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Search Results: 1 - 10 of 489810 matches for " Alfredo Ramírez-García "
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Underlying Assets Distribution in Derivatives: The BRIC Case  [PDF]
José Antonio Nú?ez, Mario I. Contreras-Valdez, Alfredo Ramírez-García, Eduardo Sánchez-Ruenes
Theoretical Economics Letters (TEL) , 2018, DOI: 10.4236/tel.2018.83035
Abstract: This paper addresses one of the main issues regarding numerical derivatives valuation, particularly the search for an alternative to the normality assumption of underlying asset returns, to obtain the price by using numerical techniques. There might be difficulties in making normality assumptions, which could produce over-valuated or sub-valuated prices of derivatives. Under this consideration, the Generalized Hyperbolic family has been proven to be a proper selection to model heavy tailed distribution behavior. The Normal Inverse Gaussian (NIG) distribution is a member flexible enough to model financial returns. NIG distribution can be used to model distribution returns under different states of nature. The indexes of the Brazil, Russia, India and China (BRIC) economies were studied at different time-periods using return data series from 2002 to 2005, 2006 to 2010 and 2011 to 2015, in such a manner to demonstrate with statistical criteria that NIG fits the empirical distribution in the three periods; even throughout economic downturn. This result may be used as an improvement in derivatives valuation with indexes as underlying assets.
Which stressors are responsible for the worsening in the clinical symptomatology of lupus?  [PDF]
M. I. Peralta-Ramírez, J. Jiménez-Alonso, M. Pérez-García
Health (Health) , 2009, DOI: 10.4236/health.2009.14051
Abstract: Objective: The purpose of this study was to test which stressors worsen the symptoms perceived by patients with lupus, thus broadening and corroborating results obtained in a previous study published in Psychosomatic Medicine. Methods: In order to examine this question, we selected 43 patients with lupus whose symp-toms worsened due to the effects of daily stress. These patients were divided into two groups: patients whose increase in clinical lupus symp-tomatology was predicted by an increase in daily stressors on the same day (G1) and pa-tients whose increase in clinical lupus symp-tomatology was predicted by an increase in daily stressors the day before and the same day (G2). Later, three factorial analyses were con-ducted with the items related to stressors and the items related to lupic symptoms. Results: The results showed that in G1 there were three factors that made up a total of 35.08% of the explained variance. The stressors associated with certain symptoms of the illness in this group are feeling ill or being worried about their physical appearance, with the main stressor being the illness itself. However, in G2, two factors were found that made up a total of 40.37% of the explained variance for lag=0 and 38.67% for lag=1. The stressors associated with the majority of the lupus symptoms are of an interpersonal and work-related nature. This as-sociation was maintained when we carried out the factorial analyses with the items of the symptoms from the following day. Conclusions: The interpersonal and work-related stressors are related to a worsening in the majority of the lupic symptoms in the patients whose sympto-matology worsens as a result of daily stress experienced the day before.
Integración económica de los inmigrantes mexicanos en la Zona Metropolitana de Los ángeles
Alarcón, Rafael;Ramírez-García, Telésforo;
Papeles de población , 2011,
Abstract: mexican migration to the united states has a century-old history. however, there is currently ample concern about its integration into the u.s. society due to its massive volume and high percentage of undocumented persons. using data from the 2007 american community survey, this article examines the economic integration of mexican immigrants in the metropolitan region of los angeles, through a comparative analysis of the following indicators: education, english proficiency, naturalization, labor market participation and home ownership. the findings reveal that mexican immigrants have comparatively a disadvantageous integration pattern, however, in spite of this; they are strongly integrated into the los angeles economy that has experienced a severe restructuring process, degradation and informality.
Diversidad de Cantharidae, Lampyridae, Lycidae, Phengodidae y Telegeusidae (Coleoptera: Elateroidea) en un bosque tropical caducifolio de la sierra de San Javier, Sonora, México
Zaragoza-Caballero, Santiago;Ramírez-García, Enrique;
Revista mexicana de biodiversidad , 2009,
Abstract: the faunal diversity of the families cantharidae, lampyridae, lycidae, phengodidae and telegeusidae (coleoptera: elateroidea), was studied in a dry forest in the sierra de san javier, sonora, mexico. light trapping and insect nets were utilized in november 2003, february, april, july, august, september and october 2004 for 5 days of each month, including the rainy season (july-october) and the dry season (november-april). a total of 1 501 individuals, 30 species, and 15 genera were recorded. the most abundant family was cantharidae with 696 individuals, followed by lycidae with 561, lampyridae with 166, phengodidae with 66 and telegeusidae with 12 individuals. the most diverse family was lycidae with 12 species, followed by cantharidae with 11 species, lampyridae with 3 species, phengodidae with 3 species and telegeusidae with 1 species. few species were abundant; most were represented by few individuals. abundance and species richness varied over time and space for each family. a species accumulation curve was elaborated, and the indices of diversity shannon-wiener, equitability (pielou), dominance of simpson and similarity (bray-curtis) were calculated.
Integración económica de los inmigrantes mexicanos en la Zona Metropolitana de Los ángeles
Rafael ALARCóN,Telésforo RAMíREZ-GARCíA
Papeles de población , 2011,
Abstract: La migración de mexicanos a Estados Unidos tiene una historia centenaria. Sin embargo, en la actualidad hay mucha preocupación sobre su integración en la sociedad estadounidense por su gran volumen y alto porcentaje de personas indocumentadas. Con el uso de datos de la American Community Survey de 2007, este artículo analiza la integración económica de los inmigrantes mexicanos en la zona metropolitana de Los ángeles, mediante un análisis comparativo de indicadores tales como: nivel de escolaridad, manejo del idioma inglés, naturalización, participación en el mercado laboral y propiedad de la vivienda. Los resultados del estudio revelan que los inmigrantes mexicanos presentan comparativamente un patrón de integración en desventaja, sin embargo, a pesar de esto, están fuertemente integrados a la economía de Los ángeles que ha experimentado un grave proceso de reestructuración, degradación e informalidad.
Diversidad de Cantharidae, Lampyridae, Lycidae, Phengodidae y Telegeusidae (Coleoptera: Elateroidea) en un bosque tropical caducifolio de la sierra de San Javier, Sonora, México Diversity of Cantharidae, Lampyridae, Lycidae, Phengodidae and Telegeusidae (Coleoptera: Elateroidea) in a tropical dry forest of the Sierra San Javier, Sonora, Mexico
Santiago Zaragoza-Caballero,Enrique Ramírez-García
Revista mexicana de biodiversidad , 2009,
Abstract: Se presenta un estudio de la diversidad faunística de las familias Cantharidae, Lampyridae, Lycidae, Phengodidae y Telegeusidae (Coleoptera: Elateroidea), presentes en un bosque tropical caducifolio de la sierra de San Javier, Sonora, México, que corresponde al límite boreal de este biotopo en América. La recolección incluyó trampas de atracción luminosa y red entomológica aérea, se realizó en noviembre de 2003, febrero y abril de 2004, y de julio a octubre de ese mismo a o, durante 5 días de cada mes. Comprende la época lluviosa (julio-octubre) y la temporada seca (noviembre-abril). Se capturó un total de 1 501 individuos que representan 30 especies. La familia más abundante fue Cantharidae con 696 individuos, seguida de Lycidae con 561, Lampyridae con 166, Phengodidae con 66 y Telegeusidae con 12. La más rica en especies fue Lycidae con 12, seguida de Cantharidae con 11, Lampyridae con 3, Phengodidae con 3 y Telegeusidae con 1. Pocas especies fueron abundantes y la mayoría estuvieron representadas por pocos individuos. La abundancia y riqueza específica varió en el tiempo y espacio para cada familia. Se elaboró una curva de acumulación de especies, se calcularon los índices de diversidad de Shannon-Wiener, de equidad (Pielou), de dominancia de Simpson y de similitud (Bray-Curtis). The faunal diversity of the families Cantharidae, Lampyridae, Lycidae, Phengodidae and Telegeusidae (Coleoptera: Elateroidea), was studied in a dry forest in the Sierra de San Javier, Sonora, Mexico. Light trapping and insect nets were utilized in November 2003, February, April, July, August, September and October 2004 for 5 days of each month, including the rainy season (July-October) and the dry season (November-April). A total of 1 501 individuals, 30 species, and 15 genera were recorded. The most abundant family was Cantharidae with 696 individuals, followed by Lycidae with 561, Lampyridae with 166, Phengodidae with 66 and Telegeusidae with 12 individuals. The most diverse family was Lycidae with 12 species, followed by Cantharidae with 11 species, Lampyridae with 3 species, Phengodidae with 3 species and Telegeusidae with 1 species. Few species were abundant; most were represented by few individuals. Abundance and species richness varied over time and space for each family. A species accumulation curve was elaborated, and the indices of diversity Shannon-Wiener, equitability (Pielou), dominance of Simpson and similarity (Bray-Curtis) were calculated.
Atypical Variations of Water Conductivity Prior to Tectonic Earthquakes  [PDF]
Fidel Martínez-García, Arturo Colín-Cruz, Salvador Adame-Martínez, Jorge J. Ramírez-García
International Journal of Geosciences (IJG) , 2015, DOI: 10.4236/ijg.2015.612108
Abstract: Within the framework of precursor events related to earthquakes, this paper analyzes the possible effect on the aquatic environment of the surrounding energy that accompanies earthquakes, particularly in the area where oceanic and continental plates collide (Cocos Plate and North American Plate, south of Mexico). As a preamble, the types of precursor events, characteristics, and their possible origin are described. A project was designed under the assumption that in areas with high frequency and intensity seismicity there is an electrical and electromagnetic potential promoter which is detectable and assessable indirectly by measuring water conductivity behavior, which also may have atypical variations of data; the outcome of intensive conductivity monitoring in different settings, natural as well as manmade (wellsprings, artesian well and a cistern), are presented herein. The results of the conductivity monitoring for seven months, highlight two patterns in data behavior: one pattern shows the subtle dependence of data behavior on the geographic location of data monitoring instruments, revealing that could have a slight relationship between areas with increased seismic frequency and intensity and the presence of atypical conductivity variations. Another pattern reveals the possible relationship between atypical variations in conductivity and subsequent earthquake events; a total of 241 seismic events were analyzed and 59 of them are provided as evidence related with patterns mentioned.
Fase gametofítica del helecho Microgramma nitida (Polypodiaceae)
Ramírez,Ma. del Rosario; Pérez-García,Blanca;
Revista de Biología Tropical , 1998,
Abstract: the development of the gametophytic phase of microgramma nitida is described based on spore samples that was obtained of fertil specimens gathered on veracruz state, mexico. the spore sowing density was 40 spores/cm2 ; it is characterized by vittaria-type germination of the spore, a germinal filament of six cells; young gametophytes are naked, spathulated and later are transformed in cordate-elongated adult gametophytes with wavy borders; marginal, superficial capitated, unicellular hairs; the meristematic cell is wedge-shaped and is quickly replaced by a pluricellular meristem. the antheridia and archegonia are of the usual polypodiaceae s. str.type. prothallial development is thus of the drynaria-type. the first leaf of the sporophyte appeared eight months after spore sowing. the leaf is spathulated, with smooth borders and the margin has a row of cells without chlorophyll; bifurcated and pluricellular hairs; anomocytic stomata; the epidermic cells of the sporophyte have wavy walls on upper and lower surfaces.
Fase gametofítica del helecho Microgramma nitida (Polypodiaceae)
Ma. del Rosario Ramírez,Blanca Pérez-García
Revista de Biología Tropical , 1998,
Abstract: Se describe la fase gametofítica del helecho Microgramma nitid con esporas de Veracruz, México (siembra promedio 40 esporas/ cm2). La morfogénesis se caracteriza por: germinación tipo Vittaria, un filamento inicial de seis células protálicas; gametofitos jóvenes espatulados que se transforman en gametofitos adultos cordiformes-alargados, con márgenes ondulados y tricomas unicelulares-capitados en los margenes y en las superficies; aparición de una célula meristemática obcónica apical, que es reemplazada rápidamente por un meristemo pluricelular. Los anteridios y arquegonios son del tipo usual de las Polypodiaceae s.str. El desarrollo protálico es del tipo Drynaria. Ocho meses después de la siembra apareció la primera hoja del esporofito; ésta es espatulada, con márgenes lisos y una hilera de células aclorofílicas, tricomas pluricelulares, bifurcados y estomas anomocíticos. Las células epidérmicas de la hoja del esporofito tienen paredes laterales onduladas en las superficies dorsal y ventral. The development of the gametophytic phase of Microgramma nitida is described based on spore samples that was obtained of fertil specimens gathered on Veracruz State, Mexico. The spore sowing density was 40 spores/cm2 ; it is characterized by Vittaria-type germination of the spore, a germinal filament of six cells; young gametophytes are naked, spathulated and later are transformed in cordate-elongated adult gametophytes with wavy borders; marginal, superficial capitated, unicellular hairs; the meristematic cell is wedge-shaped and is quickly replaced by a pluricellular meristem. The antheridia and archegonia are of the usual Polypodiaceae s. str.type. Prothallial development is thus of the Drynaria-type. The first leaf of the sporophyte appeared eight months after spore sowing. The leaf is spathulated, with smooth borders and the margin has a row of cells without chlorophyll; bifurcated and pluricellular hairs; anomocytic stomata; the epidermic cells of the sporophyte have wavy walls on upper and lower surfaces.
Facile Synthesis of Monodisperse ZnO Nanocrystals by Direct Liquid Phase Precipitation
Lan Chen,Justin D. Holmes,Sonia Ramírez-García,Michael A. Morris
Journal of Nanomaterials , 2011, DOI: 10.1155/2011/853832
Abstract: ZnO nanocrystals can be synthesized by a variety of methods. Among them, only a few nonhydrolytic methods have been successful at low synthesis temperatures in terms of size, crystallinity, morphology and surface-defect control. These methods require very careful control of conditions and carefully engineered precursors. A new methodology—direct liquid phase precipitation—is reported here that can produce nanocrystals (NCs) which are a little difficult to obtain for these complex synthesis techniques in a more facile and efficient way (i.e., at room temperature). This technique results in high quality ZnO nanocrystals of diameter 5–12 nm and different morphologies. Characterisation of ZnO products shows that both synthesis and ageing conditions have significant effects on the formation of the nanocrystals. Capping agents and ageing temperature/time can be used to control both size and crystallinity of the products. The use of in situ or ex situ ageing conditions can result in different particle morphologies. Both in situ and ex situ ageing shows that mild ageing conditions (e.g., 60–80°C and 24–48 hours) are required to produce the highest quality nanomaterials.
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