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Open access

Jerzy Łukaszewicz and Krzysztof Zieliński

Durability and narrow pore size distribution (PSD) of carbons fabricated from Salix viminalis wood

Microporous carbon molecular sieves of extremely narrow pore size distribution were obtained by carbonization of a novel raw material (Salix viminalis). The precursor is inexpensive and widely accessible. The pore capacity and specific surface area are upgradable by H3PO4 treatment without significant change of narrowed PSD. The dominating pore size indicates that these molecular sieves are a potential competitor to other nanoporous materials such as opened and purified carbon nanotubes.

Open access

Dominik Tomaszewski and Jerzy Zieliński

Abstract

Wax layer formation accompanies the processes of epidermis and cuticle formation. To examine these changes, observationsalong current-year long shoots of four woody species (Acer negundo, A. rufinerve, Gymnocladus dioica, and Gingko biloba) were made. Long shoots are suitable objects for such observations, because from the same stem, several samples can be obtained that represent a well-defined sequence of fragments of different ages.

The data that were obtained from different and sometimes distant stem regions suggest that epicuticular wax crystals appear on the stems very early and quickly, since they are found near the stem apex during intensive plant growth. This was confirmed for the four examined species. Some differences, however, were noted.

Very rapid production of prominent wax crystals was observed in stems. In an experiment involving mechanical wax removal from the A. negundo stem surface and subsequent analysis of the surface after several days via scanning electron microscopy (SEM), it was shown that wax regenerates very quickly. After only several hours, new emerging crystals were observed and their morphologies were essentially the same. Nearly full regeneration was observed several days after removal.

Open access

Sadowski Jerzy, WoŁosz Paweł, Zieliński Janusz, Niźnikowski Tomasz and Buszta Mariusz

Abstract

Introduction. The purpose of this investigation was to examine the structure of coordination motor abilities (CMA) in male basketball players at different levels of competition. Material and methods. The study included 183 male basketball players from 10 Polish sports clubs. The examined groups consisted of seniors (n=42) aged 24.5 (± 3.3), juniors (n=37) aged 16.8 (± 0.6), cadets (n=54) aged 14.5 (± 0.1) and children (n=50) aged 13.4 (± 0.2). A battery of motor tests was administered to assess the following CMA: kinesthetic differentiation of movements, spatio-temporal orientation, reaction time, movement coupling, sense of balance, sense of rhythm and adjustment of movements. The structure of CMA under investigation was determined based on the results of Hotelling's principal component analysis in Tucker's modification, completed with Kaiser's Varimax rotation [1, 2]. Results. The CMA structure of basketball players was composed of three or four factors. Most often these included rhythm, movement differentiation, movement coupling and adjustment of movements. Less frequently the structure consisted of spatio-temporal orientation, balance and reaction time. An in-depth analysis of the CMA structure revealed that factors ranged from heterogeneous (children and cadets) to homogeneous ones (juniors and seniors). The distribution of identified factors in the common variance was the smallest in children and cadets (58.9% and 62.9%, respectively) and the biggest in juniors and seniors (69.3% and 68.48%, respectively).

Open access

Artur Adamczak, Waldemar Buchwald, Jerzy Zieliński and Sebastian Mielcarek

We determined the level of flavonoids, citric acid and ascorbic acid in hips of rose species from the Caninae section occurring in Poland. We performed phytochemical analyses of 75 samples representing 11 species: Rosa agrestis Savi, R. canina L., R. dumalis Bechst., R. glauca Pourret, R. inodora Fries, R. jundzillii Besser, R. rubiginosa L., R. sherardii Davies, R. tomentosa Sm., R. villosa L. and R. zalana Wiesb. Flavonoid content was determined spectrophotometrically, and organic acid concentrations by HPLC. The content of the studied compounds varied greatly. Interspecific differences in the amount of flavonoids and ascorbic acid were highly significant. The most common species, Rosa canina, showed low average content of vitamin C (0.51 g/100 g of dry matter) and flavonoids (41 mg/100 g DM) and high content of citric acid (3.48 g/100 g DM). Ascorbic acid was highest in R. villosa hips (avg. 2.25 g/100 g DM), flavonoids were highest in R. rubiginosa (72 mg/100 g DM), and citric acid was highest in R. tomentosa (4.34 g/100 g DM). Flavonoid level correlated negatively with the amount of citric acid (r=-0.47, p<0.001). Cluster analysis of rose species based on the content of the investigated compounds confirmed the validity of the division of sect. Caninae into three subsections: Rubiginosae, Vestitae and Rubrifoliae. The phytochemical variation of these roses reflects their probable phylogenetic relationships as determined from morphology.

Open access

Lech Raczyński, Paweł Moskal, Paweł Kowalski, Wojciech Wiślicki, Tomasz Bednarski, Piotr Białas, Eryk Czerwiński, Aleksander Gajos, Łukasz Kapłon, Andrzej Kochanowski, Grzegorz Korcyl, Jakub Kowal, Tomasz Kozik, Wojciech Krzemień, Ewelina Kubicz, Szymon Niedźwiecki, Marek Pałka, Zbigniew Rudy, Piotr Salabura, Neha Gupta-Sharma, Michał Silarski, Artur Słomski, Jerzy Smyrski, Adam Strzelecki, Anna Wieczorek, Marcin Zieliński and Natalia Zoń

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.