Phase management in single-crystalline vanadium dioxide beams

A systematic study of various metal-insulator transition (MIT) associated phases of VO2, including metallic R phase and insulating phases (T, M1, M2), is required to uncover the physics of MIT and trigger their promising applications. Here, through an oxide inhibitor-assisted stoichiometry engineering, we show that all the insulating phases can be selectively stabilized in single-crystalline VO2 beams at room temperature. The stoichiometry engineering strategy also provides precise spatial control of the phase configurations in as-grown VO2 beams at the submicron-scale, introducing a fresh concept of phase transition route devices. For instance, the combination of different phase transition routes at the two sides of VO2 beams gives birth to a family of single-crystalline VO2 actuators with highly improved performance and functional diversity. This work provides a substantial understanding of the stoichiometry-temperature phase diagram and a stoichiometry engineering strategy for the effective phase management of VO2

Proteomic Analysis of Rat Hypothalamus Revealed the Role of Ubiquitin–Proteasome System in the Genesis of DR or DIO

Obesity has become a global epidemic, contributing to the increasing burdens of cardiovascular disease and type 2 diabetes. However, the precise molecular mechanisms of obesity remain poorly elucidated. The hypothalamus plays a major part in regulating energy homeostasis by integrating all kinds of nutritional signals. This study investigated the hypothalamus protein profile in diet-induced obese (DIO) and diet-resistant (DR) rats using two dimensional gel electrophoresis (2-DE) combined with MALDI-TOF/TOF–MS analysis. Twenty-two proteins were identified in the hypothalamus of DIO or DR rats. These include metabolic enzymes, antioxidant proteins, proteasome related proteins, and signaling proteins, some of which are related to AMP-activated protein kinase (AMPK) signaling or mitochondrial respiration. Among these proteins, in comparison with the normal-diet group, Ubiquitin was significantly decreased in DR rats but not changed in DIO rats, while Ubiquitin carboxyl-terminal esterase L1 (UCHL-1) was decreased in DIO rats but not changed in DR rats. The expression level of Ubiquitin and UCHL-1 were further validated using Western blot analysis. Our study reveals that Ubiquitin and UCHL-1 are obesity-related factors in the hypothalamus that may play an important role in the genesis of DR or DIO by interfering with the integrated signaling network that control energy balance and feeding

Systems signatures reveal unique remission-path of Type 2 diabetes following Roux-en-Y gastric bypass surgery

Roux-en-Y Gastric bypass surgery (RYGB) is emerging as a powerful tool for treatment of obesity and may also cause remission of type 2 diabetes. However, the molecular mechanism of RYGB leading to diabetes remission independent of weight loss remains elusive. In this study, we profiled plasma metabolites and proteins of 10 normal glucose-tolerant obese (NO) and 9 diabetic obese (DO) patients before and 1-week, 3-months, 1-year after RYGB. 146 proteins and 128 metabolites from both NO and DO groups at all four stages were selected for further analysis. By analyzing a set of bi-molecular associations among the corresponding network of the subjects with our newly developed computational method, we defined the represented physiological states (called the edge-states that reflect the interactions among the bio-molecules), and the related molecular networks of NO and DO patients, respectively. The principal component analyses (PCA) revealed that the edge states of the post-RYGB NO subjects were significantly different from those of the post-RYGB DO patients. Particularly, the time-dependent changes of the molecular hub-networks differed between DO and NO groups after RYGB. In conclusion, by developing molecular network-based systems signatures, we for the first time reveal that RYGB generates a unique path for diabetes remission independent of weight loss

Role of Hydrogen Migrations in Carbonyl Peroxy Radicals in the Atmosphere

Carbonyl peroxy radicals (RC(O)O-2) are the ubiquitous radical intermediates in the atmospheric oxidation of volatile organic compounds. In this work, theoretical studies are carried out to explore the role of the unimolecular H-migration in the carbonyl peroxy radicals by using quantum chemistry and kinetics calculations. The results showed that H-migration could be significant in the atmosphere at least in CH3CH2CH2C(O)O-2 and (CH3)(2)CHCH2C(O)O-2 with rates of similar to 0.012 and similar to 0.58 s(-1) at 298 K. Subsequent reactions of CH3CHCH2C(O)OOH would lead to the products with multi-functional groups, which might affect the aerosol formation process; while (CH3)(2)CCH2C(O)OOH would transform to formaldehyde and acetone in a few steps. These processes would be important for the atmospheric modelling of volatile organic compounds under low-NOx conditions

Effects of process parameters on dimensional precision and tensile strength of wax patterns for investment casting by selective laser sintering

Turbine blades, produced by the directional solidifi cation (DS) process, often require high dimensional accuracy and excellent mechanical properties. A critical step in their production is the fabrication of wax patterns. However, the traditional manufacturing process has many disadvantages, such as long-term production, low material utilization rate, and the high cost of producing a complex-shaped wax pattern. Selective laser sintering (SLS) is one of the most extensively used additive manufacturing techniques that substantially shortens the production cycle. In this study, SLS was adopted to fabricate the wax pattern instead of the traditional manufacturing process. The orthogonal experiment method was carried out to investigate the effects of laser power, scanning speed, scanning space, and layer thickness on the dimensional precision and morphologies of the SLS parts. The SLS parts showed a minimum dimensional deviation when laser power, scanning speed, scanning space, and layer thickness were 10 W, 3000 mm•s-1, 0.18 mm, and 0.25 mm, respectively. In addition, the tensile strength and fracture morphologies were closely associated with the laser volumetric energy density (VED). The tensile strength reached a maximum when the VED was 0.0762 J•mm-3, with an evident brittle fracture morphology. The wax pattern manufactured in this way meets the accuracy and strength requirements for investment casting. This research offers a novel path for the production of wax patterns for complex-shaped turbine blades by SLS

Recent advances in fabrication strategies, phase transition modulation, and advanced applications of vanadium dioxide

Vanadium dioxide (VO2), with the first-order metal-insulator phase transition at near room temperature, has attracted increasing attention in the past few decades. With rapid electrical switching, the phase transition in VO 2 also triggers the colossal property changes in various aspects, such as optical properties, magnetic properties, and strain, and, thus, enables a wide range of modern applications. In this review, we present a complete picture of the latest advances of VO2, including the fabrication strategies, property modulation, and advanced applications. This review summarizes several typical fabrication methods of VO2 crystals as well as some common problems and their possible solutions. The strategies for the fabrication of single-crystalline VO2 arrays are also discussed to meet the requirements of the high-performance devices at the macro-scale. This review concerns the typical approaches for the modulation of (metal-insulator transition) MIT and emphasizes on the domain study of VO2 single crystals at the nanoscale. We aim at a clear explanation of the effect of various inhomogeneities on the MIT behavior of VO2 and the importance of the accurate control of MIT at the domain level. After summarizing the preparation and modification of VO2, we focus on the applications of this amazing smart material in various aspects, including strain engineering, optical modulation, electrical switching, and multi-responsive sensing