Computational modelling of the impact of particle size to the heat transfer coefficient between biomass particles and a fluidised bed

The fluid–particle interaction and the impact of different heat transfer conditions on pyrolysis of biomass inside a 150 g/h fluidised bed reactor are modelled. Two different size biomass particles (350 µm and 550 µm in diameter) are injected into the fluidised bed. The different biomass particle sizes result in different heat transfer conditions. This is due to the fact that the 350 µm diameter particle is smaller than the sand particles of the reactor (440 µm), while the 550 µm one is larger. The bed-to-particle heat transfer for both cases is calculated according to the literature. Conductive heat transfer is assumed for the larger biomass particle (550 µm) inside the bed, while biomass–sand contacts for the smaller biomass particle (350 µm) were considered unimportant. The Eulerian approach is used to model the bubbling behaviour of the sand, which is treated as a continuum. Biomass reaction kinetics is modelled according to the literature using a two-stage, semi-global model which takes into account secondary reactions. The particle motion inside the reactor is computed using drag laws, dependent on the local volume fraction of each phase. FLUENT 6.2 has been used as the modelling framework of the simulations with the whole pyrolysis model incorporated in the form of User Defined Function (UDF).

Magnetic susceptibility and particle size for the Shilou red clay section on the eastern Chinese Loess Plateau

The Chinese Loess Plateau red clay sequences display a continuous alternation of sedimentary cycles that represent recurrent climatic fluctuations from 2.58 Ma to the Miocene. Deciphering such a record can provide us with vital information on global and Asian climatic variations. Lack of fossils and failure of absolute dating methods made magnetostratigraphy a leading method to build age models for the red clay sequences. Here we test the magnetostratigraphic age model against cyclostratigraphy. For this purpose we investigate the climate cyclicity recorded in magnetic susceptibility and sedimentary grain size in a red clay section previously dated 11Myr old with magnetostratigraphy alone. Magnetostratigraphy dating based on only visual correlation could potentially lead to erroneous age model. In this study the correlation is executed through the iteration procedure until it is supported by cyclostratigraphy; i.e., Milankovitch cycles are resolved in the best possible manner. Our new age model provides an age of 5.2Ma for the Shilou profile. Based on the new age model, wavelet analysis reveals the well-preserved 400 kyr and possible 100 kyr eccentricity cycles on the eastern Chinese Loess Plateau. Further, paleomonsoon evolution during 2.58-5.2Ma is reconstructed and divided into three intervals (2.58-3.6Ma, 3.6-4.5Ma, and 4.5-5.2Ma). The upper part, the youngest stage, is characterized by a relatively intensified summer monsoon, the middle stage reflects an intensification of the winter monsoon and aridification in Asia, and the earliest stage indicates that summer and winter monsoon cycles may have rapidly altered. The use of cyclostratigraphy along withmagnetostratigraphy gives us an effectivemethod of dating red clay sequences, and our results imply that many presently published age models for the red clay deposits should be perhaps re-evaluated.

Wire EDM mechanism of MMCs with the variation of reinforced particle size

The size of reinforced particles notably affects the electro-discharge machining (EDM) of metal matrix composites (MMCs). This paper explores the mechanism of wire EDM of MMCs with different sizes of reinforced particles as well as the corresponding unreinforced matrix material. The mechanisms of material removal, surface generation, and taper kerf formation were investigated. This study shows that the particles’ ability to protect matrix materials from the intense heat of electric arc controls the material removal rate, surface generation, and taper of kerf. The low melting point matrix material is removed very easily, but the heat resistance reinforced particles delay the removal of material and facilitate the transfer of the workpiece material to wire electrode and vice versa. Thus, the material stays longer in touch with intense heat and affects the surface generation, wire electrode wear, and width of the kerf.

Ti-SrO metal matrix composites for bone implant materials

Titanium-strontia (Ti-SrO) metal matrix composites (MMCs) with 0, 1, 3 and 5% (weight ratio) of SrO have been fabricated through the powder metallurgy method. Increasing the weight ratio of SrO from 0 to 5%, the compressive strength of Ti-SrO MMCs increased from 982 MPa to 1753 MPa, while the ultimate strain decreased from 0.28 to 0.05. The elastic moduli of Ti-3SrO and Ti-5SrO MMCs were higher than those of Ti and Ti-1SrO MMC samples. Additionally, the micro hardness of Ti-SrO MMCs was enhanced from 59% to 190% with the addition of SrO. The enhanced compression strength and micro hardness of Ti-SrO MMCs were attributed to the Hall-Petch effect and the SrO dispersion strengthening in the Ti matrix. MTS assay results demonstrated that Ti-SrO MMCs with 3% SrO exhibited enhanced proliferation of osteoblast-like cells. Alkaline phosphatase activity of cells was not influenced significantly on the surface of Ti-SrO MMCs compared with pure Ti in a term longer than 10 days. The cell morphology on the Ti-SrO MMCs was observed using confocal microscopy and scanning electron microscopy, which confirmed that the Ti-3%SrO MMCs showed optimal in vitro biocompatibility. This journal is © the Partner Organisations 2014.

Correlation between optical and SEM measurements of wool cortical cell size

Wool fibres consist of micro to nano scale protein constituents that could be used for innovative applications. While techniques for extracting these constituents or making wool fibres into organic powders have been developed, effectively dispersing the particles and accurately determining their size has been difficult in practice. In this study, an ultrasonic method was employed to disperse cortical cells extracted from wool fibres into an
immersion oil or ethanol. Specimens of the cortical cells were then observed under optical microscopy and scanning electron microscopy, respectively. Cell length and maximum cell diameter were measured to quantify the cell size. The results suggest significant discrepancies exist in the cortical cell size obtained from the two different measurement techniques. The maximum diameter of wool cortical cells obtained from the optical microscope was much larger than that from the scanning electron microscope, while the length was much shorter. A correction factor is given so that cortical cell size obtained from the two measurement techniques can be compared.

Particles induce apical plasma membrane enlargement in epithelial lung cell line depending on particle surface area dose

Background Airborne particles entering the respiratory tract may interact with the apical plasma membrane (APM) of epithelial cells and enter them. Differences in the entering mechanisms of fine (between 0.1 μm and 2.5 μm) and ultrafine ( ≤ 0.1 μm) particles may be associated with different effects on the APM. Therefore, we studied particle-induced changes in APM surface area in relation to applied and intracellular particle size, surface and number. Methods Human pulmonary epithelial cells (A549 cell line) were incubated with various concentrations of different sized fluorescent polystyrene spheres without surface charge (∅ fine – 1.062 μm, ultrafine – 0.041 μm) by submersed exposure for 24 h. APM surface area of A549 cells was estimated by design-based stereology and transmission electron microscopy. Intracellular particles were visualized and quantified by confocal laser scanning microscopy. Results Particle exposure induced an increase in APM surface area compared to negative control (p < 0.01) at the same surface area concentration of fine and ultrafine particles a finding not observed at low particle concentrations. Ultrafine particle entering was less pronounced than fine particle entering into epithelial cells, however, at the same particle surface area dose, the number of intracellular ultrafine particles was higher than that of fine particles. The number of intracellular particles showed a stronger increase for fine than for ultrafine particles at rising particle concentrations. Conclusion This study demonstrates a particle-induced enlargement of the APM surface area of a pulmonary epithelial cell line, depending on particle surface area dose. Particle uptake by epithelial cells does not seem to be responsible for this effect. We propose that direct interactions between particle surface area and cell membrane cause the enlargement of the APM.

Size-Dependent Uptake of Particles by Pulmonary Antigen-Presenting Cell Populations and Trafficking to Regional Lymph Nodes

The respiratory tract is an attractive target organ for novel diagnostic and therapeutic applications with nano-sized carriers, but their immune effects and interactions with key resident antigen-presenting cells (APCs) such as dendritic cells (DCs) and alveolar macrophages (AMs) in different anatomical compartments remain poorly understood. Polystyrene particles ranging from 20 nm to 1,000 nm were instilled intranasally in BALB/c mice, and their interactions with APC populations in airways, lung parenchyma, and lung-draining lymph nodes (LDLNs) were examined after 2 and 24 hours by flow cytometry and confocal microscopy. In the main conducting airways and lung parenchyma, DC subpopulations preferentially captured 20-nm particles, compared with 1,000-nm particles that were transported to the LDLNs by migratory CD11blow DCs and that were observed in close proximity to CD3+ T cells. Generally, the uptake of particles increased the expression of CD40 and CD86 in all DC populations, independent of particle size, whereas 20-nm particles induced enhanced antigen presentation to CD4+ T cells in LDLNs in vivo. Despite measurable uptake by DCs, the majority of particles were taken up by AMs, irrespective of size. Confocal microscopy and FACS analysis showed few particles in the main conducting airways, but a homogeneous distribution of all particle sizes was evident in the lung parenchyma, mostly confined to AMs. Particulate size as a key parameter determining uptake and trafficking therefore determines the fate of inhaled particulates, and this may have important consequences in the development of novel carriers for pulmonary diagnostic or therapeutic applications.

Characterisation of a harvesting step for monoclonal antibodies from mammalian cell culture

The focus of this research was defined by a poorly characterised filtration train employed to clarify culture broth containing monoclonal antibodies secreted by GS-NSO cells: the filtration train blinded unpredictably and the ability of the positively charged filters to adsorb DNA from process material was unknown. To direct the development of an assay to quantify the ability of depth filters to adsorb DNA, the molecular weight of DNA from a large-scale, fed-batch, mammalian cell culture vessel was evaluated as process material passed through the initial stages of the purification scheme. High molecular weight DNA was substantially cleared from the broth after passage through a disc stack centrifuge and the remaining low molecular weight DNA was largely unaffected by passage through a series of depth filters and a sterilising grade membrane. Removal of high molecular weight DNA was shown to be coupled with clarification of the process stream. The DNA from cell culture supernatant showed a pattern of internucleosomal cleavage of chromatin when fractionated by electrophoresis but the presence of both necrotic and apoptotic cells throughout the fermentation meant that the origin of the fragmented DNA could not be unequivocally determined. An intercalating fluorochrome, PicoGreen, was elected for development of a suitable DNA assay because of its ability to respond to low molecular weight DNA. It was assessed for its ability to determine the concentration of DNA in clarified mammalian cell culture broths containing pertinent monoclonal antibodies. Fluorescent signal suppression was ameliorated by sample dilution or by performing the assay above the pI of secreted IgG. The source of fluorescence in clarified culture broth was validated by incubation with RNase A and DNase I. At least 89.0 % of fluorescence was attributable to nucleic acid and pre-digestion with RNase A was shown to be a requirement for successful quantification of DNA in such samples. Application of the fluorescence based assay resulted in characterisation of the physical parameters governing adsorption of DNA by various positively charged depth filters and membranes in test solutions and the DNA adsorption profile of the manufacturing scale filtration train. Buffers that reduced or neutralised the depth filter or membrane charge, and those that impeded hydrophobic interactions were shown to affect their operational capacity, demonstrating that DNA was adsorbed by a combination of electrostatic and hydrophobic interactions. Production-scale centrifugation of harvest broth containing therapeutic protein resulted in the reduction of total DNA in the process stream from 79.8 μg m1-1 to 9.3 μg m1-1 whereas the concentration of DNA in the supernatant of pre-and post-filtration samples had only marginally reduced DNA content: from 6.3 to 6.0 μg m1-1 respectively. Hence the filtration train was shown to ineffective in DNA removal. Historically, blinding of the depth filters had been unpredictable with data such as numbers of viable cells, non-viable cells, product titre, or process shape (batch, fed-batch, or draw and fill) failing to inform on the durability of depth filters in the harvest step. To investigate this, key fouling contaminants were identified by challenging depth filters with the same mass of one of the following: viable healthy cells, cells that had died by the process of apoptosis, and cells that had died through the process of necrosis. The pressure increase across a Cuno Zeta Plus 10SP depth filter was 2.8 and 16.5 times more sensitive to debris from apoptotic and necrotic cells respectively, when compared to viable cells. The condition of DNA released into the culture broth was assessed. Necrotic cells released predominantly high molecular weight DNA in contrast to apoptotic cells which released chiefly low molecular weight DNA. The blinding of the filters was found to be largely unaffected by variations in the particle size distribution of material in, and viscosity of, solutions with which they were challenged. The exceptional response of the depth filters to necrotic cells may suggest the cause of previously noted unpredictable filter blinding whereby a number of necrotic cells have a more significant impact on the life of a depth filter than a similar number of viable or apoptotic cells. In a final set of experiments the pressure drop caused by non-viable necrotic culture broths which had been treated with DNase I or benzonase was found to be smaller when compared to untreated broths: the abilities of the enzyme treated cultures to foul the depth filter were reduced by 70.4% and 75.4% respectively indicating the importance of DNA in the blinding of the depth filter studied.

Assessment and application of clustering techniques to atmospheric particle number size distribution for the purpose of source apportionment

Long-term measurements of particle number size distribution (PNSD) produce a very large number of observations and their analysis requires an efficient approach in order to produce results in the least possible time and with maximum accuracy. Clustering techniques are a family of sophisticated methods which have been recently employed to analyse PNSD data, however, very little information is available comparing the performance of different clustering techniques on PNSD data. This study aims to apply several clustering techniques (i.e. K-means, PAM, CLARA and SOM) to PNSD data, in order to identify and apply the optimum technique to PNSD data measured at 25 sites across Brisbane, Australia. A new method, based on the Generalised Additive Model (GAM) with a basis of penalised B-splines, was proposed to parameterise the PNSD data and the temporal weight of each cluster was also estimated using the GAM. In addition, each cluster was associated with its possible source based on the results of this parameterisation, together with the characteristics of each cluster. The performances of four clustering techniques were compared using the Dunn index and Silhouette width validation values and the K-means technique was found to have the highest performance, with five clusters being the optimum. Therefore, five clusters were found within the data using the K-means technique. The diurnal occurrence of each cluster was used together with other air quality parameters, temporal trends and the physical properties of each cluster, in order to attribute each cluster to its source and origin. The five clusters were attributed to three major sources and origins, including regional background particles, photochemically induced nucleated particles and vehicle generated particles. Overall, clustering was found to be an effective technique for attributing each particle size spectra to its source and the GAM was suitable to parameterise the PNSD data. These two techniques can help researchers immensely in analysing PNSD data for characterisation and source apportionment purposes.

Numerical investigation of motion and deformation of a single red blood cell in a stenosed capillary

It is generally assumed that influence of the red blood cells (RBCs) is predominant in blood rheology. The healthy RBCs are highly deformable and can thus easily squeeze through the smallest capillaries having internal diameter less than their characteristic size. On the other hand, RBCs infected by malaria or other diseases are stiffer and so less deformable. Thus it is harder for them to flow through the smallest capillaries. Therefore, it is very important to critically and realistically investigate the mechanical behavior of both healthy and infected RBCs which is a current gap in knowledge. The motion and the steady state deformed shape of the RBCs depend on many factors, such as the geometrical parameters of the capillary through which blood flows, the membrane bending stiffness and the mean velocity of the blood flow. In this study, motion and deformation of a single two-dimensional RBC in a stenosed capillary is explored by using smoothed particle hydrodynamics (SPH) method. An elastic spring network is used to model the RBC membrane, while the RBC's inside fluid and outside fluid are treated as SPH particles. The effect of RBC's membrane stiffness (kb), inlet pressure (P) and geometrical parameters of the capillary on the motion and deformation of the RBC is studied. The deformation index, RBC's mean velocity and the cell membrane energy are analyzed when the cell passes through the stenosed capillary. The simulation results demonstrate that the kb, P and the geometrical parameters of the capillary have a significant impact on the RBCs' motion and deformation in the stenosed section.

Size-resolved particle distribution and gaseous concentrations by real-world road tunnel measurement

Measurements of aerosol particle number size distributions (15-700 nm), CO and NOx were performed in a bus tunnel, Australia. Daily mean particle size distributions of mixed diesel/CNG (Compressed Natural Gas) buses traffic flow were determined in 4 consecutive measurement days. EFs (Emission Factors) of Particle size distribution of diesel buses and CNG buses were obtained by MLR (Multiple Linear Regression) methods, particle distributions of diesel buses and CNG buses were observed as single accumulation mode and nuclei-mode separately. Particle size distributions of mixed traffic flow were decomposed by two log-normal fitting curves for each 30 minutes interval mean scans, all the mix fleet PSD emission can be well fitted by the summation of two log-normal distribution curves, and these were composed of nuclei mode curve and accumulation curve, which were affirmed as the CNG buses and diesel buses PN emission curves respectively. Finally, particle size distributions of diesel buses and CNG buses were quantified by statistical whisker-box charts. For log-normal particle size distribution of diesel buses, accumulation mode diameters were 74.5～87.5nm, geometric standard deviations were 1.89～1.98. As to log-normal particle size distribution of CNG buses, nuclei-mode diameters were 21～24 nm, geometric standard deviations were 1.27～1.31.

Silica vesicles as nanocarriers and adjuvants for generating both antibody and T-cell mediated immune resposes to Bovine Viral Diarrhoea Virus E2 protein

Bovine Viral Diarrhoea Virus (BVDV) is widely distributed in cattle industries and causes significant economic losses worldwide annually. A limiting factor in the development of subunit vaccines for BVDV is the need to elicit both antibody and T-cell-mediated immunity as well as addressing the toxicity of adjuvants. In this study, we have prepared novel silica vesicles (SV) as the new generation antigen carriers and adjuvants. With small particle size of 50 nm, thin wall (similar to 6 nm), large cavity (similar to 40 nm) and large entrance size (5.9 nm for SV-100 and 16 nm for SV-140), the SV showed high loading capacity (similar to 250 mu g/mg) and controlled release of codon-optimised E2 (oE2) protein, a major immunogenic determinant of BVDV. The in vivo functionality of the system was validated in mice immunisation trials comparing oE2 plus Quil A (50 mu g of oE2 plus 10 mu g of Quil A, a conventional adjuvant) to the oE2/SV-140 (50 mu g of oE2 adsorbed to 250 mu g of SV-140) or oE2/SV-140 together with 10 mu g of Quil A. Compared to the oE2 plus Quil A, which generated BVDV specific antibody responses at a titre of 10(4), the oE2/SV-140 group induced a 10 times higher antibody response. In addition, the cell-mediated response, which is essential to recognise and eliminate the invading pathogens, was also found to be higher [1954-2628 spot forming units (SFU)/million cells] in mice immunised with oE2/SV-140 in comparison to oE2 plus Quil A (512-1369 SFU/million cells). Our study has demonstrated that SV can be used as the next-generation nanocarriers and adjuvants for enhanced veterinary vaccine delivery. (C) 2014 Elsevier Ltd. All rights reserved.