Acumulación de materia seca, N, P, K y Ca en Manihot esculenta

Se determinó el acumulo de materia seca, N, P, y Ca en diversas partes de plantas de mandioca, que crecieron en un suelo abonado mensualmente y en un suelo sin abonar, a lo largo de su período vegetativo. Los análisis se realizaron sobre cinco plantas de cada variante, muestran que el ritmo de acumulación de materia seca y de los elementos analizados, es lenta durante los dos primeros meses, intenso en los dos meses siguientes para luego bajar en los dos últimos. Las curvas determinadas son muy similares para cada variante, es decir que ritmo de acumulación es independiente de la riqueza mineral del medio edáfico, si bien la cantidad absoluta acumulada fue mayor en las plantas que crecieron en suelos abonados

Absorción foliar

Las plantas absorben normalmente los elementos nutritivos por las raíces. Sin embargo, se ha demostrado que la parte aérea es también capaz de desempeñar esta función. Aunque la nutrición foliar no llegara a reemplazar a las aplicaciones al suelo como práctica general, todavía sería de gran utilidad para solucionar ciertos problemas como la deficiencia de ciertos elementos menores, o para suministrar complementos -nutritivos en etapas críticas del desarrollo de las plantas

UN MODELLO ALLE DIFFERENZE FINITE DI UN PANNELLO FOTOVOLTAICO ACCOPPIATO A MATERIALE A CAMBIAMENTO DI FASE

La diffusione commerciale dei dispositivi fotovoltaici presenta negli ultimi anni un trend di crescita significativa a livello internazionale. Numerose ricerche sono state svolte al fine di incrementare l\u2019efficienza di conversione elettrica dei pannelli fotovoltaici e tra le soluzioni indagate \ue8 stato sperimentato l\u2019impiego di materiali a cambiamento di fase (MCF) per ridurre i picchi di temperatura di funzionamento. Nel lavoro \ue8 stato sviluppato un algoritmo di calcolo in grado di fornire l\u2019andamento temporale della temperatura di un pannello fotovoltaico accoppiato a materiale a cambiamento di fase (Sistema PV-MCF). La determinazione della distribuzione di temperature che interessano un sistema PV-MCF \ue8 stata affrontata con il metodo delle differenze finite in geometria monodimensionale. Sono state definite le equazioni di conservazione dell\u2019energia per ogni punto nodale in cui \ue8 stato discretizzato il sistema fisico, differenziandole per i nodi \u201cinterni\u201d e per i nodi \u201csuperficiali\u201d. Le equazioni alle differenze finite sono state formulate esplicitamente rispetto alla variabile temporale e sono state codificate in un apposito software. Il confronto con alcune soluzioni analitiche largamente impiegate nella bibliografia di settore ha permesso di verificare la correttezza e la validit\ue0 dell\u2019approccio sviluppato

Trajectory Discrimination and Peripersonal Space Perception in Newborns

The ability to discriminate the trajectories of moving objects is highly adaptive and fundamental for physical and social interactions. Therefore, we could reasonably expect sensitivity to different trajectories already at birth, as a precursor of later communicative and defensive abilities. To investigate this possibility, we measured newborns' looking behavior to evaluate their ability to discriminate between visual stimuli depicting motion along different trajectories happening within the space surrounding their body. Differently from previous studies, we did not take into account defensive reactions, which may not be elicited by impending collision as newborns might not categorize approaching stimuli as possible dangers. In two experiments, we showed that newborns display a spontaneous visual preference for trajectories directed toward their body. We found this visual preference when visual stimuli depicted motion in opposite directions (approaching vs. receding) as well as when they both moved toward the peripersonal space and differed only in their specific target (i.e., the body vs. the space around it). These findings suggest that at birth human infants seem to be already equipped with visual mechanisms predisposing them to perceive their presence in the environment and to adaptively focus their attention on the peripersonal space and their bodily self

Biological Properties of IRIM, the Iridium(III) Analogue of (Imidazolium (Bisimidazole) Tetrachlororuthenate) (ICR)

Some biological aspects of the new complex imidazolium bisimidazole tetrachloro iridate(III)-IRIM- the iridium(III) analogue of ICR, were considered. More in detail the conformational effects produced by IRIM on DNA and the cytotoxic properties of IRIM on some selected human cell lines were measured. Dialysis experiments and DNA thermal denaturation studies are suggestive of poor binding of IRIM to DNA; formation of interstrand crosslinks is not observed. In any case CD measurements suggest that addition of increasing amounts of IRIM to calf thymus DNA results into significant spectral changes, that are diagnostic of a direct interaction with DNA. A number of experiments carried out on the A2780 human ovarian carcinoma, B16 murine melanoma, MCF7 and TS mammary adenocarcinoma tumor cell lines strongly point out that IRIM does not exhibit significant growth inhibition effects within the concentration range 10-4-10-6 M. It is suggested that the lower biological effects of IRIM compared to ICR are a consequence of the larger kinetic inertness of the iridium(III) center with respect to ruthenium(III)

Newborn body perception: sensitivity to spatial congruency

Studies on adults have demonstrated that the perception our own body can be manipulated by varying both temporal and spatial properties of multisensory information. While human newborns are capable of detecting the temporal synchrony of visuo-tactile body-related cues, it remains unknown whether they also utilise spatial information for body perception. Twenty newborns were presented with a video of an infant's face touched with a paintbrush, while their own face was touched either in the spatially congruent, or an incongruent, location. We found that newborns show a visual preference for spatially congruent synchronous events, supporting the view that newborns have a rudimentary sense of their own body

The relationship between soil humic substances and the mineral nutrition of plants

El objetivo de esta revisión se limita a un aspecto particular de Das sustancias húmicas y es el referido a la relación de las mismas con la nutrición mineral de (as plantas superiores a la luz de algunos resultados experimentales obtenidos por este grupo. Se presenta una breve descripción de la materia orgánica del suelo y de uno de sus principales componentes, las sustancias húmicas, algunas características físico-químicas, composición y fraccionamiento. Utilizando métodos de fraccionamiento físicos y la posterior marcación con radioisótopos de las fracciones, se determinaron algunas de sus características fisicoquímicas relacionadas con la nutrición mineral de las plantas. Se postula que las fracciones de bajo peso molecular juegan un papel importante en la movilidad y disponibilidad de los micronutrienies.The objective of this review ís limíted to a particular aspect of the soil humic substances ireferred to their relationship with the mineral nutrition of plants in the light of some experimental iresults obtained by this group. A shorf description of the soil organic imatter is presented with emphasis in one of its maín components, the humic substances. Some physico-chemical characteristics, composition and fractionation are presented. By means of physical fractionation and the subsequent labelled of the fraction with iradioisotopes, it were determinad some of their physico-chemical characteristics relatad to the mineral nutrition of the plants. it was postuiated that the fractions of low molecular weight piay an important trole in the mobifity and avaiiabiiiiy of micronutrients.Facultad de Ciencias Agrarias y Forestale