4-甲基-2,6-二羟基嘧啶对B-Z振荡反应的影响

因为生命体内存在周期性振荡现象,因而药物对振荡反应的影响成为人们日益关注的问题。合成了一种药物中间体,并对其进行了元素分析、红外光谱、核磁共振表征,证明它是4-甲基-2,6-二羟基嘧啶。在不同温度和不同浓度下在B-Z振荡反应体系中加入4-甲基-2,6-二羟基嘧啶,考察其对B-Z振荡反应体系的影响。实验结果表明,温度升高使B-Z振荡反应体系的振荡周期减小。4-甲基-2,6-二羟基嘧啶浓度增大使B-Z振荡反应体系的振荡周期和振幅均产生减小现象。并对4-甲基-2,6-二羟基嘧啶的反应机理进行了推测。     

糖水-水小孔泄漏振荡周期与小孔孔径的关系

对溶液小孔泄漏振荡现象进行了实验研究,通过对振荡周期的测量和分析,发现泄漏振荡周期与小孔直径的2.84次幂成反比.这与关于此现象的早期理论分析结果不尽一致.     

纳米银粒子对表面吸附罗丹明B的光谱学性质的影响及电解质效应研究

基于贵金属纳米粒子的局域场增强效应,利用透射电子显微镜、紫外-可见分光光度计和荧光分光光度计等分析手段研究了纳米银粒子对表面吸附罗丹明B的光谱学性质的影响以及罗丹明B-纳米银体系中加入电解质离子后,电解质离子与纳米银、染料分子间的相互关系和作用.研究结果表明,当罗丹明B溶液的浓度小于0.6μmol·L-1时,微量纳米银...     

三能级体系的Z回波核磁共振粉末谱

本文提出一个Z回波核磁共振(NMR)脉冲序列,可以获得三能级体系的纯偶极或纯四极谱。Z回波NMR谱不仅与化学位移各向异性无关,而且在强射频场条件下,与射频场非均匀性无关。该方法明显优于章动NMR技术。以上结论经过理论分析和实验结果的验证。 关键词：     

磁性多层膜层间交换耦合的自由电子模型研究

基于自由电子模型,考虑到不同膜厚和不同磁化排列的费密能的不同,自洽地给出费密能。利用这种方法,计算了材料铁磁层和非磁层电子密度对层间耦合振荡周期的影响,并比较了我们所得结果与他人按巨势法得到的结果的异同,发现振荡周期随着电子密度的变化而改变,并且当铁磁层和非磁层的电子密度不同时,将出现不等周期的振荡。这一新的理论结果与最近的实验相符。此外,还计算了极化强度和由于能带不匹配造成的接触势对耦合强度及振荡相位的影响:前者是决定耦合强度的主要因素,后者则会影响振荡相位,甚至周期。 关键词：     

关于洛伦兹力演示实验的研究

文章分析电解质溶液中带电粒子在电磁场中的运动现象,探讨决定洛伦兹力大小的各影响因素,并对其进行详尽的理论分析.其中电解质溶液之间的关系为实验重要影响因素,理论推导得到二者间的函数关系,通过实验测得电导率和溶液浓度之间关系曲线,并将实验结果与理论分析进行了对比.研究发现洛伦兹力演示实验的关键性因素为电解质溶液的电导率和溶液浓度之间的关系,结合实验结果找到电导率最大时溶液浓度的范围.     

利用Z扫描技术确定非局域非线性介质的非线性折射率

采用高斯分解法,分析并讨论了非局域非线性介质的Z扫描特性.基于介质的非线性响应函数为高斯型,给出了用于确定非局域非线性介质的非线性折射率系数的透过率表达式,分析了非局域非线性介质的非局域程度对透过率曲线的影响,得到了计算非局域非线性介质的非线性折射率系数以及非局域程度的方法,讨论了由于非局域性条件所带来的对实验上的一些参数的调整,提出了测量介质非局域程度的可行的实验方法并说明了其他注意事项.同时还数值模拟了在介质的响应函数为双曲正割型情况下通过薄样品的远场Z扫描曲线,并与高斯响应情况下的结果进行了比较.     

19F+27Al反应产物的角分布、角分散与耗散机制

完成了114MeV¹⁹F+²⁷Al深部非弹性碰撞产物的角分布测量.分析了反应产物B,C,N,O,F,Ne,Na,Mg和Al的实验室系角分布,讨论了反应形成的中间双核系统随时间演化过程中角分布所表现出的耗散特点.从实验上提取了反应产物各元素的角分散参数并作了角分散参数的理论拟合,讨论了角分散参数的物理意义以及角分散参数与耗散反应产物的电荷数Z之间的依赖关系.     

浸没于带电纳米粒子溶液中的聚电解质刷:强拉伸理论

纳米粒子是调控聚电解质刷行为的一种新手段,聚电解质刷是调控纳米粒子与表面相互作用的一种重要媒介,本文应用强拉伸理论研究了聚电解质刷浸没于带同种电荷的纳米粒子溶液中的行为.给出了聚电解质刷、纳米粒子、反离子的密度分布和刷厚度的解析表达式,基于解析表达式,得到了体系的特征标度关系.当纳米粒子浓度Φ较高,电量Z较低时,纳米粒子可以渗入聚电解质刷内部.当纳米粒子浓度Φ相对较低,电量Z较高时,纳米粒子几乎不能渗入刷内部,但依然可以影响刷的厚度.在前一种情形下,刷行为由反离子、纳米粒子的渗透压与链的熵弹性之间的竞争决定,刷厚度满足的标度关系为H≈(ZΦ)~(-1/3);在后一种情形下,刷行为由反离子的渗透压与链的熵弹性之间的竞争决定,刷厚度满足的标度关系为H≈(ZΦ)~(-1).本文还探究了纳米粒子多分散性的效应.     

电解质的加入对Au@Ag纳米粒子SERS效应的影响

通过先采用Frens法制备粒径约为12nm的Au NPs,以此为基础通过以抗坏血酸为还原剂,采用种子生长法成功制得Au@Ag纳米粒子,通过UV-Vis表征发现具有很好的稳定性。接着以4-巯基吡啶(4-MPy)分子为探针,考察了加入电解质的量、加入顺序、电解质的阳离子、电解质的阴离子对纳米粒子SERS活性的影响,并结合UV-Vis光谱进行了分析。结果显示加入电解质的量一般会有一个最佳值,加入阳离子种类以及加入顺序对纳米粒子SERS活性影响不是很明显。不同阴离子的加入对纳米粒子影响不同,这主要是由于阴离子的加入使溶胶发生聚集以及阴离子与Au@Ag纳米粒子银表面相互作用的结果。     

外控弱周期电流约束下电极B-Z反应体系中的时间自组织

以经典BZ化学反应体系的三变量Oregonator模型及电极过程动力学为基础,提出了外控弱周期电极电流约束下电极BZ反应体系与体相BZ反应体系相互耦合的动力学模型.在体相处于稳定定态参数条件下,系统地研究了外控弱周期电流约束下电极BZ反应体系中的动力学行为,定量分析了电流慢变流型上的准定态稳定性及有利于出现极限环振荡区域.研究表明,与以前所报道的外控弱周期电位约束情况类似,在外控弱周期电流约束下电极BZ反应体系中的极限环振荡区域亦发生了蜕变,但体系对外控电流约束中的这种持续性之周期扰动的响应表现在两个方面:有利于出现极限环振荡区域的缩变及原非振荡区胁迫振荡的出现.     

Effect of monocationic ionic liquids as electrolyte additives on the electrochemical and thermal properties of Li-ion batteries

The conventional electrolyte system has been compared with the ionic liquid (IL) additive containing electrolyte system at room temperature as well as elevated temperature. In this work, two types of monocationic ILs such as 1-butyl-3-methylpyrrolidinium hexafluorophosphate (Pyr IL) and 1-ethyl-3-methylimidazolium hexafluorophosphate (IMI IL) are added as an additive at two different weight ratios in 1.15 M LiPF₆ (EC/EMC = 3/7 v/v) electrolyte solution, the structural, electrochemical and thermal characteristics of LiNi_0.80Co_0.15Al_0.05O₂ (NCA)/carbon full-cell in different electrolyte formulations have been reconnoitered. X-ray diffraction (XRD) studies have proved that IL as an electrolyte additive does not alter the structural stability of cathode materials after cycling. Under room temperature, Pyr IL additives at 1 wt% and 3 wt% deliver better cycleability than others, with the retention ratios of 93.62% and 92.8%, respectively. At elevated temperature, only 1 wt% Pyr IL additive is giving stable capacity retention ratio of 80.74%. Ionic conductivity and self-extinguishing time (SET) values are increasing with respect to the amount of additive added to the electrolyte. Thermal studies reveal that 3 wt% Pyr IL is favorable regarding the safety of the battery as it shows shifting of peak to higher temperature of 272.10 °C. Among the IL additives evaluated in this study, addition of 1 wt% Pyr IL is the most desirable additive for achieving the best cycling performance as well as thermal behavior of Li-ion batteries.     

Self-assembly of Polyaniline: Mechanism Study

在水热环境下合成出\掺杂电荷诱导自组装纳米纤维阵列结构的聚苯胺平板,并通过一系列设计实验研究了这种自组装微观结构的形成机理,例如在反应溶液中引入不参与反应、对电荷组装起干扰作用的电解质,以及用计算模拟体系静电能与纳米纤维阵列夹角的相互关系等实验．实验结果发现,由掺杂离子引起的静电相互作用在形成聚苯胺自组装结构的过程中起了重要的作用．     

The electrochemical performance of super P carbon black in reversible Li/Na ion uptake

Super P carbon black (SPCB) has been widely used as a conducting additive in Li/Na ion batteries to improve the electronic conductivity. However, there has not yet been a comprehensive study on its structure and electrochemical properties for Li/Na ion uptake, though it is important to characterize its contribution in any study of active materials that uses this additive in non-negligible amounts. In this article the structure of SPCB has been characterized and a comprehensive study on the electrochemical Li/Na ion uptake capability and reaction mechanisms are reported. SPCB exhibits a considerable lithiation capacity (up to 310 mAh g~(–1)) from the Li ion intercalation in the graphite structure. Sodiation in SPCB undergoes two stages: Na ion intercalation into the layers between the graphene sheets and the Na plating in the pores between the nano-graphitic domains, and a sodiation capacity up to 145 mAh g~(–1) has been achieved. Moreover, the influence of the type and content of binders on the lithiation and sodiation properties has been investigated. The cycling stability is much enhanced with sodium carboxymethyl cellulose (NaCMC) binder in the electrode and fluoroethylene carbonate (FEC) in the electrolyte; and a higher content of binder improves the Coulombic efficiency during dis-/charge.     

Rhythms of the brain: an examination of mixed mode oscillation approaches to the analysis of neurophysiological data

In the nervous system many behaviorally relevant dynamical processes are characterized by episodes of complex oscillatory states, whose periodicity may be expressed over multiple temporal and spatial scales. In at least some of these instances the variability in oscillatory amplitude and frequency can be explained in terms of deterministic dynamics, rather than being purely noise-driven. Recently interest has increased in studying the application of mixed-mode oscillations (MMOs) to neurophysiological data. MMOs are complex periodic waveforms where each period is comprised of several maxima and minima of different amplitudes. While MMOs might be expected to occur in brain kinetics, only a few examples have been identified thus far. In this article, we review recent theoretical and experimental findings on brain oscillatory rhythms in relation to MMOs, focusing on examples at the single neuron level but also briefly touching on possible instances of the phenomenon across local and global brain networks.     

Kinetic oscillations in the rate of CO oxidation on Pd(110)

The oxidation of carbon monoxide on a Pd(110) single crystal plane has been studied using work function changes (Δφ) and mass spectrometric measurements. The rate of reaction showed oscillatory behaviour for oxygen pressures greater than 10⁻³ Torr. The existence region for oscillations was determined for pressures ranging from 10⁻³ to 1.0 Torr and depended on the pressures of oxygen and carbon monoxide and the sample temperature (P_co, PO₂ T). Transitions from regular oscillation to chaos via period doubling have been observed in certain areas of the existence region. A comparison between Pd(110) and platinum single crystal surfaces that exhibit oscillations showed that similar but not identical oscillatory behaviour and existence regions exist in each case. Our results indicate that oscillations can occur on other metal single crystal surface that are less likely than platinum to reconstruct under reaction conditions. The extension of oscillations from UHV conditions to the 1.0 Torr pressure region indicates that the mechanism responsible for isothermal oscillations is basically independent of the reactant pressure up to several Torr.     

氨基酸-BrO-3-Mn2+-H2SO4-丙酮振荡体系的非线性动力学及热力学研究

通过所获得的4种氨基酸(丙氨酸Ala,甘氨酸Gly,丝氨酸Ser及酪氨酸Tyr)在氨基酸-KBrO3--Mn2+-H2SO4-丙酮振荡体系的动力学参数(诱导期及周期的速率常数Kin、kp及表观活化能Ein、Ep)及Oregonator模型和不可逆过程热力学理论,获得了该振荡体系的热力学函数(△Hin,△Gin,Sin及...     

Ignition and transient dynamics of sub-limit premixed flames in microchannels

We examine, via two-dimensional numerical simulation of a model system, some unsteady transient ignition scenarios and sustained oscillatory combustion modes that can occur in a single-pass, conductive channel, premixed microburner. These issues are relevant to the problem of ignition, evolution to stable combustion and the operational modes of microcombustors. First, we describe an unsteady ignition sequence that may occur when a single-pass microburner with initially cold walls has its exit walls heated and maintained at a fixed temperature. In particular, we demonstrate that as the heat from the exit walls propagates down the microburner walls, a reaction wave is driven rapidly down the channel towards the inlet via a sequence of oscillatory ignition and quenching transients. This scenario has been observed experimentally during the ignition of a single-pass microburner. Secondly, we show how an initial axial wall temperature gradient can lead to a variety of sustained combustion modes within the channel, including stable stationary flames, regimes of periodic motion involving quenching and re-ignition, regimes of regular oscillatory combustion, and regimes consisting of a combination of re-ignition/quenching events and regular oscillatory motions, all of which have been observed experimentally.     

Time-dependent quantum dynamics study for reaction of D+CH4→CH3+HD

The semirigid vibrating rotor target (SVRT) model has been applied to the study of the reaction of D+CH_4→CH_3+HD using a time-dependent wave packet method. The energy dependence of the calculated reaction probability shows oscillatory structures similar to those observed in the abstraction reaction of H+H_2, H+CH_4 etc. We have also studied the influence of rotational and vibrational excitation of the reacting molecule (CH_4) on reaction probability. The excitation of the H－CH_3 stretching vibration gives significant enhancement of reaction probability, which rises significantly with the enhancement of rotational quantum number j. Finally, we have compared the cross section and the rate constant of the D+CH_4 system with that of the H+CH_4 system.