Two-dimensional state sum models and spin structures

The state sum models in two dimensions introduced by Fukuma, Hosono and Kawai are generalised by allowing algebraic data from a non-symmetric Frobenius algebra. Without any further data, this leads to a state sum model on the sphere. When the data is augmented with a crossing map, the partition function is defined for any oriented surface with a spin structure. An algebraic condition that is necessary for the state sum model to be sensitive to spin structure is determined. Some examples of state sum models that distinguish topologically-inequivalent spin structures are calculated.Comment: 43 pages. Mathematica script in ancillary file. v2: nomenclature of models and their properties changed, some proofs simplified, more detailed explanations. v3: extended introduction, presentational improvements; final versio

The effect of polydispersity on the ordering transition of adsorbed self-assembled rigid rods

Extensive Monte Carlo simulations were carried out to investigate the nature of the ordering transition of a model of adsorbed self-assembled rigid rods on the bonds of a square lattice [Tavares et. al., Phys. Rev E 79, 021505 (2009)]. The polydisperse rods undergo a continuous ordering transition that is found to be in the two-dimensional Ising universality class, as in models where the rods are monodisperse. This finding is in sharp contrast with the recent claim that equilibrium polydispersity changes the nature of the phase transition in this class of models [L`opez et. al., Phys. Rev E 80, 040105(R)(2009)].Comment: 19 pages, 5 figure

What wrist should you wear your actigraphy device on? Analysis of dominant vs. non-dominant wrist actigraphy for measuring sleep in healthy adults

OBJECTIVE: Differences in sleep results due to the placement of actigraphy devices (non-dominant vs. dominant wrist) are yet to be determined. METHODS: 65 nights of data from 13 adult participants was collected while participants wore two actigraphy devices, one on each wrist. Sleep indices including total sleep time (TST), total time in bed (TTB), sleep efficiency (SE%), sleep latency (SL), wake after sleep onset (WASO), sleep onset time (SOT) and wake time (WT) were assessed between the two devices. RESULTS: There were no significant differences between devices for any of the measured sleep variables (p>0.05). SE%, SL and WASO resulted in high correlations between devices (0.89, 0.89 and 0.76, respectively), with all other sleep variables resulting in very high correlations (>0.90) between devices. CONCLUSIONS: Based on our results, it does not seem critical which wrist the actigraphy device is worn on for measuring key sleep variables

The influence of ion binding and ion specific potentials on the double layer pressure between charged bilayers at low salt concentrations

Measurements of surface forces between double-chained cationic bilayers adsorbed onto molecularly smooth mica surfaces across different millimolar salt solutions have revealed a large degree of ion specificity [Pashley et al., J. Phys. Chem. 90, 1637 (1986)]. This has been interpreted in terms of highly specific anion binding to the adsorbed bilayers. We show here that inclusion in the double layer theory of nonspecific ion binding and ion specific nonelectrostatic potentials acting between ions and the two surfaces can account for the phenomenon. It also gives the right Hofmeister series for the double layer pressure.M.B. thanks the Swedish Research Council and the German Arbeitsgemeinschaft industrieller Forschungvereinigungen Otto von Guericke e.V. AiF for financial support. E.R.A.L. and F.W.T. thank FAPERJ and CNPq the Brazilian Agencies for financial support