3,724 research outputs found

    Hispanics in the e-commerce business

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    This project focuses on developing links between the emerging e-commerce industry and Hispanic owned business community of Haverhill, Massachusetts (US). (Library-derived description)de la Cruz, J. E. (2000). Hispanics in the e-commerce business. Retrieved from http://academicarchive.snhu.eduMaster of Science (M.S.)School of Community Economic Developmen

    Estimating the Collapse Pressure of an Inflatable Aerodynamic Decelerator

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    The collapse pressure of an inflatable membrane is the minimum differential pressure which will sustain a specific desired shape under an applied load. In this paper, we present a method for estimating the collapse pressure of a tension-cone inflatable aerodynamic decelerator (IAD) that is subject to a static aerodynamic load. The IAD surface is modeled as an elastic membrane. For a given aerodynamic load and sufficiently high torus differential pressure, the IAD assumes a stable axisymmetric equilibrium shape. When the torus pressure is reduced sufficiently, the symmetric equilibrium state becomes unstable and we define this instance to be the critical pressure Pcr. In this paper, we will compare our predicted critical torus pressure with the corresponding observed torus collapse pressure (OTCP) for fifteen tests that were conducted by the third author and his collaborators at the NASA Glenn Research Center 10x10 Supersonic Wind Tunnel in April 2008. One of the difficulties with these types of comparisons is establishing the instance of torus collapse and determining the OTCP from quantities measured during the experiment. In many cases, torus collapse is gradual and the OTCP is not well-defined. However, in eight of the fifteen wind tunnel tests where the OTCP is well-defined, we find that the average of the relative differences (Pcr - OTCP/Pcr) was 8.9%. For completeness, we will also discuss the seven tests where the observed torus collapse pressure is not well-defined

    Modelo de toma de decisiones para la selección del sistema de propulsión

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    History it has become evident that the military industry and its thriving action has generated change and development in different areas, and it is to be expected that a project as ambitious as the Strategic Surface Platform - PES focuses on the impact that internal combustion systems can generate in the design, therefore an evaluation model is developed for the selection of the propulsion system of the platform, which was based on the life cycle cost and performance of the main mechanical equipment, providing an additional tool for decision making. The cost side was estimated by breaking down the ROM (Rough Order of Magnitude) acquisition costs, maintenance costs and fuel and lubricant consumption costs, which leaves the performance side evaluated under the technical characteristics, considering the criteria of performance, reliability, delivered power and installation footprint; without leaving aside the mandatory requirements such as IMO TIER III gas emissions, reduction of the acoustic signature and the use of redundancy.A través de la historia se ha hecho evidente cómo la industria militar y su pujante accionar ha generado cambio y desarrollo en las diferentes áreas, y es de esperar que un proyecto tan ambicioso como lo es la Plataforma Estratégica de Superficie – PES se enfoque en el impacto que los sistemas de combustión interna pueden generar en el diseño, por lo anterior se desarrolla un modelo de evaluación para la selección del sistema de propulsión de la plataforma, el cual fue basado en el costo del ciclo de vida y el desempeño de los equipos mecánicos principales, brindando una herramienta adicional para la toma de decisiones. La arista del costo se estimó desglosando los costos de adquisición del tipo ROM (Rough Order of Magnitude), costos de mantenimiento y costos de consumo de combustible y lubricante, lo que deja la arista de desempeño evaluada bajo las características técnicas, considerando los criterios de rendimiento, confiabilidad, potencia entregada y huella de instalación; sin dejar a un lado los requisitos de obligatorio cumplimiento como lo son las emisiones de gases IMO TIER III, la reducción de la firma acústica y el empleo de la redundancia

    A reassessment of the taxonomic status of Paraglyptodon Castellanos, 1932 (Mammalia, Cingulata, Glyptodontia)

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    Castellanos described and published about new genera of glyptodonts, according to a phylogenetic scheme mainly based on the evolution of the external surface of the dorsal carapace. Among these new genera, Castellanos proposed Paraglyptodon as the predecessor of Glyptodon, and included within Paraglyptodon all known species of Glyptodontinae recovered from “horizontes pre-Ensenadenses”, and within Glyptodon all known species from “Horizontes pampeanos”, restricting the latter to the Quaternary. All the species that belong to Paraglyptodon, that is Paraglyptodon chapalmalensis, Paraglyptodon uquiensis, Paraglyptodon dubius, and Paraglyptodon paranensis were established based on one, two or few osteoderms, mostly from the dorsal carapace. Regarding P. paranensis and P. dubius, Oliva and collaborators consider the first as a nomen vanum, representing an indeterminate Glyptodontinae, and the second as a synonym of P. chapalmalensis. Upon re-examination of the holotypes of P. chapalmalensis and P. uquiensis together with their comparison with other well-known specimens of glyptodonts, mainly with Glyptodon (of both juvenile and adult stages), we found the same ornamentation in different sections of the dorsal carapaces, particularly in P. chapalmalensis and in juvenile stages of Glyptodon spp.We could not identify features that would allow us to make a distinction between the holotype of P. uquiensis and Glyptodon spp. Therefore, we consider that a new taxon guide for naming the Upper Chapadmalalan biozone is necessary. The biostratigraphic range of Glyptodon could possibly be extended to the late Pliocene. However, new records and studies are needed to verify the existence of this taxon in the Chapadmalalan Stage/Age in its type locality.Facultad de Ciencias Naturales y Muse

    Enantioselective Transesterification by Candida antarctica Lipase B Immobilized on Fumed Silica

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    Enzymatic catalysis to produce molecules such as perfumes, flavors, and fragrances has the advantage of allowing the products to be labeled “natural” for marketing in the U.S., in addition to the exquisite selectivity and stereoselectivity of enzymes that can be an advantage over chemical catalysis. Enzymatic catalysis in organic solvents is attractive if solubility issues of reactants or products, or thermodynamic issues (water as a product in esterification) complicate or prevent aqueous enzymatic catalysis. Immobilization of the enzyme on a solid support can address the generally poor solubility of enzymes in most solvents. We have recently reported on a novel immobilization method for Candida antarctica Lipase B on fumed silica to improve the enzymatic activity in hexane. This research is extended here to study the enantioselective transesterification of (RS)-1-phenylethanol with vinyl acetate. The maximum catalytic activity for this preparation exceeded the activity (on an equal enzyme amount basis) of the commercial Novozyme 435® significantly. The steady-state conversion for (R)-1-phenylethanol was about 75% as confirmed via forward and reverse reaction. The catalytic activity steeply increases with increasing nominal surface coverage of the support until a maximum is reached at a nominal surface coverage of 230%. We hypothesize that the physical state of the enzyme molecules at a low surface coverage is dominated in this case by detrimental strong enzyme-substrate interactions. Enzyme-enzyme interactions may stabilize the active form of the enzyme as surface coverage increases while diffusion limitations reduce the apparent catalytic performance again at multi-layer coverage. The temperature-, solvent-, and long-term stability for CALB/fumed silica preparations showed that these preparations can tolerate temperatures up to 70°C, continuous exposure to solvents, and long term storage

    Propiedades de las rocas volcánicas de Canarias (España) utilizadas como material de escollera

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    In the Canary Islands, there is a wide spectrum of volcanic rocks with different properties to be used in public works. The aim of this study is to analyse the physical-mechanical properties of all the volcanic rocks present in the Canary Island archipelago in order to determine their suitability for use in maritime construction works. The great variety of volcanic rocks present on the islands have been grouped into lithotypes based on similar geo-mechanical behaviour. The laboratory test results obtained for these lithotypes establish their suitability or not to be used as breakwater material in accordance with Spanish regulations.En el archipiélago canario existe un amplio espectro de rocas volcánicas con diferentes propiedades para ser utilizadas en obras públicas. El objetivo de este estudio es analizar las propiedades físico-mecánicas de todas las rocas volcánicas presentes en el archipiélago canario con el fin de determinar su idoneidad para ser utilizadas en obras de construcción marítima. La gran variedad de rocas volcánicas presentes en las islas, se han agrupado en litotipos basados en un comportamiento geomecánico similar. Los resultados de los ensayos de laboratorio obtenidos para estos litotipos establecen su idoneidad o no para ser utilizados como material de escollera de acuerdo con la normativa española

    Autoimmune (auto-inflammatory) syndrome induced by adjuvants (ASIA) - Animal models as a proof of concept

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    ASIA syndrome, 'Autoimmune (Auto-inflammatory) Syndromes Induced by Adjuvants' includes at least four conditions which share a similar complex of signs and symptoms and have been defined by hyperactive immune responses: siliconosis, macrophagic myofasciitis syndrome, Gulf war syndrome and post-vaccination phenomena. Exposure to adjuvants has been documented in these four medical conditions, suggesting that the common denominator to these syndromes is a trigger entailing adjuvant activity. An important role of animal models in proving the ASIA concept has been established. Experimentally animal models of autoimmune diseases induced by adjuvants are currently widely used to understand the mechanisms and etiology and pathogenesis of these diseases and might thus promote the development of new diagnostic, predictive and therapeutic methods. In the current review we wish to unveil the variety of ASIA animal models associated with systemic and organ specific autoimmune diseases induced by adjuvants. We included in this review animal models for rheumatoid arthritis-like disease, for systemic lupus erythematosus-like disease, autoimmune thyroid disease-like disease, antiphospholipid syndrome, myocarditis and others. All these models support the concept of ASIA, as the Autoimmune (Auto-inflammatory) Syndrome Induced by Adjuvants. © 2013 Bentham Science Publishers

    Polarization networks around the SDGs in the press from 2020 to 2023

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    Polarization in the media is a phenomenon classified as ambivalent and volatile because radical positions change to moderate and neutral. The objective of the study was to demonstrate this process in press releases and expert evaluations regarding the Sustainable Development Goals (SDG). A documentary, cross-sectional, exploratory, and retrospective work was carried out with a sample of press releases with national circulation and published from 2020 to 2023 headed with SDGs. The results verify the null hypothesis of significant differences between the theoretical structures concerning the empirical observations. The scope and limits of the study are discussed, as well as a local risk communication policy

    Amphibians and Reptiles of Luzon Island, Philippines: the Herpetofauna of Pantabangan-Carranglan Watershed, Nueva Ecija Province, Caraballo Mountain Range

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    We present detailed species accounts for fifty-nine (59) species of amphibians and reptiles (17 frogs, 14 skinks, 3 agamids, 6 gekkonid lizards, 2 varanids, and 17 snakes) from Pantabangan-Carranglan Watershed, which lies within the Caraballo Mountain Range, whose biota is poorly-known. This was also the first extensive survey of herpetofauna within the watershed. Together with data from previous literature reviews, our records bring the total number of species of amphibians and reptiles for the Caraballo Mountain Range to 66. Forty-two (42) species from the area were Philippine endemics, with 25 species recorded only from Luzon faunal region. Seven species of herpetofauna are associated with unresolved taxonomic issues (new species and species complexes needing taxonomic partitioning, e.g. splitting of species groups). Two species recorded from the area were rarely represented in museum collections. Major distributional and elevational range extensions were recorded for several species. Comparison with Luzon’s other mountain ranges showed that the Caraballo Mountain Range is similar, in terms of species composition, to the northern Sierra Madre and Cordillera Mountain Ranges. The result of this survey showed the Caraballo Mountain Range and its mountains as a possible new center of herpetofaunal diversity and endemicity within Luzon. The importance of the Caraballo Mountain Range as an important biogeographic link merits further study
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