Discrepancies In Shape Research Articles

Diagnosis of acute lung embolism with spiral CT and 3D reconstruction. Development of an animal model and technical probe in an ex-vivo experiment

To develop a model for simulation the CT morphologic situation of acute pulmonary embolism, to evaluate the accuracy of spiral CT and 3D reconstruction in the detection of artificial emboli and to investigate the influence of the orientation of emboli depending on z-axis orientation. Standardized artificial emboli made of wax and of defined size and shape were positioned into the pulmonary arteries of porcine lungs. Castings of the embolized pulmonary arterial trees were made by injection of a special opaque resin. After performance of spiral CT the data sets of the emboli and the pulmonary arteries were post-processed. The 3D segmentations were compared with the anatomic preparation to evaluate the accuracy of spiral CT/3D reconstruction-technique. Technical specimens simulating CT-morphology of acute embolized vessels underwent spiral CT in six different positions with respect to the z-axis. The CT data were reconstructed using a standardized and a contrastadapted method with interactive correction. The 3D emboli were analysed under qualitative aspects, and measurements of their extent were done. In nearly 91%, there was complete agreement between CT and the corresponding findings at the anatomical preparation. Measurements of the 3D reconstructed technical specimens showed discrepancies of shape and size in dependence of the size of the original preparation, orientation and reconstruction technique. Overestimation up to 4 mm and underestimation to 2.2 mm were observed. Measurements of preparations with heights from 14 to 26 mm showed variances of +/- 1.5 mm (approximately 6-11%). The presented models are suitable to simulate CT morphology of acute pulmonary embolism under ex-vivo conditions. Accuracy in the detection of artificial emboli using spiral CT/3D reconstruction is affected by localization, size and orientation of the emboli and the reconstruction technique.

Measurements of the Differential Cross Sections for Elastic and Inelastic Scattering of 14-MeV Neutrons in Natural Chromium, Iron, Nickel, and Niobium

The time-of-flight technique was used with the “ring” scattering geometry in a laboratory with low neutron-scattering background to measure the angular distributions of the cross sections for elastic and inelastic scattering of 14-MeV neutrons in natural chromium, iron, nickel, and niobium. Specifically for inelastic scattering, the measurements included the 1.43- and 4.56-MeV levels of 52Cr; the 0.85-, (2.94 to 3.12)-, and (4.46 to 4.51)-MeV level groups of 56Fe; the 1.33-MeV level of 60Ni combined with the 1.45-MeV level of 58Ni; and the 4.48-MeV level of 58Ni. Pulses of neutrons with time width of 0.9 to 1.1 ns were produced via the D-T reaction in a 150-keV linear accelerator, with average intensities of 9 × 108 n/s. The scattering angles ranged from ~16 to ~160 deg, with a typical step of ~10 deg. The overall uncertainty for the elastic scattering cross section was in the range of 7 to 10% for all materials, except around the minima of the angular distribution for niobium. The uncertainties for the inelastic scattering cross sections were estimated to be between 8 and 24%. The measured angular distributions were compared with the evaluations in the ENDF/B-VI, JENDL-3, CENDL-2, BROND-2, and JEF-2 nuclear data libraries. For elastic scattering, there are no significant discrepancies in general, neither among the evaluations nor between the present data and the evaluations. For the inelastic scattering there are substantial discrepancies both in shape and magnitude among the evaluations (when available) as well as between the present data and the evaluations.

Anthropometry, body composition and body image in dieting and non‐dieting 8‐16‐year‐old Swedish girls

Anthropometry, body composition and body image were studied in 122 Swedish 8‐16‐y‐old girls and their parents. The subjects participated in a 3‐y prospective longitudinal study and were selected randomly after stratification for grades from those scoring in the upper vs. the lower thirds of the Children's Eating Attitudes Test (ChEAT) score distribution. The ChEAT was completed 6 mo before the present study together with a demographic and dieting questionnaire and a questionnaire for the estimation of body size. In total 43%(n = 52) admitted ever dieting (“Dieters”) and 25%(n = 30) admitted that they were currently trying to lose weight. The anthropometric and body composition data indicated that ChEAT High‐scorers and Dieters were somewhat fatter than Low‐scorers and Non‐dieters, although this pattern was not shown among the 8‐y‐olds or the 14‐y‐olds (High‐scorers). The mothers of the ChEAT High‐scorers were found to be somewhat fatter than the other mothers. A current vs.ideal body shape discrepancy was shown for both High‐scorers and Dieters, with a larger discrepancy for the Dieters. All groups believed that their parents were aspiring for a leaner body. □Anthropometry, body composition, dieting behaviour, schoolgirls

Why are buckyonions round?

Multi-layered round carbon particles (onions) containing tens to hundreds of thousands of atoms form during electron irradiation of graphite. However, theoretical models of large icosahedral fullerenes predict highly faceted shapes for molecules with more than a few hundred atoms. This discrepancy in shape may be explained by the presence of defects during the formation of carbon onions. Here, we use the semi-empirical tight-binding method for carbon to simulate the incorporation of pentagon-heptagon defects on to the surface of large icosahedral fullerenes. We show a simple mechanism that results in energetically competitive derivative structures and a global change in molecular shape from faceted to round. Our results provide a plausible explanation of the apparent discrepancy between experimental observations of round buckyonions and theoretical predictions of faceted icosahedral fullerenes.

Inadequacy of Arrhenius plots as a graphical method for determination of localized states

An extended bibliographical analysis first allows one to establish that the method of graphical determination of gap state parameters, from Arrhenius plots of either conductivity or carrier densities, is very commonly substituted for exact methods of computer simulations of equations associated with the invoked models. Second, and in order to show the scope of risks incurred in this graphical method, models proposed by some authors to interpret their experimental curves are simulated exactly. Comparison of results with those curves generally shows large discrepancies in either curve shapes or parameter values (activation energies, densities of states). Other models are then proposed, allowing good fitting of experimental data. Hence, concrete illustration of the largely misappreciated, misleading character of the graphical method is given.

Visualization of liquid-solid interface morphologies in gallium subject to natural convection

Melting and solidification of pure gallium is studied using real-time radioscopy methods. Sharp contrast between melt and solid phases with a 3% density difference is illustrated. The interfacial shape reflects convective flow in the liquid phase. Comparisons are made between real-time non-intrusive X-ray observations and results gained from probing techniques and numerical simulations reported in the literature. Similar qualitative trends in temperature distribution, yet discrepancies in interfacial location and shape, are exhibited.

New constraints on the positron annihilation media from the direction of the Galactic center based on the 511 keV line profiles

view Abstract Citations (10) References (39) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS New Constraints on the Positron Annihilation Media from the Direction of the Galactic Center Based on the 511 keV Line Profiles Wallyn, P. ; Durouchoux, Ph. ; Chapuis, C. ; Matteson, J. ; Bowman, B. ; Pelling, M. ; Peterson, L. ; Lin, R. ; Smith, D. ; Feffer, P. ; Hurley, K. ; Vedrenne, G. ; von Ballmoos, P. ; Malet, I. Abstract We present an analysis of the profiles and intensities of the 511 keV annihilation line observed in the direction of the Galactic center by high energy resolution detectors. We first investigate the HEXAGONE 1989 May data, where the point source was in a rather low state. We find that a warm medium (temperature of 8000 K) can describe the annihilation of the positrons from the diffuse component of the line. We compare these results with the Bell/Sandia 1977, and GRIS 1988 October flights during high states of the central source, and we then show that the discrepancy in the line shape and width between these two sets of data is explained if the time-variable component of the line coming from the annihilation of the positrons emitted by the central source annihilates in a cold medium around 80 K). Publication: The Astrophysical Journal Pub Date: February 1993 DOI: 10.1086/172232 Bibcode: 1993ApJ...403..621W Keywords: Galactic Nuclei; Line Spectra; Milky Way Galaxy; Positron Annihilation; Astronomical Spectroscopy; Interstellar Matter; Molecular Clouds; Point Sources; Astrophysics; GALAXY: CENTER; GAMMA RAYS: OBSERVATIONS full text sources ADS | data products SIMBAD (2)

Progress in modeling the ionospheric peak and topside electron density

The electron density in the topside ionosphere strongly depends on the critical frequency of the F2 region, foF2. foF2 determines the peak density NmF2 and has considerable influence on the shape of the topside density profile. The most widely applied foF2 model is the well-known CCIR description. Recent improvements of this older model are discussed and compared with models deduced from ISS-b data. Furthermore, the topside profile is mainly dependent on geomagnetic latitude and solar activity. Several recent studies have shown that the widely used Bent and IRI models underestimate the measured topside densities close to the magnetic equator, even though simultaneous measured peak densities agree fairly well with the CCIR predictions. These discrepancies in shape were found in comparisons with Faraday electron content measurements, as well as AEROS satellite measurements and incoherent scatter measurements. The flexible IRI topside formula allows for an easy correction of this misinterpretation, resulting in a satisfactory description of the satellite data that represent low solar activity. The remaining underestimation of the high solar activity data indicates the need for further corrections of the IRI formula, when more data become available.

Thermal Finite Element Formulation and Solution Versus Experimental Results for Thin-Plate GTA Welding

The problem of steady-state and transient heat transport associated with thin-plate welding is formulated and solved using the finite element method. Phase change is accurately accounted for through an element phase property averaging and quadratic/integral capacitance fitting technique. Three cases of quasi-steady welding of SS (stainless steel) 304 plates were simulated: input powers of 285, 405, and 588 W with corresponding velocities of 0.408 × 10−3, 1.270 × 10−3, and 2.540 × 10−3 m/s. Comparison to experimental results shows good agreement of weld pool size with a shape discrepancy developing as welder power and velocity increase. Arc heat flux and weld pool convection effects are discussed. A review of these results, combined with a survey of current literature, enabled possible causes of these weld pool shape differences to be identified and enabled recommendations for future research to be made.

Angular distribution of electrons elastically scattered from gases: 2-400 eV on He. I

The angular distribution of electrons elastically scattered from He has been measured by electron impact utilizing a crossed-beam method. The energy and angular range measured were from 2.0 to 400 eV and from -96\ifmmode^\circ\else\textdegree\fi{} to + 156\ifmmode^\circ\else\textdegree\fi{}, respectively. The present results have been normalized to LaBahn and Callaway's theoretical value at 10.0 eV. The present results agree, in general, with a few previous measurements; however, there are still discrepancies in a detailed shape and magnitude among the measurements. The various theories need more improvements, especially for the backward scattering. It is found that the Born approximation is not yet adequate at 400-eV incident energy.

Genetic analysis of occlusal variation in twins

Orthodontists usually assume that genetic factors are of major significance to the development of malocclusion. Studies of twin similarities have lent support to this concept. Use of the twin model to estimate genetic variance, however, involves the assumptions that there are no mean or total variance inequalities between monozygotic and dizygotic twins. The environmental (including biologic) differences between monozygotic and dizygotic twin development may therefore constitute a source of bias. Genetic variance and heritability were estimated for a series of arch and occlusal traits in sixty twins using recently developed methods that are unbiased by variance heterogeneity between zygosities. Heterogeneity was demonstrated for twenty of the forty traits, suggesting considerable amounts of hidden environmental determinance. Tooth-displacement means differed between monozygotes and dizygotes, indicating bias in that trait's genetic variance analysis. Significant heritability could not be demonstrated for overbite, overjet, buccal segment relation, total tooth displacement, and occlusal discrepancies in arch shape. Arch size, individual tooth displacement scores, and cross-bite show significant genetic variance, averaging only about 36 percent of the total variance of these traits.

Dynamics Of Icelandic Ice Caps And Outlet Glaciers

Abstract Since late 1972, when the first Landsat images of Iceland became available, the ice caps of Iceland and their outlet glaciers have been under intensive study with Landsat images. The original emphasis of the Landsat research of Icelandic ice caps was to record and quantitatively measure dynamic change of glaciers and phenomena related to glaciers. A comparison of Landsat images with the best available topographic maps revealed a number of discrepancies in the planimetric shape and size of Icelandic ice caps and in the mapping of prominent surface features. Some of the surface features recorded on Landsat images turned out to be the subdued morphological expression of subglacial topography and geologic structure or the surficial response to subglacial volcanic and geothermal activity. Of particular interest was a winter image of Vatnajökull, acquired at a solar elevation angle of 7°, which revealed a number of surficial features not recorded before, including a large volcanic caldera in the Kverkfjöll area. A computer-enhanced early fall image of Vatnajökull revealed similar phenomena, and computer-enhancement techniques have also been applied to summer images of Hofsjökull, Langjökull, Mýrdalsjökull, and Eyjafjallajökull. In the case of Hofsjökull a subglacial volcanic edifice with the approximate dimensions of the Dyngjufjöll massif in north-central Iceland, and possibly with a caldera, may exist. Radio echo-sounding surveys have been carried out over some parts of Vatnajökull and Mýrdalsjökull to determine the precise nature of the subglacial topography, and it is of great interest to compare the results of these surveys of glacier bed topography with the surface features recorded on Landsat and other imagery. Landsat images are also being used to plan the optimum location of field traverses and as a navigational tool (map substitute) during field work.

Dynamics Of Icelandic Ice Caps And Outlet Glaciers

AbstractSince late 1972, when the first Landsat images of Iceland became available, the ice caps of Iceland and their outlet glaciers have been under intensive study with Landsat images. The original emphasis of the Landsat research of Icelandic ice caps was to record and quantitatively measure dynamic change of glaciers and phenomena related to glaciers. A comparison of Landsat images with the best available topographic maps revealed a number of discrepancies in the planimetric shape and size of Icelandic ice caps and in the mapping of prominent surface features. Some of the surface features recorded on Landsat images turned out to be the subdued morphological expression of subglacial topography and geologic structure or the surficial response to subglacial volcanic and geothermal activity. Of particular interest was a winter image of Vatnajökull, acquired at a solar elevation angle of 7°, which revealed a number of surficial features not recorded before, including a large volcanic caldera in the Kverkfjöll area. A computer-enhanced early fall image of Vatnajökull revealed similar phenomena, and computer-enhancement techniques have also been applied to summer images of Hofsjökull, Langjökull, Mýrdalsjökull, and Eyjafjallajökull. In the case of Hofsjökull a subglacial volcanic edifice with the approximate dimensions of the Dyngjufjöll massif in north-central Iceland, and possibly with a caldera, may exist. Radio echo-sounding surveys have been carried out over some parts of Vatnajökull and Mýrdalsjökull to determine the precise nature of the subglacial topography, and it is of great interest to compare the results of these surveys of glacier bed topography with the surface features recorded on Landsat and other imagery. Landsat images are also being used to plan the optimum location of field traverses and as a navigational tool (map substitute) during field work.

A study of the 58Ni, 90Zr and 208Pb(p, d) reactions at 121 MeV

Abstract The (p, d) reaction has been studied on 58Ni, 90Zr and 208Pb at 121 MeV in order to test the applicability of the usual DWBA methods to higher energy data. The calculations describe the angular distribution for the strongly excited low-lying states reasonably well when adiabatic-deuteron optical potentials are used. Some discrepancies in shape persist, however, and some values of the spectroscopic factors differ from lower energy data in spite of many variations in the calculations. By use of exact finite-range calculations a value of D02 = 1.23 × 104 MeV2 · fm3 was found for use at 121 MeV. Deuteron D-state contributions were negligible at forward angles and two-step contributions do not appear more significant than for data at lower energy.

Coulomb potentials and the energy-angular momentum balance in heavy ion transfer reactions

Coulomb terms in optical model parameters and in the effective interaction are discussed for DWBA in charged particle transfer in heavy ion reactions. It is shown that certain discrepancies in shapes of calculated angular distributions are due to incorrect treatment of Coulomb terms.

Discrepancy between electron heating and cooling rates derived from atmosphere Explorer-C measurements

The present theory of electron temperature in the daytime mid-latitude ionosphere is tested by using Atmosphere Explorer-C measurements. In the region below 300 km, where a balance is expected between electron heating by photoelectron impact and electron cooling to ions and neutrals, we find an imbalance in which the cooling rate is consistently higher than the heating rate. The shapes of the altitude profiles also differ substantially. The cooling rate has a sharp peak at about 220 km, while the heating rate exhibits a broad peak about 30 km lower. Improved agreement is achieved at higher altitudes by using an oxygen fine structure loss rate smaller by a factor of 2, based on more recent collision strength calculations. Although this improves the overall agreement of the heating and cooling rates, the shape discrepancy remains, and the new cooling rate falls consistently below the heating rate below 200 km.

Comparisons of predictions from two intranuclear-cascade models with measured secondary proton spectra at several angles from 62 - and 39 - MeV protons on various elements

Detailed comparisons of correlated energy-angle proton spectra corresponding to continuum state transtions have been made between experimental data and two versions---Brookhaven National Laboratory (BNL) and Oak Ridge National Laboratory (ORNL)---of the intranuclear-cascade model for 62- and 39-MeV protons incident on carbon, iron, and bismuth. These energies were selected because detailed experimental data are available and because the energy limit of validity of the intranuclear-cascade approach could be examined. The calculated spectra are in good agreement (\ensuremath{\le} 30%) with the shapes and magnitudes of the measured integral spectra for the 62-MeV reactions. However, the comparisons of the spectra at angles \ensuremath{\le} 20\ifmmode^\circ\else\textdegree\fi{} and g 90\ifmmode^\circ\else\textdegree\fi{} are poor. There is a much greater discrepancy in the correlated energy-angle data from reactions at 39 MeV. The BNL version, which contains the greater physical detail, tends to reduce the discrepancies in the spectral shape at small and large angles between the experimental data and the simpler intranuclear-cascade version (ORNL). Examples of these discrepancies are: a high estimated quasifree peak at small angles and a small scattering intensity at back angles. However, the BNL version reduces the particle yield for heavy targets so that the comparisons of the predicted absolute cross sections with the experimental data are often poor. The effects of reflection and refraction, which are included in the BNL version only, appear to be in the right direction to compensate for the discrepancies of the ORNL version, but some modification in the manner that this phenomenon is incorporated may be required to avoid the discrepancies in absolute cross sections.NUCLEAR REACTIONS $^{12}\mathrm{C}(p, {p}^{\ensuremath{'}}X)$, $^{54}\mathrm{Fe}(p, {p}^{\ensuremath{'}}X)$, $^{209}\mathrm{Bi}(p, {p}^{\ensuremath{'}}X)$ calculated $\ensuremath{\sigma}(E;{E}_{{p}^{\ensuremath{'}}},\ensuremath{\theta})$, $\ensuremath{\sigma}(E)$; $E=39, 62$ MeV. Intranuclear-cascade models.

A COMPARISON OF OCULAR IMAGERY

The work which in recent years has been developed at the Dartmouth Eye Institute, Hanover, N. H., by Ames and his associates 1 has become familiar to most ophthalmologists. The practical clinical application of the correction of aniseikonia has apparently not been demonstrated sufficiently to establish in the minds of practicing physicians the need for considering the condition a part of the symptom complex of asthenopia. The reaction of many physicians and laymen has been that there has been considerable publicity without a commensurate guarantee of symptomatic relief. This paper consists of a comparison of two instruments designed for the purpose of measuring the relative discrepancy in size and shape between the ocular images of the two eyes. The first instrument is the eikonometer, designed by the Dartmouth Eye Institute 2 in conjunction with the American Optical Company. The other is the comparator, 3 designed by Kerry and his co-workers