关键词： Cardiopulmonary resuscitation (CPR)   Mechanical resuscitation device   Manikin  

摘要： Purpose: The goal of this randomized, open, controlled crossover manikin study was to compare the performance of "Animax", a manually operated hand-powered mechanical resuscitation device (MRD) to standard single rescuer basic life support (BLS). Methods: Following training, 80 medical students performed either standard BLS or used an MRD for 12 min in random order. We compared the quality of chest compressions (effective compressions, compression depth and rate, absolute hands-off time, hand position, decompression), and of ventilation including the number of gastric inflations. An effective compression was defined as a compression performed with correct depth, hand position and decompression. Results: The use of the MRD resulted in a significantly higher number of effective compressions compared to standard BLS (67 +/- 34 vs. 41 +/- 34%, p < 0.001). In a comparison with standard BLS, the use of the MRD resulted in less absolute hands-off time (264 +/- 57 vs. 79 +/- 40 s, p < 0.001) and in a higher minute-volume (1.86 +/- 0.7 vs. 1.62 +/- 0.71, p = 0.020). However, ventilation volumes were below the 2005 ERC guidelines for both methods. Gastric inflations occurred only in 0 +/- 0.1% with the MRD compared to 3 +/- 7% during standard BLS (p < 0.001). Conclusion: Single rescuer cardio-pulmonary resuscitation with the manually operated MRD was superior to standard BLS regarding chest compressions in this simulation study. The MRD delivered a higher minute-volume but did not achieve the recommended minimal volume. Further clinical studies are needed to test the MRD's safety and efficacy in patients. (C) 2011 Elsevier Ireland Ltd. All rights reserved.

关键词： Calcium carbonate  

摘要： polyester poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB) containing 5 mol% 4HB was composited with different calcium carbonate (CaCO3) fillers. The effect of CaCO3 contents on thermal properties, mechanical property, and crystallization kinetics was evaluated. The thermal stability of P3/4HB was reduced by mixing with CaCO3 particles. With increasing CaCO3 content, the elongation at break, tensile strength, and impact strength decrease;however, elastic modulus increases. When P3/4HB with 20 mol% 4HB was added into the P3/4HB/CaCO3 composite, the impact strength were enhanced significantly;however, the elongation at break and tensile strength were only slight to moderate improvements. However, when compared with nano-and light-CaCO3, heavy CaCO3 had the best mechanical properties. The nonisothermal and isothermal crystallization results demonstrated that the crystallization rate of P3/4HB was reduced and the highest crystallinity was obtained for all kinds of CaCO3 fillers at 40 phr content. POLYM. COMPOS., 32: 1134-1142, 2011. (C) 2011 Society of Plastics Engineers

关键词： atrial function   cardiac resynchronization therapy   strain echocardiography  

摘要： OBJECTIVES The aim of this study was to evaluate atrial and ventricular function in patients undergoing cardiac resynchronization therapy (CRT). BACKGROUND Right atrial pacing (AP) in CRT induces delays in electrical and mechanical activation of the left atrium. The influence of atrial sensing (AS) versus AP on ventricular performance in CRT and the mechanisms underlying the differences between AS and AP in CRT have not been fully elucidated. METHODS Fifty-five patients with heart failure undergoing CRT for 9 +/- 12.5 months and 22 control subjects without heart failure were enrolled. Conventional and tissue Doppler echocardiography was performed to examine atrial and ventricular mechanics and hemodynamic status. RESULTS The optimal atrioventricular interval was shorter in AS compared with AP mode (126 +/- 19 ms vs. 155 +/- 20 ms, p < 0.0001). Left ventricular (LV) outflow tract time-velocity integral (22 +/- 7 cm vs. 20 +/- 7 cm, p < 0.001), diastolic filling period (468 +/- 124 ms vs. 380 +/- 93 ms, p < 0.001), and global strain (-32 +/- 24% vs. -27 +/- 22%, p = 0.001) were greater in AS compared with AP mode. Atrial strain was higher in AS compared with AP mode in the right atrium (-28.2 +/- 8.6% vs. -22.6 +/- 7.6%, p = 0.0007), interatrial septum (-17.1 +/- 6.5% vs. -13.2 +/- 5.4%, p = 0.002), and left atrium (-16.4 +/- 11.0% vs. -13.6 +/- 8.5%, p = 0.02). There was no difference in intraventricular dyssynchrony but significantly lower atrial dyssynchrony in AS compared with AP mode (31 +/- 19 ms vs. 42 +/- 24 ms, p = 0.0002). CONCLUSIONS AS is associated with preserved atrial contractility and atrial synchrony, resulting in optimal LV diastolic filling, stroke volume, and LV systolic mechanics. This pacing mode maximizes LV performance and the hemodynamic benefit of CRT in patients with heart failure. (J Am Coll Cardiol Img 2011;4:691-8) (C) 2011 by the American College of Cardiology Foundation

关键词： LIGNINS   MECHANICAL pulping process   INDUSTRIAL wastes   FLY ash   ADSORPTION   DIFFUSION   SORBENTS   POLLUTANTS  

摘要： The possible application of adsorption for the removal of lignin-related material found in wastewater generated by mechanical pulping was investigated. Activated charcoal and fly ash were used as adsorbents in batch experiments. The lignin-related material exhibited properties well-suited for adsorption onto both adsorbents, although the sorption capacity of activated charcoal exceeds that of fly ash. The experimental data were fitted to pseudo-first- and pseudo-second-order rate kinetic expressions, and an attempt was made to find the rate-limiting step involved in the adsorption processes. The results showed that lignin adsorption onto both activated charcoal and fly ash follows pseudo-second-order rate kinetics and that both boundary-layer diffusion and intraparticle diffusion are likely involved in the rate-limiting mechanisms. Adsorption is an interesting option in advanced wastewater treatment, and fly ash appears to be a suitable low-cost adsorbent for recalcitrant organic pollutants. [ABSTRACT FROM AUTHOR]

关键词： Nucleotides   Transmembrane domains   empty   Active Site   Nucleosome Binding Domain   kinetic simulation   ATP-Binding Cassette Transporters   ATP Hydrolysis   Molecular Dynamics Simulation  

摘要： ATP-binding cassette transporters use the energy of ATP hydrolysis to transport substrates across cellular membranes. They have two transmembrane domains and two cytosolic nucleotide-binding domains. Biochemical studies have characterized an occluded state of the transporter in which nucleotide is tenaciously bound in one active site, whereas the opposite active site is empty or binds nucleotide loosely. Here, we report molecular-dynamics simulations of the bacterial multidrug ATP-binding cassette transporter Sav1866. In two simulations of the ATP/apo state, the empty site opened substantially by way of rotation of the nucleotide-binding domain (NBD) core subdomain, whereas the ATP-bound site remained occluded and intact. We correlate our findings with elastic network and molecular-dynamics simulation analyses of the 5av1866 NBD monomer, and with existing experimental data, to argue that the observed transition is physiological, and that the final structure observed in the ATP/apo simulations corresponds to the tight/loose state of the NBD dimer characterized experimentally.

关键词： antimony alloys   brittleness   cobalt alloys   deformation   molecular dynamics method   nanostructured materials   Poisson ratio   skutterudites   specific heat   stress-strain relations   thermal conductivity   thermal expansion   thermoelectricity   Young's modulus  

摘要： Molecular dynamics simulations have been performed to study the fundamental thermodynamic and mechanical properties of single-crystalline skutterudite CoSb3 in the nanometric scale. The several interesting thermodynamic predictions, including linear thermal expansion coefficient, specific heat capacity, thermal conductivity, and temperature dependence of elastic constants, show excellent agreement with data available in the literature. The classic mechanical tests of uniaxial tension and compression are performed respectively at constant temperatures. The CoSb3 single-crystal exhibits nonlinear elastic response during the deformation process and the sustainable stress is very high, demonstrating its outstanding stability. An interesting phenomenon occurs at compression that the stress-strain curve undergoes a transition. The cause of the transition is an atomic reconstruction, which is observed and interpreted on the basis of interatomic interactions. Both of the failure patterns under tension and compression reveal brittleness of the material. The increasing of temperature would result in a linear degradation of the effective Young's modulus and ultimate strength, but its effect on Poisson's ratio is negligible. The results provide the groundwork for future studies of service behavior of the skutterudites-based thermoelectric devices. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3598116]

关键词： Kinetics   Manganese(IV)   1,8-Bis(2-hydroxybenzamido)-3,6-diazaoctane   Glyoxylic acid  

摘要： The oxidation of glyoxylic acid (HGI) by (MnL)-L-IV {L4- = tetra deprotonated 1,8-bis(2-hydroxybenzamido)-3,6-diazaoctane) was investigated in the pH range 1.67-10.18, at 25-45 degrees C and 0.5 M ionic strength. The reaction exhibited biphasic kinetics with (MnL-)-L-III as the reactive intermediate. Mn-IV was reduced to Mn-II. The products of oxidation of HGI were identified as formic acid and CO2 in acidic medium, and oxalate in basic medium, consistent with the stoichiometry: -Delta[Mn-IV]/-Delta[HGI] = 1. In acidic medium, both (MnL)-L-IV and (MnL-)-L-III formed outer-sphere adducts with the neutral HGI {HC(OH)(2)COOH} molecule, with an association constant Q(IV) of 28 and 70 M-1, respectively. A similar adduct formation was not observed for the glyoxylate mono anion (Gl(-), CH(OH)(2)(CO2-)) and glyoxylate dianion {Gl(2-), CH(OH)(O-)CO2-}. The rate and activation parameters for the various paths are reported and an outersphere electron transfer mechanism is suggested. (C) 2011 Elsevier Ltd. All rights reserved.

关键词： Thermoset   Molecular dynamics   Glass transition   Conversion degree  

摘要： We use molecular dynamics (MD) to perform an extensive characterization of the thermo-mechanical response of a thermoset polymer composed of epoxy EPON862 and curing agent DETDA. Our simulations, with no adjustable parameters, show that atomistic simulation can capture non-trivial behavior of amorphous thermosets including the role of polymerization degree, thermal history, strain rate and temperature on the glass transition temperature (T-g) and mechanical response (including ultimate properties) and lead to predictions in quantitative agreement with experiments. We find a significant increase in T-g, Young's modulus and yield stress with degree of polymerization while yield strain is significantly less sensitive to it. For structures cured beyond the gel point (percolation of a 3D network) conversion degree and temperature affect yield stress in a similar way with yield stress linearly dependent on T T-g: however, we find non-linear and non-universal relationship below the gel point. Our results show that a relative small variation in polymerization degree (similar to 5%) can explain the spread in experimental measurements of T-g and elastic constants available in the literature. (c) 2011 Elsevier Ltd. All rights reserved.

关键词： 机械密封   瞬态特性   启停   密封性能   泄漏  

摘要： 启停过程顺利与否直接关系到机械密封的可靠和长寿命运行。考虑密封端面流固力耦合作用、微观空化及端面接触的影响,通过建立机械密封瞬态启停动力学模型,计算瞬态启停过程中密封浮动环的轴向位移、密封端面液膜厚度变化、端面接触力及泄漏率等密封参量,研究了机械密封启停过程中的瞬态密封行为,分析了动环轴向跳动等对机械密封性能的影响。结果表明:受轴向跳动和启停过程速度变化的影响,密封参量呈现瞬态扰动现象,且轴向跳动越大,扰动越大。该模型和计算方法对完善机械密封设计方法、评价机械密封设计合理性具有一定的参考价值。