Nanotechnology in the context of organic food processing

Nanotechnology, the science of the ultra small, is up-and-coming as the technological platform for the next wave of development and transformation of agri-food systems. It is quickly moving from the laboratory onto supermarket shelves and our kitchen tables (Scrinis and Lyons, 2007). Therefore we investigated in a literature review and a comparison of the findings with the EU regulation of organic farming to what degree nanotechnology can be applied in organic food production. The regulations do not restrict the use of nanotechnology in general. Because little is known about the impact on environment and human health, precaution should be taken when it comes to applying this technology in organic food production

Tailoring the Phonon Band Structure in Binary Colloidal Mixtures

We analyze the phonon spectra of periodic structures formed by two-dimensional mixtures of dipolar colloidal particles. These mixtures display an enormous variety of complex ordered configurations [J. Fornleitner {\it et al.}, Soft Matter {\bf 4}, 480 (2008)], allowing for the systematic investigation of the ensuing phonon spectra and the control of phononic gaps. We show how the shape of the phonon bands and the number and width of the phonon gaps can be controlled by changing the susceptibility ratio, the concentration and the mass ratio between the two components.Comment: 4 pages 3 figure

Zero temperature phase diagram of the square-shoulder system

Particles that interact via a square-shoulder potential, consisting of an impenetrable hard core with an adjacent, repulsive, step-like corona, are able to self-organize in a surprisingly rich variety of rather unconventional ordered structures. Using optimization strategies that are based on ideas of genetic algorithms we encounter, as we systematically increase the pressure, the following archetypes of aggregates: low-symmetry cluster and columnar phases, followed by lamellar particle arrangements, until at high pressure values compact, high-symmetry lattices emerge. These structures are characterized in the NPT ensemble as configurations of minimum Gibbs free energy. Based on simple considerations, i.e., basically minimizing the number of overlapping coronae while maximizing at the same time the density, the sequence of emerging structures can easily be understood.Comment: Submitted to J. Chem. Phy

Formation of Polymorphic Cluster Phases for Purely Repulsive Soft Spheres

We present results from density functional theory and computer simulations that unambiguously predict the occurrence of first-order freezing transitions for a large class of ultrasoft model systems into cluster crystals. The clusters consist of fully overlapping particles and arise without the existence of attractive forces. The number of particles participating in a cluster scales linearly with density, therefore the crystals feature density-independent lattice constants. Clustering is accompanied by polymorphic bcc-fcc transitions, with fcc being the stable phase at high densities.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Let

Degree Sequences and the Existence of kk-Factors

We consider sufficient conditions for a degree sequence $\pi$ to be forcibly $k$-factor graphical. We note that previous work on degrees and factors has focused primarily on finding conditions for a degree sequence to be potentially $k$-factor graphical. We first give a theorem for $\pi$ to be forcibly 1-factor graphical and, more generally, forcibly graphical with deficiency at most $\beta\ge0$. These theorems are equal in strength to Chv\'atal's well-known hamiltonian theorem, i.e., the best monotone degree condition for hamiltonicity. We then give an equally strong theorem for $\pi$ to be forcibly 2-factor graphical. Unfortunately, the number of nonredundant conditions that must be checked increases significantly in moving from $k=1$ to $k=2$, and we conjecture that the number of nonredundant conditions in a best monotone theorem for a $k$-factor will increase superpolynomially in $k$. This suggests the desirability of finding a theorem for $\pi$ to be forcibly $k$-factor graphical whose algorithmic complexity grows more slowly. In the final section, we present such a theorem for any $k\ge2$, based on Tutte's well-known factor theorem. While this theorem is not best monotone, we show that it is nevertheless tight in a precise way, and give examples illustrating this tightness.Comment: 19 page

Finding Publicly Available Data for Extension Planning and Programming: Developing Community Portraits

Although there have been calls for many years for Extension professionals to use secondary data in their work, finding appropriate data online can still be a challenge. With the multitude of data sources available online, it can be helpful to use the concept of developing a community portrait as the context for becoming proficient at locating secondary data. Once compiled, the data in a community portrait can have multiple uses. In this article, we provide direction for finding specific online data sources and using those sources to compile a community portrait, tips on using data websites, and a quick guide to help with locating data

Computer Assembly of Cluster-Forming Amphiphilic Dendrimers

Recent theoretical studies have predicted a new clustering mechanism for soft matter particles that interact via a certain kind of purely repulsive, bounded potentials. At sufficiently high densities, clusters of overlapping particles are formed in the fluid, which upon further compression crystallize into cubic lattices with density-independent lattice constants. In this work we show that amphiphilic dendrimers are suitable colloids for the experimental realization of this phenomenon. Thereby, we pave the way for the synthesis of such macromolecules, which form the basis for a novel class of materials with unusual properties.Comment: 4 pages, 4 figures, 1 tabl

Graphs with the maximum or minimum number of 1-factors

AbstractRecently Alon and Friedland have shown that graphs which are the union of complete regular bipartite graphs have the maximum number of 1-factors over all graphs with the same degree sequence. We identify two families of graphs that have the maximum number of 1-factors over all graphs with the same number of vertices and edges: the almost regular graphs which are unions of complete regular bipartite graphs, and complete graphs with a matching removed. The first family is determined using the Alon and Friedland bound. For the second family, we show that a graph transformation which is known to increase network reliability also increases the number of 1-factors. In fact, more is true: this graph transformation increases the number of k-factors for all k≥1, and “in reverse” also shows that in general, threshold graphs have the fewest k-factors. We are then able to determine precisely which threshold graphs have the fewest 1-factors. We conjecture that the same graphs have the fewest k-factors for all k≥2 as well