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We have studied the adhesion state (also denoted by docking state) of lipid vesicles as induced by the divalent ions Ca or Mg at well-controlled ion concentration, lipid composition, and charge density. The bilayer structure and the interbilayer distance in the docking state were analyzed by small-angle x-ray scattering. A strong adhesion state was observed for DOPC:DOPS vesicles, indicating like-charge attraction resulting from ion correlations. The observed interbilayer separations of ∼1.6 nm agree quantitatively with the predictions of electrostatics in the strong coupling regime. Although this phenomenon was observed when mixing anionic and zwitterionic (or neutral) lipids, pure anionic membranes (DOPS) with highest charge density σ resulted in a direct phase transition to a multilamellar state, which must be accompanied by rupture and fusion of vesicles. To extend the structural assay toward protein-controlled docking and fusion, we have characterized reconstituted N-ethylmaleimide-sensitive factor attachment protein receptors in controlled proteoliposome suspensions by small-angle x-ray scattering.

Based on both adaptive and fuzzy control techniques, this paper proposes a faulttolerant control (FTC) approach for near space vehicle (NSV) re-entry attitude dynamics with a stuck actuator fault. A Takagi-Sugeno fuzzy model is used to describe complex NSV attitude dynamics. The principle of this FTC approach is to design an iterative learning observer, which is used to estimate the system state and produce control input adjustment and then to reconfigure the control law to compensate for the effect of the stuck actuator. The FTC scheme ensures that the NSV output dynamics asymptotically track that of a reference model under both fault-free conditions and with a stuck actuator. The boundedness of the error dynamics is analysed using the Lyapunov stability theory. Finally, simulation results are given to illustrate the effectiveness and potential of the proposed FTC technique.

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Abstract-Functional coupling between the motor cortex and muscle activity is usually detected and characterised using the spectral method of cortico-muscular coherence (CMC). This functional coupling occurs with a time delay which, if not properly accounted for, may decrease the coherence and make the synchrony difficult to detect. In this paper we introduce the concept of cortico-muscular coherence with time lag (CMCTL), that is the coherence between segments of motor cortex electroencephalogram (EEG) and electromyography (EMG) signals displaced from a central observation point. This concept is motivated by the need to compensate for the unknown delay between coupled cortex and muscle processes. We demonstrate using simulated data that under certain conditions the time lag between EEG and EMG segments at points of local maxima of CMCTL corresponds to the average delay along the involved cortico-muscular conduction pathways. Using neurophysiological data, we then show that CMCTL with appropriate time lag enhances the coherence between cortical and muscle signals, and that time lags which correspond to local maxima of CMCTL provide estimates of delays involved in cortico-muscular coupling that are consistent with the underlying physiology.

Transmembrane β-peptides are promising candidates for the design of well-controlled membrane anchors in lipid membranes. Here, we present the synthesis of transmembrane β-peptides with and without tryptophan anchors, as well as a novel iodine-labeled d-β(3) -amino acid. By using one or more of the heavy-atom labeled amino acids as markers, the orientation of the helical peptide was inferred based on the electron-density profile determined by X-ray reflectivity. The β-peptides were synthesized through manual Fmoc-based solid-phase peptide synthesis (SPPS) and reconstituted in unilamellar vesicles forming a right-handed 314 -helix secondary structure, as shown by circular dichroism spectroscopy. We then integrated the β-peptide into solid-supported membrane stacks and carried out X-ray reflectivity and grazing incidence small-angle X-ray scattering to determine the β-peptide orientation and its effect on the membrane bilayers. These β-peptides adopt a well-ordered transmembrane motif in the solid-supported model membrane, maintaining the basic structure of the original bilayer with some distinct alterations. Notably, the helical tilt angle, which accommodates the positive hydrophobic mismatch, induces a tilt of the acyl chains. The tilted chains, in turn, lead to a membrane thinning effect.

We have investigated the structure and interaction of solid-supported multilamellar phospholipid bilayers in view of stalk formation as model systems for membrane fusion. The multi-component bilayers were composed of ternary and quaternary mixtures, containing phosphatidylcholines, phosphatidylethanolamines, sphingomyelin, cholesterol, diacylglycerol, and phosphatidylinositol. Analysis of the obtained electron density profiles and the pressure-distance curves reveals systematic changes in structure and hydration repulsion. The osmotic pressure needed to induce stalk formation at the transition from the fluid lamellar to the rhombohedral phase indicates how membrane fusion properties are modified by bilayer composition.

The surface with the gradient non-wettability intensely appeals to researchers because of its academic significance and applications for directional droplet movement. Herein, we developed a homogeneous structure superhydrophobic surface with the gradient non-wettability by a combination strategy of chemical etching and vapor diffusion modification. As a consequence, the as-prepared surface exhibits a remarkable gradient characteristic of water repellency, and the water contact angle is mainly located within the range of 162 ± 0.5 to 149 ± 0.4°. Meanwhile, the sliding angle also exhibits a corresponding change from 3 to 11°. On this basis, the gradient characteristic of non-wettability induces the distinguishing droplet adhesion on the surface, that is, from 19 μN for the most hydrophobic end to 57 μN for the opposite one. Because of the difference of the water adhesion force, droplets on the as-prepared surface can well roll alongside a specific direction (i.e., gradient direction of nonwettability). In terms of dynamic impact droplets, they can rapidly rebound off the sample surface with the short contact time of 12.8 ms, and the finally fallen droplets mainly deviate toward weaker regions because of water repellency. To analyze this phenomenon, it is found that the asymmetric mechanic behavior is mainly caused by the unbalanced retraction force between the both ends of the impact droplet. This work provides a novel strategy to construct the homogeneous structure superhydrophobic surface with the gradient non-wettability for the applications in the droplet movement control or transport.