Characterization of core-shell nanoparticles by small angle neutron scattering

The Ni₃Si-type nanoparticles dispersed in a mixture of H₂O/D₂O were characterised by SANS using the contrast variation method. The existence of a core-shell structure in the nanoparticles with a Ni₃Si(Al) core and amorphous SiO_x shell is confirmed by the SANS measurements. The nanoparticles were produced by extracting precipitates from a bulk Ni-13.3Si-2Al ( at. %) alloy using electrochemical phase separation technique and were pre-characterised by X-ray diffraction and transmission electron microscopy. By comparing the precipitate morphology in the Ni-Si-Al alloy with the extracted nanoparticles in the SANS measurements, it is clearly established that the precipitates shape and size are unaffected by the extraction process and that the amorphous shell forms on top of the particle core. However, the present measurement could not confirm or exclude the presence of H atoms in the shell structure. PACS 61.12.Ex; 61.12.-q; 61.46.Df; 61.82.Rx     

Pattern formation and ordering in thin films of crystallisable block copolymers

We show that tapping-mode atomic force microscopy provides real-space and time-resolved observations of morphology and pattern formation resulting from crystallisation of annealed thin films of polyethelenoxide or microphase-separated low-molecular-weight hydrogenated poly(butadiene-b-ethyleneoxide) diblock copolymers. Differences in viscoelastic properties allow distinguishing crystalline and molten (amorphous) areas with a nanometer resolution.     

Quantum Pseudo-Telepathy

Quantum information processing is at the crossroads of physics, mathematics and computer science. It is concerned with what we can and cannot do with quantum information that goes beyond the abilities of classical information processing devices. Communication complexity is an area of classical computer science that aims at quantifying the amount of communication necessary to solve distributed computational problems. Quantum communication complexity uses quantum mechanics to reduce the amount of communication that would be classically required. Pseudo-telepathy is a surprising application of quantum information processing to communication complexity. Thanks to entanglement, perhaps the most nonclassical manifestation of quantum mechanics, two or more quantum players can accomplish a distributed task with no need for communication whatsoever, which would be an impossible feat for classical players. After a detailed overview of the principle and purpose of pseudo-telepathy, we present a survey of recent and not-so-recent work on the subject. In particular, we describe and analyse all the pseudo-telepathy games currently known to the authors. Supported in Part by Canada’s Natural Sciences and Engineering Research Council (NSERC), the Canada Research Chair programme and the Canadian Institute for Advanced Research (CIAR). Supported in part by a scholarship from Canada’s NSERC. Supported in part by Canada’s NSERC Québec’s Fonds de recherche sur la nature et les technologies (FQRNT), the CIAR and the Mathematics of Information Technology and Complex Systems Network (MITACS).     

Crystallization of zinc lactate in presence of malic acid

The influence of malic acid, which acts as an impurity on the cooling crystallization of zinc lactate is investigated in this paper by monitoring the relative supersaturation and the number of crystals during crystallization. The presence of malic acid increases the solution solubility and makes the metastable zone wider; it also changes the habit of the crystal. The purity of the final products is shown to be influenced by the amount and size of seed crystals, cooling rate, seeding temperature and final temperature, but appears to depend mainly on the particle size and level of supersaturation. Residual supersaturation thresholds are observed that depend on the final temperature. A model is proposed to predict the steady-state supersaturation value from the final temperature at a given impurity concentration. This model is based on Kubota and Gibbs equations.     

A column generation algorithm for tactical timber transportation planning

We present a tactical wood flow model that appears in the context of the Canadian forestry industry, and describe the implementation of a decision support system created for use by an industrial partner. In this problem, mill demands and harvested volumes of a heterogeneous set of log types are given over a multi-period planning horizon. Wood can be stored at the forest roadside before delivery at a financial cost. Rather than solve this as a network linear programme on the basis of out-and-back deliveries, we choose to model this problem as a generalization of a log-truck scheduling problem. By routing and scheduling the trucks in the resolution, this allows us to both anticipate potential backhaul opportunities for cost and fuel savings, and also minimize queuing times at log-loaders, management of which is a major concern in the industry. We model this problem as a mixed integer linear programme and solve it via column generation. The methodology is tested on several case studies.     

Second mode transition in microstructured optical fibers: determination of the critical geometrical parameter and study of the matrix refractive index and effects of cladding size

We carried out a numerical study of the second mode transition in finite-sized, microstructured optical fibers (MOFs) for several values of the matrix refractive index. We determined a unique critical geometrical parameter for the second mode cutoff that is valid for all the matrix refractive indices studied. Finite size effects and extrapolated results for infinite structures are described. Using scaling laws, we provide a generalized phase diagram for solid-core MOFs that is valid for all refractive indices, including those of the promising chalcogenide MOFs.     

A model for the oxidation of Mg(0001) based upon LEED,AES, ELS and work function measurements

The Mg(0001) face is subjected to oxygen adsorption from 0 to 10³ L. Three characteristic stages of oxygen adsorption are detected from 0 to 10 L. The AES signal of clean Mg decays exponentially against exposure with slopes α _ai such that α_A2 (0.75 → 3 L) >α_A1 (0 → 0.75 L)>α_A3 (3 → 10 L). For increasing exposures, they correspond to: (1) a clear (1 × 1)-Mg(0001), (2) a diffuse (1 × 1)-Mg(0001) and (3) a (1 × 1) with a weaker (1 × 1)-R30°-MgO(111) LEED patterns, respectively. At the end of the third stage, a supplementary ($\text{7}\text{×}\text{7}\text{2}\text{)?R19°?MgO(111)}$ pattern is observed. In ELS, a very fast intensity decrease of energy loss peaks due to surface and bulk plasmon excitations of the clean metal is recorded during the first stage. The energy loss peak due to the oxidized surface plasmon excitation reaches a maximum intensity at the end of the second stage. Energy loss peaks to be attributed to excitations in bulk MgO appear during the third stage. The work function of the sample decreases and shows a minimum around 6 L, and then slowly increases. Beyond 10 L, a logarithmic relation between oxide thickness and exposure seems to exist. These results are interpreted by the following sequential processes: stage 1: random oxygen chemisorption followed by oxygen incorporation (α_A1); stage 2: assembling into islands and lateral island growth (α_A2); stage 3: oxide formation (α_A3) and stage 4: oxide thickening. Lattice models describing these processes are proposed and discussed. The influence of surface roughness on the results is emphasized.     

Simultaneous fabrication of superhydrophobic and superhydrophilic polyimide surfaces with low hysteresis

Polyimide is of great interest in the field of MEMS and microtechnology. It is often used for its chemical, thermal, mechanical, and optical properties. In this paper, an original study is performed on controlled variation of polyimide film wettability. A two-step microtexturing method is developed to transform hydrophilic polyimide surfaces into a superhydrophobic surface with low magnitude of hysteresis (Δθ ≈ 0° and contact angle θ ≈ 158°). This method is based on the conception of a new kind of fakir surface with triangular cross-section micropillars, the use of a two-scale roughening, and a C(4)F(8) coating. We demonstrate that the absence of hysteresis is related to a combination of two scales of structuring and the pillar shape. The technology that has been developed results in the simultaneous fabrication of adjacent superhydrophobic and superhydrophilic small areas, which allows an effect of self-positioning of water droplets when deposited on such a checkerboard-like surface.     

Direct functionalisation of group 10 N-heterocyclic carbene complexes for diversity enhancement

The synthesis of alkyne-substituted N-heterocyclic carbene complexes of Pd(II) and Pt(II) is reported. Catalyzed 1,3-dipolar cycloaddition with azides has been applied as a modular way of functionalisation of group 10 transition metal NHC complexes to generate potentially new metallodrugs.