Characterization and modelling of guillotine constraints

This paper focuses on guillotine cuts which often arise in real-life cutting stock problems. In order to construct a solution verifying guillotine constraints, the first step is to know how to determine whether a given cutting pattern is a guillotine pattern. For this purpose, we first characterize guillotine patterns by proving a necessary and sufficient condition. Then, we propose a polynomial algorithm to check this condition. Based on this mathematical characterization of guillotine patterns, we then show that guillotine constraints can be formulated into linear inequalities. The performance of the algorithm to check guillotine cutting patterns is evaluated by means of computational results.     

A convenient synthetic route to a useful synthon: 4-bromo-2-pyridinecarboxaldehyde

We have developed a novel four-step method to synthesise 4-bromo-2-pyridinecarboxaldehyde, from 2-picoline-N-oxide via 4-nitro-2-pyridinecarboxaldehyde, under mild reaction conditions.     

Oxygen,nitrogen and air broadening of HCN spectral lines at terahertz frequencies

The room-temperature nitrogen- and oxygen-broadening coefficients of hydrogen cyanide spectral lines have been measured in the 0.5–3 THz (17–100 cm^?1) frequency range (purely rotational transitions with 5?J?36) by a continuous-wave terahertz spectrometer based on a photomixing source. An improved version of the Robert and Bonamy semiclassical formalism has been used to calculate the oxygen-broadening coefficients and resulted in a good agreement with these measurements. The nitrogen and oxygen data are combined to provide the air-broadening coefficients as used by the HITRAN database. A significant difference is observed between the measured and tabulated values for transitions with high values of the rotational quantum number. A new polynomial representation is suggested for inclusion in HITRAN. A similar polynomial expression has been derived for the nitrogen broadening to aid the studies of Titan's atmosphere.     

Enantiodivergent synthesis of P-chirogenic phosphines

Several approaches for the enantiodivergent synthesis of P-chirogenic mono- and diphosphines are described, using ephedrine methodology and phosphine borane chemistry. Firstly, both enantiomers of a tertiary phosphine can be obtained starting from the same oxazaphospholidine borane complex, prepared from (+)-ephedrine, when changing the order of addition of the organolithium reagents during the synthetic pathway. The second approach is based on the chlorophosphine boranes, which react with an organolithium reagent, to afford the corresponding phosphines with inversion of configuration. In the case where the chlorophosphine borane reacts with the t-butyl lithium reagent, a metal-halogen exchange occurs to afford the corresponding phosphide borane with retention of the configuration. The reaction of the phosphide borane with an alkyl halide leads to the same phosphine, but with the opposite configuration. Another approach depends on the diastereoselective preparation of the starting oxazaphospholidine borane complex from (?)-ephedrine, which leads according the case, to either one or the other enantiomer of a phosphine. Finally, the synthesis of (R,R)- and (S,S)-1,2-bis(methylphenylphosphino)ethane is also demonstrated using both enantiomers of the P-chirogenic diphosphinite diborane, which simultaneously allows the introduction of alkyl- or aryl substituents on the phosphorus atoms. In summary, these approaches show the great efficiency of the “ephedrine methodology” for the enantiodivergent synthesis of P-chirogenic mono- and diphosphines, and bearing alkyl or aryl substituents.     

Dynamical flow arrest in confined gravity driven flows of soft jammed particles

Using numerical simulations, we study the gravity driven flow of jammed soft disks in confined channels. We demonstrate that confinement results in increasing the yield threshold for the Poiseuille flow, in contrast to the planar Couette flow. By solving a nonlocal flow model for such systems, we show that this effect is due to the correlated dynamics responsible for flow, coupled with the stress heterogeneity imposed for the Poiseuille flow. We also observe that with increasing confinement, the cooperative nature of the flow results in increasing intermittent behavior. Our studies indicate that such features are generic properties of a wide variety of jammed materials.     

Liquid friction on charged surfaces: from hydrodynamic slippage to electrokinetics

Hydrodynamic behavior at the vicinity of a confining wall is closely related to the friction properties of the liquid/solid interface. Here we consider, using molecular dynamics simulations, the electric contribution to friction for charged surfaces, and the induced modification of the hydrodynamic boundary condition at the confining boundary. The consequences of liquid slippage for electrokinetic phenomena, through the coupling between hydrodynamics and electrostatics within the electric double layer, are explored. Strong amplification of electro-osmotic effects is revealed, and the nontrivial effect of surface charge is discussed. This work allows us to reconsider existing experimental data, concerning zeta potentials of hydrophobic surfaces and suggests the possibility to generate "giant" electro-osmotic and electrophoretic effects, with direct applications in microfluidics.     

Nature of adhesion of condensed organic films on platinum by first-principles simulations

Understanding the nature of the adhesion of an organic liquid on a metal surface is of paramount importance for elucidating the stability and chemical reactivity at these complex interfaces. However, to date, the morphology, layering and chemical properties at organic liquid metal interfaces have been rarely known. Using semi-empirical dispersion corrected density functional theory calculations and ab initio molecular dynamics simulations, we show that carbon tetrachloride and ethanol films confined to a platinum surface alter their intrinsic properties and exhibit interfacial reactivity. A few interface carbon tetrachloride (ethanol) molecules adsorb dissociatively (molecularly) on platinum thanks to the surrounding medium. The adsorption strength of the interfacial molecules is consequently increased in the condensed phase as compared to the gas phase. This remarkable effect is rationalized by an interaction energy decomposition model and an electrostatic potential analysis.     

An interfacial chemistry study of methylene diphenyl diisocyanate and tantalum for heat exchanger applications

The interactions between oxidised tantalum and methylene diphenyl diisocyanate (MDI) have been investigated by X-ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectrometry (ToF-SIMS). Thin (approximately 2 nm) and thick layers of polymeric MDI were deposited on tantalum; one set was cured at 200°C, the other dried at ambient temperature (20°C). The thick layers serve as a characteristic pMDI layer, and thin layers contain information relating to the nature of interfacial bonding. By careful fitting of the N1s region contributions relating to interfacial bonding have been established. All spectra show an N^δ+ contribution indicative of acid–base bonding; in the case of the thick films, this is of an intermolecular nature whereas in the thin films, the more intense contribution is a result of such forces between pMDI and substrate. This is confirmed by ToF-SIMS. A lower binding energy component at ca 396 eV on the air-dried thin layer of pMDI is the result of a formal reaction between pMDI and tantalum yielding a nitride-like species in the N1s spectrum.     

A case of polymicrogyria in macaque monkey: impact on anatomy and function of the motor system

Background  

Polymicrogyria is a malformation of the cerebral cortex often resulting in epilepsy or mental retardation. It remains unclear whether this pathology affects the structure and function of the corticospinal (CS) system. The anatomy and histology of the brain of one macaque monkey exhibiting a spontaneous polymicrogyria (PMG monkey) were examined and compared to the brain of normal monkeys. The CS tract was labelled by injecting a neuronal tracer (BDA) unilaterally in a region where low intensity electrical microstimulation elicited contralateral hand movements (presumably the primary motor cortex in the PMG monkey).     

Synthesis of 1,2 diamines under environmentally benign conditions: application for the preparation of imidazolidiniums

An environmentally friendly and economically attractive access to unsymmetrical and symmetrical 1,2-diamines has been developed. Chemoselective N-monoalkylation in water and alcoholic solvents was demonstrated. This method represents a simple and scalable preparation (2-3 steps) of symmetrical and unsymmetrical imidazolidinium salts, precursors of N-Heterocyclic Carbenes.