Microfluidics for Energy Applications

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Microfluidic methods developed primarily for medical applications have much to offer energy applications. This short paper will provide the motivation and outline my group’s recent work in two such areas: (1) microfluidics and optics for bioenergy and (2) microfluidics for carbon management. Full details will be provided in talk. Within the bioenergy theme, we are developing photobioreactor architectures that leverage micro-optics and microfluidics to cater both light and fluids to maximize productivity of microalgae. Within the carbon management theme we are developing a suite of methods to study porescale transport and reactivity in carbon sequestration and enhanced oil recovery. Results indicate potential for order of magnitude gains in photobioreactor technology and a 100-fold improvement over current subsurface fluid transport analysis methods

High resolution imaging of the Venus night side using a Rockwell 128x128 HgCdTe array

The University of Hawaii operates an infrared camera with a 128x128 HgCdTe detector array on loan from JPL's High Resolution Imaging Spectrometer (HIRIS) project. The characteristics of this camera system are discussed. The infrared camera was used to obtain images of the night side of Venus prior to and after inferior conjunction in 1988. The images confirm Allen and Crawford's (1984) discovery of bright features on the dark hemisphere of Venus visible in the H and K bands. Our images of these features are the best obtained to date. Researchers derive a pseudo rotation period of 6.5 days for these features and 1.74 microns brightness temperatures between 425 K and 480 K. The features are produced by nonuniform absorption in the middle cloud layer (47 to 57 Km altitude) of thermal radiation from the lower Venus atmosphere (20 to 30 Km altitude). A more detailed analysis of the data is in progress

Corner accumulation behavior of spermatozoa in microchannels

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.In this study, microfluidic approaches and fluorescence microscopy were used to study cross-sectional distribution of bull spermatozoa in a rectangular microchannel. The results indicate a strong corner accumulation behavior of bull spermatozoa in a rectangular microchannel. Results indicate that 74% of spermatozoa accumulate near boundaries and only 26% of spermatozoa are bulk swimmers. Furthermore, 66% of wall swimmers are corner swimmers. The distinction and quantification of wall vs. corner vs. bulk swimmers was enabled by the unique head-on microchannel imaging approach applied here

Applications of the quasi-steady-state photoconductance technique

The main applications of photoconductance measurements of silicon wafers are the determination of implicit device voltages, bulk minority carrier lifetimes, emitter recombination currents and surface recombination velocities. These applications are illustrated with selected experiments. Multicrystalline and single crystal silicon wafers are used with different surface conditions. The practical situations considered here range from industrial process control to advanced research. Interpreting photoconductance in terms of implicit device voltage is particularly useful: the swept illumination conditions used in a quasi-steady-state photoconductance measurement permit the determination of complete I-V characteristic curves, ideality factors and saturation currents. The more classical interpretation in terms of an effective lifetime teff allows to discriminate different recombination mechanisms. Shockley-Read-Hall bulk recombination with a large asymmetry between the fundamental electron and hole lifetimes is found to explain the strong variation of teff at low injection level observed in some samples. Measurements in the high injection range permit the determination of the emitter saturation current density. This saturation current can impose quite restrictive limits on the measurable minority carrier lifetimes at low injection, particularly for low resistivity wafers. The surface recombination velocity of the Si/SiO2 interface can also be a source of variability of teff

Interplay of bulk and surface properties for steady-state measurements of minority carrier lifetimes

The measurement of the minority carrier lifetime is a powerful tool in the field of semiconductor material characterization as it is very sensitive to electrically active defects. Furthermore, it is applicable to a wide range of samples such as ingots or wafers. In this work, a systematic theoretical analysis of the steady-state approach is presented. It is shown how the measured lifetime relates to the intrinsic bulk lifetime for a given material quality, sample thickness, and surface passivation. This makes the bulk properties experimentally accessible by separating them from the surface effects. In particular, closed analytical solutions of the most important cases, such as passivated and unpassivated wafers and blocks are given. Based on these results, a criterion for a critical sample thickness is given beyond which a lifetime measurement allows deducing the bulk properties for a given surface recombination. These results are of particular interest for semiconductor material diagnostics especially for photovoltaic applications but not limited to this field.Comment: 17 pages, 3 figure

1994 Northern Goshawk inventory on portions of Los Alamos National Laboratory, Los Alamos, NM

Northern goshawks (Accipiter gentilis) (hereafter referred to as goshawk) are large forest dwelling hawks. They are the largest species of the Accipiter genus which also includes sharp-shinned hawks (A. striatus) and the Cooper`s hawk (A. cooperii). Goshawks are holarctic in distribution and nest in coniferous, deciduous, and mixed species forests. In the southwest they primarily nest in ponderosa pine (Pinus ponderosa), mixed species, and spruce-fir forests. Goshawks may be declining in population and reproduction in the southwestern United States. In 1982 the USDA-Forest Service listed the goshawk as a {open_quotes}sensitive species{close_quotes} and in 1992 the U.S. Fish and Wildlife Service listed the goshawk as a {open_quotes}Category 2 species{close_quotes} in accordance with the Endangered Species Act. Reasons for the possible decline in goshawk populations include timber harvesting resulting in the loss of nesting habitat, toxic chemicals, and the effects of drought, fire, and disease. Thus, there is a need to determine their population status and assess impacts of management activities in potential goshawk habitat. Goshawk inventory was conducted during the 1993 nesting season with no adult goshawk responses detected within the LANL survey area. As noted by Sinton and Kennedy, these results may be interpreted in several ways: (1) no goshawk territory(ies) occur in the inventoried area; (2) goshawk territory(ies) exist but have failed prior to the survey and thus were not detected; or (3) territory(ies) exist and were successful but the goshawks did not respond to tapes or their responses were undetected by the observer. For those reasons, a goshawk inventory was conducted in 1994. This report summarizes the results of this inventory

Recovering the state sequence of hidden Markov models using mean-field approximations

Inferring the sequence of states from observations is one of the most fundamental problems in Hidden Markov Models. In statistical physics language, this problem is equivalent to computing the marginals of a one-dimensional model with a random external field. While this task can be accomplished through transfer matrix methods, it becomes quickly intractable when the underlying state space is large. This paper develops several low-complexity approximate algorithms to address this inference problem when the state space becomes large. The new algorithms are based on various mean-field approximations of the transfer matrix. Their performances are studied in detail on a simple realistic model for DNA pyrosequencing.Comment: 43 pages, 41 figure

Evidence for a broadly distributed Samoan-plume signature in the northern Lau and North Fiji Basins

Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 15 (2014): 986–1008, doi:10.1002/2013GC005061.Geochemical enrichment of lavas in the northern Lau Basin may reflect the influx of Samoan-plume mantle into the region. We report major and trace element abundances and He-Sr-Nd-Hf-Pb-isotopic measurements for 23 submarine volcanic glasses covering 10 locations in the northern Lau and North Fiji Basins, and for three samples from Wallis Island, which lies between Samoa and the Lau Basin. These data extend the western limit of geochemical observations in the Basins and improve the resolution of North-South variations in isotopic ratios. The Samoan hot spot track runs along the length of the northern trace of the Lau and North Fiji Basins. We find evidence for a Samoan-plume component in lavas as far West as South Pandora Ridge (SPR), North Fiji Basin. Isotopic signatures in SPR samples are similar to those found in Samoan Upolu shield lavas, but show a slight shift toward MORB-like compositions. We explain the origin of the enriched signatures by a model in which Samoan-plume material and ambient depleted mantle undergo decompression melting during upwelling after transiting from beneath the thick Pacific lithosphere to beneath the thin lithosphere in the northern Lau and North Fiji Basins. Other lavas found in the region with highly depleted isotopic signatures may represent isolated pockets of depleted mantle in the basins that evaded this enrichment process. We further find that mixing between the two components in our model, a variably degassed high-3He/4He Samoan component and depleted MORB, can explain the diversity among geochemical data from the northern Lau Basin.M.G.J. acknowledges support from NSF grants OCE-1061134, OCE-1153894, and EAR-1145202 and J.B.T. acknowledges support from the French Agence Nationale de la Recherche (grant ANR-10-BLANC-0603 M&Ms—Mantle Melting—Measurements, Models, Mechanisms).2014-10-1