Co2TiO4/reduced graphene oxide nanohybrids for electrochemical sensing applications

For the first time, the synthesis, characterization, and analytical application for hydrogen peroxide quantification of the hybrid materials of Co2TiO4 (CTO) and reduced graphene oxide (RGO) is reported, using in situ (CTO/RGO) and ex situ (CTO+RGO) preparations. This synthesis for obtaining nanostructured CTO is based on a one-step hydrothermal synthesis, with new precursors and low temperatures. The morphology, structure, and composition of the synthesized materials were examined using scanning electron microscopy, X-ray diffraction (XRD), neutron powder diffraction (NPD), and X-ray photoelectron spectroscopy (XPS). Rietveld refinements using neutron diffraction data were conducted to determine the cation distributions in CTO. Hybrid materials were also characterized by Brunauer-Emmett-Teller adsorption isotherms, Scanning Electron microscopy, and scanning electrochemical microscopy. From an analytical point of view, we evaluated the electrochemical reduction of hydrogen peroxide on glassy carbon electrodes modified with hybrid materials. The analytical detection of hydrogen peroxide using CTO/RGO showed 11 and 5 times greater sensitivity in the detection of hydrogen peroxide compared with that of pristine CTO and RGO, respectively, and a two-fold increase compared with that of the RGO+CTO modified electrode. These results demonstrate that there is a synergistic effect between CTO and RGO that is more significant when the hybrid is synthetized through in situ methodology.Fil: Venegas, Constanza J.. Universidad de Chile; Chile. Universidad de Santiago de Chile; ChileFil: Gutierrez, Fabiana Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Eguílaz Rubio, Marcos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Marco, José F.. Consejo Superior de Investigaciones Científicas; EspañaFil: Reeves-McLaren, Nik. University Of Sheffield; Reino UnidoFil: Rivas, Gustavo Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Ruiz-León, Domingo. Universidad de Santiago de Chile; ChileFil: Bollo, Soledad. Universidad de Chile; Chil

Carbon nanotubes non-covalently functionalized with cytochrome c: A new bioanalytical platform for building bienzymatic biosensors

We report for the first time the use of glassy carbon electrodes (GCE) modified by drop-coating with multi-walled carbon nanotubes (MWCNTs) dispersed in cytochrome c as platform for the construction of bienzymatic biosensors, using the glycoenzyme glucose oxidase (GOx) as model. The sensitivity of the resulting biosensor at -0.050 V towards glucose using hydroquinone (H2Q) as redox mediator was (96 ± 2) μA M-1, with a linear range between 1.00 × 10-4 M and 1.00 × 10-3 M and a detection limit of 8 μM. The biosensor demonstrated to be highly reproducible with RSD. values of 6.1% for five different bioelectrodes. The combination of the excellent dispersing properties of Cyt c, the stability of MWCNTs-Cyt c dispersion and the intimate interaction between Cyt c, MWCNTs and GOx, allowed the construction of an efficient glucose biosensor successfully used to determine glucose in commercial beverages.Fil: Eguilaz Rubio, Marcos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Venegas, Constanza J.. Universidad de Chile; ChileFil: Gutierrez, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Rivas, Gustavo Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Bollo, Soledad. Universidad de Chile; Chil

Intraseasonal variation in southeast Pacific blue whale acoustic presence, zooplankton backscatter, and oceanographic variables on a feeding ground in Northern Chilean Patagonia

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Buchan, S. J., Perez-Santos, I., Narvaez, D., Castro, L., Stafford, K. M., Baumgartner, M. F., Valle-Levinson, A., Montero, P., Gutierrez, L., Rojas, C., Daneri, G., & Neira, S. Intraseasonal variation in southeast Pacific blue whale acoustic presence, zooplankton backscatter, and oceanographic variables on a feeding ground in Northern Chilean Patagonia. Progress in Oceanography, 199,(2021): 102709, https://doi.org/10.1016/j.pocean.2021.102709.Seasonal variation in the acoustic presence of blue whale calls has been widely reported for feeding grounds worldwide, however variation over the submonthly scale (several days to <1 month) has been examined to a much lesser extent. This study combines passive acoustic, hydroacoustic, and in situ oceanographic observations collected at a mooring in the Corcovado Gulf, Northern Chilean Patagonia, from January 2016-February 2017, to examine the temporal variation in blue whale acoustic occurrence and prey backscatter over seasonal and submonthly scales. Time series data for a) Southeast Pacific blue whale song calls and D-calls, b) zooplankton backscatter, c) tidal amplitude, and d) meridional and zonal wind stress were examined visually for seasonal trends. To examine submonthly timescales over the summer feeding season (January-June), wavelet transforms and wavelet coherence were applied; generalized linear models (GLM) were also applied. There was a 3-month lag between the seasonal onsets of high zooplankton backscatter (October) and blue whale acoustic presence (January), and an almost immediate drop in blue whale acoustic presence with the seasonal decrease of backscatter (June). This may be due to the use of memory by animals when timing their arrival on the feeding ground, but the timing of their departure may be related to detection of low prey availability. Over the summer feeding season, blue whale acoustic presence was strongly associated with zooplankton backscatter (GLM coefficient p ≪ 0.0001). Song calls followed a seasonal cycle, but D-calls appeared to respond to short term variations in environmental conditions over submonthly scales. Results suggest that spring tides may increase prey aggregation and/or transport into the Corcovado Gulf, leading to increased blue whale acoustic presence over 15-day or 30-day cycles; and short-lived events of increased wind stress with periodicities of 2–8 days and 16–30 days, may also contribute to the aggregation of prey. We discuss the strengths and limitations of coupling passive and active acoustic data to examine drivers of blue whale distribution.Financial support was provided by Centro COPAS Sur-Austral ANID AFB170006 and COPAS Coastal FB10021 https://www.anid.cl/, and Office of Naval Research Global and Office of Naval Research grant N00014-17-1-2606

Effects of Bipolar Radiofrequency on Collagen Synthesis from Patients with Brachial Ptosis

Background:. Radiofrequency is frequently used for skin rejuvenation, localized fat elimination and cellulite treatment. It prompts the expression of thermal shock proteins that lead to dermal thickening as a result of collagen synthesis. The authors report a histological and clinical analysis of the arm subdermal changes before and after bipolar radiofrequency treatment plus liposuction to determine their benefits for arm contouring. Methods:. Inclusion criteria included patients with stage 1, 2a, and 2b brachial ptosis (Duncan classification) and upper limb fat deposits who were considered candidates for third-generation ultrasound-assisted liposculpture plus radiofrequency-assisted lipolysis/skin tightening. Arm subdermal tissue samples (5 mm³) were analyzed before and after the intervention. We used 10% formaldehyde for tissue fixation and stained each sample with hematoxylin/eosin, Masson trichrome, and antibody markers against the cell cycle Ki-67 protein. Results:. We analyzed a total of 12 biopsies from six patients who meet the inclusion/exclusion criteria. Histological findings with hematoxylin/eosin revealed hyperplastic and metaplastic changes with focal distribution within the papillary and reticular dermis. Masson trichrome staining showed an increase of the characteristic basophilia of thin type-I and type-III collagen fibers. In contrast, molecular analysis reported an increase in fibroblast activity mediated by the activation of the heat shock protein HSP47. Conclusion:. Radiofrequency may be a great alternative to improve skin retraction in patients with mild to moderate brachial dermatochalasis through the activation of HSP47 heat shock protein and the production of type-I and type-III collagen