Repositorio Institucional UCSC (Univ. Católica de la Santísima Concepción)
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Rising temperatures, falling fisheries: causes and consequences of crossing the tipping point in a small-pelagic community
Get PDFGlobal change has profound effects on marine species, communities, and ecosystems. Among these impacts, small pelagics have emerged as valuable indicators for detecting regime shifts in fish stocks. They exhibit swift responses to changes in ocean variables, including decreased abundances, accelerated juvenile growth rates, early maturation, and reduced adult sizes in warm waters. However, each pelagic species occupies a unique local ecological niche, that reflects the sum of all environmental conditions. Consequently, their responses to environmental changes manifest in distinct ways. We explore here how global change affects small pelagics in the Madeira Archipelago (NE Atlantic Ocean) at (i) community level, by studying the effects of climate change over a 40-year (1980–2019) period on small pelagic landings, and (ii) population level, by studying the effects on the life-history traits of the two most abundant species, Scomber colias and Trachurus picturatus. Our study demonstrated that anomalies in the Sea Surface Temperature and the North Atlantic Oscillation caused a regime shift within the small pelagic community. Both environmental predictors explained 88.9% of the community landings oscillations. S. colias appears to exhibit a relatively more favorable adaptive response to climate change compared to T. picturatus. Understanding the species-specific ecological responses of small pelagic fish to global change is crucial for effective management and conservation efforts in the face of ongoing environmental scenarios
Exploring the electronic and steric effects on the dimerization of intramolecular frustrated Lewis pairs: a comparison between aminoboranes and aminoalanes
No full textThe dimerization of intramolecular aminoborane and aminoalane frustrated Lewis pairs was investigated using density functional theory. We systematically varied the substituents to gradually increase their bulkiness, including H, CH3, t-Bu, Ph, and Mes groups. Starting from the most stable conformer of the monomers, a frustrated Lewis pair or classic Lewis adduct, we studied the dimerization process for all systems, revealing significant variations in the Gibbs free energy. Dimerization was favored in four aminoboranes and six aminoalanes, depending on the specific combinations of substituents. Applying an energy decomposition analysis, we found that the preparation energy of the monomers and the non-orbital interactions between them are the primary contributors to the observed energetic differences, showing a clear linear relationship. Additionally, we analyzed the electronic effects by increasing the acidity of the Lewis acid, observing a shift toward endergonic and exergonic directions in aminoboranes and aminoalanes, respectively. This shift was attributed to the stabilization of a classic Lewis adduct. This study underscores three crucial factors influencing dimer formation: (i) substituent size, (ii) stabilization of the classic Lewis adduct conformation, and (iii) covalent radii of the Lewis centers. Understanding these factors is essential for designing FLPs and preventing unwanted dimerization that could affect their catalytic performance in H2 activation processes
Green Synthesis of Fe2O3 Nanoparticles Using Eucalyptus globulus Leaf Extract on Pinus radiata Sawdust for Cationic Dye Adsorption
Get PDFThe present study reports the synthesis of Fe2O3 nanoparticles on Pinus radiata sawdust (Fe2O3@PS) using a Eucalyptus globulus leaf extract. The morphology and structure of Fe2O3@PS were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and UV–Vis diffuse reflectance. The adsorption capacity of the system was evaluated by testing its ability to remove the Rhodamine B (RhB) dye. The optimization of the system was carried out using the Plackett–Burman design (PBD) and the response surface methodology (steepest ascent and the Box–Behnken design), which provided information on the main parameters affecting the adsorption process. The PBD results showed that the most important parameters for the removal of RhB using Fe2O3@PS were the removal time, the RhB concentration, and the initial pH of the system. The reusability of Fe2O3@PS under optimal conditions was tested and it was found to maintain its efficiency after five cycles of use. The efficiency and rate of RhB removal observed at pH values near 7.0 were found to be predominantly influenced by electrostatic interactions. In contrast, the analyses conducted at pH values near 8.3 exhibited reduced influence from electrostatic attractions, with π–π interactions and hydrogen bonds emerging as dominant forces. At pH values exceeding 8.3, all potential interactions between RhB and Fe2O3@PS exhibited diminished strength. This research provides valuable information on the formation of eco-friendly nanoparticles immobilized on a forest residue such as sawdust, which can effectively remove organic pollutants like RhB. This contributes to the valorization of resources and the search for solutions to water pollution
Tcf4 dysfunction alters dorsal and ventral cortical neurogenesis in Pitt-Hopkins syndrome mouse model showing sexual dimorphism
No full textPitt-Hopkins syndrome (PTHS) is a neurodevelopmental disorder caused by haploinsufficiency of transcription factor 4 (TCF4). In this work, we focused on the cerebral cortex and investigated in detail the progenitor cell dynamics and the outcome of neurogenesis in a PTHS mouse model. Labeling and quantification of progenitors and newly generated neurons at various time points during embryonic development revealed alterations affecting the dynamic of cortical progenitors since the earliest stages of cortex formation in PTHS mice. Consequently, establishment of neuronal populations and layering of the cortex were found to be altered in heterozygotes subjects at birth. Interestingly, defective layering process of pyramidal neurons was partially rescued by reintroducing TCF4 expression using focal in utero electroporation in the cerebral cortex. Coincidentally with a defective dorsal neurogenesis, we found that ventral generation of interneurons was also defective in this model, which may lead to an excitation/inhibition imbalance in PTHS. Overall, sex-dependent differences were detected with more marked effects evidenced in males compared with females. All of this contributes to expand our understanding of PTHS, paralleling the advances of research in autism spectrum disorder and further validating the PTHS mouse model as an important tool to advance preclinical studies
Critical swimming speed at different temperatures for small-bodied freshwater native riverine fish species
Get PDFThis study evaluated the efect of fsh total length (LT) and three water temperatures (10, 15 and 20 °C) on the critical swimming speed (Ucrit) of the species Percilia irwini (2.9–6.3 cm LT), Cheirodon galusdae (3.4–5.5 cm LT), and Trichomycterus areolatus (4.0–6.3 cm LT). An Ucrit estimation model was constructed for each species as a function of temperature and size. The results showed mean Ucrit for P. irwini of 44.56, 53.83 and 63.2 cm s−1 at 10, 15 and 20 °C, respectively: 55.34, 61.74 and 70.05 cm s−1 for C. galusdae and 56.18, 63.01 and 71.09 cm s−1 for T. areolatus. Critical velocity depended on the interaction between species, body length and water. The swimming performance increased signifcantly with rising temperature in all three species. The velocity also increased with greater fsh total length. After controlling for fsh total length, velocity also increased with higher temperature in the three species. This research is relevant to small fsh species that require conservation measures
Fetal hyperthyroidism secondary to maternal basedow–graves' disease
Get PDFFetal hyperthyroidism is a rare prenatal disease and can be life-threatening. The diagnosis is based on ultrasound in mothers with a history of Basedow–Graves' disease and elevation of thyrotropin receptor antibodies (TRAbs) levels. The treatment consists of antithyroid drugs. We present a mother with Basedow–Graves' disease, treated with radioactive iodine 16 years ago. She had an unplanned pregnancy at the age of 29 years, and an elevation of TRAbs (21 U/L) was found at the sixth week of pregnancy. At 22 weeks of gestation, fetal ultrasound displayed tachycardia, goiter, exophthalmos, and suspicion of craniosynostosis, hence methimazole was started. Concomitantly, suppressed maternal thyroid-stimulating hormone (TSH) was found. Her daughter was born at 33 + 6 weeks showing clinical and laboratory findings of hyperthyroidism. Consequently, treatment with methimazole was prescribed. Normal thyroid function was documented in the mother after giving birth. Clear explanation has not been found for the alteration of maternal TSH during pregnancy
Self-reported and electroencephalogram responses to evaluate sponsorship congruence efficacy
No full textInformation for measuring the performance of a commercial action is essential for any organization. Sponsorship actions have increased significantly in the last few decades, but academics and practitioners have not yet found a suitable indicator for measuring their performance. This is the first study to propose an objective indicator—frontal alpha asymmetry using an electroencephalogram. Our goal was to investigate the effectiveness of sports sponsorships by examining both stated preferences and neural responses. We measured the congruence of the stated preferences, attitude, purchase intention, and loyalty, as well as the effective congruence. A 76-subject experiment revealed greater left frontal activity (approach behavior) during congruent versus incongruent sponsorship (avoidance behavior). electroencephalogram results were consistent with self-reports, but we found that frontal alpha asymmetry is positively related to loyalty when sponsorship is congruent and inversely related in the incongruent case. This new indicator of sponsorship effectiveness could be useful for examining the performance of commercial action at both academic and professional levels
Cosmology Large Angular Scale Surveyor (CLASS): 90 GHz telescope pointing, beam profile, window function, and polarization performance
Get PDFThe Cosmology Large Angular Scale Surveyor (CLASS) is a telescope array that observes the cosmic microwave background (CMB) over ∼75% of the sky from the Atacama Desert, Chile, at frequency bands centered near 40, 90, 150, and 220 GHz. CLASS measures the large angular scale CMB polarization to constrain the tensor-to-scalar ratio and the optical depth to last scattering. This paper presents the optical characterization of the 90 GHz telescope. Observations of the Moon establish the pointing while dedicated observations of Jupiter are used for beam calibration. The standard deviations of the pointing error in azimuth, elevation, and boresight angle are 1 3, 2 1, and 2 0, respectively, over the first 3 yr of observations. This corresponds to a pointing uncertainty ∼7% of the beam’s full width at half-maximum (FWHM). The effective azimuthally symmetrized instrument 1D beam estimated at 90 GHz has an FWHM of 0°. 620 ± 0°.003 and a solid angle of 138.7 ± 0.6(stats.) ± 1.1(sys.) μsr integrated to a radius of 4°. The corresponding beam window function drops to bℓ = 0.93, 0.71, 0.14 2 at ℓ = 30, 100, 300, respectively. Far-sidelobes are studied using detector-centered intensity maps of the Moon and measured to be at a level of 10−3 or below relative to the peak. The polarization angle of Tau A estimated from preliminary survey maps is 149°.6 ± 0°.2(stats.) in equatorial coordinates. The instrumental temperature-to-polarization (T → P) leakage fraction, inferred from per-detector demodulated Jupiter scan data, has a monopole component at the level of 1.7 × 10−3, a dipole component with an amplitude of 4.3 × 10−3, with no evidence of quadrupolar leakage