The diffusion of quasiparticle excitations in superconducting aluminum films has been observed. The measured diffusion constant $D=22.5\mathrm{}$ ${\mathrm{cm}}^2$ ${\sec }^{-1\mathrm{}}$ is in good agreement with an estimate based on the normal-state resistivity of the films.

We have used tunneling to study the superconductivity of small Sn particles imbedded in an oxide film. In contradiction to existing theories, no lower size limit for superconductivity has been found down to a particle radius $\mathcal{r}=25\mathrm{}$ Å. The junction characteristic shows a large peak in resistance at zero bias even for normal particles. This resistance maximum can be explained in terms of a capacitor model of the particle.

The $\mathrm{XY}$ model of a quantum lattice fluid or a ferromagnet is studied by the method of exact high-temperature series expansion. Nine terms are obtained in the free-energy series and seven in the series for the square of the fluctuation in the long-range order. Analysis of these series yields the critical values $\frac{k{T}_c}{J}=4.84\mathrm{}\pm 0.06$, $\gamma =1.00\mathrm{}\pm 0.07$, and $\alpha =-0.20\mathrm{}\pm 0.20$ for the fcc lattice.

An expression for the transmission coefficient for the general case of an arbitrary number of open channels, valid for all values of the ratio of the average partial width to the average spacing, is obtained from a completely unitary matrix. For the purely elastic-scattering case, the average value and the mean-square deviation of the elastic-scattering cross section are expressed in terms of the potential-scattering phase shift and the ratio of the average width to the average spacing.

A model for cosmic-ray propagation derived by Jokipii is modified to take into account particle mirroring. The diffusion coefficient for particles of known velocity and rigidity is then determined by a limited portion of the field spectrum, instead of being affected by all frequencies above a limiting one.

The non-Newtonian perihelion precession for the asteroid Icarus has been deduced from optical observations and found to agree with the predictions of general relativity to well within the estimated uncertainty of 20%. If observations are made this June when Icarus passes close to the earth, this uncertainty could be reduced to 8%. With such new data a marginally useful bound could also be placed on the quadrupole moment of the sun's gravitational field.

Differential cross-section measurements for the reaction $e^{-}+p\to e^{-}+n+{\pi }^{+}$ in the region of the $N^{*}\mathrm{}\left(1236\right)\mathrm{}$ resonance are compared with the dispersion theories of Adler and Zagury at four-momentum transfers between 1.2 and 15.3 ${\mathrm{F}}^{-2\mathrm{}}$ using the pion form factor as a free parameter. The results suggest a form factor similar to that of the proton.

We report differential cross sections for ${\pi }^{-}p$ elastic scattering near 180° at incident pion momenta of 8 and 16 GeV/c. For $\mathrm{}\left|u\right|<0.5\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$ the formula $\frac{d\sigma }{\mathrm{du}}=A\exp \mathrm{}\left(\mathrm{Bu}\right)\mathrm{}$ fits the data very well. At 8 GeV/c, $A=3.75\mathrm{}\pm 0.35$ μb/${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$ and $B=3.16\mathrm{}\pm 0.24$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{-2\mathrm{}}$. At 16 GeV/c, $A=0.91\mathrm{}\pm 0.13$ μb/${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$ and $B=4.23\mathrm{}\pm 0.40$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{-2\mathrm{}}$. A Reggepole model fit to these data gives for the ${\Delta }_{\delta }$ trajectory $\alpha \mathrm{}\left(u\right)=(-0.06\mathrm{}\pm 0.12)+(0.8\pm 0.3)u$.

A comparison of the reactions $\gamma p\to {\pi }^{+}n$ and ${\pi }^{-}p\to {\rho }^{0}n$ at 4 and 8 GeV/c has been made using the vector-dominance model. Although the ${\rho }^0$ data are insufficient to show the very narrow forward peak observed in the photoproduction data, agreement is obtained to within errors for $\mathrm{}\left|t\right|\mathrm{}\lesssim 0.1$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$. Taking interference effects into account, this agreement can be extended to $\mathrm{}\left|t\right|\mathrm{}\approx 1.5$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$ at 4 GeV/c, but only to 0.3 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$ at 8 GeV/c.

We show that the recent electron-positron colliding-beam experiment at Novosibirsk and $\rho$-photoproduction experiment at Deutsches Elektronen-Synchrotron yield $\rho$ couplings which are consistent with the predictions of simple SU(2)⊗SU(2) effective Lagrangian theories containing an axial-vector meson. This includes the prediction of the virtual $\rho$ mass dependence of ${\gamma }_{\rho \pi \pi }$.

A new current × current weak interaction is constructed from the neutral vector and axial-vector currents which preserves the hypothesis of conserved vector current, universality, lepton conservation, and $\mathrm{CPT}$ invariance, but violates $\mathrm{CP}$ conservation. The complete weak interaction Hamiltonian is shown to be in agreement with present experiments.

The effective single-particle weak parity-nonconserving potential is recalculated including parity-nonconserving one-pion exchange forces and the two-body correlations induced by the hard cores in the nucleon-nucleon potential. The circular polarization of the $\gamma$ ray from the 482-keV transition in ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$ is calculated to be -(0.2±0.1)×${10}^{-4\mathrm{}}$. The measured value is -(0.06±0.01)×${10}^{-4\mathrm{}}$, showing that the observed parity nonconservation in nonleptonic $\Delta S=0\mathrm{}$ transitions is in agreement with the Cabibbo theory of weak interactions.

The consequences of the assumptions that (1) the intermediate boson $W$ has pair strong interactions and (2) $W^{\pm }=a^{\pm }$ particles of Lee (thus leading to $\mathrm{CP}$ nonconservation) are studied and found to lead to a consistent picture.

A simplified tow-state theory is used to predict the total cross section for resonant charge transfer in Li-${\mathrm{Li}}^{+}$ collisions. This cross section exhibits oscillations for collision energies below 10 keV and is in qualitative agreement with preliminary experimental measurements.

A calculation of mode-mode coupling for resistive drift waves, based on the ion and electron fluid equations, shows a stable limit cycle with rather small harmonic distortion. The calculated density modulation, however, is significantly larger than observed in experiments. Cross-field transport in the direction of pump-out appears when ion-ion collisions are introduced.

The form of the multiple-correlation function in the Ornstein-Zernike approximation is investigated. As a result it is suggested that the index $\nu$, which describes the behavior of correlations in the critical region, is not determined by the indices which describe critical thermodynamic behavior. The "scaling law" relations for $\nu$ represent an approximation which is good for the Ising model in sufficiently few dimensions.

The motion of negative ions trapped in quantized vortex lines in rotating helium II has been measured down to 0.8°K by means of a time-of-flight apparatus. Trapped ions always move more slowly than free ions at the same temperature. The contribution of the extra retardation due to the vortex line appears to vary as $\exp (-\frac{\Delta }{\mathrm{kT}})$, where $\frac{\Delta }{k}=1.87\mathrm{}°$K between 0.8 and 1.5°K.

A new criterion is proposed for linearizing many-body equations of motion which is well defined and is related to a stationary principle. The method is applied to the problem of correlation in a narrow $s$ band and the results differ considerably from Hubbard's treatment of this problem.