Mass transport parameters of aspen wood chip beds via stimulus-response tracer techniques

A stimulus-response tracer technique has been used to characterize packed beds of untreated, as well as acid prehydrolyzed, and enzymatically hydrolyzed aspen wood chips. Glucose was used as the tracer. Bulk liquid phase dispersion, interphase mass transfer, and intraparticle diffusion coefficients were determined for these materials as well as effective porosities and tortuosities. The untreated and prehydrolyzed aspen wood chips were found to have effective coid fractions of ca. 0.8, while the enzymatically hydrolyzed wood chips exhibited a void fraction of 0.37. Intraparticle diffusion was approximately twice as rapid in the prehydrolyzed and enzymatically hydrolyzed wood chips as in the untreated wood chips. Also, under the current experimental conditions, intraparticle diffusional transport resistance accounted for roughly half of the total tracer pulse dispersion. It is demonstrated that stimulus-response tracer techniques can be useful and convenient probes for beds of lignocellulosic, or other conversion and/or treatment. (c) 1993 John Wiley & Sons, Inc.     

Critical assessment of iron binary systems with light rare earths La,Ce, Pr,and Nd

Literature data regarding phase equilibria and crystal structure data in the R–Fe systems with R = La, Ce, Pr, Nd have been assessed and the corresponding phase diagrams are presented and discussed. Selected investigations on other constitutive properties (such as magnetic, electronic, thermodynamic) of the R–Fe alloys are also briefly reported.Owing to the numerous investigations some uncertainties remain in the R–Fe phase diagrams and further investigations would be useful.     

Combinatorial approaches to materials discovery

Using a mixture of scientific intuition, iteration and serendipity, combinatorial materials science is an approach to the discovery and study of new materials that combines high-speed chemical synthesis, high-throughput screening and high-capacity information processing to create, analyse and interpret large numbers of new and diverse material compositions. Technology has now been developed that makes this powerful integration possible. The classes of materials under investigation include catalysts, luminescent, optical, magnetic and dielectric materials, and structural polymers.     

X-ray diffraction evidence for the existence of 102.0- and 230.0-nm transverse periodicities in striated muscle

Synchrotron radiation techniques have enabled us to record meridional x-ray diffraction patterns from frog sartorius muscle at resolutions ranging from approximately 2,800 to 38 nm (i.e., overlapping with the optical microscope and the region normally accessible with low angle diffraction cameras). These diffraction patterns represent the transform of the low resolution structure of muscle projected on the sarcomere axis and sampled by its repeat. Altering the sarcomere length results in the sampling of different parts of this transform, which induces changes in the positions and the integrated intensities of the diffraction maxima. This effect has been used to determine the transform of the mass projection on the muscle axis in a quasicontinuous fashion. The results reveal the existence of maxima arising from long-range periodicities in the structure. Determination of the zeroes in the transforms has been used to obtain phase information from which electron density maps have been calculated. The x-ray diffraction diagrams and the resulting electron density maps show the existence of a series of mass bands, disposed transversely to the sarcomere axis and distributed at regular intervals. A set of these transverse structures is associated with thin filaments, and their 102.0-nm repeat suggests a close structural relationship with their known molecular components. A second set, spaced by approximately 230.0 nm, is also present; from diffraction theory one has to conclude that this repeat simultaneously exists in thick and thin filament regions.     

Electronic,transport, magnetic,and optical properties of graphene nanoribbons and their optical sensing applications: A comprehensive review

Low dimensional materials have attracted great research interest from both theoretical and experimental point of views. These materials exhibit novel physical and chemical properties due to the confinement effect in low dimensions. The experimental observations of graphene open a new platform to study the physical properties of materials restricted to two dimensions. This featured article provides a review on the novel properties of quasi one-dimensional (1D) material known as graphene nanoribbon. Graphene nanoribbons can be obtained by unzipping carbon nanotubes (CNT) or cutting the graphene sheet. Alternatively, it is also called the finite termination of graphene edges. It gives rise to different edge geometries, namely zigzag and armchair, among others. There are various physical and chemical techniques to realize these materials. Depending on the edge type termination, these are called the zigzag and armchair graphene nanoribbons (ZGNR and AGNR). These edges play an important role in controlling the properties of graphene nanoribbons. The present review article provides an overview of the electronic, transport, optical, and magnetic properties of graphene nanoribbons. However, there are different ways to tune these properties for device applications. Here, some of them, such as external perturbations and chemical modifications, are highlighted. Few applications of graphene nanoribbon have also been briefly discussed.     

Bacteriorhodopsin variants as versatile media in optical processing

The photochromic properties of bacteriorhodopsin (BR), in addition to its longevity and excellent reversibility, are attractive features for the construction of light-sensitive media for optical information processing. However, the various optical techniques require media with specifically adapted and widely differing properties. Genetic engineering of BR and biotechnological production of mutated BRs is the key for the utilization of this photochromic compound in optical applications. Mutated BRs, generated by single and double amino acid exchanges, have been used as recording media for optical applications such as phase conjugation or long-term data storage at room temperature.     

Amplification of fluorescence with packed beads to enhance the sensitivity of miniaturized detection in microfluidic chip

This paper reports the pre-concentration of C-reactive protein (CRP) antigen with packed beads in a microfluidic chamber to enhance the sensitivity of the miniaturized fluorescence detection system for portable point-of-care testing devices. Although integrated optical systems in microfluidic chips have been demonstrated by many groups to replace bulky optical systems, the problem of low sensitivity is a hurdle for on-site clinical applications. Hence we integrated the pre-concentration module with miniaturized detection in microfluidic chips (MDMC) to improve analytical sensitivity. Cheap silicon-based photodiodes with optical filter were packaged in PDMS microfluidic chips and beads were packed by a frit structure for pre-concentration. The beads were coated with CRP antibodies to capture antigens and the concentrated antigens were eluted by an acid buffer. The pre-concentration amplified the fluorescence intensity by about 20-fold and the fluorescence signal was linearly proportional to the concentration of antigens. Then the CRP antigen was analyzed by competitive immunoassay with an MDMC. The experimental result demonstrated that the analytical sensitivity was enhanced up to 1.4 nM owing to the higher signal-to-noise ratio. The amplification of fluorescence by pre-concentration of bead-based immunoassay is expected to be one of the methods for portable fluorescence detection system.     

生物基分子介导纳米金属材料的制备及其应用

纳米金属材料具有纳米晶强化效应、光吸收率大、较高的表面能和单磁畴性能等优点,因其在医药、化学催化、抗菌抑毒等方面发挥着越来越重要的作用而受到人们广泛关注.近年来,随着全球石化资源消耗与曰俱增,环境污染加剧,基于可再生资源的生物基分子介导纳米材料的制备研究方兴未艾.生物基分子是指直接或间接来源于生物质的小分子或大分子物质...     

Selecting peptides for use in nanoscale materials using phage-displayed combinatorial peptide libraries

Materials that combine inorganic components and biological molecules provide a new paradigm for synthesizing nanoscale and larger structures with tailored physical properties. These synthesis techniques utilize the molecular recognition properties of many biological molecules to nucleate and control growth of the nanoscale structure. Phage-displayed peptide libraries are a powerful tool to identify peptides that selectively recognize and bind to a variety of inorganic surfaces that are utilized in electronic and photonic devices. These libraries have been used extensively to study the peptide-mediated nucleation and growth of some metallic and semiconducting materials, and the application to designed nanostructures has been demonstrated.     

单细胞机械性能检测方法与应用研究进展

细胞机械性能与细胞的生理状态与功能存在密切联系。早期对于细胞机械性能的研究受制于技术条件,只能获得细胞群的弹性或剪切模量,使得少量异质细胞的机械表型被淹没。近年来,单细胞机械性能检测技术得到了蓬勃发展。原子力显微镜、微吸管技术、光镊与光学拉伸、磁扭转流变仪与磁镊等单细胞机械性能检测技术展现出非常高的检测精度,但检测通量相对较低。新型微流控高通量检测方法的出现使检测通量呈几何式增长,有望解决大样本快速检测的需求。本文首先综述原子力显微镜、微吸管、光镊与光学拉伸和磁扭转流变仪与磁镊等单细胞机械性能检测技术。在此基础上,重点介绍细胞过孔、剪切诱导细胞变形和拉伸诱导细胞变形3种新兴微流控高通量检测技术的工作原理及最新研究进展,探讨各类方法的优缺点。最后,本文展望单细胞机械性能检测技术的未来发展方向。     

Selection and analysis of solid-binding peptides

Nature has long used peptide- and protein-based manufacturing to create structures whose remarkable mechanical, transport, optical, and even magnetic properties are determined by a fine control of composition and architecture extending from the nanoscale to the macroscale. Although there is much to learn from the tools and strategies that have been evolutionary selected for building biomaterials, accessing compositions and architectures of engineering interest is crucial to the development of the next generation of hybrid functional materials. In recent years, portable amino acid sequences selected from combinatorial libraries and supporting the assembly, nucleation, and geometrical organization of solid phases have emerged as attractive tools for bionanofabrication. Here, we review how these polypeptides are selected and progress in the understanding of their interaction with inorganic and synthetic materials.     

Elastic light scattering from single cells: orientational dynamics in optical trap

Light-scattering diagrams (phase functions) from single living cells and beads suspended in an optical trap were recorded with 30-ms time resolution. The intensity of the scattered light was recorded over an angular range of 0.5-179.5 degrees using an optical setup based on an elliptical mirror and rotating aperture. Experiments revealed that light-scattering diagrams from biological cells exhibit significant and complex time dependence. We have attributed this dependence to the cell's orientational dynamics within the trap. We have also used experimentally measured phase function information to calculate the time dependence of the optical radiation pressure force on the trapped particle and show how it changes depending on the orientation of the particle. Relevance of these experiments to potential improvement in the sensitivity of label-free flow cytometry is discussed.     

Addition of hydrophilic and lipophilic compounds of biological relevance to the monoolein/water system. I. Phase behavior

The solubilization of hydrophilic and lipophilic molecules, with biological relevance, in the monoolein/water (MO/W) system has been investigated for phase behavior. Small angle X-ray scattering (SAXS), nuclear magnetic resonance (NMR) and optical microscopy (OM) have been used to characterize the microstructure of the liquid crystalline phases. Partial phase diagrams of the MO/W system in the presence of sodium decanoate, 1-adamantanamine hydrochloride, decanoic and dodecanoic acids, acetyl salicilic acid and retinol have been determined. The stability of the various phases has been followed for at least eight months. The polarity and the molecular structure of the additive determine whether it is located at the polar interface or in the apolar region of the lipid layer. Therefore, the additive affects the interfacial curvature of the lipid layer differently, which in turn will trigger transition to disparate phases. A cubic-to-reverse hexagonal phase transition has been observed with time for most of the ternary systems, with the exception of 1-adamantanamine hydrochloride and retinol. The release of free glycerol and oleic acid due to MO hydrolysis has been clearly demonstrated by 13C NMR. This would account for the changes in phase behavior observed with time. The released oleic acid, located in the MO acyl chain region, favors the inverse interfacial curvature. The average lipid dimensions in the cubic and in the reverse hexagonal phases have been calculated from SAXS data.     

Polymer materials for enzyme immobilization and their application in bioreactors

Enzymatic catalysis has been pursued extensively in a wide range of important chemical processes for their unparalleled selectivity and mild reaction conditions. However, enzymes are usually costly and easy to inactivate in their free forms. Immobilization is the key to optimizing the in-service performance of an enzyme in industrial processes, particularly in the field of non-aqueous phase catalysis. Since the immobilization process for enzymes will inevitably result in some loss of activity, improving the activity retention of the immobilized enzyme is critical. To some extent, the performance of an immobilized enzyme is mainly governed by the supports used for immobilization, thus it is important to fully understand the properties of supporting materials and immobilization processes. In recent years, there has been growing concern in using polymeric materials as supports for their good mechanical and easily adjustable properties. Furthermore, a great many work has been done in order to improve the activity retention and stabilities of immobilized enzymes. Some introduce a spacer arm onto the support surface to improve the enzyme mobility. The support surface is also modified towards biocompatibility to reduce non-biospecific interactions between the enzyme and support. Besides, natural materials can be used directly as supporting materials owning to their inert and biocompatible properties. This review is focused on recent advances in using polymeric materials as hosts for lipase immobilization by two different methods, surface attachment and encapsulation. Polymeric materials of different forms, such as particles, membranes and nanofibers, are discussed in detail. The prospective applications of immobilized enzymes, especially the enzyme-immobilized membrane bioreactors (EMBR) are also discussed.     

A Review and Perspective on Cathodoluminescence Analysis of Halide Perovskites

Halide perovskite solar cells have achieved a certified efficiency of 25.2%, surpassing CdTe and CuInGaSe₂, which have long been regarded as the most‐efficient thin‐film photovoltaic materials. As this exciting class of materials continues to mature, researchers will require characterization techniques capable of exposing the interplay among structure, chemistry, and optoelectronic properties to inform processing strategies and increase both device efficiencies and long‐term stability. Cathodoluminescence microscopy is an ideal technique to provide such information due to the high spatial resolution and robust optical information acquired. Here, the current body of work related to cathodoluminescence analysis of halide perovskite materials for optoelectronic applications is surveyed. This review demonstrates how cathodoluminescence can monitor degradation due to environmental stressors, phase segregation resulting from material processing, and other halide perovskite‐centric material issues. A persistent concern associated with e‐beam‐based analysis of halide perovskites is what effect the electron beam has on the material properties being probed. Addressing this, a detailed discussion is provided on the origin of the cathodoluminescence signal and a review of studies focused on revealing changes in the properties of halide perovskites resulting from e‐beam excitation. Finally, a perspective on future opportunities to expand the role of cathodoluminescence analysis for halide perovskites is provided.     

Mode Controlling of Surface Plasmon Polaritons by Geometric Phases

Metasurfaces are made of two-dimensional arrays of subwavelength nanostructures that form a spatially varying optical response, to control the wave fronts of optical waves. As the feature size of its constituent materials is nanoscale, investigation of the light-nanostructure interactions in the near field is critical for understanding the novel properties of metasurfaces. Here, we used a scanning near-field optical microscope (SNOM) to observe the near-field distribution of surface plasmon polaritons (SPPs) from a ring-shaped metasurface under illumination of circularly polarized light. It was found that with an additional degree of freedom of the geometric phase provided by the regularly arranged metamolecules, control over the near-field interference of the SPPs can be achieved, which is governed by the metasurface geometric symmetry that can be tuned by its topological charge. Meanwhile, the planar chiral character of the metamolecules exerts a deep influence on the near-field interference patterns. Our results can pave the way for active control of SPP propagation in near fields and have potential applications in highly integrated optical communication systems.

     

聚合物微流控芯片消毒灭菌技术研究进展

聚合物微流控芯片成本低、易加工,目前在医药、生物检测和化学合成等领域得到了普遍应用。以热塑性聚合物聚甲基丙烯酸甲酯(polymethylmethacrylate,PMMA)和热固型聚合物聚二甲基硅氧烷(polydimethy lsiloxane,PDMS)为基材的高分子聚合物材料因具有较好的生物相容性和光学透明性,已逐渐成为聚合物微流控芯片加工的主导材料,被广泛应用于生物医药类微流控芯片的制备。鉴于该类芯片应用场景的特殊性,需在使用前进行消毒灭菌处理以避免微生物干扰。目前,针对PMMA和PDMS的消毒灭菌方法包括高压蒸汽灭菌、紫外线灭菌、电子束、60Co γ射线辐射灭菌、超临界二氧化碳灭菌、乙醇消毒、环氧乙烷灭菌、过氧化氢低温等离子体灭菌、绿原酸消毒、清洗剂消毒。本文从基本原理、消毒灭菌方法、应用场景等方面,回顾和总结了相关技术在PMMA和PDMS基体微流控芯片中的实现方法,并在芯片材质、适用范围等方面分析了所适用的消毒灭菌方法,为以聚合物为基材的生物医药类微流控芯片的消毒灭菌提供有益参考。     

高时空分辨的脑功能光学成像研究进展

脑功能成像技术对深入分析脑的信息加工过程,揭示脑的高级功能至关重要,是目前国际研究热点,已经在神经科学研究和神经系统疾病的临床诊断方面取得了很大的进展.已有脑功能成像技术如:功能磁共振成像(fMRI)、正电子断层成像(PET)、脑电图(EEG)、脑磁图(MEG)等等,虽然已被成功用于脑功能研究,但是目前这些方法也存在着时间或空间分辨率不够的局限.比较而言,光学成像方法表现出其独特魅力.激光散斑衬比成像和内源信号光学成像由于能提供空间取样、时间分辨率及空间分辨率三者的最佳组合和不需加入外源性标记物等特点,与其他脑功能成像技术相比其优势可能更为突出.具有较高的时间和空间分辨率的这两种脑功能光学成像技术及其应用都取得了重大发展,成为研究脑皮层功能构筑和脑病理生理的有力工具.但是目前这两种成像方法也面临着一些挑战.     

Microfibrillated cellulose - Its barrier properties and applications in cellulosic materials: A review

Interest in microfibrillated cellulose (MFC) has been increasing exponentially. During the last decade, this bio-based nanomaterial was essentially used in nanocomposites for its reinforcement property. Its nano-scale dimensions and its ability to form a strong entangled nanoporous network, however, have encouraged the emergence of new high-value applications. In previous years, its mode of production has completely changed, as many forms of optimization have been developed. New sources, new mechanical processes, and new pre- and post-treatments are currently under development to reduce the high energy consumption and produce new types of MFC materials on an industrial scale. The nanoscale characterization possibilities of different MFC materials are thus increasing intensively. Therefore, it is critical to review such MFC materials and their properties. Moreover, very recent studies have proved the significant barrier properties of MFC. Hence, it is proposed to focus on the barrier properties of MFC used in films, in nanocomposites, or in paper coating.     

Simulation of the propagation effects in the HF-EPR spectra of non-diluted magnetic materials

The high field EPR spectra of non-diluted magnetic material are affected by propagation effects when the wavelength of the exciting radiation is of the same order of magnitude of the optical path within the sample. Beyond the optical path, the shape of the spectra is determined by the dielectric constant and by the magnetization of the material and through these quantities it depends on the temperature. A detailed knowledge of the physical properties of the material is therefore mandatory for a complete study of the phenomenon. In order to demonstrate the propagation effect, the 285 GHz EPR spectra of tetramethyl-ammonium manganese chloride (TMMC) were recorded as a function of temperature and a simulation of the spectra was performed on the basis of a simplified model of the propagation of far infrared radiation around the resonance field. The universality of the effect was illustrated by measuring other magnetic materials such as ferrite.