The reliability and accuracy of two methods for proximal caries detection and depth on directly visible proximal surfaces: an in vitro study

This study aimed to determine the reliability and accuracy of the ICDAS and radiographs in detecting and estimating the depth of proximal lesions on extracted teeth. The lesions were visible to the naked eye. Three trained examiners scored a total of 132 sound/carious proximal surfaces from 106 primary teeth and 160 sound/carious proximal surfaces from 140 permanent teeth. The selected surfaces were first scored visually, using the 7 classes in the ICDAS. They were then assessed on radiographs using a 5-point classification system. Reexaminations were conducted with both scoring systems. Teeth were then sectioned and the selected surfaces histologically classified using a stereomicroscope (×5). Intrareproducibility values (weighted kappa statistics) for the ICDAS for both primary and permanent teeth were >0.9, and for the radiographs between 0.6 and 0.8. Interreproducibility values for the ICDAS were >0.85, for the radiographs >0.6. For both primary and permanent teeth, the accuracy of each examiner (Spearman's correlation coefficient) for the ICDAS was ≥0.85, and for the radiographs ≥0.45. Corresponding data were achieved when using pooled data from the 3 examiners for both the ICDAS and the radiographs. The associations between the 2 detection methods were measured to be moderate. In particular, the ICDAS was accurate in predicting lesion depth (histologically) confined to the enamel/outer third of the dentine versus deeper lesions. This study shows that when proximal lesions are open for inspection, the ICDAS is a more reliable and accurate method than the radiograph for detecting and estimating the depth of the lesion in both primary and permanent teeth.

Vorticity generation in creeping flow past a magnetic obstacle

The generation of vorticity in the two-dimensional creeping flow of an incompressible, electrically conducting viscous fluid past a localized magnetic field distribution is analyzed under the low magnetic Reynolds number approximation. It is shown that the Lorentz force produced by the interaction of the induced electric currents with the nonuniform magnetic field acts as an obstacle for the flow, creating different steady flow patterns that are reminiscent of those observed in the flow past bluff bodies. First, analytic solutions are obtained for a creeping flow past a magnetic point dipole, modeled as a Gaussian distribution. Using a perturbation scheme, the vorticity is expressed as an expansion in the small Reynolds number, and first- and second-order approximations are calculated. The induced magnetic field, pressure, and stream function are also determined. Further, full numerical finite difference solutions are obtained for a uniform creeping flow past a finite size magnetic field distribution produced by a square magnetized plate. Hartmann numbers in the range 1< or =Ha< or =100 are explored. Depending on the strength of the magnetic force, stagnation zones or steady vortical structures are obtained. The analysis contributes to the understanding of flows in nonuniform magnetic fields and flows produced by localized forces.

Optimal behavior of viscoelastic flow at resonant frequencies

The global entropy generation rate in the zero-mean oscillatory flow of a Maxwell fluid in a pipe is analyzed with the aim of determining its behavior at resonant flow conditions. This quantity is calculated explicitly using the analytic expression for the velocity field and assuming isothermal conditions. The global entropy generation rate shows well-defined peaks at the resonant frequencies where the flow displays maximum velocities. It was found that resonant frequencies can be considered optimal in the sense that they maximize the power transmitted to the pulsating flow at the expense of maximum dissipation.

Dynamic permeability of electrically conducting fluids under magnetic fields in annular ducts

The dynamic response of an electrically conducting fluid (either Newtonian or Maxwellian) flowing between straight concentric circular cylinders under a constant radial magnetic field, is analyzed. The isothermal flow is studied using the time Fourier transform, so that the dynamic generalization of Darcy's law in the frequency domain is obtained and analytical expressions for the dynamic permeability are derived. For the Newtonian case, the range of frequencies where the dynamic permeability approaches the static value is enlarged the smaller the gap between the cylinders and the higher the magnetic-field strength. For the Maxwell fluid, the presence of the inner cylinder shifts the frequencies that lead to the enhancement of the real part of the dynamic permeability to larger values and increases its maximum values relative to the case where the inner cylinder is absent. In addition, the Ohmic dissipation causes the damping of the amplitude of the response.

Efficiency of the Hartmann test with different subpupil forms for the measurement of turbulence-induced phase distortions

The reconstruction quality of turbulence-induced phase distortions from Hartmann data is calculated for masks with different subpupil forms by means of computer simulations. Four subpupil forms are considered: the circle, the square, the hexagon, and the polar segment. We show that, for the case of a circular aperture, the mask with polar segment subpupils provides the best reconstruction quality.

Method of random wave vectors in simulation of anisoplanatic effects

A generalization of the method of random wave vectors [Appl. Opt. 36, 464 (1997)] that is suitable for a simulation of turbulence-induced anisoplanatic effects is proposed. A simulation of the cross-correlated phase fluctuations produced by two initially plane waves propagating through weak turbulence is considered. The variation of C(n)(2) along a propagation path and an effect of the finite outer scale of the turbulence are included in the simulation. The validity of the simulation method is verified by comparison of theoretical and simulated results. The simulation approach developed can be used in the problems related to adaptive optics, speckle inteferometry, guide stars, and imaging through turbulence.

Modal compensation and the atmospheric-turbulence outer scale: computer simulations

The influence of the turbulence outer scale on the Strehl ratio obtained with low-order adaptive optics systems is examined by numerical simulation. The Karhunen-Loeve approach is used to generate wave-front samples. A method that allows construction of the outer-scale-dependent Karhunen-Loeve functions is described. It is shown that the Strehl ratio produced by a second-order adaptive optics correction (tip-tilt, defocus, and astigmatism) is affected quite strongly by the finite outer scale. For the higher-order correction, the effect under study is weak and appears only when the outer-scale magnitude becomes less than the aperture diameter. It is also shown that the finite outer scale has a positive effect on the Strehl ratio of the uncorrected long-exposure image.

[Elimination of Helicobacter pylori in patients with recurrent abdominal pain with simultaneous administration of ranitidine, bismuth subsalicylate and clarithromycin]

OBJECTIVE

Elimination of Helicobacter pylori with Chlaritromicin, Bismuth subsalicylate and Ranitidine; and improvement of recurrent abdominal pain. ANTECEDENT: Different antibiotics, antagonist H2 and others has been used for elimination and, or eradication of Helicobacter pylori.

METHOD

22 children with recurrent abdominal pain associated to gastritis and histologic identification of Helicobacter pylori were studied under a period of 18 months (january 1992 to june 1993), at Instituto Nacional de Pediatría, México, D:F: All children were treated simultaneously with: Chlaritromicin, 15 days, Plus ranitidine and bismuth subsalicylate for one month.

RESULTS

Helicobacter pylori was eliminate in 14 of 22 children studied. All these children had an important improvement of recurrent abdominal pain.

CONCLUSION

Elimination of Helicobacter pylori and clinical improvement was present in 14 of 22 children studied (63.7%).

Active primary mirror support for the 2.1-m telescope at the San Pedro Mártir Observatory

We have designed and installed a new set of actuators for the suspension of the primary mirror of the 2.1-m telescope at San Pedro Mártir. This active optics system has allowed us to correct low-order aberrations identified by several wave-front analysis techniques.