A New Apparatus for Combined Measurements of the Viscosity and Density of Fluids for Temperatures from 233 To 523 K at Pressures up to 30 Mpa

A new apparatus for measuring the viscosity and density of fluids is presented. The main element of the instrument is an electronically controlled magnetic suspension coupling. For the density measurement (buoyancy principle according to the single-sinker method), this coupling is used for the contactless transfer of the forces acting on a sinker in the measuring cell to an analytical balance. The coupling also serves as a frictionless bearing for a slender rotating cylindrical body which is slowed down due to the viscous drag of the fluid surrounding the cylinder. The viscosity of the fluid can be directly determined from the decay rate of the rotational frequency. The new combined viscometer-densimeter covers a viscosity range of 5 to 150 Pa·s and a density range from 20 to 2000 kg·m^–3 at temperatures from 233 to 523 K and pressures up to 30 MPa. Test measurements on the viscosities and densities of nitrogen and carbon dioxide at 253, 293, and 523 K at pressures up to 30 MPa show an estimated total uncertainty of ±0.6 to ±1.0% in viscosity and of ±0.02 to ±0.05% in density.     

Material properties of a

A study was carried out to investigate changes in mechanical properties and degradation of self-reinforced fibrillated poly-96L/4D-lactide (SR-PLA96) rods in vitro and in vivo. The viscosity-average molecular weight, Mv, of the intact sterile (gamma irradiated) rods was around 50 000 g mol-1. The SR-PLA96 rods of diameter 1.1 mm by 30 mm and diameter 4.5 mm by 50 mm were immersed in phosphate-buffered saline or implanted in the dorsal subcutis of rabbits. Bending, shear and torsion strength and bending modulus, together with the changes of viscosity and crystallinity, were measured up to 24 wk. The strength values showed only a slight decrease during the follow-up period with the exception of torsion strength, that decreased to 52% of the initial value during 24 wk. There were no statistically significant differences in the strength retention between in vitro and in vivo groups. Crystallinity increased over time, being 46–49% at 24 wk. The Mv of the rods decreased over 50% by 24 wk. These promising results motivated us to continue the studies with the fixation of experimental cortical bone osteotomies with SR-PLA96 intramedullary rods. © 1999 Kluwer Academic Publishers     

A comparison of biological activities of a new soya biopeptide studied in an in vitro skin equivalent model and human volunteers

During aging, the epidermis and dermis become thin and an efficient anti-aging product should be able to stimulate the metabolism of senescent fibroblast and keratinocytes, in order to increase the quantity of extra-cellular matrix components such as collagen and glycosaminoglycans. A study performed in parallel on an in vitro skin equivalent model, and in vivo, with human volunteers, demonstrated the efficacy of one specific soya biopeptide for anti-aging properties. Such a biopeptide induces a significant increase of glycosaminoglycans synthesis in vitro and in vivo after a one-month treatment. We also showed that this new cosmetic ingredient is able to stimulate favourably the collagen synthesis in vitro and in vivo. This study provided the proof for anti-aging properties of a new soya biopeptide and also validated the skin equivalent model developed for this experimentation as an alternative method to animal or human testing for some cosmetic efficacy evaluations.     

Two-beam cross-correlation: a method to characterize transport phenomena in micrometer-sized structures

To determine flow properties, namely, the velocity and angle of the flow in microstructured channels, an experimental realization based on fluorescence correlation spectroscopy is described. For this purpose, two micrometer-sized spatially separated volume elements have been created. The cross-correlation signal from these has been recorded and evaluated mathematically. In addition to previous results, two-beam cross-correlation allows for fast and easy determination of even small (down to 200 μm/s) flow velocities, as well as simultaneous measurement of diffusion properties of single dye molecules within a rather short detection time of 5-100 s and an error rate of less than 20%. The spatial flow resolution is around 1-2 μm, limited by the diameter of the volume element. Furthermore, vectorial flow data can be obtained and evaluated. A discussion of the theoretical background and an experimental verification of the theoretical results is performed. The feasibility of fast and easy data processing is shown if the flow time is the only desired information. Possible applications of this precise and simple method are the determination of transportation effects within artificial microstructures for CE and HPLC, fast chemical kinetics, and high-throughput screening.     

Chemical imaging of patterned inorganic thin-film structures by lateral force microscopy

Factors influencing the chemical image formation by lateral force microscopy (LFM, or friction force microscopy, FFM) under normal ambient conditions were studied by applying LFM to patterned specimens of inorganic thin films deposited predominantly by atomic layer epitaxy. The patterned steps on SnO(2)/Si, CaS/Si, CeO(2)/Si, and Pt/Al(2)O(3) samples were formed by chemical etching or lift-off processing. The results of semiquantitative AFM and LFM studies were compared to the static contact angle studies using capillary force evaluation. The chemical contrast in LFM images of the patterned specimens was the highest in cases where silicon was present. This is in accordance with contact angle data, which showed much higher hydrophilicity on Si than on the other materials studied. Further experiments with a patterned SnO(2)/Si specimen indicated that chemical contrast can be significantly affected (i) by whether the surface was pretreated with ethanol, (ii) by the loading force (2-50 nN or 1-10 μN) applied, and (iii) by using SnO(2)-coated AFM probes instead of the conventional Si probes.     

On-line solid-phase extraction of triazine herbicides using a molecularly imprinted polymer for selective sample enrichment

A coupled-column system, consisting of a combination of a molecularly imprinted polymer (MIP) and a C(18)-silica column, was used for selective triazine detection in the HPLC mode. Complex aqueous samples, spiked with triazines, were selectively extracted by the MIP followed by subsequent identification by analytical reversed-phase chromatography. The MIP showed good performance for selectively discriminating triazines from humic acid, whereas urine and apple extract had some tendency to be retained by the MIP. Enrichment was observed in all cases, and triazine-enrichment factors of up to 100 could be recorded, with good extraction efficiency (74-77%). The results indicate that the high selectivity of MIPs can be favorably used for selective sample enrichment in conjunction with reversed-phase HPLC.     

Hardware-based rendering of full-parallax synthetic holograms

We present a method for efficiently calculating the interference of complex-valued two-dimensional wave patterns that is useful during the generation of synthetic holograms. These patterns are represented as a special kind of images (textures), and the interference is calculated in a computer graphics rendering process. This enables us to leverage hardware support for holographic imaging that is implemented in many state-of-the-art computer workstations. Using this approach, we gain a speedup of a factor of 60-90 compared with conventional calculation methods for interfering wave patterns. Our method is evaluated numerically, examples are shown, and the program code is outlined.     

Incoupling waveguide holograms for simultaneous focusing into multiple arbitrary positions

A design method is presented that enables the realization of a novel type of incoupling waveguide hologram (IWGH) that simultaneously focuses the incoupled light to any desired positions in the waveguide. IWGH's, or grating couplers, are gratinglike structures etched into the waveguide surface. They couple the light incident from free space into the waveguide. The grating lines can be dislocated with respect to each other to provide phase modulation of the incoupled light. By use of this phase modulation, novel beam splitting and focusing functions can be built into the IWGH's. The new design algorithm is based on a model that assumes a simple relation between the incident light wave and the locally excited guided wave. This model is used to obtain an efficient formulation of the optimization problem. Four different IWGH's were designed and fabricated in InP for light at 1550-nm wavelength. Experiments confirm that these IWGH's are capable of incoupling the incident wave and simultaneously splitting and focusing the guided wave into multiple positions in the waveguide at different distances from the IWGH.     

Polarization discrimination of coherently propagating light in turbid media

We describe the use of degree of polarization to discriminate unscattered and weakly scattered light from multiply scattered light in an optically turbid material. We use spatially resolved measurements of the degree of polarization to compare how well linearly and circularly polarized light survives in a sample. Experiments were performed on common tissue phantoms consisting of polystyrene and Intralipid microsphere suspensions and on adipose and arterial tissue. The results indicate that polarization is maintained even after unpolarized irradiance through each sample has been extinguished by several orders of magnitude. The results also show that polarized light propagation in common tissue phantoms is distinctly different from polarized light propagation in the two tissues investigated. Further, these experiments illustrate when polarization is an effective discrimination criterion and when it is not. The potential of a polarization-based discrimination scheme to image through the biological and nonbiological samples investigated here is also discussed.