Coupling langmuir with michaelis-menten-a practical alternative to estimate se content in rice?

Selenium plays an important, but vastly neglected role in human nutrition with a narrow gap between dietary deficiency and toxicity. For a potential biofortification of food with Se, as well as for toxicity-risk assessment in sites contaminated by Se, modelling of local and global Se cycling is essential. As bioavailability of Se for rice plants depends on the speciation of Se and the resulting interactions with mineral surfaces as well as the interaction with Se uptake mechanisms in plants, resulting plant Se content is complex to model. Unfortunately, simple experimental models to estimate Se uptake into plants from substrates have been lacking. Therefore, a mass balance of Se transfer between lithosphere (represented by kaolinite), hydrosphere (represented by a controlled nutrient solution), and biosphere (represented by rice plants) has been established. In a controlled, closed, lab-scale system, rice plants were grown hydroponically in nutrient solution supplemented with 0–10000 μgL¯¹ Se of either selenite or selenite. Furthermore, in a series of batch experiments, adsorption and desorption were studied for selenite and selenite in competition with each of the major nutrient oxy-anions, nitrate, sulfate and phosphate. In a third step, the hydroponical plants experiments were coupled with sorption experiments to study synergy effects. These data were used to develop a mass balance fitting model of Se uptake and partitioning. Adsorption was well-described by Langmuir isotherms, despite competing anions, however, a certain percentage of Se always remained bio-unavailable to the plant. Uptake of selenite or selenite by transporters into the rice plant was fitted with the non-time differentiated Michaelis-Menten equation. Subsequent sequestration of Se to the shoot was better described using a substrate-inhibited variation of the Michaelis-Menten equation. These fitted parameters were then integrated into a mass balance model of Se transfer

Specific Electrogram Characteristics Identify the Extra-Pulmonary Vein Arrhythmogenic Sources of Persistent Atrial Fibrillation – Characterization of the Arrhythmogenic Electrogram Patterns During Atrial Fibrillation and Sinus Rhythm

Identification of atrial sites that perpetuate atrial fibrillation (AF), and ablation thereof terminates AF, is challenging. We hypothesized that specific electrogram (EGM) characteristics identify AF-termination sites (AFTS). Twenty-one patients in whom low-voltage-guided ablation after pulmonary vein isolation terminated clinical persistent AF were included. Patients were included if short RF-delivery for <8sec at a given atrial site was associated with acute termination of clinical persistent AF. EGM-characteristics at 21 AFTS, 105 targeted sites without termination and 105 non-targeted control sites were analyzed. Alteration of EGM-characteristics by local fibrosis was evaluated in a three-dimensional high resolution (100 µm)-computational AF model. AFTS demonstrated lower EGM-voltage, higher EGM-cycle-length-coverage, shorter AF-cycle-length and higher pattern consistency than control sites (0.49 ± 0.39 mV vs. 0.83 ± 0.76 mV, p < 0.0001; 79 ± 16% vs. 59 ± 22%, p = 0.0022; 173 ± 49 ms vs. 198 ± 34 ms, p = 0.047; 80% vs. 30%, p < 0.01). Among targeted sites, AFTS had higher EGM-cycle-length coverage, shorter local AF-cycle-length and higher pattern consistency than targeted sites without AF-termination (79 ± 16% vs. 63 ± 23%, p = 0.02; 173 ± 49 ms vs. 210 ± 44 ms, p = 0.002; 80% vs. 40%, p = 0.01). Low voltage (0.52 ± 0.3 mV) fractionated EGMs (79 ± 24 ms) with delayed components in sinus rhythm (‘atrial late potentials’, respectively ‘ALP’) were observed at 71% of AFTS. EGMs recorded from fibrotic areas in computational models demonstrated comparable EGM-characteristics both in simulated AF and sinus rhythm. AFTS may therefore be identified by locally consistent, fractionated low-voltage EGMs with high cycle-length-coverage and rapid activity in AF, with low-voltage, fractionated EGMs with delayed components/ ‘atrial late potentials’ (ALP) persisting in sinus rhythm

CVAR-Seg: An Automated Signal Segmentation Pipeline for Conduction Velocity and Amplitude Restitution

Background: Rate-varying S1S2 stimulation protocols can be used for restitution studies to characterize atrial substrate, ionic remodeling, and atrial fibrillation risk. Clinical restitution studies with numerous patients create large amounts of these data. Thus, an automated pipeline to evaluate clinically acquired S1S2 stimulation protocol data necessitates consistent, robust, reproducible, and precise evaluation of local activation times, electrogram amplitude, and conduction velocity. Here, we present the CVAR-Seg pipeline, developed focusing on three challenges: (i) No previous knowledge of the stimulation parameters is available, thus, arbitrary protocols are supported. (ii) The pipeline remains robust under different noise conditions. (iii) The pipeline supports segmentation of atrial activities in close temporal proximity to the stimulation artifact, which is challenging due to larger amplitude and slope of the stimulus compared to the atrial activity. Methods and Results: The S1 basic cycle length was estimated by time interval detection. Stimulation time windows were segmented by detecting synchronous peaks in different channels surpassing an amplitude threshold and identifying time intervals between detected stimuli. Elimination of the stimulation artifact by a matched filter allowed detection of local activation times in temporal proximity. A non-linear signal energy operator was used to segment periods of atrial activity. Geodesic and Euclidean inter electrode distances allowed approximation of conduction velocity. The automatic segmentation performance of the CVAR-Seg pipeline was evaluated on 37 synthetic datasets with decreasing signal-to-noise ratios. Noise was modeled by reconstructing the frequency spectrum of clinical noise. The pipeline retained a median local activation time error below a single sample (1 ms) for signal-to-noise ratios as low as 0 dB representing a high clinical noise level. As a proof of concept, the pipeline was tested on a CARTO case of a paroxysmal atrial fibrillation patient and yielded plausible restitution curves for conduction speed and amplitude. Conclusion: The proposed openly available CVAR-Seg pipeline promises fast, fully automated, robust, and accurate evaluations of atrial signals even with low signal-to-noise ratios. This is achieved by solving the proximity problem of stimulation and atrial activity to enable standardized evaluation without introducing human bias for large data sets

Using Machine Learning to Characterize Atrial Fibrotic Substrate from Intracardiac Signals with a Hybrid in silico and in vivo Dataset

[EN] In patients with atrial fibrillation, intracardiac electrogram signal amplitude is known to decrease with increased structural tissue remodeling, referred to as fibrosis. In addition to the isolation of the pulmonary veins, fibrotic sites are considered a suitable target for catheter ablation. However, it remains an open challenge to find fibrotic areas and to differentiate their density and transmurality. This study aims to identify the volume fraction and transmurality of fibrosis in the atrial substrate. Simulated cardiac electrograms, combined with a generalized model of clinical noise, reproduce clinically measured signals. Our hybrid dataset approach combines in silico and clinical electrograms to train a decision tree classifier to characterize the fibrotic atrial substrate. This approach captures different in vivo dynamics of the electrical propagation reflected on healthy electrogram morphology and synergistically combines it with synthetic fibrotic electrograms from in silico experiments. The machine learning algorithm was tested on five patients and compared against clinical voltage maps as a proof of concept, distinguishing non-fibrotic from fibrotic tissue and characterizing the patient's fibrotic tissue in terms of density and transmurality. The proposed approach can be used to overcome a single voltage cut-off value to identify fibrotic tissue and guide ablation targeting fibrotic areas.We gratefully acknowledge financial support by the Deutsche Forschungsgemeinschaft (DFG) through DO637/22-3, LO2093/1-1 and LU 2294/1-1, by the European Union's Horizon 2020 programme (grant agreement No.766082, MY-ATRIA project), by the KIT-Publication Fund of the Karlsruhe Institute of Technology and by the Plan Estatal de Investigacion Cientifica y Tecnica y de Innovacion 2017-2020 from the Ministerio de Ciencia e Innovacion y Universidades (PID2019-104356RB-C41/AEI/10.13039/501100011033)Sánchez Arciniegas, JP.; Luongo, G.; Nothstein, M.; Unger, LA.; Saiz Rodríguez, FJ.; Trenor Gomis, BA.; Luik, A.... (2021). Using Machine Learning to Characterize Atrial Fibrotic Substrate from Intracardiac Signals with a Hybrid in silico and in vivo Dataset. Frontiers in Physiology. 12:1-15. https://doi.org/10.3389/fphys.2021.699291S1151

El fantasma teleológico y las metáforas de intencionalidad en los libros de texto no distinguidas por estudiantes novatos: un posible obstáculo para el aprendizaje

En la Biología actual, las explicaciones con sentido teleológico o conducta intencional ocasionan una paradoja con importantes implicancias didácticas: utilizar explicaciones predarwinianas o incluso antidarwinianas distorsiona la comprensión del hecho biológico a la luz de la teoría de la evolución, al no tener en cuenta los carácteres teleomático, teleonómico y adaptativo involucrados. En este trabajo, en cambio, el objetivo se dirigió a indagar si tales enunciados cargados de teleología y metáforas de intencionalidad eran reconocidas y diferenciadas por estudiantes universitarios novatos de primer año frente a expresiones con el mismo sentido biológico que no incluyeran tales errores de expresión. No obstante, las evidencias mostradas en este trabajo, dan cuenta de que los estudiantes no logran distinguir entre ambos tipos de expresiones; por lo cual, sería probable que las implicaciones de la utilización de estos términos teleológicos o intencionales se convierta en un obstáculo epistemológico. Al menos, origina la sospecha de que consideren que tienen un sentido biológico tan válido como el que describen expresiones de causa-efecto ya sean teleonómicas, telemáticas o de adaptación. De allí que el profesor, como un “cazafantasmas” también debe estar atento y no bajar la guardia para una “vigilancia epistemológica” que evite se infiltren los modos de expresión del pensamiento teleológico.Facultad de Humanidades y Ciencias de la Educació

El fantasma teleológico y las metáforas de intencionalidad en los libros de texto no distinguidas por estudiantes novatos : Un posible obstáculo para el aprendizaje

En la Biología actual, las explicaciones con sentido teleológico o conducta intencional ocasionan una paradoja con importantes implicancias didácticas: utilizar explicaciones predarwinianas o incluso antidarwinianas distorsiona la comprensión del hecho biológico a la luz de la teoría de la evolución, al no tener en cuenta los carácteres teleomático, teleonómico y adaptativo involucrados. En este trabajo, en cambio, el objetivo se dirigió a indagar si tales enunciados cargados de teleología y metáforas de intencionalidad eran reconocidas y diferenciadas por estudiantes universitarios novatos de primer año frente a expresiones con el mismo sentido biológico que no incluyeran tales errores de expresión. No obstante, las evidencias mostradas en este trabajo, dan cuenta de que los estudiantes no logran distinguir entre ambos tipos de expresiones; por lo cual, sería probable que las implicaciones de la utilización de estos términos teleológicos o intencionales se convierta en un obstáculo epistemológico. Al menos, origina la sospecha de que consideren que tienen un sentido biológico tan válido como el que describen expresiones de causa-efecto ya sean teleonómicas, telemáticas o de adaptación. De allí que el profesor, como un "cazafantasmas" también debe estar atento y no bajar la guardia para una "vigilancia epistemológica" que evite se infiltren los modos de expresión del pensamiento teleológic

El fantasma teleológico y las metáforas de intencionalidad en los libros de texto no distinguidas por estudiantes novatos : Un posible obstáculo para el aprendizaje

En la Biología actual, las explicaciones con sentido teleológico o conducta intencional ocasionan una paradoja con importantes implicancias didácticas: utilizar explicaciones predarwinianas o incluso antidarwinianas distorsiona la comprensión del hecho biológico a la luz de la teoría de la evolución, al no tener en cuenta los carácteres teleomático, teleonómico y adaptativo involucrados. En este trabajo, en cambio, el objetivo se dirigió a indagar si tales enunciados cargados de teleología y metáforas de intencionalidad eran reconocidas y diferenciadas por estudiantes universitarios novatos de primer año frente a expresiones con el mismo sentido biológico que no incluyeran tales errores de expresión. No obstante, las evidencias mostradas en este trabajo, dan cuenta de que los estudiantes no logran distinguir entre ambos tipos de expresiones; por lo cual, sería probable que las implicaciones de la utilización de estos términos teleológicos o intencionales se convierta en un obstáculo epistemológico. Al menos, origina la sospecha de que consideren que tienen un sentido biológico tan válido como el que describen expresiones de causa-efecto ya sean teleonómicas, telemáticas o de adaptación. De allí que el profesor, como un "cazafantasmas" también debe estar atento y no bajar la guardia para una "vigilancia epistemológica" que evite se infiltren los modos de expresión del pensamiento teleológic