Effect of Surface Morphology on Crack Growth at a Sol-Gel Reinforced Epoxy/Aluminum Interface

The Boeing sol-gel conversion coating (Boegel-EPII), derived from an acid-catalyzed aqueous solution of organofunctional silane and zirconium alkoxide precursors, is being used as an adhesion promoter for adhesive bonding and painting applications in the aerospace industry. A unique advantage of the sol-gel process is that strong and durable bonds are produced without the hazardous chemical usage and rinse-water requirements of conventional anodizing or etching processes. In this study, a fracture mechanics method was used to investigate the adhesion properties of sol-gel-reinforced epoxy/aluminum joints. The Hugh Brown asymmetric double cantilever beam (ADCB) wedge test was employed, which allowed the measurements of the critical energy-release rate, subcritical crack-growth kinetics, and threshold energy-release rate on a single sample in a reasonably short period of time. These experiments were carried out with aluminum substrates on which the surface morphology was systematically varied by polishing, sanding, grit-blasting, and chemical etching. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to identify the locus of failure. The surface morphology of the substrates was characterized with SEM, optical profilometry, and spreading kinetics. The macrorough structures drive the crack to within a thin epoxy layer close to the polymer/metal interface, which enhances the initial strength of the sol-gel-reinforced interface. The microroughness of the substrate is, however, more effective than the macroroughness in enhancing the durability. Lastly, an attempt has been made to correlate the energy-release rate with the fractal dimension for sol-gel-reinforced joints with macrorough substrates.     

Local-scale analysis of carbon mitigation strategies: Tompkins County,New York,USA

The costs and potential for several carbon mitigation options were analyzed for Tompkins County, NY, within several categories: terrestrial carbon sequestration, local power generation, transportation, and energy end-use efficiency. The total county emissions are about 340 Gg C/year, with current biomass sequestration rates of about 121 Gg C/year. The potential for mitigation with the options examined, assuming full market penetration, amounts to at least 234 Gg C/year (69%), with 100 Gg C/year (29%) at no net cost to the consumer. Effective carbon mitigation strategies for this county based on costs per mg carbon and maximum potential include reforestation of abandoned agricultural lands for terrestrial carbon sequestration, biomass production for residential heating and co-firing in coal power plants, changes in personal behavior related to transportation (e.g., carpooling or using public transportation), installation of numerous residential energy-efficient products and development of local wind power. The principal barriers to the implementation of these approaches are discussed and policies for overcoming these barriers are analyzed.     

A pilot study of the efficacy of residuum lodges for managing sediment delivery to impoundment reservoirs

Residuum lodges comprise small dams constructed on feeder streams immediately before they enter a reservoir, behind which ponds form, where sediment is deposited. Despite their construction on many impoundment reservoirs (IRE) and catchwaters, little research has previously investigated their efficacy at removing sediments from feeder streams. The current pilot study has, therefore, been carried out at an IRE supplying Halifax, West Yorkshire, UK, where a residuum lodge was recently cleaned out. Sediment concentrations reaching the reservoir were reduced by up to 42% although no certain impacts were noted on the other water quality variables that were measured. Moreover, it was found that the clearance operation did not result in the release of excessive quantities of sediment into the reservoir. It was estimated that the cleared residuum lodge would take 12 years to refill. A survey of other residuum lodges in the Yorkshire region showed there to be considerable differences in their remaining capacities.     

Acoustic reflex threshold and loudness discomfort level: relationships in children with profound hearing losses

Acoustic reflex thresholds (ART) and loudness discomfort levels (LDL) were obtained from 51 ears of 34 deaf children using broad band noise and pure tones. Both thresholds and levels were recorded using the psychophysical method of tracking. Results indicate that the relationship between ART and LDL is at variance with similar data for normal hearing individuals. Specifically, in over 39% of these deaf children LDL was obtained at a lower intensity than ART. Implications for hearing aid fitting with deaf children are discussed.     

When the patient wants facial cosmetic surgery

Cosmetic facial surgery can improve appearance but it cannot make everyone beautiful (or handsome) or solve all problems. The patient must be well motivated and must comprehend the limitations of the procedures. Procedures useful in providing a more youthful appearance include blepharoplasty, browlift and face-lift. Sometimes all three are indicated. Chemical face peeling is used for correction of fine skin lines.     

Neural control of ventilation in the lamprey

Tidal breathing of adult lampreys is produced by a single phase of excitation that compresses the branchial basket for exhalation. Inhalation is due to passive recoil. Motoneurons are located primarily in the ipsilateral motor nucleus of the vagus and exhibit periodic bursts of excitatory synaptic potentials from unidentified generator cells in the medulla. Respiratory discharges continue in the isolated brain and can be recorded from the vagal roots. The frequency of bursts increases with temperature in a manner roughly similar to that of intact animals. However, the discharges of the isolated brain are not very sensitive to altered pH or oxygen content in the bathing fluid. Mechanoreceptors in the gill can initiate "cough" responses and may modulate normal breathing.