Phosphorus availability and dynamics in soil affected by long-term ruzigrass cover crop.

The use of grasses as cover crops in the off-season of cash crops under no-till has been largely adopted. However, soil phosphorus (P) uptake was previously shown to be reduced when ruzigrass is introduced in the rotation, affecting the viability and sustainability of this cropping system. The objective of this study was to assess the effect of ruzigrass on soil P availability and desorption kinetics under different P fertilizer application rates. A long-term field experiment where soybean (Glycine max) has been grown in rotation with ruzigrass (Urochloa ruziziensis) or fallow for 10 years, with the application of 0, 13, and 26 kg ha-1 of P, was evaluated for two consecutive years. Soil P desorption kinetics was assessed using diffusive equilibrium (DET) and gradient in thin films (DGT) techniques, as well as the DGT-induced fluxes in soils model (DIFS). Microbial biomass P (MBP) was assessed to verify if soil solution P (PDET) was reduced due to immobilization by microorganisms. Ruzigrass reduced MBP and PDET especially when P fertilizer was applied. The concentration of labile P (PDGT) was also lower after ruzigrass than in fallow. The soil ability to resupply P to soil solution was lower after ruzigrass regardless of P rates due to a slower desorption in response to the perturbation imposed by DGT. Growing ruzigrass as cover crop in the soybean off-season decreases soil P availability regardless of P fertilizer application rates by fundamentally reducing P mobility and P resupply from soil solid phase into soil solution.

The impact of age on blastocyst scoring after single and double embryo transfers.

OBJECTIVE: The aim of the present study was to assess the putative relationship between patient's age and blastocyst scores, in single (SET) or double (DET) transfer cycles, that resulted in single or twin pregnancy or non-pregnancy. Second, we analyzed the effect of maternal age on clinical gestation and implantation rates after single and double blastocyst transfers. METHODS: Retrospective analysis of 164 assisted reproduction cycles with embryo transfers. RESULTS: Data demonstrated that for both, young (<35 years of age) and older (≥35 years of age) women, trophectoderm (TE) score is the most important parameter to assess concerning embryo selection. However, inner cell mass (ICM) also plays an important role on blastocyst selection in the group of older patients. In addition, our data shows that for young women the transfer of a single blastocyst results in similar gestational rates as those for DET. CONCLUSION: We suggest that blastocyst grading for patients aged 35 years or above shall be performed using a strict grading policy, possibly not of a single parameter, but TE, ICM and expansion grades together, to choose the "best combined-score blastocyst". DETs should be considered, particularly after previous cycles with pregnancy failures.

Postes prefabricados de fibra: consideraciones para su uso clínico / Prefabricated fiber posts: clinical aspects

En la década de los 90 los Postes Prefabricados de Fibra (PPF) se introdujeron al mercado como alternativa a los sistemas metálicos o cerámicos. Hasta la fecha se mantienen en uso, modificando de manera constante sus presentaciones comerciales y estrategias de fijación. Sus cualidades mecánicas como su bajo Módulo Elástico (ME) similar al dentinario, introducen un nuevo paradigma en la rehabilitación del Diente Endodónticamente Tratado (DET): "el poste debe acompañar en forma solidatria la flexión de los tejidos dentarios frente a las cargas". Sus actuales cualidades estéticas, la fácil remoción y la posibilidad de su cementado adhesivo, los han convertido en una alternativa válida a las soluciones convencionales. Sin embargo, algunos resultados contradictorios junto con la importante dificultad de lograr hidratación en la dentina radicular, mantienen interrogantes a resolver en el futuro. Se indican en casos donde se prevea retratamiento, en pacientes jóvenes, de alta exigencia estética y toda vez que se quiera y pueda eludir los costos de aleaciones nobles. En el presente artículo se analizan los fundamentos clínicos y experimentales de distintos autores, extrapolándose consideraciones prácticas para su uso. Los mismos se ilustran en un caso clínico para un paciente joven, con antecedente de traumatismo y con altas expectativas estéticas.