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•MWW derived materials are active catalysts for gas phase glycerol dehydration.•Higher acrolein selectivity is attained using ITQ-2.•ITQ-2 can be successfully recycled by coke ...burning.•Air co-feeding decreases deactivation by coke formation.•ITQ-2 has proved to be a good candidate for a long-time stability catalyst.
The materials derived from MWW layered precursor (MCM-22, MCM-36 and ITQ-2) were synthesized with molar ratio SiO2/Al2O3=30, characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), textural analysis by N2 physisorption, temperature programmed desorption of ammonia (NH3-TPD) and diffuse reflectance infrared spectroscopy (DRIFTS) of adsorbed pyridine and evaluated in gas phase glycerol dehydration to acrolein. The delaminated material (ITQ-2) has presented better catalytic performance than MCM-22 zeolite or MCM-36 pillared material, in both glycerol conversion and acrolein selectivity. These results were interpreted based on the textural properties and acidity changes. ITQ-2 excellent performance is due to higher accessibility and improved acidity when compared to pillared MCM-36 or parent MCM-22 zeolite. Long-term stability under either nitrogen or air co-feeding was investigated for ITQ-2.
Aerosol single scattering albedo omega (the ratio of scattering to extinction) is important in determining aerosol climatic effects, in explaining relationships between calculated and measured ...radiative fluxes, and in retrieving aerosol optical depths from satellite radiances. Recently, two experiments in the North Atlantic region, the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) and the Second Aerosol Characterization Experiment (ACE-2), determined aerosol omega by a variety of techniques.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Direct observations and size‐distribution‐based estimates of light‐scattering coefficients (bsp) are presented for the Yosemite Aerosol Characterization Study (YACS), which took place during the ...summer of 2002, an active fire year. Uncertainty in the estimates of bsp were found to be sensitive to the choice of the aerosol refractive indices, which were retrieved by aligning optical particle counter measurements to differential mobility analyzer observations and, in addition, were calculated from composition measurements. Aerosol composition during the study was dominated by organic carbon, with highest levels observed during periods impacted by biomass burning smoke influenced hazes. As a result, estimates of the aerosol refractive index from composition measurements were highly sensitive to the assumed properties of organic carbon. Retrieved and calculated refractive indices were in agreement for reasonable assumptions for properties of organic carbon. Excellent agreement (within 6%) was found between measured bsp and size‐distribution derived bsp if the imaginary component of the refractive index, determined from composition measurements and assuming all species were internally mixed, was included in the Mie calculation. Under the internally mixed assumption, aerosols sampled during the study were modeled as weakly absorbing, with computed dry single scattering albedo ranging from 0.86 to 0.94. Calculated light absorption coefficients yielded a study‐averaged dry aerosol mass absorption efficiency of 0.37 ± 0.05 m2g−1.
Fish sounds are important components of Azorean soundscapes. Therefore, unraveling their patterns can contribute to a better assessment of local biodiversity dynamics.
Passive Acoustic Monitoring ...(PAM) is a cost-effective, non-intrusive method providing long-term information regardless of weather or logistic conditions, which can be especially useful when monitoring remote areas. Using PAM, we assess temporal dynamics of fish vocal activity in a protected seamount and validate PAM as an important tool for biodiversity assessment in deep-sea fish communities. Thus, we evaluated the annual, seasonal and diel patterns of variation of putative fish sounds identified in an Azorean protected seamount, the Condor (ca.190 m depth). Here, 3 years (2008, 2010 and 2012) of acoustic data were collected and analysed for diversity and abundance of the most prevalent fish sounds. We compared abundance and diversity of fish sounds before and after the establishment of the marine protected area in 2010, to assess its initial protection effects. We also compared abundance and biodiversity measures (richness and Shannon diversity index) of acoustic data with fishing data from deep-water longline surveys, to verify if acoustic diversity and taxonomic diversity show a similar trend. Additionally, we estimated a likely distance range of fish sound sources from the acoustic data loggers for local background noise and typical fish sound levels. Estimated detection distance of different fish sounds, considering Condor background noise level and reported fish sound source levels, were typically larger than 10 m and could reach hundreds of meters in some species suggesting that this study potentially targeted sounds of the deep-sea fish fauna. Fish acoustic activity was prevalent at dusks and nights of all years, while no overall seasonal pattern was detected. However, one sound sequence (#1) was dominant in the autumns of all studied period. A decrease in abundance and richness of sounds was observed from 2008 to 2012 in line with the results of fishing surveys. Although unexpected, these consistent trends suggest that PAM provides a reliable representation of fish biodiversity dynamics. Taken together, this study shows that monitoring fish sounds with PAM is a valid and promising tool for fish biodiversity assessment in deep Azorean seamounts.
•Diel patterns of fish sounds were detected at ca. 190 m depth.•Highest abundances of sound sequences were observed at dusk and night.•Trends of abundance and diversity of vocalizations were similar to catch trends in fishery surveys.•Acoustic monitoring is a useful tool to assess biodiversity in deep seamounts.
This book addresses the issue of determinism in Avicenna and Averroes through an analysis of their views on chance, matter and divine providence. It sets the debate against the ...philosophical/historical background of Aristotelianism, Neoplatonism and Islamic theology.
During the ACE‐Asia campaign in March–May 2001, in situ measurements of aerosol optical properties were made from multiple airborne and land‐ or ship‐based platforms. Using a suite of direct ...interplatform comparisons and a campaign‐wide statistical comparison, we test the precision of these measurements, and we determine whether the platforms sampled similar aerosol. Data included in the study are from the National Center for Atmospheric Research C‐130 aircraft; the CIRPAS Twin Otter aircraft; the National Oceanographic and Atmospheric Administration (NOAA) ship R.V. Ronald H. Brown; and the Gosan surface station on Jeju Island, located off the southern tip of South Korea. Comparisons were made of total and submicron light scattering at 450, 550, and 700 nm; total and submicron absorption at 550 nm; the Ångström exponent; single scatter albedo of the total aerosol, submicron and supermicron aerosol at 550 nm; hemispheric backscatter fraction at 550 nm; and light scattering hygroscopic growth at 550 nm. For the campaign‐wide comparison, the data are broken down by light scattering fine mode fraction since the aerosol in the ACE‐Asia study region were a variable mix of pollution, dust, and sea salt. Finally, we calculate how the observed uncertainties in the aerosol optical properties propagate to uncertainties in top‐of‐atmosphere radiative forcing. Single scatter albedo showed excellent agreement among all platforms other than the Twin Otter, with discrepancies generally <0.02. These data sets combine to give campaign‐wide values of single scatter albedo of 0.885 ± 0.023 for the submicron aerosol (i.e. pollution) and 0.957 ± 0.031 for the supermicron aerosol (which, for these data, was predominantly dust). The data also indicated that, as expected, the Low Turbulent Inlet on the C‐130 produced enhanced concentrations of coarse mode aerosol. There also may have been significant coarse mode particle losses on the other platforms. These effects combined to produce generally lower fine mode fractions and Ångström exponents on the C‐130 than on the other platforms. Large discrepancies in hemispheric backscatter fraction and light scattering hygroscopic growth were observed in both the side‐by‐side and statistical comparisons. We are not able to explain these differences, though possible causes are discussed. Studies of the TSI, Inc. nephelometer backscatter measurement and of the two methods used here to measure hygroscopic growth are needed to clarify the source of these observed discrepancies. A better understanding of the effects of nonsphericity on hemispheric backscatter fraction is also needed.
Large uncertainties remain in understanding the effects of ambient aerosols on climate. As part of the First Aerosol Characterization Experiment (ACE 1, November 15 to December 15, 1995), the total ...light scattering and backscattering coefficients by particles (σsp and σbsp) were measured at Cape Grim, Tasmania. Such measurements were made to characterize aerosol radiative forcing relevant to climate change at a southern hemisphere site. A controlled relative humidity (RH) nephelometry system (humidograph) was used to measure the dependence of σsp and σbsp upon controlled RH, upper particle diameter (Dp), and wavelength of light (λ). Parameters derived from the measurements necessary to incorporate aerosols into climate models include the dependence of light scattering on aerosol hygroscopic growth (ƒ(RH)) and the hemispheric backscatter fraction (b), both as functions of wavelength of light. Differences in parameter values during clean marine and non‐clean‐marine time periods were greatest for σsp and σbsp for Dp ≤ 1 μm and were least for ƒ(RH) and b. During clean marine conditions, for Dp ≤ 10 μm, and at λ=550 nm, means and standard deviations of key parameters measured included ƒ(RH equal to 82%) = 1.98±0.08 for σsp, ƒ(RH equal to 82%) = 1.48±0.09 for σbsp, b = 0.16±0.01 at RH equal to 22%, and b = 0.12±0.03 at RH equal to 82%. These measurements contribute to characterizing aerosol optical properties at a remote marine site, serve as a basis of comparison to polluted sites, and may provide input to climate models.
Measurements of chemical, physical, and optical properties of ambient aerosol particles were obtained at Bondville, Illinois. This research was completed to increase the spatial and temporal ...resolution of measured aerosol. Results from measurements describe (1) the physical and chemical characteristics of the aerosol and (2) the dependence of light scattering and backscattering on wavelength of light λ, controlled relative humidity RH, and aerosol particle chemical composition. Formulations for the hygroscopic growth factor f(RH), and backscatter ratio b, as functions of λ and RH and estimates of the upscatter fraction
β¯
, and Ångström exponent å are also provided. For aerosol sampled at the site from January to December 1995, the mean gravimetric mass concentration for particles with aerodynamic diameter (dpa)≤1 μm had an arithmetic mean and standard deviation of 10.6±6.5 μg/m3, respectively. Ion chromatography (IC) speciated 53% of the total gravimetric mass for particles with dpa≤1 μm. Most of the IC‐identified material (88.0±13.5%) consisted of NH4+ and SO42−. Material not identified with IC was primarily elemental and organic carbon. The total aerosol light‐scattering coefficient at λ = 550 nm and RH≤40% was 51.6±43.2 Mm−1 for dpa≤10 μm and 42.0±34.9 Mm−1 for dpa≤1 μm. Mean values of f(RH = 82.5%, λ) for total scattering ranged between 1.4 and 1.5 and for back scattering between 1.1 and 1.2. Mean values of b(λ) ranged from 0.11 to 0.18 for RH<40% and from 0.09 to 0.14 for RH = 82.5%. Mean values of
β¯
ranged from 0.21 to 0.30 depending on λ, RH, and the particle size distribution. Mean values of å ranged between 1.8 and 2.4 for RH<40% and 1.8 and 2.1 for RH = 82.5%. These measured properties are now available for use in models to reduce uncertainties when quantifying direct aerosol radiative forcing at a continental site influenced by aerosol with anthropogenic origin.
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