MEM

MEM
  • 文章类型: Journal Article
    增材制造仍然是当今世界发展最快的技术。三维打印由于其众多的优点而变得流行,如时间短、成本低,与传统方法如注塑成型相比。因此,对以所需功能特性为特征的新材料和材料体系的需求正在明显增长。作为这项工作的一部分,致力于开发和制备专用于3D打印应用的新型聚合物复合材料,特别是在FDM/FFF/MEM技术。填料的含量和用量的影响,如用氧化铝(S)改性的二氧化硅和用季铵盐(B)改性的膨润土,关于由传统塑料制成的市售纤维的功能特性,如聚碳酸酯,以细丝(PCF)的形式获得,已确定。发现B的添加显着增加了聚合物的流动性,以1.5%的量引入填料允许获得比PCF(16.8g/10min)高6%的结果,而3%的金额高出20%。所获得的质量熔体流动速率(MFR)结果通过测定所产生的聚合物复合材料的粘度来确认。获得了令人满意的力学性能结果,主要包括:发现引入的改性填料增加了材料的弹性。与聚合物相比,引入改性二氧化硅导致在0.5%S和1%S含量下杨氏模量降低10.02%,降低8.64%。引入的改性填料S显着提高了聚碳酸酯的热稳定性(T5%等于449°C)对于PCF/0.5%S为23°C,对于PCF/1%S为14°C,分别。SEM和WAXS结果证实了填料在聚合物基体中的适当分散,这表明了用于组分的均质化过程和随后的样品生产的良好选择的条件。详细表征所选填料对聚合物基质-聚碳酸酯的功能特性的影响,从而增加了聚合物复合材料的范围及其在快速成型技术中的用途,以及补充有关所获得材料特征的数据库文献。
    Additive manufacturing is still the fastest-developing technology in the modern world. Three-dimensional printing has become popular due to the method\'s numerous advantages, such as its short time and low cost, compared to conventional methods such as injection molding. Therefore, the demand for new materials and material systems that will be characterized by the desired functional properties is clearly growing. As part of this work, work was carried out on the development and preparation of new polymer composites dedicated to 3D printing applications, especially in FDM/FFF/MEM technologies. The influence of the content and amount of fillers, such as silica modified with alumina (S) and bentonite modified with a quaternary ammonium salt (B), on the functional properties of a commercially available fiber made of traditional plastic, such as polycarbonate, obtained in the form of a filament (PCF), was determined. It was found that the addition of B significantly increased the fluidity of the polymer, the introduction of a filler in the amount of 1.5% allowed to obtain a result that was 6% higher compared to PCF (16.8 g/10 min), while the amount of 3% was 20% higher. The obtained mass melt flow rate (MFR) results were confirmed by determining the viscosity of the produced polymer composites. Satisfactory results of mechanical properties were obtained, including the following: it was found that the introduced modified fillers increased the elasticity of the material. The introduction of modified silica resulted in a reduction in Young\'s modulus by 10.02% at the content of 0.5% S and at 1% S by 8.64% compared to the polymer. The introduced modified filler S significantly increased the thermostability of polycarbonate (T5% equal to 449 °C) by 23 °C for PCF/0.5% S and 14 °C for PCF/1% S, respectively. The SEM and WAXS results confirmed the appropriate dispersion of the fillers in the polymer matrix, which indicates well-selected conditions for the homogenization process of the components and the subsequent production of samples. Detailed characterization of the influence of selected fillers on the functional properties of the polymer matrix-polycarbonate allowed for an increase in the range of polymer composites and their use in rapid prototyping technologies, as well as supplementing the literature on databases regarding the characteristics of the obtained materials.
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  • 文章类型: Journal Article
    在原位透射电子显微镜(TEM)观察期间,不同的样品架的不同功能起着至关重要的作用。我们在此提供主要类型的持有人的全面概述,与广泛使用的加热和气体加热方法有关的相关技术和案例研究,从最初的发展到最近的进步。除了传统的方法,我们还讨论了采用微机电系统(MEMS)芯片进行原位观察的支架的出现。MEMS技术在单个芯片内提供多种功能,从而增强了保持器的能力和多功能性。MEMS芯片已用于环境电池设计,使定制制造不同的形状。这项创新促进了它们在气体和液体环境中进行原位观测的应用,特别是在催化和电池反应的研究中。我们总结了最近使用原位液体TEM进行的值得注意的研究。这些研究突出了重大进步,并为MEMS芯片在环境电池中的利用提供了有价值的见解。以及原位液体TEM在各种研究领域的扩展能力。
    During the in situ transmission electron microscopy (TEM) observations, the diverse functionalities of different specimen holders play a crucial role. We hereby provide a comprehensive overview of the main types of holders, associated technologies and case studies pertaining to the widely employed heating and gas heating methods, from their initial developments to the latest advancement. In addition to the conventional approaches, we also discuss the emergence of holders that incorporate a micro-electro-mechanical system (MEMS) chip for in situ observations. The MEMS technology offers a multitude of functions within a single chip, thereby enhancing the capabilities and versatility of the holders. MEMS chips have been utilized in environmental-cell designs, enabling customized fabrication of diverse shapes. This innovation has facilitated their application in conducting in situ observations within gas and liquid environments, particularly in the investigation of catalytic and battery reactions. We summarize recent noteworthy studies conducted using in situ liquid TEM. These studies highlight significant advancements and provide valuable insights into the utilization of MEMS chips in environmental-cells, as well as the expanding capabilities of in situ liquid TEM in various research domains.
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  • 文章类型: Journal Article
    本文包括对使用聚合物材料生产谐波驱动器的可能性的分析。添加方法的使用极大地简化和加速了柔性花键的制造。在使用快速成型(RP)方法由聚合物材料制成的齿轮的情况下,问题往往在于它们的机械强度。在谐波驱动中,车轮受到独特的损坏,因为在工作中,它变形,并额外加载扭矩。因此,在Abaqus程序中使用有限元方法(FEM)进行了数值计算。因此,获得了有关柔轮中应力分布及其最大值的信息。在此基础上,可以确定由特定聚合物制成的柔轮是否可以用于商业谐波驱动器,或者它们是否仅足以生产原型。
    This article includes an analysis of the possibility of using polymer materials for the production of harmonic drive. The use of additive methods greatly eases and accelerates the manufacturing of the flexspline. In the case of gears made of polymeric materials using rapid prototyping (RP) methods, the problem is often with their mechanical strength. In a harmonic drive, the wheel is uniquely exposed to damage, because during work, it deforms and is additionally loaded with torque. Therefore, numerical calculations were conducted using the finite element method (FEM) in the Abaqus program. As a result, information was obtained on the distribution of stresses in the flexspline and their maximum values. On this basis, it was possible to determine whether a flexspline made of specific polymers could be used in commercial harmonic drives or whether they were only adequate for the production of prototypes.
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  • 文章类型: Journal Article
    As part of this work, polymer composites based on polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) were obtained and used in 3D printing technology, particularly Melted Extrusion Modeling (MEM) technology. The influence of selected fillers on the properties of the obtained composites was investigated. For this purpose, modified fillers such as silica modified with alumina, bentonite modified with a quaternary ammonium salt, and hybrid lignin/silicon dioxide filler were introduced into the PC/ABS matrix. In the first part of this work, polymer blends and their composites containing 1.5-3 wt. of the filler were used to obtain the filament using the proprietary technological line. Moldings for testing the performance properties were obtained using additive manufacturing techniques and injection molding. In the subsequent part of this work, rheological properties (mass flow rate (MFR) and viscosity curves) and mechanical properties (Rockwell hardness and static tensile strength with Young\'s modulus) were examined. The structures of the obtained composites were also determined by scanning electron microscopy (SEM/EDS). The obtained results confirmed the results obtained from a wide-angle X-ray scattering analysis (WAXS). In turn, the physicochemical properties were characterized on the basis of the results of tests using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Based on the obtained results, it was found that the introduced modified additives had a significant impact on the processing and functional properties of the tested composites.
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  • 文章类型: Journal Article
    作为工作的一部分,开发了专用于3D打印应用的创新聚合物复合材料。为此,改性填料的影响,如用氧化铝改性的二氧化硅,用季铵盐改性的膨润土,和混合填料木质素/二氧化硅,研究了基于乙二醇改性的聚对苯二甲酸乙二醇酯(PET-G)复合材料的功能性能。在工作的第一部分,使用专有技术线,获得来自未填充聚合物及其复合材料的长丝,其包含1.5重量%至3.0重量%的量的改性填料。使用熔融和挤出制造(MEM)技术和注塑成型技术中的3D打印技术获得了用于功能性能测试的配件。在工作的后期,流变性能,如质量熔体流动速率(MFR)和粘度,以及洛氏硬度等机械性能,夏比冲击强度,给出了静态拉伸强度与杨氏模量的关系。还描述了所获得的复合材料的结构,并使用扫描电子显微镜进行了化学组成的显微分析(SEM/EDS)和原子力显微镜(AFM)。通过广角X射线散射分析(WAXS)确认填料在聚合物基质中的正确分散。反过来,在研究结果的基础上提出了物理化学性质:热重分析(TGA),差示扫描量热法(DSC),傅里叶变换红外光谱(FT-IR)。在得到的结果的基础上,研究发现,填料的用量和类型都会显著影响所测试复合材料的功能性能。
    As part of the work, innovative polymer composites dedicated to 3D printing applications were developed. For this purpose, the influence of modified fillers, such as silica modified with alumina, bentonite modified with quaternary ammonium salt, and hybrid filler lignin/silicon dioxide, on the functional properties of composites based on glycol-modified poly(ethylene terephthalate) (PET-G) was investigated. In the first part of the work, using the proprietary technological line, filaments from unfilled polymer and its composites were obtained, which contained modified fillers in an amount from 1.5% to 3.0% by weight. The fittings for the testing of functional properties were obtained using the 3D printing technique in the Melted and Extruded Manufacturing (MEM) technology and the injection molding technique. In a later part of the work, rheological properties such as mass melt flow rate (MFR) and viscosity, and mechanical properties such as Rockwell hardness, Charpy impact strength, and static tensile strength with Young\'s modulus were presented. The structure of the obtained composites was also described and determined using scanning electron microscopy with an attachment for the microanalysis of chemical composition (SEM/EDS) and the atomic force microscope (AFM). The correct dispersion of the fillers in the polymer matrix was confirmed by wide-angle X-ray scattering analysis (WAXS). In turn, the physicochemical properties were presented on the basis of the research results: thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FT-IR). On the basis of the obtained results, it was found that both the amount and the type of fillers used significantly affected the functional properties of the tested composites.
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  • 文章类型: Journal Article
    目前正在探索和评估VITEK质谱(MS)检测细菌耐药性的能力。在这项研究中,我们开发并验证了VITEKMS方法,以快速检测产碳青霉烯酶的肺炎克雷伯菌(CPKP).溶剂,抗生素浓度,晶体条件和时间,离心速度,和其他因素进行了优化,设计了VITEKMS检测CPKP的快速样品预处理工艺。在仪器上调整质谱的相关参数以建立CPKP检测模式。选取深圳市人民医院微生物实验室2004-2017年临床分离的133株CPKP进行准确性评价。2020年微生物实验室的新鲜疑似菌株用于完成临床验证。两种抗生素,美罗培南(MEM)和亚胺培南(IPM),用作底物。将这两种底物与可疑的CPKP孵育,并通过VITEKMS检测获得结果。使用此方法,不同类型的CPKP检测结果不同,所有产KPC-2和IMP-4碳青霉烯酶的CPKP菌株均用VITEKMS检测。因此,VITEKMS可用于CPKP的快速检测,特别是对于一些常见类型的CPKP。该方法提供了高的检测精度和速度。结合其成本优势,在确定标准操作程序后,它在临床微生物学实验室中可能非常有价值。
    The ability of VITEK mass spectrometry (MS) in detection of bacterial resistance is currently under exploration and evaluation. In this study, we developed and validated a VITEK MS method to rapidly test carbapenemase-producing Klebsiella pneumoniae (CPKP). Solvents, antibiotic concentrations, crystal conditions and times, centrifugation speeds, and other factors were optimized to design a rapid sample pretreatment process for CPKP detection by VITEK MS. The related parameters of the mass spectrum were adjusted on the instrument to establish an CPKP detection mode. 133 clinically isolated strains of CPKP in the microbiology laboratory at the Shenzhen People\'s Hospital from 2004 to 2017 were selected for accuracy evaluation. The fresh suspected strains from the microbiology laboratory in 2020 were used to complete the clinical verification. Two antibiotics, meropenem (MEM) and imipenem (IPM), were used as substrates. These two substrates were incubated with suspected CPKP, and the results were obtained by VITEK MS detection. Using this method, different types of CPKP showed different detection results and all the CPKP strains producing KPC-2 and IMP-4 carbapenemase were detected by VITEK MS. Thus, VITEK MS can be used for rapid detection of CPKP, especially for some common types of CPKP. This method provides high accuracy and speed of detection. Combined with its cost advantages, it can be intensely valuable in clinical microbiology laboratories after the standard operating procedures are determined.
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  • 文章类型: Journal Article
    This paper aims to measure the performance of early detection methods, which are usually used for infectious diseases.
    By using real data of confirmed Coronavirus cases from the Kingdom of Saudi Arabia and Italy, the moving epidemic method (MEM) and the moving average cumulative sums (Mov. Avg Cusum) methods are used in our simulation study.
    Our results suggested that the CUSUM method outperforms the MEM in detecting the start of the Coronavirus outbreak.
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  • 文章类型: Journal Article
    作为目前工作的一部分,用于3D打印技术的聚合物复合材料,特别是在熔化和挤压制造(MEM)技术中,已获得。改性填料如氧化铝改性二氧化硅的影响,季铵膨润土,研究了木质素/二氧化硅杂化填料和未改性多壁碳纳米管对聚碳酸酯(PC)复合材料性能的影响。在工作的第一部分,聚合物及其复合材料含有0.5-3wt。使用专有技术线使用%的填料来获得长丝。使用3D打印和注塑技术获得用于测试功能特性的模制品。在工作的下一部分,流变性能-质量流量(MFR)和机械性能-洛氏硬度,夏比冲击强度和静态拉伸强度与杨氏模量进行了检查。还使用扫描电子显微镜(SEM)描述并确定了所得复合材料的结构。孔隙度,还确定了通过3D打印获得的样品的粗糙度和尺寸稳定性。另一方面,根据热重分析(TGA)的研究结果,差示扫描量热法(DSC),广角X射线散射分析(WAXS)和傅里叶变换红外光谱(FT-IR)。此外,研究了所得复合材料的导电性。在得到的结果的基础上,研究发现,填料的用量和类型都会显著影响研究中测试的复合材料的功能性能。
    As part of the present work, polymer composites used in 3D printing technology, especially in Melted and Extruded Manufacturing (MEM) technology, were obtained. The influence of modified fillers such as alumina modified silica, quaternary ammonium bentonite, lignin/silicon dioxide hybrid filler and unmodified multiwalled carbon nanotubes on the properties of polycarbonate (PC) composites was investigated. In the first part of the work, the polymer and its composites containing 0.5-3 wt.% filler were used to obtain a filament using the proprietary technological line. The moldings for testing functional properties were obtained with the use of 3D printing and injection molding techniques. In the next part of the work, the rheological properties-mass flow rate (MFR) and mechanical properties-Rockwell hardness, Charpy impact strength and static tensile strength with Young\'s modulus were examined. The structure of the obtained composites was also described and determined using scanning electron microscopy (SEM). The porosity, roughness and dimensional stability of samples obtained by 3D printing were also determined. On the other hand, the physicochemical properties were presented on the basis of the research results using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), wide angle X-ray scattering analysis (WAXS) and Fourier Transform infrared spectroscopy (FT-IR). Additionally, the electrical conductivity of the obtained composites was investigated. On the basis of the obtained results, it was found that both the amount and the type of filler significantly affected the functional properties of the composites tested in the study.
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  • 文章类型: Journal Article
    BACKGROUND: Seeding is usually the initial step of high-throughput sequence aligners. Two popular seeding strategies are fixed-size seeding (k-mers, minimizers) and variable-size seeding (MEMs, SMEMs, maximal spanning seeds). The former strategy supports fast seed computation, while the latter one benefits from a high seed uniqueness. Algorithmic bridges between instances of both seeding strategies are of interest for combining their respective advantages.
    RESULTS: We introduce an efficient strategy for computing MEMs out of fixed-size seeds (k-mers or minimizers). In contrast to previously proposed extend-purge strategies, our merge-extend strategy prevents the creation and filtering of duplicate MEMs. Further, we describe techniques for extracting SMEMs or maximal spanning seeds out of MEMs. A comprehensive benchmarking shows the applicability, strengths, shortcomings and computational requirements of all discussed seeding techniques. Additionally, we report the effects of seed occurrence filters in the context of these techniques. Aside from our novel algorithmic approaches, we analyze hierarchies within fixed-size and variable-size seeding along with a mapping between instances of both seeding strategies.
    CONCLUSIONS: Benchmarking shows that our proposed merge-extend strategy for MEM computation outperforms previous extend-purge strategies in the context of PacBio reads. The observed superiority grows with increasing read size and read quality. Further, the presented filters for extracting SMEMs or maximal spanning seeds out of MEMs outperform FMD-index based extension techniques. All code used for benchmarking is available via GitHub at https://github.com/ITBE-Lab/seed-evaluation .
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  • 文章类型: Journal Article
    In Slovenia, the respiratory syncytial virus (RSV) surveillance is based on national laboratory data. The weeks with more than 10% of samples tested positive compose RSV epidemic season. The use of real-time multiplex PCR, which identifies other respiratory pathogens in parallel with RSV, caused more testing but the percentage of RSV positives lowered. The 10% threshold was reached with delay, which raised concern about its suitability for defining RSV seasonality.
    To describe the seasonality of RSV, the onset, offset and duration of the RSV epidemic season across 10 years (from week 40, 2008/2009 to week 39, 2017/2018), four calculative methods were deployed including moving epidemic method, MEM, and epidemiological parameters were compared.
    In 10 years, 10 969 (12%) out of 90 264 samples tested positive for RSV. The number of tested samples increased remarkably from the first to last season with a drop in the percentage of positive samples from 23% to 10%. The onset of RSV epidemic varied considerably regardless of the calculative method used (from 10 to 13 weeks). The unevenness in the RSV epidemic season end was also observed. The average duration of RSV epidemic season was the shortest when moving epidemic method has been used (15.7 weeks) and longest with ≥3% method (22.9 weeks).
    The ≥3% calculative method could be used as an early warning of the RSV season. However, ≥7% calculative method was found to be reliable enough to define the epidemiological parameters of an ongoing season and to support public health response. The potential of the moving epidemic method should be further explored.
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