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  • 1
    Electronic Resource
    Electronic Resource
    High-voltage electron diffraction measurement of the Debye temperatures of Cr, α-Fe and their disordered alloys (1975)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 31 (1975), S. 174-177 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The critical-voltage effect of high-voltage electron diffraction has been used to measure the X-ray Debye temperatures of Cr, α-Fe and their disordered alloys. The 220 critical voltages were measured at room and elevated temperatures for the pure metals and at room temperature for five intermediate compositions. The data for the pure metals were sufficient to determine both the Debye temperature and the deviation from the free-atom value of the atomic scattering factor at the first-order reflection position. The results agree with those of other workers. The scattering factor deviations were assumed to be the same in the alloys as in the pure metals, and this made it possible to determine the alloy Debye temperatures from a single room-temperature measurement of the critical voltage at each intermediate composition. The Debye temperatures are analyzed successfully in terms of a simple one-parameter theory, and are correlated with the alloy melting-point data through Lindemann's formula.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739475000344
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  • 2
    Electronic Resource
    Electronic Resource
    Bloch wave notation in many-beam electron diffraction theory (1971)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 27 (1971), S. 42-45 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: There are a number of different Bloch wave labelling systems currently in use in the theory of the diffraction of electrons by crystals. It is suggested that the Bloch wave labelling scheme for electron diffraction which is the simplest and the most logical is an ordered labelling scheme in which the top branch of the dispersion surface corresponds to wave 1, the second branch to wave 2, the third branch to wave 3, and so on. Such a scheme would be consistent with accepted notations in other forms of Bloch wave propagation. The essential mathematical unity of all forms of wave propagation in crystals is discussed, and the use of the proposed notation in describing the critical voltage effect is briefly considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739471000081
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  • 3
    Electronic Resource
    Electronic Resource
    Structure factors and Debye temperatures of Al–Li solid-solution alloys (1987)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 43 (1987), S. 260-265 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: By combining the accurate low-angle X-ray structure factors of A1-Li solid-solution alloys (containing 5.25 and 8.06 at.% Li) determined by the critical voltage technique in high-energy electron diffraction (HEED) with higher-angle values obtained by interpolation between best pure-element form factors, a complete set of accurate X-ray structure factors for these alloys has been produced. From the measured Debye-Wailer factors for the alloys it was found to be difficult to determine a Debye temperature trend with composition for AI-Li solid-solution alloys because of the extent of the experimental errors, although the results suggest that the Debye temperatures of the alloys are higher than that of pure aluminium. This is obviously consistent with an increase in Young's modulus; i.e. the stiffness of the alloys appears to be greater than that of pure aluminium. This increase appears to arise predominantly from an increase in the force constant between nearest-neighbour (n.n.) lithium atoms in the alloy as compared with the value for pure lithium. This occurs because n.n. lithium atoms are closer together in Al-Li solid-solution alloys than they are in pure lithium. Because the lithium atoms are closer together in the alloys, the electron charge density, ρ, associated with the valence electrons in the alloys is likely to be higher than if ρ is considered unchanged by alloying. This suggested increase in the charge density of the alloy valence electrons was confirmed, as the experimental 111 low-angle structure factors of the alloys were found to be significantly higher than the equivalent values obtained by interpolation between the best pure-element form factors. Such electronic changes are to be expected for Al-Li alloys as aluminium and lithium have a valency difference of two.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S010876738709946X
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  • 4
    Electronic Resource
    Electronic Resource
    An accurate reappraisal of the elemental form factors and charge density of copper (1990)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 46 (1990), S. 165-170 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The best X-ray atomic scattering factors for copper have been examined carefully to see which are most appropriate for charge density studies. The most consistent values were then used to generate a deformation charge density map, and it would appear that bonding in copper arises from electron charge build up between nearest-neighbour (n.n.) atoms, next-n.n. atoms etc. This is in agreement with conclusions obtained from γ-ray diffraction experiments and the best band-structure calculations, but in marked disagreement with the charge density obtained from earlier band-structure form factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767389011141
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  • 5
    Electronic Resource
    Electronic Resource
    Observations on the behaviours of three European cuckoo bumble bee species (Psithyrus) (1988)
    Springer
    Insectes sociaux 35 (1988), S. 341-354 
    Details
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Resume Nous avons introduit des femelles de trois espèces européennes (P. bohemicus, P. vestalis etP. compestris) dans des colonies de laboratoire de leur hôteBombus (B. lucorum, B. terrestris etB. pascuorum) pouvant fourrager librement. Pour chaque espèce de bourdon, nous avons étudié le développement d'une colonie, où des parasites avaient été introduits avec succès. Les femellesPsithyrus ont cohabité avec les reines et les ouvrières hôtes, mais ont monopolisé le développement du couvain à travers l'oophagie, l'expulsion des larves, et les tentatives de dominer les bourdons hôtes. Une partie du couvainPsithyrus a été détruite aussi, et les bourdons hôtes des trois colonies ont réussi à élever du couvain de reproducteurs. Les contacts sociaux prolongés entre les femallesPsithyrus et leurs hôtes, ainsi que la possibilité de reproduction de l'hôte au sein des colonies parasitées semblent indiquer que des complexités coévolutives dans les rapportsBombus-Psithyrus ne sont pas rares.
    Notes: Summary Females of three European species of cuckoo bumble bees (P. bohemicus, P. vestalis, andP. campestris) were introduced into free-foraging laboratory colonies of theirBombus hosts (B. locorum, B. Terrestris andB. pascuorum, respectively). The colony development of one successfully parasitized colony of each bumble bee species was studied.Psithyrus females cohabited with host queens and workers, but monopolized brood development through oophagy, larval ejection and the attempted dominance of host bees. SomePsithyrus brood also was destroyed, and host bees in all three colonies were successful in rearing reproductive offspring. Prolonged social contact betweenPsithyrus females and their hosts, and the possibility of host reproduction in parasitized colonies, suggest that there is considerable opportunity for coevolutionary complexity inBombus-Psithyrus relationships.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02225810
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  • 6
    Electronic Resource
    Electronic Resource
    Host recognition and the study of a chemical basis for attraction by cuckoo bumble bees (Hymenoptera: Apidae) (1993)
    Springer
    Journal of chemical ecology 19 (1993), S. 771-786 
    Details
    ISSN: 1573-1561
    Keywords: Host recognition ; volatiles ; social parasitism ; cuckoo bumble bees ; Bombus terrestris ; Bombus terricola ; Psithyrus vestalis ; Psithyrus ashtoni ; Hymenoptera ; Apidae ; Dufour's gland ; tergal gland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Species ofPsithyrus (Hymenoptera; Apidae) are obligate bumble bee social parasites. In this study, females ofP. vestalis andP. ashtoni were presented with pentane extracts prepared from different body parts of queens of their respective host species,Bombus terrestris andB. terricola. Parasites of both species were capable of distinguishing host bees from other bumble bee species using chemical cues contained within extracts. Among extracts of several body parts presented to parasites, the abdomen produced the greatest behavioral response, with Dufour's gland and terminal tergal segments eliciting the greatest response among abdominal regions. Extracts of these two body parts obtained fromB. terrestris queens shared a number of compounds, identified by GC-MS. Among the identified compounds are a number that have been reported to be of importance in bee sociochemistry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00985008
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  • 7
    Electronic Resource
    Electronic Resource
    Electrical conductivity of lunar surface rocks and chondritic meteorites (1971)
    Springer
    Earth, moon and planets 2 (1971), S. 408-422 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The electrical conductivities of several samples from returned Apollo 11 and 12 lunar rocks and from chondritic meteorites were measured from 300 to 1100K. Collectively the lunar samples represent all three of the major NASA classifications of lunar surface rocks. Of general interest is the observation that the conductivities of the lunar samples are much larger than the values which have previously been used in theoretical discussions of lunar phenomena. It is also found that the conductivity at 300K,σ (300), is extremely sensitive to the thermal history of the sample for both lunar and meteoritic material. Magnetic measurements are presented to help characterize the changes which occur upon heating.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00562878
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  • 8
    Electronic Resource
    Electronic Resource
    Lunar rock magnetism (1972)
    Springer
    Earth, moon and planets 4 (1972), S. 160-186 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The relationship between the magnetization and temperature in a high constant magnetic field for a temperature range between 5 K and 1100 K was examined for Apollo 11, 12 and 14 lunar materials. The average value of Curie point temperature is (768.2 ± 3.5)°C for the lunar igneous rocks and (762.5 ± 3.4)°C for the lunar fines and breccias. A tentative conclusion about the ferromagnetic substance in the lunar materials would be that Fe is absolutely dominant with a slight association of Ni and Co, and probably Si also, in the lunar native irons. The antiferromagnetic phase of ilmenite and the paramagnetic phase of pyroxenes are considerably abundant in all lunar materials. However, a discrepancy of observed magnetization from a simulated value based on known magnetic elements for the temperature range between 10 and 40 K suggests that pyroxene phase represented by (M x Fe1-x ) SiO3 (whereM = Ca2+, Mg2+, etc and 0 ≤x ≤1/4) also may behave antiferromagnetically. Magnetic hysteresis curves are obtained at 5 K and 300 K, and the viscous magnetic properties also are examined for a number of lunar materials. The superparamagnetically viscous magnetization has been experimentally proven as due to fine grains of metallic iron less than 200 Å in mean diameter. The viscous magnetization is dominant in the lunar fines and breccias which is classified into Type II, while it is much smaller than the stable magnetic component in lunar igneous rocks (Type I). The superparamagnetically fine particles of metallic iron are mostly blocked at 5 K in temperature; thus coercive force (H c ) and saturation remanent magnetization (I R ) become much large at 5 K as compared with the corresponding values at 300 K. Strongly impact-metamorphosed parts of lunar breccias have an extremely stable NRM which could be attributed to TRM. NRM of the lunar igneous rocks and majority of breccias (or clastic rocks) are intermediately stable, but their stability is considerably higher than that of IRM of the same intensity. This result may imply that some mechanism which causes an appreciable magnitude of NRM and the higher stability, such as the shock effect, may take place on the lunar surface in addition to TRM mechanism for special cases. A particular igneous rock (Sample 14053) is found to have an unusually strong magnetism owing to a high content of metallic iron (about 1 weight percent), and its NRM amounts to 2 × 10−3 emu/g. The abundance of such highly magnetic rocks is not known as yet but it seems that the observed magnetic anomalies on the lunar surface could be related to such highly magnetized rock masses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00562924
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  • 9
    Electronic Resource
    Electronic Resource
    D.C. electrical conductivity of lunar surface rocks (1972)
    Springer
    Earth, moon and planets 4 (1972), S. 187-189 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00562925
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  • 10
    Electronic Resource
    Electronic Resource
    Some characteristic magnetic properties of lunar materials (1974)
    Springer
    Earth, moon and planets 9 (1974), S. 63-77 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract One of the typical magnetic characteristics of lunar materials is the composition of their ferromagnetic constituent. Lunar breccias often contain kamacite (less than 7 weight per cent of Ni content) as well as almost pure metallic iron. Metallic ferromagnetics in most igneous rocks are almost pure iron, but the kamacite phase also has been found in some Apollo 15 igneous rocks. It seems likely therefore the metallic ferromagnetics in the lunar crust are more or less similar to those in chondrites. Another typical magnetic characteristic of lunar materials is the presence of a considerable amount of superparamagnetically fine particles of metallic iron. A higher relative content of such fine iron particles results in a higher value of the ratio of magnetic susceptibility (χo) to saturation magnetization (I s), a smaller ratio of the coercive force (H c) to remanence coercive force (H RC), and an extremely higher ratio of the viscous component (ΔI v) to the stable one (I s) of the remanent magnetization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00565393
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