Effect of CeO2 on the Glass Structure of Sodium Germanate Glasses

Germanate glasses have potential applications as optical fibers. Materials doped with rare earth ions are good candidates for optical, lasing, and magnetic applications. Based on the ternary system, CeO₂–Na₂O–GeO₂ a series of six glasses were fabricated using powder fusion, and varying the Na₂O content from 0 to 45 mol%, and a CeO₂ content constant at 3 mol%. The glasses were analyzed by FT‐IR, Raman and X‐ray photoelectron (XPS) spectroscopies to obtain information about the glass structure, cerium oxidation's state and how it is introduced in the glass network. FT‐IR and Raman spectra revealed the presence of GeO₆ and GeO₄ groups as well as Q² and Q³ units in the glasses with alkali low content. XPS spectra analysis revealed that the cerium ions were reduced from Ce⁴⁺ to Ce³⁺. The nonbonding to total oxygen ratio was estimated from the curve fitting of the O 1s core level spectra. Density and elastic parameters showed a nonlineal tendency in the change of the physical properties as a function of Na₂O content. Finally, photoluminescence spectroscopy confirmed the presence of Ce³⁺ ions. The characteristic 4f → 5d electronic transitions at 360 nm were detected, when a 280 nm excitation line of pulsed laser was used as excitation source.     

Biological half-lives of eight polycyclic aromatic hydrocarbons (PAHs) in rainbow trout (Salmo gairdneri)

Adult rainbow trout were exposed to a single oral dose containing a mixture of eight PAHs, and fish were sampled at intervals between 5–48 days after exposure. Regression analyses on whole fish indicate levels declined significantly in four of the compounds monitored. Their biological half-lives were estimated as 9 days for phenanthrene, 7 days for fluorene and anthracene and 6 days for fluoranthene. No reliable estimates could be derived for benzo[a]pyrene, benz[a]anthracene, chrysene or pyrene because of low or nondetectable concentrations at the first sample interval although it could be suggested that their half-lives would be less than several days. The data also suggested that these PAHs are poorly absorbed by trout.     

Magnetically triggered nanocomposite membranes: a versatile platform for triggered drug release

Drug delivery devices based on nanocomposite membranes containing thermoresponsive nanogels and superparamagnetic nanoparticles have been demonstrated to provide reversible, on-off drug release upon application (and removal) of an oscillating magnetic field. We show that the dose of drug delivered across the membrane can be tuned by engineering the phase transition temperature of the nanogel, the loading density of nanogels in the membrane, and the membrane thickness, allowing for on-state delivery of model drugs over at least 2 orders of magnitude (0.1-10 μg/h). The zero-order kinetics of drug release across the membranes permit drug doses from a specific device to be tuned according to the duration of the magnetic field. Drugs over a broad range of molecular weights (500-40000 Da) can be delivered by the same membrane device. Membrane-to-membrane and cycle-to-cycle reproducibility is demonstrated, suggesting the general utility of these membranes for drug delivery.     

Nanoparticle-based cerebral drug-delivery systems and antiangiogenic approach in gliomas treatment

The efficacy of current anti-cancer multimodal therapeutic strategies in gliomas is limited by the lack of specific therapies against malignant cells and the prognosis in patients affected by cerebral gliomas remains very unfavorable. Glial tumors seem to be able to create a favorable environment for the invasion of neoplastic cells when they combine with the extracellular matrix through the up-regulation of crucial pathways such as angiogenesis and invasion. The major problem in brain drug delivery is the presence of the blood brain barrier which limits the delivery of many chemotherapeutic agents and other kinds of therapeutic molecules. This event often contributes to the failure of the treatment. Nanoparticle systems can represent ideal devices for delivery of specific compounds to brain tumors across the blood brain barrier. The specificity of hybridization makes antisense method an interesting strategy to selectively modulate the expression of genes involved in tumorigenesis. In this review we will focus on the mechanisms of angiogenesis into gliomas, their importance into tumor progression and the possibilities to block these mechanisms with new nanoparticle-based therapeutic strategies. We will also report the results of preclinical and/or clinical studies that adopt nanoparticle-based antiangiogenic therapeutic approach in cerebral gliomas, considering also some patents deal with antiangiogenic strategy.     

Main aspects of geothermal energy in Mexico

With an installed geothermal electric capacity of 853 MW_e, Mexico is currently the third largest producer of geothermal power worldwide, after the USA and the Philippines. There are four geothermal fields now under exploitation: Cerro Prieto, Los Azufres, Los Humeros and Las Tres Vírgenes. Cerro Prieto is the second largest field in the world, with 720 MW_e and 138 production wells in operation; sedimentary (sandstone) rocks host its geothermal fluids. Los Azufres (88 MW_e), Los Humeros (35 MW_e) and Las Tres Vírgenes (10 MW_e) are volcanic fields, with fluids hosted by volcanic (andesites) and intrusive (granodiorite) rocks. Four additional units, 25 MW_e each, are under construction in Los Azufres and due to go into operation in April 2003. One small (300 kW) binary-cycle unit is operating in Maguarichi, a small village in an isolated area with no link to the national grid. The geothermal power installed in Mexico represents 2% of the total installed electric capacity, but the electricity generated from geothermal accounts for almost 3% of the national total.     

Digital compensation of second‐ and third‐order nonlinear distortions generated by blocker signals

Deeply integrated systems in chips commonly include a digital and an analog front end on the same die. These analog front‐end schemes for wireless communications could be implemented under the concept called software‐defined radio (SDR). Digital signal processing is commonly used to perform signal filtering and channel equalization, and, recently, to improve front‐end radio performance by removing the undesirable effects of the analog front‐end imperfections. These wide‐band SDR are currently implemented without the surface acoustic wave (SAW) filter, because it is difficult to integrate a highly configurable one, as is required in wide‐band systems. An analog front end without this filter has no efficient protection against blocker signal effects, specifically against nonlinear distortions due to the analog front‐end imperfections. This paper proposes an algorithm to simultaneously remove second‐ and third‐order nonlinear distortions caused by a blocker signal, departing from a behavioral model and a band‐pass sampling pure digital algorithm to recover the blocker signal information. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

VoIP traffic in wireless mesh networks: a MOS‐based routing scheme

Support of Voice over Internet Protocol (VoIP) services in wireless mesh networks requires implementation of efficient policies to support low‐delay data delivery. Multipath routing is typically supported in wireless mesh networks at the network level to provide high fault tolerance and load balancing because links in the proximity of the wireless mesh gateways can be very stressed and overloaded, thus causing scarce performance. As a consequence of using multipath solutions, lower delay and higher throughput can be supported also when a given path is broken because of mobility or bad channel conditions, and alternative routes are available. This can be a relevant improvement especially when assuming that real‐time traffic, such as VoIP, travels into the network. In this paper, we address the problem of Quality of Service (QoS) support in wireless mesh networks and propose a multipath routing strategy that exploits the Mean Opinion Score (MOS) metric to select the most suitable paths for supporting VoIP applications and performing adaptive load balancing among the available paths to equalize network traffic. Performance results assess the effectiveness of the proposed approach when compared with other existing methodologies. Copyright © 2015 John Wiley & Sons, Ltd.     

Nurse′s A‐Phase: Synthesis and Characterization in the Binary System Ca2SiO4–Ca3(PO4)2

In the present study, a new single phase Si–Ca–P‐based ceramic was obtained by conventional sintering of compacted mixtures of calcium hydrogen phosphate anhydrous, calcium carbonate, and silicon oxide. The synthesis conditions were the followings: heated up to 1550°C for a total period of time of 72 h (3 d), with quenching in liquid nitrogen, milling, pressing, and reheating every 24 h. Second, heating at 1300°C/3 h and subsequent annealed at 1200°C/24 h. Mineralogical and microstructural characterization of the obtained Si–Ca–P‐based material was determined by Differential Thermal Analysis, X‐ray diffraction, Scanning Electron Microscopy with attached wavelength dispersive spectroscopy, Micro‐Raman and Fourier Transform Infrared Spectrometer. The results showed a single Si–Ca–P phase material with a Ca₂SiO₄/Ca₃(PO₄)₂ molar ratio equal to 2:1. The parameters of the Weibull distribution of strength, determined by diametrical compression of disks, were: modulus, m = 13, and characteristic strength σ₀ = 0.60 MPa.     

Analytical investigation of elastic period of infilled RC MRF buildings

Fundamental period of vibration, dependent on mass and stiffness structure characteristics, is a key parameter in assessing seismic demand. The period can be evaluated both by means of empirical formulas and modal analysis carried out on a structure numerical model. The presence of external or internal infill elements, usually considered as “non-structural” elements, is generally not taken into account in structural modelling, although these elements can significantly increase the lateral stiffness of a Reinforced Concrete (RC) Moment Resisting Frame (MRF) building leading to a modification in dynamic properties.In this study, results of modal analyses carried out on 3D numerical RC MRF building models are presented, varying structure morphology (height, surface area, ratio between plan dimensions) and infill characteristics. Simplified formulas based on regression analysis of obtained numerical data are presented and discussed. These relationships are also compared with similar literature numerical expressions and empirical data from experimental measurements on existing buildings.     

Atomic and electronic properties of realizable size single-crystal GaN nanotubes by first principles

We studied the diameter and wall thickness dependent atomic and electronic properties of practical size single-crystal GaN nanotubes using first principle calculations. Single-crystal GaN nanotubes are similar to the hexagonal GaN nanowires, grown in the [0001] direction with [10-10] facets, except there is an axial hexagonal void in them. We first demonstrated that the atomic and electronic properties of these tubes are mainly determined by the thickness of their wurtzite walls; and their diameters have negligible effects. Then, considering the individual walls of GaN nanotubes in two-dimensional slab calculations we examine the bond distances, formation energy, band gap, effective electron mass and the evolution of electronic density of the states as a function of thickness for unsaturated and hydrogen-saturated slabs of GaN. Calculations revealed that the unsaturated dangling bonds at the surfaces induce defect states in the band gap region of unsaturated tubes. Therefore, regardless of diameter and wall thickness, their band gaps are always smaller than that of the bulk GaN. However, the band gaps of the hydrogen-saturated tubes are found to be amplified with respect to bulk GaN. The amplification in the band gaps as a function of wall thickness in the range of 5.6-16.9 A and 16.9-28.1 A scales with a factor of 1/d(0.9281) and 1/d(1.769), respectively. Our results show that, regardless of diameter, hydrogen saturated single-crystal GaN tubes with the wall thickness as small as 28.1 A would be stable and they would have a noticeably larger band gap with respect to the band gap of bulk GaN.