Validity of Wrist-worn Physical Activity Monitors to Measure Heart Rate

Numerous physical activity monitors exist and are used to track and improve fitness levels. Due to the increasing popularity of these devices, newer products have been developed that measure heart rate (HR) at the wrist. Little is known about how accurate these devices are at measuring HR at the wrist and how they compare to each other. PURPOSE: To determine how accurately HR was measured by three different wrist-worn physical activity monitors. METHODS: Recreationally active men (n=9) and women (n=3) participated in this study. The average age and weight of participants was 22 ± 3 years and 73.9 ± 12 kg. TomTom Cardio (TT), Fitbit Surge (FB) and Microsoft Band (MB) physical activity monitors were used. The TT, FB, and MB were randomly assigned to the right or left wrist for each participant. The testing procedure included speeds of 2, 3, 4, 5, and 6 mph with each speed lasting three minutes. HR was measured by electrocardiography (ECG) using standard limb lead II and by the three different physical activity monitors. HR was recorded from each device every minute throughout the duration of the procedure. Pearson product moment correlations and bias between electrocardiography (ECG) and physical activity monitors with 95% limits of agreement (Bland-Altman analysis) were calculated. Repeated measures ANOVA [Speed x Device] were also calculated. Statistical significance was set at pRESULTS: At 2 mph and 3 mph, only TT HR was significantly correlated with ECG heart rate (r=0.693, p=0.012 and r=0.592, p=0.043). At 4 mph and 6 mph TT was significantly correlated with ECG (r=0.911, pCONCLUSION: With increasing speeds, physical activity monitors more accurately measure HR but individuals should be aware that these devices may overestimate HR during slower walking speeds

Direct metabolite detection with an n-type accumulation mode organic electrochemical transistor.

The inherent specificity and electrochemical reversibility of enzymes poise them as the biorecognition element of choice for a wide range of metabolites. To use enzymes efficiently in biosensors, the redox centers of the protein should have good electrical communication with the transducing electrode, which requires either the use of mediators or tedious biofunctionalization approaches. We report an all-polymer micrometer-scale transistor platform for the detection of lactate, a significant metabolite in cellular metabolic pathways associated with critical health care conditions. The device embodies a new concept in metabolite sensing where we take advantage of the ion-to-electron transducing qualities of an electron-transporting (n-type) organic semiconductor and the inherent amplification properties of an ion-to-electron converting device, the organic electrochemical transistor. The n-type polymer incorporates hydrophilic side chains to enhance ion transport/injection, as well as to facilitate enzyme conjugation. The material is capable of accepting electrons of the enzymatic reaction and acts as a series of redox centers capable of switching between the neutral and reduced state. The result is a fast, selective, and sensitive metabolite sensor. The advantage of this device compared to traditional amperometric sensors is the amplification of the input signal endowed by the electrochemical transistor circuit and the design simplicity obviating the need for a reference electrode. The combination of redox enzymes and electron-transporting polymers will open up an avenue not only for the field of biosensors but also for the development of enzyme-based electrocatalytic energy generation/storage devices

Critical analysis of self-doping and water-soluble n-type organic semiconductors: structures and mechanisms

Self-doping organic semiconductors provide a promising route to avoid instabilities and morphological issues associated with molecular n-type dopants. Structural characterization of a naphthalenetetracarboxylic diimide (NDI) semiconductor covalently bound to an ammonium hydroxide group is presented. The dopant precursor was found to be the product of an unexpected base catalyzed hydrolysis, which was reversible. The reversible hydrolysis had profound consequences on the chemical composition, morphology, and electronic performance of the doped films. In addition, we investigated the degradation mechanism of the quaternary ammonium group and the subsequent doping of NDI. These findings reveal that the products of more than one chemical reaction during processing of films must be considered when utilizing this promising class of water-soluble semiconductors

Durabilité de la culture cotonnière selon l'utilisation des insecticides : cas du Togo de 1991-2010

Dans la perception des profanes, le coton est encore associé à la culture consommant le plus d'insecticides néfastes pour la santé et l'environnement. Une telle mauvaise image n'est plus méritée selon une étude internationale, mais les pays producteurs ont peu analysé et informé sur l'évolution de l'utilisation d'insecticides. Cette communication comble la lacune dans le cas du Togo. L'étude est basée sur la reconstitution des séries de données des surfaces emblavées et d'insecticides distribués aux producteurs de coton du Togo, de 1990 à 2010. Les données sur les insecticides concernent les volumes distribués ainsi que leurs compositions en matières actives, permettant ainsi de déduire la consommation de matières actives par hectare. Par ailleurs, les charges toxicologiques vis-à-vis de divers éléments de la faune ont été calculées à partir des indices d'écotoxicité établis par la FAO pour chaque matière active. La consommation de matières actives insecticides au Togo a chuté régulièrement jusqu'à un litre/hectare, du même niveau que l'Australie qui recourt par ailleurs aux variétés génétiquement modifiées. La charge toxicologique, pesant sur l'homme mais aussi sur divers éléments de la faune comme les abeilles ou les daphnés des cours d'eau, a diminué quoique de manière moins régulière. Cette évolution est la conséquence d'une protection limitée depuis trois décennies à moins de six traitements et de l'adoption de nouvelles générations de molécules insecticides. Au Togo, l'utilisation des insecticides dans la culture cotonnière a évolué dans une direction plus compatible avec le souci de la santé humaine et de la préservation de l'environnement, mais cette évolution est extrapolable à tous les pays cotonniers de l'Afrique francophone. Il convient de poursuivre l'évolution engagée dans les décisions relatives aux insecticides à commander, en s'inspirant des indicateurs utilisés dans cette étude. (Résumé d'auteur

The development of organic semiconductors for p- and n-type accumulation mode organic electrochemical transistors (OECTs)

The thesis reports on the development of organic semiconductors for p- and n-type accumulation mode organic electrochemical transistors (OECTs). First, the development of a series of alkoxy benzodithiophene (alkoxy-BDT) copolymers is presented. The materials series were prepared and characterised for their electrochemical redox activity in aqueous electrolytes. In addition, the materials were tested in OECTs where the performance differences between the copolymers were related to their microstructure and redox stability. After the successful development of p-type OECT materials, the redox stability of alkoxy-BDT copolymers was investigated, where a strong dependence of the electrochemical redox stability was observed. It was found that alkoxy-BDT copolymers with a large ionisation potential (IP) formed a quinone side product whilst copolymers with small IPs were found to be redox stable. The formation of the quinone structure affects the performance copolymers in OECTs significantly and the formation of the quinone must be avoided for use of materials in OECTs. Based on the results of the alkoxy-BDT copolymer study, a new copolymer was developed showing a high performance in accumulation mode OECTs. It was shown that the choice of the side chain is highly important to facilitate the copolymer with a high ion mobility. Finally, the development of the first accumulation mode ambipolar OECT material is reported. The design strategy for the polymer is presented and it was observed that a large electron affinity (EA) is needed to operate the n-type polymer with a high stability. This demonstration opens the possibility to develop complementary circuits and enable sensing of biomolecules with the aid of enzymatic reactions.Open Acces

Role of the Anion on the Transport and Structure of Organic Mixed Conductors

Organic mixed conductors are increasingly employed in electrochemical devices operating in aqueous solutions that leverage simultaneous transport of ions and electrons. Indeed, their mode of operation relies on changing their doping (oxidation) state by the migration of ions to compensate for electronic charges. Nevertheless, the structural and morphological changes that organic mixed conductors experience when ions and water penetrate the material are not fully understood. Through a combination of electrochemical, gravimetric, and structural characterization, the effects of water and anions with a hydrophilic conjugated polymer are elucidated. Using a series of sodium-ion aqueous salts of varying anion size, hydration shells, and acidity, the links between the nature of the anion and the transport and structural properties of the polymer are systematically studied. Upon doping, ions intercalate in the crystallites, permanently modifying the lattice spacings, and residual water swells the film. The polymer, however, maintains electrochemical reversibility. The performance of electrochemical transistors reveals that doping with larger, less hydrated, anions increases their transconductance but decreases switching speed. This study highlights the complexity of electrolyte-mixed conductor interactions and advances materials design, emphasizing the coupled role of polymer and electrolyte (solvent and ion) in device performance

Operation Mechanism of Organic Electrochemical Transistors as Redox Chemical Transducers

There is intense interest in utilizing the redox activity of Organic Mixed Ionic Electronic Conductors for faradaic chemical sensing. In particular, the investigation of organic electrochemical transistors (OECTs) as biosensors due to their low operational potentials, ease of fabrication (e.g. by inkjet printing), biocompatibility, and large transconductance. It has become common practice in the OECT community to combine both chemical detection and transistor function within the same compartment, assuming that the sensor signal is amplified seamlessly by the sensing OECT. These devices however routinely encounter several challenges whose origins often remained unclear. Some of these challenges are 1) small changes in drain current, contradicting OECT’s oft-touted current-amplifying abilities. 2) Irreversible chemical changes to the semiconducting polymer electrodes. 3) Parasitic side reactions convoluting the sensing signal, exacerbated by applied voltages. In this manuscript, we show that optimization of OECT-based sensors requires more rigorous characterization of electrode potentials to elucidate electrochemical phenomena, a practice that is often largely absent in current reports. Our analysis of fundamental device physics of various OECT architectures shows that despite what a large fraction of the organic bioelectronics community still believes, amperometric OECTs either 1) do not display any transistor behavior, and in fact operate merely as electrodes or 2) Undergo irreversible changes and are extremely complex to calibrate, or both 1) and 2). Indeed, to fully utilize the OECT’s large transconductance, a separate 2-electrode Reaction Cell which is utilized to gate a separate OECT is needed (RC-OECT). In this manuscript, in addition to showing that the RC-OECT resolves the fundamentally and irreconcilably contradicting design principles of amperometric OECTs, we demonstrate that it provides great device and materials design flexibility. Finally, we elucidate the basic principles on how to further optimize the RC-OECT. We believe that our findings will be of great interest to researchers in the fields of bioelectronics as a call to action to re-evaluate present approaches of utilizing OECTs for chemical detection and to help practitioners select materials and designs to optimize redox sensors based on organic semiconductors. </p