Combustion-Wave Propagation and Phase-Formation Mechanism in the “Molybdenum–Carbon-Active Additive” System

The combustion of a mixture of molybdenum and carbon activated by a high-energy magnesium–fluoroplastic mixture was studied. The adiabatic combustion temperature and the equilibrium compositions of the combustion products were calculated and, experimental dependences of the combustion temperature and rate on the main parameters of the process are obtained. It is shown that the activation of the formation of molybdenum carbides is of a thermal nature. The two observed mechanisms of formation of molybdenum carbides are found to differ in combustion temperature: at T < 2470 K, formation of carbides proceeds by a diffusion mechanism, and at T > 2470 K it proceeds by crystallization from a melt. The possibility of synthesis of single-phase Mo₂C in the combustion regime is shown.     

Two-dimensional ultrahigh-density X-ray optical memory

Most important aspect of nanotechnology applications in the information ultrahigh storage is the miniaturization of data carrier elements of the storage media with emphasis on the long-term stability. Proposed two-dimensional ultrahigh-density X-ray optical memory, named X-ROM, with long-term stability is an information carrier basically destined for digital data archiving. X-ROM is a semiconductor wafer, in which the high-reflectivity nanosized X-ray mirrors are embedded. Data are encoded due to certain positions of the mirrors. Ultrahigh-density data recording procedure can e.g., be performed via mask-less zone-plate-array lithography (ZPAL), spatial-phase-locked electron-beam lithography (SPLEBL), or focused ion-beam lithography (FIB). X-ROM manufactured by nanolithography technique is a write-once memory useful for terabit-scale memory applications, if the surface area of the smallest recording pits is less than 100 nm2. In this case the X-ROM surface-storage capacity of a square centimetre becomes by two orders of magnitude higher than the volumetric data density really achieved for three-dimensional optical data storage medium. Digital data read-out procedure from proposed X-ROM can e.g., be performed via glancing-angle incident X-ray micro beam (GIX) using the well-developed X-ray reflectometry technique. In presented theoretical paper the crystal-analyser operating like an image magnifier is added to the set-up of X-ROM data handling system for the purpose analogous to case of application the higher numerical aperture objective in optical data read-out system. We also propose the set-up of the X-ROM readout system based on more the one incident X-ray micro beam. Presented scheme of two-beam data handling system, which operates on two mutually perpendicular well-collimated monochromatic incident X-ray micro beams, essentially increases the reliability of the digital information read-out procedure. According the graphs of characteristic functions presented in paper, one may choose optimally the incident radiation wavelength, as well as the angle of incidence of X-ray micro beams, appropriate for proposed digital data read-out procedure.     

Immunogenicity of MultiTEP-Platform-Based Recombinant Protein Vaccine,PV-1950R,Targeting Three B-Cell Antigenic Determinants of Pathological α-Synuclein

Parkinson’s disease (PD) and dementia with Lewy bodies (DLB) are characterized by the aberrant accumulation of intracytoplasmic misfolded and aggregated α-synuclein (α-Syn), resulting in neurodegeneration associated with inflammation. The propagation of α-Syn aggregates from cell to cell is implicated in the spreading of pathological α-Syn in the brain and disease progression. We and others demonstrated that antibodies generated after active and passive vaccinations could inhibit the propagation of pathological α-Syn in the extracellular space and prevent/inhibit disease/s in the relevant animal models. We recently tested the immunogenicity and efficacy of four DNA vaccines on the basis of the universal MultiTEP platform technology in the DLB/PD mouse model. The antibodies generated by these vaccines efficiently reduced/inhibited the accumulation of pathological α-Syn in the different brain regions and improved the motor deficit of immunized female mice. The most immunogenic and preclinically effective vaccine, PV-1950D, targeting three B-cell epitopes of pathological α-Syn simultaneously, has been selected for future IND-enabling studies. However, to ensure therapeutically potent concentrations of α-Syn antibodies in the periphery of the vaccinated elderly, we developed a recombinant protein-based MultiTEP vaccine, PV-1950R/A, and tested its immunogenicity in young and aged D-line mice. Antibody responses induced by immunizations with the PV-1950R/A vaccine and its homologous DNA counterpart, PV-1950D, in a mouse model of PD/DLB have been compared.     

Chemical transformation mechanism and combustion regimes in the system silicon-carbon-fluoroplastic

The combustion mechanism and regimes are studied for the mixture Si–C–(–C₂F₄–)_ir Experimental curves are given for dependences of combustion wave parameters for the mixture on the ratio of original components, inert atmosphere pressure, ignition source temperature, and specimen diameter. It is shown that depending on these parameters the process may occur in two steady-state regimes: low-temperature, when there is only formation of silicon fluorides, and high-temperature, when there is successive formation of silicon fluorides and carbides.Erevan. Translated from Fizika Goreniya i Vzryva, Vol. 27, No. 6, pp. 77–81, November–December, 1991.     

High‐temperature stability of YSZ and MSZ ceramic materials in CaF2–MgF2–MgO molten salt system

The high‐temperature stability of YSZ and MSZ specimens was investigated in CaF₂–MgF₂–MgO molten salt at 1200°C. YSZ was mostly composed of m‐ZrO₂ and a small part of YF₃ in the early stages. The formation of YF₃ was attributed to the chemical reaction between Y₂O₃ and MgF₂, which can lead to the leaching of Y₂O₃ from YSZ. With an increase in exposure time, the degraded surface was coarser, and considerable amount of cracks, pores, and spallations were formed. Furthermore, no Y₂O₃ was found up to 120 μm of the YSZ bulk in the early stages. MSZ was composed of t‐ZrO₂ after 24 hours. However, the volume fraction of m‐ZrO₂ was 72% after 72 hours, and CaZrO₃ was formed by the chemical reaction between CaO and ZrO₂ after 168 hours. In addition, the volume fraction of m‐ZrO₂ was 60% in 2.5 wt% MgO and 49% in 10 wt% MgO. In 5 wt% MgO, CaZrO₃ was formed. We demonstrate that the high‐temperature stability of MSZ was better than that of YSZ, and that 10 wt% MgO was much more stable than the other concentrations of MgO.     

Solar-grade silicon powder prepared by combining combustion synthesis with hydrometallurgy

Solar-grade silicon microparticles have been prepared by a two-stage technique consisting of a combustion process in a SiO₂+αMg (α is the mole number of Mg) system in an inert atmosphere and the hydrometallurgical treatment of the combustion product. It has been shown that the refining behavior of the metallic impurities from combustion-synthesized silicon (CS-Si) is better than that of metallic impurities from metallurgical-grade silicon (MG-Si) since CS-Si particles have a unique microporous network structure, which makes the hydrometallurgical treatment process very efficient. Inductively coupled plasma (ICP) analysis results indicate that silicon of purity greater than 99.99% can be obtained by the developed technique. The principle of the hydrometallurgical purification of CS-Si is discussed in the context of particle morphology and a comprehensive explanation for porous structure formation is provided.     

Microstructural and thermochemical properties of Al/AlN/CuAl2 composite prepared by a combination of combustion synthesis and spark plasma sintering

A combination of combustion synthesis (CS) and spark plasma sintering (SPS) technology was employed in the fabrication of Al/AlN/CuAl₂ dense composites. Al/AlN/CuAl₂ composite powders in which a portion of the AlN was present in macro- and nanofiber forms were prepared by combustion of Al–Cu–5 wt.% (C₂F₄)_n, under a nitrogen atmosphere. The resulting composite powders were then subjected to consolidation by SPS at a dwell temperature level of 1500 °C, mechanical pressure of 60 MPa, and a non-isothermal heating time of 10 min. It is found that the actual thermal conductivity of Al/AlN/CuAl₂ composites fabricated with 5 wt.% (C₂F₄)_n is much higher than that of materials prepared in the absence (C₂F₄)_n. Maximum thermal conductivity (320 W/m K) was recorded for the samples prepared from an 0.8Al–0.2Cu–5 wt.% (C₂F₄)_n mixture. The influence of (C₂F₄)_n on the growth mechanism of AlN fibers and thermal conductivity of composite samples is discussed in light of the experimental data.     

Activated combustion of the SiO2-Al-C system and synthesis of SiC/Al2O3 composite powders

The mechanism of initiation and combustion of the 3SiO₂-4Al-3C system is studied under conditions of activation of the combustion reaction by a high-energy additive of Al+αKNO₃. It is shown that combustion of this system is possible only when a certain quantity of the additive is introduced into the starting mixture. The mechanism of activation of the reaction is established, and the processes involved in the reduction stage of the combustion are shown to play a leading role in the reaction. Optimal conditions for synthesis of a SiC/Al₂O₃ composite powder containing SiC fibers are determined. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 2, pp. 51–55, March–April, 2000.     

Transformation of the Thermal Structure of the Combustion Wave and Morphology of the Combustion Products of the SiO2–Al(Zr)–C System near the Extinction Limit

The combustion of the SiO₂–Al(Zr)–C system is studied near the extinction limit. Temperature distribution over the combustion zone is obtained using the thermocouple procedure. It is shown that in combustion of samples with diameter not exceeding 8 mm, thermal losses give rise to a temperature gradient over a section of the sample, which transforms the thermal structure of the combustion wave and leads to inhomogeneity of the end product. New data on the formation mechanism of the reaction products are given.     

The Involvement of Insulin-Like Growth Factor 1 and Nerve Growth Factor in Alzheimer’s Disease-Like Pathology and Survival Role of the Mix of Embryonic Proteoglycans: Electrophysiological Fingerprint,Structural Changes and Regulatory Effects on Neurotrophins

Alzheimer’s disease (AD)-associated neurodegeneration is triggered by different fragments of amyloid beta (Aβ). Among them, Aβ (25–35) fragment plays a critical role in the development of neurodegeneration—it reduces synaptic integrity by disruption of excitatory/inhibitory ratio across networks and alters the growth factors synthesis. Thus, in this study, we aimed to identify the involvement of neurotrophic factors—the insulin-like growth factor 1 (IGF-1) and nerve growth factor (NGF)—of AD-like neurodegeneration induced by Aβ (25–35). Taking into account our previous findings on the neuroprotective effects of the mix of proteoglycans of embryonic genesis (PEG), it was suggested to test its regulatory effect on IGF-1 and NGF levels. To evaluate the progress of neurodegeneration, in vivo electrophysiological investigation of synaptic activity disruption of the entorhinal cortex–hippocampus circuit at AD was performed and the potential recovery effects of PEG with relative structural changes were provided. To reveal the direct effects of PEG on brain functional activity, the electrophysiological pattern of the single cells from nucleus supraopticus, sensomotor cortex and hippocampus after acute injection of PEG was examined. Our results demonstrated that after i.c.v. injection of Aβ (25–35), the level of NGF decreased in cerebral cortex and hypothalamus, and, in contrast, increased in hippocampus, prompting its multidirectional role in case of brain damage. The concentration of IGF-1 significantly increased in all investigated brain structures. The administration of PEG balanced the growth factor levels accompanied by substantial restoration of neural tissue architecture and synaptic activity. Acute injection of PEG activated the hypothalamic nucleus supraopticus and hippocampal neurons. IGF-1 and NGF levels were found to be elevated in animals receiving PEG in an absence of amyloid exposure. We suggest that IGF-1 and NGF play a critical role in the development of AD. At the same time, it becomes clear that the neuroprotective effects of PEG are likely mediated via the regulation of neurotrophins.