Exploratory Study of the Potential Airborne Health Hazard of Dusts Generated by Quarrying Volcanic Deposits

Occupational exposure to dust generated by quarrying siliceous rocks (i.e. sandstone, coal) is a well documented respiratory hazard. Hazard of volcanic ash inhalation is also routinely studied (although less well understood), but the specific respiratory hazard of quarried volcanic deposits is entirely under-researched and is the focus of this study. The two main factors potentially implicated in respiratory toxicity of volcanic quarry dust are: i) crystalline silica content implicated in silicosis and lung cancer; and ii) iron-catalysed hydroxyl radical generation, implicated in inflammation and carcinogenesis. Twelve sites (in New Zealand, Montserrat and Greece), quarrying a range of volcanic deposits, were investigated and compared with volcanic ash samples (to test suitability as an analogue) and dust from non-volcanic quarries (greywacke and sandstone) in an investigation of the physicochemical characteristics which may influence particle surface reactivity. Samples of deposited dust (<1mm size fraction) were collected and 11 of these separated to ≤10μm for further analyses. Compositional analyses (XRF) showed the samples spanned the range of magmatic compositions from mafic to felsic (44-76 wt.% SiO2). The finest material was generated by drilling lava flows (8.3-27.5 cu.vol% <10 μm diameter particles in <1mm fraction), however, several other sample types (i.e. dust on processor) contained high levels of respirable material, akin to volcanic ash from equivalent eruption settings. SEM analyses confirmed particles to be blocky and angular, having aspect ratios between 0.59-0.70 (<10μm fraction). Crystalline silica content was highest (up to 28 wt. %) in dusts from intermediate and felsic quarries where lava domes (or collapse deposits) are mined. Similar levels were observed for dome-collapse ash and greywacke quarry dusts; however, the sandstone quarry dust was 99 wt.% crystalline silica. Hydroxyl radical generation was lower for quarried volcanic samples than for either volcanic ash or sandstone (significant to p≤0.01 for mafic ash/quarry dust). Haemolysis (erythrocyte membrane rupture, an indicator of quartz reactivity) was exhibited by six samples from three quarries, and comparable to the DQ12 quartz positive standard, when adjusted for surface area. These findings may be influenced by the presence of clays, however, as haemolytic samples included those with little crystalline silica. Airborne dust levels (both role-specific and ambient) were measured in the quarries and were mostly within international exposure limits, however, interpretations were limited by the duration of measurements so further work is required. Some workers’ shifts were longer than 8 hours, and workers on Montserrat may also be simultaneously exposed to volcanic ashfall, which should be considered with respect to adherence to regulations in those quarries. Mitigation measures were variable and workers would benefit from better awareness regarding use of non-mandatory respiratory protection. Volcanic quarries pose a hazard distinct from volcanic ash and from non-volcanic quarries. Overall, hazard may be lower than for quarrying other rock types, but further research is needed to better constrain the potential hazards. Until then, a precautionary approach might be taken in quarries where respirable dust levels are high and deposits may contain crystalline silica or iron

Bipolar conductance switching of single anthradithiophene molecules

The authors acknowledge funding by the Emmy-Noether-Program of the Deutsche Forschungsgemeinschaft, the SFB 767, and the Baden-Württemberg Stiftung. R.P. and A.A. thank the Basque Departamento de Universidades e Investigacion (grant no. IT-756-13) and the Spanish Ministerio de Economia y Competitividad (grant no. FIS2013-48286-C2-8752-P) for financial support.Single molecular switches are basic device elements in organic electronics. The pentacene analogue anthradithiophene (ADT) shows a fully reversible binary switching between different adsorption conformations on a metallic surface accompanied by a charge transfer. These transitions are activated locally in single molecules in a low-temperature scanning tunneling microscope . The switching induces changes between bistable orbital structures and energy level alignment at the interface. The most stable geometry, the “off” state, which all molecules adopt upon evaporation, corresponds to a short adsorption distance at which the electronic interactions of the acene rings bend the central part of the molecule toward the surface accompanied by a significant charge transfer from the metallic surface to the ADT molecules. This leads to a shift of the lowest unoccupied molecular orbital down to the Fermi level (EF). In the “on” state the molecule has a flat geometry at a larger distance from the surface; consequently the interaction is weaker, resulting in a negligible charge transfer with an orbital structure resembling the highest occupied molecular orbital when imaged close to EF. The potential barrier between these two states can be overcome reversibly by injecting charge carriers locally into individual molecules. Voltage-controlled current traces show a hysteresis characteristic of a bipolar switching behavior. The interpretation is supported by first-principles calculations.PostprintPeer reviewe

Remotely controlled isomer selective molecular switching

Nonlocal addressing—the “remote control”—of molecular switches promises more efficient processing for information technology, where fast speed of switching is essential. The surface state of the (111) facets of noble metals, a confined two-dimensional electron gas, provides a medium that enables transport of signals over large distances and hence can be used to address an entire ensemble of molecules simultaneously with a single stimulus. In this study we employ this characteristic to trigger a conformational switch in anthradithiophene (ADT) molecules by injection of hot carriers from a scanning tunneling microscope (STM) tip into the surface state of Cu(111). The carriers propagate laterally and trigger the switch in molecules at distances as far as 100 nm from the tip location. The switching process is shown to be long-ranged, fully reversible, and isomer selective, discriminating between cis and trans diastereomers, enabling maximum control.PostprintPeer reviewe

Electric-field-driven direct desulfurization

The ability to elucidate the elementary steps of a chemical reaction at the atomic scale is important for the detailed understanding of the processes involved, which is key to uncover avenues for improved reaction paths. Here, we track the chemical pathway of an irreversible direct desulfurization reaction of tetracenothiophene adsorbed on the Cu(111) closed-packed surface at the submolecular level. Using the precise control of the tip position in a scanning tunneling microscope and the electric field applied across the tunnel junction, the two carbon–sulfur bonds of a thiophene unit are successively cleaved. Comparison of spatially mapped molecular states close to the Fermi level of the metallic substrate acquired at each reaction step with density functional theory calculations reveals the two elementary steps of this reaction mechanism. The first reaction step is activated by an electric field larger than 2 V nm–1, practically in absence of tunneling electrons, opening the thiophene ring and leading to a transient intermediate. Subsequently, at the same threshold electric field and with simultaneous injection of electrons into the molecule, the exergonic detachment of the sulfur atom is triggered. Thus, a stable molecule with a bifurcated end is obtained, which is covalently bound to the metallic surface. The sulfur atom is expelled from the vicinity of the molecule.PostprintPeer reviewe

Chiral and catalytic effects of site-specific molecular adsorption

Open access funded by Max Planck Society. The authors acknowledge the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy-EXC-2123 Quantum Frontiers - 390837967; Core program PC2-PN23080202 and the PN-III-P2-2.1-PED-2021-0378 (contract no. 575PED/2022) granted projects, financed by the Romanian Ministry of Research, Innovation and Digitalization/UEFISCDI; and the generous allocation of computer time at the computing center of Donostia International Physics Center and at the Red Española de Supercomputación (project QHS-2021-2-0019). A.A. acknowledges support from Project No. PID2019-103910GB-I00, funded by MCIN/AEI/10.13039/501100011033/ and FEDER Una manera de hacer Europa, and Project No. IT-1527-22 funded by the Basque Government.The changes of properties and preferential interactions based on subtle energetic differences are important characteristics of organic molecules, particularly for their functionalities in biological systems. Only slightly energetically favored interactions are important for the molecular adsorption and bonding to surfaces, which define their properties for further technological applications. Here, prochiral tetracenothiophene molecules are adsorbed on the Cu(111) surface. The chiral adsorption configurations are determined by Scanning Tunneling Microscopy studies and confirmed by first-principles calculations. Remarkably, the selection of the adsorption sites by chemically different moieties of the molecules is dictated by the arrangement of the atoms in the first and second surface layers. Furthermore, we have investigated the thermal effects on the direct desulfurization reaction that occurs under the catalytic activity of the Cu substrate. This reaction leads to a product that is covalently bound to the surface in chiral configurations.Publisher PDFPeer reviewe

Controlling single molecule conductance by a locally induced chemical reaction on individual thiophene units

The authors acknowledge the Emmy-Noether-Program of the Deutsche Forschungsgemeinschaft, the SFB 767, Core Program PN19-03 (contract number 21 N/08.02.2019) founded by the Romanian Ministry of Research and Innovation, Basque Departamento de Universidades e Investigación (grant no. IT-756-13), the Spanish Ministerio de Economía y Competitividad (grant no. FIS2013-48286-C2-8752-P and FIS2016-75862-P) andthe Operational Programme Research, Development and Education financed by European Structural and Investment Funds and the Czech Ministry of Education, Youth and Sports (Project No. SOLID21 CZ.02.1.01/0.0/0.0/16_019/0000760).Among the prerequisites for the progress of single‐molecule‐based electronic devices are a better understanding of the electronic properties at the individual molecular level and the development of methods to tune the charge transport through molecular junctions. Scanning tunneling microscopy (STM) is an ideal tool not only for the characterization, but also for the manipulation of single atoms and molecules on surfaces. The conductance through a single molecule can be measured by contacting the molecule with atomic precision and forming a molecular bridge between the metallic STM tip electrode and the metallic surface electrode. The parameters affecting the conductance are mainly related to their electronic structure and to the coupling to the metallic electrodes. Here, the experimental and theoretical analyses are focused on single tetracenothiophene molecules and demonstrate that an in situ‐induced direct desulfurization reaction of the thiophene moiety strongly improves the molecular anchoring by forming covalent bonds between molecular carbon and copper surface atoms. This bond formation leads to an increase of the conductance by about 50 % compared to the initial state.Publisher PDFPeer reviewe

Lyrebird [TM]: Developing Spoken Dialog Systems Using Examples

An early release software product for the rapid development of spoken dialog systems SDS's), known as Lyrebird [TM] [1][2][3], will be demonstrated that makes use of grammatical inference to build natural language, mixed initiative, speech recognition applications. The demonstration will consist of the presenter developing a spoken dialog system using Lyrebird [TM], and will include a demonstration of some features that are still in the prototype phase

Fast Molecular Compression by a Hyperthermal Collision Gives Bond-Selective Mechanochemistry

Using electrospray ion beam deposition, we collide the complex molecule Reichardt’s Dye (C41H30NO+) at low, hyperthermal translational energy (2 - 50 eV) with a Cu(100) surface and image the outcome at single-molecule level by scanning tunneling microscopy. We observe bond-selective reaction induced by the translational kinetic energy. The collision impulse compresses the molecule and bends specific bonds, prompting them to react selectively. This dynamics drives the system to seek thermally inaccessible reactive pathways, since the compression timescale (sub-ps) is much shorter than the thermalization timescale (ns), thereby yielding reaction products that are unobtainable thermally

Next-generation sequencing: A challenge to meet the increasing demand for training workshops in Australia

The widespread adoption of high-throughput next-generation sequencing (NGS) technology among the Australian life science research community is highlighting an urgent need to up-skill biologists in tools required for handling and analysing their NGS data. There is currently a shortage of cutting-edge bioinformatics training courses in Australia as a consequence of a scarcity of skilled trainers with time and funding to develop and deliver training courses. To address this, a consortium of Australian research organizations, including Bioplatforms Australia, the Commonwealth Scientific and Industrial Research Organisation and the Australian Bioinformatics Network, have been collaborating with EMBL-EBI training team. A group of Australian bioinformaticians attended the train-the-trainer workshop to improve training skills in developing and delivering bioinformatics workshop curriculum. A 2-day NGS workshop was jointly developed to provide hands-on knowledge and understanding of typical NGS data analysis workflows. The road show–style workshop was successfully delivered at five geographically distant venues in Australia using the newly established Australian NeCTAR Research Cloud. We highlight the challenges we had to overcome at different stages from design to delivery, including the establishment of an Australian bioinformatics training network and the computing infrastructure and resource development. A virtual machine image, workshop materials and scripts for configuring a machine with workshop contents have all been made available under a Creative Commons Attribution 3.0 Unported License. This means participants continue to have convenient access to an environment they had become familiar and bioinformatics trainers are able to access and reuse these resources.Nathan S.Watson-Haigh, Catherine A. Shang, Matthias Haimel, Myrto Kostadima, Remco Loos, Nandan Deshpande, Konsta Duesing, Xi Li, Annette McGrath, Sean McWilliam, Simon Michnowicz, Paula Moolhuijzen, Steve Quenette, Jerico Nico De Leon Revote, SonikaTyagi and Maria V. Schneide