Yectivani Juárez's research while affiliated with Universidad Nacional Autónoma de México and other places

Publications (20)

Article
Full-text available
Context renewal is identified when the conditioned response (CR) elicited by an extinguished conditioned stimulus (CS) reappears as a result of changing the contextual cues during the test. Two experiments were designed for testing contextual renewal in a conditioned taste aversion preparation. Experiment 1 assessed ABA and AAB context renewal, whe...
Article
Full-text available
Context renewal is identified when the conditioned response (CR) elicited by an extinguished conditioned stimulus (CS) reappears as a result of changing the contextual cues during the test. Two experiments were designed for testing contextual renewal in a conditioned taste aversion preparation. Experiment 1 assessed ABA and AAB context renewal, whe...
Article
Full-text available
Resumen este experimento se diseñó para evaluar la re-novación ABC con un procedimiento de condi-cionamiento de aversión al sabor (CAS) en tres fases: adquisición, extinción y prueba. Durante la adquisición, 15 ratas Wistar, asignadas a los grupos ABC y ABB, tuvieron acceso a una solu-ción con sacarosa y posteriormente recibieron una inyección de c...
Article
Full-text available
Resumen este experimento se diseñó para evaluar la re-novación ABC con un procedimiento de condi-cionamiento de aversión al sabor (CAS) en tres fases: adquisición, extinción y prueba. Durante la adquisición, 15 ratas Wistar, asignadas a los grupos ABC y ABB, tuvieron acceso a una solu-ción con sacarosa y posteriormente recibieron una inyección de c...
Article
Full-text available
This experiment was designed to evaluate ABC renewal in a conditioned taste aversion (CTA) procedure consisting of three phases: acquisition, extinction and test. During the acquisition phase, 15 Wistar rats assigned to groups ABC and ABB had access to a sucrose solution, after which they were injected with lithium chloride (LiCl) in Context A. In...
Article
Full-text available
We investigate the obscuration and star formation activity in local AGN by exploiting a large compilation of Spitzer-IRS spectra. In order to avoid biases due to the obscuration itself and to measure the intrinsic luminosity in a homogeneous manner in both, obscured and unobscured objects, we have selected a sample of local AGN observed with Spitze...
Article
Full-text available
The aim of this work was to determine the effects of scopolamine, a cholinergic antagonist, on the conditioning of an instrumental response and the contextual conditioning of this response. Five groups of rats were trained to lever-press on a Variable Interval 30 s schedule in context A. Scopolamine was administered 15 min before each conditioning...
Article
Full-text available
The aim of this work was to determine the effects of scopolamine, a cholinergic antagonist, on the conditioning of an instrumental response and the contextual conditioning of this response. Five groups of rats were trained to lever-press on a Variable Interval 30 s schedule in context A. Scopolamine was administered 15 min before each conditioning...
Article
Resumen este experimento se diseñó para evaluar la re-novación ABC con un procedimiento de condi-cionamiento de aversión al sabor (CAS) en tres fases: adquisición, extinción y prueba. Durante la adquisición, 15 ratas Wistar, asignadas a los grupos ABC y ABB, tuvieron acceso a una solu-ción con sacarosa y posteriormente recibieron una inyección de c...
Article
Full-text available
Quasars are among the most luminous objects in the Universe, and therefore they can be detected and investigated in detail even at very high redshifts, up to z > 6 (Fan et al. 2001, 2003, 2004). The prominent emission line spectrum of high redshift quasars contains important information on the enrichment history of the gas and, therefore, provide c...
Article
Full-text available
We investigate the metallicity of the broad line region (BLR) of a sample of 30 quasars in the redshift range 4<z<6.4, by using near-IR and optical spectra. We focus on the ratio of the broad lines (SiIV1397+OIV]1402)/CIV1549, which is a good metallicity tracer of the BLR. We find that the metallicity of the BLR is very high even in QSOs at z~6. Th...
Article
Full-text available
The observations in the submm/mm range are important to study the dust properties in the high redshift regime. FIR to mm observations show that most of the energy gener-ated in star formation at z > 1 is absorbed by dust, which re-emits the energy at FIR wave-lengths, a spectral range that is red-shifted into the transparent submm/mm atmospheric wi...
Article
Full-text available
Quasars are among the most luminous objects in the Universe, and allow us to study the ISM in their host galaxies at very high redshift, up to z > 6 (Fan et al. 2001, 2003, 2004). The spectra of high redshift quasars contain important information about the enrichment history of the gas and, therefore, provide constraints on the star formation histo...
Article
Full-text available
At the moment, one of the big issues in astronomy is the determination of the metallicity of QSOs at different redshifts. This is a powerful tool to probe star-forming activity and evolution in galactic nuclei at different epochs of the universe.
Article
We carried out IR spectrocopy for 22 QSOs with redshifts in the range 3.0 < z < 6.4 in order to investigate the iron abundance relative to alpha-elements by comparing the FeII UV bump (redshifted into the near-IR) it with the MgIIlambda2798 flux. The uniform observational technique and the wide redshift range allow a study of the trend of the FeII/...
Article
Full-text available
We present near-IR, low resolution spectra of eight of the most distant quasars known, with redshifts in the range 4.9<z<6.4. Half of these quasars are characterized by deep, broad and blueshifted absorption features associated with both high and low ionization species (CIV, SiIV, AlIII, MgII), i.e. they belong to the class of Broad Absorption Line...
Article
Full-text available
We present the classification of optical identifications and radio spectra of six radio sources from a complete (in flux density) sample in the declination range 10° to 12°30′ (J2000.0). The observations were carried out with the 6-m Special Astrophysical Observatory telescope (Russia) in the wavelength range 3600–10000 Å, the 2.1-m GHAO telescope...
Article
Full-text available
The iron abundance relative to alpha-elements in the circumnuclear region of quasars is regarded as a clock of the star formation history and, more specifically, of the enrichment by SNIa. We investigate the iron abundance in a sample of 22 quasars in the redshift range 3.0<z<6.4 by measuring their rest frame UV FeII bump, which is shifted into the...
Article
Full-text available
We have optically identified a complete sub-sample of ROSAT All-Sky Survey (RASS) X-ray sources (Appenzeller et al. 1998) contained in 6 study areas (Zickgraf et al. 1997). Of the original 12x12 degree area near the NEP only one quarter was observed until now in order to keep the number of sources on a manageable size. This area is of particular in...
Article
We have optically identified a complete sub-sample of ROSAT All-Sky Survey (RASS) X-ray sources contained in 6 study areas. Of the original 12° × 12° area near the NEP, only one-quarter was observed until now in order to keep the number of sources to a manageable size. This area is of particular interest because the RASS integration time is about a...

Citations

... Very high M BH values may turn out to be more challenging for ΛCDM cosmology if they are found at higher redshift. It is not only the high mass, but also the relatively high metal content (especially iron) of the line emitting gas that needs to be accounted for (Juarez et al., 2009). Clearly, metal enrichment in the proximity of a black hole may be decoupled from the host galaxy via circumnuclear star formation. ...
... Los procesos de aprendizaje y memoria son fundamentales para que los organismos logren adaptarse a los continuos cambios del medio ambiente. Dado que dichos procesos siempre ocurren en un lugar o contexto específico, no es de sorprender que los investigadores resalten la importancia de conocer el papel que juegan los estímulos contextuales en el aprendizaje y la recuperación de la información (Balsam & Tomie, 1985;Bouton, 2010;Smith, 2007). Sin embargo, esta tarea no ha sido fácil debido a que en la literatura existen hallazgos que muestran que el contexto no siempre es importante para controlar la recuperación de la información (ver Bouton & Woods, 2008). ...
... Al presente esta reaparición de la respuesta extinguida ha sido observada no solo al presentar el contexto de adquisición conocido como renovación ABA. Esta reaparición de la respuesta puede observarse tambien al presentar un contexto novedoso y es conocido como renovación AAB o ABC (Bernal-Gamboa, et al, 2012;Ritchey et al., 2021;Ritchey et al., 2022). Una posible explicación de este fenómeno supone la imposición de un nuevo aprendizaje durante el tratamiento el cual se hace dependiente del contexto al ser contrario al primer aprendizaje. ...
... Metallicity is often used as an important probe of past star formation, since cycles of star formation progressively enrich the interstellar medium (ISM) with metalrich material. Therefore, it is interesting that despite the low SFR of optically luminous quasars, quasars are metal rich across all redshifts (Simon & Hamann 2010;Shemmer et al. 2004;Warner et al. 2004;Nagao et al. 2006;Jiang et al. 2007;Juarez et al. 2009). Previous studies regarding this puzzle have concluded that broadline region (BLR) metallicity is independent of the ongoing star formation of the host galaxy, which is responsible for the far-infrared (FIR)-bright quasars. ...
... In general, [Fe/ ] is expected to decline toward higher redshifts because elements are predominantly produced in core-collapse supernovae (CCSNe), whereas iron is mainly released in type Ia SNe with a long delay time of 0.5 Gyr (e.g., Matteucci & Greggio 1986;Matteucci & Recchi 2001;Maoz et al. 2010;Homma et al. 2015). However, quasar observations show that the Fe II/Mg II flux ratio does not decrease but appears to be almost constant up to ∼ 7.5, by which type Ia SNe hardly make a contribution to iron production (Iwamuro et al. 2002;Dietrich et al. 2003;Maiolino et al. 2003;De Rosa et al. 2011;Mazzucchelli et al. 2017;Shin et al. 2019;Onoue et al. 2020;Schindler et al. 2020;Yang et al. 2021). Moreover, Sameshima et al. (2017Sameshima et al. ( , 2020 have extensively analyzed the observed spectra of high-z quasars and found that the high Fe II/Mg II flux ratio is caused by overproduction of iron, namely an extremely high iron to magnesium abundance ratio [Fe/Mg] > 0.2. ...
... The number of discovered BAL quasars has kept increasing with the growing number of quasars with spectroscopic observations of enough quality and enough spectral coverage to probe at least the most prominent BAL features. A first guess for a BAL quasar fraction as high as 50% at z ∼ 6 had been previously suggested by Maiolino et al. (2004), based on a very small sample of eight quasars. A BAL fraction of 16-24 % was later reported by Shen et al. (2019); Schindler et al. (2020); Yang et al. (2021), although the BAL identification was mostly based on visual inspection and/or limited spectral range and SNR of the quasar spectra. ...