A Glassy Carbon Electrode Modified with Cellulose Nanofibrils from Ammophila arenaria for the Sensitive Detection of L-Trytophan

L-tryptophan is an essential amino acid for human health. Nanofibrillated cellulose (NFC) from marram grass (Ammophila arenaria) extracted from plants harvested in the center of Tunisia was used for the first time for the modification of a glassy carbon electrode (GCE), for the sensitive detection of L-tryptophan (Trp). After spectroscopic and morphological characterization of the extracted NFC, the GC electrode modification was monitored through cyclic voltammetry. The NFC-modified electrode exhibited good analytical performance in detecting Trp with a wide linear range between 7.5 × 10−4 mM and 10−2 mM, a detection limit of 0.2 µM, and a high sensitivity of 140.0 µA∙mM−1. Additionally, the NFC/GCE showed a good reproducibility, good selectivity versus other amino acids, uric acid, ascorbic acid, and good applicability to the detection of Trp in urine samples.

不同方法对根管内氢氧化钙去除效果的micro-CT评价

目的:应用显微CT(micro-computed tomography,micro-CT)建立磨牙根管模型,评价不同方法对氢氧化钙的清除效率。方法:收集2023年10月—2024年2月口腔综合科门诊拔除的11颗磨牙(24个根管),按照标准根管治疗流程,镍钛器械预备完成后,在根管内置入氢氧化钙,1周后,根据不同冲洗方法将样本随机分为侧方开口注射器组、超声荡洗组(EMS组)和声波震荡组(EDDY组)等3组(n=8)。冲洗前后使用micro-CT重建根管系统并使用不同颜色标记独立根管,计算各个根管氢氧化钙体积,比较各组氢氧化钙清除率。采用SPSS 19.0软件包对数据进行统计学分析。结果:3种方法均无法完全去净根管内氢氧化钙。使用次氯酸钠作为冲洗液时,超声荡洗和声波震荡清除效果优于侧方开口冲洗器(P<0.05);超声荡洗和声波震荡去除氢氧化钙效率相当,差异无统计学意义(P>0.05);氢氧化钙残留部位集中于根尖区。结论:Micro-CT能较为高效地重建磨牙根管模型,可用于评价氢氧化钙去除效果。超声荡洗组和声波震荡组清除氢氧化钙效率相当,优于侧方开口注射器组。

Ultrathin and Flexible CNTs/MXene/Cellulose Nanofibrils Composite Paper for Electromagnetic Interference Shielding

As the rapid development of portable and wearable devices,different electromagnetic interference(EMI)shielding materials with high efficiency have been desired to eliminate the resulting radiation pollution.However,limited EMI shielding materials are successfully used in practical applications,due to the heavy thickness and absence of sufficient strength or flexibility.Herein,an ultrathin and flexible carbon nanotubes/MXene/cellulose nanofibrils composite paper with gradient and sandwich structure is constructed for EMI shielding application via a facile alternating vacuum-assisted filtration process.The composite paper exhibits outstanding mechanical properties with a tensile strength of 97.9±5.0 MPa and a fracture strain of 4.6±0.2%.Particularly,the paper shows a high electrical conductivity of 2506.6 S m?1 and EMI shielding effectiveness(EMI SE)of 38.4 dB due to the sandwich structure in improving EMI SE,and the gradient structure on regulating the contributions from reflection and absorption.This strategy is of great significance in fabricating ultrathin and flexible composite paper for highly efficient EMI shielding performance and in broadening the practical applications of MXene-based composite materials.

Micro LED车灯投影光学系统设计与优化

本文提出了一种基于Micro LED阵列的车灯投影方案,设计了以像素尺寸为80μm×80μm的200×150白光Micro LED阵列作为显示光源,视场角为16°×34°的车灯投影光学系统,并对物面倾斜角度和光学系统结构进行了优化。此外,分别采用反向畸变处理方法和像素灰度调制方法用以解决车灯投影图像的梯形畸变和照度均匀性问题,并搭建了投影实验平台,对图像校正方法进行了验证。实验结果表明:校正后图像梯形畸变系数p1,p2分别从0.0932和0.3680下降至0.0835和0.0373,像面照度均匀性从83.2%提高到93.2%。本文通过对基于Micro LED的倾斜投影车灯光学系统进行优化设计及采用图像校正方法,实现了高光效、低畸变的车灯投影。

Morphological, Mechanical and Thermal Properties of Poly(lactic acid)(PLA)/Cellulose Nanofibrils(CNF) Composites Nanofiber for Tissue Engineering

Composite nanofiber membranes based on biodegradable poly(lactic acid)(PLA) and cellulose nanofibrils(CNF) were produced via electrospinning. The influence of CNF content on the morphology, thermal properties, and mechanical properties of PLA/CNF composite nanofiber membranes were characterized by field scanning electron microscopy(FE-SEM), differential scanning calorimetry(DSC), thermogravimetric analysis(TGA), and dynamic mechanical analysis(DMA), respectively. The results show that the PLA/CNF composite nanofibers with smooth, free-bead surface can be successfully fabricated with various CNF contents. The introduction of CNF is an effective approach to improve the crystalline ability, thermal stability and mechanical properties for PLA/CNF composite fibers. The Young's moduli and tensile strength of the PLA/CNF composite nanofiber reach 106.6 MPa and 2.7 MPa when the CNF content is 3%, respectively, which are one times higher and 1.5 times than those of pure PLA nanofiber. Additionally, the water contact angle of PLA/CNF composite nanofiber membranes decreases with the increase of the CNF loading, resulting in the enhancement of their hydrophilicity.

Sol-Gel Template Synthesis and Photocatalytic Activity of TiO_2 Nanofibrils Loaded on Al_2O_3 Template

TiO2 nanofibrils were prepared within the pores of alumina template membrane by use of sol-gel chemistry. The TiO2 nanofibrils have good crystallinity and size. There is agglomeration free among the particulates of TiO2 and the fibrils show high catalytic activity.

光子晶体Micro LED微显示阵列加工及光学特性分析

Micro LED器件具有高亮度、低功耗和高可靠性等优点,但Micro LED显示像素巨量转移和光提取效率低的问题为其应用带来挑战。开发了具有高转移效率和出光效率的单片64×64 Micro LED微显示阵列,提出了倒装型GaN基单片Micro LED微显示阵列芯片和Si基驱动电路的设计方法及集成工艺。通过时域有限差分(FDTD)方法对Micro LED微显示阵列光学特性进行了建模分析,设计了一种提高Micro LED微显示阵列出光效率的光提取结构。结合仿真结果,开发了一种在Micro LED蓝宝石衬底表面制备光子晶体结构的聚焦离子束(FIB)微纳加工工艺,并进行了器件加工。测试结果表明,蓝宝石衬底上加工的光子晶体结构可以提高Micro LED器件的表面出光效率,光功率平均值提升了16.36%,对Micro LED微显示阵列加工及微显示像素光提取问题具有借鉴意义。

Simultaneous Extraction of Carboxylated Celulose Nanocrystals and Nanofibrils via Citric Acid Hydrolysis--A Sustainable Route

In this study, cellulose nanocrystals(CNC) with surface carboxylic groups were prepared from bleached softwood pulp by hydrolysis with concentrated citric acid at concentrations of 60 wt%~80 wt%. The solid residues from acid hydrolysis were collected for producing cellulose nanofibrils(CNF) via post high-pressure homogenization. Citric acid could be easily recovered after hydrolysis reactions through crystallization due to its low water solubility or through precipitation as a calcium salt followed by acidification. Several important properties of CNC and CNF, such as dimension, crystallinity, surface chemistry, thermal stability, were evaluated. Results showed that the obtained CNC and CNF surfaces contained carboxylic acid groups that facilitated functionalization and dispersion in aqueous processing. The recyclability of citric acid and the carboxylated CNC/CNF give the renewable cellulose nanomaterial huge potential for a wide range of industrial applications. Furthermore, the resultant CNC and CNF were used as reinforcing agents to make sodium carboxymethyl cellulose(CMC) films. Both CNC and CNF showed reinforcing effects in CMC composite films. The tensile strength of CMC films increased by 54.3% and 85.7% with 10 wt% inclusion of CNC and CNF, respectively. This study provides detailed information on carboxylated nanocellulose prepared by critic acid hydrolysis; a sustainable approach for the preparation of CNC/CNF is of significant importance for their various uses.

Water-Based Processing of Fiberboard of Acrylic Resin Composites Reinforced With Cellulose Wood Pulp and Cellulose Nanofibrils

Despite the great potential of cellulose wood pulp and cellulose nanofibrils as reinforcing filler in thermoplastics,its use is limited due to its tendency to form agglomerates and due to its high hydrophilic character.Here we describe fiberboard composites with high contents of wood pulp or cellulose nanofibrils,and a resin of poly(styrene-methyl-methacrylate-acrylic acid)used as water-based emulsion.Cellulose wood pulp and cellulose nanofibrils were used directly in the form of water suspensions.The method is based on the flocculation of the polymer emulsion followed by agglomeration of a mixture of the polymer emulsion and cellulose suspension,leading to the co-precipitation of the composite material,which can be easily separated from the water phase.Composites with acrylic polymer/cellulose fibers in the proportions of 75:25,50:50 and 25:75 wt%were prepared.Composites were characterized by scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR),thermogravimetric analysis(TGA),dynamic mechanical analysis(DMA)and water absorption tests.SEM analysis revealed a very good dispersion of the fibers without evidence of agglomeration,which led to superior mechanical properties.These results showed the effectiveness of the methodology and the potential of cellulose wood pulp and CNF as reinforcement fillers in fiberboard composites and any other high fiber-content materials.

Preparation of Cellulose Nanofibrils by Multi-Site Regioselective Oxidation

Cellulose nanofibrils(CNFs)are promising sustainable materials that can be applied to nanocomposites,as well as medical and life-sciences devices.However,methods for the preparation of these important materials are energy intensive because heating and mechanical disintegration are required to produce cellulose fibers below 100 nm in size.In this study,CNFs were prepared through the multi-site regioselective oxidation of cellulose with 2,2,6,6-tetramethylpiperidine-1-oxyl(TEMPO)and periodate at room temperature(20–25°C),without any mechanical-disintegration treatment.Transmission electron microscopy(TEM)revealed that the CNFs had the average widths of 14.1,55.4,and 81.9 nm for three different treatments.Fourier-transform infrared spectroscopy revealed that carboxyl groups were created on the surfaces of the microfibrils,while X-ray diffraction studies showed that the cellulose I structure was maintained after oxidation,and that the cellulose nanofibril crystallinity index exceeded 70%.These results demonstrate that CNFs can be prepared by multi-site regioselective oxidation at room temperature in the absence of mechanical disintegration.In addition,a model was developed to calculate the total content of carboxylate and aldehyde groups of CNFs prepared by the TEMPO mediate oxidation,the periodate oxidation,and the multi-site regioselective oxidation methods based on the particle width determined by TEM.The calculated values of the model were in good agreement with the total content(experimental value)of carboxylate and aldehyde groups of CNFs prepared by the TEMPO-mediated oxidation and the multi-site regioselective oxidation methods.However,the model was not valid for CNFs prepared by the periodate oxidation method.

An Alternative Strategy to Obtain Cellulose Nanofibrils from Parenchyma Cellulose of Bagasse Pith and the Performance of Its Nanopaper

Cellulose nanofibrils(CNFs)were obtained through one-step mechano-partial dissolution by ball milling in N,N-dimethyl acetamide with a low concentration of LiCl from agricultural waste bagasse pith(BP).Compared with fibrous cellulose,parenchyma cellulose(PC)is less uniform in diameter and less aligned,causing PC to dissociate into CNFs during this process without pretreatment.The results showed that the CNFs prepared from PC of BP had a diameter of 30-200 nm and a length of several micrometers.The as-obtained CNFs,along with dissolved cellulose,formed a wet-stable and highly transparent nanopaper in a sorbitol aqueous solution bath,which exhibited a high strain of 101%and a low Young's modulus of 4.3 MPa owing to the addition of the plasticizer sorbitol.This type of nanopaper with favorable transparency,high tensile property,and low Young's modulus has great potential for use as electronic skin and medical dressing material.

Okara Cellulose Nanofibrils Produced by Pretreatment with Sustainable Deep Eutectic Solvent Coupled with Various Mechanical Treatments

In this study,a green,environmentally friendly method for rapid cellulose nanofribril(CNF)preparation with a significant cost advantage was developed.Pretreatment with a deep eutectic solvent(DES)synthesized from oxalic acid dihydrate and choline chloride(ChCl-O)was combined with various mechanical treatment methods to produce okara CNFs from agricultural waste,with different diameter distributions.The results showed that high-speed stirring produced CNFs with an average diameter of 27 nm.This method was advantageous because it consumed about 94%less energy than traditional high-pressure homogenization method.The DES recovery rate was more than 90%,and DES served as a highly effective treatment,indicating that DES pretreatment is an economical,convenient,and effective strategy for okara CNF preparation.

基于Micro CT的铜导线短路熔痕孔洞特征分析

导线短路是造成电气火灾的重要原因之一。现行国家标准中将导线短路熔痕分为起火前发生的一次短路熔痕和起火后造成的二次短路熔痕,然而现行国家标准中的鉴定仅停留在定性判断的阶段。火灾现场铜导线短路熔痕特征的量化分析研究是国内外研究人员主要关注的重点。本文应用Micro CT技术对铜导线短路熔痕进行断层扫描检测并重构铜导线短路熔痕的3D图像数据,在此基础上统计、归纳、总结铜导线短路熔痕内部孔洞形态及分布等孔洞特征。研究表明,Micro CT能够全面采集铜导线短路熔痕的整体形态和内部孔洞特征,一次短路熔痕与二次短路熔痕内部孔洞半径、表面积、紧密度的特征数据存在差别,可为短路熔痕定性和定量分析判据研究提供新的理论依据。

Micro-CT分析跟骨内骨小梁分布及结构特征

背景:跟骨位于足的后下部,受力较大。跟骨外形复杂且不规则,外周有较薄的皮质骨包绕,内部充满大量的骨小梁,探讨骨小梁的微观结构、走行及分布特征有助于提高对跟骨骨折的认识。目的:采用微计算机断层扫描仪(Micro-CT)扫描跟骨标本获得其影像资料,对其内部骨小梁结构进行分析,探讨跟骨内骨小梁的形态、分布及结构特征。方法:采用Micro-CT连续扫描干燥成人跟骨标本,扫描后获得影像图像,将其以DICOM格式存储。导入影像资料到Hiscan Analyzer软件,显示清晰完整的成人跟骨矢状面、冠状面、水平面的图像,逐层观察骨小梁的走行,依据骨小梁走行特点将跟骨矢状面分为6个部分,在以7 mm为标准的相同厚度下,每个部分选择1个49 mm2等面积的兴趣区,三维重建后获得跟骨及骨小梁的立体微观结构,二值化后运用软件计算感兴趣区域内骨小梁的体积分数、表面密度、骨小梁厚度、骨小梁间隙和骨小梁数量参数。结果与结论:①跟骨表面皮质层很薄,内部充满大量骨松质,在Gissane角的骨皮质明显增厚;②跟骨上部的骨小梁体积分数大于跟骨下部前端、中和三角区、跟骨下后部、跟骨结节部、跟骨底部,跟骨结节部的骨小梁体积分数大于跟骨下部前端、中和三角区、跟骨下后部、跟骨底部;跟骨结节部的骨小梁表面密度大于跟骨下部前端、中和三角区、跟骨底部,跟骨上部、跟骨下后部的骨小梁表面密度大于中和三角区;跟骨上部的骨小梁厚度大于跟骨结节部;中和三角区的骨小梁间隙大于跟骨上部、跟骨结节部;跟骨结节部的骨小梁数量大于中和三角区;③中和三角区主要分布杆状骨小梁,骨小梁表面密度最小、体积分数较小、骨小梁间隙最大;该部位骨质较疏松,受到高冲击力时抗压缩能力差,骨小梁最先发生断裂,是易发生骨折的部位。

N,P co-doped porous graphene with high electrochemical properties obtained via the laser induction of cellulose nanofibrils

Cellulose and its derivatives are natural materials with high carbon contents, but it is challenging to convert their carbon into high value-added carbonaceous materials(e.g., graphene). Here, an approach to convert the carbon in cellulose into N, P co-doped porous graphene(LIG) materials via laser induction is proposed. Cellulose nanofibrils(CNFs), a cellulose derivative with high dispersion uniformity and abundant surface hydroxyl groups, were easily formed on a bulk substrate(thickness ≥5 mm) containing ammonium polyphosphate(APP). Then, a 10.6 μm CO2 laser was used to scribe for 1–5 passes on the CNFs/APP substrate under an ambient environment to produce N, P co-doped porous LIG. Upon increasing the number of laser scribing passes, the IG/IDof LIG first increased and then decreased, reaching a maximum of 1.68 at 4 passes. The good pore structure and low resistance also showed that 4 laser passes were ideal. Besides, the N, P co-doped LIG also showed excellent electrochemical performance, with a specific capacitance of 221.4 FF·g^(-1) and capacitance retention of 89.9%. This method exploits the advantages of nanocellulose and overcomes the difficulties associated with directly compounding cellulosic materials, providing a method for the further development of biomass nanomaterials.

Micro segment analysis of supercritical methane thermal-hydraulic performance and pseudo-boiling in a PCHE straight channel

The printed circuit heat exchanger(PCHE) is receiving wide attention as a new kind of compact heat exchanger and is considered as a promising vaporizer in the LNG process. In this paper, a PCHE straight channel in the length of 500 mm is established, with a semicircular cross section in a diameter of 1.2 mm.Numerical simulation is employed to investigate the flow and heat transfer performance of supercritical methane in the channel. The pseudo-boiling theory is adopted and the liquid-like, two-phase-like, and vapor-like regimes are divided for supercritical methane to analyze the heat transfer and flow features.The results are presented in micro segment to show the local convective heat transfer coefficient and pressure drop. It shows that the convective heat transfer coefficient in segments along the channel has a significant peak feature near the pseudo-critical point and a heat transfer deterioration when the average fluid temperature in the segment is higher than the pseudo-critical point. The reason is explained with the generation of vapor-like film near the channel wall that the peak feature related to a nucleateboiling-like state and heat transfer deterioration related to a film-boiling-like state. The effects of parameters, including mass flow rate, pressure, and wall heat flux on flow and heat transfer were analyzed.In calculating of the averaged heat transfer coefficient of the whole channel, the traditional method shows significant deviation and the micro segment weighted average method is adopted. The pressure drop can mainly be affected by the mass flux and pressure and little affected by the wall heat flux. The peak of the convective heat transfer coefficient can only form at high mass flux, low wall heat flux, and near critical pressure, in which condition the nucleate-boiling-like state is easier to appear. Moreover,heat transfer deterioration will always appear, since the supercritical flow will finally develop into a filmboiling-like state. So heat transfer deterioration should be taken seriously in the design and safe operation of vaporizer PCHE. The study of this work clarified the local heat transfer and flow feature of supercritical methane in microchannel and contributed to the deep understanding of supercritical methane flow of the vaporization process in PCHE.

Injectable self-healing nanocellulose hydrogels crosslinked by aluminum:Cellulose nanocrystals vs.cellulose nanofibrils

With excellent biocompatibility and unique physiochemical properties,nanocelluloses including cellulose nanocrystals(CNCs)and cellulose nanofibrils(CNFs)are promising candidates for preparing biomedical hydrogels.CNCs and CNFs are different in morphology and surface charges.Herein,CNCs and two CNFs(CNFs-C,Carboxylated CNFs;CNFs-P,Phosphorylated CNFs)were synthesized and applied to fabricate hydrogels through metal crosslinking.Aluminum crosslinking was found to be the best choice for enhancing the strength.This study systematically compared the morphologies,storage modulus,loss factor,continuous shear ramp,self-healing,swelling,in vitro degradation and injectable properties of the fabricated hydrogels,Further,a radar chart is summarized as guidelines to direct the rational selection to meet the specific requirements of further biomedical applications.At the same nanocellulose concentration and after Al^(3+)crosslinking,CNCs hydrogels had strong water holding capacity twice as much as that of CNFs hydrogels.While CNFs hydrogels showed higher hardness and stronger resistance to degradation than that of CNCs.These results provide detailed insights into nanocellulose hydrogels,making it possible to use these guidelines to select hydrogels for desired performance.

Advances in microfluidic-based DNA methylation analysis

DNA methylation has been extensively investigated in recent years,not least because of its known relationship with various diseases.Progress in analytical methods can greatly increase the relevance of DNA methylation studies to both clinical medicine and scientific research.Microflu-idic chips are excellent carriers for molecular analysis,and their use can provide improvements from multiple aspects.On-chip molecular analysis has received extensive attention owing to its advantages of portability,high throughput,low cost,and high efficiency.In recent years,the use of novel microfluidic chips for DNA methylation analysis has been widely reported and has shown obvious superiority to conventional methods.In this review,wefirst focus on DNA methylation and its applications.Then,we discuss advanced microfluidic-based methods for DNA methylation analysis and describe the great progress that has been made in recent years.Finally,we summarize the advantages that microfluidic technology brings to DNA methylation analysis and describe several challenges and perspectives for on-chip DNA methylation analysis.This review should help researchers improve their understanding and make progress in developing microfluidic-based methods for DNA methylation analysis.

高亮绿光氮化镓基Micro-LED微型显示器制备

Micro-LED作为一种新型的显示技术,具有对比度高、响应快及寿命长等优点,已成为当前研究的热点。然而,尽管潜力巨大,Micro-LED技术的商业化之路仍面临诸多技术上的挑战与瓶颈。本文旨在探讨高亮绿光氮化镓基Micro-LED微型显示器的制备过程及其相关技术。基于WVGA041全数字信号电路CMOS硅基驱动电路,制作了0.41 inch、分辨率为800×480的主动式单色绿光Micro-LED微型显示器。利用高精度倒装焊接技术实现了CMOS驱动电路与LED发光芯片的电气连接。结果表明,制备出LED显示芯片正常启亮电压为2.8V,EL光谱峰值波长524nm;在硅基CMOS电路驱动范围内,Micro-LED微型显示器在5V电压下,器件亮度为108000cd/m^(2)(最大亮度可达250000 cd/m^(2)),电流密度达到0.61A/cm^(2)时色坐标为(0.175,0.756)。当电流密度从0.3A/cm^(2)增加到1.3A/cm^(2)时,色坐标从(0.178,0.757)变化到(0.175,0.746),器件的色稳定性能够满足实际应用要求。

Dispersive Ability of Carboxylated Cellulose Nanofibrils for Aqueous Monolayer Montmorillonite Dispersion:Influence of Na^(+) and Ca^(2+) Concentrations

Carboxylated cellulose nanofibrils(CNFs)have emerged as effective green dispersants for monolayer montmorillonite(MMT)dispersions.However,their dispersion capability is sensitive to the metal ion concentration in aqueous solutions.Hence,this study investigated the effects of Na^(+) and Ca^(2+) concentrations on the dispersive ability of carboxylated CNFs for monolayer MMTs in water.Quartz crystal microbalance with dissipation monitoring(QCM-D)and atomic force microscopy(AFM)were utilized to explore the interfacial interactions between the carboxylated CNFs and monolayer MMTs under different Na^(+) and Ca^(2+) concentrations.When the concentration of Na^(+) reached 0.1 mmol/L,the adhesion mass of carboxylated CNFs on MMT-coated wafer peaked at 24.47 mg/m^(2),higher than control sample(carboxylated CNF-dispersed monolayer MMT dispersion without metal ions,16.03 mg/m^(2)).Moreover,the electrostatic shielding effect promoted a better dispersion of monolayer MMTs by carboxylated CNF dispersant.With a further increase in the Na^(+) concentration,the surface charge of CNFs and MMTs would be reversed resulting from the improved electrostatic shielding effect,which weaken the dispersive ability of carboxylated CNFs.The addition of Ca^(2+) reduced the dispersive ability of carboxylated CNFs for monolayer MMTs,because Ca^(2+) required a lower concentration for the onset of charge reversal compared to Na^(+).This study provides interfacial scale insights into the influence of metal ion concentration on carboxylated CNF-dispersed monolayer MMT dispersions.It also provides a strategy to enhance the dispersive ability of carboxylated CNFs for monolayer MMTs.