My first five years in science.

Linus Pauling, a giant of modern chemistry, died on 19 August (see page 584 of last week's issue). What follows is an account, in his own words, of his first years as a research scientist.

Analysis of a hyperdeformed band of 152(66)Dy86 on the basis of a structure with two revolving clusters, each with a previously unrecognized two-tiered structure.

Analysis on the basis of the two-revolving-cluster model has been made of a cascade of 11 gamma-rays constituting a hyperdeformed band of 152(66)Dy86 (or possibly 153Dy) reported by Galindo-Uribarri et al. [Galindo-Uribarri, A., et al. (1993) Phys. Rev. Lett. 73, 231-234], leading to the conclusions that the band extends from values K approximately 82-104 for the angular-momentum quantum number, that the moment of inertia is approximately 5650 Da.fm2, that the composition of the central sphere is p40n50 and that of each of the clusters is p13n18, that each of the clusters consists of two tiers of spherons, and that the radii of revolution of the inner and outer tiers have values of about 8.00 and 11.20 fm, respectively.

Analysis of the ground-state band and a closely related intercalated band of 235(92)U143 by the two-revolving-cluster model with consideration of symmetric and antisymmetric resonance of the two dissimilar clusters.

The reported ground-state band of 235(92)U143 extending from J = 7/2- to 51/2- is found to be two intercalated bands, one beginning with 7/2- and the other with 9/2-, each with DeltaJ = 2. Analysis by the two-resonating-cluster model leads to 3875 Da.fm2 for the moment of inertia for the first few levels, then increasing by centrifugal stretching. This value is interpreted by the structure p70n112 for the central sphere with clusters p11n16 and p11n15 with radius of revolution R = 8.55 fm. The major principal axis of the Poinsot ellipsoid is taken to be determined by an unquantized number K, with vector intermediate in orientation between L and J. The values of K are found by empirical analysis to equal L + 0.28, with the theory of rotation of the ellipsoid giving L + 0.28 for 7/2-, slowly decreasing to L + 0.251 for 51/2-. The 7/2- band is based on odd values of L (negative parity) and the 9/2- band on even values (positive parity). Negative parity for both bands is achieved by symmetric resonance of the two dissimilar clusters in the 7/2- band and antisymmetric resonance in the 9/2- band.

Puzzling questions about excited superdeformed rotational bands of atomic nuclei are answered by the two-revolving-cluster model.

The two-revolving-cluster model provides explanations of several questions about excited superdeformed bands: restriction to the lanthanons and the Hg-Tl-Pb region and to the smaller values of the neutron number for each element, truncation of the gamma-ray cascades, differences in shape of the lanthanon and Hg-Tl-Pb bands, alignment of quantified spins, and the existence of pairs of bands with nearly identical gamma-ray sequences. A previously unrecognized kind of pairing (intercalation of gamma-ray values) is also reported and a discussion is given of the values of electric quadrupole moments.

Molecular structure of Ti8C12 and related complexes.

Application of valence-bond theory leads to the assignment to the molecule Ti8C12 of a cubic structure, point group Ohm3m, with 8 Ti at the cube corners, +/-(x x x, x, x x [symbol, see text]) where x = 1.78 A, and with 12 C in pairs in the cube faces, +/-(0 y z, [symbol, see text], 0, y z [symbol, see text]) where y = 1.78 A and z = 0.71 A. The Ti-C and C-C bonds have bond number 4/3, corresponding to resonance of single and double bonds in 2:1 ratio.

Analysis of gamma-ray energies for 56 excited superdeformed rotational bands of nuclei of lanthanons La to Dy and of Hg, Tl, and Pb on the basis of the two-revolving-cluster model, with evaluation of moments of inertia and radii of revolution and assignment of nucleonic compositions to the clusters and the central sphere.

Analysis of the gamma-ray energies of 28 excited superdeformed bands of lanthanon nuclei by application of the two-revolving-cluster model yields the result that the central sphere for all 28 has the semimagic-magic composition p40n50, with the range p8n12 to p14n18 for the clusters and the radius of revolution increasing from 7.31 to 7.76 fm. Similar analysis of 28 excited bands of Hg, Tl, and Pb nuclei leads to p56n82 (semimagic-magic) for the central sphere of 24 bands, p64n82 (semimagic-magic) for 2, and p64n90 (doubly semimagic) for 2, with cluster range p8n12 to p14n16 and values of the radius of revolution from 8.70 to 8.92 fm for 26 bands and 9.2 fm for 2.

Effect of ascorbic acid on incidence of spontaneous mammary tumors and UV-light-induced skin tumors in mice.

Two large-scale studies of the effect of different amounts of L-ascorbic acid in the food on tumor-free survival have been conducted. One involved the incidence of spontaneous mammary tumors in RIII mice, with seven ascorbic acid and three control groups, 50 mice per group. With increasing ascorbic acid in the diet, there was a highly significant delay before appearance of the first tumor. Median age at first tumor was 82.5 wk in ad libitum controls, 124.9 wk in the highest-dose ascorbate group. The proportion of mice with tumors was also reduced. The other study involved dermal neoplasms in mice irradiated with ultraviolet light. A pronounced effect of vitamin C in decreasing the incidence and delaying the onset of malignant lesions was observed with high statistical significance. By 20 wk approximately five times as many mice had developed serious lesions in the zero-ascorbate as in the high-ascorbate group.

Analysis of the energy of the first four excited states of the ground-state rotational bands of the even-even nuclei from 6C8 to 56Ba90 with the model of a single cluster of nucleons revolving about a sphere.

The results of the analysis of the first four energy levels of the ground-state rotational bands of even-even nuclei from 6C8 to 56Ba90 on the basis of the revolving-cluster model are reported. Values of the nucleon number of the revolving cluster are assigned on the basis in part of the shell model and in part of the expectation that the corresponding values of the radius of revolution would change only slightly from one energy level to an adjacent level or from one nucleus to an adjacent nucleus. The values of the radius of revolution are found to change gradually from about 5 to 6 fm for the lighter nuclei to 7 to 8 fm for the heavier nuclei in the sequence studied.

The structure of K3C60 and the mechanism of superconductivity.

Analysis of the interatomic distances in the superconducting substance K3C60 indicates that each of the K atoms in tetrahedral interstices between C60 spheres accepts three electrons from C60, thus becoming quadricovalent; its four bonds resonate among the 24 adjacent carbon atoms to give a strong framework in which the negative charges are localized on these K atoms. The electric current is carried by the motion of positive charges (holes) through the network of C60 spheres and the K atoms in octahedral holes. Superconductivity is favored by the localization of the negative charges on the tetrahedral K atoms and their noninvolvement in valence-bond resonance, decreasing the rate of mutual extinction of electrons and holes.

Analysis of pulsed-neutron powder diffraction patterns of the icosahedral quasicrystals Pd3Siu and AlCuLiMg (three alloys) as twinned cubic crystals with large units.

The low-Q peaks on three pulsed-neutron powder patterns (total, U differential, and Pd differential) of the icosahedral quasicrystal Pd3SiU have been indexed on the basis of an assumed cubic structure of the crystals that by icosahedral twinning form the quasicrystal. The primitive unit cube is found to have edge length 56.20 A and to contain approximately 12,100 atoms. Similar analyses of pulsed-neutron patterns of Al55Cu10Li35, Al55Cu10Li30Mg5, and Al510Cu125Li235Mg130 give values of the cube edge length 58.3, 58.5, and 58.4 A, respectively, with approximately 11,650 atoms in the unit cube. It is suggested that the unit contains eight complexes in the beta-W positions, plus some small interstitial groups of atoms, with each complex consisting of a centered icosahedron of 13 clusters, each of 116 atoms with the icosahedral structure found in the body-centered cubic crystal Mg32(Al,Zn)49.

Analysis of the energy of the first four excited states of the ground- state rotational bands of the even-even lanthanon nuclei (58Ce to 70Yb) with the model of a single cluster of nucleons revolving about a sphere.

Analysis of the first four excited energy levels of the ground-state rotational bands of 82 nuclei (isotopes of the seven even-even lanthanons from 58Ce to 70Yb) has provided values of the radius of revolution of a single cluster about a sphere in each nucleus. The number of nucleons m in each cluster is taken to be 2 for neutron number N = 82 in each case for the first excited state, usually increasing by 2 with change in Z or N by +/-2, but sometimes changing by 0 or by 4 or more. The radius of revolution R decreases to a minimum (about 6.7 fm) at N approximately 78, rises sharply at N approximately 86, reaches a maximum (about 7.8 fm) at N approximately 96, and then decreases.

Transition from one revolving cluster to two revolving clusters in the ground-state rotational bands of nuclei in the lanthanon region.

Whereas 234(92)U142 and other actinon nuclei have ground-state bands that indicate that each nucleus consists of a sphere and a single revolving cluster with constant composition and with only a steady increase in the moment of inertia with increase in J, the angular-momentum quantum number, many of the lanthanon ground-state bands show discontinuities, usually with an initial slightly or strongly curved segment followed by one or two nearly straight segments. The transition to nearly straight segments is interpreted as a change in structure from one revolving cluster to two revolving clusters. The proton-neutron compositions of the clusters and the central sphere are assigned, leading to values of the radius of revolution. The approximation of the two-cluster sequences to linearity is attributed to the very small values of the quadrupole polarizability of the central sphere. Values of the nucleon numbers of clusters and spheres, of the radius of revolution, and of promotion energy are discussed.

Immunological evidence for the accumulation of lipoprotein(a) in the atherosclerotic lesion of the hypoascorbemic guinea pig.

Lipoprotein(a) [Lp(a)] is an extremely atherogenic lipoprotein. Lp(a) has been found in the plasma of humans and other primates, but until now only in a few other species. The mechanism by which it exerts its atherogenicity is still poorly understood. We observed that Lp(a) has been found in the plasma of several species unable to synthesize ascorbate and not in other species. We have now detected apoprotein(a) in the plasma of the guinea pig. We induced atherosclerosis in this animal by dietary ascorbate depletion and, using SDS/PAGE and subsequent immunoblotting, we identified Lp(a) as accumulating in the atherosclerotic plaque. Most importantly, adequate amounts of ascorbate (40 mg per kg of body weight per day) prevent the development of atherosclerotic lesions in this animal model and the accumulation of Lp(a) in the arterial wall. We suggest an analogous mechanism in humans because of the similarity between guinea pigs and humans with respect to both the lack of endogenous ascorbate production and the role of Lp(a) in human atherosclerosis.

Evidence from electron micrographs that icosahedral quasicrystals are icosahedral twins of cubic crystals.

An analysis of electron micrographs of Al5Mn quasicrystals obtained by rapidly cooling a molten alloy with composition Al17Mn and removing the Al matrix by electrosolution, revealing aggregates of 20 microcrystals at the corners of a pentagonal dodecahedron, supports the proposal that these microcrystals are cubic crystals twinned about an icosahedral seed, with each cubic microcrystal sharing a threefold axis and three symmetry planes with the seed.

Suppression of human immunodeficiency virus replication by ascorbate in chronically and acutely infected cells.

We have studied the action of ascorbate (vitamin C) on human immunodeficiency virus type 1 (HIV-1), the etiological agent clinically associated with AIDS. We report the suppression of virus production and cell fusion in HIV-infected T-lymphocytic cell lines grown in the presence of nontoxic concentrations of ascorbate. In chronically infected cells expressing HIV at peak levels, ascorbate reduced the levels of extracellular reverse transcriptase (RT) activity (by greater than 99%) and of p24 antigen (by 90%) in the culture supernatant. Under similar conditions, no detectable inhibitory effects on cell viability, host metabolic activity, and protein synthesis were observed. In freshly infected CD4+ cells, ascorbate inhibited the formation of giant-cell syncytia (by approximately 93%). Exposure of cell-free virus to ascorbate at 37 degrees C for 1 day had no effect on its RT activity or syncytium-forming ability. Prolonged exposure of virus (37 degrees C for 4 days) in the presence of ascorbate (100-150 micrograms/ml) resulted in the drop by a factor of 3-14 in RT activity as compared to a reduction by a factor of 25-172 in extracellular RT released from chronically infected cells. These results indicate that ascorbate mediates an anti-HIV effect by diminishing viral protein production in infected cells and RT stability in extracellular virions.