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Biomedical subjects

R B Laughlin

Publications and source records attributed to R B Laughlin.

12 recordsLinked to original sources
PubMed2005

Multiple bosonic mode coupling in the electron self-energy of (La2-xSrx)CuO4.

High resolution angle-resolved photoemission spectroscopy data along the (0,0)-(pi,pi) nodal direction with significantly improved statistics reveal fine structure in the electron self-energy of the underdoped (La2-xSrx)CuO4 samples in the normal state. Fine structure at energies of (40-46) meV and (58-63) meV, and possible fine structure at energies of (23-29) meV and (75-85) meV, have been identified. These observations indicate that, in (La2-xSrx)CuO4, more than one bosonic modes are involved in the coupling with electrons.

Journal Article↗
PubMed2001

Spinon-holon attraction in the supersymmetric t-J model with 1/r(2) interaction.

We derive the coordinate representation of the one-spinon one-holon wave function for the supersymmetric t-J model with 1/r(2) interaction. This result allows us to show that a spinon and a holon attract each other at short distance. The attraction gets stronger as the size of the system is increased and, in the thermodynamic limit, it is responsible for the square-root singularity in the hole spectral function [Y. Kato, Phys. Rev. Lett. 81, 5402 (1998)].

Journal Article↗
PubMed2001

Quantum interference and ballistic transmission in nanotube electron waveguides.

The electron transport properties of well-contacted individual single-walled carbon nanotubes are investigated in the ballistic regime. Phase coherent transport and electron interference manifest as conductance fluctuations as a function of Fermi energy. Resonance with standing waves in finite-length tubes and localized states due to imperfections are observed for various Fermi energies. Two units of quantum conductance 2G(0) = 4e(2)/h are measured for the first time, corresponding to the maximum conductance limit for ballistic transport in two channels of a nanotube.

Electron Transport↗
PubMed2001

Balanced branching in transcription termination.

The theory of stochastic transcription termination based on free-energy competition [von Hippel, P. H. & Yager, T. D. (1992) Science 255, 809-812 and von Hippel, P. H. & Yager, T. D. (1991) Proc. Natl. Acad. Sci. USA 88, 2307-2311] requires two or more reaction rates to be delicately balanced over a wide range of physical conditions. A large body of work on glasses and large molecules suggests that this balancing should be impossible in such a large system in the absence of a new organizing principle of matter. We review the experimental literature of termination and find no evidence for such a principle, but do find many troubling inconsistencies, most notably, anomalous memory effects. These effects suggest that termination has a deterministic component and may conceivably not be stochastic at all. We find that a key experiment by Wilson and von Hippel [Wilson, K. S. & von Hippel, P. H. (1994) J. Mol. Biol. 244, 36-51] thought to demonstrate stochastic termination was an incorrectly analyzed regulatory effect of Mg(2+) binding.

Bacteriophages↗
PubMed2001

Spinon attraction in spin- 1/2 antiferromagnetic chains.

We derive the representation of the two-spinon wave function for the Haldane-Shastry model in terms of the spinon coordinates. This result allows us to rigorously analyze spinon interaction and its physical effects. We show that spinons attract one another. The attraction gets stronger as the size of the system is increased and, in the thermodynamic limit, determines the power law with which the susceptibility diverges.

Journal Article↗
PubMed2000

The theory of everything.

We discuss recent developments in our understanding of matter, broadly construed, and their implications for contemporary research in fundamental physics.

Journal Article↗
PubMed2000

The middle way.

Mesoscopic organization in soft, hard, and biological matter is examined in the context of our present understanding of the principles responsible for emergent organized behavior (crystallinity, ferromagnetism, superconductivity, etc.) at long wavelengths in very large aggregations of particles. Particular attention is paid to the possibility that as-yet-undiscovered organizing principles might be at work at the mesoscopic scale, intermediate between atomic and macroscopic dimensions, and the implications of their discovery for biology and the physical sciences. The search for the existence and universality of such rules, the proof or disproof of organizing principles appropriate to the mesoscopic domain, is called the middle way.

Macromolecular Substances↗
PubMed1999

Differential light scattering: probing the sonoluminescence collapse.

We have developed a light scattering technique based on differential measurement and polarization (differential light scattering, DLS) capable in principle of retrieving timing information with picosecond resolution without the need for fast electronics. DLS was applied to sonoluminescence, duplicating known results (sharp turnaround, self-similar collapse); the resolution was limited by intensity noise to about 0.5 ns. Preliminary evidence indicates a smooth turnaround on a less than approximately 0.5-ns time scale, and suggests the existence of subnanosecond features within a few nanoseconds of the turnaround.

Journal Article↗
PubMed1989

A study of steady state and kinetic regulation of chloride ion and osmotic pressure in hemolymph of oysters, Crassostrea virginica, exposed to tri-n-butyltin.

Two sets of experiments were made to determine if bis(tri-n-butyl)tin oxide (TBT) [IUPAC: hexabutyldistannoxane] influenced osmotic pressure or chloride ion concentration in hemolymph of adult American oysters, Crassostrea virginica. In the first set, oysters were acclimated to 5, 25 or 40%;, then exposed to bis(tri-n-butyl)tin oxide dissolved in seawater (0.5, 1.0 or 2.0 micrograms/L) for 11 days. Measurements of the total osmotic pressure and chloride ion concentration in hemolymph indicated that mean values of neither was significantly affected under steady state conditions. Oysters exposed to TBT exhibited a higher variation around the mean value for both total osmotic pressure and chloride ion concentration. There was significant mortality of oysters exposed to TBT in 25 and 40, but not in 5%. In a second experiment, adult oysters were acclimated to 25%, and simultaneously exposed to the TBT concentrations listed above for 10 days. Then, subgroups of oysters were abruptly moved to 5 or 40% and the time-course of adjustment of hemolymph osmotic pressure and chloride ion concentration was measured. During the first 25 hr, there was little adjustment to 5% in controls or TBT exposed oysters; apparently, they remained closed most or all of the time. In marked contrast, hemolymph of oysters moved to higher salinities rapidly readjusted. Exposure to TBT had a delaying effect on the schedule of the increase in hemolymph osmotic pressure and chloride ion concentration. Results of these experiments show that TBT has an indirect effect on osmotic pressure and chloride ion concentration adjustment in oysters; it does not appear to act strongly as an anionophore to influence anion transfer across epithelia.

Animals↗