A surface extraction analysis in a multi-material test part for computed tomography in metrology applications

The main advantage of Computed Tomography is the capability of making measurements of non-accessible internal features in a test piece. One of the cases that can usually be found in this sense is the contact zone between two elements that are forming a common surface boundary, where the main complexity is to determine which surface belongs to which piece. Nowadays, this kind of surfaces are measurable only by utilizing Computed Tomography, taking into account that the characteristics of the Tomography can significantly vary depending on the material of the elements that are in contact. In this article a piece that has two different interfaces is analyzed: a Piece in contact with Air, and Material A in contact with Material B. Three different surface extraction algorithms are analyzed for multi-material parts, Threshold, Canny and Deriche, and the results and conclusions obtained are presented

Metamorphism on Chromite Ores from the Dobromirtsi Ultramafic Massif, Rhodope Mountains (SE Bulgaria)

Podiform chromitite bodies occur in highly serpentinized peridotites at Dobromirtsi Ultramafic Massif (Rhodope Mountains, southeastern Bulgaria). The ultramafic body is believed to represent a fragment of Palaeozoic ophiolite mantle. The ophiolite sequence is associated with greenschist - lower-temperature amphibolite facies metamorphosed rocks (biotitic gneisses hosting amphibolite). This association suggests that peridotites, chromitites and metamorphic rocks underwent a common metamorphic evolution. Chromitites at Dobromirtsi have been strongly altered. Their degree of alteration depends on the chromite/silicate ratio and to a lesser extent, on the size of chromitite bodies. Alteration is recorded in individual chromite grains in the form of optical and chemical zoning. Core to rim chemical trends are expressed by MgO- and Al2O3- impoverishment, mainly compensated by FeO and/or Fe2O3 increases. Such chemical variations correspond with three main alteration events. The first one was associated with ocean-floor metamorphism and was characterized by a lizardite replacement of olivine and the absence of chromite alteration. The second event took place during greenchist facies metamorphism. During this event, MgO- and SiO2-rich fluids (derived from low temperatura serpentinization of olivine and pyroxenes) reacted with chromite to form chlorite; as a consequence, chromite became altered to a FeO- and Cr2O3-rich, Al2O3-poor chromite. The third event, mainly developed during lower temperature amphibolite facies metamorphism, caused the replacement of the primary and previously altered chromite by Fe2O3-rich chromite (ferritchromite)

Analysis of surface extraction methods based on gradient operators for computed tomography in metrology applications

Among the multiple factors influencing the accuracy of Computed Tomography measurements, the surface extraction process is a significant contributor. The location of the surface for metrological applications is generally based on the definition of a gray value as a characteristic of similarity to define the regions of interest. A different approach is to perform the detection or location of the surface based on the discontinuity or gradient. In this paper, an adapted 3D Deriche algorithm based on gradient information is presented and compared with a previously developed adapted Canny algorithm for different surface types. Both algorithms have been applied to nine calibrated workpieces with different geometries and materials. Both the systematic error and measurement uncertainty have been determined. The results show a significant reduction of the deviations obtained with the Deriche-based algorithm in the dimensions defined by flat surfaces

INSECTICIDAS EN LA TRANSMISIÓN DEL VIRUS DE LA MANCHA ANULAR DE Carica papaya L., MEDIANTE Aphis nerii (Boyer de Fonscolombe)

The papaya ringspot virus (PRSV-p) is transmitted in a non-persistent way by females of Aphis nerii and other aphid species (Hemiptera: Aphididae). The effectiveness of the application of insecticides to reduce viral transmission has been questioned. Viral transmission tests have been performed with adult females of A. nerii in the laboratory, on papaya plants (Carica papaya). One, two, five and ten winged and wingless female adults of A. nerii were used. The presence of the PRSV-p was determined through the ELISA test. The effect of six insecticides/acaricides with different modes of action was evaluated (malathion, deltamethrin, imidacloprid, fenbutatin oxide, pymetrozine and rotenone), on the viral transmission and mortality of aphids. The products formulated were applied at the lowest recommended dose; later, they to papaya trees were exposed to the inoculating aphids for 24 h. The phytotoxicity was recorded visually in the laboratory. No significant differences were found (p<0.05) in the viral transmission between winged or wingless aphids. The greatest transmission (75 % to 80 %) was obtained with 10 adults and the lowest (15 % to 20 %) with one adult. The significantly lowest transmissions were obtained by using pymetrozine (19 %) and rotenone (29 %), while the highest were with deltamethrin (81 %) and malathion (66 %). Imidacloprid and malathion caused 100 % mortality at 24 h, while pymetrozine and fenbutatin oxide produced the lowest mortality (46 %). Rotenone caused phytotoxicity in papaya leaves. Pymetrozine has potential in the prevention of non-persistent viral transmission.El virus de la mancha anular del papayo (PRSV-p) es transmitido de forma no-persistente por hembras de Aphis nerii y otras especies de áfidos (Hemiptera: Aphididae). Se ha cuestionado la efectividad de la aplicación de insecticidas para reducir la transmisión viral. Se realizaron pruebas de transmisión viral con hembras adultas de A. nerii en laboratorio, sobre plantas de papayo (Carica papaya). Se utilizaron 1, 2, 5 y 10 hembras adultas aladas y ápteras de A. nerii. Se determinó la presencia del PRSV-p mediante la prueba de ELISA. Se evaluó el efecto de seis insecticidas/acaricidas con diferentes modos de acción (malatión, deltametrina, imidacloprid, óxido de fenbutatín, pymetrozine y rotenona), en la transmisión viral y mortalidad de áfidos. Los productos formulados se aplicaron a plantas de papayo a las dosis más bajas recomendadas; posteriormente se expusieron a los áfidos inoculativos por 24 h. La fitotoxicidad se registró visualmente en laboratorio. No presentaron diferencias significativas (p<0.05) en la transmisión viral entre áfidos alados o ápteros. La mayor transmisión (75% a 80%) se obtuvo con 10 adultos y la menor (15% a 20%) con un adulto. Las transmisiones significativamente más bajas se obtuvieron al usar pymetrozine (19%) y rotenona (29%), mientras que las mayores fueron con deltametrina (81%) y malatión (66%). El imidacloprid y malatión ocasionaron 100% de mortalidad a 24 h, mientras pymetrozine y óxido de fenbutatín produjeron la mortalidad más baja (46%). Rotenona ocasionó fitotoxicidad en hojas de papaya. Pymetrozine tiene potencial en la prevención de transmisión viral nopersistente

RENTABILIDAD DE LA REPRODUCIÓN DE ENEMIGOS NATURALES DE ÁCAROS DEL PAPAYO (Carica papaya L.)

The papaya tree production in the central zone of the state of Veracruz, México, under intensive management, is highly profitable. The crop presents high populations of spider mites, commonly controlled with acaricides. However, this practice contaminates the environment, leaves residues in the fruit, causes poisoning of applicators and promotes the fast development of resistance to pest-control substances in the acari. An effective biological control of the pest can be achieved with predatory mites, massively produced. Therefore, the technical and economic viability of establishing a Center forMassive Reproduction of Phytoseiulus persimilis in the central area of Veracruz was evaluated. The internal rate of return (IRR), the net presen value (NPV) and the benefit/cost (B/C) were calculated in a horizon of five years, with three variations of price of the product per hectare: (MX) $1,000,$1,250 and $1,500. The opinion of producers was requested through a survey regarding the product that the Center would generate. The project shows acceptable profitability, with IRR values of 41.5, 115.6 and 187.2$411,368, $1’633,913 and$2’837,815, for the three prices of the product; and B/C relation of 1.01 in the first year with the lowest price of the product, up to 1.83 with the highest price obtained on the fifth year. The main competition in the region is the sale of acaricides such as dicofol, abamectin, fenbutatin oxide and imidacloprid. Of the producers, 61.4 % are willing to use predatory mites at a cost of $1,000 per hectare. As this product cannot be stored for long periods, the success lies in a production coordinated with groups of producers.La producción de papayo en la zona Centro del estado de Veracruz, México bajo manejo intensivo es altamente rentable. El cultivo presenta altas poblaciones de ácaros plaga, controladas comúnmente con acaricidas. Sin embargo, esta práctica contamina el ambiente, deja residuos en la fruta, intoxica a los aplicadores y promueve el rápido desarrollo de la resistencia a plaguicidas en los ácaros. Se puede lograr un control biológico efectivo de la plaga con ácaros depredadores, pero para lograrlo estos se deben producir masivamente. Por ello se evaluó la viabilidad técnica y económica de establecer un Centro de Reproducción Masiva de Phytoseiulus persimilis en la zona Centro de Veracruz. Se calculó la tasa interna de rentabilidad (TIR), el valor actual neto (VAN) y el beneficio/costo (B/C) en un horizonte de cinco años, con tres variaciones de precio del producto por hectárea: (MX)$1,000, $1,250 y$1,500. Se solicitó la opinión de los productores mediante una encuesta respecto al producto que generaría el Centro. El proyecto muestra rentabilidad aceptable, con valores de TIR de 41.5, 115.6 y 187.2 %; una VAN de $411,368,$1’633,913 y $2’837,815, para los tres precios del producto; y relación B/C de 1.01 en el primer año con el precio más bajo de producto, hasta 1.83 con el precio más alto obtenido en el quinto año. La principal competencia en la región es la venta de acaricidas como dicofol, abamectina, óxido de fembutatín e imidacloprid. El 61.4$1,000 por hectárea. Debido a que este producto no puede ser almacenado por largos períodos, el éxito depende de una producción coordinada con grupos de productores

Controlling litter effects to enhance rigor and reproducibility with rodent models of neurodevelopmental disorders

Research with rodents is crucial for expanding our understanding of genetic and environmental risk factors for neurodevelopmental disorders (NDD). However, there is growing concern about the number of animal studies that are difficult to replicate, potentially undermining the validity of results. These concerns have prompted funding agencies and academic journals to implement more rigorous standards in an effort to increase reproducibility in research. However, these standards fail to address a major source of variability in rodent research brought on by the “litter effect,” the fact that rodents from the same litter are phenotypically more similar to one other than rodents from different litters of the same strain. We show that the litter effect accounts for 30–60% of the variability associated with commonly studied phenotypes, including brain, placenta, and body weight. Moreover, we show how failure to control for litter-to-litter variation can mask a phenotype in Chd8V986*/+ mice that model haploinsufficiency of CHD8, a high-confidence autism gene. Thus, if not properly controlled, the litter effect has the potential to negatively influence rigor and reproducibility of NDD research. While efforts have been made to educate scientists on the importance of controlling for litter effects in previous publications, our analysis of the recent literature (2015–2020) shows that the vast majority of NDD studies focused on genetic risks, including mutant mouse studies, and environmental risks, such as air pollution and valproic acid exposure, do not correct for litter effects or report information on the number of litters used. We outline best practices to help scientists minimize the impact of litter-to-litter variability and to enhance rigor and reproducibility in future NDD studies using rodent models

Ophiolite-Related Ultramafic Rocks (Serpentinites) in the Caribbean Region: A Review of their Occurrence, Composition, Origin, Emplacement and Ni-Laterite Soil Formation

Ultramafic rocks, mainly serpentinized peridotites of mantle origin, are mostly associated with the ophiolites of Mesozoic age that occur in belts along three of the margins of the Caribbean plate. The most extensive exposures are in Cuba. The ultramafic-mafic association (ophiolites) were formed and emplaced in several different tectonic environments. Mineralogical studies of the ultramafic rocks and the chemistry of the associated mafic rocks indicate that most of the ultramafic-mafic associations in both the northern and southern margins of the plate were formed in arc-related environments. There is little mantle peridotite exposed in the ophiolitic associations of the west coast of Central America, in the south Caribbean in Curacao and in the Andean belts in Colombia. In these occurrences the chemistry and age of the mafic rocks indicates that this association is mainly part of the 89 Ma Caribbean plateau province. The age of the mantle peridotites and associated ophiolites is probably mainly late Jurassic or Early Cretaceous. Emplacement of the ophiolites possibly began in the Early Cretaceous in Hispaniola and Puerto Rico, but most emplacement took place in the Late Cretaceous to Eocene (e.g. Cuba). Along the northern South America plate margin, in the Caribbean mountain belt, emplacement was by major thrusting and probably was not completed until the Oligocene or even the early Miocene. Caribbean mantle peridotites, before serpentinization, were mainly harzburgites, but dunites and lherzolites are also present. In detail, the mineralogical and chemical composition varies even within one ultramafic body, reflecting melting processes and peridotite/melt interaction in the upper mantle. At least for the northern Caribbean, uplift (postemplacement tectonics) exposed the ultramafic massifs as a land surface to effective laterization in the beginning of the Miocene. Tectonic factors, determining the uplift, exposing the peridotites to weathering varied. In the northern Caribbean, in Guatemala, Jamaica, and Hispaniola, uplift occurred as a result of transpresional movement along pre-existing major faults. In Cuba, uplift occurred on a regional scale, determined by isostatic adjustment. In the south Caribbean, uplift of the Cordillera de la Costa and Serrania del Interior exposing the peridotites, also appears to be related to strike-slip movement along the El Pilar fault system. In the Caribbean, Ni-laterite deposits are currently being mined in the central Dominican Republic, eastern Cuba, northern Venezuela and northwest Colombia. Although apparently formed over ultramafic rocks of similar composition and under similar climatic conditions, the composition of the lateritic soils varies. Factors that probably determined these differences in laterite composition are geomorphology, topography, drainage and tectonics. According to the mineralogy of principal ore-bearing phases, Dominican Ni-laterite deposits are classified as the hydrous silicate-type. The main Ni-bearing minerals are hydrated Mg-Ni silicates (serpentine and “garnierite”) occurring deeper in the profile (saprolite horizon). In contrast, in the deposits of eastern Cuba, the Ni and Co occurs mainly in the limonite zone composed of Fe hydroxides and oxides as the dominant mineralogy in the upper part of the profile, and are classified as the oxide-type

GFC-Robust Risk Management Strategies under the Basel Accord

A risk management strategy is proposed as being robust to the Global Financial Crisis (GFC) by selecting a Value-at-Risk (VaR) forecast that combines the forecasts of different VaR models. The robust forecast is based on the median of the point VaR forecasts of a set of conditional volatility models. This risk management strategy is GFC-robust in the sense that maintaining the same risk management strategies before, during and after a financial crisis would lead to comparatively low daily capital charges and violation penalties. The new method is illustrated by using the S&P500 index before, during and after the 2008-09 global financial crisis. We investigate the performance of a variety of single and combined VaR forecasts in terms of daily capital requirements and violation penalties under the Basel II Accord, as well as other criteria. The median VaR risk management strategy is GFC-robust as it provides stable results across different periods relative to other VaR forecasting models. The new strategy based on combined forecasts of single models is straightforward to incorporate into existing computer software packages that are used by banks and other financial institutions