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Assessing MS-based quantitation strategies for low-level impurities in peptide reference materials: application to angiotensin II
No full textIdentification and quantitation of related impurities is vital in obtaining corrected purity values for peptide certified reference materials. The sensitivity and selectivity of high-resolution mass spectrometry (MS) renders it an indispensable technique in this arena. Typical quantitation efforts involve constructing external calibration curves, although analysis of dilute peptide solutions can be complicated by analyte adsorption to vial walls, instrument tubing, etc. The standard addition method alleviates many concerns associated with this sample loss as the calibrant solutions more closely match the matrix of the samples. Yet, both strategies require acquisition of synthetic impurity peptide standards. Label-free proteomics relies on electrospray ionization (ESI)-MS signals to quantify identical peptides across multiple samples; however, peptides of differing sequence can exhibit widely disparate ESI-MS responses. This study explores the use of peak area ratios to quantitate sequence-related peptide impurities in an angiotensin II candidate certified reference material. Using synthetic standards of five abundant substances, impurity mass fractions calculated via the relative response method are in reasonable agreement with those determined from standard addition experiments, whereas external calibration measurements frequently overestimate impurity amounts. For a synthetic peptide and its related sequence impurities, the relative response method can expedite analysis and lower expenditures, and in some cases improve data quality.Peer reviewed: YesNRC publication: Ye
Birefringent \u3c0-phase-shifted fiber bragg gratings for sensing at 1000 \ub0C fabricated using an infrared femtosecond laser and a phase mask
No full textBirefringent \u3c0-phase-shifted Bragg gratings for multi-parameter sensing at temperatures ~1000 \ub0C are written inside a standard single mode silica optical fiber (SMF-28) with infrared femtosecond pulses and a special phase mask one half of which is shifted with respect to the other by 5/4 of the mask period. The birefringence is caused by the presence of light-induced sub-wavelength periodic planar nanostructures in the fiber core, whose orientation is controlled by the laser polarization, and is maximized when the laser pulse polarization is aligned perpendicular to the fiber core. The birefringence can reach ~4.2
7 10 -4 at room temperature at the 1.5
7 10 -4 level after 100 h annealing at 1000 \ub0C. Erasure and rewriting of the planar nanostructures inside fiber Bragg gratings by changing the laser pulse polarization is demonstrated.Peer reviewed: YesNRC publication: Ye
Developing the ngDVA 15m composite reflector concept
No full textThe Next Generation Very Large Array (ngVLA) project to replace the VLA telescope in New Mexico is just beginning. As a part of the initial Community Studies phase, we have contributed the concept design of a 15m feed-low wheel and track design. This telescope, the Next Generation Dish Verification Antenna 15m (ngDVA-15) follows on from the DVA-1 and DVA-2 antennas developed at the Dominion Radio Astrophysical Observatory (DRAO) between 2012 and the present day. This paper will concentrate on the design and optimization process for the ngDVA-15 back-up structure. Topology and free-size optimization were used to develop the initial design concepts. Both methods helped to steer the back-up structure in the initial design phase, but ultimately engineering intuition also played a role. Topology optimization can lead directly to useful solutions in some cases but hardware and software limitations still limit the physical size of the model. Also, topological routines cannot yet correctly model truss-type networks with no moment transfer at the joints, and optimizing structures with only gravitational loads proved to be challenging for the current generation of optimization routines. Size optimization was also used once the design was sufficiently refined. The initial stage of design involved minimization of reflector surface deflections under gravitational loads only. FEA modelling of surface deflections together with in-house developed fitting algorithms were used to determine primary surface accuracy. Surface accuracies of better than 80 microns RMS were achieved which met the initial design goal for telescope operation at 120GHz.Peer reviewed: YesNRC publication: Ye
Effect of swirl ratio on NG/diesel dual-fuel combustion at low to high engine load conditions
No full textRecent regulation on pollutant and greenhouse gas (GHG) emissions has exerted great pressure on diesel engine industries which generate significant amount of GHG and pollutants. The concept of lean burn pilot ignited natural gas/diesel dual-fuel (NDDF) combustion is considered as one of the most suitable engine platforms to meet emissions and fuel economy regulations over a short to medium term. However, a major challenge is the slightly lower fuel efficiency and high level of methane (CH4) and carbon monoxide (CO) emissions, especially under low to medium engine load conditions. This paper numerically investigates the influence of swirl ratio on the combustion performance and emissions of a NDDF engine under low to high load conditions. The results at low load-low speed condition and retarded injection timing of 14 crank angle degrees before top dead center (BTDC) suggest that increasing swirl ratio from 0.5 to 1.5 significantly improves fuel efficiency and CH4 and CO emissions. However, under the same engine load-speed condition but at advanced injection timing of 30 crank angle degrees BTDC, increasing swirl ratio deteriorates the fuel efficiency and CH4 and CO emissions. Under a medium load-high speed condition, swirl ratio significantly improves diffusion combustion and turbulent flame propagation of natural gas. The results show that OH radical propagates more rapidly in the azimuthal direction when increasing the swirl ratio from 0.5 to 1.5. Further increase in the swirl ratio causes the peak pressure to exceed the limit (160\u202fbar). At high load-low speed condition, increasing the swirl ratio significantly improves diesel diffusion and flame propagation of natural gas, which consequently enhances fuel efficiency. Under this engine load-speed condition, OH radical distribution shows that the combustion progresses rapidly within each jet in both the azimuthal and radial directions. Considering fuel efficiency and emissions, a swirl ratio of 1.5 is found to be the optimum. Overall, it is concluded that swirl motion may provide better mixture preparation, diesel diffusion, and natural gas flame propagation. However, this benefit may not persist under very high swirl ratio (swirl ratio\u202f>\u202f1.5) due to higher heat losses.Peer reviewed: YesNRC publication: Ye
Fluorescence\u2010based real time monitoring and diagnostics of recombinant Pichia pastoris cultivations in a bioreactor
No full textThis study describes the application of the multivariate curve resolution (MCR) analysis technique for real\u2010time analysis of culture fluorescence during recombinant Pichia pastoris cultivation in a bioreactor. Fluorescence spectra were acquired with an on\u2010line dual excitation wavelength fluorometer and then used to develop a real time MCR\u2010based bioprocess monitoring and diagnostics tool. Initial bioreactor experiments using two similar recombinant antibody secreting P. pastoris cell lines showed significant differences in protein production. To distinguish between the contributions of operating conditions and the specific cell line's genetic composition to the observed differences in protein production, the bioreactor experiments were repeated and accompanied by real time MCR analysis. The tests demonstrated high sensitivity of MCR\u2010derived \u201cpure concentration\u201d profiles to growth as well as to initial conditions, thus enabling real\u2010time cultivation process trend diagnostics and fault detection.Peer reviewed: YesNRC publication: Ye
Fully printed parallel plate capacitance humidity sensors
No full textPrinted humidity sensors on flexible substrates has potential to be low cost platform. A novel capacitance-humidity sensor was screen printed with silver electrodes and cellulose acetate butyrate (CAB) as the dielectric on flexible polyethylene terephthalate (PET) substrate. The parallel plate design achieves capacitance between 400-500pF at ambient conditions. This study found that the sensor exhibits superior linearity from 10-70%RH with R2 of 0.9975, and acceptable linearity between 10-85% with R2 of 0.9779 with <10s response times.Peer reviewed: YesNRC publication: Ye
Individual pathways in the formation of magic-size clusters and conventional quantum dots
No full textThe formation relationship between colloidal magic-size clusters (MSCs) and conventional quantum dots (QDs) has not been well established. Here, we report our systematic study on their formation pathways, using cadmium sulfide (CdS) as a model system. Two Cd precursors were prepared from CdO with branched 2-methyloctadecanoic acid (C16H33CH(CH3)\u2013COOH) and linear oleic acid (C16H31CH2\u2013COOH), reacting with elemental S powder in 1-octadecene (ODE). We show that the presence of MSC-311 (exhibiting a sharp absorption peaking at 311 nm) is regulated by the growth of conventional QDs. We demonstrate that MSC-311 cannot directly convert into conventional QDs but to its immediate precursor (IP-311), which is transparent in optical absorption (>310 nm). We propose that there are two individual pathways for the formation of MSCs and conventional QDs, linked by an intrinsic pathway from MSCs to IPs to fragments to QDs. The present study introduces new avenues to precisely control their formation.Peer reviewed: YesNRC publication: Ye
Random fiber gratings fabricated using Fs-IR laser for distributed temperature sensor application
No full textBy using the plane-by-plane grating inscription method with a fs-IR laser, random fiber gratings were fabricated in SMF-28 fiber with different phase shifts between different planes for temperature sensing. With the well-defined bandwidth of the enhanced backscattering, the random grating based distributed temperature sensing system shows high accuracy of temperature measurement and low laser-induced loss.Peer reviewed: YesNRC publication: Ye
Tank car sloshing on rail transportation safety under various loading, track and in-train force conditions
No full textAnalytical work was conducted to study if movement of liquid in a tank car (or sloshing) could contribute in any way to derailments of trains carrying dangerous goods liquids. A liquid sloshing model was developed for railway tank car with formulas generated based on available finite element analysis data. An empty tank car dynamics simulation model validated with measured data was used as the base model to implement the liquid sloshing model. Hundreds of thousands of dynamics simulations were conducted for the tank car with liquid cargo at various fill ratios and with equivalent solid (i.e., rigid) cargo on more than 1000 measured curves. The results show that under some conditions tank car sloshing could increase the risk of derailment. The detrimental effect of tank car sloshing on rail safety increases with the increase of outage, trailing tonnage, grade, car length difference, curvature, train speed and track geometry irregularities. Quantitative risk analysis could be improved by considering the effects of tank car sloshing on derailment risk. The findings can be used by regulators and the railroads to improve train marshalling practice and risk mapping of railway networks.Peer reviewed: YesNRC publication: Ye
The direct and accurate determination of major elements Ca, K, Mg and Na in water by HR-ICPMS
No full textA direct, accurate and precise method is reported for major elements Ca, K, Mg and Na measurements in river and drinking water using a high resolution ICP-MS. Double isotope dilution calibration was used for the determination of Mg whereas the combined standard addition and internal standardization (Sc) was used for Ca, K and Na measurements. The method is validated by analysis fresh water SLRS-5, SLRS-6 and SRM1640a with satisfactory results characterized by high precisions of 0.055% to 0.66% RSD (or 0.29\u20131.8% relative combined uncertainty) for all four analytes, superior to those reported in earlier studies. As noted, use of internal standard Sc has significantly (3\u201333 times) improved measurement precisions for Ca, K and Na compared to standard addition calibration alone. The proposed method was applied for the determination of major elements Ca, K, Mg and Na in a candidate drinking water CRM AQUA-1. Values of 1.908\u2009\ub1\u20090.007\u2009\ub5g\u2009g 121, 8.27\u2009\ub1\u20090.14\u2009\ub5g\u2009g 121, 0.660\u2009\ub1\u20090.010\u2009\ub5g\u2009g 121 and 13.76\u2009\ub1\u20090.05\u2009\ub5g\u2009g 121 (u, k\u2009=\u20091) were obtained for Mg, Ca, K and Na in AQUA-1 drinking water, respectively.Peer reviewed: YesNRC publication: Ye