The Oxidation State of Iron in Silicate Minerals from the Matrices of CO Carbonaceous Chondrites

No abstract available

Understanding images in biological and computer vision

yesThis issue of Interface Focus is a collection of papers arising out of a Royal Society Discussion meeting entitled ‘Understanding images in biological and computer vision’ held at Carlton Terrace on the 19th and 20th February, 2018. There is a strong tradition of inter-disciplinarity in the study of visual perception and visual cognition. Many of the great natural scientists including Newton [1], Young [2] and Maxwell (see [3]) were intrigued by the relationship between light, surfaces and perceived colour considering both physical and perceptual processes. Brewster [4] invented both the lenticular stereoscope and the binocular camera but also studied the perception of shape-from-shading. More recently, Marr's [5] description of visual perception as an information processing problem led to great advances in our understanding of both biological and computer vision: both the computer vision and biological vision communities have a Marr medal. The recent successes of deep neural networks in classifying the images that we see and the fMRI images that reveal the activity in our brains during the act of seeing are both intriguing. The links between machine vision systems and biology may at sometimes be weak but the similarity of some of the operations is nonetheless striking [6]. This two-day meeting brought together researchers from the fields of biological and computer vision, robotics, neuroscience, computer science and psychology to discuss the most recent developments in the field. The meeting was divided into four themes: vision for action, visual appearance, vision for recognition and machine learning

The nutrient status of Wilson Inlet 1984-1985

In response to the concern of local residents about the condition of Wilson Inlet, a study of the inlet and its catchment was undertaken during 1982-83. While the results for that study were clear, it occurred during an atypical year; the winter had a particularly low rainfall and the sand bar between the estuary and the ocean was breached for the shortest period of any winter. To obtain some understanding of the variability likely to be encountered in the estuary between years, another, smaller study was undertaken in 1984-85. The main conclusions about nutrient concentrations in plant tissues, the importance of phosphorus, total plant biomass and general ecosystem behaviour were si111ilar to those reached in the earlier study, despite very different winters. Catchment behaviour, in relation to nutrient losses to streamflow was also generally similar, with somewhat higher concentrations of nutrients associated with a winter of higher runoff. The main contrast was the large amount of nitrogen, especially in the form of nitrate, which came from the larger subcatchments during the present study. Rainfall was much closer to the long-term mean in 1984 and there was a 2.8 times increase in streamflow for the whole Wilson Inlet catchment compared to 1982. The phosphorus load of 19 tonnes was lower than the 30 tonnes predicted for an average year on the basis of the 1982 results. The nitrogen load of 340 tonnes was slightly higher than predicted for an average year from the 1982 study. Salinities were lower and nutrient concentrations and water column loads higher in winter in the present study due to the higher streamflows. Chlorophyll 'a' concentrations and water column load were also higher, presumably in response to the higher nutrient loads. Estimates of total plant biomass in winter were similar, and the results of both studies show that Ruppia biomass is one of the major nutrient banks in the Inlet. Sediment nutrient loads were similar in both studies. A nutrient budget was calculated for one cycle of bar opening and closing. There was a net retention of phosphorus of 9 tonnes (49% of total input), and net retention of nitrogen of 217 tonnes (63%). The percentage of total riverine phosphorus load retained by the inlet was similar in both studies. In contrast, it was estimated that there was net export of nitrogen in the previous study

Probing e-e interactions in a periodic array of GaAs quantum wires

We present the results of non-linear tunnelling spectroscopy between an array of independent quantum wires and an adjacent two-dimensional electron gas (2DEG) in a double-quantum-well structure. The two layers are separately contacted using a surface-gate scheme, and the wires are all very regular, with dimensions chosen carefully so that there is minimal modulation of the 2DEG by the gates defining the wires. We have mapped the dispersion spectrum of the 1D wires down to the depletion of the last 1D subband by measuring the conductance \emph{G} as a function of the in-plane magnetic field \emph{B}, the interlayer bias $V_{\rm dc}$ and the wire gate voltage. There is a strong suppression of tunnelling at zero bias, with temperature and dc-bias dependences consistent with power laws, as expected for a Tomonaga-Luttinger Liquid caused by electron-electron interactions in the wires. In addition, the current peaks fit the free-electron model quite well, but with just one 1D subband there is extra structure that may indicate interactions.Comment: 3 pages, 3 figures; formatting correcte

The Oxidation State of Iron in Silicate Minerals from the Matrices of CO Carbonaceous Chondrites

No abstract available

Inter-relation of sylvatic and domestic transmission of Trypanosoma cruzi in areas with and without domestic vectorial transmission in Minas Gerais, Brazil

During the period 1980-1986, we captured triatomine bugs and mammalian reservoir hosts from sylvatic and domestic situations in different municipalities of the State of Minas Gerais. Trypanosoma cruzi was isolated from captured bugs, mammals and patients. After cultivation in LIT medium, the electrophoretic enzyme profiles were determined. We obtained a total of 32 parasite isolates from regions with active domestic transmission, and 24 isolates from areas under control. For the first areas the results suggest introduction of T. cruzi from sylvatic habitats, through incursion of infected opossums and/or sylvatic T. sordida, which appears to have given rise to at least one acute human infection. Of particular interest is the finding of sylvatic opossums and a T. sordida nymph infected with ZB, that could indicate return of parasites from chronic human infections to sylvatic transmission cycles. For the areas under control we also interpret the results as interaction between sylvatic and domestic cycles of transmission, here through the invasion of houses by bugs carrying the Z1 zymodeme from the sylvatic environment. The Multivariate Correspondence Analysis gives a spatial description between the different parasite isolates and confirms the existence of a bridge in the opposite direction in the region with active vectorial transmission including the exporting of Z2 through the peridomestic environment into the sylvatic cycle. For the other areas this bridge corresponds especially to Panstrongylus megistus, importing Z1 into the domestic environment

Indications of coherence-incoherence crossover in layered transport

For many layered metals the temperature dependence of the interlayer resistance has a different behavior than the intralayer resistance. In order to better understand interlayer transport we consider a concrete model which exhibits this behavior. A small polaron model is used to illustrate how the interlayer transport is related to the coherence of quasi-particles within the layers. Explicit results are given for the electron spectral function, interlayer optical conductivity and the interlayer magnetoresistance. All these quantities have two contributions: one coherent (dominant at low temperatures) and one incoherent (dominant at high temperatures).Comment: 6 pages, 4 figures, REVTEX

Repulsion-Sustained Supercurrent and Flux Quantization in Rings of Symmetric Hubbard Clusters

We test the response to a threading magnetic field of rings of 5-site $C_{4v}$-symmetric repulsive Hubbard clusters connected by weak intercell links; each 5-site unit has the topology of a CuO$_{4}$ cluster and a repulsive interaction is included on every site. In a numerical study of the three-unit ring with 8 particles, we take advantage of a novel exact-diagonalization technique which can be generally applied to many-fermion problems. For O-O hopping we find Superconducting Flux Quantization (SFQ), but for purely Cu-Cu links bound pair propagation is hindered by symmetry. The results agree with W=0 pairing theory.Comment: 4 pages, 2 figure