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Formation of hydrated layers in PMMA thin films in aqueous solution
No full textNeutron reflectometry (NR) measurements have been made on thin (70–150 Å) poly(methylmethacrylate) (PMMA) films on Si/SiOx substrates in aqueous conditions, and compared with parameters measured using ellipsometry and X-Ray reflectometry (XRR) on dry films. All techniques show that the thin films prepared using spin-coating techniques were uniform and had low roughness at both the silicon and subphase interfaces, and similar surface energetics to thicker PMMA films. In aqueous solution, NR measurements at 25 °C showed that PMMA forms a partially hydrated layer at the SiOx interface 10 Å under the film, while the bulk film remains intact and contains around 4% water. Both the PMMA film layer and the sublayer showed minimal swelling over a period of 24 h. At 50 °C, PMMA films in aqueous solution roughen and swell, without loss of PMMA material at the surface. After cooling back to 25 °C, swelling and roughening increases further, with loss of material from the PMMA layer. © 2017 Elsevier B.V
Bioprocessing and immobilization of cell envelope proteinases from Lactobacillus delbrueckii subsp. lactis 313, for protein degradation
No full textProteolytic enzymes are a useful class of biomolecules due to their ubiquity and the plethora of physiological roles they play in living systems. These enzymes are esponsible for the breakdown of proteins to peptides and have several applications in food, pharmaceuticals, diagnostics, photographic, waste treatments, bioremediation, and in the textile industry. Cell-envelope proteinases (CEPs) are a special class of industrially relevant extracellular proteolytic enzymes obtained from lactic acid bacteria. In the food industry, CEPs have been known to improve the texture and organoleptic characteristics of dairy products and also have the potential to release bioactive peptides encrypted in dairy proteins. However, research is lacking on detailed optimisation of fermentation parameters essential for the generation of CEPs of organisms in the genera Lactobacillus. The proteolytic system and CEPs from lactobacilli are also not fully characterized and further; the use of free CEPs in industrial processes is currently suboptimal and presents certain drawbacks such as poor operational stability. Regulatory requirements such as that of the United Nations Food and Agriculture Organization demand the separation of enzymes from certain food and pharmaceutical products when enzymes are involved in the production process. This is difficult to do, if not impossible, for soluble enzymes. These make soluble CEP-based process economically unfeasible, especially when combined with the usual challenges associated with the use of most soluble enzymes, i.e. high cost, poor stability, and lack of multiple utility. This study therefore explored the production of CEPs expressed in Lactobacillus delbrueckii subsp. lactis 313 (LDL 313) in a cost effective manner. Immobilization techniques were also deployed for the design and production of cheap, reusable and stable biocatalysts of LDL 313 CEPs, for use in protein degradation. LDL 313 was an understudied bacterium, thus, initial work considered it’s growth characterization for the purpose of CEP production. As expected, cell growth was dependent on fermentation conditions such as temperature and initial pH. However, cell growth rates under anaerobic conditions were markedly higher than growth under microaerophilic conditions. The caseinolytic specificity of LDL 313 CEPs was also identified. Being proteolytic for for β -casein and κ-casein, CEPs from LDL 313 were classified as class I CEP (CEPI)of the lactococcal proteinase classification system. Studies were also done to optimize the batch culture conditions that enhance CEPs expression. Using a combination of conventional sequential techniques, the batch growth conditions (inoculum concentration, culture agitation speed, incubation temperature, starting pH, and carbon/nitrogen ratio of production medium) were optimized, for the first time, to ensure profuse CEP production in LDL 313. Moreover, since CEPs are cell-envelope-bound enzymes they are relatively easy to extract from lactic acid bacteria cells. When CEP extraction was studied with different extraction agents, 5 M LiCl was observed to be the most suitable. Sub-cellular localization studies also showed that about 95% of CEP activity was detected in cell-wall fractions implying that CEPs in LDL 313 are located in the peptidoglycan cell-wall. Together, these results provide insights into conditions and parameters that ensure optimum cell growth, high CEP yields and extraction protocol to release high levels of CEPs. Following this, two different strategies for making stable biocatalysts from CEPs were explored, namely, the immobilization of enzymes onto a fabric carrier, and, cross-linking enzyme aggregates. Firstly, CEPs and trypsin (as a model enzyme in comparison with CEP) were immobilized in a simple, cheap and quick approach onto polyester via support functionalization with ethylene diamine and cross-linking with glutaraldehyde. Secondly, cross-linked enzyme aggregates were prepared from CEPs via coupled precipitation/cross-linking with ammonium sulphate and glutaraldehyde respectively. The immobilized biocatalysts had good activity characteristics and properties. For example, immobilized enzymes had good recovered activity (85% for CEP immobilized on polyester; and ~ 22% and ~ 41% respectively for CLCEPA prepared in the absence and presence of proteic feeders). They also had the ability to be used at other than usual conditions such as high temperatures (40 - 70 °C); and organic solvent conditions (CLCEPA still retained activity in 20 – 100 % ethanol/buffer mixtures). Both immobilized enzymes had the ability to be recycled (CLCEPA retained ~ 22% initial activity whereas CEPs immobilized on polyester retained ~ 41% when recycled 5 times. Additionally, both immobilized biocatalyst had proteolytic properties, effectively hydrolysing several macromolecular proteins substrates (casein, bovine serum albumin, whey protein isolate, β-lactoglobulin, skimmed-milk protein and chicken egg albumin). The immobilized CEPs biocatalysts could be utilized for protein degradation to obtain two streams of industrially relevant products namely protein/peptide-rich product mixture from casein; and whey protein/peptide-based surface active foams – both of which can be used for food applications. In summary, the potential of Lactobacillus delbrueckii subsp. lactis 313 to produce cell-envelope proteinases was explored and the development of stable forms of these enzymes was studied, optimized and tested with several food proteins. The outcome is a whole systems approach to developing and establishing an enzyme framework for protein degradation in a cheap cost-effective manner. This therefore has the potential for various industrial applications in protein degradation and/or peptide production
Large throughput analysis of crystal structures for identification of promising li-ion battery materials
No full textIt is a popular research pursuit to improve the properties of rechargeable batteries. The motivation for this research is to make rechargeable batteries more suitable for powering electric vehicles as well as increasing the operating time of portable electronics. Cheaply storing large amounts of electricity from renewable energy sources such as solar and wind as well as providing grid electricity buffering for electricity generation would also help offset peak electricity demand.
Unfortunately, current battery materials are experiencing a plateau in performance improvements due to the maximum intrinsic capacity and cost of commonly used cathode materials. As a result, further research into improving battery performance will require either a change in battery technology or the discovery of a new cathode material with different or superior properties.
All active battery materials must possess ionic conductivity as the electrochemical reactions which produce electrical energy for rechargeable batteries operate by transferring electrons and mobile ions between two structures of different energies. It is often a relatively straightforward process to modify the electrical and mechanical properties of existing cathode materials using chemical doping, mechanical grinding or nanostructuring in order to optimise their properties. However, it is usually not possible by any type of processing to impart any significant ionic conductivity to a material which it does not already possess. As a result, this study focuses on searching for new intercalation cathode materials and solid ionic conductors by searching for new materials which have high ionic conductivity.
The Inorganic Crystal Structure Database (ICSD) contains crystal structural details about most currently known inorganic crystalline materials (~166,000) and most of these have never been tested to determine their ionic conductivity. The two main methods available to survey the ionic conductivity of materials are experimental and computational.
Unfortunately, experimental methods are not suitable for surveying very large numbers of different types of materials as this would be very costly and time consuming. Various accurate computational methods are also not suited to large surveys due to the complexity and time consumption of these methods. However, several computational methods still remain suitable for use as a large survey tool.
The Bond Valence Sum Map (BVSM) and Bond Valence Energy Landscape (BVEL) methods were selected to perform a computational survey of a large number of known oxide materials from the ICSD to approximate their ionic conductivity
Biking for research [website]
No full textRadon is an excellent tracer of other gases because it is unreactive and its short half-life (3.8 days) prevents any significant build-up in the atmosphere over long time scales.
The KNMI (Royal Netherlands Meteorological Institute) Cabauw Experimental Site for Atmospheric Research with its 213m meteorological tower has been a focus of experimental boundary layer research since the 1970s.
Over the years, the site has expanded the scope of its research applications to include land-atmosphere interactions. In 2006 and 2007, ANSTO designed and built two 1500L detectors for 222Rn radon observations which were installed on the Cabauw tower, drawing air from 200m and 20m AGL, respectively.
These observations are an important part of a larger program to characterise regional emissions of greenhouse gases and other pollutants, to evaluate the performance of climate and atmospheric transport models, and to quantify turbulent mixing processes in the lower atmosphere.
Radon gas is emitted naturally from soils, where it is formed by radioactive transformation of 226Ra radium as part of the decay chain of primordial 238U uranium in the earth’s crust. The strength of radon emissions from the land surface into the atmosphere depends on the soil mineralogy and porosity, and to a lesser extent also varies with changes in atmospheric pressure and soil moisture.
As the oceanic radon flux is effectively negligible (at least 100 times smaller than that from land), significant radon concentrations measured in air samples indicate that the air mass has been in contact with land within the previous few weeks.
The use of radon as a tracer in atmospheric and climate research is limited by large uncertainties in the magnitude and distribution of the radon flux density over the Earth’s surface. Maps of radon emissions have previously been generated by assigning a constant value to large geographical areas (sometimes reducing at high latitudes according to known changes in snow and ice coverage), or from aerial surveys using terrestrial gamma radiation as a proxy.
The only direct method of measuring radon exhalation from soil is by using an accumulation chamber. Such measurements are rare, and the new ANSTO designed and built radon emanometer has been uniquely designed with this purpose in mind.
The ANSTO portable accumulation chamber allows radon to accumulate in a chamber placed over the soil. The evolution of the measured radon concentration within the chamber is continuously monitored, and the surface flux at that location can then be estimated after a given time period from the integrated measurements.
Equipped with the ANSTO portable emanometer, a shovel, GPS locator, soil type maps of the area and the soil moisture probe, Sylvester Werczynski moved around the Cabauw tower on a three-wheeled pushbike that he hired locally.
“The pushbike was actually the most practical means to access the various measurement locations, as the survey area consisted of a network of flat green polders with thousands of canals, windmills and farm houses - a typical country landscape in the Netherlands,”
says Werczynski.
- See more at: http://www.ansto.gov.au/AboutANSTO/MediaCentre/News/ACS049714#sthash.thIt2IZi.dpu
Measurement of fallout radionuclides, 239,240Pu and 137Cs, in soil and creek sediment: Sydney Basin, Australia
No full textSoil and sediment samples from the Sydney basin were measured to ascertain fallout radionuclide activity concentrations and atom ratios. Caesium-137 (137Cs) was measured using gamma spectroscopy, and plutonium isotopes (239Pu and 240Pu) were quantified using accelerator mass spectrometry (AMS).
Fallout radionuclide activity concentrations were variable ranging from 0.6 to 26.1 Bq/kg for 137Cs and 0.02–0.52 Bq/kg for 239+240Pu. Radionuclides in creek sediment samples were an order of magnitude lower than in soils. 137Cs and 239+240Pu activity concentration in soils were well correlated (r2 = 0.80) although some deviation was observed in samples collected at higher elevations. Soil ratios of 137Cs/239+240Pu (decay corrected to 1/1/2014) ranged from 11.5 to 52.1 (average = 37.0 ± 12.4) and showed more variability than previous studies.
240Pu/239Pu atom ratios ranged from 0.117 to 0.165 with an average of 0.146 (±0.013) and an error weighted mean of 0.138 (±0.001). These ratios are lower than a previously reported ratio for Sydney, and lower than the global average. However, these ratios are similar to those reported for other sites within Australia that are located away from former weapons testing sites and indicate that atom ratio measurements from other parts of the world are unlikely to be applicable to the Australian context. © 2015, Elsevier Ltd
Ice core measurements of 14CH4 show no evidence of methane release from methane hydrates or old permafrost carbon during a large warming event 11,600 years ago
Get PDFThawing permafrost and marine methane hydrate destabilization in the Arctic and elsewhere have been proposed as large sources of methane to the atmosphere in the future warming world. To evaluate this hypothesis it is useful to ask whether such methane releases happened during past warming events. The two major abrupt warming events of the last deglaciation, Oldest Dryas - Bølling (OD-B, ≈ 14,500 years ago) and Younger Dryas - Preboreal (YD-PB; ≈11,600 years ago), were associated with large (up to 50%) increases in atmospheric methane (CH4) concentrations. The sources of these large warming-driven CH4 increases remain incompletely understood, with possible contributions from tropical and boreal wetlands, thawing permafrost as well as marine CH4 hydrates. We present new measurements of 14C of paleoatmospheric CH4 over the YD-PB transition from ancient ice outcropping at Taylor Glacier, Antarctica. 14C can unambiguously identify CH4 emissions from "old carbon" sources, such as permafrost and CH4 hydrates. The only prior study of paleoatmospheric 14CH4 (from Greenland ice) suggested that wetlands were the main driver of the YD-PB CH4 increase, but the results were weakened by an unexpected and poorly understood 14CH4 component from in situ cosmogenic production directly in near-surface ice. In this new study, we have been able to accurately characterize and correct for the cosmogenic 14CH4 component. All samples from before, during and after the abrupt warming and associated CH4 increase yielded 14CH4 values that are consistent with 14C of atmospheric CO2 at that time, indicating a purely contemporaneous methane source. These new measurements rule out the possibility of large CH4 releases to the atmosphere from methane hydrates or old permafrost carbon in response to the large and rapid YD-PB warming. To the extent that the characteristics of the YD-PB warming are comparable to those of the current anthropogenic warming, our measurements suggest that large future atmospheric methane increases from old carbon sources in the Arctic are unlikely. Instead, our measurements indicate that global wetlands will likely respond to the warming with increased methane emissions. © European Geosciences UnionYellow Posters session, Y7
Microstructural design for thermal creep and radiation damage resistance of titanium aluminide alloys for high-temperature nuclear structural applications
No full textMicrostructure plays an important role in strengthening of metallic materials. Various microstructures can be developed in titanium aluminide (TiAl) alloys, which can enable different combinations of properties for various extreme environments in advanced nuclear systems. In the present paper the mechanisms for microstructural strengthening and the effects of various microstructural features on thermal creep and radiation damage resistance of TiAl alloys are reviewed and compared. On the basis of the results, the evidence-based optimum microstructure for the best combination of thermal creep and radiation damage resistance of TiAl alloys is proposed. The heat treatment processes for manufacturing the optimal microstructure are also discussed. © 2014, Elsevier Ltd
Towards improvement in Al Assay in quartz for in situ cosmogenic 26Al exposure dating
No full textAccuracy and precision in the measurement of natural aluminium abundances in quartz can affect the reliability of 26Al exposure dating and 26Al/10Be burial dating. At ANSTO, aliquots extracted from the HF solutions of dissolved quartz are treated in our laboratory, whereas ICP-OES analysis is performed at a commercial laboratory. The long-term inter-run reproducibility of our in-house standards show a limiting precision in Al measurements of 3-4% (1sigma), which is lower than the claimed precision of Al analysis by ICP-OES. This indicates that unaccounted random errors are incorporated during our aliquot preparation. In this study, we performed several controlled tests to investigate effects of possible inconsistencies and variances during our aliquot preparation procedure. The results indicate that our procedure is robust against any subtle change in the preparation procedure, e.g., fuming temperatures, fuming reagents, and drying conditions. We found that the density of the solutions dispatched for ICP analysis is occasionally variable due to the presence of residual fuming reagents in the solution. A comparison of the results between the calibration curve and standard addition methods show that the former results are consistently lower than the latter by up to ~14%. Similar offsets have been reported by previous studies. The reason for these discrepancies is mostly likely matrix effect, which is not accounted for by the calibration curve method. Further tests by varying matrix with impurities such as HF, HClO4, H2SO4 and Si identified that Si could cause lower offset in Al measurements; however, our ICP solutions are confirmed to be free from Si and the cause of matrix effect remains to be investigated. Hence, care must be taken for the measurement of Al concentrations in quartz by ICP-OES, either by ensuring that matrix effect is fully accounted for or by routinely employing standard additions when required.© The Author
Analysis of compositionally ungraded FGM analogues: Neutron diffraction measurements of residual stress and mechanical testing of pressure sintered Mo-Y2O3 and Mo-Al2O3
No full textFunctionally graded materials (FGMs) are a type of naturally inspired composite materials whose properties (e.g. microstructure, chemical or phase composition) vary over one or more dimensions. The FGMs were first proposed as an advanced engineering material in 1972 and research into application for Biomaterials, Aerospace, Chemical Plants, Mining, and Building material commodities[1, 2] is ever present. Within the nuclear industry FGMs can be engineered to effectively resist corrosion, radiation and are a potential choice for nuclear reactor components e.g. first wall for fusion reactors and fuel pellets. Additionally FGM’s have been proposed as potential plasma facing components (PFC) whereby the PFC would gradually vary from a refractory material (tungsten, plasma face) to a heat sink material (copper, coolant side). In the case of a metal-ceramic FGM, the composite mates the strength and ductility of a metal with the hardness and toughness of a ceramic [3-5]. The authors have sought to elucidate the development of residual stress in FGMs using neutron measurements on the Kowari Strain Scanner, ANSTO for the Mo-Y2O3 and Mo-Al2O3 system. Due to their extreme gradients FGM’s are not optimal for fast neutron measurements due to the high spatial resolution requirements and long measurement times. An alternative approach was employed to examine compositionally ungraded analogues of varying metal-ceramic ratios. All sample were manufactured using constituent powders, mixed and subsequently sintered using a hot press with close monitoring of the sintering curve. Optical microscopy and scanning electron microscopy were used to look at the resultant samples to observe the grain growth and the defect-like cracks attributable to the thermally induced stresses. Relaxation due to micro cracking and micro-fracturing are evaluated in light of the neutron residual stress measurements and mechanical strength measurements of : (a) bending stiffness using a three point bend tests, (b) bulk modulus through GrindoSonic techniques and (c) statistically averaged micro-hardness. Further evaluation of the residual stress is done through comparison between established analytical models, neutron diffraction and preliminary FEA. The major contribution of residual stress are further realised and evaluated in light of the interfacial instabilities present and the appropriate ways to optimise the thermal protection characteristics of a compositional gradient
Chinese puzzle molecule: A 15 hydride, 28 copper atom nanoball
No full textThe syntheses of the first rhombicuboctahedral copper polyhydride complexes [Cu28(H)15(S2CNR)12]PF6 (NR=NnPr2 or aza-15-crown-5) are reported. These complexes were analyzed by single-crystal X-ray and one by neutron diffraction. The core of each copper hydride nanoparticle comprises one central interstitial hydride and eight outer-triangular-face-capping hydrides. A further six face-truncating hydrides form an unprecedented bridge between the inner and outer copper atom arrays. The irregular inner Cu4 tetrahedron is encapsulated within the Cu24 rhombicuboctahedral cage, which is further enclosed by an array of twelve dithiocarbamate ligands that subtends the truncated octahedron of 24 sulfur atoms, which is concentric with the Cu24 rhombicuboctahedron and Cu4 tetrahedron about the innermost hydride. For these compounds, an intriguing, albeit limited, H2 evolution was observed at room temperature, which is accompanied by formation of the known ion [Cu8(H)(S2CNR)6]+ upon exposure of solutions to sunlight, under mild thermolytic conditions, and on reaction with weak (or strong) acids. © 2014, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim