Abstract
An optical fiber interferometer for measuring the d(33) coefficient of piezoelectric samples is described. Its configuration is based on the Mach-Zehnder interferometer, and a double incidence on the thin-film samples successfully suppresses the undesirable bending effect of the substrate. Detection of the small displacement is based on an active homodyne scheme. Results are reported for a bulk piezoelectric transducer (PZT) sample and a PZT thin-film incorporated in a microactuator. (C) 2002 American Institute of Physics.

Abstract
We describe and demonstrate a new hybrid current sensor system which uses a novel time division multiplexed fiber network for the measurement of three-phase currents at high potential. The sensor arrangement combines a conventional current transformer with a fiber-optic interferometer such that the signal is transmitted optically to ground. Sensitivities of ~0.5 A/vHz are obtained in each phase at the line frequency of 50 Hz. The sensitivity and dynamic range of each sensor can be tailored for a specific level of current or according to an individual application.

Abstract
Fused biconical wavelength division multiplexers have been used to replace standard couplers in an intensity-sensor multiplexing network. The wavelength-selective power splitting and the low insertion losses of these devices (< 0.2dB) improve the power budget, while providing network overall optical isolations > 30dB. With this isolation, crosstalk effects in the network are proven to be negligible.

Abstract
As mesenchymal stem cells (MSCs) can differentiate into multiple cell types, the delivery of exogenous genes to this type of cell can be an important tool in tissue regeneration and engineering. However transfection of MSCs using nonviral gene delivery vectors is difficult, the development of more efficient and safe DNA vehicles being necessary. Moreover, specific transfection of MSCs may be required to avoid unwanted side effects in other tissues. In this study, a novel family of gene delivery vectors based on poly(amidoamine) (PAMAM) dendrimers functionalized with peptides displaying high affinity toward MSCs was prepared. The vectors were characterized with respect to their ability to neutralize, bind and compact plasmid DNA (pDNA). The complexes formed between the vectors and pDNA were analyzed concerning their size, zeta-potential, capacity of being internalized by cells and transfection efficiency. These new vectors exhibited low cytotoxicity, receptor-mediated gene delivery into MSCs and transfection efficiencies superior to those presented by native dendrimers and by partially degraded dendrimers.

Abstract
Poly(amidoamine) dendrimers (generations 5 and 6) with amine termini were conjugated with peptides containing the arginine-glycine-aspartic acid (RGD) sequence having in view their application as gene delivery vectors. The idea behind the work was to take advantage of the cationic nature of dendrimers and of the integrin targeting capabilities of the RGD motif to improve gene delivery. Dendrimers were used as scaffolds for RGD clustering and, by controlling the number of peptides (4, 8, and 16) linked to each dendrimer, it was possible to evaluate the effect of RGD density on the gene delivery process. The new vectors were characterized in respect to their ability to neutralize and compact plasmid DNA (pDNA). The complexes formed by the vectors and pDNA were studied concerning their size, zeta potential, capacity of being internalized by cells and ability of transferring genes. Transfection efficiency was analyzed, first, by using a pDNA encoding for Enhanced Green Fluorescent Protein and Firefly Luciferase and, second, by using a pDNA encoding for Bone Morphogenetic Protein-2. Gene expression in mesenchymal stem cells was enhanced using the new vectors in comparison to native dendrimers and was shown to be dependent on the electrostatic interaction established between the dendrimer moiety and the cell surface, as well as on the RGD density of nanoclusters. The use of dendrimer scaffolds for RGD cluster formation is a new approach that can be extended beyond gene delivery applications, whenever RGD clustering is important for modulating cellular responses.

Abstract
A reflective multimode interference based-fiber optic sensor is described, aimed at measuring refractive index variations by means of intensity variation based on the fiber tip-interaction concept. The sensing head is a section of a multimode fiber, spliced to a single-mode fiber at the input end; its characteristics are studied when two multimode fibers, with distinct core diameters (viz. 50 and 105 mu m), are considered. The multimode fiber end face is placed in contact with the liquid sample, so as to provide a refractive index measurement via variation in amplitude of the interference spectral peaks - which is essentially insensitive to temperature changes. Therefore, the proposed configuration permits measurement of refractive index variations free from system temperature cross-sensitivity effects. Resolutions of 2.2 x 10(-4) RIU and 3.8 x 10(-4) RIU, for multimode fiber tips with core diameters of 50 mu m and 105 mu m, respectively, could be achieved.