Phalaris paradoxa L. (Poaceae: Phalaridinae), nueva maleza introducida en Chile central

Se da a conocer la presencia de Phalaris paradoxa L. (Poaceae), nueva especie para la flora advena de Chile, recolectadacomo maleza de cultivos agrícolas en la Región del Libertador Bernardo O’Higgins, 34°39’S, 71°23’W. Se incluye unaclave para determinar las especies de Phalaris que crecen en Chile.Se da a conocer la presencia de Phalaris paradoxa L. (Poaceae), nueva especie para la flora advena de Chile, recolectadacomo maleza de cultivos agrícolas en la Región del Libertador Bernardo O’Higgins, 34°39’S, 71°23’W. Se incluye unaclave para determinar las especies de Phalaris que crecen en Chile

Analysis of Deterioration in a Plasma Focus Device

Indexación: Scopus.The Plasma Focus (PF) is a kind of dense transient plasmas in with high-pulsed voltage. To produce devices for eld application it is necessary to obtain PF equipment able to operate for a long period of time. Thus, a reliability analysis is indispensable. In this work a reliability analysis program for plasma focus devices is presented. The program considers a criticality analysis using Failure Modes and Effects Criticality Analysis (FMECA) to identify the most important failure modes of the system. Said failure modes are studied operating the Plasma Focus for many cycles, obtaining from them the characteristic curves of V(t) and İ(t). Feature Extraction (FE) techniques are applied to obtain a list of parameters that correlate to the degrading process. Furthermore, Machine Learning tools are used to learn from the obtained data, linking the changes in these parameters during its life cycle to the decay of the system in hope for future implementation of a predictive maintenance system and a reference for data analysis and prediction in PFs. The study was applied to a portable plasma focus device operated at 2 joules of stored energy. © Published under licence by IOP Publishing Ltd.The work is supported by IAEA CRP contract 20370 and by grant ACT-1115, CONICYT, Chile.https://iopscience.iop.org/article/10.1088/1742-6596/1043/1/01204

Efecto de herbicidas aplicados durante la madurez del grano de trigo en el rendimiento y calidad del grano

Seven trials with spring bread wheat (Triticum aestivum L.) cultivar Domo-INIA were carried out during the 2001-2002 and 2002-2003 seasons, to evaluate the effect of diverse herbicides applied during grain ripening on yield and grain quality. A randomized complete block design with five treatments and four replications was used. The difference in the trials was the stage of maturity at the moment the herbicides were sprayed. The used herbicides were: 2,4-D, glyphosate, glyphosate + MCPA, and paraquat, plus a control treatment without herbicide. The evaluated parameters were: grain yield, hectoliter weight, 1000 grain weight, seed germination (%), sedimentation index and wet gluten. The experiments were located in an Andisoil soil at the Santa Rosa Experimental Station (36\ub031' S lat; 71\ub054' W long), Quilamapu Research Center, Chill\ue1n, Chile belonging to the National Agriculture Research Institute. The results indicated that the herbicide 2,4-D can be applied when grains have a milky consistency, as well, results obtained in one season indicated that 2,4-D also could be applied when the grain has a watery consistency. From the stage of semihard grain and on, any of the herbicides used in these trials can be applied , without affecting grain yield and germination, as well as hectoliter weight, sedimentation value and gluten content.Se realizaron siete ensayos en trigo harinero ( Triticum aestivum L.), cultivar de primavera Domo-INIA, durante las temporadas 2001-2002 y 2002-2003, para evaluar el efecto de diversos herbicidas aplicados durante la madurez del grano de trigo sobre el rendimiento y calidad del grano. Se us\uf3 un dise\uf1o de bloques completos al azar con cinco tratamientos y cuatro repeticiones. La diferencia entre los ensayos fue el estado de madurez del trigo al momento de aplicar los herbicidas. Los herbicidas usados fueron: 2,4-D, glifosato, glifosato+MCPA, y paraquat, adem\ue1s, se incluy\uf3 un tratamiento testigo sin herbicida. Los par\ue1metros evaluados fueron: rendimiento de grano, peso del hectolitro, peso de 1.000 granos, porcentaje de germinaci\uf3n, \uedndice de sedimentaci\uf3n y gl\ufaten h\ufamedo. Los ensayos se ubicaron en un suelo Andisol del Campo Experimental Santa Rosa (36\ub031' lat. Sur, 71\ub054'long. Oeste), perteneciente al Instituto de Investigaciones Agropecuarias (INIA), en el Centro Regional de Investigaci\uf3n Quilamapu, Chill\ue1n, Chile. Los resultados indicaron que el 2,4-D puede ser aplicado a una sementera en estado de grano lechoso; adem\ue1s, los efectos obtenidos en un a\uf1o indicaron que el 2,4-D podr\ueda ser aplicado cuando el grano tiene consistencia acuosa. Desde el estado de grano semiduro en adelante, cualquiera de los herbicidas usados en estos experimentos se puede aplicar sin afectar el rendimiento de grano y su germinaci\uf3n, as\ued como peso del hectolitro, el \uedndice de sedimentaci\uf3n y el contenido de gl\ufaten

The Proper Motion of the Large Magellanic Cloud: A Reanalysis

We have determined the proper motion (PM) of the Large Magellanic Cloud (LMC) relative to four background quasi-stellar objects, combining data from two previous studies made by our group, and new observations carried out in four epochs not included the original investigations. The new observations provided a significant increase in the time base and in the number of frames, relative to what was available in our previous studies. We have derived a total LMC PM of $\mu$ = ($+2.0\pm$0.1) mas yr$^{-1}$, with a position angle of $\theta$ = (62.4$\pm$3.1)$^\circ$. Our new values agree well with most results obtained by other authors, and we believe we have clarified the large discrepancy between previous results from our group. Using published values of the radial velocity for the center of the LMC, in combination with the transverse velocity vector derived from our measured PM, we have calculated the absolute space velocity of the LMC. This value, along with some assumptions regarding the mass distribution of the Galaxy, has in turn been used to calculate the mass of the Milky Way. Our measured PM also indicates that the LMC is not a member of a proposed stream of galaxies with similar orbits around our galaxy.Comment: Accepted for publication in A

The VMC Survey - VI. Quasars behind the Magellanic system

The number and spatial distribution of confirmed quasi-stellar objects (QSOs) behind the Magellanic system is limited. This undermines their use as astrometric reference objects for different types of studies. We have searched for criteria to identify candidate QSOs using observations from the VISTA survey of the Magellanic Clouds system (VMC) that provides photometry in the YJKs bands and 12 epochs in the Ks band. The (Y-J) versus (J-Ks) diagram has been used to distinguish QSO candidates from Milky Way stars and stars of the Magellanic Clouds. Then, the slope of variation in the Ks band has been used to identify a sample of high confidence candidates. These criteria were developed based on the properties of 117 known QSOs presently observed by the VMC survey. VMC YJKs magnitudes and Ks light-curves of known QSOs behind the Magellanic system are presented. About 75% of them show a slope of variation in Ks>10^-4 mag/day and the shape of the light-curve is in general irregular and without any clear periodicity. The number of QSO candidates found in tiles including the South Ecliptic Pole and the 30 Doradus regions is 22 and 26, respectively, with a ~20% contamination by young stellar objects, planetary nebulae, stars and normal galaxies. By extrapolating the number of QSO candidates to the entire VMC survey area we expect to find about 1200 QSOs behind the LMC, 400 behind the SMC, 200 behind the Bridge and 30 behind the Stream areas, but not all will be suitable for astrometry. Further, the Ks band light-curves can help support investigations of the mechanism responsible for the variations.Comment: 17 pages, 15 figures, replaced with accepted version by Astronomy & Astrophysic

A search for OB associations near southern long-period Cepheids. V. AQ Puppis and V620 Puppis

Publisher's Version/PDFA photometric UBV survey is presented for 610 stars in a region surrounding the Cepheid AQ Puppis and centered southwest of the variable, based upon photoelectric measures for 14 stars and calibrated iris photometry of photographic plates of the field for 596 stars. An analysis of reddening and distance for program stars indicates that the major dust complex in this direction is ∼1.8 kpc distant, producing differential extinction described by a ratio of total-to-selective extinction of R = AV /EB−V = 3.10±0.20. Zero-age main-sequence fitting for the main group of B-type stars along the line of sight yields a distance of 3.21 ± 0.19 kpc (V0 − MV = 12.53 ± 0.13 s.e.). The 29d.97 Cepheid AQ Pup, of field reddening EB−V = 0.47 ± 0.07 (EB−V (B0) = 0.51 ± 0.07), appears to be associated with B-type stars lying within 5′ of it as well as with a sparse group of stars, designated Turner 14, centered south of it at J2000.0 = 07:58:37, −29:25:00, with a mean reddening of EB−V = 0.81 ± 0.01. AQ Pup has an inferred luminosity as a cluster member of ⟨MV⟩ = −5.40 ± 0.25 and an evolutionary age of 3 × 107 yr. Its observed rate of period increase of +300.1 ± 1.2 s yr−1 is an order of magnitude larger than what is observed for Cepheids of comparable period in the third crossing of the instability strip, and may be indicative of a high rate of mass loss or a putative fifth crossing. Another sparse cluster, designated Turner 13, surrounds the newly recognized 2d.59 Cepheid V620 Pup, of space reddening EB−V = 0.64 ± 0.02 (EB−V (B0) = 0.68 ± 0.02), distance 2.88 ± 0.11 kpc (V0 − MV = 12.30 ± 0.08 s.e.), evolutionary age 108 yr, and an inferred luminosity as a likely cluster member of ⟨MV⟩ = −2.74 ± 0.11. V620 Pup is tentatively identified as a first crosser, pending additional observations

Ionization yield measurement in a germanium CDMSlite detector using photo-neutron sources

Two photo-neutron sources, $^{88}$Y$^{9}$Be and $^{124}$Sb$^{9}$Be, have been used to investigate the ionization yield of nuclear recoils in the CDMSlite germanium detectors by the SuperCDMS collaboration. This work evaluates the yield for nuclear recoil energies between 1 keV and 7 keV at a temperature of $\sim$ 50 mK. We use a Geant4 simulation to model the neutron spectrum assuming a charge yield model that is a generalization of the standard Lindhard model and consists of two energy dependent parameters. We perform a likelihood analysis using the simulated neutron spectrum, modeled background, and experimental data to obtain the best fit values of the yield model. The ionization yield between recoil energies of 1 keV and 7 keV is shown to be significantly lower than predicted by the standard Lindhard model for germanium. There is a general lack of agreement among different experiments using a variety of techniques studying the low-energy range of the nuclear recoil yield, which is most critical for interpretation of direct dark matter searches. This suggests complexity in the physical process that many direct detection experiments use to model their primary signal detection mechanism and highlights the need for further studies to clarify underlying systematic effects that have not been well understood up to this point

Search for low-mass dark matter via bremsstrahlung radiation and the Migdal effect in SuperCDMS

We present a new analysis of previously published SuperCDMS data using a profile likelihood framework to search for sub-GeV dark matter (DM) particles through two inelastic scattering channels: bremsstrahlung radiation and the Migdal effect. By considering these possible inelastic scattering channels, experimental sensitivity can be extended to DM masses that are undetectable through the DM-nucleon elastic scattering channel, given the energy threshold of current experiments. We exclude DM masses down to 220  MeV/c2 at 2.7×10−30  cm2 via the bremsstrahlung channel. The Migdal channel search provides overall considerably more stringent limits and excludes DM masses down to 30  MeV/c2 at 5.0×10−30  cm2

First measurement of the nuclear-recoil ionization yield in silicon at 100 eV

We measured the nuclear--recoil ionization yield in silicon with a cryogenic phonon-sensitive gram-scale detector. Neutrons from a mono-energetic beam scatter off of the silicon nuclei at angles corresponding to energy depositions from 4\,keV down to 100\,eV, the lowest energy probed so far. The results show no sign of an ionization production threshold above 100\,eV. These results call for further investigation of the ionization yield theory and a comprehensive determination of the detector response function at energies below the keV scale