2,674 research outputs found
Periostracal mineralization in the gastrochaenid bivalve Spengleria
No full textWe investigated the spikes on the outer shell surface of the endolithic gastrochaenid bivalve genus Spengleria with a view to understand the mechanism by which they form and evaluate their homology with spikes in other heterodont and palaeoheterodont bivalves. We discovered that spike formation varied in mechanism between different parts of the valve. In the posterior region, spikes form within the translucent layer of the periostracum but separated from the calcareous part of the shell. By contrast those spikes in the anterior and ventral region, despite also forming within the translucent periostracal layer, become incorporated into the outer shell layer. Spikes in the posterior area of Spengleria mytiloides form only on the outer surface of the periostracum and are therefore, not encased in periostracal material. Despite differences in construction between these gastrochaenid spikes and those of other heterodont and palaeoheterodont bivalves, all involve calcification of the inner translucent periostracal layer which may indicate a deeper homology
The role of educative thought in the life and work of Antonio Gramsci
No full textMany philosophers have propounded a vision of an improved society, what distinguishes Antonio Gramsci is his continuous effort to make it happen by understanding the process in order to put into practice. Gramsci's conviction about the importance of educative development came from both theory and experience. While there has been considerable examination of Gramsci's work in relation to the Prison Notebooks, this study will seek to address a lacuna in Gramsci scholarship. Using Gramsci's philological method, I analyse Gramsci's pre-prison activity; his pre-prison articles and letters, which, together with his letters from prison, formed part of his educative mission. This educative process was necessary, in order to construct a new party which would develop a collective will, collaboratively, with the masses.In this study therefore, I explore the contexts and formative experiences of the first part of his life together with the intellectual sources from which Gramsci developed his later theories, making central hitherto underemphasised connections between them which informed his writing and ideas. I intend to illustrate that Gramsci's underlying purpose in his writing, and political activity, was not only practical, on how to create a new socialist ruling class, but also educative in forming the mindset and values of his comrades. So that in addition to outlining his vision of a new order, he implicitly guided or explicitly explained the processes by which the necessary changes in social relations and moral climate could be made in order to achieve it. Each person had to engage with the values of the new order so that each could contribute to the construction of a new robust state. It was essential to build a hegemony at the most profound level, one which was dependent on collective understandings and a collective will
Tightly shut: flexible valve margins and microstructural asymmetry in pterioid bivalves
No full textAbstract: An organic-rich columnar prismatic outer shell layer, which extends far beyond the underlying nacre, has allowed pterioid bivalves (the pearl oysters and their allies) to develop flexible valve margins, allowing a tight hermetic seal when shut. In some taxa, the microstructural arrangement is known to be asymmetrically developed between the two valves. The asymmetry was surveyed across 29 taxa of pterioids (including representatives of known genera) confirming that it is typically the right valve which has a greater expanse of prism-only shell (and less nacre) and showing that this portion of the right valve has more organic content (more than twice the value in some instances) than the equivalent in the left. A more detailed investigation of prismatic material in Pteria penguin comparing the right and left valves revealed that the right valve flange has a higher density of smaller prisms, each with its organic envelope, and not a greater thickness of the organic envelopes themselves. The flange is also thinner on the right valve and shown here to be very flexible when wet. This allows it to bend against the rigid left valve when the shell is closed. Comparison of this structural asymmetry in the pterioids with five outgroup taxa in the Ostreidae and Pinnidae suggests that clades with the asymmetry have been freed from the constraints of a flattened valve morphology and to develop inequivalved forms
Le parole di Antonio. Statisticamente parlando
No full textA corpus composed of ten documents written by Antonio Capelo in Padua during the period 1996-1999 has been analysed to recognize the characteristic features of the different pseudonyms used by the author. By means of a lexicon-textual coding approach and correspondence analysis this work attempts to understand something more about his personality and inner magic world
El Tlacuache Núm. 625 (2014). 625 Año 13 (2014) junio. El Tlacuache
No full textEntre la Fiesta y el quebranto. 1er Encuentro Regional de Tekuanis y la Fiesta de Ascensión en Xoxocotla 2014 por Marco Antonio Tafolla Soriano. - El grabado en hueso: una visión arqueológica y experimental por G. Alejandro Cool Argüelles
Detección e identificación de componentes orgánicos en conchas de moluscos
No full textEn moluscos, la matriz orgánica de la concha se compone de un gran número de proteínas, glicoproteínas y polisacáridos, que son secretados por el epitelio calcificante del manto, y que juegan un papel fundamental en las funciones de la síntesis de la concha.
El estudio de la biomineralización se enfrenta a dos grandes retos, uno de ellos está representado por la microestructura lamelar cruzada, el otro por el nácar. La lamelar cruzada es con diferencia la microestrcutura más abundante, pero pese a ello apenas hemos comenzado a desvelar sus secretos. El nácar, es la microestructura más estudiada pero aun alberga muchas incógnitas, no solo en cuanto a su desarrollo, sino también en lo que respecta a la propia estructura.
En este estudio, se ha caracterizado bioquímicamente la matriz asociada a la estructura lamelar cruzada de la concha reina, Lobatus gigas. Las matrices orgánicas soluble e insoluble representan una fracción minoritaria de la concha. Ambas están compuestas por una pequeña proporción de proteínas. De ellas se han purificado tres fracciones dominantes mediante electroforesis SDS-PAGE preparativa, denominadas como 1P3, 2P3 y 3P3, y posteriormente han sido caracterizadas. Comparada con otras matrices, ésta está débilmente glicosilada (3%). Sólo la fracción 3P3 se presenta notablemente glicosilada. La composición de azúcares muestra que la manosa es el monosacárido principal. Siendo la primera vez que se constata este dato. Las proteínas purificadas interaccionan con el carbonato cálcico durante el proceso de cristalización in vitro, pero esta interacción es moderada. Se empleó el anticuerpo obtenido frente a 3P3 se usó para localizar a estas proteínas en las conchas mediante inmunogold.
Se han estudiado las fibras de quitina en conchas con estructura nacarada. Aunque de manera general se acepta que las fibras de quitina se presentan en las membranas interlamelares del nácar, la disposición de estas fibras ha sido discutida. Hasta ahora la mayoría de las observaciones se habían realizado en conchas desmineralizadas, donde la estructura original se pierde. En nuestro estudio hemos aplicado diferentes técnicas de marcaje (inmunofluorescencia directa e inmunogold) de las fibras de quitina en conchas no desmineralizadas. Hemos puesto así de manifiesto la disposición y la naturaleza de las diferentes fibras en la superficie del nácar sin desmineralizar, de los bivalvos Neotrigonia sp., Haliotis rufescens y Pteria Hirundo, trabajando con microscopía confocal y con microscopía electrónica de barrido (SEM). Durante el desarrollo experimental se encontraron evidencias de la presencia de quitina intracristalina en las plaquitas de nácar. Las observaciones realizadas, y los resultados experimentales, nos han ayudado a desvelar las dinámicas de crecimiento del nácar, mediante la interacción de la materia orgánica con el carbonato cálcico.In molluscs, the shell organic matrix comprises a large set of biomineral-occluded proteins, glycoproteins and polysaccharides, that are secreted by the calcifying mantle epithelium, and display several and fundamental functions related to the synthesis of the shell.
The study of biomineralization faces two major challenges, one is represented by the crossed-lamellar microstructure, the other by the nacre. The crossed-lamellar is the most abundant microstructure with difference, but nevertheless we have barely begun to reveal its secrets. Nacre, despite being the most studied microstructure, still harbors considerable uncertainties, not only in terms of its development, but also in regard to the structure itself.
In the present PhD Thesis, we have characterized biochemically the shell matrix associated to the crossed-lamellar structure of the giant queen conch Lobatus gigas. The acid-soluble (ASM) and acid-insoluble (AIM) matrices represent an extremely minor fraction of the shell. Both are constituted by a few discrete polidisperse proteins. Among which, three fractions, obtained by preparative SDS-PAGE and named 1P3, 2P3 and 3P3, are dominant and were further characterized. Compared to other matrices, the acid-soluble matrix is weakly glycosylated (3%) and among the discrete components, only 3P3 seems noticeably glycosylated. The monosaccharide composition of the ASM shows that mannose represents the main monosaccharide. To our knowledge, this is the first report of a high ratio of this sugar in a skeletal matrix. Furthermore, the ASM interacts with the in vitro crystallization of calcium carbonate, but this interaction is moderate. It differs from that of the isolated 1P3 fraction but is similar to that of the 2P3 and 3P3 fractions. At last, antibodies developed from the 3P3 fraction were used to localize this fraction within the shell by immunogold.
On the other hand, we have studied the chitin fibers in the interlamellar membranes of shell nacre. Although it is generally accepted that chitin is found as fibers in the interlamellar membranes of nacre, the disposition of these fibers has been discussed. So far most of the observations have been taken on previously demineralized shells, where the original structure disappears. We, however, have applied different labeling techniques (direct immunofluorescence and inmunogold) on non-demineralized nacreous shells. We have revealed the disposition and nature of the different fibers that can be observed on the surface of the nacreous shell of the bivalve Neotrigonia sp., Haliotis rufescens and Pteria hirundo by confocal microscopy and scanning electron microscopy (SEM). During the experimental development we found evidence of intracrystaline chitin in nacre platelets. They have helped to reveal the growth dynamics of nacre, through the interaction of organic matter with calcium carbonate.Tesis Univ. Granada. Programa Oficial de Doctorado en: Biología Fundamental y de SistemasLa investigación realizada ha sido financiada por el Ministerio de Educación, mediante la concesión de una beca predoctoral FPI (conv.2008/2012), y por el proyecto “Biomineralización en Invertebrados con énfasis en moluscos. Organización, génesis y evolución de microestructuras”, CGL2010.20748
Interview of author Rick Riordan
No full textRick Riordan, author of the "Tres Navarre" series of detective novels, talks about his teaching and writing careers, his life in San Antonio, and the need to write authentically about real places, people, language, culture, and history. He discusses his characters and the situations in which he places them, his own limits in writing about social injustice from which he has not suffered, but being familiar with life in San Antonio and the multicultural environment in the community. Riordan is also known for writing the "Percy Jackson & the Olympians" series. Riordan is interviewed by Diana Rivera at the 2005 Left Coast Crime Conference held in El Paso, Texas
PBO Fibres: from saliling design towards architectural performance
No full textp. 3013-3023PBO fibres, also called "high-performance" polymer fibres, are a group of materials known as "rigid rods". Through this work it is pretended to make some considerations about the use of these new generation fibres. Poly (p-phenylene-2.6-benzobisoxazole)(PBO) is rigid-rod isotropic crystal polymer. PBO fibre is a high performance fibre developed by TOYOBO (Japan) PBO fibre is quite flexible and has very soft handling, in spite of its extremely high mechanical properties. Over the past ten years Future Fibres Company has pioneered the use of PBO for yacht rigging and has proven it to provide remarkable performance and longevity. Their method of producing these PBO cables delivers the lightest, smallest cables available on the market today. The PBO cable is formed by combining the incredible properties of PBO (poly(p-phenylene-2,6- benzobisoxazole)) fibre with the simple yet undeniably reliable process of continuous winding.
A PBO cable is dry fibre tightly compacted and does not rely on a resin matrix that, if impacted, can be compromised. The cover of the cable is a vital component and whilst PBO is an excellent material for yacht rigging purposes, due to its extreme strength, low elongation and general robustness it must be protected from sunlight and seawater. Future Fibres has perfected its cover design that comprises a consolidating film, environmental protection layer and a customizable braided cover that can be tailored to suit any specific application. PBO has great potential to be used in construction or rehabilitation applications. At the same time the fibres, following further testing, would open up several design opportunities for high quality architectural projects.Gough, CE.; Pobo Blasco, M.; Ruiz Checa, JR. (2009). PBO Fibres: from saliling design towards architectural performance. Editorial Universitat Politècnica de València. https://riunet.upv.es/handle/10251/670
SEM, EBSD, laser confocal microscopy and FE-SEM data from modern Glycymeris shell layers
No full textHere, we provide the dataset associated with the research article “Orientation patterns of aragonitic crossed-lamellar, fibrous prismatic and myostracal microstructures of modern Glycymeris shells” [1]. Based on several tools (SEM, EBSD, laser confocal microscopy and FE-SEM) we present original data relative to the microstructure and texture of aragonite crystallites in all Glycymeris shell layers (crossed-lamellar, complex crossed-lamellar, fibrous prismatic and pedal retractor and adductor myostraca) and address texture characteristics at the transition from one layer to the other, identifying similarities and differences among the different layers. Shells were cut transversely, obliquely and longitudinally in order to obtain different orientated sections of the outer and inner layer and of the myostraca. The identification of major microstructural elements was provided by detailed SEM and laser confocal microscopy images. Microstructure and texture characterization was based on EBSD measurements presented as band contrast images and as color-coded crystal orientation maps with corresponding pole figures. Crystal co-orientation was measured with the MUD value. Finally, the distribution of the organic matrix occluded within the outer crossed-lamellar layer was revealed using FE-SEM. These data, besides providing a modern unaltered Glycymeris reference to detect diagenetic alteration in fossil analogs used for paleoenvironmental reconstructions, are useful to better comprehend the mechanisms of bivalve shell formation
Motion detection technology as a tool for cardiopulmonary resuscitation (CPR) quality improvement
No full textThe most popular method of training in basic life support and AED remains instructor-led training courses. Recent reviews provide good evidence to support alternative methods of training including lay instructors, self-directed learning (web, video, poster) and CPR feedback/prompt devices
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