The preparation and characterisation of monomeric and linked metal carbonyl clusters containing the closo-Si2Co4 pseudo-octahedral core

PhSiH3 reacts with [Co₄(CO)₁₂] at 50 °C in hydrocarbon solvents to give [(µ₄-SiPh)₂Co₄(CO)₁₁], 2c, shown by an X-ray crystal structure determination to have a pseudo-octahedral Si₂Co₄ core. Substituted aryl-silanes behaved similarly. Mixtures of PhSiH₃, H₃SiC₆H₄SiH₃ and [Co₄(CO)₁₂] in a ca. 2 1 2 ratio gave the dimeric cluster [{Co₄(µ₄-SiPh)(CO)₁₁Si}₂C₆H₄], 3a, which has the two Si₂Co₄ cores linked by a C₆H₄ group to give a rigid molecule which an X-ray structure analysis shows to be over 23 Å long. Related dimers linked by –(CH₂)₈– groups were isolated from mixtures of PhSiH₃, α ,ω-(H₃Si)₂(CH₂)₈ and [Co₄(CO)₁₂]. Electrochemical studies show the two cluster units in 3a do not interact electronically

Advantages of 3D time-of-flight range imaging cameras in machine vision applications

Machine vision using image processing of traditional intensity images is in wide spread use. In many situations environmental conditions or object colours or shades cannot be controlled, leading to difficulties in correctly processing the images and requiring complicated processing algorithms. Many of these complications can be avoided by using range image data, instead of intensity data. This is because range image data represents the physical properties of object location and shape, practically independently of object colour or shading. The advantages of range image processing are presented, along with three example applications that show how robust machine vision results can be obtained with relatively simple range image processing in real-time applications

Characterisation of Candida albicans adhesion to epithelial cells

The aims of this study were (i) to analyse an adhesin from C. albicans and (ii) to identify the epithelial cell molecule(s) to which the adhesin binds. Extracellular polymeric material (EP), composed mainly of mannoprotein, is thought to originate from the cell surface when yeasts are grown in medium containing a high concentration of galactose. Previous work has shown that this material contains a proteinaceous adhesin. More recently, a complete purification scheme for the yeast adhesin was devised (Tosh and Douglas, 1992) which made use of the findings from earlier studies on adhesion mechanisms. The purification protocol involves the stepwise treatment of EP with N-glycanase, papain, and dilute alkali followed by affinity adsorption with the trisaccharide determinant of the H (type 2) blood group antigen on inert silica beads. Adhesin purified in this way is devoid of carbohydrate, can inhibit adhesion of yeasts to buccal epithelial cells (BEC) by up to 80%, and consists of one major component as determined by reverse-phase fast protein liquid chromatography (FPLC). Purified adhesin was prepared in this study and it was found to inhibit adhesion of C. albicans GDH 2346 cells to BEC by up to 74.81%. EP was subjected to some of the treatments previously found to have an effect on its adhesion-inhibition activity, prior to analysis by reverse-phase high performance liquid chromatography (RP-HPLC). Each of the treatments produced some alteration in the HPLC profile of EP and the combined treatment of EP with all the above reagents (N-glycanase, papain, and dilute alkali) resulted in the production of a number of protein fragments. The fragments appeared to be more hydrophobic than the parent molecule. The purified adhesin was analysed further. Amino acid analysis showed that it was mainly composed of the amino acids Thr, Pro, Ala, Ser, Val, Gly, Asx and Glx, which made up around 80% of the total amino acids. No Cys was detected and there was very little Met, Phe and Arg. This composition is remarkably similar to a large number of microbial adhesins which would appear to indicate a relationship between the amino acid composition of lectin-like proteins and their function as carbohydrate binding molecules. In previous studies, the visualisation of EP and purified adhesin on SDS-PAGE proved difficult. However, in this study, an alternative approach to protein visualisation was employed. Purified adhesin was biotinylated prior to SDS-PAGE and Western blot analysis. The adhesin was then probed for using 125I-streptavidin and, after autoradiography, was seen as a strong band with a molecular mass of approximately 15.7 kDa. Its successful visualisation meant that partial amino acid sequencing could be attempted. The following sequence was obtained; Phe-Asp-Tyr-Glu-His-Val-Asp-X- Ala-Val. There was no complete match found in the protein database but the purified adhesin sequence contains an interesting motif, FDYE, that is found in a wide range of proteins from a variety of sources. The partial amino acid sequence obtained for the adhesin is most probably an internal sequence, produced as a result of enzymic cleavage by the action of papain. The second aim of this study was to identify receptors for C. albicans on buccal epithelial cells. BEC glycolipids were prepared and a glycolipid chromatogram overlay system was employed. This system has been used to characterise a number of microbial adhesin-receptor relationships. Six strains in total were examined for their ability to bind to separated glycolipids. (Abstract shortened by ProQuest.)

Calibration and control of a robot arm using a range imaging camera

Time of flight range imaging is an emerging technology that has numerous applications in machine vision. In this paper we cover the use of a commercial time of flight range imaging camera for calibrating a robotic arm. We do this by identifying retro-reflective targets attached to the arm, and centroiding on calibrated spatial data, which allows precise measurement of three dimensional target locations. The robotic arm is an inexpensive model that does not have positional feedback, so a series of movements are performed to calibrate the servos signals to the physical position of the arm. The calibration showed a good linear response between the control signal and servo angles. The calibration procedure also provided a transformation between the camera and arm coordinate systems. Inverse kinematic control was then used to position the arm. The range camera could also be used to identify objects in the scene. With the object location now known in the arm's coordinate system (transformed from the camera's coordinate system) the arm was able to move allowing it to grasp the object