In Memoriam D. Stanley Tarbell (1913–1999), Chemist and Historian of Chemistry

Dr. Dean Stanley Tarbell, Distinguished Professor Emeritus of chemistry at Vanderbilt University, where he served on the faculty from 1967 to 1981, died on May 26, 1999 in Bolingbrook, Ill. Earlier he taught for many years and chaired the chemistry department at the University of Rochester. In retirement, he and his wife, Ann Tracy Tarbell, researched and wrote articles and books on the history of chemistry in the U.S. For his writings he received the American Chemical Societys Dexter Award for Distinguished Contributions to the History of Chemistry in 1989. He was an avid reader and book collector, a linguist who taught himself Arabic, Russian, and classical Greek, and a lifelong baseball fan.     

Structure of the first parallel DNA quadruplex-drug complex

The first crystal structure of a drug (daunomycin) bound to a parallel-stranded intermolecular telomeric G4 quadruplex (d(TGGGGT)4) has been determined to high resolution. A planar assemblage of three daunomycin molecules stacks onto the 5' end of the G4 column, with the daunosamine substituents occupying three of the four quadruplex grooves. The surface area of the terminal G-quartet in this parallel DNA quadruplex, presently occupied by three daunomycins, is sufficiently large that it could easily accommodate other potential telomerase inhibitors such as substituted porphyrins or telomestatin.     

Synthesis of 2,3,4,5-tetranitropyrrole

Dealkylation of 1-tert-butyl-2,3,4-trinitropyrrole in boiling trifluroacetic acid gave 2,3,4-trinitropyrrole, the structure of which was confirmed by X-ray crystallography. Treatment of this trinitropyrrole with nitric acid/oleum briefly at 60° gave 2,3,4,5-tetranitropyrrole.     

Development of combinatorial chemistry methods for coatings: high-throughput adhesion evaluation and scale-up of combinatorial leads

Coupling of combinatorial chemistry methods with high-throughput (HT) performance testing and measurements of resulting properties has provided a powerful set of tools for the 10-fold accelerated discovery of new high-performance coating materials for automotive applications. Our approach replaces labor-intensive steps with automated systems for evaluation of adhesion of 8 x 6 arrays of coating elements that are discretely deposited on a single 9 x 12 cm plastic substrate. Performance of coatings is evaluated with respect to their resistance to adhesion loss, because this parameter is one of the primary considerations in end-use automotive applications. Our HT adhesion evaluation provides previously unavailable capabilities of high speed and reproducibility of testing by using a robotic automation, an expanded range of types of tested coatings by using the coating tagging strategy, and an improved quantitation by using high signal-to-noise automatic imaging. Upon testing, the coatings undergo changes that are impossible to quantitatively predict using existing knowledge. Using our HT methodology, we have developed several coatings leads. These HT screening results for the best coating compositions have been validated on the traditional scales of coating formulation and adhesion loss testing. These validation results have confirmed the superb performance of combinatorially developed coatings over conventional coatings on the traditional scale.     

Electron-capture negative ionization calibrants for magnetic sector mass spectrometers

Fomblin [poly(perfluoropropylene oxide)], PFK (perfluorokerosene) and FC-43 (perfluorotributylamine) are investigated as mass calibrants in electron-capture negative ionization mass spectrometry on a magnetic sector hybrod mass spectrometer. This work provides exact negative ion mass tables of these three calibrants obtained using high-resolution peak matching of representative ions of the calibrants against ions of known mass. The suitability of these calibrants for full data system control in the negative ionization mode is demonstrated for the techniques of high-resolution scanning, selected ion recording and calibration of the quadrupole sector of a hybrid instrument.     

Criticality and phase transitions in ionic fluids

Recent experimental investigations of criticality and phase separation in ionic fluids have revealed behavior of great theoretical interest. In seeking to understand the experiments, some of which appear to exhibit argonlike criticality and some of which exhibit classical (mean-field) criticality, a convenient starting point is the restricted primitive model (RPM) of symmetrically charged hard spheres, all of equal diameter , each sphere bearing a positive or negative charge of magnitudeq. There is overall charge neutrality, so that the expected number densities of the anions and cations are equal, ₊= _-. Studies of RPM charge-charge and density-density correlation functions indicate that the fluctuation-suppressing mechanism that yields mean-field critical behavior in nonionic systems with long-range interparticle potentials is not operative in the RPM. On the basis of plausible assumptions, Ising-like behavior is instead expected. The above work is summarized. New work of Zhang and the author is outlined, showing that when one loses the RPM symmetry (through, e.g., different valence, diameter, or dipole moment of anions and cations) a strong coupling between charge-charge and density-density correlation ensues. The way in which this can be expected to give rise to mean-field or mean-field-like behavior is noted. Other new observations concern the mean-field analogy found by Høye and the author between the parameter 2/(d–2) (d is the dimensionality) in that model and the monomer number in high polymers, with respect to the coexistence-curve shape dependence on those parameters.     

Relativistic quarks bound with a one-body tensor potential

A dipole fit to electromagnetic form factors is used to determine a quark density in the nucleon. A radial tensor potential is used to bind the quarks into states of goodJ, J _z, and parity. The tensor potential radial component is taken to satisfy the equationT = T ₀, whereT ₀ is a parameter of the model. This linear divergence equation can be simultaneously solved with the Dirac equation for the bound quark wave functions. A self-consistent solution is possible where the mass density used as the source for the binding potential is the same as that determined from the solution for the quark wave functions.     

Chaos in thermal pulse combustion

An experimental thermal pulse combustor and a differential equation model of this device are shown to exhibit chaotic behavior under certain conditions. Chaos arises in the model by means of a progression of period-doubling bifurcations that occur when operating parameters such as combustor wall temperature or air/fuel flow are adjusted to push the system toward flameout. Bifurcation sequences have not yet been reproduced experimentally, but similarities are demonstrated between the dynamic features of pressure fluctuations in the model and experiment. Correlation dimension, Kolmogorov entropy, and projections of reconstructed attractors using chaotic time series analysis are demonstrated to be useful in classifying dynamical behavior of the experimental combustor and for comparison of test data to the model results. Ways to improve the model are suggested. (c) 1995 American Institute of Physics.     

Parameter choice by discrepancy principles for ill-posed problems leading to optimal convergence rates

Schock (Ref. 1) considered a general a posteriori parameter choice strategy for the Tikhonov regularization of the ill-posed operator equationTx=y which provides nearly the optimal rate of convergence if the minimal-norm least-squares solution belongs to the range of the operator (T ^* T) ^v , o<v1. Recently, Nair (Ref. 2) improved the result of Schock and also provided the optimal rate ifv=1. In this note, we further improve the result and show in particular that the optimal rate can be achieved for 1/2v1.The final version of this work was written while M. T. Nair was a Visiting Fellow at the Centre for Mathematics and Its Applications, Australian National University, Canberra, Australia. The work of S. George was supported by a Senior Research Fellowship from CSIR, India.     

Lehmer pairs of zeros,the de Bruijn-Newman constant Λ, and the Riemann Hypothesis

We give here a rigorous formulation for a pair of consecutive simple positive zeros of the functionH ₀ (which is closely related to the Riemann -function) to be a Lehmer pair of zeros ofH ₀. With this formulation, we establish that each such pair of zeros gives a lower bound for the de Bruijn-Newman constant (where the Riemann Hypothesis is equivalent to the assertion that 0). We also numerically obtain the following new lower bound for :