Thermodynamically Stable One-Component Metallic Quasicrystals

Classical density-functional theory is employed to study finite-temperature trends in the relative stabilities of one-component quasicrystals interacting via effective metallic pair potentials derived from pseudopotential theory. Comparing the free energies of several periodic crystals and rational approximant models of quasicrystals over a range of pseudopotential parameters, thermodynamically stable quasicrystals are predicted for parameters approaching the limits of mechanical stability of the crystalline structures. The results support and significantly extend conclusions of previous ground-state lattice-sum studies.Comment: REVTeX, 13 pages + 2 figures, to appear, Europhys. Let

Enhanced entrainability of genetic oscillators by period mismatch

Biological oscillators coordinate individual cellular components so that they function coherently and collectively. They are typically composed of multiple feedback loops, and period mismatch is unavoidable in biological implementations. We investigated the advantageous effect of this period mismatch in terms of a synchronization response to external stimuli. Specifically, we considered two fundamental models of genetic circuits: smooth- and relaxation oscillators. Using phase reduction and Floquet multipliers, we numerically analyzed their entrainability under different coupling strengths and period ratios. We found that a period mismatch induces better entrainment in both types of oscillator; the enhancement occurs in the vicinity of the bifurcation on their limit cycles. In the smooth oscillator, the optimal period ratio for the enhancement coincides with the experimentally observed ratio, which suggests biological exploitation of the period mismatch. Although the origin of multiple feedback loops is often explained as a passive mechanism to ensure robustness against perturbation, we study the active benefits of the period mismatch, which include increasing the efficiency of the genetic oscillators. Our findings show a qualitatively different perspective for both the inherent advantages of multiple loops and their essentiality.Comment: 28 pages, 13 figure

Super-resolution imaging and estimation of protein copy numbers at single synapses with DNA-PAINT

In the brain, the strength of each individual synapse is defined by the complement of proteins present or the "local proteome." Activity-dependent changes in synaptic strength are the result of changes in this local proteome and posttranslational protein modifications. Although most synaptic proteins have been identified, we still know little about protein copy numbers in individual synapses and variations between synapses. We use DNA-point accumulation for imaging in nanoscale topography as a single-molecule super-resolution imaging technique to visualize and quantify protein copy numbers in single synapses. The imaging technique provides near-molecular spatial resolution, is unaffected by photobleaching, enables imaging of large field of views, and provides quantitative molecular information. We demonstrate these benefits by accessing copy numbers of surface AMPA-type receptors at single synapses of rat hippocampal neurons along dendritic segments

Systemic epidermal nevus with involvement of the oral mucosa due to FGFR3 mutation

Our results show that activating FGFR3 mutations can also affect the oral mucosa and that extracutaneous manifestations of EN syndrome can be subtle. We highlight the theoretical risk of the patient having an offspring with thanatophoric dysplasia as gonadal mosaicism for the R248C mutation cannot be excluded

Dynamic Autoregressive Liquidity (DArLiQ)

Motivated beliefs theory suggests the absorption of information may be biased, especially when it bears consequences for the ego. This paper finds empirical support for that hypothesis in the field, using longitudinal data on teenagers’ memories of mathematics report card grades and administrative data on actual grades. Students: i) make more errors in recalling lower grades; ii) update their academic self-confidence in association with recalled grades rather than actual grades; and iii) have more flattering memories of grades when the survey was administered with a longer delay. The first two results bolster recent research in demonstrating that patterns of motivated recall are robust to within-individual estimation. The last result extends the field literature in showing that a large part of the mechanism for motivated information absorption is memory loss over time. A structural model is used to represent memories as the outcome of a subconscious choice problem, disentangling competing motives to enhance self-confidence and respect reality. The estimated model indicates that the costs of memory distortions decrease as time passes after information transmission, and students with low self-confidence had a greatly diminished preference for inflating self-confidence via memory distortion

Estimation of a Multiplicative Covariance Structure in the Large Dimensional Case

We propose a Kronecker product structure for large covariance or correlation matrices. One feature of this model is that it scales logarithmically with dimension in the sense that the number of free parameters increases logarithmically with the dimension of the matrix. We propose an estimation method of the parameters based on a log-linear property of the structure, and also a quasi-maximum likelihood estimation (QMLE) method. We establish the rate of convergence of the estimated parameters when the size of the matrix diverges. We also establish a central limit theorem (CLT) for our method. We derive the asymptotic distributions of the estimators of the parameters of the spectral distribution of the Kronecker product correlation matrix, of the extreme logarithmic eigenvalues of this matrix, and of the variance of the minimum variance portfolio formed using this matrix. We also develop tools of inference including a test for over-identification. We apply our methods to portfolio choice for S&P500 daily returns and compare with sample covariance-based methods and with the recent Fan, Liao, and Mincheva (2013) method

Unifying Parsimonious Tree Reconciliation

Evolution is a process that is influenced by various environmental factors, e.g. the interactions between different species, genes, and biogeographical properties. Hence, it is interesting to study the combined evolutionary history of multiple species, their genes, and the environment they live in. A common approach to address this research problem is to describe each individual evolution as a phylogenetic tree and construct a tree reconciliation which is parsimonious with respect to a given event model. Unfortunately, most of the previous approaches are designed only either for host-parasite systems, for gene tree/species tree reconciliation, or biogeography. Hence, a method is desirable, which addresses the general problem of mapping phylogenetic trees and covering all varieties of coevolving systems, including e.g., predator-prey and symbiotic relationships. To overcome this gap, we introduce a generalized cophylogenetic event model considering the combinatorial complete set of local coevolutionary events. We give a dynamic programming based heuristic for solving the maximum parsimony reconciliation problem in time O(n^2), for two phylogenies each with at most n leaves. Furthermore, we present an exact branch-and-bound algorithm which uses the results from the dynamic programming heuristic for discarding partial reconciliations. The approach has been implemented as a Java application which is freely available from http://pacosy.informatik.uni-leipzig.de/coresym.Comment: Peer-reviewed and presented as part of the 13th Workshop on Algorithms in Bioinformatics (WABI2013

Laser Processing of CFRP

The key issue for laser-processing of carbon fiberreinforced plastics (CFRP) is the thermal damage ofboth, the matrix material and the carbon fibres. Thispaper describes the basic mechanisms leading tosuch thermal damage and its implications on thedesign of appropriate laser processing systems

Phonon-phason coupling in icosahedral quasicrystals

From relaxation simulations of decoration-based quasicrystal structure models using microscopically based interatomic pair potentials, we have calculated the (usually neglected) phonon-phason coupling constant. Its sign is opposite for the two alloys studied, i-AlMn and i-(Al,Cu)Li; a dimensionless measure of its magnitude relative to the phonon and phason elastic constants is of order 1/10, suggesting its effects are small but detectable. We also give a criterion for when phonon-phason effects are noticeable in diffuse tails of Bragg peaks.Comment: 7 pages, LaTeX, uses Europhys Lett macros (included

Results and insight gained from applying the EnergyCat energy-saving serious game in UK social housing

Concerns about climate change associated with the combustion of fossil fuels urge a call for widespread reductions in household energy use. Determining means of achieving this is a key challenge faced by environmental scientists. The current research presents insights gained from a 12-month empirical trial of new serious game for energy, ‘EnergyCat’; which was designed to encourage household energy reductions in the UK social housing sector. Effects of gameplay on consumption behaviours and energy awareness were explored using 82 UK social housing households (versus a no-game control). Results indicated the intervention did not lead to any substantive changes in awareness or consumption practices. However, post-intervention feedback highlighted several issues in terms of game design and usability that may explain why the game failed to change behaviour in this instance. We provide a framework of suggestions as to how the game design process could be improved in order to engage residents in future, including use of adaptive fonts for older residents, and provision of clearer instructions on gameplay objectives at the outset. In addition, researchers should ensure close collaboration is maintained with residents throughout the design process in future efforts, in order to maximise likelihood of ongoing engagement from this population