Electrochemical system for the simultaneous monitoring of algal motility and phototaxis

A compact electrochemical system equipped with dual electrodes was developed for the simultaneous monitoring of motility and phototaxis of flagellates. Photoinduced behavior of unicellular flagellate alga Chlamydomonas reinhardtii in the presence of diltiazem, azide, or ethanol was recorded as changes in the redox currents for a coexisiting redox marker. The system responded to the chemicals in significantly different ways; it allows qualitative and semiquantitative evaluation of influences of chemical species on the algal cells. Therefore, the present system is potentially applicable to not only aquatic risk assessment but also screening of newly found and synthesized compounds in terms of hazard probability and severity. Additionally, it unveiled some new and interesting behaviors of the algae.     

Polarization analyses of aerial images produced by an optical lithography system

The influence of polarization on the image formation of one-dimensional periodic patterns in a projection optical lithography system has been investigated. Assuming a linear polarizer at thelens pupil, I derived a simple expression representing the image intensity as the summation over spatial-frequency harmonics as well as three orthogonal polarizations. I calculated the coefficient for each image component as a function of the pattern frequency by independently varying the degree of partial coherence such that the image qualities of the two extreme polarization cases could be thoroughly compared.     

空分生产气体成分监测系统的建立

介绍了国内大中型空分设备气体成分监测系统存在的问题及原因 ,分析了建立一个完整的气体成分监测系统应包含的四个方面及一套大中型空分设备需配套分析仪器的种类 ,最后论述了监测系统及分析仪器发挥其作用需建立的质量标准体系。     

Needle-type dual microsensor for the simultaneous monitoring of glucose and insulin

A miniature needle-type sensor suitable for the simultaneous amperometric monitoring of glucose and insulin is described. The integrated microsensor consists of dual (biologically and chemically) modified carbon-paste working electrodes inserted into a 14-guage needle. The glucose probe is based on the biocatalytic action of glucose oxidase, and the insulin one relies on the electrocatalytic activity of ruthenium oxide. The analytical performance of the dual sensor is assessed under flow injection conditions. The needle dual detector exhibits a very rapid response to dynamic changes in the concentrations of glucose and insulin. No apparent cross reactivity is observed in mixtures containing millimolar glucose levels and nanomolar insulin concentrations. The response is highly linear (to at least 1000 nM insulin and 14 mM glucose) and reproducible (RSD = 2.6-4.1%). The combination microsensor holds great promise for real-time measurements of the insulin/glucose ratio and for improved management of diabetes.     

Novel nanostructure-based electrochemical sensor for simultaneous determination of dopamine and acetaminophen

A carbon-paste electrode modified with a novel molybdenum (VI) complex and carbon nanotubes have been applied to the electrocatalytic oxidation of dopamine (DA) which reduced the overpotential by about 125 mV with obviously increase the current response. Due to its strong electrocatalytic activity towards DA, the modified carbon-paste electrode can resolve the overlapped voltammetric waves of DA and acetaminophen (AC) into two well-defined voltammetric peaks with peak-to-peak separation in potentials of about 230 mV. This property allows to selective determination of DA in the presence of AC. The transfer coefficient (a) for the electrocatalytic oxidation of DA and diffusion coefficient of this substance under the experimental conditions were also investigated. In phosphate buffer solution of pH 7.0, the oxidation current increased linearly with two concentration intervals of DA, one is 0.1 to 40.0 μM and, the other is 40.0 to 800.0 μM. The detection limit (3σ) obtained by DPV was 76.0 nM. The proposed method was successfully applied to the determination of DA, and AC in some commercial pharmaceutical samples.     

Synthesis and characterization of monodispersed orthorhombic manganese oxide nanoparticles produced by Bacillus sp. cells simultaneous to its bioremediation

A heavy metal resistant strain of Bacillus sp. (MTCC10650) is reported. The strain exhibited the property of bioaccumulating manganese, simultaneous to its remediation. The nanoparticles thus formed were characterized and identified using energy dispersive X-ray analysis (EDAX), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (PXRD) and atomic force microscopy (AFM). When the cells were challenged with manganese, the cells effectively synthesized nanoparticles of average size 4.62 ± 0.14 nm. These were mostly spherical and monodispersed. The ex situ enzymatically synthesized nanoparticles exhibited an absorbance maximum at 329 nm. These were more discrete, small and uniform, than the manganese oxide nanoparticles recovered after cell sonication. The use of Bacillus sp. cells seems promising and advantageous approach. Since, it serves dual purposes of (i) remediation and (ii) nanoparticle synthesis. Considering the increasing demand of developing environmental friendly and cost effective technologies for nanoparticle synthesis, these cells can be exploited for the remediation of manganese from the environment in conjunction with development of a greener process for the controlled synthesis of manganese oxide nanoparticles.     

Integrated microdevice for long-term automated perfusion culture without shear stress and real-time electrochemical monitoring of cells

Electrochemical techniques based on ultramicroelectrodes (UMEs) play a significant role in real-time monitoring of chemical messengers' release from single cells. Conversely, precise monitoring of cells in vitro strongly depends on the adequate construction of cellular physiological microenvironment. In this paper, we developed a multilayer microdevice which integrated high aspect ratio poly(dimethylsiloxane) (PDMS) microfluidic device for long-term automated perfusion culture of cells without shear stress and an independently addressable microelectrodes array (IAMEA) for electrochemical monitoring of the cultured cells in real time. Novel design using high aspect ratio between circular "moat" and ring-shaped micropillar array surrounding cell culture chamber combined with automated "circular-centre" and "bottom-up" perfusion model successfully provided continuous fresh medium and a stable and uniform microenvironment for cells. Two weeks automated culture of human umbilical endothelial cell line (ECV304) and neuronal differentiation of rat pheochromocytoma (PC12) cells have been realized using this device. Furthermore, the quantal release of dopamine from individual PC12 cells during their culture or propagation process was amperometrically monitored in real time. The multifunctional microdevice developed in this paper integrated cellular microenvironment construction and real-time monitoring of cells during their physiological process, and would possibly provide a versatile platform for cell-based biomedical analysis.     

Simultaneously monitoring gene expression kinetics and genetic noise in single cells by optical well arrays

An optical fiber based well array platform was used for simultaneous, dynamic gene expression monitoring from hundreds of individual live Escherichia coli cells carrying promoter-fluorescent reporter gene fusions. High information content about gene expression kinetics and cell-to-cell gene expression variability can be collected from a single experiment. These data are invaluable for investigating gene regulation and gene networks as well as for systems biology applications.     

Autonomous multielectrode system for monitoring the interactions of isoflavonoids with lung cancer cells

The cytotoxic effect of isoflavonoids in the development of different forms of cancer has been reported by epidemiological and dietary studies. Consequently, there is a search for an accurate and reliable method for monitoring the interactions of these chemicals with cancerous cells. We have developed and optimized a fully autonomous electrochemical biosensor for studying the role of isoflavonoids on A549 lung adenocarcinoma cell line. This advanced biosensor uses a prototype 96-electrode (DOX-96) well-type device that allows the measurement of cell respiratory activity via the consumption of dissolved oxygen. The system provides a continuous, real-time monitoring of cell activity upon exposure to naturally occurring polyphenols, specifically resveratrol, genistein, and quercetin. The system is equipped with a multipotentiostat, a 96-electrode well for measurements and cell culturing with 3 disposable electrodes fitted into each well. A comparison with classical "cell culture" techniques indicates that the biosensor provides real-time measurement with no added reagents. A detection limit of 1 x 10(4) was recorded versus 200 and 6 x 10(3) cells/well for MTT and fluorescence assays, respectively. This method was optimized with respect to cell stability, reproducibility, applied potential, cell density per well, volume/composition of cell culture medium per well, and incubation. Others include total measuring time, temperature, and sterilization procedure. This study represents a basic research tool that may allow researchers to study the type, level, and specific influence of isoflavonoids on cells.     

Processing and electrochemical characterization of Ni2Si intermetallic compound produced by vacuum sintering

In this study, a powder metallurgy approach for fabrication of Ni₂Si intermetallic compound was utilized. In this regard, mechanically activated Ni-33 at.% Si powders were used as feedstock. The powders were investigated by differential scanning calorimetry to study phase transformations that occurred during heating in the calorimeter. It was shown that the milled powders reacted after heating up to 850 °C. In order to fabricate bulk Ni-33 at.% Si, the as-milled powders were cold-pressed and subsequently sintered at 900 °C for 1 h in a vacuum furnace. X-ray diffraction results indicated that the phase composition of sintered materials consisted of only δ-Ni₂Si intermetallic. Consolidated samples exhibit 12% porosity and microhardness up to 773 HV_0.05. Further investigations showed the corrosion rate of sintered compound is higher than that of Ni–Si alloys reported in the literature. Here, anodic dissolution near the surface pores seems to be corrosion mechanism which resulted in increase in surface porosity up to 27% after corrosion.     

Improved electrochemical microsensor for the real-time simultaneous analysis of endogenous nitric oxide and carbon monoxide generation

An amperometric dual NO/CO microsensor was developed on the basis of a working electrode incorporating dual Pt microdisks (each diameter, 76 μm) and a Ag/AgCl reference electrode covered with a gas permeable membrane. One of the Pt disks was sequentially electrodeposited with Pt and Sn; the other Pt disk was deposited with Pt-Fe(III) oxide nanocomposites. The first showed activity for the oxidation of both NO and CO; the second showed activity only for NO oxidation. In the copresence of NO and CO, the currents measured at each electrode, respectively, represented the concentrations of CO and NO. The sensor showed high stability during the monitoring of organ tissue for at least 2.5 h and high selectivity to NO over CO at the Pt-Fe(III) oxide working electrode. Real-time coupled dynamic changes of NO and CO generated by a living C57 mouse kidney were monitored simultaneously and quantitatively in response to a NO synthase inhibitor (N(G)-nitro-l-arginine methyl ester), for the first time. CO was found to increase and NO decreased upon addition of the inhibitor, suggesting a possible reciprocal interaction between these endogenous gases.     

Gold nanoelectrode ensembles for the simultaneous electrochemical detection of ultratrace arsenic, mercury, and copper

Simultaneous electrochemical detection of As(III), Hg(II), and Cu(II) using a highly sensitive platform based on gold nanoelectrode ensembles (GNEEs) is described. GNEEs were grown by colloidal chemical approach on thiol-functionalized solgel derived three-dimensional silicate network preassembled on a polycrystalline gold (Au) electrode. GNEEs on the silicate network have been characterized by field emission scanning electron microscopy, X-ray diffraction, diffuse reflectance spectroscopy, and electrochemical measurements. Square wave anodic stripping voltammetry (SWASV) has been used for the detection of As(III) and Hg(II) without any interference from Cu(II) at the potentials of 0.06 and 0.53 V, respectively. The GNEE electrode is highly sensitive, and it shows linear response for As(III) and Hg(II) up to 15 ppb. The detection limit (signal-to-noise ratio = 4) of the GNEE electrode toward As(III) and Hg(II) is 0.02 ppb, which is well below the guideline value given by the World Health Organization (WHO). The potential application of the GNEE electrode for the detection of As(III) in a real sample collected from the arsenic-contaminated water in 24 North Parganas, West Bengal is demonstrated. The GNEE electrode has been successfully used for the simultaneous detection of As(III), Cu(II), and Hg(II) at sub-part-per-billion level without any interference for the first time. The nanostructured electrode shows individual voltammetric peaks for As(III), Cu(II), and Hg(II) at 0.06, 0.35, and 0.53 V, respectively. The analytical performance of the GNEE electrode is superior to the existing electrodes.     

A digital optical sensor for the remote monitoring of temperature

A method for the continuous monitoring of the change in temperature of remote physical objects based on waveguide ring microwave resonators, and also its diagramatic representation, is proposed. The results of calculations, which enable the range of accuracy of temperature measurements to be optimized using a digital optical sensor, are presented. The short response time and the small dimensions and mass of the proposed sensor enable continuous remote monitoring of the temperature to be achieved in locations that are difficult to access. __________ Translated from Izmeritel’naya Tekhnika, No. 3, pp. 54–57, March, 2007.     

Combined atomic force microscopy and optical microscopy measurements as a method to investigate particle uptake by cells

We propose a combination of atomic force microscopy (AFM) and optical microscopy for the investigation of particle uptake by cells. Positively and negatively charged polymer microcapsules were chosen as model particles, because their interaction with cells had already been investigated in detail. AFM measurements allowed the recording of adhesion forces on a single-molecule level. Due to the micrometer size of the capsules, the number of ingested capsules could be counted by optical microscopy. The combination of both methods allowed combined measurement of the adhesion forces and the uptake rate for the same model particle. As a demonstration of this system, the correlation between the adhesion of positively or negatively charged polymer microcapsules onto cell surfaces and the uptake of these microcapsules by cells has been investigated for several cell lines. As is to be expected, we find a correlation between both processes, which is in agreement with adsorption-dependent uptake of the polymer microcapsules by cells.     

空分气体在线与离线监测的有关问题

阐述了在线与离线分析仪在空分生产中的作用 ,各自的应用范围和应注意的问题。强调指出空分气体在线与离线分析仪器对空分生产的重要意义。     

Bivariate semiparametric control charts for simultaneous monitoring of process mean and variance

In the present article, two semiparametric bivariate control charts are presented, which use order statistics and are effective in jointly monitoring of possible shifts in the process mean and/or variance. To achieve that both the median location (or more generally the location of a specific order statistic) and the number of specific observations of the test sample lying between the control limits are taken into account. The false alarm rate and the in-control average run length are not affected by the marginal distributions, while the effect of the dependence structure on them is negligible; therefore, they can be used as fully nonparametric charts. A performance-comparison study is carried out, and an illustrative example is provided using a real-world data set.     

A portable Raman acoustic levitation spectroscopic system for the identification and environmental monitoring of algal cells

We report the coupling of a portable Raman spectrometer to an acoustic levitation device to enable environmental monitoring and the potential taxonomic identification of microalgae. Spectra of living cells were recorded at 785 nm using a fiber-optic probe coupled to a portable Raman spectrometer. The spectra exhibit an excellent signal-to-noise ratio and clearly show bands from chlorophyll a and beta-carotene. Spectra of levitated photobleached microalgae clearly show a reduction in chlorophyll a concentration relative to beta-carotene after 10 min of exposure to a quartz halogen lamp. Spectra recorded from levitated nitrogen-limited cells also show a significant reduction in bands associated with chlorophyll a, as compared to nitrogen-replete cells. To investigate the diagnostic capability of the technique, four species of microalgae were analyzed. Good quality spectra of all four species were obtained showing varying ratios of beta-carotene to chlorophyll. The combination of an acoustic levitation device and a portable Raman spectrometer shows potential as a taxonomic and environmental monitoring tool with direct application to field studies in remote environments.