We report the development of a hand-held instrument capable of performing two simultaneous microchip separations (gel and zone electrophoresis), and demonstrate this instrument for the detection of protein biotoxins. Two orthogonal analysis methods are chosen over a single method in order to improve the probability of positive identification of the biotoxin in an unknown mixture. Separations are performed on a single fused-silica wafer containing two separation channels. The chip is housed in a microfluidic manifold that utilizes o-ring sealed fittings to enable facile and reproducible fluidic connection to the chip. Sample is introduced by syringe injection into a septum-sealed port on the device exterior that connects to a sample loop etched onto the chip. Detection of low nanomolar concentrations of fluorescamine-labeled proteins is achieved using a miniaturized laser-induced fluorescence detection module employing two diode lasers, one per separation channel. Independently controlled miniature high-voltage power supplies enable fully programmable electrokinetic sample injection and analysis. As a demonstration of the portability of this instrument, we evaluated its performance in a laboratory field test at the Defence Science and Technology Laboratory with a series of biotoxin variants. The two separation methods cleanly distinguish between members of a biotoxin test set. Analysis of naturally occurring variants of ricin and two closely related staphylococcal enterotoxins indicates the two methods can be used to readily identify ricin in its different forms and can discriminate between two enterotoxin isoforms.
We present a rapid method for the identification of viruses using microfluidic chip gel electrophoresis (CGE) of high-copy number proteins to generate unique protein profiles. Viral proteins are solubilized by heating at 95 degrees C in borate buffer containing detergent (5 min), then labeled with fluorescamine dye (10 s), and analyzed using the microChemLab CGE system (5 min). Analyses of closely related T2 and T4 bacteriophage demonstrate sufficient assay sensitivity and peak resolution to distinguish the two phage. CGE analyses of four additional viruses--MS2 bacteriophage, Epstein-Barr, respiratory syncytial, and vaccinia viruses--demonstrate reproducible and visually distinct protein profiles. To evaluate the suitability of the method for unique identification of viruses, we employed a Bayesian classification approach. Using a subset of 126 replicate electropherograms of the six viruses and phage for training purposes, successful classification with non-training data was 66/69 or 95% with no false positives. The classification method is based on a single attribute (elution time), although other attributes such as peak width, peak amplitude, or peak shape could be incorporated and may improve performance further. The encouraging results suggest a rapid and simple way to identify viruses without requiring specialty reagents such as PCR probes and antibodies.
AbsfracePerformance of an electromagnetic induction launcher is considered for three types of armatures. These are: solid, l-element wound and 16-element wound aluminum armatures. The one element wound armature has uniform current density throughout and thus can withstand field reversal (working against embedded armature flux) and still maintain low temperature. Slingshot simulations were performed for several configurations. Best performance was obtained for a single element wound armature with two field reversals. For a 60 kg projectile, 10.5 cm coil inner radius and 5.5 cm coil build, the velocity after 50 meters of launcher length (670 stages) exceeded 3.5 Wsec with an overall efficiency of about 45%. For the same parameters the solid and 16-element wound armatures reach a velocity of about 3.3 kmlsec after 800 stages (60 meters of launcher length) but without field reversal. A velocity of 3.5 km/ sec is possible after 60 meters of launcher length with the 16-element wound armature with one field reversal, but the temperature is close to the melting temperature of aluminum. In all simulations with a solid armature, melting of some of the surface material occurs. However, it is shown that most of the melting occurs after contribution has been made to the forward going pressure, that is, melting does not affect the electrical performance of the launcher. The effect of coil firing time jitter on launcher performance is also considered and is found to be very small for realistic perturbations. For f 2 p-secs random jitter, the reduction in the final velocity for a 60 meter launcher with a solid armature is less than 0.1% and the increase in temperature is only 2%. This holds for all types of armatures. I. WIXODUC~ONThe electromagnetic induction coil launcher accelerates a conducting armature by inducing armature current opposite to coil c m n t s . The armature current is induced in an attempt to exclude magnetic flux from the armature. The interaction of the net radial magnetic field with the azimuthal armature current results in an axial force that accelerates the armature [l-21. If the launcher geometry, the coil firing times and current rise lengths are adjusted properly, a near constant acceleration can be maintained. A snapshot of coils. armature and magnetic field lines for a typical induction launcher is shown in Fig. 1.Because of the finite resistivity the armature current decays and the magnetic field diffuses into the armature. For a solid armature, if the firing position of the coils is advanced (slipped) to account for field diffusion, near constant axial acceleration can be maintained 133. For a 1-element wound armature, no slipping is needed, but there is still field diffusion due to the finite resistivity. A multiple element wound armature with many elements behaves in a similar manner to This work was supported by the U.S. Department of Energy under Contract NO. DE-AC04-94ALS.5000.a solid armature with the exception that the current is distributed uniformly in the radial direction.After a period ...
Field-deployable detection technologies in the nation's water supplies have become a high priority in recent years. The unattended water sensor is presented which employs microfluidic chip-based gel electrophoresis for monitoring proteinaceous analytes in a small integrated sensor platform. The instrument collects samples directly from a domestic water flow. The sample is then processed in an automated microfluidic module using in-house designed fittings, microfluidic pumps and valves prior to analysis via Sandia's microChemLab module, which couples chip-based electrophoresis separations with sensitive LIF detection. The system is controlled using LabVIEW software to analyze water samples about every 12 min. The sample preparation, detection and data analysis has all been fully automated. Pressure transducers and a positive control verify correct operation of the system, remotely. A two-color LIF detector with internal standards allows corrections to migration time to account for ambient temperature changes. The initial unattended water sensor prototype is configured to detect protein biotoxins such as ricin as a first step toward a total bioanalysis capability based on protein profiling. The system has undergone significant testing at two water utilities. The design and optimization of the sample preparation train is presented with results from both laboratory and field testing.
Abstruct -Coilguns have the ability to provide magnetic pressure to projectiles which results in near constant acceleration. We have developed coils to produce an effective projectile base pressure of 100 MPa (lkbar) as a step toward reaching base pressures of 200 MPa. The design uses a scalable technology applicable to the entire range of breech to muzzle coils of a multi-stage launcher. This paper presents the design of capacitor-driven coils for launching nominal 50 mm, 350 gram projectiles. Design criteria, constraints, mechanical stress analysis, launcher performance, and test results are discussed. I. BACKGROUNDResearch at Sandia National Laboratorieshlew Mexico for the last few years has demonstrated induction coilgun technology in small scale for military and space applications. The coilgun technology may lead to long-range artillery guns or very long launchers that are capable of deploying small satellites into low Earth orbit [I-21. We are now also developing this technology for applications in transportation and industrial processing.Our induction coilgun is an electromagnetic launcher which consists of individual magnetic field coils stacked endto-end to form a barrel. The coils are energized sequentially to generate a travelling wave of magnetic energy that pushes an electrically conducting projectile. The principle of concept, launcher hardware, and description of operation are thoroughly described in a previous paper which also discusses our first litz wire coils [3].To readily compare the performance of our technology to other guns, we calculate an average effective base pressure, P , on the projectile. This pressure is the muzzle kinetic energy divided by the barrel volume, or the pressure on the base of the projectile averaged over the barrel length. The instantaneous value of effective base pressure in our gun is -Manuscript received April 19,1994. R. J. Kaye, phone 505-845-7658, fax 505-845-7003. This work was supported by the U.S. Department of Energy under Contract DE-ACO4-94AL85000.where Mp, a, , , and Abase are the projectile mass, acceleration, and base area respectively.Initial tests of encapsulated litz wire cable coils appeared promising. Single layer coils operated successfully at a of 40 MPa (0.4 kbar), but failed to reach the 75 MPa criteria for our next launcher. Applications of interest require pressure near 200 MPa to keep the launcher lengths practical. Mechanical stress analysis, diagnostics of coil deformation, and launcher testing confirmed the need for development of a higher strength coil. COIL DESIGN GOALS AND CRITERIAIn August 1992 we elected to develop a new coil in 50 mm scale which would be capable of operating at the magnetic field and stress (mechanical, thermal, and electric) levels required for an average effective base pressure of 200 MPa accelerating 200 mm outer diameter (OD), 60 kg projectiles to 3.5 km/s. The small-scale coil would be designed for low duty-cycle operation to develop an average effective base pressure of 100 MPa over the length of a few coils t...
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