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Skin-friction results are presented for fouling-release (FR) hull coatings in the unexposed, clean condition and after dynamic exposure to diatomaceous biofilms for 3 and 6 months. The experiments were conducted in a fully developed turbulent channel flow facility spanning a wide Reynolds number range. The results show that the clean FR coatings tested were hydraulically smooth over much of the Reynolds number range. Biofilms, however, resulted in an increase in skin-friction of up to 70%. The roughness functions for the biofilm-covered surfaces did not display universal behavior, but instead varied with the percentage coverage by the biofilm. The effect of the biofilm was observed to scale with its mean thickness and the square root of the percentage coverage. A new effective roughness length scale (keff) for biofilms based on these parameters is proposed. Boundary layer similarity-law scaling is used to predict the impact of these biofilms on the required shaft power for a mid-sized naval surface combatant at cruising speed. The increase in power is estimated to be between 1.5% and 10.1% depending on the biofilm thickness and percentage coverage.

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In the present study, the overall economic impact of hull fouling on a mid-sized naval surface ship (Arleigh Burke-class destroyer DDG-51) has been analyzed. A range of costs associated with hull fouling was examined, including expenditures for fuel, hull coatings, hull coating application and removal, and hull cleaning. The results indicate that the primary cost associated with fouling is due to increased fuel consumption attributable to increased frictional drag. The costs related to hull cleaning and painting are much lower than the fuel costs. The overall cost associated with hull fouling for the Navy's present coating, cleaning, and fouling level is estimated to be $56M per year for the entire DDG-51 class or $1B over 15 years. The results of this study provide guidance as to the amount of money that can be reasonably spent for research, development, acquisition, and implementation of new technologies or management strategies to combat hull fouling.

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Since fouling-release coating systems do not prevent settlement, various methods to quantify the tenacity of adhesion of fouling organisms on these systems have been offered. One such method is the turbulent channel flow apparatus. The question remains how the results from laboratory scale tests relate to the self-cleaning of a ship coated with a fouling-release surface. This paper relates the detachment strength of low form fouling determined in the laboratory using a turbulent channel flow to the conditions necessary for detachment of these organisms in a turbulent boundary layer at ship scale. A power-law formula, the ITTC-57 formula, and a computational fluid dynamics (CFD) model are used to predict the skin-friction at ship scale. The results from all three methods show good agreement and are illustrated using turbulent channel flow data for sporelings of the green macrofouling alga Enteromorpha growing on a fouling-release coating.

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The contribution of biofilms to skin friction drag is not clearly defined, and as regulations continue to restrict the use of biocides in antifouling paints, they are likely to form a greater presence on ship hulls. This paper reviews the flow regime around a ship's hull, the basics of boundary layer structure, and the effects of rigid surface roughness on drag. A review of experimental studies of biofilms in turbulent shear flows at laboratory and ship-scale is made. The consensus of these studies shows that biofilms increase skin friction drag. Some measurements carried out in turbulent boundary layer flow using a two-component, laser Doppler velocimeter (LDV) are also presented. These results indicate an increase in skin friction for biofilms that is dependent on composition as well as thickness.

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A photoactivatable glutathione-drug conjugate (35)S-labeled-azidophenacyl-glutathione (APA-SG) was synthesized and used to identify protein(s) involved in recognition and/or transport of glutathione conjugates of electrophilic drug species. A approximately 460-kDa protein was found to be highly labeled by (35)S-labeled APA-SG in an Adriamycin-resistant HL-60 (HL-60/ADR) cell line and identified as the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) by amino acid sequence analysis, Western blot, and immunoprecipitation with specific antibodies. Binding specificity was confirmed by competition isotope dilution assays with purified proteins. A 15- to 20-fold increase in DNA-PKcs expression in the HL-60/ADR cell line was accompanied by an equivalent increase in (35)S-labeled APA-SG binding. APA-SG, along with other glutathione conjugates and analogs inhibited the DNA-PK-mediated phosphorylation of an in vitro peptide substrate in a concentration-dependent manner. Using different antibodies to immunoprecipitate the individual components of the DNA-PK complex (DNA-PKcs, Ku70, and Ku80), it was shown that APA-SG caused a destabilization of the trimeric holoenzyme complex by dissociating the catalytic subunit from the Ku heterodimer. These data suggest that the kinase-mediated signaling is inhibited when glutathione conjugates bind to DNA-PKcs and may also indicate a possible strategy for design of novel DNA-PK inhibitors.

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Field testing of non-toxic antifouling coatings has required the development of test protocols that can quantify their performance. This includes the evaluation of the biofouling communities, the measurement of biofouling adhesion using a calibrated water jet and the measurement of barnacle adhesion in shear. Data are presented for several test surfaces, and the results are discussed with respect to the coating characteristics.