Harry Carothers Wiess

Address given October 23, 1958, before the Master, Associates, and Members of Wiess College, the Rice Institut

A New Determination of e/m from the Zeeman Effect

Values of e/m have been determined from the Zeeman separations of the Cd line 6439 and the Zn line 6362. For these lines the g-factors can be accurately determined from the theory. A magnetic field of 7300 gauss was produced by an air core solenoid in which the variation of field strength over a length of 6 cm at the center was less than 0.1 percent. The field to current ratio, K, of this solenoid was determined in terms of the calculated ratios of three single layer standard solenoids. The field strength during an exposure was then given by the product of this constant and the current flowing. Evaporation of Zn and Cd in the short (6 cm) positive column of a helium discharge tube gave the desired lines. The Zeeman patterns were photographed with a Fabry-Perot interferometer. The result is e/m = 1.7579 ± 0.0025 × 10^7 e.m.u. per gram

Motion of magnetic flux through superconducting strips

Electric resistance of superconducting strips in magnetic fiel

Ferromagnetic resonance force microscopy on a thin permalloy film

Ferromagnetic Resonance Force Microscopy (FMRFM) offers a means of performing local ferromagnetic resonance. We have studied the evolution of the FMRFM force spectra in a continuous 50 nm thick permalloy film as a function of probe-film distance and performed numerical simulations of the intensity of the FMRFM probe-film interaction force, accounting for the presence of the localized strongly nonuniform magnetic field of the FMRFM probe magnet. Excellent agreement between the experimental data and the simulation results provides insight into the mechanism of FMR mode excitation in an FMRFM experiment.Comment: 9 pages, 2 figure

The appearance of "forbidden lines" in spectra

A rough calculation shows that the quadrupole term in the radiation of a forbidden line is usually larger than the dipole produced by an external electric field. This is not true, however, when there is an intermediate state, with which both initial and final states combine, and which lies close to one of them. If the J selection rule is violated, and the Laporte rule is obeyed, the radiation cannot be due to the quadrupole term and must be ascribed to the octopole. Hg 2270 is such a line. An octopole transition will have a Zeeman effect distinctively different from that of a dipole or quadrupole

Connexin-Mediated Signaling in Nonsensory Cells Is Crucial for the Development of Sensory Inner Hair Cells in the Mouse Cochlea

Mutations in the genes encoding for gap junction proteins connexin 26 (Cx26) and connexin 30 (Cx30) have been linked to syndromic and nonsyndromic hearing loss in mice and humans. The release of ATP from connexin hemichannels in cochlear nonsensory cells has been proposed to be the main trigger for action potential activity in immature sensory inner hair cells (IHCs), which is crucial for the refinement of the developing auditory circuitry. Using connexin knock-out mice, we show that IHCs fire spontaneous action potentials even in the absence of ATP-dependent intercellular Ca(2+) signaling in the nonsensory cells. However, this signaling from nonsensory cells was able to increase the intrinsic IHC firing frequency. We also found that connexin expression is key to IHC functional maturation. In Cx26 conditional knock-out mice (Cx26(Sox10-Cre)), the maturation of IHCs, which normally occurs at approximately postnatal day 12, was partially prevented. Although Cx30 has been shown not to be required for hearing in young adult mice, IHCs from Cx30 knock-out mice exhibited a comprehensive brake in their development, such that their basolateral membrane currents and synaptic machinery retain a prehearing phenotype. We propose that IHC functional differentiation into mature sensory receptors is initiated in the prehearing cochlea provided that the expression of either connexin reaches a threshold level. As such, connexins regulate one of the most crucial functional refinements in the mammalian cochlea, the disruption of which contributes to the deafness phenotype observed in mice and DFNB1 patients. SIGNIFICANCE STATEMENT: The correct development and function of the mammalian cochlea relies not only on the sensory hair cells, but also on the surrounding nonsensory cells. Although the nonsensory cells have been largely implicated in the general homeostasis in the mature cochlea, their involvement in the initial functional differentiation of the sensory inner hair cells is less clear. Using mutant mouse models for the most common form of congenital deafness in humans, which are knock-outs for the gap-junction channels connexin 26 and connexin 30 genes, we show that defects in nonsensory cells prevented the functional maturation of inner hair cells. In connexin knock-outs, inner hair cells remained stuck at a prehearing stage of development and, as such, are unable to process sound information

Landau-Zener transitions in a linear chain

We present an exact asymptotic solution for electron transition amplitudes in an infinite linear chain driven by an external homogeneous time-dependent electric field. This solution extends the Landau-Zener theory for the case of infinite number of states in discrete spectrum. In addition to transition amplitudes we calculate an effective diffusion constant.Comment: 3 figure

Numerical study of the spherically-symmetric Gross-Pitaevskii equation in two space dimensions

We present a numerical study of the time-dependent and time-independent Gross-Pitaevskii (GP) equation in two space dimensions, which describes the Bose-Einstein condensate of trapped bosons at ultralow temperature with both attractive and repulsive interatomic interactions. Both time-dependent and time-independent GP equations are used to study the stationary problems. In addition the time-dependent approach is used to study some evolution problems of the condensate. Specifically, we study the evolution problem where the trap energy is suddenly changed in a stable preformed condensate. In this case the system oscillates with increasing amplitude and does not remain limited between two stable configurations. Good convergence is obtained in all cases studied.Comment: 9 latex pages, 7 postscript figures, To appear in Phys. Rev.