The fast kinetics of induction and relaxation of bacteriochlorophyll prompt and delayed fluorescence together with absorption changes of the reaction center (RC) dimer (P) were measured by combination of flashes from laser diodes in intact cells of wild type, carotenoidless (R-26) and cytochrome c 2 deficient (CYCA) mutants of photosynthetic bacteria Rhodobacter sphaeroides. The fluorescence induction under high intensity of continuous light splits into fast and slow rises both overlapped by the (carotenoid and/or bacteriochlorophyll) triplet quenching. The fast phase is purely photochemical as it depends strongly on the number of photons absorbed. The slow phase is the combination of thermal and photochemical reactions and reflects the multiple turnover of the system. Upon short flash, the fluorescence yield cannot reach the maximum due to partial reopening of the RCs by rapid donor and acceptor side reactions. Longer flashes are needed to close the RC completely. Contrary to higher plants, the kinetics of induction and relaxation of the fluorescence yield in bacteria are controlled principally by P þ . The reactions on the quinone side play minor role. The quantitative determination of the cyclic electron transfer rate can be based on calibration to the quantity of P þ . 2797-SympDesign and Engineering of a Light-Activated Potassium Channel

We present measurements on the Kondo effect in a small quantum dot connected strongly to one lead and weakly to the other. The conductance of the dot reveals an offset of the Kondo resonance at zero magnetic field. While the resonance persists in the negative bias regime, it is suppressed in the opposite direction. This demonstrates the pinning of the Kondo resonance to the Fermi levels of the leads. PACS numbers: 72.15.Qm, 73.23.Hk The Kondo effect is a well-known phenomenon in solid state physics [1]-the hybridization of conduction electrons with the localized electron spin of a magnetic impurity atom in a metal leads to an enhancement of resistivity at low temperatures. The current interest stems from the fact that mesoscopic devices such as quantum dots allow one to study such complex solid state phenomena on highly controllable systems [2]. The Kondo effect in quantum dots was proposed in early theoretical work [3,4] and then demonstrated in beautiful experiments by 6] and Cronenwett et al. [7]. The main features of the Kondo effect in quantum dots are a zero-bias conductance resonance, its specific temperature dependence, and a splitting in a magnetic field.The novel feature of realizing Kondo physics in a semiconductor quantum dot is the possibility to apply a finite bias V sd across the sample, which is not possible in the case of an ordinary metal. In contrast to previous work we focus on the nonequilibrium properties of a quantum dot in the Kondo regime with the tunneling barriers connected to the leads with different strengths.The Kondo effect leads to an enhanced local density of states of the quantum dot at the Fermi levels of the electron reservoirs. In the case of symmetric barriers this results in an enhanced conductance at zero bias which is rapidly decreasing for V sd fi 0. Previous measurements [5,7] have been carried out with symmetric barriers, i.e., they met the condition G L G R , where G L,R denote the tunnel couplings of the dot to the left and right barrier, respectively. However, the very essence of the Kondo resonance lies in the fact that it is pinned to the Fermi level of each contact which might also lead to the occurrence of a conductance anomaly at nonzero bias. In related work on single charge traps in tunnel junctions a bias splitting was found [8], while it was not perfectly clear how the barrier transmission of the electron trap was involved.Here, we demonstrate that by tuning a quantum dot into strongly asymmetric coupling an offset of the Kondo conductance resonance to nonzero bias can be observed at B 0 T. This effect is due to the pinning of the resonance to the Fermi level of the more strongly coupled lead.Following the idea of Kondo physics in a dot we build a small quantum dot similar to the one fabricated by Goldhaber-Gordon et al. [5]. Metallic gates are deposited on the top of an AlGaAs͞GaAs heterostructure with its two-dimensional electron gas (2DEG) 50 nm below the surface. The 2DEG has a low temperature mobility of 8 3 10 5 cm 2 ͞V s and a density of 1.6 3 10 1...

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A self-assembled DNA-based molecular device is described which can be switched between three distinct mechanical states. The device consists of two supramolecular “arms” connected by a hinge. The arms can be in a closed, relaxed, or stretched configuration. The operation of the device is monitored by fluorescence resonance energy transfer. Variations in the design of the device have a strong influence on the operation kinetics of the device.

Soft robotics aims at creating systems with improved performance of movement and adaptability in unknown, challenging, environments and with higher level of safety during interactions with humans. This Roadmap on Soft Robotics covers selected aspects for the design of soft robots significantly linked to the area of multifunctional materials, as these are considered a fundamental component in the design of soft robots for an improvement of their peculiar abilities, such as morphing, adaptivity and growth. The roadmap includes different approaches for components and systems design, bioinspired materials, methodologies for building soft robots, strategies for the implementation and control of their functionalities and behaviour, and examples of soft-bodied systems showing abilities across different environments. For each covered topic, the author(s) describe the current status and research directions, current and future challenges, and perspective advances in science and technology to meet the challenges.