Stochastic population dynamics in turbulent fields

The behavior of interacting populations typically displays irregular temporal and spatial patterns that are difficult to reconcile with an underlying deterministic dynamics. A classical example is the heterogeneous distribution of plankton communities, which has been observed to be patchy over a wide range of spatial and temporal scales. Here, we use plankton communities as prototype systems to present theoretical approaches for the analysis of the combined effects of turbulent advection and stochastic growth in the spatiotemporal dynamics of the population. Incorporation of these two factors into mathematical models brings an extra level of realism to the description and leads to better agreement with experimental data than that of previously proposed models based on reaction-diffusion equations.Comment: 11 pages, 9 figures. Submitted to EPJ Special Topic

Failure of the work-Hamiltonian connection for free energy calculations

Extensions of statistical mechanics are routinely being used to infer free energies from the work performed over single-molecule nonequilibrium trajectories. A key element of this approach is the ubiquitous expression dW/dt=\partial H(x,t)/ \partial t which connects the microscopic work W performed by a time-dependent force on the coordinate x with the corresponding Hamiltonian H(x,t) at time t. Here we show that this connection, as pivotal as it is, cannot be used to estimate free energy changes. We discuss the implications of this result for single-molecule experiments and atomistic molecular simulations and point out possible avenues to overcome these limitations

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

Perancangan Sistem Pengelolaan Penanggulangan Bencana Alam Garut Berbasis Sistem Informasi Geografis

Kabupaten Garut setiap tahunnya tidak terlepas dari namanya bencana alam, salah satunya yang sempat mengejutkan di tahun 2016 yaitu bencana banjir bandang Garut, namun proses penyebaran informasi mitigasi bencana dirasakan masih belum optimal sehingga kebutuhan informasi proses mitigasi bencana alam harus bisa disampaikan dengan cepat kepada pihak-pihak terkait. Teknologi Sistem Informasi Geografis (SIG) merupakan perangkat lunak yang berfungsi untuk memasukan, menyimpan, memanipulasi serta menampilkan informasi geografis beserta atribut-atributnya, sehingga teknologi SIG ini sangat cocok diterapkan dalam sistem informasi pengelolaan dan penanggulangan bencana alam. Tujuan dari penelitian ini adalah untuk membuat sarana informasi dalam hal mitigasi bencana alam dengan memanfaatkan sistem informasi geografis, yaitu dengan membuat perangkat lunak aplikasi pengelolaan dan penanggulangan bencana alam Garut berbasis Sistem Informasi Geografis, sehingga dapat digunakan oleh pihak yang berkepentingan dalam kemudahan pengelolaan dan pemberian informasi mitigasi bencana alam di Kabupaten Garut. &nbsp

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

Unifying thermodynamic and kinetic descriptions of single-molecule processes: RNA unfolding under tension

We use mesoscopic non-equilibrium thermodynamics theory to describe RNA unfolding under tension. The theory introduces reaction coordinates, characterizing a continuum of states for each bond in the molecule. The unfolding considered is so slow that one can assume local equilibrium in the space of the reaction coordinates. In the quasi-stationary limit of high sequential barriers, our theory yields the master equation of a recently proposed sequential-step model. Non-linear switching kinetics is found between open and closed states. Our theory unifies the thermodynamic and kinetic descriptions and offers a systematic procedure to characterize the dynamics of the unfolding processComment: 13 pages, 3 figure

Epitaxial ferroelectric memristors integrated with silicon

Neuromorphic computing requires the development of solid-state units able to electrically mimic the behavior of biological neurons and synapses. This can be achieved by developing memristive systems based on ferroelectric oxides. In this work we fabricate and characterize high quality epitaxial BaTiO3-based memristors integrated with silicon. After proving the ferroelectric character of BaTiO3 we tested the memristive response of LaNiO3/BaTiO3/Pt microstructures and found a complex behavior which includes the co-existence of volatile and non-volatile effects, arising from the modulation of the BaTiO3/Pt Schottky interface by the direction of the polarization coupled to oxygen vacancy electromigration to/from the interface. This produces remanent resistance loops with tunable ON/OFF ratio and asymmetric resistance relaxations. These properties might be harnessed for the development of neuromorphic hardware compatible with existing silicon-based technology

Symbiosis by Persons with Disabilities: Perspectives from Interviews

This study reports on an interview perspective on symbiosis by persons with disabilities. A main theme, Elements of Symbiotic Collaboration, emerged from the data, along with several subthemes. Symbioses described by participants are closely related to the concepts of independence and interdependence in the Disability Studies literature