关键词： Cross-bridge   Kinetics   ATP effect   Sinusoidal analysis   Stopped flow  

摘要： Our goal is to correlate kinetic constants obtained from fluorescence studies of myofibril suspension with those from mechanical studies of skinned muscle fibers from rabbit psoas. In myofibril studies, the stopped-flow technique with tryptophan fluorescence was used;in muscle fiber studies, tension transients with small amplitude sinusoidal length perturbations were used. All experiments were performed using the equivalent solution conditions (200 mM ionic strength, pH 7.00) at 10A degrees C. The concentration of MgATP was varied to characterize kinetic constants of the ATP binding step 1 (K (1): dissociation constant), the binding induced cross-bridge detachment step 2 (k (2), k (-2): rate constants), and the ATP cleavage step 3 (k (3), k (-3)). In myofibrils we found that K (1) = 0.52 +/- A 0.08 mM (+/- 95% confidence limits), k (2) = 242 +/- A 24 s(-1), and k (-2) a parts per thousand 0;in muscle fibers, K (1) = 0.46 +/- A 0.06 mM, k (2) = 286 +/- A 32 s(-1), and k (-2) = 57 +/- A 21 s(-1). From these results, we conclude that myofibrils and muscle fibers exhibit nearly equal ATP binding step, and nearly equal ATP binding induced cross-bridge detachment step. Consequently, there is a good correlation between process C (phase 2 of step analysis) and the cross-bridge detachment step. The reverse detachment step is finite in fibers, but almost absent in myofibrils. We further studied partially cross-linked myofibrils and found little change in steps 2 and 3, indicating that cross-linking does not affect these steps. However, we found that K (1) is 2.5x of native myofibrils, indicating that MgATP binding is weakened by the presence of the extra load. We further studied the phosphate (Pi) effect in myofibrils, and found that Pi is a competitive inhibitor of MgATP, with the inhibitory dissociation constant of similar to 9 mM. Similar results were also deduced from fiber studies. To characterize the ATP cleavage step in myofibrils, we measured the slow rate constant in

关键词： configuration interactions   ground states   Hessian matrices   molecular configurations   molecular dynamics method   photodissociation   potential energy surfaces   SCF calculations  

摘要： The stationary and intersection structures on the S-0 and S-1 potential energy surfaces of CH3COCH2Cl have been determined by the CAS(10,8)/cc-pVDZ optimizations and their relative energies are refined by the CASPT2//CAS(10,8)/cc-pVDZ single-point calculations. Non-adiabatic molecular dynamics simulations were performed on the basis of the state-averaged CAS(10,8)/cc-pVDZ calculated energies, energy gradients, and Hessian matrix for the S-0 and S-1 states. It is found that the features of the S-1 potential energy surface and non-adiabatic effect control the selectivity of the two alpha-C-C bond fissions, which provides a reasonable explanation why one alpha-C-C bond was observed as a primary channel and the other is ruled out even if CH3COCH2Cl is excited at 193 nm. The beta-C-Cl fission is determined to be a dominant channel once the CH3COCH2Cl molecule is excited to the S-1 state and the beta-C-Cl:alpha-C-C branching ratio is estimated by the RRKM rate theory to be 15:1 at 193 nm, which is overestimated in comparison with the value of similar to 11:1 inferred experimentally. The present calculation reveals that the alpha-C-C fission might take place in the ground electronic state as a result of the S1 -> S-0 internal conversion upon photolysis at 308 nm. However, the measured kinetic energy distributions of the alpha-C-C fission products suggest that the fission does not involve internal conversion to the ground state. To solve this issue, we need to perform non-adiabatic quantum dynamics simulation on accurate S-0, S-1, and S-2 potential energy surfaces, which is still a challenging task currently. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3660356]

关键词： kappa-Carrageenan   glucose syrup   caffeine   mechanical T-g  

摘要： An investigation of the diffusional mobility of a bioactive compound (caffeine) within the high-solid (80.0% w/w) matrices of glucose syrup and ?-carrageenan plus glucose syrup exhibiting distinct mechanical glass transition properties is reported. The experimental temperature range was from 20 to -60 degrees C, and the techniques of modulated differential scanning calorimetry, small deformation dynamic oscillation in shear, and UV spectrometry were employed. Calorimetric and mechanical measurements were complementary in recording the relaxation dynamics of high-solid matrices upon controlled heating. Predictions of the reaction rate theory and the combined WLF/free volume framework were further utilized to pinpoint the glass transition temperature (T-g) of the two matrices in the softening dispersion. Independent of composition, calorimetry yielded similar T-g predictions for both matrices at this level of solids. Mechanical experimentation, however, was able to detect the effect of adding gelling polysaccharide to glucose syrup as an accelerated pattern of vitrification leading to a higher value of T-g. Kinetic rates of caffeine diffusion within the experimental temperature range were taken with UV spectroscopy. These demonstrated the pronounced effect of the gelling kappa-carrageenan/glucose syrup mixture to retard diffusion of the bioactive compound near the mechanical T-g. Modeling of the diffusional mobility of caffeine produced activation energy and fractional free-volume estimates, which were distinct from those of the carbohydrate matrix within the glass transition region. This result emphasizes the importance of molecular interactions between macromolecular matrix and small bioactive compound in glass-related relaxation phenomena.

关键词： 农村富余劳动力   农业机械化   中国   新型农民   农村劳动力   第三产业   第一产业   工业化  

摘要： 农业机械化使中国平均每年产生1000万农村富余劳动力，为中国工业化、城镇化和第二、第三产业的发展提供有力支撑。 农业机械化在解放中国大批农村劳动力的同时，也造就了无数新型农民，这些农民有知识、有技术，利用现代化信息和工具，极大地提高了生产力，从事第一产业的人员每年在大量减少，但人均的生产率10年间却翻了3倍。如今，农忙时节外出打工的农民纷纷回乡务农的情形已经不复存在，

关键词： 工程机械行业   东方红柴油机   动力元件   上海新国际博览中心   宝马   展放   品牌   亚太地区  

摘要： 1 展会情况 “上海宝马工程机械展”是世界最大的工程机械展bauma在中国的延伸，同时也是2010年亚太地区最具影响力的国际性行业博览会。bauma China 2010暨第5届中国国际工程机械、建材机械、工程车辆及设备博览会于2010年11月23—26日在上海新国际博览中心召开。本届展会展示面积超过23万m2，

关键词： 水下机械手   动力学   水环境   流干扰  

摘要： 研究了四功能深海电驱动机械手所受的水动力。以Morison公式为计算基础,利用拉格朗日方法,建立了流干扰下的水下机械手动力学模型。仿真研究了水阻力、浮力、定常流以及非定常流对水下机械手动力学的影响。结果表明,在各水动力影响因素中,浮力影响最大,流干扰次之,而水下机械手运动搅水引起的水动力甚微。

关键词： 呼吸,人工   右美托咪定   镇静   血流动力学  

摘要： 目的:观察不同剂量右美托咪定对机械通气患者镇静效果和血流动力学的影响。方法:入监护室行机械通气的咽成形术后患者45例,随机分为A、B、C组,每组15例,按分组静脉微泵给予右美托咪定。A组:负荷剂量0.5μg/kg,维持剂量0.2μg/(kg·h);B组:负荷剂量0.75μg/kg,维持剂量0.3μg/(kg·h);C组:负荷剂量1.0μg/kg,维持剂量0.4μg/(kg·h)。如患者躁动,静脉单次给予吗啡5mg。机械通气24h后,停止右美托咪定输注,待患者完全清醒,肌力恢复,满足拔管条件后拔除气管导管。观察并记录给药前即刻(T0)、给药结束后即刻(T1)、给药后30min(T2)、给药后1h(T3)、给药后6h(T4)、给药后12h(T5)、给药后24h(T6)的无创动脉血压和心率,观察并记录上述各时点的镇静评分(Ramsay分级法),记录各组吗啡的总用量,观察并记录各组停止右美托咪定输注后至拔管所需时间。结果:血流动力学:A、B、C组部分时点动脉血压、心率较T0有所改变,差异有统计学意义;C组与A、B组间部分时点动脉血压、呼吸频率差异有统计学意义(P<0.05)。镇静评分:A、B、C各组各时点镇静评分与T0时比较差异无统计学意义;A、B、C各组相同时点镇静评分差异无统计学意义(P>0.05)。吗啡总用量:A、B、C各组吗啡总用量差异无统计学意义(P>0.05)。拔管所需时间:B组与A组之间,C组与B、A组之间拔管所需时间差异有统计学意义(P<0.05)。结论:随着右美托咪定给药剂量的增加,血流动力学变化加剧,拔除气管导管时间延长,但没有加深镇静程度。

关键词： 金砖四国   建筑机械行业   基础设施   投资   建筑机械市场   装载机   吸引力   俄罗斯  

摘要： 全球范围内，最具吸引力的建筑机械市场：巴西、俄罗斯、印度与中国（金砖四国），紧随其后的是非洲与中东； 价值链各环节竞争激烈； 重点产品领域：挖掘机与装载机、反铲装载机；

关键词： 混合动力   氢动力   工程机械   发动机  

摘要： 混合动力工程机械和氢动力发动机是开发利用新能源的典型代表。概述了二者的研究现状、在工程和汽车领域里的应用及其关键技术。为进一步降低排耗,分别针对工程机械的能量回收率、燃料利用率低和氢气的储运以及发动机的早燃、回火等问题提出了不同的解决策略。最后,对混合动力工程机械和氢动力发动机的发展趋势进行了总结和展望。研究结果表明,这些措施都有较好的可行性。