Adhesion attenuation and enhancement in aqueous solutions

When two surfaces confine water layers between them at the nanoscale, the behaviour of these confined water molecules can deviate significantly from the behaviour of bulk water, and it could reflect on the adhesion of such surfaces. This study assesses the role of confined water layers on the adhesion of hydrophilic surfaces and how sensitive this adhesion is to the presence of contaminants. Our methodology used atomic force microscopy adhesion measurements, whereby an alumina-sputtered sphere-tipped cantilever was interacted versus a flat alumina single crystal. Testing was performed under immersed conditions using (i) water, (ii) water/dimethylformamide mixtures, (iii) water/ethanol mixtures, and (iv) water/formamide mixtures. These solutions were intended to assess the influence of dielectric constant, molecule size, and the number of hydrogen bonding opportunities available to molecules upon confinement between surfaces. It was found that dilute concentrations of ethanol and formamide decreased the adhesion. In contrast, the adhesion increased in the presence of dilute concentrations of dimethylformamide. The adhesion was attenuated by in excess of two orders of magnitude for high concentrations of the organic solutes

Acknowledgements

All of us at the William Joiner Center for the Study of War and Social Consequences are extremely grateful to our friends at the Trotter Institute for the opportunity to collaborate on this issue of the Trotter Review. It seems especially appropriate that this issue is being published at the time of the tenth anniversary of the founding of the center, named after William Joiner, Jr., an African-American veteran of the Vietnam War and the university\u27s first director of Veterans\u27 Affairs who died of cancer in 1981

From a Troubled Past to an Uncertain Future: Vietnam Veterans, A Community at Risk: Five-Year Follow-Up Report on the Status of Vietnam Veterans in the Commonwealth of Massachusetts

This report on the concerns of Vietnam and Vietnam-Era veterans in Massachusetts comes at a critical moment. When the inquiry was initiated in 1988, few people anticipated the precipitous decline in the state and national economy, fewer could have foreseen the rapid sequence of events leading to American entry into another war. As the state fiscal crisis has eroded gains made by veterans over the last 20 years and military service in the Gulf has changed the lives of a new generation of Americans, it becomes all the more urgent to recognize the long-term, multi-generational consequences of war and to affirm the need for a comprehensive program on behalf of veterans. In 1992 Vietnam-Era veterans will become the majority veteran population in this country, a major constituency supporting the need for such a comprehensive program. The William Joiner Center\u27s follow-up investigation into the status of Vietnam and Vietnam-Era Veterans indicates that, far from diminishing, the physical, psychological, economic, and educational problems faced by Vietnam and Vietnam-Era veterans are becoming more acute and that in many cases these problems extend to the lives of their children

Accurate micron-scale modification of AFM cantilevers

Atomic force microscopy has provided the modern researcher with the ability to perform accurate force measurements between a probe and a surface. The data obtained can be used in the development of biosensors, surfactants, and materials with enhanced properties, to name only a few applications. The atomic force microscope (AFM) is undoubtedly suited for making repeated force measurements. Standard AFM cantilevers can be modified through the attachment of a colloid probe such as silica, and employed in the analysis of forces between surfaces. Resin-based or glass bond adhesives are suitable for probe bonding, as they are insoluble in water once set. However, such adhesives often require heating to reduce their viscosity, which makes the procedure quite difficult to carry out. The particle is usually attached to the apex of the cantilever, so that measurements can be performed with optimum force resolution. Particle attachment is traditionally carried out under an optical microscope using thin wire as a guide. However, there is no guarantee that the colloid particle has been accurately positioned on the apex of the cantilever

The Design and Implementation of a High-Speed Incremental Portable Prolog Compiler

The design and implementation of a relatively portable Prolog compiler achieving 12K LIPS on the standard benchmark is described. The compiler is incremental and uses decompilation to implement retract, clause, and listing, as well as support the needs of its four-port debugger. The system supports modules, garbage collection, database pointers, and a full range of built-ins