Prevailing Intermolecular Bonding for Dinitrotoluene Self-Assembled Monolayers on Au(111)

The self-assembly of 2,4- and 2,6-dinitrotoluene was investigated on Au(111) surfaces using a combined experimental and density functional theory approach. Well-ordered monolayers were observed with rectangular unit cells commensurate with the Au substrate along the next-nearest-neighbor direction. The unit cell is made of two molecules per cell in an unusual vertical configuration, driven by a strong dipole–dipole interaction between molecules and with lesser interaction with the substrate. van der Waals density functional theory models of bonding in the molecular layer show strong intermolecular interactions that dominate over substrate interactions with cohesive energies near 24 kcal/mol. The calculations are corroborated by temperature-programmed desorption experiments and demonstrate that intermolecular interactions dominate the self-assembly of this molecular adsorption system. Both dipole–dipole and van der Waals interactions are significant contributors to the bonding, and the importance of van der Waals corrected density functional theory is shown. We argue that the molecule–molecule vs molecule–substrate interactions are controlled by the optimization of energy per unit surface area

Combustion characteristics of H 2/N 2 and H 2/CO syngas nonpremixed flames

Turbulent nonpremixed H2/N2 and H2/CO syngas flames were simulated using 3D large eddy simulations coupled with a laminar flamelet combustion model. Four different syngas fuel mixtures varying from H2-rich to CO-rich including N2 have been modelled. The computations solved the Large Eddy Simulation governing equations on a structured non-uniform Cartesian grid using the finite volume method, where the Smagorinsky eddy viscosity model with the localised dynamic procedure is used to model the sub-grid scale turbulence. Non-premixed combustion has been incorporated using the steady laminar flamelet model. Both instantaneous and time-averaged quantities are analysed and data were also compared to experimental data for one of the four H2-rich flames. Results show significant differences in both unsteady and steady flame temperature and major combustion products depending on the ratio of H2/N2 and H2/CO in syngas fuel mixture

Energy absorption of aluminum panels subjected to gelatin projectile impact

Abstract Digital image correlation (DIC) method has been widely used on dynamical experiments. This full-field and real-time method can fill in the gap of traditional point-based measurements of typical structures subjected to soft body impact such as bird strike. In order to get further understandings of soft body impact process, the present study analyzed the time-dependent energy exchange during impact experiments. The dynamic responses of the aluminum target panels were obtained using 3D digital image correlation method so that their displacement and strain field histories can be tracked. By introducing the material properties of the targets, their time-dependent stress state and consequently the strain energy can be calculated. With the help of time-dependent profiles of target panels, their energy absorption properties were theoretically analyzed, including the exchange of kinetic energy and plastic work. The results showed that when the impact loadings were increased, the plastic work generated by radial membrane force became the major source of energy dissipation. The transverse movements consumed more kinetic energies than rotatory moments. This research may provide a further application of DIC results and help to better understand the soft body impact process on targets with large deformations.</div

Influence of light intensity on chloroplast development and pigment accumulation in the wild-type and etiolated mutant plants of <i>Anthurium andraeanum</i> ‘Sonate’

<p>Seedlings of wild-type and etiolate mutant plants of <i>Anthurium andraeanum</i> cultivar ‘Sonate’ were treated for 15 d with different light intensities (20, 100, and 400 µmol·m⁻²·s⁻¹) to analyze leaf plastid development and pigment content. Significant changes appeared in treated seedlings, including in leaf color, plastid ultrastructure, chloroplast development gene <i>AaGLK</i> expression, chlorophyll and anthocyanin contents, and protoplast shape. Wild-type and etiolated plants exhibited different plastid structures under the same light condition. The results suggest that light intensity is a crucial environmental factor influencing plastid development and leaf color formation in the <i>A. andraeanum</i> cultivar ‘Sonate’.</p

Supporting Data 1 from Composition, mineralization potential and release risk of nitrogen in the sediments of Keluke Lake, a Tibetan Plateau freshwater lake in China

Content of N in sediments and the changes of N forms in incubatio

Supporting Data 2 from Composition, mineralization potential and release risk of nitrogen in the sediments of Keluke Lake, a Tibetan Plateau freshwater lake in China

Content of TP in sediments and release flux of P on the water-sediment interfac

Higher-order-modes enhanced phase-matched dispersive-wave generation in the deep-blue and UV spectral region

During the last few decades, solid-core photonic crystal fibers (PCFs) have been extensively explored to generate broadband, high-coherence supercontinua (SC). Limited by the material absorption and relatively low nonlinearity of fused silica, spectral broadening in silica PCF-based SCs is usually restricted to the blue to near-infrared spectral regions, even in developed commercial sources. The output spectra of these sources are missing short wavelengths of the full range. Many efforts have been spent to break the limitation. Among them, dispersive-wave (DW) generation has been investigated for triggering new frequencies in short wavelengths. With satisfied phase-matching conditions, excessive energy can be directly transferred from solitons of the anomalous dispersion region to DWs of the short wavelengths. However, a systematical study of factors, including phase-matched DWs, strongly related to the dispersion tailoring of higher-order modes (HOMs), has rarely been shown. This study reports the experimental observations of HOM-enhanced phase-matchings for the DW generation in the deep-blue and ultraviolet regions. A solid-core PCF-based, UV-extended SC source spanning a 2.8-octave-wide (350 nm to 2500 nm) is demonstrated. Meanwhile, we carefully verify our findings via numerical calculations

Supplement 1: Orbital-angular-momentum-preserving helical Bloch modes in twisted photonic crystal fiber

Originally published in Optica on 20 September 2014 (optica-1-3-165

A Site-Specific Integrative Plasmid Found in Pseudomonas aeruginosa Clinical Isolate HS87 along with A Plasmid Carrying an Aminoglycoside-Resistant Gene

Plasmids play critical roles in bacterial fitness and evolution of Pseudomonas aeruginosa. Here two plasmids found in a drug-resistant P. aeruginosa clinical isolate HS87 were completely sequenced. The pHS87b plasmid (11.2 kb) carries phage-related genes and function-unknown genes. Notably, pHS87b encodes an integrase and has an adjacent tRNAThr-associated attachment site. A corresponding integrated form of pHS87b at the tRNAThr locus was identified on the chromosome of P. aeruginosa, showing that pHS87b is able to site-specifically integrate into the 3'-end of the tRNAThr gene. The pHS87a plasmid (26.8 kb) displays a plastic structure containing a putative replication module, stability factors and a variable region. The RepA of pHS87a shows significant similarity to the replication proteins of pPT23A-family plasmids. pHS87a carries a transposon Tn6049, a truncated insertion sequence ΔIS1071 and a Tn402-like class 1 integron which contains an aacA4 cassette that may confer aminoglycoside resistance. Thus, pHS87b is a site-specific integrative plasmid whereas pHS87a is a plastic antibiotic resistance plasmid. The two native plasmids may promote the fitness and evolution of P. aeruginosa

Supplement 1: Stable subpicosecond soliton fiber laser passively mode-locked by gigahertz acoustic resonance in photonic crystal fiber core

Originally published in Optica on 20 April 2015 (optica-2-4-339