Reactive kinetics of carbon dioxide loaded aqueous blend of 2-amino-2-ethyl-1,3-propanediol and piperazine using a pressure drop method

In this study, a new pressure drop method has been used to investigate the kinetics of carbon dioxide reaction with aqueous blend of 2-amino-2-ethyl-1,3-propanediol (AEPD) with piperazine (PZ). The blending of a small amount of PZ with AEPD has a significant effect on the observed rate constant, k_obs. It was observed that k_obs values of the blend increased more than twice than the summation of k_obs values of individual alkanolamines. The reaction kinetics in this study were modeled by assuming a termolecular mechanism. The addition of 0.1 mol/L of PZ to 1 mol/L AEPD exhibited an observed rate constant, k_obs of 8824.1 s⁻¹, which is comparable to other alkanolamine mixtures. Hence, PZ/AEPD mixtures can be potentially used for rapid carbon dioxide capture.     

On the squared Smith method for large‐scale Stein equations

A squared Smith type algorithm for solving large‐scale discrete‐time Stein equations is developed. The algorithm uses restarted Krylov spaces to compute approximations of the squared Smith iterations in low‐rank factored form. Fast convergence results when very few iterations of the alternating direction implicit method are applied to the Stein equation beforehand. The convergence of the algorithm is discussed and its performance is demonstrated by several test examples. Copyright © 2013 John Wiley & Sons, Ltd.     

Helical molecular programming: folding of oligopyridine-dicarboxamides into molecular single helices

Molecular strands composed of alternating 2,6-diaminopyridine and 2,6-pyridinedicarbonyl units have been designed to self-organize into single stranded helical structures upon forming intramolecular hydrogen bonds. Pentameric strands 11, 12, and 14, heptameric strands 1 and 20, and undecameric strand 15 have been synthesized using stepwise convergent strategies. Single helical conformations have been characterized in the solid state by single crystal X-ray diffraction analysis for four of these compounds. Helices from pentameric strands 12 and 14 extend over one turn, and helices from heptameric 20 and undecameric 15 species extend to one and a half and two and a half turns, respectively. Intramolecular hydrogen bonds are responsible for the strong bending of the strands. 1H NMR shifts both in polar and nonpolar organic solvents indicate intramolecular overlap between the peripheral aromatic groups. Thus, helical conformations also predominate in solution. Molecular stochastic dynamic simulations of strand folding starting from a high energy extended linear conformer show a rapid (600 ps at 300 K) conversion into a stable helical conformation.     

Photochemical patterning of a self-assembled monolayer of 7-diazomethylcarbonyl-2,4,9-trithiaadmantane on gold films via Wolff rearrangement

Photolithographic attachment of functional organic molecules via ester or amide linkages to self-assembled monolayers (SAMs) on gold thin films was achieved by employing a novel photoreactive surface anchor, 7-diazomethylcarbonyl-2,4,9-trithiaadmantane. The photoreactive SAM was prepared by the spontaneous physical adsorption of the photoreactive surface anchor onto gold surfaces. The alpha-diazo ketone moiety of the SAM was found to display the classical Wolff rearrangement reactivity to produce a ketene intermediate on the exposed area. Organic molecules such as alcohols and amines can thus be attached to the gold surfaces selectively by the facile in situ formation of ester or amide linkages. The structure and reactivity of the photoreactive surface anchor were characterized by real-time FT-IR, fluorescence, and polarization modulation infrared reflectance absorption spectroscopy (PM-IRRAS). The Wolff rearrangement reactivity of the SAM suggested that a "surface-isolated" carbonylcarbene may be generated when the SAM was exposed to 255-nm irradiation.     

Monolithic metal–organic framework MIL‐53(Al)‐polymethacrylate composite column for the reversed‐phase capillary liquid chromatography separation of small aromatics

A monolithic capillary column containing a composite of metal–organic framework MIL‐53(Al) incorporated into hexyl methacrylate‐co‐ethylene dimethacrylate was prepared to enhance the separation of mixtures of small aromatic compounds by using capillary liquid chromatography. The addition of 10 mg/mL MIL‐53(Al) microparticles increased the micropore content in the monolithic matrix and increased the Brunauer–Emmett–Teller surface area from 26.92 to 85.12 m²/g. The presence of 1,4‐benzenedicarboxylate moieties within the structure of MIL‐53(Al) as an organic linker greatly influenced the separation of aromatic mixtures through π–π interactions. High‐resolution separation was obtained for a series of alkylbenzenes (with resolution factors in the range 0.96–1.75) in less than 8 min, with 14 710 plates/m efficiency for propylbenzene, using a binary polar mobile phase of water/acetonitrile in isocratic mode. A reversed‐phase separation mechanism was indicated by the increased retention factor and resolution as the water percentage in the mobile phase increased. A stability study on the composite column showed excellent mechanical stability under various conditions. The higher resolution and faster separation observed at increased temperature indicated an exothermic separation, whereas the negative values for the free energy change of transfer indicated a spontaneous process.     

Multiphoton path entanglement by nonlocal bunching

Multiphoton path entanglement is created without applying postselection, by manipulating the state of stimulated parametric down-conversion. A specific measurement on one of the two output spatial modes leads to the nonlocal bunching of the photons of the other mode, forming the desired multiphoton path entangled state. We present experimental results for the case of a heralded two-photon path entangled state and show how to extend this scheme to higher photon numbers.     

Phase-restricted heterogeneous correlation

We introduce a new phase-restricted algorithm for producing a heterogeneous correlation filter that permits new in-class members to be added without changing the phase of the filter. This heterogeneous correlation filter uses amplitude modulation both to enhance in-class cross correlations and to suppress selected out-of-class correlations. This new algorithm should substantially improve the performance of existing class-associative correlators and improve their operation.     

Oligomers from biphenyl,biphenyl-d10, or p-terphenyl with aluminium chloride-cupric chloride: Mechanism,ESR, and conductivity

Biphenyl and biphenyl-d₁₀ were coupled by aluminum chloride-cupric chloride. For the two systems, the yields of p-quaterphenyl, p-sexiphenyl, and sublimation residue were compared. The results, which have mechanistic significance, are similar to those reported earlier for benzene versus benzene-d₆; that is, a decrease in DP for the deuterated substrate. p-Sexiphenyl, obtained from biphenyl or p-terphenyl and aluminum chloride-cupric chloride, displayed a concentration of 3 × 10¹⁷ spins/g in ESR. There was little or no change in spin density after sublimation or crystallization. Even after drastic purification by a variety of techniques the radical character persisted. Biphenyl was polymerized by aluminum chloride-cupric chloride at temperatures in the 50–155°C range. Processable polymers with m- and p-phenylene linkages were produced. When doped with AsF₅, the highest conductivity obtained was 7.3 × 10^?2 Ω^?1 cm^?1.