Heart Rate Estimation During Physical Exercise Using Wrist-Type Ppg Sensors

Accurate heart rate monitoring during intense physical exercise is a challenging problem due to the high levels of motion artifacts (MA) in photoplethysmography (PPG) sensors. PPG is a non-invasive optical sensor that is being used in wearable devices to measure blood flow changes using the property of light reflection and absorption, allowing the extraction of vital signals such as the heart rate (HR). However, the sensor is susceptible to MA which increases during physical activity. This occurs since the frequency range of movement and HR overlaps, difficulting correct HR estimation. For this reason, MA removal has remained an active topic under research. Several approaches have been developed in the recent past and among these, a Kalman filter (KF) based approach showed promising results for an accurate estimation and tracking using PPG sensors. However, this previous tracker was demonstrated for a particular dataset, with manually tuned parameters. Moreover, such trackers do not account for the correct method for fusing data. Such a custom approach might not perform accurately in practical scenarios, where the amount of MA and the heart rate variability (HRV) depend on numerous, unpredictable factors. Thus, an approach to automatically tune the KF based on the Expectation-Maximization (EM) algorithm, with a measurement fusion approach is developed. The applicability of such a method is demonstrated using an open-source PPG database, as well as a developed synthetic generation tool that models PPG and accelerometer (ACC) signals during predetermined physical activities

Induced biotic response in Amazonian ant-plants: the role of leaf damage intensity and plant-derived food rewards on ant recruitment

Although plant-ants respond to cues indicating the presence of herbivores, it remains unclear how ant workers are stimulated by herbivory cues with varying intensity. I hypothesized that ants respond more quickly to intense foliar damage, and ants inhabiting myrmecophytes that provide food resource recruit workers to any intensity of foliar damage. I tested the induced response in three ant-plant systems: two that provide food resources and another one that does not provide. I simulated leaf damage using different concentrations of foliar extracts. In all systems the plant-ant recruitment increased after damage simulations. In food providing system ants did not distinguish between different intensity damages, although one system have shown a mixed response to that intensity. This result indicates that ants defend more intensely their host plant to avoid damages that diminish food provisioning. In the non-food providing system ants responded more quickly to simulation of high foliar damage. This faster recruitment to leaves with high damage suggests that ants are searching for hot spots that potentially have more insects for feeding on. I suggested that future works could manipulate plant size and quality, and food provisioning to better understand why mutual ant-plant systems with very distinct characteristics are evolutionarily stabilized

Reflexiones sobre la necesidad o importancia de la información en la contemporaneidad

The article seeks to reflect on a possible balance between the flow and the demand for information in contemporary society, as being demonstrated the existence of a huge informational flow based on the paradox: provision of information and limits absorption and processing by Individuals. Thus, the proposal was to link the theoretical data with some practical insights for the reader's information preliminarily scheduled curious about the subject