A user-friendly PC-based data acquisition and analysis system for respirometric investigations

We have developed an easy-to-use computer-based system for recording, displaying, storing and analyzing signals generated by Clark-type oxygen electrodes. A user-friendly interface of Windows-based program BioMed significantly increases the productivity of investigations. It allows to process, control, present and archive the experimental data in real time. A 12-bit analog-to-digital-converter, analog and digital filters, a possibility to zoom the obtained respiratory curves and calculation of the respiration rates by a linear regression method increase the resolution of the estimated oxygen consumption rates. The new system enables to register even small changes, such as 3-5 ngatoms O/min, in respiration rates of biological objects -- enzymes, mitochondria and permeabilized muscle fibers. The system has been developed and is regularly used for the respirometric investigations at the Laboratory of Biochemistry, Institute for Biomedical Research, Kaunas University of Medicine.     

Molecular weight distribution in cellulose triacetates and its effect on the mechanical properties of fibres

Conclusions 1. A precise method is defined for determination of the molecular-weight distribution of the original cellulose acetate by fractional precipitation of 1% methylene chloride solutions of the TAC in ethanol.2. A method is developed for quantitative determination of low-molecular fractions which is based on extraction of the polymer from a mixture of methylene chloride and ethanol at 25°C with addition of ammonium thiocyanate.3. The dependence of the physical and mechanical properties of triacetate fibres on the average molecular weight of the polymer is demonstrated.Tashkent Institute for Textiles and Light Industry; HIIKhTTs MKhP SSSR, Tashkent; Kaunas Factory. Translated from Khimicheskie Volokna, No. 5, pp. 48–50, September–October, 1969.     

The Dynamic Emission Zone in Sandwich Polymer Light‐Emitting Electrochemical Cells

In light‐emitting electrochemical cells (LECs), the position of the emission zone (EZ) is not predefined via a multilayer architecture design, but governed by a complex motion of electrical and ionic charges. As a result of the evolution of doped charge transport layers that enclose a dynamic intrinsic region until steady state is reached, the EZ is often dynamic during turn‐on. For thick sandwich polymer LECs, a continuous change of the emission color provides a direct visual indication of a moving EZ. Results from an optical and electrical analysis indicate that the intrinsic zone is narrow at early times, but starts to widen during operation, notably well before the electrical device optimum is reached. Results from numerical simulations demonstrate that the only precondition for this event to occur is that the mobilities of anions (μ_a) and cations (μ_c) are not equal, and the direction of the EZ shift dictates μ_c > μ_a. Quantitative ion profiles reveal that the displacement of ions stops when the intrinsic zone stabilizes, confirming the relation between ion movement and EZ shift. Finally, simulations indicate that the experimental current peak for constant‐voltage operation is intrinsic and the subsequent decay does not result from degradation, as commonly stated.     

Polymorphism of Alpha-Synuclein Amyloid Fibrils Depends on Ionic Strength and Protein Concentration

Protein aggregate formation is linked with multiple amyloidoses, including Alzheimer‘s and Parkinson‘s diseases. Currently, the understanding of such fibrillar structure formation and propagation is still not sufficient, the outcome of which is a lack of potent, anti-amyloid drugs. The environmental conditions used during in vitro protein aggregation assays play an important role in determining both the aggregation kinetic parameters, as well as resulting fibril structure. In the case of alpha-synuclein, ionic strength has been shown as a crucial factor in its amyloid aggregation. In this work, we examine a large sample size of alpha-synuclein aggregation reactions under thirty different ionic strength and protein concentration combinations and determine the resulting fibril structural variations using their dye-binding properties, secondary structure and morphology. We show that both ionic strength and protein concentration determine the structural variability of alpha-synuclein amyloid fibrils and that sometimes even identical conditions can result in up to four distinct types of aggregates.     

Reduced Efficiency Roll‐Off and Improved Stability of Mixed 2D/3D Perovskite Light Emitting Diodes by Balancing Charge Injection

Perovskite light emitting diodes (PeLEDs) have reached external quantum efficiencies (EQEs) over 21%. Their EQE, however, drops at increasing current densities (J) and their lifetime is still limited to just a few hours. The mechanisms leading to EQE roll‐off and device instability require thorough investigation. Here, improvement in EQE, EQE roll‐off, and lifetime of PeLEDs is demonstrated by tuning the balance of electron/hole transport into a mixed 2D/3D perovskite emissive layer. The mixed 2D/3D perovskite layer induces exciton confinement and beneficially influences the electron/hole distribution inside the perovskite layer. By tuning the electron injection to match the hole injection in such active layer, a nearly flat EQE for J = 0.1–200 mA cm^?2, a reduced EQE roll‐off until J = 250 mA cm^?2, and a half‐lifetime of ≈47 h at J = 10 mA cm^?2 is reached. A model is also proposed to explain these improvements that account for the spatial electron/hole distributions.     

Alkali-activated blends of calcined AlF3 production waste and clay

Recently, alkali-activated materials have shown great potential for use in the construction industry. The aim of this research was to study the properties of alkali-activated clay and the effect of incorporating AlF₃ production waste from a fertilizer production plant. The AlF₃ production waste, which was rich in alumina and silica, contributed to improved mechanical behaviour for all the mixtures investigated. This demonstrated the potential for use of this waste material. It was also noted that the dosage of Na₂O, Al₂O₃, and SiO₂ are significant factors that influence the binding mechanism and properties of alkali-activated clay samples. The raw materials, precursors, and alkali-activated samples were investigated by X-ray diffraction, fluorescence spectroscopy, and scanning electron microscopy. The highest compressive strength (17.50?MPa) was observed for alkali-activated clay samples containing 25% AlF₃ production waste, with an increase in compressive strength of up to 64% compared to the samples without the AlF₃ production waste. Deleterious natrite was shown to form in the samples without the production waste, which could be the reason for the lower observed mechanical properties of such samples.     

Double Charge Transfer Dominates in Carrier Localization in Low Bandgap Sites of Heterogeneous Lead Halide Perovskites

Heterogeneous organic-inorganic halide perovskites possess inherent non-uniformities in bandgap that are sometimes engineered and exploited on purpose, like in quasi-2D perovskites. In these systems, charge carrier and excitation energy migration to lower-bandgap sites are key processes governing luminescence. The question, which of them dominates in particular materials and under specific experimental conditions, still remains unanswered, especially when charge carriers comprise excitons. In this study transient absorption (TA) and transient photoluminescence (PL) techniques are combined to address the excited state dynamics in quasi-2D and other heterogeneous perovskite structures in broad temperature range, from room temperature down to 15 K. The data provide clear evidence that charge carrier transfer rather than energy migration dominates in heterogeneous quasi-2D perovskite films.