Analytic quasi-steady evolution of a marginally unstable wave in the presence of drag and scattering

The 1D bump-on-tail problem is studied in order to determine the influence of drag on quasi-steady solutions near marginal stability ($1-\gamma_d/\gamma_L\ll 1$) when effective collisions are much larger than the instability growth rate ($\nu \gg \gamma$). In this common tokamak regime, it is rigorously shown that the paradigmatic Berk-Breizman cubic equation for the nonlinear mode evolution reduces to a much simpler differential equation, dubbed the time-local cubic equation, which can be solved directly. It is found that in addition to increasing the saturation amplitude, drag introduces a shift in the apparent oscillation frequency by modulating the saturated wave envelope. Excellent agreement is found between the analytic solution for the mode evolution and both the numerically integrated Berk-Breizman cubic equation and fully nonlinear 1D Vlasov simulations. Experimentally isolating the contribution of drag to the saturated mode amplitude for verification purposes is explored but complicated by the reality that the amount of drag can not be varied independently of other key parameters in realistic scenarios. While the effect of drag is modest when the ratio of drag to scattering $\alpha/\nu$ is very small, it can become substantial when $\alpha/\nu \gtrsim 0.5$, suggesting that drag should be accounted for in quantitative models of fast-ion-driven instabilities in fusion plasmas.Comment: 22 pages, 11 figure

Shifting and splitting of resonance lines due to dynamical friction in plasmas

A quasilinear plasma transport theory that incorporates Fokker-Planck dynamical friction (drag) and scattering is self-consistently derived from first principles for an isolated, marginally-unstable mode resonating with an energetic minority species. It is found that drag fundamentally changes the structure of the wave-particle resonance, breaking its symmetry and leading to the shifting and splitting of resonance lines. In contrast, scattering broadens the resonance in a symmetric fashion. Comparison with fully nonlinear simulations shows that the proposed quasilinear system preserves the exact instability saturation amplitude and the corresponding particle redistribution of the fully nonlinear theory. Even though drag is shown to lead to a relatively small resonance shift, it underpins major changes in the redistribution of resonant particles. These findings suggest that drag can play a key role in modeling the energetic particle confinement in future burning fusion plasmas

Next generation multiplexing for digital PCR using a novel melt-based hairpin probe design

Digital PCR (dPCR) is a powerful tool for research and diagnostic applications that require absolute quantification of target molecules or detection of rare events, but the number of nucleic acid targets that can be distinguished within an assay has limited its usefulness. For most dPCR systems, one target is detected per optical channel and the total number of targets is limited by the number of optical channels on the platform. Higher-order multiplexing has the potential to dramatically increase the usefulness of dPCR, especially in scenarios with limited sample. Other potential benefits of multiplexing include lower cost, additional information generated by more probes, and higher throughput. To address this unmet need, we developed a novel melt-based hairpin probe design to provide a robust option for multiplexing digital PCR. A prototype multiplex digital PCR (mdPCR) assay using three melt-based hairpin probes per optical channel in a 16-well microfluidic digital PCR platform accurately distinguished and quantified 12 nucleic acid targets per well. For samples with 10,000 human genome equivalents, the probe-specific ranges for limit of blank were 0.00%–0.13%, and those for analytical limit of detection were 0.00%–0.20%. Inter-laboratory reproducibility was excellent (r2 = 0.997). Importantly, this novel melt-based hairpin probe design has potential to achieve multiplexing beyond the 12 targets/well of this prototype assay. This easy-to-use mdPCR technology with excellent performance characteristics has the potential to revolutionize the use of digital PCR in research and diagnostic settings

Novel internal measurements of ion cyclotron frequency range fast-ion driven modes

Novel internal measurements and analysis of ion cyclotron frequency range fast-ion driven modes in DIII-D are presented. Observations, including internal density fluctuation (˜n) measurements obtained via Doppler backscattering, are presented for modes at low harmonics of the ion cyclotron frequency localized in the edge. The measurements indicate that these waves, identified as coherent ion cyclotron emission (ICE), have high wave number, k⊥ρfast1, consistent with the cyclotron harmonic wave branch of the magnetoacoustic cyclotron instability, or electrostatic instability mechanisms. Measurements show extended spatial structure (at least ∼1/6 the minor radius). These edge ICE modes undergo amplitude modulation correlated with edge localized modes (ELM) that is qualitatively consistent with expectations for ELM-induced fast-ion transport

DIRECT WATER INJECTION COOLING FOR MILITARY ENGINES AND EFFECTS ON THE DIESEL CYCLE PRACTICAL SYSTEMS

A study was conducted on the feasibility" of totally cooling a single-cylinder diesel engine by direct injection of water into the combustion chanlber. The term "total cooling" can be taken to mean stabilized cooling at all loads and speeds so as to eliminate need for conventional cooling jackets, cooling fins, or oil spray jets. The engine used was a CLR Direct Injection Diesel with 42.5 cubic inch displacement and a compression ratio of 16:1. Most of the running was at 1800 rpm and 92 psi IMEP. Separate measurements were made of heat rejection to the cylinder tread, liner, and crankease oil to determine more accurately where the cooling effect was being applied. Water injection was by means of a Bosch pnmp and various pencil-type nozzles installed, adjacent to the fuel injector in the cylinder head. Port injection and port induction were also briefly investigated. A five-hole, 90 ~ included angle nozzle was used, as was a three-hole, 30 ~ included angle unit. For comparison, a nozzle directing one spray obliquely at the cylinder wall was also tested. Firing pressure was monitored using a piezo-eleetric transducer; both pressure-time and pressure~volume (indicator) records were obtained. In order to determine timing of both fuel and water injection, needle lift was monitored using a differential transformer pickup. The results of this study indicate: Optimum total engine cooling by direct water injection was accomplished over a wide range of water injection timings (from 450 to 720 CA degrees after TDC power stroke) at water/fuel ratios of 2.9 to 3.7 with output power and brake specific fuel consumption improved 5 to 20%, respectively, over that with the standard jacket-cooled CLR engine. Emissions are affected in an expected manner by the presence of water: NOx is decreased, sometimes substantially, while the other emissions (HC, CO) tend to increase. When cooling the exhaust, the condensate becomes an effective scrubber of sulfur oxides. NO~ was not significantly reduced by scrubbing, but if the condensate is made su~eiently alkaline (pH :>8), CO2 was unintentionally scrubbed out. The quail W of the uncondensed exhaust for turbooharglng is attractive. A thenretical gain of about 17.5% in available exhaust enerKy due to generation of steam was calculated, along with a temperature decrease of several hundred degrees Fahrenheit. Water contamination of the lubricating oil varies from negligible to extreme, depending on injection quantity, timing, and spray pattern. By not directing water at the liner wall, and by keeping the oil above 212~ one can maintain the oil in a dry condition. Based on this work, several pertinent recommendations have been made: (1) utilize water injection fl)r short-duration, very high-output operation which would otherwise be destructive due to thermal overload ; (2) use water induction cooling in event of loss of conventional liqnid coolant; (3) utilize exhaust scrnbbing in stationary applications to permit burning of high-sulfur fuels without producing sulfur oxide emissions; nitrogen oxides could likewise be reduced by the injection of small amounts of water; and (4) since 2-stroke-cycle engines are an important category of diesel engines, some work similar to this effort should be done to this engine type; prospects are good for success, but conditions are apt to be more restrictive

Genetic associations of hemoglobin in children with chronic kidney disease in the PediGFR Consortium

BACKGROUND: Genome-wide association studies (GWAS) in healthy populations have identified variants associated with erythrocyte traits, but genetic causes of hemoglobin variation in children with CKD are incompletely understood