3,150 research outputs found
Resultados Preliminares sobre Estudios de Evapotranspiración del Cacao.
El objeto de este trabajo fue determinar los requerimientos de agua por el cacaotero. De los múltiples métodos que existen para este fin, solo el que hace uso de la evapotranspirometría da la solución deseada. El método se basa en que el agua del suelo establece un equilibrio entre el agua que entra, como resultado de la precipitación y el agua que sale a través de la evaporación y transpiración. Para este estudio se están usando cuatro evapotranspirómetros de 2 x 2 metros en la parte superior y 1.20 metros de profundidad: un quinto tanque sirve de fosa colectora, donde se tienen las canecas que recogen las aguas de drenajes. A los evapotranspirómetros se trasplantaron cacaoteros de tres y medio años de edad del Clon 6. Posteriormente fueron rellenados consuelo del mismo lugar y procedente de la excavación. La estación de evapotranspirometría se localizó en medio de una plantación comerciaal de cacao del clon 6 de la misma edad, en la que se ha demarcado una zona buffer de 50 x 50 mts., ésta se riega en la misma forma que los tanques evapotranspirómetros. A éstos se les aplica una cantidad medida de agua cuando no llueve en las 24 horas anteriores. La evapotranspiración potencial se mide restando del agua aplicarla la la cantidad recogida en las canecas, esto se hace para cada tanque todos los días a las 8 a.m. Además de la evapotranspiración potencial, diariamente se toman datos metereológicos en aparatos localizados junto a los tanques experimentales. La información para tres meses; indica que el agua de lluvia sólo suministró el 42.19% y el 63.33% de los requerimientos de agua para el cacaotero en los meses de febrero y marzo respectivamente. En el mes de abril la precipitación fue superior a los requerimientos de agua, va que el consumo fue de 58.46 mm. Y la precipitación de 129.5 mm. Debido a la información tan escasa (tres meses solamente) aquí presentada, es imposible, por el momento, sacar cualquier conclusión. La respuesta a este problema de los requerimientos de agua por el cacaotero, debe esperar por los menos 2 años de intensa investigación evapotranspirométrica
Non-critically squeezed light via spontaneous rotational symmetry breaking
We theoretically address squeezed light generation through the spontaneous
breaking of the rotational invariance occuring in a type I degenerate optical
parametric oscillator (DOPO) pumped above threshold. We show that a DOPO with
spherical mirrors, in which the signal and idler fields correspond to first
order Laguerre-Gauss modes, produces a perfectly squeezed vacuum with the shape
of a Hermite-Gauss mode, within the linearized theory. This occurs at any
pumping level above threshold, hence the phenomenon is non-critical.
Imperfections of the rotational symmetry, due e.g. to cavity anisotropy, are
shown to have a small impact, hence the result is not singular.Comment: 4 pages, 1 figure, replaced with resubmitted versio
Enhancement of the immunoregulatory potency of mesenchymal stromal cells by treatment with immunosuppressive drugs
Background aims Multipotent mesenchymal stromal cells (MSCs) are distinguished by their ability to differentiate into a number of stromal derivatives of interest for regenerative medicine, but they also have immunoregulatory properties that are being tested in a number of clinical settings. Methods We show that brief incubations with rapamycin, everolimus, FK506 or cyclosporine A increase the immunosuppressive potency of MSCs and other cell types. Results The treated MSCs are up to 5-fold more potent at inhibiting the induced proliferation of T lymphocytes in vitro. We show that this effect probably is due to adsorption of the drug by the MSCs during pre-treatment, with subsequent diffusion into co-cultures at concentrations sufficient to inhibit T-cell proliferation. MSCs contain measurable amounts of rapamycin after a 15-min exposure, and the potentiating effect is blocked by a neutralizing antibody to the drug. With the use of a pre-clinical model of acute graft-versus-host disease, we demonstrate that a low dose of rapamycin-treated but not untreated umbilical cord–derived MSCs significantly inhibit the onset of disease. Conclusions The use of treated MSCs may achieve clinical end points not reached with untreated MSCs and allow for infusion of fewer cells to reduce costs and minimize potential side effects
Protein modification and maintenance systems as biomarkers of ageing
Changes in the abundance and post-translational modification of proteins and accumulation of some covalently modified proteins have been proposed to represent hallmarks of biological ageing. Within the frame of the Mark-Age project, the workpackage dedicated to "markers based on proteins and their modifications" has been firstly focused on enzymatic and non-enzymatic post-translational modifications of serum proteins by carbohydrates. The second focus of the workpackage has been directed towards protein maintenance systems that are involved either in protein quality control (ApoJ/Clusterin) or in the removal of oxidatively damaged proteins through degradation and repair (proteasome and methionine sulfoxide reductase systems). This review describes the most relevant features of these protein modifications and maintenance systems, their fate during ageing and/or their implication in ageing and longevity
Novel U-Shaped D-A-D π-conjugated Systems with Mechanochromic Properties: An Experimental and Theoretical Vibrational Spectroscopic Investigation
Π-conjugated compounds have been widely studied in the last few decades due to their huge field of application in organic electronics. Specifically, stimuli-responsive Π-conjugated materials which are sensitive to external stimulus (i.e., temperature, pressure, etc) have several uses like sensors, probes and security inks, for example.1 In this work, we study two U-shape Donor-Acceptor-Donor (D-A-D) systems that are found to exhibit interesting thermal- and pressure-dependent properties. 2 They consist on two different conformers of phenothiazine-dibenzo[a,j]phenazine-phenothiazine which differs from the position of the phenothiazine respect to the dibenzophenzaine central core. Compound 1R is the equatorial-equatorial conformer and 1Y is the axial-axial conformer (Figure 1). The dibenzophenzaine group acts as an electron-acceptor whereas the phenothiazine unit acts as an electron-donor. It has been reported that this U-shape D-A-D compound shows a multi-active color changing in 3 steps and their luminescence changes with temperature, pressure and acid exposition.2 In this work, we aim to elucidate how the external stimuli (i.e. temperature, pressure, acid ambient) affects the molecular structure at both intra- and intermolecular level. To this end, we use UV-Vis absorption, Raman (Figure 1) and Infrared spectroscopy experiments in combination with DFT calculations.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Conversion from forests to pastures in the Colombian Amazon leads to contrasting soil carbon dynamics depending on land management practices
This is the author accepted manuscript. The final version is available from Wiley via the DOI in this recordStrategies to mitigate climate change by reducing deforestation and forest degradation (e.g. REDD+) require country- or region-specific information on temporal changes in forest carbon (C) pools to develop accurate emission factors. The soil C pool is one of the most important C reservoirs, but is rarely included in national forest reference emission levels due to a lack of data. Here, we present the soil organic C (SOC) dynamics along 20 years of forest-to-pasture conversion in two subregions with different management practices during pasture establishment in the Colombian Amazon: high-grazing intensity (HG) and low-grazing intensity (LG) subregions. We determined the pattern of SOC change resulting from the conversion from forest (C3 plants) to pasture (C4 plants) by analysing total SOC stocks and the natural abundance of the stable isotopes (13) C along two 20-year chronosequences identified in each subregion. We also analysed soil N stocks and the natural abundance of (15) N during pasture establishment. In general, total SOC stocks at 30 cm depth in the forest were similar for both subregions, with an average of 47.1 ± 1.8 Mg C ha(-1) in HG and 48.7 ± 3.1 Mg C ha(-1) in LG. However, 20 years after forest-to-pasture conversion SOC in HG decreased by 20%, whereas in LG SOC increased by 41%. This net SOC decrease in HG was due to a larger reduction in C3-derived input and to a comparatively smaller increase in C4-derived C input. In LG both C3- and C4-derived C input increased along the chronosequence. N stocks were generally similar in both subregions and soil N stock changes during pasture establishment were correlated with SOC changes. These results emphasize the importance of management practices involving low-grazing intensity in cattle activities to preserve SOC stocks and to reduce C emissions after land-cover change from forest to pasture in the Colombian Amazon.This study was funded by AXA Research Fund (2012‐Doc‐University‐of‐Exeter‐NAVARRETE‐D)
Condrosarcoma metatarsiano: aportación de un caso
Se presenta un caso de condrosarcoma de bajo grado de malignidad, de localización
y evolución inusual. Se revisa la literatura y los criterios disponibles en la actualidad
para el diagnóstico de estas lesiones controvertidas tanto histológica como clínicamente.We report a low grade chondrosarcoma with atypical behaviour and localitation.
The main histologic features in the diagnosis of these controversial lesion are discussed
Bioevents correlation of planktic foraminifers and radiolarians from the Cenomanian to Turonian, southeastern Mexico
Abstrac
Impact of the dicyanomethylene substitution position on the cyclophane macrocycle formation in carbazole-based biradicals
π-Conjugated biradical compounds, featuring unique unsaturated valences and radical centers in the ground state, are fundamentally important for understanding the nature of chemical bonds and have potential applications in material science. [1] Recently, it has been demonstrated that several -conjugated mono- and biradicals systems form long strain -bonds between two unpaired electrons resulting in macrocyclic or staircase oligomers or polymers by self-assembly processes. [2] Therefore, these materials are potential building blocks for dynamic covalent chemistry (DCC) since the aggregates can be formed or broken upon soft external stimuli. For instance, 2,7-dicyanomethylene-9-(2-ethylhexyl)carbazole biradical (p-Cz-alkyl in Figure 1) reversibly converts upon soft stimuli (temperature, pressure, light) to a cyclophane tetramer as a result from the formation (or bond cleavage) of long C-C single bonds.[3] Here, we present an experimental and theoretical study in order to investigate how the N-substitution and the change from para- to meta-dicyanomethylene substitution on carbazole-based biradicals affects their biradical character and thus, their tendency to act as useful motifs for DCC (see Figure 1).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec
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