Cavities Of Different Sizes Research Articles

Adsorption in a spherical cavity.

This paper reports on studies of adsorption in spherical cavities of different sizes. The calculations have been carried out by the density functional approach. We have studied the influence of the cavity size and attractive particle-cavity forces on the phase behavior of confined fluids. We find that capillary condensation occurs. As the radius of the cavity is decreased, the transition is shifted toward lower densities of the bulk fluid, which is in equilibrium with the fluid in the cavity.

The "bottle brush": a new concept for uncemented anchorage of bone implants. Preliminary mechanical and biomechanical studies.

We present a new concept for bone of implants, the "bottle brush". It may be suitable for joint prostheses, dental or percutaneous implants, or other devices fixed into bone. Mechanical pullout studies in artificial brass cavities of different sizes and shapes and implantation studies in 20 rabbits, have been successfully carried out. Further experimental and clinical studies are in progress.

Theoretical and experimental study of plane wave propagation in asymmetrical rectangular waveguide filters

A first type of acoustical waveguide filter, made of identical cavities, was developed and studied thoroughly. The noise control performance of that device was limited to a narrow frequency band. A new type of waveguide filter, made of rectangular cavities of different sizes, is proposed in order to extend the band of frequencies for which noise reduction occurs. Furthermore, recent studies, revealing the highly anisotropic behavior of the device, suggested that its performance would improve greatly if the incidence of the acoustic waves was kept normal to the inlet slit of the device. This paper is, therefore, concerned with a theoretical two-dimensional study of plane wave propagation in such a device. The mathematical model used was originally used in the field of microwave propagation in waveguides, where good theoretical prediction was obtained. The sound pressure level and phase differences between two points are evaluated with the theoretical model and compared with experimental values. Those points are chosen to allow a far field prediction of the sound level and phase. The theoretical and experimental results are in good agreement. Observations on the effective extension of the pass-band region are presented.

Acoustique des cavités : modèles et applications

The purpose of this paper is to present the main developments in the theory of the acoustics of dissipative fluids at rest in bounded spaces (principally cavities of different sizes and shapes), from the early beginnings (in the 1850's) until now, including a brief indication of possible approaches for future developments. Several applications of interest, and current research concerned with miniaturisation, are presented, with emphasis being given to the work done on the acoustic gyrometer and on its potential to be miniaturized, which include the miniaturization of acoustical transducers (on silicon chips)

Synthesis of sterically rigid macrocycles by the use of pressure-induced repetitive Diels-Alder reactions

Syntheses of the syn-dimethanotetrahydroanthracene and -tetracene derivatives 2a– d and 6a, b are described. Highly stereoselective, pressure-induced repetitive Diels-Alder reactions of these bis-dienophiles with bis-diene 7 lead to the sterically rigid macrocycles 10a, 10d, 13a and 14a, b having well defined cavities of different size.

Discrimination between PD pulse shapes using different neural network paradigms

A comparison has been carried out on the partial discharge (PD) pulse shape recognition capabilities of neural networks, using the nearest neighbor classifier, learning vector quantization and multilayer perceptron paradigms. The PD pattern recognition capabilities were assessed on artificial cylindrical cavities of different sizes. The performance of the three neural network paradigms was found to be equivalent in all respects, with the exception of the case where a distinction was required between small cavity sizes; under those circumstances, the learning vector quantization paradigm was distinctly superior to the two other paradigms. The experimental results also demonstrated that, even with simple metallic electrode cavities, the discrimination capabilities of the three types of neural networks are not always perfect.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Precision measurement of the orthopositronium decay rate using the vacuum technique.

A focused beam of 700-eV positrons is used to form orthopositronium ({ital o}-Ps) in evacuated, MgO-lined cavities of different sizes. The {ital o}-Ps decay rate {lambda}{sub {ital T}} is determined to be 7.0482{plus minus}0.0016 {mu}s{sup {minus}1} after extrapolation to infinite cavity size. This 230-ppm result is 4 times more accurate than previous measurements utilizing the vacuum technique. Subject to radically different systematic effects, it corroborates at the 6.2{sigma} level the discrepancy between theory and a recent 200-ppm measurement of {lambda}{sub {ital T}} in gases.

ChemInform Abstract: New Water‐soluble Macrobicyclic Cavities.

AbstractThe title compounds (III), (VI), (Xb), and (XIb) bearing large endolipophilic cavities of different sizes and shapes are synthesized for the first time.

Neue wasserlösliche makrobicyclische Großhohlräume

New Watersoluble Macrobicyclic CavitiesThe watersoluble macrobicyclic compounds 1, 3, 5a, and 5b have been synthesized for the first time bearing large endolipophilic cavities of different sizes and shapes. They were studied with respect to their interactions towards lipophilic guest compounds. The “in/out” isomerism of the hitherto largest endolipophilic cavities 4a, 4b, 5a, and 5b has been investigated by 1H‐, 13C‐NMR spectroscopy and FAB mass spectrometry. The absence of significant 1H‐NMR high‐field shifts in hostguest studies is attributed to the rigidity of cavities 1 and 3, whilst the isomeric cavities 5a and 5b contain very large openings. Orientational fluorescence spectroscopy investigations, however, suggest hostguest interactions of the isomers 5a and 5b with ammonium 8‐anilino‐1‐naphthalenesulfonate (8,1‐ANS).

Direct Probe Fourier Transform Far-Infrared Spectroscopy of Metal Atoms, Metal Ions, and Metal Clusters in Zeolites

Abstract A class of crystalline aluminosilicates, known as the zeolites, are widely used as effective heterogeneous catalysts in the chemical industry. They possess excellent stability, activity and selectivity patterns for a wide range of hydrocarbon transformations [1–10]. X-ray diffraction studies have shown that zeolites are giant macromolecules formed by AlO4 and SiO4 tetrahedra joined by shared oxygens, and the structures of many synthetic and naturally occurring zeolites are now known and well documented [11]. As a simplification we can think of certain zeolites as a three-dimensional channelled network of interconnected cavities of different sizes. The excess negative charge on the framework of the zeolite, due to the AlO4 tetrahedra, is either balanced by positively charged metal ions or protons which usually reside at well-defined sites in the zeolite lattice. The presence of exchangeable cations makes some zeolitic materials especially attractive in applications involving water treatment, such ...

Lipoide Transformation der Mitochondrien in Nebennierenrindenzellen nach Aminoglutäthimid (Elipten® Ciba)

Aminoglutethimide (Elipten® Ciba) interferes with the biosynthesis of adrenocortical hormones by blocking the conversion of cholesterol into Δ 5-pregnenolone. The ultrastructural alterations of adrenocortical mitochondria produced by administering Eliptene orally to female albino rats was studied. In almost all adrenocortical layers there was a diffuse transformation of mitochondrial internal structure as the vesicular “fasciculata type” and a mitochondrial enlargement. Such alterations were presumably due to the increase in ACTH-stimulation of adrenocortical cells. The most striking focal mitochondrial changes were intramitochondrial membranebound cavities of different size (diameter up to 6 μ), which should be regarded as a pathological equivalent to mitochondrial vesicles. In electron micrographs the cavities were either empty or contained fine fibrillar or homogeneous lipid material of moderate electron density. At the periphery of this intramitochondrial lipid material myelin-like patterns were often found. After the dissolution of the membranous component of mitochondria, which had undergone “lipoid transformation”, free cytoplasmic lipid aggregates and large lipid droplets developed, frequently with remainders of myelin-like patterns.

Radium dosage patterns in the treatment of uterine carcinoma.

In the radium treatment of endometrial carcinoma using Heyman's packing technique, variations in shape and size of malignant uteri become very important in evaluation of the dose delivered to uterine walls and the adjacent structures. Because of these difficulties, an unsatisfactory method of stating dosage in milligram-hours of radium has been retained in gynelogic curie therapy.An experimental program to determine the distribution of radiation along the periphery of the uterine wall as well as to structures of anatomic importance was recently completed. Multiple measurements were performed in different sizes of uterine models using Sievert miniature ionization chambers, lithium fluoride dosimeters and slow films. A limited computer program was written to check the pattern of experimental measurements. The results were satisfactory and an extensive computer program was started to develop a system of complete radium dosage patterns for uterine cavities of different size and shape and their associated radi...

Calcul de la résistivité des cavités sphériques dans le cuivre

The authors have calculated the resistivity introduced in copper by spherical cavities of different sizes. These voids are represented by square potentials whose height is calculated in order to determine exactly the influence of the screening conduction electrons. The diffusion problem has been completely solved by the partial wave method. The supplementary resistivity increment due to one vacancy exhibits a small maximum for voids composed of two vacancies, and slowly decreases for the larger cavities. This resistivity increment is only decreased by one-half of its initial value for voids containing 100 vacancies. The effective diffusion cross-section is still much smaller, in this case, than the classical cross-section of a hard sphere of the same radius.