Microscopic metals

Although the mechanism remains undetermined, the injection of naked DNA into skeletal muscle has demonstrated relatively high transfection efficiency. In this setting, DNA is precipitated onto the surface of microscopic metal beads (e.g., gold) and the microprojectiles are accelerated and penetrate intact tissue to several cell layers. 

Michaels, R. H., A. D. Darrow II, and R. D. Rauh. Photoelectrochemical deposition of microscopic metal film patterns on Si and GaAs. 

On the assumption that the same elementary quantum of electricity is concerned both here and in electrolysis (which can be verified approximately by experiment), we are led to the conclusion that the mass of these negative particles of electricity is about an 1830th part of that of a hydrogen atom. These carriers of negative electricity are called electrons and it can be shown, by optical and electrical experiments, that they exist as structural units in all matter. By making use of the fact that it is possible to produce on very small (ultra-microscopic) metal particles, and oil drops, a charge of only a few electrons, and to measure it, very accurate values have been found for the charge carried by an electron. Millikan found. ... 

Oil in machines carries the products of deterioration resulting from wear and mechanical failure. Analyzing the oil resident in a machine or the debris the oil carries allows predictions to be made about the state of health of the machine. The critical measurement reflecting the condition of machine wear is the number of microscopic metal wear particles that are suspended in the oil system of the machine. The spectrometric oil analysis process is a laboratory technique that uses various instruments to analyze a used oil sample from a machine. The spectrometric result is compared to a baseline level of metal found to be typically suspended in the oil under normal operating conditions. When the wear is meaningful, the sample will show high levels (in parts per million) of wear metals compared to the baseline oil sample. 

It should be noted at this point that there are three distinctly different solder balls referred to in this chapter and in publications discussing SMT. The solder sphere test refers to the ability of a volume of solder to form a ball shape due to its inherent surface tension when reflowed (melted). This ball formation is dependent on minimum oxides on the microscopic metal balls that make up the paste, the second type of solder ball. It is also dependent on the abUity of the flux to reduce the oxides that are present, as well as the ramp up of temperature during the preheat and drying phases of the reflow oven profile. Too steep a time/temperature slope can cause rapid escape of entrapped volatile solvents, resulting in expulsion of small amounts of metal, which will form undesirable solder balls of the third type, that is, small metal balls scattered around the solder joint(s) on the substrate itself rather than on the tinned metal of the joint. 

Fig. 4.2 Comparison between the cake structure obtained from a liquid formulation of Human Recombinant Interferon 02b for (a) spontaneous nucleation and (b) forced nucleation scanning electron microscope, metallized samples.

Fumes are tiny solid particles formed by heating or vaporisation, and oxidation, of a metal. These microscopic metal oxide particles then condense in the air. Fume particles are usually less than or equal to 1-2 nucrons in diameter. This size of particle is readily respirable and reaches the air sacs (alveoU) of the lungs. 

---