171,785 research outputs found
A Guide to the Zygotic Embryo Culture of Coconut Palms (Cocos nucifera L.)
No full textCrop Production/Industries,
Properties of the Subduction System in Mexico
No full textThis thesis presents seismic imaging results of the structure of the Mexican subduction zone using receiver function (RF) based on teleseismic P-to-S converted waves, in order to gain insight into the physical and chemical factors associated with internal geodynamic processes. More specifically, this thesis investigates (1) the nature of tectonic processes involved in the buildup and subsequent modification of continental and oceanic lithosphere, and (2) the determination of mineralogy/petrology and fluidphase
reactions in the subducting Cocos oceanic crust.
Utilizing the data acquired from two dense broadband seismic lines in Mexico, the geometries and seismic properties of the interface of the subducting Cocos plate beneath Mexico are determined from the RFs. The RF image for central Mexico shows that the subducting oceanic crust dips shallowly north at 15 degrees for a distance of 80 km from Acapulco at the Pacific coast, and then horizontally underplates the continental crust for approximately 200 km to the Trans-Mexican Volcanic Belt (TMVB). Modeling of the RF conversion amplitudes and timings of the underplated features reveals a thin very-low velocity zone between the plate and the continental crust that appears to absorb nearly all of the strain between the upper plate and the slab. The migrated image of the RFs shows that the slab dips steeply into the mantle at an angle of about 75 degrees beneath the TMVB.
The RF results for southern Mexico in the Isthmus of Tehuantepec show an image of the Cocos slab down to about 100 km depth. The same cross-section image also reveals a slab-like south-dipping structure interpreted to be subducted from the Gulf of Mexico. This anomalous slab with the opposite dip direction of the Cocos slab appears to cut off the Cocos slab at 150 km depth. There is no tectonic explanation for the south-dipping slab under the current paradigm of Caribbean plate reconstructions. We present in this thesis the case for a new reconstruction of the Gulf of Mexico and propose that the slab may be due to the collision of the Yucatan Block into Mexico in the Miocene, and may also be responsible for the Cocos plate truncation imaged from previous tomography studies. This hypothesis explains the Chiapas Fold and Thrust Belt to the south of the Yucatan Block and may explain the unusual volcanic arc configuration in southern Mexico.
We formulate and apply a new inversion technique based on the plane wave conversion to obtain the seismic parameters (S wave velocity, Vs, and density) of the oceanic crust. We use such parameters to infer mineralogical properties of subducting oceanic crust. From this effort, we provide tighter constraints on physical properties of the subducting Cocos oceanic crust, and explain the difference in the slab geometries betweeen central and southern Mexico from the mineral physics point of view. Anomalously low Vs (2.4−3.4 km/s) in the upper part of the flat oceanic crust in central Mexico points to elevated Poisson’s and Vp/Vs ratios of the oceanic crust. This directly relates to the presence of water and hydrous minerals or high pore pressure; the mechanically weak hydrous layer may explain current subduction geometry at very shallow depth of about 45 km without strong coupling between the plates.
Using Vp/Vs as a function of Vs in a range of likely pressure and temperature for candidate hydrous phases, we identify the major hydrous mineral phases present in the upper (3−5 km thickness) and lower parts (3−5 km thickness) of the subducted oceanic crust of central and southern Mexico. In central Mexico, the upper oceanic crust in the flat slab region is enriched with hydrous minerals such as talc over the normal oceanic crustal compositions such as MORB-like gabbro. Petrologically, the generation of talc during subduction of the oceanic crust is nearly impossible. One possible mechanism to produce such a low-velocity anomaly at the upper oceanic crust is that lower crustal rocks are hydrated with 15-20 percent of free water to reduce the seismic velocities significantly. We thus propose that the thin low-velocity, talc-rich layer in the upper oceanic crust is then generated from the mantle wedge side during the slab flattening process coupled with trench rollback. The talc-rich rocks at the slab interface can be formed in the mantle by the addition of silica transported by rising fluids via the dehydration reaction from the subducting oceanic crust and by mechanical mixing of mantle and siliceous rocks. The evolution of the thin low-strength zone, which decouples the horizontal slab from the continental crust, originating from the mantle wedge side rather than the trench side, has important implications for the dynamics of the subduction system, including the flattening process of the slab, as well as the geochemistry of the mantle wedge and arc in central Mexico. After passing through the flat segment, the major compositions of the steeply subducting oceanic crust underneath the TMVB are zoisite and lawsonite from 60 to 100 km in depth. The eclogitization occurs at the depth of about 100 km. The dominant mineral phase in the upper oceanic crust of southern Mexico from 45 to 120 km depth is amphibole on top of unaltered gabbroic oceanic crust.</p
Sovereign CoCos and debt forgiveness
No full textWe study a sovereign default model in which the government issues CoCos (contingent convertible bonds) that stipulate a suspension of debt payments upon a sizable increase of the global risk premium (and thus, of the government’s borrowing cost). We find that CoCos allow the government to smooth out the effects of risk-premium shocks on consumption, but they increase the default frequency. By suspending debt payments, CoCos imply higher debt levels and, thus, higher default probabilities after adverse shocks. We also study CoCos that, in addition to the payment suspension, stipulate debt forgiveness after adverse shocks. In contrast with no-forgiveness CoCos, debt-forgiveness CoCos reduce debt levels after adverse shocks, thereby reducing default probabilities. Debt-forgiveness CoCos also yield larger welfare gains.Hatchondo, J. C., Martinez, L., Önder, Y. K., & Roch, F. (2025).
Sovereign CoCos and debt forgiveness. Journal of Monetary
Economics, 153, 103784.
https://doi.org/10.1016/j.jmoneco.2025.10378
Immunochemical characterization of Cocos nucifera pollen
No full textThe Cocos nucifera pollen, as one of the sources of allergen responsible for immediate hypersensitivity reaction, was confirmed by skin prick test, bronchial provocation test, and RAST. The whole pollen extract (WPE) of C. nucifera was fractionated by combination of gel filtration and ion-exchange columns with fast protein liquid chromatography (Pharmacia, Uppsala, Sweden). Three protein peaks designated Cocos II, Cocos VI, and Cocos VII exhibited allergenic properties, as tested by skin prick test, direct IgE ELISA, bronchial provocation test, and immunoblot analysis. In RAST inhibition, Cocos IIa (a high-molecular-weight protein) obtained by fractionation of Cocos II on Mono Q column (fast protein liquid chromatography) (Pharmacia) was found to be the most potent allergen in Cocos WPE, followed by Cocos VI and Cocos VII, which are low-molecular-weight proteins. The reference patterns of Cocos WPE on crossed immunoelectrophoresis and thin-layer isoelectric focusing were established for future standardization of Cocos WPE to be used in the diagnosis and immunotherapy of allergic patients
Efecto de la ceniza de fibra de coco (cocos nucifera) en la resistencia a compresión de adoquines de f´c=380 kg/cm2, Jaén – 2024
No full textLa investigación se centró en determinar el efecto de la incorporación de ceniza de fibra de coco (Cocos nucifera) en porcentajes de 1.5%, 3.0% y 4.5% sobre la resistencia a la compresión de adoquines de concreto, con una resistencia de diseño de f´c=380 kg/cm2. El objetivo fue evaluar la influencia de estas proporciones en dicha propiedad mecánica. La metodología empleada correspondió a un diseño experimental verdadero, mediante el cual se elaboraron 36 especímenes (9 por cada proporción, incluido el grupo control), los cuales fueron sometidos a ensayos de compresión a 7, 14 y 28 días de curado. Se utilizaron técnicas de observación estructurada y análisis estadístico para interpretar los datos. Los resultados mostraron que las mayores resistencias a los 28 días se alcanzaron con las adiciones del 3.0% (395.87 kg/cm2) y 4.5% (416.35 kg/cm2), superando al patrón (390.12 kg/cm2), mientras que la menor resistencia (369.45 kg/cm2) se registró con el 1.5%. Se concluyó que la incorporación de ceniza mejora significativamente la resistencia a la compresión del concreto en adoquines, siendo más efectiva la dosificación del 4.5% a los 28 días, con un incremento del 6.72% respecto al patró
Studi Pendahuluan tentang Enkapsulasi Vitamin C dalam Liposom Kelapa (Cocos nucifera L.)
No full textPenelitian ini bertujuan untuk mempelajari enkapsulasi vitamin C dalam liposom kelapa (Cocos nucifera L.). Efisiensi enkapsulasi liposom kelapa diperoleh sebesar 80,76%. Penambahan kolesterol pada membran liposom mempengaruhi besarnya efisiensi enkapsulasi. Penambahan kolesterol sebesar 30% meningkatkan efisiensi enkapsulasi menjadi sebesar 92,71%. Suhu mempengaruhi kemampuan liposom kelapa untuk menyimpan vitamin C dalam 8 hari. Penyimpanan pada suhu 5°C menurunkan kebocoran liposom kelapa.Penelitian ini bertujuan untuk mempelajari enkapsulasi vitamin C dalam liposom kelapa (Cocos nucifera L.). Efisiensi enkapsulasi liposom kelapa diperoleh sebesar 80,76%. Penambahan kolesterol pada membran liposom mempengaruhi besarnya efisiensi enkapsulasi. Penambahan kolesterol sebesar 30% meningkatkan efisiensi enkapsulasi menjadi sebesar 92,71%. Suhu mempengaruhi kemampuan liposom kelapa untuk menyimpan vitamin C dalam 8 hari. Penyimpanan pada suhu 5°C menurunkan kebocoran liposom kelapa.</jats:p
COCOS: A typicality based COncept COmbination System
No full textIn this short paper we describe COCOS, a tool we are currently developing in order to account for the phenomenon of combining prototypical concepts, an open problem in the fields of AI and cognitive modelling. COCOS is based on a probabilistic extension of the logic of typicality ALC + TR by inclusions p:: T(C) ⊆ D ("we have probability p that typical Cs are Ds") and it embeds a set of cognitive heuristics for concept combination
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Obtención de biodiesel a partir de aceite de residuos de la industrialización de coco (Cocos Nucifera L.)
No full textEn la industria agroalimentaria se generan una variedad de residuos que, si no reciben una gestión adecuada genera contaminación ambiental afectando el suelo y agua principalmente. Sin embargo, estos residuos pueden ser utilizados como materia prima para la obtención de nuevos productos amigables con el medio ambiente. Es así que, el objetivo de la investigación fue obtener y caracterizar biodiesel a partir de aceite de residuos de la industrialización del coco (Cocos nucifera L.). Se utilizó equipo Soxhlet para la extracción del aceite, se obtuvo biodiesel mediante reacción de transesterificación con metanol, usando 0.2 g de NaOH como catalizador para cada relación molar aceite/metanol (1:10, 2:13, 1:5, 4:13) a una temperatura constante de 60 °C con un tiempo de reacción de 1 h. Los resultados obtenidos indican que es posible obtener biodiesel a partir de aceite de afrecho de coco, siendo la mejor relación molar 2:13 (aceite/metanol), con una densidad 0.86 g/cm3, índice de cetano 47.81, índice de acidez 0.34 mg KOH/g y punto nube 6 °C, viscosidad cinemática de 1.60 mm2/s, punto de inflamación de 104.33 °C y punto de ebullición de 259.83 °C. Se obtuvo biodiesel con un rendimiento promedio de 86.29%, siendo la relación molar 2:13 la que se aproxima a los estándares establecidos en la NTP 321.125 (2008)
Close form pricing formulas for Coupon Cancellable CoCos
No full textConteúdo online de acesso restrito pelo editorContingent Convertibles ('CoCos') are contingent capital instruments which convert into shares, or have a principal write down, if a trigger event takes place. CoCos exhibit the undesirable so-called death-spiral effect: by actively hedging the equity risk, investors can (unintentionally) force the conversion by making the share price deteriorate and eventually trigger the conversion. In this paper we introduce and analyse Coupon Cancellable CoCos ('CoCa CoCos'), a new type of CoCo where coupons can be cancelled during the lifetime of the note. We provide closed-form pricing formulas for CoCa CoCos, we study the impact of coupon cancellations in the price of the bond and we show that death-spiral effect is reduced. (C) 2014 Elsevier B.V. All rights reserved
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