Sub-wavelength imaging at infrared frequencies using an array of metallic nanorods

We demonstrate that an array of metallic nanorods enables sub-wavelength (near-field) imaging at infrared frequencies. Using an homogenization approach, it is theoretically proved that under certain conditions the incoming radiation can be transmitted by the array of nanorods over a significant distance with fairly low attenuation. The propagation mechanism does not involve a resonance of material parameters and thus the resolution is not strongly affected by material losses and has wide bandwidth. The sub-wavelength imaging with $\lambda/10$ resolution by silver rods at 30 THz is demonstrated numerically using full-wave electromagnetic simulator.Comment: 12 pages, 16 figures, submitted to PR

Incomplete quantum process tomography and principle of maximal entropy

The main goal of this paper is to extend and apply the principle of maximum entropy (MaxEnt) to incomplete quantum process estimation tasks. We will define a so-called process entropy function being the von Neumann entropy of the state associated with the quantum process via Choi-Jamiolkowski isomorphism. It will be shown that an arbitrary process estimation experiment can be reformulated in a unified framework and MaxEnt principle can be consistently exploited. We will argue that the suggested choice for the process entropy satisfies natural list of properties and it reduces to the state MaxEnt principle, if applied to preparator devices.Comment: 8 pages, comments welcome, references adde

Behavioral strategies for periodontal health.

The impact of lifestyle factors has been increasingly studied and discussed in oral healthcare. Positive lifestyle factors are important in maintaining oral health or controlling disease, but they are not easy to adopt over the long term. Along with public health initiatives within communities and groups, there is a role for behavior change interventions delivered in dental practice settings to improve the periodontal health of individuals. Behavior management is now seen as a part of both prevention and therapy of periodontal diseases. This article summarizes the evidence on behavioral strategies for periodontal health to inform and assist oral healthcare professionals in implementing behavior change in their practice. In addition, strategies for education and training in communication and behavior change techniques are considered

Simulation of indivisible qubit channels in collision models

A sequence of controlled collisions between a quantum system and its environment (composed of a set of quantum objects) naturally simulates (with arbitrary precision) any Markovian quantum dynamics of the system under consideration. In this paper we propose and study the problem of simulation of an {\it arbitrary} quantum channel via collision models. We show that a correlated environment is capable to simulate {\it non-Markovian} evolutions leading to any indivisible qubit channel. In particular, we derive the corresponding master equation generating a continuous time non-Markovian dynamics implementing the universal NOT gate being an example of the most non-Markovian quantum channels.Comment: 6 pages, 2 figures, submitted to JP

Biot-Savart-like law in electrostatics

The Biot-Savart law is a well-known and powerful theoretical tool used to calculate magnetic fields due to currents in magnetostatics. We extend the range of applicability and the formal structure of the Biot-Savart law to electrostatics by deriving a Biot-Savart-like law suitable for calculating electric fields. We show that, under certain circumstances, the traditional Dirichlet problem can be mapped onto a much simpler Biot-Savart-like problem. We find an integral expression for the electric field due to an arbitrarily shaped, planar region kept at a fixed electric potential, in an otherwise grounded plane. As a by-product we present a very simple formula to compute the field produced in the plane defined by such a region. We illustrate the usefulness of our approach by calculating the electric field produced by planar regions of a few nontrivial shapes.Comment: 14 pages, 6 figures, RevTex, accepted for publication in the European Journal of Physic

Microplastic and natural sediment in bed load saltation: material does not dictate the fate

Microplastic (MP) pollution is a well document threat to our aquatic and terrestrial ecosystems, however, the mechanisms by which MPs are transported in river flows are still unknown. The transport of MPs and natural sediment in aquatic flows could be somewhat comparable, as particles are similar in size. However, it is unknown how the lower density of MPs and their different material properties impact their transport dynamics. To answer this, novel laboratory experiments on bed load saltation dynamics in an open-channel flow, using high-speed camera imaging and the detection of 11,035 individual saltation events were used to identify the similarities and differences between spherical MPs and spherical natural sediments transport. The tested MPs varied in terms of size and material properties (density and elasticity). Our analysis shows that the Rouse number accurately describes saltation length, height, transport velocity and collision angles equally well for both MPs and natural sediments. Through statistical inference, the distribution functions of saltation trajectory characteristics for MPs were analogous to natural sediment with only one sediment experiment (1.4 % of cases) differing from all other plastic experiments. Similarly, only nine experiments (9.3 % of cases) showed that collision angles for MPs differed from those of natural sediment experiments. Differences observed in terms of restitution become negligible in overall transport dynamics as turbulence overcomes the kinetic energy lost at particle-bed impact, which keeps particle motion independent from impact. Overall, spherical MP particles behave similarly to spherical natural sediments in aquatic environments under the examined experimental conditions. This is significant because there is an established body of knowledge for sediment transport that can serve as a foundation for the study of MP transport

Process POVM: A mathematical framework for the description of process tomography experiments

In this paper we shall introduce the mathematical framework for the description of measurements of quantum processes. Using this framework the process estimation problems can be treated in the similar way as the state estimation problems, only replacing the concept of positive operator valued measure (POVM) by the concept of process POVM (PPOVM). In particular, we will show that any measurement of qudit channels can be described by a collection of effects (positive operators) defined on two-qudit system. However, the effects forming a PPOVM are not normalized in the usual sense. We will demonstrate the usage of this formalism in discrimination problems by showing that perfect channel discrimination is equivalent to a specific unambiguous state discrimination.Comment: 4 pages, comments are welcom

Sandpiles with height restrictions

We study stochastic sandpile models with a height restriction in one and two dimensions. A site can topple if it has a height of two, as in Manna's model, but, in contrast to previously studied sandpiles, here the height (or number of particles per site), cannot exceed two. This yields a considerable simplification over the unrestricted case, in which the number of states per site is unbounded. Two toppling rules are considered: in one, the particles are redistributed independently, while the other involves some cooperativity. We study the fixed-energy system (no input or loss of particles) using cluster approximations and extensive simulations, and find that it exhibits a continuous phase transition to an absorbing state at a critical value zeta_c of the particle density. The critical exponents agree with those of the unrestricted Manna sandpile.Comment: 10 pages, 14 figure

Molecular structure and polymorphism of a cyclohexanediol: trans-1,4-cyclohexanedimethanol

This study aims to investigate the molecular structure and polymorphism of trans-1,4-cyclohexanedimethanol, including the bi-axial/bi-equatorial equilibrium and the nature of the intermolecular H-bond networks in condensed phases created by the hydroxyl group torsions. The full conformational space of the single molecule was explored by MP2 calculations, showing that the optimized bi-equatorial conformers have similar stability and the bi-axial ones have much higher energies. The hydroxymethyl substituents have preference for gauche/anti or gauche+/gauche− conformations. Polymorphic forms were generated by crystallization from solutions and by cooling the melt, which were characterized by a combination of techniques: DSC, PLTM and XRD. Two polymorphs were isolated and their crystal structures were solved by direct methods based on single-crystal X-ray analysis. Both were found to contain two of the most stable conformers found in the computational calculations. The influence of H-bonding in the polymorphic structures was verified by analysis of the structural differences between the geometries present in the polymorphs determined by XRD and their single molecule counterparts resulting from the theoretical calculations. The bi-axial conformations are destabilized over the bi-equatorial ones in isolated and crystalline forms of trans-1,4-cyclohexanedimethanol