Performance of Two Fluorescence-Based Real-Time Bioaerosol Detectors: BioScout vs. UVAPS

A 405 nm diode laser-based on-line bioaerosol detector, BioScout, was tested and compared with the Ultraviolet Aerodynamic Particle Sizer (UVAPS). Both instruments are based on laser-induced fluorescence of particles. Only a fraction of microbial particles produce enough fluorescence light to be detected by the instruments. This fluorescent particle fraction (FPF) is aerosol and instrument specific. The FPF values for common bacterial and fungal spores and biochemical particles were experimentally determined for both instruments. The BioScout exhibited higher FPF values for all the test aerosols except coenzyme NADH. The difference was higher for smaller particles. The FPF values of fungal spores and bacteria varied between 0.34 to 0.77 and 0.13 to 0.54 for the BioScout and the UVAPS, respectively. The results indicate that the 405 nm diode laser is a useful excitation source for fluorescence-based real-time detection of microbial aerosols. The FPF results of this study can be utilized to estimate the actual concentrations of bacterial and fungal spores in fluorescence-based ambient measurements.

Copyright 2014 American Association for Aerosol Research     

X-ray diffraction study of Ba0.985Na0.015Ti0.985Nb0.015O3, Ba0.6Na0.4Ti0.6Nb0.4O3 and Ba0.3Na0.7Ti0.3Nb0.7O3 compositions

The Ba_0.985Na_0.015Ti_0.985Nb_0.015O₃, Ba_0.6Na_0.4Ti_0.6Nb_0.4O₃ and Ba_0.3Na_0.7Ti_0.3Nb_0.7O₃ compositions of the (1 − x) BaTiO₃–xNaNbO₃ (BTNNx) system have been studied by X-ray diffraction and by measurements of dielectric properties. The specimens with composition BTNN (x = 0.015, 0.40 and 0.70) have been refined by the JANA program from X-ray powder diffraction data. Ceramic samples with composition (1 − x) BaTiO₃ + xNaNbO₃ (where x = 0.015, 0.40 and 0.70) were prepared by calcinations from appropriate mixture of BaCO₃, TiO₂, Na₂CO₃ and Nb₂O₅. The calcined powder was sintered at temperature range 1200–1400 °C. As the composition x increased from 0.015 (and 0.70), the ferroelectric ceramics (x = 0.015, FE) with tetragonal phase changed to the ferroelectric relaxors (RFE, x = 0.40). RFE ceramics showed a peculiar diffuse phase transition and dielectric relaxation at the low temperature (down to 180 K) due to a frustration between RFE and FE state. These ceramics present the classical ferroelectric character when 0 ≤ x < 0.075 and 0.55 < x ≤ 1 and relaxor character when 0.075 ≤ x ≤ 0.55.     

Comparison of the Properties of TiC/Fe-AI Composites Produced by Self-Propagating High-Temperature Synthesis and Hot Isostatic Pressing

Self-propagating high-temperature synthesis (SHS) and hot isostatic pressing (HIP) techniques were used to produce TiC-20 wt.% Fe-Al and TiC-40 wt.% Fe-Al composite materials. The microstructure of the materials produced by the SHS technique consisted of spherical carbide particles embedded in an iron aluminide matrix whereas the microstructure of the materials produced by the HIP technique was less regular. A maximum hardness of 1820 HV was measured for the material produced using HIP and a maximum fracture toughness of 16.3 MPa ^1/2 was obtained for the material produced by SHS. Hardness values obtained from samples produced by the HIP technique were higher than those obtained from samples produced by the SHS technique. The SHS samples had better fracture toughness. The results of the oxidation resistance tests showed that TiC/Fe-Al composite materials can be recommended for use in oxidative environments holding temperatures up to 800^°C.     

Effect of catalyst calcination temperature on the synthesis of MWCNT-alumina hybrid compound using methane decomposition method

This work focuses on synthesis of MWCNT-alumina hybrid compound via methane decomposition process using Ni-Al₂O₃ catalyst. The catalysts prepared through in situ process by using nickel salt and aluminium powder which are then calcined at three different calcination temperatures (700 °C, 900 °C and 1100 °C). The catalyst calcined at 900 °C followed by methane decomposition process successfully yielded MWCNT-alumina hybrid compound. No trace of CNT was detected for catalyst calcined at 700 °C and 1100 °C. The scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) micrograph confirmed the formation of MWCNT with homogenous dispersion on alumina particles.     

Protein Arginine N‐Methyltransferase Substrate Preferences for Different Nη‐Substituted Arginyl Peptides

Protein arginine N‐methyltransferases (PRMTs) catalyze methyl‐group transfer from S‐adenosyl‐L ‐methionine onto arginine residues in proteins. In this study, modifications were introduced at the guanidine moiety of a peptidyl arginine residue to investigate how changes to the PRMT substrate can modulate enzyme activity. We found that peptides bearing Nη‐hydroxy or Nη‐amino substituted arginine showed higher apparent k_cat values than for the monomethylated substrate when using PRMT1, whereas this catalytic preference was not observed for PRMT4 and PRMT6. Methylation by compromised PRMT1 variants E153Q and D51N further supports the finding that the N‐hydroxy substitution facilitates methyl transfer by tuning the reactivity of the guanidine moiety. In contrast, Nη‐nitro and Nη‐canavanine substituted substrates inhibit PRMT activity. These findings demonstrate that methylation of these PRMT substrates is dependent on the nature of the modification at the guanidine moiety.     

Distinguishing fuel and lubricating oil combustion products in diesel engine exhaust particles

The main sources of particulate emissions from engines are fuel and lubricating oil. In this study, particles emitted by a medium speed diesel engine for locomotive use were characterized chemically by using a soot particle aerosol mass spectrometer (SP-AMS). Additionally, positive matrix factorization (PMF) was applied to the SP-AMS data for the separation of fuel from lubricating oil and/or oil additives in diesel engine emissions. The mass spectra of refractory species, i.e., metals and rBC, were included in the PMF input matrix in addition to organics in order to utilize the benefit of the SP-AMS to measure non-refractory and refractory species. In general, particulate matter emitted by the diesel engine was dominated by organics (51%) followed by refractory black carbon (rBC; 48%), trace metals and inorganic species (1%). Regarding the sources of particles, PMF indicated four factors for particle mass of which two were related to lubricating oil-like aerosol (LOA1, 29% and LOA2, 24%) and two others to diesel-like fuel aerosol (DFA1, 35% and DFA2, 12%). The main difference between LOA1 and LOA2 was the presence of soot in LOA1 and metals in LOA2 factors. DFA factors represented burned (DFA1) and unburned fuel (DFA2). The results from the PMF analysis were completed with particle size distributions, volatility measurements and particle morphology analyses.

Copyright © 2019 American Association for Aerosol Research     

Symmetric and asymmetric impacts of the palm oil industry on carbon dioxide emissions in Malaysia based on linear and nonlinear autoregressive distributed lag models

Clean Technologies and Environmental Policy - Palm oil is a major global commodity that is vital for the well-being of many communities. Despite its significant contribution to the attainment of...     

Driver training interests of a Spanish sample of young drivers and its relationship with their self-assessment skills concerning risky driving behavior

Poor driving self-assessment skills (e.g., over-confidence) have been pointed out as an important explanatory factor behind young drivers’ accident involvement. This paper explores (1) what young drivers miss in their training as drivers in order to analyze whether an assessment of one's own driving skills plays an important role in their desire to improve as drivers, and (2) how these training interests are related to an estimate of their self-assessment skills concerning risky driving behavior. For this purpose, a study was conducted using a survey with a blocked sampling design of novice drivers. The survey solicited respondents’ self-report about (1) the contents of training courses that they feel would improve their driving, (2) their risky driving behavior, and (3) their likelihood of being involved in a risky driving situation. From the initial sample invited to participate, of nearly 1300 people, we finally obtained complete data from 321 young Spanish drivers. Two main results were apparent from our data analysis: (1) the novice drivers were mainly interested in improving their ability to recognize their strengths and weaknesses as drivers (i.e., self-assessment skills); (2) a significant relationship was found between novice drivers’ interests and their current self-assessment skills concerning risky driving behavior. Specifically, there was greater general interest expressed in post-license training by the under-confident self-assessors than the over-confident ones. These results provide a relevant input which should be taken into account when designing driver training programs for novice drivers. Moreover, the relationship between their training interests and their risky driving self-assessment skills introduces an additional factor to be considered in the implementation of these training programs.     

Semi-automatic detection and counting of oil palm trees from high spatial resolution airborne imagery

Plantation inventory and management require a range of fine-scale remote-sensing data. Remote-sensing images with high spatial and spectral resolution are an efficient source of such information. This article presents an approach to the extraction and counting of oil palm trees from high spatial resolution airborne imagery data. Counting oil palm trees is a crucial problem in specific agricultural areas, especially in Malaysia. The proposed scheme comprises six major parts: (1) discrimination of oil palms from non-oil palms using spectral analysis, (2) texture analysis, (3) edge enhancement, (4) segmentation process, (5) morphological analysis and (6) blob analysis. The average accuracy obtained was 95%, which indicates that high spatial resolution airborne imagery data with an appropriate assessment technique have the potential to provide us with vital information for oil palm plantation management. Information on the number of oil palm trees is crucial to the ability of plantation management to assess the value of the plantation and to monitor its production.