Distinct Nature of Static and Dynamic Magnetic Stripes in Cuprate Superconductors.

We present detailed neutron scattering studies of the static and dynamic stripes in an optimally doped high-temperature superconductor, La_{2}CuO_{4+y}. We observe that the dynamic stripes do not disperse towards the static stripes in the limit of vanishing energy transfer. Therefore, the dynamic stripes observed in neutron scattering experiments are not the Goldstone modes associated with the broken symmetry of the simultaneously observed static stripes, and the signals originate from different domains in the sample. These observations support real-space electronic phase separation in the crystal, where the static stripes in one phase are pinned versions of the dynamic stripes in the other, having slightly different periods. Our results explain earlier observations of unusual dispersions in underdoped La_{2-x}Sr_{x}CuO_{4} (x=0.07) and La_{2-x}Ba_{x}CuO_{4} (x=0.095).

Use of spatially distributed time-integrated sediment sampling networks and distributed fine sediment modelling to inform catchment management.

Under the EU Water Framework Directive, suspended sediment is omitted from environmental quality standards and compliance targets. This omission is partly explained by difficulties in assessing the complex dose-response of ecological communities. But equally, it is hindered by a lack of spatially distributed estimates of suspended sediment variability across catchments. In this paper, we demonstrate the inability of traditional, discrete sampling campaigns for assessing exposure to fine sediment. Sampling frequencies based on Environmental Quality Standard protocols, whilst reflecting typical manual sampling constraints, are unable to determine the magnitude of sediment exposure with an acceptable level of precision. Deviations from actual concentrations range between -35 and +20% based on the interquartile range of simulations. As an alternative, we assess the value of low-cost, suspended sediment sampling networks for quantifying suspended sediment transfer (SST). In this study of the 362 km2 upland Esk catchment we observe that spatial patterns of sediment flux are consistent over the two year monitoring period across a network of 17 monitoring sites. This enables the key contributing sub-catchments of Butter Beck (SST: 1141 t km2 yr-1) and Glaisdale Beck (SST: 841 t km2 yr-1) to be identified. The time-integrated samplers offer a feasible alternative to traditional infrequent and discrete sampling approaches for assessing spatio-temporal changes in contamination. In conjunction with a spatially distributed diffuse pollution model (SCIMAP), time-integrated sediment sampling is an effective means of identifying critical sediment source areas in the catchment, which can better inform sediment management strategies for pollution prevention and control.

Unusual behavior in magnesium-copper cluster matter produced by helium droplet mediated deposition.

We demonstrate the ability to produce core-shell nanoclusters of materials that typically undergo intermetallic reactions using helium droplet mediated deposition. Composite structures of magnesium and copper were produced by sequential condensation of metal vapors inside the 0.4 K helium droplet baths and then gently deposited onto a substrate for analysis. Upon deposition, the individual clusters, with diameters ∼5 nm, form a cluster material which was subsequently characterized using scanning and transmission electron microscopies. Results of this analysis reveal the following about the deposited cluster material: it is in the un-alloyed chemical state, it maintains a stable core-shell 5 nm structure at sub-monolayer quantities, and it aggregates into unreacted structures of ∼75 nm during further deposition. Surprisingly, high angle annular dark field scanning transmission electron microscopy images revealed that the copper appears to displace the magnesium at the core of the composite cluster despite magnesium being the initially condensed species within the droplet. This phenomenon was studied further using preliminary density functional theory which revealed that copper atoms, when added sequentially to magnesium clusters, penetrate into the magnesium cores.

Effects of Manduca diuresin on neonates of the tobacco hornworm, Manduca sexta.

Manduca diuresin (MD), a 30 amino acid peptide, was isolated and identified from the type IIb median neurosecretory cells in the brain of adult Manduca sexta (Blackburn et al., Biochem. Biophys. Res. Commun., 181, 927-932, 1991). The synthetic hormone stimulates water loss in the adult moth both in vitro using isolated Malphigian tubule preparations and in vivo using decapitated adult moths as bioassay animals (Blackburn and Ma, Arch. Insect Biochem. Physiol., 27, 3-10, 1994). In the present study, MD was shown to have adverse physiological effects on neonates of Manduca sexta when fed synthetic hormone-treated leaf discs. With a sustained diet of MD-treated discs, neonates exhibited symptoms of reduced food consumption and marginal weight increases. In addition to slowed growth and reduced developmental rates, a high percentage of these neonates failed to molt into second instar larvae and death usually followed shortly thereafter. This is a first report that a synthetic insect neuropeptide has shown detrimental effect on insect larvae by ingestion. The possibility of utilizing this peptide in plant protection is discussed.