Structural Characterization and Comparison of Monovalent Cation-Exchanged Zeolite-W

We report comparative structural changes of potassium-contained zeolite-W (K-MER, structural analogue of natural zeolite merlinoite) and monovalent extra-framework cation (EFC)-exchanged M-MERs (M = Li+, Na+, Ag+, and Rb+). High-resolution synchrotron X-ray powder diffraction study precisely determines that crystal symmetry of MERs is tetragonal (I4/mmm). Rietveld refinement results reveal that frameworks of all MERs are geometrically composed of disordered Al/Si tetrahedra, bridged by linkage oxygen atoms. We observe a structural relationship between a group of Li-, Na-, and Ag-MER and the group of K- and Rb-MER by EFC radius and position of M(1) site inside double 8-membered ring unit (d8r). In the former group, a-axes decrease reciprocally, c-axes gradually extend by EFC size, and M(1) cations are located at the middle of the d8r. In the latter group, a- and c-axes lengths become longer and shorter, respectively, than axes of the former group, and these axial changes come from middle-to-edge migration of M(1) cations inside the d8r channel. Unit cell volumes of the Na-, Ag-, and K-MER are ca. 2005 Å3, and the volume expansion in the MER series is limited by EFC size, the number of water molecules, and the distribution of extra-framework species inside the MER channel. EFC sites of M(1) and M(2) show disordered and ordered distribution in the former group, and all EFC sites change to disordered distribution after migration of the M(1) site in the latter group. The amount of water molecules and porosities are inversely proportional to EFC size due to the limitation of volume expansion of MERs. The channel opening area of a pau composite building unit and the amount of water molecules are universally related as a function of cation size because water molecules are mainly distributed inside a pau channel.

Risks and etiology of bacterial vaginosis revealed by species dominance network analysis

BV (bacterial vaginosis) influences 20-40% of women but its etiology is still poorly understood. An open question about the BV is which of the hundreds of bacteria found in the human vaginal microbiome (HVM) are the causal pathogens of BV? Existing attempts to identify them have failed for at least two reasons: (i) a focus on species per se that ignores species interactions; (ii) a lack of systems-level understanding of the HVM. Here, we recast the question of microbial causality of BV by asking if there are any reliable 'signatures' of community composition (or poly-microbial 'cults') associated with it? We apply a new framework (species dominance network analysis by Ma & Ellison (2019: Ecological Monographs) to detect critical structures in HVM networks associated with BV risks and etiology. We reanalyzed the metagenomic datasets of a mixed-cohort of 25 BV patients and healthy women. In these datasets, we detected 15 trio-motifs that occurred exclusively in BV patients. We failed to find any of these 15 trio-motifs in three additional cohorts of 1535 healthy women. Most member-species of the 15 trio motifs are BV-associated anaerobic bacteria (BVAB), Ravel's community-state type indicators, or the most dominant species; virtually all species interactions in these trios are high-salience skeletons, suggesting that those trios are strongly connected 'cults'. The presence of trio motifs unique to BV may act as indicators for its personalized diagnosis and could help elucidate a more mechanistic interpretation of its risks and etiology.

Seedling Recruitment of Native Tree Species in Active Restoration Forest

Since 1970’s, large are of deforestation and forest conversion to agriculture in the northern mountains of Thailand grew concern of environmental impact. Forest restoration became an important strategy to rapidly increase forest habitat in a wide-scale in Thailand. The Framework Species (FWS) technique is an active forest restoration that has been developed to restored forest habitat and ecosystem on former-agriculture land in the northern Thailand. After planting 20-30 framework species, the method then relies on incoming native tree species to sustain forest succession. However, there has been little known about the recruitment of native tree species and factors limiting the recruitment in this area. The study compared recruit native tree species in the seedling community of the FWS restoration and nearby seed source to assess how many of those are recruit or absent from the community. The factor of seed-dispersed agents and seed sized was investigated as the possible limited factors of the recruitment and compared among 3 restoration periods (at age 6, 10, and 14 years). The result reveals half of native species were absent from the seedling community across all 3 restoration ages. Seed available was a major limitation for the recruitment of native tree species. Big-seeded species had higher chance to be limited than small-seeded species to recruit in the restoration site (p-value = 0.0249 by the Tukey test). whilst seed-dispersed agents were not limited (p-values=0.420 by Chi square). The FWS forests efficiently facilitated seedlings of native tree species to recruit at the similar recruitment rates across all 3 ages of restoration. However, the technique was still limited in regard of seed available. Species of less common or rarer might need to be included for the FWS plantation in the future to enhance species diversity and better outcome of the restoration.

Uranyl Ion Complexes of Polycarboxylates: Steps towards Isolated Photoactive Cavities

Consideration of the extensive family of known uranyl ion complexes of polycarboxylate ligands shows that there are quite numerous examples of crystalline solids containing capsular, closed oligomeric species with the potential for use as selective heterogeneous photo-oxidation catalysts. None of them have yet been assessed for this purpose, and some have obvious deficiencies, although related framework species have been shown to have the necessary luminescence, porosity and, to some degree, selectivity. Aspects of ligand design and complex composition necessary for the synthesis of uranyl ion cages with appropriate luminescence and chemical properties for use in selective photo-oxidation catalysis have been analysed in relation to the characteristics of known capsules.

Applying a floristic originality index in tropical forests of south Sinaloa, Mexico

Sinaloa is among the states of Mexico harboring the highest deforestation rates. Reforestation programs have been put up in south Sinaloa with species chosen for their high seedling rates, structural importance or strong restoration value. However, species criteria such as level of endemism as well as rarity appear to be underestimated. Eight sampling sites were randomly selected and a botanical survey was carried out at least every month from 2015 to 2017. In order to rank species over conservation stakes, a Floristic Originality Index method was elaborated using species level of endemism, rarity and conservation status. The floristic inventory enabled the identification of a set of 250 species with the Fabaceae being the most represented family with 51 species. Using the Floristic Originality Index, a subset of 51 species was selected as priority for conservation along with 23 other species all displaying characteristics of “framework” species. Features of reproduction and types of ideal soil conditions for reforestation are presented for each species. The method developed to determine floristic originality has proven a set of most vulnerable and rare species to select “priority” and “framework” tree species able to restore forests structure and biodiversity as well as ecosystem functions. This evaluation is made from a conservation biology point of view and appears to be well adapted for studies at a local scale.

The encapsulation selectivity for anionic fission products imparted by an electride

The nanoporous oxide 12CaO·7Al2O3 (C12A7) can capture large concentrations of extra-framework species inside its nanopores, while maintaining its thermodynamical stability. Here we use atomistic simulation to predict the efficacy of C12A7 to encapsulate volatile fission products, in its stoichiometric and much more effective electride forms. In the stoichiometric form, while Xe, Kr and Cs are not captured, Br, I and Te exhibit strong encapsulation energies while Rb is only weakly encapsulated from atoms. The high electronegativities of Br, I and Te stabilize their encapsulation as anions. The electride form of C12A7 shows a significant enhancement in the encapsulation of Br, I and Te with all three stable as anions from their atom and dimer reference states. Successive encapsulation of multiple Br, I and Te as single anions in adjacent cages is also energetically favourable. Conversely, Xe, Kr, Rb and Cs are unbound. Encapsulation of homonuclear dimers (Br2, I2 and Te2) and heteronuclear dimers (CsBr and CsI) in a single cage is also unfavourable. Thus, C12A7 offers the desirable prospect of species selectivity.