Large scale synthesis of acetylene dicarboxaldehyde mono and diacetal

An easy, high yield, large scale, and atom economical, synthesis of the valuable acetylene dicarboxaldehyde dimethyl and tetramethyl acetals was described starting from 2,5-dimethoxy-2,5-furan.     

Toward automated chromatographic fingerprinting: A non-alignment approach to gas chromatography mass spectrometry data

In contrast to targeted analysis of volatile compounds, non-targeted approaches take information of known and unknown compounds into account, are inherently more comprehensive and give a more holistic representation of the sample composition. Although several non-targeted approaches have been developed, there's still a demand for automated data processing tools, especially for complex multi-way data such as chromatographic data obtained from multichannel detectors. This work was therefore aimed at developing a data processing procedure for gas chromatography mass spectrometry (GC–MS) data obtained from non-targeted analysis of volatile compounds. The developed approach uses basic matrix manipulation of segmented GC–MS chromatograms and PARAFAC multi-way modelling. The approach takes retention time shifts and peak shape deformations between samples into account and can be done with the freely available N-way toolbox for MATLAB. A demonstration of the new fingerprinting approach is presented using an artificial GC–MS data set and an experimental full-scan GC–MS data set obtained for a set of experimental wines.     

Characterization of highly porous polymeric materials with pore diameters larger than 100 nm by mercury porosimetry and X-ray scattering methods

Highly porous polymeric materials with pore sizes ranging from 100 nm to 1 microm are a very challenging class of materials not only to prepare synthetically (due to the high capillary pressures generated upon solvent removal) but also to characterize structurally. Through the examples of three different types of porous compounds synthesized in our laboratory (i) high-density melamine-based "MF-hd" with monomodal pore diameters around 500-900 nm, (ii) low-density melamine-based "MF-ld" with bimodal pore size distribution and average diameters around 2.3 microm and 350 nm, (iii) highly porous polyurethane "PU" with monomodal pore sizes around 150 nm, we confirm the limitations of mercury porosimetry as a means to investigate the architecture of materials with very high porosity (>80 vol %) and low compressive strength. Instead, a combination of high-resolution scanning electron microscopy and small-angle and ultrasmall-angle X-ray scattering (SAXS and USAXS, respectively) studies of these three types of materials helps in determining both the network and the pore structures. This work elucidates the need and applicability of the SAXS/USAXS techniques in characterizing such porous materials. For instance, the polyurethane specimens can only be quantitatively characterized by scattering techniques, the results of which are corroborated by high-resolution scanning electron microscopy observations.     

Molecular structure and vibrational spectra of 1,3-bis(4-pyridyl)propane by quantum chemical calculations

The experimental and theoretical study on the structures and vibrations of 1,3-bis(4-pyridyl)propane are presented. The FT-IR and Raman spectra of molecule have been measured. The optimized geometric bond lengths have been obtained by DFT show the best agreements with experimental values. The harmonic vibrational frequencies were calculated and scaled values have been compared with experimental FT-IR and FT-Raman spectra. Majority of the computed wavenumbers were found to be in good agreement with experimental observations. A complete assignment of the fundamentals was proposed based on the total energy distribution (TED) calculation.     

Mean velocity profile in confined turbulent convection

In this Letter, highly resolved measurements of the horizontal velocity inside the boundary layer of turbulent Rayleigh-Bénard convection are reported. They were performed in a cylindrical box with an aspect ratio Gamma=1.13 which was filled with air with a Prandtl number Pr=0.7. The horizontal velocity was measured along the central axis close to the cooling plate in a range of Rayleigh numbers between Ra=10;{11} and Ra=10;{12} using a two-dimensional laser Doppler velocimeter. We demonstrate that the profile of the mean velocity strongly differs from that of classical shear flows like the Blasius shape of a laminar flat plate boundary layer or a turbulent logarithmic velocity profile with standard coefficients.     

The first trialkylphosphane telluride complexes of Ag(I): molecular, ionic and supramolecular structural alternatives

The structures of the first phosphane telluride complexes of silver(I), obtained from i-Pr3PTe (1) with AgNMs2 [Ms = SO2CH3] and with AgSbF6, reveal the superior coordinating ability of 1, particularly as a bridging ligand, compared with related i-Pr3PS and i-Pr3PSe ligands.     

Radically perfect prime ideals in polynomial rings

We call an ideal I of a commutative ring R radically perfect if among the ideals of R whose radical is equal to the radical of I the one with the least number of generators has this number of generators equal to the height of I. Let R be a Noetherian integral domain of Krull dimension one containing a field of characteristic zero. Then each prime ideal of the polynomial ring R[X] is radically perfect if and only if R is a Dedekind domain with torsion ideal class group. We also show that over a finite dimensional Bézout domain R, the polynomial ring R[X] has the property that each prime ideal of it is radically perfect if and only if R is of dimension one and each prime ideal of R is the radical of a principal ideal.     

Laser induced and controlled chemical reaction of carbon monoxide and hydrogen

Bimolecular chemical reaction control of gaseous CO and H(2) at room temperature and atmospheric pressure, without any catalyst, using shaped femtosecond laser pulses is presented. High intensity laser radiation applied to a reaction cell facilitates non-resonant bond breakage and the formation of a range of ions, which can then react to form new products. Stable reaction products are measured after irradiation of a reaction cell, using time of flight mass spectroscopy. Bond formation of C-O, C-C, and C-H bonds is demonstrated as CO(2)(+), C(2)H(2)(+), CH(+), and CH(3)(+) were observed in the time of flight mass spectrum of the product gas, analyzed after irradiation. The formation of CO(2) is shown to be dependent on laser intensity, irradiation time, and on the presence of H(2) in the reaction cell. Using negatively chirped laser pulses more C-O bond formation takes place as compared to more C-C bond formation for unchirped pulses.     

Homogeneous Solutions of Fully Nonlinear Elliptic Equations in Four Dimensions

We prove that there is no nontrivial homogeneous order 2 analytic outside zero solutions of fully nonlinear, uniformly elliptic equations in ?. © 2013 Wiley Periodicals, Inc.