Metal-Insulator Transition in a Generalized Hubbard Model with Correlated Hopping at Half-Filling

In the present paper metal-insulator transition is studied in a generalized Hubbard model with correlated hopping at half-filling and zero temperature. Single-particle Green function and energy spectrum of electron system are calculated. The expressions for energy gap width and the concentration of polar states (holes or doublons) are obtained. The conditions for metallic and insulating states are found.Comment: 11 pages, 2 eps figures, Latex 2.09, submitted to Phys. Stat. Sol. (B

Point-contact study of the LuNi2B2C borocarbide superconducting film

We present point-contact (PC) Andreev-reflection measurements of a superconducting epitaxial c-axis oriented nickel borocarbide film LuNi2B2C (Tc=15.9 K). The averaged value of the superconducting gap is found to be 2.6 +/-0.2 meV in the one-gap approach, whereas the two-gap approach results in 2.14+/-0.36 meV and 3.0+/-0.27 meV. The better fit of the Andreev-reflection spectra for the LuNi2B2C - Cu PC obtained by the two-gap approach provides evidence for multiband superconductivity in LuNi2B2C. For the first time, PC electron-phonon interaction (EPI) spectra have been measured for this compound. They demonstrate pronounced phonon maximum at 8.5+/-0.4meV and a second shallow one at 15.8+/-0.6 meV. The electron-phonon coupling constant estimated from the PC EPI spectra turned out to be small (~ 0.1), like in other superconducting rare-earth nickel borocarbides. Possible reasons for this are discussed.Comment: 5 pages, 5 figures, V2: figs. 2 & 5 captions are corrected, and new Refs. 4, 6, 12, 13, 14 are adde

Post-acute Brain Injury Urinary Signature: A New Resource for Molecular Diagnostics

Heterogeneity within brain injury presents a challenge to the development of informative molecular diagnostics. Recent studies show progress particularly in cerebrospinal fluid with biomarker assays targeting one or a few structural proteins. Protein-based assays in peripheral fluids, however, have been more challenging to develop in part due to restricted and intermittent barrier access. Further, a greater number of molecular variables may be required to inform on patient status given the multifactorial nature of brain injury. Presented is an alternative approach profiling peripheral fluid for a class of small metabolic by-products rendered by ongoing brain pathobiology. Urine specimens were collected for head trauma subjects upon admission to acute brain injury rehabilitation and nontraumatized matched controls. An innovative data-independent mass spectrometry approach was employed for reproducible molecular quantification across osmolarity-normalized samples. The postacute human traumatic brain injury urinary signature encompassed 2,476 discriminant variables reproducibly measured in specimens for subject classification. Multiple sub-profiles were then discerned in correlation with injury severity per Glasgow Comma Scale and behavioral and neurocognitive function per Patient Competency Rating Scale and Frontal Systems Behavioral Scale. Identified peptide constituents were enriched for outgrowth and guidance, extracellular matrix and post-synaptic density proteins, which were reflective of ongoing post-acute neuroplastic processes demonstrating pathobiological relevance. Taken together, these findings support further development of diagnostics based on brain injury urinary signatures using either combinatorial quantitative models or patternrecognition methods. Particularly, these findings espouse assay development to address unmet diagnostic and theragnostic needs in brain injury rehabilitative medicine

Physical activity attitudes, intentions and behaviour among 18-25 year olds: a mixed method study

Peer reviewedPublisher PD

Epitaxial growth and anisotropy of La(O,F)FeAs thin films deposited by Pulsed Laser Deposition

LaFeAsO1-xFx thin films were deposited successfully on (001)-oriented LaAlO3 and MgO substrates from stoichiometric LaFeAsO1-xFx polycrystalline targets with fluorine concentrations up to x = 0.25 by PLD. Room temperature deposition and post annealing of the films yield nearly phase pure films with a pronounced c-axis texture and a strong biaxial in-plane orientation. Transport measurements show metallic resistance and onset of superconductivity at 11 K. Hc2(T) was determined by resistive measurements and yield Hc2 values of 3 T at 3.6 K for B||c and 6 T at 6.4 K for B||ab.Comment: 11 pages, 5 figure

Radar interferometry based settlement monitoring in tunnelling: visualisation and accuracy analyses

Background The accurate, efficient and economical monitoring of settlements caused by tunnel boring machines, especially in regions of particular interest such as critical inner city areas, has become an important aspect of the tunnelling operation. Besides conventional terrestrial based methods to capture settlements, satellite based techniques that can accurately determine displacements remotely, are increasingly being used to augment standard terrestrial measurements. However, not much attention has been paid to analyse the accuracy of satellite based measurement data. In addition, there is also a lack of studies on how to visualise the resulting huge amount of data in the context of both the tunnel advancement and the existing building infrastructure. Methods This paper introduces the basics of settlement monitoring using radar interferometry methods, in particular showing the results obtained by processing radar images from the TerraSAR-X satellite to monitor a downtown construction site in Düsseldorf, Germany, where a new underground line (“Wehrhahn-Linie”) is being built. By comparing terrestrial measurements with remote satellite based settlement data in temporal and spatial corridors, the accuracy of the radar interferometry method is shown. Moreover, a 4D visualisation concept is presented that correlates satellite and terrestrial based settlement data correlated with above-ground buildings and boring machine performance parameters within a Virtual Reality (VR) environment. Results By comparing up to 23,000 pairs of satellite and terrestrial based settlement data points of a real tunnelling project an accuracy of about ±1.5 mm in the measurement of deformation using the method of radar interferometry in urban areas can be stated. In addition, providing a visual analysis of data sources within a VR environment, the accuracy of terrestrial and satellite-based measurements can be visualised in different time steps. Sources of error that affect the degree of accuracy, such as atmospheric conditions, systematic errors in the evaluation of radar images and local events in the spatial corridor, can be quantified. In addition, the 4D visualisation can help reveal direct interdependencies between settlement data and boring machine performance data. Conclusions The Persistent Scatterer Interferometry (PSI) based on high resolution radar images of the TerraSAR-X satellite, in combination with conventional ground-based terrestrial measurements, provides a new settlement monitoring approach in tunnelling. For example, due to minimized surveying works and disruptions of construction activities on site and due to the large settlement area coming with a high magnitude of settlement data points, this combined monitoring approach is very practical and economical. Moreover, by visualizing the settlement data properly, the risk of damage of surface structures can be analysed and understood more precisely, which increases the safety of underground works

Differences in the QBO response to stratospheric aerosol modification depending on injection strategy and species

A known adverse side effect of stratospheric aerosol modification (SAM) is the modification of the quasi-biennial oscillation (QBO), which is caused by the stratospheric heating associated with an artificial aerosol layer. Multiple studies found the QBO to slow down or even completely vanish for point-like injections of SO2 at the equator. The cause for this was found to be a modification of the thermal wind balance and a stronger tropical upwelling. For other injection strategies, different responses of the QBO have been observed. It has not yet been presented a theory which is able to explain those differences in a comprehensive manner, which is further complicated by the fact that the simulated QBO response is highly sensitive to the used model even under identical boundary conditions. Therefore, within this study we investigate the response of the QBO to SAM for three different injection strategies (point-like injection at the equator, point-like injection at 30° N and 30° S simultaneously, and areal injection into a 60° wide belt along the equator). Our simulations confirm that the QBO response significantly depends on the injection location. Based on the thermal wind balance, we demonstrate that this dependency is explained by differences in the meridional structure of the aerosol-induced stratospheric warming, i.e. the location and meridional extension of the maximum warming. Additionally, we also tested two different injection species (SO2 and H2SO4). The QBO response is qualitatively similar for both investigated injection species. Comparing the results to corresponding results of a second model, we further demonstrate the generality of our theory as well as the importance of an interactive treatment of stratospheric ozone for the simulated QBO response

Assessing the controllability of Arctic sea ice extent by sulfate aerosol geoengineering

In an assessment of how Arctic sea ice cover could be remediated in a warming world, we simulated the injection of SO2 into the Arctic stratosphere making annual adjustments to injection rates. We treated one climate model realization as a surrogate “real world” with imperfect “observations” and no rerunning or reference to control simulations. SO2 injection rates were proposed using a novel model predictive control regime which incorporated a second simpler climate model to forecast “optimal” decision pathways. Commencing the simulation in 2018, Arctic sea ice cover was remediated by 2043 and maintained until solar geoengineering was terminated. We found quantifying climate side effects problematic because internal climate variability hampered detection of regional climate changes beyond the Arctic. Nevertheless, through decision maker learning and the accumulation of at least 10 years time series data exploited through an annual review cycle, uncertainties in observations and forcings were successfully managed

Cost-benefit analysis of various California renewable portfolio standard targets: Is a 33% RPS optimal?

Renewable portfolio standards (RPSs׳) require a certain fraction of the electricity generated for a given region be produced from renewable resources. California׳s RPS mandates that by 2020, 33% of the electricity sold in the state must be generated from renewables. Such mandates have important implications for the electricity sector as well as for the whole society. In this paper, we estimate the costs and benefits of varying 2020 California RPS targets on electricity prices, greenhouse gas (GHG) emissions, criteria pollutant emissions, the electricity generation mix, the labor market, renewable investment decisions, and social welfare. We have extended the RPS Calculator model, developed by Energy and Environmental Economics (E3) Inc., to account for distributions of fuel and generation costs, to incorporate demand functions, and to estimate the effects of RPS targets on GHG emissions, criteria pollutant emissions, and employment. The results of our modeling provide the following policy insights: (1) the average 2020 electricity price increases as the RPS target rises, with values ranging between $0.152 and$0.175/kW h (2008 dollars) for the 20% RPS to 50% RPS, respectively; (2) the 33% and 50% RPS targets decrease the GHG emissions by about 17.6 and 35.8 million metric tons of carbon dioxide equivalent (MMTCO2e) relative to the 20% RPS; (3) the GHG emission reduction costs of the RPS options are high ($71–$94 per ton) relative to results from policy options other than RPS or prices that are common in the carbon markets; and (4) a lower target (e.g., a 27% RPS) provides higher social welfare than the 33% RPS (mandate) under low and moderate CO2 social costs (lower than $35/ton); while a higher RPS target (e.g., 50%) is more beneficial when using high CO2 social costs or rapid renewable technology diffusion. However, under all studied scenarios, the mandated 33% RPS for California would not provide the best cost/benefit values among the possible targets and would not maximize the net social benefit objective

Combining eye and hand in search is suboptimal

When performing everyday tasks, we often move our eyes and hand together: we look where we are reaching in order to better guide the hand. This coordinated pattern with the eye leading the hand is presumably optimal behaviour. But eyes and hands can move to different locations if they are involved in different tasks. To find out whether this leads to optimal performance, we studied the combination of visual and haptic search. We asked ten participants to perform a combined visual and haptic search for a target that was present in both modalities and compared their search times to those on visual only and haptic only search tasks. Without distractors, search times were faster for visual search than for haptic search. With many visual distractors, search times were longer for visual than for haptic search. For the combined search, performance was poorer than the optimal strategy whereby each modality searched a different part of the display. The results are consistent with several alternative accounts, for instance with vision and touch searching independently at the same time