Dirty Surfaces Research Articles

Poststaining sections for electron microscopy.

“Dirt” on electron microscopic sections can generally be avoided by the simple strategem of preventing dry sections from coming in contract with any solution with a dirty surface layer. Wet sections can be pushed through the surface layer of such solutions without ill effect. The first and last solutions to touch a section must be dean, preferably distilled water from a plastic wash bottle.Mention of a trademark name, proprietary product, or specific equipment does not constitute a guarantee or warranty by the USDA, nor does it imply its approval to the exclurion of other products that may also be suitable.

Polygonization of KI surfaces by photon irradiation

Abstract Surface features are reported on KI after irradiation with ultra-violet light. The mechanism proposed to explain these features involves the three different sputtering rates which occur at the pure crystal surface, a dirty surface and a region of high dislocation density. This model differs from an earlier one proposed by Ag[acaron]rbiceanu and Teodorescu following electron irradiation although both types of experiment produced identical features.

Experiments on the Kapitza Resistance

The Kapitza resistances of samples of copper, gold, tungsten, single-crystal lithium fluoride, and single-crystal silicon have been measured in the temperature range from 1.25 to 2.10\ifmmode^\circ\else\textdegree\fi{}K. We find that a clean copper surface prepared by machining under liquid helium exhibits a Kapitza resistance whose magnitude and temperature dependence are considerably greater than that which a dirty copper surface exhibits. The Kapitza resistances which these samples exhibited can be represented by a power law as follows: Au, $8{T}^{\ensuremath{-}3}$; LiF, $23{T}^{\ensuremath{-}3.75}$; Cu (clean), $19{T}^{\ensuremath{-}3.6}$; Si (unetched, 7 dislocations/${\mathrm{cm}}^{2}$), $21{T}^{\ensuremath{-}3.2}$; Cu (dirty), $7{T}^{\ensuremath{-}2.6}$; Si (etched, 7 dislocations/${\mathrm{cm}}^{2}$), $35{T}^{\ensuremath{-}4.15}$; W, $39{T}^{3.5}$; Si (etched, 800 dislocations/${\mathrm{cm}}^{2}$), $35{T}^{\ensuremath{-}4.15}$ (units are deg ${\mathrm{W}}^{\ensuremath{-}1}$ ${\mathrm{cm}}^{2}$). The interfacial surface of the lithium fluoride crystal was a (100) cleavage plane. The interfacial surfaces of the silicon crystals were (111) planes which were ground, polished, and in some cases, etched. We have considered these results in relation to the theories of Khalatnikov, Little, and a modification of the Khalatnikov theory by Challis, Dransfeld, and Wilks. These theories failed to predict both the absolute magnitude and temperature dependence of the Kapitza resistances and the relative magnitude of the resistances for different samples. In addition, we have found no evidence in our experiments on cleaned copper of the mechanism proposed by Bloch involving the conduction electrons.

A Technique for the Removal of Gunpowder Tattoos

The explosion of gunpowder in proximity to exposed skin surfaces can result in the ingraining of numerous pigmented particles in the dermis. The cosmetic defect of such tattooing, if extensive, can be great. Similar particulate matter embedded in the skin following abrasive contact of skin areas with hard, dirty surfaces can be removed by brushing the anesthetized wound with a stiff brush. However, gunpowder tattooing, because of its depth in and intimate adherence to the dermis, can be completely resistant to such brushing, as well as to other direct methods of removal. In the course of treating a case of extensive gunpowder tattooing of the face, a technique for removal of the embedded particles was evolved. This technique facilitated the removal of more than 600 separate conglomerations of pigmented matter from the forehead, eyelids, nose, cheeks, and ears in a reasonable period of time, with virtually no residual scarring. Because

1—THE EFFECT OF ANTI-STATIC AGENTS ON THE SOILING OF GARMENTS AND ON THE EASE OF SOIL REMOVAL DURING WASHING

A study has been made of the effect of several anti-static agents on the soiling of fabrics soiled both artificially and in wear. It is concluded that electrostatic effects may be responsible for approximately half the total soiling observed on women's waist slips, made from fibres of high electrical resistance, but that electrostatic soiling is negligible on women's cardigans, which soil more by contact with dirty surfaces than by any other mechanism. Results are also given of the effect of some anti-static agents on the ease with which soil may be removed from fabrics during washing.

H1−Production by Hydrogen Positive Ion Bombardment of a Tungsten Surface

A study of the energy distribution of the negative ions is described. One-kilovolt ions are used. The double mass spectrograph used allows analysis of both the incoming positive- and outgoing negative-ion beams. Two peaks are studied: a low-energy peak of negative hydrogen ions created by the bombardment of a dirty surface by an assortment of positive ions, and a high-energy peak of negative hydrogen ions created only under bombardment of a surface by ${\mathrm{H}}_{2}^{+}$ and ${\mathrm{H}}_{1}^{+}$. The height of the low-energy peak is found to be proportional to the amount of hydrogen on the surface. The curve has a peak three volts wide at its half-maximum, and a tail 25 volts long on the high self-energy side. The high-energy peak ranges from zero self-energy to a value resulting from a head-on collision between a proton in the incoming ion beam and one of the atoms in the surface. This curve is flat over its whole-energy range, dropping to zero at the low self-energy end independent of incident ion energy. On a clean surface the shape of this curve is independent of target temperature.The shape of the high-energy curve is compared with curves predicted by a random walk-collision theory and a theory based on the loss and gain, due to scattering, of particles in velocity groups. The shape of the low-energy curve is compared with curves predicted by a theory of thermal desorption of ions from a surface coupled with a mechanism for neutralization of ions as they leave the surface.

Enzymatic debridement with bovine fibrinolysin

Abstract Bovine fibrinolysin, alone or in combination with desoxyribonuclease, appears to be of value in the enzymatic debridement of ulcerating wounds. This agent achieved more rapid and frequently more effective superficial debridement of a significant proportion of ulcerating surfaces which had failed to respond satisfactorily to other forms of local care. This is not a miracle drug, but it can be considered a useful adjunct in the preparation of a dirty or infected ulcerative surface for grafting, secondary closure or spontaneous epithelialization.

Enzymatic débridement with bovine fibrinolysin

Bovine fibrinolysin, alone or in combination with desoxyribonuclease, appears to be of value in the enzymatic débridement of ulcerating wounds. This agent achieved more rapid and frequently more effective superficial débridement of a significant proportion of ulcerating surfaces which had failed to respond satisfactorily to other forms of local care. This is not a miracle drug, but it can be considered a useful adjunct in the preparation of a dirty or infected ulcerative surface for grafting, secondary closure or spontaneous epithelialization.

Heat Transfer in Nucleate Boiling : III. Effect of Pressure

In the previous report an equation of nucleate boiling heat transfer was proposed, but the equation can be applied only to the clean smooth heating surface. This equation must be corrected by means of foamability for the dirty or roughened surface, and the coefficient in the corrected equation plays similarly to the emissivity in the radiative heat transfer. Further, when the experimental results under a pressure higher or lower than the atmospheric pressure are correlated by this new equation, the experimental points are separated according with the magnitudes of pressure. In this case the pressure ratio needs to be taken into consideration. Lastly, the correlating equation which is applied to all cases in nucleate boiling heat transfer, becomes as follows : [numerical formula] where fζ≡ζ/ζs=foamability, fp≡p/ps=pressure ratio, ζ=coefficient of foaming ability for any combination of surface and liquid, ζs=coefficient of foaming ability for the combination of clean smooth surface and pure liquid, ps=atmospheric pressure, p=any pressure, and X and Y=number of no dimension mentioned in the previous report.

Emission of Secondary Electrons from Nickel and Molybdenum by Neutral Atoms of Mercury and Potassium

Investigations have been carried out on the emission of secondary electrons from N1 and Mo produced by high speed neutral atoms of mercury and potassium. The mercury particles were produced by neutralizing a homogeneous beam of accelerated ions from a hot-cathode mercury arc on the walls of a narrow nickel canal which they strike at grazing incidence. The neutral atoms of potassium were produced by passing a beam of fast ions of definite velocities through vapours of potassium where they are neutralized by electron exchange with neutral K atoms. It is observed that the secondary emission rises with the number and the energy of the particles and that the energy distribution among the secondary electrons is always Maxwellian, suggesting that the emission is probably due to intense local heating. The effective temperatures of the target have been calculated in typical conditions. It is also shown that the targets scatter neutral atoms, dirty surfaces scatter more Hg atoms than clean ones but the reverse is the case with K particles.

A quantum mechanical theory of energy exchanges between inert gas atoms and a solid surface

The interaction between gas atoms and solid surfaces has been studied experimentally for many years. The first detailed study of the nature of this interaction was perhaps due to Knudsen, who in his classical researches introduced the idea of the accommodation coefficients for energy or momentum exchanges between gas atoms and a solid surface, when the gas atoms and the solid are at different temperatures or possess different mass motions. Knudsen and other investigators have given numerical values for these accommodation coefficients for various gases and solid surfaces, which seem to indicate that the accommodation coefficients are never small and are often of the order unity. This means that the gas molecules before reflection accommodate themselves almost completely to equilibrium with the temperature or motion of the wall. Before the recent work of Roberts referred to below, which has inspired this paper, no special precautions had been taken in the preparation of the wall surface, and as we now know the walls used by all previous investigators must have been completely covered with at least a mono-molecular film of gas. Thus the old observations of the accommodation coefficient do not determine it under precise conditions, and find in fact a value many times larger than that found by Roberts for the energy exchanges between the gas and a clean tungsten surface. For helium and metal with a dirty surface the value of the accommodation coefficient is some 6 times as large as the true value for the clean surface. The older values of the coefficients were so large that there were apparently grave difficulties in the way of any simple theory, but this is so no longer.