Hybrid metallic nanoparticles for excitation of surface plasmon resonance

A Ag nanostructure was put forward in this paper. There are two types of Ag nanoparticles, spherical and pyramidal particles. Both of them have the same period, but different height and shapes. The hybrid nanoparticles can produce the localized surface plasmon resonance (LSPR), which couples each other and leads to an extra peak transmission. Our UV-visible-IR spectrophotometer measurement results show that some extra small and sharp peaks appear besides the normal LSPR wave peaks in the transmittance spectrum. The hybrid Ag nanoparticles being used as nanosensors will be more sensitive and selective than the conventional LSPR-based nanosensors. © 2007 American Institute of Physics

Physico-Chemical and Antifungal Properties of a Trypsin Inhibitor from the Roots of Pseudostellaria heterophylla

Plant peptidase inhibitors play essential roles in the defense systems of plants. A trypsin inhibitor (PHTI) with a molecular mass of 20.5 kDa was isolated from the fresh roots of the medicinal herb, Pseudostellaria heterophylla. The purification process involved ammonium sulfate precipitation, gel filtration chromatography on Sephadex G50, and ion-exchange chromatography on DEAE 650M. The PHTI contained 3.7% α-helix, 42.1% β-sheets, 21.2% β-turns, and 33% disordered structures, which showed similarity with several Kunitz-type trypsin inhibitors. Inhibition kinetic studies indicated that PHTI was a competitive inhibitor, with a Ki value of 3.01 × 10−9 M, indicating a high affinity to trypsin. The PHTI exhibited considerable stability over a broad range of pH (2–10) and temperatures (20–70 °C); however, metal ions, including Fe3+, Ba2+, Mn2+, and Al3+, could inactivate PHTI to different degrees. Results of fluorescence spectroscopy and circular dichroism showed that Fe3+ could bind to TI with an association constant of 2.75 × 105 M−1 to form a 1:1 complex, inducing conformation changes and inactivation of PHTI. In addition, PHTI could inhibit the growth of the phytopathogens, Colletotrichum gloeosporioides and Fusarium oxysporum, through disruption of the cell membrane integrity. The present study extended research on Pseudostellaria heterophylla proteins and makes PHTI an exploitable candidate as an antifungal protein for further investigation

In Vitro Antioxidant Activities of Enzymatic Hydrolysate from Schizochytrium sp. and Its Hepatoprotective Effects on Acute Alcohol-Induced Liver Injury In Vivo

Schizochytrium protein hydrolysate (SPH) was prepared through stepwise enzymatic hydrolysis by alcalase and flavourzyme sequentially. The proportion of hydrophobic amino acids of SPH was 34.71%. The molecular weight (MW) of SPH was principally concentrated at 180–3000 Da (52.29%). SPH was divided into two fractions by ultrafiltration: SPH-I (MW < 3 kDa) and SPH-II (MW > 3 kDa). Besides showing lipid peroxidation inhibitory activity in vitro, SPH-I exhibited high DPPH and ABTS radicals scavenging activities with IC50 of 350 μg/mL and 17.5 μg/mL, respectively. In addition, the antioxidant activity of SPH-I was estimated in vivo using the model of acute alcohol-induced liver injury in mice. For the hepatoprotective effects, oral administration of SPH-I at different concentrations (100, 300 mg/kg BW) to the mice subjected to alcohol significantly decreased serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities and hepatic malondialdehyde (MDA) level compared to the untreated mice. Besides, SPH-I could effectively restore the hepatic superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities and glutathione (GSH) level. Results suggested that SPH was rich in biopeptides that could be exploited as antioxidant molecules against oxidative stress in human body

A Specific Peptide with Calcium-Binding Capacity from Defatted Schizochytrium sp. Protein Hydrolysates and the Molecular Properties

Marine microorganisms have been proposed as a new kind of protein source. Efforts are needed in order to transform the protein-rich biological wastes left after lipid extraction into value-added bio-products. Thus, the utilization of protein recovered from defatted Schizochytrium sp. by-products presents an opportunity. A specific peptide Tyr-Leu (YL) with calcium-binding capacity was purified from defatted Schizochytrium sp. protein hydrolysates through gel filtration chromatography and RP-HPLC. The calcium-binding activity of YL reached 126.34 ± 3.40 μg/mg. The calcium-binding mechanism was investigated through ultraviolet, fluorescence and infrared spectroscopy. The results showed that calcium ions could form dative bonds with carboxyl oxygen atoms and amino nitrogen atoms as well as the nitrogen and oxygen atoms of amide bonds. YL-Ca exhibited excellent thermal stability and solubility, which was beneficial for its absorption and transport in the basic intestinal tract of the human body. Moreover, the cellular uptake of calcium in Caco-2 cells showed that YL-Ca could enhance calcium uptake efficiency and protect calcium ions against precipitation caused by dietary inhibitors such as tannic acid, oxalate, phytate and metal ions. The findings indicate that the by-product of Schizochytrium sp. is a promising source for making peptide-calcium bio-products as algae-based functional supplements for human beings

High Spatiotemporal Resolution PM2.5 Concentration Estimation with Machine Learning Algorithm: A Case Study for Wildfire in California

As an aggregate of suspended particulate matter in the air, atmospheric aerosols can affect the regional climate. With the help of satellite remote sensing technology to retrieve AOD (aerosol optical depth) on a global or regional scale, accurate estimation of PM2.5 concentration has become an important task to quantify the spatiotemporal distribution of AOD and PM2.5. However, due to the limitations of satellite platforms, sensors, and inversion algorithms, the spatiotemporal resolution of current major AOD products is still relatively low. Meanwhile, for the impact of cloud, the AOD products often have a serious data gap problem, which also objectively limits the spatiotemporal coverage of predicted PM2.5 concentration. Therefore, how to effectively improve the spatiotemporal resolution and coverage of PM2.5 concentration under the requisite accuracy is still a grand challenge. In this study, the fused high spatial-temporal resolution AOD data in our previous study were used to estimate the ground PM2.5 concentration through machine learning algorithms, the deep belief network (DBN). The PM2.5 data had spatiotemporal autocorrelation in geostatistics and followed the Gaussian kernel distribution. Hence, the autocorrelation model modified by Gaussian kernel function integrated with DBN algorithm, named Geoi-DBN, was used to estimate PM2.5 concentration. The cross-validation results showed that the Geoi-DBN (R2 = 0.86, RMSE = 6.84 µg m−3) performed better than the original DBN (R2 = 0.67, RMSE = 10.46 µg m−3). The final high quality PM2.5 concentration data can be applied for urban air quality monitoring and related PM2.5 exposure risk assessment such as wildfire

Bioinspired scaffolds with hierarchical structures for tailored mechanical behaviour and cell migration

Replacement and regeneration of damaged bone, particularly for those defects with critical size, are still major challenges in orthopaedic surgery. The conventional bone implants, normally with poor internal architecture design, may cause significant issues owing to the mechanical and structural mismatches between target bone and the implants. In this work, as inspired by hierarchical natural bone, for the first time, we developed hydroxyapatite (HA) and beta-tricalcium phosphate (β-TCP) scaffolds with three-level hierarchical structures across macro to nano scale using combined 3D printing (3DP) and freeze casting routines. It is clear these hierarchical porous scaffolds significantly enhance cell penetration (over 7 times) while maintaining cell proliferation ability. With three levels of hierarchies, the overall mechanical behaviour of the scaffolds can be tailored to be comparable to general cancellous bone (ranging from 1 to 6 MPa), demonstrating great potential for practical applications. Additionally, the combination of nanoindentation and mechanics model makes it possible to predict the mechanical behaviour of scaffolds at micro and macro scales.</p

High capacity and mobility in germanium sulfide/graphene (GeS/Gr) van der Waals heterostructure as anode materials for sodium–ion batteries: A first-principles investigation

As a two-dimensional (2D) transition metal dichalcogenide (TMD), GeS has attracted considerable attention as an anode material for rechargeable batteries due to large surface-volume ratio, abundant adsorption sites and short diffusion paths. However, its poor electrical conductivity and large volume change upon cycling have hindered its practical application. To overcome these drawbacks, we propose a GeS/graphene (GeS/Gr) van der Waals heterostructure to be used as a high-performance composite anode in sodium-ion batteries (SIBs). Using first-principles density functional theory (DFT) calculations we systematically explore the potential of GeS/Gr heterostructure in terms of structural, electronic, mechanical and thermal properties. The introduction of the graphene layer improves the mechanical strength (Young's modulus of 415.88 Nm−1), ensuring excellent structural stability which can effectively withstand large strains with less deformation. The GeS/Gr anode undergoes a semiconductor-to-metal transition upon Na adsorption, demonstrating enhanced electrical conductivity. The hybrid anode exhibits an excellent Na storage capacity of 714.27 mA h g−1 and a low energy barrier of 0.05 eV for Na diffusion. Our ab-initio molecular dynamics (AIMD) simulations further confirm that Na adsorption induce no structural distortion demonstrating excellent cycling stability. Based on these results, we suggest that GeS/Gr heterostructure can be a promising anode material for SIBs.</p

Swelled Mechanism of Crumb Rubber and Technical Properties of Crumb Rubber Modified Bitumen

Crumb rubber modified bitumen (CRMB) has excellent high-temperature performance and fatigue resistance, and is widely used in asphalt pavement to cope with increasing traffic axle load and changing climate. Under conventional preparation conditions, the swelling degree of CR can directly impact the comprehensive properties of CRMB; however, physical and chemical properties research on swelling crumb rubber (SCR) and crumb rubber recycled bitumen (CRRB) in CRMB is relatively lacking. In this paper, the working performance of CRMB and CRRB in high-temperature and low-temperature conditions were studied through physical and working performance testing of bitumen. The CR and SCR were tested by scanning electron microscope (SEM), Fourier transform infrared spectrometer (FTIR), gel permeation chromatography (GPC), and particle size distribution (PSD) tests to study the physicochemical behavior and microscopic effects before and after CR swelling. The results showed that CR dosage was in the range of 10%, 15%, and 20%, as well as that CR dosages have a positive effect on the high- and low-temperature performance, storage stability, and elastic recovery of bitumen. The high-temperature PG grades of bitumen were directly improved by four grades, and the elastic recovery rate increased by 339.9%. CR improved the ultra-low temperature crack resistance of bitumen. Due to the absorption of lighter components by CR, the relative content of the heavy component of bitumen increased; however, its low-temperature performance decreased significantly. After swelling, the CR particle size increased and the range became wider, the surface complexity of CR became higher, and the specific surface area was larger. At the same time, CR carried out the transformation process from large and medium molecules to small molecules. During the swelling process, a new benzene ring structure appeared in the CR, and the C–C bond and C–S bond of CR broke, forming part of the C=C bond

Strengthening effects of twin interface in Cu/Ni multilayer thin films – A\ud molecular dynamics study

Molecular dynamics (MD) simulations of Cu/Ni multilayers with coherent, semi-coherent and coherent twin interfaces\ud under tension at temperatures of 10 K, 100 K and 300 K are carried out to study the effects of the interfaces\ud on the overallmechanical behavior. The microstructure and evolution of defects are investigated in detail to\ud understand the strengthening mechanisms. It is found that all kinds of interfaces can act as potent impediments\ud to the motion of dislocations. However, only the coherent twin interface shows significant strengthening effects\ud via plastic deformation. The reason is attributed to the fact that the twin interface can absorb inclined dislocations\ud and decrease its density, and therefore strengthen the layered structures