Electrically Produced Standard Aerosols in a Wide Size Range

Non-uniformly charged particles cause a major problem in electrical methods for producing standard aerosols, imposing strict limitations on the usability of the obtained standard aerosols. This article gives a quick overview of this problem, examining the ways how differently charged particles affect the generation of standard aerosols, and presenting a new method for producing standard aerosols and avoiding the effects of multiply charged particles, with the key idea that the probability for small particles to have more than one charge is very low. A two-stage aerosol generator is used. Small silver particles (d< 40 nm) generated by homogeneous nucleation of silver vapors obtain in bipolar charger not more than one elementary charge. These condensation nuclei are enlarged by a condensational growth device. Big particles are now also not more than singly charged, and narrow size distribution can be obtained by electrical separation. Properties of standard aerosols produced experimentally by both the conventional and the new method, are compared and the validity of the new idea behind the new method is confirmed.     

Magnetic response of soils and vegetation to heavy metal pollution--a case study

Fast and cost-effective detection of industrial pollution can significantly promote its ecological, economic, and social assessment. A magnetometric method, used for qualitative determination of anthropogenic contamination, meets these requirements but needs further development in more quantitative terms. It could be used successfully in numerous cases when the heavy metals coexist with strongly magnetic iron oxide particles in the source dust. We present an integrated magnetic and geochemical study that examines the utility of magnetometric techniques for rapid, qualitative detection of metallic pollutants in soils and vegetation. The new aspect of our approach, in comparison with previously published articles on this subject, is the combined investigation (magnetic and geochemical) of both soils and vegetation, thus using an additional medium for employing the magnetometry as a pollution proxy at a site. The study area is a small (approximately 3 km2) region in the suburbs of Sofia (Bulgaria), with the main pollution source being a metallurgical factory. Soil samples have been taken from the topmost 20 cm from private gardens, located at different distances from the factory. Vegetation samples were taken from ryegrass (both leaves and roots) and leaves from two kinds of deciduous trees (maple and acacia). The results show that both vegetation and soils are characterized by enhanced magnetic properties, compared to background material, which is due to the presence of magnetite particles of anthropogenic origin accompanying heavy metal emissions. SEM images and microprobe analyses reveal the presence of a significant amount of particles, containing heavy metals (including iron) in vegetation samples taken close to the main pollution source. Correlation analyses show a statistically significant link (correlation coefficients ranging from 0.6 to 0.7) between magnetic susceptibility and the main heavy metals (Cu, Zn, Pb) in soil samples, indicating that the magnetic susceptibility can provide a proxy method for identifying the relative contribution of industrial pollution in soils and vegetation, that is reliable, inexpensive, and less time-consuming than standard chemical analyses.     

Double‐frequency buck converter as a candidate topology for integrated envelope elimination and restoration applications in power supply of RFPAs

This paper proposes the use of double‐frequency (DF) buck converter architecture consisting of a merged structure of high and low frequency buck cells as a candidate topology for envelope elimination and restoration (EER) applications and integrated power supply of RF power amplifiers (RFPA) to obtain favorable tradeoffs in terms of efficiency, switching ripple, bandwidth, and tracking capability. It is shown that having two degrees of freedom in designing the DF buck helps to achieve high efficiency, low output ripples, and tracking capability with low ripples, simultaneously. A comparison analysis is done with regards to the mentioned performance indexes with the standard and three‐level buck converters; in addition, the results are validated in HSPICE in BSIM3V3 0.35‐µm CMOS process. Copyright © 2015 John Wiley & Sons, Ltd.     

A Review of Microfluidic Experimental Designs for Nanoparticle Synthesis

Microfluidics is defined as emerging science and technology based on precisely manipulating fluids through miniaturized devices with micro-scale channels and chambers. Such microfluidic systems can be used for numerous applications, including reactions, separations, or detection of various compounds. Therefore, due to their potential as microreactors, a particular research focus was noted in exploring various microchannel configurations for on-chip chemical syntheses of materials with tailored properties. Given the significant number of studies in the field, this paper aims to review the recently developed microfluidic devices based on their geometry particularities, starting from a brief presentation of nanoparticle synthesis and mixing within microchannels, further moving to a more detailed discussion of different chip configurations with potential use in nanomaterial fabrication.     

Validated Growth Rate-Dependent Regulation of Lipid Metabolism in Yarrowia lipolytica

Given the strong potential of Yarrowia lipolytica to produce lipids for use as renewable fuels and oleochemicals, it is important to gain in-depth understanding of the molecular mechanism underlying its lipid accumulation. As cellular growth rate affects biomass lipid content, we performed a comparative proteomic analysis of Y. lipolytica grown in nitrogen-limited chemostat cultures at different dilution rates. After confirming the correlation between growth rate and lipid accumulation, we were able to identify various cellular functions and biological mechanisms involved in oleaginousness. Inspection of significantly up- and downregulated proteins revealed nonintuitive processes associated with lipid accumulation in this yeast. This included proteins related to endoplasmic reticulum (ER) stress, ER–plasma membrane tether proteins, and arginase. Genetic engineering of selected targets validated that some genes indeed affected lipid accumulation. They were able to increase lipid content and were complementary to other genetic engineering strategies to optimize lipid yield.     

Dynamic Regulation of Mitochondrial [Ca2+] in Hippocampal Neurons

While neuronal mitochondria have been studied extensively in their role in health and disease, the rules that govern calcium regulation in mitochondria remain somewhat vague. In the present study using cultured rat hippocampal neurons transfected with the mtRCaMP mitochondrial calcium sensor, we investigated the effects of cytosolic calcium surges on the dynamics of mitochondrial calcium ([Ca²⁺]m). Cytosolic calcium ([Ca²⁺]c) was measured using the high affinity sensor Fluo-2. We recorded two types of calcium events: local and global ones. Local events were limited to a small, 2–5 µm section of the dendrite, presumably caused by local synaptic activity, while global events were associated with network bursts and extended throughout the imaged dendrite. In both cases, cytosolic surges were followed by a delayed rise in [Ca²⁺]m. In global events, the rise lasted longer and was observed in all mitochondrial clusters. At the end of the descending part of the global event, [Ca²⁺]m was still high. Global events were accompanied by short and rather high [Ca²⁺]m surges which we called spikelets, and were present until the complete decay of the cytosolic event. In the case of local events, selective short-term responses were limited to the part of the mitochondrial cluster that was located directly in the center of [Ca²⁺]c activity, and faded quickly, while responses in the neighboring regions were rarely observed. Caffeine (which recruits ryanodine receptors to supply calcium to the mitochondria), and carbonyl cyanide m-chlorophenyl hydrazine (CCCP, a mitochondrial uncoupler) could affect [Ca²⁺]m in both global and local events. We constructed a computational model to simulate the fundamental role of mitochondria in restricting calcium signals within a narrow range under synapses, preventing diffusion into adjacent regions of the dendrite. Our results indicate that local cytoplasmic and mitochondrial calcium concentrations are highly correlated. This reflects a key role of signaling pathways that connect the postsynaptic membrane to local mitochondrial clusters.     

Absolute Adsorption Isotherms for Pseudocumene + n-Octane + Zeolite NaX System: Determination of the Activity Coefficients of the Adsorbed Phase

Protection of Metals and Physical Chemistry of Surfaces - The excess adsorption isotherms of pseudocumene from solutions in n-octane in zeolite NaX have been measured at 303.15, 338.15 and 363.15 K...     

Fungal aerosol composition in moldy basements

Experimental aerosolization studies revealed that fungal fragments including small fragments in the submicrometer size are released from fungal cultures and have been suggested to represent an important fraction of overall fungal aerosols in indoor environments. However, their prevalence indoors and outdoors remains poorly characterized. Moldy basements were investigated for airborne fungal particles including spores, submicron fragments, and larger fragments. Particles were collected onto poly‐L‐lysine‐coated polycarbonate filters and qualitatively and quantitatively analyzed using immunogold labeling combined with field emission scanning electron microscopy. We found that the total fungal aerosol levels including spores, submicrometer, and larger fragments in the moldy basements (median: 80 × 10³ m^?3) were not different from that estimated in control basements (63 × 10³ m^?3) and outdoor (90 × 10³ m^?3). However, mixed effect modeling of the fungal aerosol composition revealed that the fraction of fragments increased significantly in moldy basements, versus the spore fraction that increased significantly in outdoor air. These findings provide new insight on the compositional variation of mixed fungal aerosols in indoor as compared to outdoor air. Our results also suggest that further studies, aiming to investigate the role of fungal aerosols in the fungal exposure‐disease relationships, should consider the mixed composition of various types of fungal particles.     

Characterization and pro-inflammatory potential of indoor mold particles

A number of epidemiological studies find an association between indoor air dampness and respiratory health effects. This is often suggested to be linked to enhanced mold growth. However, the role of mold is obviously difficult to disentangle from other dampness-related exposure including microbes as well as non-biological particles and chemical pollutants. The association may partly be due to visible mycelial growth and a characteristic musty smell of mold. Thus, the potential role of mold exposure should be further explored by evaluating information from experimental studies elucidating possible mechanistic links. Such studies show that exposure to spores and hyphal fragments may act as allergens and pro-inflammatory mediators and that they may damage airways by the production of toxins, enzymes, and volatile organic compounds. In the present review, we hypothesize that continuous exposure to mold particles may result in chronic low-grade pro-inflammatory responses contributing to respiratory diseases. We summarize some of the main methods for detection and characterization of fungal aerosols and highlight in vitro research elucidating how molds may induce toxicity and pro-inflammatory reactions in human cell models relevant for airway exposure. Data suggest that the fraction of fungal hyphal fragments in indoor air is much higher than that of airborne spores, and the hyphal fragments often have a higher pro-inflammatory potential. Thus, hyphal fragments of prevalent mold species with strong pro-inflammatory potential may be particularly relevant candidates for respiratory diseases associated with damp/mold-contaminated indoor air. Future studies linking of indoor air dampness with health effects should assess the toxicity and pro-inflammatory potential of indoor air particulate matter and combined this information with a better characterization of biological components including hyphal fragments from both pathogenic and non-pathogenic mold species. Such studies may increase our understanding of the potential role of mold exposure.