Ultrasound evaluation of mechanical injury of bovine knee articular cartilage under arthroscopic control

A local cartilage injury can trigger development of posttraumatic osteoarthritis (OA). Surgical methods have been developed for repairing cartilage injuries. Objective and sensitive methods are needed for planning an optimal surgery as well as for monitoring the surgical outcome. In this laboratory study, the feasibility of an arthroscopic ultrasound technique for diagnosing cartilage injuries was investigated. In bovine knees (n = 7) articular cartilage in the central patella and femoral sulcus was mechanically degraded with a steel brush modified for use under arthroscopic control. Subsequently, mechanically degraded and intact adjacent tissue was imaged with a high frequency (40 MHz) intravascular ultrasound device operated under arthroscopic guidance. After opening the knee joint, mechanical indentation measurements were also conducted with an arthroscopic device at each predefined anatomical site. Finally, cylindrical osteochondral samples were extracted from the measurement sites and prepared for histological analysis. Quantitative parameters, i.e., reflection coefficient (R), integrated reflection coefficient (IRC), apparent integrated backscattering (AIB), and ultrasound roughness index (URI) were calculated from the ultrasound signals. The reproducibilities (sCV %) of the measurements of ultrasound parameters were variable (3.7% to 26.1%). Reflection and roughness parameters were significantly different between mechanically degraded and adjacent intact tissue (p < 0.05). Surface fibrillation of mechanically degraded tissue could be visualized in ultrasound images. Furthermore, R and IRC correlated significantly with the indentation stiffness. The present results are encouraging; however, further technical development of the arthroscopic ultrasound technique is needed for evaluation of the integrity of human articular cartilage in vivo.     

Additive colour mixing by surface relief gratings utilizing the power spectrum of a fluorescent lamp

Additive colour mixing produced by diffractive grating structures is studied. The gratings produce almost monochromatic primary colours to a selected viewing angle, providing thus a very large colour gamut. The colours inside the gamut are obtained by additive colour mixing in the reflected diffraction order. The amount of a single primary in the additive colour mixing within one colour pixel is determined by the area fraction of the corresponding grating. We demonstrated the concept by fabricating samples which appear white at 30° viewing angle when illuminated by 4000?K fluorescent lamp.     

Treatment of PAH‐contaminated soil by combination of Fenton's reaction and biodegradation

A combination of modified Fenton and biological treatment was used to remove polycyclic aromatic hydrocarbons (PAHs) from creosote oil‐contaminated soil. After modified Fenton reaction the toxicity of column leachate and soil to Vibrio fischeri increased. The number of intact bacterial cells and utilisation of PAHs in PAH utilisation microplate assay decreased after modified Fenton reaction. However, bacteria in chemically treated soil utilised PAHs without addition of other carbon sources. The activity of extracellular esterases increased during incubation of modified Fenton‐treated soil. PAH removal in combined chemical oxidation and incubation (43–59%) was higher than in incubation alone (22–30%). Residual H₂O₂ in soil allowed chemical oxidation of PAHs during incubation. Copyright © 2006 Society of Chemical Industry     

Microbial growth control in water hydraulic systems by conventional filtration

As a service to readers who understand German, French or Spanish better than English, the abstract of the research article in this issue follows in these languages.     

Improving the storage stability of Bifidobacterium breve in low pH fruit juice

Bifidobacterial food applications are limited since bifidobacteria are sensitive to e.g. acidic conditions prevalent in many food matrices. The aim of the present study was to investigate whether a low pH selection step alone or combined to UV mutagenesis could improve the viability of an acid sensitive Bifidobacterium strain, B. breve 99, in low pH food matrices. Furthermore, the potential of carriers and an oat fibre preparation to further improve the stability was studied. The best performing low pH tolerant variants in the present study were generated by UV-mutagenesis with 70-700 μJ/cm² followed by incubation in growth medium at pH 4.5. The most promising variants regarding the low pH tolerance showed, in repeated tests with cells grown without pH control, about one Log-value better survival in pH 3.8 fruit juice after one week storage at 4 °C compared to wild-type B. breve 99. Cells grown with pH control, PDX formulated and then frozen showed poorer viability in low pH fruit juice than cells grown with no pH control. For frozen concentrates pH 3.8 was too stressful and no or small differences between the variants and the wild-type strain were seen. The differences detected at pH 3.8 with the cells grown without pH control were also seen with the frozen concentrates at pH 4.5. Some improvement in the stability could be achieved by using a combination of trehalose, vitamin C and PDX as a freezing carrier material, whereas a significant improvement in the stability was seen when oat fibre was added into the fruit juice together with the frozen cells. Due to the initial very poor fruit juice tolerance of B. breve 99 the obtained improvement in the stability was not enough for commercial applications. However, the same methods could be applied to initially better performing strains to further improve their stability in the fruit juice.     

White LED light coupling into light guides with diffraction gratings

Radial diffractive gratings are used to couple light of a white LED into a light guide. Theoretical coupling efficiencies are evaluated with rigorous diffraction theory in a pure conical mounting. It is shown that when the refractive index of the grating increases from 1.46 to 2.05 the incoupling efficiency increases from 42% to 63%. Also, with the increasing refractive index the incoupling efficiency is shown to become more nearly uniform over the visible spectrum. Experimental results for the incoupled efficiencies and the color coordinates of the incoupled spectra are introduced for refractive indices n=1.46 and n=1.56.     

Occurrence of bacteria in industrial fluid power systems

Water hydraulic systems use water as a pressure medium to minimize the adverse environmental impacts of oil-using hydraulics. Microbial growth in the systems may restrict the applicability of this technology. In this work, occurrence of bacteria in three different full-scale water hydraulic applications operating in different industries was studied. Bacteria were found from different parts of diesel engine direct water injection (DWI) systems in the range of 1.8×10⁵–1.0×10⁷ cells/ml. Filters designed for removal of mechanical particles released bacteria and particles into the pressure medium indicating that a more frequent change of filters was needed or better filters for microbial control should be developed. The microbiological quality of the pressure medium in the DWI systems did not significantly change during the hydraulic circuit indicating suitability for long-term operation. The DWI studies showed that tap water quality is sufficient to ensure the long-term operation of full-scale water hydraulic applications. The microbiological quality of the pressure medium in a nuclear power plant remained stable (1.4–2.1×10⁵ cells/ml) over long-term operation. The results confirmed that water hydraulics, with demineralized water as a pressure medium, can be used in such demanding applications as nuclear power plants. In the pressure medium of the hydraulic system of a wood processing plant, microbial growth resulted in malfunction. Bacteria should be controlled by a better quality pressure medium rather than the use of a biocide. Electronic Publication     

Diffraction of conic and Gaussian beams by a spiral phase plate

An analytical expression for the spatial spectrum of the conic wave diffracted by a spiral phase plate (SPP) with arbitrary integer singularity of order n is obtained. Conic wave diffraction by the SPP is equivalent to plane-wave diffraction by a helical axicon. A comparison of the conic wave and Gaussian beam diffraction on a SPP is made. It is shown that in both cases a light ring is formed, with the intensity function growing in proportion to rho(2n) at small values of radial variable rho and decreasing as n(2)rho(-4) at large rho. By use of direct e-beam writing on the resist, a 32 level SPP of the 2nd order and diameter 5 mm is manufactured. By use of this SPP, a He-Ne laser beam is transformed into a beam with phase singularity and ringlike intensity distribution. A four-order binary diffractive optical element (DOE) with its transmittance proportional to a linear superposition of four angular harmonics is also manufactured. With this DOE, simultaneous optical trapping of several polystyrene beads of diameter 5 microm is performed.