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Goutam Koley - One of the best experts on this subject based on the ideXlab platform.
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impact of Volatile Organic Compound exposure on electrical breakdown in gan dual channel microcantilevers
Applied Physics Letters, 2019Co-Authors: Sean Gorman, Durga Gajula, Goutam KoleyAbstract:The impact of Volatile Organic Compound (VOC) exposure on the electrical breakdown of GaN in the inter channel region of dual channel microcantilever heaters has been studied. Exposure to three different VOCs with different latent heats of evaporation resulted in changes in breakdown voltage of varying magnitudes that can be correlated with their latent heats. A physical model has been proposed to explain the observed shift in breakdown voltage upon VOC exposure based on changes in thermal and electrical profiles at the microcantilever apex, which is caused by the molecular interaction and amplified by its unique tapered geometry. The critical breakdown field of the inter channel GaN has been observed to reduce dramatically by almost 50 times compared to that of bulk GaN at room temperature. The inter-channel current rises dramatically at the onset of breakdown induced by VOC exposure, at specific bias voltages corresponding to VOCs, which can be utilized for detecting them with high sensitivity as well as selectivity.
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dual channel microcantilever heaters for Volatile Organic Compound detection and mixture analysis
Scientific Reports, 2016Co-Authors: Ifat Jahangir, Goutam KoleyAbstract:We report on novel microcantilever heater sensors with separate AlGaN/GaN heterostructure based heater and sensor channels to perform advanced Volatile Organic Compound (VOC) detection and mixture analysis. Operating without any surface functionalization or treatment, these microcantilevers utilize the strong surface polarization of AlGaN, as well as the unique heater and sensor channel geometries, to perform selective detection of analytes based on their latent heat of evaporation and molecular dipole moment over a wide concentration range with sub-ppm detection limit. The dual-channel microcantilevers have demonstrated much superior sensing behavior compared to the single-channel ones, with the capability to not only identify individual VOCs with much higher specificity, but also uniquely detect them in a generic multi-component mixture of VOCs. In addition, utilizing two different dual channel configurations and sensing modalities, we have been able to quantitatively determine individual analyte concentration in a VOC mixture. An algorithm for complete mixture analysis, with unique identification of components and accurate determination of their concentration, has been presented based on simultaneous operation of an array of these microcantilever heaters in multiple sensing modalities.
Flavia Gasperi - One of the best experts on this subject based on the ideXlab platform.
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Effects of dairy system, herd within dairy system, and individual cow characteristics on the Volatile Organic Compound profile of ripened model cheeses
Journal of dairy science, 2015Co-Authors: Matteo Bergamaschi, Eugenio Aprea, Emanuela Betta, Franco Biasioli, Claudio Cipolat-gotet, Alessio Cecchinato, Giovanni Bittante, Flavia GasperiAbstract:Abstract The objective of this work was to study the effect of dairy system, herd within dairy system, and characteristics of individual cows (parity, days in milk, and daily milk yield) on the Volatile Organic Compound profile of model cheeses produced under controlled conditions from the milk of individual cows of the Brown Swiss breed. One hundred fifty model cheeses were selected from 1,272 produced for a wider study of the phenotypic and genetic variability of Brown Swiss cows. In our study, we selected 30 herds representing 5 different dairy systems. The cows sampled presented different milk yields (12.3–43.2kg/d), stages of lactation (10–412 d in milk), and parity (1–7). In total, 55 Volatile Compounds were detected by solid-phase microextraction and gas chromatography-mass spectrometry, including 14 alcohols, 13 esters, 11 free fatty acids, 8 ketones, 4 aldehydes, 3 lactones, 1 terpene, and 1 pyrazine. The most important sources of variation in the Volatile Organic profiles of model cheeses were dairy system (18 Compounds) and days in milk (10 Compounds), followed by parity (3 Compounds) and milk yield (5 Compounds). The model cheeses produced from the milk of tied cows reared on traditional farms had lower quantities of 3-methyl-butan-1-ol, 6-pentyloxan-2-one, 2-phenylethanol, and dihydrofuran-2(3H)-one compared with those reared in freestalls on modern farms. Of these, milk from farms using total mixed rations had higher contents of alcohols (hexan-1-ol, octan-1-ol) and esters (ethyl butanoate, ethyl pentanoate, ethyl hexanoate, and ethyl octanoate) and lower contents of acetic acid compared with those using separate feeds. Moreover, dairy systems that added silage to the total mixed ration produced cheeses with lower levels of Volatile Organic Compounds, in particular alcohols (butan-1-ol, pentan-1-ol, heptan-1-ol), compared with those that did not. The amounts of butan-2-ol, butanoic acid, ethyl-2-methylpropanoate, ethyl-3-methylbutanoate, and 6-propyloxan-2-one increased linearly during lactation, whereas octan-1-ol, 3-methyl-3-buten-1-ol, 2-butoxyethanol, 6-pentyloxan-2-one, and 2,6-dimethylpyrazine showed a more complex pattern during lactation. The effect of the number of lactations (parity) was significant for octan-1-ol, butanoic acid, and heptanoic acid. Finally, concentrations of octan-1-ol, 2-phenylethanol, pentanoic acid, and heptanoic acid increased with increasing daily milk yield, whereas dihydrofuran-2(3H)-one decreased. In conclusion, the Volatile Organic Compound profile of model cheeses from the milk of individual cows was affected by dairy farming system and stage of lactation and, to lesser extent, by parity and daily milk yield.
Alex Guenther - One of the best experts on this subject based on the ideXlab platform.
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a biogenic Volatile Organic Compound emission inventory for hong kong
Atmospheric Environment, 2009Co-Authors: Jeanie Kinyin Tsui, Alex Guenther, Wingkin Yip, Feng ChenAbstract:Atmospheric Environment 43 (2009) 6442–6448 Contents lists available at ScienceDirect Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv A biogenic Volatile Organic Compound emission inventory for Hong Kong Jeanie Kin-Yin Tsui a , Alex Guenther b , Wing-Kin Yip a , Feng Chen a, * a b School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China National Center for Atmospheric Research, Atmospheric Chemistry Division, CO 80307-3000, USA a r t i c l e i n f o a b s t r a c t Article history: Received 13 August 2007 Received in revised form 14 January 2008 Accepted 14 January 2008 Biogenic Volatile Organic Compounds (BVOCs) in the atmosphere react to form ozone and secondary Organic aerosols, which deteriorate air quality, affect human health, and indirectly influence global climate changes. The present study aims to provide a preliminary assessment of BVOC emissions in Hong Kong (HKSAR). Thriteen local tree species were measured for their isoprene emission potential. Tree distribution was estimated for country park areas based on field survey data. Plant emission data obtained from measurements and the literature, tree distribution estimation data, land use information, and meteorological data were combined to estimate annual BVOC emissions of 8.610 9 g C for Hong Kong. Isoprene, monoterpenes, and other VOCs contributed about 30%, 40%, and 30% of the estimated total annual emissions, respectively. Although hundreds of plant species are found in Hong Kong country parks, the model results indicate that only 10 tree species contribute about 76% of total annual VOC emissions. Prominent seasonal and diurnal variations in emissions were also predicted by the model. The present study lays a solid foundation for future local research, and results can be applied for studying BVOC emissions in nearby southern China and Asian regions that share similar climate and plant distributions. O 2008 Elsevier Ltd. All rights reserved. Keywords: Hong Kong BVOC Isoprene Monoterpenes Emission modeling 1. Introduction Air pollution is drawing more attention than ever before from the Government as well as the general public of Hong Kong, as various negative impacts of poor air quality have been recognized, ranging from increased incidents of pulmonary diseases in the population, to its adverse effects on economy and tourism. Volatile Organic Compounds (VOCs) play an important role in air pollution in Hong Kong. VOC emissions from anthropogenic sources (AVOCs), such as power plant and road traffic have been well studied (e.g., Guo et al., 2007). However, little is known about VOC emissions from biogenic sources in Hong Kong. Vegetation is the primary source of biogenic Volatile Organic Compounds (BVOCs) which include terpenoids (e.g., isoprene and monoterpenes), hexenal family Compounds (hexenals, hexenols, and hexenyl esters), methanol, and acetone (Guenther et al., 2000). In the presence of sunlight and nitrogen oxides (NO x ), reaction of VOCs contributes to the formation of ozone (O 3 ) (Atkinson, 2000; Fuentes et al., 2000). The impact of BVOC on O 3 formation becomes more prominent in summer, when both photochemical activity and BVOC emissions reach the peak. * Corresponding author. Tel.: þ852 2299 0309; fax: þ852 2299 0311. E-mail address: sfchen@hkusua.hku.hk (F. Chen). 1352-2310/$ – see front matter O 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2008.01.027 Tropospheric O 3 is a greenhouse gas. In addition, through its chemical impact on hydroxyl radical (OH), it modifies the lifetimes of other greenhouse gases, such as methane (CH 4 ) (IPCC, 2001). Hence, climate change is indirectly promoted by BVOC emissions. O 3 also adversely affects public health. Exposure to ozone reduces pulmonary function, causes cough and chest tightness (Abelsohn et al., 2002), and exacerbates asthma (Watson and Sheppeard, 2005). Local studies show significant association between O 3 and hospital admission due to respiratory diseases (Wong et al., 1999; Lee et al., 2006). Studies also suggest that elevated O 3 concentration would lead to increase in total, cardiovascular and respiratory mortality (Zhang et al., 2006; Zeller et al., 2006; Bell et al., 2007). Photooxidation of isoprene (Claeys et al., 2004) and mono- terpenes (Hoffmann et al., 1997; Kavouras et al., 1998) also contributes to the formation of secondary Organic aerosol (SOA). Atmospheric aerosols play a critical role in climate change by modifying the radiative balance of the atmosphere by scattering or absorbing solar radiation (IPCC, 2001). It is estimated that Organics contribute w20–50% of total fine aerosol mass on a global scale and as high as 90% in tropical forested areas (Andreae and Crutzen, 1997; Kanakidou et al., 2005) where biomass burning and biogenic sources dominate. Biogenic VOCs are typically more reactive than AVOCs (Abelson, 1988), and their reactivity has been estimated to be two to three times that of their counterparts from gasoline combustion (Carter, 1994).
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a global model of natural Volatile Organic Compound emissions
Journal of Geophysical Research, 1995Co-Authors: Alex Guenther, P Harley, Nicholas C Hewitt, Ray Fall, Thomas E. Graedel, David J Erickson, Chris Geron, L Klinger, Manuel T. Lerdau, W A MckayAbstract:Numerical assessments of global air quality and potential changes in atmospheric chemical constituents require estimates of the surface fluxes of a variety of trace gas species. We have developed a global model to estimate emissions of Volatile Organic Compounds from natural sources (NVOC). Methane is not considered here and has been reviewed in detail elsewhere. The model has a highly resolved spatial grid (0.5° × 0.5° latitude/longitude) and generates hourly average emission estimates. Chemical species are grouped into four categories: isoprene, monoterpenes, other reactive VOC (ORVOC), and other VOC (OVOC). NVOC emissions from oceans are estimated as a function of geophysical variables from a general circulation model and ocean color satellite data. Emissions from plant foliage are estimated from ecosystem specific biomass and emission factors and algorithms describing light and temperature dependence of NVOC emissions. Foliar density estimates are based on climatic variables and satellite data. Temporal variations in the model are driven by monthly estimates of biomass and temperature and hourly light estimates. The annual global VOC flux is estimated to be 1150 Tg C, composed of 44% isoprene, 11% monoterpenes, 22.5% other reactive VOC, and 22.5% other VOC. Large uncertainties exist for each of these estimates and particularly for Compounds other than isoprene and monoterpenes. Tropical woodlands (rain forest, seasonal, drought-deciduous, and savanna) contribute about half of all global natural VOC emissions. Croplands, shrublands and other woodlands contribute 10–20% apiece. Isoprene emissions calculated for temperate regions are as much as a factor of 5 higher than previous estimates.
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natural Volatile Organic Compound emission rate estimates for u s woodland landscapes
Atmospheric Environment, 1994Co-Authors: Alex Guenther, P R Zimmerman, Mary C WildermuthAbstract:Volatile Organic Compound (VOC) emission rate factors are estimated for 49 tree genera based on a review of foliar emission rate measurements. Foliar VOC emissions are grouped into three categories: isoprene, monoterpenes and other VOCs. Typical emission rates at a leaf temperature of 30°C and a light intensity of 1000 μmol m−2 s−1 range from <0.1 to 70 μg C g−1 h−1 for isoprene, <0.1 to 3 μg C g−1 h−1 for monoterpenes, and < 0.5 to 5 μg C g−1 h−1 for other VOCs. Isoprene emission factors are given for biogenic emission models that incorporate canopy shading effects and thus require leaf-level emission rates and for emission models that do not include a canopy model and therefore require branch-level isoprene emission factors which already account for some shading. Landscape-level emission rates are estimated by combining emission rate factors determined for tree genera with species composition and foliar mass data. Landscape emission rate factors are determined for each of the 91 woodland landscapes in the high resolution (1.1 km) gridded land-cover database compiled by the EROS Data Center (EDC) from satellite and ancillary data. This database covers the entire contiguous United States of America. Landscape emission rates are also be determined using gridded tree distribution data, based on aerial photographs and ground measurements, such as that available in the U.S. Forest Service (USES) Easlwide Forest Inventory Database (EFID). Emission rates are reported for 41 of the 65 tree genera in the EFID including all of the most common genera. Total VOC emission rate factors for the 91 EDC woodland-cover types range from 0.8 to 11 mg C m−2h−1 at a standard condition of 30°C and 1000 μmol m−2s−1. These landscape factors are based on branch-level emission factors and thus already incorporate canopy shading effects. The estimated fluxes of isoprene and monoterpenes are in relatively good agreement with field measurements of area-averaged fluxes if accurate species composition data (e.g. from the EFID) are available. Total VOC emission rate estimates range from 0.8 to 4.3 mg C m−2h−1 for scrub woodlands and 2.2 to 11 mg C m−2h−1 for mixed deciduous/coniferous woodlands. The chemical composition of the VOC flux ranges from 8 to 91 isoprene, 1 to 56% for monoterpenes and 8 to 73% for other VOC. On an area-weighted basis, the U.S. average total VOC emission rate factor of 5.1 mg m−2h−1 for all woodlands is comprised of 58% isoprene, 18% monoterpenes and 24% other VOC. In comparison to previous estimates, these emission rates are generally higher for isoprene and lower for monoterpenes.
Tim G.j. De Meij - One of the best experts on this subject based on the ideXlab platform.
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Application of Fecal Volatile Organic Compound Analysis in Clinical Practice: Current State and Future Perspectives
Chemosensors, 2018Co-Authors: Sofia El Manouni El Hassani, Daniel J.c. Berkhout, Nanne K H De Boer, Sofie Bosch, Marc A. Benninga, Tim G.j. De MeijAbstract:Increasing interest is noticed in the potential of Volatile Organic Compound (VOC) analysis as non-invasive diagnostic biomarker in clinical medical practice. The spectrum of VOCs, originating from (patho)physiological metabolic processes in the human body and detectable in bodily excrements, such as exhaled breath, urine and feces, harbors a magnificent source of information. Thus far, the majority of studies have focused on VOC analysis in exhaled breath, aiming at identification of disease-specific VOC profiles. Recently, an increasing number of studies have evaluated the usability of VOC present in the headspace of feces in the diagnostic work-up of a wide range of gastrointestinal diseases. Promising results have been demonstrated particularly in those diseases in which microbiota alterations are considered to play a significant etiological role, such as colorectal carcinoma, inflammatory bowel disease, irritable bowel syndrome, celiac disease and infectious bowel diseases. In addition, fecal VOC analysis seems to have potential as a diagnostic biomarker for extra-intestinal diseases, including bronchopulmonary dysplasia and sepsis. Different methods for VOC analysis have been used in medical studies, such as gas-chromatography mass spectrometry, selected-ion flow tube-mass spectrometry, ion-mobility spectrometry, and electronic nose devices. In this review, the available literature on the potential of fecal VOCs as diagnostic biomarker, including an overview of relevant VOC detection techniques, is discussed. In addition, future hurdles, which need to be taken prior to implementation of VOC analysis in daily clinical practice, are outlined.
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Effects of sampling conditions and environmental factors on fecal Volatile Organic Compound analysis by an electronic nose device
Sensors (Switzerland), 2016Co-Authors: Daniel J.c. Berkhout, Ruby M. Van Stein, Hendrik J. Niemarkt, Paul Brinkman, Nanne K H De Boer, Marc A. Benninga, Tim G.j. De MeijAbstract:Prior to implementation of Volatile Organic Compound (VOC) analysis in clinical practice, substantial challenges, including methodological, biological and analytical difficulties are faced. The aim of this study was to evaluate the influence of several sampling conditions and environmental factors on fecal VOC profiles, analyzed by an electronic nose (eNose). Effects of fecal sample mass, water content, duration of storage at room temperature, fecal sample temperature, number of freeze–thaw cycles and effect of sampling method (rectal swabs vs. fecal samples) on VOC profiles were assessed by analysis of totally 725 fecal samples by means of an eNose (Cyranose320®). Furthermore, fecal VOC profiles of totally 1285 fecal samples from 71 infants born at three different hospitals were compared to assess the influence of center of origin on VOC outcome. We observed that all analyzed variables significantly influenced fecal VOC composition. It was feasible to capture a VOC profile using rectal swabs, although this differed significantly from fecal VOC profiles of similar subjects. In addition, 1285 fecal VOC-profiles could significantly be discriminated based on center of birth. In conclusion, standardization of methodology is necessary before fecal VOC analysis can live up to its potential as diagnostic tool in clinical practice.
Matteo Bergamaschi - One of the best experts on this subject based on the ideXlab platform.
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Effects of dairy system, herd within dairy system, and individual cow characteristics on the Volatile Organic Compound profile of ripened model cheeses
Journal of dairy science, 2015Co-Authors: Matteo Bergamaschi, Eugenio Aprea, Emanuela Betta, Franco Biasioli, Claudio Cipolat-gotet, Alessio Cecchinato, Giovanni Bittante, Flavia GasperiAbstract:Abstract The objective of this work was to study the effect of dairy system, herd within dairy system, and characteristics of individual cows (parity, days in milk, and daily milk yield) on the Volatile Organic Compound profile of model cheeses produced under controlled conditions from the milk of individual cows of the Brown Swiss breed. One hundred fifty model cheeses were selected from 1,272 produced for a wider study of the phenotypic and genetic variability of Brown Swiss cows. In our study, we selected 30 herds representing 5 different dairy systems. The cows sampled presented different milk yields (12.3–43.2kg/d), stages of lactation (10–412 d in milk), and parity (1–7). In total, 55 Volatile Compounds were detected by solid-phase microextraction and gas chromatography-mass spectrometry, including 14 alcohols, 13 esters, 11 free fatty acids, 8 ketones, 4 aldehydes, 3 lactones, 1 terpene, and 1 pyrazine. The most important sources of variation in the Volatile Organic profiles of model cheeses were dairy system (18 Compounds) and days in milk (10 Compounds), followed by parity (3 Compounds) and milk yield (5 Compounds). The model cheeses produced from the milk of tied cows reared on traditional farms had lower quantities of 3-methyl-butan-1-ol, 6-pentyloxan-2-one, 2-phenylethanol, and dihydrofuran-2(3H)-one compared with those reared in freestalls on modern farms. Of these, milk from farms using total mixed rations had higher contents of alcohols (hexan-1-ol, octan-1-ol) and esters (ethyl butanoate, ethyl pentanoate, ethyl hexanoate, and ethyl octanoate) and lower contents of acetic acid compared with those using separate feeds. Moreover, dairy systems that added silage to the total mixed ration produced cheeses with lower levels of Volatile Organic Compounds, in particular alcohols (butan-1-ol, pentan-1-ol, heptan-1-ol), compared with those that did not. The amounts of butan-2-ol, butanoic acid, ethyl-2-methylpropanoate, ethyl-3-methylbutanoate, and 6-propyloxan-2-one increased linearly during lactation, whereas octan-1-ol, 3-methyl-3-buten-1-ol, 2-butoxyethanol, 6-pentyloxan-2-one, and 2,6-dimethylpyrazine showed a more complex pattern during lactation. The effect of the number of lactations (parity) was significant for octan-1-ol, butanoic acid, and heptanoic acid. Finally, concentrations of octan-1-ol, 2-phenylethanol, pentanoic acid, and heptanoic acid increased with increasing daily milk yield, whereas dihydrofuran-2(3H)-one decreased. In conclusion, the Volatile Organic Compound profile of model cheeses from the milk of individual cows was affected by dairy farming system and stage of lactation and, to lesser extent, by parity and daily milk yield.
