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Although a ubiquitous natural phenomenon, the onset and subsequent process of surface wave breaking are not fully understood. Breaking affects how steep waves become and drives air–sea exchanges1. Most seminal and state-of-the-art research on breaking is underpinned by the assumption of two-dimensionality, although ocean waves are three dimensional. We present experimental results that assess how three-dimensionality affects breaking, without putting limits on the direction of travel of the waves. We show that the breaking-onset steepness of the most directionally spread case is double that of its unidirectional counterpart. We identify three breaking regimes. As directional spreading increases, horizontally overturning ‘travelling-wave breaking’ (I), which forms the basis of two-dimensional breaking, is replaced by vertically jetting ‘standing-wave breaking’ (II). In between, ‘travelling-standing-wave breaking’ (III) is characterized by the formation of vertical jets along a fast-moving crest. The mechanisms in each regime determine how breaking limits steepness and affects subsequent air–sea exchanges. Unlike in two dimensions, three-dimensional wave-breaking onset does not limit how steep waves may become, and we produce directionally spread waves 80% steeper than at breaking onset and four times steeper than equivalent two-dimensional waves at their breaking onset. Our observations challenge the validity of state-of-the-art methods used to calculate energy dissipation and to design offshore structures in highly directionally spread seas.

The size and shape of micelles formed by dimeric polyoxyethylene (nonionic gemini) surfactants having the structure (Cn-2H2n-3CHCH2(OCH2CH2)mOH)2(CH2)6 with alkyl and ethoxy chain lengths ranging from n = 12−20 and m = 5−30 have been determined using small angle neutron scattering (SANS). The surfactants are polydisperse in the hydrophilic groups but otherwise analogous to the widely studied monomeric poly(oxyethylene) alkanols. We find that longer ethoxylated chains are needed to confer solubility on the gemini surfactants and that these chains in the hydrophilic corona around the alkyl core of the micelles are reasonably well described as a homogeneous random coil in a good solvent. Spherical micelles are formed by the surfactants with the longest ethoxylated chains. Shorter chains lead first to rods and ultimately a vesicle dispersion. These solutions exhibit conventional cloud point behavior, and on warming, a sphere to rod transition can be observed. For the n = 20 and m = 15 surfactant, this shape transition is accompanied by a striking increase in viscosity at low concentration and gelation at higher concentrations.

The compositions of the adsorbed aggregates at the mica−solution interface have been directly determined for mixtures of pyridinium chloride hydrocarbon and fluorocarbon surfactants by solution depletion measurements, including direct determination of the adsorbed layer composition for partially miscible surfactants. The measured adsorbed aggregate compositions are compared with predictions for bulk micelles using the group contribution method and regular solution theory. For fully miscible surfactants, there is good agreement between the models and experimental results. The group contribution method successfully predicts the existence of a miscibility gap for some mixtures, but adsorption experiments reveal some unusual features; the adsorbed layer consists of only one of the two coexisting micelle compositions, and its composition differs from that predicted. This effect is attributed to the substrate.

The adsorbed layer structure of tetradecylpyridinium, hexadecylpyridinium, heptadecafluorodecylpyridinium, and tetradecyltriethylammonium chloride and their mixtures on mica has been determined by AFM imaging. In addition, the composition of the mixed adsorbed layers has been measured, showing a significant surface enrichment of the pyridinium surfactants, particularly the partially fluorinated species. Shape transitions in the adsorbed layer are correlated with surface and bulk compositions and explained by consideration of the adsorption mechanism.

ω-Hydroxy quaternary ammonium bolaform surfactants form much smaller micelles in solution than the corresponding non-hydroxy (conventional) surfactants. Aggregation numbers for micelles formed by the ω-hydroxy surfactants, determined using ¹H NMR spectroscopy and steady-state fluorescence quenching, are very small (N = 5−18). The micelle size is consistent with aggregates of about half the diameter of a conventional surfactant. This implies that both the quaternary ammonium and the terminal hydroxyl are positioned at the micelle/water interface. The critical micelle concentrations of the bolaform surfactants, determined using ¹H NMR and the conductivity method, are between 3 and 9 times greater than those of the corresponding non-hydroxy surfactants.

The Davey desilverizing procedure was introduced at the Noyelles-Godault lead refinery in 1976–1977, following earlier small-scale tests. The procedure is a two-stage, one-kettle operation which completely eliminates the labor associated with skimming second-stage (low-grade) crusts, or scraping the kettle sides during the final cooling stage. The second-stage crusts are formed as a bridge in the kettle by cooling the bath surface with a water-cooled steel tray and simultaneously stirring the lead at a controlled rate. The main advantage of the new procedure is a reduction in labor. In addition, crane requirements, zinc consumption, total time of treatment, and kettle maintenance are reduced; the refinery is cleaner (due to elimination of return crusts); and more consistent low final silver figures are obtained. Fuel consumption may be slightly increased, and two extra pieces of equipment are required — the tray cooler, and a stirrer with a modified impellor or a variable-speed drive. Over half a million tons** The figures given as “tons” in this paper all refer to metric tons. of lead have been desilverized by this procedure at Noyelles-Godault. The process is covered by a U.S. patent1and applications in other countries.

The electrical conductivities of chalcogenide glasses, two of which contained selenium: Se15Ge23As31Te31 and Se15Ge33As27Te25, and two of which contained sulphur: S15Ge23As31Te31 and S15Ge33As27Te25, have been determined over the temperature range 20 to 1150‡ C. To prevent volatilization loss from the liquid glasses, the conductance cells were enclosed in an internally heated pressure vessel containing high-pressure argon. At the lowest temperatures the plots of logσ against 1/T(K) for the solid glasses were found to be linear, indicative of semiconductive behaviour. At temperatures just above the glass transition regions, these plots deviated from linearity and showed a marked upward curvature; this suggested that a conduction process, involving both metallic and semiconductive modes in the melt, was already operating. Comparison with the results for arsenic triselenide lent support to this idea. A similar study was carried out on the well-known switching glass, As30Te48Ge10Si12. In all cases, the liquid glasses showed metallic levels of conductivity at the highest temperatures.

Substitution of a triethyl for a trimethyl headgroup in alkyltrimethylammonium or (ω-hydroxyalkyl)trimethylammonium bromide surfactants leads to a significant reduction in the Krafft temperature. This substitution allowed us to produce asymmetric bolaform surfactants that form micellar solutions at room temperature. It is reasoned that the proximity of the bromide counterion to the quaternary ammonium center stabilizes the hydrated crystal of the conventional and bolaform surfactants through Coulombic interactions. The bolaform surfactants experience further stabilization as a result of bonding between the hydroxyl functionality and the quaternary nitrogen and bromide. Substitution of ethyl for methyl groups in the headgroup increases the ion−ion and ion−dipole distances, lowering the stability of the hydrated crystal, which in turn lowers the Krafft temperature.

The electrical conductivity of liquid sulphur has been measured from the melting point to 900° C, evaporation of the sulphur being prevented by use of an atmosphere of argon at elevated pressure. With rise in temperature, the conductivity increases except at the polymerization maximum near 170° C where a minimum in the conductivity is confirmed. Above 400° C the plot of logs versus 1/T is linear, and on the assumption that the conductivity at these temperatures is intrinsic, a value of ~3.1 eV is obtained for the energy gap. Although the rise in conductivity above 400° C is accompanied by a decrease in mean chain length in the liquid, there is no simple relationship between the two properties. The behaviour of sulphur is compared with that of liquid selenium.

Stress corrosion tests were carried out on friction welds in prestressing wire. Testing was undertaken in 3% sodium chloride solution, using both plain and pre-cracked samples. The results indicated that there was no significant difference between the see sensitivity of parent wire and that of friction welds. However, enhanced pitting attack at friction welds was found. associated with the microstructural reorientation in this area.

A surface aggregate phase transition is described. Atomic force microscopy has been used to image the equilibrium association of sodium dodecyl sulfate (SDS) and 1-dodecanol molecules at the interface between graphite and aqueous solutions. In pure SDS solutions, the molecules associate into long, parallel hemicylindrical surface aggregates over a concentration range from about one-third to at least 10 times the critical micelle concentration (cmc). Above the cmc, dodecanol has little influence on the surface aggregate structure, probably because dodecanol is partitioned into the bulk micelles. Below the cmc, dodecanol causes a transition from hemicylindrical aggregates to a two-phase mixture in which flat sheets coexist with swollen hemicylindrical aggregates. In this mixture, the hemicylindrical aggregates are preferentially located at and parallel to steps on the underlying graphite substrate. Under conditions where hemicylinders and flat sheets coexist, an increase in bulk dodecanol concentration results in an increase in surface coverage by flat sheets. No bulk solution changes were detected by NMR in the region where the surface phase transition was observed.

The fundamental principles by which bismuth may be removed from lead by pyrometallurgical processes are enumerated. Qualitative discussion of the phase diagrams concerned is followed by presentation of quantitative diagrams. Brief mention is made of the practical aspects. Data presented show how chemical lead (<0.005 pet Bi) may be produced by the Jollivet, Dittmer, and Kroll-Betterton processes.

In a relatively simple smelting plant at Oruro, Bolivia, the total recovery of tin was 93% of the input. The operating economics are good, and could be improved by optimizing with a computer program.

The draft has been prepared under the direction of the Nuclear Engineering Standards Committee and is based on Technical Report 4826–1979 by Technical Committee 85 of the International Organization for Standardization.