High Density Objects Research Articles

The influence of variations in atmospheric pressure on the uncertainty budget of weighing results

The various assays in quantitative analytical chemistry always include mass determinations, along with other operations, and the same is true for the uncertainty budget of such a procedure. In order to obtain an accurate weighing result it is necessary to consider air buoyancy, which depends on, besides other parameters, atmospheric pressure. In contrast to air temperature and humidity, it is not possible to control the atmospheric pressure in a conventional laboratory. Therefore, it can be necessary to consider the uncertainty of pressure in uncertainty calculations of weighing operations, depending on the mass and density of the weighed object. The theoretical relationship between pressure variations and obtained weight value are derived. Experimental confirmation was obtained on the one hand by the mass determination of five Pyrex glass bottles over a period of 6 months; these are objects with a lower density than the reference weights of the balance, thus showing a negative dependence of weight value on atmospheric pressure. On the other hand, a tungsten cylinder was weighed over several weeks; this high-density object has a positive dependence. In both cases the experimental slopes agreed with the theoretical values. The consequences on the uncertainty budget of a weighing operation are remarkable: the total uncertainty of the mass determination of a 90 g glass bottle is 0.3 mg whereas it is 4 μg for a 4.6 g tungsten cylinder. The contributions originating from the pressure variation alone are 0.3 mg and 3.5 μg, respectively, i.e., the pressure uncertainty dominates and is much more important than the uncertainty contributions of balance repeatability and linearity.

443産業用高エネルギーX線CTとその応用

A high energy industrial X-ray computed tomography system using silicon semiconductor detectors (Si-SSD) and electron linear accelerator (LINAC) was developed to obtain high resolution 3D images of high density and large scale object. To increase photon sensitivity, detector elements were placed parallel to the X-ray beams. The obtained sensitivity of 20% for X-ray of 3MeV was 3×104 times higher than that of X-ray films. It was clarified that the photon sensitivity of X-ray detectors restricts the performance of high energy X-ray CT, and it is shown that a CT image of 200mm thick iron object can be obtained with 0.2mm space resolution.

Découverte fortuite d'un thrombus calcifié de l'artère pulmonaireIncidental detection of calcified pulmonary thrombus

The discovery during a thoracic helical CT imaging of a high density object filling a pulmonary artery lead to a search for its origin. Patient antecedents and comparison with previous CT imaging indicated the diagnosis of calcified pulmonary thrombus.

Découverte fortuite d'un thrombus calcifié de l'artère pulmonaire

The discovery during a thoracic helical CT imaging of a high density object filling a pulmonary artery lead to a search for its origin. Patient antecedents and comparison with previous CT imaging indicated the diagnosis of calcified pulmonary thrombus.

Quasar Constraints on the Cosmic String Models

The number densities of quasars and high-redshift galaxies introduce strict constraints on theories of large-scale structure formation. We compute the comoving space densities of these objects with cosmic string models and compare results with observations. We show that the cosmic string models can produce enough high-density objects to account for the observations. We also show that, because of non-Gaussian initial conditions, the number density of quasars is higher than expected from conventional Gaussian Press-Schechter analysis. The cosmic string model is consistent with the QSO abundance limit at z = 4.5, both in Ω = 1.0 and in Ω = 0.2 cases. However, there are problems with large-scale structure when the stringy power spectrum is compared with the three-dimensional Automatic Plate Measuring Facility (APM) spectrum in Cambridge, England.

Memory representations underlying motor commands used during manipulation of common and novel objects.

1. While subjects lifted a variety of commonly handled objects of different shapes, weights, and densities, the isometric vertical lifting force opposing the object's weight was recorded from an analog weight scale, which was instrumented with high-stiffness strain gauge transducers. 2. The force output was scaled differently for the various objects from the first lift, before sensory information related to the object's weight was available. The force output was successfully specified from information in memory related to the weight of common objects, because only small changes in the force-rate profiles occurred across 10 consecutive lifts. This information was retrieved during a process related to visual identification of the target object. 3. The amount of practice necessary to appropriately scale the vertical lifting and grip (pinch) force was also studied when novel objects (equipped with force transducers at the grip surfaces) of different densities were encountered. The mass of a test object that subjects had not seen previously was adjusted to either 300 or 1,000 g by inserting an appropriate mass in the object's base without altering its appearance. This resulted in either a density that was in the range of most common objects (1.2 kg/l) or a density that was unusually high (4.0 kg/l). 4. Low vertical-lifting and grip-force rates were used initially with the high-density object, as if a lighter object had been expected. However, within the first few trials, the duration of the loading phase (period of isometric force increase before lift-off) was reduced by nearly 50% and the employed force-rate profiles were targeted for the weight of the object.(ABSTRACT TRUNCATED AT 250 WORDS)

Application of cadmium telluride detectors to high energy computed tomography

15 years ago, cadmium telluride detectors have been investigated in our laboratory as possible detectors for medical scanners [1]. Today most of these machines are using high pressure xenon gas as multicells detectors, and BGO or CdWO4 scintillators for industrial computerized tomography. Xenon gas detectors are well suited for the detection of 100 keV X-rays and enables one to built 1000 cells of homogeneous detector with a dynamic range of 3 decades. BGO and CdWO4 scintillators, associated with photomultipliers or photodiodes, are used for higher energy (400 keV). They present a low afterglow and a dynamic range of 4–5 decades. Nondestructive testing of very absorbing objects (e.g. 2 m diameter solid rocket motor) by X-ray tomography requires much higher energy X-rays (16 MeV) and doses up to 12 000 rad/min at 1 m. For this application cadmium telluride detectors operating as photoconductors are well suited. A prototype tomograph machine, able to scan ∅ 0.5 m high density objects has been realized with 25 CdTe detectors (25×15×0.8 mm3). It produces good quality 1024×1024 tomographic images.

Quasi-Periodic Oscillations in Celestial X-Ray Sources

Much of what we know about x-ray sources in our galaxy derives from regularities in the way the intensity of their radiation varies with time. Cyclic increases and decreases in intensity can indicate that a star is orbiting the x-ray source, eclipsing it periodically. X-ray pulses uniformly spaced less than a few seconds apart, on the other hand, imply that the source is a high-density object, know as a neutron star, that happens to be strongly magnetized and spinning rapidly as well. Intermittent bursts of x rays also indicated the presence of a neutron star, but one on whose surface enormous thermonuclear explosions are taking place. In late 1984 and early 1985, the author and his colleagues realized that their observations of one of the brightest galactic-bulge sources, GX5-1, had revealed a peculiar type of regular variation in its x-ray intensity. The observations were made with a satellite of the European Space Agency, the x-ray observatory, EXOSAT. The variations observed in the intensity of GX5-1's x-ray emissions were particularly surprising because they were not strictly periodic: in any given observation the interval between x-ray intensity peaks was likely to be close to .03 second, but often it was a bitmore » longer or shorter. Such not quite periodic fluctuations are generally called quasi-periodic oscillations (QPO's). 6 figs.« less

The internal dynamics of the planetary nebulae in the Large Magellanic Cloud

view Abstract Citations (67) References (38) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Internal Dynamics of the Planetary Nebulae in the Large Magellanic Cloud Dopita, Michael A. ; Meatheringham, Stephen J. ; Webster, B. Louise ; Ford, Holland C. Abstract The radial velocity and expansion velocity in the [O III] λ5007 line have been determined for a sample of 94 planetary nebulae (PN) in the Large Magellanic Cloud. In addition, densities and expansion velocities have been determined for a subset of 44 objects in both the Large and Small Magellanic Clouds using the [O II] λλ3727, 3729 doublet. With a few notable exceptions, the [O II] expansion velocities are well correlated with, but are systematically higher than, the [O III] expansion velocities. For a given excitation class, there appears to be an upper limit to the density, in the sense that very high density objects are always of low excitation, but low-density objects can occur at any excitation. The population of PN in the Magellanic Clouds appears to form a sheet in dynamical age/excitation class/nebular density space, and therefore represents a two-parameter family. The implication of this is that the nebular parameters are entirely determined by the properties of the central star. This fact could represent the basis of a solution to the distance scale problem for Galactic PN. Publication: The Astrophysical Journal Pub Date: April 1988 DOI: 10.1086/166221 Bibcode: 1988ApJ...327..639D Keywords: Astrodynamics; H Beta Line; Magellanic Clouds; Planetary Evolution; Planetary Nebulae; Stellar Spectra; Computational Astrophysics; Emission Spectra; Line Of Sight; Radial Velocity; Stellar Evolution; Astrophysics; GALAXIES: MAGELLANIC CLOUDS; NEBULAE: PLANETARY; STARS: EVOLUTION full text sources ADS | data products SIMBAD (83)

CT diagnosis of common bile duct stone.

Common bile duct stones were demonstrated as high-density objects on CT in 22 of 45 cases. About 96% of the remaining cases (22 of 23) exhibited other abnormal CT findings which included common bile duct dilatation, concomitant gallbladder stones, and/or presence of intraductal air. CT is a useful diagnostic modality in the elevation of patients with suspected choledocholithiasis.

片側性副鼻こう炎症例におけるＣＴ‐ｓｃａｎ像とゆがみ 上がくどう後壁骨肥厚像の検討とファントーム実験

Recently CT-scan has been widely used for the observation and diagnosis of various diseases in the otorhinolaryngological field. Findings of CT-scan might be available for the dicision of the staging of maxillary cancer. Meanwhile, there are some artifacts on the image of CT-scan, especially of the nasal and paranasal sinuses, which are consisted with complicated thin bony walls. We sometimes observed apparent thickening of the posterior bone wall of the maxillary sinus in the cases of unilateral sinusitis, but it was not observed during the operation. To be proved any artifact of CT-scan, phantom studies using with hen's egg in various condition were done. It suggests that the image of the posterior bone wall was sometimes affected and was made as "thickened" by the overlapping of the high density object, i. e., mucopurulent discharge or really thickened maxillary membrane. If there is early stage of maxillary cancer, the small bone destruction might be cancelled with this artifact and misdiagnosis will be made. We should pay special attention to define the false shadow on the CT-scan in the case of unilateral sinusitis or of the maxillary cancer.

Industrial Tomography Applications

The technique of computerized photon tomography has been applied in the nondestructive evaluation of a number of inanimate objects. 1,2,3 Hardware and software capabilities for industrial tomographic analysis, particularly of high-density objects, have been developed. Spatial resolution is on the order of 1-2mm for density variations of a few percent.

AN EMISSION-LINE OBJECT FOUND IN THE ORION NEBULA

ABSTRACT T. R. GULL Kitt Peak National Observatoryt, Tucson L. GOAD Harvard College Observatory H-Y. CHIU Goddard Institute for Space Studies S. P. MARAN AND R. W. HOBBS NASA, Goddard Space Flight Center A small, low-temperature, high-density object has been found superimposed upon the Orion nebula. The observed spectrum suggests it is a Herbig-Haro object. Key words: interstellar medium - diffuse nebulae - Orion nebula - emission-line object

Criteria for the source of Australites

Recent data on the composition of the lunar surface indicates that material of tektite composition is not present at the sites sampled. The hypothesis of terrestrial impact origin for the Australian and east Asian tektite strewn field, which is supported by geochemical evidence, is examined. The apparent absence of a deep crater (analogous to the Arizona crater) indicates that high density (meteorite or asteroid) objects were not involved. The surface evidence expected from impact of a low density comet (analogous to the Tunguska event) is examined. It is suggested that the Australian and east Asian tektites originated in a super-Tunguska event, and search for wide shallow craters should be concentrated in areas of appropriate composition (sub-greywacke sandstone).