Key building blocks for high-capacity WDM photonic transportnetworks

The objective of this paper is to give an overview of the different studies we have performed at the research level regarding the design and implementation of a photonic wavelength division multiplexing (WDM) layer providing transparent transport services to client layers (SONET/SDH, ATM, etc.). Such a network requires a number of enabling factors to be assessed in order to become a reality. Among these factors are the availability of high-capacity WDM transmission systems and efficient optical routing nodes based on mature technology, the design of robust networks optimizing the utilization of resources, and the development of a management system in accordance with presently applied standards for transport networks. We review our achievements in these different fields     

Circuit macromodels and large-signal behaviour of fet-input operational amplifiers

The origin of the slew rate asymmetry found experimentally in FET-input LF355 op amps is analysed in order to explain why macromodels based on a strict build-up technique can fail when used to simulate the behaviour of amplifiers driven by out-of-band large voltage signals. These simulations may be very important in predicting the effects of electromagnetic interferences conveyed to the circuit input port. Other performances of op amp macromodels designed either by build-up techniques or by simplification/build-up techniques are also compared and discussed.     

Modeling HERG and its interactions with drugs: recent advances in light of current potassium channel simulations

The hERG K(+) channel is responsible for the rapid delayed rectifier current in cardiac myocytes, and a block of its functioning may be related with the (inherited or drug-induced) long QT syndrome. For this reason, in recent times, some interest has arisen around computational studies aimed at developing hERG/drug models for the prediction of drug binding (docking) modes, in view of the assessment of the hERG blocking potential. On the other hand, voltage-gated K(+) channels have been the subject of molecular simulations for several years, and rigorous protocols for studying the main aspects of their functions (permeation, gating, voltage sensing) have been published. In this article, we briefly introduce these classical computational works on K(+) channels, and then review in depth the reports on the latest advanced modeling studies on hERG. The aim is to put the hERG modeling work in the more general context of the ion channel simulations field, to show the peculiarity of hERG on the one side, and also to indicate some possible new avenues in the use of modeling techniques to increase our knowledge of this important channel.     

Mechanism of ammoxidation of propane on a Sb/V/O system

The mechanism of the direct ammoxidation of propane is investigated on a Sb/V mixed oxide catalyst (atomic ratio 5/1) in order to understand the sequence of the intermediates and the role of ammonia in the formation of acrylonitrile. The sample was characterized by different techniques (BET, FTIR, XRD and XPS) and tested in different conditions (oxidation and ammoxidation of propane and propene). It is proposed that propane is first converted to propene and hence to ``oxidation products' (which could be acrolein or an intermediate absorbed on the catalyst surface, as allyl radical). In the absence of ammonia these ``oxidation products' are converted to carbon oxide. But in its presence they are converted into acrylonitrile, which is appreciably more stable and undergoes minor degrees of oxidative degradation. This revised version was published online in July 2006 with corrections to the Cover Date.     

In vitro antioxidant capacity of honeybee-collected pollen of selected floral origin harvested from Romania

Total phenolic phytochemical concentration was measured in 12 honeybee-collected pollens of selected floral species as well as their antioxidant capacity. The content of total polyphenols was measured spectrophotometrically using the Folin–Ciocalteu reagent with gallic acid as standard. The antioxidant properties were evaluated by 2,2-diphenyl-picrylhydrazyl radical scavenging capacity (DPPH) assay, Trolox equivalent antioxidant Capacity procedure and Ferric ion reducing antioxidant power assay. A great variability regarding the correspondence between the antioxidant activity and the content of total polyphenols of honeybee-collected pollens with different botanical origin was found. Antioxidant activities were different for each floral species and were not clearly associated to their total phenolic content.     

The electrochromic response of tungsten bronzes MxWO3 with different ions and insertion rates

The electrochemical intercalation of Li⁺ and Na⁺ into thin WO₃ films prepared by evaporation (130 nm thick) has been performed starting from liquid electrolytes with very low water content (< 20 ppm). Transmittance and reflectace measurements have been performed ‘in-situ’ during the electrochemical formation of the tungsten bronzes under controlled current. For inserted charges larger than 20 mCcm⁻² there is an optical transition responsible for a pale yellow coloration instead of the typical dark blue. This transition is irreversible since the subsequent bleaching of the film is not complete and a part of the inserted charge cannot be extracted again. When the insertion rate is high (0.4 mAcm⁻²) the irreversible transition occurs earlier (around 10 mCcm⁻²) in the case of Na⁺, which is known to diffuse slowly into the film. This limit composition for reversible electrochromic reaction is therefore reached earlier near the film surface, where the accumulation of the Na ions is responsible for an optical transition seen in the reflectance and for a phase change shown by a typical inflection in the electrode potential curve.     

Necrotizing Enterocolitis: Overview on In Vitro Models

Necrotizing enterocolitis (NEC) is a gut inflammatory disorder which constitutes one of the leading causes of morbidity and mortality for preterm infants. The pathophysiology of NEC is yet to be fully understood; several observational studies have led to the identification of multiple factors involved in the pathophysiology of the disease, including gut immaturity and dysbiosis of the intestinal microbiome. Given the complex interactions between microbiota, enterocytes, and immune cells, and the limited access to fetal human tissues for experimental studies, animal models have long been essential to describe NEC mechanisms. However, at present there is no animal model perfectly mimicking human NEC; furthermore, the disease mechanisms appear too complex to be studied in single-cell cultures. Thus, researchers have developed new approaches in which intestinal epithelial cells are exposed to a combination of environmental and microbial factors which can potentially trigger NEC. In addition, organoids have gained increasing attention as promising models for studying NEC development. Currently, several in vitro models have been proposed and have contributed to describe the disease in deeper detail. In this paper, we will provide an updated review of available in vitro models of NEC and an overview of current knowledge regarding its molecular underpinnings.     

Rutile-type Cr/Sb mixed oxides as heterogeneous catalysts for the ammoxidation of propane to acrylonitrile

Cr/Sb mixed oxides with a rutile-type structure were synthesized by calcining (700°C) a mixture of oxohydrates obtained by coprecipitation from an alcohol solution containing the required amount of the components. The samples were characterized using X-ray powder diffraction (XRD), FT-IR spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). In the Cr/Sb/O compound prepared with Cr/Sb 1/0.8 (atomic ratio), an almost stoichiometric CrSbO₄develops (no antimony or chromium oxides are found), which however is characterized by enrichment in Sb in outmost rutile atomic layers, and thus by a non-homogeneous intracrystalline distribution of the two components. For Cr/Sb ratios lower than 1, the amount of Sb in the rutile-type structure exceeds the stoichiometric value. The reactivity of Cr/Sb/O catalysts with increasing Sb contents (from Cr/Sb 1/0.8 to 1/2.8) is slightly affected by the Cr/Sb atomic ratio. In particular, the selectivity increases with increasing Sb content, while the catalytic activity is higher for the samples having higher Cr/Sb ratios. The Cr/Sb/O system presents considerable differences with respect to the V/Sb/O rutile system; these differences are discussed in reference to the properties of the transition metal components of the rutile mixed oxides.     

A companion macromodelling approach for the transient analysis of MOS large-scale integrated circuits

Purpose of this work is to present a new macromodelling approach for the simulation at the device level of large MOS integrated circuits, requiring only marginal modifications to be implemented in the widely used circuit simulator SPICE. This method results in a substantial saving in computing time and guarantees the same accuracy of SPICE. A prototype simulator based on this method has been developed and used to analyse several significant circuits. In addition, since the method is particularly suitable to be implemented in parallel computers, some results obtained with the CRAY-YMP/432 computer are provided.     

Optical routing of asynchronous, variable length packets

We discuss the introduction/implementation of optical IP routers, then we introduce a novel scheduling algorithm incorporating void filling and aimed at optical routing of asynchronous, variable packet length packets. We describe its structure and discuss the complexity issues. Albeit introduced with the purpose of cancelling expensive optical synchronization, we argue that this approach represents the most viable all-optical approach for implementing packets-over-SONET (IP-centric scenario). We also present simulations under self-similar traffic conditions which point to the inefficiency of optical buffering to combat the effects of self-similarity, and we outline alternative strategies for proper buffer dimensioning.