Will photosynthesis of maize (Zea mays) in the US corn belt increase in future [CO2] rich atmospheres? An analysis of diurnal courses of [CO2] uptake under Free-Air Concentration Enrichmnent (FACE).

published or submitted for publicatio

Shetlands Islands field trip May 2014 : summary of results

This report provides a record of a field excursion to the Shetland Islands in May 2014 to investigate sediments deposited from tsunamis generated from submarine landslides mainly located off the coast of Norway. The research was funded under a NERC Consortium Grant for a project entitled ‘Will climate change in the Arctic increase the landslide-tsunami risk to the UK?’ It was part of Work Block 2 (WB2): ‘What is the timing of tsunami deposits on the UK coastline, and how is it related to the age of major Arctic slides’? The best known and most studied tsunami from the Norwegian submarine landslides is the Storegga event dated at 8,200BP. Sediments deposited from this tsunami are commonly found along the west coast of Norway, east coast of mainland Scotland, and also on the Shetland and Faeroe islands. However, there are other landslides off of Norway for which no associated tsunami has been identified, which poses the question as to whether these events did not generate a tsunami or whether the evidence for a tsunami has not yet been found. Although evidence for seabed slumping off Norway was first discovered in the 1950’s (Holtedahl, 1955, 1971) and the scale and morphology of a massive submarine landslide, subsequently termed Storegga, mapped in the 1970’s (Bugge, 1983), it was not until 1985 that an associated tsunami was first proposed (Svendsen, 1985). The first supporting sedimentary evidence of the tsunami was first identified on mainland Scotland in 1988 (Dawson et al., 1988) then, subsequently, similar sediments were identified on the Shetland Islands (Smith, 1993a). The Storegga Slide has been dated to 8,150BP (Haflidason et al., 2005), however more recent research on the deposits on the Shetlands suggests that some may not all be from Storegga, because 14C age dating gives younger ages of ~5,000 and 1,500 cal yr BP (Bondevik et al., 2005). A major challenge posed by the ages of these younger dates is that they are confined to the Shetlands; there is no indication of these younger tsunamis on mainland Scotland. If the dating is correct and the sediments are indeed from tsunamis, then the submarine landslides off Norway would be an unlikely source, so a local source seems most likely, but none has yet been identified. Alternatively a non-tsunami source for the sediments may explain their presence. The objectives of WB2 therefore are to investigate the tsunami deposits on Shetland that post-date the Storegga Slide, to validate their ages and, if possible, identify possible source locations of the submarine landslides that generated the tsunamis. On Shetland research on tsunami sediments was mainly based on evidence from coastal exposures around Sullom Voe where tsunami sands are dated as coeval with Storegga. The younger sands are mainly preserved in lake cores at locations on Shetland Mainland (Bondevik et al., 2005) where those of 5,000 BP overlie sands of Storegga age at 8,200 years BP age. At coastal sites along Basta Voe on Yell and at a mainland site at Dury Voe very young age dates of ~1,500 BP suggest an additional and very recent, late Holocene event (Bondevik et al., 2005; Dawson et al, 2006). A preliminary field excursion to the Shetlands carried out in 2013 discovered possible new tsunami deposits preserved in peat on central Yell at Whale Firth, Mid Yell Voe and Kirkabister. Subsequent 14C age dating of these deposits resulted in a variety of ages, many much younger than that of Storegga. The 14C method is known to be subject to major uncertainties because of contamination, for example initial age dating in the 1990’s at sites around Sullom Voe returned ages of around 5,000 years BP, although these were subsequently rejected in favour of the earlier, 8,200 BP Storegga event. Thus, validating the ages of the deposits on Yell, prospectively from a number of deposits laid down successively at one site (thereby reducing the sole reliance on 14C dating) was critical in validating the presence of more than one tsunami event on Shetland. The objective of the 2014 field visit to the Shetlands, therefore, was to return to Yell and validate the preliminary results from 2013; revisiting the sites at Whale Firth, Mid Yell and Kirkabister and searching the coastlines of Unst, Fetlar, Yell and north Mainland for additional sites where tsunami sediments might be preserved. Just before the visit new 14C dates from Mid Yell from samples collected in 2013 confirmed the previous results from other locations that had given a wide range of ages; at Whale Firth a single date gave a ‘young’ age of ~5,000 years BP, a range of ages with the oldest at 8,200 years BP were returned from Mid Yell Voe. We first visited sites on north Mainland around Sullom Voe, as it was here that the first indications of the Storegga tsunami were identified on Shetland in 1992. The deposits are classic as they contain rip-up clasts characteristic of tsunami deposits elsewhere. We then visited the sites at Basta Voe, Whale Firth, Mid Yell and Kirkabister. We carried out reconnaissance surveys on Unst, Fetlar, Yell and north Mainland. Preliminary results: 1. The new evidence supports the presence of tsunami sediments on Yell at Mid Yell Voe and Whale Firth, but the age of these sediments requires further research to confirm previous dating and their possible sources, 2. The youngest dated sediments (~1,500 BP) at Vasta Voe are most likely from a tsunami, but their limited areal extent suggests a local source, as yet undetermined, 3. The presence of three events at Mid Yell Voe based on surveys in 2013 was not confirmed, 4. The similarity of the deposits on Mid Yell with those around Sullom Voe on Mainland are suggestive of a similar source, 5. The wide range of the preliminary age dating at the Mid Yell sites (Whale Firth and Mid Yell Voe) is analogous to the early age dating of coastal deposits around Sullom Voe, suggesting the possibility of contamination of the peat material dated, 6. Whereas the 5,500BP event is identified in lake cores, no strongly supportive evidence for sands of this age were identified in the coastal sections, 7. Of the proposed three tsunami events proposed for Shetland only one, Storegga, has a confirmed source, 8. Further analysis of the peat stratigraphy at the coastal sites, reflects vegetation changes over the past ~8,000 years related to climate change, and these could be used to provide a broader context for the 14C age dating that may resolve the present dating issues, 9. Newly discovered sediments at Kirkabister require further research to determine their origin, 10. The origin(s) of the laminated deposits at Whale Firth, Mid Yell and Vatsetter is/are uncertain, but they are probably not from a tsunami, 11. No additional coastal exposures of peat with tsunami sands were located during the reconnaissance surveys on Mainland, Yell, Unst and Fetlar. Postscript; Immediately after this report was finalised, age dating of peat sections at Whale Firth and Mid Yell Voe confirmed that the sands preserved in the woody peat here are of Storegga age, ~8,200 cal yr BP

Hourly and seasonal variation in photosynthesis and stomatal conductance of soybean grown at future CO2 and ozone concentrations for three years under fully open air conditions.

published or submitted for publicatio

Diffusio-osmosis and wetting on solid surfaces: a unified description based on a virtual work principle

In order to account for diffusio-osmosis, Derjaguin proposed long ago that there is an excess pressure confined within a layer of typically a few nanometers in the vicinity of a solid surface immersed in a liquid and resulting from the interaction between the liquid and the surface. In the presence of a composition gradient in the liquid a confined pressure gradient parallel to the surface is therefore responsible for the diffusio-osmotic flow. This picture appears in contradiction with the contact theorem of colloidal science according to which such excess pressure does not exist. We propose a theoretical description for calculating hydrodynamic flows in inhomogeneous liquids in the vicinity of solid interfaces which is consistent with the contact theorem. This approach is based on a Gibbs free energy and a virtual work principle for calculating the driving forces in the liquid due to inhomogeneous composition along a capillary and to the interaction with the solid interfaces. Our approach allows us to show that the physics at play is the same in wetting or in diffusio-osmosis experiments, as one can go continuously from the latter to the former by making composition gradients sharper. We obtain an explicit expression for the diffusio-osmotic mobility which depends on the Gibbs free energy density in the vicinity of the interface and its dependance on the solute concentration in the liquid beyond the interfacial region, and which is inversely proportional to the liquid viscosity

Migration of nanoparticles across a polymer–polymer interface: theory and simulation

We proposed recently a theoretical description for hydrodynamic flows in inhomogeneous liquids in the vicinity of solid interfaces, consistent with current theoretical descriptions of the thermodynamical equilibrium of liquids in the vicinity of solid surfaces and with the Onsager formalism for linear response theory in out-of-equilibrium liquids. We showed that these equations allow for describing diffusio-osmosis along a capillary and also wetting/dewetting dynamics of liquids on a solid substrate. We now apply this physical model to the wetting/dewetting dynamics of nano-particles in polymer blends, showing how they reach equilibrium at the interface between two liquids at rest and how they migrate from the non-preferred polymer to the preferred one under applied flow

A far-ultraviolet variable with an 18-minute period in the globular cluster NGC 1851

We present the detection of a variable star with an 18.05 minute period in far-ultraviolet (FUV) images of the globular cluster NGC 1851 taken with the Hubble Space Telescope (HST). A candidate optical counterpart lies on the red horizontal branch or the asymptotic giant branch star of the cluster, but it is statistically possible that this is a chance superposition. This interpretation is supported by optical spectroscopt obtained with HST/STIS: the spectrum contains none of the strong emission lines that would be expected if the object was a symbiotic star (i.e. a compact accretor fed by a giant donor). We therefore consider two other possibilities for the nature of FUV variable: (i) an intermediate polar (i.e. a compact binary containing an accreting magnetic white dwarf), or (ii) an AM CVn star (i.e. an interacting double-degenerate system). In the intermediate polar scenario, the object is expected to be an X-ray source. However, no X-rays are detected at its location in ? 65 ksec of Chandra imaging, which limits the X-ray luminosity to LX ? 1032 erg s?1. We therefore favour the AM CVn interpretation, but a FUV spectrum is needed to distinguish conclusively between the two possibilities. If the object is an AM CVn binary, it would be the first such system known in any globular cluster

Local chain deformation and overstrain in reinforced elastomers: An NMR study

A molecular-level understanding of the strain response of elastomers is a key to connect microscopic dynamics to macroscopic properties. In this study we investigate the local strain response of vulcanized, natural rubber systems and the effect of nanometer-sized filler particles, which are known to lead to highly improved mechanical properties. A multiple-quantum NMR approach enables the separation of relatively low fractions of network defects and allows to quantitatively and selectively study the local deformation distribution in the strained networks matrix on the microscopic (molecular) scale. We find that the presence of nondeformable filler particles induces an enhanced local deformation of the matrix (commonly referred to as overstrain), a slightly increased local stress/strain heterogeneity, and a reduced anisotropy. Furthermore, a careful analysis of the small nonelastic defect fraction provides new evidence that previous NMR and scattering results of strained defect-rich elastomers cannot be interpreted without explicitly taking the nonelastic defect fraction into account

Magnetic and Mössbauer spectroscopy studies of nanocrystalline iron oxide aerogels

A sol-gel synthesis was used to produce iron oxide aerogels. These nanocrystalline aerogels have a pore-solid structure similar to silica aerogels but are composed entirely of iron oxides. Mössbauer experiments and x-ray diffraction showed that the as-prepared aerogel is an amorphous or poorly crystalline iron oxide, which crystallized as a partially oxidized magnetite during heating in argon. After further heat treatment in air, the nanocrystallites are fully converted to maghemite. The particles are superparamagnetic at high temperatures, but the magnetic properties are strongly influenced by magnetic interactions between the particles at lower temperatures

System 1 Is Not Scope Insensitive

Companies can create value by differentiating their products and services along quantitative attributes. Existing research suggests that consumers’ tendency to rely on relatively effortless and affect-based processes reduces their sensitivity to the scope of quantitative attributes and that this explains why increments along quantitative attributes often have diminishing marginal value. The current article sheds new light on how “system 1” processes moderate the effect of quantitative product attributes on subjective value. Seven studies provide evidence that system 1 processes can produce diminishing marginal value, but also increasing marginal value, or any combination of the two, depending on the composition of the choice set. This is because system 1 processes facilitate ordinal comparisons (e.g., 256 GB is more than 128 GB, which is more than 64 GB) while system 2 processes, which are relatively more effortful and calculation based, facilitate cardinal comparisons (e.g., the difference between 256 and 128 GB is twice as large as between 128 and 64 GB)