopy
Autorzy:
Sienkiewicz, A.
Kierys, A.
Gorgol, M.
Zaleski, R.
Powiązania:
https://bibliotekanauki.pl/articles/1033934.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.Rm
68.43.-h
81.70.-q
78.70.Bj
36.10.Dr
Opis:
The comparison of pore size distributions obtained with the use of two porosimetric methods: low temperature nitrogen sorption (LN2) and positron annihilation lifetime spectroscopy (PALS), was performed for porous silica monoliths. Four investigated samples were prepared under various synthesis conditions. Nitrogen sorption showed the presence of bottle-shaped pores in all investigated samples. In addition, it seems that the presence of methanol during synthesis influences porosity to a greater extent than organic additives. Quite good agreement between the LN2 and PALS results was observed only for the silica monolith synthesized with β-cyclodextrins as pore directing agent. The biggest discrepancy in the results obtained from these two techniques was observed for the silica gel synthesized with no additives. The origin of such discrepancies, taking into account the shape of pore size distribution and deficiencies of data analysis techniques, is discussed.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1568-1571
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł

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