Stress tensor mesostructures for freeform shaping of thin substrates

Stress-induced shaping, which deforms thin substrates utilizing stressed surface coatings, has enabled and enhanced a host of applications in past decades. Owing to the touchless fabrication process compatible with modern planar technology, the method has been applied from microscale to macroscale applications such as self-assembled micro-structures and space mirrors. However, the deformations created by existing stress-control schemes are limited to certain classes of geometries (such as sphere, coma and astigmatism) or rely on boundary constraints and hinges because the stress is unary, e.g., equibiaxial stress or uniaxial stress with fixed orientation. Here, we present novel stress tensor mesostructures to spatially control the three required stress tensor components, i.e., two normal stresses and a shear stress, over the surface of thin substrates. Three different mesostructure types have been created, each offering distinct advantages. For demonstration, we patterned these mesostructures on the back sides of silicon wafers for freeform shape generation and correction which are not achievable by conventional methods. Stress tensor mesostructures will unleash the value of fields related to stress-induced bending from microscale to macroscopy, such as thin freeform substrates that will become increasingly important with the rise of wearable and space optics

Toward Large-Area Sub-Arcsecond X-Ray Telescopes II

In order to advance significantly scientific objectives, future x-ray astronomy missions will likely call for x-ray telescopes with large aperture areas (approx. = 3 sq m) and fine angular resolution (approx. = 1"). Achieving such performance is programmatically and technologically challenging due to the mass and envelope constraints of space-borne telescopes and to the need for densely nested grazing-incidence optics. Such an x-ray telescope will require precision fabrication, alignment, mounting, and assembly of large areas (approx. = 600 sq m) of lightweight (approx. = 2 kg/sq m areal density) high-quality mirrors, at an acceptable cost (approx. = 1 M$/sq m of mirror surface area). This paper reviews relevant programmatic and technological issues, as well as possible approaches for addressing these issues-including direct fabrication of monocrystalline silicon mirrors, active (in-space adjustable) figure correction of replicated mirrors, static post-fabrication correction using ion implantation, differential erosion or deposition, and coating-stress manipulation of thin substrates

Amorphous In–Ga–Zn–O Powder with High Gas Selectivity towards Wide Range Concentration of C2H5OH

Amorphous indium gallium zinc oxide (a-IGZO) powder was prepared by typical solution-based process and post-annealing process. The sample was used as sensor for detecting C2H5OH, H2, and CO. Gas-sensing performance was found to be highly sensitive to C2H5OH gas in a wide range of concentration (0.5–1250 ppm) with the response of 2.0 towards 0.5 ppm and 89.2 towards 1250 ppm. Obvious difference of response towards C2H5OH, H2, and CO was found that the response e.g., was 33.20, 6.64, and 2.84 respectively at the concentration of 200 ppm. The response time and recovery time of was 32 s and 14 s respectively towards 200 ppm concentration of C2H5OH gas under heating voltage of 6.5 V

Tunability of photoluminescence of InAs/GaAs quantum dots by growth pause introduced ripening

The effect of dot ripening pause on self organized InAs/GaAs QD's grown by MBE at two different growth rates and the resulting tunability of emission properties were studied with the help of PL and AFM experiments. We found the evolution of larger coherent islands with dot-pause due to high surface mobility of the In adatoms at the growth temperature resulting in a redshift in the PL spectra. A small blue shift in the emission is observed in case of the islands grown at higher growth rate and being allowed to ripen for sufficient time due to In desorption at high growth temperature

An Intermolecular Hydroarylation of Unactivated Arylcyclopropane via Re₂O₇/HFIP-Mediated Ring Opening

In this paper, we describe a Re2O7-mediated ring-opening arylation of unactivated arylcyclopropane because of its functionalization with various arenes via Friedel–Crafts-type reactivity. This protocol allows facile access to functionalized 1,1-diaryl alkanes and is characterized by a broad substrate scope, mild reaction conditions, high efficiency, and high atom economy. Both density functional theory calculations and deuterium labeling experiments were carried out to justify the indispensable role of HFIP in this transformation and pointed to Re2O7-mediated ring opening being the rate-determining step

Carrier-Free Microspheres of an Anti-Cancer Drug Synthesized via a Sodium Catalyst for Controlled-Release Drug Delivery

There are several challenges involved in the development of effective anti-cancer drugs, including accurate drug delivery without toxic side effects. Possible systemic toxicity and the rapid biodegradation of drug carriers are potential risks in the use of carriers for drug-delivery formulations. Therefore, the carrier-free drug delivery of an anti-cancer drug is desirable. Herein, 4-amino-2-benzyl-6-methylpyrimidine (ABMP) was synthesized via a new method using a sodium catalyst, and proved to be effective in inducing breast cancer cell (MDA-MB-231) apoptosis. Moreover, the transparent amorphous state solid of ABMP was demonstrated to have a slow-release property in phosphate buffer solution (PBS). Microspheres of ABMP were prepared with diameters in the range of 5–15 μm. The slow-release property of the ABMP microspheres indicated their potential use for controlled-release drug delivery. We believe that microspheres of ABMP have potential as a new kind of carrier-free anti-cancer drug delivery system

Has the Inter-Regional Power Transmission Promoted Economic Development? A Quantitative Assessment in China

As one of the largest energy consumers in the world, China’s total electricity consumption has increased by 416.33% during the sample years of 2001 to 2019. In 2019, the top five provinces in terms of power use were all located on the eastern coast. They have contributed 38.39% of the total consumption, causing a power shortage of 594.5 billion kWh in the provinces, while the power generation in the central and western regions have far exceeded their electricity consumption. In order to alleviate the problem of the mismatch between the power resource centers and the load centers in China, ultra-high voltage (UHV) projects, as one of the most important projects in recent years, have bridged the resource gap between the regions and have improved the allocation efficiency of the power resources. Although the cross-provincial transmission of electricity opens the pathway for the consumption of resources, the causal effects of the project on the regions along the line have not been accurately analyzed. Firstly, by constructing a quasi-natural experiment, this paper uses county-level panel data during the period of 2000 to 2019 to analyze the economic benefits that are generated by the inter-regional power transmission project. Secondly, the pathways of the economic effects of UHV are also verified. Finally, this paper also analyzes the heterogeneous effect of power-resource-rich provinces in the construction of the project. Through the pathways of local enterprise dynamics, employment level, and industrial structure, the findings prove that cross-regional power transmission has significantly enhanced the economic growth of the related regions and has played an especially positive role for the power exporting provinces. This paper provides empirical evidence for the effect of optimal resource allocation and the infrastructure development of developing countries and supplies a policy reference for developing countries’ resource allocation optimization strategies