Generic helical edge states due to Rashba spin-orbit coupling in a topological insulator

We study the helical edge states of a two-dimensional topological insulator without axial spin symmetry due to the Rashba spin-orbit interaction. Lack of axial spin symmetry can lead to so-called generic helical edge states, which have energy-dependent spin orientation. This opens the possibility of inelastic backscattering and thereby nonquantized transport. Here we find analytically the new dispersion relations and the energy dependent spin orientation of the generic helical edge states in the presence of Rashba spin-orbit coupling within the Bernevig-Hughes-Zhang model, for both a single isolated edge and for a finite width ribbon. In the single-edge case, we analytically quantify the energy dependence of the spin orientation, which turns out to be weak for a realistic HgTe quantum well. Nevertheless, finite size effects combined with Rashba spin-orbit coupling result in two avoided crossings in the energy dispersions, where the spin orientation variation of the edge states is very significantly increased for realistic parameters. Finally, our analytical results are found to compare well to a numerical tight-binding regularization of the model.Comment: 21 pages (main text 11 pages), 11 figure

Advanced Surface Treatments for Improving the Biocompatibility of Prosthesis and Medical Implants

During the last two decades, numerous surface treatments have been developed to improve the biocompatibility of different types of prosthesis and other medical implants. Some of these devices are subject to demanding loading and friction conditions (e.g., hip, knee, and spine prosthesis). However, for other implants, there are more specific requirements as it happens for coronary stents or pacemaker electrodes. The materials used for the manufacture of the aforementioned devices are subjected to very high restrictions in terms of biocompatibility, in particular on chemical composition, corrosion resistance, or ion release. As a consequence, most of prosthesis and other implants are made of a limited number of materials such as titanium alloys, stainless steels, cobalt-chromium alloys, UHMWPE, or PEEK. Unfortunately, from a strict point of view, none of these materials meet all the requirements that would be desirable in terms of durability and prevention of infections and inflammatory processes. Coatings and other surface treatments have been developed to solve these problems and to improve biocompatibility. In this chapter, we present an updated review of the most used surface engineering technologies for biomaterials, like novel PVD coatings, ion implantation, and other plasma spray treatments, as well as a critical review of the characterization techniques. This study is completed with an insight into the future of the field

EFFECT OF PLANTING DATES AND FREQUENCIES OF INTERCROPPING ON YIELD AND INCOME OF BEAN AND BANANA

EFFECT OF PLANTING DATES AND FREQUENCIES OF INTERCROPPING ON YIELD AND INCOME OF BEAN AND BANAN

Tracking magmatism and oceanic change through the early Aptian Anoxic Event (OAE 1a) to the late Aptian: Insights from osmium isotopes from the westernmost Tethys (SE Spain) Cau Core

Some of the major Carbon cycle perturbations of the Phanerozoic occurred during the Aptian, in relation to magmatism. The highest temperatures reconstructed for the Cretaceous Period correspond to the Oceanic Anoxic Event of the early Aptian (OAE 1a), an episode of accelerated global change. Here we present a chemostratigraphic study based on osmium isotopes integrated with high-resolution Carbon-Oxygen stable isotope data from the Cau Core (Western Tethys, SE Spain), including a 6.4 Ma record from the early to the late Aptian. This high-resolution study of the continuous and expanded Cau section permits a thorough understanding of the duration of the Aptian events, as well as an evaluation of the mechanisms triggering the abrupt changes of the global carbon and osmium cycles and their interdependence. Here we show that the Large Igneous Province (LIP) Aptian magmatism initiated 550–750 kyr prior to the OAE 1a, and persisted for 1.4 Myr after the event, influencing the composition of seawater for 2.8 Myr. We show a continuous Os isotope record encompassing the OAE 1a and the late Aptian for the first time, and demonstrate that the recovery from the exceptionally unradiogenic composition of seawater Os produced by the dominance of the Ontong Java Plateau volcanism, was slow. Our results demonstrate the different time duration of some events, and the asynchronous relationship between the carbon and osmium cycles

Analytical and discrete solutions for the incipient motion of ellipsoidal sediment particles

[EN] This work introduces analytical and numerical approaches to compute the incipient motion of ellipsoidal sediment particles. Initiation of motion of spherical particles is dominated by rolling mode. However, solutions for initiation of motion for non-spherical grains have to incorporate rolling, sliding, and mixed modes. The proposed approaches include a wide variety of shapes and inclinations that represent realistic configurations of sediment bed layers. The numerical procedure is based on the discrete element method, simulating the micro-mechanics of the sediment as an aggregate of rigid ellipsoids interacting by contact. The numerical solution covers a range of incipient movements that cannot be covered by the analytical approach. Hence, some trapped modes observed in analytical calculations are complemented by the numerical computation of threshold stresses. The main results are organized as novel extended Shields diagrams for non-spherical grains, where non-dimensional critical shear stress is represented in terms of friction Reynolds number.This work was supported by the Ministerio de Ciencia e Innovación Grant [#BIA-2012-32918 and #BIA-2015-64994-P (MINECO/FEDER)].Bravo, R.; Ortiz, P.; Pérez-Aparicio, JL. (2018). Analytical and discrete solutions for the incipient motion of ellipsoidal sediment particles. Journal of Hydraulic Research. 56(1):29-43. https://doi.org/10.1080/00221686.2017.1289263S2943561Belytschko, T., & Neal, M. O. (1991). Contact-impact by the pinball algorithm with penalty and Lagrangian methods. International Journal for Numerical Methods in Engineering, 31(3), 547-572. doi:10.1002/nme.1620310309Bravo, R., Ortiz, P., & Pérez-Aparicio, J. L. (2014). Incipient sediment transport for non-cohesive landforms by the discrete element method (DEM). Applied Mathematical Modelling, 38(4), 1326-1337. doi:10.1016/j.apm.2013.08.010Bravo, R., Pérez-Aparicio, J. L., & Gómez-Hernández, J. J. (2015). Numerical sedimentation particle-size analysis using the Discrete Element Method. Advances in Water Resources, 86, 58-72. doi:10.1016/j.advwatres.2015.09.024Bravo, R., Pérez-Aparicio, J. L., & Laursen, T. A. (2012). An energy consistent frictional dissipating algorithm for particle contact problems. International Journal for Numerical Methods in Engineering, 92(9), 753-781. doi:10.1002/nme.4346Buffington, J. M., & Montgomery, D. R. (1997). A systematic analysis of eight decades of incipient motion studies, with special reference to gravel-bedded rivers. Water Resources Research, 33(8), 1993-2029. doi:10.1029/96wr03190Cheng, N.-S., & Chiew, Y.-M. (1999). Incipient sediment motion with upward seepage. Journal of Hydraulic Research, 37(5), 665-681. doi:10.1080/00221689909498522Chiew, Y.-M., & Parker, G. (1994). Incipient sediment motion on non-horizontal slopes. Journal of Hydraulic Research, 32(5), 649-660. doi:10.1080/00221689409498706Derksen, J. J. (2015). Simulations of granular bed erosion due to a mildly turbulent shear flow. Journal of Hydraulic Research, 53(5), 622-632. doi:10.1080/00221686.2015.1077354Dey, S. (1999). Sediment threshold. Applied Mathematical Modelling, 23(5), 399-417. doi:10.1016/s0307-904x(98)10081-1Dey, S. (2003). Threshold of sediment motion on combined transverse and longitudinal sloping beds. Journal of Hydraulic Research, 41(4), 405-415. doi:10.1080/00221680309499985Dey, S., Sarker, H. K. D., & Debnath, K. (1999). Sediment Threshold under Stream Flow on Horizontal and Sloping Beds. Journal of Engineering Mechanics, 125(5), 545-553. doi:10.1061/(asce)0733-9399(1999)125:5(545)Hölzer, A., & Sommerfeld, M. (2008). New simple correlation formula for the drag coefficient of non-spherical particles. Powder Technology, 184(3), 361-365. doi:10.1016/j.powtec.2007.08.021James, C. S. (1990). Prediction of entrainment conditions for nonuniform, noncohesive sediments. Journal of Hydraulic Research, 28(1), 25-41. doi:10.1080/00221689009499145Ji, C., Munjiza, A., Avital, E., Ma, J., & Williams, J. J. R. (2013). Direct numerical simulation of sediment entrainment in turbulent channel flow. Physics of Fluids, 25(5), 056601. doi:10.1063/1.4807075Klamkin, M. S. (1971). Elementary Approximations to the Area of N-Dimensional Ellipsoids. The American Mathematical Monthly, 78(3), 280. doi:10.2307/2317530Mandø, M., & Rosendahl, L. (2010). On the motion of non-spherical particles at high Reynolds number. Powder Technology, 202(1-3), 1-13. doi:10.1016/j.powtec.2010.05.001MILLER, M. C., McCAVE, I. N., & KOMAR, P. D. (1977). Threshold of sediment motion under unidirectional currents. Sedimentology, 24(4), 507-527. doi:10.1111/j.1365-3091.1977.tb00136.xWan Mohtar, W. H. M., & Munro, R. J. (2013). Threshold criteria for incipient sediment motion on an inclined bedform in the presence of oscillating-grid turbulence. Physics of Fluids, 25(1), 015103. doi:10.1063/1.4774341Ortiz, P., & Smolarkiewicz, P. K. (2006). Numerical simulation of sand dune evolution in severe winds. International Journal for Numerical Methods in Fluids, 50(10), 1229-1246. doi:10.1002/fld.1138Ortiz, P., & Smolarkiewicz, P. K. (2009). Coupling the dynamics of boundary layers and evolutionary dunes. Physical Review E, 79(4). doi:10.1103/physreve.79.041307Van Rijn, L. C. (1984). Sediment Transport, Part I: Bed Load Transport. Journal of Hydraulic Engineering, 110(10), 1431-1456. doi:10.1061/(asce)0733-9429(1984)110:10(1431)Shi, G.-H., & Goodman, R. E. (1985). Two dimensional discontinuous deformation analysis. International Journal for Numerical and Analytical Methods in Geomechanics, 9(6), 541-556. doi:10.1002/nag.1610090604Shields, A. (1936). Application of similarity principles and turbulence research to bed-load movement (Tech. Rep.). Lab. for Hydraulic Water Resources.Wellmann, C., Lillie, C., & Wriggers, P. (2008). A contact detection algorithm for superellipsoids based on the common‐normal concept. Engineering Computations, 25(5), 432-442. doi:10.1108/02644400810881374Wiberg, P. L., & Smith, J. D. (1985). A theoretical model for saltating grains in water. Journal of Geophysical Research, 90(C4), 7341. doi:10.1029/jc090ic04p0734

Integrated cyclostratigraphy of the Cau core (SE Spain) - a timescale for climate change during the early Aptian Anoxic Event (OAE 1a) and the late Aptian

We report a cyclostratigraphic study performed on the Cau core (Spain), which is considered an Aptian stratigraphic reference for global correlation and paleoenvironmental reconstruction. This investigation presents an astronomical timescale for the Aptian from Ap2a to Ap14 carbon-isotope stages. Based on the evaluation of a multiproxy dataset from the Cau core, we recalibrate the age and duration of the different biozones, bioevents, chemostratigraphic substages and horizons from the early and late Aptian, with special focus on the Selli Event, providing a new astronomical timescale framework for the Aptian climate. From the recognition of 14 long-eccentricity cycles, we propose a time span of 5.67 Ma for the Ap2a to top of Ap14 C-isotope segments, and ages of 120.82 Ma for the onset of the nannoconid crisis, and 120.20 Ma for the onset of the oceanic anoxic event (OAE) 1a. Calculations yield a duration of 1.47 Ma for the OAE 1a. We estimate the age for the onset of the main Os isotope non-radiogenic phase as 120.08 Ma, 120 ka after the onset of the OAE 1a. The high-resolution data from the Cau core provides further insights in the temporal constraints of the OAE 1a and other Aptian paleoclimatic events. The onset of the main Os-isotope non-radiogenic excursion occurring 120 ka after the onset of the OAE 1a reinforces the theory of rapid destabilization of methane hydrates as the trigger of the anoxic event, that preceded the onset of large-scale volcanism

Agriculture, Food and Natural Resources Handbook 2011

The use of lead (Pb) ammunition in the form of shot pellets has been identified as a Pb exposure risk in wildlife and their human consumers. We explore the hypothesis that Pb shot ban enforcement reduces the risk of avian Pb poisoning as well as Pb exposure in game meat consumers. We assessed compliance with a partial ban on Pb shot commencing in 2003 by examination of 937 waterbirds harvested by hunters between 2007 and 2012 in the Ebro delta (Spain). Prevalence of Pb shot ingestion was determined, as were Pb concentrations in liver and muscle tissue to evaluate the potential for Pb exposure in game meat consumers. Hunted birds with only embedded Pb shot (no steel) declined from 26.9% in 2007–08 to < 2% over the following three hunting seasons after ban reinforcement. Pb shot ingestion in mallards decreased from a pre-ban value of 30.2% to 15.5% in the post-ban period. Liver Pb levels were predominantly defined by the presence of ingested shot, whereas muscle levels were defined by the presence of both ingested and embedded shot. Only 2.5% of mallard muscle tissue had Pb levels above European Union regulations for meat (0.1 μg/g wet weight) in the 2008–09 season, when Pb shot ingestion prevalence was also at a minimum (5.1%). Effective restrictions in Pb ammunition use have a dual benefit since this reduces Pb exposure for game meat consumers due to embedded ammunition as well as reducing Pb poisoning in waterbirds

Progradation of a shallow carbonate platform developed on a fault-block in the Western Tethys (lower Aptian, Sierra de Bedmar-Jódar, Prebetic of Jaén, Spain).

The Middle Member of the Llopis Fm in the Sierra de Bedmar-Jódar Unit of the Prebetic Zone of Jaén (southern Spain) was deposited on a shallow-marine platform of the Southern Iberian Continental Margin during the earliest Aptian. Detailed field logging of nine stratigraphic sections and facies mapping have allowed seven lithofacies associations (L1–L6) to be distinguished, one siliciclastic (L1) and five carbonate facies (L2–6). The succession is composed of eight consecutive elemental sequences of lithofacies associations L1–L6. Each elemental sequence is interpreted as representing one episode of shallowing-upwards carbonate deposition in a very shallow platform-lagoon that was bounded shoreward by clastic/ooid bars and passed seaward either to stromatoporoid bioconstructions (bioherms and biostromes) or rudist biostromes. The successive elemental sequences show north-eastward progradational geometries. Three phases of platform development are identified: (1) installation of the shallow platform; (2) development of a lagoon bounded by a stromatoporoid barrier and (3) development of an Urgonian-type platform dominated by rudists. During the early Aptian, the Bedmar-Jódar platform was partially isolated from the rest of the Prebetic platform and showed overall progradation towards the NE, in contrast to the general south-eastward progradational trend of the Prebetic platform. Sedimentation was controlled by rift-generated extensional tectonics that resulted in tilting of the platform block, causing the deviation of progradation from the general trends of the Prebetic Platform. In addition, climatic influence is inferred from the presence of siliciclastic sediments derived from weathering of the hinterland, which restricted the carbonate factory.Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEUniversidad de JaénSecretaría de Estado de I + D + iJunta de Andalucíapu

Vehicle Classification in Traffic Environments Using the Growing Neural Gas

Traffic monitoring is one of the most popular applications of automated video surveillance. Classification of the vehicles into types is important in order to provide the human traffic controllers with updated information about the characteristics of the traffic flow, which facilitates their decision making process. In this work, a video surveillance system is proposed to carry out such classification. First of all, a feature extraction process is carried out to obtain the most significant features of the detected vehicles. After that, a set of Growing Neural Gas neural networks is employed to determine their types. A qualitative and quantitative assessment of the proposal is carried out on a set of benchmark traffic video sequences, with favorable results.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech