Stabilization of interferometric response using a polarization scrambler

This paper shows, theoretically and experimentally, how a polarization scrambler increases the response stability of a fiber Mach–Zehnder interferometer. We have studied the situation when the scrambler is placed in one of the interferometer branches and also when it is placed at the interferometer input. The measurements carried out using a scrambler based on the Faraday effect, agree with the simulation results.     

Synthesis,characterisation and chromatographic evaluation of polyether dendrimer stationary phases

Supercritical carbon dioxide has attracted attention as a potential replacement for traditional organic solvents due to its simplified workup procedures and reduced environmental impact—providing a green chemistry approach for organic solvent-free functionalisation. In addition to the environmental benefits, the enhanced diffusivity observed in supercritical solvents can often enhance reaction rates. We have applied these valuable features to the preparation of silica-bonded stationary phases and examined their potential in liquid chromatography. We report the successful preparation and characterisation of polyether silica based on Frechet dendrimers—this significantly enhances the range of stationary-phase chemistries that can be prepared in supercritical fluids. First- and second-generation polyether silicas were prepared, characterised, end-capped and evaluated for use as stationary phases for liquid chromatography. Figure SRM1649 on 2nd generation polyether silica Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

Modeling the cis-oxo-labile binding site motif of non-heme iron oxygenases: water exchange and oxidation reactivity of a non-heme iron(IV)-oxo compound bearing a tripodal tetradentate ligand

The spectroscopic and chemical characterization of a new synthetic non-heme iron(IV)-oxo species [Fe(IV)(O)((Me,H) Pytacn)(S)](2+) (2, (Me,H)Pytacn=1-(2'-pyridylmethyl)-4,7-dimethyl-1,4,7-triazacyclononane, S=CH(3)CN or H(2)O) is described. Complex 2 was prepared by reaction of [Fe(II)(CF(3)SO(3))(2)((Me,H) Pytacn)] (1) with peracetic acid. Complex 2 bears a tetradentate N(4) ligand that leaves two cis sites available for binding an oxo group and a second external ligand but, unlike the related iron(IV)-oxo species with tetradentate ligands, it is remarkably stable at room temperature (t(1/2)>2 h at 288 K). Its ability to exchange the oxygen atom of the oxo ligand with water has been analyzed in detail by means of kinetic studies, and a mechanism is proposed on the basis of DFT calculations. Hydrogen-atom abstraction from C-H bonds and oxygen-atom transfer to sulfides by 2 have also been studied. Despite its thermal stability, 2 proves to be a very powerful oxidant that is capable of breaking the strong C-H bond of cyclohexane (bond dissociation energy=99.3 kcal mol(-1)).     

Costs of Fiber-to-the-Home Passive Optical Network Unbundling

Abstract

This work considers different unbundling options for local loop unbundling in order to provide multi-operator access and consider the economical impact for the fiber-to-the-home next-generation access entrants to deploy such alternatives. It is shown that deploying wavelength division multiplexing networks is an efficient strategy to perform local loop unbundling while upgrading the gigabit passive optical network for the new era where high bandwidths are necessary for satisfying customer demand. In areas with a high population density, wavelength division multiplexing techniques are the most suitable for entrant operators to access the incumbent's network and provide service.     

Evaluation of MRI issues for a new neurological implant,the Sensor Reservoir

Background and Purpose

A new neurological implant, the Sensor-Reservoir, was developed to provide a relative measurement of ICP, which permits a noninvasive technique to detect and localize occlusions in ventricular drainage systems and, thus, to identify mechanical damage to shunt valves. The “reservoir” of this device can be used to administer medication or a contrast agent, to extract cerebral spinal fluid (CSF), and with the possibility of directly measuring ICP. The Sensor-Reservoir was evaluated to identify possible MRI-related issues at 1.5-T/64-MHz and 3-T/128-MHz.

Materials and Methods

Standard testing techniques were utilized to evaluate magnetic field interactions (i.e., translational attraction and torque), MRI-related heating, and artifacts at 3-T for the Sensor-Reservoir. In addition, 12 samples of the Sensor-Reservoir underwent testing to determine if the function of these devices was affected by exposures to various MRI conditions at 1.5-T/64-MHz and 3-T/128-MHz.

Results

Magnetic field interactions for the Sensor-Reservoir were not substantial. The heating results indicated a highest temperature rise of 1.8 °C, which poses no patient risks. Artifacts were relatively small in relation to the size and shape of the Sensor-Reservoir, but may interfere diagnostically if the area of interest is near the device. All devices were unaffected by exposures to MRI conditions at 1.5-T/64-MHz and 3-T/128-MHz.

Conclusion

When specific guidelines are followed, the Sensor-Reservoir is “MR conditional” for patients undergoing MRI examinations at 3-T or less.     

Gas Injection in a Liquid Saturated Porous Medium. Influence of Gas Pressurization and Liquid Films

We study numerically and experimentally the displacement of a liquid by a gas in a two-dimensional model porous medium. In contrast with previous pore network studies on drainage in porous media, the gas pressurization is fully taken into account. The influence of the gas injection rate on the displacement pattern, breakthrough time and the evolution of the pressure in the gas phase due in part to gas compressibility are investigated. A good agreement is found between the simulations and the experiments as regards the invasion patterns. The agreement is also good on the drainage kinetics when the dynamic liquid films are taken into account.     

PMD Characterization of a Dispersion Managed Link up to the Second-order with High Accuracy

We report an algorithm on the characterization up to second-order polarization mode dispersion (PMD). Our algorithm is able to characterize very short link with low PMD coefficient (less than 0.04 ps/ ). The link includes dispersion compensating fiber modules and loss compensating optical amplifiers. The estimation for first- and second-order PMD is successfully performed for dispersion-managed links of 85 and 265 km using the Jones matrix eigen-analysis (JME). The algorithm was developed to detect the evolution of the principal state of polarization (PSP) and subsequent calculation of second-order PMD components such as polarization-dependence, chromatic dispersion (PDCD) and depolarization.