Dynamic screening and energy loss of antiprotons colliding with excited Al clusters

We use time-dependent density functional theory to calculate the energy loss of an antiproton colliding with a small Al cluster previously excited. The velocity of the antiproton is such that non-linear effects in the electronic response of the Al cluster are relevant. We obtain that an antiproton penetrating an excited cluster transfers less energy to the cluster than an antiproton penetrating a ground state cluster. We quantify this difference and analyze it in terms of the cluster excitation spectrum.Comment: 23 pages, 4 figures, to be published in Nuclear Instruments and Methods B as a proceeding of the IISC-19 Workshop on Inelastic Ion-Surface Collision

Direct resolution of unoccupied states in solids via two photon photoemission

Non-linear effects in photoemission are shown to open a new access to the band structure of unoccupied states in solids, totally different from hitherto used photoemission spectroscopy. Despite its second-order nature, strong resonant transitions occur, obeying exact selection rules of energy, crystal symmetry, and momentum. Ab-initio calculations are used to demonstrate that such structures are present in low-energy laser spectroscopy experimental measurements on Si previously published. Similar resonances are expected in ultraviolet angle-resolved photoemission spectra, as shown in a model calculation on Al.Comment: 12 pages, including 4 figure

Dynamic screening of a localized hole during photoemission from a metal cluster

Recent advances in attosecond spectroscopy techniques have fueled the interest in the theoretical description of electronic processes taking place in the subfemtosecond time scale. Here we study the coupled dynamic screening of a localized hole and a photoelectron emitted from a metal cluster using a semi-classical model. Electron density dynamics in the cluster is calculated with Time-Dependent Density Functional Theory and the motion of the photoemitted electron is described classically. We show that the dynamic screening of the hole by the cluster electrons affects the motion of the photoemitted electron. At the very beginning of its trajectory, the photoemitted electron interacts with the cluster electrons that pile up to screen the hole. Within our model, this gives rise to a significant reduction of the energy lost by the photoelectron. Thus, this is a velocity dependent effect that should be accounted for when calculating the average losses suffered by photoemitted electrons in metals.Comment: 15 pages, 5 figure

In vitro effect of comercial pesticides on Trichoderma harzianum strain A- 34

El trabajo tuvo como objetivo evaluar el efecto in vitro de seis plaguicidas comerciales sobre el crecimiento micelial, la esporulación y la germinación de los conidios de Trichoderma harzianum cepa A-34. El ensayo fue llevado a cabo con los siguientes productos: folpet (Folpam 80 PH), mancozeb (Mancozeb 75 PH) y zineb (Zineb 80 PH), así como de tres insecticidas: cipermetrina (Cipermetrina 10 EC), lambda cialotrina (Karate 5 EC) y abamectina (Abamectina 1,8 EC) a las concentraciones de 10, 100, 200, 500, 1000 y 2000 mg L-1. Fue evaluada la inhibición del crecimiento micelial de la colonia del hongo y la acción sobre la producción y la germinación de los conidios. Los plaguicidas fueron clasificados por su toxicidad sobre el antagonista de acuerdo con la escala de la OILB y por su compatibilidad según el valor T. Los tres fungicidas folpet, mancozeb y zineb tienen efecto inhibitorio sobre el crecimiento del micelio del hongo T. harzianum al igual que abamectina y son clasificados como ligeramente tóxicos. Sin embargo al considerar el valor T se clasifica a zineb, como muy tóxico, y a mancozeb y folpet como moderadamente tóxicos, mientras que los insecticidas resultaron no tóxicos. Los fungicidas afectan la germinación de los conidios del antagonista pero los insecticidas no.The work aims to evaluate the in vitro effect of six commercial pesticides on the mycelia growth, the spore production and conidia germination of Trichoderma harzianum strain A-34. The assay was carried out with the following products: folpet (Folpam 80 PH), zineb (Zineb 80 PH), mancozeb (Mancozeb 75 PH), cipermetrina (Cipermetrina 10 EC), lambda cialotrina (Karate 5 EC) and abamectina (Abamectin 1.8 EC) to the concentrations of 10, 100, 200, 500, 1000 and 2000 mg L-1. The growth inhibition of the fungus colony, the effect of the pesticides on the spore production and the conidia germination were evaluated. The pesticides were classified according to their toxicity on the antagonist by the OILB scale and their compatibility according to the T value. The folpet, mancozeb and zineb fungicides, and the abamectina insecticide have inhibitory effect on the growth of the mycelia of the fungus T. harzianum, and they are classified as lightly toxic. However, when considering the T value, zineb is classified as very toxic, and mancozeb and folpet as moderately toxic, while the insecticides are not toxic to the antagonist. Fungicides affect the germination of the antagonist's conidia but insecticides do not.Fil: Castellanos González, Leónides . Universidad de Cienfuegos (Cuba)Fil: Lorenzo Nicao, María E.. Cienfuegos (Cuba). Laboratorio Provincial de Sanidad Vegetal Cienfuegos.Fil: Lina Muiño, Berta. Instituto de Investigación de Sanidad Vegetal (La Habana, Cuba)Fil: Hernández Pérez, Ricardo. Centro Agrobiotecnológico (México)Fil: Guillen Sánchez, Dagoberto. Universidad Autónoma del Estado de Morelos (México). Escuela de Estudios Superiores de Xalosto

Scattering effects from neighboring atoms in core-level WSe2 photoemission

Methods of attosecond science originally developed to investigate systems in the gas phase are currently being adapted to obtain temporal information on the electron dynamics that takes place in condensed-matter systems. In particular, streaking measurements have recently been performed to determine photoemission time delays from the WSe2 dichalcogenide. In this work we present a fully atomistic description of the photoemission process in WSe2 and provide angularly resolved photoemission cross sections and time delays from the W 4f, Se 3d and Se 4s core states of the system. Since these states are spatially localized, we propose a cluster approach in which we build up from smaller to larger clusters, so that we can assess the importance of scattering effects by each new layer of neighboring atoms. We use a static-exchange density functional theory method with B-spline functions, where a one-center angular-momentum expansion is supplemented by off-center expansions with fewer partial waves. This enhances convergence in comparison with a one-center expansion, which would require very high angular momenta to characterize the localized fast oscillations near each off-center atomic core. We find that the photoemission delays and fully differential cross sections are strongly affected by scattering events that take place off the neighboring atoms, implying the need to consider their effects for quantitative descriptions of the photoemission proces

Bienestar animal de corderos ternascos durante su espera en matadero

El presente trabajo consistió en valorar la respuesta de estrés al que son sometidos los corderos desde que llegan al matadero hasta su sacrificio en distintas épocas del año, primavera y verano. Se tomaron muestras de sangre durante el sacrificio del animal para la valoración de diferentes parámetros sanguíneos de respuesta de estrés y tras el faenado se valoró la calidad de la canal y de la carne de los corderos. Se encontraron diferencias significativas con mayores valores para los corderos sacrificados en verano en el número de linfocitos, lactato deshidrogenasa (LDH), cortisol y pHs y menores en el número de leucocitos, neutrófilos, relación neutrófilos/linfocitos, volumen corpuscular medio, concentración de glucosa y rendimiento de la canal. Los corderos sacrificados en verano tuvieron más comprometido su nivel de bienestar por el mayor nivel de cortisol y LDH junto con unos pHs más elevados, lo que hace que la calidad de la carne sea inferior a los sacrificados en primavera

Intracellular calcium movements of boar spermatozoa during 'in vitro' capacitation and subsequent acrosome exocytosis follow a multiple-storage place, extracellular calcium-dependent model

This work analysed intracellular calcium stores of boar spermatozoa subjected to invitro' capacitation (IVC) and subsequent progesterone-induced acrosome exocytosis (IVAE). Intracellular calcium was analysed through two calcium markers with different physico-chemical properties, Fluo-3 and Rhod-5N. Indicative parameters of IVC and IVAE were also evaluated. Fluo-3 was located at both the midpiece and the whole head. Rhod-5N was present at the sperm head. This distribution did not change in any of the assayed conditions. Induction of IVC was concomitant with an increase in both head and midpiece Ca2+ signals. Additionally, while IVC induction was concurrent with a significant (p<0.05) increase in sperm membrane permeability, no significant changes were observed in O-2 consumption and ATP levels. Incubation of boar spermatozoa in the absence of calcium showed a loss of both Ca2+ labellings concomitantly with the sperm's inability to achieve IVC. The absence of extracellular calcium also induced a severe decrease in the percentage of spermatozoa exhibiting high mitochondrial membrane potential (hMMP). The IVAE was accompanied by a fast increase in both Ca2+ signalling in control spermatozoa. These peaks were either not detected or much lessened in the absence of calcium. Remarkably, Fluo-3 marking at the midpiece increased after progesterone addition to sperm cells incubated in a medium without Ca2+. The simultaneous addition of progesterone with the calcium chelant EGTA inhibited IVAE, and this was accompanied by a significant (p<0.05) decrease in the intensity of progesterone Ca2+-induced peak, O-2 consumption and ATP levels. Our results suggest that boar spermatozoa present different calcium deposits with a dynamic equilibrium among them and with the extracellular environment. Additionally, the modulation role of the intracellular calcium in spermatozoa function seems to rely on its precise localization in boar spermatozoa

Melatonin MT1 and MT2 receptors in the ram reproductive tract

Some melatonin functions in mammals are exerted through MT1 and MT2 receptors. However, there are no reports of their presence in the reproductive tract of the ram, a seasonal species. Thus, we have investigated their existence in the ram testis, epididymis, accessory glands and ductus deferens. Real-time polymerase chain reaction (qPCR) revealed higher levels of m-RNA for both receptors in the testis, ampulla, seminal vesicles, and vas deferens, than in the other organs of the reproductive tract (p < 0.05). Western blot analyses showed protein bands compatible with the MT1 in the testis and cauda epididymis, and for the MT2 in the cauda epididymis and deferent duct. Immunohistochemistry analyses revealed the presence of MT1 receptors in spermatogonias, spermatocytes, and spermatids, and MT2 receptors in the newly-formed spermatozoa in the testis, whereas both receptors were located in the epithelial cells of the ampulla, seminal vesicles, and ductus deferens. Indirect immunofluorescence showed significant differences in the immunolocation of both receptors in spermatozoa during their transit in the epididymis. In conclusion, it was demonstrated that melatonin receptors are present in the ram reproductive tract. These results open the way for new studies on the molecular mechanism of melatonin and the biological significance of its receptors

Nuevas citas botánicas para la provincia de La Pampa (Argentina)

Blackstonia perfoliata, Huds. (Gentianaceae) y Samolus valerandi L. (Primulaceae), new records for La Pampa province are reported with information about life forms, habitat and common names.Se cita por primera vez Blackslonia perfoliata, Huds. (Gentianaceae) y Samolus valerandi L. (Primulaceae) para la provincia de La Pampa. Se consignan sus formas de vida, ambientes y nombres vulgares

Orchestration of Floral Initiation by APETALA1

The MADS-domain transcription factor APETALA1 (AP1) is a key regulator of Arabidopsis flower development. To understand the molecular mechanisms underlying AP1 function, we identified its target genes during floral initiation using a combination of gene expression profiling and genome-wide binding studies. Many of its targets encode transcriptional regulators, including known floral repressors. The latter genes are down-regulated by AP1, suggesting that it initiates floral development by abrogating the inhibitory effects of these genes. Although AP1 acts predominantly as a transcriptional repressor during the earliest stages of flower development, at more advanced stages it also activates regulatory genes required for floral organ formation, indicating a dynamic mode of action. Our results further imply that AP1 orchestrates floral initiation by integrating growth, patterning, and hormonal pathways