High-resolution heat-capacity, tilt-angle, and polarization measurements have been carried out in the vicinity of the smectic-A (SmA) –chiral-smectic-C (Sm$C^{\mathrm{*}}$) phase transition of p-(n-decyloxybenzylidene)-p-amino-(2-methylbutyl)cinnamate (DOBAMBC). Heat-capacity studies were done on two different samples obtained from two laboratories. Different results were obtained. Almost simultaneous measurements of the tilt angle (theta) and polarization (P) on one of the samples allow us to reveal one surprising temperature dependence of the ratio P/theta. The anomaly in the ratio P/theta seems to be closely related to the anomaly in the helical pitch just below the SmA-Sm$C^{\mathrm{*}}$ transition.

In light of our high-resolution and almost simultaneous measurements of the tilt angle and polarization in the chiral-smectic-C phase of p-(n-decyloxybenzylidene)-p-amino-(2-methylbutyl)- cinnamate (DOBAMBC), we have proposed a generalized mean-field model to describe the important features related to the smectic-A–chiral-smectic-C transition. This mean-field model is similar to the one proposed by Zeks. After carrying out least-squares fittings to the generalized mean-field model, we demonstrated that the temperature dependences of the tilt angle, polarization, and their ratio are well described by the model. The fitting to the temperature variation of the helical pitch is less satisfactory but the qualitative feature of the helical pitch anomaly is obtained. Furthermore, all the mean-field expansion coefficients can be calculated. Among the eleven coefficients, seven are in good agreement with the existing reported results, the four remaining will be reported here for the first time. The shortcoming of the prevailing phenomenological mean-field theory by Pikin and Indenbom will be discussed in detail.

An interfacial instability driven by concentration diffusion in a solid system is studied with use of simulations based on an Ising lattice-gas model with conserved dynamics. Interfacial thermodynamic properties including the effect of surface tension are built in at the microscopic level. Finger structures evolve on a reasonable scale compared to any thermal characteristic lengths. The dynamics and universality of the growth process are studied. Evidence is presented for power-law growth, and for a scaling form in the evolution of the Fourier transform of the interface shape.

Freely suspended liquid-crystal films of the smectic-I phase of HOBACPC [R(-) hexyloxybenzylidene p’-amino-2-chloropropyl cinnamate] display distinctive stripe and droplet textures. We derive these patterns from a Landau expansion of the free energy using a vector order parameter. Strong pinning boundary conditions lead to boojums in the droplets and stable defect lines between the stripes. The boojum is a two-dimensional version of its namesake in superfluid ${}_{}{}^3{}_{}{}^{}\mathit{A}$. The surface defect in the boojum is expelled from the smectic-I droplet in order to lower the internal gradient energy, leaving a defect-free texture. The expulsion distance and the width of the stripes are calculated in terms of the elastic constants.

We construct a consistent solution of the Bhatnagar-Gross-Krook (BGK) model kinetic equation describing a system in a steady state with constant pressure and nonuniform temperature. The thermal profile is not linear and depends on the interaction potential. All the moments of the distribution function are given as polynomials in the local thermal gradient. In particular, the heat flux always obeys the (linear) Fourier law.

Relationships between the optical third-harmonic-generation susceptibility ${\chi }_{\mathrm{ijkl}}^{\mathrm{}\left(3\right)\mathrm{}}$(-3ω;ω,ω,ω) and the nonvanishing order parameters 〈$P_2$〉 and 〈$P_4$〉 for a nematic-liquid-crystal phase are presented. Third-harmonic-generation experiments were performed on the nematic N-(p-methoxybenzylidene)-p-butylaniline (MBBA) using the wedge-maker fringe method as a function of polarization and temperature to demonstrate the simultaneous determination of 〈$P_2$〉 and 〈$P_4$〉. The results are in agreement with previous experimental results from nuclear magnetic resonance and Raman scattering studies. Local-field corrections are considered, and based on the data, local-field factors do not appear to depend on the long-range anisotropy of the macroscopic medium.

Numerical results on the dynamics in a Lennard-Jones system close to the glass transition are presented, using a kinetic model presented in an earlier paper. The theory is based on the Zwanzig-Mori procedure for deriving formally exact transport equations combined with mode-coupling approximations. Results for a number of different dynamical quantities of experimental interest are presented and the model is shown to reproduce many of the characteristic features of a liquid-glass transition. Comparisons are made with available computer simulation data and analytical results for the same mode-coupling model.

Calculations for an inhomogeneous electron gas using density-functional theory require suitable exchange and correlation potentials. We present here the local exchange and correlation potential ($V_{\mathrm{xc}}$) for the two-dimensional electron gas over a wide range of temperatures and densities based upon summation of ring graphs. A suitable parametric fit for $V_{\mathrm{xc}}$ is presented which is good to within 2% of the exact values. Various limits and graphs of the polarizability are presented.

We present a method by which a quantum-mechanical partition function can be approximated from below by an effective classical partition function. The associated potential is obtained by a simple smearing procedure. For a strongly anharmonic oscillator and a double-well potential, the lowest approximation gives a free energy which is accurate to a few percent, even at zero temperature.

An analytical treatment of the ballistic-driven-aggregation model with a one-sided rain of particles onto the aggregate is presented. The probability distributions for the width and the height of the resulting fanlike structure are obtained. Though the distribution for the width is exactly derived, that for the height is found to depend on the nature of the top surface and approximate expressions for the distribution of the height are given. For large width, the fan structure is shown to be contained in a cone with semivertical angle ${\mathrm{theta}}_c$ of about 20°. The limiting density is around 0.5.

We consider several aspects of the irreversible deposition of particles on surfaces. We show by direct numerical simulation that the well-known ‘‘tangent rule’’ for the orientation of the columnar microstructure is only qualitatively correct. We demonstrate that the interface width of the deposit for normal incidence scales according to the hypothesis of Family and Vicsek. This means that the width scales as h${¯}^{\nu }$ for short times and $l^{\alpha }$ for the steady state where h¯ is the mean height and l the width. We find by simulation ν≃(1/3),α≃(1/2) in two dimensions (2D) and ν≃(1/4),α≃(1/3) in 3D. We give an analytic treatment which maps the problem onto a spin model. We find ν=(1/3),α=(1/2) for 2D in agreement with our simulations but ν=0,α=0 for 3D.

The relativistic correction to the limiting bond length found by Pucci and March for heavy, almost spherical molecules typified by the series ${\mathrm{CH}}_4$,...,${\mathrm{PbH}}_4$ is calculated as a function of the fine-structure constant α by means of relativistic Thomas-Fermi theory. The correction is found to remain nonzero in the limit as the atomic number of the central atom X in the X${\mathrm{H}}_4$ series tends to infinity. However, putting α=(1/137), the numerical change in bond length is extremely small.

With interactions chosen to satisfy Poisson’s equation in d dimensions, the form of the total energy E(Z,N,d) of an atomic ion having nuclear charge Ze and N electrons is considered for large Z within the context of the 1/Z expansion. In particular, the form of the coefficients of this expansion is displayed at large N, the nth order coefficient being shown to be proportional to $N^{n+\alpha }$ where α is given explicitly and depends solely on dimensionality. The singular point is at d=4, in contrast to the situation when the 1/r Coulomb interaction is directly taken over into d dimensions.

The shifted 1/N expansion has been used for solving the Schrödinger equation for exponential cosine screened Coulomb potential. The analytic expressions for the energies $E_n$,l yield fairly accurate results for a wide range of values of n,l and the screening parameter λ. The energy values obtained by this method have been compared and found to be in excellent agreement with the Padé-approximation calculations.

We analyze the possibility of large oscillatory wake effects in secondary-electron emission induced by molecular ions, which were proposed in previous interpretations of results derived from beam-foil experiments. We show that theoretical expectations are in disagreement with the description of such oscillatory effects in terms of wake phenomena. Our analysis of various experimental evidences suggests a different origin for the effect. We propose a simple explanation for the molecular effect in secondary-electron emission, which is based on previous knowledge of electron emission from solid targets, and of molecular effects in the energy loss of ion clusters in solid foils.

Low spin-relaxation rates of optically pumped Cs atoms are obtained in paraffin-wall-coated cells. The data are analyzed to determine the electron randomization rate for cesium-wall collisions. Pumping of cesium atoms by the paraffin wall coating is also observed.

The convergence of the Sturmian expansion of the multiphoton matrix element for hydrogen is accelerated by regularizing, in a convenient way, the outgoing part of the stationary wave of the emergent electron. Some results are presented.

The argon K absorption suprastructure features are assigned using ab initio calculations and tabulated experimental final-state energies. The assignments are supported by estimates of relative intensities. It is suggested on the basis of the analysis that the origin of the Kβ’’ satellite is due to initial states with triple-vacancy 1sback103$p^2$ core configurations.

External bremsstrahlung generated by the β particles of the radioactive sources ${}_{}{}^{90}{}_{}{}^{}\mathrm{-}_{}^{90}{}_{}{}^{}$Y (2274 keV) and ${}_{}{}^{99}{}_{}{}^{}\mathrm{Tc}$ (292 keV) in targets of Cu, Mo, Ag, Cd, and Pb sufficiently thick to stop all β particles has been studied using a 4.35×5.08-${\mathrm{cm}}^2$ NaI(Tl) scintillation spectrometer. The spectra unfolded using the Liden and Starfelt procedure are compared with the Bethe-Heitler, Elwert-corrected Bethe-Heitler, Morgan-corrected Bethe-Heitler, and Tseng and Pratt theories. The spectra generated by the high end-point energy source agree mostly with the Tseng and Pratt theory whereas those of the low end-point energy source agree mostly with the Elwert-corrected Bethe-Heitler theory. Deviations at high-energy regions of the spectra still exist.

The theory of a one-dimensional fluid of hard rods has received much attention because it often yields exact results which serve as a guide to understanding the properties of more complicated fluids. Of particular interest recently has been the density distribution of nonuniform fluids in external potentials or between solid walls. The purpose of this paper is to report an explicit solution of the nonlinear integral equation derived by Percus for the density distribution of hard rods.