The structural parameters of six
coals were determined by X-ray
diffraction (XRD), scanning electron microscope (SEM), and Raman and
FTIR spectroscopy. The results reveal that the derivative coals prepared
by calcination and HF acidification contain much crystalline carbon
like graphite structure and are improved significantly in aromaticity,
coal rank, and hydroxyl concentration. The increase of hydroxyl (OH)
bonds is very beneficial to the surface modification of coal crystalline
layers. In addition, the derivative coals have an obvious decrease
of the aliphatic C–H content and a significant increase of
the aromatic C–H content in FTIR spectra compared to that for
the raw coal (AY). They are consistent with the changes of aromaticity
and crystalline carbon measured by XRD and Raman spectra. With the
increase of coal rank, the content of defect crystalline carbon and
amorphous carbon decreases gradually from AY to the coal prepared
by calcination and HF acidification (AY-C-HF). The particles of AY-C-HF
with about 20 nm in thickness have better dispersibility with simultaneously
a lot of pore space. The process of first calcination and then acidification
can help us delaminate the aromatic layers in the coals and obtain
the superfine crystalline carbon materials like graphite structure.
Since its discovery in 2008, New Delhi metallo-β-lactamase-1 (NDM-1)-producing Enterobacteriaceae have disseminated globally, facilitated predominantly by gut colonization and the spread of plasmids carrying the bla NDM-1 gene. With few effective antibiotics against NDM-1 producers, and resistance developing to those which remain, there is an urgent need to develop new treatments. To date, most drug design in this area has been focused on developing an NDM-1 inhibitor and has been aided by the wealth of structural and mechanistic information available from high resolution x-ray crystallography and molecular modeling. This review aims to summarize current knowledge regarding the detection of NDM-1 producers, the mechanism of action of NDM-1 and to highlight recent attempts toward the development of clinically useful inhibitors.
Mixed
surfactants have a prominent synergistic effect and show
advantages in many aspects. In this work, the effects of a mixture
of dodecyltrimethylammonium bromide (DTAB) and sodium dodecyl sulfate
(SDS) on the flotation of low-rank coal were studied from the wetting
rate, contact angle, surface tension, and zeta potential. Furthermore,
the adsorption configuration of the mixed surfactant on the surface
of oxygen-containing graphite was simulated at the molecular level
by molecular dynamics simulation. The experimental results show that
the combustible matter recovery of low-rank coal flotation is improved
using the mixed surfactant, and the contact angle test and wetting
rate test confirmed the synergistic effect of the mixed surfactant.
In the mixed surfactant system, the addition of SDS with an opposite
charge to DTAB can reduce the mutual repulsion between DTAB molecules
and enhance the degree of DTAB alignment in solution, which was analyzed
by surface tension and zeta potential tests. Meanwhile, the simulation
results reveal the adsorption behavior of anionic and cationic surfactants
on the surface of oxygen-containing graphite from the molecular level
and also verify the experimental results. This investigation provides
a good understanding of the interaction mechanism of mixed surfactants
in low-rank coal flotation.
The charge density distribution in 2,2'-Dihydroxy-1,1'-naphthalazine (Pigment Yellow 101; P.Y.101) has been determined using high-resolution X-ray diffraction and multipole refinement, along with density functional theory calculations. Topological analysis of the resulting densities highlights the localisation of single/double bonds in the central C=N-N=C moiety of the molecule in its ground state. The density in the N-N is examined in detail, where we show that very small differences between experiment and theory are amplified by use of the Laplacian of the density. Quantification of hydrogen bonds highlights the importance of the intramolecular N-H…O interaction, known to be vital for retention of fluorescence in the solid state, relative to the many but weak intermolecular contacts located.However, a popular method for deriving H-bond strengths from density data appears to struggle with the intramolecular N-H…O interaction. We also show that theoretical estimation of anisotropic displacements for hydrogen atoms brings little benefit overall, and degrades agreement with experiment for one intra-molecular contact.2
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