Restricted scaling range models for turbulent velocity and scalar energy transfers in decaying turbulence

The effect of finite Reynolds numbers and/or internal intermittency on the total kinetic energy and scalar energy transfers is examined in detail. For this purpose, two distinct models for velocity and scalar energy transfer are proposed in the specific context of freely decaying isotropic turbulence. The first one extends the already existing dynamical models (hereafter DYM, i.e. based on transport equations originated in Navier–Stokes and advection-diffusion transport equations). The second one relies on the characteristic time of the strain at a specific scale (hereafter SBM). Both models account for the Reynolds number dependence of the scaling exponent of the second-order structure functions, over a range of scales where such exponents may be defined, i.e. a restricted scaling range (RSR). Therefore, the models developed aim at reproducing the energy transfer over the RSR. The predicted energy transfer is very sensible to variations of the scaling exponent, especially at low Reynolds numbers. The approach towards the asymptotic 4/3 law is closely reproduced by the two models. The dynamical model reproduces the experimental results accurately especially in the vicinity of the Taylor microscale, while the SBM agrees almost perfectly with measurements at nearly all scales.     

Vortex Dipoles Impinging on Finite Aspect Ratio Rectangular Obstacles

Numerical simulations of a vortex dipole rebound from finite aspect ratio rectangular obstacles are presented. Compared to the dipole interaction with infinite flat walls studied by Orlandi (Phys. Fluids A2 (1990) 1429) new phenomena are observed. Secondary dipoles formed after the first rebound can undergo head-on collisions and partner exchange. A new lifting dipole is generated, moving in the opposite direction of the initial dipole. This phenomenon occurs for a ratio between the half-width of the obstacle and the dipole radius lower than a critical value depending on the Reynolds number of the flow. Scatter plots show a quasi-linear vorticity-stream function relationship for the lifting dipole. Some passive control strategies to inhibit the generation of lifting dipoles are also suggested.     

Optimal Relay Location for Resource-limited Energy-efficient Wireless Communication

In the design of wireless networks, techniques for improving energy efficiency and extending network lifetime have great importance, particularly for defense and civil/rescue applications where resupplying transmitters with new batteries is not feasible. In this paper we study a method for improving the lifetime of wireless networks by minimizing the length of the longest edge in the interconnecting tree by deploying additional relay nodes at specific locations. This optimization problem, known as the Bottleneck Steiner Tree Problem (BSTP), asks to find a Steiner tree for n terminals with at most k Steiner points such that the length of the longest edge in the tree is minimized. We present a ratio- polynomial time approximation algorithm for BSTP, where is an arbitrary positive number.     

Ergodic Subequivalence Relations Induced by a Bernoulli Action

Let Γ be a countable group and denote by S{\mathcal{S}} the equivalence relation induced by the Bernoulli action G\curvearrowright [0, 1]^G{\Gamma\curvearrowright [0, 1]^{\Gamma}}, where [0, 1]^Γ is endowed with the product Lebesgue measure. We prove that, for any subequivalence relation R{\mathcal{R}} of S{\mathcal{S}}, there exists a partition {X _i } _i≥0 of [0, 1]^Γ into R{\mathcal{R}}-invariant measurable sets such that R_|X0{\mathcal{R}_{\vert X_{0}}} is hyperfinite and R_|Xi{\mathcal{R}_{\vert X_{i}}} is strongly ergodic (hence ergodic and non-hyperfinite), for every i ≥ 1.     

Polysaccharide-Based Drug Delivery Systems for the Treatment of Periodontitis

Periodontal diseases are worldwide health problems that negatively affect the lifestyle of many people. The long-term effect of the classical treatments, including the mechanical removal of bacterial plaque, is not effective enough, causing the scientific world to find other alternatives. Polymer–drug systems, which have different forms of presentation, chosen depending on the nature of the disease, the mode of administration, the type of polymer used, etc., have become very promising. Hydrogels, for example (in the form of films, micro-/nanoparticles, implants, inserts, etc.), contain the drug included, encapsulated, or adsorbed on the surface. Biologically active compounds can also be associated directly with the polymer chains by covalent or ionic binding (polymer–drug conjugates). Not just any polymer can be used as a support for drug combination due to the constraints imposed by the fact that the system works inside the body. Biopolymers, especially polysaccharides and their derivatives and to a lesser extent proteins, are preferred for this purpose. This paper aims to review in detail the biopolymer–drug systems that have emerged in the last decade as alternatives to the classical treatment of periodontal disease.     

Instrumental analysis and molecular modelling of inclusion complexes containing artesunate

Journal of Thermal Analysis and Calorimetry - The following work experimentally and numerically investigated the thermal performance of a hybrid nanofluid, prepared by decorating a nanostructured...     

Metallized electrospun polymeric fibers for electrochemical sensors and actuators

Electrospun polymeric fibers present an emerging alternative for the development of flexible electronics, enabling applications in wearable sensors and biosensors for continuous monitoring, and actuators for tissue engineering. The possibility to prepare sub-micrometric polymeric scaffolds, their processing for increasing the conductivity, their modification with different materials, conductive polymers and biomolecules in order to obtain functional flexible electrodes, allows the development of innovative devices for healthcare, and biomedical applications. In this review, the impact of metallized electrospun polymeric fibers in electrochemical (bio)sensors and actuators is discussed. A relation between their structure and functionality is provided, alongside with an overview of the different methods to obtain functional conductive fibers.     

Polymer-assisted crystallization of low-dimensional lead sulfide particles

PbS micro- and nanoparticles were synthesized by a simple precipitation reaction of lead nitrate with thioacetamide in hydrosoluble polymer water solutions. The effects of four water soluble polymers: polyacrylamide (PAM), polyvinyl alcohol (PVA), polyethylene glycol (PEG) and poly-N-vinyl pyrrolidone (PVP) on the PbS crystallites morphology and structural properties were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that for the PbS particles obtained in the PVA, PEG and PVP, the (2 0 0) diffraction peak of the nanocrystals becomes dominant. The highest texture in the [2 0 0] direction was observed for the crystallites obtained in the presence of PVP. Polydisperse PbS particles with cubic morphology and size ranging from 100 nm to several microns are obtained in the case of PAM and PEG. Monodisperse cubic PbS crystallites with an average size of 200 nm are formed in the presence of PVA and PVP.