New Triterpenes from the Bark of Western White Pine (Pinus monticola DOUGL.)

Eleven new triterpenes with the lanostene-type skeleton were isolated from the benzene extract of western white pine bark. Their structures were determined mainly on the basis of physical and spectral data.     

Experimental demonstration of a technique to generate arbitrary quantum superposition states of a harmonically bound spin-1/2 particle

Using a single, harmonically trapped 9Be(+) ion, we experimentally demonstrate a technique for generation of arbitrary states of a two-level particle confined by a harmonic potential. Rather than engineering a single Hamiltonian that evolves the system to a desired final state, we implement a technique that applies a sequence of simple operations to synthesize the state.     

Einstein Meets Hilbert: At the Crossroads of Physics and Mathematics

One of the most famous episodes in the early history of general relativity involves the "race" in November 1915 between Albert Einstein and David Hilbert to uncover the "correct" form for the ten gravitational field equations. In light of recent archival findings, however, this story now has become a topic of renewed interest and controversy among historians of physics and mathematics. Drawing on recent studies and newly found sources, the present essay takes up this familiar tale from a new perspective, one that has seldom received due attention in the standard literature, namely, the mathematical issues at the heart of Einstein's theory. Told from this angle, the leading actors are Einstein's collaborator Marcel Grossmann, his critic Tullio Levi-Civita, his competitor David Hilbert, and several other mathematicians, many of them connected with Hilbert's Göttingen colleagues such as Hermann Weyl, Felix Klein, and Emmy Noether. As Einstein was the first to admit, Göttingen was far more important than Berlin as an active center for research in general relativity. Any account which, like this one, tries to understand both the actions and motives of the leading players must confront the problem of interpreting the rather sparse documentary evidence available. The interpretation offered herein, whatever its merits, aims first and foremost to show how mathematical issues deeply permeated the early history of general relativity.     

Measurement of excitation functions in the reactions 197Au(11C, xn)208-xAt using a radioactive 11C beam

A light-element radioactive ion-beam capability has been developed at the LBNL 88-Inch Cyclotron. The system is based on the coupled-cyclotrons method and utilizes short-lived species, e.g., 11C, 14O, 13N produced by (p,n) and (p,alpha) reactions at the LBNL Biomedical Isotope Facility Cyclotron. In a first experiment, 197Au(11C,xn)208-xAt excitation functions have been measured for energies ranging from the Coulomb barrier up to 110 MeV using a beam of 11C with intensities up to (1-2)x10(8) ions/sec on target. The results of this experiment are compared to measurements of 197Au(12C, xn)209-xAt excitation functions.     

Synthesis of aminomethyl and amino analogs of 5-benzylacyclouridine and 5-benzyloxybenzylacyclouridine

Amino analogs of BAU (5-benzylacyclouridine) and BBAU (5-benzyloxybenzylacyclouridine) and their 2′-hydroxymethyl derivatives were synthesized for evaluation as inhibitors of uridine phosphorylase and hence potential cancer chemotherapeutic agents. Both aminomethyl analogs were found to be potent inhibitors of this enzyme and good potentiators of the anti-tumor action of FUdR.     

Modelling the initial motion of large cylindrical and spherical bubbles

A two-dimensional, transient, finite difference technique based on a volume fraction specification of the free surface position and accounting for the effects of surface tension is shown to accurately predict the initial motion of large cylindrical and spherical bubbles. The predictions compare very favourably with the experimental data of Walters and Davidson. The initial acceleration of cylindrical and spherical bubbles is properly predicted as g and 2g respectively. The penetration of a tongue of liquid from below is the dominant process by which large deformations from the original shape take place and is well predicted by the model in both cases. For the spherical case the eventual transition into a toroidal bubble is demonstrated and the circulation associated with a rising toroidal bubble as a function of its volume upon release is shown to agree very well with experiments. Iterative linear equation-solving techniques applicable to the special nature of the linear system resulting from such a free surface specification are surveyed and a simple Jacobi iteration based on red-black ordering is found to perform well. The impact of the free surface on the relaxation of the linear system and the convergence criteria is also explored.     

Synthesis of 5-benzyl and 5-benzyloxybenzyl-3′-azido-2′,3′-dideoxyuridine and their analogues as potential anti-AIDS agents

5-Benzyl and 5-benzyloxybenzyl-substituted 3′-azido-2′,3′-dideoxyuridine, ( 8a and 8b ), 3′-halogeno-2′,3′-dideoxyuridine, 9a, 9b, 10a, 10b, 11a and 11b , and 2′,3′-dideoxyuridine, 12a and 12b , of Scheme I were synthesized as potential anti AIDS agents. Synthesis of epimers of 8a and 8b , 5-benzyl- and 5-benzyloxybenzyl-1-(3′-azido-2′,3′-dideoxy-β-D-threo-pentafuranosyl)uracil, 15a and 15b , and 5-benzyl- and 5-benzyloxy-5′-azido-2′,5′-dideoxyuridine, 16a and 16b , shown in Scheme II, were also reported.