Apex Plane Research Articles

Integrated correlation analysis of the thickness of buccal bone and gingiva of maxillary incisors.

This study aimed to validate the integrated correlation between the buccal bone and gingival thickness of the anterior maxilla, and to gain insight into the reference plane selection when measuring these two tissues before treatment with implants. Cone beam computed tomography (CBCT) and model scans of 350 human subjects were registered in the coDiagnostiX software to obtain sagittal maxillary incisor sections. The buccal bone thickness was measured at the coronal (2, 4, and 6 mm apical to the cementoenamel junction [CEJ]) and apical (0, 2, and 4 mm coronal to the apex plane) regions. The buccal gingival thickness was measured at the supra-CEJ (0, 1mm coronal to the CEJ) and sub-CEJ regions (1, 2, 4, and 6 mm apical to the CEJ). Canonical correlation analysis was performed for intergroup correlation analysis and investigation of key parameters. The mean thicknesses of the buccal bone and gingiva at different levels were 0.64~1.88 mm and 0.66~1.37 mm, respectively. There was a strong intergroup canonical correlation between the thickness of the buccal bone and that of the gingiva (r=0.837). The thickness of the buccal bone and gingiva at 2 mm apical to the CEJ are the most important indices with the highest canonical correlation coefficient and loadings. The most and least prevalent subgroups were the thin bone and thick gingiva group (accounting for 47.6%) and the thick bone and thick gingiva group (accounting for 8.6%). Within the limitations of this retrospective study, the thickness of the buccal bone is significantly correlated with that of the buccal gingiva, and the 2 mm region apical to the CEJ is a vital plane for quantifying the thickness of these two tissues.

Biomechanical characteristics in the carotid artery: Noninvasive assessment using subharmonic emissions from microbubbles.

Stroke is closely related to carotid atherosclerotic plaques, which tend to occur in specific parts of the arteries, especially at the bifurcations, and are considered to be caused by biomechanical factors. Quantitative analysis of hemodynamic stress characteristics of the carotid sinus in vivo provides a mechanical basis for the development of atherosclerotic plaque in the carotid sinus. Previous studies found that ultrasound (US) contrast agent microbubbles would vibrate nonlinearly under the excitation of sound pressure, generating subharmonics (transmission fundamental frequency, i.e., f0 and subharmonic frequency at f0 /2), which have the highest sensitivity to pressure changes and exhibit an inverse linear relationship with environmental pressure. This study employed subharmonic aided pressure estimation (SHAPE) technology to reflect carotid artery hydrodynamic characteristics in the carotid lumen. From May 2021 to December 2021, this prospective study reviewed a total of 26 normal carotid arteries of 13 participants, all of whom received bilateral carotid artery routine US and SHAPE US examinations. During this study, the lumen of the bilateral distal segment of the common carotid artery (Distal-CCA), carotid artery bifurcation (CAB), and carotid bulb (CB) were scanned section by section from bottom to top in longitudinal and transverse sections. Subsequently, the subharmonic amplitudes in the lumen of normal carotid arteries were collected and analyzed. This study found that the amplitude of subharmonic amplitude in the carotid was distributed unevenly, with the amplitudes of subharmonic at the CAB being higher. Specifically, the subharmonic gradient of the carotid artery bifurcation apex plane was maximum (9.72±4.31dB), while the average subharmonic amplitude of the outer lateral layer of the carotid artery was higher (-56.40±6.31dB) (p<0.001). The SHAPE technique is capable of indirectly reflecting the pressure changes of vascular system tissues, which may provide a new monitoring method for evaluating mechanical characteristics obviating invasion.

Computational investigation of drop behavior and breakup in peristaltic flow

The behavior of liquid drops in the retropulsive jet produced by a peristaltic wave is investigated computationally. The computational geometry consists of a tube which is closed at one end, with the peristaltic wave that deforms the boundary moving toward it. A modified solver with the capability to couple mesh deformation and adaptive mesh refinement around moving drops was developed and validated with experimental data, and good agreement was found. A parametric study was then performed to determine the effect of interfacial tension, viscosity ratio, relative occlusion, and initial drop position on the drop's behavior and breakup characteristics. In particular, breakup regimes on graphs of capillary number vs viscosity ratio were determined for each initial drop position and relative occlusion. It was found that these breakup regimes were bounded above and below, and an optimal capillary number for breakup was determined. The volume of the parent drop after breakup decreased linearly with capillary number for low capillary numbers and was independent of the viscosity ratio. For higher capillary numbers, this volume generally increased with the viscosity ratio. It was also found that a drop with lower interfacial tension reached the apex plane sooner than a drop with higher interfacial tension, but once there, took longer to pass through this plane and longer to breakup. The viscosity ratio had negligible influence on the drop transit times for viscosity ratios less than one, while the breakup time generally increased with the viscosity ratio.

Simulation of Corneal imaging properties for near objects.

Using raytracing simulation to study the effect of corneal imaging metrics for different aperture sizes as a function of object distances with different schematic model eyes. This raytracing simulation determined the best focus (with the least root-mean-square (rms) ray scatter) and the best wavefront focus (with least rms wavefront error) for four schematic model eyes (Liou-Brennan (LBME), Atchison (ATCHME), Gullstrand (GULLME) and Navarro (NAVME)) with 4 aperture sizes (2-5mm) and 30 object distances in a logscale from 10cm to 10m plus infinity. For each configuration, 10,000 rays were traced through the cornea, and the aperture stop was located at the lens front apex plane as described in the model eyes. The wavefront was decomposed into Zernike components to extract the spherical aberration term. The focal distance with respect to the corneal front apex increases from around 31mm for objects at infinity to around 40mm for objects at 10cm. The best (wavefront) focus was systematically closer to the cornea compared with the paraxial focus, and the overestimation of focal length with the paraxial focus was larger for large aperture sizes and small object distances. The rms ray scatter and wavefront error were both systematically larger with large aperture and small object sizes. At best focus the rms wavefront error was systematically larger, and the rms ray scatter was systematically smaller compared to the best wavefront focus. Spherical aberration varied more with GULLME than with LBME or NAVME, and increased strongly at smaller object distances. The imaging properties of the cornea, especially spherical aberration, increase strongly as the object distance decreases. This effect should be considered, especially when considering aberration correcting lenses for near vision such as multifocal or enhanced depth of focus lenses.

Prediction model for best focus, power, and spherical aberration of the cornea: Raytracing on a large dataset of OCT data.

PurposeTo analyse corneal power based on a large optical coherence tomography dataset using raytracing, and to evaluate corneal power with respect to the corneal front apex plane for different definitions of best focus.MethodsA large OCT dataset (10,218 eyes of 8,430 patients) from the Casia 2 (Tomey, Japan) was post-processed in MATLAB (MathWorks, USA). Using radius of curvature, corneal front and back surface asphericity, central corneal thickness, and pupil size (aperture) a bundle of rays was traced through the cornea. Various best focus definitions were tested: a) minimum wavefront error, b) root mean squared ray scatter, c) mean absolute ray scatter, and d) total spot diameter. All 4 target optimisation criteria were tested with each best focus plane. With the best-fit keratometer index the difference of corneal power and keratometric power was evaluated using a multivariate linear model.ResultsThe mean corneal powers for a/b/c/d were 43.02±1.61/42.92±1.58/42.91±1.58/42.94±1.59 dpt respectively. The root mean squared deviations of corneal power from keratometric power (nK = 1.3317/1.3309/1.3308/1.3311 for a/b/c/d) were 0.308/0.185/0.171/0.209 dpt. With the multivariate linear model the respective RMS error was reduced to 0.110/0.052/0.043/0.065 dpt (R² = 0.872/0.921/0.935/0.904).ConclusionsRaytracing improves on linear Gaussian optics by considering the asphericity of both refracting surfaces and using Snell’s law of refraction in preference to paraxial simplifications. However, there is no unique definition of best focus, and therefore the calculated corneal power varies depending on the definition of best focus. The multivariate linear model enabled more precise estimation of corneal power compared to the simple keratometer equation.

On the flow organization of a chevron synthetic jet

In the present study, the flow fields generated by two synthetic jets with a chevron and a conventional circular nozzle exits are studied and compared. For both configurations, the devices are operated at the same input electrical power, thus leading to Reynolds and Strouhal numbers equal to 5600 and 0.115 (for the circular exit) and 6000 and 0.106 (for the chevron exit). Phase-locked stereoscopic particle image velocimetry measurements are used to reconstruct the three-dimensional coherent vortex structures. Time-averaged and phase-averaged mean and turbulent statistics are analysed and discussed. The flow field strongly depends on the exit geometry. In presence of the chevron exit, the conventional vortex ring issued through the circular nozzle exit, is replaced by a non-circular vortex ring with additional streamwise vortices. The mutual interaction between these structures prevents the axis-switching of the non-circular vortex ring during its convection. These streamwise vortices disappear convecting downstream and the vortex ring assumes a circular shape. Comparing the two configurations, the chevron exit generates a larger time-averaged streamwise velocity along the centreline but with lower turbulent kinetic energy intensity. Differences are also present between the notch and the apex planes of the chevron exit. In the notch plane, both the time-averaged axial velocity component profile in the spanwise direction and the shearlayer width are wider than in the apex plane. Furthermore, the presence of the streamwise vortices causes a flow motion towards the jet axis in the apex plane and an opposite motion in the notch plane.

Biodegradable Microfabricated Plug-Filters for Glaucoma Drainage Devices

We report on the development of a batch fabricated biodegradable truncated-cone-shaped plug filter to overcome the postoperative hypotony in nonvalved glaucoma drainage devices. Plug filters are composed of biodegradable polymers that disappear once wound healing and bleb formation has progressed past the stage where hypotony from overfiltration may cause complications in the human eye. The biodegradable nature of device eliminates the risks associated with permanent valves that may become blocked or influence the aqueous fluid flow rate in the long term. The plug-filter geometry simplifies its integration with commercial shunts. Aqueous humor outflow regulation is achieved by controlling the diameter of a laser-drilled through-hole. The batch compatible fabrication involves a modified SU-8 molding to achieve truncated-cone-shaped pillars, polydimethylsiloxane micromolding, and hot embossing of biodegradable polymers. The developed plug filter is 500 μm long with base and apex plane diameters of 500 and 300 μm, respectively, and incorporates a laser-drilled through-hole with 44-μm effective diameter in the center.

Planning Implants Crown Down—A Systematic Quality Control for Proof of Concept

We evaluated an innovative approach for conventional surgical or transmucosal implantation applying backward planning with bone oriented crown down implant positions, followed by immediate restoration. Our workflow combined computer-assisted preoperative planning with the well-known intraoperative handling of surgical templates. To guarantee optimal accuracy, the complete process was bone borne, not soft tissue borne. Furthermore, in this concept, the definite prosthesis was manufactured on a plaster cast and fixed with technical implants inserted into the model using the same drilling template applied for intraoperative guidance of the drill. This bone-based workflow avoids the accumulation of errors throughout all steps of the treatment. In the present study, we have provided a concise quantitative quality control using 4 in vivo implants. This goal was accomplished by image matching of the preoperative plan with the corresponding postoperative computed tomography scan, applying descriptive statistics, the 1-sample t test, and the Student t test. Statistical evaluation showed that the bone-borne drilling template provides sufficient accuracy for immediate restoration with the definite prosthesis at the end of the operation. Deviation in the apex plane was 0.8 ± 0.42 mm, with 0.33 at the maximum. The angular deviation was 3.18° ± 0.78°. Our workflow is a promising approach with respect to handling, accuracy, and intraoperative safety.

Site‐controlled InGaAs quantum dots grown on a GaAs multi‐faceted microstructure for single photon emissions

AbstractThis study demonstrates the single photon emissions form site‐controlled InGaAs quantum dots (QDs) grown on an apex plane of a GaAs multifaceted structure by pattern‐growth techniques, multifaceted structure comprises the top (001) plane, and {111} and {011} side wall facets. The QDs formed on the apex plane rather than the side wall facet because the growth rate of apex plane is exceeded that of side wall facet. Microphotoluminescence (μ PL), μ PL excitation (μ PLE) and theoretical calculations are adopted to estimate the growth rate of the {111} ({011}) facets as ∼82% (∼69%) lower than that of the (001) plane. Since the (001) plane growth rate is higher than that of the side wall facets, the QDs can be carefully controlled. This method is effective in the fabrication of a single photon source. (© 2008 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

High extractive single-photon emissions from InGaAs quantum dots on a GaAspyramid-like multifaceted structure

This work investigates the single-photon emissions from self-assembled InGaAs quantumdots that are grown on an apex plane of a GaAs pyramid-like multifaceted structure. Thenumber of QDs on a multifaceted structure is estimated by scanning electronmicroscopy. Single-exciton emissions from individual quantum dots are examinedby micro-photoluminescence and by making photon correlation measurements.This experiment demonstrates the improvement of the single-photon extractionefficiency as quantum dots are grown on a reduced apex plane of a multifacetedstructure.

Compound Fresnel Zone Lens Conformal to Truncated Cone: Antenna Application

A millimeter wave antenna consisting of two Fresnel zone plate lenses, plane and conical, is examined numerically by use of the vector diffraction theory. The lenses are of Wood-Wiltse (double-dielectric) or Soret (half-open) type, and are designed for the frequency of 117 GHz. The lenses are made conformal to a truncated circular cone with a base diameter of 500 mm and a plateau diameter of 250 mm. Designs for two opening semi-angles, 45° and 75° each of them with a particular lens thickness are presented. For the angle of 90° the cone lens becomes a plane ring lens, which in combination with the plateau zone lens forms a plane lens of size equal to the cone base diameter. Illuminated by directive feeds set at a focal distance of 525 mm from the cone apex, the double-dielectric and half-open compound and plane lenses, form three pairs of Fresnel zone lens antennas, the co-polar and cross-polar radiation characteristics of which have been compared numerically. The double-dielectric lens antennas examined are about 5 dB superior in gain to the half-open lens antennas, which has a gain of approximately 45 dBi. Because all lenses are of equal transverse aperture, the corresponding lens antennas exhibit the same −3 dB beamwidth of about 0.33 degrees. The plane zone lens antenna is very thin and simple. Instead, the antenna comprising a 3-D compound Fresnel zone lens is thicker but can be made conformal to a specific surface shape and possesses more levels of design and optimization freedom.

Diffraction by a small aperture in conical geometry: Application to metal-coated tips used in near-field scanning optical microscopy

Light diffraction through a subwavelength aperture located at the apex of a metallic screen with conical geometry is investigated theoretically. A method based on a multipole field expansion is developed to solve Maxwell's equations analytically using boundary conditions adapted both for the conical geometry and for the finite conductivity of a real metal. The topological properties of the diffracted field are discussed in detail and compared to those of the field diffracted through a small aperture in a flat screen, i.e., the Bethe problem. The model is applied to coated, conically tapered optical fiber tips that are used in near-field scanning optical microscopy. It is demonstrated that such tips behave over a large portion of space like a simple combination of two effective dipoles located in the apex plane (an electric dipole and a magnetic dipole parallel to the incident fields at the apex) whose exact expressions are determined. However, the large "backward" emission in the P plane--a salient experimental fact that has remained unexplained so far--is recovered in our analysis, which goes beyond the two-dipole approximation.

Experiments on individual alumina-supported adatoms and clusters

To contribute to an understanding of growth conditions and electronic properties of metal clusters on technologically relevant oxides we have examined the mobility of individual, alumina-supported Pt-adatoms and the optical properties of single supported Ag-clusters. Using field-ion microscopy (FIM) we have prepared and imaged an individual Pt-adatom at approximately 40 K, both on the apex plane of a [1 1 0]-oriented NiAl tip and on a thin alumina film, grown on the same NiAl specimen by oxidation. On the alumina film, the onset temperature for Pt surface diffusion approaches 100 K being distinctively lower than the value 165 K measured on NiAl(1 1 0). Employing the tip of a scanning tunneling microscope (STM) as a local electron source, photon emission from individual, alumina-supported Ag-clusters was spectroscopically analyzed. The occurrence of a distinct emission line is explained by the decay of a collective electron oscillation (Mie-plasmon resonance). For decreasing Ag-cluster diameter, the emission lines (i) shift to higher energies and (ii) their widths increase. To explain these observations, we discuss (i) the reduced screening of the plasmon oscillation due to the Ag 4d electrons and (ii) an enhanced electron surface scattering rate in small clusters.

Theoretical investigations of a coaxial probe concept for scanning near-field optical microscopy

In this paper we present a concept of a coaxial probe for near-field optical microscopy that can be realized utilizing micromachining technology processes. Numerical calculations were performed to prove the optical benefits of the coaxial probe in comparison to conventional aperture tips. Furthermore, the influence of the coaxial probe geometry with respect to its transmission efficiency and field confinement in the apex plane was investigated in detail.

Surface diffusion measurements from digitized FEM images: analysis of local brightness fluctuations

An extension of the field-emission current fluctuation method to study surface diffusion on the surface of a field emitter tip is proposed. The present approach is based on an analysis of the local brightness fluctuations extracted from digitized FEM video-images instead of the conventional probe-hole technique. “Virtual probe-holes” which correspond to probed surface regions of nanometer size can be placed in chosen areas of the image and the integrated intensity in these windows can be monitored with the time resolution of video frames (40 ms in our case). For the Li/Pt[1 0 0] tip system, the autocorrelation and crosscorrelation analyses of the local FEM brightness fluctuations have been performed. From a comparison of the experimentally obtained and theoretically calculated autocorrelation functions and from the crosscorrelation functions we determine the surface diffusion parameters for Li adatoms on the apex plane of the [1 0 0]-oriented Pt field emitter tip.

Field ionization of O 2 on oxygen-covered Pt(111) and W(111) as studied using field ion appearance energy spectroscopy

The local (probe hole) mass-to-charge-resolved retarding potential analysis of O 2 + ions originated from a few surface sites of the apex plane of a [1 1 1]-oriented Pt and W field emitter tips was performed. Applying a thermionic cycle, field-dependent values of the binding energies of O 2 molecularly adsorbed on Pt(1 1 1) and W(1 1 1) were derived from the field-ion appearance energies of O 2 + emitted at 79 K. Two different possible (noble-gas-like and field desorption) mechanisms of the field ionization of molecular oxygen supplied as imaging gas in the field-ion microscope (FIM) are considered on the basis of experimental data.

Molecular adsorption states of O 2 on W(111) at low temperatures (down to 5 K)

Adsorption of O 2 on W(111) at temperatures down to 5 K is studied using molecular beam (MB) and thermodesorption spectroscopy (TD) methods. The low-temperature TD spectra for the molecularly adsorbed O 2 on W(111) contain three peaks at 25, 27 and 60 K corresponding respectively to multilayer condensation, physisorption and weak molecular chemisorption. The role of the substrate structure for the O 2 chemisorption is discussed on the basis of present results for W(111) and earlier data for different metal surfaces. Field-effect on the O 2W(111) interaction is studied using field ion appearance energy spectroscopy (FIAES) of O + 2 ions emitted from the apex plane of a [111]-oriented W field emitter tip. Applying a thermionic cycle, field-modified binding energies for O 2 W(111) are derived from the O + 2 appearance energies measured at 79 K. FIAES data reveals a field-adsorbed O 2 layer as the origin of O + 2 field ions emitted from W(111) for field ion imaging.

Study of CO surface diffusion on [formula omitted] by analysis of CO + field ion rate fluctuations

An analysis of field ion rate fluctuations is proposed for studying the mechanism of the reactive imaging gas supply in a field ion microscope (FIM). In the experiment CO + ions emitted from a few selected surface sites of the apex plane of a [111]-oriented W tip and mass-to-charge resolved in a magnetic sector field are registered. The CO + ion rate fluctuations are analyzed by a method developed by Gomer for analyzing field electron current fluctuations. The CO gas supply toward the probed surface sites is found to have a diffusion character, confirming the role of the weakly bound CO layer in the localized field ionization of CO used as imaging gas in a FIM.

Noble-gas-like mechanism of localized field ionization of nitrogen as detected by field ion appearance energy spectroscopy

A local (probe-hole) mass-to-charge resolved retarding potential analysis of N 2 + emitted from a few surface sites of the apex plane of a [111]-oriented W tip is carried out and corresponding field ion appearance energies are obtained. A comparison of the results of N 2 + W(111) field ion appearance energy spectroscopy with independently obtained field-free nitrogen adsorption data reveals a noble-gas-like mechanism for the localized field ionization of N 2, supplied as imaging gas in the field ion microscope. The differences in the physical nature of the field-dependent terms of the appearance energy of N 2 + and CO + field ions are discussed in relation to the peculiarities of the high-field modified interaction of nitrogen and carbon monoxide with the tungsten surface.

Non-paraxial relations of equivalence between an arbitrary refracting surface of revolution and the phase transmittance function

A pair of simple equations is evaluated which enables easy parametric determination of the shape of the refracting surface of revolution from an arbitrary phase transmittance function of rotational symmetry, which is given at the apex plane. The corresponding inverse relations are also established permitting the phase transmittance function to be parametrically specified for an arbitrary refracting surface of revolution. The presented derivation is not restrained to the paraxial approximation.