Understanding visual map formation through vortex dynamics of spin Hamiltonian models

The pattern formation in orientation and ocular dominance columns is one of the most investigated problems in the brain. From a known cortical structure, we build spin-like Hamiltonian models with long-range interactions of the Mexican hat type. These Hamiltonian models allow a coherent interpretation of the diverse phenomena in the visual map formation with the help of relaxation dynamics of spin systems. In particular, we explain various phenomena of self-organization in orientation and ocular dominance map formation including the pinwheel annihilation and its dependency on the columnar wave vector and boundary conditions.Comment: 4 pages, 15 figure

Quantifying inter-field movements of the western corn rootworm (Diabrotica virgifera virgifera LeConte) — A Central European field study

Dispersal plays a key role in the adaptation of species. It has been suggested that even in a stable and predictable environment, it is essential for any given population to “send” a certain portion of its offspring to disperse (referred as evolutionary stable dispersal rate). Although the literature on the flight behaviour of one of the major maize pests, the western corn rootworm, is rich, relatively little is known about its inter-field movements under field conditions. In the present study, inter-field movement of adult beetles was observed in Central-Europe under quasi-isolated conditions of infested continuous and un-infested first year maize fields, and related to candidate predictor variables. Percent of immigrants (net percent of adults within a given population leaving their natal maize field and arriving in first-year maize) varied greatly across years and locations (0.4–93.3%, mean = 38.7%). Results of the study provided field evidence of the assumption that western corn rootworm performs density dependent inter-field movement. Independent from pest densities, it appeared that about 1/3 of an adult beetle population always leaves its natal maize field, which likely allows the species to find new food sources and oviposition sites. The distance between maize fields and the phenological status of maize influenced inter-field movements but at a much less extent than it could have been expected from laboratory research findings

ASpect: A new spectrum and line analysis package for IRAF

We examined several publicly available spectral analysis software packages looking for one with enough functionality and versatility to meet the analysis needs of astronomers during the next decade. None of those examined can satisfactorily support the wide variety of panchromatic science programs that are now becoming possible. Furthermore, we concluded that none of these packages can be simply modified to include critical functions because of their original (limited) designs. During the next two years we will write a new spectral analysis package, ASpect, that will incorporate the latest analysis techniques for astronomical spectra in all wavelength domains. The ASpect package has several functional requirements. It must operate on spectra from a wide variety of ground-based and space-based instruments spanning wavelengths from radio to gamma rays. It must accommodate non-linear dispersion relations. It must provide a variety of functions, individually or in combination, with which to fit spectral features and the continuum. It is vitally important that known bad data be masked and that, uncertainties be propagated throughout the calculations in order for astronomers to evaluate the reliability of results. Finally, this new package must provide a powerful, intuitive graphical user interface to handle the burden of data input/output (I/O), on-line 'help,' selection of relevant features for analysis, plotting and graphical interaction, and data base management--all in a comprehensible environment. We anticipate that ASpect will take the form of an external package in IRAF (such as the NOAO and STSDAS packages) and will be layered upon the IRAF virtual Operating System to make it available on as many platforms as possible, while making it resistant to changes in operating systems and compilers. Our choice of IRAF is motivated by its portability, its wide use within the astronomical community, and its rich set of existing user applications

Warming, euxinia and sea level rise during the Paleocene–Eocene Thermal Maximum on the Gulf Coastal Plain: implications for ocean oxygenation and nutrient cycling

The Paleocene–Eocene Thermal Maximum(PETM, ?56 Ma) was a ?200 kyr episode of globalwarming, associated with massive injections of 13C-depletedcarbon into the ocean–atmosphere system. Although climatechange during the PETM is relatively well constrained,effects on marine oxygen concentrations and nutrientcycling remain largely unclear. We identify the PETM in asediment core from the US margin of the Gulf of Mexico.Biomarker-based paleotemperature proxies (methylationof branched tetraether–cyclization of branched tetraether(MBT–CBT) and TEX86) indicate that continental air andsea surface temperatures warmed from 27–29 to ?35 ?C,although variations in the relative abundances of terrestrialand marine biomarkers may have influenced these estimates.Vegetation changes, as recorded from pollen assemblages,support this warming.The PETM is bracketed by two unconformities. It overliesPaleocene silt- and mudstones and is rich in angular(thus in situ produced; autochthonous) glauconite grains,which indicate sedimentary condensation. A drop in the relativeabundance of terrestrial organic matter and changesin the dinoflagellate cyst assemblages suggest that risingsea level shifted the deposition of terrigenous material landward.This is consistent with previous findings of eustatic sealevel rise during the PETM. Regionally, the attribution of theglauconite-rich unit to the PETM implicates the dating of aprimate fossil, argued to represent the oldest North Americanspecimen on record.The biomarker isorenieratene within the PETM indicatesthat euxinic photic zone conditions developed, likely seasonally,along the Gulf Coastal Plain. A global data compilationindicates that O2 concentrations dropped in allocean basins in response to warming, hydrological change,and carbon cycle feedbacks. This culminated in (seasonal)anoxia along many continental margins, analogous to moderntrends. Seafloor deoxygenation and widespread (seasonal)anoxia likely caused phosphorus regeneration fromsuboxic and anoxic sediments.We argue that this fueled shelfeutrophication, as widely recorded from microfossil studies,increasing organic carbon burial along many continentalPublished by Copernicus Publications on behalf of the European Geosciences Union.Warming, euxinia and sea level rise during the PETMmargins as a negative feedback to carbon input and globalwarming. If properly quantified with future work, the PETMoffers the opportunity to assess the biogeochemical effects ofenhanced phosphorus regeneration, as well as the timescaleson which this feedback operates in view of modern and futureocean deoxygenation

WFPC2 Observations of the Hubble Deep Field-South

The Hubble Deep Field-South observations targeted a high-galactic-latitude field near QSO J2233-606. We present WFPC2 observations of the field in four wide bandpasses centered at roughly 300, 450, 606, and 814 nm. Observations, data reduction procedures, and noise properties of the final images are discussed in detail. A catalog of sources is presented, and the number counts and color distributions of the galaxies are compared to a new catalog of the HDF-N that has been constructed in an identical manner. The two fields are qualitatively similar, with the galaxy number counts for the two fields agreeing to within 20%. The HDF-S has more candidate Lyman-break galaxies at z > 2 than the HDF-N. The star-formation rate per unit volume computed from the HDF-S, based on the UV luminosity of high-redshift candidates, is a factor of 1.9 higher than from the HDF-N at z ~ 2.7, and a factor of 1.3 higher at z ~ 4.Comment: 93 pages, 25 figures; contains very long table

On the Black-Hole/Qubit Correspondence

The entanglement classification of four qubits is related to the extremal black holes of the 4-dimensional STU model via a time-like reduction to three dimensions. This correspondence is generalised to the entanglement classification of a very special four-way entanglement of eight qubits and the black holes of the maximally supersymmetric N = 8 and exceptional magic N = 2 supergravity theories.Comment: 32 pages, very minor changes at the start of Sec. 4.1. Version to appear in The European Physical Journal - Plu