A method is described for substituting gold for osmium as a marker in the unlabeled antibody technique. The gold marker can be detected in the light or electron microscope. The gold-labeled reaction product can be detected in lower concentrations than osmium and can be used as the basis for quantitating antigen concentrations in cells and tissues with the scanning electron microscope and energy dispersive x-ray analysis.

It is generally conceded that, under ideal circumstances, the best source of information regarding the sequence of events surrounding a vehicular accident lies in accurate, complete, and absolutely reliable eyewitness accounts. When, however, as is most often the case, eyewitnesses are missing or the information which they provide is incomplete or conflicting, it is necessary to rely upon data derived from the evaluation of physical evidence recovered from the accident scene and from the vehicles themselves. Evidence of this kind is likely to include glass, paint, soil, fractured metal surfaces, and, frequently overlooked, headlight and taillight filaments, the microscopic examination of which provides information relating to the operating condition of the vehicles' headlights and taillights before, during, and after the accident.

A co-operative investigation was made by a task group of ASTM Committee E-24 Subcommittee II to correlate the microfractography and macrofractography of notch tension specimens of 4340 steel heat treated to 8 strength levels. Selected testing temperatures provided fractures with macroscopic topography representing the complete fracture transition of each material. The observed microscopic fracture modes were correlated with the two macroscopic zones of fracture surface configurations (fibrous and radial) and the final area of separation. Regardless of tempering temperature the fibrous zone of all materials consisted of microvoid coalescence and holes. Radial zones consisted of quasi cleavage for specimens tempered at high temperatures, and intergranular fracture with grain boundary microvoid coalescence for specimens tempered at low temperatures. Mixtures of these modes were observed in radial zones on specimens tempered at intermediate temperatures. The amount of each of these modes present in the radial zone depended on both testing and tempering temperatures. This correlation and the strong temperature dependencies become evident by the examination of fractures representing the complete macroscopic transitional appearances of sufficient materials obtained by different tempering temperatures.

Before aluminum alloys are welded, they are usually subjected to some kind of surface treatment. This may involve machining, solvent degreasing, chemical cleaning, anodizing, etc. Storage time until welding often means exposure to a variety of environmental conditions.It has long been known that weld quality depends on the condition of the surface. A systematic program was started in our laboratory (ref. 1) to investigate and characterize surfaces and the associated weld-defect potential as a function of different treatments. The characterization of surfaces includes topography, metallography, quantitative and qualitative determination of adsorption of contaminants, and the nature of the oxide layer by electron microscopy. The electron replication studies are reported herein.