Choice of Metrics used in Collaborative Filtering and their Impact on Recommender Systems

The capacity of recommender systems to make correct predictions is essentially determined by the quality and suitability of the collaborative filtering that implements them. The common memory-based metrics are Pearson correlation and cosine, however, their use is not always the most appropriate or sufficiently justified. In this paper, we analyze these two metrics together with the less common mean squared difference (MSD) to discover their advantages and drawbacks in very important aspects such as the impact when introducing different values of k-neighborhoods, minimization of the MAE error, capacity to carry out a sufficient number of predictions, percentage of correct and incorrect predictions and behavior when attempting to recommend the n-best items. The paper lists the results and practical conclusions that have been obtained after carrying out a comparative study of the metrics based on 135 experiments on the MovieLens database of 100,000 ratios

Graphical tools for helping firefighters in victim rescues. Assessment during a live fire training program

This study compares three different methods to communicate the features of a building to firefighters, before starting a victim rescue during a live fire training program. Participants in this study did not previously know the hotel used for developing the activities. The effective number of participants was 144, all professional firefighters. One of the exercises in this training program was thoroughly designed not only for training purposes, but also to test different guide versions. The innovative guides were based on two different technologies (simple stapled sheets of paper and digital content displayed on a tablet) and were developed using several graphical tools (conventional pictures, aerial images captured with drone, 3D models, 360° pictures, etc.). With the intention of facilitating firefighters’ activity during a victim rescue, results obtained using these tools were compared with a conventional communication method. The assessment methodology applied in this study included the use of an anonym questionnaire, as well as the analysis of the videos captured with action cameras, attached with a harness to the chest of two of the four firefighters in every team, during the training activities. Thanks to these videos, it was possible to compare the time required for rescuing the victim and to observe followed paths, visited rooms and substantial information about the tested tools, including valuable participants’ comments. For in emergency situations, the tools described in this paper were preferred to the already existent self-protection plans, usually considered too extensive for fast communication, a matter of special importance in victim rescues

Magnetic order and magnetic properties of the oxygen deficient SmBaMn2O5 layered perovskite

Magnetism in SmBaMn2O5 was investigated on a single crystal by magnetic and neutron diffraction measurements. This is an oxygen deficient perovskite with a layered ordering of Sm and Ba cations. Mn atoms are coordinated with five oxygens forming a square pyramid and they are ordered in a checkerboard pattern of expanded-compressed pyramids in the ab-plane. The neutron diffraction study revealed a ferrimagnetic ordering of Mn moments below TN=134 K. Macroscopic measurements reveal a very anisotropic behavior. Measurements with the external magnetic field parallel (M||c) and perpendicular (M¿c) to the c-axis confirm that this is the easy axis above 10 K. Below this temperature, the Sm sublattice begins to polarize and the magnetization M||c decreases while M¿c experiences a huge increase. This indicates that Sm moments begin to order around 10 K in the ab-plane with a minor component on the c-axis that opposes the overall magnetization from Mn sublattices

Configuración del Paisaje y Conservación de Hábitat Dunares: Las Dunas de Coterillo en la Región de Murcia (España)

El paisaje de Coterillo se caracteriza por hábitats que comparten el territorio con especies exóticas-invasoras y otras especies, que se plantaron a principios del siglo XX para fijar las dunas que invadían los estanques salineros. La metodología se ha basado muestreos de campo, análisis bibliográfico y del paisaje de cartografía histórica, del vuelo aéreo de 1957 y del satélite de 2016, para analizar la evolución de los hábitats y de las especies exóticas-invasoras. En la actualidad hay 15 hábitats de interés comunitario, entre los que destacan los prioritarios 1510 Estepas salinas mediterráneas Limonietalia y 2250 Dunas litorales con Juniperus sp, con problemas de conservación por uso recreativo del territorio y competencia con especies exóticas-invasoras. Se analizan las acciones de gestión de la administración para recuperar los hábitats, entre las que destacan el control de especies exóticas-invasoras y ordenación del uso público. La prioridad es la recuperación de los hábitats originarios de dunas, por lo que se recomienda mantener las actuaciones emprendidas por la administración, en particular reforzar la sustitución de las especies arbóreas introducidas, sobre todo Pinus halepensis, por Juniperus turbinata y otras especies de dunas, así como reforzar las actuaciones para erradicar las especies exóticas invasoras.-- The landscape of Coterillo is characterized by habitats that share the territory with exotic-invasive species and other species, which were planted in the early twentieth century to fix the dunes that invaded the salt ponds. The methodology has been based on field samplings, bibliographic and landscape analysis of historical cartography, the 1957 aerial flight and the 2016 satellite, to analyze the evolution of habitats and exotic-invasive species. At present there are 15 habitats of community interest, among which the priority ones are 1510 Mediterranean salt stepas Limonietalia and 2250 coastal dunes with Juniperus sp, with conservation problems due to recreational use of the territory and competition with exotic-invasive species. The management actions of the administration are analyzed to recover the habitats, among which the control of exotic-invasive species and public use management stand out. The priority is the recovery of habitats originating from dunes, which is why it is recommended to maintain the actions undertaken by the administration, in particular to reinforce the substitution of introduced tree species, especially Pinus halepensis, for Juniperus turbinata and other dune species, as well as reinforce actions to eradicate invasive alien species. Keywords: Coterillo; dunes; species; exotic-invasive; managemen

Modeling Optical and Electronic Properties of Silica Nano-Clusters in Silicon Rich Oxide Films

Quantum effects are very important in nano scale systems such as molecules and clusters constituted of particles from a few to hundreds or a few thousands of atoms. Their optical and electronic properties are often dependent on the size of the systems and the way in which the atoms in these molecules or clusters are bonded. Generally, these nano-structures display optical and electronic properties significantly different of the bulk materials. Silica agglomerates expected in Silicon Rich Oxide (SRO) films have optical properties, which depend directly on size, and their rationalization can lead to new applications with a potential impact on many fields of science and technology. On the other hand, the room temperature photoluminescence (PL) of Si : SiO2 or Si : SiOx structures usually found in SRO has recently generated an enormous interest due to their possible applications in optoelectronic devices. However, the understanding of the emission mechanism is still under debate. In this research, we employed the Density Functional Theory with a functional B3LYP and a basis set 6-31 G* to calculate the electronic and optical properties of molecules and clusters of silicon dioxide. With the theoretical calculation of the structural and optical properties of silicon dioxide clusters is possible to evaluate the contribution of silica in the luminescent emission mechanism experimentally found in thin SRO films. It was found that silica contribution to the luminescent phenomenon in SRO thin films is less important than that of the silicon monoxide agglomerates because the number of silica structures, which may show emission in the visible spectrum, is much lower [1], compared to the number of silicon monoxide structures which emit in this region. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3192

The causal boundary of wave-type spacetimes

A complete and systematic approach to compute the causal boundary of wave-type spacetimes is carried out. The case of a 1-dimensional boundary is specially analyzed and its critical appearance in pp-wave type spacetimes is emphasized. In particular, the corresponding results obtained in the framework of the AdS/CFT correspondence for holography on the boundary, are reinterpreted and very widely generalized. Technically, a recent new definition of causal boundary is used and stressed. Moreover, a set of mathematical tools is introduced (analytical functional approach, Sturm-Liouville theory, Fermat-type arrival time, Busemann-type functions).Comment: 41 pages, 1 table. Included 4 new figures, and some small modifications. To appear in JHE

Validación de dos algoritmos para la localización 3D del instrumental laparoscópico a partir de la imagen de vídeo endoscópico

Uno de los aspectos fundamentales en un sistema de cirugía guiada por imagen (CGI) es la localización del instrumental quirúrgico con respecto a la anatomía del paciente. Los sistemas basados en sensores ofrecen buenos niveles de precisión, pero son sensibles a distintas fuentes de ruido en el quirófano y contribuyen a la sobrecarga tecnológica del mismo. Una alternativa novedosa es analizar la imagen del vídeo endoscópico para llevar a cabo la detección y localización espacial del instrumental. Se presenta en este trabajo la validación de dos métodos, basados en el diámetro aparente y en la sección transversal del instrumental, para la localización espacial del instrumental a partir de los bordes y la posición 2D de la punta en la imagen. La validación, llevada a cabo en un simulador físico, se realiza comparando los resultados con el sistema Kinescan/IBV. Los resultados muestran para cada método un error medio de 12,7 y 12,8 mm respectivamente. La incorporación de estos algoritmos dentro del paradigma de navegación propuesto en el proyecto THEMIS permitirá al cirujano conocer la posición del instrumental de forma no intrusiva y transparente, sin necesidad de equipamiento adicional en el quirófano

Development of new remediation technologies for contaminated soils based on the application of zero-valent iron nanoparticles and bioremediation with compost

This study aimed to develop new techniques for the remediation of contaminated soils based on the applicationof zero-valent iron nanoparticles (nZVI) and bioremediation with compost from organic wastesand a mixed technique of both. An assessment of the effectiveness of remediation in two soils contaminatedwith hydrocarbons and heavy metals was carried out, with the aim of looking for positive synergiesby combining the two techniques, and demonstrating their viability on an industrial scale. The applicationof nZVI for in situ immobilization of As and Cr in two different soils (Soil I from a contaminatedindustrial site and Soil II, contaminated artificially) showed a decrease in the concentration of As in SoilI and Soil II, as well as a decrease in Cr concentration for Soil I and Soil II in the leachate of both soils.The addition of compost and nanoparticles under uncontrolled environmental conditions in biopiles wasable to produce a decrease in the concentration of aliphatic hydrocarbons of up to 60% in the two soils.Especially, degradation and transformation of longer chains occurred. A significant reduction of ecotoxicitywas observed throughout the process in the biopile of soil II, not reaching the LC50 even with 100%of the sample after the treatment, in both earthworm and seeds growth tests

Colgajo de vasto lateral de pedículo distal para cobertura de lesiones complejas de rodilla

El tratamiento de las heridas complejas articulares se muestra siempre complicado, el abordaje razonable conjunto por traumatólogos y cirujanos plásticos mejora el resultado clínico, funcional y estético. Presentamos el caso de un paciente politraumatizado con pérdida de sustancia a nivel de la rodilla secundaria a artritis séptica, necrosis de patela y exposición de cóndilos femorales que fue tratado mediante colgajo muscular de vastus lateralis de pedículo distal. El vastus lateralis permite la cobertura eficiente de l articulación expuesta sin afectar la extensión de la rodilla y dejando mínima secuela estética.The treatment of the joint complex wounds is difficult. A good clinic, functional and aesthetic outcome is possible when multidisciplinary approach by orthopaedics and plastic surgeons is carried out. We report a case of a patient with multiple fractures who presents a severe loss of soft tissue at the knee. This lesion was due to a septic arthritis with patellar necrosis and condillar exposition. The treatment was made by a distally pedicled vastus lateralis muscular flap. This flap lets efficient coverage for the exposed joint as well as the integrity of the extensión knee function without aesthetic seque

High-level quinolone resistance is associated with the overexpression of smeVWX in Stenotrophomonas maltophilia clinical isolates

AbstractStenotrophomonas maltophilia is the only known bacterium in which quinolone-resistant isolates do not present mutations in the genes encoding bacterial topoisomerases. The expression of the intrinsic quinolone resistance elements smeDEF, smeVWX and Smqnr was analysed in 31 clinical S. maltophilia isolates presenting a minimum inhibitory concentration (MIC) range to ciprofloxacin between 0.5 and > 32 μg/mL; 11 (35.5%) overexpressed smeDEF, 2 (6.5%) presenting the highest quinolone MICs overexpressed smeVWX and 1 (3.2%) overexpressed Smqnr. Both strains overexpressing smeVWX presented changes at the Gly266 position of SmeRv, the repressor of smeVWX. Changes at the same position were previously observed in in vitro selected S. maltophilia quinolone-resistant mutants, indicating this amino acid is highly relevant for the activity of SmeRv in repressing smeVWX expression. For the first time SmeVWX overexpression is associated with quinolone resistance of S. maltophilia clinical isolates