Null Surfaces and Legendre Submanifolds

It is shown that the main variable Z of the Null Surface Formulation of GR is the generating function of a constrained Lagrange submanifold that lives on the energy surface H=0 and that its level surfaces Z=const. are Legendre submanifolds on that energy surface. The behaviour of the variable Z at the caustic points is analysed and a genralization of this variable is discussed.Comment: 28 pages, 7 figure

Buenas preguntas del estudiantado en clases de biología, a partir de cuestiones socio-científicas

Actualmente se habla de la importancia que tiene el desarrollo de la competencia de elaborar buenas preguntas en la clase de ciencia por parte del estudiantado, puesto que éstas confieren un rol protagónico en los procesos de enseñanza y aprendizaje de las ciencias. Por esto, conseguir estrategias concretas que promuevan mejores preguntas, se plantea como un desafío para la investigación en didáctica de las ciencias. Esta investigación analiza cómo actividades escritas que utilizan cuestiones socio-científicas, favorecen mejoras en la elaboración de preguntas escritas en los estudiantes, a través de su aplicación durante una unidad didáctica. De acuerdo a esto, el estudiantado participante de esta investigación muestra avances en la elaboración de buenas preguntas, aumentando progresivamente las preguntas de alto nivel cognitivo

Development of biotechnological tools for the in vitro propagation of elite trees for the Basque Country forest

278 p.Located in the North of Spain, Basque Country has edaphoclimatic conditions that have allowedthe establishment and development of an important forestry sector at European level. In thissense, 54.8% of the territory is dedicated to natural and cultivated forests. The most cultivatedspecies in the Basque territory is Pinus radiata, whose first report of forest plantationestablishment dates back to 1897. From that year to the present, its cultivation has increased inthe Basque Country, reporting for the year 2022 the largest total area (25.9 %) and the highestforest productivity (80-85% of the annual cuts).Pinus radiata, has a natural distribution from the central coast of California to Mexico. Theversatility and quality of the wood, together with the rapid growth of the species, has allowed itsplantations to extended to countries such as Australia, Chile, New Zealand, South Africa andSpain. However, in recent years P. radiata in the Basque Country has been affected by severaldiseases caused mainly by fungi: Pine canker caused by Fusarium circinatum, Dothistromaneedle blight caused by Dothistroma septosporum and Dothistroma pini, and brown spot needleblight caused by Lecanosticta acicula. This last disease has affected 3,300 ha in Gipuzkoa,Basque Country. In addition, P. radiata plantations in the Basque Country have decreased from123,921 ha (2016) to 102,488 ha (2022), a decrease that coincides with a historical outbreak ofthe needle blight during the years 2018-2019. For all of the abovementioned reasons, andtogether with the increase in the world population that causes a strong demand for timber andnon-timber products, the forestry sector and HAZI (www.hazi.eus) proposed a list of candidatespecies to be used, compatible with the demand of the forestry sector, as well as socially andculturally accepted.Using the list of possible alternative species, the following were selected for this study:Cryptomeria japonica (Thunb. ex L.f.) D. Don, Pinus ponderosa (P. Lawson and C. Lawson),Sequoia sempervirens ( D.Don). Endl and apparently tolerant genotypes of P. radiata.However, these species display desirable characteristics for clonal propagation at maturity,when traditional vegetative propagation and rooting are unfeasible. Therefore, the developmentof alternative methods of propagation, such as in vitro propagation, for these species isnecessary. In vitro propagation through tissue culture could be performed mainly byorganogenesis or somatic embryogenesis; those techniques combined with traditional onescould be efficient for the vegetative propagation of the abovementioned alternative species. Inaddition, these methods allow to improve the quality, yield and health of commercially valuableforest species. In this context, organogenesis in species of the Pinaceae family is generallyrestricted to zygotic embryos, part of them or young seedlings as initial source of explant, andattempts to clone selected adult individuals have been feasible but have faced severaldifficulties. In this regard, in our laboratory at Neiker, several in vitro propagation protocolshave been successfully developed for Pinus pinaster Ait, Pinus sylvestris L., Pinus pinea L.,Pinus radiata or Pinus halepensis among others.Taking into account all this information, the general hypothesis of this work is that themodification of the physico-chemical environment in the micropropagation process caninfluence the regeneration efficiency of elite trees of forest species such as C. japonica, P.ponderosa and S. sempervirens to be considered as an alternative to P. radiata in the BasqueCountry. The second hypothesis to be corroborated is that adult P. radiata trees with apparenttolerance to pine needle blight can be used as a source of material for in vitro propagation.In this context, the objective of the first chapter of the thesis was to analyze the influence ofcollection dates and different concentrations of 6-benzyladenine (BA) in the shoot inductionphase, as well as the effect of different types of light on growth success of rooting. Also, theeffect of physico-chemical factors in the content of amino acids and carbohydrates in the shootsdeveloped in vitro was studied. Although reinvigorated shoots were obtained in both BA concentrations (22 or 44 ¿M), the highest BA concentration showed the best results in terms of shoot induction and number of shoots per explant when the explants were collected in the first week of February. In addition, in shoots developed in vitro a significantly higher differences were found in the different phases of the rooting process in the levels of fructose, glucose and sucrose and in the threonine and tyrosine contents.The objective in the second chapter was to optimize the micropropagation method of C. japonica using adult trees as a source of plant material. In a first experiment, the effect of different types of initial explants and three basal culture media on shoot induction was studied. In addition, two sucrose concentrations and two light treatments (LED versus fluorescent lights) were tested for rooting stage. In a second experiment, the effect of different growth regulators (6-benzylaminopurine, metatopolin and thidiazuron) on shoot induction and subsequent phases of the organogenesis process were analysed. As main results, the highest number of shoots was obtained when using basal explants longer than 1.5 cm of length grown in the QL culture medium (Quoirin and Lepoivre, 1977). The shoots produced a higher number of roots when grown under red LED lights. Finally, root induction was significantly higher in shoots previously induced with meta-topolin.The third chapter was focused on the analysis of the influence of different types of explants, basal culture media, cytokinins, auxins and light treatments on the in vitro propagation success in P. ponderosa. In this sense, whole zygotic embryos cultured in 44 ¿M BA performed better in terms of explant survival. For shoot organogenesis, whole zygotic embryos and half LP (LP medium, Quoirin and Lepoivre, 1977, modified by Aitken-Christie et al., 1988) macronutrients were selected. Regarding the light treatments applied, a significantly higher percentage of rootable shoots was obtained under blue LED light. However, the percentage of acclimatization was higher in shoots previously cultivated under fluorescent light. Furthermore, anatomical studies using optical and scanning microscopy showed that light treatments promoted differences in anatomical aspects in in vitro shoots; needles of plantlets exposed to red and blue LEDs showed less stomata compared with needles from plantlets exposed to fluorescent light.The objective in the fourth chapter was to optimize the micropropagation of adult elite trees of S. sempervirens. To accomplish this objective, the effect of different cytokinins (6-benzylaminopurine, meta-Topolin and Kinetin), and four types of explants in shoot induction were studied. At rooting stage, the effect of two types of auxins was evaluated: 1-naphthalene acetic acid, indole-3-butyric acid and a mixture of both. The best induction rate was obtained when apical explants longer than 1.5 cm were induced with 4.4 ¿M BA. Regarding the rooting, shoots previously induced in 4.4 ¿M BA and rooted in a culture medium with 50 ¿M 1-naphthalene acetic acid showed the best result. However, acclimatization was better when explants had been cultivated with Kinetin and rooted in a culture medium with indole-3-butyric acid.Our study demonstrated that in vitro culture method can be used as an alternative for the propagation of elite individuals of C. japonica, P. ponderosa, P. radiata and S. sempervirens. Furthermore, the success of in vitro propagation in these species is influenced by genetic factors, collection dates, and physicochemical conditions of the culture environment.Neiker Eusko Jaurlaritza UNA:Univerdiad Nacional de Costa Rica Inisefo

Prenatal gene-nutrient interactions and their relationship with development and health in the offspring

Insuficiència en cobalamina prenatal s’associa amb salut adversa en la descendència a Àsia. Es desconeix si aplica a altres països i si la ruta de la betaïna-dimetilglicina prenatal afecta el creixement fetal i la salut de l’infant. Es va investigar - les associacions entre l'homocisteïna plasmàtica total en dejú (tHcy), l'estat en cobalamina prenatal i la “metabolic score” (MetSco) en infants (6-8 anys) en 293 diades mare-fill. - les associacions entre la betaïna plasmàtica , la dimetilglicina (DMG)/betaïna prenatal, el genotip BHMT matern c.716G>A i el creixement fetal en 748 diades mare-neonat. - l'associació entre la betaïna plasmàtica prenatal i la MetSco en infants (7,5 anys) en 213 diades mare-fill. - l'estat en metabòlits infantils segons l'estat en metabolisme monocarbonat prenatal - les correlacions entre els metabòlits plasmàtics infantils i antropometria en 238 nens. La tHcy de l'embaràs moderadament elevada, i baix estat en cobalamina es van associar amb una MetSco més alt en nens. La betaïna plasmàtica del cordó es va associar inversament amb el creixement fetal. Els nadons nascuts de mares amb el genotip BHMT c.716 AA tenien més risc de ser petits per a l'edat gestacional comparat amb els genotips GG i GA+GG. La ruta de la betaïna-DMG prenatal no es va associar amb MetSco infantil. La betaïna plasmàtica va ser més alta en els nens nascuts de mares en el tercíl més baix de la cobalamina plasmàtica prenatal comparat amb els tercíls mitjans-alts. El triptòfan plasmàtic va ser més baix en els nascuts de mares amb tHcy prenatal en el tercíl més alt versus baix-mitjà. La betaïna plasmàtica infantil, la cisteïna, l'àcid 3-hidroxiantranílic, l'àcid quinurènic, la histidina i la dimetilarginina asimètrica es van correlacionar positivament amb l'adipositat mentre que l'àcid picolínic, la trigonel·lina i la neopterina es van associar negativament.En Asia la insuficiencia prenatal de cobalamina se ha asociado con problemas de salud en la descendencia. Se desconoce si sucede lo mismo en otros países. Además, poco se conoce sobre si la ruta de la betaína-dimetilglicina prenatal afecta al crecimiento fetal y la salud del niño. Se investigó -las asociaciones entre la homocisteína plasmática total (tHcy), el estado en cobalamina prenatal y un “metabolic score” (MetSco) en niños (6-8 años) en 293 díadas madre-hijo. -las asociaciones entre la betaína, la dimetilglicina (DMG)/betaína prenatal plasmática, el genotipo BHMT c.716G>A y el crecimiento fetal en 748 díadas madre-neonato. -la asociación entre la betaína plasmática prenatal y el MetSco en niños (7,5 años) en 213 díadas madre-hijo. -el estado de los metabolitos infantiles según el estado en metabolismo monocarbonato prenatal -correlaciones entre los metabolitos plasmáticos infantiles y antropometría en 238 niños. La tHcy del embarazo moderadamente elevada, y un estado bajo en cobalamina se asociaron con un mayor MetSco en niños. La betaína plasmática del cordón se asoció inversamente con el crecimiento fetal. Los bebés nacidos de madres con el genotipo BHMT c.716 AA tenían mayor riesgo de ser pequeños para la edad gestacional comparado con los genotipos GG y GA+GG. La ruta de la betaína-DMG prenatal no se asoció con MetSco infantil. La betaína plasmática fue más alta en los niños nacidos de madres en el tercil más bajo de la cobalamina plasmática prenatal comparado con los terciles medios-altos. El triptófano plasmático fue más bajo en los nacidos de madres con tHcy prenatal en el tercil más alto versus tercil bajo-medio. La betaína plasmática infantil, la cisteína, el ácido 3-hidroxiantranílico, el ácido quinurénico, la histidina y la dimetilarginina asimétrica se correlacionaron positivamente con la adiposidad mientras que el ácido picolínico, la trigonelina y la neopterina se asociaron negativamente.Inadequate pregnancy cobalamin status has been associated with adverse offspring health in Asia but there are few studies in countries with low prevalence of cobalamin deficiency. Less is known regarding the association between the betaine-dimethylglycine pathway during pregnancy, foetal growth and mid-childhood health. The associations between pregnancy fasting plasma total homocysteine (tHcy), cobalamin status (cobalamin, holotranscobalamin (holoTC), methylmalonic acid (MMA)) and mid-childhood (6-8y) metabolic score (MetSco) (including fat mass index, homeostatic model assessment of insulin resistance and dyslipidemia) were studied in a prospective study of 293 mother–child dyads. Associations between pregnancy fasting plasma betaine, dimethylglycine (DMG)/betaine, c.716G>A BHMT genotype and foetal growth were investigated in a prospective study of 748 mother–neonate dyads. The association between pregnancy fasting plasma betaine and mid-childhood (7.5 y) MetSco was investigated in 213 mother–child dyads. Child plasma metabolite status was studied according to pregnancy 1C metabolism status and bivariate correlations between child plasma metabolites and anthropometric measurements in 238 children were studied to identify potential biomarkers associated with the metabolic syndrome. Moderately elevated pregnancy tHcy, low holoTC and high MMA were associated with increased mid-childhood MetSco in boys. Cord plasma betaine was inversely associated with foetal growth. Babies born to mothers with the BHMT c.716 AA genotype had a higher risk of small for gestational age (SGA) compared to GG, and GA+GG genotypes. The pregnancy betaine-DMG pathway was not associated with child MetSco. Plasma betaine was higher in children born to mothers in the lowest tertile of pregnancy plasma cobalamin compared to the mid-high tertiles, while plasma tryptophan was lowest in those born to mothers in the highest vs low-mid maternal pregnancy plasma tHcy tertiles. Child plasma betaine, cysteine, 3-hydroxyanthranilic acid, kynurenic acid, histidine and asymmetric dimethylarginine were positively correlated with adiposity while picolinic acid, trigonelline and neopterin were negatively associated

The impact of international standards on the protection of irregular migrant workers in Colombia

En la globalización, el fenómeno de la migración afecta a todos los países, aunque de diferente forma. Los Estados desarrollan políticas para el acceso legal de los inmigrantes; sin embargo, en muchas ocasiones, existe un alto ingreso de migración irregular. En este contexto, el Derecho Público internacional ha desarrollado una serie de estándares para la protección de los derechos de los inmigrantes irregulares. El presente artículo tiene por objeto analizar dichos estándares en el caso colombiano.In globalization, the phenomenon of migration affects all countries, albeit in different ways. States develop policies for the legal access of immigrants; however, in many cases, there is a high entry of irregular migration. In this context, Public International Law has developed a series of standards for the protection of the rights of irregular immigrants. The purpose of this article is to analyze these standards in the case of Colombia

Propuesta didáctica para la enseñanza de los números enteros

Este artículo pretende evidenciar la importancia que tiene la enseñanza de los números enteros, siendo este un proceso de bastante complejidad, el cual debe buscar por diversos medios generar un aprendizaje significativo en los estudiantes, para esto escogimos como metodología la teoría de situaciones didácticas de Brousseau, siendo esta una herramienta que permitirá a través de unas actividades, la construcción del objeto matemático por parte de los estudiantes, para determinar este aprendizaje se realizará una evaluación constante en los estudiantes con el fin de observar y analizar que ocurre en los diversos aprendizajes individuales, llegando de ese modo a una reflexión sobre lo ocurrido durante toda la gestión del docente

Propuesta didáctica para la enseñanza de los métodos para resolver un sistema de ecuaciones lineales

Este artículo pretende evidenciar la importancia que tiene la enseñanza de los métodos para resolver sistemas de ecuaciones lineales, de manera posterior a la función lineal, para esto se trabajará como metodología la teoría de situaciones didácticas de Brousseau, buscando la construcción propia de cada estudiantes, generando en ellos un aprendizaje significativo; esto se buscará a partir de un contexto familiar para ellos, impulsando las buenas aptitudes de los estudiantes y el ánimo para envolverse dentro de la situación

Estudio comparado de la relación entre la inclusión social de los habitantes de calle en Bogotá y la implementación de la política pública de hogares de paso en los gobiernos de Samuel Moreno y Gustavo Petro

El presente artículo académico, busca realizar un análisis documental de la relación existente entre la implementación de la política pública de hogares de paso en los gobiernos de Samuel Moreno y Gustavo Petro sobre la inclusión social de los habitantes de calle en Bogotá. A lo largo de la investigación se pretende demostrar que dicha política pública, consiste en un primer acercamiento para que esta población abandone la calle, de allí que la política pública este formulada en la atención integral encaminada a la inclusión social. Así mismo, el artículo da cuenta de lo que ha sido el proceso de ayuda a dicha población para finalmente llegar a la atención integral teniendo en cuenta las alcaldías anteriores. Para lograr dicho objetivo se realizó el análisis de los planes de desarrollo, decretos que respectan sobre habitantes de calle, documentos institucionales sobre hogares de paso, presupuestos locales e informes de rendición de cuentas de las dos alcaldías.The present academic article seeks to analyze the relationship between the shelter policy implementation in Samuel Moreno and Gustavo Petro governments over social inclusion of the street people in Bogotá. It will be show along the investigation that this policy is not enough by itself and it could be consider as the first approach to achieve that this population leave the streets, therefore the formulation of this policy has to be related with full assistance routed for social inclusion. The article also describes how the process was followed to finally provide a full social service to this population taking into account previous mayors. To accomplish this objective, intuitional documents were analyzed such as: development plans, legal statue about street people, documents about shelters, local budget and accountability documents

Propuesta didáctica para la enseñanza de las nociones topológicas

Por medio de este trabajo se quiere mostrar una experiencia de aula encaminada hacia la enseñanza de las nociones topológicas, las cuales son de bastante importancia ya que los niños desde muy pequeños están relacionándose con diversos espacios, teniendo la necesidad de desenvolverse en un medio a partir de su orientación o indicaciones producidas por los demás, viendo la obligación de utilizar sus sentidos y demás herramientas que se deben ir complejizando a medida que se les potencie su pensamientos espacial, el cual es considerado entre las inteligencias múltiples propuestas por Howard Gardner

Maize and the Green Revolution: Guatemala in the Global Context of Agricultural Research, 1954–1964

This article presents the results of an investigation whose objective was to establish the international links that Guatemala formed with diverse latitudes of the globe, for the purpose of applied scientific research into maize from 1954 to 1964, a period marked by the advancement of the green revolution in Central America. From a global history perspective, the study of the green revolution will be addressed as a process which involved the articulation of networks conformed through the circulation of specialists, civil servants and students, as well as the exchange of knowledge and agricultural materials. The sources used include a specialized bibliography and archive documents