Artificial intelligence-based software (AID-FOREST) for tree detection: A new framework for fast and accurate forest inventorying using LiDAR point clouds

Forest inventories are essential to accurately estimate different dendrometric and forest stand parameters. However, classical forest inventories are time consuming, slow to conduct, sometimes inaccurate and costly. To address this problem, an efficient alternative approach has been sought and designed that will make this type of field work cheaper, faster, more accurate, and easier to complete. The implementation of this concept has required the development of a specifically designed software called "Artificial Intelligence for Digital Forest (AID-FOREST)", which is able to process point clouds obtained via mobile terrestrial laser scanning (MTLS) and then, to provide an array of multiple useful and accurate dendrometric and forest stand parameters. Singular characteristics of this approach are: No data pre-processing is required either pre-treatment of forest stand; fully automatic process once launched; no limitations by the size of the point cloud file and fast computations.To validate AID-FOREST, results provided by this software were compared against the obtained from in-situ classical forest inventories. To guaranty the soundness and generality of the comparison, different tree spe-cies, plot sizes, and tree densities were measured and analysed. A total of 76 plots (10,887 trees) were selected to conduct both a classic forest inventory reference method and a MTLS (ZEB-HORIZON, Geoslam, ltd.) scanning to obtain point clouds for AID-FOREST processing, known as the MTLS-AIDFOREST method. Thus, we compared the data collected by both methods estimating the average number of trees and diameter at breast height (DBH) for each plot. Moreover, 71 additional individual trees were scanned with MTLS and processed by AID-FOREST and were then felled and divided into logs measuring 1 m in length. This allowed us to accurately measure the DBH, total height, and total volume of the stems.When we compared the results obtained with each methodology, the mean detectability was 97% and ranged from 81.3 to 100%, with a bias (underestimation by MTLS-AIDFOREST method) in the number of trees per plot of 2.8% and a relative root-mean-square error (RMSE) of 9.2%. Species, plot size, and tree density did not significantly affect detectability. However, this parameter was significantly affected by the ecosystem visual complexity index (EVCI). The average DBH per plot was underestimated (but was not significantly different from 0) by the MTLS-AIDFOREST, with the average bias for pooled data being 1.8% with a RMSE of 7.5%. Similarly, there was no statistically significant differences between the two distribution functions of the DBH at the 95.0% confidence level.Regarding the individual tree parameters, MTLS-AIDFOREST underestimated DBH by 0.16 % (RMSE = 5.2 %) and overestimated the stem volume (Vt) by 1.37 % (RMSE = 14.3 %, although the BIAS was not statistically significantly different from 0). However, the MTLS-AIDFOREST method overestimated the total height (Ht) of the trees by a mean 1.33 m (5.1 %; relative RMSE = 11.5 %), because of the different height concepts measured by both methodological approaches. Finally, AID-FOREST required 30 to 66 min per ha-1 to fully automatically process the point cloud data from the *.las file corresponding to a given hectare plot. Thus, applying our MTLS-AIDFOREST methodology to make full forest inventories, required a 57.3 % of the time required to perform classical plot forest inventories (excluding the data postprocessing time in the latter case). A free trial of AID -FOREST can be requested at [email protected]

Electromechanics of charge shuttling in dissipative nanostructures

We investigate the current-voltage (IV) characteristics of a model single-electron transistor where mechanical motion, subject to strong dissipation, of a small metallic grain is possible. The system is studied both by using Monte Carlo simulations and by using an analytical approach. We show that electromechanical coupling results in a highly nonlinear IV-curve. For voltages above the Coulomb blockade threshold, two distinct regimes of charge transfer occur: At low voltages the system behave as a static asymmetric double junction and tunneling is the dominating charge transfer mechanism. At higher voltages an abrupt transition to a new shuttle regime appears, where the grain performs an oscillatory motion back and forth between the leads. In this regime the current is mainly mediated by charges that are carried on the grain as it moves from one lead to the other.Comment: 8 pages, 10 figures, final version to be published in PR

Thymocyte regulatory variant alters transcription factor binding and protects from type 1 diabetes in infants

We recently mapped a genetic susceptibility locus on chromosome 6q22.33 for type 1 diabetes (T1D) diagnosed below the age of 7 years between the PTPRK and thymocyte-selection-associated (THEMIS) genes. As the thymus plays a central role in shaping the T cell repertoire, we aimed to identify the most likely causal genetic factors behind this association using thymocyte genomic data. In four thymocyte populations, we identified 253 DNA sequence motifs underlying histone modifications. The G insertion allele of rs138300818, associated with protection from diabetes, created thymocyte motifs for multiple histone modifications and thymocyte types. In a parallel approach to identifying variants that alter transcription factor binding motifs, the same variant disrupted a predicted motif for Rfx7, which is abundantly expressed in the thymus. Chromatin state and RNA sequencing data suggested strong transcription overlapping rs138300818 in fetal thymus, while expression quantitative trait locus and chromatin conformation data associate the insertion with lower THEMIS expression. Extending the analysis to other T1D loci further highlighted rs66733041 affecting the GATA3 transcription factor binding in the AFF3 locus. Taken together, our results support a role for thymic THEMIS gene expression and the rs138300818 variant in promoting the development of early-onset T1D.Peer reviewe

Evolution of an eruptive flare loop system

<p><b>Context:</b> Flares, eruptive prominences and coronal mass ejections are phenomena where magnetic reconnection plays an important role. However, the location and the rate of the reconnection, as well as the mechanisms of particle interaction with ambient and chromospheric plasma are still unclear.</p> <p><b>Aims:</b> In order to contribute to the comprehension of the above mentioned processes we studied the evolution of the eruptive flare loop system in an active region where a flare, a prominence eruption and a CME occurred on August 24, 2002.</p> <p><b>Methods:</b> We measured the rate of expansion of the flare loop arcade using TRACE 195 Å images and determined the rising velocity and the evolution of the low and high energy hard X-ray sources using RHESSI data. We also fitted HXR spectra and considered the radio emission at 17 and 34 GHZ.</p> <p><b>Results:</b> We observed that the top of the eruptive flare loop system initially rises with a linear behavior and then, after 120 mn from the start of the event registered by GOES at 1–8 Å, it slows down. We also observed that the heating source (low energy X-ray) rises faster than the top of the loops at 195 Å and that the high energy X-ray emission (30–40 keV) changes in time, changing from footpoint emission at the very onset of the flare to being coincident during the flare peak with the whole flare loop arcade.</p> <p><b>Conclusions:</b> The evolution of the loop system and of the X-ray sources allowed us to interpret this event in the framework of the Lin & Forbes model (2000), where the absolute rate of reconnection decreases when the current sheet is located at an altitude where the Alfvén speed decreases with height. We estimated that the lower limit for the altitude of the current sheet is km. Moreover, we interpreted the unusual variation of the high energy HXR emission as a manifestation of the non thermal coronal thick-target process which appears during the flare in a manner consistent with the inferred increase in coronal column density.</p&gt

Free-electron Model for Mesoscopic Force Fluctuations in Nanowires

When two metal electrodes are separated, a nanometer sized wire (nanowire) is formed just before the contact breaks. The electrical conduction measured during this retraction process shows signs of quantized conductance in units of G_0=2e^2/h. Recent experiments show that the force acting on the wire during separation fluctuates, which has been interpreted as being due to atomic rearrangements. In this report we use a simple free electron model, for two simple geometries, and show that the electronic contribution to the force fluctuations is comparable to the experimentally found values, about 2 nN.Comment: 4 pages, 3 figures, reference correcte

Statin pretreatment diminishes the levels of myocardial ischemia markers not only in CABG

A response to Ege E, Dereli Y, Kurban S, Sarigul A: Atorvastatin pretreatment diminishes the levels of myocardial ischemia markers early after CABG operation: an observational study. J Cardiothorac Surg 2010, 5:60

Inversed linear dichroism in F <em>K</em>-edge NEXAFS spectra of fluorinated planar aromatic molecules

et al.The symmetry and energy distribution of unoccupied molecular orbitals is addressed in this work by means of NEXAFS and density functional theory calculations for planar, fluorinated organic semiconductors (perfluorinated copper phthalocyanines and perfluoropentacene). We demonstrate how molecular orbitals with significant density of states on the fluorine atoms show different symmetry from those mainly located on C and N atoms. As a result, the angle-dependent linear dichroism in NEXAFS F K-edge spectra is inversed with respect to that in the C and N K-edges. In addition, the significant overlap in energy of π * and σ * orbitals throughout the F K-edge spectrum hampers its use for analysis of molecular orientations from angle-dependent NEXAFS measurements. © 2012 American Physical Society.J.E.O. and A.R. acknowledge funding from the Spanish MEC through Grants No. FIS2011-65702-C02-01, No. MAT2010-21156-C03-01, and No. PIB2010US-00652, and from the Basque Government through Grants No. IT-257-07 and No. IT-319-07. A.R. additionally acknowledges that financial support was provided by ACI-Promociona Grant No. ACI2009-1036 and the European Research Council Advanced Grant DYNamo (ERC-2010-AdG, Proposal No. 267374). A.S. acknowledges the support of the Research Funds of the University of Helsinki and the Academy of Finland through Contract No. 1127462, Centers of Excellence Program, and the National Graduate School in Materials Physics. J.M.G.L. acknowledges support from The Lundbeck Foundation’s Center for Atomic-Scale Materials Design and the Danish Center for Scientific Computing.Peer Reviewe