Long before the rise of New World slavery, West Africans were adept swimmers, divers, canoe makers, and canoeists. They lived along riverbanks, near lakes, or close to the ocean. In those waterways, ...they became proficient in diverse maritime skills, while incorporating water and aquatics into spiritual understandings of the world. Transported to the Americas, slaves carried with them these West African skills and cultural values. Indeed, according to Kevin Dawson's examination of water culture in the African diaspora, the aquatic abilities of people of African descent often surpassed those of Europeans and their descendants from the age of discovery until well into the nineteenth century.As Dawson argues, histories of slavery have largely chronicled the fields of the New World, whether tobacco, sugar, indigo, rice, or cotton. However, most plantations were located near waterways to facilitate the transportation of goods to market, and large numbers of agricultural slaves had ready access to water in which to sustain their abilities and interests. Swimming and canoeing provided respite from the monotony of agricultural bondage and brief moments of bodily privacy. In some instances, enslaved laborers exchanged their aquatic expertise for unique privileges, including wages, opportunities to work free of direct white supervision, and even in rare circumstances, freedom.Dawson builds his analysis around a discussion of African traditions and the ways in which similar traditions—swimming, diving, boat making, even surfing—emerged within African diasporic communities. Undercurrents of Power not only chronicles the experiences of enslaved maritime workers, but also traverses the waters of the Atlantic repeatedly to trace and untangle cultural and social traditions.
A boat sales receipt produces the legal effects of a valid sales contract. The receipt is a document proving the ownership of a boat on the basis of which an entry is made in the register of boats.
The performance analysis of Olympic sailor's has typically been based on race outcomes, two boat testing, and formative feedback from athletes and coaches. Sailors body-motions are thought to be a ...key factor in the up-wind performance of a sailor. However, despite the focus of a large portion of sailing literature on improving body-motions, and international rules restricting the use of them in competition, no methods have been formulated to predict the performance impact of these motions, or to measure the unsteady loadings they exert on the sailboat. A sailing-specific pose-capture method to estimate sailor loadings was developed and evaluated. StickMan uses a network of seven wireless inertial-magnetic motion trackers to measure a sailor's hiking pose and boat orientation. A human mass distribution model was used to estimate body-segment mass properties to derive the external loads sailors exert on their boat. Hiking (roll) moment estimates were evaluated for accuracy using an instrumented motion platform under sinusoidal roll motion for sequences of static and dynamic hiking poses. Hiking moments estimated using pose-capture had an average 10.0% overestimate under dynamic conditions. The estimate had excellent transient and tracked reference measurements even under explosively dynamic hiking motion spanning 1000 Nm. A global sensitivity analysis was performed on hiking moment estimates. The uncertainty for hiking poses was 712 ± 38 Nm (5.3%) which the human mass distribution model contributed up to 70 % towards. Instrumentation uncertainty, including orientation drift, was not significant for hiking poses over 8 knots of wind. A case-study was performed to demonstrate the use of the method applied to the performance analysis of roll tacks and upwind hiking moment to make initial assessments of the performance implications of a sailor's ability to perform roll tacks. GPS positions and wind sensors were used to build a simple model of how a sailor-controlled hiking moment can a↵ect boat speed. This shows the method was suitable for analysing dynamic hiking methods in terms of boat performance.
N1,N4-Di-tert-butyl-3,6-dimethyl-1,4-dihydro-1,2,4,5-tetrazine-1,4-dicarboxamide was prepared from 3,6-dimethyl-1,6-dihydro-1,2,4,5-tetrazine, and its structure was confirmed by single-crystal X-ray ...diffraction. This reaction yields the 1,4-dicarboxamide derivative rather than the 1,2-dicarboxamide derivative. The central six-member ring of the title compound has a boat conformation and therefore, is not homoaromatic.
N1,N4,3,6-Tetramethyl-N1,N4-diphenyl-1,4-dihydro-1,2,4,5-tetrazine-1,4-dicarboxamide was prepared from 3,6-dimethyl-1,6-dihydro-1,2,4,5-tetrazine, bis(trichloromethyl) carbonate and N-methylaniline. ...Its structure was confirmed by single-crystal X-ray diffraction. This reaction yields the title compound rather than N1,N2,3,6-tetramethyl-N1,N2-diphenyl-1,2-dihydro-1,2,4,5-tetrazine-1,2- dicarboxamide. The central tetrazine ring of the title compound exhibits a boat conformation and is therefore not homoaromatic.
