Introducción. Es necesario investigar prácticas agronómicas, como la fertilización potásica y la densidad de siembra, para aumentar la productividad del cultivo del maíz. Objetivo. Evaluar el efecto ...de la densidad de siembra y dosis crecientes de K2O sobre componentes de rendimiento y eficiencia agronómica en el cultivo de maíz variedad Los Diamantes 8843. Materiales y métodos. El experimento se realizó en la Finca Experimental Santa Cruz (FESC), de la Universidad de Costa Rica durante septiembre y diciembre de 2018. Las densidades evaluadas fueron 50 000, 57 143, y 66 666 plantas.ha-1, mientras las dosis de K2O fueron 0, 70, 140, 210 kg.ha-1. Se evaluó el rendimiento del grano, altura de la planta, grosor de tallo, peso seco, absorción de nutrientes y se ajustó un análisis de varianza para cada variable. Asimismo, se calculó la eficiencia fisiológica, eficiencia agronómica, factor parcial de productividad, eficiencia aparente de recuperación y eficiencia interna de utilización. Resultados. La absorción de los nutrimentos incrementaron con dosis altas de K2O. Mientras que la calidad de mazorca y los componentes de rendimiento no presentaron diferencia significativa según la dosis. La densidad de siembra más baja presentó valores mayores en las variables agronómicas, sin embargo, este factor no afectó la calidad de mazorca, la absorción de nutrientes, ni los componentes de rendimiento. Los mayores índices de eficiencia se obtuvieron para la densidad de 66 666 plantas. ha-1 y 70 kg.ha-1 de K20. Conclusión. En suelos con altos contenidos de K, dosis de 70 kg.ha-1 de K2O logran satisfacer las necesidades del cultivo, sin embargo, se recomienda suplir la necesidad de la planta (131,7 kg.ha-1 K) sin disminuir las concentraciones de K en el suelo.
We found that multi-periodic low-mass stars discovered by Kepler K2 in the Upper Scorpius association are close binaries with typical separations of the order of 10 au and large mass ratios. These ...stars were surveyed by speckle interferometry at the SOAR telescope with spatial resolution of 0 04. Out of 129 observed targets, we resolved 70 pairs (including 16 previously known ones and three new triple systems). The distribution of projected separations of binaries with primary stars less massive than the Sun corresponds to a log-normal with median of 11.6 au and logarithmic dispersion of 0.60 dex, similar to M dwarfs in the field. Future orbits of newly discovered binaries will provide accurate measurements of masses to calibrate pre-main-sequence evolutionary tracks; a tentative orbit of one previously known binary is determined here.
We present results of a large-scale, multiepoch optical survey of the Orion OB1 association, carried out with the QUEST camera at the Venezuela National Astronomical Observatory. We identify for the ...first time the widely spread low-mass, young population in the Ori OB1a and OB1b subassociations. Candidate members were picked up by their variability in the V band and position in color-magnitude diagrams. We obtained spectra to confirm membership. In a region spanning ~68 deg2, we found 197 new young stars; of these, 56 are located in the Ori OB1a subassociation and 141 in Ori OB1b. The spatial distribution of the low-mass young stars is spatially coincident with that of the high-mass members but suggests a much sharper edge to the association. Comparison with the spatial extent of molecular gas and extinction maps indicates that the subassociation Ori OB1b is concentrated within a ringlike structure of radius ~2°(~15 pc at 440 pc), centered roughly on the star Ori in the Orion belt. The ring is apparent in 13CO and corresponds to a region with an extinction AV >= 1. The stars exhibiting strong Ha emission, an indicator of active accretion, are found along this ring, whereas the center is populated with weak Ha-emitting stars. In contrast, Ori OB1a is located in a region devoid of gas and dust. We identify a grouping of stars within a ~3 deg2 area located in Ori OB1a, roughly clustered around the B2 star 25 Ori. The Herbig Ae/Be star V346 Ori is also associated with this grouping, which could be an older analog of s Ori. Using several sets of evolutionary tracks, we find an age of 7-10 Myr for Ori OB1a and of ~4-6 Myr for Ori OB1b, consistent with previous estimates from OB stars. Indicators such as the equivalent width of Ha and near-IR excesses show that the number of accreting low-mass stars decreases sharply between Ori OB1b and Ori OB1a. These results indicate that although a substantial fraction of accreting disks remain at ages ~5 Myr, inner disks are essentially dissipated by 10 Myr.
Abstract
We present the results of the second year of exoplanet candidate host speckle observations from the SOAR TESS survey. We find 89 of the 589 newly observed TESS planet candidate hosts have ...companions within 3″, resulting in light-curve dilution, that, if not accounted for, leads to underestimated planetary radii. We combined these observations with those from Paper I to search for evidence of the impact binary stars have on planetary systems. Removing the one-quarter of the targets observed identified as false-positive planet detections, we find that transiting planets are suppressed by nearly a factor of seven in close solar-type binaries, nearly twice the suppression previously reported. The result on planet occurrence rates that are based on magnitude-limited surveys is an overestimation by a factor of two if binary suppression is not taken into account. We also find tentative evidence for similar close binary suppression of planets in M-dwarf systems. Last, we find that the high rates of widely separated companions to hot Jupiter hosts previously reported was likely a result of false-positive contamination in our sample.
A Census of the Low Accretors. I. The Catalog Thanathibodee, Thanawuth; Calvet, Nuria; Hernández, Jesús ...
The Astronomical journal,
02/2022, Letnik:
163, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Abstract
Observations have shown that the disk frequency and the fraction of accreting pre-main-sequence stars decrease with the age of the population and that some stars appear to have disks while ...their accretion has stopped. Still, it is unclear how disk-bearing stars stop their accretion. To provide insight into the last stages of accretion in low-mass young stars, we conducted a survey of disk-bearing stars that are thought to be non-accretors to identify stars still accreting at very low rates. Here we present the first catalog of the survey of 170 disk-bearing non-accreting stars in Chamaeleon I, Orion OB1, Upper Scorpius,
γ
Velorum, and Upper Centaurus–Lupus, using He
i
λ
10830 as a sensitive probe of accretion. We classify the line profiles into six types and argue that those showing redshifted and/or blueshifted absorption are still accreting. Using these classifications, we found that, among disk-bearing stars previously classified as non-accretors, at least 20%–30% are still accreting, with a larger fraction of those at younger population ages. While the difference between the outer disk signature and accretion status is unclear, we found a difference between the inner disk excess and accretion status. There is no preference in the mass of the newly identified accretors, suggesting that the processes inhibiting accretion do not directly depend on mass in the typical mass range of T Tauri stars. Lastly, we found that at a low accretion level, the “H
α
width at the 10% height” criterion mischaracterizes a larger fraction of accretors than the line’s equivalent width.
We present the discovery of a transiting hot Jupiter orbiting HIP 67522 (Teff ∼ 5650 K; M* ∼ 1.2M ) in the 10-20 Myr old Sco-Cen OB association. We identified the transits in the TESS data using our ...custom notch filter planet search pipeline and characterize the system with additional photometry from Spitzer; spectroscopy from SOAR/Goodman, SALT/HRS, LCOGT/NRES, and SMARTS/CHIRON; and speckle imaging from SOAR/HRCam. We model the photometry as a periodic Gaussian process with transits to account for stellar variability and find an orbital period of days and radius of R⊕. We also identify a single transit of an additional candidate planet with radius R⊕ that has an orbital period of 23 days. The validated planet HIP 67522b is currently the youngest transiting hot Jupiter discovered and is an ideal candidate for transmission spectroscopy and radial velocity follow-up studies, while also demonstrating that some young giant planets either form in situ at small orbital radii or else migrate promptly from formation sites farther out in the disk.
Mohs micrographic surgery (MMS) for sebaceous carcinoma (SC) may reduce local recurrence rates, but published case series have small cohorts and limited follow-up. Mohs micrographic surgery is ...particularly suitable for sensitive functional and cosmetic locations, such as the face, because it facilitates tissue conservation using complete peripheral and deep margin assessment before reconstruction. Coordinated care between Mohs and oculoplastic surgeons has not been described.
To assess rates of local recurrence and metastasis after MMS of facial SC and to describe coordinated care between Mohs and oculoplastic surgeons.
Retrospective review identified facial SC cases treated with MMS at a single institution from January 2005 to August 2020. Tumor characteristics and outcomes were recorded. Descriptive and predictive analyses were performed.
Forty-nine cases were reviewed with a mean follow-up of 51 months. The most common sites were periorbital, infraorbital cheek, and nasal ala. No patients experienced regional recurrence after MMS. One patient with Muir-Torre syndrome developed metastatic recurrence (at 82.9 months). All patients underwent 2-stage reconstruction with dermatology-performed MMS and oculoplastic reconstruction.
Collaboration between Mohs and oculoplastic surgeons with a tissue-sparing approach of MMS can reduce recurrence and optimize cosmesis and function for central facial SC.
The treatment of refractory periorbital dermatitis Meer, Elana; Patel, Suraj; Herskowitz, William ...
Indian Journal of Ophthalmology/Indian journal of ophthalmology,
10/2023, Letnik:
71, Številka:
10
Journal Article
Recenzirano
Odprti dostop
Purpose: Refractory periorbital dermatitis has a chronic course with exacerbations leading to discomfort and cosmetic issues, yet characterization of treatment options is limited. Aims: The objective ...was to present comprehensive demographic data and medical management of a series of patients with refractory periorbital dermatitis. Settings and Design: Retrospective review identified patients treated at a single institution from January 2010 to August 2020. Methods: Descriptive analyses were performed. Demographic data and treatment history were reviewed and data including medication, use, date of use and discontinued use, reason for discontinuation (if applicable), refractory status, formulation, concentration, and dose frequency were extracted. Statistical Analysis Used: Descriptive analyses. Results: Forty-five patients were included. The average age at first diagnosis was 60.3 years (sd 14.9). 82.2% were women and 84.4% identified as Caucasian. Triamcinolone cream was most frequently used followed by tobramycin-dexamethasone, tacrolimus, and neomycin-polymyxin-dexamethasone. Less than 30% of patients on triamcinolone were refractory. 13.3% of patients used topical hydrocortisone, with over 80% of these patients experiencing refractory episodes of persistent irritation and erythema. Most patients were refractory during initial use or the first recurrence of periorbital dermatitis flare. Conclusions: By better characterizing the diverse treatment regimens in a unique subset of refractory patients, we hope to better inform potential courses of medical management for periorbital dermatitis.
Introducción. La pitahaya, que pertenece a la familia de las cactáceas, es una fruta exótica de múltiples usos gastronómicos y nutracéuticos, y se consume desde tiempos precolombinos. En Costa Rica ...su consumo no es tradicional y el cultivo comercial no es muy conocido por los agricultores, por lo que es necesario estimular el interés como cultivo alternativo y económi1camente rentable principalmente para la región Chorotega y Región Pacífico Central. Objetivo. Evaluar el efecto de diferentes tamaños de cla1dodios y soluciones naturales (bioestimulantes), sobre el crecimiento, desarrollo de raíces y brotes. Materiales y métodos. El experimento se desarrolló en la Finca Experimental de Santa Cruz de la Universidad de Costa Rica, durante 2016 – 2017. Se desarrollaron dos experimentos; en el primero se utilizaron cladodios de 40 cm bajo tres soluciones naturales (agua de pipa, coco y lentejas) a concentraciones de 150, 300 y 600 ml.L-1. En el segundo, se evaluó el tamaño de los cladodios entre los 20 y 110 cm. Todos los cladodios se sembraron durante 60 días en bolsas de vivero (2 L) y luego se midió el largo y ancho del brote, longitud y número de raíces, peso seco y fresco de raíces, y la medida alométrica “LxA”. Resultados. La solución con agua de coco a 300 y 600 ml.L-1 mostró 8 cm más de longitud del brote que el testigo, mientras que el agua de pipa a 300 ml.L-1 evidenció el mayor peso seco y fresco de las raíces. Asimismo, se demostró que a un mayor tamaño del cladodio se presenta una mayor brotación. Conclusión. Tamaños de cladodios de 400 cm2 en LxA (> 60 cm) garantiza el mejor desarrollo de la semilla asexual y los cladodios que presenten un área de 200 y 400 cm2 (≈ 30 - 60 cm) son de calidad media.
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