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Mass Loading (mass + loading)
Selected AbstractsRetrieval of microphysical and morphological properties of volcanic ash plumes from satellite data: Application to Mt Ruapehu, New ZealandTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 576 2001A. J. Prata Abstract A quantitative analysis of the properties of several Mt Ruapehu, New Zealand, ash plumes has been performed using multispectral satellite data from the AVHRR-2 and ATSR-2 instruments. The analysis includes: identification of the plume from background clouds using the ,reverse' absorption effect in the thermal channels: modelling and retrieval of particle sizes; determination of the plume height from cloud shadows, stereoscopy and meteorological data; and estimates of the mass of fine particles (radii less than 10 ,m). A new spectral technique for identifying opaque, silica-rich ash clouds is demonstrated by utilizing the near-infrared (1.6 ,m) and visible (0.67 ,m) channels of the ATSR-2, and the optical properties of a simple volcanic cloud are presented for use in radiative transfer studies. It is found that the Ruapehu eruption cloud contained silica-rich ash particles with radii generally less than a few micrometres. The distribution of fine particles is monomodal with a dominant mode peak of about 3 ,m radius. Mass loadings of fine particles are found to be in the range ,1 to ,7 mg m,3, and are consistent with estimates of mass loadings of volcanic clouds from eruptions of other volcanoes. The height of the plume top, derived from radiosonde data and plume-top temperatures in the opaque regions, was found to be between 7.5 and 8.5 km, while the plume thickness was estimated to be between 1.5 and 3 km. Cloud height derived from ATSR-2 stereoscopy on a different plume gave heights in the range 5 to 8 km. The results of this study provide important information on the optical properties of nascent volcanic eruption plumes. This information may prove useful in determining the potential effects of volcanic clouds on local climate, and in assessing any hazard to aviation. [source] Nanoparticle-Structured Ligand Framework as Electrode InterfacesELECTROANALYSIS, Issue 1-2 2004Nancy Abstract Nanostructured thin film assemblies derived from metal or oxide nanocrystal cores and functionalized molecular shells provide large surface-to-volume ratio and three-dimensional ligand frameworks. In this article, we report results of an investigation of the nanostructured materials for electroanalysis. Monolayer-capped gold nanoparticles of 2-nm core diameter and carboxylic acid-functionalized alkyl thiols were assembled on electrode surfaces via an exchange-crosslinking-precipitation reaction route, and were studied as a model system. The network assemblies exhibit open frameworks in which the void space forms channels with the nanometer sized cores defining its size and the shell structures defining its chemical specificity. Such nanostructures were exploited to demonstrate the viability of responsive materials for interfacial incorporation and fluxes of ionic species. The nanomaterials were characterized by an array of techniques, including cyclic voltammetry, electrochemical quartz-crystal nanobalance, flow injection analysis, and surface infrared reflection spectroscopy. The current responses and mass loading as a result of the incorporation of ionic species into the nanostructure have been analyzed. The potential application of the nanostructured thin films for electrochemical detection in microfluidic systems is also discussed. [source] Basis functions for the consistent and accurate representation of surface mass loadingGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2007Peter J. Clarke SUMMARY Inversion of geodetic site displacement data to infer surface mass loads has previously been demonstrated using a spherical harmonic representation of the load. This method suffers from the continent-rich, ocean-poor distribution of geodetic data, coupled with the predominance of the continental load (water storage and atmospheric pressure) compared with the ocean bottom pressure (including the inverse barometer response). Finer-scale inversion becomes unstable due to the rapidly increasing number of parameters which are poorly constrained by the data geometry. Several approaches have previously been tried to mitigate this, including the adoption of constraints over the oceanic domain derived from ocean circulation models, the use of smoothness constraints for the oceanic load, and the incorporation of GRACE gravity field data. However, these methods do not provide appropriate treatment of mass conservation and of the ocean's equilibrium-tide response to the total gravitational field. Instead, we propose a modified set of basis functions as an alternative to standard spherical harmonics. Our basis functions allow variability of the load over continental regions, but impose global mass conservation and equilibrium tidal behaviour of the oceans. We test our basis functions first for the efficiency of fitting to realistic modelled surface loads, and then for accuracy of the estimates of the inferred load compared with the known model load, using synthetic geodetic displacements with real GPS network geometry. Compared to standard spherical harmonics, our basis functions yield a better fit to the model loads over the period 1997,2005, for an equivalent number of parameters, and provide a more accurate and stable fit using the synthetic geodetic displacements. In particular, recovery of the low-degree coefficients is greatly improved. Using a nine-parameter fit we are able to model 58 per cent of the variance in the synthetic degree-1 zonal coefficient time-series, 38,41 per cent of the degree-1 non-zonal coefficients, and 80 per cent of the degree-2 zonal coefficient. An equivalent spherical harmonic estimate truncated at degree 2 is able to model the degree-1 zonal coefficient similarly (56 per cent of variance), but only models 59 per cent of the degree-2 zonal coefficient variance and is unable to model the degree-1 non-zonal coefficients. [source] Sensitivity of an Arctic regional climate model to the horizontal resolution during winter: implications for aerosol simulationINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 11 2005Eric Girard Abstract Our ability to properly simulate current climate and its future change depends upon the exactitude of the physical processes that are parameterized on the one hand, and on model configuration on the other hand. In this paper, we focus on the latter and investigate the effect of the horizontal grid resolution on the simulation of a month of January over the Arctic. A limited-area numerical climate model is used to simulate the month of January 1990 over a grid that includes the Arctic and sub-Arctic regions. Two grid resolutions are used: 50 km and 100 km. Results show that finer details appear for regional circulation, temperature, and humidity when increasing horizontal resolution. This is particularly true for continental and sea ice boundaries, which are much better resolved by high-resolution model simulations. The Canadian Archipelago and rivers in northern Russia appear to benefit the most from higher horizontal resolution. High-resolution simulations capture some frozen rivers and narrow straits between islands. Therefore, much colder surface air temperature is simulated over these areas. Precipitation is generally increased in those areas and over topography due to a better representation of surface heterogeneities when increasing resolution. Large-scale atmospheric circulation is substantially changed when horizontal resolution is increased. Feedback processes occur between surface air temperature change over heterogeneous surfaces and atmospheric circulation. High-resolution simulations develop a stronger polar vortex. The mean sea-level pressure increases over the western Arctic and Iceland and decreases over the eastern Arctic. This circulation leads to a substantial cooling of the eastern Arctic and enhanced synoptic activity over the Arctic associated with an intensification of the baroclinic zone. Aerosol mass loading, which is simulated explicitly in this model, is significantly altered by the grid resolution change with the largest differences in aerosol concentration over areas where precipitation and atmospheric circulation are the most affected. The implications of this sensitivity study to the evaluation of indirect radiative effects of anthropogenic aerosols are discussed. Copyright © 2005 Royal Meteorological Society. [source] Role of catchment area in the transport of nutrients to lakes in the Wielkopolska National Park in PolandLAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 1 2002Halina Szyper Abstract The external loading of 14 lakes in the Wielkopolska National Park was calculated, including nitrogen and phosphorus loads from point, diffuse and dispersed sources, precipitation and recreation. The basic source of nitrogen and phosphorus for most lakes in the Park is the export of diffuse pollution from the catchment area. Only four lakes are contaminated by sewage, which accounts for 0.1,61.2% of total nutrient loading. Annual unit area loads of phosphorus and nitrogen estimated for each lake were 2,51 times higher than Vollenweider's critical loading levels. Estimated mass loading and annual unit area loads of nutrients for each lake were compared with lake water quality, expressed as the trophic state index. Analysis of the physico-geographical structure of the catchment area and natural resistance of lakes to external input of nutrients allowed us to assess the role of the catchment in the deterioration of water quality and to indicate the protective measures required. [source] Detection of NH3 by Quartz Crystal Microbalance Coated with Ta2O5PLASMA PROCESSES AND POLYMERS, Issue 2 2006Velichka Georgieva Abstract Summary: This paper reports a study of the sorption properties of thin Ta2O5 films to NH3 vapors. The films are deposited using electron beam evaporation. In order to determine the sorption ability of Ta2O5 to NH3, a quartz crystal microbalance (QCM) with a thin Ta2O5 film is investigated. The Ta2O5 film is used as a receptor for the NH3 gas. The AT-cut, 14 MHz quartz resonators allow conversion of the additional mass loading that occurs as a result of sorption into a frequency shift. The experiments are carried out by measuring the resonant frequency shift of the QCM to vapors from an aqueous solution of NH3 with different concentrations from 10 to 10,000 ppm. The obtained experimental results indicate that the variations of the resonant frequency are a function of the ammonia concentration and the thickness of the Ta2O5 layer. The process of sorption is found to be reversible. The reported investigation shows that a QCM covered with a thin Ta2O5 layer is sensitive to ammonia vapors at room temperature and is able to detect NH3 concentrations in the investigated range (10,10,000 ppm). Relative change of QCM frequency versus ammonia concentration [source] Multiyear ground-based and satellite observations of aerosol properties over a tropical urban area in IndiaATMOSPHERIC SCIENCE LETTERS, Issue 1 2007K. V. S. Badarinath Abstract Aerosol particle size distributions along with their spatial and temporal variability are important for describing both direct and indirect radiative forcing. In this study, the variation of black carbon (BC) aerosols, total aerosol mass loading and aerosol optical depth (AOD) over an urban region of Hyderabad, south India, was analyzed for 3 consecutive years from 2003 to 2005. The AOD was measured using a handheld multichannel sun-photometer at six wavelengths centered on 380, 440, 500, 675, 870 and 1020 nm and aerosol mass,size distribution was made using a quartz crystal microbalance (QCM) cascade impactor. In addition, satellite remote-sensing data from nighttime DMSP-OLS images were analyzed for inferring ancillary sources of aerosols. Results from temporal analysis (2004,2006) suggest that aerosol mass loading and BC mass concentration increased considerably over the 3-year time-period mainly due to increasing vehicular traffic from urban population growth. DMSP-OLS nighttime images for different years suggested higher forest fire occurrences in the year 2004 compared to other years. The annual mean AOD at 550 nm from moderate resolution imaging spectroradiometer (MODIS) showed relatively high values during 2004. Copyright © 2007 Royal Meteorological Society [source] Effect of enzyme supplementation at moderate cellulase loadings on initial glucose and xylose release from corn stover solids pretreated by leading technologiesBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2009Rajeev Kumar Abstract Moderate loadings of cellulase enzyme supplemented with ,-glucosidase were applied to solids produced by ammonia fiber expansion (AFEX), ammonia recycle (ARP), controlled pH, dilute sulfuric acid, lime, and sulfur dioxide pretreatments to better understand factors that control glucose and xylose release following 24, 48, and 72 h of hydrolysis and define promising routes to reducing enzyme demands. Glucose removal was higher from all pretreatments than from Avicel cellulose at lower enzyme loadings, but sugar release was a bit lower for solids prepared by dilute sulfuric acid in the Sunds system and by controlled pH pretreatment than from Avicel at higher protein loadings. Inhibition by cellobiose was observed to depend on the type of substrate and pretreatment and hydrolysis times, with a corresponding impact of ,-glucosidase supplementation. Furthermore, for the first time, xylobiose and higher xylooligomers were shown to inhibit enzymatic hydrolysis of pure glucan, pure xylan, and pretreated corn stover, and xylose, xylobiose, and xylotriose were shown to have progressively greater effects on hydrolysis rates. Consistent with this, addition of xylanase and ,-xylosidase improved performance significantly. For a combined mass loading of cellulase and ,-glucosidase of 16.1 mg/g original glucan (about 7.5 FPU/g), glucose release from pretreated solids ranged from 50% to75% of the theoretical maximum and was greater for all pretreatments at all protein loadings compared to pure Avicel cellulose except for solids from controlled pH pretreatment and from dilute acid pretreatment by the Sunds pilot unit. The fraction of xylose released from pretreated solids was always less than for glucose, with the upper limit being about 60% of the maximum for ARP and the Sunds dilute acid pretreatments at a very high protein mass loading of 116 mg/g glucan (about 60 FPU). Biotechnol. Bioeng. 2009;102: 457,467. © 2008 Wiley Periodicals, Inc. [source] Retrieval of microphysical and morphological properties of volcanic ash plumes from satellite data: Application to Mt Ruapehu, New ZealandTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 576 2001A. J. Prata Abstract A quantitative analysis of the properties of several Mt Ruapehu, New Zealand, ash plumes has been performed using multispectral satellite data from the AVHRR-2 and ATSR-2 instruments. The analysis includes: identification of the plume from background clouds using the ,reverse' absorption effect in the thermal channels: modelling and retrieval of particle sizes; determination of the plume height from cloud shadows, stereoscopy and meteorological data; and estimates of the mass of fine particles (radii less than 10 ,m). A new spectral technique for identifying opaque, silica-rich ash clouds is demonstrated by utilizing the near-infrared (1.6 ,m) and visible (0.67 ,m) channels of the ATSR-2, and the optical properties of a simple volcanic cloud are presented for use in radiative transfer studies. It is found that the Ruapehu eruption cloud contained silica-rich ash particles with radii generally less than a few micrometres. The distribution of fine particles is monomodal with a dominant mode peak of about 3 ,m radius. Mass loadings of fine particles are found to be in the range ,1 to ,7 mg m,3, and are consistent with estimates of mass loadings of volcanic clouds from eruptions of other volcanoes. The height of the plume top, derived from radiosonde data and plume-top temperatures in the opaque regions, was found to be between 7.5 and 8.5 km, while the plume thickness was estimated to be between 1.5 and 3 km. Cloud height derived from ATSR-2 stereoscopy on a different plume gave heights in the range 5 to 8 km. The results of this study provide important information on the optical properties of nascent volcanic eruption plumes. This information may prove useful in determining the potential effects of volcanic clouds on local climate, and in assessing any hazard to aviation. [source] A Study of Gypsum Scale Formation using Quartz Crystal MicrobalanceASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2006T. A. Hoang The quartz crystal microbalance (QCM) has been used extensively as a mass sensor due to its extremely high sensitivity to small mass loadings. Conventional measurement of the amount of scale deposited on a surface is restricted by the sensitivity limit of analytical balances. Thefirst attempt to investigate the deposition of gypsum scale on a surface using a rotating electrochemical QCMsystem was carried out to investigate the eflects of many factors at the early stages of scale formation. Results indicated there was almost no induction time for this system, and the long induction time observed in the conventional system was due to the limited sensitivity of the analytical balance. A slow increase in scale amount was observed at the beginning of the scaling process as shown by the plot offrequency or mass change against time. After this period the curve rises steeply and becomes almost linear. The supersaturation level of the solutions and the rotating speed have significant effects on the gypsum scaling. A QCM flow-cell system has also been developed to investigate the scaling of gypsum on the pipe wall. This system is similar to a conventional pipe flow system except that its size is much smaller and the deposition of scales can be monitored with the QCM electrode throughout the scaling process. The mass change is plotted against time and results are compared for the rotating QCM system and the conventional system. It is noticed that the formation of gypsum on the QCM electrode is greatly dependent on both the supersaturation of the solution and the flow rate of the fluid passing through the flow cell. [source] Effects of cellulase and xylanase enzymes on the deconstruction of solids from pretreatment of poplar by leading technologiesBIOTECHNOLOGY PROGRESS, Issue 2 2009Rajeev Kumar Abstract Comparative data is presented on glucose and xylose release for enzymatic hydrolysis of solids produced by pretreatment of poplar wood by ammonia fiber expansion (AFEX), ammonia recycled percolation (ARP), controlled pH, dilute acid, flowthrough (FT), lime, and sulfur dioxide (SO2) technologies. Sugar solubilization was measured for times of up to 72 h using cellulase supplemented with ,-glucosidase at an activity ratio of 1:2, respectively, at combined protein mass loadings of 5.8,116 mg/g of glucan in poplar wood prior to pretreatment. In addition, the enzyme cocktail was augmented with up to 11.0 g of xylanase protein per gram of cellulase protein at combined cellulase and ,-glucosidase mass loadings of 14.5 and 29.0 mg protein (about 7.5 and 15 FPU, respectively)/g of original potential glucose to evaluate cellulase,xylanase interactions. All pretreated poplar solids required high protein loadings to realize good sugar yields via enzymatic hydrolysis, and performance tended to be better for low pH pretreatments by dilute sulfuric acid and sulfur dioxide, possibly due to higher xylose removal. Glucose release increased nearly linearly with residual xylose removal by enzymes for all pretreatments, xylanase leverage on glucan removal decreased at high cellulase loadings. Washing the solids improved digestion for all pretreatments and was particularly beneficial for controlled pH pretreatment. Furthermore, incubation of pretreated solids with BSA, Tween 20, or PEG6000 prior to adding enzymes enhanced yields, but the effectiveness of these additives varied with the type of pretreatment. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] | ||||||||||||||||