New conductive thick-film paste based on silver nanopowder for high power and high temperature applications

A new thick-film material for screen-printing technology, based on nanoscale silver powders with the particle size distribution 5-55 nm is presented. Silver nanopowder used for paste preparation was elaborated by the authors. The compatibility of investigated paste was proven with alumina, silicon, Kapton foil and glass. The main advantage of this paste is sinterability at much lower temperatures (around 300 °C) compared to pastes obtained from micro-powders (650-850 °C). The thicknesses of obtained layers are 2-3 μm. The elaborated layers are dense and well sintered, exhibit good adhesion to all above mentioned substrates and low resistivity as well as very good resistance to high power and elevated temperatures. The results of loading the layers deposited on alumina substrates with high current and exposed to high temperature are presented as well.     

MIP model for efficient dimensioning of real-world FTTH trees

We propose a mixed-integer programming (MIP) formulation for a problem of optimal dimensioning of equipment of the fiber-to-the-home optical access network (FTTH-OAN). The optimization aims at minimizing capital expenditures (CAPEX) related to deployment of the FTTH-OAN, i.e., the cost of active equipment (OLTs and OLT cards), cost of passive equipment (optical splitters, cables, fibers, fibers terminations, splices, closures), cost of site preparations (building, cabinets), and cost of necessary labor (duct preparation and rollout of cables). The formulation has been implemented and validated. General results based on selected real-world scale numerical experiments are presented.     

Optimization of link load balancing in multiple spanning tree routing networks

In telecommunication networks based on the current Ethernet technology, routing of traffic demands is based on multiple spanning trees: the network operator configures different routing spanning trees and assigns each demand to be routed in one of the selected spanning trees. A major optimization issue in this solution is the combined determination of (i) a?set of appropriate spanning trees, and (ii) assignment of demands to the trees, in order to achieve an optimal load balancing on the links of the network. In this paper we consider models and solving techniques for lexicographical optimization of two load balancing objective functions. The first objective is the min-max optimization of the n worst link loads (with n up to the total number of network links), and the second objective is the minimization of the average link load (when n is smaller than the total number of network links). Besides exact methods, a heuristic technique that can compute both feasible solutions and lower bounds for the addressed optimization problem is proposed. Finally, we discuss effectiveness of different solution using results of a numerical study of realistic case studies.     

Functionalized Graphdiyne Nanowires: On‐Surface Synthesis and Assessment of Band Structure,Flexibility, and Information Storage Potential

Carbon nanomaterials exhibit extraordinary mechanical and electronic properties desirable for future technologies. Beyond the popular sp²‐scaffolds, there is growing interest in their graphdiyne‐related counterparts incorporating both sp² and sp bonding in a regular scheme. Herein, we introduce carbonitrile‐functionalized graphdiyne nanowires, as a novel conjugated, one‐dimensional (1D) carbon nanomaterial systematically combining the virtues of covalent coupling and supramolecular concepts that are fabricated by on‐surface synthesis. Specifically, a terphenylene backbone is extended with reactive terminal alkyne and polar carbonitrile (CN) moieties providing the required functionalities. It is demonstrated that the CN functionalization enables highly selective alkyne homocoupling forming polymer strands and gives rise to mutual lateral attraction entailing room‐temperature stable double‐stranded assemblies. By exploiting the templating effect of the vicinal Ag(455) surface, 40 nm long semiconducting nanowires are obtained and the first experimental assessment of their electronic band structure is achieved by angle‐resolved photoemission spectroscopy indicating an effective mass below 0.1m₀ for the top of the highest occupied band. Via molecular manipulation it is showcased that the novel oligomer exhibits extreme mechanical flexibility and opens unexplored ways of information encoding in clearly distinguishable CN‐phenyl trans–cis species. Thus, conformational data storage with density of 0.36 bit nm^?2 and temperature stability beyond 150 K comes in reach.     

Identifying the Molecular Mechanisms and Types of Cell Death Induced by bio- and pyr-Silica Nanoparticles in Endothelial Cells

The term “nanosilica” refers to materials containing ultrafine particles. They have gained a rapid increase in popularity in a variety of applications and in numerous aspects of human life. Due to their unique physicochemical properties, SiO₂ nanoparticles have attracted significant attention in the field of biomedicine. This study aimed to elucidate the mechanism underlying the cellular response to stress which is induced by the exposure of cells to both biogenic and pyrogenic silica nanoparticles and which may lead to their death. Both TEM and fluorescence microscopy investigations confirmed molecular changes in cells after treatment with silica nanoparticles. The cytotoxic activity of the compounds and intracellular RNS were determined in relation to HMEC-1 cells using the fluorimetric method. Apoptosis was quantified by microscopic assessment and by flow cytometry. Furthermore, the impact of nanosilica on cell migration and cell cycle arrest were determined. The obtained results compared the biological effects of mesoporous silica nanoparticles extracted from Urtica dioica L. and pyrogenic material and indicated that both types of NPs have an impact on RNS production causing apoptosis, necrosis, and autophagy. Although mesoporous silica nanoparticles did not cause cell cycle arrest, at the concentration of 50 μg/mL and higher they could disturb redox balance and stimulate cell migration.     

Identification of house price bubbles using robust methodology: evidence from Polish provincial capitals

This article aims to check whether there has been a price bubble in the Polish major housing markets in recent years. To accomplish this goal, the log price-to-rent ratios in Polish provincial cities were analysed. In order to avoid incorrect conclusions, the log price-to-rent ratio using the instrumental variable estimation and ordinary least squares methods was decomposed into two components: fundamental and non-fundamental. The latter was then examined using the Phillips, Shi, and Yu procedure to detect explosive and downward movements. The results of the study showed that, in general, over 2011, actual log price-to-rent ratios in the analysed cities were below their fundamental values, i.e., a negative price bubble existed. However, more or less since the beginning of 2013, the surveyed markets have seen an increasing level of the non-fundamental component of the index under study, and its particularly explosive movements are visible in the first quarters of 2014. Finally, this analysis indicated future research directions and study implications for Polish policy-makers, housing investors, and households.

     

Influence of lamination process on optical fiber sensors embedded in composite material

In the paper we present the results of our research on optical fiber sensors embedded into composite material samples. We investigate the influence of the lamination process, axial orientation of an optical fiber sensor and coating of a fiber on stress monitoring of a composite material. In the paper we present two approaches to the case of composite condition monitoring, using a polarimetric fiber optic sensor as well as fiber Bragg gratings. We also present experimental evidence that interaction between a composite material and fiber optic sensors is very significant and depends on many factors such as fiber optic axial orientation and the coating layer surrounding an optical fiber.     

Protein Corona Hinders N-CQDs Oxidative Potential and Favors Their Application as Nanobiocatalytic System

The oxidative properties of nanomaterials arouse legitimate concerns about oxidative damage in biological systems. On the other hand, the undisputable benefits of nanomaterials promote them for biomedical applications; thus, the strategies to reduce oxidative potential are urgently needed. We aimed at analysis of nitrogen-containing carbon quantum dots (N-CQDs) in terms of their biocompatibility and internalization by different cells. Surprisingly, N-CQD uptake does not contribute to the increased oxidative stress inside cells and lacks cytotoxic influence even at high concentrations, primarily through protein corona formation. We proved experimentally that the protein coating effectively limits the oxidative capacity of N-CQDs. Thus, N-CQDs served as an immobilization support for three different enzymes with the potential to be used as therapeutics. Various kinetic parameters of immobilized enzymes were analyzed. Regardless of the enzyme structure and type of reaction catalyzed, adsorption on the nanocarrier resulted in increased catalytic efficiency. The enzymatic-protein-to-nanomaterial ratio is the pivotal factor determining the course of kinetic parameter changes that can be tailored for enzyme application. We conclude that the above properties of N-CQDs make them an ideal support for enzymatic drugs required for multiple biomedical applications, including personalized medical therapies.