Pulsed field gel electrophoresis

The development of pulsed field gel electrophoresis has increased by 2 orders of magnitude the size of DNA molecules that can be routinely fractionated and analyzed. This increase is of major importance to molecular biology because it simplifies many previously laborious investigations and makes possible many new ones. Its range of application spans all organisms, from bacteria and viruses to mammals.     

外延薄膜生长的实时监测分析研究

利用反射式高能电子衍射(RHEED)在超高真空中对SrTiO3(100)、LaAlO3(100)、Si(100)单晶基片进行分析,讨论了衍射花样与晶体表面结构的对应关系,计算出表面的晶体学参数,同时采用激光分子束外延技术同质外延生长SrTiO3薄膜，根据RHEED衍射图样及强度振荡曲线实时监控薄膜的生长。     

Inactivation of microorganisms within collagen gel biomatrices using pulsed electric field treatment

Pulsed electric field (PEF) treatment was examined as a potential decontamination method for tissue engineering biomatrices by determining the susceptibility of a range of microorganisms whilst within a collagen gel. High intensity pulsed electric fields were applied to collagen gel biomatrices containing either Escherichia coli, Pseudomonas aeruginosa, Staphylococcus epidermidis, Candida albicans, Saccharomyces cerevisiae or the spores of Aspergillus niger. The results established varying degrees of microbial PEF susceptibility. When high initial cell densities (10⁶–10⁷ CFU ml⁻¹) were PEF treated with 100 pulses at 45 kV cm⁻¹, the greatest log reduction was achieved with S. cerevisiae (~6.5 log₁₀ CFU ml⁻¹) and the lowest reduction achieved with S. epidermidis (~0.5 log₁₀ CFU ml⁻¹). The results demonstrate that inactivation is influenced by the intrinsic properties of the microorganism treated. Further investigations are required to optimise the microbial inactivation kinetics associated with PEF treatment of collagen gel biomatrices.     

Capillary gel affinity electrophoresis of DNA fragments.

The incorporation of an affinity ligand within a polyacrylamide gel provides a general means of manipulating the selectivity of capillary gel electrophoresis separations. As an example of this approach, high resolution of DNA restriction fragments by capillary gel affinity electrophoresis has been achieved by adding a soluble intercalating agent, ethidium bromide, to the gel-buffer system. A migration model has been developed that can be used for selectivity optimization. Various parameters, such as ligand concentration and applied electric field, have been examined in terms of their influence on retention and selectivity of different-size DNA molecules. From this study, high-resolution separations have been developed with efficiencies as high as 10(7) theoretical plates per meter.     

Direct analysis in real time for reaction monitoring in drug discovery

Direct analysis in real time (DART) is a novel ionization technique that provides for the rapid ionization of small molecules under ambient conditions. In this study, several commercially available drugs as well as actual compounds from drug discovery research were examined by LC/UV/ESI-MS and DART interfaced to a quadrupole mass spectrometer. For most compounds, the molecular ions observed by ESI-MS were observed by DART/MS. DART/MS was also studied as a means to quickly monitor synthetic organic reactions and to obtain nearly instantaneous molecular weight confirmations of final products in drug discovery. For simple, synthetic organic transformations, the trends in the intensities of the mass spectral signals for the reactant and product obtained by DART/MS scaled closely with those of the diode array or the total ion chromatogram obtained by LC/UV/ESI-MS. In summary, DART is a new tool that complements electrospray ionization for the rapid ionization and subsequent mass spectral analysis of compounds in drug discovery.     

基于PLC的实时监控系统在辐射产业的应用

针对辐射产业中广泛应用的EPS加速器束下工艺落后的现状 ,提出采用PLC和工业PC两级控制方式 ,实现对EPS加速器束下工艺的自动控制。实践证明 ,该系统有效地提高了产品辐照质量 ,并且性能可靠 ,调试方便 ,维护简单 ,可移植性好。     

On-line parallel factor analysis. A step forward in the monitoring of bioprocesses in real time

There is a widely growing interest to obtain robust and rapid methodologies capable of monitoring bioprocesses in real time. Different analytical methods have been adapted to measure cell density evolution throughout a culture, and fluorescence spectroscopy is becoming promising technique due to its sensitivity, selectivity towards important chemical analytes and its easy implementation as a non-invasive procedure.

This work is focused on showing the advantages of coupling the trilinear algorithm Parallel Factor Analysis (PARAFAC) to the Multivariate Statistical Process Control (MSPC) as a monitoring and real-time control tool for bioprocesses. In this context, both induced (growing on methanol) and non induced (growing on glycerol) Pichia pastoris cultures were monitored by multiwavelength-fluorescence. In the first one methanol was used as substrate; whereas glycerol was used in the second one. Taking advantages of the mathematical properties of PARAFAC, batches of a bioprocess measured under normal operating conditions (NOC) were used to develop a calibration models. Residuals of the model in combination with MSPC were used to establish two control limits. The control limits were used for new batches in real time.

Fluorescence spectroscopy combined with PARAFAC and MSPC is a feasible approach for controlling and performing fault diagnosis of bioprocesses offering the opportunity of performing real-time process surveillance based on relevant quality measurements.     

脉冲电磁场对草酸钴粒度的控制

在脉冲电磁场(PEMF)作用下,以氯化钴为母液、草酸铵为沉淀剂,采用草酸盐沉淀法制备了尺度较小且粒度分布均匀的草酸钴粉体.初步分析了PEMF与草酸钴制备体系的交互作用机理.同时,利用FTIR争电导率实验为机理模型提供了强有力的实验证据.结果表明,施加PEMF条件下获得的沉淀产物为β-CoC2O4·2H2O,其平均粒径为3.5403μm,与未施加PEMF条件下制备的样品相比降低了60.13%.PEMF作用下,反应体系中稳定晶核数量的增加以及形核率的提高是草酸钴粒度减小及粒度分布得到改善的原因所在.     

Comprehensive interpretation of gel electrophoresis data

From temperature analysis of polyacrylamide gel electrophoresis data for rigid-rod DNA analytes, it is proposed that an entropic force term is responsible for the discrepancy between Ogston-Morris-Rodbard-Chrambach model predictions and experimental results. This entropic force originates from reduction of the orientational freedom of anisotropic analytes in small pores of polyacrylamide gels. Time-dependent fluorescence anisotropy decay measurements confirm that, even in the absence of an external field, orientation of anisotropic analytes is restricted in polyacrylamide gels. A new comprehensive model is proposed that takes this effect into consideration. Predictions based on this model are found to compare favorably with experimental data for linear and three-arm asymmetrically branched rigid-rod DNA analytes covering a broad range of molecular aspect ratios and sizes. A new length scale is also proposed for describing the effect of analyte topology on electrophoretic mobility. This length scale reduces to the analyte radius of gyration in the limiting cases of spherically symmetric and linear rigid-rod species. Based on these results, a general approach is proposed for interpreting gel electrophoresis data of charged analytes possessing simple and complex topologies.     

Process monitoring in real time: Empirical bayes approach—discrete case

In this paper an empirical Bayes model is developed to monitor and analyse discrete data generated in a manufacturing process for printed circuit boards. A key feature of this analysis is the use of the current observation at time t and the posterior estimates of the distribution of the proportion nonconforming at time t – 1 to obtain a new, updated estimate of the posterior distribution at time t. The derived approach is widely applicable to statistical process control and provides a simple and fast algorithm for updating.     

In situ monitoring in real time of fatigue-induced damage growth in composite materials by acoustography

There are growing concerns about the effects of accidental impact damage on the structural integrity of aerospace composites and about the possible growth of the damage due to in-service fatigue. There has been some success in the use of established methods (ultrasonic C-scan, thermography, X-rays) to monitor damage development during fatigue experiments by interrupting a test and removing the specimen for damage inspection but this stop-and-restart test procedure is far from satisfactory. Real-time damage monitoring in composite materials during fatigue has now become possible by the emergence of a new ultrasonic imaging technology, acoustography. The successful integration of acoustography and a servo-hydraulic fatigue test machine has resulted in a new measurement system which can be used for the in situ monitoring in real time of damage growth in composite specimens during long-term fatigue tests. Results are presented which show damage-area growth during fatigue cycling under high compressive loads. After an initial small enlargement (stage 1), damage grows at a constant rate (stage 2) until the third stage is reached when there is further growth at an increasing rate to final failure. However, a ‘fatigue limit’ has also been observed. At stresses below this fatigue limit, a zero damage-growth régime has been found in studies of >10⁶ fatigue cycles. The results obtained have important implications for the understanding of the effects of damage on fatigue life and for the design of ‘safe’ damage-tolerant structures.     

Electromagnetic field monitoring and control systems: state-of-the-art and work-in-progress

The development of EMF monitoring and control systems unquestionably represents one of the major innovations in the range of methodologies for evaluating, through measurement, the so-called environmental electromagnetic pollution. The interest recently shown by ARPA and municipal and provincial councils for setting up electromagnetic field monitoring and control systems has created significant developments in the field under examination. This paper attempts to provide a complete overview of the technical possibilities provided by electromagnetic field monitoring and control systems in the environment and their possible applications. Equipment currently available and under development is described, as well as the most significant work-in-progress in this sector. In the near future, several monitoring systems will be proposed and set up by municipalities and provinces, or directly by telecommunications companies. For this reason, it is more than ever necessary that agreement be reached at a national level to define a unified methodological and operating approach to enable monitoring data from different sources to be compared.     

Acrylamide polymerization kinetics in gel electrophoresis capillaries. A Raman microprobe study.

The formation of 3.5% T, 3.3% C cross-linked polyacrylamide is monitored in 75-microns-i.d. electrophoresis capillaries by Raman microprobe spectroscopy. The disappearance of the acrylamide 1292-cm-1 band is followed with 60-s time resolution for 30 min, and 2-4 min resolution for up to 10 h. Polymerization is 98% complete in 1.5 h and greater than 99% complete after 2 h. In the 900-1700-cm-1 region no bands attributable to cross-linking are observable. Reaction in the capillary follows second-order kinetics. The reaction is faster in the bulk system because heat dissipation is not sufficient to maintain a constant temperature.     

A data acquisition and real time processing system for field use—dynamic strain indicator

A microprocessor based data acquisition and real time processing system used for in-situ agricultural machinery experimentation is introduced in this paper.
The devlopment, principle and error of the system are discussed, and some practical trials are related.     

Method of real time signal restoration

Translated from Izmeritel'naya Tekhnika, No. 9, pp. 39–40, September, 1988.     

Apta-biosensors for nonlabeled real time detection of human IgE based on carbon nanotube field effect transistors

In this study, we demonstrated the aptamer-based biosensor (apta-biosensor) using CNT-FET devices for label free detection of allergy diagnosis by IgE detection. In order to detect the IgE, two kinds of receptor (monoclonal IgE antibody and anti-IgE aptamer)-modified CNT-FET devices were fabricated. The binding event of the target IgE onto receptors was detected by monitoring the gating effect caused by the charges of the target proteins. Since the CNT-FET biosensors were used in buffer solution, it was crucial to use small-size receptors like aptamers than whole antibodies so that the charged target IgE could approach the CNT surface within the Debye length distance to give a large gating effect. The results show that CNT-FET biosensors using monoclonal IgE antibody had very low sensitivity (minimum detectable level 1000 ng/mL), while those based on anti-IgE aptamer could detect 50 ng/mL. Moreover, the aptamer-modified CNT-FET herein could successfully block non-target proteins and could selectively detect the target protein in an environment similar to human serum electrolyte. Therefore, aptamer-based CNT-FET devices enable the production of label-free ultrasensitive electronic biosensors to detect clinically important biomarkers for disease diagnosis.     

Three DNA sequencing methods using capillary gel electrophoresis and laser-induced fluorescence.

Capillary gel electrophoresis is demonstrated for the four-spectral-channel sequencing technique of Smith, the two-spectral-channel sequencing technique of Prober, and the one-spectral-channel sequencing technique of Richardson and Tabor. Sequencing rates up to 1000 bases/h are obtained at electric field strengths of 465 V/cm. At lower electric field strengths, capillary electrophoresis produces useful data for fragments greater than 550 nucleotides in length with 2 times better resolution than slab gel electrophoresis. An on-column detector produces detection limits of 200 zmol (1 zmol = 10(-21) mol = 600 molecules) for the four-spectral-channel technique. A postcolumn detector, based on the sheath flow cuvette, produces detection limits of 20 and 2 zmol for the two- and one-spectral-channel techniques, respectively.     

Specific base recognition of oligodeoxynucleotides by capillary affinity gel electrophoresis using polyacrylamide-poly(9-vinyladenine) conjugated gel.

Poly(9-vinyladenine) was synthesized and utilized as an affinity macroligand entrapped within the gel matrix. Base-specific separation of oligodeoxynucleotides was achieved with high resolution and high speed by electrophoresis, using capillaries filled with conjugated polyacrylamide-poly(9-vinyladenine) gel. Oligothymidylic acids were selectively separated from the mixture of oligothymidylic and oligodeoxyadenylic acids by utilizing a specific hydrogen bonding between poly(9-vinyladenine) and oligothymidylic acids. Migration time and resolution of oligodeoxynucleotides were influenced by several parameters, such as the size of poly(9-vinyladenine), capillary temperature, and concentrations of poly(9-vinyladenine) and urea. Some guidelines are presented, based on the theoretical formulation of the effect of these parameters, in order to find optimum electrophoretic conditions. Analytical capillary affinity gel electrophoresis was developed for the selective and sensitive base recognition of oligodeoxynucleotides with efficiencies as high as several 10(6) plates/m by using a urea-gel capillary with poly(9-vinyladenine) and temperature-programming.     

Real time process monitoring and adaptive control during CNC deep hole drilling

A system which enables unattended CNC machining with small diameter long twist drills is described. The system monitors the drilling thrust and torque and controls accordingly the machining parameters feed rate, spindle-speed and tool position in order to ensure safety of the tool and workpiece under high penetration rates during unattended machining. Other functions of the system include tool life monitoring based on feed force pattern and issuing of alarms, data acquisition and display, while its software structure allows for continuous expansion and improvement.