Academic Research as a Career

The real student in science — with a consuming curiosity into the laws of nature and with top scholastic status — may be of the caliber required to become the recognized authority in some fiel

Science on View

Book review of "Envisioning Science: The Design and Craft of the Science Image," by Felice Frankel, MIT Press, 2002

A new role for science - II

We are entering a period of change in the very styles of science

Molecular Architecture and Biological Reactions

Answers to many basic problems of biology—nature of growth, mechanism of duplication of viruses and genes , action of enzymes, mechanism, of physiological activity of drugs, hormones, and vitamins, structure and action of nerve and brain tissue—may lie in knowledge of molecular structure and intermolecular reactions

Centralizers in endomorphism rings

We prove that the centralizer Cen(f) in Hom_R(M,M) of a nilpotent endomorphism f of a finitely generated semisimple left R-module M (over an arbitrary ring R) is the homomorphic image of the opposite of a certain Z(R)-subalgebra of the full m x m matrix algebra M_m(R[z]), where m is the dimension (composition length) of ker(f). If R is a local ring, then we provide an explicit description of the above Cen(f). If in addition Z(R) is a field and R/J(R) is finite dimensional over Z(R), then we give a formula for the Z(R)-dimension of Cen(f). If R is a local ring, f is as above and g is an arbitrary element of Hom_R(M,M), then we give a complete description of the containment Cen(f) in Cen(g) in terms of an appropriate R-generating set of M. Using our results about nilpotent endomorphisms, for an arbitrary (not necessarily nilpotent) linear map f in Hom_K(V,V) of a finite dimensional vector space V over a field K we determine the PI-degree of Cen(f) and give other information about the polynomial identities of Cen(f)

Priestley Medal Address: Chemistry and the World of Tomorrow

This article is based on the Priestley Medal Address presented by Linus C. Pauling on April 9, during the ACS spring meeting in St. Louis. Still active at 83, Pauling is director of the Linus Pauling Institute of Science & Medicine, Palo Alto, Calif., where he continues his scientific research. Much of his work has dealt with the nature of the chemical bond. The Priestley Medal, ACS's highest award, recognizes his contributions in this and other areas, and is the latest in a long list of honors and awards Pauling has received, including the 1954 Nobel Prize in Chemistry and the 1962 Nobel Peace Prize

Unsolved Problems of Structural Chemistry

Linus Pauling, Theodore William Richards Medalist for 1947, has made notable contributions to quantum mechanics, valence theory, crystal structure, and also to electron diffraction

The X-Ray Photoionized Wind in Cen X-3/V779 Cen

We analyze the ASCA spectrum of the Cen X-3 X-ray binary system in eclipse using atomic models appropriate to recombination-dominated level population kinetics in an overionized plasma. In order to estimate the wind characteristics, we first fit the eclipse spectrum to a single-zone photoionized plasma model. We then fit spectra from a range of orbital phases using global models of photoionized winds from the companion star and the accretion disk that account for the continuous distribution of density and ionization state. We find that the spectrum can be reproduced by a density distribution of the form derived by Castor, Abbot, & Klein (1975) for radiation-driven winds with with the value of the mass-loss rate divided by the terminal velocity consistent with values for isolated stars of the same stellar type. This is surprising because the neutron star is very luminous (~10^38 erg/s) and the X-rays from the neutron star should ionize the wind and destroy the ions that provide the opacity for the radiation-driven wind. Using the same functional form for the density profile, we also fit the spectrum to a spherically symmetric wind centered on the neutron star, a configuration chosen to represent a disk wind. We argue that the relatively modest orbital variation of the discrete spectrum rules out a disk wind hypothesis.Comment: ApJ accepte

Asteroseismology and calibration of alpha Cen binary system

Using the oscillation frequencies of alpha Cen A recently discovered by Bouchy & Carrier, the available astrometric, photometric and spectroscopic data, we tried to improve the calibration of the visual binary system alpha Cen. With the revisited masses of Pourbaix et al. (2002) we do not succeed to obtain a solution satisfying all the seismic observational constraints. Relaxing the constraints on the masses, we have found an age t_alpha Cen=4850+-500 Myr, an initial helium mass fraction Y_i = 0.300+-0.008, and an initial metallicity (Z/X)_i=0.0459+-0.0019, with M_A=1.100+-0.006M_o and M_B=0.907+-0.006M_o for alpha Cen A&B.Comment: accepted for publication as a letter in A&

A new role for science - I

Science and technology are in desperate need of change, just because they have been extraordinarily successful