Melting of Colloidal Crystals
Inelastic light scattering is used to study the dynamics of an ordered suspension of macromolecules.Received 4 August 1975DOI:https://doi.org/10.1103/PhysRevLett.35.1448©1975 American Physical Society
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Neutron-scattering studies on beta-alumina
The elastic constants (in units of 10 11 dyn cm -2 ) of Na beta -alumina as measured by inelastic neutron scattering are c 11 =33.8, c 33 =24.5, c 44 =5.0 and c 12 =14.3, c 44 varies with the substitution of other ions for Na, with c 44 =5.6, 6.2 and 7.3 for Ag, K and Rb respectively. A dispersionless phonon mode obse…
Optical spectrum of Cr3+in the spinel LiGa5O8
The optical absorption and luminescence spectra of chromium ions in the LiGa 5 O 8 spinel are investigated. Measurements are made in the temperature range 1.6-300K. The absorption spectra consist of broad (split into three) spin-allowed bands connected with the transitions 4 A 2 to 4 T 2 and 4 A 2 to a 4 T 1 , and sha…
epsilon -expansion analysis of some physically realizable n⩾4 vector models
Four different n>or=4 component Hamiltonians describing phase transitions in certain physical systems are derived. The corresponding critical behaviour is studied using the exact renormalization group in d=4- epsilon dimensions. In particular, although TbD 2 , Nd and K 2 IrCl 6 have different symmetries, their critica…
Molecular mobility and structure of elastin deduced from the solvent and temperature dependence of carbon-13 magnetic resonance relaxation data
13C relaxation parameters, T1, line width, and NOE, have been determined for backbone carbons of ligamentum nuchae elastin swollen by 0.15 M NaCl, 0.15 M NaCl-formamide, 0.15 M NaCl-ethanol, dimethyl sulfoxide, and formamide. The data have been analyzed in terms of (a) a single correlation time model and (b) a model e…
Modification of arginine and lysine in proteins with 2,4-pentanedione
Primary amines react with 2,4-pentanedione at pH 6-9 to form enamines, N-alkyl-4-amino-3-penten-2-ones. The latter compounds readily regenerate the primary amine at low pH or on treatment with hydroxylamine. Guanidine and substituted guanidines react with 2,4-pentanedione to form N-substituted 2-amino-4,6-dimethylpyri…
Two-Photon Decay of the 6.05-MeV State ofO16
A triple-coincidence, five-parameter technique was employed to search for two-photon emission in the decay of the $^{16}\mathrm{O}$(6.05-MeV) state. Data were event-recorded and analyzed in parallel with events associated with decay of the $^{16}\mathrm{O}$(6.13-MeV) and the $^{16}\mathrm{O}$(7.12-MeV) states. Our mea…
Effect of „Forest” Dislocations in the {1122} 〈1123〉 system on hardening in Mg single crystals under basal slip
Experimental results are given of the dependence of work hardening parameters (critical shear stress, τc, work hardening coefficient, θA, and stage length ϵA at easy glide) in Mg crystals under basal slip on the density of pyramidal dislocations ϱf of various kinds. A relation between the kind of basal–pyramidal dislo…
Formation of vacancy-type dislocation loops in tungsten bombarded by 60 keV Au ions
The formation of vacancy-type dislocation loops in tungsten specimens as produced by irradiation with 60 keV Au ions is investigated by transmission electron microscopy. The majority of the loops is found to have Burgers vectors b=1/2〈111〉 and loop planes normal to n ≈︁ {110} (∢(b, n) ≈︁ 35°). The 12 different loop or…
Order-disorder phenomenon in sodium nitrate studied by low-frequency Raman scattering
The low-frequency Raman spectrum of a single crystal of NaN${\mathrm{O}}_{3}$ has been measured for temperatures from 25 to 300\ifmmode^\circ\else\textdegree\fi{}C covering both ordered and disordered phases. The crystal is partially disordered below the transition temperature and the corresponding Raman spectra are i…
Paramagnetic defects in irradiated ferroelectric (NH4)2SO4
EPR studies of x-ray damaged crystals of (NH4)2SO4 show that long lived defects, NH3+ ions, are produced in two inequivalent sites with each site having two magnetically inequivalent orientations. All sites have approximately the same isotropic hyperfine splittings which are found to be 19.0 G for nitrogen and −24.6 G…
Conductivity relaxation in positive dielectric liquid crystals
Measurements are reported of the frequency dependence of the conductivities σ⊥ and σ∥ in some nematic liquid crystals with strong positive dielectric anisotropy which are nematic at room temperature. The conductivity relaxation which causes σ∥ to increase already at frequencies <100 Hz in highly deionized liqui…
Boundary scattering of phonons in noncrystalline materials
Thermal-conductance measurements on thin Mylar and glass plates indicate that abrasion of the plate surfaces does not suppress specular reflection of phonons, contrary to the behavior in crystalline materials. This reinforces the suggestion that nonspecular reflection at crystal surfaces is caused primarily by lattice…
Lattice dynamics ofα-quartz
The phonon dispersion curves, the temperature dependence of the Debye temperature, and the static elastic, dielectric, and piezoelectric constants of $\ensuremath{\alpha}$-Si${\mathrm{O}}_{2}$ have been calculated from a modified rigid-ion model with an effective charge, with short-range central forces for the two Si-…
Elasticity measurements in the layered dichalcogenides TaSe2and NbSe2
We have measured the Young's modulus and internal friction in the two-dimensional layered dichalcogenides $2H$-Ta${\mathrm{Se}}_{2}$ and $2H$-Nb${\mathrm{Se}}_{2}$ using a vibrating reed technique. Weak elastic anomalies are observed at the incommensurate charge-density-wave transitions in Ta${\mathrm{Se}}_{2}$ and Nb…
Application of scanning electron microscopy to determination of surface recombination velocity: GaAs
A method is reported for the determination of the surface recombination velocity by scanning electron microscopy; this method is based on an established relationship between the effective diffusion length of the minority carriers, the penetration depth of the electron beam, and the surface recombination velocity. Valu…
Origin of the second-order optical susceptibilities of crystalline substituted benzene
An analysis of the second-order optical nonlinearities of crystalline substituted benzene is presented. A new irreducible tensor formalism for the decomposition of a crystal tensor as the sum of the contributions of microscopic units is developed and applied to the study of the second-order susceptibility in four benz…
Phonon thermal transport in noncrystalline materials
The thermal conductivities of a borosilicate glass and a polycarbonate have been measured in the temperature range 0.04-60 K. Some samples contained well-defined holes to provide an additional source of phonon scattering. The results at low temperatures are consistent with the predictions of the Debye model using expe…
Transitions conserving parallel momentum in photoemission from the (111) face of copper
Photoelectric yields and directional photoemission spectra for clean (100) and (111) faces of copper measured with provision for varying the angle of incidence and the light polarization, and with photon energies up to 6.60 eV, are presented. Contrasting the structureless Fowler-like behavior of the (100) face, the (1…
Shrinkage behaviour of polyacrylonitrile during thermal treatment
Abstract A detailed study of the shrinkage behaviour of homopolymers and copolymers of acrylonitrile has been made. Apart from chemical shrinkage, a physical shrinkage, which is independent of temperature and oxidizing gas was observed. This shrinkage occurs even at temperatures below 180°C. The effect of temperature…