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Context. Silicon solid-state detectors are commonly used for measuring the specific ionization, dE∕dx, in instruments designed for identifying energetic nuclei using the dE∕dx versus total energy technique in space and in the laboratory. The energy threshold and species resolution of the technique strongly depend on the thickness and thickness uniformity of these detectors. Aims. Research has been carried out to develop processes for fabricating detectors that are thinner than 15 μm, that have a thickness uniformity better than 0.2 μm over cm2 areas, and that are rugged enough to survive the acoustic and vibration environments of a spacecraft launch. Methods. Silicon-on-insulator wafers that have a device layer of the desired detector thickness supported by a thick handle layer were used as starting material. Standard processing techniques were used to fabricate detectors on the device layer, and the underlying handle-layer material was etched away leaving a thin, uniform detector surrounded by a thick, supporting frame. Results. Detectors as thin as 12 μm were fabricated in two laboratories and successfully subjected to environmental and performance tests. Two detector designs were used in the High-energy Energetic Particles Instrument, which is part of the Integrated Science Investigation of the Sun instrument suite on NASA’s Parker Solar Probe spacecraft. These detectors have been performing well for more than two years in space. Conclusions. Thin silicon detectors in d E∕dx versus total energy instruments enable the identification of nuclei with energies down to ~1 MeV nuc−1. This research suggests that detectors at least a factor of two thinner should be achievable using this fabrication technique.

The melting point and phase behaviour of cocoa butter under CO2 pressure were observed in a high-pressure view cell. The melting point decreases from 35 to 23 °C at CO2 pressures higher than 5 MPa. A static analytical procedure was used to measure the solubility of CO2 in cocoa butter at 40, 80 and 100 °C and pressures of 2–35 MPa in an autoclave set-up. The density and viscosity of the CO2-saturated cocoa butter was measured simultaneously in this set-up. The experimental procedure was first validated by comparing the data measured for the system CO2/hexadecane with literature data. The highest solubility of CO2 in cocoa butter of 36 wt.% occurs at 40 °C and 35 MPa. The measured solubilities differed from those previously reported in literature. This can be attributed to differences in the cocoa butter used for measurements. The density of CO2-saturated cocoa butter increases with pressure, whereas the viscosity decreases. The Grunberg equation was used to correlate the viscosity of CO2-saturated cocoa butter. The measured data were used to estimate the theoretical gas assisted mechanical expression (GAME) yields. In GAME CO2-saturated cocoa nibs are mechanically expressed. The calculated GAME yields deviate from the experimental ones due to the oversimplification of the mechanism involved in GAME.

Mathematical and numerical modeling of drying coating layers is of interest to both industrial and academic communities. Compositional changes that occur during the drying process make the implementation of practical and efficient numerical models rather difficult. In this paper we present a three-dimensional mathematical and numerical model based on the lubrication approximation for the flow of drying paint films on horizontal substrates. The paint is modeled as a multicomponent liquid with one nonvolatile and one volatile component, termed the "resin" and the "solvent" respectively. Our model includes the effects of surface tension and gravitational forces as well as surface tension gradient effects which arise due to solvent evaporation. The dependence of viscosity, diffusivity, and evaporation rate on resin concentration is also incorporated in the model. A closed-form Linearized solution has been found for coating layers that are of almost uniform thickness. The numerical solution agrees closely with the linear solution in the appropriate Limit. A model simulation demonstrates the effect of surface tension gradients due to compositional changes in a three-dimensional flow field, and we suggest methods by which these gradients may be used to obtain a more uniform final coating layer.

Following the application of a liquid coating to a curved substrate, surface tension forces will act to redistribute the coating layer. The coating will thin at outside corners and thicken at inside corners as the free surface contracts to minimize the surface energy. If the coating is a multicomponent liquid with a volatile component, the dynamics of the thinning process may be quite complex. Compositional changes in the bulk liquid during drying and convection of surfactant may cause surface tension gradient or Marangoni effects. In addition there may be viscosity variations due to concentration changes and the liquid may exhibit shear-thinning rheology. A numerical model has been developed, based on the lubrication approximations, for predicting the time-evolution of the coating layer thickness of a complex liquid on a curved substrate. Substrate geometry is modeled as a time-independent overpressure distribution and the model includes such effects as evaporation, convection, and diffusion of solvent in the bulk liquid, and convection and diffusion of a soluble surfactant. For a given starting profile and substrate geometry, the temporal and spatial evolution of the free surface, bulk composition, surfactant concentration, surface tension, and layer-averaged viscosity are calculated until the drying process is complete. We show that convection of surfactant away from outside corners may slow the thinning in these regions. In addition, solvent evaporation may lead to Marangoni forces in the corner region, causing a “rebound” effect. Surface tension forces will initially displace liquid from corner regions, but the thinning will produce surface tension gradients which act to pull liquid back to the corner region. If the evaporation time scale is suitably matched to the time scale for flow induced by surface tension gradients, corner defects in the final dry coating layer can be substantially mitigated.

International audience; The authors realized an ultrahigh quality factor nanocavity in a GaAs membrane with the highest loaded Q reported to date of 250 000 in a side-coupled cavity-waveguide system. This result could be obtained using an original aluminum-free material system combined with a carefully adjusted fabrication technology, yielding a device with small roughness and very good verticality of holes as well as small disorder. The authors show that the intrinsic Q factor is around 3.0x105 using a coupled-mode model.

This chapter elaborates the thermodynamic and fluid dynamic aspects of the hydrogenation of triglycerides and esters in the presence of supercritical fluids (SCF). Hydrogenation of liquids in the presence of supercritical solvents can be much faster than when using conventional conditions. SCF may increase the ratio of available hydrogen. For the hydrogenation of (C=C)-double bonds in triglycerides it was found that the solvent power of the SCFs increases from carbon dioxide over propane to dimethyl ether. For carbon dioxide, it was not possible to reach a homogeneous mixture, which corresponds to the finding that the rates in the presence of carbon dioxide are lower than in the presence of propane, which is a solvent that allows reaching homogeneous conditions at rather moderate pressures. The knowledge of the typically complex phase behavior in near-critical or supercritical systems is essential for planning hydrogenations and for interpretation of the results. For binary or ternary systems, experimental studies on thermodynamic and fluid dynamics are feasible. For systems with a larger number of compounds, a combination of predictive modeling, experimental verification, and optimization of the models is a suitable method for choosing and comparing SCFs, identifying boundary conditions of the reactions, and for designing processes.

The particle-size and size-distribution of solid materials produced in industrial processes are not usually those desired for subsequent use of these materials and, as a result, comminution and recrystallization operations are carried out. Well-known processes for particle size redistribution are crushing and grinding, air micronization, sublimation, and recrystallization from solution. There are several practical problems associated with the above-mentioned processes. Some substances are unstable under conventional milling conditions, and in recrystallization processes, the product is contaminated with solvent and waste solvent streams are produced. Applying supercritical fluids may overcome the drawbacks of conventional processes. Numerous processes for powder generation using supercritical fluids have been developed. The specific properties of dense gases allow obtaining fine dispersed solids, especially of substances with low melting point temperatures, high viscosities, and very waxy or sticky properties. The economic evaluation of the process shows that these compounds cannot be efficiently and economically processed by conventional mechanical processes and there is a big advantage of the use of supercritical fluids.

The authors investigate the nonlinear and bistable behavior of a high-Q GaAs photonic crystal heterostructure nanocavity, side coupled to a line-defect slab waveguide. The observations agree well with a model incorporating the relevant nonlinearities. The power threshold for bistable behavior is at least one order of magnitude lower than what is reported so far.

A swelling response by the polaroplast organelle initiated microsporidian invasion tube extrusions by Glugea hertwigi spores. The tumescence was induced by the displacement of internal calcium. Sodium citrate, phosphate, and the calcium ionophore A23187 were effective in initiating polaroplast swelling and spore discharge; however, the addition of external CaCl2 switched the expanded polaroplasts to a contracted state and blocked spore discharge. Unlike CaCl2, equivalent concentrations of KCl, NaCl, MgCl2, and BaCl2 did not induced polaroplast contraction, and spore discharge was not blocked. 45CaCl2 readily incorporated into spores with expanded polaroplasts; however, little calcium uptake was apparent in spores with contracted polaroplasts. Metallochromic arsenazo III yielded a color spectrum characteristic of the dye-Ca++ complex in the polaroplast region; furthermore, a membrane association with calcium was indicated by strong chlorotetracycline fluorescence within the polaroplast; this fluorescence was extinguished by pretreating spores with ionophore A23187. An association of the membrane with calcium was also indicated by a potassium ferrocyanide-osmium tetroxide technique. All evidence indicates that an internal calcium displacement is an important initial step in the swelling response of the polaroplast organelle.

The extrusion apparatus of the microsporidian parasitic protozoan Nosema michaelis discharges an invasion (or polar) tube with a velocity suitalbe for piercing cells and injecting infective sporoplasm. The tube is composed of a polar tube protein (PTP) which consists of a single, low molecular weight polypeptide slightly smaller than chymotrypsinogen-A. Assembled PTP tubes resist dissociation in sodium dodecyl sulfate and brief exposures in media at extreme ends of the pH range; however, the tubes are reduced by mercaptoethanol and dithiothreitol. When acidified, mercaptoethanol-reduced PTP self-assembles into plastic, two-dimensional monolayers. Dithiothreitol-reduced PTP will not reassemble when acidified. Evidence is presented which indicates that PTP is assembled as a tube within the spore; that the ejected tube has plasticity during sporoplasm passage; and, finally, that the subunits within the tube polymer are bound together, in part, by interprotein disulfide linkages.

The microsporidian spore extrusion apparatus activates with a calcium influx from Spraguea lophii spore wall/plasma membrane; this influx requires preconditioning with an extrasporular shift in medium pH to the alkaline in the presence of the polyanions mucin or polyglutamate. Undischarged S. lophii spores display calcium bound to the wall/plasma membrane with a characteristic calcium-chlorotetracycline fluorescence; this fluorescence declines significantly during spore discharge. S. lophii spores do not discharge when spore wall/plasma membrane calcium is removed with EGTA. Extrasporular mucin or polyglutamate and a pH shift to the alkaline appear to be necessary preconditions for the triggering of the influx of spore wall/plasma membrane-bound 45Ca2+. Ionophore A-23187 also effectively activates spore discharge without other extrasporular polyanions. Micromolar concentrations of the calcium antagonists lanthanum or verapamil prevent spore discharge, and micromolar concentrations of calmodulin inhibitors chlorpromazine and trifluroperazine prevent spore discharge. Calmodulin, visualized with a calmodulin antibody and a peroxidase conjugate, is localized particularly on the plasma membrane and the polaroplast membranes of the extrusion apparatus.