We report a rapid and robust separation of Saccharomyces cerevisiae and MS2 bacteriophage using acoustic focusing in a microfluidic device. A piezoelectric transducer (PZT) generates acoustic standing waves in the microchannel. These standing waves induce acoustic radiation force fields that direct microparticles towards the nodes (i.e., pressure minima) or the anti-nodes (i.e., pressure maxima) of the standing waves depending on the relative compressidensity between the particle and the suspending liquid.[1] For particles larger than 2 {micro}m, the transverse velocities generated by these force fields enable continuous, high throughput separation. Extensive work in the last decade [2-4] has demonstrated acoustic focusing for manipulating microparticles or biological samples in microfluidic devices. This prior work has primarily focused on experimental realization of acoustic focusing without modeling or with limited one-dimensional modeling estimates. We recently developed a finite element modeling tool to predict the two-dimensional acoustic radiation force field perpendicular to the flow direction in microfluidic devices.[1] Here we compare results from this model with experimental parametric studies including variations of the PZT driving frequencies and voltages as well as various particle sizes and compressidensities. These experimental parametric studies also provide insight into the development of an adjustable 'virtual' pore-size filter as well as …

Prompt doses from x-rays generated as result of laser beam interaction with target material are calculated at different locations inside the National Ignition Facility (NIF). The maximum dose outside a Target Chamber diagnostic port is {approx} 1 rem for a shot utilizing the 192 laser beams and 1.8 MJ of laser energy. The dose during a single bundle shot (8 laser beams) drops to {approx} 40 mrem. Doses calculated outside the Target Bay doors and inside the Switchyards (except for the 17 ft.-6 in. level) range from a fraction of mrem to about 11 mrem for 192 beams, and scales down proportionally with smaller number of beams. At the 17ft.-6 in. level, two diagnostic ports are directly facing two of the Target Bay doors and the maximum doses outside the doors are 51 and 15.5 mrem, respectively. Shielding each of the two Target Bay doors with 1/4 in. Pb reduces the dose by factor of fifty. One or two bundle shots (8 to 16 laser beams) present a small hazard to personnel in the Switchyards.

The effect of hydrogen on the burst properties Type 304L stainless steel vessels was investigated. The purpose of the study was to compare the burst properties of hydrogen-exposed stainless steel vessels burst with different media: water, helium gas, or deuterium gas. A second purpose of the tests was to provide data for the development of a predictive finite-element model. The burst tests were conducted on hydrogen-exposed and unexposed axially-flawed cylindrical vessels. The results indicate that samples burst pneumatically had lower volume ductility than those tested hydraulically. Deuterium gas tests had slightly lower ductility than helium gas tests. Burst pressures were not affected by burst media. Hydrogen-charged samples had lower volume ductility and slightly higher burst pressures than uncharged samples. Samples burst with deuterium gas fractured by quasi-cleavage near the inside wall. The results of the tests were used to improve a previously developed predictive finite-element model. The results show that predicting burst behavior requires as a material input the effect of hydrogen on the plastic strain to fracture from tensile tests. The burst test model shows that a reduction in the plastic strain to fracture of the material will result in lower volume ductility without a reduction in burst pressure …

Automated front-end sample preparation technologies can significantly enhance the sensitivity and reliability of biodetection assays [1]. We are developing advanced sample preparation technologies for biowarfare detection and medical point-of-care diagnostics using microfluidic systems with continuous sample processing capabilities. Here we report an electrophoretically assisted acoustic focusing technique to rapidly extract and enrich viral and bacterial loads from 'complex samples', applied in this case to human nasopharyngeal samples as well as simplified surrogates. The acoustic forces capture and remove large particles (> 2 {micro}m) such as host cells, debris, dust, and pollen from the sample. We simultaneously apply an electric field transverse to the flow direction to transport small ({le} 2 {micro}m), negatively-charged analytes into a separate purified recovery fluid using a modified H-filter configuration [Micronics US Patent 5,716,852]. Hunter and O'Brien combined transverse electrophoresis and acoustic focusing to measure the surface charge on large particles, [2] but to our knowledge, our work is the first demonstration combining these two techniques in a continuous flow device. Marina et al. demonstrated superimposed dielectrophoresis (DEP) and acoustic focusing for enhanced separations [3], but these devices have limited throughput due to the rapid decay of DEP forces. Both acoustic standing waves and electric fields …

Single-sided and mobile nuclear magnetic resonance (NMR) sensors have the advantages of portability, low cost, and low power consumption compared to conventional high-field NMR and magnetic resonance imaging (MRI) systems. We present fast, flexible, and easy-to-implement target field algorithms for mobile NMR and MRI magnet design. The optimization finds a global optimum ina cost function that minimizes the error in the target magnetic field in the sense of least squares. When the technique is tested on a ring array of permanent-magnet elements, the solution matches the classical dipole Halbach solution. For a single-sided handheld NMR sensor, the algorithm yields a 640 G field homogeneous to 16 100 ppm across a 1.9 cc volume located 1.5 cm above the top of the magnets and homogeneous to 32 200 ppm over a 7.6 cc volume. This regime is adequate for MRI applications. We demonstrate that the homogeneous region can be continuously moved away from the sensor by rotating magnet rod elements, opening the way for NMR sensors with adjustable"sensitive volumes."

The resonant Auger effect of atomic neon exposed to high-intensity x-ray radiation in resonance with the 1s {yields} 3p transition is discussed. High intensity here means that the x-ray peak intensity is sufficient ({approx} 10{sup 18} W/cm{sup 2}) to induce Rabi oscillations between the neon ground state and the 1s{sup -1}3p ({sup 1}P) state within the relaxation lifetime of the inner-shell vacancy. For the numerical analysis presented, an effective two-level model, including a description of the resonant Auger decay process, is employed. Both coherent and chaotic x-ray pulses are treated. The latter are used to simulate radiation from x-ray free-electron lasers based on the principle of self-amplified spontaneous emission. Observing x-ray-driven atomic population dynamics in the time domain is challenging for chaotic pulse ensembles. A more practical option for experiments using x-ray free-electron lasers is to measure the line profiles in the kinetic energy distribution of the resonant Auger electron. This provides information on both atomic population dynamics and x-ray pulse properties.

In order to develop plasma diagnostic for reduced-size hot hohlraums under laser irradiation, they have studied the L-shell emission from highly charged gold ions in the SuperEBIT electron beam ion trap. The resolving power necessary to identify emission features from individual charge states in a picket fence pattern has been estimated, and the observed radiation features have been compared with atomic structure calculations. They find that the strong 3d{sub 5/2} {yields} 2p{sub 3/2} emission features are particularly useful in determining the charge state distribution and average ion charge <Z>, which are strongly sensitive to the electron temperature.