Development of methods based on neural networks in the estimation of mineral resources

Debido a limitaciones económicas y físicas, nuestra comprensión de los recursos minerales en un área de interés específica es limitada y fragmentada. Tradicionalmente, este problema se ha resuelto utilizando el método geoestadístico de Kriging, donde la ley del mineral se estima en ubicaciones sin mediciones utilizando valores conocidos de la ley en puntos circundantes. La ventaja de este método radica en el cálculo de pesos a través de un modelo de variabilidad espacial conocido como variograma. Sin embargo, su desventaja es que se basa en el supuesto de estacionariedad, aditividad, linealidad y de cierta forma el modelado variográfico es subjetivo. Este estudio propone abordar el problema de estimación de recursos minerales como un problema de regresión utilizando redes neuronales, que no están sujetas a las restricciones de estacionariedad, aditividad, linealidad y modelado espacial de los métodos geoestadísticos. Se han comparado el Kriging y una red neuronal de función de base radial y un perceptrón multicapa utilizando distintas métricas de validación. Los resultados muestran que un modelo de red neuronal adecuadamente entrenado, con un etiquetado apropiado de la ley mineral y sus características de entrada, logra resultados similares al enfoque geoestadístico con una reducción de tiempo significativo, evitando a su vez todos los supuestos antes señalados. Sin embargo, las redes neuronales no consideran la correlación espacial de la ley del mineral ni la reproducen en los lugares donde se midió, características que han marcado desconfianza en su implementación industrial y que se discuten en este artículo proponiendo finalmente un ajuste entre ambos enfoques a un mínimo sacrificio del coste temporal y de mano de obra

Wear tests on PTFE+pb linings for linear pneumatic actuator guide bushings

Guide bushings for linear actuators are subject to intense mechanical stress and wear, especially when external radial forces are applied. Carrying out simplified wear tests on the materials used in these bushings is important in making it possible to estimate how many cycles the actuator can perform before the bushing must be replaced. This paper presents the results of tribological pin-on-disk testing on an anti-friction lining consisting of a porous bronze sinter impregnated and coated with PTFE+Pb. Test specimens were worn with a steel ball, and wear and friction coefficients were determined experimentally with increasing loads and speeds

Scaffold Optimisation of Tetravalent Antagonists of the Mannose Binding Lectin

Antagonists of mannose binding lectin (MBL) have shown a protective role against brain reperfusion damage after acute ischemic stroke. Here we describe the design and streamlined synthesis of glycomimetic MBL antagonists based on a new tetravalent dendron scaffold. The dendron was developed by optimisation of a known polyester structure previously demonstrated to be very efficient for ligand presentation to MBL. Replacement of a labile succinyl ester bond with a more robust amide functionality, use of a longer and more hydrophilic linker, fast modular synthesis and orthogonal functionalisation at the focal point are the main features of the new scaffold. The glycoconjugate constructs become stable to silica gel chromatography and to water solutions at physiological pH, while preserving water solubility and activity in an SPR assay against the murine MBL-C isoform. Higher-order constructs were easily assembled, as demonstrated by the synthesis of a 16-valent dendrimer, which leads to two orders of magnitude increase in activity over the tetravalent version against MBL-C

Stimulation of Ca2+-ATPase Transport Activity by a Small-Molecule Drug

The sarco(endo)plasmic reticulum Ca(2+)−ATPase (SERCA) hydrolyzes ATP to transport Ca(2+) from the cytoplasm to the sarcoplasmic reticulum (SR) lumen, thereby inducing muscle relaxation. Dysfunctional SERCA has been related to various diseases. The identification of small‐molecule drugs that can activate SERCA may offer a therapeutic approach to treat pathologies connected with SERCA malfunction. Herein, we propose a method to study the mechanism of interaction between SERCA and novel SERCA activators, i. e. CDN1163, using a solid supported membrane (SSM) biosensing approach. Native SR vesicles or reconstituted proteoliposomes containing SERCA were adsorbed on the SSM and activated by ATP concentration jumps. We observed that CDN1163 reversibly interacts with SERCA and enhances ATP‐dependent Ca(2+) translocation. The concentration dependence of the CDN1163 effect provided an EC(50)=6.0±0.3 μM. CDN1163 was shown to act directly on SERCA and to exert its stimulatory effect under physiological Ca(2+) concentrations. These results suggest that CDN1163 interaction with SERCA can promote a protein conformational state that favors Ca(2+) release into the SR lumen

From optimized monovalent ligands to size-controlled dendrimers : an efficient strategy towards high-activity DC-SIGN antagonists

This short review describes our work on the development of dendrimeric antagonists of DC-SIGN, a dendritic cells (DCs) receptor recognizing highly mannosylated structures and primarily involved in the recognition of viruses such as HIV. The structure of pseudo-di-mannoside and pseudo-tri-mannoside compounds was first finely modified to obtain DC-SIGN ligands that were more stable and selective than mannose. Their DC-SIGN affinity differences were amplified once presented on multivalent dendrimer-like scaffolds, including poly-alkyne terminated and phenylene-ethynylene rod-like ones. Libraries of mannosylated dendrimers were synthesized, improving their stability and maximizing their monodispersity. The effect of the dendrimers valency, structure, and size on DC-SIGN affinity and antiviral potency was investigated. Both the valency and the topology of the architectures were revealed as key parameters for activity optimization, together with the intrinsic affinity of the monovalent ligand. The stability, rigidity, and length of the scaffolds were also tuned. The design of geometrically adapted scaffolds afforded one of the most potent inhibitors of DC-SIGN mediated HIV infections to date. This monodispersed, not cytotoxic, and highly active compound was also tested with DCs; its internalization into endolysosomal compartments and its ability to induce the overexpression of signaling molecules makes it a good precursor to produce pathogen-entry inhibitors with immunomodulant properties

EVALUACIÓN A CORTO PLAZO DE LA BIOMETRÍA Y CRECIMIENTO DE LUTJANUS GUTTATUS, LUTJANUS PERU Y LUTJANUS ARGENTIVENTRIS, BÚCARO, PANAMÁ

The size and growth assessment of Lutjanus guttatus, L. peru, and L. argentiventris, captured by the artisanal fleet that disembarks in the community of Búcaro, Panama, for a period of six months, the size composition is described, the weight vs. height relationship, growth was estimated based on the monthly length structure, for which L?, catabolic coefficient k, the hypothetical age to for height 0, and the evaluation index of ? 'and the longevity A0.95, the von Bertalanffy equation was developed for each species and the analysis of the modal progression "VBGF". The length varied between 204 and 648 mm and the weight ranged between 85 and 3 373 g, in the three species, the relationship of these variables showed an isometric growth, the modal progression indicated two cohorts defined in L. guttatus, not so in the other species. The results are a baseline contribution for the development of the study of artisanal fishing biology in the Central American Pacific zone.Se realizó la evaluación de longitud y el crecimiento de Lutjanus guttatus, L. peru y L. argentiventris, capturados por la flota artesanal que desembarca en la comunidad de Búcaro, Panamá, por un período de seis meses, se describe la composición de tallas, la relación peso vs longitud total, se estimó el crecimiento basado en la estructura de tallas mensuales, para lo cual se describe L? , coeficiente catabólico k, la edad hipotética to para la longitud 0, además el índice de evaluación de ?’ y la longevidad A0,95, se desarrolló la ecuación de von Bertalanffy para cada especie y el análisis de la progresión modal “VBGF”. La longitud total varió entre 204 y 648 mm y el peso osciló entre 85 y 3 373 g, para las tres especies, la relación de estas variables mostró un crecimiento isométrico, la progresión modal indicó dos cohortes definidas de L. guttatus, no así en las otras especies. Los resultados son un aporte de línea base para el desarrollo del estudio de la biología pesquera artesanal de la zona del Pacífico centroamericano

Absolute frequency measurement of a Yb optical clock at the limit of the Cs fountain

We present the new absolute frequency measurement of ytterbium (171Yb) obtained at INRiM with the optical lattice clock IT-Yb1 against the cryogenic caesium (133Cs) fountain IT-CsF2, evaluated through a measurement campaign that lasted 14 months. Measurements are performed by either using a hydrogen maser as a transfer oscillator or by synthesizing a low-noise microwave for Cs interrogation using an optical frequency comb. The frequency of the 171Yb unperturbed clock transition ${^1}$S$_0\rightarrow {^3}$P0 results to be 518 295 836 590 863.44(14) Hz, with a total fractional uncertainty of $2.7 \times 10^{-16}$ that is limited by the uncertainty of IT-CsF2. Our measurement is in agreement with the Yb frequency recommended by the Consultative Committee for Time and Frequency. This result confirms the reliability of Yb as a secondary representation of the second and is relevant to the process of redefining the second in the International System of Units on an optical transition

Reproductive biology of spotted rose snapper Lutjanus guttatus (Teleostei: Lutjanidae) from Ensenada Búcaro, external border of Panama ecoregion

Se realizó un muestreo quincenal, por seis meses, de los desembarcos del pargo de la mancha (Lutjanus guttatus) en la comunidad de Búcaro, Panamá. Se recolectaron 237 individuos y se determinó sus variables morfométricas. Se seleccionaron 25 ejemplares para el análisis histológico de las gónadas. Se obtuvo un intervalo de talla entre 205 a 605 mm LT, y una proporción sexual que no difirió significativamente de la esperada 1M:1H. Se describen cuatro estadios de desarrollo gonadal en hembras y tres en machos. El índice gonadosomático y el factor de condición máximos en hembras fue de 1,67 en noviembre y de 1,24 en enero respectivamente, la talla de primera madurez sexual se estimó en 396,60 mm LT para hembras y 361,29 mm LT en machos. La información obtenida sugiere que la reproducción ocurre principalmente entre noviembre y enero.A biweekly sampling was carried out, for six months, of the landings of the spotted rose (Lutjanus guttatus) in the community of Búcaro, Panama. A total of 237 individuals was collected, and their morphometric variables were determined, 25 specimens were selected for the histological analysis of the gonads. A range of size 205 to 605 mm LT was obtained, the sex ratio was 1M: 1F. Four stages of gonadal development are described in females and three in males. Tre maximum values for the gonadosomatic index and the maximum condition factor in females were 1.67 in November and 1.24 in January respectively. The length at first sexual maturity was estimated at 396.60 mm LT for females and 361.29 mm LT for males. The information obtained suggests that reproduction occurs mainly between November and December. &nbsp

Alteración de la comunidad meiobentónica por efecto del pisoteo en la zona intermareal baja de playa arenosa

The importance of knowing the meiobenthic composition of coastal ecosystems has been enhanced for the evaluation of trophic relationships, especially as indicators of stress and pollution on beaches. This research aimed to determine the abundance and diversity of the meiofauna in the intertidal zone of Venao Beach and evaluate the effect of trampling by users on these organisms. The individuals were collected by using 29.85 mm diameter PVC nucleators, buried 0.05 m under the sediment, during low tide periods, on days with the presence and absence of people, over two months. In addition, the granulometric characteristics were evaluated and the variations in the beach profile were measured. Differences in species composition were observed between these periods, in addition, between areas of beach use with the presence of users, however, there was no relationship between abundance and richness, with the environmental characteristics evaluated, so it follows that the Hydrodynamic characteristics exert an effect on the distribution of organisms.La importancia del conocimiento de la composición meiobentónica de los ecosistemas costeros ha sido potenciada para la evaluación de las relaciones tróficas, sobre todo, como indicadores de estrés y contaminación en las playas. El objetivo de la presente investigación fue determinar la abundancia y diversidad de la meiofauna en la zona intermareal de playa Venao y evaluar el efecto del pisoteo de los usuarios sobre estos organismos. Los individuos fueron colectados mediante el uso de nucleadores de pvc de 0,029 m de diámetro, enterrados a 0,05 m bajo el sedimento, en períodos de marea baja, en días con presencia y ausencia de personas, en un lapso de dos meses. Además, se evaluó las características granulométricas y se midió las variaciones del perfil de la playa.  Se observó diferencias en composición de especies entre estos períodos, además, entre zonas de uso de la playa con presencia de usuarios, sin embargo, no hubo relación de la abundancia y riqueza, con las características ambientales evaluadas, por lo que se desprende que las características hidrodinámicas ejercen efecto sobre la distribución de los organismos