Indoor emissions of total and fluorescent supermicron particles during HOMEChem

Inhalation of particulate matter is associated with adverse health outcomes. The fluorescent portion of supermicron particulate matter has been used as a proxy for bioaerosols. The sources and emission rates of fluorescent particles in residential environments are not well-understood. Using an ultraviolet aerodynamic particle sizer (UVAPS), emissions of total and fluorescent supermicron particles from common human activities were investigated during the HOMEChem campaign, a test-house investigation of the chemistry of indoor environments. Human occupancy and activities, including cooking and mopping, were found to be considerable sources of indoor supermicron fluorescent particles, which enhanced the indoor particle concentrations by two orders of magnitude above baseline levels. The estimated total (fluorescent) mass emission rates for the activities tested were in the range of 4-30 (1-11) mg per person meal for cooking and 0.1-4.9 (0.05-4.7) mg/h for occupancy and mopping. Model calculations indicate that, once released, the dominant fate of coarse particles (2.5-10 micrometer in diameter) was deposition onto indoor surfaces, allowing for the possibility of subsequent resuspension and consequent exposures over durations much longer than the ventilation time scale. Indoor coarse particle deposition would also contribute to soiling of indoor surfaces.     

Novel peroxide‐vulcanized NBR‐PAni.DBSA blends,part 2: Effects of conductive filler particles alignment

Dicumyl peroxide (DCP) vulcanized poly(butadiene‐co‐acrylonitrile)‐polyaniline dodecylbenzenesulfonate [NBR‐PAni.DBSA] blends were successfully prepared by using the practical thermomechanical mixing method. The effect of alignment of PAni.DBSA particles on the mechanical and electrical properties of vulcanized blends was studied (by passing the blends through a two roll‐mills). All vulcanized blends strained parallel to the flow direction when passed through the two roll‐mills had their electrical conductivities enhanced with increasing strain in tension. Good historical memory in term of the electrical conductivities during three cycles of straining (with 300 times of strain loading and unloading motion for each cycle) was observed for all vulcanized blends (99% retention of original value before straining). These vulcanized blends also showed better mechanical properties (i.e., higher tensile strength and tear strength) than the ones strained perpendicularly to the flow direction. With the ideal mechanical properties and reversible electrical behavior, this type of blend can potentially emerge as a new class of flexible smart material. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Quantifying particle pick up at a pendant bubble: A study of non-hydrophobic particle–bubble interaction

To study bubble interaction with non-hydrophobic particles an imaging technique has been developed to quantify particle pick up at a pendant bubble by measuring the bubble–particle attachment angle (BPA) made by the particle bed on the bubble. The technique was verified by correlating pick up mass against BPA. Pick up of alumina was shown to correlate with difference in alumina and bubble zeta potential supporting an electrostatic model of interaction with non-hydrophobic particles. Pick up also correlated with contact angle (Washburn method) indicating the electrostatic force is sufficient to establish a solid–air interface.     

Application of Dispersed Particle Gel to Inhibit Surfactant Adsorption on Sand

This article highlights an efficient and cost-effective additive-dispersed particle gel (DPG) to reduce surfactant adsorption on sand. Indoor experiments were conducted to study the effect of DPG on static adsorption and dynamic adsorption of the surfactant. The static adsorption data were evaluated using different isotherm models and the Redlich–Peterson isotherm matched the best. Results showed a significant inhibition of surfactant adsorption in the presence of DPG. The dynamic adsorption of SDS on sand decreased to 0.78, 0.68 and 0.61 mg/g compared with original value of 1.17 mg/g by adding 0.1, 0.2 and 0.3 wt% DPG particles, respectively. This study suggests that DPG can inhibit the adsorption of surfactant on sand effectively.     

Parametric optimization of fused deposition modeling and vapour smoothing processes for surface finishing of biomedical implant replicas

This study focuses on formulation of robust design for vapour smoothing, an advanced surface finishing technique for finishing ABS replicas where hot vapours tend to level the uneven surface asperities. The process parameters of combined Fused Deposition Modeling (FDM) and Vapour smoothing (VS) process are optimized for sustainability of ABS replicas for biomedical applications. Six input parameters have been investigated, two of FDM and four of VS processes while surface roughness and hardness of ABS part is taken as response. The vapour smoothing process ensue ultra smooth finish with negligible deterioration of upper surface deducing maximum contribution of smoothing time (51.07%) and number of cycles (40.08%) on surface roughness. Hardness of replica has been slightly increased by maximum impact of orientation angle (34.69%) and postcooling time (44.46%) of ABS replicas which endorsed the use of FDM replicas for investment casting of biomedical implants.     

The collision efficiency of small bubbles with large particles

Bubble–particle interactions play an important role in many technological processes, e.g., in flotation. Although mineral flotation involves fine particles, this work focuses on the interactions between a small bubble and larger spherical particle and determining their collision efficiency. Based on the theoretical and experimental work, a simple relation for estimating the collision efficiency is proposed. The calculated efficiencies are compared to a large set of experimental data and are found to be in excellent agreement.     

Modelling and analysis of bacterial tracks suggest an active reorientation mechanism in Rhodobacter sphaeroides

Most free-swimming bacteria move in approximately straight lines, interspersed with random reorientation phases. A key open question concerns varying mechanisms by which reorientation occurs. We combine mathematical modelling with analysis of a large tracking dataset to study the poorly understood reorientation mechanism in the monoflagellate species Rhodobacter sphaeroides. The flagellum on this species rotates counterclockwise to propel the bacterium, periodically ceasing rotation to enable reorientation. When rotation restarts the cell body usually points in a new direction. It has been assumed that the new direction is simply the result of Brownian rotation. We consider three variants of a self-propelled particle model of bacterial motility. The first considers rotational diffusion only, corresponding to a non-chemotactic mutant strain. Two further models incorporate stochastic reorientations, describing ‘run-and-tumble’ motility. We derive expressions for key summary statistics and simulate each model using a stochastic computational algorithm. We also discuss the effect of cell geometry on rotational diffusion. Working with a previously published tracking dataset, we compare predictions of the models with data on individual stopping events in R. sphaeroides. This provides strong evidence that this species undergoes some form of active reorientation rather than simple reorientation by Brownian rotation.     

CO2 welding with an additional cold filler wire

The results of investigations carried out to improve the quality of the CO₂ welding process with an additional filler wire (AFW), fed into the tail part of the molten pool in the cold state, are presented. The effect of the AFW on the quality of the produced bead is studied. The results of metallographic studies of the welded joint and also of the impact bend test are presented. When using the AFW, the quality of the welded joint is considerably higher with better external appearance of the welded joint, and the productivity of the process is also increased.     

Interaction Between an Ethoxylated Alkylphenol Polymer with Formaldehyde and Triblock polyEO–polyPO–polyEO Copolymer in Aqueous Solutions

The interaction between an ethoxylated alkylphenol polymer with formaldehyde (EAPPF) and a triblock polyEO–polyPO–polyEO copolymer (TBCP) in aqueous solutions has been investigated in detail by means of surface tension, steady-state fluorescence, dynamic light scattering (DLS) measurements and computer simulations. For comparison, the ethoxylated alkylphenol oligomer (EAPO), which is the monomer unit of EAPPF, and another nonionic water-soluble polymer PEG were also selected to get more information about the interaction between different types of surfactants and polymers. The surface properties of mixed systems at the air/water surface were evaluated from surface tension measurements. Information about the hydrophobic microenvironment and size of the aggregates was obtained from steady-state fluorescence using pyrene as a hydrophobic probe and DLS measurements, respectively. The dissipative particle dynamics simulation method was applied to simulate the interaction between EAPPF (or EAPO) and TBCP (or PEG) in aqueous solutions. The synergetic interaction between EAPPF (or EAPO) and TBCP in binary mixed solution enhanced the adsorption of surfactant molecules (EAPPF or EAPO) at the interface, while no obvious interaction between EAPPF (or EAPO) and PEG was observed.