Describing soil surface microrelief by crossover length and fractal dimension

International audienceAccurate description of soil surface topography is essential because different tillage tools produce different soil surface roughness conditions, which in turn affects many processes across the soil surface boundary. Advantages of fractal analysis in soil microrelief assessment have been recognised but the use of fractal indices in practice remains challenging. There is also little information on how soil surface roughness decays under natural rainfall conditions. The objectives of this work were to investigate the decay of initial surface roughness induced by natural rainfall under different soil tillage systems and to compare the performances of a classical statistical index and fractal microrelief indices. Field experiments were performed on an Oxisol at Campinas, São Paulo State (Brazil). Six tillage treatments, namely, disc harrow, disc plow, chisel plow, disc harrow + disc level, disc plow + disc level and chisel plow + disc level were tested. Measurements were made four times, firstly just after tillage and subsequently with increasing amounts of natural rainfall. Duplicated measurements were taken per treatment and date, yielding a total of 48 experimental surfaces. The sampling scheme was a square grid with 25×25 mm point spacing and the plot size was 1350×1350 mm, so that each data set consisted of 3025 individual elevation points. Statistical and fractal indices were calculated both for oriented and random roughness conditions, i.e. after height reading have been corrected for slope and for slope and tillage tool marks. The main drawback of the standard statistical index random roughness, RR, lies in its no spatial nature. The fractal approach requires two indices, fractal dimension, D, which describes how roughness changes with scale, and crossover length, l, specifying the variance of surface microrelief at a reference scale. Fractal parameters D and l, were estimated by two independent self-affine models, semivariogram (SMV) and local root mean square (RMS). Both algorithms, SMV and RMS, gave equivalent results for D and l indices, irrespective of trend removal procedure, even if some bias was present which is in accordance with previous work. Treatments with two tillage operations had the greatest D values, irrespective of evolution stage under rainfall and trend removal procedure. Primary tillage had the greatest initial values of RR and l. Differences in D values between treatments with primary tillage and those with two successive tillage operations were significant for oriented but not for random conditions. The statistical index RR and the fractal indices l and D decreased with increasing cumulative rainfall following different patterns. The l and D decay from initial value was very sharp after the first 24.4 mm cumulative rainfall. For five out of six tillage treatments a significant relationship between D and l was found for the random microrelief conditions allowing a covariance analysis. It was concluded that using RR or l together with D best allow joint description of vertical and horizontal soil roughness variations

Temperature dependence of the magnetization processes in Co/Al oxide/Permalloy trilayers

The magnetization process of Co/Al oxide/Py trilayers and its evolution with the temperature have been analyzed. The particular behavior of the Co layers, including the shift of the hysteresis loops and a coercivity increase with the decrease of temperature, is related with the apparition of a CoO layer at the Co/Al-oxide interface

Rockfall Hazard Assessment in Volcanic Regions Based on ISVS and IRVS Geomechanical Indices

In volcanic regions, rockfalls represent a major hazard strongly conditioned by the geomechanical behaviour of volcanic materials, the geomorphological characteristics of the relief and the climatic conditions. Volcanic rocks possess very different properties to those of other lithological groups, presenting highly heterogeneous geomechanical behaviours. Nevertheless, they have received little research attention in the field of geological and geotechnical engineering. To date, the application of geomechanical classifications to characterise and estimate volcanic slope stability has not yielded reliable results, indicating the need to establish specific criteria for these rocks. Consequently, we developed indices to estimate rockfall susceptibility, hazard and risk in volcanic slopes. The index of susceptibility for volcanic slopes (ISVS) is designed to estimate slope susceptibility to instability, which is related to the level of hazard, while the index of risk for volcanic slopes (IRVS) is designed to estimate the level of risk as a function of the potential damage or economic loss caused as a result of rockfalls on slopes. Both indices were developed in order to provide an easily applied procedure that facilitates the adoption of short-term preventive measures against rockfalls. The indices were applied in Tenerife (Canary Islands), which presents exceptional conditions for analysing slope stability in volcanic rocks because of its mountainous orography with very steep slopes and a wide variety of materials. These conditions have frequently precipitated slope instability, causing significant damage to housing, beaches, roads and other infrastructures. After applying these indices to a number of slopes representative of the island’s wide variety of geological, geomorphological and climatic conditions, the results obtained were compared with the actual behaviour of the slopes, determined from extensive rockfall inventory data and in situ geomechanical survey

Multivariate analysis and extraction of parameters in resistive RAMs using the Quantum Point Contact model

A multivariate analysis of the parameters that characterize the reset process in RRAMs has been performed. The different correlations obtained can help to shed light on the current components that contribute in the Low Resistance State (LRS) of the technology considered. In addition, a screening method for the Quantum Point Contact (QPC) current component is presented. For this purpose the second derivative of the current has been obtained using a novel numerical method which allows determining the QPC model parameters. Once the procedure is completed, a whole RS series of thousands of curves is studied by means of a genetic algorithm. The extracted QPC parameter distributions are characterized in depth to get information about the filamentary pathways associated with LRS in the low voltage conduction regime.Spanish Ministry of Economy and Competitiveness TEC2014-52152-C3-2-R , MTM2013-47929-P (also supported by the FEDER program)IMB-CNM Spanish Ministry of Economy and Competitiveness TEC2014-52152-C3-1-R and TEC2014-54906-JIN (supported by the FEDER program)ENIAC Joint Undertaking-PANACHE project.Spanish ICTS Network MICRONANOFAB

Streblidae (Diptera: pupipara) ectoparásitos de murciélagos, en las tierras bajas del Parque Nacional Darién, provincia de Darién, Panamá

En este trabajo Artibeus jamaicensis, A. phaeotis, Carollia castanea, C. perspicillata, Chiroderma salvini, Phillostomus hastatus, Sturnira lilium y Uroderma bilobatum son las especies de murciélagos donde la diversidad ectoparasítica estuvo representada por 14 especies de Streblidae; mientras que Artibeus lituratus, A. watsoni y Vampiressa pusilla forman el grupo de los no parasitados. El parásito Trichobius joblingi resultó ser el Streblidae más abundante (53 individuos). Reportamos por primera vez para Panamá a Artibeus phaeotis como hospedero de Neotrichobius stenopterus. Las especies Mastoptera guimaraesi, Speiseria ambigua, Strebla mirabilis, Trichobius longipes y T. sparsus son especies de Streblidae reportadas por primera vez para la Provincia de Darié

STREBLIDAE (DIPTERA: PUPIPARA) ECTOPARÁSITOS DE MURCIÉLAGOS, EN LAS TIERRAS BAJAS DEL PARQUE NACIONAL DARIÉN, PROVINCIA DE DARIÉN, PANAMA.

  In this work Artibeus jamaicensis, A. phaeotis, Carollia castanea, C. perspicillata, Chiroderma salvini, Phillostomus hastatus, Sturnira lilium and Uroderma bilobatum are the species of parasited bats by Streblidae, while Artibeus lituratus, A. watsoni and Vampiressa pusilla form the group of the non-parasited bats. Trichobius joblingi is the most abundant Streblidae (53 specimens). We reported for first time in Panama the species Artibeus phaeotis as host for the Neotrichobius stenopterus. Mastoptera guimaraesi, Speiseira ambigua, Strebla mirabilis, Trichobius longipes and T. sparsus are the species of Streblidae reported in the province of Darien.  En este trabajo Artibeus jamaicensis, A. phaeotis, Carollia castanea, C. perspicillata, Chiroderma salvini, Phillostomus hastatus, Sturnira lilium y Uroderma bilobatum son las especies de murciélagos donde la diversidad ectoparasítica estuvo representada por 14 especies de Streblidae; mientras que Artibeus lituratus, A. watsoni y Vampiressa pusilla forman el grupo de los no parasitados. El parásito Trichobius joblingi resultó ser el Streblidae más abundante (53 individuos). Reportamos por primera vez para Panamá a Artibeus phaeotis como hospedero de Neotrichobius stenopterus. Las especies Mastoptera guimaraesi, Speiseria ambigua, Strebla mirabilis, Trichobius longipes y T. sparsus son especies de Streblidae reportadas por primera vez para la Provincia de Darién

Analysis and control of the intermediate memory states of RRAM devices by means of admittance parameters

Producción CientíficaA thorough study of the admittance of TiN/Ti/HfO2/W bipolar resistive memories [resistance random access memory (RRAM)] was carried out under different bias conditions and in a wide range of ac signal frequencies. We demonstrate that a continuum of intermediate states can be obtained by applying appropriate dc bias waveforms. Cumulative writing and erasing admittance cycles were performed by applying triangular voltage waveform of increasing amplitude. The influence of the initial conditions on the variation of the real (conductance) and imaginary (susceptance) components of the admittance is described. An accurate control of the memory state is achieved both in terms of the conductance and the susceptance by means of an adequate selection of the voltage values previously applied. A method to obtain three-dimensional voltage-conductance-susceptance state-plots is described in detail. Memory maps of admittance parameters as a function of the programming voltage are made by sensing the memory state at 0 V, without static power consumption. The multilevel nature of RRAM devices and their suitability for neuromorphic computation are demonstrated.Ministerio de Economía, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (grants TEC2014-52152-C3-3-R and TEC2014- 52152-C3-1-R

Lack of association between TLR4 rs4986790 polymorphism and risk of cardiovascular disease in patients with rheumatoid arthritis

This is copy of an article published in the DNA and cell biology 2012 © Mary Ann Liebert, Inc.; DNA and cell bilogy is available online at: http://online.liebertpub.comRheumatoid arthritis (RA) is a chronic inflammatory disease associated with increased cardiovascular (CV) mortality. Toll-like receptor-4 (TLR4) activates the innate immune response via NF-kB pathway and mitogenactivated protein kinase signaling, leading to expression of proinflammatory cytokines and chemokines. The G allele of TLR4 rs4986790 (+ 896A > G, Asp299Gly) gene polymorphism has been implicated in reduction of risk of atherosclerosis. In this study, 1481 RA patients fulfilling the 1987 American College of Rheumatology (ACR) criteria were genotyped for the rs4986790 TLR4 variant to determine the influence of this variant in the risk of CV events in these patients. Also, HLA-DRB1 status was determined using molecular based methods. Moreover, potential influence of rs4986790 variant in the development of subclinical atherosclerosis was assessed in a subgroup of RA patients with no history of CV events by the measurement of surrogate markers of subclinical atherosclerosis. No statistically significant differences in allele or genotype frequencies for the rs4986790 variant between RA patients who experienced CV events or not were found. Likewise, no significant association between this gene variant and any of the surrogate markers of subclinical atherosclerosis was found. In summary, results in our study do not support the hypothesis that the rs4986790 (+ 896A > G, Asp299Gly) TLR4 variant may influence predisposition for subclinical atherosclerosis and clinically evident CV disease in RA patientsThis study was supported by two grants from Fondo de Investigaciones Sanitarias PI06-0024 and PS09/00748 (Spain). This work was partially supported by RETICS Program, RD08/0075 (RIER) from Instituto de Salud Carlos III (ISCIII), within the VI PN de I +D+ i 2008–2011 (FEDER). M.G.B. is supported by a grant from Fundación Española de Reumatología (FER). R.L.M. is supported by a grant by IFIMAV, Santander (Spain)

Chaotic Dynamics of Spin-Valve Oscillators

Recent experimental and theoretical studies on the magnetization dynamics driven by an electric current have uncovered a number of unprecedented rich dynamic phenomena. We predict an intrinsic chaotic dynamics that has not been previously anticipated. We explicitly show that the transition to chaotic dynamics occurs through a series of period doubling bifurcations. In chaotic regime, two dramatically different power spectra, one with a well-defined peak and the other with a broadly distributed noise, are identified and explained