关键词： 2-(2-cresyl)-4H-1-3-2-benzodioxaphosphorin-2-oxide   Dealkylation   additional mass   Cholinesterases   mass measurement   adduct   salicyl alcohol  

摘要： Aerotoxic syndrome is assumed to be caused by exposure to tricresyl phosphate (TCP), an antiwear additive in jet engine lubricants and hydraulic fluid. CBDP (2-(ortho-cresyl)4H-1,2,3-benzodioxaphosphoran-2-one) is the toxic metabolite of triortho-cresylphosphate, a component of TCP. Human butyrylcholinesterase (BChE;EC 3.***.1.8) and human acetylcholinesterase (AChE;EC 3.***.1.7) are irreversibly inhibited by CBDP. The bimolecular rate constants of inhibition (k(i)), determined under pseudo-first-order conditions, displayed a biphasic time course of inhibition with k(i) of 1.6 x 10(8) M-1 min(-1) and 2.7 x 10(7) M-1 min(-1) for E and E' forms of BChE. The inhibition constants for AChE were 1 to 2 orders of magnitude slower than those for BChE. CBDP-phosphorylated cholinesterases are nonreactivatable due to ultra fast aging. Mass spectrometry analysis showed an initial BChE adduct with an added mass of 170 Da from cresylphosphate, followed by dealkylation to a structure with an added mass of 80 Da. Mass spectrometry in O-18-water showed that O-18 was incorporated only during the final aging step to form phospho-serine as the final aged BChE adduct. The crystal structure of CBDP-inhibited BChE confirmed that the phosphate adduct is the ultimate aging product. CBDP is the first organophosphorus agent that leads to a fully dealkylated phospho-serine BChE adduct.

关键词： EPOXY compounds   COPPER   DYNAMICS of a particle   MOLECULAR models   STRAINS & stresses (Mechanics)   MECHANICS (Physics)  

摘要： The current paper successively applies molecular modeling and mesoscale modeling to scale mechanical models from an atomistic angstrom level to a sub-micron level and determine modulus, stress/strain behavior and defect formation in an epoxy and epoxy-copper interface. The results will show that molecular modeling may be applied directly to parameterize the bead properties used in the mesoscale model, which scale to the physical properties so could provide a means to understand interface behavior linked directly back to molecular origins. (C) 2011 Elsevier Ltd. All rights reserved.

关键词： Complexity   Entropy   Heart rate variability   Weaning outcome  

摘要： Purpose: The aim of the study was to investigate heart rate (HR) and respiratory rate (RR) complexity in patients with weaning failure or success, using both linear and nonlinear techniques. Materials and Methods: Forty-two surgical patients were enrolled in the study. There were 24 who passed and 18 who failed a weaning trial. Signals were analyzed for 10 minutes during 2 phases: (1) pressure support (PS) ventilation (15-20 cm H2O) and (2) weaning trials with PS (5 cm H2O). Low-and high-frequency (LF, HF) components of HR signals, HR multiscale entropy (MSE), RR sample entropy, cross-sample entropy between cardiorespiratory signals, Poincare plots, and alpha 1 exponent were computed in all patients and during the 2 phases of PS. Results: Weaning failure patients exhibited significantly decreased RR sample entropy, LF, HF, and alpha 1 exponent, compared with weaning success subjects (P < .001). Their changes were opposite between the 2 phases, except for MSE that increased between and within groups (P < .001). A new model including rapid shallow breathing index (RSBI), alpha 1 exponent, RR, and cross-sample entropies predicted better weaning outcome compared with RSBI, airway occlusion pressure at 0.1 second (P-0.1), and RSBI x P-0.1 (conventional model, R-2 = 0.887 vs 0.463;P < .001). Areas under the curve were 0.92 vs 0.86, respectively (P < .005). Conclusions: We suggest that nonlinear analysis of cardiorespiratory dynamics has increased prognostic impact upon weaning outcome in surgical patients. (C) 2011 Elsevier Inc. All rights reserved.

关键词： FLUID mechanics   SHEAR (Mechanics)   RELAXATION phenomena   ELASTICITY   NONLINEAR theories   LANGEVIN equations   RHEOLOGY   COUPLING constants (Nuclear physics)  

摘要： We apply the quiescent and mechanically driven versions of nonlinear Langevin equation theory to study how particle softness influences the shear modulus, the connection between shear elasticity and activated relaxation, and nonlinear rheology of the repulsive Hertzian contact model of dense soft sphere fluids. Below the soft jamming threshold, the shear modulus follows a power law dependence on volume fraction over a narrow interval with an apparent exponent that grows with particle stiffness. To a first approximation, the elastic modulus and transient localization length are controlled by a single coupling constant determined by local fluid structure. In contrast to the behavior of hard spheres, an approximately linear relation between the shear modulus and activation barrier is predicted. This connection has recently been observed for microgel suspensions and provides a microscopic realization of the elastic shoving model. Yielding, shear and stress thinning of the alpha relaxation time and viscosity, and flow curves are also studied. Yield strains are relatively weakly dependent on volume fraction and particle stiffness. Shear thinning commences at values of the effective Peclet number far less than unity, a signature of stress-assisted activated relaxation when barriers are high. Apparent power law reduction of the viscosity with shear rate is predicted with a thinning exponent less than unity. In the vicinity of the soft jamming threshold, a power law flow curve occurs over an intermediate reduced shear rate range with an apparent exponent that decreases as fluid volume fraction and/or repulsion strength increase. [ABSTRACT FROM AUTHOR]

标准号: BS EN ISO 22868-2011

摘要： CAUTION — Some of the test procedures specified in this International Standard involve processesthat could lead to a hazardous situation. Any person performing tests in accordance with thisInternational Standard shall be appropriately trained in the type of work to be carried *** International Standard specifies a noise test code for determining, efficiently and under standardizedconditions, the noise emission characteristics of portable, hand-held, combustion-engine-powered forest andgarden machines, including chain-saws, brush-cutters, grass-trimmers, pole-mounted powered pruners,hedge-trimmers and garden blowers/vacuums. Noise emission characteristics include the A-weightedemission sound pressure level at the operator position and the A-weighted sound power level.

关键词： elasticity   gels   soft matter   suspensions   vitrification  

摘要： The microscopic nonlinear Langevin equation theory of activated glassy dynamics is applied to dense fluids of spherical particles that interact via a finite range Hertzian contact soft repulsion. The activation barrier and mean alpha relaxation time are predicted to be rich functions of volume fraction and particle stiffness, exhibiting a non-monotonic variation with concentration at high volume fractions. The latter is due to a structural "soft jamming" crossover where the real space local cage order weakens when soft particles significantly overlap. The highly variable dependences of the relaxation time on temperature and volume fraction are reasonably well collapsed onto two distinct master curves that are qualitatively consistent with a recent scaling ansatz and computer simulation study. A kinetic vitrification diagram is constructed and compared to its dynamic crossover analog. Intersection of the dynamic crossover and soft jamming threshold boundaries occurs for particles that are sufficiently soft, implying the nonexistence of a clear activated dynamics regime or kinetic arrest transition for such particles. The isothermal dynamic fragility is predicted to vary over a wide range as a function of particle stiffness, and soft particles behave as strong glasses. Qualitative comparisons with simulations and microgel experiments reveal good agreement. (C) 2011 American Institute of Physics. [doi:10.1063/1.3592563]

关键词： muscle   work loop   motor control   neuromechanics   posture   running  

摘要： Muscles are multi-functional structures that interface neural and mechanical systems. Muscle work depends on a large multi-dimensional space of stimulus (neural) and strain (mechanical) parameters. In our companion paper, we rewrote activation to individual muscles in intact, behaving cockroaches (Blaberus discoidalis L.), revealing a specific muscle's potential to control body dynamics in different behaviours. Here, we use those results to provide the biologically relevant parameters for in situ work measurements. We test four hypotheses about how muscle function changes to provide mechanisms for the observed control responses. Under isometric conditions, a graded increase in muscle stress underlies its linear actuation during standing behaviours. Despite typically absorbing energy, this muscle can recruit two separate periods of positive work when controlling running. This functional change arises from mechanical feedback filtering a linear increase in neural activation into nonlinear work output. Changing activation phase again led to positive work recruitment, but at different times, consistent with the muscle's ability to also produce a turn. Changes in muscle work required considering the natural sequence of strides and separating swing and stance contributions of work. Both in vivo control potentials and in situ work loops were necessary to discover the neuromechanical coupling enabling control.

关键词： ab initio calculations   configuration interactions   hydrogen compounds   potential energy surfaces   reaction rate constants   triplet state   vibrational states  

摘要： A new global potential energy surface for the lowest triplet electronic state (a(3)A '') of HNO has been developed by a three-dimensional cubic spline interpolation of more than 13 000 ab initio points, which were calculated at the multireference configuration interaction level with Davidson correction using the augmented correlation-consistent polarized valence quintuple zeta basis set. Two minima and five saddle points were found on the potential energy surface. Low-lying vibrational states were obtained in this new potential using the Lanczos method and assigned. In addition, thermal rate constants for the N + OH -> H + NO reactions were obtained using an exact wave packet method. Reasonably good agreement with experimental data was obtained. (C) 2011 American Institute of Physics. [doi:10.1063/1.3592375]

关键词： activation energy   crosslinking   curing of polymers   dielectric properties   elastomers  

摘要： Peroxide crosslinkable ethylene-propylenediene monomer (EPDM) compounds are formulated systems in which the base polymer generally comprises only a small fraction of the total composition. Knowledge of the intercomponent dependency is therefore crucial for successful product development. In this study, we have investigated the effect of formulation components on key material properties of cured, filled, and oil extended EPDM. In studying the impact of individual components, the clay filler was found to have a significant and negative effect on cure performance and to a lesser extent on the dielectric strength as well. On the other hand, the oil plasticizer was found to have a positive effect on recovery of the cure efficiency in filled compounds. It was also found that the interaction of the filler, the plasticizer oil, and the peroxide impacted both the mechanical properties as well as the dielectric strength. Given the complexity of the system, a statistical experimental design method was adopted to study the interactions of the components and their impact of final properties. For selected compositions, the cure behavior and the evolution of properties with extent of cure were studied. The cure was also modeled and compared to previously proposed models available in the literature. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 2191-2200, 2011