We study the switching process in chalcogenide superlattice (CSL) phase-change memory materials by describing the motion of an atomic layer between the low and high resistance states. Two models have ...been proposed by different groups based on high-resolution electron microscope images. Model 1 proposes a transition from Ferro to Inverted Petrov state. Model 2 proposes a switch between Petrov and Inverted Petrov states. For each case, we note that the main transition is actually a vertical displacement of a Ge layer through a Te layer, followed by a lateral motion of GeTe sublayer to the final, low energy structure. Through calculating energy barriers, the rate-determining step is the displacive transition.
Honey is a natural sweetener produced by honey bees from the secretions of plants. Honey is well-known for its nutritional and medicinal values since prehistoric times. In the present study, 40 honey ...samples were collected from supermarkets in China. These samples were produced in China and also imported from other countries. These samples were explored for the detection of 16 phenolic acids and 14 flavonoids by employing high-performance liquid chromatography (HPLC). Among the phenolic compounds explored, gallic acid (phenolic acid) and chrysin (flavonoid) were found to be the most dominant phenolic compounds. The phenolic profile of honey samples was greatly influenced by geographical location and floral sources. The classification of honey samples collected from various regions and floral sources (unifloral and multi-floral) were carried out using linear discriminant analysis (LDA) and it was observed that certain phenolic compounds significantly contributed towards the classification of honey samples collected from various geographical origin and floral source. Thus, this systematic study provides a fundamental knowledge of honey quality for therapeutic product development.
Antioxidant activities of 43 commonly consumed mushrooms in China were evaluated using ABTS free radical scavenging (ABTS) assay, DPPH free radical scavenging (DPPH) assay, ferric reducing ...antioxidant power (FRAP) assay, and metal chelating ability (MCA) assay. Phenolic profiles in total phenol content (TPC) and total flavonoid contents (TFC) of mushrooms were also determined by colorimetric methods. The contents of free phenolic acids in mushrooms were determined by HPLC. The mushroom samples exhibited diverse antioxidant activity in different assays. The highest antioxidant ability was found in porcino nero in DPPH value, mulberry yellow in FRAP value, stone ear in ABTS value, and maitake in MCA value. Total phenolic and flavonoid content determination showed that all mushrooms are rich in phenolics and flavonoids. Stone ear and pine-spike had the highest phenolic and flavonoid content. Mushrooms exhibited a positive linear correlation between TPC and ABTS antioxidant capacities at the level of 0.01. Mushrooms have different phenolic acid profiles. Gallic acids were detected with high quantity in most of the mushrooms. Other phenolic acids were detected with low content, and some of phenolic acids were not detected in mushrooms.
•Phenolic profiles of commonly consumed mushroom were investigated firstly.•43 mushrooms presented substantial antioxidant activities.•Maitake possess the strongest metal chelating ability.•Gallic acid were detected in most of mushrooms.•Current findings will guide consumers and manufactures to utilize mushrooms.
GeSbTe-based chalcogenide superlattice (CSLs) phase-change memories consist of GeSbTe layer blocks separated by van der Waals bonding gaps. Recent high resolution electron microscopy found two types ...of disorder in CSLs, a chemical disorder within individual layers, and SbTe bilayer stacking faults connecting one block to an adjacent block which allows individual block heights to vary. The disorder requires a generalization of the previous switching models developed for CSL systems. Density functional calculations are used to describe the stability of various types of intra-layer disorder, how the block heights can vary by means of SbTe-based stacking faults and using a vacancy-mediated kink motion, and also to understand the nature of the switching process in more chemically disordered CSLs.
RE-containing Mg alloys used as biodegradable medical implants exhibit good promising application due to their good mechanical properties and degradation resistance. In this work, effect of Gd on the ...microstructure, mechanical properties and biodegradation of as-cast Mg-2Zn-xGd-0.5Zr alloys was investigated. The results showed that there were mainly α-Mg, I-phase, W-phase and MgZn2 phase in Mg-Zn-Gd-Zr alloys. With increase of the Gd content, the strength of the alloys was enhanced due to the second phase strengthening and grain refinement. The degradation resistance of Mg-2Zn-0.5Zr alloy was increased by adding 0.5%–1% Gd due to the uniformly distributed second phases which acted as a barrier to prevent the pitting corrosion. However, increasing Gd content to 2% reduced the degradation resistance of the alloy due to the galvanic corrosion between the matrix and the second phases. The good degradation resistance and mechanical properties of as-cast Mg-2Zn-1Gd-0.5Zr alloy makes it outstanding for biomaterial application.
Fluorescence bioimaging in the second near‐infrared spectral region (NIR‐II, 1000–1700 nm) can provide advantages of high spatial resolution and large penetration depth, due to low light scattering. ...However, NIR‐II fluorophores simultaneously possessing high brightness, good stability, and biocompatibility are very rare. Hydrophobic NIR‐II emissive PbS@CdS quantum dots (QDs) are surface‐functionalized, via a silica and amphiphilic polymer (Pluronic F‐127) dual‐layer coating method. The as‐synthesized PbS@CdS@SiO2@F‐127 nanoparticles (NPs) are aqueously dispersible and possess a quantum yield of ≈5.79%, which is much larger than those of most existing NIR‐II fluorophores. Thanks to the dual‐layer protection, PbS@CdS@SiO2@F‐127 NPs show excellent chemical stability in a wide range of pH values. The biocompatibility of PbS@CdS@SiO2@F‐127 NPs is studied, and the results show that the toxicity of the NPs in vivo could be minimal. PbS@CdS@SiO2@F‐127 NPs are then utilized for in vivo and real‐time NIR‐II fluorescence microscopic imaging of mouse brain. The architecture of blood vessels is visualized and the imaging depth reaches 950 µm. Furthermore, in vivo NIR‐II fluorescence imaging of gastrointestinal tract is achieved, by perfusing PbS@CdS@SiO2@F‐127 NPs into mice at a rather low dosage. This work illustrates the potential of ultrastable, biocompatible, and bright NIR‐II QDs in biomedical and clinical applications, which require deep tissue imaging.
NIR‐II emissive PbS@CdS quantum dots are surface‐functionalized with a dual‐layer coating method. The as‐synthesized PbS@CdS@SiO2@F‐127 nanoparticles (NPs) are aqueously dispersible, and possess certain brightness. Chemically stable and biocompatible PbS@CdS@SiO2@F‐127 NPs are utilized for deep tissue (950 µm) in vivo microscopic angiography of the mice brain. Noninvasive and large depth (3–5 mm) gastrointestinal tract imaging with high contrast is achieved.
Magnesium alloys as a class of biodegradable metals have great potential to be used as implant materials, which attract much attention. In this review, the mechanical properties of magnesium alloys ...for medical applications are summarized. The methods to improve the mechanical properties of biodegradable magnesium alloys and the mechanical behaviors of Mg alloys in biomedical application are illustrated. Finally the challenges and future development of biodegradable magnesium alloys are presented.
Cancer is one of the most lethal diseases all over the world. Despite that many drugs have been developed for cancer therapy, they still suffer from various limitations including poor treating ...efficacy, toxicity to normal human cells, and the emergence of multidrug resistance. In this study, the amphiphilic LHES polymers were prepared using hydroxyethyl starch (HES) and linoleic acid as starting materials. The content and substitution degree of linoleic acid groups in LHES polymers were analyzed. The LHES polymers were used for fabricating LHES-B nanoparticles carrying a linoleic acid modified berberine derivative (L-BBR). The LHES-B nanoparticles showed high drug loading efficiency (29%) and could quickly release L-BBR under acidic pH condition (pH = 4.5). Biological investigations revealed that LHES-B nanoparticles significantly inhibited the proliferation of HepG2 cells and exhibited higher cytotoxicity than L-BBR. In a transgenic Tg(fabp10:rtTA2s-M2; TRE2:EGFP-krasv12) zebrafish model, LHES-B nanoparticles obviously inhibited the expression of krasv12 oncogene. These results indicated that LHES carriers could improve the anticancer activity of L-BBR, and the synthesized LHES-B nanoparticles showed great potential as anticancer drug.
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•Starch-based nanoparticles carrying berberine derivative were fabricated.•The nanoparticles showed good sensitivity under acidic pH condition.•The nanoparticles inhibited the expression of krasv12 oncogene in a zebrafish model.
Edible flowers are referred to the non-toxic flowers that can be consumed by human beings for their additional nutritional or medical properties. These flowers are rich source of natural ...antioxidants, thus exert specific positive health effects on chronic diseases and act as a potential function food. This research paper is focused on the determination of total phenolic content (TPC), total flavonoids content (TFC), and antioxidant capacities of different kinds of edible flowers in China and compared systematically. Sixty-five flower samples were collected from parks in Guangzhou and also purchased from Qingping Market. TPC, TFC, and three anti-oxidative assays (DPPH free radical scavenging activity, ABTS radical scavenging activity, and Ferric reducing antioxidant capacity (FRAP) assay) were conducted. Different flowers presented diverse range of antioxidant capacities, phenolic contents, and flavonoid contents. A high correlation between TPC and antioxidant activity (as accessed using three different methods) was reported. However, a low relationship was observed between TFC value and antioxidant capacities. This study revealed that five Rosa species exhibited strong antioxidant capacities among other samples, and these can be used as potential functional foods to counterbalance the effect of reactive oxygen species (ROS) and oxidative stress.
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