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  • ASTROPHYSICS  (9)
  • Polymer and Materials Science  (2)
  • egg load  (2)
  • Astrophysics
  • 1990-1994  (13)
  • 1994  (13)
Collection
Keywords
Publisher
Years
  • 1990-1994  (13)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Host-searching behavior ofVenturia canescens (Grav.) (Hymenoptera: Ichneumonidae): Superparasitism (1994)
    Springer
    Journal of insect behavior 7 (1994), S. 455-464 
    Details
    ISSN: 1572-8889
    Keywords: superparasitism ; egg load ; host-parasitoid system ; foraging ; Venturia canescens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The foraging behavior ofVenturia canescens, a solitary endoparasitoid of lepidopteran larvae, was investigated in the laboratory. FemaleVenturia canescens with a larger number of mature eggs to lay were found to have higher levels of superparasitism (measured as numbers of eggs laid per parasitized host). Increased parasitoid density was found to result in reduced levels of superparasitism by host-deprived (i.e.,undepleted) wasps. Females which had been allowed access to hosts before the experiment (depleted wasps) laid fewer eggs per parasitized host than undepleted wasps, although there was no significant difference in the levels of superparasitism among the depletion periods of 1, 2, 5, and 7 h. It was also found that an egg which was encountered less than 15 min after oviposition was much less likely to be avoided than one which was encountered after more than 15 min had elapsed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02025443
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  • 2
    Electronic Resource
    Electronic Resource
    Host-searching behavior ofVenturia canescens (Grav.) (Hymenoptera: Ichneumonidae): Interference—the effect of mature egg load and prior behavior (1994)
    Springer
    Journal of insect behavior 7 (1994), S. 433-454 
    Details
    ISSN: 1572-8889
    Keywords: egg load ; host-parasitoid systems ; motivation ; mutual interference ; agonistic encounters ; Venturia canescens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The foraging behavior ofVenturia canescens, a solitary endoparasitoid of lepidopteran larvae, was investigated in the laboratory. Females with a greater number of mature eggs in their ovarioles and oviducts parasitized a greater number of hosts and won a greater proportion of encounters with other searching females. Wasps which had been exposed to hosts prior to an experimental trial lost a higher proportion ofagonistic encounters with conspecifics than wasps which had no prior exposure to hosts. The behavior of a wasp at the time of the encounter influenced the outcome of the encounter. Wasps involved in active search of the host medium with the ovipositor (“probing”) were more likely to win encounters than wasps in any other behavioral category. In a situation where the agonistic encounter was between two probing wasps, both contestants were equally likely to win. Results are discussed in the light of the idea that mutual interference arises, in this species, as a result of agonistic encounters between searching females and recent dynamic-programming models which suggest that parasitoid oviposition should be influenced by mature egg load.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02025442
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  • 3
    Electronic Resource
    Electronic Resource
    PBI powder processing to performance parts (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 53 (1994), S. 485-496 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new route (“direct forming”) was developed for forming dense PBI shapes from PBI powder. The new process affords the possibility of automated PBI powder shaping (“cold compaction”) and densification in batches of multiple parts by a “powder-assisted hot isostatic pressing” process. Direct forming is a more productive alternative to hot compression molding. Two developments enable PBI direct forming: (1) the discovery that PBI powders that are porous and plasticized with moisture can be shaped by compaction at ambient temperatures (cold-compacted), and (2) a finding that cold-compacted shapes can be densified in large batches by a powder-assisted hot isostatic pressing. The porous PBI powder is formed from PBI in solution by a spray-precipitation process. When plasticized with moisture, this powder is cold-compactible to PBI shapes with densities up to 94% of that of ultimate density of PBI. These shapes, which have sufficient strength to be handled, are then further consolidated via powder-assisted hot isostatic pressing to shapes with excellent thermal and mechanical properties and densities of about 99% of the ultimate. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070530503
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  • 4
    Electronic Resource
    Electronic Resource
    Torsional properties of healed canine diaphyseal defects grafted with a fibrillar collagen and hydroxyapatite/tricalcium phosphate composite (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 277-283 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The need for alternatives to autogenous bone grafts is widely recognized. This study compared the torsional strength of canine femora 1 year after grafting with one of three forms of a collagen/hydroxyapatite/tricalcium phosphate bone grafting material (COLLAGRAFT15), autogenous bone, or no graft. The groups were compared to each other and to the unoperated contralateral femora. Results of torsional testing were evaluated for torsional strength, torsional displacement, total energy to fracture and White fracture mode. Data analysis showed lower torsional strength of the operated vs. unoperated femora with the exception of morsellized COLLAGRAFT15 material, which had higher strength. However, the only difference in the operated groups was that the morsellized COLLAGRAFT15 had greater strength than several groups including the autogenous bone group. There was no difference found in angular displacement between any of the groups. However, there was a difference in the energy to fracture in both strip forms of the COLLAGRAFT15. The final conclusion is that in this model, grafting with COLLAGRAFT15 provided torsional properties at one year postoperatively at least equivalent to autogenous bone. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050402
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  • 5
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    X-ray spectroscopy of SNR E0102-72 with the ASCA satellite (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The Advanced Satellite for Cosmology and Astrophysics (ASCA) satellite has obtained a moderate-resolution energy spectrum of E0102-72, the brightest Supernova Remnant (SNR) in the Small Magellanic Cloud (SMC). This paper reports on the first results of the analysis of the high quality spectrum of E0102-72. The spectrum shows resolved emission lines of He-like K alpha, H-like K alpha and K beta from oxygen, neon, and magnesium. The intensity ratios of these lines cannot be explained by a multi-component plasma model with uniform abundances, but requires abundance inhomogeneity in the plasma. We demonstrate how the spectral capabilities of the ASCA SIS make available new diagnostics of X-ray plasmas in a state of non-equilibrium ionization. Some interpretation based on the spectral analysis is also given.
    Keywords: ASTROPHYSICS
    Type: PASJ: Publications of the Astronomical Society of Japan (ISSN 0004-6264); 46; 3; p. L121-L124
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  • 6
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    A measurement of the Hubble constant from the X-ray properties and the Sunyaev-Zel'dovich effect of Abell 2218 (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The distance of the cluster of galaxies Abell 2218, and hence the value of the Hubble constant, has been measured by comparing the X-ray properties and the Sunyaev-Zel'dovich effect of the cluster. The result for the Hubble constant is H(sub zero) = 65 +/- 25 km/s/MPC, where the error includes the random and systematic errors, combined in quadrature, and the largest contributions to the overall error come from systematic errors in the Sunyaev-Zel'dovich effect data and in the X-ray spectrum of the cluster. The X-ray and Sunyaev-Zel'dovich effect data are consistent with the same model for the intergalactic medium in Abell 2218 (an isothermal Beta-model with Beta is about 0.65 and cluster core radius about 1.0 min). A prevous report of a smaller Hubble constant, found by applying the same method on the same cluster, is shown to be based on a model for the cluster gas that is inconsistent with the Einstein IPC data. The present result for the Hubble constant is consistent with the value found earlier for the cluster Abell 665: by combining the results of the method for both clusters we conclude that the value of the Hubble constant is H(sub zero) = 55 +/- 17 km/s/MPC.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 420; 1; p. 33-43
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  • 7
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    Discovery of Be/x-ray stars in two supernova remnants in the Small Magellanic Cloud (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We present ROSAT high resolution x-ray images of two previously cataloged supernova remnants in the Small Magellanic Cloud (SMC): 0101-72.4 and 0104-72.3. These remnants were known to show optical, x-ray, and radio emission based on earlier observations: the present data show the first evidence for arcsecond-scale x-ray structure. There is no diffuse x-ray emission associated with the optically emitting shell in 0101-72.4; we set a 3 sigma upper limit of 7 x 10(exp 34) erg s(exp -1) on the 0.02-2 keV luminosity from the region. The x-ray emission comes instead from a weak pointlike object near the limb of the remnant. Optical observations of this source reveal a m(sub v) = 14.8 blue star with H alpha and H beta in emission; we identify this as a Be star in the SMC. No evidence for variability down to time scales of about 1 s was found in the ROSAT data; however, a comparison of the ROSAT and Einstein fluxes indicates possible long term variability by a factor of approximately 2 over several years. The other SNR, 0104-72.3, also contains a pointlike x-ray source with a blue optical counterpart (m(sub v) = 16.7) and H alpha emission. We tentatively identify this as a Be star as well. In addition to the point source there is weak diffuse x-ray emission from 0104-72.3 (L(sub x) approximately 1.4 x 10(exp 35) erg s(exp -1)), but the remnant's appearance in the x-ray band is considerably different from that in either the radio or optical band. We argue for a physical association between the supernova remnants (SNRs) and Be/x-ray stars. A large space velocity (greater than or approximately 100 km s(exp -1)) for the Be/x-ray binaries is required if the explosions that produced the remnants also formed the neutron stars in the binaries. Alternatively, the associations could be the result of common membership in OB associations in the SMC.
    Keywords: ASTROPHYSICS
    Type: The Astronomical Journal (ISSN 0004-6256); 107; 4; p. 1363-1370
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  • 8
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    Nonpolytropic model for the Coma Cluster (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: In this article we demonstrate, for the first time, how a physically motivated static model for both the gas and galaxies in the Coma Cluster of galaxies can jointly fit all available X-ray and optical imaging and spectroscopic data. The principal assumption of this nonpolytropic model (Cavaliere & Fusco-Femiano 1981, hereafter CFF), is that the intracluster gas temperature is proportional to the square of the galaxy velocity dispersion everywhere throughout the cluster; no other assumption about the gas temperature distribution is required. After demonstrating that the CFF nonpolytropic model is an adequate representation of the gas and galaxy distributions, the radial velocity dispersion profile, and the gas temperature distribution, we derive the following information about the Coma Cluster: 1. The central temperature is about 9 keV and the central density is 2.8 x 10(exp -3)/cm(exp 3) for the X-ray emitting plasma; 2. The binding mass of the cluster is approximately 2 x 10(exp 15) solar mass within 5 Mpc for (H(sub 0) = 50 km/sec/Mpc), with a mass-to-light ratio of approximately 160 solar mass/solar luminosity; 3. The contribution of the gas to the total virial mass increases with distance from the cluster center, and we estimate that this ratio is no greater than approximately 50% within 5 Mpc. The ability of the CFF nonpolytropic model to describe the current X-ray and optical data for the Coma Cluster suggests that a significant fraction of the thermal energy contained in the hot gas in this as well as other rich galaxy clusters may have come from the interaction between the galaxies and the ambient cluster medium. interaction between the galaxies and the ambient cluster medium.
    Keywords: ASTROPHYSICS
    Type: The Astrophysical Journal (ISSN 0004-637X); 429; 2 pt; p. 545-553
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  • 9
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    A radio/optical reference frame. 5: Additional source positions in the mid-latitude southern hemisphere (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We report new accurate radio position measurements for 30 sources, preliminary positions for two sources, improved radio postions for nine additional sources which had limited previous observations, and optical positions and optical-radio differences for six of the radio sources. The Very Long Baseline Interferometry (VLBI) observations are part of the continuing effort to establish a global radio reference frame of about 400 compact, flat spectrum sources, which are evenly distributed across the sky. The observations were made using Mark III data format in four separate sessions in 1988-89 with radio telescopes at Tidbinbilla, Australia, Kauai, USA, and Kashima, Japan. We observed a total of 54 sources, including ten calibrators and three which were undetected. The 32 new source positions bring the total number in the radio reference frame catalog to 319 (172 northern and 147 southern) and fill in the zone -25 deg greater than delta greater than -45 deg which, prior to this list, had the lowest source density. The VLBI positions have an average formal precision of less than 1 mas, although unknown radio structure effects of about 1-2 mas may be present. The six new optical postion measurements are part of the program to obtain positions of the optical counterparts of the radio reference frame source and to map accurately the optical on to the radio reference frames. The optical measurements were obtained from United States Naval Observatory (USNO) Black Birch astrograph plates and source plates from the AAT, and Kitt Peak National Observatory (KPNO) 4 m, and the European Southern Observatory (ESO) Schmidt. The optical positions have an average precision of 0.07 sec, mostly due to the zero point error when adjusted to the FK5 optical frame using the IRS catalog. To date we have measured optical positions for 46 sources.
    Keywords: ASTROPHYSICS
    Type: The Astronomical Journal (ISSN 0004-6256); 107; 1; p. 379-384
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  • 10
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    Elemental abundances of the supernova remnant G292.0+1.8: Evidence for a massive progenitor (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We present a comprehensive nonequilibrium ionization (NEI) analysis of X-ray spectral data from the Einstein Observatory and EXOSAT for the supernova remnant G292.0+1.8. The spectra are well described by a single-temperature, single-timescale NEI model with kT = 1.64(sub -0.19)(sup +0.29) keV and n(sub e)t = (5.55(sub -1.12)(sup +1.2) x 10(exp 10)s/cu cm, which establishes that this remnant is indeed young and in the ionizing phase of evolution of its X-ray spectrum. We determine the abundances of the elements O, Ne, Mg, Si, S, Ar, and Fe and examine their variation over the allowed range of column density, kT, and n(sub e)t. Numerical calculations of the nucleosynthesis expected for a 25 solar mass progenitor agree best with the fitted abundances; in fact the minimum rms percent difference between this model and the derived abundances is only 15%. From the fitted emission measure and a simple geometric model of the remnant we estimate the mass of X-ray-emitting plasma to be 9.3(sub -6.2)(sup +1.19) solar mass, for an assumed distance of 4.8 +/- 1.6 kpc. Additional errors on this mass estimate, from clumping of the ejecta, for example, may be substantial. No evidence was found for a difference in the thermodynamic state of the plasma as a function of elemental composition based on analysis of the individual ionization timescales of the various species. In this sense then, G292.0+1.8 resembles the remnant Cas A (another product of a massive star supernova), while it is different from the remnants of SN 1572 (Tycho) and SN 1006, both of which are believed to be from Type Ia supernovae.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 422; 1; p. 126-135
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