Operation of a 1-Liter-Volume Gaseous Argon Scintillation Counter

We have built a gas-phase argon ionization detector to measure small nuclear recoil energies (< 10 keVee). In this paper, we describe the detector response to X-ray and gamma calibration sources, including analysis of pulse shapes, software triggers, optimization of gas content, and energy- and position-dependence of the signal. We compare our experimental results against simulation using a 5.9-keV X-ray source, as well as higher-energy gamma sources up to 1332 keV. We conclude with a description of the detector, DAQ, and software settings optimized for a measurement of the low-energy nuclear quenching factor in gaseous argon. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory in part under Contract W-7405-Eng-48 and in part under Contract DE-AC52-07NA27344. Funded by Lab-wide LDRD. LLNL-JRNL-415990-DRAFT.Comment: 29 pages, single-column, double-spaced, 21 figure

Subharmonic energy transfer from the semidiurnal internal tide to near-diurnal motions over Kaena Ridge, Hawaii

Author Posting. © American Meteorological Society, 2013. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 43 (2013): 766–789, doi:10.1175/JPO-D-12-0141.1.Nonlinear energy transfers from the semidiurnal internal tide to high-mode, near-diurnal motions are documented near Kaena Ridge, Hawaii, an energetic generation site for the baroclinic tide. Data were collected aboard the Research Floating Instrument Platform (FLIP) over a 35-day period during the fall of 2002, as part of the Hawaii Ocean Mixing Experiment (HOME) Nearfield program. Energy transfer terms for a PSI resonant interaction at midlatitude are identified and compared to those for near-inertial PSI close to the M2 critical latitude. Bispectral techniques are used to demonstrate significant energy transfers in the Nearfield, between the low-mode M2 internal tide and subharmonic waves with frequencies near M2/2 and vertical wavelengths of O(120 m). A novel prefilter is used to test the PSI wavenumber resonance condition, which requires the subharmonic waves to propagate in opposite vertical directions. Depth–time maps of the interactions, formed by directly estimating the energy transfer terms, show that energy is transferred predominantly from the tide to subharmonic waves, but numerous reverse energy transfers are also found. A net forward energy transfer rate of 2 × 10−9 W kg−1 is found below 400 m. The suggestion is that the HOME observations of energy transfer from the tide to subharmonic waves represent a first step in the open-ocean energy cascade. Observed PSI transfer rates could account for a small but significant fraction of the turbulent dissipation of the tide within 60 km of Kaena Ridge. Further extrapolation suggests that integrated PSI energy transfers equatorward of the M2 critical latitude may be comparable to PSI energy transfers previously observed near 28.8°N.This work was supported by the National Science Foundation and the Office of Naval Research.2013-10-0

A CANDLE for a deeper in-vivo insight

A new Collaborative Approach for eNhanced Denoising under Low-light Excitation (CANDLE) is introduced for the processing of 3D laser scanning multiphoton microscopy images. CANDLE is designed to be robust for low signal-to-noise ratio (SNR) conditions typically encountered when imaging deep in scattering biological specimens. Based on an optimized non-local means filter involving the comparison of filtered patches, CANDLE locally adapts the amount of smoothing in order to deal with the noise inhomogeneity inherent to laser scanning fluorescence microscopy images. An extensive validation on synthetic data, images acquired on microspheres and in vivo images is presented. These experiments show that the CANDLE filter obtained competitive results compared to a state-of-the-art method and a locally adaptive optimized non-local means filter, especially under low SNR conditions (PSNR < 8 dB). Finally, the deeper imaging capabilities enabled by the proposed filter are demonstrated on deep tissue in vivo images of neurons and fine axonal processes in the Xenopus tadpole brain.We want to thank Florian Luisier for providing free plugin of his PureDenoise filter. We also want to thank Markku Makitalo for providing the code of their OVST. This study was supported by the Canadian Institutes of Health Research (CIHR, MOP-84360 to DLC and MOP-77567 to ESR) and Cda (CECR)-Gevas-OE016. MM holds a fellowship from the Deutscher Akademischer Austasch Dienst (DAAD) and a McGill Principal's Award. ESR is a tier 2 Canada Research Chair. This work has been partially supported by the Spanish Health Institute Carlos III through the RETICS Combiomed, RD07/0067/2001. This work benefited from the use of ImageJ.Coupé, P.; Munz, M.; Manjón Herrera, JV.; Ruthazer, ES.; Collins, DL. (2012). A CANDLE for a deeper in-vivo insight. Medical Image Analysis. 16(4):849-864. https://doi.org/10.1016/j.media.2012.01.002S84986416

Beamspace time reversal maximum likelihood estimation for microwave breast imaging

© 2014 IEEE. We consider maximum likelihood based beamspace time reversal beamforming for breast cancer localization. We reduce the computational burden of maximum likelihood estimation through reduced dimensional beamspace processing. Beamspace processing also provides additional beamspace gain which contributes to suppress strong clutter effects. We collect multistatic scattering fields through FDTD simulation and further process it in beamspace for maximum likelihood based time reversal imaging. The imaging technique is used to localize a small tumor in a dense breast. It is observed that the proposed imaging technique can localize tumors unambiguously even in dense breast phantom

NASA scientific and technical publications: A catalog of special publications, reference publications, conference publications, and technical papers, 1989

This catalog lists 190 citations of all NASA Special Publications, NASA Reference Publications, NASA Conference Publications, and NASA Technical Papers that were entered into the NASA scientific and technical information database during accession year 1989. The entries are grouped by subject category. Indexes of subject terms, personal authors, and NASA report numbers are provided

Investigation the Plugging Behavior of Virus filters

A virus filtration step is integral to the manufacturing of biopharmaceuticals to ensure viral safety. A virus filter is a single-use device that uses a size-based separation process and has a unique structure with minimal defects, so that contaminating virus particles cannot pass through the membrane pores, while therapeutic molecules can. The development of novel antibodies (Abs), including significant increases in product titers, is frequently challenged by virus filter fouling, making a better understanding of the underlying mechanisms essential. This thesis focused investigating of the effect of prefilter types, buffer type and salt content on virus filtration performance. The impact of the protein-protein interactions and their aggregates on the filtrate flux during virus filtration of highly concentrated mAb solutions are also investigated. In Chapter 2, prefiltration and flux decay studies were performed with a different concentration of polyclonal human immunoglobulin G (IgG) using two commercially Prefilters (Viresolve® pre-filter and Planova 75N) and virus filters (Viresolve® Pro and Planova BioEx). The fouling behaviors of the virus filters were strongly affected by the concentration of the feed solution and protein oligomers. The prefilters did not provide much benefit in improving the filtrate flux at high concentrations. Filtration using Planova BioEX in two runs without prefiltration shows less fouling and significant flux improvement in the second run and the application of post-filtration buffer flush with different conditions results in higher flux recovery in the second run than the first run. Size exclusion chromatography (SEC) analysis for IgG solution in different buffer conditions revealed that the aggregate concentration increases slightly as the IgG concentration increases. Results using dynamic light scattering (DLS) in the same buffer conditions shows that the mean hydrodynamic diameter increases as the increase of protein concentration and the protein tends to have attractive interactions in both buffer conditions. This IgG has a high molecular weight (250 kDa) and it is moderately hydrophobic. In Chapter 3, virus filtration was performed with an industrially monoclonal antibody (mAb C) with different concentrations up to 50 g/L in different buffer conditions using Viresolve Pro virus filter and adsorptive prefilters. This mAb was subjected to decoupled prefiltration to evaluate how different types of prefilters affected its filterability. Filter fouling is found to be strongly affected by the product concentration and the presence of aggregates. An analysis of size exclusion chromatography (SEC) showed that the presence of large amount of high molecular weight species considered as irreversible aggregates correlates with irreversible fouling that caused reduced mAb throughput and filter fouling. Results using dynamic light scattering (DLS) in different buffer conditions shows that the mean hydrodynamic diameter increases as the increase of protein concentration and the protein tend to have a stronger tendency to aggregate in tris buffer compared to sodium phosphate buffer. The pharmaceutical analysis system PA800 plus was also used to characterize the various mAb fractions from prefiltration and virus filtration. In Chapter 4, an overall conclusion for this work showing major findings and identifying areas for future study

Investigation the Plugging Behavior of Virus filters

A virus filtration step is integral to the manufacturing of biopharmaceuticals to ensure viral safety. A virus filter is a single-use device that uses a size-based separation process and has a unique structure with minimal defects, so that contaminating virus particles cannot pass through the membrane pores, while therapeutic molecules can. The development of novel antibodies (Abs), including significant increases in product titers, is frequently challenged by virus filter fouling, making a better understanding of the underlying mechanisms essential. This thesis focused investigating of the effect of prefilter types, buffer type and salt content on virus filtration performance. The impact of the protein-protein interactions and their aggregates on the filtrate flux during virus filtration of highly concentrated mAb solutions are also investigated. In Chapter 2, prefiltration and flux decay studies were performed with a different concentration of polyclonal human immunoglobulin G (IgG) using two commercially Prefilters (Viresolve® pre-filter and Planova 75N) and virus filters (Viresolve® Pro and Planova BioEx). The fouling behaviors of the virus filters were strongly affected by the concentration of the feed solution and protein oligomers. The prefilters did not provide much benefit in improving the filtrate flux at high concentrations. Filtration using Planova BioEX in two runs without prefiltration shows less fouling and significant flux improvement in the second run and the application of post-filtration buffer flush with different conditions results in higher flux recovery in the second run than the first run. Size exclusion chromatography (SEC) analysis for IgG solution in different buffer conditions revealed that the aggregate concentration increases slightly as the IgG concentration increases. Results using dynamic light scattering (DLS) in the same buffer conditions shows that the mean hydrodynamic diameter increases as the increase of protein concentration and the protein tends to have attractive interactions in both buffer conditions. This IgG has a high molecular weight (250 kDa) and it is moderately hydrophobic. In Chapter 3, virus filtration was performed with an industrially monoclonal antibody (mAb C) with different concentrations up to 50 g/L in different buffer conditions using Viresolve Pro virus filter and adsorptive prefilters. This mAb was subjected to decoupled prefiltration to evaluate how different types of prefilters affected its filterability. Filter fouling is found to be strongly affected by the product concentration and the presence of aggregates. An analysis of size exclusion chromatography (SEC) showed that the presence of large amount of high molecular weight species considered as irreversible aggregates correlates with irreversible fouling that caused reduced mAb throughput and filter fouling. Results using dynamic light scattering (DLS) in different buffer conditions shows that the mean hydrodynamic diameter increases as the increase of protein concentration and the protein tend to have a stronger tendency to aggregate in tris buffer compared to sodium phosphate buffer. The pharmaceutical analysis system PA800 plus was also used to characterize the various mAb fractions from prefiltration and virus filtration. In Chapter 4, an overall conclusion for this work showing major findings and identifying areas for future study

Small-scale CMB Temperature and Polarization Anisotropies due to Patchy Reionization

We study contributions from inhomogeneous (patchy) reionization to arcminute scale ($1000 < \ell < 10,000$) cosmic microwave background (CMB) anisotropies. We show that inhomogeneities in the ionization fraction, rather than in the mean density, dominate both the temperature and the polarization power spectra. Depending on the ionization history and the clustering bias of the ionizing sources, we find that rms temperature fluctuations range from 2 $\mu$K to 8 $\mu$K and the corresponding values for polarization are over two orders of magnitude smaller. Reionization can significantly bias cosmological parameter estimates and degrade gravitational lensing potential reconstruction from temperature maps but not from polarization maps. We demonstrate that a simple modeling of the reionization temperature power spectrum may be sufficient to remove the parameter bias. The high-$\ell$ temperature power spectrum will contain some limited information about the sources of reionization.Comment: 11 pages, 8 figures. Minor changes to match version accepted by Ap

Estimate of convection-diffusion coefficients from modulated perturbative experiments as an inverse problem

The estimate of coefficients of the Convection-Diffusion Equation (CDE) from experimental measurements belongs in the category of inverse problems, which are known to come with issues of ill-conditioning or singularity. Here we concentrate on a particular class that can be reduced to a linear algebraic problem, with explicit solution. Ill-conditioning of the problem corresponds to the vanishing of one eigenvalue of the matrix to be inverted. The comparison with algorithms based upon matching experimental data against numerical integration of the CDE sheds light on the accuracy of the parameter estimation procedures, and suggests a path for a more precise assessment of the profiles and of the related uncertainty. Several instances of the implementation of the algorithm to real data are presented.Comment: Extended version of an invited talk presented at the 2012 EPS Conference. To appear in Plasma Physics and Controlled Fusio