A ribbed strategy disrupts conventional metamaterial deformation mechanisms for superior energy absorption

\ua9 2024 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.Enhancing energy absorption in mechanical metamaterials has been a focal point in structural design. Traditional methods often include introducing heterogeneity across unit cells. Herein, we propose a straightforward ribbed strategy to achieve exceptional energy absorption. We demonstrate our concept through modified body-centered cubic (BCC) and face-centered cubic (FCC) ribbed truss-lattice metamaterials (BCCR and FCCR). Using stainless-steel 316L samples, compression tests indicate a 111% and 91% increase in specific energy absorption (SEA) for BCCR and FCCR, respectively, along with an enhancement in compression strength by 61.8% and 40.7%. Deformation mechanisms are comprehensively elucidated through both finite element analysis and theoretical calculations. The mitigation of stress concentration at nodes, redistribution of load transfer pathways within struts, and introduction of multiple plastic hinges collectively contribute to increased energy absorption and higher compression strength. Using rein-based polymer samples, the ribbed truss-lattice metamaterials also exhibit exceptional damage tolerance, experiencing only a 15% loss in maximum strength after cyclic compression at 20% strain, while maintaining a 73% higher SEA compared to their non-ribbed counterpart. This strategy extends beyond the discussed structures, presenting itself as a generic approach to enhance plateau strength and SEA

Effects of Pollen Typhae Total Flavone On β-Arrestin-2/SRC/ AKT signaling in adipose tissues of Type 2 diabetic rats

Background: Pollen Typhae total flavone (PTF), the extract from Pollen Typhae, a Chinese herbal medicine,  has been reported to improve insulin resistance in type 2 diabetic rats, but the potential mechanisms keep unclear.Materials and Methods: Type 2 diabetic model rats were induced by high-fat diet and low-dose  streptozotocin, and then were administered PTF by intragastrical gavage. After treatment for 4 weeks, insulin  receptor-β level in adipose tissues was determined by ELISA, and the protein expression was analyzed by  western blotting.Results: Administration of PTF increased insulin receptor-β level and enhanced β-arrestin-2 protein expression  in adipose tissues of type 2 diabetic rats. Although having no effect on the protein expression of Src  or Akt, PTF promoted phosphorylation of Src at Tyr416 and Akt at Ser473.Conclusion: The results indicate that PTF has beneficial effects on the β-arrestin-2/Src/Akt signaling in  adipose tissues of type 2 diabetic rats, implying the underlying mechanisms of PTF in ameliorating insulin  resistance.Key words: Chinese medicine, type 2 diabetes, signal transduction, insulin resistance, β-arrestin-

Drought events and their effects on vegetation productivity in China

Many parts of the world have experienced frequent and severe droughts during the last few decades. Most previous studies examined the effects of specific drought events on vegetation productivity. In this study, we characterized the drought events in China from 1982 to 2012 and assessed their effects on vegetation productivity inferred from satellite data. We first assessed the occurrence, spatial extent, frequency, and severity of drought using the Palmer Drought Severity Index (PDSI). We then examined the impacts of droughts on China\u27s terrestrial ecosystems using the Normalized Difference Vegetation Index (NDVI). During the period 1982–2012, China\u27s land area (%) experiencing drought showed an insignificant trend. However, the drought conditions had been more severe over most regions in northern parts of China since the end of the 1990s, indicating that droughts hit these regions more frequently due to the drier climate. The severe droughts substantially reduced annual and seasonal NDVI. The magnitude and direction of the detrended NDVI under drought stress varied with season and vegetation type. The inconsistency between the regional means of PDSI and detrended NDVI could be attributed to different responses of vegetation to drought and the timing, duration, severity, and lag effects of droughts. The negative effects of droughts on vegetation productivity were partly offset by the enhancement of plant growth resulting from factors such as lower cloudiness, warming climate, and human activities (e.g., afforestation, improved agricultural management practices)

Novel colorimetric films based on starch/polyvinyl alcohol incorporated with roselle anthocyanins for fish freshness monitoring

Novel colorimetric films were developed for real-time monitoring of fish freshness based on starch/polyvinyl alcohol (SPVA) incorporated with roselle (Hibiseus sabdariffa L.) anthocyanins (RACNs). Firstly, RACNs were extracted from roselle dehydrated calyxes. Secondly, SPVA aqueous solution was obtained with a mass rate of 2:1 (starch/PVA). Thirdly, the colorimetric films were fabricated by immobilizing 30, 60 and 120 mg RACNs/100 g starch into SPVA matrix with casting/solvent evaporation method. FTIR spectra of the colorimetric films showed that RACNs were successfully immobilized into the SPVA matrix. X-ray diffraction spectra and SEM micrographs indicated that the crystallinity of PVA was reduced during the film-forming process and the compatibility between starch and PVA was improved, owing to the presence of RACNs. The incorporation of RACNs led to a decrease of water content and tensile strength and an increase of elongation at break of the colorimetric films compared with the SPVA film. The color stability test showed that the colorimetric films were stable at refrigeration temperature and room temperature up to 14 days with relative color changes below than 5%. The colorimetric films with lower content of RACNs were found more sensitive towards ammonia. An application trial was conducted to monitor the freshness of silver carp (Hypophthalmichthys molitrix) at refrigeration temperature. The colorimetric films presented visible color changes over time due to a variety of basic volatile amines known as total volatile basic nitrogen (TVB-N). Hence, these colorimetric films can be used to monitor the real-time fish freshness for intelligent packaging

Interface magnetization transition via minority spin injection

The interface magnetization of n-type BaTiO3/La0.7Sr0.3MnO3 heterojunction is selectively probed by magnetic second-harmonic generation at 80 K. The injection of minority spins at the interface causes a sudden, reversible transition of the spin alignment of interfacial Mn ions from ferromagnetic to antiferromagnetic exchange coupled, while the bulk magnetization remains unchanged. We attribute the emergent interfacial antiferromagnetic interactions to weakening of the double-exchange mechanism caused by the strong Hund\u27s rule coupling between injected minority spins and local magnetic moments. The effect is robust and may serve as a viable route for electronic and spintronic applications. Published by AIP Publishing

Current-driven interface magnetic transition in complex oxide heterostructure

The interfacial spin state of n-type BaTiO3/La0.5Ca0.5MnO3/La0.7Sr0.3MnO3 heterojunction and its dependence on gate voltage is investigated with magnetic second-harmonic generation at 78 K. The injection of minority spins alters the interface magnetization of La0.7Sr0.3MnO3 from ferromagnetic to antiferromagnetic exchange coupled, while the bulk magnetization remains unchanged. The emergent interfacial antiferromagnetic interactions are attributed to modulations of the strong double-exchange interaction between conducting electron spins and local magnetic moments. The results will help promote the development of new interface-based functionalities and device concepts. (C) 2017 American Vacuum Society

Nanoscale Suppression of Magnetization at Atomically Assembled Manganite Interfaces

Using polarized X-rays, we compare the electronic and magnetic properties of a La(2/3)Sr(1/3)MnO(3)(LSMO)/SrTiO(3)(STO) and a modified LSMO/LaMnO(3)(LMO)/STO interface. Using the technique of X-ray resonant magnetic scattering (XRMS), we can probe the interfaces of complicated layered structures and quantitatively model depth-dependent magnetic profiles as a function of distance from the interface. Comparisons of the average electronic and magnetic properties at the interface are made independently using X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD). The XAS and the XMCD demonstrate that the electronic and magnetic structure of the LMO layer at the modified interface is qualitatively equivalent to the underlying LSMO film. From the temperature dependence of the XMCD, it is found that the near surface magnetization for both interfaces falls off faster than the bulk. For all temperatures in the range of 50K - 300K, the magnetic profiles for both systems always show a ferromagnetic component at the interface with a significantly suppressed magnetization that evolves to the bulk value over a length scale of ~1.6 - 2.4 nm. The LSMO/LMO/STO interface shows a larger ferromagnetic (FM) moment than the LSMO/STO interface, however the difference is only substantial at low temperature.Comment: 4 pages, 4 figure