Entropic Stochastic Resonance

We present a novel scheme for the appearance of Stochastic Resonance when the dynamics of a Brownian particle takes place in a confined medium. The presence of uneven boundaries, giving rise to an entropic contribution to the potential, may upon application of a periodic driving force result in an increase of the spectral amplification at an optimum value of the ambient noise level. This Entropic Stochastic Resonance (ESR), characteristic of small-scale systems, may constitute a useful mechanism for the manipulation and control of single-molecules and nano-devices.Comment: 4 pages, 3 figure

Entropically-induced asymmetric passage times of charged tracers across corrugated channels

We analyze the diffusion of charged and neutral tracers suspended in an electrolyte embedded in a channel of varying cross section. Making use of systematic approximations, the diffusion equation governing the motion of tracers is mapped into an effective 1D equation describing the dynamics along the longitudinal axis of the channel where its varying-section is encoded as an effective entropic potential. This simplified approach allows us to characterize tracer diffusion under generic confinement by measuring their mean first passage time (MFPT). In particular, we show that the interplay between geometrical confinement and electrostatic interactions strongly affect the MFTP of tracers across corrugated channels hence leading to alternative means to control tracers translocation across charged pores. Finally, our results show that the MFPTs of a charged tracer in opposite directions along an asymmetric channel may differ We expect our results to be relevant for biological as well synthetic devices whose dynamics is controlled by the detection of diluted tracer

Numerical study of multilayer adsorption on fractal surfaces

We report a numerical study of van der Waals adsoprtion and capillary condensation effects on self-similar fractal surfaces. An assembly of uncoupled spherical pores with a power-law distributin of radii is used to model fractal surfaces with adjustable dimensions. We find that the commonly used fractal Frankel-Halsey-Hill equation systematically fails to give the correct dimension due to crossover effects, consistent with the findings of recent experiments. The effects of pore coupling and curvature dependent surface tension were also studied.Comment: 11 pages, 3 figure

Canterbury game industry action plan 2022

This report reviews the video game and interactive media industry landscape, and is intended for game studios, local and international investors in the games industry, regional policy makers, central government, local government agencies, Christchurch City Council, and sector stakeholders

Configurational entropy calculation of poly(α-alkyl β,L-aspartate)s amorphous and crystalline films using gas permeation

The permeability and diffusion coefficient of gases such as N-2, O-2 and CO2 through two polymeric membranes of poly(alpha-alkyl beta,L-aspartate)s (PAALA-n) were determined by the "time-lag" method. One of these membranes was crystalline (PAALA-1) and the other one was amorphous (PAALA-6). The comparison of the obtained result for both membranes is addressed by the calculation of the so called configurational entropy. The study has been done in the range of temperatures 20 degrees C to 70 degrees C.This work was supported by the Direccion General de Investigacion Cientifica y Tecnica (DGICYT), Grant ENE-2011-Ref.24761 and also DGAPA-UNAM Proyecto IN 102512, and SEP-CONACYT 154626.Del Castillo, LF.; Andrio Balado, A.; Nava, JA.; Mollá Romano, S.; Muñoz-Guerra, S.; Compañ Moreno, V. (2014). Configurational entropy calculation of poly(α-alkyl β,L-aspartate)s amorphous and crystalline films using gas permeation. European Polymer Journal. 59:254-261. https://doi.org/10.1016/j.eurpolymj.2014.07.024S2542615

Diffusivity of methyl bromide in water

The oceans are important in the geochemical cycle of methyl bromide, as both a source of natural methyl bromide and a sink for anthropogenic methyl bromide. Air-sea exchange rate calculations are based on measured concentration differences across the air-sea surface, on various gas exchange wind speed relationships, and on the diffusivity of methyl bromide in seawater. In this study, the diffusivity of methyl bromide in pure water has been experimentally determined over the temperature range 5-20°C. The diffusivity varied from 9.85 x 10-6 cm2 s-1 at 5°C to 1.50 x 10-5 cm2 s-1 at 19.4°C. The values obtained in this study are ~ 8-35% higher than those derived from semi-empirical estimates. The diffusivity of methyl bromide in 3.5% NaCl solution was also measured at 13°C and found to be the same as the diffusivity measured in pure water. This is a surprising result given the viscosity differences between these two media. Schmidt numbers (Sc) for seawater have been calculated as a function of temperature from the pure water diffusivities. Schmidt numbers varied from 1585 at 5°C to 700 at 20°C

Do Leaf Cutting Ants Cut Undetected? Testing the Effect of Ant-Induced Plant Defences on Foraging Decisions in Atta colombica

Leaf-cutting ants (LCAs) are polyphagous, yet highly selective herbivores. The factors that govern their selection of food plants, however, remain poorly understood. We hypothesized that the induction of anti-herbivore defences by attacked food plants, which are toxic to either ants or their mutualistic fungus, should significantly affect the ants' foraging behaviour. To test this “induced defence hypothesis,” we used lima bean (Phaseolus lunatus), a plant that emits many volatile organic compounds (VOCs) upon herbivore attack with known anti-fungal or ant-repellent effects. Our results provide three important insights into the foraging ecology of LCAs. First, leaf-cutting by Atta ants can induce plant defences: Lima bean plants that were repeatedly exposed to foraging workers of Atta colombica over a period of three days emitted significantly more VOCs than undamaged control plants. Second, the level to which a plant has induced its anti-herbivore defences can affect the LCAs' foraging behaviour: In dual choice bioassays, foragers discriminated control plants from plants that have been damaged mechanically or by LCAs 24 h ago. In contrast, strong induction levels of plants after treatment with the plant hormone jasmonic acid or three days of LCA feeding strongly repelled LCA foragers relative to undamaged control plants. Third, the LCA-specific mode of damaging leaves allows them to remove larger quantities of leaf material before being recognized by the plant: While leaf loss of approximately 15% due to a chewing herbivore (coccinelid beetle) was sufficient to significantly increase VOC emission levels after 24 h, the removal of even 20% of a plant's leaf area within 20 min by LCAs did not affect its VOC emission rate after 24 h. Taken together, our results support the “induced defence hypothesis” and provide first empirical evidence that the foraging behaviour of LCAs is affected by the induction of plant defence responses

High-angular and high-contrast VLTI observations from Y to M band with the Asgard instrumental suite

This is the final version. Available from SPIE via the DOI in this recordSPIE Astronomical Telescopes + Instrumentation 2022, 17 - 22 July 2022, Montreal, CanadaThe Very Large Telescope Interferometer is one of the most proficient observatories in the world for high angular resolution. Since its first observations, it has hosted several interferometric instruments operating in various bandwidths in the infrared. As a result, the VLTI yields countless discoveries and technological breakthroughs. We introduce to the VLTI the new concept of Asgard: an instrumental suite including four natively collaborating instruments: BIFROST, a stellar interferometer dedicated to the study of the formation of multiple systems; Hi- 5, a nulling interferometer dedicated to imaging young nearby planetary systems in the M band; HEIMDALLR, an all-in-one instrument performing both fringe tracking and stellar interferometry with the same optics; Baldr, a fibre-injection optimiser. These instruments share common goals and technologies. Thus, the idea of this suite is to make the instruments interoperable and complementary to deliver unprecedented sensitivity and accuracy from J to M bands. The interoperability of the Asgard instruments and their integration in the VLTI are the main challenges of this project. In this paper, we introduce the overall optical design of the Asgard suite, the different modules, and the main challenges ahead.European Union Horizon 2020Science and Technology Facilities Council (STFC)European Research Council (ERC