Sampling and Sample Homogeneity as Introductory Topics in Analytical Chemistry Undergraduate Courses

This work deals with the development of an experiment to evaluate the effect of sample characteristics on precision and accuracy of the sampling step. Parameters such as sample homogeneity, particle sizes, and sample mass were evaluated by analyzing the standard deviations (n = 3) obtained for Ca, Fe, Mg, Na, P, S, and Zn determinations in a breakfast cereal sample by inductively coupled plasma optical emission spectrometry. The proposed experiment can improve the assimilation of important concepts such as sampling, sample representativity, precision and accuracy by undergraduate students in analytical chemistry laboratory courses.     

Determination of Slip Length in Couette Flow Based on an Analytical Simulation Incorporating Surface Interaction

An analytical simulation based on a new model incorporating surface interaction is conducted to study the slip phenomenon in the Couette flow at different scales.The velocity profile is calculated by taking account of the micro-force between molecules and macro-force from the viscous shearing effect,as they contribute to the achievement of the slip length.The calculated results are compared with those obtained from the molecular dynamics simulation,showing an excellent agreement.Further,the effect of the shear rate on the slip is investigated.The results can well predict the fluid flow behaviors on a solid substrate,but has to be proved by experiment.     

Estimation of Uncertainty in an Analytical Inverse Heat Conduction Solution

The method of sequential perturbations is applied to find the uncertainty in estimated surface temperature and heat flux from a two-dimensional analytical inverse heat conduction problem related to impinging jet quenching experiments. It is shown that for meaningful uncertainty estimates, the inverse solution itself must be formulated such that it can be interpreted as giving average surface conditions over a small period of time and space. A procedure for estimating the time and space resolution limits of the solution is proposed.     

Autofluorescence Detection in Analytical Chemistry and Biochemistry

Abstract

Label-free detection of molecules and particles based on native fluorescence excited at the ultraviolet (UV) region of the electromagnetic spectrum shows great potential for molecular analysis in life sciences. It offers simple, low-cost, and fast methods for sensitive detection of important biological analytes in nature forms. This article reviews the most significant research on label-free native fluorescence detection in analytical chemistry and biochemistry, with particular focus on the instrumental requirements and applications that cover papers published to the beginning of 2009. Future development directions for label-free optical biosensors based on native fluorescence are discussed.     

Microplasma Technology and Its Applications in Analytical Chemistry

Abstract

This review article describes some existing microplasma sources and their applications in analytical chemistry. These microplasmas mainly include direct current glow discharge (DC), microhollow-cathode discharge (MHCD) or microstructure electrode (MSE), dielectric barrier discharge (DBD), capacitively coupled microplasmas (CCμPs), miniature inductively coupled plasmas (mICPs), and microwave-induced plasmas (MIPs). The historical development and recent advances in these microplasma techniques are presented. Fundamental properties of the microplasmas, the unique features of the reduced size and volume, as well as the advantageous device structures for chemical analysis are discussed in detail, with the emphasis toward detection of gaseous samples. The analytical figures of merit obtained using these microplasmas as molecular/elemental-selective detectors for emission spectrometry and as ionization sources for mass spectrometry are also given in this review article.     

Analytical formula for two‐dimensional ring artefact suppression

Ring artefacts are the most disturbing artefacts when reconstructed volumes are segmented. A lot of effort has already been put into better X‐ray optics, scintillators and detectors in order to minimize the appearance of these artefacts. However, additional processing is often required after standard flat‐field correction. Several methods exist to suppress artefacts. One group of methods is based on minimization of the Tikhonov functional. An analytical formula for processing of a single sinogram was developed. In this paper a similar approach is used and a formula for processing two‐dimensional projections is found. Thus suppression of ring artefacts is organized as a two‐dimensional convolution of `averaged' projections with a given filter. Several approaches are discussed in order to find elements of the filter in a faster and accurate way. Examples of experimental datasets processed by the proposed method are considered.     

卟啉及其配合物在分析化学中应用进展

综述了卟啉及配合物在分析化学中的应用研究进展。重点介绍了其在光度分析、电化学、分子识别、探针等方面的应用。     

中英分析化学教材的几点差异

以常见的中英文分析化学教材为例,探讨中英文教材之间的几点差异,为实行分析化学双语或全英语教学的院系选择教材提供参考,同时为编写和国际接轨的教材提供依据。     

Incorporating Copper Nanoclusters into Metal‐Organic Frameworks: Confinement‐Assisted Emission Enhancement and Application for Trinitrotoluene Detection

Herein, a strategy for improving both the stability and the emission intensity of Cu nanoclusters based on their entrapment into metal‐organic frameworks (MOFs) is demonstrated. The latter effect reaches 20 times and is ascribed to a confinement‐assisted emission enhancement similar to the aggregation induced emission of fluorescent species in solution, evidenced by the prolonged emission lifetime. Cu nanoclusters are distributed homogeneously over the entire MOFs structure, as confirmed by combination of structural and elemental mapping studies. Toward potential applications of Cu nanocluster/MOF composites as chemical sensors, the authors demonstrate the selective quenching of their emission by 2,4,6‐trinitrotoluene attributed to specific electron‐withdrawing interactions with glutathione ligands on Cu clusters.     

Undergraduate Analytical Chemistry: To Use and Evaluate Organic Chelators for Spectrophotometric Determination of Iron

Abstract

An analytical chemistry laboratory project to use and evaluate pyridyl‐ and triazine‐containing chelators for spectrophotometric determination of iron is described. The “Iron Project” introduces students to UV‐visible spectrophotometry and Beer's law via hands‐on development and use of spectrophotometric methods for iron. Nine chelators are currently available for use. Students perform their proposed work, culminating in formal papers and posters. Student values of molar absorptivities (?_max) and λ_max for ligands 1–9 agree with published values to within ±15% (?_max) and ±3 nm (λ_max) for 75% of results obtained so far. Stoichiometries for Fe(II) chelates of ligands 1–5 are within ±1 mole of ligand of the published ratios. Student work shows a basic understanding of Beer's law as well as a need to improve writing, problem‐solving, and laboratory skills.     

核工程类专业引导课中的大学物理图解

核工程类专业是基于核科学与技术学科,面向核能与核技术行业领域人才培养需要而设置的本科类专业.物理学是核科学与技术的起源,大学物理是核工程类专业的重要基础课程.为此,在核工程类专业引导课上,构思和设计大学物理知识的溯源、建立与发展的图解,以帮助学生建立大学物理的知识框架,激发学习兴趣,科学合理规划学习安排.     

Comparison of Inductively Coupled Plasma with Classical Analytical Techniques in the Analysis of Southern Oregon Lithia Water: Inclusion of a Local Resource in the Undergraduate Chemistry Curriculum

Abstract

Lithia water, a community resource of local historical significance, is described as a central theme in the undergraduate analytical chemistry sequence. A statistical comparison of the classical determination of major cations (Na⁺, K⁺, Ca²⁺, Mg²⁺) and anions (HCO₃ ^?, Cl^?) reinforces statistical and charge‐balance concepts covered in analytical chemistry. Subsequent determination of these major cations by inductively coupled plasma (ICP) enables students to statistically evaluate the presence of bias between instrumental and classical methods. The effect of easily ionized elements on ICP calibration sensitivity and linearity via the use of cesium as an ionization suppressor is reported.     

Relay selection scheme based on deep reinforcement learning in wireless sensor networks

Cooperative communication technology has realized the enhancement in the wireless communication system’s spectrum utilization rate without resorting to any additional equipment; additionally, it ensures system reliability in transmission, increasingly becoming a research focus within the sphere of wireless sensor networks (WSNs). Since the selection of relay is crucial to cooperative communication technology, this paper proposes two different relay selection schemes subject to deep reinforcement learning (DRL), in response to the issues in WSNs with relay selection in cooperative communications, which can be summarized as the Deep-Q-Network Based Relay Selection Scheme (DQN-RSS), as well as the Proximal Policy Optimization Based Relay Selection Scheme (PPO-RSS); it further compared the commonly used Q-learning relay selection scheme (Q-RSS) with random relay selection scheme. First, the cooperative communication process in WSNs is modeled as a Markov decision process, and DRL algorithm is trained in accordance with the outage probability, as well as mutual information (MI). Under the condition of unknown instantaneous channel state information (CSI), the best relay is adaptively selected from multiple candidate relays. Thereafter, in view of the slow convergence speed of Q-RSS in high-dimensional state space, the DRL algorithm is used to accelerate the convergence. In particular, we employ DRL algorithm to deal with high-dimensional state space while speeding up learning. The experimental results reveal that under the same conditions, the random relay selection scheme always has the worst performance. And compared to Q-RSS, the two relay selection schemes designed in this paper greatly reduce the number of iterations and speed up the convergence speed, thereby reducing the computational complexity and overhead of the source node selecting the best relay strategy. In addition, the two relay selection schemes designed and raised in this paper are featured by lower-level outage probability with lower-level energy consumption and larger system capacity. In particular, PPO-RSS has higher reliability and practicability.     

混合式教学在大学物理“重修”课中的实践

针对大学物理重修课程存在的学生学习兴趣不高、课堂气氛沉闷、主动参与性差以及出勤率和及格率不高等问题,基于"网络教学综合平台"和"雨课堂",采取线上线下混合式教学模式,督促学生在课前、课中、课后进行课程的学习,实践表明在一定程度上提高了教与学的效果.     

Analytical Description of the Process of Influx of the Sample Material into an Alternating-Current Arc Discharge Plasma

Physical and mathematical models of the influx of the sample material into an alternating-current arc discharge plasma are suggested. Analytical expressions describing changes in the rate of influx of the base metal and impurities into the discharge have been derived. Experimental results on the rates of influx of elements from metal samples of gold and silver are presented. They are in good agreement with theoretical data.     

Incorporating H chemical shift determination into C-direct detected spectroscopy of intrinsically disordered proteins in solution

Exclusively heteronuclear ¹³C-detected NMR spectroscopy of proteins in solution has seen resurgence in the past several years. For disordered or unfolded proteins, which tend to have poor ¹H-amide chemical shift dispersion, these experiments offer enhanced resolution and the possibility of complete heteronuclear resonance assignment at the cost of leaving the ¹H resonances unassigned. Here we report two novel ¹³C-detected NMR experiments which incorporate a ¹H chemical shift evolution period followed by ¹³C-TOCSY mixing for aliphatic ¹H resonance assignment without reliance on ¹H detection.     

磁场中带电粒子阻尼运动的分析力学表示

研究带电粒子在磁场中作阻尼运动的分析力学表示. 首先, 求解运动微分方程的Birkhoff力学逆问题, 得到带电粒子的4个Rirkhoff表示; 其次, 导出4个状态空间中Lagrange表示和对应的4个位形空间中Lagrange表示; 第三, 构造出4个Hamilton函数; 最后, 从粒子运动的分析力学表示直接得到4个第一积分, 并求出运动方程的解.     

Process Analytical Chemistry: Applications of Ultraviolet/Visible Spectrometry in Environmental Analysis: An Overview

Abstract

Process analyzers based on the selective absorption of the ultraviolet (UV) and/or visible (VIS) radiation provide an on-line monitoring highly reliable of the composition and the industrial process control.

This review provides information about the technological advances in this area and its industrial applications, especially environmental applications.     

Process Analytical Chemistry: Applications of Near Infrared Spectrometry in Environmental and Food Analysis: An Overview

Abstract

This review provides a valuable source of information on the technological advances in near infrared absorption spectrometry area and its industrial applications, especially on the alimentary technology and environmental applications over biofuels.     

On the Plasma Chemistry of an RF Discharge Containing Aluminium Tri‐Isopropoxide Studied by FTIR Spectroscopy

In Ar and Ar/N₂ radio frequency (RF) discharges with admixtures of aluminium tri‐isopropoxide (ATI) the fragmentation of this metal‐organic precursor was studied by means of Fourier Transform Infrared (FTIR) spectroscopy using an optical long path cell providing an optical length of l = 17.2 m. The experiments were performed in an asymmetric capacitively coupled process plasma at a frequency of f = 13.56 MHz and at pres‐sure values in the range of p = 1–10.5 Pa. The discharge power was chosen between P = 10–100 W. Using FTIR spectroscopy the evolution of the concentrations of ATI and of six stable molecules, CH₄, C₂H₂, C₂H₄, C₂H₆, CO and HCN, was monitored under flowing conditions at gas flows of Φ_total = 0.5–14.5 sccm in the discharge. The concentrations of the reaction products were measured tobe between 2 x 10¹² molecules cm^–3 as e.g. found for C₂H₄and C₂H₆, and 5 x 10¹³ molecules cm^–3, as e.g. in the case of CO. In the plasma a complete dissociation of the precursor ATI was found at a power value of about P = 80 W independent on the admixture of Ar or N₂. The fragmentation efficiency (F_E) of the reaction products which originate from the ATI molecules ranges between 0.2 and 4 x 10¹⁶ molecules J^–1 while the fragmentation rate (F_R) reached up to 2.5 x 10¹⁸ molecules s^–1. The multi component detection ability of the spectrometer served to analyse the carbon balance of the by‐product formation. For all experiments, the carbon balance never exceeded 25%. Therefore, in the plasmas the majority of the provided carbon is most likely deposited at the reactor walls or forms dust particles or higher molecular C_xH_y. The conversion efficiencies (C_E) of the produced molecular species ranges between 0.1 x 10¹⁵ molecules J^–1 for C₂H₄ and 5 x 10¹⁵ molecules J^–1 for C₂H₆ depending on the discharge conditions of the RF plasma. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)