Dominant aerosol processes during high-pollution episodes over Greater Tokyo

This paper studies two high-pollution episodes over Greater Tokyo: 9 and 10 December 1999, and 31 July and 1 August 2001. Results obtained with the chemistry-transport model (CTM) Polair3D are compared to measurements of inorganic PM2.5. To understand to which extent the aerosol processes modeled in Polair3D impact simulated inorganic PM2.5, Polair3D is run with different options in the aerosol module, e.g. with/without heterogeneous reactions. To quantify the impact of processes outside the aerosol module, simulations are also done with another CTM (CMAQ). In the winter episode, sulfate is mostly impacted by condensation, coagulation, long-range transport, and deposition to a lesser extent. In the summer episode, the effect of long-range transport largely dominates. The impact of condensation/evaporation is dominant for ammonium, nitrate and chloride in both episodes. However, the impact of the thermodynamic equilibrium assumption is limited. The impact of heterogeneous reactions is large for nitrate and ammonium, and taking heterogeneous reactions into account appears to be crucial in predicting the peaks of nitrate and ammonium. The impact of deposition is the same for all inorganic PM2.5. It is small compared to the impact of other processes although it is not negligible. The impact of nucleation is negligible in the summer episode, and small in the winter episode. The impact of coagulation is larger in the winter episode than in the summer episode, because the number of small particles is higher in the winter episode as a consequence of nucleation.Comment: Journal of Geophysical Research D: Atmospheres (15/05/2007) in pres

Density, extractives and decay resistance variabilities within branch wood from four agroforestry hardwood species

Agroforestry practices like pruning trees to control the light flux to crops produce every year a large volume of branches which is valorized by farmers as mulching or energy fuel. However, according to the literature, the wood of branches shows higher rates of polyphenols than stem wood and this can open some new perspectives for branch exploitation. In this study, the wood properties (density, mechanical properties, extractive content and decay resistance) were determined on branches of different sizes from oak, chestnut, poplar and walnut trees collected in two agroforestry systems. These properties were evaluated according to the wood age and the sampling position along the radial and longitudinal axes of the branch. All samples were analyzed by NIR-Spectroscopy and a predicting model aimed to assess the branch wood properties has been developed. Wood characteristics largely vary between species and do not exactly follow the same trends from one species to another. Overall, hardwood density of branches is similar to that of trunks, the content in wood extractives follows similar evolutions, and the decay resistance of branch wood does not seem to be really impacted by its position along the branch. Reliable NIRS models were built to easily predict the wood density and extractives content of agroforestry branches. The extractives content and the decay resistance of branch hardwood appear to be substantially lower than those of trunks, which suggests a non-suitability of branch wood for developing highvalued green chemistry

Harnessing the potential of African youth for transforming health research in Africa

Africa faces a significant burden of infectious diseases, including Malaria and HIV/AIDS, along with an increasing prevalence of non-infectious diseases such as diabetes and cancer. This dual health challenge is amplified by socioeconomic difficulties, restricted access to healthcare, and lifestyle changes, thus present unique scientific needs. Effectively addressing these issues requires a skilled scientific workforce adept in comprehensive healthcare strategies. This analysis explores the critical landscape of health research in Africa, emphasizing the unique opportunity presented by the continent’s youthful population, projected to reach almost 1 billion by 2050. The youth’s innovative potential and fresh perspectives offer a chance to overcome development barriers in health research. Nevertheless, challenges such as under-resourced education, limited research training, inadequate mentorship, and funding difficulties persist. This paper urgently calls upon African leaders, international partners, and stakeholders to prioritize health research, mobilize funding, forge strategic partnerships, and empower the youth as essential steps to capitalize on the continent’s dynamic youth for breakthrough health outcomes. Such investments are vital not just for health but for the overall economic, social, and strategic growth of the continent. Through shared responsibility and a united effort, the potential of African youth can be harnessed, leading to transformative research, improved health outcomes, and a prosperous future. This perspective represents the collective voice of passionate young researchers and advocates across Africa, calling for a new era of health research on the continent

Heparan Sulfate Proteoglycans Mediate Interstitial Flow Mechanotransduction Regulating MMP-13 Expression and Cell Motility via FAK-ERK in 3D Collagen

Interstitial flow directly affects cells that reside in tissues and regulates tissue physiology and pathology by modulating important cellular processes including proliferation, differentiation, and migration. However, the structures that cells utilize to sense interstitial flow in a 3-dimensional (3D) environment have not yet been elucidated. Previously, we have shown that interstitial flow upregulates matrix metalloproteinase (MMP) expression in rat vascular smooth muscle cells (SMCs) and fibroblasts/myofibroblasts via activation of an ERK1/2-c-Jun pathway, which in turn promotes cell migration in collagen. Herein, we focused on uncovering the flow-induced mechanotransduction mechanism in 3D.Cleavage of rat vascular SMC surface glycocalyx heparan sulfate (HS) chains from proteoglycan (PG) core proteins by heparinase or disruption of HS biosynthesis by silencing N-deacetylase/N-sulfotransferase 1 (NDST1) suppressed interstitial flow-induced ERK1/2 activation, interstitial collagenase (MMP-13) expression, and SMC motility in 3D collagen. Inhibition or knockdown of focal adhesion kinase (FAK) also attenuated or blocked flow-induced ERK1/2 activation, MMP-13 expression, and cell motility. Interstitial flow induced FAK phosphorylation at Tyr925, and this activation was blocked when heparan sulfate proteoglycans (HSPGs) were disrupted. These data suggest that HSPGs mediate interstitial flow-induced mechanotransduction through FAK-ERK. In addition, we show that integrins are crucial for mechanotransduction through HSPGs as they mediate cell spreading and maintain cytoskeletal rigidity.We propose a conceptual mechanotransduction model wherein cell surface glycocalyx HSPGs, in the presence of integrin-mediated cell-matrix adhesions and cytoskeleton organization, sense interstitial flow and activate the FAK-ERK signaling axis, leading to upregulation of MMP expression and cell motility in 3D. This is the first study to describe a flow-induced mechanotransduction mechanism via HSPG-mediated FAK activation in 3D. This study will be of interest in understanding the flow-related mechanobiology in vascular lesion formation, tissue morphogenesis, cancer cell metastasis, and stem cell differentiation in 3D, and also has implications in tissue engineering

Lrp5 Is Not Required for the Proliferative Response of Osteoblasts to Strain but Regulates Proliferation and Apoptosis in a Cell Autonomous Manner

Although Lrp5 is known to be an important contributor to the mechanisms regulating bone mass, its precise role remains unclear. The aim of this study was to establish whether mutations in Lrp5 are associated with differences in the growth and/or apoptosis of osteoblast-like cells and their proliferative response to mechanical strain in vitro. Primary osteoblast-like cells were derived from cortical bone of adult mice lacking functional Lrp5 (Lrp5−/−), those heterozygous for the human G171V High Bone Mass (HBM) mutation (LRP5G171V) and their WT littermates (WTLrp5, WTHBM). Osteoblast proliferation over time was significantly higher in cultures of cells from LRP5G171V mice compared to their WTHBM littermates, and lower in Lrp5−/− cells. Cells from female LRP5G171V mice grew more rapidly than those from males, whereas cells from female Lrp5−/− mice grew more slowly than those from males. Apoptosis induced by serum withdrawal was significantly higher in cultures from Lrp5−/− mice than in those from WTHBM or LRP5G171V mice. Exposure to a single short period of dynamic mechanical strain was associated with a significant increase in cell number but this response was unaffected by genotype which also did not change the ‘threshold’ at which cells responded to strain. In conclusion, the data presented here suggest that Lrp5 loss and gain of function mutations result in cell-autonomous alterations in osteoblast proliferation and apoptosis but do not alter the proliferative response of osteoblasts to mechanical strain in vitro

Longitudinal analysis of T-cell receptor repertoires reveals persistence of antigen-driven CD4+ and CD8+ T-cell clusters in systemic sclerosis

The T-cell receptor (TCR) is a highly polymorphic surface receptor that allows T-cells to recognize antigenic peptides presented on the major histocompatibility complex (MHC). Changes in the TCR repertoire have been observed in several autoimmune conditions, and these changes are suggested to predispose autoimmunity. Multiple lines of evidence have implied an important role for T-cells in the pathogenesis of Systemic Sclerosis (SSc), a complex autoimmune disease. One of the major questions regarding the roles of T-cells is whether expansion and activation of T-cells observed in the diseases pathogenesis is antigen driven. To investigate the temporal TCR repertoire dynamics in SSc, we performed high-throughput sequencing of CD4+ and CD8+ TCRβ chains on longitudinal samples obtained from four SSc patients collected over a minimum of two years. Repertoire overlap analysis revealed that samples taken from the same individual over time shared a high number of TCRβ sequences, indicating a clear temporal persistence of the TCRβ repertoire in CD4+ as well as CD8+ T-cells. Moreover, the TCRβs that were found with a high frequency at one time point were also found with a high frequency at the other time points (even after almost four years), showing that frequencies of dominant TCRβs are largely consistent over time. We also show that TCRβ generation probability and observed TCR frequency are not related in SSc samples, showing that clonal expansion and persistence of TCRβs is caused by antigenic selection rather than convergent recombination. Moreover, we demonstrate that TCRβ diversity is lower in CD4+ and CD8+ T-cells from SSc patients compared with memory T-cells from healthy individuals, as SSc TCRβ repertoires are largely dominated by clonally expanded persistent TCRβ sequences. Lastly, using “Grouping of Lymphocyte Interactions by Paratope Hotspots” (GLIPH2), we identify clusters of TCRβ sequences with homologous sequences that potentially recognize the same antigens and contain TCRβs that are persist in SSc patients. In conclusion, our results show that CD4+ and CD8+ T-cells are highly persistent in SSc patients over time, and this persistence is likely a result from antigenic selection. Moreover, persistent TCRs form high similarity clusters with other (non-)persistent sequences that potentially recognize the same epitopes. These data provide evidence for an antigen driven expansion of CD4+/CD8+ T-cells in SSc

Non-Overlapping Functions for Pyk2 and FAK in Osteoblasts during Fluid Shear Stress-Induced Mechanotransduction

Mechanotransduction, the process by which cells convert external mechanical stimuli such as fluid shear stress (FSS) into biochemical changes, plays a critical role in maintenance of the skeleton. We have proposed that mechanical stimulation by FSS across the surfaces of bone cells results in formation of unique signaling complexes called mechanosomes that are launched from sites of adhesion with the extracellular matrix and with other bone cells [1]. Deformation of adhesion complexes at the cell membrane ultimately results in alteration of target gene expression. Recently, we reported that focal adhesion kinase (FAK) functions as a part of a mechanosome complex that is required for FSS-induced mechanotransduction in bone cells. This study extends this work to examine the role of a second member of the FAK family of non-receptor protein tyrosine kinases, proline-rich tyrosine kinase 2 (Pyk2), and determine its role during osteoblast mechanotransduction. We use osteoblasts harvested from mice as our model system in this study and compared the contributions of Pyk2 and FAK during FSS induced mechanotransduction in osteoblasts. We exposed Pyk2+/+ and Pyk2−/− primary calvarial osteoblasts to short period of oscillatory fluid flow and analyzed downstream activation of ERK1/2, and expression of c-fos, cyclooxygenase-2 and osteopontin. Unlike FAK, Pyk2 was not required for fluid flow-induced mechanotransduction as there was no significant difference in the response of Pyk2+/+ and Pyk2−/− osteoblasts to short periods of fluid flow (FF). In contrast, and as predicted, FAK−/− osteoblasts were unable to respond to FF. These data indicate that FAK and Pyk2 have distinct, non-redundant functions in launching mechanical signals during osteoblast mechanotransduction. Additionally, we compared two methods of generating FF in both cell types, oscillatory pump method and another orbital platform method. We determined that both methods of generating FF induced similar responses in both primary calvarial osteoblasts and immortalized calvarial osteoblasts

Structural, magnetic, and electronic properties of high moment FeCo nanoparticles

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Comparison of extractive chemical signatures among branch, knot and bark wood fractions from forestry and agroforestry walnut trees (Juglans regia × J. nigra) by NIR spectroscopy and LC-MS analyses

International audienceWalnut agroforestry systems require regular tree pruning, generating a large volume of biomass residues which are mainly valorized as wood-energy, Ramial Chipped Wood (RCW) or animal litter. However, walnut is recognized as a rich source of different chemical compounds, which could be recovered as valuable chemicals. This study aims to improve the knowledge on the composition of the water and ethanol extractive contents of wood, knot and bark fractions from walnut branches, harvested in agroforestry (AF) and traditional forestry control (FC) systems. LC-MS analyses were carried out to identify the chemical composition of extracts. Additionally, all samples were analyzed by near-infrared (NIR) spectroscopy with the aim of developing a fast tool to distinguish walnut branches, knots and bark wood fractions from trees grown under agroforestry and plantation management. Extractive contents and chemical composition of AF and FC wood samples were slightly different among branch, knot and bark. Despite these small chemical differences, PLS-DA models based on NIRS measurements can distinguishing among wood samples from walnut trees grown under different silvicultural regimes. In addition, in the both forestry systems, branch and knot extractive contents were significantly lower than those of bark specimens. Principal Component Analyses (PCA) based on NIR-spectrometry of raw samples revealed that the chemical composition of branch and knot woods are similar to each other and are very different compared to those of bark samples. This study provides new knowledge on branch woods from agroforestry systems, which are still very under-studied at present

Comparative Study of Nanoparticles Fe 100−x Co x Alloy Synthesized by High Energy Ball Milling and by Polyol Process

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