Optimizing of Balances of the Second Generation

At the 3rd Conference on Vacuum Microbalance Techniques in Los Angeles in 1962, we suggested the use of the equation of motion of a balance T=J+α+kα+Cα for the calculation of the unknown torque T, and the measurement for that purpose of the values of all the other quantities in this equation. The present paper discusses the consequences of two sources of error relevant for this method. First, the errors caused in the first and second derivatives of the deflection are considered, deduced from two or three deflection measurements separated by small time intervals. Secondly, the consequences of the errors caused by the uncertainties in the deflection measurements are discussed. Consideration of the two errors together leads to an optimal set of values of parameters for the balance handling. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Uncertainty of Weighing Data Obtained with Electronic Analytical Balances

Weighing is a common task in any chemical laboratory and weighing data are associated with some uncertainty, as this is common with all other working procedures and their data. This paper presents the influence factors which are part of the combined measurement uncertainty of a mass determination and their interplay, namely the technical specifications of the balance (repeatability, nonlinearity, sensitivity tolerance, and temperature coefficient of the sensitivity) and the effect of air buoyancy. Depending on the net and gross weight, the densities involved (density of air and of the weighing object in relation to the density of the reference weights) and the uncertainties of these densities the relative uncertainty of weighing data is often in the 10^–5 to 10^–4 range (10 to 100ppm). It must be kept in mind that such low values can only be obtained with simple weighing goods, i.e. in the absence of disturbances such as electrostatic charges, air drafts, evaporation, or water adsorption phenomena.     

The Impact of Control on the Development of Recording Balances

I am honored by the invitation to give a lecture at this Conference on Vacuum Microbalance Techniques. I have very good memories of such meetings over 35 years, first in the USA, and then alternating in Europe and Africa. Those who have participated in several conferences of this series know that major developments from manually operated to automated balances have been presented there and documented in the Proceedings of these Conferences. I would like to give a few examples from my own work. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Damping of Balances

The paper gives a survey of the history of damping methods for balances. Representation on Egyptian drawings demonstrate that the person performing the weighing shortened the measuring time by holding the suspension cords and touching the beam. By means of delimiters, the Romans constricted the deflection amplitudes. In the 19th century, the movements of precision balances were damped with a brush. For analytical balances, locking mechanism were developed, often combined with levers lifting the weighing scales and the beam in order to relieve the knife-edges. Half-arresting was used to curtail weighings. Air damping was invented by Arzberger in 1875, and eddy current damping by Marek in 1906. In electronic balances, lag, lead and filter elements and absorptive attenuators are used. For digital balances, the fast-reacting nullification of eddy signals is applied. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Accuracy in Microweighing in Vacuum and Controlled Environments

Accurate weighing depends on both physical factors and the weighing technique. There are two categories of physical factors: the location and support of the balance, and physical phenomena. Important such phenomena include processes of heat transfer by convection and radiation in rarefriction gases, Archimedes buoyancy, electrostatic, magnetostatic and gravitational effects, etc. Surveys of disturbances which affect the accuracy of weighing in vacuum or in controlled environments have been published elsewhere. This paper describes a high-vacuum apparatus connected to a Cahn RG ultramicrobalance. The system was adapted for investigations of long-time kinetic runs of oxygen loss in oxide superconductors in dynamic vacuum, and of other gas - solid interactions. Typical calibration curves for 'not fully compensated system' are presented in controlled environments at cryogenic temperatures. This revised version was published online in July 2006 with corrections to the Cover Date.     

固相萃取真空装置的设计与应用

目前常用的样品预处理方法——固相萃取（ＳＰＥ）,具有高效、快速、方便和高选择性等特点。国家色谱研究分析中心新近开发成功的ＳＰＥ真空装置是ＳＰＥ方法的重要组成部分,能同时处理１２个样品,利用其独特的转动上盖,可方便地在ＳＰＥ各步骤间任意切换,以收取所需要的组分。给出了利用ＳＰＥ真空装置并结合高效液相色谱法（ＨＰＬＣ）分离人血清中胆汁酸的应用实例。     

Characterization of Vacuum Brazed Joints for Superconducting Cavities

Brazing is a process to join metallic and non-metallic materials, without any melting or plastic state of the base metals. The poor wettability of ceramic may be improved by the use of alloys containing an element capable of changing the chemistry of the ceramic surface (active braze). In this paper we propose the substitution of the Electron Beam welding with Vacuum Brazing in order to join the resonator components, Nb, Cu OFHC, and Al₂O₃, with stainless steel flanges, in superconducting resonant cavities. Several combinations of brazed joints have been tested. The characterization of the joints has been performed with SEM-EDS and MICROPIXE. All the joints fulfil the requirements.     

The Flash Vacuum Thermolysis of N-Acyl Imidates

In the flash vacuum thermolysis of methyl N-acyl imidates, the loss of methanol is consistent with the intermediacy of an N-acylketenimine. Recombination and further reactions may lead to the array of products observed in these thermal reactions. An attempt to trap the intermediate N-acylketenimine by an intramolecular [2 + 2] cycloaddition was unsuccessful.     

碱性条件下废轮胎真空热裂解研究

研究了废轮胎橡胶粉在450℃～600℃真空热解系统中热解的特性,以及温度和添加Na2CO3、NaOH对热解气液态产物的影响。实验表明,真空下废轮胎热解油收率在550℃时达到最大值,为48%左右。添加3%的NaOH能明显促进废轮胎橡胶热解,480 ℃时油产率达到最大值49.66%,随后随着温度的升高油产率呈现下降趋势。添加3%的Na2CO3对热解的促进作用不明显。热解气体产物主要有H2、CO、CH4、CO2、C2H4、C2H6以及少量其他化合物。NaOH的加入使气体产品中的H2相对体积分数明显增加,而CH4、CO、C2等的体积分数降低。通过GC和GC-MS分析热解石脑油发现,热解油品中含有11%以上的柠檬油精。     

Image Formation in Low Vacuum SEM

The role of positive gaseous ions in the formation of secondary electron images in low vacuum scanning electron microscopes is discussed. This paper describes the charging processes and related effects that occur during high vacuum imaging of insulators and then discusses the influence of ions on those processes. The ions are responsible for a number of phenomena, including distortion of the electric field above and below the specimen surface due to space charge, removal of excess negative charge from the specimen, alteration of the specimen surface barrier, and scavenging/filtering of the secondary electron emission. The resulting electron-specimen-ion interactions can give rise to interesting contrast effects that are unique to this class of instruments.     

全自动比表面与孔隙度分析仪真空故障的排查与维护

针对ASAP2020M+C型全自动比表面与孔隙度分析仪开机或连续运行过程中出现的油泵和干泵真空故障,导致样品脱气处理和分析测试无法进行的问题,仔细分析查找原因,进行了有效维护.     

Preparation and Characterization of Chitosan-Graphene Transducer Assembled via Vacuum Assisted Self-assembly (VASA) Method for Trimethylamine Sensing

A reduced graphene oxide/chitosan (rGO/Chi) nanocomposite film for chemoresistive trimethylamine sensing was prepared by solution-phase mixing and deposited on nylon membrane via vacuum assisted self-assembly (VASA) method. The film was analysed using Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The electrical property of the prepared films were measured by four-point probe measurement. Using 0.40% volume fraction (v.f) it was exposed to trimethylamine vapour and its electrical resistance quickly changed. The composite film sensor exhibited linear range from 23 to 230mg/L (r²= 0.9774) and the calculated limit of detection was 20.56mg/L. It exhibited a repeatable response to trimethylamine gas.     

Enlarged Area A-type Zeolite Membranes Prepared by Vacuum Seeding Method

High quality A-type zeolite membranes, with enlarged area over 70 cm^2, were successfully synthesized on a tubular ~-A1203 support by applying the vacuum seeding method.     

A Brief History of the Balance in Society

One of the earliest measuring instruments used by human beings was the balance; evidence of this dates back more than 5.000 years. Initially, the weights of goods were measures rather of value than of mass. Besides yardsticks and graduated cups, scales are today the most widespread instruments, found in almost all laboratories, factories and households. Indeed, the balance accompanies us from birth to death. The balance very early achieved a metaphorical meaning and was used for the comparison of ethical values. It first appeared as an instrument in the death tribunal in Egyptian religion and later in Christianity. In the hands of the Grecian Gods, weighing was a deciding factor as concerns victory or death. In Judaism and for the Romans, scales become the symbol of justice. Several trade and handicraft guilds currently use the balance as an attribute, demonstrating in this way their sincerity and accuracy. The balance is of dubious significance in astrology, as one of the signs of the zodiac. This revised version was published online in July 2006 with corrections to the Cover Date.     

Flash Vacuum Thermolysis of Phenylcyclopropanecarbaldoximes and Its Methyl Ethers

Flash vacuum thermolysis of 1-phenylcyclopropane-1-carbaldoxime at 500 °C produced mainly 3-phenylpyrrole. The products after thermolysis of its oxime methyl ether were α-methoxymethylstyrene, α-methylstyrene, and a dimer 2,5-dipheny 1-1,5-hexadiene.     

Survey on mass determination systems: Part I. Fundamentals and history

The influence of mass and force on the frequency of vibrating bodies today is widely applied. In Part I of the survey the historical roots are reviewed and the physical principles of the several arrangements modes of operation explained.This revised version was published online in November 2005 with corrections to the Cover Date.     

辽河减压渣油中非卟啉镍的XAFS研究

为获得石油中非卟啉Ni的结构信息，采用荧光法对辽河减压清油中非叶琳Ni的 K边进行了XAFS测试非叶琳Ni第一配位壳层的结构和Ni-四苯基卟啉（NiTPP）的配 位结构类似，也是4个氮原子，呈平面四方构型为0.192nm，在较高的配位壳层，二 者存在一定的差别此外，根据XAFS测试，对石油中非卟啉Ni讨论.     

Heat Treatment Condition Influence on Novokuibyshevsk Vacuum Residue Component Composition

The article presents the information about thermal degradation of Novokuibyshevsk vacuum residue and change of products composition during this process. The optimal conditions for the thermal destruction of vacuum residue components were established. The regularities of material balance composition change, S_general were determined depending on cracking conditions. The basic directions of resin-asphaltene component transformations were identified, changes in their structural-group parameters in the process of initiated cracking were analyzed. Conducting of Novokuibyshevsk vacuum residue thermolysis leads to deep resins-asphaltenes average molecules structure characteristic changes. Developed alkyl and naphthenic moieties, which are presented in initial molecule, undergo degradation, amount of structural blocks in resins and asphaltenes molecules reduces, their average size decreases. Also the reduction in total content of the rings (saturated and aromatic) was established in average structural unit, at the same time decrease of rings substitution and length of the aliphatic fragments can be observed. In general the process of vacuum residue thermal cracking causes partial degradation of saturated (aliphatic and naphthenic) fragments and, partially, aromatic rings, which contain heteroatomic elements.     

Physicochemical and Quality Properties of Dried Courgette Slices: Impact of Vacuum Impregnation and Drying Methods

The aim of this study was to determine the effects that the type of impregnating solution and drying method (freeze drying (FD) and vacuum drying (VD) at 45 °C and convective drying (CD) at 50, 60, and 70 °C) had on the physicochemical and quality properties of courgettes. Courgette slices were vacuum-impregnated (6 kPa) in freshly squeezed onion, kale, and onion and kale (50:50) juices with 3% NaCl solution (N). The application of vacuum impregnation (VI) with impregnating solutions from freshly squeezed onions and kale had a beneficial effect on the bioactive values of courgette. The highest contents of quercetin (41.84 μg/g d.m.) and carotenoids (276.04 μg/g d.m.) were found in courgette impregnated with onion juice after freeze drying. The highest values of lutein and zeaxanthin (216.42 μg/g d.m.) were recorded for courgette impregnated with kale juice and convective dried. By analysing the kinetics of convective drying, the best matching of the logistic model was found. Increasing the drying process temperature from 50 to 70 °C reduced the drying time from 15% to 36%, depending on the type of impregnating solution used. Water activity < 0.6 was recorded for courgette dried by freezing, vacuum, and convection at 60 and 70 °C. Conclusions: The vacuum impregnation process and the impregnation solutions from freshly squeezed vegetables can be used to develop new snacks with high levels of bioactive compounds. The FD method is the most appropriate considering both the bioactive compounds content and the obtained colour and water activity.