Deposition of lead and cadmium released by cigarette smoke in dental structures and resin composite

Cigarette smoke is a significant source of cadmium, lead, and toxic elements, which are absorbed into the human organism. In this context, the aim of this study was to investigate in vitro the presence of toxic elements, cadmium, and lead deriving from cigarette smoke in the resin composite, dentine, and dental enamel. Eight cylindrical specimens were fabricated from resin composite, bovine enamel, and root dentin fragments that were wet ground and polished with abrasive paper to obtain sections with 6‐mm diameter and 2‐mm thickness. All specimens were exposed to the smoke of 10 cigarettes/day during 8 days. After the simulation of the cigarette smoke, the specimens were examined with scanning electron microscopy (SEM) and the energy‐dispersive X‐ray analysis. In the photomicrographic analysis in SEM, no morphological alterations were found; however, the microanalysis identified the presence of cadmium, arsenic, and lead in the different specimens. These findings suggest that the deposition of these elements derived from cigarette smoke could be favored by dental structures and resin composite. Microsc. Res. Tech., 2010. © 2010 Wiley‐Liss, Inc.     

A plastic miniature x-ray emission spectrometer based on the cylindrical von Hamos geometry

We present a short working distance miniature x-ray emission spectrometer (miniXES) based on the cylindrical von Hamos geometry. We describe the general design principles for the spectrometer and detail a specific implementation that covers Kβ and valence level emission from Fe. Large spatial and angular access to the sample region provides compatibility with environmental chambers, microprobe, and pump/probe measurements. The primary spectrometer structure and optic is plastic, printed using a 3-dimensional rapid-prototype machine. The spectrometer is inexpensive to construct and is portable; it can be quickly set up at any focused beamline with a tunable narrow bandwidth monochromator. The sample clearance is over 27 mm, providing compatibility with a variety of environment chambers. An overview is also given of the calibration and data processing procedures, which are implemented by a multiplatform user-friendly software package. Finally, representative measurements are presented. Background levels are below the level of the Kβ(2, 5) valence emission, the weakest diagram line in the system, and photometric analysis of count rates finds that the instrument is performing at the theoretical limit.     

Inactivation of Giardia muris Using Ozone and Ozone-Hydrogen Peroxide

The disinfection effects of the ozone molecule alone and that of ozone decomposition products when inactivating Giardia muris cysts were investigated at bench-scale using two different ozone demand-free laboratory buffer systems. The first water was a 0.05 M phosphate buffer with hydrogen peroxide added at a 10:1 weight ratio. The second water was a 0.05 M phosphate – 0.01 M bicarbonate buffer which quickly scavenged radical species from ozone decomposition. The C3H/HeN mouse model was used to assess the infectivity of ozone treated cysts.

The phosphate-bicarbonate buffer system had significantly greater (P ≤ 0.05) inactivation of G. muris cysts than that observed in the phosphate buffer – peroxide system where ozone was completely decomposed in less than 120 s. Consequently, the design of ozone disinfection processes should maintain ozone residual for disinfection prior to the addition of hydrogen peroxide for the oxidation of other compounds.     

Path curvature of a geared seven-bar mechanism

This paper presents a graphical technique to locate the center of curvature of the path traced by a coupler point of a planar, single-degree-of-freedom, geared seven-bar mechanism. Since this is an indeterminate mechanism then the pole for the instantaneous motion of the coupler link; i.e., the point coincident with the instantaneous center of zero velocity for this link, cannot be obtained from the Aronhold–Kennedy theorem. The graphical technique that is presented in the first part of the paper to locate the pole is believed to be an important contribution to the kinematics literature. The paper then focuses on the graphical technique to locate the center of curvature of the path traced by an arbitrary coupler point. The technique begins with replacing the seven-bar mechanism by a constrained five-bar linkage whose links are kinematically equivalent to the second-order properties of motion. Then three kinematic inversions are investigated and a four-bar linkage is obtained from each inversion. The motion of the coupler link of the final four-bar linkage is equivalent up to and including the second-order properties of motion of the coupler of the geared seven-bar. Then the center of curvature of the path traced by an arbitrary coupler point can be obtained from existing techniques, such as the Euler–Savary equation. An analytical method, referred to as the method of kinematic coefficients, is presented as an independent check of the graphical technique.     

Electrical hazards in the high energy laboratory

The unique electrical hazards that are found in a high-energy research laboratory, such as those studying fusion energy, high-power lasers, or particle accelerators, are described. Hazards due to high voltages, high currents, or large amounts of stored energy-such as chemical, mechanical, inductive, or capacitive-are discussed. Hazards associated with grounding, static electric charges and electromagnetic fields are also briefly considered. Secondary hazards, i.e., those hazards other than shock that result from or are present in conjunction with the use of electrical energy, are not covered in detail but are simply listed along with how each might be produced in a high-energy laboratory. Issues related to training, engineering controls, and administrative controls used in controlling electrical hazards in the laboratory are considered     

Midwave-infrared snapshot imaging spectrometer

We report results from a demonstration of a midwave-infrared, nonscanning, high-speed imaging spectrometer capable of simultaneously recording spatial and spectral data from a rapidly varying target scene. We demonstrated high-speed spectral imaging by collecting spectral and spatial snapshots of blackbody targets and combustion products. The instrument is based on computed tomography concepts and operates in a midwave-infrared band of 3.0-5.0 mum. We record raw images at a frame rate of 60 frames/s, using a 512 x 512 InSb focal-plane array. Reconstructed object cube estimates were sampled at 46 x 46 x 21 (x, y, lambda) elements, or 0.1-mum spectral sampling. Reconstructions of several objects are presented.     

A MAS IMPLEMENTATION FOR SYSTEM IDENTIFICATION AND PROCESS CONTROL

In this paper, a MAS for system identification and process control is presented. In particular, this MAS implements a self‐tuning regulator (STR) scheme. It has adopted FIPA specifications because they have become a stronger standard in MAS development and they involve not only agent language specifications but also agent management and conversations. In this work, an Ontology Agent (OA) is included, using DAML + OIL as ontology language. The obtained results validate this approach in the implementation of well‐known algorithms for control process.     

Hypertext: the next maintenance mountain

Hypertext documents are quickly becoming large, complex, and unwieldy. The paper considers whether lessons learned from software maintenance can be applied to the problem. Since software maintenance is a major problem and since hypertext documents share many of the characteristics of software: structure, development process, and economic value, maintaining hypertext documents is also likely to become a major problem requiring immediate action     

Synthesis of complex lossless two-ports

A new synthesis algorithm is presented for the realization of a doubly terminated complex lossless two-port from a given canonic set of scattering polynomials. the synthesis algorithm is based entirely on polynomial evaluations and thus polynomial arithmetic and routines for zero finding are not needed. the accuracy problem due to coefficient sensitivity is avoided. In particular, explicit knowledge of the intermediate polynomials is not required. the simplicity and functionality of the algorithm are based on a new representation of elementary sections given by a set of canonic parameters, namely the transmission zero of the section, the reflectance evaluated at the transmission zero and, for reciprocal sections, the return group delay evaluated at the transmission zero. A great deal of freedom is available, since transmission zeros with any multiplicity and located anywhere in the complex plane are realized independently. Also, complex networks composed exclusively of either inductors or capacitors as the dynamic elements are possible. an example is given to illustrate the robustness of the algorithm.