15 research outputs found
INFLUENCE OF MOTION OF THE LOAD DISTRIBUTED OVER A GIVEN LENGTH ON BENDING MOMENT AND SHEAR FORCE IN A TRACK MODELLED AS TIMOSHENKO BEAM
The object of consideration is a track modelled by Timoshenko beam resting on inertialess,
viscoelastic foundation of non-linear characteristic. The beam is subjected to load
distributed over a given length and moving at a constant velocity. Stationary vibrations
of the beam are described by two ordinary differential equations of the fourth order determined
from the system of two partial differential equations.
To analyze the influence of non-linearity, the method of approximation presented
in [2] was applied. The study of the load motion velocity on extreme values of bending
moments and shear forces in a track was considered taking into account the assumed types
of non-linearities
Structural properties of cyclic polyelectrolytes in dilute good solvent
Cyclic polymers display unique physical behaviors in comparison to their
linear counterparts. Theoretical, computational and experimental studies have
revealed that some of their distinctive properties are also observed in charged
variants of cyclic polymers, known as cyclic polyelectrolytes (PEs), especially
in terms of their structural responses to variations in the strength of
electrostatic interactions. In this study, we investigate the impact of cyclic
topology on the conformations of PE chains in dilute good solvent using scaling
analysis and coarse-grained bead-spring molecular dynamics simulations. Our
observations indicate that, in contrast to linear PE chains, cyclic topology
results in more compact conformations at low and intermediate Bjerrum lengths.
Moreover, two structural metrics, asphericity and prolateness, which quantify
deviations from spherical and flat molecular shapes, exhibit non-monotonic
behaviors for cyclic PEs. This stands in contrast to linear PEs, where these
shape characteristics exhibit a monotonic trend with increasing Bjerrum length.
A feasible analytical theory, developed to account for ionic distributions
around cyclic PE chains, suggests that the fundamental difference between
linear and cyclic chain conformations may be attributed to topological effects
influencing long-range electrostatic interactions
Cadmium inhibitory action leads to changes in structure of ferredoxin:NADP+ oxidoreductase
This study deals with the influence of cadmium on the structure and function of ferredoxin:NADP(+) oxidoreductase (FNR), one of the key photosynthetic enzymes. We describe changes in the secondary and tertiary structure of the enzyme upon the action of metal ions using circular dichroism measurements, Fourier transform infrared spectroscopy and fluorometry, both steady-state and time resolved. The decrease in FNR activity corresponds to a gentle unfolding of the protein, caused mostly by a nonspecific binding of metal ions to multiple sites all over the enzyme molecule. The final inhibition event is most probably related to a bond created between cadmium and cysteine in close proximity to the FNR active center. As a result, the flavin cofactor is released. The cadmium effect is compared to changes related to ionic strength and other ions known to interact with cysteine. The complete molecular mechanism of FNR inhibition by heavy metals is discussed. Electronic supplementary material The online version of this article (doi:10.1007/s10867-012-9262-z) contains supplementary material, which is available to authorized users
Cadmium inhibitory action leads to changes in structure of ferredoxin:NADP+ oxidoreductase
Methods for generating the random processes in the dynamics of vehicles
W artykule przedstawiono różne metody generowania procesów przypadkowych, szczególnie przydatne w analizie i badaniach symulacyjnych dynamiki pojazdów. Zamieszczono przykłady realizacji procesów przypadkowych z użyciem opisanych metod. Przedstawiono ważne cechy omawianych metod.The article presents the different methods of generating the random processes, particularly useful in the analysis and the simulation testing of vehicle dynamics. The examples of random processes realization with using the described methods are placed. The important features of the discussed methods are presented
Factors for Bioeconomy Development in EU Countries with Different Overall Levels of Economic Development
The aim of this article is to indicate the rationale for the development of the bioeconomy in selected EU countries depending on their overall level of economic development. The research was based on four highly developed countries, i.e., Germany, France, Finland and Denmark, and four medium-developed countries, i.e., Poland, Hungary, Czech Republic, and Slovakia for the period 2001–2018. Renewable energy consumption, biomass and agricultural production were analysed as determinants of the bioeconomy development. The question was also answered whether differences in terms of measures determining the level of bioeconomy development between countries with different levels of economic development during the studied period are decreasing or increasing, using sigma (σ)-convergence coefficients. It is shown that the development of the bioeconomy of the studied countries is related to their level of economic development. In the middle economically developed countries, real opportunities for the development of the bioeconomy are noted, through a high share of agriculture in national income; and in highly developed countries—high spending on research and development and the growth of eco-innovation, which contributes to maintaining a development advantage between these groups of countries
MTA-type cement based on ZnO-enriched tricalcium silicate – evaluation of cytotoxicity and bactericidal activity
W artykule przedstawiono wyniki badań in vitro dotyczące cytotoksyczności i działania bakteriobójczego materiału do stosowania w endodoncji – cementu typu MTA (ang. Mineral Trioxide Aggregate) o nowym składzie chemicznym. Cement wytworzono na bazie krzemianu trójwapnia wzbogaconego ZnO i płynu będącego 15% roztworem CaCl2 , a jako czynnik wprowadzający kontrast RTG zastosowano ZrO2 . Wytworzony cement MTA oceniono poprzez scharakteryzowanie właściwości fizykochemicznych obejmujących: czas wiązania, wytrzymałość na ściskanie, a także kontrast RTG i bioaktywność w roztworze symulującym osocze (SBF). Do zbadania wpływu ziaren ZrO2 na ilość i wielkość porów w cemencie wykorzystano technikę mikrotomografii komputerowej (µCT). Działanie cytotoksyczne cementów oceniano przez zastosowanie referencyjnej linii komórkowej L-929. Warunki hodowli komórkowej w kontakcie z badanymi materiałami lub ekstraktami z cementów oceniano za pomocą analizy obrazu lub testu kolorymetrycznego MTT. Do badania aktywności przeciwbakteryjnej wykorzystano dwa szczepy paciorkowców: Streptococcus mutans i Streptococcus sanguinis. Opracowany cement typu MTA charakteryzuje się odpowiednimi właściwościami użytkowymi i spełnia wymagania zawarte w normie PN-EN ISO 10993-5:2009 „Biologiczna ocena wyrobów medycznych, część 5: Badania cytotoksyczności in vitro”. Jednak, aby mógł być rozważany jako bezpieczny wyrób medyczny do wypełniania wstecznego kanałów korzeniowych, wymaga dalszych badań.The article presents the results of in vitro cytotoxicity and bactericidal activity of MTA-type cement (Mineral Trioxide Aggregate) for endodontics with a new chemical composition. The cement was made on the basis of ZnO-enriched tricalcium silicate and a liquid being a 15% CaCl2 solution. ZrO2 was used as an X-ray radiopacity agent in the cement. The produced MTA-type cement was assessed by characterizing the physicochemical properties including: setting time, compressive strength, as well as X-ray radiopacity and bioactivity in a simulated body fluid (SBF). Microtomography technique (µCT) was used to investigate the effect of ZrO2 grains on the number and size of pores in the cement. The cytotoxic activity of the cements was assessed by using the reference L-929 cell line. Cell culture conditions in contact with test materials or cement extracts were assessed by image analysis or MTT colorimetric test. Two strains of streptococci were used to test the antibacterial activity: Streptococcus mutans and Streptococcus sanguinis. The developed MTA cement has appropriate functional properties and meets the requirements of the PNEN ISO 10993-5:2009 standard "Biological evaluation of medical devices, Part 5: In vitro cytotoxicity tests". However, in order to be considered a safe medical device for retrograde root canal filling, it requires further research