Amplification by stochastic interference

A new method is introduced to obtain a strong signal by the interference of weak signals in noisy channels. The method is based on the interference of 1/f noise from parallel channels. One realization of stochastic interference is the auditory nervous system. Stochastic interference may have broad potential applications in the information transmission by parallel noisy channels

Plasmodium falciparum K13 Mutations Differentially Impact Ozonide Susceptibility and Parasite Fitness In Vitro

The emergence and spread in Southeast Asia of Plasmodium falciparum resistance to artemisinin (ART) derivatives, the cornerstone of first-line artemisinin-based combination therapies (ACTs), underscore the urgent need to identify suitable replacement drugs. Discovery and development efforts have identified a series of ozonides with attractive chemical and pharmacological properties that are being touted as suitable replacements. Partial resistance to ART, defined as delayed parasite clearance in malaria patients treated with an ART derivative or an ACT, has been associated with mutations in the P. falciparum K13 gene. In light of reports showing that ART derivatives and ozonides share similar modes of action, we have investigated whether parasites expressing mutant K13 are cross-resistant to the ozonides OZ439 (artefenomel) and OZ227 (arterolane). This work used a panel of culture-adapted clinical isolates from Cambodia that were genetically edited to express variant forms of K13. Phenotypic analyses employed ring-stage survival assays (ring-stage survival assay from 0 to 3 h [RSA0–3h]), whose results have earlier been shown to correlate with parasite clearance rates in patients. Our results document cross-resistance between OZ277 and dihydroartemisinin (DHA), a semisynthetic derivative of ART, in parasites carrying the K13 mutations C580Y, R539T, and I543T. For OZ439, we observed cross-resistance only for parasites that carried the rare K13 I543T mutation, with no evidence of cross-resistance afforded by the prevalent C580Y mutation. Mixed-culture competition experiments with isogenic lines carrying modified K13 revealed variable growth deficits depending on the K13 mutation and parasite strain and provide a rationale for the broad dissemination of the fitness-neutral K13 C580Y mutation throughout strains currently circulating in Southeast Asia

Ephemeris Updates for Seven Selected HATNet Survey Transiting Exoplanets

We refined the ephemeris of seven transiting exoplanets HAT-P-6b, HAT-P-12b, HAT-P-18b, HAT-P-22b, HAT-P-32b, HAT-P-33b, and HAT-P-52b. We observed 11 transits from eight observatories in different filters for HAT-P-6b and HAT-P-32b. Also, the Exoplanet Transit Database (ETD) observations for each of the seven exoplanets were analyzed, and the light curves of five systems were studied using Transiting light Exoplanet Survey Satellite (TESS) data. We used Exofast-v1 to simulate these ground- and space-based light curves and estimate mid-transit times. We obtained a total of 11, 175 and 67 mid-transit times for these seven exoplanets from our observations, ETD and TESS data, respectively, along with 155 mid-transit times from the literature. Then, we generated transit timing variation (TTV) diagrams for each using derived mid-transit times as well as those found in the literature. The systems' linear ephemeris was then refined and improved using the Markov Chain Monte Carlo (MCMC) method. All of the studied exoplanets, with the exception of the HAT-P-12b system, displayed an increasing trend in the orbital period in the TTV diagrams.Comment: 11 Pages, submitted to the Astrophysics journa

The known unknowns of hydraulic engineering

Hydraulic engineers and researchers deal with scientific challenges involving turbulent flow motion and its interactions with the surroundings. Turbulent flows are characterised by unpredictable behaviour, and little systematic research has yet been conducted in natural systems. This paper discusses the implications of recent developments in affordable instrumentation previously characterised by intrinsic weaknesses that adversely affect the quality of the signal outputs. A challenging application is the unsteady turbulence field in tidal bores. The interactions between open channel flows and movable boundaries and atmosphere illustrate another aspect of our limited knowledge. Rapid siltation of reservoirs and air entrainment in turbulent free-surface flows are discussed. In both applications, hydraulic engineers require some broad-based expertise. In turn the education of future hydraulic engineers is of vital importance

Drag Reduction in Open Channel Flow by Aeration and Suspended Load

In supercritical open channel flows air is entrained at the free surface. Such air-water flows, called self-aerated flows, exhibit smaller friction losses than non-aerated flows. New data on drag reduction in self-aerated flows are presented. It is shown that the drag reduction process is linked with the presence of an air concentration boundary layer next to the channel bottom. An analogy with dilute polymer solutions and micro bubble modified boundary layers is developed and it is suggested that the presence of air next to the bottom increases the effective viscosity of the mixture and the sublayer thickness. A parallel with sediment laden flows is also developed. Although the distribution of suspended sediments differs from the distribution of air bubbles, it is suggested that the mechanisms of drag reduction observed in suspended sediment flows are similar to those in self-aerated flows