Misfolded protein aggregates represent a continuum with overlapping features in neurodegenerative diseases, but differences in protein components and affected brain regions. The molecular hallmark of ...synucleinopathies such as Parkinson's disease, dementia with Lewy bodies and multiple system atrophy are megadalton α-synuclein-rich deposits suggestive of one molecular event causing distinct disease phenotypes. Glial α-synuclein (α-SYN) filamentous deposits are prominent in multiple system atrophy and neuronal α-SYN inclusions are found in Parkinson's disease and dementia with Lewy bodies. The discovery of α-SYN assemblies with different structural characteristics or 'strains' has led to the hypothesis that strains could account for the different clinico-pathological traits within synucleinopathies. In this study we show that α-SYN strain conformation and seeding propensity lead to distinct histopathological and behavioural phenotypes. We assess the properties of structurally well-defined α-SYN assemblies (oligomers, ribbons and fibrils) after injection in rat brain. We prove that α-SYN strains amplify in vivo. Fibrils seem to be the major toxic strain, resulting in progressive motor impairment and cell death, whereas ribbons cause a distinct histopathological phenotype displaying Parkinson's disease and multiple system atrophy traits. Additionally, we show that α-SYN assemblies cross the blood-brain barrier and distribute to the central nervous system after intravenous injection. Our results demonstrate that distinct α-SYN strains display differential seeding capacities, inducing strain-specific pathology and neurotoxic phenotypes.
This study uses a serial information transmission scheme to discuss the issues faced in transmitting unit average power of laser radiation from a reference converter of the corresponding standard to ...a control measuring converter. A large difference in the time constants of these converters leads to increased measurement error. To reduce this error, herein, an algorithm is proposed based on averaging the results of multiple measurements while determining the main transmission parameter of unit average power (calibration coefficient). The statistical characteristics of the estimation of the calibration coefficient are analyzed herein. In the model based on measuring transducers having lumped parameters of the first order, relationships that characterize the influence of a correlated stationary-fluctuation component related to the instability in laser radiation power are obtained to determine the calibration coefficient while averaging the results of multiple measurements. In this case, the median of the distribution of its estimate should be used as the calibration coefficient because the median is unbiased and consistent. Equations are obtained to determine the error in estimating the calibration coefficient, and dependencies are presented that enable setting the required measurement averaging time and number of readings of the measured signals. Using the proposed algorithm improves the metrological characteristics of GET 28-2016, the state primary standard of the unit of average laser radiation.
The main technologies for producing textile and other flexible electromagnetic radiation (EMR) shielding materials are studied. Designs of shields made of various materials are described. Options of ...use of modern EMR shielding materials are offered. The main merits and demerits of modern textile and other flexible shielding materials are analyzed.
We report measurements of linear and nonlinear elastic properties of polystyrene-based nanocomposites with six types of nanofillers, including single and binary mixtures of allotropic carbon ...nanoparticles. Composite samples were fabricated by the same technology and contained the same filler concentration (5% wt.), which allowed for a direct comparison of their properties. It was shown that the most significant variations of linear and nonlinear elastic properties occur in different nanocomposites. In particular, the most pronounced enhancements of linear elastic moduli (in about 50%) obtained in tensile and flexural tests and in dynamic mechanical analysis were recorded in the sample filled with spherical fullerene nanoparticles. While the most profound rise of absolute values of nonlinear elastic moduli (tens of times) was obtained in the sample filled with the mixture of carbon nanotubes and graphene. The observed tendencies demonstrated the synergistic effect of fillers of different dimensionality on the elastic properties of nanocomposites.
The influence of temperature resistance of polyparaphenylene-1,3,4-oxadiazole fibers of Arselon and Arsenol-S brands on the specific electrical conductivity, strength, rigidity modulus, and breaking ...elongation of carbon fiber based on them was studied. Existence of extremums of specific electrical conductivity, strength, and rigidity modulus of carbon fibers in the 312-475 °C temperature holding range was observed. It was found that in the indicated temperature dependencies the maximums and minimums of the specific electrical conductivity alternates with the extremums of strength and rigidity of modulus of carbon fibers in the counterphase.
The paper presents a comprehensive analysis of the elastic properties of polystyrene-based nanocomposites filled with different types of inclusions: small spherical particles (SiO
and Al
O
), ...alumosilicates (montmorillonite, halloysite natural tubules and mica), and carbon nanofillers (carbon black and multi-walled carbon nanotubes). Block samples of composites with different filler concentrations were fabricated by melt technology, and their linear and non-linear elastic properties were studied. The introduction of more rigid particles led to a more profound increase in the elastic modulus of a composite, with the highest rise of about 80% obtained with carbon fillers. Non-linear elastic moduli of composites were shown to be more sensitive to addition of filler particles to the polymer matrix than linear ones. A non-linearity modulus
comprising the combination of linear and non-linear elastic moduli of a material demonstrated considerable changes correlating with those of the Young's modulus. The changes in non-linear elasticity of fabricated composites were compared with parameters of bulk non-linear strain waves propagating in them. Variations of wave velocity and decay decrement correlated with the observed enhancement of materials' non-linearity.
Studies of the potentials of the multi-stage hot-zone drawing technique for enhancing the tensile strength (
σ
) of ultra-high-molecular-weight polyethylene (UHMWPE) gel-cast highly oriented film ...threads, the applicability of the Weibull statistics to the
σ
distribution, and the solvent role in the film thread strength are presented. It is shown that the results of a large number of mechanical measurements for two series of UHMWPE film threads drawn to an ultimate draw ratio (
λ
) of 120 from xerogels formed from 1.5 % solutions of UHMWPE in decalin or paraffin oil are satisfactorily described by the Weibull model. It is shown that the threads produced are characterised by an average strength
σ
av
= 4.7 GPa and 20 % of the samples have
σ
= 5.2–6.5 GPa. This is higher than the strength of the commercially available gel-spun oriented UHMWPE fibres of
σ
= 3.5 GPa. It is found that the solvent nature does not affect the tensile strength of the film threads but exerts a considerable influence on the long-term characteristics.
The paper describes the metrological assurance of uniformity in measuring the parameters of high-intensity laser radiation for technological and special equipment. A laser power stabilization system ...with an output power of 2–1·10
4
W has been developed and studied. The presented stabilization system reduces the error in transferring the unit of average laser power when using an industrial laser having unstable output power as part of a measurement standard. GET 28-2022 National Primary Standard for the unit of average laser power was approved; this standard includes a power-stabilized laser, as well as a standard thermoelectric measuring transducer and a measuring beam splitter. The authors studied the means of transferring the unit of average laser power from the range of 1·10
–9
–2 W to the range of 2–1·10
4
W, as well as a system for reproducing and transferring the average power unit within the range of 2–1·10
4
W. With the use of the developed industrial laser stabilization system, the laser power of the standard increased from 2 to 1·10
4
W. Within the laser power range provided by GET 28-2022, the total standard uncertainty in reproducing and transferring the unit of average laser power does not exceed 0.636%. GET 28-2022 can be used to provide metrological support for laser systems designed for various applications operating within the laser power range of 2–1·10
4
W, specifically systems intended for laser hardening, cutting, welding, etc.
New tubular conduits have been developed for the regeneration of peripheral nerves and the repair of defects that are larger than 3 cm. The conduits consist of a combination of poly(L-lactide) ...nanofibers and chitosan composite fibers with chitin nanofibrils. In vitro studies were conducted to assess the biocompatibility of the conduits using human embryonic bone marrow stromal cells (FetMSCs). The studies revealed good adhesion and differentiation of the cells on the conduits just one day after cultivation. Furthermore, an in vivo study was carried out to evaluate motor-coordination disorders using the sciatic nerve functional index (SFI) assessment. The presence of chitosan monofibers and chitosan composite fibers with chitin nanofibrils in the conduit design increased the regeneration rate of the sciatic nerve, with an SFI value ranging from 76 to 83. The degree of recovery of nerve conduction was measured by the amplitude of M-response, which showed a 46% improvement. The conduit design imitates the oriented architecture of the nerve, facilitates electrical communication between the damaged nerve's ends, and promotes the direction of nerve growth, thereby increasing the regeneration rate.
Numerous studies have been performed on different aspects of the mechanical behavior of polymer nanocomposites; however, the results obtained still lack a comprehensive comparative analysis of the ...mechanical properties of composites containing nanofillers of different shapes and concentrations and subjected to different static and dynamic loads. Carbon nanofillers were shown to provide the most significant improvement in the elastic properties of polymer composites. In this paper, we present a comparative analysis of the mechanical properties of polystyrene-based nanocomposites filled with carbon allotropes of different shapes: spherical fullerene particles, filamentary multi-walled nanotubes, and graphene platelets, fabricated by the same technology. The influence of shape and concentration of dispersed carbon fillers on mechanical and viscoelastic properties of composites in different stress–strain states was evaluated based on the results of tensile and three-point bending tests, and ultrasonic and dynamic mechanical analysis. Comparison of the static and dynamic elastic properties of nanocomposites allowed us to analyze their variations with frequency. At low concentrations of 0.1 wt% and 0.5 wt% all nanofillers did not provide significant improvement of elastic characteristics of composites. More efficient reinforcement was observed at the concentration of 5 wt%. Among the filler types, some increase in composite rigidity was observed with the addition of filamentary particles. The introduction of the layered filler provided the most pronounced rise in the composite rigidity. The weak frequency dependence of the mechanical loss tangent, which is characteristic of amorphous thermoplastics, was demonstrated for all the samples.
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