Numerical Implementation of a Critical State Model for Soft Rocks

This paper details the basic tasks for the numerical implementation of a simple elasto-plastic critical state model for bonded materials (i.e. soft rocks-hard soils) into the finite element program SNAC developed at the University of Newcastle in Australia. The first task described focusses on the derivation of the incremental constitutive relationships used to represent the mechanical response of a bonded/cemented material under saturated conditions. The second task presents how these stress-strain relations can be numerically integrated using an explicit substepping scheme with automatic error control. The third task concentrates on the verification of the substepping algorithm proposed. The model used to represent the saturated mechanical response of a bonded material combines the modified Cam clay with the constitutive relationships for cemented materials proposed in Gens & Nova (1993), but incorporates some flexibility on the degradation law adopted. The role of suction and other relevant aspects of unsaturated behaviour are also discussed at the end of the paper

Factores que influyen en la germinación del pasto (Brachiaria decumbens Stapf).

Se evaluó el efecto de prácticas culturales, almacenamiento, escarificación, fitorreguladores, temperatura, luz y profundidad de siembra sobre la germinación y desarrollo de este pasto. La semilla usada en estos estudios se cosechó en campos experimentales de la Granja La Libertad (Meta) y en otros dos municipios de este departamento. Los ensayos se realizaron en invernadero y laboratorio del Centro de Investigaciones Tibaitatá. La edad de las plantas, la fertilización y época de corte son factores que influyen en la calidad de las semillas y acortan el período de latencia. La germinación de las semillas de braquiaria alcanzó un máximo de 80 por ciento cuando se almacenó durante 7 u 8 meses. El mejor tiempo de escarificación para romper la latencia de las semillas con ácido sulfúrico fué de 5 minutos. El ácido giberélico incrementó la germinación entre un 15 a 20 por ciento cuando las emillas se inhibieron en soluciones de 50 a 200 ppm durante 25 horas. El nitrato de potasio (KNO3) en dosis de 1000 y 500 ppm estimuló la germinación entre un 12 y un 14 por ciento en semilla escarificada y un 6.7 por ciento en semilla no escarificada durante las horas de contacto ensayadas (10, 15, 20, 35 y 40). El ácido succínico en dosis de 10, 100 y 1000 ppm y las morfactinas disminuyeron la germinación. El más alto porcentaje de germinación y peso seco de las plántulas se obtuvo al sembrar las semillas a 0.5-1 cm de profundidad. La germinación aumentó en un tratamiento de 16 horas de luz a 30 grados centígrados y 8 horas de oscuridad a 20 grados centígradosMaestría en CienciasMaestrí

Status and origin of Egyptian local rabbits in comparison with Spanish common rabbits using mitochondrial DNA sequence analysis

[EN] Mitochondrial DNA (mtDNA) and cytochrome b (cyt b) gene sequences were used to determine the status of genetic diversity and phylogeny for 132 individuals from local rabbit breeds in Egypt and Spain. The Egyptian local rabbit breeds were Egyptian Red Baladi (ERB), Egyptian Black Baladi (EBB) and Egyptian Gabali Sinai (EGS). However, the Spanish local rabbit breed was Spanish common rabbit (SCR). Previous breeds were compared with European Wild Rabbit taken from Albacete, Spain (EWR). A total of 353 mutations, 290 polymorphic sites, 14 haplotypes, 0.06126 haplotype diversity and –1.900 (P<0.05) for Tajima’s D were defined in this study. Haplotype A mostly occurred in 83.3% of Egyptian rabbits and 11.7 % of EWR, while haplotype B occurred in 63.8% of Spanish rabbits and 36.2% of the EGS breed. A total of 47 domestic and wild Oryctolagus cuniculus published sequences were used to investigate the origin and relation among the rabbit breeds tested in this study. The most common haplotype (A) was combined with 44.7% of published sequences. However, haplotype B was combined with 8.5%. Haplotypes of Egyptian, SCR and EWR were scattered in cluster 1, while we found only one EGS haplotype with two haplotypes of EWR in cluster 2. Our results assumed that genetic diversity for ERB, EBB and SCR was very low. Egyptian breeds and SCR were introduced from European rabbits. We found that ERB and EBB belong to one breed.Emam, AM.; Afonso, S.; González-Redondo, P.; Mehaisen, G.; Azoz, A.; Ahmed, N.; Fernand, N. (2020). Status and origin of Egyptian local rabbits in comparison with Spanish common rabbits using mitochondrial DNA sequence analysis. World Rabbit Science. 28(2):93-102. https://doi.org/10.4995/wrs.2020.12219OJS93102282Abrantes J., Areal H., Esteves P.J. 2013. Insights into the European rabbit (Oryctolagus cuniculus) innate immune system: genetic diversity of the toll-like receptor 3(TLR3) in wild populations and domestic breeds. 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Wormholes and Ringholes in a Dark-Energy Universe

The effects that the present accelerating expansion of the universe has on the size and shape of Lorentzian wormholes and ringholes are considered. It is shown that, quite similarly to how it occurs for inflating wormholes, relative to the initial embedding-space coordinate system, whereas the shape of the considered holes is always preserved with time, their size is driven by the expansion to increase by a factor which is proportional to the scale factor of the universe. In the case that dark energy is phantom energy, which is not excluded by present constraints on the dark-energy equation of state, that size increase with time becomes quite more remarkable, and a rather speculative scenario is here presented where the big rip can be circumvented by future advanced civilizations by utilizing sufficiently grown up wormholes and ringholes as time machines that shortcut the big-rip singularity.Comment: 11 pages, RevTex, to appear in Phys. Rev.

Control selectivo de Maciega (Paspalum virgatum L.) en potreros con MSMA.

Estudio de campo en la Estación Experimental El Nus, Antioquia ICA, con el fín de averiguar las posibilidades de control de Maciega (Paspalum virgatum L.) con ácido monosodio metanoarsonato (MSMA) y otros arsenicales orgánicos en potreros. La cobertura del suelo por Maciega fué reducida de 95 a 30 por ciento o menos con dos o tres aplicaciones de 2 kg/ha de MSMA a intervalos de 12 días. Más del 75 por ciento de la cobertura presente en estos tratamientos, se debió a restablecimiento de la maleza por semilla, pues la Maciega se recupera rápidamente en los tratamientos con una sola aplicación. La adición de surfactante al MSMA no aumentó el control de Maciega, ni éste fué el mejor cuando se aplicó el herbicida sobre rebrotes suculentos. Los pastos deseables, janeiro (Eriochloa polystachya) y pará (Brachiaria mutica) fueron tolerantes a 8 P kg/ha de MSMA aplicados de una vez. Los pastos guinea (Panicum maximum) y puntero (Hyparrhemia rufa) fueron temporalmente afectados por el mismo tratamiento. Los resultados indican que el MSMA y otros arsenicales orgánicos pueden ser utilizados en el control selectivo de Maciega en potreros y algunos pastos tropicales

Abundance analysis, spectral variability, and search for the presence of a magnetic field in the typical PGa star HD 19400

The aim of this study is to carry out an abundance determination, to search for spectral variability and for the presence of a weak magnetic field in the typical PGa star HD 19400. High-resolution, high signal-to-noise High Accuracy Radial-velocity Planet Searcher (HARPS) spectropolarimetric observations of HD 19400 were obtained at three different epochs in 2011 and 2013. For the first time, we present abundances of various elements determined using an ATLAS12 model, including the abundances of a number of elements not analysed by previous studies, such as Ne I, Ga II, and Xe II. Several lines of As II are also present in the spectra of HD 19400. To study the variability, we compared the behaviour of the line profiles of various elements. We report on the first detection of anomalous shapes of line profiles belonging to Mn and Hg, and the variability of the line profiles belonging to the elements Hg, P, Mn, Fe, and Ga. We suggest that the variability of the line profiles of these elements is caused by their non-uniform surface distribution, similar to the presence of chemical spots detected in HgMn stars. The search for the presence of a magnetic field was carried out using the moment technique and the Singular Value Decomposition (SVD) method. Our measurements of the magnetic field with the moment technique using 22 Mn II lines indicate the potential existence of a weak variable longitudinal magnetic field on the first epoch. The SVD method applied to the Mn II lines indicates &lt;Bz&gt; = -76 &plusmn; 25 G on the first epoch, and at the same epoch the SVD analysis of the observations using the Fe II lines shows &lt;Bz&gt; = -91 &plusmn; 35 G. The calculated false alarm probability values, 0.008 and 0.003, respectively, are above the value 10-3, indicating no detection.</p

First Episodes of Norovirus and Sapovirus Gastroenteritis Protect Against Subsequent Episodes in a Nicaraguan Birth Cohort

Background: Norovirus and sapovirus cause a large burden of acute gastroenteritis (AGE) in young children. We assessed protection conferred by norovirus and sapovirus AGE episodes against future episodes. Methods: Between June 2017 and July 2018, we recruited 444 newborns in León, Nicaragua. Weekly household surveys identified AGE episodes over 36 months, and AGE stools were tested by reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) for norovirus genogroup (G)I/GII and sapovirus. We used recurrent-event Cox models and negative control methods to estimate protection conferred by first episodes, controlling for observed and unobserved risk factors, respectively. Results: Sapovirus episodes conferred a 69% reduced hazard of subsequent episodes using the negative control method. Norovirus GI (hazard ratio [HR] = 0.67; 95% confidence interval [CI] = 0.31, 1.3) and GII (HR = 0.20; 95% CI = 0.04, 0.44) episodes also appeared highly protective. Protection against norovirus GII was enhanced following two episodes. Conclusions: Evidence of natural immunity in early childhood provides optimism for the future success of pediatric norovirus and sapovirus vaccines

Association between breastfeeding, host genetic factors, and calicivirus gastroenteritis in a Nicaraguan birth cohort

Background Norovirus and sapovirus are important causes of childhood acute gastroenteritis (AGE). Breastfeeding prevents AGE generally; however, it is unknown if breastfeeding prevents AGE caused specifically by norovirus and sapovirus. Methods We investigated the association between breastfeeding and norovirus or sapovirus AGE episodes in a birth cohort. Weekly data on breastfeeding and AGE episodes were captured during the first year of life. Stools were collected from children with AGE and tested by RT-qPCR for norovirus and sapovirus. Time-dependent Cox models estimated associations between weekly breastfeeding and time to first norovirus or sapovirus AGE. Findings From June 2017 to July 2018, 444 newborns were enrolled in the study. In the first year of life, 69 and 34 children experienced a norovirus and a sapovirus episode, respectively. Exclusive breastfeeding lasted a median of 2 weeks, and any breastfeeding lasted a median of 43 weeks. Breastfeeding in the last week did not prevent norovirus (HR: 1.09, 95% CI: 0.62, 1.92) or sapovirus (HR: 1.00, 95% CI: 0.82, 1.21) AGE in a given week, adjusting for household sanitation, consumption of high-risk foods, and mother’s and child’s histo-blood group phenotypes. Maternal secretor-positive phenotype was protective against norovirus AGE, whereas child’s secretor-positive phenotype was a risk factor for norovirus AGE. Interpretation Exclusive breastfeeding in this population was short-lived, and no conclusions could be drawn about its potential to prevent norovirus or sapovirus AGE. Non-exclusive breastfeeding did not prevent norovirus or sapovirus AGE in the first year of life. However, maternal secretor-positive phenotype was associated with a reduced hazard of norovirus AGE