物质的量分数平衡常数Kx的剖析及应用

基于2021年山东高考题第20题中物质的量分数平衡常数K_(x)的提出,剖析了一个可逆反应分别在恒温恒容、恒温恒压条件时,K_(x)与浓度平衡常数K_(c)、压强平衡常数K_(p)的关联,并由此得出K_(x)的影响因素.在具体问题情境下,选择合适的商(Q)与平衡常数(K)解决问题,有助于提升学生分析问题、解决问题的能力,发展变化观念与平衡思想的素养.

基于化学史的深度学习研究——以“物质的量的单位——摩尔”教学为例

文章以“物质的量”为研究对象,按照“原子量→摩尔→阿伏加德罗常数→物质的量→摩尔质量”概念的产生、发展、变化的客观顺序,从化学史的角度深度学习相关抽象概念,有力地促进学生化学学科核心素养的发展。

请关注教科书中的常数表

先看两个题目:题目1.一玻璃瓶,恰能装500克乙醇,现有500克蒸馏水,问是否能装入此瓶?题目2.三个完全相同的杯子,里面装有同样的水,把质量相同的铜块、铁块、铝块分别装入三只水杯中,水都没有溢出来,问水面升高最多的是哪一只杯子?

化学平衡常数在高考试题中的延伸考查

本文研究了近几年高考试题,发现化学平衡常数的考查形式、对象出现了新变化.在浓度平衡常数概念的基础上衍生出了压强平衡常数、标准平衡常数(相对压力平衡常数)、物质的量分数平衡常数等概念.但平衡常数的意义不变,它们的大小均只受温度影响,而且应用方向几乎不变——判断可逆反应的方向、判断可逆反应进行的程度、判断可逆反应的热效应、计算可逆反应中反应物的转化率等等.同时按照多重平衡规则将浓度平衡常数与电离平衡常数、难溶电解质溶度积常数进行了关联.

肺动脉高压的肺动脉血管超声生物力学研究

目的采用超声成像技术与生物力学方法相结合的方法,对肺动脉高压(PH)进行了肺动脉(PA)的超声生物力学研究,试将PH患者肺动脉血管的生物力学性质参数用于临床评估PH。方法选择先天性心脏病室间隔缺损并肺动脉高压患者,同步记录肺动脉压力与肺动脉二维图像,从PA收缩加压与扩张开始点到PA达到压力或扩展最大程度时点,界定为10个测量时点、9个递增步骤,分别测量每个时点的PA内径值及收缩压数值及其递增量,然后使用血管生物力学数学模型分析其肺动脉应力-应变关系。结果随着PA压力的不断上升,PA血管内径的扩展性也逐渐受限,尤其是阻力型PH组的PA内径扩张明显受限制,阻力型PH组的肺动脉物质常数a值和b值的各个参数显著减小(P<0.001),表明肺动脉物质常数a值和b值在鉴别阻力型PH方面具有一定的预测作用。结论肺动脉超声生物力学方法在评估与选择先天性心脏病合并PH患者手术适应证方面具有一定的参考作用。

非牛顿磁性纳米流体旋转流动

研究非牛顿磁性纳米磁体定常旋转流动。考虑到磁化强度的特殊贡献,应用修正的非牛顿磁性流体运动方程,磁场作用是纯扩散,不受流体运动速度场的影响。给出了多种流动的解析解。应用计算机符号运算技术,软件Maple16,可以得岀非牛顿上随体Maxwell磁性纳米流体和Oldroyd B磁性纳米流体非定常流动方程的各级近似解的常微分方程,获得解析和数值解。在研究中对纳米流体的物质常数作纳米修正。

pH区带逆流色谱研究进展

pH区带逆流色谱是在逆流色谱基础上发展起来的一种新型制备型分离技术。利用物质解离常数和疏水性的不同进行分离 ,具有分离量大、分离效果好等优点 ,应用领域比较广泛 ;简单介绍了该技术的分离原理及分类 ,并对该技术在氨基酸衍生物、肽衍生物、染料、生物碱和异构体等分离纯化中的应用及其改进方向进行了较为全面的总结 。

3D electrical resistivity inversion using prior spatial shape constraints

To minimize the number of solutions in 3D resistivity inversion, an inherent problem in inversion, the amount of data considered have to be large and prior constraints need to be applied. Geological and geophysical data regarding the extent of a geological anomaly are important prior information. We propose the use of shape constraints in 3D electrical resistivity inversion, Three weighted orthogonal vectors （a normal and two tangent vectors） were used to control the resistivity differences at the boundaries of the anomaly. The spatial shape of the anomaly and the constraints on the boundaries of the anomaly are thus established. We incorporated the spatial shape constraints in the objective function of the 3D resistivity inversion and constructed the 3D resistivity inversion equation with spatial shape constraints. Subsequently, we used numerical modeling based on prior spatial shape data to constrain the direction vectors and weights of the 3D resistivity inversion. We established a reasonable range between the direction vectors and weights, and verified the feasibility and effectiveness of using spatial shape prior constraints in reducing excessive structures and the number of solutions. We applied the prior spatially shape-constrained inversion method to locate the aquifer at the Guangzhou subway. The spatial shape constraints were taken from ground penetrating radar data. The inversion results for the location and shape of the aquifer agree well with drilling data, and the number of inversion solutions is significantly reduced.

Investigation on Non-covalent Complexes of Cyclodextrins with Li＋ in Gas Phase by Mass Spectrometry

To investigate the non-covalent interaction between cyclodextrins （CD） and lithium ion, a stoichiometry of α-CD, β-CD, heptakis（2,6-di-O-methyl）-β-CD （DM-β-CD）, or heptakis（2,3,6-tri-O-methyl）-β-CD （TM-β-CD） was mixed with lithium salt, respectively, and then incubated at room temperature for 10 min to reach the equilibrium. In posi- tive mode, the electrospray ionization mass spectrometry （ESI-MS） results demonstrated that lithium ion can conjugate to α-, β-, DM-β- or TM-β-CD and form 1：1 stoichiometric non-covalent complexes. The binding of the complexes was further confirmed by collision- induced dissociation. The dissociation constants Kdl of four complexes （Li＋α-CD, Li＋β- CD, Li＋DM-β-CD, and Li＋TM-β-CD） were determined by mass spectrometric titration. The results showed Kdl were 18.7, 26.7, 33.6, 30.5 μmol/L for the complexes of Li＋ with α-CD, β-CD, DM-β-CD, and TM-β-CD, respectively. Kdl for the Li＋ complexes of/3-CD is smaller than that of DM-β-CD due to its steric effect of the partial substituted -CH3. The Kdl for the Li＋ complexes of DM-β-CD is nearly in agreement with that of TM-β-CD, indicating Li＋ is more likely to locate in the small rim of DM-β-CD＇s hydrophobic cavity. The DFT results showed through electrostatic interaction, one Li＋ can strongly conjugate to four neighboring oxygen atoms. For the （α-CD＋Li）＋ complex, one Li＋ may also situate the small rim of α-CD＇s hydrophobic cavity to form a non-specific host-guest complex.

Effects of Density—Dependent Bag Constant and Strange Star Rotation

With the emphasis on the effects of the density-dependent bag constant and the rotation of strange star the limiting mass of strange star is calculated. The obtained results show that the limiting mass and the corresponding radius of strange star increase as the rotation frequency increases, and tend to be lowered when the density-dependent bag constant is considered.

Optimizing the Interpretation of Sub-surface Resistivity in Relation with Borehole Productivity in Basement Area Applied to Seno Province （Burkina Faso）

This study aims at identifying possible correlations between shapes, types of geophysical anomalies and borehole productivity according to geological and hydrogeotogical contexts. The methodology adopted was a two-pronged one--the first step sought to： （1） interpret the electrical resistivity values from horizontal profiling and vertical electrical sounding implemented in Seno province that preceded the drilling of 513 boreholes; （ii） interpret data from pumping tests carried out on boreholes having a discharge superior to 1 m3/h （＂positive borehole＂） by using Cooper-Jacob＇s method. In the second step, according to geology, authors tried to identify possible correlations between each of the qualitative geophysical parameters： ~shape of anomaly〉〉, tttype of anomaly〉〉 and ~〈type curve〉〉 on the one hand, and hydrogeological parameters such as discharge, alteration thickness, transmissivity and saturated level on the other. The results of this study have shown that the chances of having a positive borehole in Seno province are higher when the type of anomaly is TCC （80%）, shape of anomaly is ＂W＂ and when type curve is ＂H＂ （80%） for all geological formations. Granitic formations are those that record higher discharges while schists record high transmissivity values.

Equation of State of Nuclear Matter in Chiral σ-ω Model

The equation of state of nuclear matter is studied in the 1-loop approximation of chiral linear σ-ω model.By introducing the density-dependent coupling constants, the problem of tachyon pole in the chiral σ-ω model is resolved.The 1-loop contributions ofσ and π mesons to the nucleon's binding energy are included, while the empirical properties of nuclear matter such as saturation density, binding energy, and incompressibility are well reproduced.

Quintessence Field as a Perfect Cosmic Fluid of Constant Pressure

We study the cosmology of a quintessence scalar held which is equivalent to a non-barotropic perfect fluid of constant pressure.The coincidence problem is alleviated by such a quintessence equation-of-state that interpolates between plateau of zero at large redshifts and plateau of minus one as the redshift approaches to zero.The quintessence Geld is neither a unified dark matter nor a mixture of cosmological constant and cold dark matter,relying on the facts that the quintessence density contrasts of sub-horizon modes would undergo a period of late-time dechne and the squared sound speeds of quintessence perturbations do not vanish.What a role does the quintessence play is dynamic dark energy,its clustering could remarkably reduce the growth rate of the density perturbations of non-relativistic matters.

Influence of Density-Dependent Coupling Constants on Equation of State of Infinite Symmetric Nuclear Matter

In the mean field approximation of nonlinear relativistic a-ω-p model, we have studied the influence of density-dependent coupling constants between nucleons and mesons on the equation of state （EOS） of infinite symmetric nuclear matter in different conditions. We find that the EOS of nuclear matter will become stiffer as e, d in the self- interaction of σ meson increase when the coeffcients except aω in Гω, in which the opposite occurs, are fixed. On the other hand, greater values of aσ, bσ, cσ, aω, dω and smaller values of dσ, bω, cω will lead to stiffer EOS ifc and d are fixed. Besides, greater values of Гω lead to stiffer EOS in high density region for the EOS with same incompressibility coefficient at saturation density.

Probing the sign-changeable interaction between dark energy and dark matter with current observations

We consider the models of vacuum energy interacting with cold dark matter in this study, in which the coupling can change sigh during the cosmological evolution. We parameterize the running coupling b by the form b（a） = boa ＋ be（1 - a）, where at the earlytime the coupling is given by a constant be and today the coupling is described by another constant bo. We explore six specific models with （i） Q = b（a）Hoρo, （ii） Q = b（a）Hoρde, （iii） Q = b（a）Hoρc, （iv） Q = b（a）Hρo, （v） Q = b（a）Hρde, and （vi） Q = b（a）Hρc. The current observational data sets we use to constrain the models include the JLA compilation of type Ia supernova data, the Planck 2015 distance priors data of cosmic microwave background observation, the baryon acoustic oscillations measurements and the Hubble constant direct measurement. We find that, for all the models, we have b0 〈 0 and be 〉 0 at around the lolevel, and b0 and be are in extremely strong anti-correlation. Our results show that the coupling changes sign during the evolution at about the lolevel, i.e., the energy transfer is from dark matter to dark energy when dark matter dominates the universe and the energy transfer is from dark energy to dark matter when dark energy dominates the universe.