Anhydrous CeCl3 catalyzed C3-selective propargylation of indoles with tertiary alcohols

Anhydrous CeCl₃ was successfully used as catalyst for the synthesis of several 3-propargyl indoles in good yields through the reaction of indole with propargyl alcohols in nitromethane.     

High-pressure phase equilibria of binary and ternary mixtures of carbon dioxide,triglycerides and free fatty acids: Measurement and modeling with the GC-EOS

Vapor–liquid equilibria were measured for binary systems including carbon dioxide and free fatty acids such as oleic and linoleic acid, triglycerides as triolein or vegetable oils as sunflower oil, and modelled by the Group Contribution Equation of State (GC-EoS). Binary group parameters used in the calculation and prediction of CO₂–triglycerides systems were obtained from the literature but in the case of CO₂-free fatty acids, binary group parameters were adjusted through a parameterization strategy. At the end, a unique set of parameters could be established to model systems of vegetable oils at high pressures in the presence of CO₂. Moreover, a strategy to calculate the two-phase region in a ternary diagram was also studied. The good correspondence between theoretical and experimental results suggests that the strategy and the set of binary group parameters proposed in this work can be reliable predictive tools for using GC-EoS to describe systems involving vegetable oils with a composition based mainly in free fatty acids and triglycerides, such as those which can be encountered, for example, in oil deacidification processes using supercritical CO₂.     

Intermolecular potential parameters and combining rules determined from viscosity data

The law of corresponding states has been demonstrated for a number of pure substances and binary mixtures and provides evidence that the transport properties viscosity and diffusion can be determined from a molecular shape function, often taken to be a Lennard–Jones 12‐6 potential, that requires two scaling parameters: a well depth ε_ij and a collision diameter σ_ij, both of which depend on the interacting species i and j. We obtain estimates for ε_ij and σ_ij of interacting species by finding the values that provide the best fit to viscosity data for binary mixtures and compare these to calculated parameters using several “combining rules” that have been suggested for determining parameter values for binary collisions from parameter values that describe collisions of like molecules. Different combining rules give different values for σ_ij and ε_ij, and for some mixtures the differences between these values and the best‐fit parameter values are rather large. There is a curve in (ε_ij, σ_ij) space such that parameter values on the curve generate a calculated viscosity in good agreement with measurements for a pure gas or a binary mixture. The various combining rules produce couples of parameters ε_ij, σ_ij that lie close to the curve and, therefore, generate predicted mixture viscosities in satisfactory agreement with experiment. Although the combining rules were found to underpredict the viscosity in most of the cases, Kong's rule was found to work better than the others, but none of the combining rules consistently yields parameter values near the best‐fit values, suggesting that improved rules could be developed. © 2010 Wiley Periodicals, Inc. *

1 This article is a U.S. Government work and, as such, is in the public domain of the United States of America.

Int J Chem Kinet 42: 713–723, 2010     

Reaction of a phospholipid monolayer with gas-phase ozone at the air-water interface: measurement of surface excess and surface pressure in real time

The reaction between gas-phase ozone and monolayers of the unsaturated lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, POPC, on aqueous solutions has been studied in real time using neutron reflection and surface pressure measurements. The reaction between ozone and lung surfactant, which contains POPC, leads to decreased pulmonary function, but little is known about the changes that occur to the interfacial material as a result of oxidation. The results reveal that the initial reaction of ozone with POPC leads to a rapid increase in surface pressure followed by a slow decrease to very low values. The neutron reflection measurements, performed on an isotopologue of POPC with a selectively deuterated palmitoyl strand, reveal that the reaction leads to loss of this strand from the air-water interface, suggesting either solubilization of the product lipid or degradation of the palmitoyl strand by a reactive species. Reactions of (1)H-POPC on D(2)O reveal that the headgroup region of the lipids in aqueous solution is not dramatically perturbed by the reaction of POPC monolayers with ozone supporting degradation of the palmitoyl strand rather than solubilization. The results are consistent with the reaction of ozone with the oleoyl strand of POPC at the air-water interface leading to the formation of OH radicals. The highly reactive OH radicals produced can then go on to react with the saturated palmitoyl strands leading to the formation of oxidized lipids with shorter alkyl tails.     

Exact quantum calculations of the kinetic isotope effect: cross sections and rate constants for the F+HD reaction and role of tunneling

In this paper we present integral cross sections (in the 5-220 meV collision energy range) and rate constants (in the 100-300 K range of temperature) for the F+HD reaction leading to HF+D and DF+H. The exact quantum reactive scattering calculations were carried out using the hyperquantization algorithm on an improved potential energy surface which incorporates the effects of open shell and fine structure of the fluorine atom in the entrance channel. The results reproduce satisfactorily molecular beam scattering experiments as well as chemical kinetics data for both the HF and DF channels. In particular, the agreement of the rate coefficients and the vibrational branching ratios with experimental measurements is improved with respect to previous studies. At thermal and subthermal energies, the rates are greatly influenced by tunneling through the reaction barrier. Therefore exchange of deuterium is shown to be penalized with respect to exchange of hydrogen, and the isotopic branching exhibits a strong dependence on translational energy. Also, it is found that rotational excitation of the reactant HD molecule enhances the production of HF and decreases the reactivity at the D end, obtaining insight on the reaction stereodynamics.     

Methods for reducing cutting temperature in ultrasonic cutting of bone

Ultrasonic cutting is widely used in food processing applications to produce a clean and accurate cut. However, it is yet to be adopted as an instrument of choice in orthopaedic applications, mainly due to the high temperatures that can be generated at the cut site and the consequent requirement to use additional cooling. For example, if cutting temperatures above 55-60 degrees C are reached, particularly for sustained periods, bone necrosis can occur, compromising post-operative recovery. A recent study by the authors has shown that the thermal response in natural materials, such as wood and bone, is affected by the absorption of ultrasonic energy and conduction of heat from the cut site. In this paper the dependency of cutting parameters, such as blade tip vibration velocity, applied load, tuned frequency and coupling contact conditions, on the thermal response are reported and results show that it is possible to maintain cutting temperatures within safety limits by controlling the cutting parameters. A novel cutting blade design is proposed that reduces frictional heat generated at the cut site. Through a series of experimental investigations using fresh bovine femur it is demonstrated that the cutting temperature, and hence thermal damage, can be reduced by selecting appropriate cutting parameters and blade profile.     

On the singularity of the irreducible components of a Springer fiber in {\mathfrak{s}\mathfrak{l}_n}

Let ${\mathcal{B}_u}Let B_u{\mathcal{B}_u} be the Springer fiber over a nilpotent endomorphism u ? End(\mathbbCⁿ){u\in {\rm End}(\mathbb{C}^n)}. Let J (u) be the Jordan form of u regarded as a partition of n. The irreducible components of B_u{\mathcal{B}_u} are all of the same dimension. They are labelled by Young tableaux of shape J (u). We study the question of the singularity of the components of B_u{\mathcal{B}_u} and show that all the components of B_u{\mathcal{B}_u} are nonsingular if and only if J(u) ? {(l,1,1,?), (l₁,l₂), (l₁,l₂,1), (2,2,2)}{J(u)\in\{(\lambda,1,1,\ldots), (\lambda_1,\lambda_2), (\lambda_1,\lambda_2,1), (2,2,2)\}}.     

Baseline separation of α and β‐acids homologues and isomers in hop (Humulus lupulus L.) by CD‐MEKC‐UV

An alternative method for simultaneous baseline separation of α and β‐acids homologues and isomers in hop by CD‐MEKC with UV detection was proposed. The optimized background electrolyte was composed of 30 mmol/L sodium tetraborate solution, 45 mmol/L sodium dodecyl sulfate, 20 mmol/L β‐cyclodextrin and 10% v/v acetonitrile. The instrumental conditions were evaluated by using a 3³ Box‐Benhken experimental design. In order to demonstrate the applicability of the method, 21 hop samples from different varieties were analyzed. The repeatability intra‐ and interday tests were performed and relative standard deviations lower than 7% for area and migration times were observed. The present method comprehended 8 min analysis time and revealed to be faster and more efficient when compared to previous reports from literature.     

Count-rate,linearity, and performance of new backgammon detector technology

The meander wire backgammon technology has high levels of flux and spatial linearity across a wide range of energies. One of the attractive features of these technologies is the stability of response and robustness under long X-ray exposure, compactness, and portability. A key problem historically has been the limited range of count-rate for processing to the optimum resolution. We report dramatic advances in this and other areas appropriate for high-accuracy experiments including tests of quantum electrodynamics, fundamental relativistic atomic physics, X-ray calibration, and crystallography. We illustrate this technology applied to the Kα_1,2 spectra of titanium, chromium, and copper. The quality of the spectra permits deeper insight into atomic and solid state science and permits accurate measurement of energy and relativistic atomic physics processes, below 1-μm accuracy or down to 1 ppm in energy.