Reproductive capacity of the red cusk-eel genypterus chilensis (Guichenot, 1848) in captivity

Indexación: Scopus.This work was supported by the FONDEF Project D06I 1024 “Development of technologies for the production of red cusk-eel fingerlings (Genypterus chilensis)”.Genypterus chilensis is a marine fish of high gastronomic demand, whose capture has declined in recent years due to overfishing. In the development of the farming technology, high mortalities were obtained during egg incubation. The objective of this study is to contribute to the knowledge of fecundity and eggs viability of G. chilensis in captivity. The spawns of G. chilensis were analyzed over a period of 2 years and 3 months. The total fecundity was estimated by counting the masses and eggs produced monthly throughout the period. The results confirm that G. chilensis is a partial spawner, since a female may more than two masses of eggs per day, due to a large amount of mass spawned per season (621 average). The total production of masses of the Farming Centre during the period was 2,290; of these, only 7% (166) corresponding to 15,330,517 eggs were incubated. Because of its high fecundity, G. chilensis produces numerous masses of eggs, of which only a small percentage reaches incubation, as well as it occurs in other marine fish. © 2018, Escuela de Ciencias del Mar. All rights reserved.https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-560X201800020048

The detailed chemical composition of the terrestrial planet host Kepler-10

Chemical abundance studies of the Sun and solar twins have demonstrated that the solar composition of refractory elements is depleted when compared to volatile elements, which could be due to the formation of terrestrial planets. In order to further examine this scenario, we conducted a line-by-line differential chemical abundance analysis of the terrestrial planet host Kepler-10 and fourteen of its stellar twins. Stellar parameters and elemental abundances of Kepler-10 and its stellar twins were obtained with very high precision using a strictly differential analysis of high quality CFHT, HET and Magellan spectra. When compared to the majority of thick disc twins, Kepler-10 shows a depletion in the refractory elements relative to the volatile elements, which could be due to the formation of terrestrial planets in the Kepler-10 system. The average abundance pattern corresponds to ~ 13 Earth masses, while the two known planets in Kepler-10 system have a combined ~ 20 Earth masses. For two of the eight thick disc twins, however, no depletion patterns are found. Although our results demonstrate that several factors (e.g., planet signature, stellar age, stellar birth location and Galactic chemical evolution) could lead to or affect abundance trends with condensation temperature, we find that the trends give further support for the planetary signature hypothesis.Comment: 12 pages, 11 figures, accepted for publication in MNRA

The dissimilar chemical composition of the planet-hosting stars of the XO-2 binary system

Using high-quality spectra of the twin stars in the XO-2 binary system, we have detected significant differences in the chemical composition of their photospheres. The differences correlate strongly with the elements' dust condensation temperature. In XO-2N, volatiles are enhanced by about 0.015 dex and refractories are overabundant by up to 0.090 dex. On average, our error bar in relative abundance is 0.012 dex. We present an early metal-depletion scenario in which the formation of the gas giant planets known to exist around these stars is responsible for a 0.015 dex offset in the abundances of all elements while 20 M_Earth of non-detected rocky objects that formed around XO-2S explain the additional refractory-element difference. An alternative explanation involves the late accretion of at least 20 M_Earth of planet-like material by XO-2N, allegedly as a result of the migration of the hot Jupiter detected around that star. Dust cleansing by a nearby hot star as well as age or Galactic birthplace effects can be ruled out as valid explanations for this phenomenon.Comment: ApJ, in press. Complete linelist (Table 3) available in the "Other formats -> Source" downloa

A Multinational Analysis of Mutations and Heterogeneity in PZase, RpsA, and PanD Associated with Pyrazinamide Resistance in M/XDR Mycobacterium tuberculosis.

Pyrazinamide (PZA) is an important first-line drug in all existing and new tuberculosis (TB) treatment regimens. PZA-resistance in M. tuberculosis is increasing, especially among M/XDR cases. Noted issues with PZA Drug Susceptibility Testing (DST) have driven the search for alternative tests. This study provides a comprehensive assessment of PZA molecular diagnostics in M/XDR TB cases. A set of 296, mostly XDR, clinical M. tuberculosis isolates from four countries were subjected to DST for eight drugs, confirmatory Wayne's assay, and whole-genome sequencing. Three genes implicated in PZA resistance, pncA, rpsA, and panD were investigated. Assuming all non-synonymous mutations cause resistance, we report 90% sensitivity and 65% specificity for a pncA-based molecular test. The addition of rpsA and panD potentially provides 2% increase in sensitivity. Molecular heterogeneity in pncA was associated with resistance and should be evaluated as a diagnostic tool. Mutations near the N-terminus and C-terminus of PZase were associated with East-Asian and Euro-American lineages, respectively. Finally, Euro-American isolates are most likely to have a wild-type PZase and escape molecular detection. Overall, the 8-10% resistance without markers may point to alternative mechanisms of resistance. Confirmatory mutagenesis may improve the disconcertingly low specificity but reduce sensitivity since not all mutations may cause resistance

Entropy-driven phase transition in a system of long rods on a square lattice

The isotropic-nematic (I-N) phase transition in a system of long straight rigid rods of length k on square lattices is studied by combining Monte Carlo simulations and theoretical analysis. The process is analyzed by comparing the configurational entropy of the system with the corresponding to a fully aligned system, whose calculation reduces to the 1D case. The results obtained (1) allow to estimate the minimum value of k which leads to the formation of a nematic phase and provide an interesting interpretation of this critical value; (2) provide numerical evidence on the existence of a second phase transition (from a nematic to a non-nematic state) occurring at density close to 1 and (3) allow to test the predictions of the main theoretical models developed to treat the polymers adsorption problem.Comment: 14 pages, 6 figures. Accepted for publication in JSTA

Ground state of the Kagome-like S=1/2 antiferromagnet, Volborthite Cu3V2O7(OH)2.2H2O

Volborthite compound is one of the very few realizations of S=1/2 quantum spins on a highly frustrated kagome-like lattice. Low-T SQUID measurements reveal a broad magnetic transition below 2K which is further confirmed by a peak in the 51V nuclear spin relaxation rate (1/T1) at 1.4K$\pm$0.2K. Through 51V NMR, the ground state (GS) appears to be a mixture of different spin configurations, among which 20% correspond to a well defined short range order, possibly of the $\sqrt{3} \times \sqrt{3}$ type. While the freezing involve all the Cu$^{2+}$ spins, only 40% of the copper moment is actually frozen which suggests that quantum fluctuations strongly renormalize the GS.Comment: 4 pages, 4 figures, to appear in PR

Critical behavior of repulsive linear kk-mers on triangular lattices

Monte Carlo (MC) simulations and finite-size scaling analysis have been carried out to study the critical behavior in a submonolayer two-dimensional gas of repulsive linear $k$-mers on a triangular lattice at coverage $k/(2k+1)$. A low-temperature ordered phase, characterized by a repetition of alternating files of adsorbed $k$-mers separated by $k+1$ adjacent empty sites, is separated from the disordered state by a order-disorder phase transition occurring at a finite critical temperature, $T_c$. The MC technique was combined with the recently reported Free Energy Minimization Criterion Approach (FEMCA), [F. Rom\'a et al., Phys. Rev. B, 68, 205407, (2003)], to predict the dependence of the critical temperature of the order-disorder transformation. The dependence on $k$ of the transition temperature, $T_c(k)$, observed in MC is in qualitative agreement with FEMCA. In addition, an accurate determination of the critical exponents has been obtained for adsorbate sizes ranging between $k=1$ and $k=3$. For $k>1$, the results reveal that the system does not belong to the universality class of the two-dimensional Potts model with $q=3$ ($k=1$, monomers). Based on symmetry concepts, we suggested that the behavior observed for $k=1, 2$ and 3 could be generalized to include larger particle sizes ($k \geq 2$).Comment: 17 pages, 13 figure

Evaluación de cultivares locales e introducidos de (RICINUS COMMUNIS L) higuerilla para condiciones de selva del Peru Región Ucayali 2011.

El experimento se instalo en el anexo experimental “Los Incas” de la Estación Experimental Agraria Pucallpa, departamento de Ucayali, provincia de Coronel Portillo, distrito de campo verde, el suelo donde se instalo el experimento es de altura o Ultisols. El diseño empleado fue de block completo randomizado con 04 tratamientos y 04 repeticiones, teniendo un total de 16 unidades experimentales, en un área de 1,881 m2. , los tratamientos evaluados fueron: T1 = Higuerilla BRS Nordestina, T2 = Higuerilla L1-003, T3 = Higuerilla L2-004 y T4 = Higuerilla L3-007. Se obtuvo como resultado que en las evaluaciones fenológicas en los cuatro cultivares donde para los parámetros agronómicos Higuerilla L3 – 007 e Higuerilla L 2-004, obtuvieron menor altura de planta al final del ciclo con 90 y 105 cm respectivamente siendo menor también en lo que corresponde a la altura de planta a la emisión del primer racimo que fue de 27.5 y 41 cm; asimismo el ecotipo Higuerilla L1 – 003 obtuvo 84 días a la emisión del primer racimo y 124 días a la cosecha del primer racimo siendo el más precoz con respecto a Higuerilla BRS Nordestina que obtuvo 147 días a la cosecha del primer racimo. Sin embargo en el parámetro de rendimiento de grano los ecotipos Higuerilla BRS Nordestina e Higuerilla L 2-004, rindieron un total de 602 y 524.8 kilos/ha respectivamente pero no superaron los 1,500 kg/ha