The use of mass defect in modern mass spectrometry

Mass defect is defined as the difference between a compound's exact mass and its nominal mass. This concept has been increasingly used in mass spectrometry over the years, mainly due to the growing use of high resolution mass spectrometers capable of exact mass measurements in many application areas in analytical and bioanalytical chemistry. This article is meant as an introduction to the different uses of mass defect in applications using modern MS instrumentation. Visualizing complex mass spectra may be simplified with the concept of Kendrick mass by plotting nominal mass as a function of Kendrick mass defect, based on hydrocarbons subunits, as well as slight variations on this theme. Mass defect filtering of complex MS data has been used for selectively detecting compounds of interest, including drugs and their metabolites or endogenous compounds such as peptides and small molecule metabolites. Several strategies have been applied for labeling analytes with reagents containing unique mass defect features, thus shifting molecules into a less noisy area in the mass spectrum, thus increasing their detectability, especially in the area of proteomics. All these concepts will be covered to introduce the interested reader to the plethora of possibilities of mass defect analysis of high resolution mass spectra.     

Role of the mass asymmetry of reaction on the geometry of vanishing flow

We study the transverse flow throughout the mass asymmetry range as a function of the impact parameter, keeping the total mass of the system fixed. We find that the geometry of vanishing flow (GVF) i.e. the impact parameter at which flow vanishes and its mass dependence is quite sensitive to the mass asymmetry of the reaction. With increase in the mass asymmetry, the value of GVF decreases, while its mass dependence increases. Our results indicate the sizable role of mass asymmetry on GVF as on balance energy.     

Discrimination of neutrino mass models

We consider the Majorana CP violating phases derived from right-handed Majorana mass matrices to estimate the baryon asymmetry of the universe, for different neutrino mass models, namely degenerate, inverted hierarchical and normal hierarchical models, with tri-bimaximal mixings. Considering three possible diagonal forms of Dirac neutrino mass matrix as charged-lepton, up-quark or down-quark mass matrix within the framework of left-right symmetric GUT models, the right-handed Majorana mass matrices are constructed from the light Majorana neutrino mass matrix through the inverse seesaw formula. These light neutrino mass matrices have already been tested to provide good predictions on neutrino mass parameters and mixing angles. They are again applied to predict baryon asymmetry of the universe in the present work. The normal hierarchical model gives the best prediction for baryon asymmetry, consistent with observation. The analysis may serve as additional information in the discrimination of the presently available neutrino mass models.     

气溶胶消光系数与质量浓度的相关性研究

为了利用激光雷达探测的消光系数垂直分布来反演气溶胶质量浓度的垂直分布,研究气溶胶消光系数与质量浓度之间的关系就显得十分重要.根据Mie散射理论,分析了气溶胶的质量消光系数、消光系数和质量浓度之间的关系,引进了等效参数,分析了Junge指数对等效参数的影响.用实际测量的粒子谱分布、能见度、相对湿度和气溶胶质量浓度验证了气溶胶消光系数和质晕浓度之间的关系.这对利用激光雷达测量的气溶胶消光系数垂直分布来反演气溶胶质量浓度的垂直分布是很有实用价值和指导意义的.     

Effective nucleon masses in symmetric and asymmetric nuclear matter

The momentum and isospin dependence of the in-medium nucleon mass are studied. Two definitions of the effective mass, i.e., the Dirac mass m*D and the nonrelativistic mass m*NR which parametrizes the energy spectrum, are compared. Both masses are determined from relativistic Dirac-Brueckner-Hartree-Fock calculations. The nonrelativistic mass shows a distinct peak around the Fermi momentum. The proton-neutron mass splitting in isospin asymmetric matter is m*D,nm*NR,p, which is consistent with nonrelativistic approaches.     

Dynamical Behaviour of the Mass Asymmetry Mass Parameter in Nuclear Fission

The theory of nuclear fission is reconsidered. We study the behaviour of the mass parameter as a dynamical quantity of the mass asymmetry. The dependence of the mass asymmetry mass parameter is studied as a function of the five collective coordinates. These parameters are reconsidered by including the temperature to show the temperature dependence of the mass parameter. The cranking model is used in developing all the mathematical and theoretical expressions. Numerical calculations of the obtained analytical expressions are carried out for the two fissioning nuclei ²³⁶U and ²³⁸U. The mass asymmetry mass parameters are calculated including the temperature as a function of the different five collective coordinates. The present study shows that the values of this mass asymmetry mass parameters are stable against the change of the temperature for temperature values greater than 1 MeV for all the different five collective coordinates.     

The pole mass in perturbative QCD

We review quark mass definitions in QCD, defending the identification of pole with constituent masses on the one hand and of invariant mass flavour ratios with current mass flavour ratios on the other. We prove that the pole mass is gauge-parameter independent and infrared finite at the two-loop level. We compute the two-loop mass anomalous dimension in the MS renormalization scheme. The renormalization group allows one to connect constituent with current mass ratios. For heavy flavours we predict the invariant masses.     

超声空化引起界面湍动促进的传质机理

本文分析了超声空化引起界面湍动对传质过程的影响,提出了相界面上超声空化气泡析出增强边界层液体湍动并促进传质的机理,在传质理论和流体动力学原理的基础上,建立了超声空化引起界面湍动促进的传质机理模型,获得了超声空化引起界面湍动促进的传质系数表达式。实验结果验证了模型的合理性。该模型既证实了超声对传质有强化效应,又对传质过程有很好的预测功能,为工业化提供了理论依据。     

Study of thermal conductivity and thermal rectification in exponential mass graded lattices

Concept of exponential mass variation of oscillators along the chain length of N oscillators is proposed in the present Letter. The temperature profile and thermal conductivity of one-dimensional (1D) exponential mass graded harmonic and anharmonic lattices are studied on the basis of Fermi-Pasta-Ulam (FPU) β model. Present findings conclude that the exponential mass graded chain provide higher conductivity than that of linear mass graded chain. The exponential mass graded anharmonic chain generates the thermal rectification of 70-75% which is better than linear mass graded materials, so far. Thus instead of using linear mass graded material, the use of exponential mass graded material will be a better and genuine choice for controlling the heat flow at nano-scale.     

再论质量的起源

物质的质量是怎么来的?能从理论上研究质量的起源吗?人类目前所能做的实验是否到了可探索这些质量起源的程度?本文将要介绍目前物理学对这些问题的认识.我们首先通过修改牛顿第零定律引入结合能来介绍物质的各个不同层次上的质量起源的研究链条,然后重点讨论基本粒子质量的起源,并介绍基本粒子质量与对称性的关系,最后讨论三种与质量起源有关的质量产生和分裂的机制.     

原子质量对一维三原子链色散关系的影响

本文采用数值分析方法研究原胞中原子质量对一维三原子链色散关系的影响,建立了频谱宽度和频率禁带宽度随原子质量变化的基本规律.结果表明,在原胞内只有一个原子质量发生变化的情况下,声学波频谱宽度随任一原子质量的增加而减小,光学波的频谱宽度随小原子质量的增加而增大,随大原子质量的增加而减小;两个频率禁带均随小原子质量的增加而变...     

Inertial Mass and Vacuum Fluctuations in Quantum Field Theory

Motivated by recent works on the origin of inertial mass, we revisit the relationship between the mass of charged particles and zero-point electromagnetic fields. To this end we first introduce a simple model comprising a scalar field coupled to stochastic or thermal electromagnetic fields. Then we check if it is possible to start from a zero bare mass in the renormalization process and express the finite physical mass in terms of a cut-off. In scalar QED this is indeed possible, except for the problem that all conceivable cut-offs correspond to very large masses. For spin-1/2 particles (QED with fermions) the relation between bare mass and renormalized mass is compatible with the observed electron mass and with a finite cut-off, but only if the bare mass is not zero; for any value of the cut-off the radiative correction is very small.     

MASS DRIFT FLUCTUATION AND THE SHELL EFFECT IN HEAVY ION COLLISIONS

Master equation is solved numerically for mass drift and fluctuation of three reactions.The driven potential is calculated by means of D.Myers' mass formula plus shell correction.The results indicated that the lack of mass drift in the range of zero to a considerable energy loss in heavy ion collisions could be explained by transport theory.Due to small mass mobility coefficient the mass does not drift considerably during a short time interval.The effect of shell structure in the driven potential is obvious for mass relaxation in low energy loss region.     

多组份流动质量分数保极值原理算法

对基于质量分数的Mie-Gruneisen状态方程多流体组份模型提出了新的数值方法.该模型保持混合流体的质量、动量、和能量守恒,保持各组份分质量守恒,在多流体组份界面处保持压力和速度一致.该模型是拟守恒型方程系统.对该模型系统的离散采用波传播算法.与直接对模型中所有守恒方程采用相同算法不同的是,在处理分介质质量守恒方程时,对波传播算法进行了修正,使之满足质量分数保极值原理.而不作修改的算法则不能保证质量分数在[0,1]范围.数值实验验证了该方法有效.     

All-optical mass sensing with coupled mechanical resonator systems

With the small mass, large quality-factor and high frequency, mechanical resonators (MRs) will ultimately find usage in a broad range of applications, such as electrometry, optomechanical/electromechanical signal processing, and mass detection. In this review, we focus on a particular MR application: mass sensing in an all-optical domain. Compared to the mass detection based on the electrical techniques, we have proposed an optical protocol to weigh the external particles deposited onto the surface of a mechanical resonator. This protocol, which is so far the first method to deal with the mass sensing in an all-optical domain, is based on some coupled mechanical resonator systems. Here we review our recent optical mass sensors comprehensively. These all-optical mass sensors have the potential to break through the limitation of frequency restriction and to enhance the sensitivity of mass detection.     

含整体单极子黑洞场中的吸附和辐射

本文研究了在含整体单极子的黑洞场中质量亏损效应,计算了被吸附的(落向质量中心的)中性粒子的质量亏损,进而计算了被吸附的质量球壳以及极限情况下质量球的质量亏损.这些物质的质量亏损最终将转化为能量辐射. 关键词： 广义相对论 整体单极子 黑洞 质量亏损     

A BODY MASS DEPENDENT MECHANICAL IMPEDANCE MODEL FOR APPLICATIONS IN VIBRATION SEAT TESTING

A three degree-of-freedom model is proposed to predict the biodynamic responses of the seated human body of different masses. A baseline model is initially derived to satisfy both the mean apparent mass and seat-to-head transmissibility responses proposed in ISO/DIS 5982:2000 applicable for mean body mass of 75 kg. The validity of the resultant generic mass dependent model is verified by comparing the apparent mass and driving-point mechanical impedance responses computed for total body masses of 55, 75 and 90 kg with the range of idealized values proposed for body masses within the 49-93 kg range. Considering the lack of data that could be found to define the apparent mass/mechanical impedance of subjects with different body masses when applying the experimental conditions defined in ISO/DIS 5982:2000, an attempt is made to adapt the parameters of the base model to fit the measured apparent mass data applicable to groups of automobile occupants within different mass ranges. This is achieved through constrained parametric optimization which consists of minimizing the sum of squared errors between the computed response and the mean apparent mass data measured for automobile occupants within four mass groups: less than 60 kg, 60·5-70·5 kg, 70·5-80 kg and above 80 kg. The results show a reasonably good agreement between the model responses and the measured apparent mass data, particularly at frequencies below 10 Hz. The results suggest that the proposed mass dependent model can effectively predict the apparent mass responses of automobile occupants over a wide range of body masses and for two different postures: passenger (hands-in-lap) and driver (hands-on-steering wheel) postures.     

利用非对称核物质状态方程对中子星的质量和半径的研究

在温度、密度及同位旋相关的核物质状态方程的基础上,通过求解Tol-man-Oppenheimer?Volkoff方程得到了中子星的质量与中心密度的关系,发现随着中心密度的变化,中子星存在一个最大质量.同时计算结果表明,中子星的最大质量与核物质状态方程的不可压缩系数、有效质量及对称能强度系数等密切相关.对中子星半径的研究表明,较硬的核物质状态方程给出的中子星半径较大,而且较大的对称能强度系数和较大的核子有效质量也会给出较大的中子星半径.     

Fundamental aspects of FT-ICR and applications to chemistry

Fourier transform ion cyclotron resonance (FT-ICR) spectroscopy, a modern form of mass spectrometry whose advantages were first demonstrated in our laboratory in 1974, is characterized by ultrahigh mass resolution, wide mass range, high speed and automatic mass calibration. Together with the FT-ICR double resonance experiment, these advantages make FT-ICR a powerful technique for studying complex ion/molecule reaction pathways and for general problems in analytical mass spectrometry. In addition, the high resolution principles of FT-ICR have been widely adopted around the world for precise mass measurements of nuclides.     

Mass Spectrometry,Review of the Basics: Electrospray,MALDI, and Commonly Used Mass Analyzers

Abstract

Mass spectrometry (MS) has progressed to become a powerful analytical tool for both quantitative and qualitative applications. The first mass spectrometer was constructed in 1912 and since then it has developed from only analyzing small inorganic molecules to biological macromolecules, practically with no mass limitations. Proteomics research, in particular, increasingly depends on MS technologies. The ability of mass spectrometry analyzing proteins and other biological extracts is due to the advances gained through the development of soft ionization techniques such as electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) that can transform biomolecules into ions. ESI can efficiently be interfaced with separation techniques enhancing its role in the life and health sciences. MALDI, however, has the advantage of producing singly charges ions of peptides and proteins, minimizing spectral complexity. Regardless of the ionization source, the sensitivity of a mass spectrometer is related to the mass analyzer where ion separation occurs. Both quadrupole and time of flight (ToF) mass analyzers are commonly used and they can be configured together as QToF tandem mass spectrometric instruments. Tandem mass spectrometry (MS/MS), as the name indicates, is the result of performing two or more sequential separations of ions usually coupling two or more mass analyzers. Coupling a quadrupole and time of flight resulted in the production of high-resolution mass spectrometers (i.e., Q-ToF). This article will historically introduce mass spectrometry and summarizes the advantages and disadvantages of ESI and MALDI along with quadrupole and ToF mass analyzers, including the technical marriage between the two analyzers. This article is educational in nature and intended for graduate students and senior biochemistry students as well as chemists and biochemists who are not familiar with mass spectrometry and would like to learn the basics; it is not intended for mass spectrometry experts.