Repozytorium Uniwersytetu Śląskiego RE-BUŚ
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Studies on the Molecular Dynamics at High Pressures as a Key to Identify the Sub-Rouse Mode in PMMS
No full textIn this paper, we have investigated the molecular dynamics of the
associating polymer, poly(mercaptopropyl)methylsiloxane (PMMS), at high
pressure (up to p ∼ 505 MPa) by means of broadband dielectric spectroscopy.
Previous studies revealed that PMMS exhibits two dielectric relaxation processes
observed above the glass transition temperature related, most likely, to either the
mobility within self-assemblies or the sub-Rouse mode (α′-slower process) and
segmental (α-faster process) dynamics, whereas mechanical measurements
revealed only the presence of terminal and segmental relaxations [Tarnacka et
al. Macromolecules 2020, 53 (22), 10225−10233]. In order to determine the origin
of the dielectric α′-process, further high-pressure experiments were performed. It
was found that the timescale separation between relaxation times of segmental (α)
and α′-processes is invariant to the compression, and activation volume calculated
for both kinds of motions is comparable. These dynamical features are
characteristic of the chain relaxation (called usually normal mode) found in type-A polymers. However, because mechanical data
excluded identification of the slow dielectric relaxation as normal mode, we assigned it as the sub-Rouse process. This assignment is
in the line with previous studies on poly(methylphenyl)siloxane. Further density functional theory computations revealed that the
detection of the relatively strong sub-Rouse process is most likely possible due to the presence of a highly polar side group (thiol,
−SH, moiety) that gives a strong contribution to dipole moment along the main polymer backbone. Additionally, we demonstrated
that the pressure coefficient of the glass transition temperature, dTg/dp, in PMMS is one of the smallest among those reported to
date for various polymers (dTg/dp = 156 K/GPa). This quite surprising finding was assigned to the specific interactions formed by
the thiol group. Finally, it should be emphasized that high-pressure experiments turned out to be the key element to identify the sub-
Rouse mode in dielectric spectraa process that might provide important information about the chain dynamics in polysiloxanes.
However, to finally prove this hypothesis, further studies are required to discard the eventual possibility that the slow mode is
somehow related to the nanoscopic organization in PMMS
Artichoke Leaf Extract-Mediated Neuroprotection against Effects of Aflatoxin in Male Rats
No full textAttenuation of adverse effects of aflatoxin (AFB1) in brains of B1 rats by extracts of leaves of artichoke was studied. The active
ingredients in extracts of leaves of artichoke, Cynara scolymus L., were determined by HPLC analysis. In the 42-day
experiment, rats were exposed to either sterile water, 4% DMSO, 100 mg artichoke leaf extract/kg body mass, 72 μg aflatoxin
B1/kg body mass, or AFB1 plus artichoke leaf extract. Neurotoxicity of AFB1 was determined by an increase in profile of lipids,
augmentation of plasmatic glucose and concentrations of insulin, oxidative stress, increased activities of cholinergic enzymes,
and a decrease in activities of several antioxidant enzymes and pathological changes in brain tissue. Extracts of artichoke leaf
significantly reduced adverse effects caused by AFB1, rescuing most of the parameters to values similar to unexposed controls,
which demonstrated that adverse, neurotoxic effects caused by aflatoxin B1 could be significantly reduced by simultaneous
dietary supplementation with artichoke leaf extract, which itself is not toxic
Er(r)go…,
No full texttekst w j. pol. i j. ang.…zbiorowa ślepota ludzkości: antropocen, entropocen. Mnożą się rozmaite entropie: entropia termodynamiczna, entropia biologiczna, entropia psychospołeczna, entropia informacyjna, antyentropia, antropia, negentropia. Niektórzy – nie wszyscy – zauważają pewne konsekwencje: niszczenie bioróżnorodności, nieuporządkowanie, dezorganizację, destrukcję socjoróżnorodności, rozprzestrzenianie fałszywych informacji, destrukturyzację, rozrzedzenie zasobów mineralnych, deregulację klimatu, niszczenie ekosystemów, topnienie lodowców, podnoszenie się poziomu mórz, fale upałów, powodzie, susze, rozproszenie uwagi, niszczenie umiejętności, marazm, apatię, depresje i samobójstwa, utratę zaufania, niezdolność do zawierzenia, upowszechniony mimetyzm, chaos molekularny; takie to skutki antropogenicznych wymuszeń (Fragment tekstu)
Effect of the Topology on Wetting and Drying of Hydrophobic Porous Materials
No full textEstablishing molecular mechanisms of wetting and drying of hydrophobic porous materials is a general problem for science and technology within the subcategories of the theory of liquids, chromatography, nanofluidics, energy storage, recuperation, and dissipation. In this article, we demonstrate a new way to tackle this problem by exploring the effect of the topology of pure silica nanoparticles, nanotubes, and zeolites. Using molecular
dynamics simulations, we show how secondary porosity promotes the intrusion of water into micropores and affects the hydrophobicity of materials. It is demonstrated herein that for nano-objects, the hydrophobicity can be controlled by changing the ratio of open to closed nanometer-sized lateral pores. This effect can be exploited to produce new materials for practical applications when the hydrophobicity needs to be regulated without significantly changing the chemistry or structure of the materials. Based on these simulations and
theoretical considerations, for pure silica zeolites, we examined and then classified the experimental database of intrusion pressures, thus leading to the prediction of any zeolite’s intrusion pressure. We show a correlation between the intrusion pressure and the ratio of the accessible pore surface area to total pore volume. The correlation is valid for some zeolites and mesoporous materials. It can facilitate choosing prospective candidates for further investigation and possible exploitation, especially for energy storage, recuperation, and dissipation
Mapy Sienkiewicza
No full textArtykuł poświęcony włoskim podróżom Henryka Sienkiewicza. Perpektywa uświęconego wielowiekową tradycją Grand Tour zastąpiona zostaje tu jednak doświadczeniem maladycznym. Śmierć Marii, która zmarła na gruźlicę osierociwszy dwójkę dzieci, skazała Sienkiewicza na życie w ciągłym napięciu, w jakimś stanie rozgorączkowanego niepokoju. I właśnie zapis owego niepokoju, lęku, "gorączki" - stanowi tekstowy ślad, kartograficzny zapis "mapujący" doświadczenia rozpadu
SEM-EDS and water chemistry characteristics at the early stages of glacier recession reveal biogeochemical coupling between proglacial sediments and meltwater
No full textMost glaciers worldwide are undergoing climate-forced recession, but the impact of glacier changes on biogeochemical cycles is unclear. This study examines the influence of proglacial sediment weathering on meltwater chemistry at the early stages of glacier recession in the High Arctic of Svalbard. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) in combination with a wide range of geochemical analyses were used in this study. The SEM-EDS analyses of sediments collected in front of Werenskioldbreen show general degradation of pyrite and carbonate grains with age. The outer parts of pyrite grains have a gradual decrease in sulphur and gradual increase in iron oxides due to pyrite oxidation. This process was less advanced in the proglacial zone younger than 100 years compared to older sites such as the terminal moraine from the Little Ice Age. In both the proglacial zone and the terminal moraine, physical weathering of mineral grains, including formation of microcracks and microfractures, clearly enhanced pyrite oxidation. A consequence of proglacial sediment weathering is that the river chemistry is strongly affected by carbonate dissolution driven by sulphuric acid from sulphide oxidation. Also, reactive iron oxides, a product of sulphide oxidation, are mobilized in the proglacial zone. The results of this study show that proglacial weathering in the High Arctic of Svalbard is strongly coupled to river geochemistry, especially during the early stages of proglacial exposure after glacier recession
Coralliths of tabulate corals from the Devonian of the Holy Cross Mountains (Poland)
Full text linkTabulates, an extinct Palaeozoic group of corals, developed diverse colony morphologies during the Silurian to Devonian peak of reef development. Coralliths, or circumrotatory colonies, are passively motile coral colonies constantly overturned by wave action or currents. Such overturning allows tissue growth on all sides of the colony. They are among the most rarely reported growth forms. Recent corallith-forming scleractinian corals mostly inhabit the shallowest reef environments, but coralliths can also develop at greater depths in areas of low topographic relief, unconsolidated substratum, low coral cover and high water movement. Here, we report on Devonian (Givetian Favosites goldfussi and Frasnian Alveolites? tenuissimus) coralla from the Holy Cross Moun-tains, Poland. Our analysis suggests these colonies are coralliths, although less mature than usually reported. These corals, unlike previously described growth forms of this kind, lived in relatively deep environments: probably the upper mesophotic (Givetian, Miłoszów), or deep reef fore-slope (Frasnian, Jaźwica and Kowala). Microfacies analysis of the Ja ́zwica site suggests unconsolidated substratum and high hydrodynamic energy. We conclude that these corals lived in deeper environments where bottom currents caused their autorotation. A good modern analogue for such a corallith-forming environment is the Wistari Channel (Southern Great Barrier Reef), where bottom tidal currents at nearly 30 m of depth are strong enough to overturn colonies of Stylocoeniella cf. guentheri reaching 15 cm in diameter. Our discovery shows that the spectrum of coral growth forms during the Devonian peak of reef development was broader than previously assumed, and that tabulate corals displayed numerous adaptive strategies to various environments
Wsparcie dziecka jąkającego się w środowisku edukacyjnym
Full text linkArtykuł jest poświęcony zagadnieniom związanym z sytuacją dzieci jąkających
się w środowisku edukacyjnym. Autorki zaakcentowały kwestie dotyczące możliwości
udzielania kompleksowego wsparcia uczniom z zaburzeniami płynności mowy w szkole.
W artykule zaprezentowano podstawowe problemy, z którymi zmagają się uczniowie
jąkający się, oraz zarysowano najważniejsze problemy dotyczące terapii jąkania u dzieci
w wieku szkolnym. Zagadnienie udzielania skutecznego wsparcia dziecku jąkającemu się
omówiono z różnych perspektyw – potrzeby budowania zespołu terapeutycznego oraz
wykorzystania potencjału poszczególnych jego ogniw: logopedy, nauczycieli, rodziców,
pracowników szkoły i społeczności szkolnej. W artykule zarekomendowano praktyczne
strategie udzielania pomocy przez każdy z elementów tego zespołu wsparcia terapeutycznego
Reducing bias in risk indices for COVID-19
Full text linkSpatiotemporal modelling of infectious diseases such as coronavirus disease 2019 (COVID-19) involves using a variety of epidemiological metrics such as regional proportion of cases and/or regional positivity rates. Although observing changes of these indices over time is critical to estimate the regional disease burden, the dynamical properties of these measures, as well as crossrelationships, are usually not systematically given or explained. Here we provide a spatiotemporal framework composed of six commonly used and newly constructed epidemiological metrics and conduct a case study evaluation. We introduce a refined risk estimate that is biased neither by variation in population size nor by the spatial heterogeneity of testing. In particular, the proposed methodology would be useful for unbiased identification of time periods with elevated COVID-19 risk without sensitivity to spatial heterogeneity of neither population nor testing coverage.We offer a case study in Poland that shows improvement over the bias of currently used methods. Our results also provide insights regarding regional prioritisation of testing and the consequences of potential synchronisation of epidemics between regions. The approach should apply to other infectious diseases and other geographical areas
Detection of soil pipe network by geophysical approach: Electromagnetic induction (EMI) and electrical resistivitytomography (ERT)
Full text linkStudying soil pipes is a methodological challenge that needs improvement in detection
methods in order to better recognize the role of piping erosion in land degradation
and hillslope hydrology. This study explores electromagnetic induction (EMI) and
electrical resistivity tomography (ERT) in order to identify soil pipes. The study was
conducted in a mountainous area (the Bieszczady Mountains, SE Poland) under a
temperate climate, where pipes develop in silty-clayey soils. In the plot area, eight
profiles were measured by the conductivity meter at different depths and then interpolated
to present apparent electrical conductivity (ECa). Also, six ERT profiles were
carried out using the Wenner-Schlumberger electrode configuration. The ECa values
measured by EMI are not very diversified, suggesting its lower sensitivity to changes
in the ECa, whereas the ECa values measured by ERT are characterized by greater
fluctuation, that is, better detection possibilities. ERT has revealed soil pipes as zones
of higher electrical resistivity (ER >268 Ωm) than their surroundings (characterized
below pipes by ER 427 Ωm),
whereas EMI has revealed its higher sensitivity to water content. The EMI results
have shown the lowering of the water table in the lower part of the slope, perhaps
because of the drainage by a complex pipe network. EMI allows quick measurements
of ECa providing information on water content, and thus indirectly soil pipes, but, it
cannot delineate individual pipes. Only the integration of geophysical methods
supported by field recognition provides an effective method to detect soil pipes