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La agricultura de regadío en zonas áridas favorece la degradación de la Materia Orgánica del suelo (MO), por lo que suelen aplicarse enmiendas orgánicas con la finalidad de restaurar el contenido de MO y mejorar la disponibilidad de nutrientes para los cultivos, aunque no siempre con resultados concluyentes. En este trabajo se analizan, de manera comparativa, cuatro ensayos con diferentes sistemas de aplicación de enmiendas orgánicas (prácticas agrícolas, tipo de enmienda, dosis, frecuencia y forma de aplicación y combinación con fertilizantes químicos) en oasis de regadío de Mendoza (Argentina), con la finalidad de establecer las prácticas de manejo más adecuadas para restaurar las diferentes fracciones de MO del suelo (ácidos húmicos y fúlvicos y sustancias no húmicas). El contenido de MO aumentó en el 40% de los casos analizados (n=92) y no sufrió modificaciones en el resto, mientras que los ácidos fúlvicos también aumentaron en el 40% de los casos, pero disminuyeron en el 30%. Contrariamente, los ácidos húmicos sufrieron más disminuciones que aumentos (39% vs. 26% de los casos). Estas diferencias se explican por las prácticas de manejo agrícola y las técnicas de aplicación de las enmiendas, concluyendo que: a) todas las prácticas de aplicación de enmiendas aumentan en el corto plazo la MO; b) la fracción humificada aumenta en el corto plazo, con la aplicación superficial sin laboreo; y c) el agua de riego con alto contenido de desechos orgánicos disminuye el efecto positivo de las enmiendas sobre la MO. Por tales motivos, las prácticas de manejo recomendadas para lograr la restauración de la MO del suelo en los oasis de regadío de Mendoza son: aumentar la dosis y la frecuencia en la aplicación de enmiendas, y reducir el laboreo y el uso de aguas de reuso.

Robust and fast methods for chemical or multiphase equilibrium calculation are routinely needed by chemical-process engineers working on sizing or simulation aspects. Yet, while industrial applications essentially require calculation tools capable of discriminating between stable and nonstable states and converging to nontrivial solutions, students are often introduced to the simplest and less efficient equilibrium-calculation methods. In this article, the Gibbs energy minimization technique is presented as a robust alternative way to perform phase-equilibrium calculations and is applied to the determination of 2-fluid phase equilibria in low-pressure binary systems. It is carefully explained how the combination of this technique with an efficient quasi-global minimization method makes it possible to derive a robust PT-flash algorithm. In the frame of project-based learning devoted to develop a tool for building complex phase diagrams, this approach was successfully tested with a group of 100 students.

Mp is an irradiation-induced mouse mutation associated with microphthalmia, micropinna and hind limb syndactyly. We show that Mp is caused by a 660 kb balanced inversion on chromosome 18 producing reciprocal 3-prime gene fusion events involving Fbn2 and Isoc1. The Isoc1-Fbn2 fusion gene (Isoc1(Mp)) mRNA has a frameshift and early stop codon resulting in nonsense mediated decay. Homozygous deletions of Isoc1 do not support a significant developmental role for this gene. The Fbn2-Isoc1 fusion gene (Fbn2 (Mp)) predicted protein consists of the N-terminal Fibrillin-2 (amino acids 1-2646, exons 1-62) lacking the C-terminal furin-cleavage site with a short out-of-frame extension encoded by the final exon of Isoc1. The Mp limb phenotype is consistent with that reported in Fbn2 null embryos. However, severe eye malformations, a defining feature of Mp, are not seen in Fbn2 null animals. Fibrillin-2(Mp) forms large fibrillar structures within the rough endoplasmic reticulum (rER) associated with an unfolded protein response and quantitative mass spectrometry shows a generalised defect in protein secretion in conditioned media from mutant cells. In the embryonic eye Fbn2 is expressed within the peripheral ciliary margin (CM). Mp embryos show reduced canonical Wnt-signalling in the CM - known to be essential for ciliary body development - and show subsequent aplasia of CM-derived structures. We propose that the Mp "worse-than-null" eye phenotype plausibly results from a failure in normal trafficking of proteins that are co-expressed with Fbn2 within the CM. The prediction of similar trans-acting protein effects will be an important challenge in the medical interpretation of human mutations from whole exome sequencing.

Fibrillin-1 is a ubiquitous extracellular matrix molecule that sequesters latent growth factor complexes. A role for fibrillin-1 in specifying tissue microenvironments has not been elucidated, even though the concept that fibrillin-1 provides extracellular control of growth factor signaling is currently appreciated. Mutations in FBN1 are mainly responsible for the Marfan syndrome (MFS), recognized by its pleiotropic clinical features including tall stature and arachnodactyly, aortic dilatation and dissection, and ectopia lentis. Each of the many different mutations in FBN1 known to cause MFS must lead to similar clinical features through common mechanisms, proceeding principally through the activation of TGFβ signaling. Here we show that a novel FBN1 mutation in a family with Weill-Marchesani syndrome (WMS) causes thick skin, short stature, and brachydactyly when replicated in mice. WMS mice confirm that this mutation does not cause MFS. The mutation deletes three domains in fibrillin-1, abolishing a binding site utilized by ADAMTSLIKE-2, -3, -6, and papilin. Our results place these ADAMTSLIKE proteins in a molecular pathway involving fibrillin-1 and ADAMTS-10. Investigations of microfibril ultrastructure in WMS humans and mice demonstrate that modulation of the fibrillin microfibril scaffold can influence local tissue microenvironments and link fibrillin-1 function to skin homeostasis and the regulation of dermal collagen production. Hence, pathogenetic mechanisms caused by dysregulated WMS microenvironments diverge from Marfan pathogenetic mechanisms, which lead to broad activation of TGFβ signaling in multiple tissues. We conclude that local tissue-specific microenvironments, affected in WMS, are maintained by a fibrillin-1 microfibril scaffold, modulated by ADAMTSLIKE proteins in concert with ADAMTS enzymes.

Dipolar molecules have been grafted on the surface of indium-tin-oxide plates. Using these modified substrates as anodes for organic diodes made from poly-vinylcarbazole enhances the hole current by 1-2 orders of magnitude as compared to diodes with nonmodified anodes. The organization and surface concentration of the grafted monolayer, determined by infrared spectroscopy, show that the grafted layer is not densely packed. The influence of the dipolar molecules on the energy barrier height for the injection of hole current into the organic layer is also measured by internal photoemission, evidencing that the barrier is lowered by the molecular grafting. The free space around the grafted molecules allows for their reorientation under electric field. The energy barrier height has been measured as a function of time during this reorientation. [ABSTRACT FROM AUTHOR]

Internal photoemission has been used to determine the energy barriers for electrode/organic-layer interfaces in organic light-emitting diodes. The diodes were polymer or small-molecule single-layer structures made from poly-(9-vinylcarbazole), poly-(9,9-dihexylfluorene), tris-(8-hydroxyquinolinate) aluminum, and N,N[sup ′]- Bis(3-methylphenyl)-N,N[sup ′]-diphenylbenzidine with indium tin oxide or metallic electrodes (Al, Au, or Cu). The internal photoemission yield follows the Fowler theory and the energy barriers exhibit a small lowering for increasing internal electric field due to image-force potential. There is an offset of 0.4-0.5 eV between the actual energy barriers and the naive expectations from the difference between the energy levels taken from the literature. Interface dipole effects and uncertainties concerning the electrochemical determination of the highest occupied molecular orbital levels are the most plausible origins of this difference. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]