Change in the North Atlantic circulation associated with the mid-Pleistocene transition

The southwestern Iberian margin is highly sensitive to changes in the distribution of North Atlantic currents and to the position of oceanic fronts. In this work, the evolution of oceanographic parameters from 812 to 530 ka (MIS20-MIS14) is studied based on the analysis of planktonic foraminifer assemblages from site IODP-U1385 (37 degrees 34.285' N, 10 degrees 7.562' W; 2585m b.s.l.). By comparing the obtained results with published records from other North Atlantic sites between 41 and 55 degrees N, basin-wide paleoceano-graphic conditions are reconstructed. Variations of assemblages dwelling in different water masses indicate a major change in the general North Atlantic circulation during MIS16, coinciding with the definite establishment of the 100 ky cyclicity associated with the mid-Pleistocene transition. At the surface, this change consisted in the redistribution of water masses, with the subsequent thermal variation, and occurred linked to the northwestward migration of the Arctic Front (AF), and the increase in the North Atlantic Deep Water (NADW) formation with respect to previous glacials. During glacials prior to MIS16, the NADW formation was very weak, which drastically slowed down the surface circulation; the AF was at a southerly position and the North Atlantic Current (NAC) diverted southeastwards, developing steep south-north, and east-west, thermal gradients and blocking the arrival of warm water, with associated moisture, to high latitudes. During MIS16, the increase in the meridional overturning circulation, in combination with the northwestward AF shift, allowed the arrival of the NAC to subpolar latitudes, multiplying the moisture availability for ice-sheet growth, which could have worked as a positive feedback to prolong the glacials towards 100 ky cycles.info:eu-repo/semantics/publishedVersio

Quantum mechanical analysis of the elastic propagation of electrons in the Au/Si system: application to Ballistic Electron Emission Microscopy

We present a Green's function approach based on a LCAO scheme to compute the elastic propagation of electrons injected from a STM tip into a metallic film. The obtained 2D current distribution in real and reciprocal space furnish a good representation of the elastic component of Ballistic Electron Emission Microscopy (BEEM) currents. Since this component accurately approximates the total current in the near threshold region, this procedure allows --in contrast to prior analyses-- to take into account effects of the metal band structure in the modeling of these experiments. The Au band structure, and in particular its gaps appearing in the [111] and [100] directions provides a good explanation for the previously irreconcilable results of nanometric resolution and similarity of BEEM spectra on both Au/Si(111) and Au/Si(100).Comment: 12 pages, 9 postscript figures, revte

A theoretical analysis of Ballistic Electron Emission Microscopy: k-space distributions and spectroscopy

We analyze BEEM experiments. At low temperatures and low voltages, near the threshold value of the Schottky barrier, the BEEM current is dominated by the elastic component. Elastic scattering by the lattice results in the formation of focused beams and narrow lines in real space. To obtain the current injected in the semiconductor, we compute the current distribution in reciprocal space and, assuming energy and $k_{\parallel}$ conservation. Our results show an important focalization of the injected electron beam and explain the similarity between BEEM currents for Au/Si(111) and Au/Si(100).Comment: 17 pages, 5 figures (postscript), Latex, APS, http://www.icmm.csic.es/Pandres/pedro.htm. Appl. Surf. Sci. (in press

Estimulação Térmica Dos Embriões Da Linhagem Ross® Em Escala Comercial

Artificial incubation is an essential process to obtain healthy birds with good performance; nevertheless, it requires sustained improvement. During this process, incubation temperature is considered a critical factor, which has been studied. The objective of this study was to evaluate the development of Ross® embryos after hot and cold thermal stimulation. To this end, temperatures 1.39ºC above the standard temperature and a temperature fixed at 36.00ºC that varied 1.00 to 0.30ºC below the standard temperature were applied during the final embryonic development period (days 14 to 18) for three hours, on a commercial scale. Results revealed that hot and cold thermal stimulations did not cause embryo mortality; the hatching and chick quality index were maintained and even increased. Therefore, we believe that thermal stimulation has the potential to improve hatchery index, and thus grange performance; however, adjustments are needed, varying according to each individual hatchery, before it can used as a protocol. © 2016, Universidade Federal de Santa Maria. All rights reserved.4691668167

Hot electron transport in Ballistic Electron Emission Spectroscopy: band structure effects and k-space currents

Using a Green's function approach, we investigate band structure effects in the BEEM current distribution in reciprocal space. In the elastic limit, this formalism provides a 'parameter free' solution to the BEEM problem. At low temperatures, and for thin metallic layers, the elastic approximation is enough to explain the experimental I(V) curves at low voltages. At higher voltages inelastic effects are approximately taken into account by introducing an effective RPA-electron lifetime, much in similarity with LEED theory. For thick films, however, additional damping mechanisms are required to obtain agreement with experiment.Comment: 4 pages, 3 postscript figures, revte

Surface and bulk band-structure effects on CoSi₂/Si(111) ballistic-electron emission experiments

A theoretical model of ballistic-electron-emission microscopy (BEEM) based on linear combination of atomic orbitals Hamiltonians and Keldysh Green’s functions is applied to analyze experimental data obtained for CoSi2/Si(111) contacts. Hot electrons injected from a scanning tunneling microscope tip into the silicide film form a highly focused beam, which even after propagation through films of moderate thickness is narrow enough to allow the observed atomic resolution of interfacial point defects. On (2×1) reconstructed domains a certain fraction of the initial current is injected into localized surface states, leading to the reported contrast in BEEM images, reflecting the topography at the surface. These results confirm that band-structure effects, both in the bulk and at the surface of the metallic overlayer, intricately influence the interface-related information contained in BEEM data. It is found that for a careful analysis of experimental results, a theoretical model going beyond the ballistic hypotesis is required

Multicarrier Waveform Harmonization and Complexity Analysis for an Efficient 5G Air Interface Implementation

[EN] The coexistence of multiple air interface variants in the upcoming fifth generation (5G) wireless technology remains a matter of ongoing discussion. This paper focuses on the physical layer of the 5G air interface and provides a harmonization solution for the joint implementation of several multicarrier waveform candidates. Waveforms based either on cyclic prefix-orthogonal frequency division multiplexing (CP-OFDM) or on filter bank multicarrier (FBMC) are first presented through a harmonized system model. Complexity comparisons among five different waveforms are provided. Then, the complexity of a proposed configurable hardware implementation setup for waveform transmission and reception is evaluated. As a result, the harmonized transmitter and receiver exhibit 25¿40% and 15¿25% less complexity in floating-point operations, respectively, in comparison to two standalone implementations of the most complex waveform instances of the CP-OFDM and FBMC families. This highlights the similarities between both families and illustrates the component reuse advantages associated with the proposed harmonized solution.This work was performed in the framework of the H2020 Project METIS-II with reference 671680, which is partly funded by the European Union. The authors would like to acknowledge the contributions of their colleagues in METIS-II. This work was also supported in part by the Ministerio de Economia y Competitividad, under Grant TEC2014-60258-C2-1-R.Garcia-Roger, D.; Roger Varea, S.; Flores De Valgas, J.; Monserrat, JF. (2017). Multicarrier Waveform Harmonization and Complexity Analysis for an Efficient 5G Air Interface Implementation. Wireless Communications and Mobile Computing. 2017:1-11. https://doi.org/10.1155/2017/9765614S111201

Thermal and mechanical properties of recycled poly(Lactic acid)

Biodegradable polymers have experienced increased attention in recent years because of their wide range of applications in biomedical, packaging and agriculture fields. PLA, poly(lactic acid), is a linear aliphatic biodegradable thermoplastic polyester, with good mechanical properties, thermal stability, processability and low environmental impact, widely used as an alternative to conventional polymers. PLA products can be recycled after use either by remelting and reprocessing the material, or by hydrolysis to basic lactic acid [1]. The object of this communication is the study of the possible variation in physical properties induced by sub sequent reprocessing cycles of PLA

I know your face but can’t remember your name:Age-related differences in the FNAME-12NL

OBJECTIVE: The Face-Name Associative Memory test (FNAME) has recently received attention as a test for early diagnosis of Alzheimer’s disease. So far, however, there has been no systematic investigation of the effects of aging. Here, we aimed to assess the extent to which the FNAME performance is modulated by normal ageing. METHOD: In a first step, we adapted the FNAME material to the Dutch population. In a second step, younger (n = 29) and older adults (n = 29) were compared on recall and recognition performance. RESULTS: Significant age effects on name recall were observed after the first exposure of new face-name pairs: younger adults remembered eight, whereas older adults remembered a mean of four out of twelve names. Although both age groups increased the number of recalled names with repeated face-name exposure, older adults did not catch up with the performance of the younger adults, and the age-effects remained stable. Despite of that, both age groups maintained their performance after a 30-min delay. Considering recognition, no age differences were demonstrated, and both age groups succeeded in the recognition of previously shown faces and names when presented along with distractors. CONCLUSIONS: This study presents for the first time the results of different age groups regarding cross-modal associative memory performance on the FNAME. The recall age effects support the hypothesis of age-related differences in associative memory. To use the FNAME as an early cognitive biomarker, further subscales are suggested to increase sensitivity and specificity in the clinical context