102 research outputs found
Total Synthesis of Amphidinolideâ F
Orchestrated yet nonconsonant: The challenge posed by the âumpoledâ 1,4-dioxygenation pattern characteristic for the polyketide frame of amphidinolideâ
F was mastered by a late-stage ring-closing alkyne metathesis followed by a directed transannular hydration under the aegis of a carbophilic Ï-acid catalyst. This concordant strategy enabled a concise total synthesis of this enticing marine natural product
Characterization of ply mixing rules for non-symmetric forms of fully orthotropic laminates
Stacking sequence listings are presented for fully orthotropic angle-ply
laminates, with up to 21 plies, together with rules for mixing these
sequences to form laminates containing any number of plies. The mixing
rules are demonstrated through an abridged set of sequences, which are
characterized in terms of angle- and cross-ply sub-sequence symmetries. The
abridged set of sequences is derived from a new definitive list that
supersedes previously published listings. Stacking sequences are presented
together with dimensionless parameters from which the bending stiffness
terms are readily calculated and an assessment of the bending stiffness
efficiency made for angle- and cross-ply sub-sequences. Expressions
relating the dimensionless parameters to the well-known lamination
parameters are also given, together with graphical representations of
feasible domains for all sub-sequence symmetries contained in the definitive
list. Feasible domains for extensionally isotropic and fully isotropic
laminates are also presented as important sub-sets of fully orthotropic
laminates. Finally, examples are given for tapered laminates with fully
orthotropic properties, derived from compatible sequences in the definite
list
Stacking sequences for extensionally isotropic, fully isotropic and quasi-homogeneous orthotropic laminates
Stacking sequence listings are presented for fully uncoupled Extensionally
Isotropic (EILs), Fully Isotropic (FILs) and Quasi-Homogeneous Orthotropic
(QHOLs) angle-ply Laminates, with up to 21 plies. All are sub-sets of a
definitive list of Fully Orthotropic Laminates (FOLs), containing generally
non-symmetric stacking sequences that are characterized in terms of angle-
and cross-ply sub-sequence symmetries. Dimensionless parameters are given
for each stacking sequence, from which the ABD matrix is readily derived.
Expressions relating these dimensionless parameters to the well-known
lamination parameters are also given, together with graphical
representations of the feasible domains for Pi/3 and Pi/4 EILs and angle-ply
QHOLs containing two and three ply orientations. The feasible domain for
Pi/3 FILs is represented graphically by a single point, whereas the domain
for angle-ply QHOLs containing four ply orientations is represented by a
single stacking sequence
Microorganisms
The indoor microbial community is a mixture of microorganisms resulting from outdoor ecosystems that seed the built environment. However, the biogeography of the indoor microbial community is still inadequately studied. Dust from more than 3000 dwellings across France was analyzed by qPCR using 17 targets: 10 molds, 3 bacteria groups, and 4 mites. Thus, the first spatial description of the main indoor microbial allergens on the French territory, in relation with biogeographical factors influencing the distribution of microorganisms, was realized in this study. Ten microorganisms out of 17 exhibited increasing abundance profiles across the country: Five microorganisms (DermatophagoĂŻdes pteronyssinus, DermatophagoĂŻdes spp., Streptomyces spp., Cladosporium sphaerospermum, Epicoccum nigrum) from northeast to southwest, two (Cryptococcus spp., Alternaria alternata) from northwest to southeast, Mycobacteria from east to west, Aspergillus fumigatus from south to north, and Penicillium chrysogenum from south to northeast. These geographical patterns were partly linked to climate and land cover. Multivariate analysis showed that composition of communities seemed to depend on landscapes, with species related to closed and rather cold and humid landscapes (forests, located in the northeast) and others to more open, hot, and dry landscapes (herbaceous and coastal regions, located in the west). This study highlights the importance of geographical location and outdoor factors that shape communities. In order to study the effect of microorganisms on human health (allergic diseases in particular), it is important to identify biogeographic factors that structure microbial communities on large spatial scales and to quantify the exposure with quantitative tools, such as the multi-qPCR approach
Rapid diagnostic tests relying on antigen detection from stool as an efficient point of care testing strategy for giardiasis and cryptosporidiosis? Evaluation of a new immunochromatographic duplex assay
Microscopy is the gold standard for the diagnosis of gastrointestinal parasites but is time-consuming and dependent on operator skills. Rapid diagnostic tests represent alternative methods but most evaluations have been conducted on a limited number of samples preventing their implementation in the clinical setting. We evaluated a new CE-IVD marked immunochromatographic assay (Crypto/Giardia K-SeTÂź, Coris Bioconcept) for the detection of G. intestinalis and Cryptosporidium spp. in 2 phases (retrospective and prospective) on a set of 482 stool samples including rare Cryptosporidium species. Besides G. intestinalis, this test could represent a rapid and reliable alternative to the modified Ziehl-Neelsen staining for the diagnosis of cryptosporidiosis (sensitivity/specificity were 89.2%/99.3% and 86.7%/100% for G. intestinalis and Cryptosporidium resp.), reducing diagnostic delays. Such strategy would also be time-saving by avoiding wet mount microscopy and concentrations steps, being particularly appropriate for laboratories having little expertise in microscopy or not able to implement molecular diagnostic methods
Environmental metabarcoding reveals contrasting belowground and aboveground fungal communities from poplar at a Hg phytomanagement site
Characterization of microbial communities in stressful conditions at a field level is rather scarce, especially when considering fungal communities from aboveground habitats. We aimed at characterizing fungal communities from different poplar habitats at a Hg-contaminated phytomanagement site by using Illumina-based sequencing, network analysis approach, and direct isolation of Hg-resistant fungal strains. The highest diversity estimated by the Shannon index was found for soil communities, which was negatively affected by soil Hg concentration. Among the significant correlations between soil operational taxonomic units (OTUs) in the co-occurrence network, 80% were negatively correlated revealing dominance of a pattern of mutual exclusion. The fungal communities associated with Populus roots mostly consisted of OTUs from the symbiotic guild, such as members of the Thelephoraceae, thus explaining the lowest diversity found for root communities. Additionally, root communities showed the highest network connectivity index, while rarely detected OTUs from the Glomeromycetes may have a central role in the root network. Unexpectedly high richness and diversity were found for aboveground habitats, compared to the root habitat. The aboveground habitats were dominated by yeasts from the Lalaria, Davidiella, and Bensingtonia genera, not detected in belowground habitats. Leaf and stem habitats were characterized by few dominant OTUs such as those from the Dothideomycete class producing mutual exclusion with other OTUs. Aureobasidium pullulans, one of the dominating OTUs, was further isolated from the leaf habitat, in addition to Nakazawaea populi species, which were found to be Hg resistant. Altogether, these findings will provide an improved point of reference for microbial research on inoculation-based programs of tailings dumps
The Arabidopsis ABA-Activated Kinase OST1 Phosphorylates the bZIP Transcription Factor ABF3 and Creates a 14-3-3 Binding Site Involved in Its Turnover
indicates that members of the Snf1-Related Kinases 2 family (SnRK2) are essential in mediating various stress-adaptive responses. Recent reports have indeed shown that one particular member, OPEN STOMATA (OST)1, whose kinase activity is stimulated by the stress hormone abscisic acid (ABA), is a direct target of negative regulation by the core ABA co-receptor complex composed of PYR/PYL/RCAR and clade A Protein Phosphatase 2C (PP2C) proteins. and that phospho-T451 is important for stabilization of ABF3. on T451 to create a 14-3-3 binding motif. In a wider physiological context, we propose that the long term responses to ABA that require sustained gene expression is, in part, mediated by the stabilization of ABFs driven by ABA-activated SnRK2s
Plant lectins: the ties that bind in root symbiosis and plant defense
Lectins are a diverse group of carbohydrate-binding proteins that are found within and associated with organisms from all kingdoms of life. Several different classes of plant lectins serve a diverse array of functions. The most prominent of these include participation in plant defense against predators and pathogens and involvement in symbiotic interactions between host plants and symbiotic microbes, including mycorrhizal fungi and nitrogen-fixing rhizobia. Extensive biological, biochemical, and molecular studies have shed light on the functions of plant lectins, and a plethora of uncharacterized lectin genes are being revealed at the genomic scale, suggesting unexplored and novel diversity in plant lectin structure and function. Integration of the results from these different types of research is beginning to yield a more detailed understanding of the function of lectins in symbiosis, defense, and plant biology in general
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