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Biomechanical energy harvesting-generating electricity from people during daily activities-is a promising alternative to batteries for powering increasingly sophisticated portable devices. We recently developed a wearable knee-mounted energy harvesting device that generated electricity during human walking. In this methods-focused paper, we explain the physiological principles that guided our design process and present a detailed description of our device design with an emphasis on new analyses.Effectively harvesting energy from walking requires a small lightweight device that efficiently converts intermittent, bi-directional, low speed and high torque mechanical power to electricity, and selectively engages power generation to assist muscles in performing negative mechanical work. To achieve this, our device used a one-way clutch to transmit only knee extension motions, a spur gear transmission to amplify the angular speed, a brushless DC rotary magnetic generator to convert the mechanical power into electrical power, a control system to determine when to open and close the power generation circuit based on measurements of knee angle, and a customized orthopaedic knee brace to distribute the device reaction torque over a large leg surface area.The device selectively engaged power generation towards the end of swing extension, assisting knee flexor muscles by producing substantial flexion torque (6.4 Nm), and efficiently converted the input mechanical power into electricity (54.6%). Consequently, six subjects walking at 1.5 m/s generated 4.8 +/- 0.8 W of electrical power with only a 5.0 +/- 21 W increase in metabolic cost.Biomechanical energy harvesting is capable of generating substantial amounts of electrical power from walking with little additional user effort making future versions of this technology particularly promising for charging portable medical devices.

El éxito de las perovskitas orgánico-inorgánicas en optoelectrónica está dictado por la compleja interacción entre varios fenómenos microscópicos subyacentes. Se supone que la dinámica estructural de los cationes orgánicos y la subred inorgánica después de la fotoexcitación tienen un efecto directo sobre las propiedades del material, lo que afecta el rendimiento general del dispositivo. Aquí, utilizamos la espectroscopia electrónica bidimensional (2D) detectada por heterodino ultrarrápida para revelar los modos vibracionales de excitación impulsiva de la perovskita de yoduro de plomo de metilamonio (MA), que impulsan la distorsión estructural después de la fotoexcitación. El análisis vibracional de los datos medidos nos permite monitorear el movimiento libracional evolucionado en el tiempo del catión MA junto con las coherencias vibracionales de la sub-red inorgánica. El análisis de ondículas de las coherencias vibratorias observadas revela la generación coherente del movimiento libracional del catión MA dentro de ~300 fs complementado con la evolución coherente del movimiento esquelético inorgánico. Para racionalizar esta constatación, empleamos los sencillos de interacción de configuración (CIS), que respaldan nuestras observaciones experimentales de la generación coherente de movimientos libracionales en el catión MA y resaltan la importancia de la interacción anarmónica entre el catión MA y la subretícula inorgánica. Además, nuestros cálculos teóricos avanzados predicen la transferencia de la coherencia vibratoria fotoinducida del catión MA a la sub-red inorgánica, lo que lleva a la reorganización de la red para formar un estado polarónico con una larga vida útil. Nuestro estudio descubre la interacción del catión orgánico y la subretícula inorgánica durante la formación del polarón, lo que puede conducir a nuevos principios de diseño para la próxima generación de materiales de células solares de perovskita. Le succès des pérovskites organiques-inorganiques en optoélectronique est dicté par l'interaction complexe entre divers phénomènes microscopiques sous-jacents. La dynamique structurelle des cations organiques et le sous-réseau inorganique après photoexcitation sont supposés avoir un effet direct sur les propriétés du matériau, affectant ainsi la performance globale du dispositif. Ici, nous utilisons la spectroscopie électronique bidimensionnelle (2D) à détection hétérodyne ultra-rapide pour révéler les modes vibratoires excités de manière impulsive de la pérovskite d'iodure de plomb de méthylammonium (MA), qui entraînent la distorsion structurelle après photoexcitation. L'analyse vibratoire des données mesurées nous permet de surveiller le mouvement libratoire du cation MA en fonction du temps ainsi que les cohérences vibratoires du sous-réseau inorganique. L'analyse par ondelettes des cohérences vibrationnelles observées révèle la génération cohérente du mouvement librationnel du cation MA dans ∼300 fs complétée par l'évolution cohérente du mouvement squelettique inorganique. Pour rationaliser cette observation, nous avons utilisé les simples d'interaction de configuration (CIS), qui soutiennent nos observations expérimentales de la génération cohérente de mouvements librationnels dans le cation MA et soulignent l'importance de l'interaction anharmonique entre le cation MA et le sous-réseau inorganique. De plus, nos calculs théoriques avancés prédisent le transfert de la cohérence vibrationnelle photoinduite du cation MA au sous-réseau inorganique, conduisant à la réorganisation du réseau pour former un état polaronique avec une longue durée de vie. Notre étude révèle l'interaction du cation organique et du sous-réseau inorganique lors de la formation du polaron, ce qui peut conduire à de nouveaux principes de conception pour la prochaine génération de matériaux de cellules solaires en pérovskite. The success of organic–inorganic perovskites in optoelectronics is dictated by the complex interplay between various underlying microscopic phenomena. The structural dynamics of organic cations and the inorganic sublattice after photoexcitation are hypothesized to have a direct effect on the material properties, thereby affecting the overall device performance. Here, we use ultrafast heterodyne-detected two-dimensional (2D) electronic spectroscopy to reveal impulsively excited vibrational modes of methylammonium (MA) lead iodide perovskite, which drive the structural distortion after photoexcitation. Vibrational analysis of the measured data allows us to monitor the time-evolved librational motion of the MA cation along with the vibrational coherences of the inorganic sublattice. Wavelet analysis of the observed vibrational coherences reveals the coherent generation of the librational motion of the MA cation within ∼300 fs complemented with the coherent evolution of the inorganic skeletal motion. To rationalize this observation, we employed the configuration interaction singles (CIS), which support our experimental observations of the coherent generation of librational motions in the MA cation and highlight the importance of the anharmonic interaction between the MA cation and the inorganic sublattice. Moreover, our advanced theoretical calculations predict the transfer of the photoinduced vibrational coherence from the MA cation to the inorganic sublattice, leading to reorganization of the lattice to form a polaronic state with a long lifetime. Our study uncovers the interplay of the organic cation and inorganic sublattice during formation of the polaron, which may lead to novel design principles for the next generation of perovskite solar cell materials. إن نجاح البيروفسكايت العضوي غير العضوي في الإلكترونيات البصرية يمليه التفاعل المعقد بين الظواهر المجهرية الكامنة المختلفة. من المفترض أن يكون للديناميكيات الهيكلية للكاتيونات العضوية والشبكة الفرعية غير العضوية بعد الاستثارة الضوئية تأثير مباشر على خصائص المادة، مما يؤثر على الأداء العام للجهاز. هنا، نستخدم التحليل الطيفي الإلكتروني ثنائي الأبعاد (2D) المكتشف من قبل هتروداين فائق السرعة للكشف عن الأنماط الاهتزازية المتحمسة للميثيلامونيوم (MA) بيروفسكايت يوديد الرصاص، والتي تدفع التشوه الهيكلي بعد الإثارة الضوئية. يسمح لنا التحليل الاهتزازي للبيانات المقاسة بمراقبة الحركة المكتبية التي تطورت بمرور الوقت لكاتيون MA جنبًا إلى جنب مع التماسك الاهتزازي للشبكة الفرعية غير العضوية. يكشف تحليل الموجات للترابطات الاهتزازية المرصودة عن التوليد المتماسك للحركة المكتبية لكاتيون MA ضمن 300 قدم مكملة بالتطور المتماسك للحركة الهيكلية غير العضوية. لترشيد هذه الملاحظة، استخدمنا فرادى تفاعل التكوين (CIS)، والتي تدعم ملاحظاتنا التجريبية للجيل المتماسك من الحركات المكتبية في كاتيون MA وتسلط الضوء على أهمية التفاعل اللاانسجامي بين كاتيون MA و sublattice غير العضوي. علاوة على ذلك، تتنبأ حساباتنا النظرية المتقدمة بنقل التماسك الاهتزازي المستحث ضوئيًا من كاتيون MA إلى الشبكة الفرعية غير العضوية، مما يؤدي إلى إعادة تنظيم الشبكة لتشكيل حالة قطبية ذات عمر طويل. تكشف دراستنا عن تفاعل الكاتيون العضوي والشبكة الفرعية غير العضوية أثناء تكوين القطبين، مما قد يؤدي إلى مبادئ تصميم جديدة للجيل القادم من مواد الخلايا الشمسية البيروفسكايتية.

There is evidence for strong functional antagonistic interactions between adenosine A2A receptors (A2ARs) and dopamine D2 receptors (D2Rs). Although a close physical interaction between both receptors has recently been shown using co-immunoprecipitation and co-localization assays, the existence of a A2AR-D2R protein-protein interaction still had to be demonstrated in intact living cells. In the present work, fluorescence resonance energy transfer (FRET) and bioluminescence resonance energy transfer (BRET) techniques were used to confirm the occurrence of A2AR-D2R interactions in co-transfected cells. The degree of A2AR-D2R heteromerization, measured by BRET, did not vary after receptor activation with selective agonists, alone or in combination. BRET competition experiments were performed using a chimeric D2R-D1R in which helices 5 and 6, the third intracellular loop (I3), and the third extracellular loop (E3) of the D2R were replaced by those of the dopamine D1 receptor (D1R). Although the wild type D2R was able to decrease the BRET signal, the chimera failed to achieve any effect. This suggests that the helix 5-I3-helix 6-E3 portion of D2R holds the site(s) for interaction with A2AR. Modeling of A2AR and D2R using a modified rhodopsin template followed by molecular dynamics and docking simulations gave essentially two different possible modes of interaction between D2R and A2AR. In the most probable one, helix 5 and/or helix 6 and the N-terminal portion of I3 from D2R approached helix 4 and the C-terminal portion of the C-tail from the A2AR, respectively.

Abstract The development of predictive mathematical models for water management in polymer electrolyte membrane fuel cells requires detailed understanding of water distribution and water transport across the Nafion layer. The anisotropic microstructure of Nafion suggests the measurement of water content and mass transport should be along the fuel cell functional direction, i.e. across the membrane. Non-invasive, high resolution, microscopy measurements of this type are very challenging. We report here the calibration of a minimal mathematical model for diffusive water transport in Nafion against data from high-resolution water content maps determined with a new magnetic resonance imaging methodology developed for this purpose. A mock fuel cell was designed to permit well-controlled wetting and drying boundary conditions. With no chemical potential driving force involved, we assume the water transport behavior will be dominated by diffusion. Moreover we show that, in this context, our model is mathematically equivalent to the traditional permeation models based upon saturation dependent pressure gradients via a capillary pressure ansatz. The non-linear equilibrium water distribution across the Nafion membrane measured in this work suggests a bi-modal diffusivity. The model constructed associates distinct transport behaviors to water contents above and below a critical threshold, consistent with a rearrangement of a micro-structural pore network. The experimental observation and the model prediction agree with the primary features of Weber's model of Nafion, which predicts distinct modes of transport for hydration fronts traversing the through-plane direction of the membrane.

Brain-Machine Interfaces (BMIs) have shown great potential for generating prosthetic control signals. Translating BMIs into the clinic requires fully implantable, wireless systems; however, current solutions have high power requirements which limit their usability. Lowering this power consumption typically limits the system to a single neural modality, or signal type, and thus to a relatively small clinical market. Here, we address both of these issues by investigating the use of signal power in a single narrow frequency band as a decoding feature for extracting information from electrocorticographic (ECoG), electromyographic (EMG), and intracortical neural data. We have designed and tested the Multi-modal Implantable Neural Interface (MINI), a wireless recording system which extracts and transmits signal power in a single, configurable frequency band. In prerecorded datasets, we used the MINI to explore low frequency signal features and any resulting tradeoff between power savings and decoding performance losses. When processing intracortical data, the MINI achieved a power consumption 89.7% less than a more typical system designed to extract action potential waveforms. When processing ECoG and EMG data, the MINI achieved similar power reductions of 62.7% and 78.8%. At the same time, using the single signal feature extracted by the MINI, we were able to decode all three modalities with less than a 9% drop in accuracy relative to using high-bandwidth, modality-specific signal features. We believe this system architecture can be used to produce a viable, cost-effective, clinical BMI.

ABSTRACT Systems biology postulates the balance between energy production and conservation in optimizing locomotion. Here, we analyzed how mechanical energy production and conservation influenced metabolic energy expenditure in stroke survivors during treadmill walking at different speeds. We used the body center of mass (BCoM) and segmental center of mass to calculate mechanical energy production: external and each segment's mechanical work (Wseg). We also estimated energy conservation by applying the pendular transduction framework (i.e. energy transduction within the step; Rint). Energy conservation was likely optimized by the paretic lower-limb acting as a rigid shaft while the non-paretic limb pushed the BCoM forward at the slower walking speed. Wseg production was characterized by greater movements between the limbs and body, a compensatory strategy used mainly by the non-paretic limbs. Overall, Wseg production following a stroke was characterized by non-paretic upper-limb compensation, but also by an exaggerated lift of the paretic leg. This study also highlights how post-stroke subjects may perform a more economic gait while walking on a treadmill at preferred walking speeds. Complex neural adaptations optimize energy production and conservation at the systems level, and may fundament new insights onto post-stroke neurorehabilitation. This article has and associated First Person interview with the first author of the paper.