16 research outputs found
Time resolution of the plastic scintillator strips with matrix photomultiplier readout for J-PET tomograph
Recent tests of a single module of the Jagiellonian Positron Emission
Tomography system (J-PET) consisting of 30 cm long plastic scintillator strips
have proven its applicability for the detection of annihilation quanta (0.511
MeV) with a coincidence resolving time (CRT) of 0.266 ns. The achieved
resolution is almost by a factor of two better with respect to the current
TOF-PET detectors and it can still be improved since, as it is shown in this
article, the intrinsic limit of time resolution for the determination of time
of the interaction of 0.511 MeV gamma quanta in plastic scintillators is much
lower. As the major point of the article, a method allowing to record
timestamps of several photons, at two ends of the scintillator strip, by means
of matrix of silicon photomultipliers (SiPM) is introduced. As a result of
simulations, conducted with the number of SiPM varying from 4 to 42, it is
shown that the improvement of timing resolution saturates with the growing
number of photomultipliers, and that the 2 x 5 configuration at two ends
allowing to read twenty timestamps, constitutes an optimal solution. The
conducted simulations accounted for the emission time distribution, photon
transport and absorption inside the scintillator, as well as quantum efficiency
and transit time spread of photosensors, and were checked based on the
experimental results. Application of the 2 x 5 matrix of SiPM allows for
achieving the coincidence resolving time in positron emission tomography of
0.170 ns for 15 cm axial field-of-view (AFOV) and 0.365 ns
for 100 cm AFOV. The results open perspectives for construction of a
cost-effective TOF-PET scanner with significantly better TOF resolution and
larger AFOV with respect to the current TOF-PET modalities.Comment: To be published in Phys. Med. Biol. (26 pages, 17 figures
Determination of the 3\gamma fraction from positron annihilation in mesoporous materials for symmetry violation experiment with J-PET scanner
Various mesoporous materials were investigated to choose the best material
for experiments requiring high yield of long-lived positronium. We found that
the fraction of 3\gamma annihilation determined using \gamma-ray energy spectra
and positron annihilation lifetime spectra (PAL) changed from 20% to 25%. The
3gamma fraction and o-Ps formation probability in the polymer XAD-4 is found to
be the largest. Elemental analysis performed using scanning electron microscop
(SEM) equipped with energy-dispersive X-ray spectroscop EDS show high purity of
the investigated materials.Comment: 12 pages, 2 figure
MOLECULAR DIAGNOSTICS IN BIOLOGY AND MEDICINE
W ostatnim dziesięcioleciu rozwój i wdrożenie technik molekularnych zrewolucjonizowało diagnostykę i monitorowanie chorób człowieka. Techniki badań kwasów nukleinowych, takie jak genotypowanie DNA mikroorganizmów, analiza polimorfizmu fragmentów restrykcyjnych (RFLP) i reakcja łańcuchowa polimerazy (PCR) przyczyniają się do stałego postępu w laboratoriach diagnostyki medycznej. Analiza sekwencji amplifikowanych fragmentów DNA umożliwia lepszą identyfikację patogenów, wykrywanie zmutowanych genów a także prognozowanie określonych chorób.In the last decade, the development and application of molecular techniques has revolutionised the diagnosis and monitoring of human diseases. Nucleic acids techniques, such as microbial DNA genotyping, analysis of restriction fragment length polymorphism (RFLP) and polymerase chain reaction (PCR), are making progress in medical diagnostic laboratories. Sequence analysis of amplified DNA allows better identification of pathogen, detection of mutant genes and more accurate prognosis of certain diseases
Nano-modified non-woven filter fabrics capable of holding viruses
W przypadku występowania zanieczyszczeń powietrza w postaci niebezpiecznych mikroorganizmów, sensownym staje się zastosowanie specjalnych układów filtracyjnych. Dzięki zastosowaniu odpowiednich materiałów, możemy uzyskać systemy filtracyjne w całości biodegradowalne. Poprzez zmodyfikowanie powierzchni filtra nanowłóknami, zmniejsza się ich średnice porów, równocześnie zwiększając jego powierzchnie właściwą. Dzięki temu skuteczność filtracji potrafi wzrosnąć kilkadziesiąt razy. Stosując odpowiednie metody modyfikacji nanowłókien, otrzymujemy układ filtrów selektywnych. Pozwalają one nie tylko na zatrzymywanie zanieczyszczeń oraz mikroorganizmów, ale także na ich eliminację.In case of presence of air pollution with harmful microorganisms it seems reasonable to make use of specialist filtering systems. As a result of using properly selected materials the filtration systems can be 100% biodegradable. Surface modification of the filter with nano-fibres brings reduction in mesh size and increases the specific surface area of the filter. This leads to the increase in filtering efficiency even by several dozen times. The application of proper methods of surface modification allows for creating a system of selective filters, which not only stop pollutants and micro-organisms but also may eliminate them