Abstract
Phase-shifted Bragg grating waveguides (PSBGWs) were formed in bulk fused silica glass by femtosecond laser direct writing to produce narrowband (22 +/- 3) pm filters at 1550 nm. Tunable p and other phase shifts generated narrow passbands in controlled positions of the Bragg stopband, while the accurate placement of multiple cascaded phase-shift regions yielded a rectangular-shaped bandpass filter. A waveguide birefringence of (7.5 +/- 0.3) x 10(-5) is inferred from the polarization-induced spectral shifting of the PSBGW narrowband filters. (C) 2012 Optical Society of America

Abstract
Femtosecond laser exposure produces form and stress birefringence in glasses, mainly controlled by laser polarization and pulse energy, which leads to challenges in certain applications where polarization mode dispersion or birefringence splitting is critical for the desired responses from optical devices. In this paper, parallel laser modification tracks with different geometries were applied to preferentially stress the laser-written waveguides and explore the possibility of tuning the waveguide birefringence in devices fabricated in bulk fused silica glass. Polarization splitting in Bragg grating waveguides showed the laser modification tracks to controllably add or subtract stress to the pre-existing waveguide birefringence, demonstrating independence from the nanograting induced form birefringence and the contributions from material stress. Stressing bars are shown that offer tunable birefringence in the range from similar to 0 up to 4.35 x 10(-4), possibly enabling great flexibility in designing polarization dependent devices, as well as making polarization independent devices. (C) 2012 Optical Society of America

Abstract
In this paper we examine the birefringence of buried optical waveguides written with femtosecond lasers in bulk fused silica glass. We report two modes of low and high birefringence associated with strong form birefringence and the orientation of nanogratings that align perpendicular to the writing laser polarization. The birefringence and waveguide losses are characterized over various laser exposure conditions to facilitate the fabrication of low-loss and compact wave retarders and polarization beam splitters for integration into polarization controlled circuits. Zero-order quarter-wave and half-wave retarders together with polarization beam splitters are demonstrated, all operating at telecom wavelengths. Integration of such devices is targeted for application in photonic quantum circuits. © 2012 SPIE.

Abstract
This paper explores Ampere's circuital law (ACL) from an educational perspective. The interchangeability of the amperian loop with the current loop, an intrinsic symmetry of ACL that is seldom addressed in the literature or textbooks, is illustrated here. It is verified that the symmetry axis of a circular current is an amperian loop. The attempt to apply ACL to a finite wire, a common source of student misunderstanding, is used to highlight the limitations of ACL. The generalisation of ACL is illustrated using an instructive example where the displacement current is unconfined and not spatially uniform. This work is primarily intended for teachers and more advanced undergraduate students, who may benefit from the ideas that are presented here.

Abstract
Measurements made in feces and urine of Wistar rats exposed to lead acetate (n?=?20) in drinking water since the fetal period were compared with those obtained from a control group (n?=?20) in order to assess the age influence on Pb excretion. The measurements were made in different collections of rats aging between 1 and 11?months. To determine the Pb content of the samples, total reflection X-ray fluorescence (TXRF) and electrothermal atomic absorption spectrometry (ETAAS) were used for the urine samples and energy dispersive X-ray fluorescence (EDXRF) was used for the feces.

Abstract
The concentration of lead in liver and kidneys of Wistar rats, fed with lead since fetal period in relation to their age and to a control group, was determined. A group of rats was exposed to lead acetate (n = 30) in drinking water and the other group was exposed to normal water (n = 20). Samples were collected from rats aging between 1 and 11 months and were analyzed by Energy Dispersive X-ray Fluorescence (EDXRF) without any chemical preparation. The EDXRF results were assessed by the PIXE (Proton Induced X-ray Emission) technique. The formaldehyde used to preserve the samples was also analyzed by ETAAS (Electro-Thermal Atomic Absorption Spectrometry) in order to verify if there was any loss of lead from the samples to the formaldehyde. We found that the loss was not significant (<2%). Concerning the mean values of the lead concentration measured in the contaminated soft tissues, in liver they range from 6 to 22 mu g g(-1), and in kidneys from 44 to 79 mu g g(-1). The control rats show, in general, values below the EDXRF detection limit (2 mu g g(-1)). The ratio kidney/liver ranges from 2 to 10 and is strongly positively correlated with the age of the animals. A Spearman correlation matrix to investigate the correlation between elemental concentrations and the dependence of these concentrations with age showed that there is a strong positive correlation with age for lead in the liver but not in the kidney. The correlation matrix showed also that the concentration of lead in these two soft tissues is not correlated. The lead accumulation in liver is made by different plateaus that strongly decrease with age. It was verified the existence of two levels of accumulation in kidney, not very highlighted, which might be indicative of a maximum accumulation level for lead in kidney.