Astrocyte dysfunction in Parkinson's disease: from the perspectives of transmitted α-synuclein and genetic modulation

Parkinson’s disease (PD) is a common neurodegenerative disorder that primarily affects the elderly. While the etiology of PD is likely multifactorial with the involvement of genetic, environmental, aging and other factors, α-synuclein (α-syn) pathology is a pivotal mechanism underlying the development of PD. In recent years, astrocytes have attracted considerable attention in the field. Although astrocytes perform a variety of physiological functions in the brain, they are pivotal mediators of α-syn toxicity since they internalize α-syn released from damaged neurons, and this triggers an inflammatory response, protein degradation dysfunction, mitochondrial dysfunction and endoplasmic reticulum stress. Astrocytes are indispensable coordinators in the background of several genetic mutations, including PARK7, GBA1, LRRK2, ATP13A2, PINK1, PRKN and PLA2G6. As the most abundant glial cells in the brain, functional astrocytes can be replenished and even converted to functional neurons. In this review, we discuss astrocyte dysfunction in PD with an emphasis on α-syn toxicity and genetic modulation and conclude that astrocyte replenishment is a valuable therapeutic approach in PD.

INVESTIGATING THE INFLUENCE OF ENVIRONMENTAL CONDITIONING ON EPOXY RESINS AT QUASISTATIC AND HIGH STRAIN RATES FOR MATERIAL OPERATING LIMIT

Epoxy resin-based composite panels used for armors may be subjected to a wide range of operating temperatures (-55°C to 76°C) and high strain rates on the order of 103-104 s-1. Over the life cycle, various environmental factors also affect the resin properties and hence influence the performance of the composites. Therefore, it is critical to determine the stress-strain behavior of the epoxy resin over a wide range of strain rates and temperatures for accurate multi-scale modeling of composites and to investigate the influence of environmental aging on the resin properties. Additionally, the characterization of key mechanical properties such as yield stress, modulus, and energy absorption (i.e. area under the stress-strain curve) at varying temperatures and moisture can provide critical data to calculate the material operating limits. In this study, we characterize mechanical properties of neat epoxy resin, SC-15 (currently used in structural armor) and RDL-RDC using uniaxial compression testing. RDL-RDC, developed by Huntsman Corporation, has a glass transition temperature of ~ 120°C, compared to ~ 85°C of SC-15. A split Hopkinson pressure bar is used for high strain rate testing. Quasistatic testing is conducted using a screw-driven testing machine (Instron 4484) at 10-3 s-1 and 10-1 s-1 strain rates and varying temperatures. The yield stress is fit to a modified Eyring model over the varying strain rates at room temperature. For rapid investigation of resistance to environmental aging, accelerated aging tests are conducted by immersing the specimens in 100°C water for 48 hours. Specimens are conditioned in an environmental chamber at 76 °C and 88% RH until they reach equilibrium. Tests are then conducted at five different temperatures from 0°C to 95°C, and key mechanical properties are then plotted vs. temperature. The results presented are an important step towards developing a methodology to identify environmental operating conditions for composite ground vehicle applications.

Effect of Environmental Aging on Tensile Properties of Post-Consumer Recycled (PCR) Polycarbonates

In this chapter, tensile properties of different grades of post-consumer recycled (PCR) polycarbonate (PC) plastics have been compared with conventional or virgin PC before and after different aging conditions. 50 and 75% recycled PCs showed comparable yield strength (∼57 MPa), maximum tensile strength (∼70 MPa) and maximum strain (∼190–200%) before aging, when compared to virgin PC of same melt flow rate (MFR of ∼10 g/10 min). From the fractography analysis (optical and scanning electron microscopy) of the both virgin and 50% recycled PC, it is evident that the fracture morphologies are very similar and they are indicative of ductile failure. It is observed that with the presence of temperature and humidity (60°C 90% RH) aging, tensile strength starts to drop over time but most importantly both 50% and 75% PCR grades showed similar aging behavior compared to virgin PC (10–13% strength degradation after 500 hours of aging). Reliability modelling showed comparable B10, Weibull Alpha and Weibull Beta values between Virgin PC and PCR grades after different aging conditions. Fractography analysis of fresh and aged 75% PCR also showed ductile features.

Evaluating the Potential of Polylactide Nonwovens as Bio-Based Media for Air Filtration

The presented research aims to characterize hydrolytic resistance of highly crystalline and oriented polylactide (PLA) as a prerequisite for exploiting this bio-based material in durable applications. Industrially melt-spun PLA monofilaments and nonwovens have been subjected to environmental aging in a temperature range of 50–70 °C at a wide range of relative humidity (RH) in order to identify the onset of the material degradation under application conditions. Along with the measurements of mechanical and thermal behavior of the aged samples, the suitability of FTIR spectroscopy to probe the initial changes in the crystalline structure and in chemical composition of the fibers, caused by hydrolytic degradation, has been evaluated. The diagrams of stability and hydrolytic degradation under employed environmental aging for 7–14 days are presented for both types of PLA materials. Assessment of filtration performance of the artificially aged fibrous PLA media indicated a good agreement with the established stability diagram and confirmed the application potential of PLA nonwoven media, spun from currently available PLA grades, in air filtration under moderate climatic conditions up to max 50 °C and 50% RH. The presented results advance the knowledge on hydrolytic resistance of bio-based industry-relevant fibers and therefore open new application areas for sustainable materials with biodegradable components.

Effects of Environmental Aging on The Durability of Wood-Flour Filled Recycled PET/PA6 Wood Plastic Composites

Outdoor building materials made of wood require preservatives containing chromated copper arsenate and other carcinogenic substances but still are subject to decay, hence they need to be replaced every few years. Wood plastic composite (WPC) is a novel environmental-friendly composite of wood flour/fiber reinforced thermoplastic polymers (i.e. plastic). As WPC is made of plastic to evenly cover the wood flour, it has a lower moisture content than wood. In this study, maleic anhydride grafted polyolefin (POE-g-ma) and methyl metharylate-butadiene-styrene copolymer (MBS) were used as impact modifiers to prepare recycled WPCs (rWPCs) from recycled polyethylene terephthalate (rPET) and recycled polyamide 6 (rPA6) blends (PET/PA6). The thermal properties of the WPCs with different mixing ratio polymer blends of rPET to rPA6 (E60/A40, E50/A50, and E40/A60) were investigated, as well as their mechanical properties after accelerated weathering. Furthermore, the creep property of rWPC was also investigated under different applied loading and environmental aging conditions. The higher PET content resulted in lower flowability and a higher initial decomposition temperature, with the E60/A40 rWPC having better mechanical properties. During the 10-hour creep test, the rWPC strain changed significantly with environmental aging and higher loadings. In conclusion, the rWPC composed of 60:40 PET to PA6 is more suitable for outdoor building applications.