Una aproximación a las acciones matemáticas de niños de 1 a 3 años

Se analizan las acciones vinculadas a los conocimientos matemáticos intuitivos que los niños menores de 3 años recopilan en el marco de experiencias informales. Para ello, se lleva a cabo un estudio exploratorio a partir de una metodología cuantitativa para analizar la frecuencia con la que 85 niños de 1 a 3 años realizan acciones asociadas a las matemáticas intuitivas e informales. Los resultados muestran: a) las acciones relacionadas con las cualidades sensoriales y los números y operaciones son las más habituales en todas las edades; b) las acciones vinculadas con las posiciones y las formas aparecen alrededor de los 2 años, y las acciones asociadas a atributos mesurables en los 3 años aproximadamente

Germination and growth of primary roots of inoculated bean (Vicia faba) seeds under different temperatures

ArticleTemperature stress strongly affects legumes, rhizobia, and the efficiency of legume - rhizobia interaction. An experiment in 2016 was developed to test the seed germination in Petri dishes using different microorganism inoculation under several temperature treatments (4, 8, 12 and 20 °C) . The goal of t his study was to test the effect of rhizobium inoculation under low root zone temperature, and to examine whether the addition of mycorrhiza fungi could enhance rhizobia resistance to abiotic stress and improve faba bean ( Vicia faba ) germination. Four faba bean cultivars were selected for the experiment (‘Lielplatone’, ‘Fuego’, ‘Bartek’ and ‘Karmazyn’). Four different seed inoculation variants were included in this experiment – 1) with rhizobium inoculation; 2) with a commercial preparation containing mycor rhiza fungi; 3) inoculation with both rhizobium and the mycorrhiza fungi preparation; 4) control variant. The number of germinated seeds, the length of the primary root and the primary root weight ratio were determined. The effect of inoculation was found out to be dependent not only on the temperature treatment, but it also significantly varied between the bean cultivars. Variants where seeds were inoculated with both mycorrhiza and rhizobia resulted in the highest results (length and weight ratio of prima ry roots), comparing with other inoculation variants, regardless of temperature. Variants where seeds were treated only with rhizobia mostly showed the lowest results – both length and weight ratio of primary roots, especially under treatment of 4 °C . Faba bean inoculation with only rhizobia might not be efficient, when sowing seeds under a low temperature stress. Inoculation with both rhizobia and mycorrhiza fungi could be a potential solution, when the root zone temperature is still below the optimal temp erature

New assessment tool for artificial plant lighting: case of tomato (Lycopersicon Esculentum Mill.)

Growing crops under artificial conditions need a very favourable environment, especially the spectral composition of radiation influencing the plant biometry greatly. The study objective was to find how to assess the closeness of real growing conditions to the optimal ones using a single coefficient, which would reflect several time dependencies of individual growth indicators. The plant growth friendliness factor (KG)was proposed for this purpose. Tomato transplants (Lycopersicon Esculentum Mill., ‘Polonaise F1’) were grown in a peat substrate under two lighting systems with different light quality.One system consisted of eight fluorescent lamps OSRAM L58W / 840 LUMILUX Cool White and eight lamps L58W / 77 FLUORA mounted on the standardframe, alternating the lamp types (Type I spectrum).In theother lighting system, the PCB Star LEDs with wavelengths of red 630 nm and far-red 735 nm were added(Type II spectrum). The irradiance level was maintained at 140 μmol m-2 s -1 , the photoperiod was 16 h. The ratio of long-wave flux to the total flux KL was calculated for these lighting systems (0.37 rel.units for Type I spectrum and 0.50 rel.units for Type II spectrum) and KG factor was determined by the proposed formula. The value ofKG was found to be twice as small for Type I spectrumthan for Type II spectrum. The significant difference in biometric parameters of tomato transplants grown under Type I and Type II spectrawas revealed. The plants grown in the environment characterized by higher KG, were higher; they had more significantwet mass and stem neck diameter

Catálogo de la flora vascular del Cerro del Toruño (Comarca de Los Alcores, Alcalá de Guadaíra, Sevilla)

Situado en la comarca de Los Alcores, el Cerro del Toruño es un cabezo calcarenítico incluido en el área metropolitana de Sevilla. Se encuentra protegido por la normativa provincial por el valor y naturalidad de su vegetación. El objetivo del presente estudio es la catalogación de su flora y su puesta en valor como reducto de vegetación natural en un paisaje fuertemente antropizado. Se han inventariado un total de 351 especies, 324 de ellas autóctonas, de las que tres están recogidas en la lista roja andaluza. El catálogo incluye 4 novedades corológicas de especies nativas a nivel provincial y 16 a nivel comarcal. La diversidad encontrada en la zona de estudio es comparable a la de zonas cercanas, dada la heterogeneidad de sus hábitats. Se comentan brevemente las comunidades vegetales de acebuchar, palmitar y matorral xerófilo sobre roquedos calcareníticos, en las que se ha observado un mejor grado de conservación. Finalmente se discute la importancia biogeográfica de los Alcores como isla edáfica tanto para especies calcícolas como psammófilas y litorales, dado el carácter mayoritariamente arcilloso de la Depresión del Guadalquivir.Checklist of vascular flora of the Toruño hill (Alcores region, Alcalá de Guadaira, Seville). Located in Los Alcores region, the Cerro del Toruño is a calcarenitic hill included in Sevilla’s metropolitan area. It is protected by provincial regulations due to the value and naturalness of its vegetation. The aim of this study is to catalogue its flora and highlight its importance as a patch of relict natural vegetation within a strongly anthropic landscape. We recorded 351 species, of which 324 are native and three included in the Andalusian red list. The checklist includes 4 new chorological records at the provincial level and 16 at the regional level. Species diversity is comparable to nearby areas, given its habitat heterogeneity. The wild olive copse, Mediterranean fan palm formations, and xerophilous scrublands on calcarenitic rocks display a better conservation situation and are briefly commented. Finally, we discuss the biogeographic importance of Los Alcores region as an edaphic island, surrounded by the mostly clayey Guadalquivir valley, for calcicolous and coastal sand species

Los combustibles nucleares

La energía nuclear pasará seguramente a la historia como el descubrimiento que ha incidido más profundamente en la vida de los pueblos, en forma inmediata. Pero, también, muchos años han de pasar para que esos mismos pueblos juzguen que los beneficios que la energía nuclear augura, llegan a compensar las dos primeras irrupciones que esa misma energía hiciera en su debut. Es ese comienzo dramático el que llevó a la energía nuclear a la obligada posición de primera página en que se encuentra desde el primer día, y el que ha hecho, por reacción, que se vuelquen los esfuerzos a las aplicaciones destinadas al progreso. Sin esa trágica presentación, es dudoso que la marcha posterior hubiera sido lo que es.Universidad Nacional de La Plat

Radiation use efficiency by tomato transplants grown under extended photoperiod

The study focused on the effect of an extended photoperiod on the radiation use efficiency (RUE) by the tomato transplants (Solanum lycopersicum L.) in the pre–reproductive period. In two consecutive series of experiments, the photoperiod was 16 and 22 hours. The photon irradiance at the plant tops was maintained at low, medium and high levels: 100, 170 and 240 μmol m–2 s –1 , respectively. The plants were grown under two lighting systems with different light quality. The difference was7% higher blue flux share in Spectrum II. The use of an extended photoperiod, especially in combination with high irradiance level, resulted in the plant leaf chlorosis. When varying the radiation dose components, the deviation from the reciprocity law was recorded. By the analysis results, the chlorophyll degradation was a response to the extended photoperiod rather than the radiation dose. Without additional blue flux, under a regular photoperiod, RUE reduced by 8% at the high irradiance level. Under extended photoperiod, the shift from the low to high irradiance level reduced RUE by 20–37%, with bigger reduction values being observed at higher irradiance levels. Seven percent addition of blue flux made it possible to increase RUE by 5–8% at the same and lower irradiance levels and under the regular photoperiod. With the extended photoperiod under these conditions, RUE decreased by 8–21%. The study results verify a great influence of an extended photoperiod on RUE, while the degree of influence depends on other parameters of light environment – light quality and irradiance level

Development of symbiotic interactions in the faba bean (Vicia faba L.) roots

ArticleDouble-inoculation of faba bean (Vicia faba L.) seeds before sowing with rhizobium bacteria and mycorrhizal fungi is a known agronomic practice. It improves symbiotic nitrogen fixation and enhances legume supply with mineral elements and water. Effective symbiosis makes it possible to replace some of the required mineral fertilizer needed for plant growth with symbiotically fixed. This will ensure more environmentally friendly agricultural production. The formation of an effective symbiosis depends on a number of biotic and abiotic factors affecting the biochemical signals released by the partners. The biochemical mediator for symbiosis formation is flavonoids. The aim of this experiment was to test the effects of rhizobial and mycorrhizal inocula on symbiosis formation under different temperatures. Beans are an important source of protein for animal feed and human consumption. Four cultivars of faba beans were used - two V. faba var. minor Beck. -‘Fuego’ and ‘Lielplatone’, and two V. faba var. major Harz. - ‘Bartek’ and ‘Karmazyn’. The combination of microorganisms for seed inoculation influenced the frequency of root mycorrhization and abundance of arbuscules. The content of flavonoids in seed exudates correlated (r = 0.93) with germination temperatures. The use of mycorrhizal fungi alone or in combination with rhizobia reduced the amount of flavonoids in the bean seed exudate. In the pot experiment the amount and size of nodules significantly differed between cultivars. Use of mycorrhizal preparation mitigated the effect of inadequate germination temperature. Higher degree of mycorrhization and more intense formation of arbusculs formation was observed in the bean roots grown in vegetation pots in comparison with field ones. Local bred ‘Lielplatone’ had significantly better compatibility with microsymbionts in local agroclimatic conditions

Experimental analysis of IoT based camera SI-NDVI values for tomato plant health monitoring application

This paper reveals an IoT based camera design to capture SI-NDVI parameters and describes first obtained data analysis regarding luminary spectrum impact on readings in real greenhouse application. For experimental comparison, measurements of Encore, Strabena, Audiance, Bolzano, Forticia and Chocomate tomato plants, both for the ‘best’ and the ‘weakest’ plant sample, using IoT based camera solution and portable leaf spectrometer. First experimental results show that this approach can be applied for tomato plant monitoring, and reveals some ideas about possible precision improvements

La superconductividad eléctrica

En 1908, en la pequeña ciudad universitaria holandesa de Leiden, el fundador del famoso Laboratorio Criógeno, Heike Kamerlingh Onnes, consiguió licuar el último de los denominados gases permanentes. Coronando una serie de experiencias comenzada unos veinte años atrás, obtuvo, empleando el proceso Joule-Thomson en una máquina refrigerada con hidrógeno licuado, el helio en forma de líquido de muy baja densidad, con un punto de ebullición 269 0 más bajo que el cero centígrado, o sea a 4.22° Kelvin, o absolutos. Este notable triunfo experimental abrió en seguida la posibilidad de obtener temperaturas aún más bajas, con sólo mantcner el helio en ebullición a presiones inferiores a la normal. Un equipo adecuado de bombas para aspirar con la rapidez necesaria los vapores de helio, permitió conseguir con rclativa facilidad baños termostáticos con temperaturas entte 4.22°K y aproximadamente 1°K. El límite inferior estaba dado por la capacidad de las bombas.Instituto de Física La Plat