The improvement in interfacial shear strength of wood fiber/epoxy composite by sizing with epoxy sizing agent containing MWCNTs

This paper discloses a feasible and high efficient strategy for wood fiber treatment to introducing multi‐wall carbon nanotubes (MWCNTs) to the surface of wood fibers for the aim of improving the interfacial shear strength of wood fiber/epoxy composite. Briefly, a layer of MWCNT was deposited on wood fibers through sizing wood fibers with epoxy sizing agent containing amine‐treated MWCNTs (MWCNT‐PEI). The surface functional groups, morphology, wettability, and interphase properties of MWCNTs on the surface of wood fiber were studied. The remarkable enhancements were achieved in interfacial shear strength of reinforced composites by dipping wood fiber in MWCNTCOOH suspension and wood fiber sizing containing MWCNT‐PEI.     

Fourier transform infrared spectroscopic approach to the study of the secondary cell wall development in cotton fiber

Cotton fiber maturity is a major yield component and an important fiber quality trait that is directly linked to the quantity of cellulose deposited during the secondary cell wall (SCW) biogenesis. Cotton fiber development consists of five major overlapping stages: differentiation, initiation, polar elongation, secondary cell wall development, and maturation. The transition period between 16 and 21 dpa (days post anthesis) is regarded to represent a major developmental stage between the primary cell wall and the SCW. Fourier Transform Infrared spectroscopy was used to investigate the structural changes that occur during the different developmental stages. The IR spectra of fibers harvested at different stages of development (10, 14, 17, 18, 19, 20, 21, 24, 27, 30, 36, 46, and 56 dpa) show the presence of vibrations located at 1,733 cm⁻¹ (C=O stretching originating from esters or amides) and 1,534 cm⁻¹ (NH₂ deformation corresponding to proteins or amino acids). The results converge towards the conclusion that the transition phase between the primary cell wall and the secondary cell wall occurs between 17 and 18 dpa in fibers from TX19 cultivar, while this transition occurs between 21 and 24 dpa in fibers from TX55 cultivar.     

Crystalline structure of developing cotton fibers

The crystalline structure of dried cotton fibers at varying development stages has been investigated using wide angle x-ray diffraction (WAXS) techniques. The cellulose I crystalline structure has been confirmed on dried SJ-2 Acala cotton fibers collected at varying developmental stages and at maturity. The cellulose I crystalline structure is clearly evident at the early developmental stage of 21 days postanthesis (dpa). The crystal system remains unchanged during the cotton fiber biosynthesis and at maturity. The degree of crystallinity and crystallite dimensions in the cotton fibers increase with cell development. The most significant increments are observed between 21 and 34 dpa (i.e., during the first half of the secondary wall thickening process). The unit cell sizes slightly decrease and thus the crystal density increases with fiber development. The alignment of the glucosidic rings in respect to the 002 planes improves with fiber cell development. © 1996 John Wiley & Sons, Inc.     

Influence of noncontractile motion of plasmalemma upon cotton fiber cell wall structure

Unusual noncontractile motion in vivo within the fibers growing on cotton ovules was found for four cotton genotypes. Structural investigations have shown that, in addition to the active motion related to fiber cell growth, a simultaneous spiral rotation of the cytoplasmic membrane occurs. Due to translational growth of the fiber cell apices and spiral rotation of plasmalemma, the fibers of cotton cultivars take on a twisted, corkscrew-like external shape. Optical microphotos illustrate the formation process of the fiber cell wall at different stages of growth and noncontractile motion in cotton fiber cells.     

Integrating Perovskite Solar Cells into a Flexible Fiber

Perovskite solar cells have triggered a rapid development of new photovoltaic devices because of high energy conversion efficiencies and their all‐solid‐state structures. To this end, they are particularly useful for various wearable and portable electronic devices. Perovskite solar cells with a flexible fiber structure were now prepared for the first time by continuously winding an aligned multiwalled carbon nanotube sheet electrode onto a fiber electrode; photoactive perovskite materials were incorporated in between them through a solution process. The fiber‐shaped perovskite solar cell exhibits an energy conversion efficiency of 3.3 %, which remained stable on bending. The perovskite solar cell fibers may be woven into electronic textiles for large‐scale application by well‐developed textile technologies.     

Fabrication of novel core–shell PLGA and alginate fiber for dual‐drug delivery system

Biodegradable fibers for the controlled delivery of anti‐inflammatory agent dexamethasone were developed and studied. Mono and core–shell structure fiber are prepared by wet‐spinning solutions of hydrophobic poly (lactide‐co‐glycolide) and hydrophilic alginic acid shell. The two model drugs, dexamethasone and dexamethasone‐21‐phosphate, were entrapped in core and shell, respectively. These fibers were characterized in terms of morphology, diameters, mechanical properties, in vitro degradation, and drug release. The optical microscopy and scanning electron microscopy photos revealed directly that fibers possessed core–shell structure. The release of dexamethasone and dexamethasone‐21‐phosphate was investigated, and the results showed that alginate shell retarded dexamethasone release significantly in both early and late stages. The core–shell structure fiber release shows a two stage release of dexamethasone and dexamethasone‐21‐phosphate with distinctly different release rates, and minimal initial burst release is observed. The results indicated that the prepared fibers are efficient carrier for both types of dexamethasone. Copyright © 2016 John Wiley & Sons, Ltd.     

A comparative survey of proteins from recalcitrant tissues of a non-model gymnosperm, Douglas-fir

Most research in plants and other organisms has, for the sake of convenience, focused on the use of model species to identify mechanisms that are conserved throughout the whole kingdom. Nevertheless, unique features and processes such as those related to plant cell wall and fiber formation, and to wood quality, sometimes need to be studied directly in the non-model organism of interest. Such organisms, like the economically and ecologically important gymnosperm Douglas-fir (Pseudotsuga menziesii), which is one of the crucial softwood timber species in Northern America, are often difficult to investigate. High phenolic, resin, and tannin contents in the woody tissues, as well as an incompletely sequenced genome, have contributed greatly to the species' recalcitrance for molecular biology investigations. In this study, we present a complete procedure detailing protein sample preparation, separation, and proteomic analysis based on cross-species identification of Douglas-fir. Proteins from the cambial zone, mature needles, and in vitro callus were extracted, purified, and separated via 1D and 2D SDS-PAGE. One-dimensional electrophoresis coupled with ESI-MS/MS was used for cross-species protein identification in order to evaluate the potential of this approach and reveal major differences in protein profiles among tested tissues. Identified proteins were functionally and developmentally compared. The likely contribution of these proteins to the properties of the cell wall and wood is indicated and discussed.     

Proteome profiling of keratinocytes transforming to malignancy

To shed light on the multistep process of squamous cell carcinoma development and the underlying pathologic mechanisms, we performed comparative proteome analysis of keratinocytes, keratinocytes stimulated with Il‐1beta, and A431 epidermoid carcinoma cells. Fractionation of the cells into supernatant, nucleus, and cytoplasm was followed by protein separation, proteolytic digest, and nano‐LC separation, and fragmentation using an ion trap mass spectrometer. Specific bioinformatics tools were used to generate a list of keratinocyte‐specific proteins. Ninety percent of these proteins were found to be upregulated in keratinocytes versus the A431 cells. Classification of the identified proteins by biologic function and gene set enrichment analysis revealed that keratinocytes produced more proteins involved in cell differentiation, cell adhesion, cell junction, calcium ion, calmodulin binding, cytoskeleton organization, and cytokinesis, whereas A431 produced more proteins involved in cell cycle checkpoint, cell cycle process, RNA processing and transport, DNA damage and repair, RNA and DNA binding, and chromatin remodeling. The protein signatures of A431 and normal keratinocytes treated with IL‐1beta showed marked similarity, confirming that inflammation is an important step in malignant transformation in nonmelanoma skin cancer. Thus, proteome profiling and bioinformatic processing may support the understanding of the underlying mechanisms, with the potential to facilitate development of early biomarkers and patient‐tailored therapy.     

Comparative physical and chemical analyses of cotton fibers from two near isogenic upland lines differing in fiber wall thickness

The thickness of cotton fiber cell walls is an important property that partially determines the economic value of cotton. To better understand the physical and chemical manifestations of the genetic variations that regulate the degree of fiber wall thickness, we used a comprehensive set of methods to compare fiber properties of the immature fiber (im) mutant, called immature because it produces thin-walled fibers, and its isogenic wild type Texas Marker-1 (TM-1) that is a standard upland cotton variety producing normal fibers with thick walls. Comprehensive structural analyses showed that im and TM-1 fibers shared a common developmental process of cell wall thickening, contrary to the previous report that the phase in the im fiber development might be retarded. No significant differences were found in cellulose content, crystallinity index, crystal size, matrix polymer composition, or in ribbon width between the isogenic fibers. In contrast, significant differences were detected in their linear density, cross-section micrographs of fibers from opened bolls, and in the lateral order between their cellulose microfibrils (CMFs). The cellulose mass in a given fiber length was lower and the CMFs were less organized in the im fibers compared with the TM-1 fibers. The presented results imply that the disruption of CMF organization or assembly in the cell walls may be associated with the immature phenotype of the im fibers.     

The effect of coupling agents on the interfacial properties of wood‐fiber–reinforced polyimide composites

Wood‐fiber–reinforced polyimide (PI) has been widely used in many engineering fields because of its high specific strength and stiffness. However, PI does not adhere well with wood fibers because it has a low free surface energy. In addition, high viscosity in the melted phase causes poor impregnation. In this study, surface treatment methods, ie, coupling agents with plasma treatment on wood fibers, were applied to increase the interfacial strength between the wood fibers and the PI matrix. The modified wood fiber surfaces were analyzed by X‐ray photoelectron spectroscopy and scanning electron microscopy. To analyze the effectiveness of the surface treatment method, the interlaminar shear strength (ILSS) was measured using the 3‐point bending test. From the test results, the ILSS of the specimens treated with the silane coupling agent after the plasma treatment increased by 48.7% compared with those of the untreated specimens.     

Monitoring the polymerization process of polypyrrole films by thermogravimetric and X-ray analysis

Bio-composite fibers were developed from wood pulp and polypropylene (PP) by an extrusion process. The thermo-physical and mechanical properties of wood pulp-PP composite fibers, neat PP and wood pulp were studied using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The thermal stability of bio-composite fibers was found to be significantly higher than pure wood pulp. An understanding into the melting behaviour of the composite system was obtained which would assist in selecting a suitable temperature profile for the extruder during processing. The visco-elastic properties of bio-composite fibers were also revealed from the study. The generated bio-composite fibers were also characterized using Fourier transform infrared spectroscopy (FTIR) to understand the nature of chemical interaction between wood pulp reinforcement and PP matrix. The use of maleated polypropylene (MAPP) as a compatibilizer was investigated in relation to the fiber microstructure. Changes in absorption peaks were observed in FTIR spectra of bio-composite fibers as compared to the pure wood pulp which indicated possible chemical linkages between the fiber and polymer matrix.     

2. The raw materials of CA 2.1 Wood as natural raw materials for cellulose acetate production

The molecular arrangement of wood cell wall is described in relation to the physical and mechanical properties of wood. The chemical composition of wood is also summarized to illustrate the heterogeneity in distribution of cell wall constituents to use wood plup fibers judiciously as natural raw materials for cellulose acetate production.     

Rotation and contraction of native and regenerated cellulose fibers upon swelling and dissolution: the role of morphological and stress unbalances

Upon swelling and dissolution, native cellulose fibers such as cotton hairs or wood fibers are rotating and contracting. Regenerated cellulose fibers are only contracting, not rotating. Cotton hairs show two rotation mechanisms, a well known untwisting, not seen in wood fibers, due to the unwinding of the twists initially induced by the desiccation that occurs at the end of the growth, and a “microscopic rotation” that can also be slightly observed in wood fibers. In addition to these rotation mechanisms, cotton hairs and wood fibers show a rolling up of their primary wall that is due to the higher elongation of the external layers as compared to the internal layers arising during the elongation phase of the cell. Contraction originates from the fact that the cellulose chains are in an extended conformational state due to the spinning process for the regenerated fibers and to the bio-deposition process for native fibers. The contraction is related to the relaxation of the mean conformation of cellulose chains from an extended state to a more condensed state. Physical as well as mechanical modeling will support the experimental observations.     

Multi‐Colored Fibers by Self‐Assembly of DNA,Histone Proteins,and Cationic Conjugated Polymers

The development of biomolecular fiber materials with imaging ability has become more and more useful for biological applications. In this work, cationic conjugated polymers (CCPs) were used to construct inherent fluorescent microfibers with natural biological macromolecules (DNA and histone proteins) through the interfacial polyelectrolyte complexation (IPC) procedure. Isothermal titration microcalorimetry results show that the driving forces for fiber formation are electrostatic and hydrophobic interactions, as well as the release of counterions and bound water molecules. Color‐encoded IPC fibers were also obtained based on the co‐assembly of DNA, histone proteins, and blue‐, green‐, or red‐ (RGB‐) emissive CCPs by tuning the fluorescence resonance energy‐transfer among the CCPs at a single excitation wavelength. The fibers could encapsulate GFP‐coded Escherichia coli BL21, and the expression of GFP proteins was successfully regulated by the external environment of the fibers. These multi‐colored fibers show a great potential in biomedical applications, such as biosensor, delivery, and release of biological molecules and tissue engineering.     

Multi‐Colored Fibers by Self‐Assembly of DNA,Histone Proteins,and Cationic Conjugated Polymers

The development of biomolecular fiber materials with imaging ability has become more and more useful for biological applications. In this work, cationic conjugated polymers (CCPs) were used to construct inherent fluorescent microfibers with natural biological macromolecules (DNA and histone proteins) through the interfacial polyelectrolyte complexation (IPC) procedure. Isothermal titration microcalorimetry results show that the driving forces for fiber formation are electrostatic and hydrophobic interactions, as well as the release of counterions and bound water molecules. Color‐encoded IPC fibers were also obtained based on the co‐assembly of DNA, histone proteins, and blue‐, green‐, or red‐ (RGB‐) emissive CCPs by tuning the fluorescence resonance energy‐transfer among the CCPs at a single excitation wavelength. The fibers could encapsulate GFP‐coded Escherichia coli BL21, and the expression of GFP proteins was successfully regulated by the external environment of the fibers. These multi‐colored fibers show a great potential in biomedical applications, such as biosensor, delivery, and release of biological molecules and tissue engineering.     

The interfacial adhesion of wood fiber–reinforced UHMWPE composite filled with acid‐treated clay

Wood fiber–reinforced ultrahigh molecular weight polyethylene (wood fiber/UHMWPE) composites have been filled with acid‐treated clay to enhance the adhesion. According to the modification, the interlaminar shear strength of composites has been greatly improved. X‐ray photoelectron spectroscopy and scanning electron microscopy are used to examine the microscopic properties of resultant composites. The enhanced interlaminar shear strength is attributed to the clay interlock, which improves the wetting between wood fibers and resins.     

Morphological changes in never-dried kraft fibers under mechanical shearing

The modification of bleached never-dried cellulose fibers was studied under controlled compression and shearing conditions. Fibers were further treated in a high-intensity mixing device in low-consistency to determine if the fiber structure was weakened in the in-pad attrition. The difference between the development of the softwood and hardwood fibers was examined. The fiber properties were analyzed using a fiber morphology analyzer, fractional fiber analysis and an electron microscope. The results indicate that the shearing under the controlled compression at high consistency modified the softwood and hardwood fibers already at low-energy consumptions. The fiber length and width decreased, and the formation of curls and kinks was pronounced. However, the intensive mixing after in-pad attrition revealed that the fiber structure was not weakened under compression and shear forces; conversely, the fiber cell wall was more resistant for the intensive mixing. When comparing the results for hardwood and softwood fibers, the softwood fibers were more modified during in-pad attrition, whereas the fiber wall strengthening was more significant in the hardwood fibers.     

In Vitro Osteoblast Differentiation is Negatively Regulated by Hoxc8

Hoxc8 has multiple roles in normal skeletal development. In this paper, a MC3T3-E1 subclone 4 osteogenic cell differentiation model was used to examine expression of Hoxc8 at multiple stages of osteogenesis. We found that Hoxc8 expression levels do not change in the early stage but increase in the middle stage and decrease in the late stage of osteogenesis. A knockdown of Hoxc8 by small-interfering RNA transfection in C2C12 cells indicated that Hoxc8 is a negative regulator of osteogenesis. Similarly, expression of Hoxc8 in C2C12 cells decreases alkaline phosphatase levels induced by bone morphogenetic protein-2 (BMP-2). The results of this study showed that Hoxc8 is involved in BMP-2-induced osteogenesis, and osteoblast differentiation in vitro is negatively regulated by Hoxc8, suggesting that Hoxc8 regulation is essential for osteoblast differentiation.     

Dewatering Green Sapwood Using Carbon Dioxide Undergoing Cyclical Phase Change between Supercritical Fluid and Gas

Conventional kiln drying of wood operates by the evaporation of water at elevated temperature. In the initial stage of drying, mobile water in the wood cell lumen evaporates. More slowly, water bound in the wood cell walls evaporates, requiring the breaking of hydrogen bonds between water molecules and cellulose and hemicellulose polymers in the cell wall. An alternative for wood kiln drying is a patented process for green wood dewatering through the molecular interaction of supercritical carbon dioxide with water of wood cell sap. When the system pressure is reduced to below the critical point, phase change from supercritical fluid to gas occurs with a consequent large change in CO₂ volume. This results in the efficient, rapid, mechanical expulsion of liquid sap from wood. The end-point of this cyclical phase-change process is wood dewatered to the cell wall fibre saturation point. This paper describes dewatering over a range of green wood specimen sizes, from laboratory physical chemistry studies to pilot-plant trials. Magnetic resonance imaging and nuclear magnetic resonance spectroscopy were applied to study the fundamental mechanisms of the process, which were contrasted with similar studies of conventional thermal wood drying. In conclusion, opportunities and impediments towards the commercialisation of the green wood dewatering process are discussed.     

Application of silicate electrospun nanofibers for cell culture

Silicate produced via the sol–gel process is a biocompatible material that has high purity and high homogeneity. In this study, we evaluated the feasibility of electrospun fibers of silicate formed into silicate nonwoven fabrics (SNF) developed via the sol–gel process as substrates for substance production using Chinese hamster ovarian cells CHO-K1, and as substrates for producing drug metabolism simulators from the human cell line HepG2. We compared the adherent and proliferation profiles of the two cell types on SNF with those profiles produced on a hydroxyapatite-pulp composite fiber sheet (HAPS). During 14 days of cultivation, a greater number of CHO-K1 and HepG2 cells continued to grow on SNF compared to those on HAPS. Per unit volume, the HepG2 cells on SNF showed higher hepatic-specific functions than those on HAPS. These results demonstrate the feasibility of SNF as a cell culture substrate for substrate production, and for producing drug metabolism simulators.