Bump-hunting for the proficiency tester--searching for multimodality

Kernel density estimation is a method for producing a smooth density approximation to a dataset and avoiding some of the problems associated with histograms. If it is used with a degree of smoothing determined by a fitness for purpose criterion, it can be applied to proficiency test data in order to test for multimodality in the z-scores. The bootstrap is an essential additional technique to determine how rugged the initially estimated kernel density is: the random resampling of the data in the bootstrap simulates a complete blind repeat of the proficiency test. In addition, useful estimates of the standard error of a mode can be thus obtained. It is suggested that a mode and its standard error can be used as an assigned value and its standard uncertainty.     

Call for nominations for the Heinrich-Emanuel-Merck Award

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Call for nominations for the Heinrich-Emanuel-Merck Award     

Calibration function for the orbitrap FTMS accounting for the space charge effect

Ion storage in an electrostatic trap has been implemented with the introduction of the Orbitrap Fourier transform mass spectrometer (FTMS), which demonstrates performance similar to high-field ion cyclotron resonance MS. High mass spectral characteristics resulted in rapid acceptance of the Orbitrap FTMS for Life Sciences applications. The basics of Orbitrap operation are well documented; however, like in any ion trap MS technology, its performance is limited by interactions between the ion clouds. These interactions result in ion cloud couplings, systematic errors in measured masses, interference between ion clouds of different size yet with close m/z ratios, etc. In this work, we have characterized the space-charge effect on the measured frequency for the Orbitrap FTMS, looking for the possibility to achieve sub-ppm levels of mass measurement accuracy (MMA) for peptides in a wide range of total ion population. As a result of this characterization, we proposed an m/z calibration law for the Orbitrap FTMS that accounts for the total ion population present in the trap during a data acquisition event. Using this law, we were able to achieve a zero-space charge MMA limit of 80 ppb for the commercial Orbitrap FTMS system and sub-ppm level of MMA over a wide range of total ion populations with the automatic gain control values varying from 10 to 10⁷.     

Reply for the comment

We have read the comment on our paper "Selective adsorption of tannins onto hide collagen fibres, Science in China, Series B, 2003, 46(5): 495-504".     

《盲校义务教育化学课程标准》解读

在《全日制盲校义务教育课程设置实验方案》核心思想的指导下,将之与普通学校《义务教育化学课程标准(2011年版)》对比分析,结合盲校教育对象及其教学特点,解读《盲校义务教育化学课程标准(2016年版)》的理论基础、研制原则和修订内容等。     

A Convenient Procedure for the Preparation of Reactive Zinc for the Reformatsky Reaction

A reactive zinc powder is obtained by addition of ZnCl₂ to a lithium dispersion suspended in ether. Reformatsky Reactions with the zinc powder are described.     

On the necessity for invoking a free-ion-like model for the super ionic conductors

Rice and Roth's free-ion-like model of ionic conduction relates the oscillator frequency, the hopping length, the migration activation energy, and the mass of the jumping ion. They applied their formula to atomic self-diffusion in metals and interpreted the agreement of the calculated oscillator frequencies and the observed Debye frequencies as evidence for the validity and uniqueness of their model. However, an expression of the same form can be derived for a simple harmonic oscillator hopping type model, and therefore the necessity for invoking a free-ion-like model is questionable.