Dynamic facilitation explains democratic particle motion of metabasin transitions

Transitions between metabasins in supercooled liquids seem to occur through rapid "democratic" collective particle rearrangements. Here we show that this apparent homogeneous particle motion is a direct consequence of dynamic facilitation. We do so by studying metabasin transitions in facilitated spin models and constrained lattice gases. We find that metabasin transitions occur through a sequence of locally facilitated events taking place over a relatively short time frame. When observed on small enough spatial windows these events appear sudden and homogeneous. Our results indicate that metabasin transitions are essentially "non-democratic" in origin and yet another manifestation of dynamical heterogeneity in glass formers.Comment: 6 pages, 6 figure

Effects of temperature and salinity on four species of northeastern Atlantic scyphistomae (Cnidaria Scyphozoa)

This work was funded by the MASTS pooling initiative (Marine Alliance for Science and Technology for Scotland), and we gratefully acknowledge that support. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. C.L.W. is also grateful to the US/UK Fulbright Commission and the University of St Andrews for their financial support.Laboratory incubation experiments were conducted to examine the effects of different temperatures (4, 9, 14, 19, 23°C) and salinities (21, 27, 34) on survival and asexual reproduction of scyphistomae of Cyanea capillata, C. lamarckii, Chrysaora hysoscella, and Aurelia aurita in order to better understand how climate variability may affect the timing and magnitude of jellyfish blooms. Significant mortality was observed only for C. capillata and Ch. hysoscella at the highest and lowest temperatures, respectively, but temperature and salinity significantly affected the asexual reproductive output for all species. As temperature increased, production rates of podocysts increased and, if produced, progeny scyphistomae by side budding also increased. However, strobilation rates, and therefore the mean number of ephyrae produced, decreased when scyphistomae were exposed to elevated temperatures. These results provide a mechanistic explanation for why ephyrae of these species tend to be produced during colder periods of the year whilst summer and early autumn are probably important periods for increasing the numbers of scyphistomae in natural populations.PostprintPeer reviewe

Data Modelling for Predicting Exploits

Modern society is becoming increasingly reliant on secure computer systems. Predicting which vulnerabilities are more likely to be exploited by malicious actors is therefore an important task to help prevent cyber attacks. Researchers have tried making such predictions using machine learning. However, recent research has shown that the evaluation of such models require special sampling of training and test sets, and that previous models would have had limited utility in real world settings. This study further develops the results of recent research through the use of their sampling technique for evaluation in combination with a novel data model. Moreover, contrary to recent research, we find that using open web data can help in making better predictions about exploits, and that zero-day exploits are detrimental to the predictive powers of the model. Finally, we discovered that the initial days of vulnerability information is sufficient to make the best possible model. Given our findings, we suggest that more research should be devoted to develop refined techniques for building predictive models for exploits. Gaining more knowledge in this domain would not only help preventing cyber attacks but could yield fruitful insights in the nature of exploit development

Monolithically integrated DBR waveguidelaser and intensity modulator in erbiumdoped LiNbO3

For the first time, a DBR laser has been integrated with a Mach Zehnder intensity modulator in Er diffusion doped, Z cut LiNbO,, with Ti indiffused waveguides and dry etched Bragg gratings. The monolithically integrated device has a threshold of 54.8mW incident pump power (hp = 1480nm) and emits, in a single longitudinal mode, up to 0.65 mW CW output power at hs = 1561nm. The Mach-Zehnder type intensity modulator has an optical bandwidth > 3GHz

Critical fluctuations and breakdown of Stokes-Einstein relation in the Mode-Coupling Theory of glasses

We argue that the critical dynamical fluctuations predicted by the mode-coupling theory (MCT) of glasses provide a natural mechanism to explain the breakdown of the Stokes-Einstein relation. This breakdown, observed numerically and experimentally in a region where MCT should hold, is one of the major difficulty of the theory, for which we propose a natural resolution based on the recent interpretation of the MCT transition as a bona fide critical point with a diverging length scale. We also show that the upper critical dimension of MCT is d_c=8.Comment: Proceedings of the workshop on non-equilibrium phenomena in supercooled fluids, glasses and amorphous materials (17-22 September, 2006, Pisa

2,2':6',2''-Terpyridine-functionalized redox-responsive hydrogels as a platform for multi responsive amphiphilic polymer membranes

Nanophase-separated amphiphilic polymer co-networks are ideally suited as responsive membranes due to their stable co-continuous structure. Their functionalization with redox-responsive 2,2′:6′,2′′-terpyridine–metal complexes and light-responsive spiropyran derivatives leads to a novel material with tunable optical, redox and permeability properties. The versatility of the system in complexing various metal ions, such as cobalt or iron at different concentrations, results in a perfect monitoring over the degree of crosslinking of the hydrophilic poly(2-hydroxyethyl acrylate) channels. The reversibility of the complexation, the redox state of the metal and the isomerization to the merocyanine form upon UV illumination was evidenced by cyclic voltammetry, UV-Vis and permeability measurements under sequential conditions. Thus, the membrane provides light and redox addressable functionalities due to its adjustable and mechanically stable hydrogel network

Field Theory of Fluctuations in Glasses

We develop a field-theoretical description of dynamical heterogeneities and fluctuations in supercooled liquids close to the (avoided) MCT singularity. Using quasi-equilibrium arguments we eliminate time from the description and we completely characterize fluctuations in the beta regime. We identify different sources of fluctuations and show that the most relevant ones are associated to variations of "self-induced disorder" in the initial condition of the dynamics. It follows that heterogeneites can be describes through a cubic field theory with an effective random field term. The phenomenon of perturbative dimensional reduction ensues, well known in random field problems, which implies an upper critical dimension of the theory equal to 8. We apply our theory to finite size scaling for mean-field systems and we test its prediction against numerical simulations