The Avogadro Constant for the Definition and Realization of the Mole

The International System of Units’ (SI) base unit of the quantity “amount of substance” is the mole (symbol: mol). After the revision of the SI to be implemented in 2019, when all SI units will be based solely on constants, the mole will be defined through a fixed value of the Avogadro constant N_A. One mole contains exactly 6.02214076 × 10²³ elementary entities, meaning the mole will no longer be linked to the kilogram. Currently, the mole is defined via the mass of exactly 0.012 kg of the ¹²C isotope which links it to the kilogram prototype. The history, changes, and implications of the revised definition of the mole are discussed here from the chemist's point of view. The ability to count entities such as atoms or molecules (precisely enough to enable a revision of the SI and preserve consistency of previous and future measurements) is crucial. This is achieved with the realization (Mise en Pratique) based on the X‐ray‐crystal density (XRCD) method (counting the atoms in a silicon sphere). The determination of N_A, focusing on the measurement of the molar mass of silicon highly enriched in the ²⁸Si isotope, with the lowest uncertainty so far, is presented.     

The Optical Frequency Standards for the Realization of the Meter

Optical‐frequency standards with various levels of performance are indispensable in metrology and have many applications from length measurement to atomic clocks and much more. The evolution of optical‐frequency standards has been considerable. Originally introduced as primary realizations for the meter, they have evolved to optical clocks, which surpass the uncertainty and stability of microwave clocks. Herein, the status of the development of optical‐frequency standards as far as length metrology is concerned is reviewed, giving a broad overview of the historical context, as well as an outlook about future evolution.     

电荷不连续时电容耦合介观电路的量子回路方程及其能谱

考虑电荷具有不连续性的事实对双LC介观电路进行量子化,给出耦合形式的量子回路方程以及无相互作用Hamilton本征基矢下的电路能谱.结果表明,计及电荷离散性将使回路方程的形式发生明显变化;介观电路的能谱除与电路参数相关外,还明显地依赖于电荷的量子化性质.     

Evidence for the quantum birth of our universe

We present evidence for a nonsingular origin of the Universe with intial conditions determined by quantum physics and relativistic gravity. In particular, we establish that the present temperature of the microwave background and the present density of the Universe agree well with our predictions from these intial conditions, after evolution to the present age using the Einstein-Friedmann equation. Remarkably, the quantum origin for the Universe naturally allows its evolution at exactly the critical density. We also discuss the consequences of these results to some fundamental aspects of quantum physics in the early Universe.     

表面电荷法平面元电荷系数的半解析解法

针对在线性及高次电荷估计下,表面电荷法中全解析法对平面元电荷系数求解和实现较复杂的问题,提出一种半解析法.将系数积分由局部坐标系变换到整体坐标系下分离参数的二重积分,利用内层积分存在解析解的特点,将二维问题降为一维,方便数值积分计算.对于对数奇异积分问题采用辅助函数法消除.通过算例与全解析法计算精度进行比较,结果表明,在一定的单元划分下,可达到很高精度,具有一定可行性.     

Electrostatic Charge Measurement and Charge Neutralization of Fine Aerosol Particles during the Generation Process

An aerosol charge analyzer has been constructed to measure the charge distribution of NaCl particles generated in the laboratory. A radioactive electrostatic charge neutralizer utilizing Po‐210 was used to neutralize the electrostatic charge of the particles. The atomization technique was used to generate NaCl particles with diameters of 0.2 to 0.8 μm, while the evaporation and condensation method was adopted to generate particles of 0.01 to 0.2 μm in diameter. The experimental data demonstrates that the absolute average particle charge depends on the particle diameter, and is higher than that calculated by the Boltzmann charge equilibrium for particles within the range of 0.2 to 0.8 μm. The charge increases with decreasing NaCl concentration. When these particles are neutralized using the Po‐210 neutralizer, it is found that the electrostatic charge reaches the Boltzmann charge equilibrium. For 0.01 to 0.2 μm NaCl particles generated using the evaporation and condensation method, test results show that the absolute average particle charge is higher than that calculated by the Boltzmann charge equilibrium for particles larger than 0.03 to 0.05 μm in diameter, while it is lower than that predicted by the Fuchs theory [1], for particles smaller than 0.03 to 0.05 μm. However, after charge neutralization, particles with diameter above 0.05 μm reach the Boltzmann charge equilibrium condition, and the charges for particles with diameters of 0.010 to 0.05 μm, agree well with Fuchs' theory.     

The Planck Constant for the Definition and Realization of the Kilogram

On May 20, 2019 the values of the Planck, h, and Avogadro, N_A, constants will be fixed, revising our measurement system, the International System of Units (SI), and providing a new way to get mass traceability. While the famous energy relations mc² and hf may remind many that the Planck constant is indeed related to mass, it is less recognized how this is also true for the Avogadro constant. These concepts are reviewed in the context of the upcoming revision of the SI. How the fixed values were chosen and how mass traceability will be maintained with the smallest uncertainty are also discussed.     

The Boltzmann Constant for the Definition and Realization of the Kelvin

In November 2018, the four base units, kilogram, ampere, kelvin, and mole, of the International System of Units (SI) are redefined in terms of fundamental physical constants. The redefinition comes into force on World Metrology Day, 20 May 2019. The kelvin, the base unit of thermodynamic temperature, from then is to be founded on a fixed numerical value of the Boltzmann constant. Herein, the change in the definition of the kelvin and the consequences for practical temperature measurement are explained. The primary thermometry methods applied to determine the numerical value of the Boltzmann constant for the redefinition are reviewed. The prospects for the future application of these methods are outlined.     

关于态叠加原理的认同与争议

给出了不同学者关于量子力学态叠加原理的几种表述,分析比较了关于该原理的有关观点的争议,并对其中的原因进行了讨论。     

The Search for Variation of Fundamental Constants with Clocks

In many theories beyond the Standard Model the quantities that we call “fundamental constants” become space‐time dependent, leading to corresponding variation of atomic and molecular spectra and clock frequencies. The extraordinary improvement of the atomic clock precision in the past fifteen years enabled testing the constancy of the fundamental constant at a very high level of precision. Herein, searches for the variation of fundamental constants with clocks are discussed, focusing on recent key results and future proposals, including highly charged ion, molecular, and nuclear clocks. The relevance of the recent searches for oscillatory and transient variation of fundamental constants to the major unexplained phenomena of our Universe, the nature of dark matter, is discussed.     

Implementation of a Controlled-Phase Gate and Deutsch-Jozsa Algorithm with Superconducting Charge Qubits in a Cavity

Based on superconducting quantum interference devices （SQUIDs） coupled to a cavity, we propose a scheme for implementing a quantum controlled-phase gate （QPG） and Deutsch-Jozsa （D J） algorithm by a controllable interaction. In the present scheme, the SQUID works in the charge regime, and the cavity field is ultilized as quantum data-bus, which is sequentially coupled to only one qubit at a time. The interaction between the selected qubit and the data bus, such as resonant and dispersive interaction, can be realized by turning the gate capacitance of each SQUID. Especially, the bus is not excited and thus the cavity decay is suppressed during the implementation of DJ algorithm. For the QPG operation, the mode of the bus is unchanged in the end of the operation, although its mode is really excited during the operations. Finally, for typical experiment data, we analyze simply the experimental feasibility of the proposed scheme. Based on the simple operation, our scheme may be realized in this solid-state system, and our idea may be realized in other systems.     

电矩张量与旋转带电体的磁矩

基于旋转带电体的磁矩与刚体转动惯量之间的类比关系,引入带电体的一个不同于电四极矩的电矩张量的概念,进而引入标量电矩二次曲面及电矩主轴的概念,借助正交变换及电矩张量矩阵的本征值理论,推导出沿任意方向定轴旋转带电体的磁矩的计算公式及电矩张量的若干性质,并举例说明.     

用Mathematica计算油滴电荷的基本量

密立根油滴实验的主要目的是要从大量的实验数据中证明电荷的不连续性,为提高计算效率,本文利用了Mathematica软件对实验数据进行了最小二乘处理,优化了误差的分布,得到了准确的电荷基本量值。     

The Total Charge of Carbon and Nitrogen Atoms in the Amide Bonds Acts as a New Approach to Understand the Mobile Proton Model

The mobile proton model has been the main theory to describe peptide fragmentation in mass spectrometry (MS). In this study, Gly-Ala-Tyr (GAY) was used to research the mass spectrometry cleavage mechanism. The hydroxyl radical oxidation technique was applied to change the charge distribution of the peptide. We applied MS/MS technique to obtain the tandem mass spectrum of the peptide and then obtained fragmentation efficiency curves, which indicated that the cleavage of GAY became more and more difficult as more O atoms were added. The charge distribution was obtained from quantum chemical calculations at the B3LYP/6-31G(d) level using the Gaussian 03 W program. By analyzing the charge distribution around the amide bonds, we found that the total charge of C and N atoms (Q_C + Q_N) in the amide bonds provided a reasonable prediction of peptide fragmentation efficiency. A decrease of the Q_C + Q_N value in the amide bonds leads to a low fragmentation efficiency of GAY, and vice versa. Through comparing experimental data with calculation results to research the relationship between charge distribution and the mass spectrometry cleavage mechanism, this work provides a new way to understand the mobile proton model for peptide fragmentation.     

回旋加速器中的空间电荷效应和束晕

在考虑束团内粒子之间的空间电荷相互作用力的条件下,对日本理化研究所(RIKEN)现有的一台注入器(加速常数为K70的AVF型回旋加速器)中束团的演变过程进行了模拟计算.模拟结果表明,束团的形变、束晕现象同样发生在回旋加速器中,不过,其产生机制不同于直线加速器.它不是由共振和混沌引起,而是由于粒子的排斥运动和束团内粒子的涡流运动引起的.     

密立根油滴实验数据处理方法的分析与改进

介绍了目前常用的几种密立根油滴实验数据处理的方法,并对其中一种方法进行了改进,使其更加科学,更加符合实验教学实际．     

强流AVF型迴旋加速器中的空间电荷效应和束晕

详细推导了AVF型迴旋加速器中束团粒子在曲线坐标系中的动力学方程(考虑和不考虑空间电荷相互作用力两种情况).在假定动力学方程中各参数值的前提条件下,用Lunge-Kutta方法对考虑空间电荷时的动力学方程进行了数值计算.结果表明,束晕的形成和发展同样也是强流迴旋加速器中束流损失的一个主要原因.但束晕形成的机制不同于直线加速器的情况,它不是由共振和混沌引起,而是由于粒子的排斥运动和束团内粒子的涡流运动引起的.