Forces, moment and wave pattern for surface combatant in regular head wavesPart II. Measurement results and discussions

Unsteady resistance, heave force, pitch moment and free-surface elevations for DTMB 5512 at steady forward speed and in regular head waves are investigated with different measurement systems for a fairly wide range of test conditions in the IIHR towing tank. Test data are procured for validation of Reynolds-averaged Navier–Stokes computational fluid dynamics codes and for understanding the physics of unsteady ship hydrodynamics. The second part of the paper presents the measurement results and discussions. Received: 4 October 2000 / Accepted: 23 April 2001 Published online: 29 November 2001     

Grain shear flow in a rotating drum

 In the present paper we report on the experimental activities carried out on a rotating drum partially filled with grains or glass beads. The experiments give information about rheology through velocity profiles and through the velocity covariance tensor structure. We used a LDV system to measure the velocity of the grains at several points along three vertical sections. The data were also used to obtain the grain volume concentration, with encouraging results. Instantaneous velocity data were elaborated in order to obtain velocity and pseudotemperature profiles for all the experiments; for a subset of the experiments a large set of data were elaborated to obtain the velocity covariance. The velocity covariance is not collinear with the rate of deformation tensor. An attempt to justify the rotation of the tensor axes as a consequence of the kinetically induced anisotropy and of some free surface perturbations slowly moving upstream was partially successful. Received: 23 April 1999 / Accepted: 15 July 2001     

Non‐Invasive Salivary Electrochemical Quantification of Paraquat Poisoning Using Boron Doped Diamond Electrode

The present work describes the first electrochemical method for quantifying paraquat herbicide poisoning in human saliva samples. Paraquat shows two couples of well‐defined peaks in aqueous solution using a boron doped diamond (BDD) electrode. By using square wave voltammetry (SWV) technique under optimum experimental conditions, a linear analytical curve was obtained for paraquat concentrations ranging from 0.800 to 167 µmol L^?1, with a detection limit of 70 nmol L^?1. This method was applied to quantify paraquat spikes in human saliva samples and in two different water samples (tap and river). The recovery values obtained ranged from 83.0 to 104 % and 99.1 to 105 %, respectively, which highlight the accuracy of the proposed method.     

Solid/free-surface juncture boundary layer and wake

 The Reynolds-averaged flow for a solid/free-surface juncture boundary layer and wake is documented. The three mean-velocity components and five of the Reynolds stresses are measured for a surface-piercing flat plate in a towing tank using a laser-Doppler velocimeter system for both boundary-layer and wake planes in regions close to the free surface. The experimental method is described, including the foil-plate model, laser-Doppler velocimeter system, conditions, and uncertainty analysis. The underlying flow data is in excellent agreement with benchmark data. Inner (near the plate and wake centerplane and below the free surface) and outer (near the free surface) regions of high streamwise vorticity of opposite sign are observed, which transport, respectively, high mean velocity and low turbulence from the outer to the inner and low mean velocity and high turbulence from the inner to the outer portions of the boundary layer and wake. For the wake, the inner region of vorticity is relatively weak. The physical mechanism for the streamwise vorticity is analyzed with regard to the Reynolds-averaged streamwise vorticity equation. The anisotropy of the crossplane normal Reynolds stresses closely correlates with the vorticity and, additionally, indicates similarity, i.e., its nature is such that it only depends on the proximity to the plate and free surface boundaries or wake centerplane symmetry plane. Free-surface effects on the Reynolds stresses are analyzed with regard to the behavior close to the free surface of the turbulent kinetic energy and the normal components of the anisotropy tensor and the anisotropy invariants. Close to the free surface, the turbulent kinetic energy is nearly constant and increases for the inner and outer portions, respectively, of the boundary layer and wake and the normal components of the anisotropy tensor and the anisotropy invariants roughly correspond to the limiting values for two-component turbulence. The similarities and differences between the present results and analysis with those from related studies are discussed. The data and analysis should have practical application with regard to the development of turbulence models for computational fluid dynamics methods for the Reynolds-averaged Navier–Stokes equations. Received: 27 May 1997/Accepted: 1 August 1997     

Influence of Cu(II) in the SrSnO<Subscript>3</Subscript> crystallization

Perovskite type oxides have been intensively studied due to their interesting optical, electrical, and catalytic properties. Among perovskites the alkaline earth stannates stand out, being strontium stannates (SrSnO₃) the most important material in ceramic technology among them due to their wide application as dielectric component. SrSnO₃ has also been applied as stable capacitor and humidity sensor. In the present work, SrSnO₃:Cu was synthesized by polymeric precursor method and heat treated at 700, 800, and 900 °C for 4 h. After that, the material was characterized by thermal analysis (TG/DTA), X-ray diffraction (XRD), infrared spectroscopy, and UV–vis spectroscopy. Results indicated three thermal decomposition steps and confirmed the presence of strontium carbonate and Cu²⁺ reduction to Cu⁺ at higher dopant amounts. XRD patterns indicated that the perovskite crystallization started at 700 °C with strontiatite (SrCO₃) and cassiterite (SnO₂) as intermediate phases, disappearing at higher temperatures. The amount of secondary phase was reduced with the increase in the Cu concentration.     

Scattering losses from planar waveguides with material inhomogeneity

We consider the propagation of guided waves in a planar waveguide that has a finite-length segment of inhomogeneous media. Except for the inhomogeneous segment, which varies in length from 0 to 160λ, the waveguide is piecewise homogeneous everywhere. The inhomogeneity is modelled by two-dimensional random permittivity fluctuations that are numerically generated from an assumed Gaussian correlation function.

In 2D, the Maxwell equations are solved in the frequency domain for both TE and TM polarization by using modal expansion methods, perfectly matched absorbing boundary layers and the R-matrix transfer matrix algorithm. The guided waves are excited by a Gaussian beam incident on the waveguide aperture. For various waveguide design parameters, numerical results are given for waveguide power loss per unit length of waveguide inhomogeneity. The power loss curves are calculated as the average from numerous realizations of the random permittivity and the coefficient of variation is also given.     

Wavelength-Resolved 3-Dimensional Fluorescence Lifetime Imaging

We have developed a compact system for wide-field fluorescence imaging, resolved in three spatial dimensions, lifetime and wavelength, that is based on a gated optical intensifier and an all-solid-state diode pumped Cr:LiSAF oscillator-amplifier system. Exploiting spectral separation, the system has been applied to human teeth, obtaining good lifetime contrast between enamel, dentin and caries. Exploiting spectral separation combined with depth resolution, the study of fluorescent microspheres led to an enhancement in both lifetime contrast and lateral resolution.     

Determination of N-acetylcysteine in human plasma by gas chromatography-mass spectrometry

An automatic mass spectrometric method for the quantitation of N-acetylcysteine (NAC) in human plasma has been developed. NAC was extracted from plasma with ethyl acetate and derivatized in two steps with 2-propanol and pentafluoropropionic anhydride. The volatile derivative obtained was ideal for gas chromatographic-mass spectrometric analysis. Data obtained by analysing the plasma of healthy volunteers to whom 600 mg of NAC had been orally given are reported.     

“4,7-lactams”, intermediates for penems synthesis. I. skeletal conversion of penicillanic acid to (+)-2,2,5,5-tetramethyl-9-oxo-3-oxa-6-thia-azabicyclo[5,2,01,7]nonane

The synthesis of chiral “4,7-lactam“ $\text{5}$ has been accomplished starting from natural 6-aminopenicillanic acid.