Fugitive Slaves and Ship-jumping Sailors: The Enforcement and Survival of Coerced Labor

This article explores the relationship between the law of maritime labor and the law of slavery. In the eighteenth century, both sailors and slaves were part of a broad regime of unfree labor relations, with slaves, of course, the most oppressed. In the nineteenth century, an era otherwise supposedly devoted to the ideal of free labor, sailors and slaves instead remained unfree, subject to federal laws providing for the forced return to their toils if they deserted - the Merchant Seaman\u27s Act and the Fugitive Slave Act. Both of those statutes were deemed to be within Congress\u27 authority, despite questionable foundations for those conclusions on the face of the Constitution. Exploring the similarities and differences between the conditions and legal treatment of merchant seamen and slaves may yield important insights into the understanding of the congressional reaction to those conditions and the Supreme Court\u27s understanding of Congressional power

Dynamic wetting in metering and pre-metered roll coating

Ye

Direct forward gravure coating on unsupported web

YesThis experimental study of forward gravure coating considers the effects of operating variables on air entrainment, ribbing instabilities and the thickness of the film formed. The data show that this coating method can yield very thin films of thickness of order of 15 - 20% at most of the equivalent cell depth of a gravure roller. Air free and non ribbed stable uniform films can however only be obtained in a narrow window of operating conditions at very low substrate capillary number (CaS ~ 0.02) equivalent to substrate speeds typically less than 20m/min. The paper draws a similarity with flow features observed with smooth forward roll coating and slide coating. It is shown that the onset of ribbing and the flux distribution between the gravure roller and the substrate at the exit of the nip obey approximately the same rules as in smooth forward roll coating, whereas the onset of air entrainment actually corresponds to a low-flow limit of coatability similar to that observed in slide coating

The effect of substrate roughness on air entrainment in dip coating

YesDynamic wetting failure was observed in the simple dip coating flow with a series of substrates, which had a rough side and a comparatively smoother side. When we compared the air entrainment speeds on both sides, we found a switch in behaviour at a critical viscosity. At viscosity lower than a critical value, the rough side entrained air at lower speeds than the smooth side. Above the critical viscosity the reverse was observed, the smooth side entraining air at lower speed than the rough side. Only substrates with significant roughness showed this behaviour. Below a critical roughness, the rough side always entrained air at lower speeds than the smooth side. These results have both fundamental and practical merits. They support the hydrodynamic theory of dynamic wetting failure and imply that one can coat viscous fluids at higher speeds than normal by roughening substrates. A mechanism and a model are presented to explain dynamic wetting failure on rough surfaces

Slot Coating Minimum Film Thickness in Air and in Rarefied Helium

YesThis study assesses experimentally the role of gas viscosity in controlling the minimum film thickness in slot coating in both the slot over roll and tensioned web modes. The minimum film thickness here is defined with respect to the onset of air entrainment rather than rivulets, the reason being that rivulets are an extreme form of instabilities occurring at much higher speeds. The gas viscosity effects are simulated experimentally by encasing the coaters in a sealed gas chamber in which various gases can be admitted. An appropriate choice of two gases was used to compare performances: air at atmospheric pressure and helium at sub-ambient pressure (25mbar), which we establish has a significantly lower “thin film” viscosity than atmospheric air. A capacitance sensor was used to continuously measure the film thickness on the web, which was ramped up in speed at a fixed acceleration whilst visualizations of the film stability were recorded through a viewing port in the chamber. The data collected show clearly that by coating in rarefied helium rather that atmospheric air we can reduce the minimum film thickness or air/gas entrainment low-flow limit. We attribute this widening of the stable coating window to the enhancement of dynamic wetting that results when the thin film gas viscosity is reduced. These results have evident practical significance for slot coating, the coating method of choice in many new technological applications, but it is their fundamental merit which is new and one that should be followed with further data and theoretical underpinning

Air entrainment in angled dip coating

YesThe coating flow examined here, labelled angled dip coating, is that where a substrate enters a pool of liquid forming an angle ß with the vertical so that it intersects the liquid along a wetting line which is not perpendicular to the direction of its motion. This flow situation is distinctly different from that where the substrate, inclined in the other dimension by the so-called angle of entry ¿, intersects the liquid surface perpendicularly to its motion. Experiments were carried out with various liquids to determine the effect of ß on the substrate velocity at which air is entrained into the liquid. It was observed that as this angle departs from zero, air entrainment is delayed to higher speeds. The data show that the speed which is relevant to air entrainment is not the velocity of the substrate itself but its component normal to the wetting line. This result has important practical implications and suggests that this fundamental principle is also applicable to other coating flows

Classification and analyses of of coating flows

YesA classification of coating flows is presented to facilitate a fundamental approach to their study. Four categories are observed: free, metered, transfer and gravure coating flows. They are all limited by free surface(s) which make their analysis difficult. Various analytical approaches have been used and these are briefly reviewed in this paper

Thermocapillary pumping of discrete drops in microfabricated analysis devices

A nonmechanical pumping mechanism, thermocapillary pumping (TCP), is described for moving nanoliter- and picoliter-sized drops of liquid within microfabricated flow channels. In TCP, one end of a single drop is heated to create a surface tension difference between the ends of the drop. The induced surface tension difference causes a capillary pressure difference between the two drop ends and results in drop motion. TCP velocities of up to 20 mm/min were measured for several liquids at temperature differences between 10 and 70°C. An expression developed for TCP velocity yields predictions that agree with experimental velocities within corresponding uncertainty limits. Several techniques for assisting TCP are also suggested when contact angle hysteresis, the major factor limiting TCP velocities, is too large. These techniques include using surface treatments to reduce the contact angle hysteresis, converging channels to offset hysteresis, or an applied pressure to assist in movement.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34237/1/690450215_ftp.pd