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Evaluation of electron tomography reconstruction methods for interface roughness measurement
No full textWe evaluate the suitability of simultaneous iterative reconstruction technique (SIRT), filtered back projection, and simultaneous algebraic reconstruction technique methods for buried interface roughness measurements. We also investigate the effect of total electron dose distributed over the entire tilt series on measured roughness values. We investigate the applicability of the dose fractionation theorem by evaluating the effect of an increasing number of images, i.e., decreasing tilt increment size at fixed total electron irradiation dose on the quantitative measurement of buried interface roughness. The results indicate that SIRT is the most suitable method for reconstruction and a 3\ub0 to 5\ub0 angle is optimal for the roughness measurement.Peer reviewed: YesNRC publication: Ye
WIVERN: a new satellite concept to provide global in-cloud winds, precipitation and cloud properties.
No full textA new satellite concept with a conically scanning W-band Doppler radar to provide in-cloud winds, together with estimates of global rainfall, snowfall and cloud properties.
This paper presents a conically scanning space-borne Dopplerized 94GHz radar Earth Science mission concept, WIVERN, \u2018Wind VElocity Radar Nephoscope\u2019. WIVERN aims to provide global measurements of in-cloud winds using the Doppler shifted radar returns from hydrometeors. The conically scanning radar could provide wind data with daily revisits poleward of 50\ub0, 50-km horizontal resolution and approximately 1km vertical resolution. The measured winds, when assimilated into weather forecasts and provided they are representative of the larger scale mean flow, should lead to further improvements in the accuracy and effectiveness of forecasts of severe weather and better focusing of activities to limit damage and loss of life. It should also be possible to characterize the more variable winds associated with local convection. Polarization diversity would be used to enable high wind speeds to be unambiguously observed; analysis indicates that artifacts associated with polarization diversity are rare and can be identified. Winds should be measurable down to 1 km above the ocean surface and 2 km over land. The potential impact of the WIVERN winds on reducing forecast errors is estimated by comparison with the known positive impact of cloud motion and aircraft winds. The main thrust of WIVERN is observing in-cloud winds, but WIVERN should also provide global estimates of ice water content, cloud cover and vertical distribution continuing the data series started by CloudSat with the conical scan giving increased coverage. As with CloudSat, estimates of rainfall and snowfall rates should be possible. These non-wind products may also have a positive impact when assimilated into weather forecasts.Peer reviewed: YesNRC publication: Ye
Re-evaluation of ice loads on the Molikpaq structure measured during the 1985\u201386 season
No full textThe Molikpaq drilling platform, a steel annulus filled with sand, 90 m wide, was deployed at the Amauligak I-65 location in the Beaufort Sea during the 1985\u20131986 winter. It was heavily instrumented for measurement of ice loads, using strain gauges, extensometers, and Medof panels. The original calibrations of the Medof panels were used to estimate loads. Calibration was carried out using uniform pressures up to 1.86 MPa. The actual loading in the field of the Medof panels was extremely non-uniform spatially, particularly during ice crushing, and is very different from that in the original calibration. The resulting high pressures led to softening of the polyurethane buttons in the panels, including the Mullins effect. The panels were consequently reading too high. Extensometer readings, geotechnical measurements, and those pertaining to a decelerating floe impacting the structure, support the conclusion that actual ice loads were about half those obtained using the original Medof panel calibrations.La plate-forme de forage Molikpaq, un anneau en acier rempli de sable, de 90 m de large, a \ue9t\ue9 d\ue9ploy\ue9e \ue0 l\u2019emplacement Amauligak I-65 dans la mer de Beaufort durant l\u2019hiver 1985\u20131986. On l\u2019a lourdement instrument\ue9e aux fins de mesure de charges de glace, utilisant des jauges de contrainte, des extensom\ue8tres et des panneaux Medof. Les \ue9talonnages originaux des panneaux Medof ont \ue9t\ue9 utilis\ue9s pour \ue9valuer les charges. L\u2019\ue9talonnage a \ue9t\ue9 effectu\ue9 en utilisant des pressions uniformes jusqu\u2019\ue0 1,86 MPa. Le chargement r\ue9el des panneaux Medof sur les lieux \ue9tait extr\ueamement non uniforme dans l\u2019espace, particuli\ue8rement pendant l\u2019\ue9crasement de glace, et s\u2019est av\ue9r\ue9 tr\ue8s diff\ue9rent de l\u2019\ue9talonnage original. Les hautes pressions subs\ue9quentes ont donn\ue9 lieu \ue0 l\u2019amollissement des boutons de polyur\ue9thane dans les panneaux, incluant l\u2019effet Mullins. Les panneaux indiquaient par cons\ue9quent une lecture trop \ue9lev\ue9e. Lectures des extensom\ue8tres, les mesures g\ue9otechniques, et celles qui concernent un radeau de glace en d\ue9c\ue9l\ue9ration ayant un impact sur la structure, renforcent la conclusion que les charges r\ue9elles de glace \ue9taient environ la moiti\ue9 de celles obtenues en utilisant les \ue9talonnages de panneaux Medof originaux.Peer reviewed: YesNRC publication: Ye
Additive manufacturing powder feedstock characterization using X-ray tomography
No full textTo answer the need for efficient quality control protocols for additive manufacturing processes and materials, specific testing methods for powder feedstocks should be developed. A powder feedstock may contain some defects, such as porosities, that will remain in the final parts after the building process. X-ray tomography combined with 3D image analysis offers unique advantages over other characterization methods, such as pycnometry and metallography, in respect to quantifying internal porosity in the individual particles of the feedstock. This paper presents the effect of X-ray tomography parameters on the quality of the obtained images and its impact on the image analysis. An automated image analysis routine was also developed to allow the visualization of the pores inside the particles but also, more importantly, to quantify this internal porosity contents, as well as to provide information on the morphological features of these pores, such a size distribution, number of particles containing pores and the volume fraction of a pore inside a particle.Peer reviewed: YesNRC publication: Ye
Amphiphilic quantum dots with asymmetric, mixed polymer brush layers: from single core-shell nanoparticles to salt-induced vesicle formation
No full textA mixed micelle approach is used to produce amphiphilic brush nanoparticles (ABNPs) with cadmium sulfide quantum dot (QD) cores and surface layers of densely grafted (\u3c3 = ~1 chain/nm2) and asymmetric (fPS = 0.9) mixed polymer brushes that contain hydrophobic polystyrene (PS) and hydrophilic poly(methyl methacrylate) (PMAA) chains (PS/PMAA-CdS). In aqueous media, the mixed brushes undergo conformational rearrangements that depend strongly on prior salt addition, giving rise to one of two pathways to fluorescent and morphologically disparate QD-polymer colloids. (A) In the absence of salt, centrosymmetric condensation of PS chains forms individual core-shell QD-polymer colloids. (B) In the presence of salt, non-centrosymmetric condensation of PS chains forms Janus particles, which trigger anisotropic interactions and amphiphilic self-assembly into the QD-polymer vesicles. To our knowledge, this is the first example of an ABNP building block that can form either discrete core-shell colloids or self-assembled superstructures in water depending on simple changes to the chemical conditions (i.e., salt addition). Such dramatic and finely tuned morphological variation could inform numerous applications in sensing, biolabeling, photonics, and nanomedicine.Peer reviewed: YesNRC publication: Ye
NRC-Canada at SMM4H shared task: classifying tweets mentioning adverse drug reactions and medication intake
No full textOur team, NRC-Canada, participated in two shared tasks at the AMIA-2017 Workshop on Social Media Mining for Health Applications (SMM4H): Task 1 - classification of tweets mentioning adverse drug reactions, and Task 2 - classification of tweets describing personal medication intake. For both tasks, we trained Support Vector Machine classifiers using a variety of surface-form, sentiment, and domain-specific features. With nine teams participating in each task, our submissions ranked first on Task 1 and third on Task 2. Handling considerable class imbalance proved crucial for Task 1. We applied an under-sampling technique to reduce class imbalance (from about 1:10 to 1:2). Standard n-gram features, n-grams generalized over domain terms, as well as general-domain and domain-specific word embeddings had a substantial impact on the overall performance in both tasks. On the other hand, including sentiment lexicon features did not result in any improvement.Peer reviewed: NoNRC publication: Ye
Direct online quantitation of 2-methyl-3-methoxy-4-phenyl butanoic acid for total microcystin analysis by condensed phase membrane introduction tandem mass spectrometry
No full textMicrocystins (MCs) are a potent class of hepatotoxins produced by several species of cyanobacteria, which have been responsible for illness and death in livestock and humans. Rapid detection and quantitation are important for the protection of human and environmental health. More than 200 MC variants have been reported, and nearly all release 2-methyl-3-methoxy-4-phenyl butanoic acid (MMPB) upon oxidation. The quantitation of MMPB directly in complex post-oxidation solutions is presented using online condensed phase membrane introduction mass spectrometry with a methanol acceptor phase and negative electrospray ionization. We observe a linear response over several orders of magnitude for MMPB standards, and have applied the technique to measuring total MC in algal suspensions with both positive and negative controls. Preliminary results are reported for the analysis of total microcystins after Lemieux oxidation, at detection limits relevant to regulatory levels in recreational and drinking waters, with no sample clean up. Good quantitative agreement was obtained between measurement of total MCs in an algal reference material by CP-MIMS-MS/MS and LC-MS/MS analysis of total and free MCs. The developed methodology is of interest as an important first step for further development as a rapid benchtop tool for quantitative analysis with future potential use in the field.Peer reviewed: YesNRC publication: Ye
Identification of n-6 monounsaturated fatty acids in acer seed oils
No full textSeed oils from Acer species are a potential source of the nutraceutical fatty acids, nervonic acid (cis\u201015\u2010tetracosenoic acid, NA), and \u3b3\u2010linolenic acid (cis\u20106,9,12\u2010octadecatrienoic acid, GLA). To further characterize the genus, seed fatty acid content and composition were determined for 20 species of Acer. Fatty acid content ranged from 8.2% for Acer macrophyllum to over 36% for A. mono and A. negundo. The presence of very\u2010long\u2010chain fatty acids (VLCFA), with chain length of 20\u2010carbons or greater, and GLA were characteristic features of the seed oils. In all species, erucic acid (cis\u201013\u2010docosenoic acid, EA) was the predominant VLCFA with the highest level of NA being only 8.6% in A. olivianum. Regioselective lipase digestion demonstrated that VLCFA are largely absent from the sn\u20102 position of seed triacylglycerol, whereas GLA is primarily located at this position. Five Acer species contained low levels (<2%) of cis\u201012\u2010octadecenoic acid and cis\u201014\u2010eicosenoic acid, uncommon n\u20106 fatty acids not previously reported from Acer.Peer reviewed: YesNRC publication: Ye