Ultrastructural characterization (morphological and topochemical) of wood pulp fibres

Different electron microscopy techniques including SEM (scanning electron microscopy), FE-SEM (field emission-scanning electron microscopy), TEM (transmission electron microscopy) and Immuno-gold TEM (immuno-gold transmission electron microscopy) were applied in order to gain a better understanding of the influence of the native softwood fibre cell wall ultrastructure including morphology and topochemistry (i.e. lignin and glucomannan distribution) during mechanical pulping. In thermomechanical pulp (TMP) processing, wood fibres undergo structural changes (cell wall delamination and fibrillation) that are regulated by the native fibre micro- and ultrastructure. In addition, novel information was obtained on the fibre cell wall architecture. In contrast, the stoneground wood (SGW) process inflicted severe damage to the fibre structure resulting in transverse and longitudinal fibre breakage. However, juvenile wood SGW fibres showed improved properties (strength and light scattering) compared to mature wood. Ultrastructural aspects of fibre processing and development explained the differences in physical properties observed. During the SGW process, the native morphological fibre cell wall ultrastructure and microfibrillar organization governed the manner of juvenile wood fibre development similar to TMP fibres. Ultrastructural studies on Norway spruce and Scots pine TMPs revealed fundamental features that governed the different behaviour exhibited by the two wood species. Specific ultrastructural characteristics of pine TMP fibre cell walls were explored in relation to both morphology and topochemistry and that regulating the different pine fibre development mechanisms compared to spruce. The negative behaviour shown by Scots pine during TMP processing was most likely attributable to the observed fibre development mechanism. Histochemical techniques were applied to study wood resin associated problems during mechanical and kraft pulping. Studies provided information on the spatial micro-morphological distribution/redistribution of lipophilic extractives that were visualized on single fibre and cell wall fractions. Results from histochemical staining and chemical analysis performed on Norway spruce and Scots pine TMPs showed that there were morphological and chemical differences in the redistribution of extractives between the two species. This may further contribute to the effects of extractives on pulp- and paper properties and processing. Localization of lipophilic birch wood extractives involved in pitch problems was performed using histochemical techniques. Correlated information from gas chromatography-mass spectrometry and specific staining methods gave details on how extractives are removed during processing as well as information on the mechanisms of removal

MicroRNAs in B cell development and malignancy

MicroRNAs are small RNA molecules that regulate gene expression and play critical roles in B cell development and malignancy. miRNA expression is important globally, as B cell specific knockouts of Dicer show profound defects in B cell development; and is also critical at the level of specific miRNAs. In this review, we discuss miRNAs that are involved in normal B cell development in the bone marrow and during B cell activation and terminal differentiation in the periphery. Next, we turn to miRNAs that are dysregulated during diseases of B cells, including malignant diseases and autoimmunity. Further study of miRNAs and their targets will lead to a better understanding of B cell development, and should also lead to the development of novel therapeutic strategies against B cell diseases

Morphological and cellular organization of green microalgae to cope with cold stress in subarctic environment

Microalgae are one of the most widely dispersed living organisms on Earth and can be found even in extreme environments. Especially in such habitats, the microalgal cell wall plays an essential role as it is the first barrier in continuous contact with the surrounding and changing environment. In cold conditions microalgae can show changes in their morphology, also known as phenotypic plasticity which is the ability of an organism to show different phenotypes when exposed to different environmental conditions. In addition, presence or absence of algaenan is thought to be responsible for increase/decrease permeability and stiffness of the cell wall. The aim of this work was to evaluate and compare how microalgae cells can modify their cell wall components and cellular morphology under low-temperature conditions (5 degrees C) and differ during the exponential and stationary phases. Four microalgae species were studied: Coelastrella sp. 3-4, Chlorella vulgaris sp. 13-1, Haematococcus pluvialis, and Scenedesmus sp. B2-2, which were isolated from subarctic locations. Using a histochemical approach in conjunction with light microscopy, cell features such as size, organization and cell wall ornamentation were evaluated. Staining procedures showed changes in biochemical components such as pectins and presence or absence of exopolysaccharides and lipids. Results showed that Coelastrella cultures did not grow under low-temperature conditions. However, Chlorella vulgaris, Haematococcus pluvialis and Scenedesmus species demonstrated a slower growth rate, bigger and rounded cell-shape during cold condition. Furthermore, the latter microalgal strain also showed modification in algaenan presence as one of the main components in cell wall architecture, which can be related to the permeability of cell wall. Changes in other features such as cell organization and cell wall ornamentation were investigated

Electron tomography unravels new insights into fiber cell wall nanostructure; exploring 3Dma cromolecular biopolymeric nano‑architecture of spruce fiber secondary walls

Lignocellulose biomass has a tremendous potential as renewable biomaterials for fostering the “bio-based society” and circular bioeconomy paradigm. It requires efficient use and breakdown of fiber cell walls containing mainly cellulose, hemicellulose and lignin biopolymers. Despite their great importance, there is an extensive debate on the true structure of fiber walls and knowledge on the macromolecular nano-organization is limited and remains elusive in 3D. We employed dual-axis electron tomography that allows visualization of previously unseen 3D macromolecular organization/biopolymeric nano-architecture of the secondary S2 layer of Norway spruce fiber wall. Unprecedented 3D nano-structural details with novel insights into cellulose microfibrils (~ 2 nm diameter), macrofibrils, nano-pore network and cell wall chemistry (volume %) across the S2 were explored and quantified including simulation of structure related permeability. Matrix polymer association with cellulose varied between microfibrils and macrofibrils with lignin directly associated with MFs. Simulated bio-nano-mechanical properties revealed stress distribution within the S2 and showed similar properties between the idealized 3D model and the native S2 (actual tomogram). Present work has great potential for significant advancements in lignocellulose research on nano-scale understanding of cell wall assembly/disassembly processes leading to more efficient industrial processes of functionalization, valorization and target modification technologies

Regulation of Marginal Zone B-Cell Differentiation by MicroRNA-146a.

B-cell development in the bone marrow is followed by specification into functional subsets in the spleen, including marginal zone (MZ) B-cells. MZ B-cells are classically characterized by T-independent antigenic responses and require the elaboration of distinct gene expression programs for development. Given their role in gene regulation, it is not surprising that microRNAs are important factors in B-cell development. Recent work demonstrated that deficiency of the NFκB feedback regulator, miR-146a, led to a range of hematopoietic phenotypes, but B-cell phenotypes have not been extensively characterized. Here, we found that miR-146a-deficient mice demonstrate a reduction in MZ B-cells, likely from a developmental block. Utilizing high-throughput sequencing and comparative analysis of developmental stage-specific transcriptomes, we determined that MZ cell differentiation was impaired due to decreases in Notch2 signaling. Our studies reveal miR-146a-dependent B-cell phenotypes and highlight the complex role of miR-146a in the hematopoietic system

A viable electrode material for use in microbial fuel cells for tropical regions

Electrode materials are critical for microbial fuel cells (MFC) since they influence the construction and operational costs. This study introduces a simple and efficient electrode material in the form of palm kernel shell activated carbon (AC) obtained in tropical regions. The novel introduction of this material is also targeted at introducing an inexpensive and durable electrode material, which can be produced in rural communities to improve the viability of MFCs. The maximum voltage and power density obtained (under 1000 load) using an H-shaped MFC with AC as both anode and cathode electrode material was 0.66 V and 1.74 W/m(3), respectively. The power generated by AC was as high as 86% of the value obtained with the extensively used carbon paper. Scanning electron microscopy and Denaturing Gradient Gel Electrophoresis (DGGE) analysis of AC anode biofilms confirmed that electrogenic bacteria were present on the electrode surface for substrate oxidation and the formation of nanowires

SEER: Safe Efficient Exploration for Aerial Robots using Learning to Predict Information Gain

We address the problem of efficient 3-D exploration in indoor environments for micro aerial vehicles with limited sensing capabilities and payload/power constraints. We develop an indoor exploration framework that uses learning to predict the occupancy of unseen areas, extracts semantic features, samples viewpoints to predict information gains for different exploration goals, and plans informative trajectories to enable safe and smart exploration. Extensive experimentation in simulated and real-world environments shows the proposed approach outperforms the state-of-the-art exploration framework by 24% in terms of the total path length in a structured indoor environment and with a higher success rate during exploration

Inocula selection in microbial fuel cells based on anodic biofilm abundance of <i>Geobacter sulfurreducens</i>

Microbial fuel cells (MFCs) rely on microbial conversion of organic substrates to electricity. The optimal performance depends on the establishment of a microbial community rich in electrogenic bacteria. Usually this microbial community is established from inoculation of the MFC anode chamber with naturally occurring mixed inocula. In this study, the electrochemical performance of MFCs and microbial community evolution were evaluated for three inocula including domestic wastewater (DW), lake sediment (LS) and biogas sludge (BS) with varying substrate loading (L-sub) and external resistance (R-ext) on the MFC. The electrogenic bacterium Geobacter sulfurreducens was identified in all inocula and its abundance during MFC operation was positively linked to the MFC performance. The LS inoculated MFCs showed highest abundance (18%+/- 1%) of G. sulfurreducens, maximum current density [I-max = (690 +/- 30) mA.m(-2)] and coulombic efficiency (CE = 29% +/- 1%) with acetate as the substrate. I-max and CE increased to (1780 +/- 30) mA.m(-2) and 58% +/- 1%, respectively, after decreasing the R-ext from 1000 Omega to 200 Omega, which also correlated to a higher abundance of G. sulfurreducens (21% +/- 0.7%) on the MFC anodic biofilm. The data obtained contribute to understanding the microbial community response to L-sub and R-ext for optimizing electricity generation in MFCs