Synthesis of Carbon–Nitrogen–Phosphorous Materials with an Unprecedented High Amount of Phosphorous toward an Efficient Fire‐Retardant Material

Phosphorus incorporation into carbon can greatly modify its chemical, electronic, and thermal stability properties. To date this has been limited to low levels of phosphorus. Now a simple, large‐scale synthesis of carbon–nitrogen–phosphorus (CNP) materials is reported with tunable elemental composition, leading to excellent thermal stability to oxidation and fire‐retardant properties. The synthesis consists of using monomers that are liquid at high temperatures as the reaction precursors. The molten‐state stage leads to good monomer miscibility and enhanced reactivity at high temperatures and formation of CNP materials with up to 32 wt % phosphorus incorporation. The CNP composition and fire‐retardant properties can be tuned by modifying the starting monomers ratio and the final calcination temperature. The CNP materials demonstrate great resistance to oxidation and excellent fire‐retardant properties, with up to 90 % of the materials preserved upon heating to 800 °C in air.     

Selective biomolecular nanoarrays for parallel single-molecule investigations

The ability to direct the self-assembly of biomolecules on surfaces with true nanoscale control is key for the creation of functional substrates. Herein we report the fabrication of nanoscale biomolecular arrays via selective self-assembly on nanopatterned surfaces and minimized nonspecific adsorption. We demonstrate that the platform developed allows for the simultaneous screening of specific protein-DNA binding events at the single-molecule level. The strategy presented here is generally applicable and enables high-throughput monitoring of biological activity in real time and with single-molecule resolution.     

Phase transition of a second kind in nickel as observed through optical reflection under pressure

The magnetic permeability of materials at optical frequencies is usually suggested in the literature to be $\mu =1$. In this case one cannot expect to measure the magnetic second order phase transition at optical frequencies. The main novel idea of this paper is that the magnetic permeability μ is not equal to 1 for optical frequency and a phase transition of magnetism was measured experimentally with an optical frequency. In particular, this work presents the detection of a magnetic second order phase transition in nickel with temperature and at different pressures, by reflectivity measurements at an optical frequency. Based on our experiments the magnetic permeability is calculated as a function of temperature for pressures of 0.3, 5 and 10 GPa attained in a diamond anvil cell (DAC).     

Location-allocation models for traffic police patrol vehicles on an interurban network

This research investigates the traffic police routine patrol vehicle (RPV) assignment problem on an interurban road network through a series of integer linear programs. The traffic police RPV’s main task, like other emergency services, is to handle calls-for-service. Emergency services allocation models are generally based on the shortest path algorithm however, the traffic police RPV also handles other roles, namely patrolling to create a presence that acts as a deterrence, and issuing tickets to offenders. The RPVs need to be located dynamically on both hazardous sections and on roads with heavy traffic in order to increase their presence and conspicuousness, in an attempt to prevent or reduce traffic offences, road accidents and traffic congestion. Due to the importance of the traffic patrol vehicle’s location with regard to their additional roles, allocation of the RPVs adheres to an exogenous, legal, time-to-arrival constraint. We develop location-allocation models and apply them to a case study of the road network in northern Israel. The results of the four models are compared to each other and in relation to the current chosen locations. The multiple formulations provide alternatives that jointly account for road safety and policing objectives which aid decision-makers in the selection of their preferred RPV assignments. The results of the models present a location-allocation configuration per RPV per shift with full call-for-service coverage whilst maximizing police presence and conspicuousness as a proxy for road safety.     

Efficient Water Cleaning by Self-standing Carbon Nitride Films Derived from Supramolecular Hydrogels

The design of efficient self-standing hybrid systems for water purification that combines good adsorption properties with high photodegradation ability is highly challenging owing to the difficulty in simultaneously controlling the band structure and porosity of a semiconductor while maintaining its self-standing nature. Here, we report the synthesis of carbon-rich carbon nitride self-standing filters from supramolecular hydrogels composed of melamine and cyanobenzoic acid. The influence of the chemical structure on the properties of the hydrogels and the final films was studied by tuning parameters such as monomer nature, molar ratio, and pyrolysis temperature. Thanks to their ability to combine the adsorption and photodegradation of organic pollutants, the prepared self-standing films showed remarkable activity and stability in flow conditions (>95 % efficiency after 10 consecutive cycles). Additionally, the photocatalytic activity of the films was assessed in the powder form for the hydrogen evolution reaction and photocurrent generation in a photoelectrochemical cell. The reported work opens opportunities for the controlled synthesis of multifunctional filters for water purification and other energy-related and sustainable technologies.     

Crystallographic report: Trimethylaminedibromopropoxycarbonylborane

The conformation around the boron atom is nearly tetrahedral, with Br? B? Br bond angles of 109.14(19)° and slightly wider N? B? C bond angles up to 113.6(3)°. Copyright © 2005 John Wiley & Sons, Ltd.     

Negative curvature from a cohomological viewpoint and cocycle superrigidity

In the framework of general negatively curved spaces, we present new superrigidity results and introduce new techniques based on bounded cohomology. This applies to irreducible lattices, and more generally to cocycles, of products of arbitrary locally compact groups. Together with a new vanishing result for higher rank groups, this also generalizes and unifies all previously known results in that direction. The non-vanishing results provide a large class of examples for our results on orbit equivalence rigidity (Monod and Shalom, Ann. of Math., in press). We prove the ‘toy-case’ of actions on trees. To cite this article: N. Monod, Y. Shalom, C. R. Acad. Sci. Paris, Ser. I 337 (2003).     

Relaxation dispersion in MRI induced by fictitious magnetic fields

A new method entitled Relaxation Along a Fictitious Field (RAFF) was recently introduced for investigating relaxations in rotating frames of rank ≥ 2. RAFF generates a fictitious field (E) by applying frequency-swept pulses with sine and cosine amplitude and frequency modulation operating in a sub-adiabatic regime. In the present work, MRI contrast is created by varying the orientation of E, i.e. the angle ε between E and the z″ axis of the second rotating frame. When ε > 45°, the amplitude of the fictitious field E generated during RAFF is significantly larger than the RF field amplitude used for transmitting the sine/cosine pulses. Relaxation during RAFF was investigated using an invariant-trajectory approach and the Bloch-McConnell formalism. Dipole-dipole interactions between identical (like) spins and anisochronous exchange (e.g., exchange between spins with different chemical shifts) in the fast exchange regime were considered. Experimental verifications were performed in vivo in human and mouse brain. Theoretical and experimental results demonstrated that changes in ε induced a dispersion of the relaxation rate constants. The fastest relaxation was achieved at ε ≈ 56°, where the averaged contributions from transverse components during the pulse are maximal and the contribution from longitudinal components are minimal. RAFF relaxation dispersion was compared with the relaxation dispersion achieved with off-resonance spin lock T(?ρ) experiments. As compared with the off-resonance spin lock T(?ρ) method, a slower rotating frame relaxation rate was observed with RAFF, which under certain experimental conditions is desirable.