High-resolution Fourier transform infrared absorption spectroscopy of the ν6 band of c-C3H2

The gas-phase high-resolution absorption spectrum of the ν(6) band of cyclopropenylidene (c-C(3)H(2)) has been observed using a Fourier transform infrared spectrometer for the first time. The molecule has been produced by microwave discharge in an allene (3.3 Pa) and Ar (4.0 Pa) mixture inside a side arm glass tube. The observed spectrum shows a pattern of c-type ro-vibrational transitions in which the Q-branch lines strongly and distinctly stand out in the spectrum. A combined least-squares analysis of the observed 216 ro-vibrational transitions together with 28 millimeter-wave rotational transitions from the previous study has resulted in an accurate determination of the molecular constants in the ν(6) state. The band center is found to be at 776.11622(13) cm(-1) with one standard deviation in parentheses, which is 2.3% lower than the matrix isolation value. The intensity ratio I(3)(ν(3))/I(6)(ν(6)) obtained from the observed ν(3) and ν(6) bands, 1.90(9), is somewhat lower than the ratio estimated from ab initio (2.4-2.6) and DFT (2.8) calculations.     

Theoretical studies of host-guest interaction in gas hydrates

Ab initio calculations and atoms-in-molecules (AIM) analysis have been used to investigate the host-guest interaction in dodecahedral water cages using a variety of guest species that include monatomic (He, Ne, Ar, Kr, and Xe), diatomic (CO, H(2), N(2), O(2), and NO), triatomic (CO(2), NO(2), and O(3)), and polyatomic (CH(4) and NH(3)) molecules. Geometry optimization for the guest species, host cage, and their complexes was carried out using the second order M?ller-Plesset perturbation method with the 6-31G** basis set. Single point energy calculations using the same method but different basis sets (6-31++G**, 6-311++G**, aug-cc-pVDZ, and aug-cc-pVTZ) were carried out for the MP2/6-31G** optimized geometries. The interaction energy between the guest species and the host cage has been obtained in the complete basis set limit by basis set extrapolation.     

Bayesian calibration of model coefficients for a simulation of flow over porous material involving SVM classification

In this contribution the identification of the model coefficients of a novel turbulent flow model over porous media is concerned. The flow is modeled with a volume and Reynolds averaged compressible Navier-Stokes equations approach. The main focus of this contribution is to calibrate the model coefficients starting from expert prior knowledge by incorporating DNS data of the velocity field and the Reynolds stresses. For the inverse problem general Polynomial Chaos Expansions (gPCE) based surrogate model was used. To avoid the identification of nonphysical coefficient setups, these parametric regions were filtered out by identifying a decision boundary by the support vector machine binary classification. The machinery of the Markov Chain Monte Carlo (MCMC) was used for the data assimilation combined with a nonlinear Minimum Mean Square Estimator (MMSE) for speeding up the convergence of the random walk of the MCMC. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Sonoemulsion Synthesis of Long CuO Nanorods with Enhanced Catalytic Thermal Decomposition of Potassium Perchlorate

A facile sonoemulsion route using suitable non-ionic surfactant, polyethylene glycol with molecular weight of 8000 (PEG8000) was developed to synthesize long CuO nanorods with average diameter of 15–20 nm and lengths up to 1.5 μm. The as-developed CuO nanorods were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, SAED and Raman spectroscopy. The Raman spectrum of as-synthesized nanorods was found to be red-shifted and broadened due to possible consequence of phonon confinement, electron–LO–phonon-coupling and internal compressive stresses. The dynamics of nanorod growth was elaborated in context of size aggregation effect fueled by ultra-sonication and steric hindrance effect imposed by PEG8000. The catalytic activity of CuO nanorods in thermal decomposition of potassium perchlorate was examined by thermogravimetric analysis technique. The CuO nanorods prepared by sonoemulsion route was found to be very effective in thermal decomposition of potassium perchlorate with significant reduction in thermal decomposition temperature.     

Efficient One-Pot Synthesis of 4-Aroyl-2-pyrones: Nucleophilic Addition of Active Methylene Groups to 1,2-Diaroylacetylenes

An efficient synthesis of 3,6-disubstituted-4-aroyl-2-pyrones in a single-step reaction through Michael addition of 1,2-diaroylacetylenes with active methylene compounds in the presence of NaH in dimethylsulfoxide at room temperature is reported. The structures have been confirmed by spectral data analyses.

Bare Clusters Derived from Protein Templates: Au25+, Au38+ and Au102+

A discrete sequence of bare gold clusters of well‐defined nuclearity, namely Au₂₅⁺, Au₃₈⁺ and Au₁₀₂⁺, formed in a process that starts from gold‐bound adducts of the protein lysozyme, were detected in the gas phase. It is proposed that subsequent to laser desorption ionization, gold clusters form in the gas phase, with the protein serving as a confining growth environment that provides an effective reservoir for dissipation of the cluster aggregation and stabilization energy. First‐principles calculations reveal that the growing gold clusters can be electronically stabilized in the protein environment, achieving electronic closed‐shell structures as a result of bonding interactions with the protein. Calculations for a cluster with 38 gold atoms reveal that gold interaction with the protein results in breaking of the disulfide bonds of the cystine units, and that the binding of the cysteine residues to the cluster depletes the number of delocalized electrons in the cluster, resulting in opening of a super‐atom electronic gap. This shell‐closure stabilization mechanism confers enhanced stability to the gold clusters. Once formed as stable magic number aggregates in the protein growth medium, the gold clusters become detached from the protein template and are observed as bare Au_n⁺ (n=25, 38, and 102) clusters.     

Metal matrix composites for sustainable lotus-effect surfaces

The lotus effect involving roughness-induced superhydrophobicity is a way to design nonwetting, self-cleaning, omniphobic, icephobic, and antifouling surfaces. However, such surfaces require micropatterning, which is extremely vulnerable to even small wear rates. This limits the applicability of the lotus effects to situations when wear is practically absent. To design sustainable superhydrophobic surfaces, we suggest using metal matrix composites (MMCs) with hydrophobic reinforcement in the bulk of the material, rather than only at its surface. Such surfaces, if properly designed, provide roughness and heterogeneity needed for superhydrophobicity. In addition, they are sustainable, since when the surface layer is deteriorated and removed due to wear, hydrophobic reinforcement and roughness remains. We present a model and experimental data on wetting of MMCs. We also conducted selected experiments with graphite-reinforced MMCs and showed that the contact angle can be determined from the model. In order to decouple the effects of reinforcement and roughness, the experiments were conducted for initially smooth and etched matrix and composite materials.     

Functionalization of mesoporous carbon with superbasic MgO nanoparticles for the efficient synthesis of sulfinamides

Highly basic MgO nanoparticles with different sizes have been successfully immobilized over mesoporous carbon with different pore diameters by a simple wet-impregnation method. The prepared catalysts have been characterized by various sophisticated techniques, such as XRD, nitrogen adsorption, electron energy loss spectroscopy, high-resolution TEM, X-ray photoelectron spectroscopy, and the temperature-programmed desorption of CO(2). XRD results reveal that the mesostructure of the support is retained even after the huge loading of MgO nanoparticles inside the mesochannels of the support. It is also demonstrated that the particle size and dispersion of the MgO nanoparticles on the support can be finely controlled by the simple adjustment of the textural parameters of the supports. Among the support materials studied, mesoporous carbon with the largest pore diameter and large pore volume offered highly crystalline small-size cubic-phase MgO nanoparticles with a high dispersion. The basicity of the MgO-supported mesoporous carbons can also be controlled by simply changing the loading of the MgO and the pore diameter of the support. These materials have been employed as heterogeneous catalysts for the first time in the selective synthesis of sulfinamides. Among the catalysts investigated, the support with the large pore diameter and high loading of MgO showed the highest activity with an excellent yield of sulfinamides. The catalyst also showed much higher activity than the pristine MgO nanoparticles. The effects of the reaction parameters, including the solvents and reaction temperature, and textural parameters of the supports in the activity of the catalyst have also been demonstrated. Most importantly, the catalyst was found to be highly stable, showing excellent activity even after the third cycle of reaction.     

Free Vibration Analysis of RC Box-Girder Bridges Using FEM

The free vibration analysis of simply supported box-girder bridges is carried out using the finite element method. The fundamental frequency is determined in straight, skew, curved and skew-curved box-girder bridges. It is important to analyse the combined effect of skewness and curvature because skew-curved box-girder bridge behaviour cannot be predicted by simply adding the individual effects of skewness and curvature. At first, an existing model is considered to validate the present approach. A convergence study is carried out to decide the mesh size in the finite element method. An exhaustive parametric study is conducted to determine the fundamental frequency of box-girder bridges with varying skew angle, curve angle, span, span-depth ratio and cell number. The skew angle is varied from 0° to 60°, curve angle is varied from 0° to 60°, span is changed from 25 to 50 m, span-depth ratio is varied from 10 to 16, and single cell & double cell are used in the present study. A total of 420 bridge models are used for parametric study in the investigation. Mode shapes of the skew-curved bridge are also presented. The fundamental frequency of the skew-curved box-girder bridge is found to be more than the straight bridge, so, the skew-curved box-girder bridge is preferable. The present study may be useful in the design of box-girder bridges.     

Sol–gel route of synthesis of nanoparticles of MgFe2O4 and XRD,FTIR and VSM study

Nanoparticles of MgFe₂O₄ are synthesized using sol–gel autocombustion method. Structural studies are carried out using X-ray diffraction (XRD). The XRD pattern of MgFe₂O₄ provides information about single-phase formation of spinel structure with cubic symmetry. The grain size and lattice constant are obtained using XRD data. The cation distribution is also proposed theoretically. The change in site preference of cations in nano-MgFe₂O₄ is compared with its bulk counterpart. The structural morphology of the nanoparticles is studied using Scanning Electron Microscopy (SEM). Formation of spinel structure is conformed using Fourier transform infrared spectroscopy (FTIR), which also lends support for the cation distribution proposed using XRD data. The effect of nanoregime on parameters such as bond length, vibration frequency and force constant are discussed with the help of FTIR data. The M–H loop of MgFe₂O₄ has been traced using the Vibrating Sample Magnetometer (VSM) and magnetic parameters such as saturation magnetization (M_S), coercivity (H_C) and retentivity (M_R) are obtained from VSM data.