High-temperature series expansions of the spin-spin correlation functions of the planerotator and classical Heisenberg models have been obtained to order ${\left(\frac{J}{\mathrm{kT}}\right)}^{10}$ on the triangular lattice. An analysis of the moment series provides good evidence for a phase transition.

Results are reported for angular distributions of the reaction ${\mathrm{Zr}}^{90}({\mathrm{He}}^3, t){\mathrm{Nb}}^{90}$ at 21 MeV. It is found that for targets in the $f_{\frac{7}{2}}$ shell this reaction favors specific final states in which a neutron is replaced by a proton in the same shell-model orbit, coupled to any allowed angular momentum. The angular distributions differ in a systematic way depending on the spin of the final state. The nine states of the $T_{<}$ ${\left(g_{\frac{9}{2}}\right)}^2$ multiplet are tentatively identified. A multipole decomposition leads to coefficients very similar to those of the ${\left(f_{\frac{7}{2}}\right)}^2$ multiplet, showing an enhanced quadrupole coefficient.

The total $n-p$ cross section has been measured using the neutron time-of-flight spectrometer at the Karlsruhe isochronous cyclotron. The measurements span the energy range from 0.7 to 32 MeV with statistical accuracy which varies from 0.2 to 1.0% and an energy resolution of 0.7 keV at 0.7 MeV and 200 keV at 30 MeV. No evidence was found for the recently reported oscillations in the total $n-p$ scattering cross section.

A three-fluid hydrodynamical model for nuclei is proposed and it is shown that the observed rise in proton density near the surface of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ can be accounted for in this model.

Fradkin's "compressibility under deformation" parameter $\xi$ is calculated using the deformed Nilsson model of the nucleus. Numerical values in the range $-0.21\mathrm{}<~\xi <~+0.26\mathrm{}$ are obtained for ${}_{62}{}^{}{}_{}{}^{}\mathrm{Sm}$, ${}_{64}{}^{}{}_{}{}^{}\mathrm{Gd}$, ${}_{70}{}^{}{}_{}{}^{}\mathrm{Yb}$, and ${}_{92}{}^{}{}_{}{}^{}\mathrm{U}$ and for $-0.1\mathrm{}<~{\beta }_{\omega }<~+0.3\mathrm{}$, to be compared with the empirical value $\xi \sim -0.2\mathrm{}\pm 0.1$. It is suggested that the effect comes from the saturation property of the nuclear force.

A systematic analysis of the electric dipole sum rules in the different isospin channels is given. The connections between these sum rules and the well-known old ones are classified. A simple application is given in resolving the isospin components of the nuclear giant resonance.

We have measured the quiet-time flux and energy spectrum of primary cosmic-ray electrons in the energy range from 10 to 200 MeV in interplanetary space. This investigation was carried out with an instrument on board the satellite OGO-5 and covers the period from 25 March to 25 April 1968.

A theorem of Bell, proving that certain predictions of quantum mechanics are inconsistent with the entire family of local hidden-variable theories, is generalized so as to apply to realizable experiments. A proposed extension of the experiment of Kocher and Commins, on the polarization correlation of a pair of optical photons, will provide a decisive test between quantum mechanics and local hidden-variable theories.

Evidence is presented for four $\Xi$ resonances in the reaction $K^{-}p\to {\Xi }^{-}{\pi }^{+}{K}^0$. In addition to the well known $\Xi \mathrm{}\left(1530\right)\mathrm{}$, significant structures are observed in the $\Xi \pi$ system at masses of 1630, 1800, and 1960 MeV, although the latter two are not statistically distinguishable from a single broad structure at 1950 MeV. No significant enhancements at these masses are observed in the ${\Xi }^{-}{\pi }^0{K}^{+}$ final state.

Elastic scattering of $K^{-}$ mesons from protons in the backward direction has been measured to high accuracy in the momentum interval from 1.0 to 2.5 GeV/c. The cross sections exhibit a very fast decrease as a function of energy given by $\frac{d\sigma }{\mathrm{du}}\sim s^{-10\mathrm{}}$. The data can be fitted either by a superposition of the known resonant amplitudes in the $K^{-}p$ system, or by postulating the existence of a $Z^{*}$ Regge trajectory.

We have investigated photoproduction of $K^{+}\Lambda$ and $K^{+}{\Sigma }^0$ from hydrogen at 4.3 GeV and for $u$ values between -0.2 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$ and -0.7 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$. The data were consistent with a smooth decrease in $\frac{d\sigma }{\mathrm{du}}$ towards larger negative $u$ values. The $K^{+}$ backward photoproduction cross sections appear to be closely similar to the observed cross section for backward ${\pi }^{+}$ photoproduction. The ratio of $\frac{{\Sigma }^0}{\Lambda }$ is about 1.7, which rules out pure decuplet exchange in this region of $u$. The results are consistent with the SU(3) prediction.

Measurements are reported of the differential and total cross section for $n+p\to d+\gamma$ for neutron energies between 160 and 640 MeV. A comparison is made with the differential and total cross sections for the inverse process.

The current-algebra connection between the pion electromagnetic form factor $F_{\pi }\mathrm{}\left(t\right)\mathrm{}$ and the amplitudes for $\pi \pi \to \pi \pi$ and $\pi \pi \to \pi A_1$ is examined by explicitly extrapolating off the pion mass shell the matrix element $〈\pi \left|A_{\mu }\right|\pi \pi 〉$ which is taken to be dominated by $\pi$ and $A_1$ poles and possible subtractions. It is found that the connection is broken by the presence of an almost arbitrary subtraction function. In particular the $A\rho \pi$ interaction remains arbitrary as well as the form for $F_{\pi }\mathrm{}\left(t\right)\mathrm{}$. The results are applied briefly to the Veneziano model.

We propose an integral over the Veneziano amplitude which introduces singularities of two-body inelastic unitarity in the amplitude. The model provides a framework for a unified treatment of quantization conditions, the stability of particles, the Pomeranchuk singularity, and decay of particles by pion emission.

We suggest a general framework for unitarizing the Veneziano model for $\pi \pi$ scattering, and deduce some immediate consequences. By duality the unitarity $s$ cut generates a moving Regge cut with branch-point trajectory $1+{\alpha }^{\prime }t$ in the approximation $m_{\pi }=0\mathrm{}$, with ${\alpha }^{\prime }$ the slope of the $\rho -f^0$ trajectory. In principle $m_{\pi }$ may be calculated from the shift of the Adler zero. A crude estimate yields $m_{\pi }\approx {\left({\alpha }^{\prime }\right)}^{\frac{1}{2}}{m}_{\rho }{\Gamma }_{\rho }=95\mathrm{}$ MeV.

Evidence has been obtained that neutrons form a weak bond with electrons trapped in LiF at 4°K. The chemistry of the resulting $n^{-}$ species has been studied and shows that it decomposes at this temperature with a half-time in LiF of ∼30 sec. The bond energy is probably about 0.1 eV. Removal of the trapped electrons greatly reduces, if not completely destroys, the neutron retention in LiF.

The relativistic Vlasov dispersion relation is used to find the critical density $n_c=\frac{3{B_0}^2\kappa T}{8\pi m^2{c}^4}$ below which the extraordinary wave can propagate freely across a mirror-field plasma into the cyclotron-resonance region.

Shorting currents from a theta-pinch plasma were measured by observing the azimuthal magnetic field, $B_{\theta }$, outside the compression coil. The total current and the radial distribution of the current agree well with values predicted by a theoretical rigid-rotor model.

We have measured the specific heat of liquid ${\mathrm{He}}^4$ and four ${\mathrm{He}}^3$-${\mathrm{He}}^4$ mixtures under their saturated vapor pressure at temperatures very close to the $\lambda$ temperature of each mixture. The specific heat of mixtures with large ${\mathrm{He}}^3$ concentration is clearly cusped at the $\lambda$ line. It approaches a finite maximum with infinite slope. This supports the conjecture that the specific heat of ${\mathrm{He}}^3$-${\mathrm{He}}^4$ mixtures at constant chemical potential becomes infinite at the $\lambda$ line at all ${\mathrm{He}}^3$ concentrations.

The spectrum of light scattered from surface waves thermally excited on the liquid-vapor interface of carbon dioxide has been measured at several scattering angles in the temperature range $30°>~T_c-T>~3.5\times {10}^{-2\mathrm{}}°$K. Within experimental error no deviation of the spectrum shape from the predictions of thermodynamic fluctuation theory is observed. The temperature dependence of the surface tension is deduced from the data and fitted by the empirical law $\alpha ={\alpha }_0{(1-\frac{T}{T_c})}^{\mu }$, with $\mu =1.253\mathrm{}\pm 0.010$ and ${\alpha }_0=17.9\mathrm{}\pm 1.2$ dyn/cm. No anomaly is noticed in the temperature variation of the shear viscosity.