bluuebunny/crossref_metadata_2025_split huggingface dataset:
A versatile microfabricated platform for electrophoresis of double‐ and single‐stranded DNA
Authors: Ugaz Victor M. , Lin Rongsheng , Srivastava Nimisha , Burke David T. , Burns Mark A. 
Published: March 2003

AbstractWe demonstrate a versatile microfabricated electrophoresis platform, incorporating arrays of integrated on‐chip electrodes, heaters, and temperature sensors. This design allows a range of different sieving gels to be used within the same device to perform separations involving both single‐ and double‐stranded DNA over distances on the order of 1 cm. We use this device to compare linear and cross‐linked polyacrylamide, agarose, and thermo‐reversible Pluronic‐F127 gels on the basis of gel casting ease, reusability, and overall separation performance using a 100 base pair double‐stranded DNA ladder as a standard sample. While cross‐linked polyacrylamide matrices provide consistently high‐quality separations in our system over a wide range of DNA fragment sizes, Pluronic gels also offer compelling advantages in terms of the ability to remove and reload the gel. Agarose gels offer good separation performance, however, additional care must be exercised to ensure consistent gel properties as a consequence of the need for elevated gel loading temperatures. We also demonstrate the use of denaturing cross‐linked polyacrylamide gels at concentrations up to 19% to separate single‐stranded DNA fragments ranging in size from 18 to 400 bases in length. Primers differing by 4 bases at a read length of 30 bases can be separated with a resolution of 0.9–1.0 in under 20 min. This level of performance is sufficient to conduct a variety of genotyping assays including the rapid detection of single nucleotide polymorphisms (SNPs) in a microfabricated platform. The ability to use a single microelectrophoresis system to satisfy a wide range of separation applications offers molecular biologists an unprecedented level of flexibility in a portable and inexpensive format.
Low‐voltage electroosmosis pump for stand‐alone microfluidics devices
Authors: Takamura Yuzuru , Onoda Hiroyuki , Inokuchi Hiromichi , Adachi Sakuichiro , Oki Akio , Horiike Yasuhiro 
Published: March 2003

AbstractTwo types of low‐voltage electroosmosis pumps were developed using microfabrication technology for usage in handy or stand‐alone applications of the micrototal analysis systems (μ‐TAS) and the lab‐on‐a‐chip. This was done by making a thin (< 1 μm) region in the flow path and by only applying voltages near this thin region using electrodes inserted into the flow path. The inserted electrodes must be free from bubble formation and be gas‐tight in order to avoid pressure leakage. For these electrodes, Ag/AgCl or a gel salt bridge was used. For patterning the gel on the chip, a hydrophilic photopolymerization gel and a photolithographic technique were optimized for producing a gel with higher electric conductivity and higher mechanical strength. For high flow rate application, wide (33.2 mm) and thin (400 nm) pumping channels were compacted into a 1 mm×6 mm area by folding. This pump achieves an 800 Pa static pressure and a flow of 415 nL/min at 10 V. For high‐pressure application, a pump was designed with the thin and thick regions in series and positive and negative electrodes were inserted between them alternatively. This pump could increase the pumping pressure without increasing the supply voltage. A pump with 10‐stage connections generated a pressure of 25 kPa at 10 V.
Integration of on‐column immobilized enzyme reactor in microchip electrophoresis
Authors: Park Sung‐Soo , Cho Seung Il , Kim Min‐Su , Kim Yong‐Kweon , Kim Byung‐Gee 
Published: March 2003

AbstractA simple method integrating an immobilized enzyme reactor into a microchip electrophoresis device was developed. The enzyme immobilization into a microchip was performed by spotting and drying a drop of dissolved nitrocellulose (NC) on a glass substrate, and adsorbing enzyme on the reconstituted NC membrane. This enzyme‐immobilized glass plate was assembled with a polydimethylsiloxane substrate on which the separation channel was fabricated. The advantage of this method is the ability to easily change the position and size of the reactor within the microchip electrophoresis device. A β‐galactosidase reaction was demonstrated with fluorescein di‐β‐D‐galactopyranoside using this integrated on‐column enzyme reactor. A successful electrophoretic separation of its hydrolysis products, i.e., fluorescein mono‐β‐D‐galactopyranoside (FMG) and fluorescein, was achieved. Enzyme kinetics and inhibition of the β‐galactosidase using FMG and 2‐phenylethyl β‐D‐thiogalactoside, respectively, were also studied with microchip electrophoresis.
Identification of nuclear proteins of small cell lung cancer cell line H82: An improved procedure for the analysis of silver‐stained proteins
Authors: González Luis Javier , Castellanos‐Serra Lila , Badock Volker , Díaz Maylín , Moro Alejandro , Perea Silvio , Santos Alicia , Paz‐Lago Dalila , Otto Albrecht , Müller Eva‐Christina , Kostka Susanne , Wittmann‐Liebold Brigitte , Padrón Gabriel 
Published: March 2003

AbstractAn efficient method for digestion and extraction of proteolytic peptides from silver‐stained proteins was applied to the characterization of nuclear proteins from the small cell lung cancer H82 (ATCC HTB 175) cell line previously separated by high‐resolution large format two‐dimensional gel electrophoresis. From 68 spots, evenly distributed on the gel area and representing a wide range of spot intensities, 63 (92%) were successfully identified by matrix‐assisted laser desorption/ionization (MALDI) or electrospray ionozation‐mass spectrometry (ESI‐MS). In five cases where the identification was not possible, the presence of an intense background apparently due to the leakage of polymers from the microtubes or other plastics, was detected. Extensive analysis of peptide sequences by ESI MS/MS experiments allowed the identification of post‐translational modifications, such as acetylation, phosphorylation, deamidation of asparagine residues and the presence of isoaspartic acid. A new protein variant not reported in sequence databases was also detected.
Activation of platelet‐derived growth factor pathway in human asthmatic pulmonary‐derived mesenchymal cells
Authors: Malmström Johan , Tufvesson Ellen , Löfdahl Claes‐Göran , Hansson Lennart , Marko‐Varga György , Westergren‐Thorsson Gunilla 
Published: March 2003

AbstractCell cultures of mesenchymal type were obtained from biopsies taken after bronchoscopy from patients with asthma. It was possible to achieve outgrowth of fibroblast‐like cells from these lung biopsies, which stained for α‐smooth actin indicating that they were of myofibroblast type. Morphologically, two types of myofibroblasts could be observed: one intermediate form with more stretched cell shape and lamellipodia protrusions, and one more differentiated compact form of myofibroblast. The intermediate form was the most dominant type in these patients, indicating an active ongoing remodelling process. Further studies showed that platelet‐derived growth factor (PDGF) might be the factor that stimulates the formation of the intermediate type of myofibroblasts, since it enhance migration of normal human lung fibroblasts 4‐fold compared to control through an induced formation of stress fibers and lamellipodia protrusions. Additionally, intracellular signalling pathways involved in migration, such as RhoA and MAPkinase were stimulated 1.5‐fold and 3.5‐fold, respectively. By using two‐dimensional (2‐D) gel electrophoresis and protein identification by peptide mass finger printing matrix assisted laser desporption/ionization – time of flight – massspectrometry (MALDI‐TOF‐MS) it was possible to confirm that PDGF affected the synthesis of proteins involved in the remodelling process, such as collagen VI and post‐translational forms thereof. PDGF also stimulated the production of FK506 binding protein of 65 kDa, a protein involved in smooth muscle differentiaition, and proteins involved in the rearrangement of the cytoskeleton connected to migration such as the actin related protein ARP3, the T‐complex protein and the heat shock protein 60. We demonstrate that PDGF has a potential pathological role in asthma and formation of subepithelial fibrosis by inducing changes in the proteome.
DNA fragment analysis by an affordable multiple‐channel capillary electrophoresis system
Authors: Liu Ming S. , Amirkhanian Varouj D. 
Published: March 2003

AbstractWe are demonstrating a cost‐effective multichannel capillary electrophoresis system for a high‐efficiency double‐stranded DNA (dsDNA) fragments analysis. This bench‐type high‐performance DNA analysis (HDA™) system uses fluorescence‐type detection with inexpensive solid‐state light sources and nonmoving integrated emission collection micro‐optics. DNA samples are analyzed simultaneously by using a multiple usage and disposable multicapillary cartridge, which contains integrated capillary channels, optical fibers and an integrated sieving gel reservoir. Using commercially available dsDNA size markers as indicators, the HDA™ system provides high resolving power in 7 min separations. The system can hold a total of 192 samples in two 96‐well polymerase chain reaction (PCR) plates, which can be automatically analyzed within 2.5 h. This affordable system can be used in laboratories to replace slab gel electrophoresis for routine and high‐throughput dsDNA analysis.
A comparison between electrokinetic capillary chromatography and absorption spectroscopy for the analysis of peptide‐micelle association by weak hydrophobic interactions
Authors: Hémond Carl , Fürtös‐Matei Alexandra , Waldron Karen C. 
Published: March 2003

AbstractMicellar electrokinetic capillary chromatography (MEKC) was compared to absorption spectroscopy to estimate equilibrium association constans (Kas) for peptide‐micelle systems involving three peptides (leucine‐enkephalin, methionine‐enkephalin and leucine‐phenylalanine (LF)) and two surfactant micelles (sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB)). Buffer pH was chosen to minimize purely electrostatic interactions between peptides and micelles that could not be interrogated by absorption spectroscopy. Viscosity‐corrected MEKC mobilities gave reasonably similar estimates of Kas between the two methods for all three peptide‐SDS micelle systems, with Kas values ranging from 13.7 ± 0.3 to 49 ± 1 M‐1. For CTAB, estimates of Kas for LF‐CTAB micelle association were of the same order of magnitude as the SDS micelle by the two methods of estimation. On the other hand, enkephalin‐CTAB micelle binding was about 10 times stronger (Kas = 122 ± 3 M‐1 to 311 ± 9 M‐1) than the enkephalin‐SDS micelle binding. In addition, MEKC underestimated the Kas values relative to spectroscopy by a factor of 2–3 for the enkephalin‐CTAB system.
Identification of degradation products of aspartyl tripeptides by capillary electrophoresis‐tandem mass spectrometry
Authors: Boni Silvia De , Neusüß Christian , Pelzing Matthias , Scriba Gerhard K. E. 
Published: March 2003

AbstractCapillary electrophoresis‐electrospray tandem mass spectrometry (CE‐MS/MS) has been used to identify degradation products of the aspartyl tripeptides Phe‐Asp‐GlyNH2 and Gly‐Asp‐PheNH2 following incubation of the peptides in acidic and alkaline solution. At pH 2, the dominant decomposition products resulted from cleavage of the peptide backbone amide bonds to yield the respective dipeptides and amino acids. In addition, the cyclic aspartyl succinimide intermediate was identified by its [M+H]+ at m/z = 319 and the MS/MS spectrum exhibiting a simple fragmentation pattern with the [C8H10N]+‐ion as the principal daughter ion (a1 of Phe‐Asp‐GlyNH2). Deamidation of the C‐terminal amide as well as isomerization and enantiomerization of the Asp residue occurred upon incubation at pH 10. α‐Asp and the isomeric β‐Asp and most of the diastereomeric forms (corresponding to D/L‐Asp) could be separated by CE. All isomers could be identified based on their MS/MS spectra. Peptides with the amino acid sequence Phe‐Asp‐Gly containing the regular α‐Asp bond displayed a highly intense b2 fragment ion and a low abundant y2 ion. In contrast, the y2 and a1 fragment were high abundant daughter ions in the mass spectra of β‐Asp peptides while the b2 ion exhibited a lower abundance. Differences in the MS/MS spectra of the isomers of the peptides with the sequence Gly‐Asp‐Phe were obvious but less pronounced. In conclusion, CE‐MS/MS proved to be a useful tool to study the decomposition and enantiomerization of peptides including the isomerization of Asp residues, due to the combination of efficient separation of isomers by CE and their identification by MS/MS.
Variability in human sensitivity to 1,3‐butadiene: Influence of the allelic variants of the microsomal epoxide hydrolase gene
Authors: Abdel‐Rahman Sherif Z. , El‐Zein Randa A. , Ammenheuser Marinel M. , Yang Zhen , Stock Thomas H. , Morandi Maria , Ward Jonathan B. 
Published: March 2003

AbstractThe carcinogenic effects of 1,3‐butadiene (BD), a chemical widely used in the rubber industry, are thought to be due to its epoxide metabolites. In humans, these epoxides are detoxified predominantly by hydrolysis, a reaction mediated by the microsomal epoxide hydrolase (mEH) enzyme. The mEH gene is polymorphic and the most common mEH coding‐region variants detected in human populations are the two amino acid polymorphisms Tyr113His and His139Arg. Polymorphic amino acid substitutions at residues 113 and 139 in the human mEH protein can associate in four distinct combinations: Tyr113/His139, Tyr113/Arg139, His113/His139, and His113/Arg139. In vitro studies have shown that each of these genotypes has a unique mEH protein level that can affect net mEH enzymatic activity. In the current study, we examined the relationships among the genotypes involving these two polymorphisms and the mutagenic responses associated with occupational exposure to BD. We studied 49 nonsmoking workers from two styrene‐butadiene rubber facilities in southeast Texas using the autoradiographic HPRT mutant lymphocyte assay as a biomarker of genotoxic effect. We genotyped the study participants simultaneously for both polymorphisms, using a multiplex PCR assay developed in our laboratory, and the subjects were assigned to a specific group based on the predicted mEH activity associated with their genotypes (low, intermediate, and high). In the study population, 67% were exposed to low BD levels of <150 ppb (measured by personal badge dosimeters) and 33% were exposed to >150 ppb (mean 2,244 ppb). In the BD low‐exposure group, the mEH genotypes had no significant effect on the HPRT variant (mutant) frequency (Vf). In the high‐exposure group (BD > 150 ppb), individuals with genotypes associated with low mEH activity had a significant (P < 0.05) 3‐fold increase in HPRT Vf (Vf ± SEM = 13.95 ± 2.15 × 10−6) compared to high‐activity individuals (4.41 ± 1.19 × 10−6), and a 2‐fold increase in Vf compared to intermediate‐activity individuals (6.44 ± 2.09 × 10−6). Our results indicate that mEH genotypes may play a significant role in human sensitivity to the genotoxic effects of exposure to BD. Environ. Mol. Mutagen. 41:140–146, 2003. © 2003 Wiley‐Liss, Inc.
Time delayed control of structural systems
Authors: Udwadia Firdaus E. , von Bremen Hubertus F. , Kumar Ravi , Hosseini Mohammad 
Published: March 2003

AbstractTime delays are ubiquitous in control systems. They usually enter because of the sensors and actuators used in them. Traditionally, time delays have been thought to have a deleterious effect on both the stability and the performance of controlled systems, and much research has been done in attempting to eliminate them, compensate for them, or nullify their presence. In this paper we take a different view. We investigate whether purposefully injected time delays can be used to improve both the system's stability and performance. Our analytical, numerical, and experimental investigation shows that this can indeed be done. Analytical results of the effects of time delays on collocated and non‐collocated control of classically damped and non‐classically damped systems are given. Experimental and numerical results confirm the theoretical expectations. Issues of system uncertainties and robustness of time delayed control are addressed. The results are of practical value in improving the performance and stability of controllers because these characteristics (performance and stability) improve dramatically with the intentional injection of small time delays in the control system. The introduction of such time delays constitutes a ‘minimal change’ to a controller already installed in a structural system for active control. Hence, from a practical standpoint, time delays can be implemented in a nearly costless and highly reliable manner to improve control performance and stability, an aspect that cannot be ignored when dealing with the economics and safety of large structural systems subjected to strong earthquake ground shaking. Copyright © 2003 John Wiley & Sons, Ltd.
Optimum multiple tuned mass dampers for structures under the ground acceleration based on the uniform distribution of system parameters
Authors: Li Chunxiang , Liu Yanxia 
Published: March 2003

AbstractThe five MTMD models, with natural frequencies being uniformly distributed around their mean frequency, have been recently presented by the first author. They are shown to have the near‐zero optimum average damping ratio (more precisely, for a given mass ratio there is an upper limit on the total number, beyond which the near‐zero optimum average damping ratio occurs). In this paper, the eight new MTMD models (i.e. the UM‐MTMD1∼UM‐MTMD3, US‐MTMD1∼US‐MTMD3, UD‐MTMD1 and UD‐MTMD2), with the system parameters (mass, stiffness and damping coefficient) being, respectively, uniformly distributed around their average values, have been, for the first time here, proposed to seek for the MTMD models without the near‐zero optimum average damping ratio. The structure is represented by the mode‐generalized system corresponding to the specific vibration mode that needs to be controlled. Through minimization of the minimum values of the maximum dynamic magnification factors (DMF) of the structure with the eight MTMD models (i.e. through the implementation of Min.Min.Max.DMF), the optimum parameters and values of Min.Min.Max.DMF for these eight MTMD models are investigated to evaluate and compare their control performance. The optimum parameters include the optimum mass spacing, stiffness spacing, damping coefficient spacing, frequency spacing, average damping ratio and tuning frequency ratio. The six MTMD models without the near‐zero optimum average damping ratio (i.e. the UM‐MTMD1∼UM‐MTMD3, US‐MTMD1, US‐MTMD2 and UD‐MTMD2) are found through extensive numerical analyses. Likewise, the optimum UM‐MTMD3 offers the higher effectiveness and robustness and requires the smaller damping with respect to the rest of the MTMD models in reducing the responses of structures subjected to earthquakes. Additionally, it is interesting to note, by comparing the optimum UM‐MTMD3 with the optimum MTMD‐1 recently investigated by the first author, that the effectiveness and robustness for the optimum UM‐MTMD3 is almost identical to that for the optimum MTMD‐1 (without inclusion of the optimum MTMD‐1 with the near‐zero optimum average damping ratio). Recognizing these performance benefits, it is preferable to employ the optimum UM‐MTMD3 or the optimum MTMD‐1 without the near‐zero optimum average damping ratio, when installing the MTMD for the suppression of undesirable oscillations of structures under earthquakes. Copyright © 2003 John Wiley & Sons, Ltd.
Airborne LiDAR in support of geomorphological and hydraulic modelling
Authors: French J. R. 
Published: March 2003

AbstractThis paper considers the application of airborne laser altimetry (LiDAR) to the provision of elevation data at accuracies and spatial densities commensurate with the current generation of high‐resolution hydraulic models. Three sets of issues are addressed with reference to a Telemac 2D model of a morphologically complex estuary in eastern England. First, the quality of airborne LiDAR data is assessed via multiscale calibration against surveyed sections and supplementary control points. Second, image processing techniques are used for (i) identification of multiple regions of interest within large LiDAR mosaics; (ii) subregional infilling of voids left by data ‘drop‐outs’; (iii) filtering and subsampling to match topographic information content with model resolution and the density of the computational mesh. Third, the implications of improved terrain data are considered with reference to the estimation of elevations and potential tidal volumes for a number of discrete flood compartments and the modelling of hypothetical inundation scenarios. After minor offset correction to ensure registration with local benchmarks, the quality of LiDAR elevation data within a 12 km × 4 km coverage is found to be consistent with the published specification (±0·10 to ±0·15 m). Image‐processing tools provide an efficient means of managing information content and interfacing this with the GIS‐based functionality of the pre‐processing software used in conjunction with the hydraulic model. The accuracy and spatial resolution of the LiDAR data allow the identification of subtle but important topographic variations between adjacent flood compartments. In many cases, differences in model results obtained using these data relative to previously estimated average flood compartment elevations are small. Importantly, however, LiDAR provides topographic information at an accuracy and resolution close to the present limits of model representation. Reliable representation of form allows the modeller to concentrate on the physical aspects of model parameterization, whilst minimizing the conflation of parameter effects with those of poorly constrained geometric representation. Copyright © 2003 John Wiley & Sons, Ltd.
Identifying critical technologies in the United States: a review of the federal effort
Authors: Wagner Caroline S. , Popper Steven W. 
Published: March 2003

AbstractThe United States government has not sponsored technology foresight as it has been defined and practised by governments in Europe, Japan and elsewhere in the world. [Foresight has been described in many places, but the original concept, as far as the authors are aware, was proposed by Martin and Irvine (1989).] [Different approaches to identifying important technologies is summarized in Wagner (1997).] Instead, the US government sponsored a parallel effort called ‘critical technologies identification’ between 1989 and 1999. This paper describes the critical technologies movement in the United States and explores why critical technologies identification was limited in its ability to capture the attention of US government officials and other decision‐makers. The authors suggest possible alternative futures for foresight in the United States. Copyright © 2003 John Wiley & Sons, Ltd.
Twelve lessons from ‘Key Technologies 2005’: the French technology foresight exercise
Authors: Durand Thomas 
Published: March 2003

AbstractThe paper draws lessons from the French technology foresight exercise ‘Key Technologies 2005’. It first describes the exercise as it took place: its context and objectives as well as the methodology that was adopted to identify, select and characterize 120 key technologies. Specifically, the paper describes the criteria used to select among the candidate key technologies, and then presents a specific tool which was developed to describe each technology (a characterization grid relating functional market needs and technological solutions to fulfil the generic need). Finally, twelve lessons are discussed. These deal with both the content of the foresight results and the methodology of running a technology foresight at national level. Copyright © 2003 John Wiley & Sons, Ltd.