Fabrication and characterization of 3D printed biocomposite scaffolds based on PCL and zirconia nanoparticles

The application of three-dimensional printed polymer scaffolds in repairing bone defects is a promising strategy.Among them,polycaprolactone(PCL)scaffolds are widely studied due to their good processability and controlled degradation rate.However,as an alternative graft for repairing bone defects,PCL materials have poor hydrophilicity,which is not conducive to cell adhesion and growth.In addition,the poor mechanical properties of PCL materials cannot meet the strength required to repair bone defects.In this paper,nano-zirconium dioxide(ZrO2)powder is embedded in PCL material through a meltmixing process,and a regular grid scaffold is constructed by 3D printing.The embedding of nanometer zirconium dioxide powder improves the hydrophilicity and water absorption of the composite scaffold,which is conducive to cell adhesion,proliferation and growth and is beneficial to the exchange of nutrients.Therefore,the PCL/ZrO2 composite scaffold showed better biological activity in vitro.At the same time,the PCL/ZrO2 composite material system significantly improves the mechanical properties of the scaffold.Among them,compared with the pure PCL scaffold,the Young’s modulus is increased by about 0.4 times,and the compressive strength is increased by about 0.5 times.In addition,the osteogenic differentiation results also showed that the PCL/ZrO2 composite scaffold group showed better ALP activity and more effective bone mineralization than the pure PCL group.We believe that the 3D printed PCL/ZrO2 composite scaffold has certain application prospects in repairing bone defects.

黑龙江北极村国家级自然保护区鸟类与兽类多样性

物种多样性是生物多样性最主要的结构和功能单位,维持其稳定在保护珍稀濒危物种方面发挥着独特和不可替代的作用。为探究我国大兴安岭地区物种多样性并完善其基础数据,本研究于2022年1月至2023年6月在黑龙江北极村国家级自然保护区102个相机位点布设了127台红外相机,并结合规划的30条4 km长的样线,在2022年冷季和2023年暖季开展固定样线调查。在调查期间,红外相机累计工作19,881 d,共获得独立有效照片1,704张,记录到研究地区的野生鸟类和兽类共94种,其中兽类19种(4目10科18属),鸟类75种(12目24科49属),包括国家一级重点保护野生动物7种,特别是20世纪60年代以来在本研究区域已经绝迹的东北虎(Panthera tigris altaica),本次发现为半个世纪以来首次监测到。红外相机拍摄到的兽类中拍摄率前三位的依次是猞猁(Lynx lynx, RAI=21.88)、狍(Capreolus pygargus, RAI=18.36)、野猪(Sus scrofa, RAI=10.00);鸟类中拍摄率前三位的依次是小嘴乌鸦(Corvus corone, RAI=1.91)、渡鸦(C. corax, RAI=0.70)、松鸦(Garrulus glandarius, RAI=0.45)。在样线调查结果中,兽类物种中痕迹遇见率最多的依次为紫貂(Martes zibeuina)、狍、马鹿(Cervus elaphus)、驼鹿(Alces alces)和雪兔(Lepustimidus)。本次调查填补了北极村国家级自然保护区生物多样性数据的空白,为保护区野生动物多样性的进一步研究和后续的保护管理提供了基础数据。

Flexible multichannel electrodes for acute recording in nonhuman primates

Flexible electrodes have demonstrated better biocompatibility than rigid electrodes in relieving tissue encapsulation and long-term recording.Nonhuman primates are closer to humans in their brains’structural and functional properties,thus making them more suitable than rodents as animal models for potential clinical usage.However,the application of flexible electrodes on nonhuman primates has rarely been reported.In the present study,a flexible multichannel electrode array for nonhuman primates was developed and implemented for extracellular recording in behaving monkeys.To minimize the window of durotomy for reducing possible risks,a guide-tube-compatible implantation solution was designed to deliver the flexible electrodes through the dura into the cortex.The proposed structure for inserting flexible electrodes was characterized ex vivo and validated in vivo.Furthermore,acute recording of multichannel flexible electrodes for the primates was performed.The results showed that the flexible electrodes and implantation method used in this study meet the needs of extracellular recording in nonhuman primates.Task-related neuronal activities with a high signal-to-noise ratio of spikes demonstrated that our whole device is currently a minimally invasive and clinically viable approach for extracellular recording.

Effects of medium fluid cavitation on fluctuation characteristics of magnetic fluid seal interface in agricultural centrifugal pump

The fluctuation law of magnetic fluid seal interface of an agricultural centrifugal pump is theoretically unknown;the pressure and velocity fluctuations are crucial factors that cause interface fluctuation.In this study,the pressure and velocity fluctuations of the sealing interface on an agricultural centrifugal pump during cavitation were investigated based on the methods of Ansys CFX numerical calculation and experimental verification.The results demonstrated that at the same flow rate,the pressure fluctuation amplitude of the sealing interface decreased gradually from the shaft surface to the bottom of the polar tooth.At different flow rates,the amplitude of the pressure fluctuation decreased with an increase in the flow rate.The cavitation of the medium aggravated the impact and water hammer of the liquid,leading to the occurrence of the jitter phenomenon in the sealing interface to accelerate the fluctuation frequency of the axial velocity of the sealing liquid,which accelerated the emulsification of the magnetic fluid.This law can provide a reference for the design of magnetic fluid sealing devices for agricultural centrifugal pumps.

Graph convolution machine for context-aware recommender system

The latest advance in recommendation shows that better user and item representations can be learned via performing graph convolutions on the user-item interaction graph.However,such finding is mostly restricted to the collaborative filtering(CF)scenario,where the interaction contexts are not available.In this work,we extend the advantages of graph convolutions to context-aware recommender system(CARS,which represents a generic type of models that can handle various side information).We propose Graph Convolution Machine(GCM),an end-to-end framework that consists of three components:an encoder,graph convolution(GC)layers,and a decoder.The encoder projects users,items,and contexts into embedding vectors,which are passed to the GC layers that refine user and item embeddings with context-aware graph convolutions on the user-item graph.The decoder digests the refined embeddings to output the prediction score by considering the interactions among user,item,and context embeddings.We conduct experiments on three real-world datasets from Yelp and Amazon,validating the effectiveness of GCM and the benefits of performing graph convolutions for CARS.

Ribosome Profiling Reveals Genome-wide Cellular Translational Regulation upon Heat Stress in Escherichia coli

Heat shock response is a classical stress-induced regulatory system in bacteria, character- ized by extensive transcriptional reprogramming. To compare the impact of heat stress on the tran- scriptome and translatome in Escherich＆ coli, we conducted ribosome profiling in parallel with RNA-Seq to investigate the alterations in transcription and translation efficiency when E. coli cells were exposed to a mild heat stress （from 30 ~C to 45 ~C）. While general changes in ribosome foot- prints correlate with the changes of mRNA transcripts upon heat stress, a number of genes show differential changes at the transcription and translation levels. Translation efficiency of a few genes that are related to environment stimulus response is up-regulated, and in contrast, some genes func- tioning in mRNA translation and amino acid biosynthesis are down-regulated at the translation level in response to heat stress. Moreover, our ribosome occupancy data suggest that in generalribosomes accumulate remarkably in the starting regions of ORFs upon heat stress. This study pro- vides additional insights into bacterial gene expression in response to heat stress, and suggests the presence of stress-induced but yet-to-be characterized cellular regulatory mechanisms of gene expression at translation level.