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  • Polymer and Materials Science  (25)
  • ASTROPHYSICS  (6)
  • Cell & Developmental Biology  (6)
  • Condensed Matter: Structure, etc.  (4)
  • 1
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Four different acetabular replacement designs and 2 femoral head replacement designs made out of high density alumina ceramic have been tested in sheep with postoperative survival times of up to 11 months (Frialit 99: Al2O3 99.6%, MgO 0.4%).It can be concluded from these experiments that a cement free implantation technique with alumina requires a primary rigid fixation of the implant to bone, with the possibility for new bone growth along the ceramic and into grooves and macroscopic holes for further interdigitation. Three different solutions for the acetabular component can be recommended for human application.In addition, an all ceramic femoral prosthesis has been tested for bending strength in its neck region. Twenty prostheses have been fractured, all of which showed values for bending strength far higher than the physiological neck fracture level (900 kp/cm2). The present state of development of all ceramic prostheses is discussed. Up to now, the development of fibrous tissue between the bone and the ceramic implant has caused reservations with human implantation. The direct definite anchorage problem has to be resolved first.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2011-03-06
    Description: Author(s): Nuno A. M. Araújo, José S. Andrade, Jr., Robert M. Ziff, and Hans J. Herrmann The suitable interpolation between classical percolation and a special variant of explosive percolation enables the explicit realization of a tricritical percolation point. With high-precision simulations of the order parameter and the second moment of the cluster size distribution a fully consisten... [Phys. Rev. Lett. 106, 095703] Published Fri Mar 04, 2011
    Keywords: Condensed Matter: Structure, etc.
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
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  • 3
    Publication Date: 2014-10-11
    Description: Author(s): Cláudio L. N. Oliveira, Nuno A. M. Araújo, José S. Andrade, Jr., and Hans J. Herrmann We introduce a theoretical model to investigate the electric breakdown of a substrate on which highly conducting particles are adsorbed and desorbed with a probability that depends on the local electric field. We find that, by tuning the relative strength q of this dependence, the breakdown can chan... [Phys. Rev. Lett. 113, 155701] Published Fri Oct 10, 2014
    Keywords: Condensed Matter: Structure, etc.
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
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  • 4
    Publication Date: 2018-04-25
    Description: Author(s): Cesar I. N. Sampaio Filho, José S. Andrade, Jr., Hans J. Herrmann, and André A. Moreira The elastic backbone is the set of all shortest paths. We found a new phase transition at p eb above the classical percolation threshold at which the elastic backbone becomes dense. At this transition in 2D, its fractal dimension is 1.750 ± 0.003 , and one obtains a novel set of critical exponents β eb = 0... [Phys. Rev. Lett. 120, 175701] Published Tue Apr 24, 2018
    Keywords: Condensed Matter: Structure, etc.
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
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  • 5
    Publication Date: 2016-12-30
    Description: Author(s): Cesar I. N. Sampaio Filho, André A. Moreira, Nuno A. M. Araújo, José S. Andrade, Jr, and Hans J. Herrmann We report on a novel dynamic phase in electrical networks, in which current channels perpetually change in time. This occurs when the elementary units of the network are fuse-antifuse devices, namely, become insulators within a certain finite interval of local applied voltages. As a consequence, the… [Phys. Rev. Lett. 117, 275702] Published Thu Dec 29, 2016
    Keywords: Condensed Matter: Structure, etc.
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
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  • 6
    Publication Date: 2019-07-27
    Description: One of the outstanding uncertainties in the understanding of the heliosphere concerns the character of the interaction between the outflowing solar wind and the interstellar medium. A new possibility for obtaining information on this topic is suggested. The cosmically abundant elements neon, oxygen, carbon, and nitrogen will be affected differently at their interface passage depending upon the character of this region. Consequently, the distribution of these atoms and their ions will vary within the inner heliosphere. The study of resonantly scattered solar radiation from these species will then provide information on the nature of the interface. A preliminary evaluation of this approach has been carried out, and the results are encouraging. The relevant lines to be studied are in the extreme and far ulraviolet. The existing data in these bands are reviewed; unfortunately, past instrumentation has had insufficient resolution and sensitivity to provide useful information. The capabilities of future approved missions with capabilities in this area are evaluated.
    Keywords: ASTROPHYSICS
    Type: COSPAR Colloquium; Sept. 19-22, 1989; Warsaw; Poland
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  • 7
    Publication Date: 2019-08-28
    Description: We derive an analytical formula for the maginification of an extended source with constant surface brightness lensed by a point mass. We find that the magnification for an extended source is significantly different from that for a point source when the impact parameter is comparable to the source size. In particular, the peak magnification for an extended source can be larger or smaller than the peak magnification for a point source. The results are relevant to the short-duration (approximately day) and high-magnification events in the search of massive compact halo objects in the Galactic halo by microlensing.
    Keywords: ASTROPHYSICS
    Type: The Astrophysical Journal (ISSN 0004-637X); 430; 2 pt; p. 505-510
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  • 8
    Publication Date: 2019-08-28
    Description: We present a method of computing the velocity distribution of the caustic network due to the random motion of stars in the lensing galaxy. This method is illustrated on the example of the two-point mass lens and then applied to a large sample of stars. We conclude that the proper motion of the stars increases significantly the frequency of the high magnification events in comparison with a static lens configuration with constant stream or constant bulk velocity. The stream velocity is the velocity of the star field relative to the global bulk velocity of the galaxy. We show that the global bulk and the stream velocity of the star field have to be considered separately for any microlensing situation. The higher the surface mass density of the stars in the lensing galaxy, the higher the influence of proper motion of stars on the statistics of high magnification events. The influence of a Gaussian velocity distribution of the stars in the lensing galaxy compared with a constant stream velocity of the stars increases the number of high magnification events by a factor 1.30 +/- 0.06 for a normalized surface density of the stars cr = 0.1 and by a factor 1.7 +/- 0.1 for sigma = 0.5. This means that for some microlensing situations the proper motion of the stars in a lensing galaxy has to be considered for exact microlensing predictions.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 409; 2; p. 537-547.
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  • 9
    Publication Date: 2019-08-28
    Description: It is well known that multiply imaged quasars are likely to be affected by microlensing. Quadruply imaged systems are especially useful laboratories for studying microlensing because their macrolens models are relatively well constrained. We begin with analytical results for a simple family of galaxy models. These results can be used to estimate the magnifications and time delays for the quadruple systems. We compute expected brightness fluctuations due to microlensing in several such systems for a range of source sizes. Among these we treat for the first time the limiting case of a completely unresolved source. For the case of MG 0414+0534 we interpret the discrepant optical-to-radio flux ratios for the different components as the result of microlensing. On the assumption that the lensing galaxy is roughly isothermal this gives a 95% confidence upper limit on the optical source size of 10(exp 16) cm x (mean value of M)/0.1 solar mass(exp 1/2) where (M) is the average stellar mass of the lensing galaxy. For more centrally concentrated macromodels the upper limit is greater. Sufficiently long strings of photometric observations can in principle constrain the degree of concentration.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 443; 1; p. 18-28
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  • 10
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    In:  Other Sources
    Publication Date: 2019-08-27
    Description: We point out the uncertainties in the potential models of the foreground galaxy in the gravitational lens Q2237 + 0305. The surface densities and external shears are uncertain by a factor of appproximately less than 2. Very long light curves are calculated for different models using the method developed by Witt (1993) and Lewis et al. (1993). We find that the probability of images being in a quiescent state depends strongly on the potential models and the direction of the source motion relative to the alignment of the (gravitational lens) shear term of the macroimages. For example, the probabilities of finding variations smaller than 0.1 mag and for a period of longer than 0.5 Einstein radii (approximately equals 3-5 yr) in image C and D are approximately 30%. This offers an explanation of why image C and D showed relatively small variations. The quiescent images are more likely to be demagnified, consistent with the observations. Further, the higher the magnification of the macroimages, the weaker are the microlensing events. In addition, we conclude that a simple Gaussian profile has some difficulties in explaining the asymmetric shape and the small amplitude of the observed high-magnification events if they are typical. Source models in which the emission is produced by a brightt compact core and a more extended halo can occur better explain the observed double peak events. More data are needed to clearly distinguish different galaxy potential models.
    Keywords: ASTROPHYSICS
    Type: The Astrophysical Journal, Part 1 (ISSN 0004-637X); 429; 1; p. 66-76
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