Identification of 1‐palmitoyl‐2‐linoleoyl‐phosphatidylethanolamine modifications under oxidative stress conditions by LC‐MS/MS

Phosphatidylethanolamines are a major class of phospholipids found in cellular membranes. Identification of the alterations in these phospholipids, induced by free radicals, could provide new tools for in vivo diagnosis of oxidative stress. In this study, 1‐palmitoyl‐2‐linoleoyl‐phosphatidylethanolamine oxidation products, induced by the hydroxyl radical, were studied using LC‐MS and LC‐MS/MS. Data obtained allowed the identification and separation of isomeric oxidative products with modifications in the sn‐2 acyl chain, attributed to long‐ and short‐chain products. Among long‐chain products keto, keto‐hydroxy, hydroxy, poly‐hydroxy, peroxy and hydroxy–peroxy derivatives were identified. Product ions formed by loss of two H₂O molecules vs loss of HOOH, allowed the identification of, respectively, di‐ (or poli‐) hydroxy vs peroxy derivatives. Location of functional groups was determined by the product ions formed by cleavage of C–C bonds, in the vicinity of the oxidation positions, allowing the identification of C9, C12 and C13 as the predominant substituted positions. Short‐chain products identified comprised aldehydes, hydroxy‐aldehydes and carboxylic derivatives, with modified sn‐2 acyl lengths of C7–C9 and C11, C12. Among the short‐chain products identified, C9 products showed higher relative abundance. Copyright © 2009 John Wiley & Sons, Ltd.     

Flow-Invariant Hypersurfaces in Semi-Dispersing Billiards

This work results from our attempts to solve Boltzmann–Sinai’s hypothesis about the ergodicity of hard ball gases. A crucial element in the studies of the dynamics of hard balls is the analysis of special hypersurfaces in the phase space consisting of degenerate trajectories (which lack complete hyperbolicity). We prove that if a flow-invariant hypersurface J in the phase space of a semi-dispersing billiard has a negative Lyapunov function, then the volume of the forward image of J grows at least linearly in time. Our proof is independent of the solution of the Boltzmann–Sinai hypothesis, and we provide a complete and self-contained argument here. Submitted: March 14, 2006. Accepted: August 2, 2006.     

Stability islands in domains of separatrix crossings in slow-fast Hamiltonian systems

We consider a two-degrees-of-freedom Hamiltonian system with one degree of freedom corresponding to fast motion and the other corresponding to slow motion. The ratio of typical velocities of changes of the slow and fast variables is the small parameter ɛ of the problem. At frozen values of the slow variables, there is a separatrix on the phase plane of the fast variables, and there is a region in the phase space (the domain of separatrix crossings) where the projections of phase points onto the plane of the fast variables repeatedly cross the separatrix in the process of evolution of the slow variables. Under a certain symmetry condition, we prove the existence of many (of order 1/ɛ) stable periodic trajectories in the domain of separatrix crossings. Each of these trajectories is surrounded by a stability island whose measure is estimated from below by a value of order ɛ. So, the total measure of the stability islands is estimated from below by a value independent of ɛ. The proof is based on an analysis of asymptotic formulas for the corresponding Poincaré map.     

Monitoring of Portland cement chemical reaction and quantification of the hydrated products by XRD and TG in function of the stoppage hydration technique

Journal of Thermal Analysis and Calorimetry - Cement hydration occurs according to a sequence of reactions whose products have a direct influence on the working properties of concretes and mortars...     

BIMP-Catalyzed 1,3-Prototropic Shift for the Highly Enantioselective Synthesis of Conjugated Cyclohexenones

A bifunctional iminophosphorane (BIMP)-catalysed enantioselective synthesis of α,β-unsaturated cyclohexenones through a facially selective 1,3-prototropic shift of β,γ-unsaturated prochiral isomers, under mild reaction conditions and in short reaction times, on a range of structurally diverse substrates, is reported. α,β-Unsaturated cyclohexenone products primed for downstream derivatisation were obtained in high yields (up to 99 %) and consistently high enantioselectivity (up to 99 % ee). Computational studies into the reaction mechanism and origins of enantioselectivity, including multivariate linear regression of TS energy, were carried out and the obtained data were found to be in good agreement with experimental findings.     

Plated and Intact Femur Strains in Fracture Fixation Using Fiber Bragg Gratings and Strain Gauges

This paper presents an experimental methodology to determine plated and intact femur strains using fiber Bragg gratings and strain gauges. A plated and an intact synthetic femur were used and loaded under a simplistic static load of 600 N. A stainless steel (316L) plate was used to fixate a simulated 45° fracture on one femur. Strains were recoded at the same sites on both femurs. Strain shielding is shown to be more pronounced at the distal region of the plated femur. The experimental methodology based on fiber Bragg grating sensors is a novel approach to assess bone plate strains, which could also be used to obtain biologic tissue and implant surface strains in locations where conventional strain gauge use is not technically feasible.     

Molecularly imprinted polymers for selective solid-phase extraction of phospholipids from human milk samples

Microchimica Acta - The authors describe a method for the extraction and determination of phospholipids (PLs) from human milk fat by using a molecularly imprinted polymer (MIP) as the sorbent...     

Submatrices of non-tree-realizable distance matrices

We deal with distance matrices of real (this means, not necessarily integer) numbers. It is known that a distance matrix D of order n is tree-realizable if and only if all its principal submatrices of order 4 are tree-realizable. We discuss bounds for the number, denoted Q_i(D), of non-tree-realizable principal submatrices of order i ? 4 of a non-tree-realizable distance matrix D of order n?i, and we construct some distance matrices which meet extremal conditions on Q_i(D). Our starting point is a proof that a non-tree-realizable distance matrix of order 5 has at least two non-tree-realizable principal submatrices of order 4. Optimal realizations (by graphs with circuits) of distance matrices which are not tree-realizable are not yet as well known as optimal realizations which are trees. Using as starting point the optimal realization of the (arbitrary) distance matrix of order 4, we investigate optimal realizations of non-tree-realizable distance matrices with the minimum number of non-tree-realizable principal submatrices of order 4.     

Indium-incorporation-induced transformation of optical, photoluminescence and lasing properties of InGaN epilayers

A comparative combined study of photoluminescence (PL), PL kinetics, stimulated emission (SE) and photoreflectance (PR) properties in In_xGa_1−xN epilayers is carried out in the composition range 0≤x≤0.19. In-incorporation up to 4% leads to the sufficient longer radiative recombination decay time due to the decrease in non-radiative recombination channels, which are peculiar to GaN, and band-to-band optical transitions predominate the spontaneous PL spectrum. Further In-incorporation (x>4%) leads to the localization of carriers and/or excitons at band-tails in the In-rich areas. Correlation between the position of dominant low-energy PR oscillation due to the main band gap and SE peak position shows that band-to-band transitions are responsible for lasing and dominate the PL spectrum in all highly pumped In_xGa_1−xN samples.