The self-plasticization, i.e., the increase in the polymer chains' mobility by including its monomer, has a major impact on a polymer's structural, thermal, and mechanical properties. In this study, differential scanning calorimetry (DSC), optical and Raman microscopies, thermo-mechanical analysis (TMA), size exclusion chromatography equipped with a multi-angle light scattering detector (SEC-MALS), and X-ray diffraction analysis (XRD) are used to investigate the effect of thermally induced self-plasticization of poly-(p-dioxanone), PDX, on the crystal growths from the amorphous and molten states. Significant changes in the crystallization behavior and mechanical properties of PDX are found only for samples self-plasticized at the depolymerization temperature (Td) above 150 °C. The intense self-plasticization leads to the decrease of the crystallization temperature, increase of the crystal growth rapidity, disappearance of the distinct α→α' polymorphic transition, reduction of the overall melting temperature, and segregation of the redundant monomer. Although the morphology of the crystalline phase has a major impact on the mechanical properties of PDX, the self-plasticization itself does not seem to result in any major changes in the magnitude, localization, or morphology of formed crystallites (these are primarily driven by the temperature of crystal growth). The manifestation of the variable activation energy concept is discussed for the present crystallization data.

• Klíčová slova
• crystallization, depolymerization, differential scanning calorimetry, polydioxanone, self‐plasticization,
• MeSH
• diferenciální skenovací kalorimetrie MeSH
• difrakce rentgenového záření MeSH
• dioxany * chemie   MeSH
• krystalizace * MeSH
• nízká teplota MeSH
• polymerizace * MeSH
• polymery * chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• dioxany * MeSH
• poly-4-dioxan-2-one MeSH Prohlížeč
• polymery * MeSH

Plastic products, especially in the packaging industry, have become the main commodities penetrating virtually every aspect of our lives. Unfortunately, their omnipresence is not neutral to the natural environment. Pollution in the form of microplastics is a global problem. Therefore, green technologies that enter into the circular economy become an important topic. As part of the research work, the modification of poly(lactic acid) has been studied for use in the packaging industry. Due to its intrinsic rigidity, plasticizing substances had to be introduced in PLA in order to improve its plastic deformability. Both high-molecular compounds such as ethoxylated lauryl alcohol, block copolymer of ethylene oxide and propylene oxide, and ethoxylated stearic acid as well as low-molecular compounds such as di-2-ethylhexyl adipate, di-2-ethylhexyl sebacate, and triethyl citrate were used. The samples extruded from plasticized polymers were characterized using differential scanning calorimetry, thermal gravimetric analysis, and mechanical properties including Young's modulus. The melt flow rate (MFR) and molar mass distribution were determined. For all modified samples the glass transition temperature, depending on the plasticizer used, was shifted towards lower values compared to the base polymer. The best result was obtained for di-2-ethylhexyl adipate (ADO) and di-2-ethylhexyl sebacate (SDO). The elongation at break increased significantly for ADO at about 21%. The highest elongation was obtained for SDO (about 35%), although it obtained a higher glass temperature. The degradation of the polymer was not observed for both plasticizers. For these plasticizers (ADO and SDO) it also lowered Young's module by about 26%, and at the infrared spectrum deformation of peaks were observed, which may indicate the interaction of the ester carbonyl group of PLA with plasticizers. Therefore it can be concluded that they are good modifiers. The selected plasticizers that are used in the production of food contact materials, in particular in the production of PVC (polyvinyl chloride) food films, also exhibited great potential to be applied to PLA food films, and exhibit better properties than the citrate, which are indicated in many publications as PLA plasticizers.

• Klíčová slova
• FTIR-ATR, SEC-MALS, biodegradable polymers, plasticization, polylactic acid,
• Publikační typ
• časopisecké články MeSH

Commercially available antibacterial semisolid preparations intended for topical application provide only short-term drug release. A sustained kinetics is possible by exploitation of a biodegradable polymer carrier. The purpose of this work is to formulate a mucoadhesive system with aciclovir (ACV) based on a solid molecular dispersion of this drug in poly(lactic-co-glycolic acid) branched on tripenterythritol (PLGA/T). The ACV incorporation into PLGA/T was carried out either by solvent method, or melting method, or plasticization method using various plasticizers. The drug-polymer miscibility, plasticizer efficiency and content of residual solvent were found out employing DSC. Viscosity was measured at the shear rate range from 0.10 to 10.00 s(-1) at three temperatures and data were analyzed by Newtonian model. The mucoadhesive properties were ascertained in the tensile test on a mucin substrate. The amount of ACV released was carried out in a wash-off dissolution test. The DSC results indicate a transformation of crystalline form of ACV into an amorphous dissolved in branched polyester carrier, and absence of methyl formate residuals in formulation. All the tested plasticizers are efficient at Tg depression and viscosity decrease. The non-conventional ethyl pyruvate possessing supportive anti-inflammatory activity was evaluated as the most suitable plasticizer. The ACV release was strongly dependent on the ethyl pyruvate concentration and lasted from 1 to 10 days. The formulated PLGA/T system with ACV exhibits increased adhesion to mucosal hydrophilic surfaces and prolonged ACV release controllable by degradation process and viscosity parameters.

• Klíčová slova
• Acyclovir, branched molecule, drug release, ethyl pyruvate, mucoadhesivity, plasticization, poly(lactic-co-glycolic acid), solid dispersion,
• MeSH
• acyklovir aplikace a dávkování   chemie   MeSH
• biokompatibilní materiály chemie   MeSH
• časové faktory MeSH
• hydrofobní a hydrofilní interakce MeSH
• kopolymer kyseliny glykolové a mléčné MeSH
• kyselina mléčná chemie   MeSH
• kyselina polyglykolová chemie   MeSH
• léky s prodlouženým účinkem MeSH
• povrchové vlastnosti MeSH
• uvolňování léčiv MeSH
• velikost částic MeSH
• změkčovadla aplikace a dávkování   chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• acyklovir MeSH
• biokompatibilní materiály MeSH
• kopolymer kyseliny glykolové a mléčné MeSH
• kyselina mléčná MeSH
• kyselina polyglykolová MeSH
• léky s prodlouženým účinkem MeSH
• změkčovadla MeSH

Chemical grafting or crosslinking of polyimide chains are known to be feasible approaches to increase polymer gas-pair selectivity and specific gas permeance. Different co-polyimides; 6FDA-ODA and 6FDA-ODA:DABA were synthesized using a two-step condensation method. Six different cross-linkers were used: (i) m-xylylene diamine; (ii) n-ethylamine; and (iii) n-butylamine, by reacting with 6FDA-ODA's imide groups in a solid state crosslinking; while (iv) ethylene glycol monosalicylate (EGmSal); (v) ethylene glycol anhydrous (EGAn); and (vi) thermally labile iron (III) acetylacetonate (FeAc), by reacting with DABA carboxyl groups in 6FDA-ODA:DABA. The gas separation performances were evaluated by feeding an equimolar CO₂ and CH₄ binary mixture, at a constant feed pressure of 5 bar, at 25 °C. Fractional free volume (FFV) was calculated using Bondi's contribution method by considering the membrane solid density property, measured by pycnometer. Other characterization techniques: thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) were performed accordingly. Depending on the type of amine, the CO₂/CH₄ selectivity of 6FDA-ODA increased between 25 to 100% at the expense of CO₂ permeance. We observed the similar trend for 6FDA-ODA:DABA EGmSal-crosslinked with 143% selectivity enhancement. FeAc-crosslinked membranes showed an increment in both selectivity and CO₂ permeability by 126% and 29% respectively. Interestingly, FeAc acted as both cross-linker which reduces chain mobility; consequently improving the selectivity and as micro-pore former; thus increases the gas permeability. The separation stability was further evaluated using 25⁻75% CO₂ in the feed with CH₄ as the remaining, between 2 and 8 bar at 25 °C. We also observed no CO₂-induced plasticization to the measured pressure with high CO₂ content (max. 75%).

• Klíčová slova
• chemical crosslinking, gas separation, grafting, plasticization resistance, polyimide,
• Publikační typ
• časopisecké články MeSH

Plasticity is a specific endowment of the nervous system to develop, to react or to adjust to the internal and external 'environmental changes, both in the physiological and pathological conditions. Cumulative evidence has revealed the dynamism of the nervous system, based on the balance between the rigidity and plasticity. Different aspects of neuroplasticity can employ common general cellular mechanism. Effects of plasticity can be either positive or negative changes during the development (evolutional plasticity), after the short-term exposition (reactive plasticity), after the long-term or permanent stimuli (adaptational plasticity), and during functional or structural recovery of the damaged neuronal circuits (reparation plasticity). Manifestations of plasticity have probably the same basis, irrespective of a cause, which triggered them, or the brain region where they were accomplished. Activity of neuroplastic processes appears to be especially high in the immature nervous tissue.

• MeSH
• lidé MeSH
• nervový systém embryologie   MeSH
• neurony fyziologie   MeSH
• neuroplasticita fyziologie   MeSH
• regenerace nervu fyziologie   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH

Marine plastic litter (MPL) was collected from beaches (n = 3) of the Arauco Gulf in central Chile in spring 2021 and summer 2022. MPL was analyzed for physical and chemical characteristics, and plasticizers were also screened using FTIR-ATR. Three hundred seventeen plastic items with an accumulated weight of 226.8 g were found. MPL densities ranged from 0.4 to 17.1 items m-2. Significant differences (p < 0.05) between seasons were observed for Arauco and Maule beaches, being ∼ten times higher in summer compared to spring. Solid pieces were the predominant shape, macroplastics were the most abundant (>2.5 cm), and white and blue colors were dominant. Polypropylene (52 %) and polyethylene (31 %) were the predominant polymers. Plasticizers (n = 3) were detected in the MPL in the study area (dioctyl phthalate, polybutene, and alpha-methylstyrene) for the first time. This study contributes new information related to MPL in coastal areas of central Chile and their chemical composition.

• Klíčová slova
• Beaches, Phthalates, Plastic pollution, Polymer composition,
• MeSH
• chemické látky znečišťující vodu * analýza   MeSH
• koupací pláže MeSH
• monitorování životního prostředí * MeSH
• plastické hmoty * analýza   MeSH
• změkčovadla * analýza   MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Chile MeSH
• Názvy látek
• chemické látky znečišťující vodu * MeSH
• plastické hmoty * MeSH
• změkčovadla * MeSH

Surgical treatment of obesity is complex solution and include several basic tasks, without which treatment would not be successful. The medical care depends on the level of obesity, surgical treatment is indicated for patients with BMI over 35 with complications, otherwise over 40. Postbariatric plastic surgery includes set of pre-operative planning and operating procedures that remove skin excess and reduce the health complications associated with it, mainly return the patient to his normal body and return his lost self-confidence and enables its integration into society. Considerable variability of the condition and the local finding of patients after weight reduction make this part of plastic or general surgery a very heterogeneous area - with spectrum and range of outputs and adaptations after successful treatment of obesity. Keywords: obesity, bariatric surgery, body contouring, lower body lifting, armlift, thightlift, gluteoplasty.

• Klíčová slova
• armlift, bariatric surgery, body contouring, gluteoplasty, lower body lifting, obesity, thightlift,
• MeSH
• bariatrická chirurgie * MeSH
• hmotnostní úbytek MeSH
• lidé MeSH
• obezita MeSH
• plastická chirurgie * MeSH
• zákroky plastické chirurgie * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

In neural computation, the essential information is generally encoded into the neurons via their spiking configurations, activation values or (attractor) dynamics. The synapses and their associated plasticity mechanisms are, by contrast, mainly used to process this information and implement the crucial learning features. Here, we propose a novel Turing complete paradigm of neural computation where the essential information is encoded into discrete synaptic states, and the updating of this information achieved via synaptic plasticity mechanisms. More specifically, we prove that any 2-counter machine-and hence any Turing machine-can be simulated by a rational-weighted recurrent neural network employing spike-timing-dependent plasticity (STDP) rules. The computational states and counter values of the machine are encoded into discrete synaptic strengths. The transitions between those synaptic weights are then achieved via STDP. These considerations show that a Turing complete synaptic-based paradigm of neural computation is theoretically possible and potentially exploitable. They support the idea that synapses are not only crucially involved in information processing and learning features, but also in the encoding of essential information. This approach represents a paradigm shift in the field of neural computation.

• MeSH
• algoritmy MeSH
• modely neurologické * MeSH
• neuronové sítě MeSH
• neurony fyziologie   MeSH
• neuroplasticita * MeSH
• synapse fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH

• Klíčová slova
• SURGERY, PLASTIC *,
• MeSH
• lidé MeSH
• plastická chirurgie * MeSH
• zákroky plastické chirurgie * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

• Klíčová slova
• SURGERY, PLASTIC *,
• MeSH
• lidé MeSH
• plastická chirurgie * MeSH
• plastické hmoty * MeSH
• zákroky plastické chirurgie * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• plastické hmoty * MeSH