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  • Author: Grzegorz Zieliński x
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Preparation of sorbents from selected polymers

Preparation of sorbents from selected polymers

In this work, the results of studies on the preparation of sorbents from selected polymers were presented. The polymers were carbonized and subsequently physically activated by steam or carbon dioxide, or alternatively, chemically activated with potassium hydroxide. For the obtained materials, a specific area was evaluated by means of low-temperature nitrogen adsorption and benzene adsorption, iodine number was also determined. The obtained results indicated a possibility to procure hydrophobic sorbents of microporous structure. Sorbents having the best properties, i.e. the specific area of above 2000 m2/g were produced from poly(ethylene terephthalate) and phenol-formaldehyde resin.

Open access
The influence of the sensitivity of the trapezius muscle on the changes within the bioelectric tensions of the masticatory muscles

Abstract

Introduction. Pathological muscle tone can cause changes in the facial skeleton, including tension headaches, tinnitus, temporomandibular joint dysfunctions. The complexity of pathologies and their spectrum may also indicate changes beyond the facial skeleton. The aim of the study was to determine the possible correlation between the pressure pain threshold of the trapezius muscle and the bioelectrical tension on the masticatory muscles.

Aim. The aim of the study was to determine the possible correlation between the pressure pain threshold of the trapezius muscle and the bioelectric tension on the masticatory muscles.

Material and methods. The number of 36 women applied for the study. They were all examined using an algometer within a trapezius muscle to determine the pressure pain threshold. The electromyographic study was carried out in accordance with the SENIAM guidelines. The resting activity of selected masticatory muscles (temporal and masseter) was recorded for 10 sec. The study involved an 8-channel BioEMG IIITM surface electromyography apparatus with BioPak Measurement System (BioResearch Associates, Inc. Milwaukee, WI, USA). Statistical analysis was carried out using the r-Pearson test. The level of significance was set at 5%.

Results. After comparing the bioelectric tension of the masticatory muscles and the pressure pain threshold, left-sided correlation was observed (p<0.05). Both in the right-hand and general comparison, the results did not reach the required level of statistical significance (p>0.05).

Conclusions. The pressure pain threshold seems to be linked to the bioelectrical muscle tone of the masticatory muscles. To confirm this observation, further research into a larger and more diverse group of participants is recommended.

Open access
Geomorphosite Assessment in the Proposed Geopark Vistula River Gap (E Poland)

Abstract

Geomorphosites are among major assets for the development of geotourism. An accurate assessment of spatial distribution of their scientific, educational and economic characteristics provides the basis for appropriate design and management of proposed geoparks. Although the problem of assessing their value for geotourism has been discussed by numerous authors, consistent methodology for the assessment of geomorphosites has not been devised so far. In the present study, we conducted a geotourist evaluation of geomorphosites located within the proposed geopark Vistula River Gap. We assessed a total of 76 sites using 18 assessment criteria. The results indicate not uniform spatial distribution of sites having the highest value. The application of cluster analysis to evaluation results enabled us to distinguish groups of sites with similar characteristics and thus to identify groups of geomorphosites in relation to which various measures should be taken in order to increase the possibilities of their tourist use.

Open access
Comparison of coagulation behaviour and floc characteristics of polyaluminium chloride (PAX 18, PAX XL19H, ALCAT) with surface water treatment

Abstract

Coagulation behaviour of polyaluminium chloride (PACl) was comparatively investigated in terms of the removal of turbidity and colour with surface water. The growth of flocs was also compared. The results show that the decrease in saturation and values of dissolved oxygen was ca. 20% for ALCAT and PAX 18 at both dosages and 15% for PAX XL 19H, respectively. The floc formation growth indicated that PACl coagulation occurred not only by charge neutralization but also by a form of sweep flocculation. Besides, flocs formed by ALCAT had better sizes than the flocs formed by PAX 18 and PAX XL19H. The rate of sedimentation was stable during coagulation with higher doses, and it was dependent on the substance used.

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

Abstract

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.

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

Abstract

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.

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

Abstract

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.

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

Abstract

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.

Open access
Application of the compress sensing theory for improvement of the TOF resolution in a novel J-PET instrument

Abstract

Nowadays, in positron emission tomography (PET) systems, a time of flight (TOF) information is used to improve the image reconstruction process. In TOF-PET, fast detectors are able to measure the difference in the arrival time of the two gamma rays, with the precision enabling to shorten significantly a range along the line-of-response (LOR) where the annihilation occurred. In the new concept, called J-PET scanner, gamma rays are detected in plastic scintillators. In a single strip of J-PET system, time values are obtained by probing signals in the amplitude domain. Owing to compressive sensing (CS) theory, information about the shape and amplitude of the signals is recovered. In this paper, we demonstrate that based on the acquired signals parameters, a better signal normalization may be provided in order to improve the TOF resolution. The procedure was tested using large sample of data registered by a dedicated detection setup enabling sampling of signals with 50-ps intervals. Experimental setup provided irradiation of a chosen position in the plastic scintillator strip with annihilation gamma quanta.

Open access
Processing optimization with parallel computing for the J-PET scanner

Abstract

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 field 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.

Open access