Enhancement of osteoblast activity on nanostructured NiTi/hydroxyapatite coatings on additive manufactured NiTi metal implants by nanosecond pulsed laser sintering

Background: The osteoinductive behaviors of nitinol (NiTi)-based metal implants for bone regeneration are largely dependent on their surface composition and topology. Continuous-mode laser sintering often results in complete melting of the materials and aggregation of particles, which lack control of heat transfer, as well as microstructural changes during sintering of the nanocomposite materials. Methods: In the current study, in situ direct laser deposition was used to additively manufacture three-dimensional NiTi structures from Ni and Ti powders. The mechanical property of NiTi has been shown to be similar to bone. Nanosecond pulsed laser sintering process was then utilized to generate a nanoporous composite surface with NiTi alloy and hydroxyapatite (HA) by ultrafast laser heating and cooling of Ni, Ti, and HA nanoparticles mixtures precoated on the 3D NiTi substrates; HA was added in order to improve the biocompatibility of the alloy. We then studied the underlying mechanism in the formation of NiTi/HA nanocomposite, and the synergistic effect of the sintered HA component and the nanoporous topology of the composite coating. In addition, we examined the activity of bone-forming osteoblasts on the NiTi/HA surfaces. For this, osteoblast cell morphology and various biomarkers were examined to evaluate cellular activity and function. Results: We found that the nanoscale porosity delivered by nanosecond pulsed laser sintering and the HA component positively contributed to osteoblast differentiation, as indicated by an increase in the expression of collagen and alkaline phosphatase, both of which are necessary for osteoblast mineralization. In addition, we observed topological complexities which appeared to boost the activity of osteoblasts, including an increase in actin cytoskeletal structures and adhesion structures. Conclusion: These findings demonstrate that the pulsed laser sintering method is an effective tool to generate biocompatible coatings in complex alloy-composite material systems with desired composition and topology. Our findings also provide a better understanding of the osteoinductive behavior of the sintered nanocomposite coatings for use in orthopedic and bone regeneration applications

Estimation of the flux at 1450MHz of OB stars for FAST and SKA

Radio observation is crucial to understanding the wind mechanism of OB stars but very scarce. This work estimates the flux at 1450MHz ($S_{\rm 1.4GHz}$) of about 5,000 OB stars identified by the LAMOST spectroscopic survey and confirmed by the Gaia astrometric as well as astrophysical measurements. The calculation is performed under the free-free emission mechanism for wind with the mass loss rate derived from stellar parameters. The estimated $S_{\rm 1.4GHz}$ distributes from $10^{-11}$Jy to $10^{-3}$Jy with the peak at about $10^{-8}$Jy. This implies that the complete SKA-II can detect more than half of them, and some tens of objects are detectable by FAST without considering source confusion. An array of FAST would increase the detectable sample by two orders of magnitude.Comment: 15 pages. 8 figure

Probabilistic prediction of wind power based on improved Bayesian neural network

Deterministic wind power prediction can be used for long time-scale optimization of power dispatching systems, but the probability and fluctuation range of prediction results cannot be calculated. A Bayesian LSTM neural network (BNN-LSTM) is constructed based on Bayesian networks by placing a priori distributions on top of the LSTM network layer weight parameters. First, the temporal convolutional neural network (TCNN) is used to process the historical time-series data for wind power prediction, which is used to extract the correlation features of the time-series data and learn the trend changes of the time-series data. Then, the mutual information entropy method is used to analyze the meteorological dataset of wind power, which is used to eliminate the variables with small correlation and reduce the dimension of the meteorological dataset, so as to simplify the overall structure of the prediction model. At the same time, the Embedding structure is used to learn the temporal classification features of wind power. Finally, the time series data processed by TCNN, the meteorological data after dimensionality reduction, and the time classification feature data are fed into the BNN-LSTM prediction model together. Compared with a Bayesian neural network, continuous interval method, and Temporal Fusion Transformer (TFT), which is one of the most advanced time series prediction networks, the improved BNN-LSTM can respond more accurately to wind power fluctuations with better prediction results. The comprehensive index of probability prediction of pinball loss is smaller than those of the other three methods by 53.2%, 24.4%, and 11.3%, and the Winkler index is 3.5 %, 34.6 %, and 8.2 % smaller, respectively

Lightweight Mechanical Metamaterials Based on Hollow Lattices and Triply Periodic Minimal Surfaces

Lightweight mechanical metamaterials with exception specific stiffness and strength are useful in many applications, such as transportation, aerospace, architectures and etc. These materials show great potential in mechanical tasks where weight of the material is restrained due to economy or energy reasons. To achieve both the lightweight and the high specific mechanical properties, the metamaterials are often in form of periodic cellular structures with well-designed unit cells. The strategies in designing and improving such cellular structures become the key in the studies of such mechanical metamaterials. In this work, we use both experimental and numerical approaches while probing three types of mechanical metamaterials: i) composite bending dominated hollow lattices (HLs); ii) triply periodic minimal surfaces (TPMSs) and extended TPMSs (eTPMSs); iii) corrugated TPMSs. We have demonstrated a few strategies in designing and improving the specific stiffness or strength via these examples of mechanical metamaterials. Using carbon/ceramic composite in the bending dominated HLs, we prove that using the composite layered material against the single layer ceramic is effective in improving the specific mechanical performances of the mechanical metamaterials. Next, while studying the nature of TPMS, we discover that under isotropic deformation TPMSs are stretch dominated with no stress concentrations within the shell structure. They also have an optimal specific bulk modulus approaching the H-S upper bound. Furthermore, we establish a strategy to smoothly connect the zero-mean-curvature surfaces in TPMSs with the extension of zero-Gaussion-curvature surfaces, forming new ‘eTPMSs”. These new shellular structures trade off its isotropy and have improved specific Young’s modulus along their stiffest orientation compared to their TPMS base structures. Lastly, we introduce corrugated sub-structures to existing TPMSs to improve their mechanical properties, such as Young’s modulus, yield strength and failure strength in compression. It is found that the corrugated substructure can effectively suppress the local bending behavior and redirect crack propagation while such structures were under uniaxial compression

Estimation of the Flux at 1450 MHz of OB Stars for FAST and SKA

Radio observation is crucial to understanding the wind mechanism of OB stars but very scarce. This work estimates the flux at 1450 MHz ( S _1.4GHz ) of about 5000 OB stars identified by the LAMOST spectroscopic survey and confirmed by the Gaia astrometric as well as astrophysical measurements. The calculation is performed under the free–free emission mechanism for wind with the mass-loss rate derived from stellar parameters. The estimated S _1.4GHz distributes from 10 ^−11 to 10 ^−3 Jy with the peak at about 10 ^−8 Jy. This implies that the complete SKA-II can detect more than half of them, and some tens of objects are detectable by FAST without considering source confusion. An array of FAST would increase the detectable sample by 2 orders of magnitude

Evaluation of Cottonseed Meal as an Alternative to Fish Meal in Diet for Juvenile Asian Red-Tailed Catfish Hemibagrus wyckioides

A 10-week trial was performed to investigate the effects of replacing fishmeal with cottonseed meal (CSM) on the growth rate, protein metabolism, and antioxidant response of Asian red-tailed catfish Hemibagrus wyckioides. Five isonitrogenous and isocaloric diets (C0, C8.5, C17.2, C25.7, and C34.4) were prepared to contain 0%, 8.5%, 17.2%, 25.7%, and 34.4% CSM replacing fishmeal, respectively. The weight gain, daily growth coefficient, pepsin, and intestinal amylase activities initially increased and then decreased with the raising dietary CSM levels; the highest values were observed in the C17.2 group (P0.05). Dietary CSM inclusion regardless of levels increased the plasma growth hormone level as well as hepatic aspartate aminotransferase (AST) and γ-glutamyl transpeptidase activities but decreased the plasma glutamate dehydrogenase and AST activities (P0.05). The plasma immunoglobulin M content and hepatic glutathione reductase activity initially increased but then decreased with the raising dietary CSM levels; the highest values were found in the C17.2 group. These results indicated that dietary CSM inclusion level up to 17.2% improved the growth rate, feed cost, digestive enzyme activity, and protein metabolism without compromising antioxidant capacity of H. wyckioide, whereas these parameters were depressed by further inclusion of CSM. CSM is a potentially cost-effective alternative plant protein source in diet of H. wyckioide

Magnetic field assisted growth of highly dense alpha-Fe2O3 single crystal nanosheets and their application in water treatment

Highly dense 2D nanostructures are desirable in photocatalysis, water treatment and energy storage, due to their high surface to volume areas. This paper describes a novel approach combining thermal stress and magnetic force to generate highly dense alpha-Fe2O3 nanosheets on the surface of various iron substrates, including plates and powders. This technique involves the thermal oxidation of iron substrates on a hot plate with a magnetic field. The Lorentz force acting on the ions induced by the magnetic field facilitates the lateral growth of nanosheets. This effect results in a highly porous nanostructure consisting of dense 2D nanosheets with extremely large BET surface areas. The application of these nanosheets is explored in water treatment. Electron microscopic studies indicate that these nanosheets show a parabolic relation with time of thermal oxidation for the growth in the width direction. A comparison of heavymetal (As, Cr) ion adsorption of nanosheets and nanowires was also performed, which shows that nanosheets have a much better adsorption rate than nanowires