Efectos de la reducción de la densidad de siembra en soja

La densidad óptima está sujeta a las condiciones ambientales y edáficas de cada zona. La variación de la cantidad de plantas afecta la capacidad de crecimiento individual debido la competencia en la línea de siembra. Sin embargo, el efecto en el rendimiento no es lineal, dado que los cambios en la disponibilidad de recursos estimulan mecanismos de compensación. En el caso de la Provincia de Entre Ríos la presencia de suelos vertisoles con elevado contenido de arcillas restringe el crecimiento de los cultivos. Con el objetivo de determinar la posibilidad de lograr altos rendimientos con densidades de siembra inferiores a las utilizadas en los planteos agrícolas actuales y determinar los mecanismos de compensación, se realizaron 4 ensayos durante 2013-2016 en lotes con suelos de textura arcillosa donde se utilizaron cultivares de grupo de madurez V y VI con densidades de 3 a 40 plantas m-2. Las menores densidades de 10 y 15 plantas m-2 presentaron diferencias en la intercepción de radiación en el inicio de llenado de granos. Se hallaron diferencias en el número de granos entre las densidades. Sin embargo, este componente presentó poca variación con una disminución del 15-32% al reducir en 61-80% el stand de plantas. El número de granos fue el componente que explicó las diferencias de rendimiento; A bajas densidades se observó mayor generación de nudos en las ramificaciones y además una mayor capacidad de fijar granos por planta. El peso de granos no fue afectado por la variación en la densidad. Esto permitió determinar que en estos cultivares de GM VI el rendimiento relativo del 95% se logra con densidades de 15-20 pl m-2. En los cultivares de GM V este umbral se encontraría en las 25 pl m-2, donde por debajo de este número de plantas el rendimiento se deprime

Modes in silver-iodide-lined hollow metallic waveguides mapped by terahertz near-field time-domain microscopy

Thin dielectric layers inside hollow metallic waveguides are used to improve the waveguide transmission characteristics as the dominant waveguide mode changes into the hybrid HE11 mode. We investigate the effect of 1 μm thick silver iodide (AgI) coatings on the fundamental modes in cylindrical waveguides at terahertz (THz) frequencies, in the regime of the dielectric layer being thinner than the optimal thickness hopt(2 THz) ̃ 20 μm. In the region of 1-3.2 THz, the lowest-order modes are similar in profile to the TE11 and TM11 modes, as determined by the timeresolved near-field measurements and verified numerically. Higher-order modes are detected experimentally as mode mixtures due to the multimode propagation. Numerical electromagnetic modeling is applied to resolve the mode structure ambiguity, allowing us to correlate experimentally detected patterns with a superposition of the TM11 and the higher-order mode, TE12. Mode profiles determined here indicate that in the regime of ultrathin dielectric (h c 0.1γeff ), the dielectric layer does not transform the dominant mode into the low-loss HE11 mode. Experimental mode patterns similar to the HE11 and the TE01 modes nevertheless can be formed due to mode beating. The results indicate that the Ag/AgI waveguides can be used for guiding THz waves in the TE01 mode or the TE12 mode with high discrimination against other modes. © 2012 Optical Society of America

You Are What You Eat: Within-Subject Increases in Fruit and Vegetable Consumption Confer Beneficial Skin-Color Changes

R Whitehead was funded by an ESRC Studentship.Background: Fruit and vegetable consumption and ingestion of carotenoids have been found to be associated with human skin-color (yellowness) in a recent cross-sectional study. This carotenoid-based coloration contributes beneficially to the appearance of health in humans and is held to be a sexually selected cue of condition in other species. Methodology and Principal Findings: Here we investigate the effects of fruit and vegetable consumption on skin-color longitudinally to determine the magnitude and duration of diet change required to change skin-color perceptibly. Diet and skin-color were recorded at baseline and after three and six weeks, in a group of 35 individuals who were without makeup, self-tanning agents and/or recent intensive UV exposure. Six-week changes in fruit and vegetable consumption were significantly correlated with changes in skin redness and yellowness over this period, and diet-linked skin reflectance changes were significantly associated with the spectral absorption of carotenoids and not melanin. We also used psychophysical methods to investigate the minimum color change required to confer perceptibly healthier and more attractive skin-coloration. Modest dietary changes are required to enhance apparent health (2.91 portions per day) and attractiveness (3.30 portions). Conclusions: Increased fruit and vegetable consumption confers measurable and perceptibly beneficial effects on Caucasian skin appearance within six weeks. This effect could potentially be used as a motivational tool in dietary intervention.Publisher PDFPeer reviewe

Daily consumption of a fruit and vegetable smoothie alters facial skin color

Consumption of dietary carotenoids or carotenoid supplements can alter the color (yellowness) of human skin through increased carotenoid deposition in the skin. As fruit and vegetables are the main dietary sources of carotenoids, skin yellowness may be a function of regular fruit and vegetable consumption. However, most previous studies have used tablets or capsules to supplement carotenoid intake, and less is known of the impact of increased fruit and vegetable consumption on skin color. Here, we examined skin color changes in an Asian population (Malaysian Chinese ethnicity) over a six week dietary intervention with a carotenoid-rich fruit smoothie. Eighty one university students (34 males, 47 females; mean age 20.48) were assigned randomly to consuming either a fruit smoothie (intervention group) or mineral water (control group) daily for six weeks. Participants’ skin yellowness (CIELab b*), redness (a*) and luminance (L*) were measured at baseline, twice during the intervention period and at a two-week follow-up, using a handheld reflectance spectrophotometer. Results showed a large increment in skin yellowness (p<0.001) and slight increment in skin redness (p<0.001) after 4 weeks of intervention for participants in the intervention group. Skin yellowness and skin redness remained elevated at the two week follow up measurement. In conclusion, intervention with a carotenoid-rich fruit smoothie is associated with increased skin redness and yellowness in an Asian population. Changes in the reflectance spectrum of the skin suggest that this color change was caused by carotenoid deposition in the skin

Evidence for Positive Selection on a Number of MicroRNA Regulatory Interactions during Recent Human Evolution

MicroRNA (miRNA)–mediated gene regulation is of critical functional importance in animals and is thought to be largely constrained during evolution. However, little is known regarding evolutionary changes of the miRNA network and their role in human evolution. Here we show that a number of miRNA binding sites display high levels of population differentiation in humans and thus are likely targets of local adaptation. In a subset we demonstrate that allelic differences modulate miRNA regulation in mammalian cells, including an interaction between miR-155 and TYRP1, an important melanosomal enzyme associated with human pigmentary differences. We identify alternate alleles of TYRP1 that induce or disrupt miR-155 regulation and demonstrate that these alleles are selected with different modes among human populations, causing a strong negative correlation between the frequency of miR-155 regulation of TYRP1 in human populations and their latitude of residence. We propose that local adaptation of microRNA regulation acts as a rheostat to optimize TYRP1 expression in response to differential UV radiation. Our findings illustrate the evolutionary plasticity of the microRNA regulatory network in recent human evolution

Facial Skin Coloration Affects Perceived Health of Human Faces

Numerous researchers have examined the effects of skin condition, including texture and color, on the perception of health, age, and attractiveness in human faces. They have focused on facial color distribution, homogeneity of pigmentation, or skin quality. We here investigate the role of overall skin color in determining perceptions of health from faces by allowing participants to manipulate the skin portions of color-calibrated Caucasian face photographs along CIELab color axes. To enhance healthy appearance, participants increased skin redness (a*), providing additional support for previous findings that skin blood color enhances the healthy appearance of faces. Participants also increased skin yellowness (b*) and lightness (L*), suggesting a role for high carotenoid and low melanin coloration in the healthy appearance of faces. The color preferences described here resemble the red and yellow color cues to health displayed by many species of nonhuman animals

Enhanced port-wine stain lightening achieved with combined treatment of selective photothermolysis and imiquimod

BACKGROUND: Pulsed dye laser is the gold standard for treatment of port wine stain birthmarks but multiple treatments are required and complete resolution is often not achieved. Post-treatment vessel recurrence is thought to be a factor that limits efficacy of pulsed dye laser treatment of port wine stains. Imiquimod 5% cream is an immunomodulator with anti-angiogenic effects. OBJECTIVE: To determine if application of imiquimod 5% cream after pulsed dye laser improves treatment outcome. METHODS: Healthy patients with port wine stains (n = 24) were treated with pulsed dye laser and then randomized to apply post-treatment placebo or imiquimod 5% cream for 8 weeks. Chromameter measurements (CIE L*a*b* colorspace) for 57 port wine stain sites (multiple sites per subject) were taken at baseline and compared with measurements taken 8 weeks post-treatment. The change in a* and ΔE were measured to quantify treatment outcome. RESULTS: Two subjects developed minor skin irritation. Other adverse effects weren't noted. Average Δa* was 0.43 for pulsed dye laser + placebo sites (n = 25) and 1.27 for pulsed dye laser + imiquimod sites (n = 32) (p value = 0.0294) indicating a greater reduction in erythema with imiquimod. Average ΔE was 2.59 for pulsed dye laser + placebo and 4.08 for pulsed dye laser + imiquimod (p value = 0.0363), again indicating a greater color improvement with imiquimod. LIMITATIONS: Effects were evaluated after a single treatment and duration of effect is unknown. CONCLUSION: Combined selective photothermolysis and anti-angiogenic therapy may enhance port wine stain treatment efficacy

Brazilian Consensus on Photoprotection

Brazil is a country of continental dimensions with a large heterogeneity of climates and massive mixing of the population. Almost the entire national territory is located between the Equator and the Tropic of Capricorn, and the Earth axial tilt to the south certainly makes Brazil one of the countries of the world with greater extent of land in proximity to the sun. The Brazilian coastline, where most of its population lives, is more than 8,500 km long. Due to geographic characteristics and cultural trends, Brazilians are among the peoples with the highest annual exposure to the sun. Epidemiological data show a continuing increase in the incidence of nonmelanoma and melanoma skin cancers. Photoprotection can be understood as a set of measures aimed at reducing sun exposure and at preventing the development of acute and chronic actinic damage. Due to the peculiarities of Brazilian territory and culture, it would not be advisable to replicate the concepts of photoprotection from other developed countries, places with completely different climates and populations. Thus the Brazilian Society of Dermatology has developed the Brazilian Consensus on Photoprotection, the first official document on photoprotection developed in Brazil for Brazilians, with recommendations on matters involving photoprotection