There is a risk of contamination of surgical instruments by nfectious protein residues, in particular, prions which are the agents for Creutzfeldt-Jakob Disease in humans. They are exceptionally resistant to conventional sterilization, therefore it is important to detect their presence as contaminants so that alternative cleaning procedures can be applied. We describe the development of an optimized detection system for fluorescently labelled protein, suitable for in-hospital use. We show that under optimum conditions the technique can detect ~100 zeptomoles/mm2 with an area scan speed of ~20 cm2/s and for using the system to detect other agents of biomedical interest. A theoretical analysis and experimental measurements will be discussed.
In the case of chemical accidents, terrorist attacks, or war, hazardous compounds may be released into the atmosphere. Remote sensing by Fourier-transform infrared spectrometry allows identification and quantification of these hazardous clouds. The output of current standoff detection systems is a yes/no decision by an automatic identification algorithm that analyses the measured spectrum. The interpretation of the measured spectrum by the operator is complicated and thus this task requires an expert. Even if a scanning system is used for surveillance of a large area the operator is dependent on the decision of the algorithm. In contrast to that, imaging systems allow automatic identification but also simple interpretation of the result, the image of the cloud. Therefore, an imaging spectrometer, the scanning infrared gas imaging system (SIGIS) has been developed. The system is based on an interferometer with a single detector element (Bruker OPAG 22) in combination with a telescope and a synchronised scanning mirror. The results of the analyses of the spectra are displayed by an overlay of a false colour image, the "chemical cloud image", on a video image. In this work, the first application of the system as chemical warfare agent identification and imaging system is described. The system, the data analysis method, and results of measurements of chemical warfare agents are presented.
Prion proteins are the infectious agents that cause Creutzfeldt-Jakob Disease (CJD) in humans. These proteins are particularly resistant to normal sterilization procedures, and the theoretical risk of prion transmission via surgical instruments is of current public and professional concern. We are currently investigating fluorescence methods for the detection of proteins on surfaces, with a view to developing an optical-fiber-based system for routine, online monitoring of residual protein contamination on surgical instruments, in hospital sterilization departments. This paper presents preliminary results on the detection of femtomole amounts of fluorescently labelled protein on surgical steel and discusses some of the problems involved in the detection of fluorescence from metal samples.
This is an overview of the work carried out in the UK on the stand-off detection of liquid contamination. The UK uses a two-stage concept employing LWIR (long wave infrared) reflectance imaging for location followed by Laser Induced Vapour Emission (LIVE) (patent pending) for identification of the material.
Research has been conducted into IR reflectance imaging, using a HgCdTe starring array and broad band source. 2-5mm diameter contaminant droplets were resolved at distances of 5.5 m on both painted plates and asphalt.
Short distances LIVE experiments using CW agents produced characteristic LWIR emission spectra. These spectra show clear differences between VX, GD and HD as well as backgrounds such as oil and water. Droplets were found to vaporise more efficiently from less absorbent surfaces such as metal and asphalt. A pyroprobe (a rapidly heating probe) was used to flash heat 20 μl droplets of HD, which was detected at 1 metre in a previous version of the experiment.
Longer distance experiments were successfully carried out using smaller amounts of simulant at distances of 18 m. This suggests identification of agent at 20 metres should be trivial providing the rapid heating and generation of hot vapour by remote means is successful. Further, the method is rapid: time resolved studies using a spectroradiometer capable of producing 20 spectra/second shows that 1 second data acquisition is sufficient.
A prototype optical system has been constructed that is chromatically-corrected from the deep ultraviolet (UV) to the far red (200-700nm), facilitating reliable and straightforward sample positioning, as required for quantitative resonance Raman spectroscopy (RRS). The collection side is fully achromatic, whilst the illumination side requires minimal user intervention. Results are presented that demonstrate the axial and spatial imaging performance of the instrument. Spectra illustrate the application of RRS for selective enhancement of analytes in low concentration. Variations in enhancement factor and spectral signature as a function of excitation wavelength are demonstrated. The results illustrate the need for well-characterized achromatic optics when carrying out quantitative investigation using a tuneable UV source laser. A UV-sensitive video-rate CCD is also incorporated into the optical scheme, enabling limited operation as a deep UV microscope. An imaging resolution of approximately 7 micrometers has been demonstrated.
Hot stamping foils are used in the printing industry to achieve metallic effects on packaging, pseudo-holographic images for security applications, and other products. The performance of the foil in the stamping process is in part determined by the thickness of the release coating on the carrier foil. This coating is too thin (approximately 10nm) for successful application of conventional measurement methods. We describe a fluorescence-based optical technique to measure the thickness of this release coating on-line. A fluorescent rhodamine dye added to the release coating allows excitation and detection in the visible part of the spectrum. Multimode optical fibre is used for excitation beam delivery and signal collection from a probe head situated on the coating machine. We outline the system calibration and show some representative results form industrial trials.
Stimulated blue light emission has now been produced via electrical injection through a p-n junction using MBE grown II-VI wide bandgap semiconductors. This is not yet possible using the MOVPE technique, due to the somewhat unsuccessful realization of p-type doping of ZnSe. Microgun pumped lasers (where injection is achieved using an array of microtips as an electron gun) could be an alternative solution, but requires structures of high crystalline quality based on ZnSe/ZnCdSe. In this perspective, we have studied the MOVPE growth of ZnSe layers and ZnCdSe alloys and ZnCdSe based heterostructures using two different zinc precursor adducts: triethylamine-dimethylzinc (TEA:DMZ) and tetramethylmethylenediamine dimethylzinc (TMMD:DMZ). The growth conditions have been investigated and the solid composition versus gas phase composition has been studied for both adducts. The structural properties of ZnSe layers below the critical thickness have been studied versus the initial growth conditions and optimal growth conditions are proposed. Particular attention has been devoted to the investigation of the spectroscopic properties of the heterostuctures in view of the characterization of the abruptness of the heterointerfaces. Photoluminescence, reflectance and photoreflectance experiments will be presented.