Toxicological characterization of particulate emissions from straw,Miscanthus, and poplar pellet combustion in residential boilers

Wood pellets have been used in domestic heating appliances for three decades. However, because the share of renewable energy for heating will likely rise over the next several years, alternative biomass fuels, such as short-rotation coppice or energy crops, will be utilized. We tested particulate emissions from the combustion of standard softwood pellets and three alternative pellets (poplar, Miscanthus sp., and wheat straw) for their ability to induce inflammatory, cytotoxic, and genotoxic responses in a mouse macrophage cell line. Our results showed clear differences in the chemical composition of the emissions, which was reflected in the toxicological effects. Standard softwood and straw pellet combustion resulted in the lowest PM₁ mass emissions. Miscanthus sp. and poplar combustion emissions were approximately three times higher. Emissions from the herbaceous biomass pellets contained higher amounts of chloride and organic carbon than the emissions from standard softwood pellet combustion. Additionally, the emissions of the poplar pellet combustion contained the highest concentration of metals. The emissions from the biomass alternatives caused significantly higher genotoxicity than the emissions from the standard softwood pellets. Moreover, straw pellet emissions caused higher inflammation than the other samples. Regarding cytotoxicity, the differences between the samples were smaller. Relative toxicity was generally highest for the poplar and Miscanthus sp. samples, as their emission factors were much higher. Thus, in addition to possible technical problems, alternative pellet materials may cause higher emissions and toxicity. The long-term use of alternative fuels in residential-scale appliances will require technological developments in both burners and filtration.

Copyright © 2016 American Association for Aerosol Research     

Low-Power Application-Specific Processor for FFT Computations

In this paper, a processor architecture tailored for radix-4 and mixed-radix FFT computations is described. The processor has native support for power-of-two transform sizes. Several optimizations have been used to improve the energy-efficiency of the processor and experiments show that a programmable solution can possess energy-efficiency comparable to fixed-function ASICs.     

Analysis of the linewidth of a grating-feedback GaAlAs laser

Effects of external optical feedback from a reflection grating on the linewidth of a GaAlAs semiconductor laser operating at 780 nm are investigated. Accurate linewidth measurements as a function of the laser frequency tuning have been performed by applying the self-homodyne technique with a short delay line. A realistic coupled-cavity model, which incorporates the frequency-dependent reflection from the grating, is used to explain the measured data. The agreement between the theoretical and experimental results was found to be good     

Emissions of DEHP‐free PVC flooring

Degrading 2‐ethylhexyl‐containing PVC floorings (eg DEHP‐PVC floorings) and adhesives emit 2‐ethylhexanol (2‐EH) in the indoor air. The danger of flooring degradation comes from exposing occupants to harmful phthalates plasticisers (eg DEHP), but not from 2‐EH as such. Since the EU banned the use of phthalates in sensitive applications, the market is shifting to use DEHP‐free and alternative types of plasticisers in PVC products. However, data on emissions from DEHP‐free PVC floorings are scarce. This study aimed at assessing the surface and bulk emissions of two DEHP‐free PVC floorings over three years. The floorings were glued on the screed layer of concrete casts at 75%, 85%, and 95% RH. The volatile organic compounds (VOCs) were actively sampled using FLEC (surface emissions) and micro‐chamber/thermal extractor (µ‐CTE, bulk emissions) onto Tenax TA adsorbents and analyzed with TD‐GC‐MS. 2‐EH, C9‐alcohols, and total volatile organic compound (TVOC) emissions are reported. Emissions at 75% and 85% RH were similar. As expected, the highest emissions occurred at 95% RH. 2‐EH emissions originated from the adhesive. Because the two DEHP‐free floorings tested emitted C9‐alcohols at all tested RH, it makes the detection of flooring degradation harder, particularly if the adhesive used does not emit 2‐EH.     

Improved frequency stability of an external cavity diode laser by eliminating temperature and pressure effects

The construction of a passively stabilized external cavity diode laser operating at 780 nm is reported. The sensitivity of laser frequency to changes in air pressure was studied and subsequently eliminated. The relative frequency stability obtained was 4 × 10(-9) for an integration time of 4000 s.     

Thermochromic Furofurans. IV. Approach to the synthesis of bridgehead substituted furo[3,2-b]furans and side products of McMurry reactions

Substituted dihydroxystilbenes 2 are suitable starting materials for the synthesis of photochromic systems derived from 3 / 4 . Attempts to couple the naphthones 8a - 8e by the McMurry reaction with TiCl₃/LiAlH₄ yielded mainly reduction products such as 8f , g or 9 . However, the furofuran 3b was isolated when using the zinc–copper couple for reduction. The helicene 11 was formed as an unexpected by-product in the McMurry reaction of the pivaloylnaphthalene 8d .     

Design and validation of an air-liquid interface (ALI) exposure device based on thermophoresis

In vitro, direct aerosol nanoparticle exposure of cells cultured at the air-liquid interface (ALI) has shown great potential over the conventional submerged cell exposure methods due to exposure relevancy and more accurate dose determination. Here, we present a design of an ALI cell exposure device, the thermocollector, which applies thermophoresis to deposit aerosol particles onto the cells. Computational numerical simulations were used to estimate the deposition flux and how it depended on particle properties. The deposition flux was approximately 250 particles/m²s for particles smaller than 100?nm, corresponding to an aerosol concentration of 1 #/cm³. This was also confirmed with experimental studies. For larger particles, the deposition rate depended more on particle properties; however, for fractal combustion derived soot particles, the deposition rate is practically size independent at the size range studied here. Finally, epithelial cells were exposed with wood combustion aerosol, and the toxicologic responses were investigated. The cell viability decrease and DNA damage were detected after the exposure. These effects were not detected in cells after the exposure to clean air in this cell exposure system.

Copyright © 2019 American Association for Aerosol Research     

Soil forming and plant density effects on carrot yield and internal quality

Patients with established coronary disease and abnormalities of lipid metabolism represent a particularly important subgroup, since their mortality risk is typically 10 times greater than that amongst-subjects with comparable risk factors but no clinical history. Such patients are commonly treated initially with anti-anginal therapy; if ischaemic symptoms persist they often undergo revascularization (bypass or angioplasty). While invasive procedures restore blood flow and relieve ischemia, they do not, in most cases, reduce risk of subsequent MI or death, or alter the underlying atherogenic process(es). Despite this, there has been a progressive 54% decline in age-adjusted cardiac mortality over the period 1960-1995, which appears best attributable to US lifestyle changes. In particular, the past decade has provided compelling evidence for the merits of a fourth approach: comprehensive risk factor management. Clinical outcome studies have confirmed the substantial merit of aspirin prophyllaxis and of intensive lipid-lowering therapy in secondary prevention. Prospective angiographic trials and evidence from studies of vascular biology have provided insight into mechanisms of benefit. As a consequence, lipid therapy and aspirin use have increased greatly among middle aged and older US citizens, especially those with CAD. The growth of comprehensive medical management now rivals that of invasive revascularization in secondary prevention.