ABSTRACT
A piezoelectric detection system consisting of an annular array is investigated for large depth of field photoacoustic imaging. In comparison to a single ring detection system, X-shaped imaging artifacts are suppressed. Sensitivity and image resolution studies are performed in simulations and in experiments and compared to a simulated spherical detector. In experiment an eight ring detection systems offers an extended depth of field over a range of 16 mm with almost constant lateral resolution.
ABSTRACT
A dual mode scanning acoustic microscope is investigated, yielding simultaneously images with optical and acoustical contrast. Short laser pulses are used to excite acoustic waves in a sample for the photoacoustic imaging mode. At the same time the pulses irradiate a conical target generating limited diffraction acoustic waves (X-waves) for large depth of field ultrasound imaging. For photoacoustic as well as for ultrasound imaging a focusing, ring shaped detector is applied. First phantom experiments demonstrate the possibility to acquire data for both imaging modes in a single scan, by separating images due to their different time of flight.
ABSTRACT
The influence of Be content on the corrosion behavior and strength of dental alloys was examined using experimental Ni-25Cr-10Mo-xBe alloys with graduated Be contents of 0, 0.6, 1.1, 1.6, and 2.1 wt.%. It became evident that the corrosion resistance is reduced even by a 0.6 wt.% Be content. Strength increases by 51% with increasing Be content, while ductility is reduced by 84%. The results revealed that, from the stand-point of corrosion resistance, Be-free Ni-Cr-Mo alloys should be preferred in clinical use.
Subject(s)
Beryllium/chemistry , Chromium Alloys/chemistry , Corrosion , Elasticity , Hardness , Microscopy, Electron, Scanning , Molybdenum/chemistry , Nickel/chemistry , Sodium Chloride/chemistry , Structure-Activity Relationship , Tensile Strength , X-Ray DiffractionSubject(s)
Dental Casting Technique , Titanium , Crowns , Dental Porcelain , Denture, Partial, Fixed , Denture, Partial, Removable , Humans , Quality ControlABSTRACT
The substance loss from four commercially available Ni-Cr-Mo and four Co-Cr-Mo alloys was examined using a solution of 0.1 mol/L lactic acid and 0.1 mol/L sodium chloride. Dissolved ions were analyzed over a 5-week period using atomic absorption spectroscopy. The results revealed a considerable range of corrosion rates among the Ni-Cr-Mo alloys, with average values after 35 days between 0.54 and 3,261 micrograms/cm2, while the distribution of values for the Co-Cr-Mo alloys was not as wide--between 0.43 and 34.9 micrograms/cm2.
