Nitrógeno inorgánico disuelto y contenido proteico en fracciones de material particulado en suspensión en la Bahía Blanca

Durante el período 15/jul/82 - 15/ago/1983 se llevaron a cabo 30 campañas en la porción interna de la Bahía Blanca, muestreando en una zona caracterizada por elevados valores de nutrientes, clorofila y productividad primaria. Se determinaron las concentraciones de nitrato, nitrito y amonio en agua de mar y de proteína en tres fracciones de material particulado en suspensión (>100μ , 20μ y <20μ), con el objeto de estudiar sus variaciones estacionales y ciertos aspectos del ciclo del nitrógeno. La oscilación en los valores de estas variables parece estar controlada principalmente por las fluctuaciones del plancton y por el aporte de nutrientes a través de los cursos de agua dulce.Thirty cruises were carried out in the inner zone of Blanca bay, Argentina, through the period 15/jul/82 - 15/aug/83. Sampling was done in a location with high nutrient, chlorophyll and primary productivity values. The concentrations of nitrate, nitrite and aninonium were dctcrmined in scawater, and particulate protein was measured on samples in three size classes (>10μ , 20μ y <20μ) in order to study the cycling and seasonal variation of dissolved and particulate nitrogen. The oscilation in the values of these variables appears to be controlled by plankton fluctuations and by the nutrient addition from freshwater input.Asociación Argentina de Geofísicos y Geodesta

Nanotribology and electrical properties of carbon nanotubes hybridized with covalent organic frameworks

Nanomanipulation of molecular materials such as carbon nanotubes (CNTs) or new covalent organic frameworks (COFs) is key not only for the study of their fundamental physicochemical properties, but also for building and probing nanodevices. Therefore, we have investigated the tribological properties of oxidized MWCNTs (ox-MWCNTs) and their hybridization with COF building blocks (ox-MWCNTs@COF) adsorbed on a mica surface. We used the AFM tip to apply torsional forces on individual nanotubes. Depending on the manipulation parameters, the lateral displacements of the AFM tip slide and/or bend nanotubes enabling the direct quantification of the nanotube-mica adhesion. We found striking changes in the behaviour of the lateral force needed to manipulate each carbon nanotube variant which indicates an increased adhesion of ox-MWCNTs@COF with respect to ox-MWCNTs (∼10x). In addition, the use of the AFM tip as a mobile electrode enabled the measurement of electrical transport through individual nanotubes that revealed a rectifying behaviour of the ox-MWCNTs@COF with high resistivity, which was in contrast with the near ohmic performance of ox-MWCNTsP. J.d.P. acknowledges support by grants from the Ministerio de Ciencia e Innovacion (FIS2017- 89549-R; “Maria de Maeztu” Program for Units of Excellence in R&D MDM2014-0377; and FIS2017-90701- REDT) and the Human Frontiers Science Program (HFSPO RGP0012/ 2018). R. M. ackowledges support by grant PID2019-110637RB-10

Phytoplankton size-fractionated chlorophyll-a off Baja California during winter, spring, and summer 2008

Spatial and temporal size-fractionated phytoplankton chlorophyll-a (Chl-a) variability as pico-nanoplankton (PN, 0.4- 8.0 µm) and nano-microplankton (NM, &gt;8.0 µm) off Baja California is shown. Chl-a samples from the upper 200 m were obtained from nearshore, offshore, and intermediate locations during winter, spring, and summer 2008. PN-Chl-a contribution to phytoplankton biomass was ~4 times higher than NM fraction. Chl-a PN/NM ratio increased toward offshore, while total Chl-a (PN + NM) decreased. Seasonally, offshore phytoplankton cells abundance had a comparable contribution for both size-fractions, without an apparent change by the integrated water-column total Chl-a (60 mg m?2). Vertical Chl-a profiles were similar for winter and summer seasons. The highest Chl-a concentration and phytoplankton-cells abundance arose in spring, predominantly for NM at nearshore locations, reaching from 2.7-fold (nearshore: middle) to 4.2-fold (middle: offshore) ratios. Phytoplankton Chl-a increased from winter to spring (5.4 times), with maximum contribution of NM (6.6 times) at nearshore zones. Water-column integrated phytoplankton abundance was 5-fold higher in spring than winter, and 2-fold over summer. Using optical microscopy, dinoflagellate cells were the most abundant and variable phytoplankton recognizable group at intermediate zone. Smaller phytoplankton cells sustained approximately continuous biomass off Baja California. The spatial and temporal phytoplankton biomass variability was mainly influenced by an increase of larger cells as result of spring coastal upwelling events

Changes in Coastal Benthic Algae Succession Trajectories and Assemblages Under Contrasting Nutrient and Grazer Loads

Eutrophication plays a crucial role in coastal systems, driving changes in the composition and abundance of flora and fauna with consequent effects for the entire ecosystem. Sensitive to nutrient levels, micro- and macroalgal blooms serve as valuable indicators of eutrophication. The San Antonio Bay (Northern Argentinean Patagonia, 40° 43′ S, 64° 56′ W) provides an appropriate system to study in situ eutrophication processes on coastal communities. In a multi-scale approach, using two different kind of settlement substrates (micro: polyethylene terephthalate, and macro: ceramic), the present study followed benthic algal dynamics over one year, distinguishing changes in natural succession and seasonality. Strong differences were found in the biofilm assemblages after three days, marked by tube dwelling diatoms and Cocconeis spp. under high nutrient-grazer conditions and needle like diatoms (e.g. Nitzschia spp., Tabularia spp.) under lower nutrient-grazer loads. The succession continued by the colonization of macroalgae, with a higher recruitment rate in the nutrient and grazer rich environment with a concomitant higher diversity. Our results show that under higher nutrient-grazer conditions natural benthic succession not only differs in trajectory but in its final taxa composition promoting higher biodiversity and biomass accumulation. In addition, taxa specific substrate preferences interfere with the observed eutrophication pattern, suggesting substrate dependant interrelations between the bloom forming taxa. These findings provide evidence that nutrient enrichment can not only affect an established assemblage but also affect the early succession stages, changing the succession trajectory and thus the final assemblage.Facultad de Ciencias Naturales y Muse

Factors influencing the characteristics and distribution or surface organic matter in the Pacific-Atlantic connection

The present work reports the first data set on particulate organic carbon (POC) and nitrogen (PON), and the high-resolution modelling of their stable isotope variability in the Patagonian Cold Estuarine System (PCES), with focus on particulate organic matter (POM) origin and distribution in dependence on physical, chemical and biological parameters. POC, PON, stable carbon (δ¹³C) and nitrogen isotopes (δ¹⁵N), dissolved organic nitrogen, phaeopigments, diatom, dinoflagellate and heterotrophic bacteria (HB) abundance are reported for 17 stations in different waters masses in the southern end of the Argentine shelf in late summer 2012. Most parameters denote clear differences between Beagle - Magellan Water (BMW), Subantarctic Shelf Water (SSW) and Subantarctic Water (SAW). POC and PON decreased from maxima in BMW to intermediate values in SSW and minima in SAW. There was a highly significant correlation among POC, PON and fluorescence indicators of diagenetic maturity of dissolved humic matter. This, together with the inverse correlations of salinity with POC and PON, and the wide range of C:N ratios indicate that POM in the study area is partly derived from terrestrial runoff, superimposed by autochthonous components from plankton of different life stages. HB abundance was significantly correlated with POC and dissolved organic matter (DOM), likely reflecting a resource control of HB and a significant contribution of bacterial biomass to POM in the nanoparticle fraction. The direct relationship between HB and dissolved humics suggests bacterial uptake of DOM fractions otherwise considered refractory. POM complexity was reflected in a wide variation of δ¹³C, despite the narrow temperature range of this region. The variability of stable isotopes of POC could be accounted for by a model with a degree of detail hitherto not reported in the literature. A multiple regression including C:N ratio, ammonium and the quotient between log abundance of diatoms, dinoflagellates and HB explained 92% of δ¹³C variance, mostly produced by ammonium. Despite the strong effect of ammonium on δ¹³C, δ¹⁵N variability was largely explained by a strong inverse relationship with the fraction of unutilized nitrate, suggesting dominance of nitrate uptake. However, the proportion of presumably isotopically heavier ammonium derived from continental runoff in the marine δ¹⁵N-POM pool is unknown and requires investigation of the isotopic composition of dissolved inorganic nitrogen in the PCES. The presented new information and its comparison with data from other sectors of the Argentine shelf constitute a contribution to an approach for the understanding of the organic matter dynamics that can be potentially expanded to the entire Southwest Atlantic.Facultad de Ciencias Naturales y Muse

Chatbots in social networks for the timely support of university students with attention-deficit/hyperactivity disorder symptoms

Se estima que la prevalencia del trastorno por déficit de atención con hiperactividad (TDAH) en estudiantes universitarios es del 2 al 4.5% pero varía de una universidad a otra. Sin embargo, muchos estudiantes evitan acudir a tratamiento por ansiedad, temor al estigma, porque sienten que los problemas de los otros son mayores que los propios o bien desconocen la sintomatología del TDAH. En esta contribución se presenta el diseño e implementación de un chatbot para la aplicación del cuestionario Adult Self Report Scale-Versión 1.1 (EATDAH-A) así como los resultados de la aplicación del mismo y la opinión de los usuarios en cuanto a su utilidad y experiencia como usuario.It is estimated that the prevalence of Attention Deficit Hyperactivity Disorder (ADHD) in university students is from 2 to 4.53% but varies from one university to another. However, many students avoid therapies due to grief, nervousness, fear, or because they feel that the problems of others are greater than their own or they are unaware of the symptoms of ADHD. This contribution presents the design and implementation of a chatbot for the application of the Adult Self Report Scale-Version 1.1 (ASRS v1.1) questionnaire as well as the results of its application and the opinion of users regarding its usefulness and user experience.Facultad de Informátic

Chatbots in social networks for the timely support of university students with attention-deficit/hyperactivity disorder symptoms

Se estima que la prevalencia del trastorno por déficit de atención con hiperactividad (TDAH) en estudiantes universitarios es del 2 al 4.5% pero varía de una universidad a otra. Sin embargo, muchos estudiantes evitan acudir a tratamiento por ansiedad, temor al estigma, porque sienten que los problemas de los otros son mayores que los propios o bien desconocen la sintomatología del TDAH. En esta contribución se presenta el diseño e implementación de un chatbot para la aplicación del cuestionario Adult Self Report Scale-Versión 1.1 (EATDAH-A) así como los resultados de la aplicación del mismo y la opinión de los usuarios en cuanto a su utilidad y experiencia como usuario.It is estimated that the prevalence of Attention Deficit Hyperactivity Disorder (ADHD) in university students is from 2 to 4.53% but varies from one university to another. However, many students avoid therapies due to grief, nervousness, fear, or because they feel that the problems of others are greater than their own or they are unaware of the symptoms of ADHD. This contribution presents the design and implementation of a chatbot for the application of the Adult Self Report Scale-Version 1.1 (ASRS v1.1) questionnaire as well as the results of its application and the opinion of users regarding its usefulness and user experience.Facultad de Informátic

Chatbots in social networks for the timely support of university students with attention-deficit/hyperactivity disorder symptoms

Se estima que la prevalencia del trastorno por déficit de atención con hiperactividad (TDAH) en estudiantes universitarios es del 2 al 4.5% pero varía de una universidad a otra. Sin embargo, muchos estudiantes evitan acudir a tratamiento por ansiedad, temor al estigma, porque sienten que los problemas de los otros son mayores que los propios o bien desconocen la sintomatología del TDAH. En esta contribución se presenta el diseño e implementación de un chatbot para la aplicación del cuestionario Adult Self Report Scale-Versión 1.1 (EATDAH-A) así como los resultados de la aplicación del mismo y la opinión de los usuarios en cuanto a su utilidad y experiencia como usuario.It is estimated that the prevalence of Attention Deficit Hyperactivity Disorder (ADHD) in university students is from 2 to 4.53% but varies from one university to another. However, many students avoid therapies due to grief, nervousness, fear, or because they feel that the problems of others are greater than their own or they are unaware of the symptoms of ADHD. This contribution presents the design and implementation of a chatbot for the application of the Adult Self Report Scale-Version 1.1 (ASRS v1.1) questionnaire as well as the results of its application and the opinion of users regarding its usefulness and user experience.Facultad de Informátic

Changes in Coastal Benthic Algae Succession Trajectories and Assemblages Under Contrasting Nutrient and Grazer Loads

Eutrophication plays a crucial role in coastal systems, driving changes in the composition and abundance of flora and fauna with consequent effects for the entire ecosystem. Sensitive to nutrient levels, micro- and macroalgal blooms serve as valuable indicators of eutrophication. The San Antonio Bay (Northern Argentinean Patagonia, 40° 43′ S, 64° 56′ W) provides an appropriate system to study in situ eutrophication processes on coastal communities. In a multi-scale approach, using two different kind of settlement substrates (micro: polyethylene terephthalate, and macro: ceramic), the present study followed benthic algal dynamics over one year, distinguishing changes in natural succession and seasonality. Strong differences were found in the biofilm assemblages after three days, marked by tube dwelling diatoms and Cocconeis spp. under high nutrient-grazer conditions and needle like diatoms (e.g. Nitzschia spp., Tabularia spp.) under lower nutrient-grazer loads. The succession continued by the colonization of macroalgae, with a higher recruitment rate in the nutrient and grazer rich environment with a concomitant higher diversity. Our results show that under higher nutrient-grazer conditions natural benthic succession not only differs in trajectory but in its final taxa composition promoting higher biodiversity and biomass accumulation. In addition, taxa specific substrate preferences interfere with the observed eutrophication pattern, suggesting substrate dependant interrelations between the bloom forming taxa. These findings provide evidence that nutrient enrichment can not only affect an established assemblage but also affect the early succession stages, changing the succession trajectory and thus the final assemblage.Facultad de Ciencias Naturales y Muse