Fast Restoration Based on Alternative Wavelength Paths in a Wide Area Optical IP Network

Abstract

In this article we describe an experimental investigation of IP network restoration based on wavelength recovery. We propose a procedure for metro and wide area gigabit Ethernet networks that allows us to route the wavelength in case of link failure to another existing link by exploiting wavelength division multiplexing in the fiber. Such a procedure is obtained by means of an optical switch that is managed by a loss-of-light signal that is generated by a router in case of link failure. Such a method has been tested in an IP network consisting of three core routers with optical gigabit Ethernet interfaces connected by means of 50-km-long single-mode fibers between Rome and Pomezia. Compared with other conventional restoration techniques, such as OSPF and MPLS, our method -in very fast (20 ms) and is compatible with real-time TV services and low-cost chips.     

CIT-7, a crystalline,molecular sieve with pores bounded by 8 and 10-membered rings

A new crystalline molecular sieve, denoted CIT-7, is synthesized using an imidazolium-based diquaternary organic structure directing agent (OSDA). The framework structure is determined from a combination of rotation electron diffraction and synchrotron X-ray powder diffraction data. The structure has 10 crystallographically unique tetrahedral atoms (T-atoms) in the unit cell, and can be described as an ordered arrangement of the [4²5⁴6²] mtw building unit and a previously unreported [4⁴5²] building unit. The framework contains a 2-dimensional pore system that is bounded by 10 T-atom rings (10-ring, 5.1 Å × 6.2 Å opening) that are connected with oval 8-rings (2.9 Å × 5.5 Å opening) through medium-sized cavities (∼7.9 Å) at the channel intersections. CIT-7 can be synthesized over a broad range of compositions including pure-silica and heteroatom, e.g., aluminosilicate and titanosilicate, containing variants.     

Quantitative high temperature absorption spectroscopy of NCO at 305 and 440 nm

A spectral survey of NCO absorption near the P₂ + ^pQ₁₂ head of the [A²Σ + (00⁰0)←X²Π_i(00¹0)] band was obtained at 1450°K, 0.6 atm using a remotely located cw ring dye laser source and a shock tube. Mixtures of hydrogen cyanide, oxygen and nitrous oxide diluted in argon were shock heated to provide a reproducible steady-state concentration of NCO, and narrow-line absorption was measured in repeated experiments with the laser set at different wavelengths. The peak absorption was found at 440.479 nm (vac). The experimental spectrum was compared with a theoretical model to yield an average Voigt parameter a ? 0.1. Additional experiments, in mixtures of cyanogen, oxygen and nitrous oxide diluted in argon, provided a known plateau level of NCO, which was used to infer an absolute absorption coefficient β(1450°K, 0.60 atm) = 110(-50, +130) cm^-1 atm^-1 at 440.479 nm. This value of β corresponds to an oscillator strength of 0.0026 for the (00⁰0←00¹0) band.Similar experiments were conducted to monitor the absorption around the R₁ head of the [B²Π_i(10¹0)←X²Π_i(00¹0)] band of NCO, using a frequency doubled cw ring dye laser. The observed spectrum displayed strong broadening, indicating predissociation of the upper state. At the peak absorption wavelength (304.681 nm, vac), we inferred β(1470°K, 0.63 atm) = 40(-19, +48) cm^-1 atm^-1 and a ? 9. This value of β corresponds to an oscillator strength of 0.0031 for the (10¹0←00¹0) band.     

Quality of Service Measurements over an Optical GMPLS Wide Area Access Network

The introduction of intelligence for management and control of optical networks based on internet protocol and the quality of service (QoS) are key issues for the evolution of the next generation network. In this paper the authors report experimental results on QoS measurements related to different real time multimedia services in an optical network based on a ring configuration obtained by means of the fibers contained in an installed cable between Rome and Pomezia, core routers with optical Gigabit Ethernet interfaces and configured with differentiated service over multi-protocol label switching architecture.     

Preparation of novel hybrid nanomaterials based on LaFeO3 and phosphotungstic acid as a highly efficient magnetic photocatalyst for the degradation of methylene blue dye solution

Novel magnetic hybrid nanomaterials 1 (LaFeO₃.Fe₃O₄@SiO₂-NH₂/PW₁₂) were synthesized by supporting phosphotungstic acid (H₃PW₁₂O₄₀; PW₁₂) on LaFeO₃.Fe₃O₄ nanomaterials through sono-assisted method. The synthesized nanomaterials were fully characterized by using FT-IR, XRD, UV–vis, BET-BJH, VSM, SEM, and TEM analyses. FT-IR, XRD, and UV–vis confirmed successful synthesis of nanomaterials. The SEM and TEM images revealed spherical morphology with core-shell structure for hybrid nanomaterials 1 . VSM results confirmed the magnetic property of hybrid nanomaterials 1 and suggested it as easily recyclable photocatalyst for removal of organic dyes from aqueous solution. The photocatalytic activity of hybrid nanomaterials 1 has been studied over the degradation of methylene blue (MB) and methyl orange (MO) solution under UV–vis light irradiation. Importantly the hybrid nanomaterials 1 showed outstanding degradation efficiency for MB solution in comparison with bare LaFeO₃.Fe₃O₄ and PW₁₂. The photocatalytic activity was enhanced mainly due to the high efficiency in separation of electron–hole pairs induced by the remarkable synergistic effects of LaFeO₃.Fe₃O₄ and PW₁₂ semiconductors. After the photocatalytic reaction, the nanocomposite can be easily separated from the reaction solution and reused several times without loss of its photocatalytic activity. Trapping experiments indicated that hole (h_VB⁺) and ^•OH radicals were the main reactive species for dye degradation in the present photocatalytic system. On the basis of the experimental results and estimated band gaps, the mechanism for the enhanced photocatalytic activity was proposed.     

A nanostructured hybrid material based on polymer infiltrated porous silicon layer

In this work, we report on the fabrication of an hybrid material based on a porous silicon (PSi) layer infiltrated by an amino functionalized poly(ε-caprolattone) (PCL-NH₂). The organic–inorganic structure has been characterized by variable angle spectroscopic ellipsometry, optical reflectometry and water contact angle measurements. A polymer coated PSi layer, 3 μm thick, shows improved wettability and chemical stability against long lasting, up to 18 min, exposure to an alkaline environment. Even after basic treatment, the structure still retains a very good quality optical response, so that it may be proposed as a high performance platform for biochemical sensing applications.     

Influence of the immobilization procedures on the electroanalytical performances of Trametes versicolor laccase based bioelectrode

In this work three different immobilization methods (physico-chemical, electrostatic and covalent) of fungal laccase from Trametes versicolor (TvL) on multi-walled carbon nanotubes electrodes (MWCNTs) have been characterized and compared. To this aim, in particular, the following immobilization agents were used: polyazetidine prepolymer (PAP), Nafion solution and succinimide-carbodiimide (EDC-NHS). The comparison of these procedures has been realized by evaluating the enzymatic activity of the resulting bioelectrodes and their catalytic efficiency for oxygen reduction in the presence of the 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonate) diammonium salt (ABTS) as non-phenolic redox mediator and catechol as phenolic one. Another aspect taken into account was the diffusion evaluation of several mediators as ABTS, dopamine, catechol and caffeic acid across the immobilizing layer at the pH range where the enzyme shows the maximum activity.The experimental results put in evidence the better performances of TvL-PAP-MWCNTs biosensor in terms of bioelectrochemical and diffusion properties, allowing us to asses that PAP is the best immobilizing agent thanks to its good permeability to mediators and the ability to keep the enzyme bioelectrochemical properties.     

Technological applications of chlorophyll <Emphasis Type="Italic">a</Emphasis> fluorescence for the assessment of environmental pollutants

Chlorophyll a fluorescence has been extensively studied over the last few years. As demonstrated, this phenomenon is closely related to the state of photosystem II, which plays a leading role in the photosynthetic process, and therefore it has become a powerful tool to investigate this complex and any damage occurring in it as a result of physical or chemical stresses. This means that by using photosynthetic organisms as biological probes, one can consider chlorophyll a fluorescence as one of the techniques of choice to reveal the presence of some hazardous toxicants widely spread in the environment. Herbicides, pesticides, and heavy metals, whose concentration in water and food products is generally subject to extremely severe restrictions, are a concrete example of compounds detectable by chlorophyll a fluorescence. These dangerous substances react with the photosystem II, modifying the fluorescence emitted and giving responses which vary in a concentration-dependent manner. The possibility of performing easy, fast, and direct measurements of the fluorescence, even under light conditions, has opened new frontiers for the analysis in situ of pollutants. The aim of this review is to give an overview of the different techniques based on chlorophyll a fluorescence spectrometry, focusing in particular on those which represented the starting point for applications addressed to the assessment of toxic compounds in environmental samples.     

Comparison of the absorption, emission, and resonance Raman spectra of 7-hydroxyquinoline and 8-bromo-7-hydroxyquinoline caged acetate

To better understand the deprotection reaction of the new promising phototrigger compound BHQ-OAc (8-bromo-7-hydroxyquinoline acetate), we present a detailed comparison of the UV-vis absorption, resonance Raman, and fluorescence spectra of BHQ-OAc with its parent compound 7-hydroxyquinoline in different solvents. The steady-state absorption and resonance Raman spectra provide fundamental information about the structure, properties, and population distribution of the different prototropic forms present under the different solvent conditions examined. The species present in the excited states that emit strongly were detected by fluorescence spectra. It is shown that the ground-state tautomerization process of BHQ-OAc is disfavored compared with that of 7-HQ in aqueous solutions. The observation of the tautomeric form of BHQ-OAc in neutral aqueous solutions demonstrates the occurrence of the excited-state proton-transfer process, which would be a competing process for the deprotection reaction of BHQ-OAc in aqueous solutions.     

Self-assembled biofilm of hydrophobins protects the silicon surface in the KOH wet etch process

The anisotropic wet micromachining of silicon, based on a water solution of potassium hydroxide (KOH), is a standard fabrication process that is extensively exploited in the realization of very complex microsystems, which comprise cantilevers, membranes, and bridges. A nanostructured self-assembled biofilm of amphiphilic proteins, the hydrophobins, was deposited on crystalline silicon by solution deposition and characterized by variable-angle spectroscopic ellipsometry (VASE). This procedure formed chemically and mechanically stable mono- and multilayers of self-assembled proteins. The biomolecular membrane has been tested as masking material in the KOH wet etch of the crystalline silicon. The process has been monitored by VASE and atomic force microscopy measurements. Because of the high persistence of the protein biofilm, the hydrophobin-coated silicon surface is perfectly protected during the standard KOH micromachining process.