Higher Particle Fraction Research Articles

Post mortem analysis of a JET quartz microbalance system

In the year 2001, a quartz microbalance system (QMB) was installed in the remote area of the inner JET divertor to investigate in situ material erosion and redeposition processes. When removed in 2004, the system was found to be coated all over with carbon deposits. The deposit on the quartz oscillator and the outer and inner housing was analysed by various methods, as SIMS (secondary ion mass spectroscopy), stylus depth profilometry, EPMA (electron probe microanalysis), TIPT (Tritium imaging plate technique) and colorimetry and compared to the frequency change of the quartz. The layer thickness was determined to 1.85±0.1μm in average on an area of 0.95cm2 which has to be related to the equivalent of 1.77×10−4g measured from the frequency change of 23640Hz. This corresponds to a carbon areal density of 9.3×1018 C atoms/cm2. Significant deposition was found also on the surfaces inside the QMB housing which can only be understood if reflection and low sticking is assumed for a high fraction of particles.

Mineralization of Monodispersed CdS Nanoparticles on Polyelectrolyte Superstructure Forming an Electroluminescent “Necklace-of-Beads”

We report a nonmicellar method to synthesize monodisperse semiconducting nanoparticles templated on polymer chains dissolved in solution at high yield. The monodispersity is achieved due to the beaded necklace morphology of the polyelectrolyte chains in solution where the beads are nanometer-scale nodules in the polymer chain. The resultant structure is a nanoparticles studded necklace where the particles are imbedded in the beads. Multiple cycles of synthesis on the polymer template yield nanoparticles of identical size, resulting in a nanocomposite with high particle fraction. The resultant nanocomposite has beaded-fibrilar morphology with imbedded nanoparticles and can be solution-casted to make electroluminescent thin film device.

Personal Exposure to Airborne Dust and Microorganisms in Agricultural Environments

Airborne dust and microorganisms are associated with respiratory diseases and increased mortality and morbidity. Farmers are at high risk of exposure to both of these hazards. Very limited information, however, is available on the combined exposures to both hazards on different types of farms. Moreover, most of the previous studies have measured the mass concentration of particles ignoring the particle size. In this study, farmers' exposure to airborne dust and microorganisms was studied using our newly developed personal sampling system. Particle number concentration and size distribution were measured with an optical particle counter. Simultaneously, particles were collected on a filter and analyzed for microorganisms. The field measurements were conducted in animal confinements (swine, poultry, and dairy) and during grain harvesting (corn and soybean). The results show the following average concentrations on the workers' breathing zone: 1.7 × 10 6 to 2.9 × 10 7 particles/m 3 for total dust, 0.9 × 10 3 to 3.9 × 10 4 spores/m 3 for total fungal spores, 0.3 × 10 3 to 3.6 × 10 4 CFU/m 3 for culturable fungal spores, 0.3 × 10 4 to 3.3 × 10 8 CFU/m 3 for culturable bacteria, and limit of detection (LOD) to 2.8 × 10 3 CFU/m 3 for culturable actinomycetes in animal confinements. The respective concentrations were 4.4 × 10 6 to 5.8 × 10 7 particles/m 3 , 3.4 × 10 4 to 6.1 × 10 6 spores/m 3 , 8.2 × 10 4 to 7.4 × 10 6 CFU/m 3 , 0.4 × 10 5 to 1.4 × 10 6 CFU/m 3 , and LOD to 2.6 × 10 4 CFU/m 3 during grain harvesting. The highest contribution of large particles (3–10 μ m) in total particles was found during grain harvesting, whereas the size distribution was dominated by smaller particles (< 3 μ m) in animal confinements. High fraction (up to 37%) of particles between 2–10 μ m was found to be fungal spores. The results indicate that an increase in the concentration of large dust particles (2–10 μ m) during grain harvesting was partially attributed to the increase in the concentration of the fungal spores. Overall, the combined exposure to airborne dust and microorganisms was found to be more severe during harvesting than in animal confinements.

Observations of meteoric material and implications for aerosol nucleation in the winter Arctic lower stratosphere derived from in situ particle measurements

Abstract. Number concentrations of total and non-volatile aerosol particles with size diameters &gt;0.01 μm as well as particle size distributions (0.4–23 μm diameter) were measured in situ in the Arctic lower stratosphere (10–20.5 km altitude). The measurements were obtained during the campaigns European Polar Stratospheric Cloud and Lee Wave Experiment (EUPLEX) and Envisat-Arctic-Validation (EAV). The campaigns were based in Kiruna, Sweden, and took place from January to March 2003. Measurements were conducted onboard the Russian high-altitude research aircraft Geophysica using the low-pressure Condensation Nucleus Counter COPAS (COndensation PArticle Counter System) and a modified FSSP 300 (Forward Scattering Spectrometer Probe). Around 18–20 km altitude typical total particle number concentrations nt range at 10–20 cm−3 (ambient conditions). Correlations with the trace gases nitrous oxide (N2O) and trichlorofluoromethane (CFC-11) are discussed. Inside the polar vortex the total number of particles &gt;0.01 μm increases with potential temperature while N2O is decreasing which indicates a source of particles in the above polar stratosphere or mesosphere. A separate channel of the COPAS instrument measures the fraction of aerosol particles non-volatile at 250°C. Inside the polar vortex a much higher fraction of particles contained non-volatile residues than outside the vortex (~67% inside vortex, ~24% outside vortex). This is most likely due to a strongly increased fraction of meteoric material in the particles which is transported downward from the mesosphere inside the polar vortex. The high fraction of non-volatile residual particles gives therefore experimental evidence for downward transport of mesospheric air inside the polar vortex. It is also shown that the fraction of non-volatile residual particles serves directly as a suitable experimental vortex tracer. Nanometer-sized meteoric smoke particles may also serve as nuclei for the condensation of gaseous sulfuric acid and water in the polar vortex and these additional particles may be responsible for the increase in the observed particle concentration at low N2O. The number concentrations of particles &gt;0.4 μm measured with the FSSP decrease markedly inside the polar vortex with increasing potential temperature, also a consequence of subsidence of air from higher altitudes inside the vortex. Another focus of the analysis was put on the particle measurements in the lowermost stratosphere. For the total particle density relatively high number concentrations of several hundred particles per cm3 at altitudes below ~14 km were observed in several flights. To investigate the origin of these high number concentrations we conducted air mass trajectory calculations and compared the particle measurements with other trace gas observations. The high number concentrations of total particles in the lowermost stratosphere are probably caused by transport of originally tropospheric air from lower latitudes and are potentially influenced by recent particle nucleation.

The rebound phenomenon in kinetic spraying deposition

Abstract In this study, individual particle impact tests have been carried out to probe particle impact and deposition behaviors. A rebound phenomenon was observed in which a high fraction of particles rebounded at high impact velocities. The adhesion and rebound energy were calculated to estimate the particle/substrate interaction. The particle deposition behavior was a result of the competition of adhesion and rebound energy during the impact process.

Marra Mamba Ore, Its Mineralogical Properties and Evaluation for Utilization

This paper provides an overview of chemical and physical properties of Marra Mamba ores as well as their influence on sintering performance. Evaluation tests focusing on basic characteristics, granulation ability and melting behavior have been conducted by using Ore W, a newly shipped bland of Marra Mamba ore. Although the amount of gangue minerals in Marra Mamba ores is smaller than that of other Australian ores, they have high combined water content and high fraction of fine particles. They have inferior granulation ability and required high moisture content in granulation due to their porous structure. Cohesive strength of fine ores is still low level even at high moisture content due to small kaolinite content. Penetration behavior of melt from fine particles is superior due to their low gangue mineral content, while assimilation behavior of coarse ores is inferior, resulting in poor agglomeration despite favorable behavior during heating-up in term of crack formation. Pot test results performed by BHP Billion showed decrease of strength and product yield with large amount of use. Improvement of strength was achieved by increasing moisture content during granulation. Intensification of granulation with pre-treatment or palletizing of Marra Mamba ores must be one of the key technologies for utilization of them.

Modification of Procedure to Estimate Viscosity of Bimodal Alumina/Epoxy Mixtures during a Centrifugal Process

The coefficient of viscosity η is one of the major parameters to govern the movement of particles in alumina/epoxy mixtures during the centrifugal process. During the centrifugal process, the particle fraction and corresponding values of η at a certain point varies spatiotemporally. In the present contribution, theoretical consideration to explain dependency of ηb of bimodal alumina/epoxy mixtures on particle fractions is conducted. It is found that ηb can be estimated as a function of two η's obtained for the unimodal mixtures that contain the fine and coarse particles, respectively. A modification about the definition of the coarse particle fraction from the conventional method was successfully introduced, resulting in better approximation of ηb under the conditions of high particle fractions.

Airborne haloacetic acids.

Haloacetic acid (HAA) concentrations were measured in air samples from a semi-rural and a highly urbanized site in southern Ontario throughout 2000 to investigate their sources and gas-particle partitioning behavior. Denuders were efficient for collection of gaseous HAAs, and the particle phase was collected on a downstream quartz filter with negligible breakthrough. Total HAA concentrations (i.e., gas + particles) ranged between <0.025 and 19 ng m(-3) for individual HAAs at both sites. The dominant airborne HAA was monochloroacetic acid (MCA), followed in decreasing order by dichloroacetic acid (DCA), trifluoroacetic acid (TFA), and trichloroacetic acid (TCA). Difluoroacetic acid (DFA), monofluoroacetic acid (MFA), and chlorodifluoroacetic acid (CDFA) were also frequently detected at lower concentrations. Between sites, TFA, DFA, MFA, and TCA concentrations were significantly higher in Toronto, while CDFA concentrations were higher in Guelph. HAAs were primarily in the gas phase all year; however, during colder months, particle-phase HAA concentrations increased relative to the gas phase. Trichloroacetic acid had the highest particle fraction (phi) for all detected HAAs, with a mean phi of 0.51 and 0.56 for Guelph and Toronto, respectively, and both vapor pressure and acid strength appeared to influence gas-particle partitioning. Temporal trends at both sites were partially explained by temperature, short-wave radiation, and particle mass (PM10), leading to indications of the respective sources. A simple deposition model indicated that dry deposition of TFA and TCA should not be neglected in temperate mid-latitude environments and that precipitation concentrations can be successfully predicted by the Henry's law constant.

Microstructure of Spray Formed Fe&lt;sub&gt;83&lt;/sub&gt;Nb&lt;sub&gt;4&lt;/sub&gt;ZrTiB&lt;sub&gt;9&lt;/sub&gt;Cu&lt;sub&gt;2&lt;/sub&gt; Alloy

In this study the Fe 83 Nb 4 Zr 1 Ti 1 B 9 Cu 2 (%at) alloy was processed by spray forming with the aim of investigate the formation of novel microstructures by the high cooling rate involved in this process. The ratio between the gas mass flow rate (kg/min) and the metal mass flow rate (kg/min) used was 0.25, and nitrogen was used as the atomization gas. The resulting billet, weighting about 0.8 kg, as well as the overspray powders, with a median particle diameter about 150μm, were characterized by using X-ray difflatometry, differential scanning calorimetry and scanning and transmission electron microscopy. The microstructure observed in both overspray powder and deposit was fully crystalline formed by α-Fe, fcc-Cu and the intermetallic Fe 2 Zr phases. SEM together with the EDS analysis of these phases is presented. The Fe 83 Nb 4 Zr 1 Ti 1 B 9 Cu 2 (%at) alloy presented a very fine microstructure of the α-Fe grains which decreases as the granulometric size ranges of the overspray powder diminishes due to the increasing in the cooling rate. The deposit showed irregular porosity due to the high fraction of solid particles that hit the substrate during deposition stage.

Clinical guidelines to manage malnutrition in nursing homes

Individual aerosol particles collected by a two-stage impactor on Mt. Hotaka (2165 m altitude) in central Japan in winter are studied using a transmission electron microscope and an energy-dispersive X-ray (EDX) analyzer. The size, morphology, elemental composition, mixing state and relative abundances are examined for (~ 550 ) aerosol particles with sizes of 0.1–2.0 μm collected during winter monsoon. Further smaller fine-ultrafine (~ 920) particles with sizes of 0.02–0.5 μm are also studied by electron-beam bombardment. There are potassium-containing sulfur particles, which may be originated from biomass burning or biofuel combustion in the Asian continent; sulfur would accumulate on these particles during their transport. Mineral particles and soot-containing particles constitute the minor abundance (less than 10% of all the particles). The samples collected during snowfall contain a very high fraction (> 90%) of fine sulfur-rich particles and no coarse particles are collected; precipitation may scavenge these coarse particles from the atmosphere. The electron-beam bombardment analysis reveals that the most abundant particles are the electron-beam sensitive (damaged) particles, which account for 70–90% of the total particles. On the basis of the comparison of fine particles with the diameter ranges of 0.1–0.5 μm obtained by both the EDX analysis and electron-beam bombardment analysis, the electron-beam sensitivity/insensitive particles would correspond to sulfur-containing particles/soot or mineral particles although we cannot deny out other particles such as nitrate, organics.

Densification behaviour of mixtures of hard and soft powders under pressure

The densification behaviour of mixtures of soft and hard powders during pressing is investigated. Several experimental studies using materials with miscellaneous mechanical and morphological features are summarised. The influence of mixture characteristics on the densification kinetics is discussed and several mechanisms explaining the influence of hard particles on the densification behaviour are proposed. Two main cases are distinguished. When the applied pressure is low, with regard to the yield stress of soft particles, the densification is mainly due to particle rearrangement and is favoured by a high fraction of hard particles. When soft particle deformation is the main densification mechanism, hard particles hinder the densification, with more or less significance depending on whether they are mostly isolated, are grouped in aggregates or form a percolating network.

Role of low charge state ions in electron cyclotron resonance ion source plasmas

We have tried to shed more light on the possible mechanisms of the beneficial effect of gas mixing for highly charged ion production, in particular on the presence of an ion cooling effect. For the first time a method was applied to deduct the ion temperature from all measured ionic currents. The ion temperature values derived showed a clear decreasing trend in conjunction with mass changes of the gas mixture, consisting of “pure” argon (no mixing gas), argon plus natural oxygen, argon plus isotopic O18, or argon plus Ne22. Each of the applied mixing gases gives a higher charged ion (HCI) output (highest for O18) as well as a lower ion current for the singly charged beam-particle output. The relative high particle fraction (about 40%) of singly charged nonbeam particles is an indication that effective plasma ion cooling is possible. Although the differences in ion temperature calculated are small, the effect is likely substantial, since the ion confinement has a dependency with (Ti)−5/2. Hydrogen currents (residual) are observed to be smallest for the best HCI-confined plasmas; so far no explanation for this can be given.

Zirconium-enriched particles in spray-deposited Ni 3Al-based alloys

Ni{sub 3}Al is an ordered compound with potential high temperature applications. Recent results have shown that zirconium is an effective element in increasing the creep resistance of Ni{sub 3}Al-based alloys. Microalloying with Zr has also been reported to improve the ductility of Ni{sub 3}Al-based alloys. Chiba et al. proposed that Zr acts as a scavenger of harmful impurities when added in small amounts, while Gu et al. suggested that Zr increases the grain boundary cohesion of Ni{sub 3}Al alloys. In the case of spray-deposited nickel aluminides, Rautioaho and Saven found Zr-rich inclusions to exist in as-deposited alloys. After thermomechanical treatments of these alloys, Zr-rich precipitates similar to the above inclusions were sometimes observed. SEM/EDS studies showed that all inclusions contained nitrogen and some of them also oxygen. Moreover, a minor fraction of particles were enriched in sulphur up to a concentration of 25 at.%. In addition, SEM/WDS analyses revealed that a high fraction of Zr-rich particles had a small sulphur content of 0.5 to 1 at.%. In the present investigation, the character of Zr-enriched particles was clarified by additional analyses in SEM/EDS and STEM, and by high pulse count x-ray diffraction scans.

Measurement of Toner Cohesion in Liquid Inks Using a Visualization Cell

The aim of this work is to measure the integrity of liquid toner images in both the development and transfer processes. To this end we have constructed a visualization cell in which we can observe the image deposition process due to a given applied voltage, and then measure the voltage required to break apart the image layer. Thus the cell permits the observation of both deposition and break-apart of toner images when either dc or low frequency ac fields are applied. The voltages required to compact the toner layer and to break it apart can be translated into consolidation stress and tensile strength of these materials; by this means we are able to compare inks in a quantitative manner.Using the visualization cell, we have examined the behavior of different liquid toners. We have observed the effects of different charge directors and their concentrations, as well as of different toner resins. While the cohesion varies according to the types of resins and of charge directors, there is no significant change in the behavior of the inks when charge-director concentrations are varied from a charge-director-to-toner weight ratio of 10mg/g to 50mg/g. We analyze the results with simple physical models that give a semiquantitative picture of the plastic behavior of inks at high particle fraction, up to the typical toner percentage of an image.

Short‐Term and Small‐Scale Variation in Food Availability to Natural Oyster Populations: Food, Flow and Flux

Abstract. Food resources and water flow speeds vary on short‐temporal and small‐spatial scales important to feeding in natural populations of oysters (Crassostrea virginica). To better describe food availability to the oyster population, micro‐current meters were used to measure flow 1–3 cm above the bottom and frequent water sampling was used to determine the quantity and composition of the seston on Confederate Reef, Galveston Bay, Texas. The quantity and quality of food varied on time scales at least as short as 3 h and throughout the water column. Seston was high in detrital carbon, nitrogen poor, and had a high fraction of inorganic particles. The quantity of food at the bed was not predictable from samples taken near the surface. Water flow speeds were also highly variable. Whereas rapid flow speeds were measured, flow speed tended to cluster about a narrower range of slower speeds resulting in the mean speed being much higher than the median. Fluxes of food calculated from the quantity of food and water flow speeds were low and highly variable. Under most conditions, water flow speed was more important than food quantity in determining flux. Rapid flow rates could overcome low food quantity to result in relatively high fluxes, whereas slow flow resulted in small fluxes even if food was abundant. Changes in water flow rate associated with tidal changes and changes in speed are probably the primary agents controlling food availability on a daily basis. Decreased wind speed at night normally reduced flux in the early morning hours, for example. These results stress the importance of measuring food quantity and water flow speed on spatial and temporal scales important to oyster feeding. Model simulations of oyster populations at varying densities, flow rates and clump heights across the range of measured values show that flow rate is insufficient during most hours of the day and days of the year to prevent oysters from locally reducing food supply by their filtering efforts. Thus flow rate probably limits population density and adult size on Confederate Reef.

Immunocytochemical investigation of myelin basic protein and glial fibrillary acidic protein in dysmyelinating Jimpy mouse

The near equi-atomic high-entropy alloys based on Al, Co, Cr, Fe, Ni have provided a novel microstructural template for alloy design. The face centered cubic (FCC) matrix strengthened by body centered cubic (BCC) based ordered B2 precipitates can be used to develop new generation of precipitation strengthened alloys. The present study focuses on an Al0.5CoCrFeNi hypo-eutectic alloy consisting of an as-solidified FCC + B2 microstructure. Guided by solution thermodynamic modeling, this alloy has been isothermally aged for solid-state precipitation of a high fraction of fine scale intragranular B2 particles. While, the positive influence of B2 on tensile strength, and work hardenability have been published earlier, the current work presents effect of fine scale B2 phase on sliding wear and dynamic compression properties. The flow stress at 0.02% true strain increased from ∼670 MPa to ∼1350 (102%) MPa, the ultimate compressive strength increased from ∼1160 MPa to 1500 MPa (20%), and the wear resistance increased more than 5 times with progressively increasing phase fraction of B2 precipitates.