WIFIP: a web‐based user interface for automated synchrotron beamlines

The beamline control software, through the associated graphical user interface (GUI), is the user access point to the experiment, interacting with synchrotron beamline components and providing automated routines. FIP, the French beamline for the Investigation of Proteins, is a highly automatized macromolecular crystallography (MX) beamline at the European Synchrotron Radiation Facility. On such a beamline, a significant number of users choose to control their experiment remotely. This is often performed with a limited bandwidth and from a large choice of computers and operating systems. Furthermore, this has to be possible in a rapidly evolving experimental environment, where new developments have to be easily integrated. To face these challenges, a light, platform‐independent, control software and associated GUI are required. Here, WIFIP, a web‐based user interface developed at FIP, is described. Further than being the present FIP control interface, WIFIP is also a proof of concept for future MX control software.     

Persistent Random Walks. I. Recurrence Versus Transience

We consider a walker on the line that at each step keeps the same direction with a probability which depends on the time already spent in the direction the walker is currently moving. These walks with memories of variable length can be seen as generalizations of directionally reinforced random walks introduced in Mauldin et al. (Adv Math 117(2):239–252, 1996). We give a complete and usable characterization of the recurrence or transience in terms of the probabilities to switch the direction and we formulate some laws of large numbers. The most fruitful situation emerges when the running times both have an infinite mean. In that case, these properties are related to the behaviour of some embedded random walk with an undefined drift so that these features depend on the asymptotics of the distribution tails related to the persistence times. In the other case, the criterion reduces to a null-drift condition. Finally, we deduce some criteria for a wider class of persistent random walks whose increments are encoded by a variable length Markov chain having—in full generality—no renewal pattern in such a way that their study does not reduce to a skeleton RW as for the original model.     

Studies of polylactone/poly(vinyl chloride), polylactone/poly(vinyl fluoride), and polylactone/poly(vinylidene fluoride) blends

It is shown that polyvalerolactone/poly(vinyl chloride) (PVL/PVC) blends are miscible over all compositions since a single glass transition temperature T_g is observed, intermediate between those of pure PVL and pure PVC. Melting points, enthalpies of fusion and morphologies of PVL/PVC blends are also reported. It is also shown that polyvalerolactone, poly(α-methyl-α-n-propyl-β-propiolactone), poly(α-methyl-α-ethyl-β-propiolactone), and poly(caprolactone) are immiscible with poly(vinyl fluoride) and poly(vinylidene fluoride), despite the fact that all these polylactones are miscible with PVC. Differences in electronegativity, in atomic radius, and in molar attraction between the fluoride and the chlorine atoms are probably responsible for this difference in behavior.     

Dynamic NMR studies of a potential chiroptical switch based on dithiocarbamate-iminodithiolane interconversion

[reaction: see text]. Variable temperature NMR spectra of the chiral spiro[(4-N,N-dimethyldithiocarbamato)-(2-N,N-dimethylimino)-1,3-dithiolane-5,9'-xanthene] show complex dynamics including degenerate interconversion of the dithiocarbamate and iminodithiolane groups. The rate of this switching process can be controlled by chemical modification: the analogous spiro[dithiolane-fluorene] derivative shows no interconversion. These novel materials have potential application as molecular switching elements in information storage devices.     

Nonlinear parabolic equations, relaxation and roughness

In a recent paper, Aubin and Coulouvrat (1998) dealt with equations of motion in the fluid in relaxation - mathematically: Burgers' equations, physically: continuity equations, Navier-Stokes equations, energy bilance, and equations of relaxation. A related equation of Ginzburg and Landau type (1965) extended for the kinetic depinning transitions takes its form

(0)     

Nonlinear parabolic equations, relaxation and roughness

In a recent paper, Aubin and Coulouvrat (1998) dealt with equations of motion in the fluid in relaxation - mathematically: Burgers' equations, physically: continuity equations, Navier-Stokes equations, energy bilance, and equations of relaxation. A related equation of Ginzburg-Landau type (1965) extended for the kinetic depinning transitions takes its form

(0)     

The energy-band parameters of cadmium arsenide and their variation with temperature and pressure

Using Kane's model for an HgTe-type inverted energy band structure along with available transport and optical data, various band parameters of Cd₃As₂ have been obtained at room and at low temperatures. Theoretical estimates of the variation of the energy gap at Γ as a function of temperature and pressure have also been obtained. These are found to be consistent with our band model and with our analysis of existing temperature and pressure data.     

High-precision lattice QCD confronts experiment

The recently developed Symanzik-improved staggered-quark discretization allows unquenched lattice-QCD simulations with much smaller (and more realistic) quark masses than previously possible. To test this formalism, we compare experiment with a variety of nonperturbative calculations in QCD drawn from a restricted set of "gold-plated" quantities. We find agreement to within statistical and systematic errors of 3% or less. We discuss the implications for phenomenology and, in particular, for heavy-quark physics.     

Coassembly of Nanorods and Nanospheres in Suspensions and in Stratified Films

The entropically driven coassembly of nanorods (cellulose nanocrystals, CNCs) and nanospheres (dye‐labeled spherical latex nanoparticles, NPs) was studied in aqueous suspensions and in solid films. In mixed CNC‐latex suspensions, phase separation into an isotropic latex‐NP‐rich and a chiral nematic CNC‐rich phase took place; the latter contained a significant amount of latex NPs. Drying the mixed suspension resulted in CNC‐latex films with planar disordered layers of latex NPs, which alternated with chiral nematic CNC‐rich regions. In addition, fluorescent latex NPs were embedded in the chiral nematic domains. The stratified morphology of the films, together with a random distribution of latex NPs in the anisotropic phase, led to the films having close‐to‐uniform fluorescence, birefringence, and circular dichroism properties.