The urban heat island (UHI) effect has been the subject of much research due to its adverse effects on health, energy, and the environment. The objective of this work is to investigate the key ...parameters contributing to the urban heat island effect in Beirut city and to improve the temperature forecast in the city by taking these parameters into account. This is accomplished by coupling the single – layer urban canopy model (UCM) with the Weather Research and Forecasting model (WRF), where the urban parameters in UCM are calculated or fine – tuned to minimize the difference between the measured and the forecasted temperature. Urban parameters that were tuned included the roof albedo, wall albedo, roof thermal conductivity, in addition to the anthropogenic heat. To get optimum values for these parameters, simulations with different values for each parameter were performed during the four seasons and compared with observations from stations that are distributed across the city using a novel method that has not been used before to the best of our knowledge. Comparison is based on the mean, standard deviation, mean bias, root mean square error, and correlation coefficient. We also present an assessment of the UHI in Beirut based on some metrics of urban complexity.
•We investigate key parameters that contribute to the Urban Heat Island in Beirut.•The parameters are the anthropogenic heat, roof and wall albedos, and roof thermal conductivity.•The parameters are tuned to match the forecasted temperature and wind speeds to the measured ones.•The forecasted temperature and wind speeds are obtained using the single-layer UCM with WRF.•We found that the anthropogenic heat is the major parameter contributing to the UHI.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Laboratory studies reported here and in previous work show that the reaction of NO(g) with surface adsorbed HNO3 may be a significant source of HONO in polluted urban atmospheres. If these laboratory ...studies can be extrapolated to ambient conditions, this heterogeneous reaction may generate HONO to about the same extent as the hydrolysis of NO2 on surfaces, which is greater than the heterogeneous reaction of NO, NO2 and water. It may also be involved in generating HONO in snowpacks, and important in reconciling the discrepancy between measured and modeled HNO3/NOx ratios in the troposphere.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Sesquiterpene lactones (SL) are plant secondary metabolites that are known for their anti-fungal, anti-bacterial, anti-inflammatory, and anti-tumor properties. Considering that several SL-derived ...drugs are currently in cancer clinical trials, we have tested two SL molecules, 3-β-methoxy-iso-seco-tanapartholide (β-tan) isolated from Achillea falcata and salograviolide A (Sal A) isolated from Centaurea ainetensis, for their anti-tumor properties. We used the mouse epidermal JB6P + cells as a model for tumor promotion and cellular transformation. Key players that are involved in cellular transformation and tumorigenesis are the AP-1 and NF-κB transcription factors; therefore, we assessed how β-tan and Sal A modulate their signaling pathways in JB6P + cells.
The effects of β-tan and Sal A on the growth of normal and neoplastic keratinocytes and on the tumor promotion-responsive JB6P + cells were determined using the MTT assay. Anchorage-independent cell growth transformation assays were used to evaluate the anti-tumor promoting properties of these SL molecules in JB6P + cells and dual luciferase reporter assays and western blot analysis were used to investigate their effects on tumor promoter-induced AP-1 and NF-κB activities and protein levels of key AP-1 and NF-кB target genes.
β-tan and Sal A selectively inhibited tumor promoter-induced cell growth and transformation of JB6P + cells at concentrations that do not affect JB6P + and primary keratinocytes basal cell growth. In addition, both molecules reduced basal and tumor promoter-induced NF-κB transcriptional activities, differentially regulated basal and tumor promoter-induced AP-1 transcriptional activities, and modulated key players of the AP-1 and NF-κB signaling pathways.
These results highlight the anti-tumor promoting properties of β-tan and Sal A. These SL molecules isolated from two plant species native to the Middle East may provide opportunities for complementary medicine practices.
Acetylene Chemisorption on Sn/Pt(100) Alloys Panja, Chameli; Saliba, Najat A; Koel, Bruce E
The journal of physical chemistry. B,
05/2001, Volume:
105, Issue:
18
Journal Article
Peer reviewed
Adsorption and reaction of acetylene on a hexagonally reconstructed (5 × 20)-Pt(100) surface and two ordered Sn/Pt(100) alloy surfaces were investigated using temperature programmed desorption ...spectrometry (TPD), Auger electron spectroscopy (AES), low energy electron diffraction (LEED) and X-ray photoelectron spectroscopy (XPS). Vapor deposition of Sn onto a Pt(100) single-crystal substrate was used to form two Pt−Sn alloys, the c(2 × 2) and (3√2×√2)R45° Sn/Pt(100) structures with θSn = 0.5 and 0.67 ML, respectively, depending on the initial Sn concentration and annealing temperature. Acetylene nearly completely decomposed during TPD on Pt(100) in the absence of Sn, forming hydrogen, which then desorbs as H2, and surface carbon. This decomposition, associated with irreversible dissociative adsorption, was strongly suppressed on the two Pt−Sn alloy surfaces, and a large acetylene desorption peak in TPD was observed. Additionally, 15% of the adsorbed acetylene monolayer was converted to gaseous benzene during TPD on the (3√2×√2)R45° Sn/Pt(100) alloy. No such benzene desorption occurred from the c(2 × 2) alloy. Alloyed Sn in the c(2 × 2) alloy decreased the initial sticking coefficient of acetylene on Pt(100) at 100 K by ∼40%, but additional Sn in the other alloy had no additional effect. The saturation coverage of C2D2 in the chemisorbed monolayer at 100 K decreased from that on Pt(100) by 35% on the c(2 × 2) alloy and 50% on the (3√2×√2)R45° Sn/Pt(100) alloy. However, the c(2 × 2)-Sn adlayer eliminates acetylene chemisorption, illustrating that the effectiveness of Sn to “block” sites depends crucially on its location as an adatom or alloyed atom on Pt surfaces. The acetylene chemisorption bond energy, estimated by the acetylene desorption activation energy measured in TPD, also decreased (45−65%) as the alloyed Sn concentration increased. Multiple TPD peaks for C2D2 desorption from both the c(2 × 2) and the (3√2×√2)R45°Sn/Pt(100) alloy surfaces indicate either several energetically distinguishable adsorption sites for acetylene or the rate-limiting influence of more complex surface reactions on these surfaces.
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IJS, KILJ, NUK, PNG, UL, UM
The wide application and production of nanotechnology have increased the interest in studying the toxicity of nano- and micro-sized particles escaping into air from various aspects of the production ...process. Metal oxides (MOs) are one particular class of particles that exist abundantly in ambient PM. Studies show an emphasis on biological mechanisms by which inhalation exposure to MOs leads to disease. However, different biological assays provide different redox activity rankings making it difficult to assess the contributions of various MOs to measures of aggregate toxicity in multi-pollutant systems such as ambient PM. Therefore, research to evaluate the chemical interaction between these particles and molecules that are relevant to cellular redox activity can help in establishing indicators of reactivity. In particular, this study assesses the redox activity of six MOs mainly emitted from anthropogenic industrial activities using the dithiothreitol (DTT) assay. DTT is commonly used in acellular assays due to its analogous structure to cellular glutathione. The structural and chemical behaviors between active MOs and DTT were elucidated using FTIR, NMR, and BET methods. The results indicate that the health risk (redox activity) associated with MOs is mainly a function of their surface reactivity demonstrated by the ability of the oxidized (S-H) bond in DTT to form a stable bond with the MO surface.
The wide application of nanotechnology has increased the interest in studying the toxicity of nano- and micro-sized particles escaping into air from various aspects of the production process.
Two Pt−Sn surface alloys were oxidized at 300 K by ozone (O3) exposure in UHV. Both alloys were less reactive than Pt(111), and the p(2 × 2) alloy (ϑSn = 0.25) was more reactive than the (√3x√3)R30° ...alloy (ϑSn = 0.33). The relative O3 dissociative sticking coefficients on these surfaces at 300 K were 1.0:0.79:0.33, respectively. Ozone dissociation was inhibited more easily on the alloys than on Pt(111), and large O3 doses on the p(2 × 2) and (√3x√3)R30° surface alloys produced oxygen coverages of 1.2 and 0.87 monolayers, respectively, compared to 2.4 monolayers on Pt(111). Both chemisorbed and “oxidic” oxygen states were characterized by using Auger electron spectroscopy (AES), temperature-programmed desorption (TPD), and low-energy electron diffraction (LEED). At 300 K, chemisorbed oxygen adatoms are formed at low exposures, but oxidation of Sn occurs at large oxygen coverages, as evidenced by a 1.6 eV downshift of the Sn(MNN) AES peak. Heating during TPD causes SnO x formation even at low coverages, and this decomposes to liberate O2 in desorption peaks at 1015 and 1078 K on the p(2 × 2) and (√3x√3)R30° surfaces, respectively. After oxidation of Sn, TPD indicates desorption of oxygen from chemisorbed adatoms bound at Pt sites and eventually formation of platinum oxide particles. SnO x particles formed in intimate contact with Pt by oxidation of these Pt−Sn alloys and high-temperature heating are easier (100 K) to reduce by heating in a vacuum than a corresponding thick SnO x film. We also find additional stability (130 K) imparted to PtO x particles by the presence of oxidized Sn following oxidation of these alloys. Heating these oxidized alloys to 1000 K produces a (4 × 1) LEED pattern that we have assigned to the formation of large domains of an SnO2 overlayer on both of the surface alloys.
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The variation in composition of the essential oils produced from different ratios of needles to terminal twigs of Pinus brutia Ten. in Lebanon was examined by GC and GC/MS. As the mass of the needles ...increased from 0-100% with respect to twig contents, the % oil yield decreased and the composition changed. Pure needle oil was found to be much richer in oxygenated compounds than that of pure twig oil with a corresponding reduction in amounts of monoterpene hydrocarbons. Marker compounds were chosen in order to show the chemical variation of the oils with respect to different ratio of needles to twigs distilled. By computing both physical and chemical variations, it is suggested that a fair compromise between the yield and the concentration of oxygenated compounds is the 75% needle 25% twig mixture, which appears to be the most suitable proportion of plant material for pine oil production from P. brutia.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
Ambient air pollution is a major risk to the human health and to the environment. The data presented quantifies the (PM
) contribution of the Zouk Mikael power plant to the ambient air pollution in ...Lebanon for the year 2014. The data is the outcome of a computer simulation using The Air Pollution Model (TAPM), taking into account the emission source data, the spatio-temporal meteorological conditions, the terrain height, and the land cover characteristics. The data set presents the annual, seasonal and monthly averages of the spatial distribution of the ground-level particulate (PM
) concentrations in the ambient air. The data set also includes spatial distribution of the maximum concentrations, which revealed two zones of elevated concentrations. Monthly averages and maximum concentrations in these two zones are also reported. Analysis of the data can provide information on the health risk the residents in the affected areas are subjected to. The data can also provide insight on the impact of the meteorological conditions (temperature and velocity) and the topography on pollutant dispersion in regions bounded by the sea and by a mountain range.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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