2,348 research outputs found

    MODIS airborne simulator visible and near-infrared calibration, 1991 FIRE-Cirrus field experiment. Calibration version: FIRE King 1.1

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    Calibration of the visible and near-infrared channels of the MODIS Airborne Simulator (MAS) is derived from observations of a calibrated light source. For the 1991 FIRE-Cirrus field experiment, the calibrated light source was the NASA Goddard 48-inch integrating hemisphere. Laboratory tests during the FIRE Cirrus field experiment were conducted to calibrate the hemisphere and from the hemisphere to the MAS. The purpose of this report is to summarize the FIRE-Cirrus hemisphere calibration, and then describe how the MAS was calibrated from observations of the hemisphere data. All MAS calibration measurements are presented, and determination of the MAS calibration coefficients (raw counts to radiance conversion) is discussed. Thermal sensitivity of the MAS visible and near-infrared calibration is also discussed. Typically, the MAS in-flight is 30 to 60 degrees C colder than the room temperature laboratory calibration. Results from in-flight temperature measurements and tests of the MAS in a cold chamber are given, and from these, equations are derived to adjust the MAS in-flight data to what the value would be at laboratory conditions. For FIRE-Cirrus data, only channels 3 through 6 were found to be temperature sensitive. The final section of this report describes comparisons to an independent MAS (room temperature) calibration by Ames personnel using their 30-inch integrating sphere

    Development of novel melt spinning based processing route for oxide dispersion strengthened steels

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    Melt spinning of an Fe-5Y and Fe-1Y-1Ti (wt%) alloys produced a relatively uniform spatial distribution of Y and Ti in solid solution and ribbons with consistent yield (> 60% by weight), fast processing time ( 100 g feedstock material) and repeatability. Heat treatment in the presence of Fe2O3 as an oxygen source (Rhines pack method) at 973 K validated the potential of forming < 20 nm Yrich oxides in the 1 Fe-5Y ribbons. Pulverized Fe-1Y-1Y ribbons were consolidated to bulk using the field assisted sintering technique (FAST) incorporating nano-sized Fe3O4 powder as the oxygen source. After FAST at 1273 K, 50 MPa and 30 min a comparatively high number density of sub-micron Y and/or Ti-rich oxides were developed. Further formation of fine-scale oxides took place during post-FAST annealing, resulting in an approximate 20% increase in hardness at temperatures below 573 K, but with a reduced hardening effect above 673 K due to a small fraction of persistent porosity and mechanically weak prior ribbon boundaries that were decorated with Ti-rich oxide

    SN2013fs and SN2013fr: Exploring the circumstellar-material diversity in Type II supernovae

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    We present photometry and spectroscopy of SN2013fs and SN2013fr in the first 100 days post-explosion. Both objects showed transient, relatively narrow Hα\alpha emission lines characteristic of SNeIIn, but later resembled normal SNeII-P or SNeII-L, indicative of fleeting interaction with circumstellar material (CSM). SN2013fs was discovered within 8hr of explosion. Its light curve exhibits a plateau, with spectra revealing strong CSM interaction at early times. It is a less luminous version of the transitional SNIIn PTF11iqb, further demonstrating a continuum of CSM interaction intensity between SNeII-P and IIn. It requires dense CSM within 6.5×\times1014^{14}~cm of the progenitor, from a phase of advanced pre-SN mass loss shortly before explosion. Spectropolarimetry of SN2013fs shows little continuum polarization, but noticeable line polarization during the plateau phase. SN2013fr morphed from a SNIIn at early times to a SNII-L. After the first epoch its narrow lines probably arose from host-galaxy emission, but the bright, narrow Hα\alpha emission at early times may be intrinsic. As for SN2013fs, this would point to a short-lived phase of strong CSM interaction if proven to be intrinsic, suggesting a continuum between SNeIIn and II-L. It is a low-velocity SNII-L, like SN2009kr but more luminous. SN2013fr also developed an IR excess at later times, due to warm CSM dust that require a more sustained phase of strong pre-SN mass loss.Comment: MNRAS accepted. 28 pages, 23 figures, 8 table

    Hydrodynamic bubble coarsening in off-critical vapour-liquid phase separation

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    Late-stage coarsening in off-critical vapour-liquid phase separation is re-examined. In the limit of bubbles of vapour distributed throughout a continuous liquid phase, it is argued that coarsening proceeds via inertial hydrodynamic bubble collapse. This replaces the Lifshitz-Slyozov-Wagner mechanism seen in binary liquid mixtures. The arguments are strongly supported by simulations in two dimensions using a novel single-component soft sphere fluid.Comment: 5 pages, 3 figures, revtex3.

    The effect of volume change and stack pressure on solid‐state battery cathodes

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    Solid-state lithium batteries may provide increased energy density and improved safety compared with Li-ion technology. However, in a solid-state composite cathode, mechanical degradation due to repeated cathode volume changes during cycling may occur, which may be partially mitigated by applying a significant, but often impractical, uniaxial stack pressure. Herein, we compare the behavior of composite electrodes based on Li4Ti5O12 (LTO) (negligible volume change) and Nb2O5 (+4% expansion) cycled at different stack pressures. The initial LTO capacity and retention are not affected by pressure but for Nb2O5, they are significantly lower when a stack pressure of &lt;2 MPa is applied, due to inter-particle cracking and solid-solid contact loss because of cyclic volume changes. This work confirms the importance of cathode mechanical stability and the stack pressures for long-term cyclability for solid-state batteries. This suggests that low volume-change cathode materials or a proper buffer layer are required for solid-state batteries, especially at low stack pressures

    Microstructural and mechanical characterisation of Fe-14Cr-0.22Hf alloy fabricated by spark plasma sintering

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    Fe-14Cr pre-alloyed powder and pure Hf powder were mechanically alloyed to produce powder with nominal composition Fe-14Cr-0.22Hf (wt. %) that was consolidated by the spark plasma sintering (SPS) technique in order to investigate the ability of Hf to produce a nanometric dispersion of oxide particles in a ferritic matrix. Comprehensive microstructural and mechanical characterisation of the as-milled powder and the consolidated material was performed using electron microscopy, X-ray diffraction, atom probe tomography and indentation techniques. It was shown that Hf additions can effectively produce, by internal oxidation, a fine scale dispersion of Hf-O nanoparticles in the consolidated material. A uniform grain structure was produced in the alloy. Although the nanoparticle dispersion was not homogeneous at the finest scale, the resulting dispersion strengthening contributed significantly to the hardness. According to these results, internal oxidation of reactive elements rather than direct addition of oxides may offer additional opportunities in the design and development of oxide dispersion strengthened steels

    Alpha-Cyclodextrin-Containing Beverages for Hydration Enhancement in Humans

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    A substantial portion of the world’s population may be inadequately hydrated, and dehydration is associated with several disease states and acute impairments in exercise performance. As such, there is continued interest in novel strategies to promote adequate hydration. The carbohydrate alpha-cyclodextrin has recently been shown to enhance water uptake through human aquaporins expressed in a single-cell model and promote longevity in model multicellular organisms. However, there is no relevant human research examining the potential hydrating effects of alpha-cyclodextrin-containing beverages. PURPOSE: To determine if novel beverage formulations containing alpha-cyclodextrin improve a bioimpedance-based hydration marker in humans. METHODS: In a randomized, double-blind, crossover design, eight adults (5 M, 3 F; [mean ± SD] age: 24.9 ± 4.2 years; height: 169.6 ± 5.5 cm; weight: 71.2 ± 13.2 kg; body mass index: 24.6 ± 3.2 kg/m2; body fat: 17.0 ± 5.6%) completed trials including the ingestion of 1 liter of still water (control; CON), still water plus alpha-cyclodextrin (CD), or still water plus alpha- cyclodextrin and complexing agents (B-vitamins and amino acids; Complex). Before beverage ingestion, and every 15 minutes for two hours following beverage ingestion, bioimpedance spectroscopy was performed to estimate phase angle values as a noninvasive marker of cellular hydration. Phase angle was calculated as: arctan(/) × (180°/), where Xc is the reactance (indicative of the capacitive properties of the cell membrane) and R is resistance (opposition to flow of electrical current), both obtained from bioimpedance spectroscopy. Due to the pilot nature of this trial, data were analyzed using descriptive statistics only (data presented as median ± interquartile range). RESULTS: Two hours after completion of beverage ingestion, median ± interquartile range changes in phase in angle were 3.4 ± 1.7% for CON, 4.6 ± 1.2% for CD, and 5.4 ± 3.3% for Complex. Xc changes were 9.9 ± 2.9% for CON, 10.9 ± 3.0% for CD, and 11.1 ± 3.1% for Complex. R changes were 6.5 ± 1.4% for CON, 6.8 ± 1.9% for CD, and 5.6 ± 1.1% for Complex. CONCLUSION: The results of this pilot study indicate the potential for alpha-cyclodextrin- containing beverages to improve a bioimpedance-based hydration marker, phase angle, in humans, with the potential that B-vitamins and amino acids may further enhance hydration beyond alpha-cyclodextrin alone. The larger improvements in phase angle in the Complex group were due to a greater increase in bioelectrical reactance alongside a smaller increase in bioelectrical resistance. Future research with larger sample sizes should examine the potential for these beverages to improve human hydration and health

    IRAK4 mediates colitis-induced tumorigenesis and chemoresistance in colorectal cancer

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    Aberrant activation of the NF-κB transcription factors underlies chemoresistance in various cancer types, including colorectal cancer (CRC). Targeting the activating mechanisms, particularly with inhibitors to the upstream IκB kinase (IKK) complex, is a promising strategy to augment the effect of chemotherapy. However, clinical success has been limited, largely because of low specificity and toxicities of tested compounds. In solid cancers, the IKKs are driven predominantly by the Toll-like receptor (TLR)/IL-1 receptor family members, which signal through the IL-1 receptor-associated kinases (IRAKs), with isoform 4 (IRAK4) being the most critical. The pathogenic role and therapeutic value of IRAK4 in CRC have not been investigated. We found that IRAK4 inhibition significantly abrogates colitis-induced neoplasm in APCMin/+ mice, and bone marrow transplant experiments showed an essential role of IRAK4 in immune cells during neoplastic progression. Chemotherapy significantly enhances IRAK4 and NF-κB activity in CRC cells through upregulating TLR9 expression, which can in turn be suppressed by IRAK4 and IKK inhibitors, suggesting a feed-forward pathway that protects CRC cells from chemotherapy. Lastly, increased tumor phospho-IRAK4 staining or IRAK4 mRNA expression is associated with significantly worse survival in CRC patients. Our results support targeting IRAK4 to improve the effects of chemotherapy and outcomes in CRC
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