Spirobifluorene Dimers: Understanding How The Molecular Assemblies Drive The Electronic Properties

Spirobifluorene (SBF) is one of the most important scaffolds used in the design of organic semi-conductors (OSCs) for electronics. In recent years, among all the structures developed for these applications, SBF dimers have been highlighted due to their great potential in thermally activated delayed fluorescence and in phosphorescent organic light-emitting diodes. Attaching two SBF units generate 10 dimers, each possessing its own structural specificity, which in turn drives its electronic properties. These ten SBF dimers are gathered herein. Understanding how the molecular assembly determines the electronic properties has been one of the pillars of organic electronics. This is the goal of this article. As positional isomerism is a key tool to design OSCs, defining the design guidelines for the SBF scaffold appears of interest for the future of this building block. Herein, the importance of the two main parameters involved in the electrochemical and photophysical properties, namely the nature of the phenyl linkages and the steric congestion between the two SBF units is discussed. The combination of these two parameters drives the electronic properties but their respective weight is different as a function of the regioisomer involved or of the property considered (frontier orbitals energy level, absorption, fluorescence, phosphorescence).     

A unified dynamic neural field model of goal directed eye movements

ABSTRACT

Primates heavily rely on their visual system, which exploits signals of graded precision based on the eccentricity of the target in the visual field. The interactions with the environment involve actively selecting and focusing on visual targets or regions of interest, instead of contemplating an omnidirectional visual flow. Eye-movements specifically allow foveating targets and track their motion. Once a target is brought within the central visual field, eye-movements are usually classified into catch-up saccades (jumping from one orientation or fixation to another) and smooth pursuit (continuously tracking a target with low velocity). Building on existing dynamic neural field equations, we introduce a novel model that incorporates internal projections to better estimate the current target location (associated to a peak of activity). Such estimate is then used to trigger an eye movement, leading to qualitatively different behaviours depending on the dynamics of the whole oculomotor system: (1) fixational eye-movements due to small variations in the weights of projections when the target is stationary, (2) interceptive and catch-up saccades when peaks build and relax on the neural field, (3) smooth pursuit when the peak stabilises near the centre of the field, the system reaching a fixed point attractor. Learning is nevertheless required for tracking a rapidly moving target, and the proposed model thus replicates recent results in the monkey, in which repeated exercise permits the maintenance of the target within in the central visual field at its current (here-and-now) location, despite the delays involved in transmitting retinal signals to the oculomotor neurons.     

Practical Asynchronous Interconnect Network Design

The implementation of interconnect is becoming a significant challenge in modern integrated circuit (IC) design. Both synchronous and asynchronous strategies have been suggested to manage this problem. Creating a low skew clock tree for synchronous inter-block pipeline stages is a significant challenge. Asynchronous interconnect does not require a global clock, and therefore, it has a potential advantage in terms of design effort. This paper presents an asynchronous interconnect design that can be implemented using a standard application-specific IC flow. This design is considered across a range of IC interconnect scenarios. The results demonstrate that there is a region of the design space where the implementation provides an advantage over a synchronous interconnect by removing the need for clocked inter-block pipeline stages, while maintaining high throughput. Further results demonstrate a computer-aided design tool enhancement that would significantly increase this space. A detailed comparison of power, area, and latency of the two strategies is also provided for a range of IC scenarios.     

The mapping of linear recurrence equations on regular arrays

The parallelization of many algorithms can be obtained using space-time transformations which are applied on nested do-loops or on recurrence equations. In this paper, we analyze systems of linear recurrence equations, a generalization of uniform recurrence equations. The first part of the paper describes a method for finding automatically whether such a system can be scheduled by an affine timing function, independent of the size parameter of the algorithm. In the second part, we describe a powerful method that makes it possible to transform linear recurrences into uniform recurrence equations. Both parts rely on results on integral convex polyhedra. Our results are illustrated on the Gauss elimination algorithm and on the Gauss-Jordan diagonalization algorithm. This work was partially funded by the French Coordinated Research ProgramC ³ and by a Grant from the SOREP company     

Hydrothermal synthesis of hydrated vanadium oxide nanobelts using poly (ethylene oxide) as a template

With the aim of obtaining nanodevices as batteries, sensors and fuel cells, we prepared V₂O₅ and V₃O₇·H₂O nanobelts by a simple hydrothermal process using poly (ethylene oxide) (PEO) as a template. The yielding percentage of the nanomaterial is less in polymer-free V₂O₅ nanobelts and material size is also big. It is apparent that PEO used V₃O₇·H₂O form a continuous and relatively homogeneous matrix with a clearly 1–5 μm long and 50–150 nm diameter nanobelts morphology. The SEM micrographs suggest that there is no bulk deposition of polymer on the surface of the nano-crystallites. Strong interaction between the vanadyl group and the polymer during the formation process has been identified by the shifts of the vanadyl vibration peaks. The CV curve of the electrode made of the V₃O₇·H₂O nanobelts have higher current densities than the CV curve of the electrode made of V₂O₅ nanobelts.     

Synthesis method comparison of compositionally complex rare earth-based Ruddlesden–Popper n = 1 T′-type cuprates

The multicomponent approach has been successfully expanded to the Ruddlesden–Popper structure with the synthesis of two different high-entropy cuprate compositions: (La_0.2Nd_0.2Gd_0.2Tb_0.2Dy_0.2)₂CuO₄ and (La_0.2Pr_0.2Nd_0.2Sm_0.2Eu_0.2)₂CuO₄. The effect of synthesis method is explored using both solid-state reaction and polymeric steric entrapment (PSE) methods. It is found that PSE leads to more randomly distributed cation species, providing an advantageous method of synthesis for the growing field of high entropy oxides. In situ high-temperature x-ray diffraction tracks the amorphous to crystalline phase transformation in (La_0.2Nd_0.2Gd_0.2Tb_0.2Dy_0.2)₂CuO₄ powder, synthesized using the PSE method. Using the High-Temperature XRD data, a method for gaining information on the kinetic behavior is also applied. Magnetometry of both compositions indicates ferrimagnetic behavior at low temperatures.     

Consequences of transvaginal follicular puncture on well-being in cows

The purpose of this study was to evaluate the impact of repeated follicular puncture used in the ovum pick-up technique on the welfare of cows. The evaluation relies on the physiological measurement of stress, milk production criteria, immune status, and the histological examination of ovaries. Two groups of five Holstein cows were submitted to epidural anaesthesia and genital palpation with insertion of an intravaginal ultrasound probe for transvaginal puncture (the puncture was not performed in the control group). Animals were manipulated twice a week for 8 weeks (16 manipulation sessions). The blood cortisol concentrations increased after each session; however, the concentrations were the same in both the control and the punctured groups. Two adrenocorticotrophic hormone challenge tests, performed before the first session and after the last session, showed an unchanged adrenal sensitivity through repeated puncture sessions. The transvaginal puncture did not affect milk production, or blood and milk somatic cell counts. Ovariectomies were performed on another group of four Holstein cows at various intervals (0 to 30 days) after five similar puncture sessions. Histological examination of the ovaries 4 days after puncture revealed blood-filled follicles and haemorrhagic foci in ovarian stroma, but the examination 30 days after the last puncture session demonstrated very limited, if any, fibrosis. On the basis of the criteria chosen for this study, repeated transvaginal follicular puncture on its own does not impact adversely on the welfare of cows.     

Is age irrelevant? Perceptions of young and old adult eyewitnesses

In Experiment 1, we videotaped elderly and younger adults (n = 69) reporting their memories of a crime video. The seniors were significantly less accurate than the younger adults. In Experiment 2, participants viewed the "testimony" videotapes and rated the elderly as less credible than the younger adults. In Experiment 3, participant-jurors (n = 302) evaluated transcribed testimonies provided by Experiment 1 participants. The ostensible age of the witnesses was manipulated. Thus, some participants read a senior's testimony believing it was provided by a younger adult and vice versa. Participants were apparently not biased by negative stereotypes of seniors' eyewitness capabilities.     

Rational selection of the optimum MALDI matrix for top-down proteomics by in-source decay

In-source decay (ISD) in MALDI leads to c- and z-fragment ion series enhanced by hydrogen radical donors and is a useful method for sequencing purified peptides and proteins. Until now, most efforts to improve methods using ISD concerned instrumental optimization. The most widely used ISD matrix is 2,5-dihydroxybenzoic acid (DHB). We present here a rational way to select MALDI matrixes likely to enhance ISD for top-down proteomic approaches. Starting from Takayama's model (Takayama, M. J. Am. Soc. Mass Spectrom. 2001, 12, 1044-9), according to which formation of ISD fragments (c and z) would be due to a transfer of hydrogen radical from the matrix to the analyte, we evaluated the hydrogen-donating capacities of matrixes, and thus their ISD abilities, with spirooxazines (hydrogen scavengers). The determined hydrogen-donating abilities of the matrixes are ranked as follows: picolinic acid (PA) > 1,5-diaminonaphtalene (1,5-DAN) > DHB > sinapinic acid > alpha-cyano-4-hydroxycinnamic acid. The ISD enhancement obtained by using 1,5-DAN compared to DHB was confirmed with peptides and proteins. On that basis, a matrix-enhanced ISD approach was successfully applied to sequence peptides and proteins up to approximately 8 kDa. Although PA alone is not suitable for peptide and protein ionization, ISD signals could be further enhanced when PA was used as an additive to 1,5-DAN. The optimized matrix preparation was successfully applied to identify larger proteins by large ISD tag researches in protein databases (BLASTp). Coupled with an adequate separation method, ISD is a promising tool to include in a top-down proteomic strategy.