Effect of gypsum and potassium on corn yield and on the exchangeable bases of an acid soil in La Frailesca, Chiapas

Objective: To evaluate the residual effect of gypsum in corn crops 2 years after application, in a previously limed soil, as well as the result of a new addition of gypsum combined with potassium in La Frailesca, Chiapas. Design/methodology/approach: Composite factorial: initial arrangement (2017) with four levels of gypsum (0, 1.25, 2.5 and 5 t ha-1) and four levels of potassium (0, 60, 120 and 180 kg K2O ha-1). In 2019, the plots treated with gypsum were divided into two, adding the same amount of gypsum applied in 2017 to half of each of them, and leaving the other half to evaluate the residual effect to the initial treatment. The potassium doses were the same as the original ones. Corn kernel yield, pH, exchangeable bases, and percentage of aluminium saturation were measured at depths of 0 to 7 and 7 to 14 cm from groun level. Results: The greatest effect on yield was obtained with 2.5 t ha-1 of gypsum applied in 2017 without significant increases with higher gypsum doses. The exchangeable calcium content and pH increased, but the magnesium, potassium and aluminum in the soil decreased. Limitations on study/implications: The assumed of Asphalt Stain Complex was diagnosed. Findings/conclusions: The authors point out the need to be careful when recommending gypsum as an amendment; an excessive application generates an imbalance in the exchangeable potassium and magnesium of the soil, so the incorporation of these should be considered in the fertilization plan.Objective: To evaluate the residual effect of gypsum in corn crops (2 years after its application in a previously limed soil), as well as the result of a new addition of gypsum combined with potassium in La Frailesca, Chiapas, Mexico. Design/Methodology/Approach: We used a composite factorial design. The initial arrangement (2017) consisted of four levels of gypsum (0, 1.25, 2.5, and 5 t ha-1) and four levels of potassium (0, 60, 120, and 180 kg K2O ha-1). In 2019, the gypsum-treated plots were divided in half: the same amount of gypsum applied in 2017 was added to the first half and the other half was used to assess the residual effect of the initial treatment. The potassium doses were the same as the original. Corn grain yield, pH, exchangeable bases, and aluminum saturation percentage were measured at 0 to 7 and 7 to 14 cm below ground level. Results: The greatest effect on yield was obtained with 2.5 t ha-1 of gypsum applied in 2017; no significant increases were recorded with higher gypsum doses. The exchangeable calcium content and pH level increased, while magnesium, potassium, and aluminum in the soil decreased. Study Limitations/Implications: Suspected presence of Tar Spot Complex was diagnosed. Findings/Conclusions: An excessive application of gypsum generates an imbalance in exchangeable potassium and magnesium in the soil; therefore, producers must exercise caution in the use of these products as part of their fertilization plan

Finite element meshes for optimal modelling of plasticity induced crack closure

The main goal here is to optimise the finite element mesh used to predict plasticity induced crack closure (PICC). A numerical model was developed for a M(T) specimen made of 6016-T4 aluminium alloy. The parameters studied were the size of most refined region perpendicularly to crack flank (ym) and along propagation direction (xr), the size of finite elements near crack tip (L1) and the vertical size of refinement close to crack flank (yA/B). A maximum size of about 1.3mm was found for ym, but a smaller value has a limited impact on PICC. An analytical expression was proposed for xr, dependent on δK and Kmax. An optimum value seems to exist for L1.info:eu-repo/semantics/publishedVersio

Effect of compressive loads on plasticity induced crack closure

Compressive stresses play an important role on tension-compression fatigue which can be attributed to plasticity induced crack closure (PICC). The objective here is to study numerically the effect of compressive stresses on PICC and to discuss the applicability of PICC to explain the effect of negative stress ratios on fatigue crack growth rate. The compression produces reversed plastic deformation at the crack tip, reducing linearly the crack opening level. The incursion to negative stress ratios did not produce sudden changes in the behavior of PICC and no saturation with the decrease of minimum load was observed for δKeff. Crack closure was able to collapse da/dN-δK curves with negative stress ratios, indicating the applicability of the crack closure concept to explain the effect of negative R. The analysis of crack tip plastic strain range with and without contact of crack flanks confirmed the validity of crack closure concept.info:eu-repo/semantics/publishedVersio

Long-distance soliton transmission through ultralong fiber lasers

We present the first experimental demonstration (to our knowledge) of long-distance unperturbed fundamental optical soliton transmission in conventional single-mode optical fiber. The virtual transparency in the fiber required for soliton transmission, over 15 complete periods, was achieved by using an ultralong Raman fiber laser amplification scheme. Optical soliton pulse duration, pulse bandwidth, and peak intensity are shown to remain constant along the transmission length. Frequency-resolved optical gating spectrograms and numerical simulations confirm the observed optical soliton dynamics

Análisis numérico bidimensional del efecto de campos de tensiones no uniformes en grietas en modo mixto

La probeta con taladro centrado es un tipo de geometría a partir de la cual las grietas se propagan con frecuencia. En algunos casos, el análisis combinado de carga en modo mixto I y II tiene cierta relevancia industrial. Por este motivo, se ha realizado un análisis numérico bidimensional de una grieta que emana de un taladro en una placa de aleación de aluminio. Se han calculado las áreas plastificadas y los desplazamientos alrededor de la grieta para siete estados de carga biaxial diferentes. Para ello, se ha modificado el ángulo de aplicación de la carga desde 23.4° (modos I+II) hasta 90° (modo I puro) considerando incrementos de 11.1°, y se ha mantenido constante el valor nominal de carga. Con el objetivo de obtener áreas más precisas, se ha utilizado un análisis de elementos finitos basado en el submodelado. Posteriormente, para contrastar los resultados, se han comparado los campos de desplazamiento en la superficie alrededor de la grieta con los resultados obtenidos de forma experimental usando la técnica de correlación de imágenes. Después de la validación del modelo, se ha estudiado la evolución de las zonas plastificadas en condiciones de tensión y deformación plana para diferentes valores de carga nominal.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Experimental and analytical study of cracks under biaxial fatigue

Most mechanical components experience multi-axial cyclic loading conditions during service. Experimental analysis of fatigue cracks under such conditions is not easy and most works tend to focus more on the simpler but less realistic case of uni-axial loading. Consequently, there are many uncertainties related to the load sequence effect that are now well known and are not normally incorporated into the growth models. The current work presents a new methodology for evaluating overload effect in biaxial fatigue cracks. The methodology includes evaluation of mixed-mode (KI and KII) stress intensity factor and the Crack Opening Displacement for samples with and without overload cycle under biaxial loading. The methodology is tested under a range of crack lengths. All crack-tip information is obtained with a hybrid methodology that combines experimental full-field digital image correlation data and Williams' elastic model describing the crack-tip field

Local Gene Regulation Details a Recognition Code within the LacI Transcriptional Factor Family

The specific binding of regulatory proteins to DNA sequences exhibits no clear patterns of association between amino acids (AAs) and nucleotides (NTs). This complexity of protein-DNA interactions raises the question of whether a simple set of wide-coverage recognition rules can ever be identified. Here, we analyzed this issue using the extensive LacI family of transcriptional factors (TFs). We searched for recognition patterns by introducing a new approach to phylogenetic footprinting, based on the pervasive presence of local regulation in prokaryotic transcriptional networks. We identified a set of specificity correlations –determined by two AAs of the TFs and two NTs in the binding sites– that is conserved throughout a dominant subgroup within the family regardless of the evolutionary distance, and that act as a relatively consistent recognition code. The proposed rules are confirmed with data of previous experimental studies and by events of convergent evolution in the phylogenetic tree. The presence of a code emphasizes the stable structural context of the LacI family, while defining a precise blueprint to reprogram TF specificity with many practical applications.Ministerio de Ciencia e Innovación, Spain (Formación de Profesorado Universitario fellowship)Ministerio de Ciencia e Innovación, Spain (grant BFU2008-03632/BMC)Madrid (Spain : Region) (grant CCG08-CSIC/SAL-3651

Negative Autoregulation by Fas Stabilizes Adult Erythropoiesis and Accelerates Its Stress Response

Erythropoiesis maintains a stable hematocrit and tissue oxygenation in the basal state, while mounting a stress response that accelerates red cell production in anemia, blood loss or high altitude. Thus, tissue hypoxia increases secretion of the hormone erythropoietin (Epo), stimulating an increase in erythroid progenitors and erythropoietic rate. Several cell divisions must elapse, however, before Epo-responsive progenitors mature into red cells. This inherent delay is expected to reduce the stability of erythropoiesis and to slow its response to stress. Here we identify a mechanism that helps to offset these effects. We recently showed that splenic early erythroblasts, ‘EryA’, negatively regulate their own survival by co-expressing the death receptor Fas, and its ligand, FasL. Here we studied mice mutant for either Fas or FasL, bred onto an immune-deficient background, in order to avoid an autoimmune syndrome associated with Fas deficiency. Mutant mice had a higher hematocrit, lower serum Epo, and an increased number of splenic erythroid progenitors, suggesting that Fas negatively regulates erythropoiesis at the level of the whole animal. In addition, Fas-mediated autoregulation stabilizes the size of the splenic early erythroblast pool, since mutant mice had a significantly more variable EryA pool than matched control mice. Unexpectedly, in spite of the loss of a negative regulator, the expansion of EryA and ProE progenitors in response to high Epo in vivo, as well as the increase in erythropoietic rate in mice injected with Epo or placed in a hypoxic environment, lagged significantly in the mutant mice. This suggests that Fas-mediated autoregulation accelerates the erythropoietic response to stress. Therefore, Fas-mediated negative autoregulation within splenic erythropoietic tissue optimizes key dynamic features in the operation of the erythropoietic network as a whole, helping to maintain erythroid homeostasis in the basal state, while accelerating the stress response

The Escherichia coli SOS Gene dinF Protects against Oxidative Stress and Bile Salts

DNA is constantly damaged by physical and chemical factors, including reactive oxygen species (ROS), such as superoxide radical (O2−), hydrogen peroxide (H2O2) and hydroxyl radical (•OH). Specific mechanisms to protect and repair DNA lesions produced by ROS have been developed in living beings. In Escherichia coli the SOS system, an inducible response activated to rescue cells from severe DNA damage, is a network that regulates the expression of more than 40 genes in response to this damage, many of them playing important roles in DNA damage tolerance mechanisms. Although the function of most of these genes has been elucidated, the activity of some others, such as dinF, remains unknown. The DinF deduced polypeptide sequence shows a high homology with membrane proteins of the multidrug and toxic compound extrusion (MATE) family. We describe here that expression of dinF protects against bile salts, probably by decreasing the effects of ROS, which is consistent with the observed decrease in H2O2-killing and protein carbonylation. These results, together with its ability to decrease the level of intracellular ROS, suggests that DinF can detoxify, either direct or indirectly, oxidizing molecules that can damage DNA and proteins from both the bacterial metabolism and the environment. Although the exact mechanism of DinF activity remains to be identified, we describe for the first time a role for dinF