Effect of Gamma Irradiation on the Thermal Switching of a GeS:Nd Single Crystal

Semiconductors - The effect of the thermal switching of a layered GeS:Nd single crystal is investigated in a wide range of temperatures (T = 80–350 K). The effect of γ irradiation on the...     

Design of Trehalose-Based Amide/Sulfonamide C-type Lectin Receptor Signaling Compounds

Mincle agonists have been shown to induce inflammatory cytokine production, such as tumor necrosis factor-alpha (TNF) and promote the development of a Th1/Th17 immune response that might be crucial to development of effective vaccination against pathogens such as Mycobacterium tuberculosis. As an expansion of our previous work, a library of 6,6′-amide and sulfonamide α,α-d -trehalose compounds with various substituents on the aromatic ring was synthesized efficiently in good to excellent yields. These compounds were evaluated for their ability to activate the human C-type lectin receptor Mincle by the induction of cytokines from human peripheral blood mononuclear cells. A preliminary structure–activity relationship (SAR) of these novel trehalose diamides and sulfonamides revealed that aryl amide-linked trehalose compounds demonstrated improved activity and relatively high potency cytokine production compared to the Mincle ligand trehalose dibehenate adjuvant (TDB) and the natural ligand trehalose dimycolate (TDM) inducing dose-dependent and human-Mincle-specific stimulation in a HEK reporter cell line.     

Spark plasma sintering of B4C and B4C-TiB2 composites: Deformation and failure mechanisms under quasistatic and dynamic loading

Spark plasma sintering (SPS) was employed to consolidate powder specimens consisting of B₄C and various B₄C-TiB₂ compositions. SPS allowed for consolidation of pure B₄C, B₄C-13 vol.%TiB₂, and B₄C-23 vol.%TiB₂ composites achieving ≥99 % theoretical density without sintering additives, residual phases (e.g., graphite), and excessive grain growth due to long sintering times. Electron and x-ray microscopies determined homogeneous microstructures along with excellent distribution of TiB₂ phase in both small and larger-scaled composites. An optimized B₄C-23 vol.%TiB₂ composite with a targeted low density of ～3.0 g/cm³ exhibited 30–35 % increased hardness, fracture toughness, and flexural bend strength compared to several commercial armor-grade ceramics, with the flexural strength being strain rate insensitive under quasistatic and dynamic loading. Mechanistic studies determined that the improvements are a result of a) no residual graphitic carbon in the composites, b) interfacial microcrack toughening due to thermal expansion coefficient differences placing the B₄C matrix in compression and TiB₂ phase in tension, and c) TiB₂ phase aids in crack deflection thereby increasing the amount of intergranular fracture. Collectively, the addition of TiB₂ serves as a toughening and strengthening phase, and scaling of SPS samples show promise for the manufacture of ceramic composites for body armor.     

Research and development of liquid hydrogen (LH2) temperature monitoring system for marine applications

Monitoring the temperature in liquid hydrogen (LH₂) storage tanks on ships is important for the safety of maritime navigation. In addition, accurate temperature measurement is also required for commercial transactions. Temperature and pressure define the density of liquid hydrogen, which is directly linked to trading interests. In this study, we developed and tested a liquid hydrogen temperature monitoring system that uses platinum resistance sensors with a nominal electrical resistance of approximately 1000 Ω at room temperature, PT-1000, for marine applications. The temperature measurements were carried out using a newly developed temperature monitoring system under different pressure conditions. The measured values are compared with a calibrated reference PT-1000 resistance thermometer. We confirm a measurement accuracy of ±50 mK in a pressure range of 0.1 MPa–0.5 MPa.     

Influence of photovoltaic generation model and time resolution on the reliability evaluation of distribution systems

This paper aims to investigate the influence of photovoltaic (PV) generation on reliability evaluation of distribution systems. Two PV generation models are used to predict the output power injected into the grid, taking into account the main relevant environmental variables, the irradiance and ambient temperature. Issues that directly affect the output power, such as the spatial smoothing effect due to the plant size and the influence of the irradiance and temperature measurement interval are taken into consideration. Using measurement time series of irradiance and local temperature, the models are used to generate power series in 4‐minute and hourly resolutions. The generated power series are used in a reliability assessment model, with the objective of evaluating the impact of solar resource variability on the reliability indices of the system. Case studies on the IEEE RBTS‐Bus 2 and on the real distribution system of Fernando de Noronha in Brazil are presented and discussed, for power plants of different capacities, considering the effect of the PV generation models, the temporal resolution of the time series and the spatial smoothing of the power output fluctuations. The results show that the power time series in hourly resolution significantly underestimates the frequency of interruptions. For the real system, this index is underestimated at the system level (up to 43%) and at the load points (up to 72%). On the other hand, for the interruption duration index, the temporal aggregation results in a small underestimation (just 4%). The results also indicates that the smoothing effect is irrelevant for typical PV system sizes of distribution systems with discretization equal to or above 4 minutes.     

Dielectric and electrical properties of MoO3-doped borophosphate glass: dielectric spectroscopy investigations

A series of (50 ? x) P₂O₅–20B₂O₃–20CaO–10Na₂O (x?=?0–15 mol% MoO₃) glass composition was prepared. Glass structure was analyzed using infrared absorption, UV–visible spectroscopy, electron spin resonance, density, and molar volume calculations. FTIR confirmed that Mo ions are contributed as MoO₆ octahedral units in the glassy matrix, resulting in an increase in the pyrophosphate and BO₃ groups at the expense of metaphosphate and BO₄ units. UV–visible and ESR spectra detected Mo³⁺ and Mo⁵⁺ ions as species in the host glass due to the increase in MoO₃ content. Broadband dielectric spectroscopy investigation on a broad range of frequencies and at different temperatures indicated that the enhancement of electrical conductivity of the prepared glasses due to molybdenum doping was prevented using confinement effect at the wells, causing demobilization of the charge carriers. Hence the dielectric spectra were caused by the mobility of charge carriers rather than the dynamics at the molecular scale. There is a clear correlation between the transport mechanism and dynamics at the interface of the charge carriers. Presently, the challenge is to understand if optimizing the accumulation of charges at the interfaces and electrodes is the origin of electrical storage energy.

     

Quasi-solid-state dye-sensitized solar cells utilizing TiO2/graphite composite counter electrode and TiO2/N719 sensitizer photoelectrode for low-cost power generation

Journal of Materials Science: Materials in Electronics - Dye-sensitized solar cells (DSCs) have evolved through the highest devotion of the research community as a low-cost alternative for...     

The influence of small hydrogen addition on the structural and magnetocaloric properties of high-purity nanocrystalline terbium

Hydrogen absorption often induces changes of various properties of rare-earth metals. In this paper, we study the influence of hydrogenation on the structural, magnetic and magnetocaloric properties of high-purity nanocrystalline terbium. Strong (00l) texture present in the parent Tb sample is practically destroyed after the hydrogenation procedure. We observe formation of agglomerates of different sizes and shapes depending on the hydrogen content in the samples. We find traces of β-hydride (TbH₂) in the main α-hydride TbH_x phase. For TbH_x with x = 0.25 and 0.5 at.H/f.u. The effect of hydrogenation on the magnetocaloric properties is studied in magnetic fields up to 9 T. The magnetocaloric effect decreases after hydrogenation. The -ΔS_M(T) curves feature a table-like effect in the vicinity of the magnetic phase transitions in magnetic fields exceeding 1 T.     

Unique structure of fibrous ZSM-5 catalyst expedited prolonged hydrogen atom restoration for selective production of propylene from methanol

A unique mesostructured fibrous silica@ZSM-5 (HSi@ZSM-5) catalyst was synthesized via microemulsion ZSM-5 zeolite seed assisted synthesis method and successfully applied in enhanced propylene formation in methanol to olefin (MTO) process. Characterization of the catalysts were carried out by FESEM, TEM, XRD, TGA, N₂ adsorption-desorption, NH₃ and KBr probed FTIR. Catalytic performance of as-synthesized catalyst was examined using a micro-pulse reactor and compared with the commercial HZSM-5. The reaction mechanism was elucidated by in-situ methanol FTIR spectroscopy. It was found that HSi@ZSM-5 produced higher propylene selectivity (56%) and was stable for long time on stream (80 h), nearly three-fold higher than that of commercial HZSM-5. In addition, HSi@ZSM-5 displayed higher rate of methanol dehydration, surface methoxy species generation and olefin methylation, indicating that alkene catalytic cycle is the dominant reaction mechanism. The higher selectivity towards propylene was correlated to the existence of moderate acidity which impeded the formation of paraffins and polymethylbenzene intermediates. These observations are further supported by KBr probed FTIR findings which revealed negligible paraffinic carbon species on HSi@ZSM-5. Thus, the unique fibrous silica@ZSM-5 retarded coke deposition due to suppression of undesired side reactions thereby signifying intensified propylene formation, which is highly desirable in commercial MTO processes.