Solid–liquid interfacial free energy of ice Ih, ice Ic, and ice 0 within a mono-atomic model of water via the capillary wave method

We apply the capillarywave method, based on measurements of fluctuations in a ribbon-like interfacial geometry, to determine the solid–liquid interfacial free energy for both polytypes of ice I and the recently proposed ice 0 within a mono-atomic model of water. We discuss various choices for the molecular order parameter, which distinguishes solid from liquid, and demonstrate the influence of this choice on the interfacial stiffness. We quantify the influence of discretisation error when sampling the interfacial profile and the limits on accuracy imposed by the assumption of quasi onedimensional geometry. The interfacial free energies of the two ice I polytypes are indistinguishable to within achievable statistical error and the small ambiguity which arises from the choice of order parameter. In the case of ice 0, we find that the large surface unit cell for low index interfaces constrains the width of the interfacial ribbon such that the accuracy of results is reduced. Nevertheless, we establish that the interfacial free energy of ice 0 at its melting temperature is similar to that of ice I under the same conditions. The rationality of a core–shell model for the nucleation of ice I within ice 0 is questioned within the context of our results. © 2017 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). [http://dx.doi.org/10.1063/1.4975776

Integrated and dynamical oceanographic data management - IDOD

The goal of the IDOD project was to provide the federal government, the scientific community and other users with an up-to-date tool for collecting, managing and analysing marine scientific data.The resulting “marine information system” is hosted by the Belgian Marine Data Centre (BMDC), a team within the Management Unit of the Mathematical Mode's of the North Sec (MUMM). The BMDC committed itself to keep the IDOD information system alive and evolving. A remote user interface is available online at http:/ /www.mumm.ac.be/ datacentre.The project faced all the aspects of modern scientific data management. A major challenge was to establish a fruitful dialog with the data providers. This has been done through extensive discussions in the Users committee and during bilateral meetings. The topics that have then been clarified range from the principles (in order to write down a standard common “Rights and duties" agreement) to the very technical and scientific details, specific to each data set .A substantial effort has been put on the definition of guidelines for ensuring the data quality throughout their way from the field to the data centre. This has resulted, for instance, in the development of a “On-board registration of samples" computer programme, in a check list of meta-information to document the data or in the definition of a “common layout" for reporting data sets to the data centre.On the technical side, the variety and complexity of the data to be stored and made available for further use lead us to elaborate a complex and robust data base scheme, after an in-depth conceptual analysis. The database itself is implemented using the ORACLE technology.In parallel, a set of dedicated analysis and visualisation tools has been developed. They help the users and the data managers to tackle the data in their space and time dimensions and also allow cross-analysis between different parameters.The primary providers of data for the information system were the various teams participating in the (first) Programme for a sustainable development of the North Sea, financed by the Belgian Federal Office for scientific, technical and cultural affairs. These data are being complemented by data from other (earlier) scientific programmes and from governmental surveys.The project has been performed by MUMM, in partnership with the SURFACES laboratory (University of Liege) and the University Centre of Statistics (University of Leuven)

Approximating multi-dimensional Hamiltonian flows by billiards

Consider a family of smooth potentials $V_{\epsilon}$, which, in the limit $\epsilon\to0$, become a singular hard-wall potential of a multi-dimensional billiard. We define auxiliary billiard domains that asymptote, as $\epsilon\to0$ to the original billiard, and provide asymptotic expansion of the smooth Hamiltonian solution in terms of these billiard approximations. The asymptotic expansion includes error estimates in the $C^{r}$ norm and an iteration scheme for improving this approximation. Applying this theory to smooth potentials which limit to the multi-dimensional close to ellipsoidal billiards, we predict when the separatrix splitting persists for various types of potentials

Convergence of invariant densities in the small-noise limit

This paper presents a systematic numerical study of the effects of noise on the invariant probability densities of dynamical systems with varying degrees of hyperbolicity. It is found that the rate of convergence of invariant densities in the small-noise limit is frequently governed by power laws. In addition, a simple heuristic is proposed and found to correctly predict the power law exponent in exponentially mixing systems. In systems which are not exponentially mixing, the heuristic provides only an upper bound on the power law exponent. As this numerical study requires the computation of invariant densities across more than 2 decades of noise amplitudes, it also provides an opportunity to discuss and compare standard numerical methods for computing invariant probability densities.Comment: 27 pages, 19 figures, revised with minor correction

A maximum density rule for surfaces of quasicrystals

A rule due to Bravais of wide validity for crystals is that their surfaces correspond to the densest planes of atoms in the bulk of the material. Comparing a theoretical model of i-AlPdMn with experimental results, we find that this correspondence breaks down and that surfaces parallel to the densest planes in the bulk are not the most stable, i.e. they are not so-called bulk terminations. The correspondence can be restored by recognizing that there is a contribution to the surface not just from one geometrical plane but from a layer of stacked atoms, possibly containing more than one plane. We find that not only does the stability of high-symmetry surfaces match the density of the corresponding layer-like bulk terminations but the exact spacings between surface terraces and their degree of pittedness may be determined by a simple analysis of the density of layers predicted by the bulk geometric model.Comment: 8 pages of ps-file, 3 Figs (jpg

How metal films de-wet substrates - identifying the kinetic pathways and energetic driving forces

We study how single-crystal chromium films of uniform thickness on W(110) substrates are converted to arrays of three-dimensional (3D) Cr islands during annealing. We use low-energy electron microscopy (LEEM) to directly observe a kinetic pathway that produces trenches that expose the wetting layer. Adjacent film steps move simultaneously uphill and downhill relative to the staircase of atomic steps on the substrate. This step motion thickens the film regions where steps advance. Where film steps retract, the film thins, eventually exposing the stable wetting layer. Since our analysis shows that thick Cr films have a lattice constant close to bulk Cr, we propose that surface and interface stress provide a possible driving force for the observed morphological instability. Atomistic simulations and analytic elastic models show that surface and interface stress can cause a dependence of film energy on thickness that leads to an instability to simultaneous thinning and thickening. We observe that de-wetting is also initiated at bunches of substrate steps in two other systems, Ag/W(110) and Ag/Ru(0001). We additionally describe how Cr films are converted into patterns of unidirectional stripes as the trenches that expose the wetting layer lengthen along the W[001] direction. Finally, we observe how 3D Cr islands form directly during film growth at elevated temperature. The Cr mesas (wedges) form as Cr film steps advance down the staircase of substrate steps, another example of the critical role that substrate steps play in 3D island formation

On stochastic sea of the standard map

Consider a generic one-parameter unfolding of a homoclinic tangency of an area preserving surface diffeomorphism. We show that for many parameters (residual subset in an open set approaching the critical value) the corresponding diffeomorphism has a transitive invariant set $\Omega$ of full Hausdorff dimension. The set $\Omega$ is a topological limit of hyperbolic sets and is accumulated by elliptic islands. As an application we prove that stochastic sea of the standard map has full Hausdorff dimension for sufficiently large topologically generic parameters.Comment: 36 pages, 5 figure

Highly efficient separation of actinides from lanthanides by a phenanthroline-derived bis-triazine ligand

The synthesis, lanthanide complexation, and solvent ex- traction of actinide(III) and lanthanide(III) radiotracers from nitric acid solutions by a phenanthroline-derived quadridentate bis-triazine ligand are described. The ligand separates Am(III) and Cm(III) from the lanthanides with remarkably high efficiency, high selectivity, and fast extraction kinetics compared to its 2,2'-bipyridine counterpart. Structures of the 1:2 bis-complexes of the ligand with Eu(III) and Yb(III) were elucidated by X-ray crystallography and force field calculations, respec-tively. The Eu(III) bis-complex is the first 1:2 bis-complex of a quadridentate bis-triazine ligand to be characterized by crystallography. The faster rates of extraction were verified by kinetics measurements using the rotating membrane cell technique in several diluents. The improved kinetics of metal ion extraction are related to the higher surface activity of the ligand at the phase interface. The improvement in the ligand's properties on replacing the bipyridine unit with a phenanthroline unit far exceeds what was anticipated based on ligand design alone

In vitro production of bovine embryos derived from individual donors in the Corral® dish

Background: Since the identity of the embryo is of outmost importance during commercial in vitro embryo production, bovine oocytes and embryos have to be cultured strictly per donor. Due to the rather low yield of oocytes collected after ovum pick-up (OPU) per individual cow, oocyte maturation and embryo culture take place in small groups, which is often associated with inferior embryo development. The objective of this study was to improve embryonic development in small donor groups by using the Corral (R) dish. This commercial dish is designed for human embryo production. It contains two central wells that are divided into quadrants by a semi-permeable wall. In human embryo culture, one embryo is placed per quadrant, allowing individual follow-up while embryos are exposed to a common medium. In our study, small groups of oocytes and subsequently embryos of different bovine donors were placed in the Corral (R) dish, each donor group in a separate quadrant. Results: In two experiments, the Corral (R) dish was evaluated during in vitro maturation (IVM) and/or in vitro culture (IVC) by grouping oocytes and embryos of individual bovine donors per quadrant. At day 7, a significantly higher blastocyst rate was noted in the Corral (R) dish used during IVM and IVC than when only used during IVM (12.9% +/- 2.10 versus 22.8% +/- 2.67) (P < 0.05). However, no significant differences in blastocyst yield were observed anymore between treatment groups at day 8 post insemination. Conclusions: In the present study, the Corral (R) dish was used for in vitro embryo production (IVP) in cattle; allowing to allocate oocytes and/or embryos per donor. As fresh embryo transfers on day 7 have higher pregnancy outcomes, the Corral (R) dish offers an added value for commercial OPU/IVP, since a higher blastocyst development at day 7 is obtained when the Corral (R) dish is used during IVM and IVC

STRATEGIJA GOSPODARSKOG RAZVOJA REPUBLIKE HRVATSKE

Polazište rada ide za tim da pri definiranju strategije gospodarskog razvoja valja poći od nalaza teorije o determinantama rasta i od poruka empirijskog procesa gospodarskog razvoja iz proteklih 46 poslijeratnih godina. Analizom prvog ukazuje se na šest ključnih determinanti rasta, s posebnim akcentom na ulogu znanja (odnosno, ljudskog kapitala) i infrastrukture (fizičke i socijalne), a analizom drugog na ulogu konkurencije, ali istodobno i na potencijal države u stimuliranju procesa rasta. Država mora napustiti funkciju proizvodnje i alokacije dobara, jer se ove ostvaruju najbolje kroz tržišnu konkurenciju, ali mora voditi brigu o: unapređivanju infrastrukture, ulaganjima u ljudski kapital i poticanju znanstvenih istraživanja i inovacija koje doprinose porastu opće produktivnosti činilaca. Briga o unapređivanju (fizičke i socijalne) infrastrukture implicira između inoga, kreiranje niz aktivnosti na liniji poticanja razvoja tržišta i konkurentne mikroekonomije, jasnog definiranja i zaštite vlasničkih prava, privlačenja kapitala, otvorenosti i stabilne makroekonomije. Slijedi, u našem se primjeru kao sastavni element strategije i pretpostavka razvoja nameće ubrzana tranzicija iz "naslijeđenog" komandnog u poduzetničko gospodarstvo i pretvorba društva u cjelini u istinsko "tržišno društvo". Privatizacija "društvenog vlasništva" i aktiviranje financijskog tržišta preduvjet su ostvarivanja te tranzicije, pa je time u mnogome determiniran i izbor modela provedbe privatizacije, odnosno pretvorbe društvenih poduzeća. Zadnji odjeljak rada bavi se pitanjem odnosa razvoja i kvalitete upravljanja (shvaćenog kao zadaće političke vlasti da rukovodi poslovima nacije), odnosno pitanjem što predstavlja dobro upravljanje - upravljanje koje ne koči, već potiče razvoj