Instability and wavelength selection during step flow growth of metal surfaces vicinal to fcc(001)

We study the onset and development of ledge instabilities during growth of vicinal metal surfaces using kinetic Monte Carlo simulations. We observe the formation of periodic patterns at [110] close packed step edges on surfaces vicinal to fcc(001) under realistic molecular beam epitaxy conditions. The corresponding wavelength and its temperature dependence are studied by monitoring the autocorrelation function for step edge position. Simulations suggest that the ledge instability on fcc(1,1,m) vicinal surfaces is controlled by the strong kink Ehrlich-Schwoebel barrier, with the wavelength determined by dimer nucleation at the step edge. Our results are in agreement with recent continuum theoretical predictions, and experiments on Cu(1,1,17) vicinal surfaces.Comment: 4 pages, 4 figures, RevTe

Finite temperature phase diagram of a polarized Fermi gas in an optical lattice

We present phase diagrams for a polarized Fermi gas in an optical lattice as a function of temperature, polarization, and lattice filling factor. We consider the Fulde-Ferrel-Larkin-Ovchinnikov (FFLO), Sarma or breached pair (BP), and BCS phases, and the normal state and phase separation. We show that the FFLO phase appears in a considerable portion of the phase diagram. The diagrams have two critical points of different nature. We show how various phases leave clear signatures to momentum distributions of the atoms which can be observed after time of flight expansion.Comment: Journal versio

Monitoring aggregation processes in multiphase systems: a review

Particle aggregation is essential in many industrial processes, spanning the pharmaceutical and food industries, polymer production, and the environment, among others. However, aggregation can also occur, in some processes, as a non-desired side effect. Thus, to be able to monitor aggregation in industrial processes is of high importance to guarantee that the final, required product characteristics are obtained. In this paper, we present an extensive review of the different techniques available for monitoring particle characteristics in industrial processes involving particulate materials, with special emphasis on aggregation processes. These methods include both off-line and on-line techniques, based either on image acquisition techniques or different radiation scattering techniques (light-scattering and ultrasound spectroscopy). The principles behind each technique are addressed, together with their relevant applications, advantages, and disadvantages

Noise correlations of the ultra-cold Fermi gas in an optical lattice

In this paper we study the density noise correlations of the two component Fermi gas in optical lattices. Three different type of phases, the BCS-state (Bardeen, Cooper, and Schieffer), the FFLO-state (Fulde, Ferrel, Larkin, and Ovchinnikov), and BP (breach pair) state, are considered. We show how these states differ in their noise correlations. The noise correlations are calculated not only at zero temperature, but also at non-zero temperatures paying particular attention to how much the finite temperature effects might complicate the detection of different phases. Since one-dimensional systems have been shown to be very promising candidates to observe FFLO states, we apply our results also to the computation of correlation signals in a one-dimensional lattice. We find that the density noise correlations reveal important information about the structure of the underlying order parameter as well as about the quasiparticle dispersions.Comment: 25 pages, 11 figures. Some figures are updated and text has been modifie

Fulde-Ferrell-Larkin-Ovchinnikov phase in the presence of pair hopping interaction

The recent experimental support for the presence of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase in the CeCoIn5 directed the attention towards the mechanisms responsible for this type of superconductivity. We investigate the FFLO state in a model where on--site/inter--site pairing coexists with repulsive pair hopping interaction. The latter interaction is interesting in that it leads to pairing with nonzero momentum of the Cooper pairs even in the absence of the external magnetic field (the so-called eta-pairing). It turns out that depending on the strength of the pair hopping interaction the magnetic field can induce one of two types of the FFLO phase with different spatial modulations of the order parameter. It is argued that the properties of the FFLO phase may give information about the magnitude of the pair hopping interaction. We also show that eta-pairing and d-wave superconductivity may coexist in the FFLO state. It holds true also for superconductors which in the absence of magnetic field are of pure d-wave type.Comment: 16 pages, 8 figure

Mixing of high-consistency fiber-foam suspensions

Foam-forming has been gaining attention recently to manufacture sustainable packaging and cushioning products in various sectors, including food, automobile and construction [1]. Conventionally, foam suspension is made in a mixing tank at a lower fibre consistency, ≤ 2% resulting in large volumes of water consumption. Besides, the excess moisture from the final foam-formed product needs to be removed by drying. Replacing the current foaming methods with High-consistency foam (HCF) can reduce water consumption, drying energy and equipment footprint. However, increasing the fibre consistency makes the rheology of fibre-foam suspension complex [2], posing challenges in mixing. The present work focuses on mixing this complex suspension to generate a homogeneous HCF by selecting proper impeller geometry, mixing time and surfactant dosage. The lab-scale testing facility consisted of a 0.43 m tall and 0.16 m wide transparent acrylic tank equipped with a top-mount impeller assembly. Three impeller geometries, namely bend-disc, Bakker turbine and high solidity pitched blade turbine, and four impeller combinations were used. Chemi-thermomechanical pulp (CTMP) with a mean fibre length of 2.0 mm, a width of 39 μm and Canadian standard freeness (CSF) of 600 ml was used as the fibre material. The consistency varied from 5% to 15%. An 80/20 mol% mixture of sodium dodecyl sulphate (SDS) and Tween 20 (T 20) was used as the surfactant. The surfactant dosage was varied from 0.5 g/l to 2.0 g/l based on fibre consistency. The quality of the HCF was assessed in terms of air content, foaming time and X-ray microtomography. Preliminary results indicated that the used impeller combination should be selected on the base of fibre consistency. No improvement in the air content was noticed beyond 1.2 g/l surfactant dosage. However, increasing the surfactant dosage reduced foaming time at higher consistencies. Currently, experiments are carried out to understand the role of fibre length and the addition of binders such as guar gum in the mixing. In summary, this work provides an understanding of the mixing geometry and foam chemistry that enables the manufacturing of sustainable packaging products at a much lower water consumption

Walckenaeria furcillata (Menge, 1869) and Walckenaeria lepida (Kulczynski, 1885) in Finland (Araneae, Linyphiidae)

Walckenaeria furcillata (Menge, 1869) and W. lepida (Kulczynski, 1885) are reported from Finland. Their diagnostics with figures, and distributions and ecological requirements are given. Comparative drawings of genitalia for closely related W. lepida and W. unicornis O. P.-Cambridge, 1861 are presented. The identity of “Pseudotigellinus” subadults figured by Palmgren (1976) is discussed