On the Impact of Linear Siloxanated Side Chains on the Molecular Self-Assembling and Charge Transport Properties of Conjugated Polymers

Herein reported is the impact of the functionalization of four different semiconducting polymer structures by a linear siloxane-terminated side-chains. The latter is tetrasiloxane (Si₄) or trisiloxane (Si₃) chains, substituted at their extremity to a pentylene linker. The polymer structure is based on 5,6-difluorobenzothiadiazole comonomer (PF2), a diketopyrrolopyrrole unit (PDPP-TT), a naphtalediimide unit (PNDI-T₂), and a poly[bis(thiophen-2-yl)thieno[3,2,b]thiophene (PBTTT). The properties of these siloxane-functionalized polymers are scrutinized and compared with the ones of their alkyl-substituted polymer analogues. The impact of the alkyl-to-siloxane chain substitution clearly depends on the molecular section of the side chains. When a branched 2-octyldodecyl chain (C₂₀) is replaced by a Si₄ chain of same molecular section, the greatest impact is the strong increase of the π-stacking overlap of the polymer backbones. This effect leads to a significative enhancement of the charge mobility values of the polymers. As in-plane and out-of-plane mobility are increased simultaneously, this π-overlap enhancement effect happens to be preponderant over the polymer orientation variations. When a linear tetradecyl chain (C₁₄) is replaced by a linear Si₃ chain of twice larger molecular section, the polymer structure is profoundly affected. While PBTTT-C₁₄ is crystalline and purely edge-on, PBTTT-Si₃ is mesomorphic and shows a mixed face-on/edge-on orientation.     

A belief function-based forecasting link breakage indicator for VANETs

Wireless Networks - In Vehicular Ad-Hoc Networks, a link failure may occur due to non-optimal channel conditions, congestion or node mobility which causes data loss. Common proposed approaches try...     

Conducting and Superconducting BEDT-TTF Based Synmetals

The synthesis, crystal structures and band electronic structures of BEDT-TTF based synmetals are discussed, where BEDT-TTF is bis(ethylenedithio)-tetrathiofulvalene here abbreviated to “ET”. The electrical properties of ET:X salts above their phase transitions are either 1D [for (ET)₂X, where X⁻ = ICl₂⁻, AuBr₂⁻, Au(CN)₂⁻ and Ag(CN)₂⁻], 2D metallic [for (ET)₂X, where X⁻ = I₃⁻, AuI₂⁻, IBr₂⁻ and I₂Br⁻] or 3D metallic [for (ET)Ag₄(CN)₅]. The β-(ET)₂X (X⁻ = I₃⁻, AuI₂⁻ and IBr₂⁻) salts become ambient pressure organic superconductors at 1,4 K (or ∼ 8 K under pressure), 5.0 K, and 2.8 K, respectively. The variation of critical temperatures of this series of β-(ET)₂X salts are correlated to the respective changes in unit cell volume or in the density of electronic states at the Fermi level.     

How is body orientation controlled during somersaulting?

How body orientation is controlled during somersaulting was investigated in 2 experiments that analyzed the kinematics of 223 backward standing somersaults. In Experiment 1, open-loop, initial-condition (flight duration), and prospective (time to contact, or TC?) control strategies were tested as candidates for the regulation of body moment of inertia during the jump. Decreasing between-trials variability of body orientation over time as well as a negative correlation between body angular velocity and TC? suggested that the moment of inertia was regulated prospectively. In Experiment 2, the visual basis for this regulation was examined by asking experts and novices to execute somersaults either with eyes closed or open. Results showed that the prospective regulation observed in the vision condition disappeared in the no-vision condition with the experts, arguing in favor of a visual control during the jump. Such a coupling was absent with the novices, thus illustrating the role played by the perception–action cycle in the learning process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Manual and Automatic Design for UMTS Networks

This paper describes manual and automatic design strategies of UMTS networks. The design aims at adjusting antenna parameters: antenna pattern, tilt and azimuth angles, as well as the common channels' transmitted power to improve the network performance in terms of coverage, capacity, quality of service and service continuity. The manual design strategy is based on an expert system that analyzes different quality criteria of the network and suggests the designer the most effective parameter modifications. The automatic design strategy is based on a Genetic Algorithm that orchestrates the design process. Two optimisation models are considered: the first one uses constant load hypotheses in the network evaluation; the second one takes into account inhomogeneous traffic distribution and utilizes accurate modelling of basic UMTS quantities such as power, load and interference. Detailed examples of network optimization illustrate the effectiveness of the design strategies.     

Quantitative Determination of Brönsted Acid Sites on Zeolites: A New Approach Towards the Chemical Composition of Zeolites

An original quantitative method based on H/D exchange between H₂O/D₂O molecules and the OH groups of different zeolites has been developed for the titration of the Brönsted acid sites present on the solid surface. The measured Brönsted acid sites density appears to be in good agreement with the theoretical amount estimated by the Si/Al ratio. In contrary to classical methods, this non-destructive anhydride method titrates the whole quantity of Brönsted acid sites of zeolites.     

Simultaneous Edge‐on to Face‐on Reorientation and 1D Alignment of Small π‐Conjugated Molecules Using Room‐Temperature Mechanical Rubbing

In this study, room‐temperature mechanical rubbing is used to control the 3D orientation of small π‐conjugated molecular systems in solution‐processed polycrystalline thin films without using any alignment substrate. High absorption dichroic ratio and significant anisotropy in charge carrier mobilities (up to 130) measured in transistor configuration are obtained in rubbed organic films based on the ambipolar quinoidal quaterthiophene (QQT(CN)4). Moreover, a solvent vapor annealing treatment of the rubbed film is found to improve the optical and charge transport anisotropy due to an increased crystallinity. X‐ray diffraction and atomic force microscopy measurements demonstrate that rubbing does not only lead to an excellent 1D orientation of the QQT(CN)4 molecules over large areas but also modifies the orientation of the crystals, moving molecules from an edge‐on to a face‐on configuration. The reasons why a mechanical alignment technique can be used at room temperature for such a polycrystalline film are rationalized, by the plastic characteristics of the QQT(CN)4 layer and the role of the flexible alkyl side chains in the molecular packing. This nearly complete conversion from edge‐on to face‐on orientation by mechanical treatment in polycrystalline small‐molecule‐based thin films opens perspectives in terms of fundamental research and practical applications in organic optoelectronics.     

A Review of Redundant Parallel Kinematic Mechanisms

Parallel kinematic mechanisms (PKM) have received particular attention due to their higher stiffness, increased payload capacity, and agility, when compared to their serial counterparts. Despite these significant advantages, however, most PKM designs, typically, yield limited workspace, problematic singularities, and configuration-dependent stiffness. In response, mechanism redundancy has emerged as an effective tool to address these and other problems. In this paper, we present an in-depth discussion of past research on PKM redundancy. The methodical review of the pertinent literature, first, introduces the concept of redundancy based on the number of actuators and the number of degrees of freedom required to perform a task and, then, discusses the two main types of redundancy according to the mobility of the mechanism, i.e., kinematic and actuation redundancy. Subsequently, research on the design aspects of redundant PKMs, including the various criteria used for design optimization is detailed. Primary advantages of PKM redundancy include workspace enlargement, singularity elimination/ avoidance, and improved joint-torque distribution. In this paper, these advantages are discussed in contrast to the main challenges redundant mechanisms present, such as in motion planning and control, and calibration. Other issues of PKM redundancy, briefly, presented herein for completeness are fault-tolerance, reconfigurability, cable-driven and hyper-redundant PKMs.