Marius Radulescu

Compact modeling and fast simulation of on-chip interconnect lines

An efficient methodology to extract compact models for microstrip lines on lossy silicon substrate is presented. The transversal magnetic field equations are solved by dual finite integration technique (dFIT), a numerical method which allows the accuracy control of the computed frequency dependent line parameters. Several techniques are used to accelerate the process of p.u.l. parameters extraction, such as minimal virtual boundary, minimal mesh and minimal frequency samples set. The solution of the transmission line equations with frequency dependent parameters is then approximated by a rational function of appropriate degree in order to extract the compact model and its SPICE equivalent circuit. The behavior of the obtained compact model of order 10 shows good agreement with respect to the measured data

Antimicrobial Chitosan based formulations with impact on different biomedical applications.

Owing to its physico-chemical characteristics, the biodegradable and biocompatible polymer derived from crustacean shells, Chitosan is one of the preferred candidates for green biomedical applications and also for several industries. Its solubility in acid solutions and ability to form complexes with anionic macromolecules to yield nanoparticles, microparticles and hydrogels, as well as the ability of chitosan based nanocomposites to remain stable at physiological pH recommend this polymer for the development of efficient drug delivery systems. This paper reviews the main utilities of chitosan as a drug delivery component and describes the most recent technologies which utilize this polymer for developing nanostructured systems with antimicrobial effect, offering a perspective of using these findings in new, ecological biomedical applications.

Absorbing boundary conditions for compact modeling of on‐chip passive structures

Purpose – The paper has the purpose of proposing a new open boundary condition to be used in conjunction with the finite integration technique (FIT) for the modelling of passive on‐chip components.Design/methodology/approach – This boundary condition is ensured by using a virtual layer that surrounds the computational domain.Findings – The paper proves which are the optimal material properties of the equivalent layer of open boundary.Practical implications – When modelling passive on‐chip components with FIT, the method proposed is more efficient than the strategic dual image technique.Originality/value – The paper shows the advantage of this approach – that the analysis algorithm remains unchanged, while saving the field‐circuit compatibility properties, such as current conservation.

Silver Nanocoatings for Reducing the Exogenous Microbial Colonization of Wound Dressings

The aim of this work was to obtain an antimicrobial coating (NanoAg) for polyester-nylon wound dressings (WDs) for reducing the risk of exogenous wound related infections. The as-prepared NanoAg-WDs were characterized by XRD (X-ray Diffraction), SEM (Scanning Electron Microscopy), TEM (Transmission Electron Microscopy), SAED (Selected Area Electron Diffraction) and IRM (InfraRed Microscopy). Biological characterization consisted of in vitro evaluation of the interaction with fibroblast cell cultures and in vivo biodistribution studies of AgNPs on mice models. Then, specimens of commercial WDs were immersed in a glucose and NaOH solution of silver nanoparticles, followed by the subsequent dropwise addition of AgNO3 solution. The antimicrobial efficiency of the NanoAg-WDs was assessed by in vitro qualitative and quantitative analyses on Staphylococcus aureus and Pseudomonas aeruginosa strains. The in vitro and in vivo studies demonstrated that the tested nanoparticles utilized to coat WDs have a good biocompatibility, allowing the normal development of cultured human cells and revealing a normal biodistribution within a mouse model, without toxic effects. The modified and viable cells count analyses proved that the modified WDs exhibit an improved inhibitory activity of microbial colonization, attachment and biofilm growth. The reported data recommend this type of coatings to obtain modified WDs with antibacterial properties, able to prevent the exogenous microbial contamination of the wound tissue, colonization and further biofilm development.

Magnetite: from synthesis to applications.

In this review the synthesis, functionalization and some applications of magnetite nanoparticles (MNPs) were highlighted. It is our intention to highlight the correlations between the synthesis routes, related synthesis parameters, functionalization strategies and the properties expected for the materials containing MNPs. The uses of MNPs are strongly influenced by the properties of the materials. Therefore this review is trying to discuss the applications of the magnetite and magnetite based nanomaterials by taking into account all the factors that can influence the properties of the final materials and consequently their potential applications.

Kinetics of Cesium and Strontium Ions Removal from Wastewater on Gel and Macroporous Resins

Abstract Ion exchange kinetics of H+/Cs+ and H+/Sr2+ on strong and weak acid resins with gel and macroporous matrices was investigated at constant temperature. The rate was measured in a batch reactor using a potentiometric method under conditions favoring a particle diffusion controlled mechanism. Intraparticle interdiffusion coefficients were obtained by modeling the data with quasi‐homogeneous resin phase and bidisperse pore kinetic models, considering a two‐stage and parallel diffusion in macro‐ and micro‐pores, respectively. The ratios of the functional groups grafted in the micro‐ and macro‐pores were evaluated for different cases. The macroporous matrix produces a greater retarding effect than the gel skeleton.

Tetracycline loaded collagen/hydroxyapatite composite materials for biomedical applications

The paper describes the preparation, characterisation, and testing of tetracycline loaded collagen-carboxymethylcellulose/ hydroxyapatite ternary composite materials. The synthesis of this drug delivery system consists in two steps: the first step is the mineralization of collagen-carboxymethylcellulose gel while the second step corresponds to the loading of the ternary composite material with tetracycline. The obtained DDS is characterised by physicochemical, morphological, and release behaviour by using FTIR spectroscopy and microscopy, scanning electron microscopy, and UV-VIS spectroscopy. Based on the release study, it can be assumed that tetracycline is released in a prolonged way, assuring at least 6 days of antiseptic properties.

A Procedure to Monitor Sulfonation of Macroporous Styrene‐Divinylbenzene Resins

Abstract The ratio between the number of functional groups grafted in micro and macropores for Purolite C 150 resin, a macroporous styrene‐divinylbenzene copolymer, with –SO3H functional groups, was evaluated using a kinetic procedure based on a bidisperse pore model. The proposed procedure requires potentiometric measurement at constant temperature in batch system of the fractional approach to equilibrium for H+/Na+ ion exchange process on the macroporous resin in concentrated external solution, 1.00 mol/L NaCl. The macropore integral interdiffusion coefficients were computed at each point on the fractional approach to equilibrium versus time curve, for different values of the β/α parameter of the model, which is three times the ratio of micropore and macropore uptake at equilibrium. Several discrimination criteria were used to select a reliable β/α value. The result for Purolite C 150 resin is β/α ≤ 0.03; the ratio between the sulfonic groups grafted onto micro and macropores is equal to or lower than 1/100.

Trends in Materials Science for Ligament Reconstruction

The number of ligament injuries increases every year and concomitantly the need for materials or systems that can reconstruct the ligament. Limitations imposed by autografts and allografts in ligament reconstruction together with the advances in materials science and biology have attracted a lot of interest for developing systems and materials for ligament replacement or reconstruction. This review intends to synthesize the major steps taken in the development of polymer-based materials for anterior cruciate ligament, their advantages and drawbacks and the results of different in vitro and in vivo tests. Until present, there is no successful polymer system for ligament reconstruction implanted in humans. The developing field of synthetic polymers for ligament reconstruction still has a lot of potential. In addition, several nano-structured materials, made of nanofibers or in the form of ceramic/polymeric nanocomposites, are attracting the interest of several groups due to their potential use as engineered scaffolds that mimic the native environment of cells, increasing the chances for tissue regeneration. Here, we review the last 15 years of literature in order to obtain a better understanding on the state-of-the-art that includes the usage of nano- and poly-meric materials for ligament reconstruction, and to draw perspectives on the future development of the field.

Advances in Drug Delivery Systems, from 0 to 3D superstructures.

BACKGROUND Nanomedicine is currently exploited for manufacturing therapeutic DDS and treatments protocols for various diseases and disorders. To obtain DDS, different types of materials are used, from organic to inorganic, polar to non-polar, micro to nanomaterials from 0D to 3D structured materials, respectively. Many of these materials were extensively studied and reviewed in the literature. OBJECTIVE The objectives of this review is to make a clear overview on drug delivery systems depending several aspects related to delivery mechanisms, the type of supports, the active agents ant the potential applications in the prevention or treatment of various diseases. RESULTS Following aspects are extensively debated: synthesis issues, characteristics and potential uses of 0, 1, 2 and 3D drug delivery systems according to their nature and applications. These systems can be can be tailored according to the delivery mechanism (0-3D delivery) as well as by using more active agents, with more therapeutic activity or same activity but with different mechanisms of action. The size and morphology of the drug delivery system is essential, especially when talking about the internalization into the tumor cells while the mobility is especially dependent on the size. The influence of the nature of the supports and their polarity was extensively studied during the last decades, as well as the importance of the porosity and pore size, but only limited papers are devoted to the holistic analysis of the dimensionality of the support and the ways of delivering the active agents. CONCLUSION This review is devoted to a holistic insight into the drug delivery systems, from a new, only marginally studied point of view, meaning the dimensionality of the drug delivery systems and the characteristics of the delivery.