Wyniki wyszukiwania - BazTech

1

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

|

2015

|

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.

2

Searches for discrete symmetries violation in ortho-positronium decay using the J-PET detector

Kamińska D., Gajos A., Czerwiński E., Bednarski T., Białas P., Gorgol M., Jasińska B., Kapłon Ł., 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., Słomski A., Strzelecki A., Wieczorek A., Wiślicki W., Zieliński M., Zgardzińska B., Moskal P.

Nukleonika

|

2015

|

Vol. 60, No. 4, part 1

729--732

EN

In this paper, we present prospects for using the Jagiellonian positron emission tomograph (J-PET) detector to search for discrete symmetries violations in a purely leptonic system of the positronium atom. We discuss tests of CP and CPT symmetries by means of ortho-positronium decays into three photons. No zero expectation values for chosen correlations between ortho-positronium spin and momentum vectors of photons would imply the existence of physics phenomena beyond the standard model. Previous measurements resulted in violation amplitude parameters for CP and CPT symmetries consistent with zero, with an uncertainty of about 10−3. The J-PET detector allows to determine those values with better precision, thanks to the unique time and angular resolution combined with a high geometrical acceptance. Achieving the aforementioned is possible because of the application of polymer scintillators instead of crystals as detectors of annihilation quanta.

3

Reconstruction of hit time and hit position of annihilation quanta in the J-PET detector using the Mahalanobis distance

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

Nukleonika

|

2015

|

Vol. 60, No. 4, part 1

765--769

EN

The J-PET detector being developed at the Jagiellonian University is a positron emission tomograph composed of the long strips of polymer scintillators. At the same time, it is a detector system that will be used for studies of the decays of positronium atoms. The shape of photomultiplier signals depends on the hit time and hit position of the gamma quantum. In order to take advantage of this fact, a dedicated sampling front-end electronics that enables to sample signals in voltage domain with the time precision of about 20 ps and novel reconstruction method based on the comparison of examined signal with the model signals stored in the library has been developed. As a measure of the similarity, we use the Mahalanobis distance. The achievable position and time resolution depend on the number and values of the threshold levels at which the signal is sampled. A reconstruction method as well as preliminary results are presented and discussed.

4

Processing optimization with parallel computing for the J-PET scanner

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

Nukleonika

|

2015

|

Vol. 60, No. 4, part 1

745--748

EN

The Jagiellonian Positron Emission Tomograph (J-PET) collaboration is developing a prototype time of flight (TOF)-positron emission tomograph (PET) detector based on long polymer scintillators. This novel approach exploits the excellent time properties of the plastic scintillators, which permit very precise time measurements. The very fast fi eld programmable gate array (FPGA)-based front-end electronics and the data acquisition system, as well as low- and high-level reconstruction algorithms were specially developed to be used with the J-PET scanner. The TOF-PET data processing and reconstruction are time and resource demanding operations, especially in the case of a large acceptance detector that works in triggerless data acquisition mode. In this article, we discuss the parallel computing methods applied to optimize the data processing for the J-PET detector. We begin with general concepts of parallel computing and then we discuss several applications of those techniques in the J-PET data processing.

5

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

|

2015

|

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.