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Origin and spread of wheat in China
No full textWheat was added as a new crop to the existing millet and rice based agricultural systems of China. Here we present 35 radiocarbon ages from wheat seeds collected from 18 sites between western (Xinjiang Province) and eastern (Henan Province) China. The earliest wheat ages cluster around 2100–1800 BCE in northern China's Hexi corridor of Gansu Province, where millet was already a well-established crop. Wheat first appears in Xinjiang and Henan about 300–400 years later, and perhaps a little earlier than this in Xinjiang, and we hypothesize that the likely route of wheat into China was via Russia through Gansu. © 2013, Elsevier Ltd
Negative thermal expansion in LnCo(CN)6 (Ln=La, Pr, Sm, Ho, Lu, Y): mechanisms and compositional trends
No full textNegative thermal expansion (NTE) is a comparatively rare phenomenon that is found in a growing number of materials.1 The discovery of new NTE materials and the elucidation of mechanisms underpinning their behavior is important both in extending the field and enabling tailored thermal expansion properties. NTE has been found throughout a broad family of cyanide coordination frameworks,2 arising from thermal population of low-energy transverse vibrations of the cyanide bridges, which reduce the average metal–metal distances, and thus the lattice parameters, with increasing temperature. More complex mechanisms have been established in metal–organic framework materials, in which both local and long-range modes contribute to NTE.3 The low-energy dynamics of metal-based materials are often modeled in terms of rigid unit modes (RUMs), wherein the metal-centered polyhedra are treated as rigid, with only the linkage being flexible. © 2013, Wiley-Vch Verlag GmbH & Co
The thermophysical properties of calcium and barium zirconium phosphate
No full textThe thermophysical and structural properties of calcium and barium zirconium phosphate ceramics (CZP and BZP) have been investigated for their potential candidacy as actinide hosts for inert matrix fuels (IMF) in nuclear reactors. These phosphate ceramics, which can accommodate minor actinides as well as the resulting fission products, are found to be thermally stable to 1600 °C in air, however they begin to decompose in an inert atmosphere above approximately 1400 °C. The heat capacity, thermal conductivity and bulk thermal-expansion were measured from room temperature up to 1200 °C. Structural changes in this temperature region as well as the anisotropic thermal-expansion behaviour were studied using high-temperature X-ray diffraction. A phase change from R-3 to R-3c was identified for Ba0.5Zr2(PO4)3 near 880 °C. The thermal conductivity for these ceramics at 1000 °C was found to be 1.0 W m−1 K−1, a relatively low thermal conductivity that was increased to 5.0 W m−1 K−1 at 1000 °C for BZP:Ni (25:75 mass ratio) cermet composites.
© 2012, Elsevier Ltd
Aqueous chemical synthesis of Ln2Sn2O7 pyrochlore-structured ceramics
No full textPyrochlore-structured lanthanide stannate ceramic (Ln2Sn2O7) has been synthesized via a new complex precipitation method. A suite of characterization techniques, including FTIR, Raman, X-ray, and electron diffraction as well as nitrogen sorption were employed to investigate the structural evolution of the synthesized and calcined powder. Raman, XRD, and selected area electron diffraction results confirm the presence of the pyrochlore structure after calcination of the powder above 1200°C. TEM imaging shows fine crystallites gradually increased in size from approximately 100 nm to about 500 nm with higher calcination temperatures. Grain growth and powder densification upon increasing the calcination temperature was confirmed by nitrogen sorption results. This aqueous synthetic method provides a simple pathway for the preparation of homogeneous lanthanide stannate ceramics. © 2013, The American Ceramic Society
Paleoclimate studies and natural-resource management in the Murray-Darling Basin I: past, present and future climates
No full textThis paper provides an incisive review of paleoclimate science and its relevance to natural-resource management within the Murray-Darling Basin (MDB). The drought of 1997–2010 focussed scientific, public and media attention on intrinsic climate variability and the confounding effect of human activity, especially in terms of water-resource management. Many policy and research reviews make statements about future planning with little consideration of climate change and without useful actionable knowledge. In order to understand future climate changes, modellers need, and demand, better paleoclimate data to constrain their model projections. Here, we present an insight into a number of existing long-term paleoclimate studies relevant to the MDB. Past records of climate, in response to orbital forcing (glacial–interglacial cycles) are found within, and immediately outside, the MDB. High-resolution temperature records, spanning the last 105 years, exist from floodplains and cave speleothems, as well as evidence from lakes and their associated lunettes. More recently, historical climate records show major changes in relation to El Niño–Southern Oscillation cycles and decadal shifts in rainfall regimes. A considerable body of research currently exists on the past climates of southeastern Australia but, this has not been collated and validated over large spatial scales. It is clear that a number of knowledge gaps still exist, and there is a pressing need for the establishment of new paleoclimatic research within the MDB catchment and within adjacent, sensitive catchments if past climate science is to fulfil its potential to provide policy-relevant information to natural-resource management into the future. © 2013, Taylor & Francis
Residual stress distributions in bi-metal (ferritic to austenitic steel) joints made by laser welding
No full textIn this work, autogenous laser welding was used to join thin plates of low carbon ferritic and austenitic stainless steel. Due to the differences in the thermo-physical properties of base metals, this kind of welds exhibit a complex microstructure, which frequently leads to an overall loss of joint quality. Four welded samples were prepared by using different sets of processing parameters, with the aim of minimizing the induced residual stress field. Microstructural characterization and residual strain scanning (by neutron diffraction) were used to assess the joints’ features. © 2014, Trans Tech Publications
Effective gamma-surfaces in {111} plane in FCC Ni and L1(2) Ni3Al intermetallic compound
No full textThe well-known concept of γ surfaces originally suggested by Prof. Vitek is extended to the case of a shift of one part of a crystal with respect to the other part in two adjacent {111} planes of a stacking fault. The proposed approach is used to construct the effective γ surfaces in the {111} plane in fcc Ni and L12 Ni3Al of intermetallic compound. It is shown that Ni3Al can have five metastable stacking faults in this plane, namely, an intrinsic superlattice stacking fault, an extrinsic superlattice stacking fault, a complex stacking fault, an antiphase boundary, and a complex extrinsic stacking fault. The existence of the latter in the {111} plane in the L12 Ni3Al intermetallic compound has not been reported previously. The shift of the crystal in two close-packed planes in fcc Ni makes it possible to avoid the formation of a high-energy stacking fault which arises when constructing an ordinary γ-surface, as well as to self-consistently include the extrinsic stacking fault into consideration. © 2013, Pleiades Publishing, Ltd
Accelerator Mass spectrometry: revealing subtle signals in ice sheets
No full textAccelerator Mass Spectrometry (AMS) determines the ratio of a rare isotope, normally radioactive and of intermediate half-life, to a stable isotope. AMS permits
the detection of individual atoms in a sample and so is an inherently sensitive analytical technique. A well-known
example is radiocarbon dating (14C, t1/2 = 5730 a), where measurement of the 14C/12C ratio permits determination of the age of an artifact. Such AMS measurements can be
performed rapidly (~ 20 min), at good precision (~ 0.3 ‰), with high sensitivity (< 10-15) and on very small samples
(as little a few μg of carbon). Radiometric measurements, by contrast, require much larger sample masses and much longer measurement times in order to obtain
good precision. Besides its use as a chronometer, 14C is increasingly used as a tracer in geophysical studies as
the amount of carbon required for a measurement has decreased.At ANSTO we routinely measure 14C, 10Be, 26Al and the
Actinides by AMS and in 2010 we added 7Be to the
list. Here I give some examples from the ice sheets in
Greenland and Antarctica of palaeoclimate research I
have been involved in. In each case AMS has provided
the unique key to unlock these important climate archives.
I will discuss 14C studies of atmospheric gases from firn air and ice core bubbles, with the objective of learning more about the natural and anthropogenic sources of
the important greenhouse gas methane. Additionally, I
will discuss studies of the beryllium isotopes, 7Be (t1/2 = 53 d) and 10Be (t1/2 = 1.4 _ 106 a) in snow and ice, with the objective of improving the use of 10Be as a proxy for Solar variability
222Rn calibrated mercury fluxes from terrestrial surfaces of southern Africa derived from observations at Cape Point, South Africa
Get PDFGaseous elemental mercury (GEM) and 222Rn, a radioactive gas of primarily terrestrial origin with a half-life of 3.8 days, have been measured simultaneously at Cape Point, South Africa, since March 2007. Between March 2007 and December 2009 altogether 59 events with high 222Rn concentrations were
identified. GEM correlated with 222Rn in 41 of the events and was constant during the remaining events without significant correlation. The average GEM/222Rn emission ratio of all events was -0.0047 ± 0.0054 pg
mBq-1, with ± 0.0054 being the standard error of the average. With an emission rate of 1.1 222Rn atoms cm-2 s-1 and a correction for the transport duration, this emission ratio corresponds to a radon calibrated flux of about -0.53 ± 0.62 ng m-2 h-1 which is statistically not distinguishable from zero. With wet deposition, which is not included in this estimate, the terrestrial surface of southern Africa appears to be a net mercury sink. © Owned by the authors, published by EDP Sciences, 201
Relative sea-level fall along Eastern Australia between 1200 and 800 year BP
No full textAOGS (Asia Oceania Geosciences Society) will hold their 10th Anniversary meeting for the first time in the Southern Hemisphere at the Brisbane Convention and Exhibition Centre from the 24th to 28th of June 2013.
AOGS was established in 2003 to promote geosciences and its application for the benefit of humanity, specifically in Asia and Oceania and with an overarching approach to global issues.
AOGS holds annual conventions providing a unique opportunity of exchanging scientific knowledge and discussion to address important geo-scientific issues among academia, research institution and public.Asia Oceania Geosciences Society (AOGS) was established in 2003 to promote geosciences and its application for the benefit of humanity, specifically in Asia and Oceania and with an overarching approach to global issues.
Asia- Oceania region is particularly vulnerable to natural hazards, accounting for almost 80% human lives lost globally. AOGS is deeply involved in addressing hazard related issues through improving our understanding of the genesis of hazards through scientific, social and technical approaches.
AOGS holds annual conventions providing a unique opportunity of exchanging scientific knowledge and discussion to address important geo-scientific issues among academia, research institution and public.
Recognizing the need of global collaboration, AOGS has developed good co-operation with other international geo-science societies and unions such as the European Geosciences Union (EGU), American Geophysical Union (AGU), International Union of Geodesy and Geophysics (IUGG), Japan Geo-science Union (JpGU), and Science Council of Asia (SCA). © 2013, AOGS