Thin, nano-porous, highly adherent layers of anodised aluminium formed on the surface of titanium alloys are being developed as coatings for metallic surgical implants. The layers are formed by anodisation of a 1-5 microm thick layer of aluminium which has been deposited on substrate material by electron beam evaporation. The surface ceramic layer so produced is alumina with 6-8 wt % phosphate ions and contains approximately 5 x 10(8) cm(-2) pores with a approximately 160 nm average diameter, running perpendicular to the surface. Mechanical testing showed the coatings' shear and tensile strength to be at least 20 and 10 MPa, respectively. Initial cell/material studies show promising cellular response to the nano-porous alumina. A normal osteoblastic growth pattern with cell number increasing from day 1 to 21 was shown, with slightly higher proliferative activity on the nano-porous alumina compared to the Thermanox control. Scanning electron microscopy (SEM) examination of the cells on the porous alumina membrane showed normal osteoblast morphology. Flattened cells with filopodia attaching to the pores and good coverage were also observed. In addition, the pore structure produced in these ceramic coatings is expected to be suitable for loading with bioactive material to enhance further their biological properties.
A new method is proposed for coating implants that produces a metal implant covered in a layer of nano-porous alumina ceramic. These layers are produced by first depositing a layer of aluminium on the implant surface and then anodising it in phosphoric acid to produce the nano-porous structure. This process results in the conversion of the aluminium to alumina containing 6-8wt% phosphate ions. The surface alumina layer is bonded to the substrate via an interfacial layer of fully dense anodised titanium oxide. Mechanical measurements have shown that the shear and tensile strength of this coating are in excess of 20MPa and 10MPa, respectively.The biological performance of nano-porous alumina material has been assessed and shown to be highly favourable, supporting normal osteoblastic activity and maintaining the osteoblastic phenotype. The filling of the nano-porous coating with bioactive material to achieve enhanced biological performance has been investigated using colloidal silica as an analogue for a Bioglass sol. The coating has been loaded with silica by dipping in colloidal silica with a pH of 5.6. Pore filling equivalent to 1.3 wt% SiO 2 in the coating as a whole has been achieved in this way.
Immobilized cells of a Citrobacter sp. can remove
heavy
metals from wastewaters by deposition of metals with
enzymatically liberated phosphate. Nickel is not
removed
effectively by this technique, but Ni2+ can be
intercalated
into cell-bound, crystalline HUO2PO4
previously deposited
enzymatically. This technique for efficient removal
of
Ni from solution has been generically termed microbially
enhanced chemisorption of heavy metals (MECHM). The
nickel uranyl phosphate deposits bound to Citrobacter
sp.
cells immobilized in polyacrylamide gel (PAG) were
analyzed using scanning transmission electron microscopy
with electron probe X-ray microanalysis (EPXMA) and
proton-induced X-ray emission analysis (PIXE). Both
methods
gave the molar ratios of nickel, uranium, and phosphorus
in the deposits as close to 1:2:2 in all analyzed parts of
the
sample. EPXMA proved that the deposits were localized
on the surface of cells inside PAG particles as well as
those immobilized on the edge. Small deposits of
nickel
uranyl phosphate were also found in PAG between the
cells, indicating the possible involvement of
extracellular
polymeric substances (EPS) in the creation of
intercellular
deposits. These findings confirm the mechanism of
MECHM
and show that this mechanism operates throughout the
immobilized cell matrix. The use of two independent
methods
of solid-state analysis in a common sample provides
validation of both techniques for the spatial and
quantitative
analysis of biomass-bound elements.
The focus in this study was to study time intensity (TI) methodology and procedures of getting the sensory panel acquainted with this technique. By means of a descriptive profiling exercise effects of altering the structure of a β‐lacto‐globulin gel, laced with banana aroma on the perception of banana flavor were obtained and a suitable attribute for TI was selected. Samples made up by protein, without any fat are not ideal for a TI study of flavor release because of the fast release of aroma. However, although the concentration of banana aroma was identical in the four groups of gels the intensity was perceived as different. This was reflected in the descriptive profiling as well as in the dynamic study. The TI study showed that it is important to minimize distractive, noncrucial information during the exercise. The assessors had different abilities to connect with the dynamic data acquisition procedure and training made the assessments more congruent. The results also indicate a relationship between the appearance of the TI‐curve and the score of the total banana aftertaste.
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