A flexible Tool for Model Building: the Relevant Transformation of the Inputs Network Approach (RETINA)

A new method, called relevant transformation of the inputs network approach (RETINA) is proposed as a tool for model building and selection. It is designed to improve some of the shortcomings of neural networks. It has the flexibility of neural network models, the concavity of the likelihood in the weights of the usual likelihood models, and the ability to identify a parsimonious set of attributes that are likely to be relevant for predicting out of sample outcomes. RETINA expands the range of models by considering transformations of the original inputs; splits the sample in three disjoint subsamples, sorts the candidate regressors by a saliency feature, chooses the models in subsample 1, uses subsample 2 for parameter estimation and subsample 3 for cross-validation. It is modular, can be used as a data exploratory tool and is computationally feasible in personal computers. In tests on simulated data, it achieves high rates of successes when the sample size or the R2 are large enough. As our experiments show, it is superior to alternative procedures such as the non negative garrote and forward and backward stepwise regression.

Swimming abilities of temperate pelagic fish larvae prove that they may control their dispersion in coastal areas

The Sense Acuity and Behavioral (SAAB) Hypothesis proposes that the swimming capabilities and sensorial acuity of temperate fish larvae allows them to find and swim towards coastal nursery areas, which are crucial for their recruitment. To gather further evidence to support this theory, it is necessary to understand how horizontal swimming capability varies along fish larvae ontogeny. Therefore, we studied the swimming capability of white seabream Diplodus sargus (Linnaeus, 1758) larvae along ontogeny, and their relationship with physiological condition. Thus, critical swimming speed (U-crit) and the distance swam (km) during endurance tests were determined for fish larvae from 15 to 55 days post-hatching (DPH), and their physiological condition (RNA, DNA and protein contents) was assessed. The critical swimming speed of white seabream larvae increased along ontogeny from 1.1 cm s(-1) (15 DPH) to 23 cm s(-1) (50 and 55 DPH), and the distance swam by larvae in the endurance experiments increased from 0.01 km (15 DPH) to 86.5 km (45 DPH). This finding supports one of the premises of the SAAB hypothesis, which proposes that fish larvae can influence their transport and distribution in coastal areas due to their swimming capabilities. The relationship between larvae's physiological condition and swimming capabilities were not evident in this study. Overall, this study provides critical information for understanding the link between population dynamics and connectivity with the management and conservation of fish stocks.Funding Agency Portuguese Foundation for Science and Technology SFRH/BD/104209/2014 Portuguese Foundation for Science and Technology UID/Multi/04326/2019 FCT, under the Transitional Norm DL57/2016/CP[1361]/CT[CT0008 CLIMFISH project-A framework for assess vulnerability of coastal fisheries to climate change in Portuguese coast n2/SAICT/2017-SAICTinfo:eu-repo/semantics/publishedVersio

Impact of the laminar flame speed correlation on the results of a quasi-dimensional combustion model for Spark-Ignition engine

Abstract In the present study, the impact of the laminar flame speed correlation on the prediction of the combustion process and performance of a gasoline engine is investigated using a 1D numerical approach. The model predictions are compared with experimental data available for full- and part-load operations of a small-size naturally aspirated Spark-Ignition (SI) engine, equipped with an external EGR circuit. A 1D model of the whole engine is developed in the GT-Power™ environment and is integrated with refined sub-models of the in-cylinder processes. In particular, the combustion is modelled using the fractal approach, where the burning rate is directly related to the laminar flame speed. In this work, three laminar flame speed correlations are assessed, including both experimentally- and numerically-derived formulations, the latter resulting from the fitting of laminar flame speeds computed by a chemical kinetic solver. Each correlation is implemented within the combustion sub-model, which is properly tuned to reproduce the experimental performance of the engine at full load. Then, the reliability of the considered flame speed formulations is proved at part-loads, even under external EGR operations

An integrated 0D/1D/3D numerical framework to predict performance, emissions, knock and heat transfer in ICEs fueled with NH3–H2 mixtures: The conversion of a marine Diesel engine as case study

In the maritime transportation, e-fuels represent a valid alternative to fossil energy sour- ces, in order to accomplish the European Union goals in terms of climate neutrality. Among the e-fuels, the ammonia-hydrogen mixtures can play a leading role, as the combination of the two allows to exploit the advantages of each one, simultaneously compensating their gaps. The main goal of the present publication is the proposal of a robust numerical frame- work based on 0D, 1D and 3D tools for CFD analyses of internal combustion engines fueled with ammonia-hydrogen mixtures. The 1D engine model provides boundary conditions for the multi-dimensional in- vestigations and estimates the overall engine performance. 3D in-cylinder detailed ana- lyses are proficiently used to predict combustion efficiency (via the well-established G-equation model supported by laminar flame speed correlations for both ammonia and hydrogen) and emissions (with a detailed chemistry based approach). Heat transfer and knock tendency are evaluated as well, by in-house developed models. As for the 0D/1D chemical kinetics calculations, firstly they support 3D analyses (for example via the gen- eration of ignition delay time tables). Moreover, they allow insights on aspects such as NOx formation, to individuate mixture qualities able to strongly reduce the emissions

Risk Modelling and Management: An Overview

The papers in this special issue of Mathematics and Computers in Simulation are substantially revised versions of the papers that were presented at the 2011 Madrid International Conference on “Risk Modelling and Management” (RMM2011). The papers cover the following topics: currency hedging strategies using dynamic multivariate GARCH, risk management of risk under the Basel Accord: A Bayesian approach to forecasting value-at-risk of VIX futures, fast clustering of GARCH processes via Gaussian mixture models, GFC-robust risk management under the Basel Accord using extreme value methodologies, volatility spillovers from the Chinese stock market to economic neighbours, a detailed comparison of Value-at-Risk estimates, the dynamics of BRICS's country risk ratings and domestic stock markets, U.S. stock market and oil price, forecasting value-at-risk with a duration-based POT method, and extreme market risk and extreme value theory

Risk Management of Risk under the Basel Accord: Forecasting Value-at-Risk of VIX Futures

The Basel II Accord requires that banks and other Authorized Deposit-taking Institutions (ADIs) communicate their daily risk forecasts to the appropriate monetary authorities at the beginning of each trading day, using one or more risk models to measure Value-at-Risk (VaR). The risk estimates of these models are used to determine capital requirements and associated capital costs of ADIs, depending in part on the number of previous violations, whereby realised losses exceed the estimated VaR. McAleer, Jimenez-Martin and Perez-Amaral (2009) proposed a new approach to model selection for predicting VaR, consisting of combining alternative risk models, and comparing conservative and aggressive strategies for choosing between VaR models. This paper addresses the question of risk management of risk, namely VaR of VIX futures prices. We examine how different risk management strategies performed during the 2008-09 global financial crisis (GFC). We find that an aggressive strategy of choosing the Supremum of the single model forecasts is preferred to the other alternatives, and is robust during the GFC. However, this strategy implies relatively high numbers of violations and accumulated losses, though these are admissible under the Basel II Accord

EFFECT OF THE FOLLICULAR DEVELOPMENT STAGE AT THE TIME OF MATING ON THE OVULATION AND EMBRYONIC SURVIVAL IN ALPACAS

El objetivo del presente estudio fue evaluar el efecto del estadio del desarrollo folicular del folículo dominante (fd) al momento de la cópula, sobre la ovulación y supervivencia embrionaria en alpacas. Se utilizaron 116 animales con descanso post-parto ³15 días, que fueron evaluadas por ecografía transrectal para distribuirlas en 4 grupos: G1 (fd en estadio de crecimiento, diámetro: 6 mm), G2 (fd en estadio de crecimiento, diámetro: ³ 7 y £ 12 mm), G3 (fd en estadio estático, diámetro: ³7 mm) y G4 (fd en estadio de regresión, diámetro: ³7 mm). Posteriormente, fueron sometidos a monta controlada, a excepción de 5 alpacas del grupo G1 que rechazaron al macho. El día del empadre fue considerado el día 0. Evaluaciones ecográficas adicionales se realizaron los días 2 (ocurrencia de ovulación), 9 (presencia y tamaño del cuerpo lúteo); 20, 25, 30 y 35 (presencia de vesícula embrionaria o embrión). El día 15 post cópula se realizó la prueba de receptividad sexual. El 97.3% de alpacas empadradas (n = 111) presentaron ovulación al día 2 post cópula, sin diferencia significativa (p<0.05) entre grupos. En el día 9 post cópula, no se encontraron diferencias significativas en el tamaño promedio del cuerpo lúteo entre grupos. El porcentaje de supervivencia embrionaria fue estadísticamente similar para todos los grupos, aunque hubo una tendencia a un mayor nivel de supervivencia para el grupo G2 (65.5%) en comparación con los demás grupos al día 35 post cópula. Estos resultados indicarían que el estadio del desarrollo folicular del folículo dominante al momento de la monta no tendría efecto significativo sobre la tasa de ovulación y supervivencia embrionaria enThe objective of this study was to evaluate the effect of the stage of the dominant follicle (df) at mating on the ovulation and embryonic survival in alpacas. A total of 116 alpacaswith ³15 day-post-partum resting period were used and evaluated by transrectal ultrasonography in order to distribute them in 4 groups: G1 (df in growing stage, diameter: 6 mm), G2 (df in growing stage, diameter: ³ 7 £ 12 mm), G3 (df in static stage, diameter: ³7 mm,) and G4 (df in regression stage, diameter: ³7 mm). Subsequently, all alpacas were mated except 5 alpacas of group G1 that rejected the male. Mating day was considered as day 0. Additional ultrasound evaluations were carried out on days 2 (occurrence of ovulation), 9 (presence and size of the corpus luteum); 20, 25, 30 and 35 (presence of embryonic vesicle or embryo). On day 15, a sexual receptiveness test was performed. Ovulationoccurredin97.3% ofalpacasthatweremated(n=111) butwithoutsignificant differences(p<0.05) betweengroups. Onday9, nosignificantdifferenceintheaverage sizeofthecorpusluteumwasobservedamonggroups. Theembryonicsurvivalratewas alsonotsignificantlydifferentamongthegroups, buttherewasatendencytoagreater rateofsurvivalforgroupG2(65.5% ) onday35aftermating. Theseresultssuggestedthat thestageoffolliculardevelopmentofthedominantfollicleduringmatingdoesnothave asignificanteffectontherateofovulationandembryonicsurvivalinalpacas

EFECTO DE LA APLICACIÓN DE ESTRADIOL Y PROGESTERONA SOBRE LA SUPERVIVENCIA EMBRIONARIA EN LLAMAS

El efecto de la aplicación de estradiol y progesterona, alrededor del momento de reconocimiento maternal de la preñez, sobre la supervivencia embrionaria, fue evaluada en 80 llamas adultas con descanso post parto ³15 días. Se les hizo una ecografía para determinar la presencia del folículo preovulatorio (³7 mm) y luego fueron sometidas a monta por un tiempo de cópula ³15 minutos. Las llamas fueron distribuidas en 4 grupos: G0, placebo;G1, 0.2mg/llama/día de estradiol; G2, 15mg/llama/día de proligestona; yG3, 0.2mg/llama/día de estradiol y 15mg/llama/día de proligestona. La administración de los compuestos se hizo el día 8 y 9 post cópula. El día de la monta fue el día 0. Se hicieron evaluaciones ecográficas el día 2 para determinar ovulación, el día 9 para medir cuerpo lúteo y los días 20, 25, 30 y 35 para observar vesícula embrionaria ypresencia del embrión. La conducta sexual fue evaluada para determinar receptividad frente al macho el día 0 y para diagnosticar gestación temprana el día 15. El porcentaje de supervivencia embrionaria entre los días 20 y 35 fuemayor en el G1 (75%), en comparación con los otros grupos: G0 (57.9%), G2 (52.6%) yG3 (55.0%), aunque sin encontrar diferencia estadística entre grupos. Por otro lado, el tamaño del cuerpo lúteo al día 9 post cópula tuvo un diámetromayor en llamas preñadas (12.8 mm) que en no preñadas (10.8 mm) al día 35. En conclusión, estos resultados indicaron que con la aplicación de estradiol entre los días 8 y 9 post cópula se presentaría unamejor respuesta sobre el porcentaje de supervivencia embrionaria en la llama.The effect of exogenous oestradiol and progesterone on embryonic survival around the period of maternal recognition of pregnancy was evaluated in 80 adult llamas with ³15 days after parturition. An ultrasound evaluation was conducted to detect a preovulatory follicle (³7mm), and then, animalswere matedwith a male for ³15 minutes of copulation time.Animals were allocated into 4 groups: G0, placebo;G1, 0.2mg/llama/day of estradiol; G2, 15mg/llama/day of proligestone, andG3, 0.2mg/llama/day of estradiol and 15 mg/llama/day of proligestone. Injection of hormones and placebo was done at days 8 and 9 after copula. Mating daywas considered as day 0. Ultrasound evaluations were done on day 2 to determine ovulation, on day 9 to measure the size of the corpus luteum, and on days 20, 25, 30 and 35 to observe the presence of the embryonic vesicle and the embryo. Sexual behaviour was evaluated to verify female receptivity on day 0 and to diagnose earlypregnancy on day15. Embryonic survival was higher in G1 (75%) as compared to other groups:G0 (57.9%), G2 (52.6%), and G3 (55.0%) until day 35, but without significant differences. The size of corpus luteumon day9was larger in pregnant (12.8mm) than in non pregnant llamas (10.8mm). In conclusion, the results suggested that the application of estradiol between days 8 and 9 aftermatingmay improve embryonic survival rate in llamas

EFECTO DEL SITIO DE DEPOSICIÓN DEL PLASMA SEMINAL SOBRE LA TASA DE OVULACIÓN Y FORMACIÓN DEL CUERPO LÚTEO EN ALPACAS

The present study was carried out to evaluate the effect of deposition site of seminal plasma on the ovulation rate and size of corpus luteum in alpacas. Non-lactating females bearing a ≥7 mm follicle detected by ultrasound were selected (n = 91). Follicular wave was synchronized by injecting 5 mg of LH and then, the presence of a dominant follicle ≥7 mm was determined 12 days later through ultrasound evaluation. Alpacas were assigned to one of six experimental groups: G1 (n=16) seminal plasma (SP) by intramuscular injection – i.m.; G2 (n=15) phosphate-buffered saline (PBS) i.m.; G3 (n=16) SP by intrauterine administration – i.u.; G4 (n=15) PBS i.u.; G5 (n=15) SP i.u. with curettage; G6 (14) PBS by i.u. with curettage. Ovulation rate and corpus luteum were determined by ultrasound evaluation on D2 and D8 (D0 = day of treatment). Serum samples were taken from the jugular vein on D0, D3 and D9 to determine progesterone profiles by radioimmunoassay. Ovulation rate was 93.7, 37.5, and 66.5% for G1, G3 and G5 respectively, while none ovulations were observed in the other three groups. Alpacas in G1 would produce 25 more ovulations than G3. Results of the present study suggested that the ovulation-inducing factor (OIF) present in seminal plasma is absorbed systemically and that the mechanical action of curettage would contribute to the absorption of the OIF present in seminal plasma.El estudio tuvo por objetivo evaluar el sitio de deposición del plasma seminal sobre la tasa de ovulación y formación del cuerpo lúteo en alpacas. Se seleccionaron 91 hembras no lactantes con folículos ≥7 mm detectados por ecografía transrectal. Se sincronizó la onda folicular con la aplicación de 5 mg de LH, y 12 días después, se determinó la presencia de un folículo dominante (≥7 mm). Las hembras se distribuyeron al azar en seis tratamientos: G1 =16 (Plasma seminal vía intramuscular), G2=15 (PBS vía intramuscular), G3=16 (Plasma seminal vía intrauterina), G4=15 (PBS vía intrauterina), G5 =15 (Plasma seminal vía intrauterina con curetaje), G6 =14 (PBS vía intrauterina con curetaje). La tasa de ovulación y presencia de cuerpo lúteo se determinó mediante ecografía el día D2 y D8 (D0 = inicio del tratamiento). Se tomó muestras de sangre los días D0, D3 y D9 para determinar perfiles séricos de progesterona mediante RIA. La tasa de ovulación fue de 93.8, 37.5 y 66.5% para G1, G3 y G5, respectivamente, y no se registraron ovulaciones en los otros grupos. Se encontró que las alpacas G1 producirían 25 veces más ovulaciones con respecto al G3. Los resultados sugieren que la absorción del factor inductor de ovulación (FIO) del plasma seminal es vía sistémica y que el curetaje facilitaría la absorción del FIO incrementando el efecto ovulatorio del plasma seminal

Efecto de la Aplicación Intramuscular de Plasma Seminal sobre la Supervivencia Embrionaria en Alpacas Poscópula

This study aimed to evaluate the effect of intramuscular application (IM) of seminal plasma on embryo survival in the alpaca after natural mating. The study was conducted in Puno, Peru. Seminal plasma was obtained from alpaca semen samples, which were collected and diluted 1:1 in phosphate buffered saline (PBS), then centrifuged and kept frozen in storage until use. Non-pregnant alpacas (n=117) were selected according to the presence of a dominant ovarian follicle (>7 mm) detected by transrectal ultrasonography. Females were naturally mated and assigned randomly into one of three groups: T1 (n=40): 1 ml of seminal plasma diluted in PBS, IM; T2 (n=39): 1 ml of GnRH analogue (0.0042 mg buserelin), IM; T3 (n=38) without administration of any product (control). Females were evaluated by transrectal ultrasonography on day 25 after mating to determine pregnancy and on day 62 for determining the embryo’s survival rate. The results showed 67.5, 51.3 and 55.3% conception rate on day 25 and 92.6, 80.0 and 85.7% of embryo’s survival rate on day 62 for groups T1, T2 and T3 respectively and without statistical differences between treatments. The results suggest that IM application of seminal plasma immediately after natural mating may increase embryo survival as compared to the application of GnRH or natural mating, however, this difference was not statistically significant.Se evaluó el efecto de la aplicación por vía intramuscular (IM) de plasma seminal sobre la supervivencia embrionaria en alpacas luego de la monta natural. El estudio se llevó a cabo en Puno, Perú. El plasma seminal se obtuvo de muestras de semen de alpaca. El semen fue colectado y diluido en proporción 1:1 en buffer fosfato salino (PBS), y posteriormente centrifugado y conservado en congelación. Se seleccionaron alpacas hembras vacías (n=117) con presencia de un folículo ovárico dominante (e»7 mm) detectado por ecografía transrectal. Los animales fueron servidos por monta natural y distribuidos aleatoriamente en tres grupos: T1(n=40), se les administró 1 ml de plasma seminal diluido en PBS, vía IM; T2(n=39), se les administró 1 ml de un análogo de GnRH (0.0042 mg de acetato de buserelina), vía IM; T3(n=38), sin administración alguna (control). Se hizo una evaluación mediante ecografía transrectal el día 25 de la monta para determinar la gestación y el día 62 para determinar la tasa de supervivencia embrionaria. La tasa de concepción al día 25 de la monta fue de 67.5, 51.3 y 55.3% y la tasa de supervivencia embrionaria al día 62 fue de 92.6, 80.0 y 85.7% para los grupos T1, T2 y T3, respectivamente, sin diferencias estadísticas. Los resultados parecieran indicar que la aplicación IM de plasma seminal inmediatamente después de la monta determina una mejora en la supervivencia embrionaria en comparación a la aplicación de GnRH o la monta natural; sin embargo dicha diferencia no es estadísticamente diferente