An Environmentally Stable and Lead‐Free Chalcogenide Perovskite

Organic–inorganic halide perovskites are intrinsically unstable when exposed to moisture and/or light. Additionally, the presence of lead in many perovskites raises toxicity concerns. Herein, a thin film of barium zirconium sulfide (BaZrS₃), a lead‐free chalcogenide perovskite, is reported. Photoluminescence and X‐ray diffraction measurements show that BaZrS₃ is far more stable than methylammonium lead iodide (MAPbI₃) in moist environments. Moisture‐ and light‐induced degradations in BaZrS₃ and MAPbI₃ are compared by using simulations and calculations based on density functional theory. The simulations reveal drastically slower degradation in BaZrS₃ due to two factors—weak interaction with water and very low rates of ion migration. BaZrS₃ photodetecting devices with photoresponsivity of ≈46.5 mA W^?1 are also reported. The devices retain ≈60% of their initial photoresponse after 4 weeks under ambient conditions. Similar MAPbI₃ devices degrade rapidly and show a ≈95% decrease in photoresponsivity in just 4 days. The findings establish the superior stability of BaZrS₃ and strengthen the case for its use in optoelectronics. New possibilities for thermoelectric energy conversion using these materials are also demonstrated.     

Rapid ultraviolet-curing of epoxy siloxane films

The ultraviolet (UV) curable epoxy siloxane polymer is shown to cross-link at low UV dosages of 130 mJ/cm², making it desirable for use in nanoimprinting and the rapid fabrication of micro/nano-scaled patterns. In this paper, the dielectric and mechanical properties of this UV-cured epoxy siloxane polymer are investigated. The results of these tests show that the rapid UV-cured polymer films have a dielectric constant of 2.7 ± 0.13, leakage current density on the order of 10⁻⁹ A/cm² under 1 MV/cm, dielectric strength of greater than 5 MV/cm, and a reduced modulus of elasticity of 6.2 GPa characterized using nanoindentation. These properties indicate that the epoxy siloxane can be used to fabricate layers for functional device applications.     

Limits of Heat Removal in Microelectronic Systems

Thermal management issues play an increasingly prominent role in microelectronic system design. The constraints on heat removal are a major factor limiting the performance of a microelectronic system. This work presents the thermodynamic limit of performance for a thermal solution utilizing air cooling to reject thermal energy as the inverse of its mass flow-heat capacity product. The minimum resistance to heat flow offered by a thermal solution is further refined by including the effects of thermal interface materials, substrate materials, and the impact of nonuniform device layer heating. Active cooling solutions may offer additional needed cooling for microelectronics systems, but the system thermal resistances limit its applicability. This work describes the minimum efficiency that an active cooling solution must provide to offer a thermal advantage over passive cooling. This minimum efficiency is dictated by the thermal resistances involved in drawing heat into the active cooler and expelling heat to the ambient environment. Knowledge of the fundamental limitations of thermal solutions gives system designers realistic expectations to set roadmaps, define architecture specifications, and evaluate the validity of thermal system performance claims     

Effects of Defects on the Temperature‐Dependent Thermal Conductivity of Suspended Monolayer Molybdenum Disulfide Grown by Chemical Vapor Deposition

It is understood that defects of the atomic arrangement of the lattice in 2D molybdenum disulfide (MoS₂) grown by chemical vapor deposition (CVD) can have a profound effect on the electronic and optical properties. Beyond these it is a major prerequisite to also understand the fundamental effect of such defects on phonon transport, to guarantee the successful integration of MoS₂ into the solid‐state devices. A comprehensive joint experiment‐theory investigation to explore the effect of lattice defects on the thermal transport of the suspended MoS₂ monolayer grown by CVD is presented. The measured room temperature thermal conductivity values are 30 ± 3.3 and 35.5 ± 3 W m^?1 K^?1 for two samples, which are more than two times smaller than that of their exfoliated counterpart. High‐resolution transmission electron microscopy shows that these CVD‐grown samples are polycrystalline in nature with low angle grain boundaries, which is primarily responsible for their reduced thermal conductivity. Higher degree of polycrystallinity and aging effects also result in smoother temperature dependency of thermal conductivity (κ) at temperatures below 100 K. First‐principles lattice dynamics simulations are carried out to understand the role of defects such as isotopes, vacancies, and grain boundaries on the phonon scattering rates of our CVD‐grown samples.     

Physicochemical characterization of interaction of ibuprofen by solid-state milling with aluminum hydroxide

This present study is a preliminary exploration of the affinity between a carboxylic model drug ibuprofen and aluminum hydroxide. Ibuprofen was comilled with aluminum hydroxide in different weight ratios in the solid state and was characterized by scanning electron microscopy (SEM), X-ray powder diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), and in vitro dissolution studies. XRD and SEM studies indicated complete interaction of ibuprofen with aluminum hydroxide and complete amorphization of aluminum hydroxide-ibuprofen complexed salt as well, on comilling with aluminum hydroxide at 1:2 ratio. FTIR data showed the disappearance of acid carbonyl peak with the appearance and the corresponding increase in absorbance of new signal at 1,682 cm(-1) in the 1:1 and 1:2 ibuprofen-aluminum hydroxide-comilled powder. The accompanied increase in the absorbance of carboxylate peak in the ibuprofen-aluminum hydroxide physical mixture, and 1:0.1, 1:0.5, 1:1, and 1:2 (IBA(pm), and IB(1)A(0.1), IB(1)A(0.5), IB(1)A(1), and IB(1)A(2), respectively) comilled powder indicated an acid-base reaction between ibuprofen and aluminum hydroxide. On storage at 40 degrees C and 75% relative humidity (RH) for 10 weeks, XRD study showed the absence of reversion to the crystalline state and FTIR data revealed continued increase of new signal at 1,682 cm(-1) relative to carboxylic acid peak and no reappearance of carboxylic acid peak. In vitro dissolution studies revealed that the percent release of ibuprofen from the aluminum hydroxide-comilled powder is in the following order: IB(1)A(2) < IB(1)A(1) < ibuprofen crystal < ibuprofen milled alone < IB(1)A(0.1) < IB(1)A(0.5). Aluminum metal cation might have interacted to form a complex through the carboxyl and carbonyl groups of ibuprofen. Improved dissolution of drug associated with IB(1)A(0.1) and IB(1)A(0.5) is because of the absence of a new signal at 1,682 cm(-1) and improved amorphization of the drug to some extent. Dissolution of drug affected in IB(1)A(2) and IB(1)A(1) may be because of the insoluble stable complex formation.     

Testing of a novel load flow algorithm for different radial distribution systems

Radial distribution systems employ special recursive techniques for load flow owing to the radial nature and high (R/X) ratio. This paper presents a new efficient technique for accomplishing the load flows in some standard test radial distribution systems. The proposed mathematical approach employs only three recursive equations devoid of any complex parameters. The steps of the load flow algorithm are presented, and possible simplifications are discussed. The algorithm has been programmed in MATLAB R2010a version and tested on different standard and IEEE test systems. The results of the proposed method are compared to those of other methods reported in the literature for distribution systems. Results show that the proposed method is effective, computationally efficient and faster than other existing methods.     

Development of embedded piezoelectric acoustic sensor array architecture

This paper examines development of novel piezoelectric acoustic sensors, which are capable of sensing high frequency acoustic emissions in a composite/metallic plate. The fabrication of the piezoelectric acoustic sensors, made from piezoceramic ribbons, is described in the paper. An attempt was made to build directionality into the sensing system itself. Continuous sensors placed at right angles on a plate are discussed as a new approach to measure and locate the source of the acoustic waves. Novel signal processing algorithms based on bio-inspired neural systems for spatial filtering of large numbers of embedded sensor arrays in laminated composite media are presented. It is expected that the present work would help in the development of microelectronic sensing aiding diagnostics and prognostics techniques for highly efficient health monitoring of integrated aerospace vehicles and structures.     

An open-terrain line source model coupled with street-canyon effects to forecast carbon monoxide at traffic roundabout

A double-lane four-arm roundabout, where traffic movement is continuous in opposite directions and at different speeds, produces a zone responsible for recirculation of emissions within a road section creating canyon-type effect. In this zone, an effect of thermally induced turbulence together with vehicle wake dominates over wind driven turbulence causing pollutant emission to flow within, resulting into more or less equal amount of pollutants upwind and downwind particularly during low winds. Beyond this region, however, the effect of winds becomes stronger, causing downwind movement of pollutants. Pollutant dispersion caused by such phenomenon cannot be described accurately by open-terrain line source model alone. This is demonstrated by estimating one-minute average carbon monoxide concentration by coupling an open-terrain line source model with a street canyon model which captures the combine effect to describe the dispersion at non-signalized roundabout. The results of the modeling matched well with the measurements compared with the line source model alone and the prediction error reduced by about 50%. The study further demonstrated this with traffic emissions calculated by field and semi-empirical methods.     

Simultaneous metabolic labeling of cells with multiple amino acids: Localization and dynamics of histone acetylation and methylation

Simultaneous metabolic labeling of cells with multiple amino acids combined with acetic acid urea-PAGE and MS was used to characterize histones in Kasumi-1 cells treated with the histone deacetylase inhibitor depsipeptide (DDP). The approach allowed for rapid targeting, identification, and subsequent characterization of peptides containing sites of acetylation or methylation. Multiple methylation sites were determined for histone H3 including: di- and tri-methylation of K9 and K27; mono- and di-methylation of K36 and K79; and mono-methylation of K37. The acetylation patterns for histones H4 and H3 were established. Quantitative analysis of the modification change after treatment with DDP was also performed and the dynamics of H4 acetylation determined. Functional analysis by RT-PCR showed that DDP unregulated p21 expression with a maximum after 18-h exposure. Chromatin immunoprecipitation experiments indicated that DDP treatment caused an accumulation of hyperacetylated histone H4 and H3 isoforms and a decrease in K9 di-methylation of H3 on the p21 promoter.