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Microfluidics in Planar Microchannels: Synthesis of Chemical Compounds On-Chip.
No full textMicroreactors are a wide class of devices that are currently playing a prominent role in several research fields such as biology, medicine, food chemistry, environmental analysis, up to the production of compounds in organic chemistry. Several typologies of microreactors have been produced with tubular or planar shapes, of different materials and designs. In this chapter, an overview of planar microchannel-based microreactors and their application to organic chemistry is given. Initially, after recalling the main theoretical parameters of microfluidics, an introduction of the proposed technology and the main requirements to perform mixing, which is essential to perform chemical synthesis on-chip, is presented. Silicon and glass microreactors, the most common planar systems for organic chemistry, are described with the aim of pointing out the most important parameters to be taken into consideration in the planning of a specific microreactor to be used for mixing, purification or crystallization of chemicals at the microscale. Then, several applications of initially described microreactors to organic chemistry for research applications are given. In the next section, the use of planar microchannel microreactors in the field of radiochemistry is reported. The radiopharmaceutical application is not casual, being a sector in which the microreactor technology is very promising, due to the need of quickly producing small and fresh amounts of products in a controlled environment. Finally, for completeness, other approaches beyond planar microchannels are mentioned: mesoreactors towards industrial level synthesis and micro-vessels for radiochemistry. © Springer International Publishing Switzerland 201
New insights into phase distribution, phase composition and disorder in Y2(Zr,Sn)2O7 ceramics from NMR spectroscopy
No full textA combination of 89Y and 119Sn NMR spectroscopy and DFT calculations are used to investigate phase evolution, local structure and disorder in Y2Zr2−xSnxO7 ceramics, where a phase change is predicted, from pyrochlore to defect fluorite, with increasing Zr content. The ability of NMR to effectively probe materials that exhibit positional and compositional disorder provides insight into the atomic-scale structure in both ordered and disordered phases and, by exploiting the quantitative nature of the technique, we are able to determine detailed information on the composition of the phase(s) present and the average coordination number (and next-nearest neighbour environment) of the cations. In contrast to previous studies, a more complex picture of the phase variation with composition emerges, with single-phase pyrochlore found only for the Sn end member, and a single defect fluorite phase only for x = 0 to 0.6. A broad two-phase region is observed, from x = 1.8 to 0.8, but the two phases present have very different composition, with a maximum of 13% Zr incorporated into the pyrochlore phase, whereas the composition of the defect fluorite phase varies throughout. Preferential ordering of the anion vacancies in the defect fluorite phase is observed, with Sn only ever found in a six-coordinate environment, while remaining vacancies are shown to be more likely to be associated with Zr than Y. Our findings are then discussed in the light of those from previous studies, many of which utilize diffraction-based approaches, where, in most cases, a single phase of fixed composition has been assumed for the refinement procedure. The significant and surprising differences encountered demonstrate the need for complementary approaches to be considered for a detailed and accurate picture of both the long- and short-range structure of a solid to be achieved. © Royal Society of Chemistry 201
Energy and temperature dependence of rigid unit modes in AlPO4-5
No full textFor structures that can be treated as networks of rigid, corner-connected polyhedra, the dominant distortion modes can be described by so-called rigid unit modes that are close to zero frequency. This type of behaviour is common in zeolitic/zeotypic materials such as the AlPO4 family of compounds and has been suggested by some authors to play a significant role in molecular diffusion within the pores of such compounds. We explore the energy and temperature dependence of these modes in AlPO4-5 using inelastic neutron scattering and heat capacity measurements. Ab initio based computational modelling is also used to assign the observed dynamic behaviour to rigid unit modes. We observe that these rigid unit modes persist down to very low temperatures and show no signs of freezing out.© 2015, the Owner Societies
Stable water isotope and surface heat flux simulation using ISOLSM: Evaluation against in-situ measurements
No full textThe stable isotopes of water are useful tracers of water sources and hydrological processes. Stable water isotope-enabled land surface modeling is a relatively new approach for characterizing the hydrological cycle, providing spatial and temporal variability for a number of hydrological processes. At the land surface, the integration of stable water isotopes with other meteorological measurements can assist in constraining surface heat flux estimates and discriminate between evaporation (E) and transpiration (T). However, research in this area has traditionally been limited by a lack of continuous in-situ isotopic observations. Here, the National Centre for Atmospheric Research stable isotope-enabled Land Surface Model (ISOLSM) is used to simulate the water and energy fluxes and stable water isotope variations. The model was run for a period of one month with meteorological data collected from a coastal sub-tropical site near Sydney, Australia. The modeled energy fluxes (latent heat and sensible heat) agreed reasonably well with eddy covariance observations, indicating that ISOLSM has the capacity to reproduce observed flux behavior. Comparison of modeled isotopic compositions of evapotranspiration (ET) against in-situ Fourier Transform Infrared spectroscopy (FTIR) measured bulk water vapor isotopic data (10 m above the ground), however, showed differences in magnitude and temporal patterns. The disparity is due to a small contribution from local ET fluxes to atmospheric boundary layer water vapor (∼1% based on calculations using ideal gas law) relative to that advected from the ocean for this particular site. Using ISOLSM simulation, the ET was partitioned into E and T with 70% being T. We also identified that soil water from different soil layers affected T and E differently based on the simulated soil isotopic patterns, which reflects the internal working of ISOLSM. These results highlighted the capacity of using the isotope-enabled models to discriminate between different hydrological components and add insight into expected hydrological behavior. © 2015, Elsevier B.V
Timing, magnitude and effects of late Holocene sea level drawdown on island habitability, Aitutaki, Cook Islands
No full textGeologist Bill Dickinson argued that prior to late Holocene sea level fall, in many Pacific island settings low-lying islands were awash, shallow nearshore environments were restricted and human settlement was constrained or sometimes impossible. Stable coastlines and islets of modern configuration only developed after the “cross-over date”, when declining high-tide levels fell below mid-Holocene low-tide levels, a regionally variable process. We evaluate evidence from the almost-atoll of Aitutaki, Cook Islands against this model, providing: (1) a local late Holocene sea level reconstruction including nine U/Th-dated microatolls; (2) 22 new AMS dates on human activities, many from small, low-lying offshore islets; and (3) elevation data for 14C-dated cultural deposits on three islets. Our results include an early first millennium sea level position 0.74–0.97 m (± 0.126) above modern height-of-living-corals, an eighth to eleventh century AD minimum relative to the long-term trend, and a sea level rise peaking in the mid-fourteenth to sixteenth centuries. This reconstruction, combined with twelfth century AD Cocos nucifera charcoal, informs on the timing and distribution of human activities across Aitutaki's evolving land and seascapes and sea level impacts. While our findings do not contradict Dickinson's model of sea level constrained island settlement, other explanations cannot be excluded. © 2016, Oceania Publications
Loss and gain of carbon during char degradation
No full textWe report results of a study examining controls on the degradation of chars produced at 300, 400 and 500 °C from radiocarbon-free wood, deployed for three years in a humid tropical rainforest soil in north Queensland, Australia. The chars were subjected to four treatments (i) no litter (ii) covered by leaf litter, (iii) covered by limestone chips to alter local pH, and (iv) covered by limestone chips mixed with leaf litter. Radiocarbon, stable isotope and proximate analyses indicate significant ingress of exogenous (environmental) carbon and mineral material, strongly correlated with loss of indigenous (char) carbon from the samples. While indigenous carbon losses over three years were generally <8% for the char produced at 500 °C char under any treatment, chars formed at lower temperatures lost 5–22% of indigenous carbon accompanied by ingress of up to 7.5% modern exogenous carbon. The data provide clear evidence of a direct link between the ingress of exogenous carbon, likely at least partly due to microbial colonization, and the extent of char decomposition. Failure to account for the ingress of exogenous carbon will lead to a significant under-estimate of the rate of char degradation. © 2016, Elsevier Ltd
Effects of fluorine and chromium doping on the performance of lithium-rich Li1+xMO2 (M = Ni, Mn, Co) positive electrodes
No full textLithium-rich metal oxides Li1+zMO2 (M = Ni, Co Mn, etc.) are promising positive electrode materials for high-energy lithium-ion batteries, with capacities of 250-300 mAh·g-1 that closely approach theoretical intercalation limits. Unfortunately, these materials suffer severe capacity fade on cycling, among other performance issues. While ion substitution can improve the performance of many of these materials, the underlying mechanisms of property modification are not completely understood. In this work we show enhanced performance of the Li1+zMO2 electrode, consisting of Li2MnO3 (with C2/m space group) and LiMO2 (with R3m space group) phases, and establish the effects of cationic and anionic substitution on the phase and structure evolution underpinning performance changes. While the undoped material has a high capacity of ∼270 mAh·g-1, only 79% of this remains after 200 cycles. Including ∼2% Cr in the material, likely at the R3m metal (3a) site, improved cycle performance by ∼13%, and including ∼5% F in the material, likely at the R3m oxygen (6c) site, enhanced capacity by ∼4-5% at the expense of a ∼12% decline in cycle performance. Moreover, Cr doping enhances energy density retention by ∼13%, and F doping suppresses this by 17%. We find that these changes arise by different mechanisms. Both anionic and cationic substitution promote faster Li diffusion, by 48% and 20%, respectively, as determined using cyclic voltammetry and leading to better rate performance. Unlike anionic substitution, cationic substitution enhances structural stability at the expense of some capacity, by suppressing lattice distortion during Li insertion and extraction. This work implicates strategic cationic-anionic codoping for enhanced electrochemical performance in lithium-rich layered metal-oxide phases. © 2017 American Chemical Society
Crossing thresholds – human responses to tsunami forcing in the Pacific
No full textThe 11 March 2011 Tohoku-oki tsunami caused widespread devastation to coastal communities in Japan. This event however was merely the latest in a long line of similar occurrences throughout the Pacific over time. All the recent large tsunamis have had their predecessors, and a growing database of palaeotsunamis in the Pacific suggests that several past events have been either similar in magnitude or greater than their historical counterparts. Not only are we gathering data concerning Pacific palaeotsunamis but we are also identifying contemporaneous punctuated histories of changing human settlement patterns across the Pacific. In particular, the almost two millennia 'long pause' in eastward Polynesian migration and the abandonment of long distance sea-voyaging in the 15th century. It is suggested that large palaeotsunamis and their generating mechanisms forced major societal responses. Given the unquestioned impacts of recent tsunamis on human societies, it is reasonable to suggest that past societal responses can be used as proxies for contemporaneous environmental forcing in those parts of the world where independent evidence of the effects of these events is still being gathered. In the Pacific there are a range of responses that extend well beyond the abandonment of long distance sea-voyaging such as the outbreak of region-wide conflict and the associated abandonment of settlements in exposed (coastal) locations. The contemporaneity of these effects across a vast region requires a driver that is external to particular island groups. Given that this must have impacted coastal resources severely and enduringly, the only possibility is that this driver was of oceanic origin. This hypothesis is compelling when considered alongside the growing database of more conventional lines of evidence. The question therefore is how well are similar threshold responses recognised throughout the World? Are there similar region-wide responses that have been pigeonholed under the more prosaic interpretations of archaeological dogma
The Centre for Accelerator Science at ANSTO
Get PDFIn 2009, the Federal government provided funding of $25m to ANSTO through the Education Investment Fund, to build state-of-the-art applied accelerator science facilities, with the
primary aim of providing world-leading accelerator mass spectrometry (AMS) and ion beam analysis (IBA) facilities. New buildings are now under construction and Building plans are now well advanced, and two new accelerators are on order with National Electrostatics Corporation, USA.
The 1MV AMS accelerator system is designed with the capability to perform high efficiency,
high precision AMS analysis across the full mass range. Large beam-optical acceptance will
ensure high quality and high throughput radiocarbon measurements. High mass resolution
analyzers, at low and high energy, coupled to a novel fast isotope switching system, will
enable high quality analysis of actinide radioisotopes.
The 6MV tandem accelerator will be instrumented with a wide range of AMS, IBA and ion irradiation facilities. The three ion sources include hydrogen and helium sources, and a MCSNICS
sputter source for solid materials. The AMS facility has end stations for (i) a gasabsorber detector for 10Be analysis, (ii) a time-of-flight detector, (iii) a gas-filled magnet and(iv) a general use ionization detector suited to 36Cl and other analyses. Initially, there will be
four IBA beamlines, including a new ion beam microprobe currently on order with Oxford
Microbeams. The other beamlines will include an on-line ion implanter, nuclear reaction
analysis and elastic recoil detection analysis facilities. The beam hall layout allows for future
expansion, including the possibility of porting the beam to the existing ANTARES beam hall for simultaneous irradiation experiments.Two buildings are currently under construction, one for the new accelerators and the other for
new chemistry laboratories for AMS and mass spectrometry facilities. The AMS chemistry
labs are planned in two stages, with the new radiocarbon labs to come in the second phase of work
Transport modelling and inversions for the interpretation of greenhouse gas measurements
No full textThe interpretation of greenhouse gas measurements can be aided by forward transport modelling while greenhouse gas fluxes can be estimated using atmospheric inversions. Here we (a) provide an update on a study of methane model simulations at Cape Grim and their use for determining methane fluxes from SE Australia and (b) show results from some recent CO2 inversions. Observed and model simulated non-baseline methane concentrations at Cape Grim have been compared (Loh et al., 2014). Two atmospheric models (CCAM and ACCESS) and six different methane emission scenarios are used. To minimise the influence of transport model errors on the analysis, deviations of Cape Grim methane concentration above baseline have been compared to coincident radon measurements. This methane to radon ratio shows a clear seasonal signal implying seasonal variations in methane emissions from SE Australia relative to a more temporally uniform radon flux. The ability of the model simulations to match the observed seasonality is dependent on the choice of methane emission scenario but all scenarios underestimate the observed methane to radon ratio in spring. We find that the most likely explanation for the discrepancy is wetland emissions that are too small in some emission scenarios or at the wrong time of year in other scenarios. CO2 inversions have been run recently for two purposes. The first is an international comparison of greenhouse gas inversions focussed on South, East and South East Asia. We have submitted a CCAM inversion for 1993-2012 using a fixed year of winds and expect to submit a second inversion with interannually varying winds. The second purpose is to use a CO2 inversion to estimate the magnitude of regional fluxes that are required to fit the larger difference in annual mean CO2 concentration between Mauna Loa and Cape Grim over recent years