Simultaneous recordings of the spontaneous mechanical input fluctuations and the electrical output fluctuations in hair cells that serve as biological microphones show that the Brownian motion of the mechanoceptive organelle, the hair bundle, is often strongly correlated with the fluctuations of the transmembrane voltage. This correlation stems from transduction of the spontaneous input noise and shows that these cells can almost reach the sensitivity limit imposed by the thermal noise at their input.

The chaotic dynamics from a nonlinear electronic circuit is shown to exhibit the universal topological structure of maps on an annulus. This suggests that the corresponding universality class is large enough to include physical systems. We suggest that low-dimensional strange attractors fall into a few classes, each characterized by distinct universal topological features.

A Monte Carlo study is carried out for the three-state Potts model in three dimensions. The correlation length is shown to remain finite and to be discontinuous at the transition point. It is also shown that the transition exhibits genuine first-order characteristics in all aspects.

Neutrinos from the decay of ${}_{}{}^8{}_{}{}^{}\mathrm{B}$ in the Sun have been observed in the Kamiokande-II detector. Based on 450 days of data in the time period January 1987 through May 1988; the measured flux obtained from data with $E_e$≥9.3 MeV is 0.46±0.13(stat)±0.08(sys) of the value predicted by the standard solar model. Within experimental errors, the Kamiokande-II value is in agreement with the corresponding value obtained in the ${}_{}{}^{37}{}_{}{}^{}\mathrm{Cl}$ radiochemical detector in essentially the same time period.

Wormhole physics from the quantum thoery of gravity coupled to the second-rank antisymmetric tensor or Goldstone-boson fields leads to an effective potential for these fields. The cosmological energy-density bound is shown to put an upper bound on the cosmological constant which wormhole physics can make zero. This upper bound, of order ${10}^{11}$ GeV, is far smaller than the Planck scale and barely compatible with the possible cosmological constant arising from grand unified theories. In addition, the effect of wormholes on the axion for the strong CP problem is discussed.

We show how to treat boundary divergences in heterotic string theory covariantly and unambiguously. The method applies even to theories with nonvanishing tadpoles; in this case the Fischler-Susskind mechanism sufficies to ensure well defined answers. Also n-point functions are well defined with no special string-tension renormalizations. As an example we find the loop corrections to the linearized background equations of motion for the O(16)×O(16) string needed to give unambiguous, finite scattering amplitudes. No splitting or projection of supermoduli space is needed.

A search for the rare decay mode $K_L$→${\pi }^0$γγ was performed using a data set from Fermilab experiment E-731. The decay is of interest in the context of chiral perturbation theory and for its contribution to the decay $K_L$→${\pi }^0$$e^{+}$$e^{\mathrm{-}}$. The result is B($K_L$→${\pi }^0$γγ)<2.7 ×${10}^{\mathrm{-}6}$ (90% confidence level) which is nearly a two-order-of magnitude improvement over the previous best limit.

The Landau theory of shape transitions in hot rotating nuclei is applied to even-even rare-earth nuclei from cerium to hafnium. The parameters of the Landau expansion are extracted from microscopic calculations based on the Nilsson-Strutinsky procedure, and are shown to follow simple systematics. In particular, the systematics of the critical temperature and the critical angular momentum of the shape transitions as functions of neutron and proton number are investigated. Simple rules are provided for the behavior of these quantities.

We report observation of a significant enhancement in the intensity of target and projectile autoionizing electrons produced in low-energy (2–15 keV) ${\mathrm{He}}^{+}$+He collisions. The target electron intensity is strongly peaked at 0° and confined to an angular range of ≊5° about the incident beam direction, while the projectile electron intensity shows a similar enhancement at 180°. We attribute this effect to Coulomb focusing, a new aspect of post-collision interaction which results from the deflection of the ejected electrons in the Coulomb field of the receding spectator ion.

A new probe for superfluid vortex line density with a response time of 400 μs and a spatial resolution of 1 mm was developed and used to investigate the growth and decay of superfluid vortex lines during the passage of a heat pulse. The evolution process turns out to be in accordance with existing theories.

Self-diffusion of water contained in a porous glass is observed to be strongly enhanced if the pore space is only partially filled. This can be explained by a novel mechanism involving indirect molecular exchange between the liquid and the vapor phase. A theoretical model fits the pulsed-field-gradient NMR diffusion measurements with no adjustable parameters. NMR relaxation measurements were performed to provide a characterization of the homogeneity of the samples.

We study, by means of computer simulation and scaling analysis, the time evolution of one-dimensional arrays of reactive lamellae described by various initial striation thickness distributions. An infinitely fast reaction A+B→2P occurs at the junctures of the lamellae. As the reaction proceeds thin striations are eaten by thick neighboring striations altering the distribution. The system converges toward a universal striation thickness distribution.

We suggest a new variational approach for quantum spin chains, based on the stochastic behavior of the quantization axes, which describes a chain in terms of a classical and a quantum contribution to the free energy. For an easy-plane ferromagnetic chain with the external field in the plane it reveals that the nonlinear excitations are predominantly described by the classical degrees of freedom. Hence it offers a fundamental basis for the description of the elementary excitations of such systems in terms of classical solitons and quantum spin waves, as suggested by various experiments.

Time-of-flight scattering and recoiling spectrometry with detection of both neutrals and ions for structure determinations is presented and applied to the clean W(211)-p(1×1) and W(211)-p(1×2)-O structures. Experimental data are presented in the form of scattering and recoiling intensities versus beam incident angle and scattering and recoiling structural contour maps. The clean surface is relaxed both laterally and vertically from the bulk truncated structure. Oxygen atoms occupy threefold trough sites where they are bound to two first-layer and one second-layer W atoms.

Static and dynamic simulations of ${\mathrm{KNbO}}_3$ with interacting polarizable ions support a model to describe the phase transitions: The niobium ions avoid their average positions in the cubic and tetragonal phases, hopping through virtual orthorhombic-phase sites between virtual rhombohedral-phase sites. This description reveals why the orthorhombic-to-rhombohedral transition fits well into the displacive model of phase transitions, while the two higher-temperature transitions exhibit both displacive and order-disorder character.

We use ab initio density functional calculations to determine the structural and electronic properties of deuterium in bulk palladium. The focus of our study is the binding and the nearest-neighbor distance between D atoms in the very concentrated limit of a hypothetical ${\mathrm{PdD}}_2$ crystal. These results are compared to analogous calculations for bulk PdD and Pd. We find that even at very high D concentrations in the bulk, the equilibrium distance between two D atoms is increased by ≊0.2 Å from the gas value of 0.74 Å. This large internuclear distance makes a cold-fusion reaction of deuterium very improbable.

Narrow-bandwidth radio-frequency pulses are used to label the ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ nuclear magnetic dipoles of CO adsorbed in specific sites at specific oreintations on Rh particles and the evolution of the labeled system is monitored by NMR spectroscopy. The results indicate surface diffusion on multifaceted particles with an activation energy of 7±1 kcal/mole Heterosite exchange is detected by selective labeling of linearly bonded CO, exclusive of nearest-neighbor bridge-bonded CO.

The frequency dependences of both proton NMR $T_1$ and ESR linewidth in polyaniline give evidence for quasi-1D spin diffusion. The on-chain diffusion rate, ${\mathit{D}}_{\mathrm{\parallel }}$, is independent on the protonation level, while the transverse diffusion, $D_{\perp }$, exhibits a sudden drop at the percolation threshold. This behavior confirms the conducting-island picture, but it is concluded that a given conducting island just consists of a single conducting chain. The room-temperature data show a strong correlation between spin dynamics and transport properties, and suggest that conductivity is governed by interchain hoppings.

The electronic properties of hydrogen in carbon-doped n-type silicon have been studied using deep-level transient spectroscopy. The results show for the first time that hydrogen in the presence of carbon forms a deep and charge-state-dependent center located ∼0.16 eV below the edge of the conduction band. This trap center is a deep donor which is only stable in the positively charged state and anneals after capture of electrons for temperatures T≥300 K.

We present the first observation of infrared light emission from a semiconductor superlattice in a resonant-tunneling experiment. Radiation from the three lowest intersubband transitions is observed, proving resonant tunneling an effective means of populating high-lying states of the superlattice. The relative strength of the emission lines enables us to estimate the electron temperature below the optical-phonon energy to reach about 140 K, whereas transitions originating above the optical-phonon energy are strongly quenched.