Study of low-temperature plasma between rotating electrodes

Results are presented from experimental studies of the electrophysical and spatiotemporal characteristics of a dielectric barrier discharge operating in atmospheric-pressure air in a discharge cell with a dielectric barrier in the form of a rotating disc. One of the electrodes of the discharge cell was stationary and placed at a certain distance from the dielectric surface, and the following two versions of the second electrode were used: (i) a metal disc electrode was attached to the surface of the rotating dielectric disc, while on the opposite surface of the disc, there was a rectangular strip electrode that was at the same potential as a metal disc electrode and had a sliding contact with the dielectric; (ii) only the strip electrode with the sliding contact was connected to the high-voltage source, while the metal disc electrode was disconnected. Due to barrier rotation, the discharge operated in a pulse mode, although it was supplied from a dc voltage source. The current-voltage characteristic of such a dielectric barrier discharge was measured and analyzed. The number of microdischarge channels arising at the stationary electrode, the geometrical parameters of the microdischarge channels, and the discharge current were studied as functions of the supplied voltage, the distance between the stationary electrode and the dielectric surface, and the rotation velocity of the barrier disc.     

Study of the surface barrier discharge generated by electrodes in the form of a series of parallel metal strips

A surface discharge in a system where metal electrodes in the form of a series of parallel strips are positioned on the dielectric surface is studied. Analytical formulas for calculating the spatial distribution of the potential and the electric field in a discharge cell are derived. It is shown that the geometry of the metal electrodes should be taken into account (along with physical and chemical characteristics of the dielectric, the voltage applied to the electrodes, and other parameters of the system) for generation of the electric field with optimal configuration in the discharge cell. The obtained results are also applicable for analysis of discharge cells with a coplanar barrier discharge where metal electrodes are positioned in the dielectric at small depths. The results are of interest since a barrier discharge is one of the efficient methods for generating non-equilibrium plasma at high pressures for a variety of technological applications.     

Microbial biomass estimation

The development of a fully automated on-line monitoring and control system is very important in bioprocesses. One of the most important parameters in these processes is biomass. This review discusses different methods for biomass quantification. A general definition of biomass and biovolume are presented. Interesting concepts about active but not culturable cells considerations are included as well as concepts that must be taken into account when selecting biomass quantification technology. Chemical methods have had few applications in biomass measurement to date; however, bioluminescence can selectively enumerate viable cells. Photometric methods including fluorescence and scattered light measurements are presented. Reference methods including dry and wet weight, viable counts and direct counts are discussed, as well as the physical methods of flow cytometry, impedancimetric and dielectric techniques.     

Practical approaches to plant volatile analysis

Plants emit volatile organic compounds (VOCs) that play important roles in their interaction with the environment and have a major impact on atmospheric chemistry. The development of static and dynamic techniques for headspace collection of volatiles in combination with gas chromatography-mass spectrometry analysis has significantly improved our understanding of the biosynthesis and ecology of plant VOCs. Advances in automated analysis of VOCs have allowed the monitoring of fast changes in VOC emissions and facilitated in vivo studies of VOC biosynthesis. This review presents an overview of methods for the analysis of plant VOCs, including their advantages and disadvantages, with a focus on the latest technical developments. It provides guidance on how to select appropriate instrumentation and protocols for biochemical, physiological and ecologically relevant applications. These include headspace analyses of plant VOCs emitted by the whole organism, organs or enzymes as well as advanced on-line analysis methods for simultaneous measurements of VOC emissions with other physiological parameters.     

Microbial Biomass Estimation

ABSTRACT

The development of a fully automated on-line monitoring and control system is very important in bioprocesses. One of the most important parameters in these processes is biomass. This review discusses different methods for biomass quantification. A general definition of biomass and biovolume are presented. Interesting concepts about active but not culturable cells considerations are included as well as concepts that must be taken into account when selecting biomass quantification technology. Chemical methods have had few applications in biomass measurement to date; however, bioluminescence can selectively enumerate viable cells. Photometric methods including fluorescence and scattered light measurements are presented. Reference methods including dry and wet weight, viable counts and direct counts are discussed, as well as the physical methods of flow cytometry, impedancimetric and dielectric techniques.     

Electrophysical Parameters of an Atmospheric-Pressure Gas Discharge over a Potassium Dichromate Solution

Plasma Physics Reports - The electrophysical parameters of an atmospheric-pressure discharge that provide stable discharge burning over potassium dichromate solution are determined. The cathode...     

电化学法快速检测微生物的发展现状及趋势

自1898年Stewart提出利用电化学法检测微生物,电化学法已发展成为一种微生物快速检测的方法。根据检测的参数不同,电化学微生物检测法可以分为阻抗微生物法和介电常数法。阻抗法主要用于食品工业中微生物的快速检测(≤10⁷ cfu/mL),尤其用于易腐食品的微生物快速检测,以期实现在其发生明显腐败之前得到检测结果。而介电常数则用于生物发酵过程中的微生物数量的快速测定,可以实现在线监测微生物数量及生物发酵过程的实时控制。电化学法由于其检测迅速、可以实现自动化检测,在工业化生产中具有广阔的应用前景。     

Electrophysical monitoring of culture process of recombinant Escherichia coli strains

A novel method for monitoring the cell culture process has been developed. The method is based on the measurements of electro-optical characteristics of cell suspension, calculation of cell structure parameters, and the relationship between accumulation of proteins and change of these parameters' employment. Application of the method for the monitoring of a culture process of a recombinant strain is considered. The process of growth of recombinant strains cannot be sufficiently predicted and the direct measurement of cell culture parameters is unlikely to be the most efficient way of solving the problem.Escherichia coli plasmid-free and recombinant strains synthesizing the fusion protein consisting of tumor necrosis factor-alpha (TNF) and thymosin-alpha(1) (T) were studied. It was found that cytoplasmic electroconductivity of the strains investigated increased during the culture process. The accumulation of insoluble recombinant pThy-315-encoded hybrid protein TNF(SINGLEBOND)T in cells resulted in a decrease of the membrane dielectric permeability. To determine variations of membrane dielectric permeability the amount of insoluble recombinant protein TNF(SINGLEBOND)T in the bacterial cells should be calculated.     

Combinatorial biosynthesis of polyketides--a perspective

Since their discovery, polyketide synthases have been attractive targets of biosynthetic engineering to make 'unnatural' natural products. Although combinatorial biosynthesis has made encouraging advances over the past two decades, the field remains in its infancy. In this enzyme-centric perspective, we discuss the scientific and technological challenges that could accelerate the adoption of combinatorial biosynthesis as a method of choice for the preparation of encoded libraries of bioactive small molecules. Borrowing a page from the protein structure prediction community, we propose a periodic challenge program to vet the most promising methods in the field, and to foster the collective development of useful tools and algorithms.     

Electrooptic analysis of Escherichia coli cell suspension for assessment of antibacterial activity of levomycetin

Influence of chloramphenicol on electrophysiologic charateristics of Escherichia coli strains susceptible (K-12 strain) and resistant (pBR-325 strain) to it has been studied. It has been shown that incubation of susceptible bacteria with chloramphenicol leads to significant change of magnitute of electrooptic (EO) signal. Significant changes in orientantional spectra of suspensions of susceptible to chloramphenicol cells incubated with different concentrations of antibiotic were observed only on first five frequencies of orienting electric field (10 - 1000 kHz). Maximal change of EO signal occurred at chloramphenicol concentration 35 mg/ml and it didn't depend on the time of antibiotic exposure. Incubation of resistant strain pBR-325 with chloramphenicol did not lead to change of EO parameters of cell suspension. Potential for use of electrophysical analytic methods for assessment of antibacterial activity of chloramphenicol to control effect of antibiotics on microorganisms has been proposed.     

基于多源遥感数据的生态保护修复项目区监测方法评述

回顾了山水林田湖草生态保护修复项目的实施背景,针对生态保护修复项目监测监管范围广、技术难等问题,强调了基于多源遥感数据开展项目遥感监测的重要性与必要性。从监测指标拟定、遥感地物信息提取、多源遥感数据融合、动态变化检测等方面评述了基于多源遥感数据的生态保护修复项目区监测方法,包括基于中高空间分辨率遥感数据的地物信息提取、融合机器学习的非线性混合像元分析、基于混合像元分析的时空融合等。在总结技术和工作推进方面的优势、局限基础上,提出要结合实际工作,持续优化国土空间生态保护修复监测指标;充分挖掘遥感数据解析的相关算法潜力,提升地物信息提取和混合像元分析的精度;加强时空融合算法与变化检测方法的研究探索,加强相关方法的实践应用;以“山水林田湖草生态保护修复工程试点”项目为平台,建立稳定的国土空间生态保护修复遥感监测运行机制,加强科技创新,形成技术标准,指导工作开展。     

红树林生态系统遥感监测研究进展

随着现代遥感技术的迅速发展,遥感监测已经成为红树林生态系统变化监测的重要手段和方法。从遥感技术在生态系统变化监测应用领域入手,综述了国内外红树林遥感监测的发展历程,系统总结了遥感技术在红树林湿地动态、种间分类、群落结构(叶面积指数、冠幅、树高等)、生物量、灾害灾情(病虫害、风暴潮等)、景观格局动态、驱动力、红树林湿地保护与管理等领域应用现状,归纳了不同应用领域遥感监测的理论、方法及研究现状。指出我国在红树林遥感监测中存在的不足。提出红树林遥感监测应在分类标准体系规范化、分类精度提升、红树林生态学特征参数(物种多样性、优势度等)、生态系统环境空间演变过程及遥感监测的尺度效应方面加大研究力度。充分发挥区域综合监测模型在红树林生态系统变化遥感监测中的作用。     

Perspectives of fluorescence spectroscopy for online monitoring in microalgae industry

Microalgae industrial production is viewed as a solution for alternative production of nutraceuticals, cosmetics, biofertilizers, and biopolymers. Throughout the years, several technological advances have been implemented, increasing the competitiveness of microalgae industry. However, online monitoring and real-time process control of a microalgae production factory still require further development. In this mini-review, non-destructive tools for online monitoring of cellular agriculture applications are described. Still, the focus is on the use of fluorescence spectroscopy to monitor several parameters (cell concentration, pigments, and lipids) in the microalgae industry. The development presented makes it the most promising solution for monitoring up-and downstream processes, different biological parameters simultaneously, and different microalgae species. The improvements needed for industrial application of this technology are also discussed.     

The molecular genetics of cyanobacterial toxicity as a basis for monitoring water quality and public health risk

Toxic cyanobacteria pose a significant hazard to human health and the environment. The recent characterisation of cyanotoxin synthetase gene clusters has resulted in an explosion of molecular detection methods for these organisms and their toxins. Conventional polymerase chain reaction (PCR) tests targeting cyanotoxin biosynthesis genes provide a rapid and sensitive means for detecting potentially toxic populations of cyanobacteria in water supplies. The adaptation of these simple PCR tests into quantitative methods has additionally enabled the monitoring of dynamic bloom populations and the identification of particularly problematic species. More recently, DNA microarray technology has been applied to cyanobacterial diagnostics offering a high-throughput option for detecting and differentiating toxic genotypes in complex samples. Together, these molecular methods are proving increasingly important for monitoring water quality.     

Multivariate statistical monitoring of batch processes: an industrial case study of fermentation supervision

This article describes the development of Multivariate Statistical Process Control (MSPC) procedures for monitoring batch processes and demonstrates its application with respect to industrial tylosin biosynthesis. Currently, the main fermentation phase is monitored using univariate statistical process control principles implemented within the G2 real-time expert system package. This development addresses integrating various process stages into a monitoring system and observing interactions among individual variables through the use of multivariate projection methods. The benefits of this approach will be discussed from an industrial perspective.     

Dielectric analysis for estimation of oil content in the mycelia of Mortierella alpina.

The dielectric behavior of the filamentous fungi Mortierella alpina SAM2104 and 1S-4, which produce polyunsaturated fatty acid enriched oil in the mycelia, was investigated. During the cultivation carried out in a 10-kL fermentor for 12-15 days, the relative permittivity and conductivity of the broth were measured in the frequency range of 100 kHz to 30 MHz. The dielectric parameters, i.e., the amplitude of dielectric relaxation (Deltaepsilon) and the characteristic frequency (f(c)), were obtained by fitting the Cole-Cole equation to the observed dielectric relaxation, and the conductivity of the medium (kappa(a)) was also measured. The value of Deltaepsilon gradually increased from the second day through the end of cultivation, suggesting that volume fraction of the cell increased with oil accumulation. The conductivity of the cytoplasm (kappa(i)) was calculated from the experimental values of f(c) and kappa(a), using a theoretical equation based on an ellipsoidal cell model. As a result, good correlation between the calculated kappa(i) and the oil content was obtained. These findings indicate that dielectric analysis enables us to estimate the oil content in the mycelia of oleaginous fungi and also provides a useful tool for monitoring cell growth and for controlling the cultivation process.     

Dielectric Properties Based Detection of Heavy Metal Contaminated Soil in the Frequency Range from 10 MHz to 1 GHz

Physical parameters based electromagnetic methods are promising technologies to detect contaminated sites. In these methods, the dielectric property is a key parameter. In this paper, we studied the dielectric characteristics of heavy metal contaminated soil. The chromium contaminated soil was made into samples, and the open-ended coaxial line was adopted as the measurement method. Experiments were conducted in the frequency band between 10 MHz and 1 GHz. The results showed that the complex permittivity, including the real part and the imaginary part, changes as the ionic content changes. Especially, at low frequencies (<50 MHz), the complex permittivity increases significantly with the increase of ionic content. In addition, it also could be seen that the water content of the soil also affects the complex permittivity. We proposed to adopt the drying method or the Time Domain Reflection method to determine the water content. The dielectric parameters are most affected by the ionic content after knowing the water content. Therefore, it is feasible to detect heavy metal contaminated sites based on dielectric properties.     

Method for monitoring deletions in the aflatoxin biosynthesis gene cluster of Aspergillus flavus with multiplex PCR

The report presents a rapid, inexpensive and simple method for monitoring indels with influence on aflatoxin biosynthesis within Aspergillus flavus populations. PCR primers were developed for 32 markers spaced approximately every 5 kb from 20 kb proximal to the aflatoxin biosynthesis gene cluster to the telomere repeat. This region includes gene clusters required for biosynthesis of aflatoxins and cyclopiazonic acid; the resulting data were named cluster amplification patterns (CAPs). CAP markers are amplified in four multiplex PCRs, greatly reducing the cost and time to monitor indels within this region across populations. The method also provides a practical tool for characterizing intraspecific variability in A. flavus not captured with other methods.

Significance and Impact of the Study

Aflatoxins, potent naturally‐occurring carcinogens, cause significant agricultural problems. The most effective method for preventing contamination of crops with aflatoxins is through use of atoxigenic strains of Aspergillus flavus to alter the population structure of this species and reduce incidences of aflatoxin producers. Cluster amplification pattern (CAP) is a rapid multiplex PCR method for identifying and monitoring indels associated with atoxigenicity in A. flavus. Compared to previous techniques, the reported method allows for increased resolution, reduced cost, and greater speed in monitoring the stability of atoxigenic strains, incidences of indel mediated atoxigenicity and the structure of A. flavus populations.     

The physical properties of the synovial fluid as a lubrication of joints

The properties of the synovial fluid and the results of the electrophysical studies of the fluid by the thermoelectret method are briefly described. The interrelation between current peaks on the thermostimulated current spectra of thermostimulated currents of the synovial fluid and the liguid-crystalline state of its components was established. The results can be used for developing the methods of diagnostics of synovial joint diseases and design of artificial joints.     

Estimating the dielectric constant of the channel protein and pore

When modelling biological ion channels using Brownian dynamics (BD) or Poisson–Nernst–Planck theory, the force encountered by permeant ions is calculated by solving Poisson’s equation. Two free parameters needed to solve this equation are the dielectric constant of water in the pore and the dielectric constant of the protein forming the channel. Although these values can in theory be deduced by various methods, they do not give a reliable answer when applied to channel-like geometries that contain charged particles. To determine the appropriate values of the dielectric constants, here we solve the inverse problem. Given the structure of the MthK channel, we attempt to determine the values of the protein and pore dielectric constants that minimize the discrepancies between the experimentally-determined current–voltage curve and the curve obtained from BD simulations. Two different methods have been applied to determine these values. First, we use all possible pairs of the pore dielectric constant of water, ranging from 20 to 80 in steps of 10, and the protein dielectric constant of 2–10 in steps of 2, and compare the simulated results with the experimental values. We find that the best agreement is obtained with experiment when a protein dielectric constant of 2 and a pore water dielectric constant of 60 is used. Second, we employ a learning-based stochastic optimization algorithm to pick out the optimum combination of the two dielectric constants. From the algorithm we obtain an optimum value of 2 for the protein dielectric constant and 64 for the pore dielectric constant.