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Antioxidant properties and lipid composition of selected microalgae
No full textMarine and freshwater microalgae were evaluated for their antioxidant properties and lipid composition. Both lipophilic (L) and hydrophilic (H) oxygen radical absorbance capacity (ORAC) values were measured. Among the tested microalgae, the marine microalga Nannochloropsis granulata showed the highest total ORAC value at 6948 \u3bcmol TE (100 g) 121, followed by the freshwater species Neochloris oleoabundans at 4508 \u3bcmol TE (100 g) 121 and Scenedesmus obliquus at 4406 \u3bcmol TE (100 g) 121 of algal biomass. Freeze-dried algal biomass was also examined for lipid content by the Folch method. Lipid content ranged from 30.9 to 49.3% and linear regression analysis revealed a statistically significant correlation between the lipid content and the ORAC values. Tested microalgae showed moderate and dose-dependent DPPH radical scavenging activity. The total phenol assay shows that marine microalga Tetraselmis chui had the highest phenolic content at 57.5 \u3bcmol GAE g 121 and N. oleoabundans had the lowest at 26.6 \u3bcmol GAE g 121 of MeOH extract. A statistically significant correlation was detected between DPPH radical scavenging activity and the phenolic content. Fatty acid analysis revealed that polyunsaturated fatty acids constituted >\u200945% of the total fatty acid content in N. oleoabundans, Phaeodactylum tricornutum, Porphyridium aerugineum, S. obliquus, and Scenedesmus sp. Total carotenoid concentration ranged from 1.1 to 29.5 mg g 121 of dry algal biomass. Lutein, zeaxanthin, and \u3b2-carotene are common carotenoids found in most of the algae tested. P. tricornutum contains significant amount of fucoxanthin at 24.3 mg g 121 algal biomass. These carotenoids also contributed to the overall antioxidative activity of microalgae.Peer reviewed: YesNRC publication: Ye
Very-long-chain fatty acid diversity in nine Heliophila seed oils
No full textHeliophila is a genus of approximately 90 recognized plant species endemic to southern Africa and considered the most morphologically diverse genus in the family Brassicaceae. To begin to characterize chemical diversity in the genus, seed oil content and fatty acid composition were determined for 9 species, with representatives from the three major recognized clades. All species produced very-long-chain fatty acids (VLCFAs) as major components of the seed triacylglycerol (TAG) oil, with considerable diversity of fatty acid chain length. The 22-carbon (C22) monounsaturated fatty acid erucic acid (cis-13-docosenoic acid) was the dominant VLCFA in the oil of Heliophila coronopifolia at 47.6% of total seed fatty acids whereas the unusual C26 fatty acid ximenic acid (cis-17-hexacosenoic acid) dominated the VLCFA profile of oil from Heliophila scoparia at 35.8%. Heliophila africana oil was identified as a potential novel source of the nutraceutical fatty acid, nervonic acid (cis-15-tetracosenoic acid). Analysis of the oil of 3 species by sn-1,3 regioselective lipase digestion demonstrated the virtual exclusion of VLCFAs from the sn-2 position of TAG. Examination of the oil from H. scoparia by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-TOF) Mass Spectrometry revealed the presence of high molecular weight TAGs and widespread distribution of VLCFAs among the TAG molecular species. Heliophila species have significant potential as sources of novel seed oil enriched in VLCFAs and as model species to study the mechanisms and evolution of VLCFA biosynthesis in plants.Peer reviewed: YesNRC publication: Ye
Characterizing bacterial glycoproteins with LC-MS
No full textIntroduction: Though eukaryotic glycoproteins have been studied since their discovery in the 1930s, the first bacterial glycoprotein was not identified until the 1970s. As a result, their role in bacterial pathogenesis is still not well understood and they remain an understudied component of bacterial virulence. In recent years, mass spectrometry has emerged as a leading technology for the study of bacterial glycoproteins, largely due to its sensitivity and versatility. Areas covered: Identification and comprehensive characterization of bacterial glycoproteins usually requires multiple complementary mass spectrometry approaches, including intact protein analysis, top-down analysis, and bottom-up methods used in combination with specialized liquid chromatography. This review provides an overview of liquid chromatography separation technologies, as well as current and emerging mass spectrometry approaches used specifically for bacterial glycoprotein identification and characterization. Expert commentary: Bacterial glycoproteins may have significant clinical utility as a result of their unique structures and exposure on the surface of the cells. Better understanding of these glycoconjugates is an essential first step towards that goal. These often unique structures, and by extension the key enzymes involved in their synthesis, represent promising targets for novel antimicrobials, while unique carbohydrate structures may be used as antigens in vaccines or as biomarkers.Peer reviewed: YesNRC publication: Ye
Concomitant reduction of lactate and ammonia accumulation in fed-batch cultures: impact on glycoprotein production and quality
No full textLactate and ammonia accumulation is a major factor limiting the performance of fed\u2010batch strategies for mammalian cell culture processes. In addition to the detrimental effects of these by\u2010products on production yield, ammonia also contributes to recombinant glycoprotein quality deterioration. In this study, we tackled the accumulation of these two inhibiting metabolic wastes by culturing in glutamine\u2010free fed\u2010batch cultures an engineered HEK293 cell line displaying an improved central carbon metabolism. Batch cultures highlighted the ability of PYC2\u2010overexpressing HEK293 cells to grow and sustain a relatively high viability in absence of glutamine without prior adaptation to the culture medium. In fed\u2010batch cultures designed to maintain glucose at high concentration by daily feeding a glutamine\u2010free concentrated nutrient feed, the maximum lactate and ammonia concentrations did not exceed 5 and 1 mM, respectively. In flask, this resulted in more than a 2.5\u2010fold increase in IFN\u3b12b titer in comparison to the control glutamine\u2010supplied fed\u2010batch. In bioreactor, this strategy led to similar reductions in lactate and ammonia accumulation and an increase in IFN\u3b12b production. Of utmost importance, this strategy did not affect IFN\u3b12b quality with respect to sialylation and glycoform distribution as confirmed by surface plasmon resonance biosensing and LC\u2010MS, respectively. Our strategy thus offers an attractive and simple approach for the development of efficient cell culture processes for the mass production of high\u2010quality therapeutic glycoproteins.Peer reviewed: YesNRC publication: Ye
Controlling high harmonic generation in tailored semiconductors
No full textThe solid state opens new possibilities for the generation of high harmonics extending to the extreme ultraviolet. Additionally, an array of tools and techniques exists for straightforward fabrication of solid-state devices, with nanoscale precision. In this work, we explore new ways to control high-harmonic emission in semiconductors using nanofabrication. We measure high-harmonic emission from tailored silicon and zinc oxide targets, up to the ninth order of the fundamental driving frequency (corresponding to a wavelength of ~225 nm). Morphology and local composition can each localize and enhance emission. We utilize this control to demonstrate prototype devices which simultaneously emit and focus harmonic radiation.Peer reviewed: YesNRC publication: Ye
Coupled electrochemical and thermal battery models for thermal management of prismatic automotive cells
No full textThis study combines a two-dimensional Ohm\u2019s law finite-volume approach determining the current distribution in prismatic battery cells with a simplified electrochemical model for the thermal state of automotive battery packs. The objective was to develop a simulation tool for assessing the effect of cooling effort applied to automotive battery packs under real-life usage conditions. The Ohm\u2019s law model was enhanced by imparting a chemical and physical basis to source terms previously found empirically. This simulation was applied to 2D electrode sheets, determining thermal generation values that were mapped volumetrically into a thermal simulation, which in turn, updated the electrochemical simulation. Battery parameters, along with capacity fade kinetics were determined by fitting experimental data to simulated results. Dynamometer data from tests under reference drive cycles provided current demands on battery cells. Thermal profiles simulated for 30\u202fA\u202fh prismatic cells at different cooling levels. Passive and forced air cooling simulations both gave endpoint temperatures upwards of 40\u202f\ub0C (313\u202fK), considered excessive for preserving the battery life. A simulation scenario which reflected a liquid cooling system kept the temperature gain for a US06 drive cycle to about 2\u202fK. With liquid cooling, an automotive battery is better protected against thermally driven degradation.Peer reviewed: YesNRC publication: Ye
Determination of kfmsr,fref Qmsr,Q0 factors for ion chambers used in the calibration of Leksell Gamma Knife Perfexion model using EGSnrc and PENELOPE Monte Carlo codes
No full textPurpose: To calculate the kfmsr,fref Qmsr,Q0 factors for nine common ionization chamber types following the small fields dosimetry formalism for the calibration of the Leksell Gamma Knife\uae(LGK) PerfexionTM using Monte Carlo simulation. This study also provides the first independent comparison of EGSnrc and PENELOPE for the calculation of kfmsr,fref Qmsr,Q0 correction factors and proposes a practical method to predict these factors based on chamber type, chamber orientation and phantom electron density. Methods: The ionization chambers are modeled using the EGSnrc and PENELOPE Monte Carlo codes based on the blueprints provided by the manufacturers. The chambers are placed in a half\u2010sphere water phantom and five spherical phantoms made of liquid water, solid water, ABS, polystyrene, and PMMA, respectively. Dose averaged over the air cavity of the chambers and a small water volume are calculated using EGSnrc and PENELOPE Monte Carlo codes for both conventional and machine specific reference (msr) setups. Using the calculated dose ratio, the kfmsr,fref Qmsr,Q0 factor is determined for all phantom materials and two possible orientations of chamber. The calculated kfmsr,fref Qmsr,Q0 factors are compared to a previous Monte Carlo study.1, 2 A relationship between the kfmsr,fref Qmsr,Q0 factor and the electron density of the phantom material is derived to predict the kfmsr,fref Qmsr,Q0 factor for any phantom material type. Applying the calculated kfmsr,fref Qmsr,Q0 factors to the measured dose rate of a recent round robin study3 improves consistency of reference dosimetry of the Leksell Gamma Knife\uae(LGK) PerfexionTM. Results: Agreement within uncertainty is observed between kfmsr,fref Qmsr,Q0 values determined in this study and the previous PEGASOS/PENELOPE study1, 2 in a liquid water phantom. The difference between kfmsr,fref Qmsr,Q0 values in parallel and perpendicular detector orientations is most significant for the PTW 31010 (1.8%) chamber. The percentage root\u2010mean\u2010square (%RMS) deviation between EGSnrc and PENELOPE calculated kfmsr,fref Qmsr,Q0 values for Exradin\u2010A1SL, A14 and A14SL chambers studies in this work was found to be 0.4%. The kfmsr,fref Qmsr,Q0 values increase linearly with electron density of the phantom material for all chamber types mainly due to the linear dependency of photon energy fluence ratios on electron density. The average percentage difference between the calculated and predicted kfmsr,fref Qmsr,Q0 values using two methods is found to be 0.15% and 0.16%. Previously measured dose rates corrected with the kfmsr,fref Qmsr,Q0 values determined in this work leads to absorbed dose values consistent to within 0.8%. Conclusions: The calculated kfmsr,fref Qmsr,Q0 values in this work will enable users to apply the appropriate correction for their own specific phantom material only knowing the electron density of the phantom material.Peer reviewed: YesNRC publication: Ye
Fertilizer usage and cadmium in soils, crops and food
No full textPhosphate fertilizers were first implicated by Schroeder and Balassa (Science 140(3568):819\u2013820, 1963) for increasing the Cd concentration in cultivated soils and crops. This suggestion has become a part of the accepted paradigm on soil toxicity. Consequently, stringent fertilizer control programs to monitor Cd have been launched. Attempts to link Cd toxicity and fertilizers to chronic diseases, sometimes with good evidence, but mostly on less certain data are frequent. A re-assessment of this \u201caccepted\u201d paradigm is timely, given the larger body of data available today. The data show that both the input and output of Cd per hectare from fertilizers are negligibly small compared to the total amount of Cd/hectare usually present in the soil itself. Calculations based on current agricultural practices are used to show that it will take centuries to double the ambient soil Cd level, even after neglecting leaching and other removal effects. The concern of long-term agriculture should be the depletion of available phosphate fertilizers, rather than the negligible contamination of the soil by trace metals from fertilizer inputs. This conclusion is confirmed by showing that the claimed correlations between fertilizer input and Cd accumulation in crops are not robust. Alternative scenarios that explain the data are presented. Thus, soil acidulation on fertilizer loading and the effect of Mg, Zn and F ions contained in fertilizers are considered using recent Cd2+, Mg2+ and F 12 ion-association theories. The protective role of ions like Zn, Se, Fe is emphasized, and the question of Cd toxicity in the presence of other ions is considered. These help to clarify difficulties in the standard point of view. This analysis does not modify the accepted views on Cd contamination by airborne delivery, smoking, and industrial activity, or algal blooms caused by phosphates.Peer reviewed: YesNRC publication: Ye
H2: the benchmark molecule for ultrafast science and technologies
No full textThis review article focuses on imaging and controlling ultrafast dynamics of the hydrogen molecule and its cation, initiated by ultrashort laser pulses. We discuss the mechanisms underlying these dynamics and theoretical methods to describe them. A broad variety of defining and influencing theoretical and experimental results is presented. We put special emphasis on the required experimental techniques, many of which have been developed in view of imaging the fastest of all nuclear dynamics.Peer reviewed: YesNRC publication: Ye
Influence of preheating and burner geometry on modeling the attachment of laminar coflow CH4/air diffusion flames
No full textA laminar coflow CH4/air diffusion flame was experimentally and numerically studied to elucidate the mechanism of flame attachment and the importance of preheating, thermal boundary condition at the fuel tube, and burner geometry to the flame attachment location. OH*-chemiluminescence images were captured using an intensified CCD camera. The temperature of the outer surface of fuel tube at 2\u202fmm below the burner exit was measured using a K-type thermocouple. Detailed simulations based on five different burner wall models were conducted to investigate the influence of preheating effect and burner geometry on flame attachment. The conjugate heat transfer between the heat-conducting burner wall and the surrounding gas flows was considered in the overall flame model to account for the preheating effect without or with less ad hoc assumptions for the burner inlet conditions. The effect of different thermal boundary conditions imposed at the fuel tube on the predicted flame attachment location was investigated. Results show that it is paramount to specify the inlet location at a certain distance upstream the burner exit to model the flame attachment phenomenon. This finding can be explained in terms of the direct heating of the fuel and air streams by the flame base or the mixing process between the fuel and air streams associated with the hydrodynamics and diffusion in the vicinity of the burner rim. The thermal boundary condition at the fuel tube only slightly affects the predicted flame attachment location. The fuel decomposition occurs inside the fuel tube mainly due to preheating by the fuel tube wall and the key chemical pyrolysis process was revealed through a detailed kinetics analysis. The efflux of CH4 to the air side over the burner rim was found responsible for the flame attachment under current conditions. The flame base kernel is established around the stoichiometric mixture and its location is controlled by the thermal condition and geometry of the burner wall. The burner geometry influences the position of flame attachment on the outer surface of the fuel tube through the fuel tube heat capacity and the shape.Peer reviewed: YesNRC publication: Ye