Spatial distribution of manganese in enamel and coronal dentine of human primary teeth

Emerging evidence indicates that excessive exposure to manganese (Mn) during the prenatal period and early childhood may result in neurodevelopmental deficits. However, accurate exposure biomarkers are not well established, limiting our understanding of exposure-response relationships over these susceptible periods of development. Naturally shed deciduous teeth are potentially a useful biomarker of environmental exposure to Mn. However, the uptake and distribution of Mn in human teeth has not been studied in detail.Mn distribution was measured at high resolution (~ 20 μm) in eight human primary teeth using laser ablation-inductively coupled plasma-mass spectrometry. A bio-imaging methodology was applied to construct detailed elemental maps of three incisors, and bone meal (NIST SRM 1486) was used to validate the analyses.The distribution of Mn in enamel and coronal dentine showed a distinct and reproducible pattern. In enamel, the ⁵⁵Mn:⁴³Ca ratio was highest at the outer edge of enamel (range = 0.57 to 4.74) for approximately 20-40 μm but was substantially lower in deeper layers (range = 0.005 to 0.013). The highest levels of Mn were observed in dentine immediately adjacent the pulpal margin (⁵⁵Mn:⁴³Ca range = 2.27 to 6.95). Importantly, a clearly demarcated high Mn zone was observed in dentine at the incisal end of the teeth. Using confocal laser scanning microscopy to visualize the neonatal line, this region was identified as being in the prenatally formed dentine.The high-resolution map of the spatial distribution of Mn in human primary teeth highlighted specific reproducible patterns of Mn distribution in enamel and coronal dentine.     

Analyzing unidentified locked-joint failures in kinematically redundant manipulators

Robots are frequently used for operations in hostile environments. The very nature of these environments, however, increases the likelihood of robot failures. Common failure-tolerance techniques rely on effective failure detection and identification. Since a failure may not always be successfully identified, or, even if identified, may not be identified soon enough, it becomes important to consider the behavior of manipulators with unidentified failures. This work investigates the behavior of robots experiencing unidentified locked-joint failures in a general class of tasks characterized by point-to-point motion. Based on the analysis, a procedure for workspace evaluation is developed that allows for the identification of regions in the manipulator's workspace in which tasks may be completed even with such failures. © 2005 Wiley Periodicals, Inc.     

Agile manufacturing of a micro-embossed case by a two-step electromagnetic forming process

A very agile method, that relies solely on simple single-sided tooling, to form open-box-like enclosures with surface detail such as highly embossed surface features is demonstrated and analyzed. For example, this method may be used to fabricate personal electronics cases. The technique uses electromagnetic forces in a two-step process. In the first step a newly developed uniform pressure electromagnetic actuator is used to make a micro-embossed pre-form that can contain very fine surface detail in the part by micro-embossing features in the forming die. This blank is then trimmed. In the second major step electromagnetic flanging is used to give greater depth and steeper walls to the case. Both electromagnetic operations use one-sided tooling and very light equipment. In principle the tooling needed for this type of process can be put to use within days or hours of finalizing the component design and precise tooling tolerances or precise alignment are not required. This work shows the essential feasibility of this approach to manufacturing either small or large lots of components.     

CAVITATION MODELING WITH A CFD APPROACH

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Fast track thrombolysis in acute myocardial infarction: a quality improvement project

To understand the clinical efficacy of traditional anti-rheumatic herbal medicines on acute and severe arthritis or immune diseases, four herbal formulas and one herb were tested in vitro to determine their effects on prostaglandin E2 (PGE2) and interleukin 2 (IL2). Peripheral blood mononuclear cells from healthy subjects were incubated with different concentrations of four herbal formulas including Shaur Yau Gan Tsao Tang (SYGTT), Shang Jong Shiah Tong Yong Tong Feng Wan (SJSTY), Shu Jin Lih An Saan (SJLAS), Ma Shing Yih Gan Tang (MSYGT) and one herb, Tripterygium wilfordii (T2) with and without mitogen stimulation. PGE2 and IL2 from culture supernatant were measured by enzyme immunoassay. The results showed that SYGTT, SJSTY, SJLAS at concentration of 100 microg and MSYGT at 500 microg/ml can significantly inhibit PGE2 release (P < 0.05) from mononuclear cells. However, T2 at 2 microg/ml expressed the same response. For the inhibition of IL2, the concentration of SYGTT, SJSTY and SJLAS must exceed 100 symbol microg/ml. MSYGT failed to inhibit IL2 at even concentrations of 500 microg/ml but T2 at a very low concentration (0.6 microg/ml) could strongly inhibit it. The findings suggest that the majority of traditional anti-rheumatic herbal formulas or herbs, except for T2, should not be used to treat acute and critical arthritis or immune diseases.     

Effect of chemical interaction between surface oxidized carbon black and carboxylated nitrile rubber on dynamic properties

Monsanto rheometric, dynamic mechanical, and solvent swelling studies indicate that functional groups of oxidized carbon black chemically react with carboxylated nitrile rubber (XNBR) when heated at high temperature for prolonged time. The reinforcing ability of the surface oxidized carbon black, measured by failure and hysteresis properties, is higher than the nonoxidized counterpart. © 1995 John Wiley & Sons, Inc.     

Stiffness-tolerant methods for transient analysis of stiff Markov chains

Three methods for numerical transient analysis of Markov chains, the modified Jensen's method (Jensen's method with steady-state detection of the underlying DTMC and computation of Poisson probabilities using the method of Fox and Glynn [1]), a third-order L-stable implicit Runge-Kutta method, and a second-order L-stable method, TR-BDF2, are compared. These methods are evaluated on the basis of their performance (accuracy of the solution and computational cost) on stiff Markov chains. Steady-state detection in Jensen's method results in large savings of computation time for Markov chains when mission time extends beyond the steady-state point. For stiff models, computation of Poisson probabilities using traditional methods runs into underflow problems. Fox and Glynn's method for computing Poisson probabilities avoids underflow problems for all practical problems and yields highly accurate solutions. We conclude that for mildly stiff Markov chains, the modified Jensen's method is the method of choice. For stiff Markov chains, we recommend the use of the L-stable ODE methods. If low accuracy (upto eight decimal places) is acceptable, then TR-BDF2 method should be used. If higher accuracy is desired, then we recommend third-order implicit Runge-Kutta method.     

Microstructural evolution of bulk nanocrystalline Ni during creep

Experiments were conducted on electrodeposited (ED) nanocrystalline (nc) Ni with an average initial grain size of about 20 nm at 393 K to study the shape of the creep curves. In addition, microstructure was examined by means of transmission electron microscopy (TEM). The results show that the creep curves are characterized by the presence of a well-defined steady-state stage. An examination of the microstructure indicates that while grain growth occurs during deformation, the grain size attains a constant value once steady state creep is approached. A comparison between grain size measurements obtained by the TEM technique and those obtained via the X-ray diffraction method shows that the use of the latter method may lead to an underestimation of the value of the average grain size.     

Synthesis of benzoic acid from chlorobenzene under pressure

Conversions as high as 76·26% and 80·85% of chlorobenzene to benzoic acid were obtained when chlorobenzene was carboxylated with carbon monoxide and water at high pressure with nickel iodide-silica gel catalyst (Ni:SiO₂ = 50:50) and without any catalyst (thermal) respectively, at the optimum temperature and pressure; these optima were much higher for the latter than for the former process. The lower yield in the catalytic process could be improved to some extent if the catalytic reaction was carried out at a pressure, reached by introducing nitrogen in addition to the usual input of carbon menoxide, almost equal to the optimum pressure of the thermal process.