Influence of ventilation and filtration on indoor particle concentrations in urban office buildings

This study aimed to quantify the efficiency of deep bag and electrostatic filters, and assess the influence of ventilation systems using these filters on indoor fine (<2.5 µm) and ultrafine particle concentrations in commercial office buildings. Measurements and modelling were conducted for different indoor and outdoor particle source scenarios at three office buildings in Brisbane, Australia. Overall, the in-situ efficiency, measured for particles in size ranges 6 to 3000 nm, of the deep bag filters ranged from 26.3 to 46.9% for the three buildings, while the in-situ efficiency of the electrostatic filter in one building was 60.2%. The highest PN and PM2.5 concentrations in one of the office buildings (up to 131% and 31% higher than the other two buildings, respectively) were due to the proximity of the building’s HVAC air intakes to a nearby bus-only roadway, as well as its higher outdoor ventilation rate. The lowest PN and PM2.5 concentrations (up to 57% and 24% lower than the other two buildings, respectively) were measured in a building that utilised both outdoor and mixing air filters in its HVAC system. Indoor PN concentrations were strongly influenced by outdoor levels and were significantly higher during rush-hours (up to 41%) and nucleation events (up to 57%), compared to working-hours, for all three buildings. This is the first time that the influence of new particle formation on indoor particle concentrations has been identified and quantified. A dynamic model for indoor PN concentration, which performed adequately in this study also revealed that using mixing/outdoor air filters can significantly reduce indoor particle concentration in buildings where indoor air was strongly influenced by outdoor particle levels. This work provides a scientific basis for the selection and location of appropriate filters and outdoor air intakes, during the design of new, or upgrade of existing, building HVAC systems. The results also serve to provide a better understanding of indoor particle dynamics and behaviours under different ventilation and particle source scenarios, and highlight effective methods to reduce exposure to particles in commercial office buildings.

Effect of Reynolds numbers on flow past four square cylinders in an in-line square configuration for different gap spacings

In this paper two-dimensional (2-D) numerical investigation of flow past four square cylinders in an in-line square configuration are performed using the lattice Boltzmann method. The gap spacing g=s/d is set at 1, 3 and 6 and Reynolds number ranging from Re=60 to 175. We observed four distinct wake patterns: (i) a steady wake pattern (Re=60 and g=1) (ii) a stable shielding wake pattern (80≤Re≤175 and g=1) (iii) a wiggling shielding wake pattern (60≤Re≤175 and g=3) (iv) a vortex shedding wake pattern (60≤Re≤175 and g=6) At g=1, the Reynolds number is observed to have a strong effect on the wake patterns. It is also found that at g=1, the secondary cylinder interaction frequency significantly contributes for drag and lift coefficients signal. It is found that the primary vortex shedding frequency dominates the flow and the role of secondary cylinder interaction frequency almost vanish at g=6. It is observed that the jet between the gaps strongly influenced the wake interaction for different gap spacing and Reynolds number combination. To fully understand the wake transformations the details vorticity contour visualization, power spectra of lift coefficient signal and time signal analysis of drag and lift coefficients also presented in this paper.

NSAM-derived total surface area vs. SMPS-derived "mobility equivalent" surface area for different environmentally relevant aerosols

The surface area of inhaled particles deposited in the alveolar region, as reported by the TSI nanoparticle surface area monitor (NSAM), was compared with the corresponding value estimated by a TSI scanning mobility particle sizer (SMPS) for a range of environmentally relevant aerosols, including petrol emissions, ETS, laser printer emissions, cooking emissions and ambient aerosols. The SMPS values were based on a mobility size distribution assuming spherical particles using the appropriate size-dependent alveolar-deposition factors provided by the ICRP. In most cases, the two instruments showed good linear agreement. With petrol emissions and ETS, the linearity extended to over 103 μm2 cm-3. With printer emissions, there was good linearity up to about 300 μm2 cm-3 while the NSAM increasingly overestimated the surface area at higher concentrations. The presence of a nucleation event in ambient air caused the NSAM to over-estimate the surface area by a factor of 2. We summarize these results and conclude that the maximum number concentration up to which the NSAM is accurate clearly depends on the type of aerosol being sampled and provide guidance for the use of the instrument.

Bending properties of Ag nanowires with pre-existing surface defects

Materials used in the engineering always contain imperfections or defects which significantly affect their performances. Based on the large-scale molecular dynamics simulation and the Euler–Bernoulli beam theory, the influence from different pre-existing surface defects on the bending properties of Ag nanowires (NWs) is studied in this paper. It is found that the nonlinear-elastic deformation, as well as the flexural rigidity of the NW is insensitive to different surface defects for the studied defects in this paper. On the contrary, an evident decrease of the yield strength is observed due to the existence of defects. In-depth inspection of the deformation process reveals that, at the onset of plastic deformation, dislocation embryos initiate from the locations of surface defects, and the plastic deformation is dominated by the nucleation and propagation of partial dislocations under the considered temperature. Particularly, the generation of stair-rod partial dislocations and Lomer–Cottrell lock are normally observed for both perfect and defected NWs. The generation of these structures has thwarted attempts of the NW to an early yielding, which leads to the phenomenon that more defects does not necessarily mean a lower critical force.

Estranged bodies and Vietnamese identities

In this paper I will explore both the regulation of migrant bodies as well as the lived experience of migrant embodiment in order to develop an analysis of the body as a vortex of meaning in the displacement process. By examining the way in which the bodies of Vietnamese immigrants are simultaneously object and agent, I will indicate how the relations between migrants and the wider society are felt and sensed through the bodily experiences of Vietnamese people. The dynamic between how Vietnamese bodies are represented and how they are experienced reveals the body to be a predominant marker of difference from both within and without, the mediator between experience and signification. I will indicate how the dominant media construction of Vietnamese bodies as defiled has sustained forms of exclusion and distancing which have influenced the way that Vietnamese bodies are lived. I thus explore the means through which the body has particular salience when attempting to understand the nature of migrant identities in Australia.

Cyclin A/CDK2 regulates multiple G2 phase pathways

The cell cycle is a carefully choreographed series of phases that when executed successfully will allow the complete replication of the genome and the equal division of the genome and other cellular content into two independent daughter cells. The inability of the cell to execute cell division successfully can result in either checkpoint activation to allow repair and/or apoptosis and/or mutations/errors that may or may not lead to tumourgenesis. Cyclin A/CDK2 is the primary cyclin/CDK regulating G2 phase progression of the cell cycle. Cyclin A/CDK2 activity peaks in G2 phase and its inhibition causes a G2 phase delay that we have termed 'the cyclin A/CDK2 dependent G2 delay'. Understanding the key pathways that are involved in the cyclin A/CDK2 dependent G2 delay has been the primary focus of this study. Characterising the cyclin A/CDK2 dependent G2 delay revealed accumulated levels of the inactive form of the mitotic regulator, cyclin B/CDK1. Surprisingly, there was also increased microtubule nucleation at the centrosomes, and the centrosomes stained for markers of cyclin B/CDK1 activity. Both microtubule nucleation at the centrosomes and phosphoprotein markers were lost with short-term treatment of CDK1/2 inhibition. Cyclin A/CDK2 localised at the centrosomes in late G2 phase after separation of the centrosomes but before the start of prophase. Thus G2 phase cyclin A/CDK2 controls the timing of entry into mitosis by controlling the subsequent activation of cyclin B/CDK1, but also has an unexpected role in coordinating the activation of cyclin B/CDK1 at the centrosome and in the nucleus. In addition to regulating the timing of cyclin B/CDK1 activation and entry into mitosis in the unperturbed cell cycle, cyclin A/CDK2 also was shown to have a role in G2 phase checkpoint recovery. Known G2 phase regulators were investigated to determine whether they had a role in imposing the cyclin A/ CDK2 dependent G2 delay. Examination of the critical G2 checkpoint arrest protein, Chk1, which also has a role during unperturbed G2/M phases revealed the presence of activated Chk1 in G2 phase, in a range of cell lines. Activated Chk1 levels were shown to accumulate in cyclin A/CDK2 depleted/inhibited cells. Further investigations revealed that Chk1, but not Chk2, depletion could reverse the cyclin A/CDK2 dependent G2 delay. It was confirmed that the accumulative activation of Chk1 was not a consequence of DNA damage induced by cyclin A depletion. The potential of cyclin A/CDK2 to regulate Chk1 revealed that the inhibitory phosphorylations, Ser286 and Ser301, were not directly catalysed by cyclin A/CDK2 in G2 phase to regulate mitotic entry. It appeared that the ability of cyclin A/CDK2 to regulate cyclin B/CDK1 activation impacted cyclin B/CDK1s phosphorylation of Chk1 on Ser286 and Ser301, thereby contributing to the delay in G2/M phase progression. Chk1 inhibition/depletion partially abrogated the cyclin A/CDK2 dependent G2 delay, and was less effective in abrogating G2 phase checkpoint suggesting that other cyclin A/CDK2 dependent mechanisms contributed to these roles of cyclin A/CDK2. In an attempt to identify these other contributing factors another G2/M phase regulator known to be regulated by cyclin A/CDK2, Cdh1 and its substrates Plk1 and Claspin were examined. Cdh1 levels were reduced in cyclin A/CDK2 depleted/inhibited cells although this had little effect on Plk1, a known Cdh1 substrate. However, the level of another substrate, Claspin, was increased. Cdh1 depletion mimicked the effect of cyclin A depletion but to a weaker extent and was sufficient at increasing Claspin levels similar to the increase caused by cyclin A depletion. Co-depletion of cyclin A and Claspin blocked the accumulation of activated Chk1 normally seen with cyclin A depletion alone. However Claspin depletion alone did not reduce the cyclin A/CDK2 dependent G2 delay but this is likely to be a result of inhibition of S phase roles of Claspin. Together, these data suggest that cyclin A/CDK2 regulates a number of different mechanisms that contribute to G2/M phase progression. Here it has been demonstrated that in normal G2/M progression and possibly to a lesser extent in G2 phase checkpoint recovery, cyclin A/CDK2 regulates the level of Cdh1 which in turn affects at least one of its substrates, Claspin, and consequently results in the increased level of activated Chk1 observed. However, the involvement of Cdh1 and Claspin alone does not explain the G2 phase delay observed with cyclin A/CDK2 depletion/inhibition. It is likely that other mechanisms, possibly including cyclin A/CDK2 regulation of Wee1 and FoxM1, as reported by others, combine with the mechanism described here to regulate normal G2/M phase progression and G2 phase checkpoint recovery. These findings support the critical role for cyclin A/CDK2 in regulating progression into mitosis and suggest that upstream regulators of cyclin A/CDK2 activation will also be critical controllers of this cell cycle transition. The pathways that work to co-ordinate cell cycle progression are very intricate and deciphering these pathways, required for normal cell cycle progression, is key to understanding tumour development. By understanding cell cycle regulatory pathways it will allow the identification of the pathway/s and their mechanism/s that become affected in tumourgenesis. This will lead to the development of better targeted therapies, inferring better efficacy with fewer side effects than commonly seen with the use of traditional therapies, such as chemotherapy. Furthermore, this has the potential to positively impact the development of personalised medicines and the customisation of healthcare.

Torsional properties of bamboo-like structured Cu nanowires

Recently, researchers reported that nanowires (NWs) are often polycrystalline, which contain grain or twin boundaries that transect the whole NW normal to its axial direction into a bamboo like structure. In this work, large-scale molecular dynamics simulation is employed to investigate the torsional behaviours of bamboo-like structured Cu NWs. The existence of grain boundaries is found to induce a considerably large reduction to the critical angle, and the more of grain boundaries the less reduction appears, whereas, the presence of twin boundaries only results in a relatively smaller reduction to the critical angle. The introduction of grain boundaries reduces the torsional rigidity of the NW, whereas, the twin boundaries exert insignificant influence to the torsional rigidity. NWs with grain boundaries are inclined to produce a local HCP structure during loading, and the plastic deformation is usually evenly distributed along the axial axis of the NW. The plastic deformation of both perfect NW and NWs with twin boundaries is dominated by the nucleation and propagation of parallel intrinsic stacking faults. This study will enrich the current understanding of the mechanical properties of NWs, which will eventually shed lights on their applications.

Morphology changes and mechanistic aspects of the electrochemically-induced reversible solid-solid transformation of microcrystalline TCNQ into Co TCNQ 2-based materials (TCNQ= 7, 7, 8, 8-Tetracyanoquinodimethane)

The chemically reversible solid−solid phase transformation of a TCNQ-modified glassy carbon, indium tin oxide, or metal electrode into Co\[TCNQ]2(H2O)2 material in the presence of Co2+(aq) containing electrolytes has been induced and monitored electrochemically. Voltammetric data reveal that the TCNQ/Co\[TCNQ]2(H2O)2 interconversion process is independent of electrode material and identity of cobalt electrolyte anion. However, a marked dependence on electrolyte concentration, scan rate, and method of electrode modification (drop casting or mechanical attachment) is found. Cyclic voltammetric and double potential step chronoamperometric measurements confirm that formation of Co\[TCNQ]2(H2O)2 occurs through a rate-determining nucleation and growth process that initially involves incorporation of Co2+(aq) ions into the reduced TCNQ crystal lattice at the TCNQ|electrode|electrolyte interface. Similarly, the reverse (oxidation) process, which involves transformation of solid Co\[TCNQ]2(H2O)2 back to parent TCNQ crystals, also is controlled by nucleation−growth kinetics. The overall chemically reversible process that represents this transformation is described by the reaction:  2TCNQ0(s) + 2e- + Co2+(aq) + 2H2O \[Co(TCNQ)2(H2O)2](s). Ex situ SEM images illustrated that this reversible TCNQ/Co\[TCNQ]2(H2O)2 conversion process is accompanied by drastic size and morphology changes in the parent solid TCNQ. In addition, different sizes of needle-shaped nanorod/nanowire crystals of Co\[TCNQ]2(H2O)2 are formed depending on the method of surface immobilization.

Electrocrystallization of phase I, CuTCNQ (TCNQ= 7, 7, 8, 8-tetracyanoquinodimethane), on indium tin oxide and boron-doped diamond electrodes

The electrochemical reduction of TCNQ to TCNQ•- in acetonitrile in the presence of [Cu(MeCN)4]+ has been undertaken at boron-doped diamond (BDD) and indium tin oxide (ITO) electrodes. The nucleation and growth process at BDD is similar to that reported previously at metal electrodes. At an ITO electrode, the electrocrystallization of more strongly adhered, larger, branched, needle-shaped phase I CuTCNQ crystals is detected under potential step conditions and also when the potential is cycled over the potential range of 0.7 to −0.1 V versus Ag/AgCl (3 M KCl). Video imaging can be used at optically transparent ITO electrodes to monitor the growth stage of the very large branched crystals formed during the course of electrochemical experiments. Both in situ video imaging and ex situ X-ray diffraction and scanning electron microscopy (SEM) data are consistent with the nucleation of CuTCNQ taking place at a discrete number of preferred sites on the ITO surface. At BDD electrodes, ex situ optical images show that the preferential growth of CuTCNQ occurs at the more highly conducting boron-rich areas of the electrode, within which there are preferred sites for CuTCNQ formation.

AFM study of morphological changes associated with electrochemical solid--solid transformation of three-dimensional crystals of TCNQ to metal derivatives (metal= Cu, Co, Ni; TCNQ= tetracyanoquinodimethane)

In situ atomic force microscopy (AFM) allows images from the upper face and sides of TCNQ crystals to be monitored during the course of the electrochemical solid–solid state conversion of 50 × 50 μm2 three-dimensional drop cast crystals of TCNQ to CuTCNQ or M[TCNQ]2(H2O)2 (M = Co, Ni). Ex situ images obtained by scanning electron microscopy (SEM) also allow the bottom face of the TCNQ crystals, in contact with the indium tin oxide or gold electrode surface and aqueous metal electrolyte solution, to be examined. Results show that by carefully controlling the reaction conditions, nearly mono-dispersed, rod-like phase I CuTCNQ or M[TCNQ]2(H2O)2 can be achieved on all faces. However, CuTCNQ has two different phases, and the transformation of rod-like phase 1 to rhombic-like phase 2 achieved under conditions of cyclic voltammetry was monitored in situ by AFM. The similarity of in situ AFM results with ex situ SEM studies accomplished previously implies that the morphology of the samples remains unchanged when the solvent environment is removed. In the process of crystal transformation, the triple phase solid∣electrode∣electrolyte junction is confirmed to be the initial nucleation site. Raman spectra and AFM images suggest that 100% interconversion is not always achieved, even after extended electrolysis of large 50 × 50 μm2 TCNQ crystals.

An investigation of silver electrodeposition from ionic liquids : influence of atmospheric water uptake on the silver electrodeposition mechanism and film morphology

The electrodeposition of silver from two ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]) and N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide ([C4mPyr][TFSI]), and an aqueous KNO3 solution on a glassy carbon electrode was undertaken. It was found by cyclic voltammetry that the electrodeposition of silver proceeds through nucleation–growth kinetics. Analysis of chronoamperometric data indicated that the nucleation–growth mechanism is instantaneous at all potentials in the case of [BMIm][BF4] and [C4mPyr][TFSI], and instantaneous at low overpotentials tending to progressive at high overpotentials for KNO3. Significantly, under ambient conditions, the silver electrodeposition mechanism changes to progressive nucleation and growth in [C4mPyr][TFSI], which is attributed to the uptake of atmospheric water in the IL. It was found that these differences in the growth mechanism impact significantly on the morphology of the resultant electrodeposit which is characterised ex situ by scanning electron microscopy and X-ray diffraction.

The formation of gold nanoparticles using hydroquinone as a reducing agent through a localized pH change upon addition of NaOH to a solution of HAuCl4

We demonstrate a rapid synthesis of gold nanoparticles using hydroquinone as a reducing agent under acidic conditions without the need for precursor seed particles. The nanoparticle formation process is facilitated by the addition of NaOH to a solution containing HAuCl4 and hydroquinone to locally change the pH; this enhances the reducing capability of hydroquinone to form gold nucleation centres, after which further growth of gold can take place through an autocatalytic mechanism. The stability of the nanoparticles is highly dependent on the initial solution pH, and both the concentration of added NaOH and hydroquinone present in solution. The gold nanoparticles were characterized by UV–visible spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, atomic force microscopy, dynamic light scattering, and zeta potential measurements. It was found that under optimal conditions that stable aqueous suspensions of 20 nm diameter nanoparticles can be achieved where benzoquinone, the oxidized product of hydroquinone, acts as a capping agent preventing nanoparticles aggregation.

Hydraulic instability onset detection in Kaplan turbines by monitoring shaft vibrations

Design of hydraulic turbines has often to deal with hydraulic instability. It is well-known that Francis and Kaplan types present hydraulic instability in their design power range. Even if modern CFD tools may help to define these dangerous operating conditions and optimize runner design, hydraulic instabilities may fortuitously arise during the turbine life and should be timely detected in order to assure a long-lasting operating life. In a previous paper, the authors have considered the phenomenon of helical vortex rope, which happens at low flow rates when a swirling flow, in the draft tube conical inlet, occupies a large portion of the inlet. In this condition, a strong helical vortex rope appears. The vortex rope causes mechanical effects on the runner, on the whole turbine and on the draft tube, which may eventually produce severe damages on the turbine unit and whose most evident symptoms are vibrations. The authors have already shown that vibration analysis is suitable for detecting vortex rope onset, thanks to an experimental test campaign performed during the commissioning of a 23 MW Kaplan hydraulic turbine unit. In this paper, the authors propose a sophisticated data driven approach to detect vortex rope onset at different power load, based on the analysis of the vibration signals in the order domain and introducing the so-called "residual order spectrogram", i.e. an order-rotation representation of the vibration signal. Some experimental test runs are presented and the possibility to detect instability onset, especially in real-time, is discussed.

FRC erection stages dynamic behaviour under wind loads

Buffeting response of a cable-stayed bridge under construction is investigated through wind tunnel tests and numerical simulations. Two configurations of the erection stage have been considered and compared in terms of dynamic response and internal forces using the results of the experimental aeroelastic models. Moreover the results of a numerical model able to simulate the simultaneous effects of vortex shedding from tower and aeroelastic response of the deck are compared to the wind tunnel ones.

The Brisbane Northbank Urban Film Studio : screening of shortlisted films

Research Statement: In this research project film groups of 4-5 students under my direction produced a 3-5 minute urban film that explored the Brisbane Northbank, and which would become the basis for an urban proposal and design of a small film studio for independent filmmakers in the site. The theoretical premise was that a film studio does not simply produce movies, it creates urban effects all around it and acts as a vortex of cultural activity and social life. For this modest facility where the cinema goes out into the street, the city itself becomes the studio. Students were called to observe the historical problematics of technique, image and effect that arise in the cinema, and to apply these to their own urban-film practice. A panel of judges working in film and architecture shortlisted the 12 best films in 2010 and a major public film screening event took place at the Tribal Cinema. The Shortlisted films today form a permanent "exhibit" in YouTube. The research project was funded by the Queensland University of Technology, School of Design and received accolades from film faculty in the Creative Industries Faculty. The diverse body of work that emanated from the screening contributed a unique analysis of the Northbank to Brisbane.