An Ultrathin Flexible Single‐Electrode Triboelectric‐Nanogenerator for Mechanical Energy Harvesting and Instantaneous Force Sensing

The trends in miniaturization of electronic devices give rise to the attention of energy harvesting technologies that gathers tiny wattages of power. Here this study demonstrates an ultrathin flexible single electrode triboelectric nanogenerator (S‐TENG) which not only could harvest mechanical energy from human movements and ambient sources, but also could sense instantaneous force without extra energy. The S‐TENG, which features an extremely simple structure, has an average output current of 78 μA, lightening up at least 70 LEDs (light‐emitting diode). Even tapped by bare finger, it exhibits an output current of 1 μA. The detection sensitivity for instantaneous force sensing is about 0.947 μA MPa^?1. Performances of the device are also systematically investigated under various motion types, press force, and triboelectric materials. The S‐TENG has great application prospects in sustainable wearable devices, sustainable medical devices, and smart wireless sensor networks owning to its thinness, light weight, energy harvesting, and sensing capacities.     

High Frequency Thermal Energy Harvesting Using Magnetic Shape Memory Films

A new method for thermal energy harvesting at small temperature difference and high cycling frequency is presented that exploits the unique magnetic properties and actuation capability of magnetic shape memory alloy (MSMA) films. Polycrystalline films of the Ni_50.4Co_3.7Mn_32.8In_13.1 alloy are tailored, showing a large abrupt change of magnetization and low thermal hysteresis well above room temperature. Based on this material, a free‐standing film device is designed that exhibits thermomagnetically induced actuation between a heat source and sink with short heat transfer times. The cycling frequency of the device is tuned by mechanical frequency up‐conversion to over 200 Hz. An integrated pick‐up coil converts the thermally induced change of magnetization as well as the kinetic energy to electricity. For a temperature change of 10 K, the maximum peak power density is in the order of 5 mW cm^‐3.     

Characterization of a novel Photosystem I-LHCI supercomplex isolated from Chlamydomonas reinhardtii under anaerobic (State II) conditions

A novel supercomplex of Photosystem I (PSI) with light harvesting complex I (LHCI) was isolated from the green alga Chlamydomonas reinhardtii. This novel supercomplex is unique as it is the first stable supercomplex of PSI together with its external antenna. The supercomplex contains 256 chlorophylls per reaction center. The supercomplex was isolated under anaerobic conditions and may represent the State II form of the photosynthetic unit. In contrast to previously reported supercomplexes isolated in State I, which contain only 4 LHC I proteins, this supercomplex contains 10-11 LHC I proteins tightly bound to the PSI core. In contrast to plants, no LHC II is tightly bound to the PSI-LHCI supercomplex in State II. Investigation of the energy transfer from the antenna system to the reaction center core shows that the LHC supercomplexes are tightly coupled to the PSI core, not only structurally but also energetically. The excitation energy transfer kinetics are completely dominated by the fast phase, with a near-complete lack of long-lived fluorescence. This tight coupling is in contrast to all reports of energy transfer in PSI-LHCI supercomplexes (in State I), which have so far been described as weakly coupled supercomplexes with low efficiency for excitation energy transfer. These results indicate that there are large and dynamic changes of the PSI-LHCI supercomplex during the acclimation from aerobic (State I) to anaerobic (State II) conditions in Chlamydomonas.     

Coherent phenomena in photosynthetic light harvesting: part two—observations in biological systems

Considerable debate surrounds the question of whether or not quantum mechanics plays a significant, non-trivial role in photosynthetic light harvesting. Many have proposed that quantum superpositions and/or quantum transport phenomena may be responsible for the efficiency and robustness of energy transport present in biological systems. The critical experimental observations comprise the observation of coherent oscillations or “quantum beats” via femtosecond laser spectroscopy, which have been observed in many different light harvesting systems. Part Two of this review aims to provide an overview of experimental observations of energy transfer in the most studied light harvesting systems. Length scales, derived from crystallographic studies, are combined with energy and time scales of the beats observed via spectroscopy. A consensus is emerging that most long-lived (hundreds of femtoseconds) coherent phenomena are of vibrational or vibronic origin, where the latter may result in coherent excitation transport within a protein complex. In contrast, energy transport between proteins is likely to be incoherent in nature. The question of whether evolution has selected for these non-trivial quantum phenomena may be an unanswerable question, as dense packings of chromophores will lead to strong coupling and hence non-trivial quantum phenomena. As such, one cannot discern whether evolution has optimised light harvesting systems for high chromophore density or for the ensuing quantum effects as these are inextricably linked and cannot be switched off.     

Photosystem II antenna complexes CP26 and CP29 are essential for nonphotochemical quenching in Chlamydomonas reinhardtii

Photosystems must balance between light harvesting to fuel the photosynthetic process for CO₂ fixation and mitigating the risk of photodamage due to absorption of light energy in excess. Eukaryotic photosynthetic organisms evolved an array of pigment-binding proteins called light harvesting complexes constituting the external antenna system in the photosystems, where both light harvesting and activation of photoprotective mechanisms occur. In this work, the balancing role of CP29 and CP26 photosystem II antenna subunits was investigated in Chlamydomonas reinhardtii using CRISPR-Cas9 technology to obtain single and double mutants depleted of monomeric antennas. Absence of CP26 and CP29 impaired both photosynthetic efficiency and photoprotection: Excitation energy transfer from external antenna to reaction centre was reduced, and state transitions were completely impaired. Moreover, differently from higher plants, photosystem II monomeric antenna proteins resulted to be essential for photoprotective thermal dissipation of excitation energy by nonphotochemical quenching.     

Triboelectric Nanogenerator Based on Fully Enclosed Rolling Spherical Structure for Harvesting Low‐Frequency Water Wave Energy

Water waves are increasingly regarded as a promising source for large‐scale energy applications. Triboelectric nanogenerators (TENGs) have been recognized as one of the most promising approaches for harvesting wave energy. This work examines a freestanding, fully enclosed TENG that encloses a rolling ball inside a rocking spherical shell. Through the optimization of materials and structural parameters, a spherical TENG of 6 cm in diameter actuated by water waves can provide a peak current of 1 μA over a wide load range from a short‐circuit condition to 10 GΩ, with an instantaneous output power of up to 10 mW. A multielectrode arrangement is also studied to improve the output of the TENG under random wave motions from all directions. Moreover, at a frequency of 1.43 Hz, the wave‐driven TENG can directly drive tens of LEDs and charge a series of supercapacitors to rated voltage within several hours. The stored energy can power an electronic thermometer for 20 min. This rolling‐structured TENG is extremely lightweight, has a simple structure, and is capable of rocking on or in water to harvest wave energy; it provides an innovative and effective approach toward large‐scale blue energy harvesting of oceans and lakes.     

An ultrasonically enhanced inclined settler for microalgae harvesting

Microalgae have vast potential as a sustainable and scalable source of biofuels and bioproducts. However, algae dewatering is a critical challenge that must be addressed. Ultrasonic settling has already been exploited for concentrating various biological cells at relatively small batch volumes and/or low throughput. Typically, these designs are operated in batch or semicontinuous mode, wherein the flow is interrupted and the cells are subsequently harvested. These batch techniques are not well suited for scaleup to the throughput levels required for harvesting microalgae from the large‐scale cultivation operations necessary for a viable algal biofuel industry. This article introduces a novel device for the acoustic harvesting of microalgae. The design is based on the coupling of the acoustophoretic force, acoustic transparent materials, and inclined settling. A filtration efficiency of 70 ± 5% and a concentration factor of 11.6 ± 2.2 were achieved at a flow rate of 25 mL·min^?1 and an energy consumption of 3.6 ± 0.9 kWh·m^?3. The effects of the applied power, flow rate, inlet cell concentration, and inclination were explored. It was found that the filtration efficiency of the device is proportional to the power applied. However, the filtration efficiency experienced a plateau at 100 W L^?1 of power density applied. The filtration efficiency also increased with increasing inlet cell concentration and was inversely proportional to the flow rate. It was also found that the optimum settling angle for maximum concentration factor occurred at an angle of 50 ± 5°. At these optimum conditions, the device had higher filtration efficiency in comparison to other similar devices reported in the previous literature. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 31:414–423, 2015     

Rotating‐Disk‐Based Direct‐Current Triboelectric Nanogenerator

An innovative design is reported of a direct‐current triboelectric nanogenerator (DC‐TENG) based on a rotating disk design for harvesting rotational mechanical energy. The DC‐TENG consists of two disks and two pairs of flexible electric brushes that are made of carbon fiber and contact two electrodes, respectively. During the rotation, two disks have distinct triboelectric polarities for a cyclic in‐plane charge separation between them and an alternating current is generated between the two electrodes. Because of the sliding contact and automatically switch between the electric brushes and the two electrodes, the current is reversed in the second half of the cycle and a direct current is generated. The role that the rotating speed and the segmentation number have is thoroughly investigated and shows that there is direct current enhancement not only at higher speed but also with more segments. The DC‐TENG has been demonstrated as a constant current source for directly and continuously driving electronic devices and/or charging an energy storage unit without a rectifier bridge. This work presents a novel DC‐TENG technology and opens up more potential applications for harvesting rotational mechanical energy and powering electronics.     

Modelling Recolonization of Second-Growth Forest Stands by the North American Red Squirrel Tamiasciurus hudsonicus

In this paper, we present a model for source–sink population dynamics where the locations of source and sink habitats change over time. We do this in the context of the population dynamics of the North American red squirrel, Tamiasciurus hudsonicus, within a forest environment subject to harvesting and regrowth. Harvested patches of forest are initially sinks, then eventually become source habitat again as the forest regrows. At the same time, each harvested patch is gradually recolonized by squirrels from other forest patches. We are interested in the interaction of forest harvesting dynamics with squirrel population dynamics. This depends on the harvesting schedule, and on the choices squirrels make when deciding whether to settle in a mature forest patch or in a recently harvested patch. We find that the time it takes for a second-growth forest patch to be recolonized at the mature forest level is longer than the time required for the habitat quality to be restored to the mature forest level. We also notice that recolonization pressure decreases squirrel populations in neighbouring patches. The connectivity between forest patches and the cutting schedule used also affect the time course of recolonization and steady-state population levels.     

Developing a structure-function model for the cryptophyte phycoerythrin 545 using ultrahigh resolution crystallography and ultrafast laser spectroscopy

Cryptophyte algae differ from cyanobacteria and red algae in the architecture of their photosynthetic light harvesting systems, even though all three are evolutionarily related. Central to cryptophyte light harvesting is the soluble antenna protein phycoerythrin 545 (PE545). The ultrahigh resolution crystal structure of PE545, isolated from a unicellular cryptophyte Rhodomonas CS24, is reported at both 1.1A and 0.97A resolution, revealing details of the conformation and environments of the chromophores. Absorption, emission and polarized steady state spectroscopy (298K, 77K), as well as ultrafast (20fs time resolution) measurements of population dynamics are reported. Coupled with complementary quantum chemical calculations of electronic transitions of the bilins, these enable assignment of spectral absorption characteristics to each chromophore in the structure. Spectral differences between the tetrapyrrole pigments due to chemical differences between bilins, as well as their binding and interaction with the local protein environment are described. Based on these assignments, and considering customized optical properties such as strong coupling, a model for light harvesting by PE545 is developed which explains the fast, directional harvesting of excitation energy. The excitation energy is funnelled from four peripheral pigments (beta158,beta82) into a central chromophore dimer (beta50/beta61) in approximately 1ps. Those chromophores, in turn, transfer the excitation energy to the red absorbing molecules located at the periphery of the complex in approximately 4ps. A final resonance energy transfer step sensitizes just one of the alpha19 bilins on a time scale of 22ps. Furthermore, it is concluded that binding of PE545 to the thylakoid membrane is not essential for efficient energy transfer to the integral membrane chlorophyll a-containing complexes associated with PS-II.     

Irrungen,Wirrungen? The Mehler reaction in relation to cyclic electron transport in C3 plants

Plants not only evolve but also reduce oxygen in photosynthesis. Considerable oxygen uptake occurs during photorespiration of C3 plants. Controversies exist on whether direct oxygen reduction in the Mehler reaction together with associated electron transport is also a major sink of electrons when leaves are exposed to sunlight. Here, preference is given to the view that it is not. Whereas photorespiration consumes ATP, the Mehler reaction does not. In isolated chloroplasts photosynthesizing in the presence of saturating bicarbonate, the Mehler reaction is suppressed. In the water – water cycle of leaves, which includes the Mehler reaction, water is oxidized and electrons flow through Photosystems II and I to oxygen producing water. The known properties of coupled electron transport suggest that the water – water cycle cannot act as an efficient electron sink. Rather, by contributing to thylakoid acidification it plays a role in the control of Photosystem II activity. Cyclic electron transport competes with the Mehler reaction for electrons. Both pathways can help to defray possible ATP deficiencies in the chloroplast stroma, but play a more important role by making intrathylakoid protein protonation possible. This is a necessary step for the dissipation of excess excitation energy as heat. Linear electron flow to oxygen relieves the inhibition of cyclic electron transport, which is observed under excessive reduction of intersystem electron carriers. In turn, cyclic electron transport replaces functions of the linear pathway in the control of Photosystem II when oxygen reduction is decreased at low temperatures or, experimentally, when the oxygen concentration of the gas phase is low. Thus, cyclic electron flow acts in flexible relationship with the water–water cycle to control Photosystem II activity. This revised version was published online in June 2006 with corrections to the Cover Date.     

Some mechanisms of nonspecific antiarrhythmic action of phosphocreatine in acute myocardial ischemia

Using isotope-labeled microspheres (diameter 15 microns) it was shown that phosphocreatine at a dose of 300 mg/kg does not affect the myocardial blood flow in the ischemic zone during acute occlusion (5 min) of the left anterior descending coronary artery (LAD) in dogs. Intravenous administration of NaCl hypertonic solution which contained the same amount of Na+ as 300 mg/kg of phosphocreatinine disodium salt prevented the development of ventricular fibrillation during acute LAD occlusion in dogs. Under these conditions excitation conduction velocity significantly increased. Experiments in isolated intraventricular rabbit septum have showed that the addition of phosphocreatine or phosphocreatinine to the perfusion medium at a concentration of 10 mmole/liter increased excitation conduction velocity in ischemic myocardium. However, when changes in perfusate Na+ and Ca2+ concentration produced by addition of phosphocreatine or phosphocreatinine were compensated, these compounds do not affect excitation conduction velocity. On the other hand, the alterations similar to those produced by the addition of phosphocreatine or phosphocreatinine led to the same increase of excitation conduction velocity. The results obtained indicate an important role of the changes of blood plasma ionic composition on intravenous administration of phosphocreatine in electrophysiological and antiarrhythmic effects of this substance during acute myocardial ischemia.     

A Long Lifetime Aqueous Organic Solar Flow Battery

Monolithically integrated solar flow batteries (SFBs) hold promise as compact stand‐alone energy systems for off‐grid solar electrification. Although considerable research is devoted to studying and improving the round‐trip efficiency of SFBs, little attention is paid to the device lifetime. Herein, a neutral pH aqueous electrolyte SFB with robust organic redox couples and inexpensive silicon‐based photoelectrodes is demonstrated. Enabled by the excellent stability of both electrolytes and protected photoelectrodes, this SFB device exhibits not only unprecedented stable continuous cycling performance over 200 h but also a capacity utilization rate higher than 80%. Moreover, through comprehensive study on the working mechanisms of SFBs, a new theory based on instantaneous solar‐to‐output electricity efficiency toward more optimized device design is developed and a significantly improved solar‐to‐output electricity efficiency of 5.4% from single‐junction silicon photoelectrodes is realized. The design principles presented in this work for extending device lifetime and boosting round trip energy efficiency will make SFBs more competitive for off‐grid applications.     

PROBING PHYCOBILISOME STRUCTURE BY IMMUNO-ELECTRON MICROSCOPY1

By immuno-electron microscopy it was shown that phycoerythrin is located on the outer surface of the phycobilisome and allophycocyanin is on the inside near the photosynthetic membrane in the red alga Porphyridium purpureum (Bory) Drew & Ross (P. cruentum). These findings are consistent with the idea that the phycobilisome junctions as a light harvesting antenna and energy sink, which directs the energy to chlorophyll in the photosynthetic membrane. A technique was devised in which unfixed phycobilisomes, attached to thylakoid vesicles, were separately reacted with three monospecific antisera (to B-phycoerythrin, R-phycocyanin and allophycocyanin) and the reaction products were secondarily marked by reaction with ferritin-conjugated goat-antirabbit gamma globulin fraction. This was subsequently followed by glutaraldehyde fixation and staining with phosphotungstic acid. The entire procedure was carried out on an electron microscope grid. The results confirm the previously proposed phycobilisome structural model.     

A Soft and Robust Spring Based Triboelectric Nanogenerator for Harvesting Arbitrary Directional Vibration Energy and Self‐Powered Vibration Sensing

Vibration is a common mechanical phenomenon and possesses mechanical energy in ambient environment, which can serve as a sustainable source of power for equipment and devices if it can be effectively collected. In the present work, a novel soft and robust triboelectric nanogenerator (TENG) made of a silicone rubber‐spring helical structure with nanocomposite‐based elastomeric electrodes is proposed. Such a spring based TENG (S‐TENG) structure operates in the contact‐separation mode upon vibrating and can effectively convert mechanical energy from ambient excitation into electrical energy. The two fundamental vibration modes resulting from the vertical and horizontal excitation are analyzed theoretically, numerically, and experimentally. Under the resonant states of the S‐TENG, its peak power density is found to be 240 and 45 mW m^?2 with an external load of 10 MΩ and an acceleration amplitude of 23 m s^?2. Additionally, the dependence of the S‐TENG's output signal on the ambient excitation can be used as a prime self‐powered active vibration sensor that can be applied to monitor the acceleration and frequency of the ambient excitation. Therefore, the newly designed S‐TENG has a great potential in harvesting arbitrary directional vibration energy and serving as a self‐powered vibration sensor.     

Crystal structure of plant light‐harvesting complex shows the active,energy‐transmitting state

Plants dissipate excess excitation energy as heat by non‐photochemical quenching (NPQ). NPQ has been thought to resemble in vitro aggregation quenching of the major antenna complex, light harvesting complex of photosystem II (LHC‐II). Both processes are widely believed to involve a conformational change that creates a quenching centre of two neighbouring pigments within the complex. Using recombinant LHC‐II lacking the pigments implicated in quenching, we show that they have no particular role. Single crystals of LHC‐II emit strong, orientation‐dependent fluorescence with an emission maximum at 680 nm. The average lifetime of the main 680 nm crystal emission at 100 K is 1.31 ns, but only 0.39 ns for LHC‐II aggregates under identical conditions. The strong emission and comparatively long fluorescence lifetimes of single LHC‐II crystals indicate that the complex is unquenched, and that therefore the crystal structure shows the active, energy‐transmitting state of LHC‐II. We conclude that quenching of excitation energy in the light‐harvesting antenna is due to the molecular interaction with external pigments in vitro or other pigment–protein complexes such as PsbS in vivo, and does not require a conformational change within the complex.     

Plastoquinone redox control of chloroplast thylakoid protein phosphorylation and distribution of excitation energy between photosystems: discovery,background, implications

Chloroplast thylakoid protein phosphorylation was discovered, and the most conspicuous phosphoproteins identified, by John Bennett at Warwick University. His initial findings were published in 1977. The phosphoproteins included apoproteins of chloroplast light harvesting complex II. Thylakoid protein phosphorylation was shown to influence distribution of excitation energy between Photosystems I and II in 1979, during a visit by Bennett to the laboratory of Charles J. Arntzen at the University of Illinois at Urbana-Champaign. That work was published by Bennett, Katherine E. Steinback and Arntzen in 1980. Control of both protein phosphorylation and excitation energy distribution by the redox state of the plastoquinone pool was first established in 1980 during the author's visit to Arntzen's laboratory. The experiments were prompted by the realization that coupling between redox state of an inter-photosystem electron carrier and excitation energy distribution provides a concrete mechanism for adaptations known as state transitions. This work was published by Allen, Bennett, Steinback, and Arntzen in 1981. This discovery and its background are discussed, together with some implications for photosynthesis and for research generally. This minireview is a personal account of the Urbana-Warwick and related collaborations in 1979–83: it includes impressions, conjectures, and acknowledgements for which the author is solely responsible. This revised version was published online in June 2006 with corrections to the Cover Date.     

Nonlinear mechanism for weak photon emission from biosystems

The nonlinear mechanism for the origin of the weak biophoton emission from biological systems is suggested. The mechanism is based on the properties of solitons that provide energy transfer and charge transport in metabolic processes. Such soliton states are formed in alpha-helical proteins. Account of the electron-phonon interaction in macromolecules results in the self-trapping of electrons in a localized soliton-like state, known as Davydov's solitons. The important role of the helical symmetry of macromolecules is elucidated for the formation, stability and dynamical properties of solitons. It is shown that the soliton with the lowest energy has an inner structure with the many-hump envelope. The total probability of the excitation in the helix is characterized by interspine oscillations with the frequency of oscillations, proportional to the soliton velocity. The radiative life-time of a soliton is calculated and shown to exceed the life-time of an excitation on an isolated peptide group by several orders of magnitude.     

The phasic structure of early disorders of functional capacity following irradiation in rats

In experiments with rats it was shown that an early decrease in physical efficiency after irradiation involves some partially mutually superimposed phases. Phases of excitation, hypokinesia and neurological disorders are identified in early transient inefficiency followed by phases of an early transient diminution of efficiency and a reversible disturbance of the accomplishment of the known operations. Simultaneously, there is a phase of an irreversible decrease of the informational capacity of CNS as well as the tolerance to early transient in efficiency upon repeated exposure.     

Long Distance Transport in Macrocystis integrifolia: III. MOVEMENT OF THO

Movement of THO and tritium-labeled photoassimilate was studied in intact fronds and frond cuttings of Macrocystis integrifolia following labeling of a mature blade by tritiated water. Both THO and tritium-labeled assimilate moved from the source blade to sink areas at velocities comparable to those recorded earlier for ¹⁴C- and ³²P-labeled compounds. In intact fronds and frond cuttings, THO and tritium-labeled assimilate showed a declining gradient with increasing distance from the source. In the exudate collected from the basal cut end of the frond, there was a marked increase in radioactivity with time in the photoassimilate, but no such gradient was evident for THO. These results support the idea that, although both tritium-labeled assimilate and THO move in the sieve elements, THO is rapidly exchanged with water in the tissues surrounding the sieve elements. Finally, it is shown that THO is transported to the sink and there “unloaded”; indeed, it can move out of the plant itself. The data on velocity and directionality of transport as well as unloading of THO at the sink are discussed, along with computations on specific mass transfer, and favor the idea that Münch's pressure-flow hypothesis is applicable in Macrocystis for long distance translocation of photoassimilates.