Fixation Probability for Competing Selective Sweeps

We consider a biological population in which a beneficial mutation is undergoing a selective sweep when a second beneficial mutation arises at a linked locus and we investigate the probability that both mutations will eventually fix in the population. Previous work has dealt with the case where the second mutation to arise confers a smaller benefit than the first. In that case population size plays almost no role. Here we consider the opposite case and observe that, by contrast, the probability of both mutations fixing can be heavily dependent on population size. Indeed the key parameter is $\rho N$, the product of the population size and the recombination rate between the two selected loci. If $\rho N$ is small, the probability that both mutations fix can be reduced through interference to almost zero while for large $\rho N$ the mutations barely influence one another. The main rigorous result is a method for calculating the fixation probability of a double mutant in the large population limit.Comment: 33 pages, 3 figure

Design, fabrication, and testing of micromachined silicone rubbermembrane valves

Technologies for fabricating silicone rubber membranes and integrating them with other processes on silicon wafers have been developed. Silicone rubber has been found to have exceptional mechanical properties including low modulus, high elongation, and good sealing. Thermopneumatically actuated, normally open, silicone rubber membrane valves with optimized components have been designed, fabricated, and tested. Suspended silicon nitride membrane heaters have been developed for low-power thermopneumatic actuation. Composite silicone rubber on Parylene valve membranes have been shown to have low permeability and modulus. Also, novel valve seats were designed to improve sealing in the presence of particles. The valves have been extensively characterized with respect to power consumption versus flow rate and transient response. Low power consumption, high flow rate, and high pressure have been demonstrated. For example, less than 40 mW is required to switch a 1-slpm nitrogen flow at 33 psi. Water requires dose to 100 mW due to the cooling effect of the liquid

Provably-secure symmetric private information retrieval with quantum cryptography

Private information retrieval (PIR) is a database query protocol that provides user privacy, in that the user can learn a particular entry of the database of his interest but his query would be hidden from the data centre. Symmetric private information retrieval (SPIR) takes PIR further by additionally offering database privacy, where the user cannot learn any additional entries of the database. Unconditionally secure SPIR solutions with multiple databases are known classically, but are unrealistic because they require long shared secret keys between the parties for secure communication and shared randomness in the protocol. Here, we propose using quantum key distribution (QKD) instead for a practical implementation, which can realise both the secure communication and shared randomness requirements. We prove that QKD maintains the security of the SPIR protocol and that it is also secure against any external eavesdropper. We also show how such a classical-quantum system could be implemented practically, using the example of a two-database SPIR protocol with keys generated by measurement device-independent QKD. Through key rate calculations, we show that such an implementation is feasible at the metropolitan level with current QKD technology.Comment: 19 page

Lagrangian Refined Kolmogorov Similarity Hypothesis for Gradient Time-evolution in Turbulent Flows

We study the time evolution of velocity and pressure gradients in isotropic turbulence, by quantifying their decorrelation time scales as one follows fluid particles in the flow. The Lagrangian analysis uses data in a public database generated using direct numerical simulation of the Naiver-Stokes equations, at a Reynolds number 430. It is confirmed that when averaging over the entire domain, correlation functions decay on timescales on the order of the mean Kolmogorov turnover time scale, computed from the globally averaged rate of dissipation and viscosity. However, when performing the analysis in different subregions of the flow, turbulence intermittency leads to large spatial variability in the decay time scales. Remarkably, excellent collapse of the auto-correlation functions is recovered when using the `local Kolmogorov time-scale' defined using the locally averaged, rather than the global, dissipation-rate. This provides new evidence for the validity of Kolmogorov's Refined Similarity Hypothesis, but from a Lagrangian viewpoint that provides a natural frame to describe the dynamical time evolution of turbulence.Comment: 4 Pages, 4 figure

A shared frailty semi-parametric markov renewal model for travel and activity time-use pattern analysis

This study investigates the influence of observed explanatory factors and unobserved random effect (heterogeneity) on episode durations of travel-activity chain. A shared frailty semiparametric proportional hazard model is proposed to estimate the transition hazard of travel/activity states. The proposed model is applied on the travel and activity episode duration analysis during evening work-to-home commute using the household travel survey data collected in the city of Lyon in France in 2005-2006. The empirical results provide useful insights for the determinants of travel and activity episode durations for evening work-to-home commute.time-use; activity duration; Markov renewal model; shared frailty; heterogeneity

Variability versus stability in daily travel and activity behaviour. The case of a one week travel diary

Temporal rhythms in travel and activity patterns are analysed thanks to a seven-day travel diary collected on 707 individuals in the city of Ghent (Belgium) in 2008. Our analysis confirms the large level of intrapersonal variability whether for daily trips, home-based tours, time use and activity sequence. However our analysis goes further by studying this variability along various time periods within the week. Moreover, we show that the systematic day-to-day variability has an extremely low share in intrapersonal variability. The influence of socio-demographic characteristics on intrapersonal variability is weak, whether for daily trips, tours, time use and activity sequence. Repetitive activity-travel behaviour is then detected, through attributes of activity at trip destination, travel mode, trip arrival time and destination location. The picture is at the same time one of diversity and of specificity in activity-travel across the week. People tend to concentrate their weekly activity-travel patterns on few combinations of attributes, despite a large dispersion. Our results on core stops are somewhat encouraging by showing some kind of concentration of activity patterns on a few "anchor" points.travel behaviour ; daily travel ; activity behaviour