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First principles calculations are employed to providea fundamental understanding of the relationship between the reactivityof synthetic calcium silicate phases and their electronic structure.Our aim is to shed light on the wide range of hydration kinetics observedin different phases of calcium silicate. For example, while the dicalciumsilicate (Ca2SiO4) phase slowly reacts withwater, the tricalcium silicate (Ca3SiO5) showsmuch faster hydration kinetics. We show that the high reactivity ofCa3SiO5is mainly related to the reactive sitesaround its more ionic oxygen atoms. Ca2SiO4doesnot contain these types of oxygen atoms, although experiments suggestthat impurities may play a role in changing the reactivity of thesematerials. We analyze the electronic structure of a wide range ofpossible substitutions in both Ca3SiO5and Ca2SiO4and show that while the influence of differenttypes of impurities on structural properties is similar, their effecton reactivity is very different. Our calculations suggest that thevariation of electronic structure is mainly related to the formationof new hybridized orbitals and the charge exchange between the impurityatoms and the bulk material. The charge localization upon introducingimpurities is quantified to predict candidate substitutions that couldincrease the reactivity of Ca2SiO4, which wouldbroaden the applicability of this lower temperature and thus lesscostly and energetically less demanding phase. [ABSTRACT FROM AUTHOR]

Abstract: The elastic properties of the most important phases present in cement pastes have been studied by force field atomistic methods. Calculations reproduce the mechanical properties of crystalline species alite, belite and portlandite fairly well. The elastic properties of amorphous calcium–silicate–hydrate (C–S–H) gel are also explained in terms of the commonly used structural models 1.4nm tobermorite and jennite, once the intrinsic porosity and the silicate chain length are concurrently considered through the appropriate micromechanical models. The findings conclude that bringing the atomic structure into contact with the mechanical properties of C–S–H gel may modify the actual view of the gel. [Copyright &y& Elsevier]

This study utilized 16S rRNA gene amplicon sequencing to describe the rumen bacterial community composition in Holstein and Jersey cows fed an identical diet by sampling the rumen microbiota via the rumen cannula or esophageal tubing. Five ruminally cannulated Holstein cows and 4 Jersey cows (not cannulated) were fed a diet composed of 51% forage and 49% concentrate during 4 wk. On the 28th day, rumen samples were collected from both Holstein and Jersey cows using the esophageal tubing, and an additional rumen sample was collected from Holstein cows via the cannula. After collection of the rumen sample via esophageal tubing, particles attached to the metal strainer were added to the sample to better represent whole rumen content and to include particle associated bacteria. Total rumen DNA was extracted using the PowerMag™ Soil DNA Isolation Kit, and the V3 region of the bacterial 16S rRNA was amplified and then sequenced using the Ion Torrent™ Personal Genome Machine. The resulting sequences were quality filtered and operational taxonomic units (OTUs) were generated at 97% similarity. Taxonomy assignment was performed using the Greengenes database. The 2 main phyla identified regardless of breed or sampling method, were Firmi-cutes and Bacteroidetes, which accounted for 44.3 and 42.9% of the sequences. Alpha diversity metrics, observed OTUs and Chaol estimates, displayed higher (P < 0.01) bacterial richness in Holstein compared to Jersey cows. However, between the samples collected via the cannula and stomach tubing in Holstein cows, no difference in species richness was detected (P > 0.40). Principal coordinate analysis using the unweighted UniFrac displayed clustering by breed suggesting that Holstein and Jersey cows may harbor distinct rumen bacterial communities. Non-parametric multivariate analysis of variance supported the significant effect of breed (P = 0.01). No significant difference in bacterial community structure was detected by sampling method (P = 0.18). Linear discriminant analysis of effect size was used to identify OTUs that differ between breeds. Family level classification of most abundant differential OTUs identified OTUs from the bacterial families Lachno-spiraceae, Veillonellaceae, Ruminococcaceae, and Fibrobac-teraceae to be more predominant in Holstein compared to Jersey cows whereas an OTU from the family Prevotellaceae was more predominant in Jersey compared to Holstein cows. Overall, results suggest that the bacterial community between Holstein and Jersey cows differ and that esophageal tubing with collection of feed particles associated with the strainer provides an adequate sampling method for rumen bacterial community studies. [ABSTRACT FROM AUTHOR]

Abstract: For first time, an experimental and computational study has been conducted to define a structural model for the C-A-S-H gel forming in alkali-activated slag (AAS) pastes that would account for the mechanical properties of these materials. The study involved a comparison with the C-S-H gel forming in a Portland cement paste. The structure of the C-A-S-H gels in AAS pastes depends on the nature of the alkali activator. When the activator is a NaOH, the structure of the C-S-H gel falls in between tobermorite 1.4nm with a mean chain length of five, and tobermorite 1.1nm with a mean length of 14. When waterglass is the activator the structure of the C-A-S-H gel is indicative of the co-existence of tobermorite 1.4nm with a chain length of 11 and tobermorite 1.1nm with a chain length of 14. This very densely packed structure gives rise to excellent mechanical properties. [Copyright &y& Elsevier]

Abstract: Ivermectin (IVM) is an antiparasitic drug, widely used in domestic animals. In mammals, IVM act as a GABA agonist. This neurotransmitter has an important role in the regulation of sexual behavior. Thus, this study sought to investigate the effects of various medically relevant doses IVM on the sexual behavior of male rats. In particular, we also wished to examine if previous sexual experience modulated responses to IVM. In the first experiment, the sexual behavior of inexperienced male rats was analyzed after they received 0.2, 0.6, 1.0 or 2.0mg/kg IVM, 15min prior to behavioral testing. In the second experiment, the effects of four previous sexual experiences on IVM treated rats (1.0 or 2.0mg/kg, 15min prior to the 5th session) were assessed. The standard therapeutic dose (0.2mg/kg) did not impair the sexual behavior of inexperienced male rats. At a more concentrated dose (0.6mg/kg), which is still within the therapeutic range, the appetitive phase of sexual behavior of inexperienced male rats was impaired. Likewise, 1.0mg/kg impaired the appetitive phase. Previous sexual experience blocked almost entirely this sexual impairment, suggesting that previous sexual experience exerts a positive effect in attenuating the sexual impairment produced by IVM treatment. Therefore, the standard therapeutic dose of IVM can be used without producing side effects on sexual behavior. Use of more concentrated therapeutic doses is not recommended during reproductive periods, unless the animals have had previous sexual experience. [Copyright &y& Elsevier]