This paper concentrates on the possible segregation of indium and gallium and competitive segregation of gallium and indium at atomically flat parallel {111}-oriented Cu-MnO interfaces. The segregation of gallium at Cu-MnO interfaces after introduction of gallium in the copper matrix of internally oxidized Cu-1 at.% Mn could be hardly detected with energy-dispersive spectrometry in a field emission gun transmission electron microscope. After a heat treatment to dissolve indium in the copper matrix, gallium has a weak (...) tendency to segregate, that is 2.5 at.% Ga per monolayer at the interface compared with 2 at.% in the copper matrix. The striking result is that this gallium segregation is observable because it does not occur at the metal side of the interface but in the first two monolayers at the oxide side. Using the same heat treatment as for introducing indium in the sample, but without indium present, gallium segregates strongly at the oxide side of the Cu-MnO interface with a concentration of about 14.3 at.% in each monolayer of the two. In contrast, the presence of gallium has no influence on the segregation of indium towards Cu-MnO interfaces, because the outermost monolayer at the metal side of the interface contains 17.6 at.% In, that is similar to previously found results. This leads to the intriguing conclusions, firstly, that, in contrast with antimony and indium, gallium segregates at the oxide side of the interface and, secondly, that the presence of indium strongly hampers gallium segregation. The results from analytical transmission electron microscopy on gallium segregation are supported by high-resolution transmission electron microscopy observations. (shrink)

The philosophical significance of Dmitri Mendeleev’s successful predictions of the properties of gallium and scandium vis a vis the acceptance of the Periodic Table 1874–1886 has been debated recently. This author presents evidence that De Boisbaudran and Cleve both respectively predicted the possible existence of gallium and scandium, but on the basis of the old TRIAD methodology. This suggests that these successful Mendeleev predictions were therefore not independent corroboration of the concept of the Periodic System. Instead the significantly (...) independent predictive successes for Mendeleev’s system were the determination of the atomic weight of the known element uranium as 240 instead of the previously accepted 120 in 1874 and the isolation of germanium by Winkler in 1886. (shrink)

The debate about the relative epistemic weights carried in favour of a theory by predictions of new phenomena as opposed to accommodations of already known phenomena has a long history. We readdress the issue through a detailed re-examination of a particular historical case that has often been discussed in connection with it—that of Mendeleev and the prediction by his periodic law of the three ‘new’ elements, gallium, scandium and germanium. We find little support for the standard story that these (...) predictive successes were outstandingly important in the success of Mendeleev's scheme. Accommodations played an equal role—notably that of argon, the first of the ‘noble gases’ to be discovered; and the methodological situation in this chemical example turns out to be in interesting ways different from that in other cases—invariably from physics—that have been discussed in this connection. The historical episode when accurately analysed provides support for a different account of the relative weight of prediction and accommodation—one that is further articulated here. (shrink)

The debate about the relative epistemic weights carried in favour of a theory by predictions of new phenomena as opposed to accommodations of already known phenomena has a long history. We readdress the issue through a detailed re-examination of a particular historical case that has often been discussed in connection with it-that of Mendeleev and the prediction by his periodic law of the three 'new' elements, gallium, scandium and germanium. We find little support for the standard story that these (...) predictive successes were outstandingly important in the success of Mendeleev's scheme. Accommodations played an equal role-notably that of argon, the first of the 'noble gases' to be discovered; and the methodological situation in this chemical example turns out to be in interesting ways different from that in other cases-invariably from physics-that have been discussed in this connection. The historical episode when accurately analysed provides support for a different account of the relative weight of prediction and accommodation-one that is further articulated here. (shrink)

The article begins with a response to a recent contribution by Jensen, in which he has criticized several aspects of the use of triads of elements, including Döbereiner’s original introduction of the concept and the modern use of atomic number triads by some authors including myself. Such triads are groups of three elements, one of which has approximately the average atomic weight of the other two elements, as well as having intermediate chemical reactivity. I also examine Jensen’s attempted reconstruction Mendeleev’s (...) use of triads in predicting the atomic weights of three hitherto unknown elements, that were subsequently named gallium, germanium and scandium. The present article then considers the use of atomic number triads, in conjunction with the phenomenon of first member anomaly, in order to offer support for Janet’s left-step periodic table, in which helium is relocated into group 2 of the table. Such a table features triads in which the 2nd and third elements of each group, without fail, fall into periods of equal length, a feature that is absent in the conventional 18-column or the conventional 32-column table. The dual sense of the term element, which is the source of much discussion in the philosophy of chemistry, is alluded to in further support of such a relocation of helium that may at first appear to contradict chemical intuition. (shrink)

We take another look at “Just-So” solar neutrino oscillations, characterizing them by the energy Eπ/2 at which the distance-varying angle is π/2, instead of by the usual Δm 2 . The rising spectrum recently observed by SuperKamiokande is consistent with an Eπ/2 ∼6–9 MeV and marginally with 48 MeV. The pp neutrinos must then be reduced to one-half the standard solar model prediction, and 7Be neutrinos must make up a significant part of the SAGE and GALLEX gallium signal. For (...) Eπ/2 close to 9 and 48 MeV, the 7Be neutrinos will also show a large seasonal variation, emphasizing the importance of direct measurements of the 7Be neutrinos. (shrink)

Though there has been an array of methods to evaluate the extent of sarcoidosis, it is generally difficult to detect central nervous system involvement. Recently it has become accepted that 18F-FDG PET is more sensitive than gallium scintigraphy in finding sarcoid lesions, however its usefulness and limitations for detecting sarcoidosis in the central nervous system, especially in the spinal cord, has rarely been investigated. Two patients with pathologically confirmed sarcoidosis manifested spinal symptoms. We conducted 18F-FDG PET along with conventional (...) imagings before and after treatment. Abnormal FDG uptakes which could not be detected by gallium scintigraphy were shown in the spinal cords in both patients. These abnormal uptakes were diminished in accordance with clinical improvement after treatment. Our findings suggest that 18F-FDG PET is effective in detecting and tracking the activity of spinal sarcoidosis. (shrink)

* Solar Neutrinos are Up - My column about recent results in neutrino physics Analog - September-1992 ] (no neutrino counts at SAGE and negative mass-squared data suggesting that the e-neutrino may be a tachyon) prompted more reader response than any other column in recent memory . Two months after I wrote it, a new result from GALLEX, the European gallium neutrino-detection experiment housed in the Grand Sasso underground laboratory in Italy, was announced. GALLEX uses the same technique as (...) the SAGE neutrino experiment described in my September column: many million dollars worth of elemental gallium (element 31) is purified and placed in underground tanks where solar neutrinos transmute stable gallium 71 to radioactive germanium 71 (half life 11.4 days). A chemical process separates the new radioactive germanium atoms from the bulk gallium and transports them to a sensitive detector where their decays are counted. (shrink)

This article traces the life of Russian chemist Dmitri Mendeleev from childhood in Siberia, through education and training to become the first formulator of the Periodic Table, the logo of chemistry. His unique contribution is described and analysed; what factors helped him be the first formulator? What did he do after making his most famous discovery? In addition the article peeps into his personal life, his dealings with his family and the authorities. Finally we look at honours he received in (...) later life. (shrink)