Quasiparticle Dynamics from the Bose–Einstein Condensation to the BCS-Like Regions of the Phase Diagram in YBa2Cu3O7?δ

In the underdoped region of the phase diagram, time-resolved opticalexperiments on quasiparticle recombination dynamics show that the state ischaracterized by a temperature independent energy gap E _g which exists at alltemperatures and has a magnitude which appears inversely proportional todoping. Close to optimum doping another, collective gap becomes visiblesimultaneously, which has a BCS-like temperature dependence and closes atT _c.     

Haptic Interaction Stability With Respect to Grasp Force

This paper addresses the contact instability of admittance control of a haptic interface. A high level of rigidity of the grasp of a subject operating the haptic interface will result in unstable behavior of the haptic interaction. Experiments with a system dedicated to measuring grasp force were performed to explore the conditions when grasp force has reached the critical grasp force that destabilizes the haptic interface. The critical grasp force was quantified for various values of virtual environment parameters. The experimental results are compared to simulation results obtained with a model of haptic interaction. To improve stability, two methods were applied: one with virtual coupling, the other with a compensator filter. A model was used to define the structure of the compensator filter and to determine the parameters of the virtual coupling and the compensator filter. Experimental and simulation results confirmed an improvement of stability. Both methods allow higher grasp forces of the human operator, and experiments show that the compensator filter allows higher grasp forces than the virtual coupling.     

The cost of attack in competing networks

Real-world attacks can be interpreted as the result of competitive interactions between networks, ranging from predator–prey networks to networks of countries under economic sanctions. Although the purpose of an attack is to damage a target network, it also curtails the ability of the attacker, which must choose the duration and magnitude of an attack to avoid negative impacts on its own functioning. Nevertheless, despite the large number of studies on interconnected networks, the consequences of initiating an attack have never been studied. Here, we address this issue by introducing a model of network competition where a resilient network is willing to partially weaken its own resilience in order to more severely damage a less resilient competitor. The attacking network can take over the competitor''s nodes after their long inactivity. However, owing to a feedback mechanism the takeovers weaken the resilience of the attacking network. We define a conservation law that relates the feedback mechanism to the resilience dynamics for two competing networks. Within this formalism, we determine the cost and optimal duration of an attack, allowing a network to evaluate the risk of initiating hostilities.     

Dynophore-Based Approach in Virtual Screening: A Case of Human DNA Topoisomerase IIα

In this study, we utilized human DNA topoisomerase IIα as a model target to outline a dynophore-based approach to catalytic inhibitor design. Based on MD simulations of a known catalytic inhibitor and the native ATP ligand analog, AMP-PNP, we derived a joint dynophore model that supplements the static structure-based-pharmacophore information with a dynamic component. Subsequently, derived pharmacophore models were employed in a virtual screening campaign of a library of natural compounds. Experimental evaluation identified flavonoid compounds with promising topoisomerase IIα catalytic inhibition and binding studies confirmed interaction with the ATPase domain. We constructed a binding model through docking and extensively investigated it with molecular dynamics MD simulations, essential dynamics, and MM-GBSA free energy calculations, thus reconnecting the new results to the initial dynophore-based screening model. We not only demonstrate a new design strategy that incorporates a dynamic component of molecular recognition, but also highlight new derivates in the established flavonoid class of topoisomerase II inhibitors.     

Stability of Erythrocyte-Derived Nanovesicles Assessed by Light Scattering and Electron Microscopy

Extracellular vesicles (EVs) are gaining increasing amounts of attention due to their potential use in diagnostics and therapy, but the poor reproducibility of the studies that have been conducted on these structures hinders their breakthrough into routine practice. We believe that a better understanding of EVs stability and methods to control their integrity are the key to resolving this issue. In this work, erythrocyte EVs (hbEVs) were isolated by centrifugation from suspensions of human erythrocytes that had been aged in vitro. The isolate was characterised by scanning (SEM) and cryo-transmission electron microscopy (cryo-TEM), flow cytometry (FCM), dynamic/static light scattering (LS), protein electrophoresis, and UV-V spectrometry. The hbEVs were exposed to various conditions (pH (4–10), osmolarity (50–1000 mOsm/L), temperature (15–60 °C), and surfactant Triton X-100 (10–500 μM)). Their stability was evaluated by LS by considering the hydrodynamic radius (R_h), intensity of scattered light (I), and the shape parameter (ρ). The morphology of the hbEVs that had been stored in phosphate-buffered saline with citrate (PBS–citrate) at 4 °C remained consistent for more than 6 months. A change in the media properties (50–1000 mOsm/L, pH 4–10) had no significant effect on the R_h (=100–130 nm). At pH values below 6 and above 8, at temperatures above 45 °C, and in the presence of Triton X-100, hbEVs degradation was indicated by a decrease in I of more than 20%. Due to the simple preparation, homogeneous morphology, and stability of hbEVs under a wide range of conditions, they are considered to be a suitable option for EV reference material.     

Evidence for polarons and itinerant carriers in superconductivity from time-resolved optical measurements on YBa2Cu3O7-△

Time-resoived optical relaxation measurements on time scales from 10^-13 to 10^-8 s as a function of energy (0.8–3 eV) and temperature give evidence for the existence of two different carrier relaxation processes, indicating the presence of two distinct electronic subsystems in the normal state in high-temperature superconductors, one exhibiting band-like relaxation properties and the other those of localized, polaronic states. Both components of the electrodynamic response exhibit significant changes atT _c , indicating that both carrier types may be involved in superconductivity. The experiments also show that both polarons and band-like carriers exist predominantly in the CuO planes, with an out-of-plane component of the order of 10–20% which is close to the experimentally observed occupancy ratio of holes of O ions of the CuO5 pyramids. Spectrally, the superconducting condensate is also found to be coupled to two distinct components in frequency (for both carriers): one below 0.1 eV and one in the range 1.5-2 eV, but with different anisotropies. A natural explanation of these datas is that the two types of carriers correspond to the two phases suggested by the structural data and as such present the first direct evidence of two-component superconductivity. The underdoped sample data can be interpreted as evidence of pre-formed pairs aboveT _c .     

Direct-laser writing of striplines on AgCl single crystals

Experiments on a localized and controlled photo-reduction of silver were carried out on a AgCl single crystal that was exposed to a UV-laser light. Basic parameters such as the peak power and the total energy dose were varied. The study showed that for a pulsed-laser beam with a high peak power (>20 W) the ablation threshold of the AgCl was exceeded, while at lower peak powers no ablation was detected, only a change in the surface morphology. The degree of silver reduction was monitored using EDS microanalyses of the irradiated trace and the crystal matrix. We showed that the formation of photo-reduced silver aggregates decreases the ablation threshold and that the formation of a continuous silver trace on the AgCl single crystal is possible when the power density of the laser beam is further reduced.     

Rapid prototyping system with sub-micrometer resolution for microfluidic applications

We report on a maskless lithography rapid prototyping system for fabrication of microfluidic circuits with sub-micrometer resolution in standard i-line photoresists. The micropatterning system uses the laser direct imaging technique with a focused ultraviolet laser beam and an acousto-optic deflector to steer the beam in two dimensions. The use of an acousto-optic deflector results in high patterning speeds due to absence of moving parts and achieves sub-micrometer beam positioning precision on the photoresist surface. Patterns up to 100 cm² with well defined edges and wall smoothness on the nanometer scale can be obtained. Direct illumination of the photoresist omits high-resolution masks and alignment with the photoresist sample, in turn making the lithography process more time- and cost-effective as well as flexible, with user control throughout the process. The system provides an efficient alternative to existing photolithography techniques and is especially suitable for rapid prototyping and laboratory use.     

New composite films based on MoO<Subscript>3−<Emphasis Type="Italic">x</Emphasis></Subscript> nanowires aligned in a liquid single crystal elastomer matrix

Abstract  

In this study, we report the preparation, structure characterization, and application of new MoO_3−x nanowires, promising candidates for lithium intercalation, hydrogen sensing, and smart windows due to their photochromic property. These nanowires are a mixture of MoO₃ and conductive Mo₅O₁₄ phase and have been used to prepare composite films based on liquid single crystal elastomers (LSCE). The structure, morphology, and thermomechanic behavior of these films are discussed. In particular, we show that the particular combination of molybdenum-based nanowires and LSCEs allows for doping of liquid single crystal elastomers, preserving the pristine mechanical and optical properties of the host matrix.     

Effect of silica/PVC composite coatings on steel-substrate corrosion protection

In this paper we focus on the preparation of thin polymer coatings synthetized from 30-nm and 600-nm silica particles dispersed in polyvinyl chloride (PVC) and deposited on two different steel substrates: duplex DSS 2205 and austenitic AISI 316L steel. We show that a silica surface modification with silane IO₇T₇(OH)₃ (trisilanol isooctyl polyhedral oligomeric silsesquioxane, POSS) significantly improves its dispersion properties when mixed with PVC. For comparison, the surface morphology and surface roughness of PVC coatings filled with both silanated and as-received (non-silanated) silica fillers were analyzed with scanning electron microscopy (SEM) and atomic force microscopy (AFM) when sprayed on the steel surface. The effect of the silica silanization is later on reflected in a decreased average surface roughness in the silanated, compared to non-silanated, silica/PVC-coatings. The wetting properties of the silanated and non-silanated silica/PVC-coatings on DSS 2205 and AISI 316L were investigated using contact-angle and surface-energy measurements, indicating an increased surface hydrophilicity in terms of a decreased static water contact angle and an increased total surface energy compared to the uncoated specimens. Finally, the beneficial corrosion resistance of the silica/PVC coatings was confirmed with potentiodynamic polarization spectroscopy in a 3.5% NaCl solution.