Two-dimensional amine and hydroxy functionalized fused aromatic covalent organic framework

Ordered two-dimensional covalent organic frameworks (COFs) have generally been synthesized using reversible reactions. It has been difficult to synthesize a similar degree of ordered COFs using irreversible reactions. Developing COFs with a fused aromatic ring system via an irreversible reaction is highly desirable but has remained a significant challenge. Here we demonstrate a COF that can be synthesized from organic building blocks via irreversible condensation (aromatization). The as-synthesized robust fused aromatic COF (F-COF) exhibits high crystallinity. Its lattice structure is characterized by scanning tunneling microscopy and X-ray diffraction pattern. Because of its fused aromatic ring system, the F-COF structure possesses high physiochemical stability, due to the absence of hydrolysable weak covalent bonds

Phylogeny and Taxonomy of the Round-Eared Sengis or Elephant-Shrews, Genus Macroscelides (Mammalia, Afrotheria, Macroscelidea)

The round-eared sengis or elephant-shrews (genus Macroscelides) exhibit striking pelage variation throughout their ranges. Over ten taxonomic names have been proposed to describe this variation, but currently only two taxa are recognized (M. proboscideus proboscideus and M. p. flavicaudatus). Here, we review the taxonomic history of Macroscelides, and we use data on the geographic distribution, morphology, and mitochondrial DNA sequence to evaluate the current taxonomy. Our data support only two taxa that correspond to the currently recognized subspecies M. p. proboscideus and M. p. flavicaudatus. Mitochondrial haplotypes of these two taxa are reciprocally monophyletic with over 13% uncorrected sequence divergence between them. PCA analysis of 14 morphological characters (mostly cranial) grouped the two taxa into non-overlapping clusters, and body mass alone is a relatively reliable distinguishing character throughout much of Macroscelides range. Although fieldworkers were unable to find sympatric populations, the two taxa were found within 50 km of each other, and genetic analysis showed no evidence of gene flow. Based upon corroborating genetic data, morphological data, near sympatry with no evidence of gene flow, and differences in habitat use, we elevate these two forms to full species

Hiding in Plain Sight: Unmasking the Diffuse Spectral Signatures of the Protonated N‑Terminus in Isolated Dipeptides Cooled in a Cryogenic Ion Trap

Survey vibrational predissociation spectra of several representative protonated peptides and model compounds reveal very diffuse absorptions near 2500 cm^–1 that are traced to pentagonal cyclic ionic hydrogen bonds (C₅ interactions) involving the excess charge centers. This broadening occurs despite the fact that the ions are cooled close to their vibrational zero-point levels and their spectra are obtained by predissociation of weakly bound adducts (H₂, N₂, CO₂) prepared in a cryogenic ion trap. The C₅ band assignments are based on H/D isotopic substitution, chemical derivatization, solvation behavior, and calculated spectra. We evaluate the extent to which this broadening is caused by anharmonic coupling in the isolated molecules by including cubic coupling terms in the normal mode expansion of the potential energy surface. This analysis indicates that the harmonic H-bonded stretching vibration is mixed with dark background states over much of the energy range covered by the observed features. The difficulty with identifying these features in earlier studies of dipeptides is traced to both the breadth and the fact they are calculated to be intrinsically weaker than cases involving linear variations of the N···H⁺···O motif

Bottom-Up View of Water Network-Mediated CO₂ Reduction Using Cryogenic Cluster Ion Spectroscopy and Direct Dynamics Simulations

The transition states of a chemical reaction in solution are generally accessed through exchange of thermal energy between the solvent and the reactants. As such, an ensemble of reacting systems approaches the transition state configuration of reactant and surrounding solvent in an incoherent manner that does not lend itself to direct experimental observation. Here we describe how gas-phase cluster chemistry can provide a detailed picture of the microscopic mechanics at play when a network of six water molecules mediates the trapping of a highly reactive “hydrated electron” onto a neutral CO₂ molecule to form a radical anion. The exothermic reaction is triggered from a metastable intermediate by selective excitation of either the reactant CO₂ or the water network, which is evidenced by the evaporative decomposition of the product cluster. Ab initio molecular dynamics simulations of energized CO₂·(H₂O)₆^– clusters are used to elucidate the nature of the network deformations that mediate intracluster electron capture, thus revealing the detailed solvent fluctuations implicit in the Marcus theory for electron-transfer kinetics in solution

Shrinkage measurements of mortars with energetically modified fly ash

The shrinkage tests performed show a significant lower final shrinkage for higher fly ash content. The shrinkage level is in the order of size that is typical for mortars, and the level of shrinkage would be much lower, say about half as large, for concrete mixtures with the same type of binders. It would be interesting to study the shrinkage, both drying shrinkage and autogenous shrinkage, for the same type of binders used in concrete mixes.Godkänd; 2005; 20080522 (ysko

The mitochondrial and nuclear genetic structure of Myotis capaccinii (Chiroptera : Vespertilionidae) in the Eurasian transition, and its taxonomic implications

WOS: 000254954700003Allopatric isolation in glacial refugia has caused differentiation and speciation in many taxa globally. In this study, we investigated the nuclear and mitochondrial genetic differentiation of the long fingered bat, Myotis capaccinii during the ice ages in south-eastern Europe and Anatolia. The mitochondrial DNA (mtDNA) analyses indicated a suture zone similar to those recorded in other animal species, including bats, suggesting the association of more than one refugium with the region. Contrary to most of the other species where a suture zone was seen in Anatolia, for M. capaccinii the geographical location of the genetic break was in south-eastern Europe. This mitochondrial differentiation was not reflected in the nuclear microsatellites, however, suggesting that the lack of contact during the ice ages did not result in reproductive isolation. Hence taxonomically, the two mitochondrial clades cannot be treated as separate species