An assessment of the strength of knots and splices used as eye terminations in a sailing environment

Research into knots, splices and other methods of forming an eye termination has been limited, despite the fact that they are essential and strongly affect the performance of a rope. The aim of this study was to carry out a comprehensive initial assessment of the breaking strength of eye terminations commonly used in a sailing environment, thereby providing direction for further work in the field. Supports for use in a regular tensile testing machine were specially developed to allow individual testing of each sample and a realistic spread of statistical data to be obtained. Over 180 break tests were carried out on four knots (the bowline, double bowline, figure-of-eight loop and perfection loop) and two splices (three-strand eye splice and braid-on-braid splice). The factors affecting their strength were investigated. A statistical approach to the analysis of the results was adopted. The type of knot was found to have a significant effect on the strength. This same effect was seen in both types of rope construction (three-strand and braid-on-braid). Conclusions were also drawn as to the effect of splice length, eye size, manufacturer and rope diameter on the breaking strength of splices. Areas of development and further investigation were identified

Discovery of three polymorphs of 7-fluoroisatin reveals challenges in using computational crystal structure prediction as a complement to experimental screening

A combined computational and experimental polymorph search was undertaken to establish the crystal forms of 7-fluoroisatin, a simple molecule with no reported crystal structures, to evaluate the value of crystal structure prediction studies as an aid to solid form discovery. Three polymorphs were found in a manual crystallisation screen, as well as two solvates. Form I ( P2(1)/c, Z0 1), found from the majority of solvent evaporation experiments, corresponded to the most stable form in the computational search of Z0 1 structures. Form III ( P21/ a, Z0 2) is probably a metastable form, which was only found concomitantly with form I, and has the same dimeric R2 2( 8) hydrogen bonding motif as form I and the majority of the computed low energy structures. However, the most thermodynamically stable polymorph, form II ( P1 , Z0 2), has an expanded four molecule R 4 4( 18) hydrogen bonding motif, which could not have been found within the routine computational study. The computed relative energies of the three forms are not in accord with experimental results. Thus, the experimental finding of three crystalline polymorphs of 7- fluoroisatin illustrates the many challenges for computational screening to be a tool for the experimental crystal engineer, in contrast to the results for an analogous investigation of 5- fluoroisatin

Solid phases of cyclopentane: combined experimental and simulation study

The phase diagram of cyclopentane has been studied by powder neutron diffraction, providing diffraction patterns for phases I, II, and III, over a range of temperatures and pressures. The putative phase IV was not observed. The structure of the ordered phase III has been solved by single-crystal diffraction. Computational modeling reveals that there are many equienergetic ordered structures for cyclopentane within a small energy range. Molecular dynamics simulations reproduce the structures and diffraction patterns for phases I and III and also show an intermediate disordered phase, which is used to interpret phase II

Constant turnover of arachidonic acid and inhibition of a potassium current in Aplysia giant neurons

Steady-state currents at hyperpolarized membrane potentials were studied in the homologous giant neurons, LP1 and R2, of Aplysia using two-electrode voltage clamp. Nearly half of the steady-state current at voltages more hyperpolarized than −70 mV had characteristics similar to the inwardly rectifying potassium current ( I R ) described previously in Aplysia neurons. The pharmacological agents 4-bromophenacylbromide, indomethacin, and the phorbol ester, 12-O-tetradecanoyl-phorbol-13-acetate were found to modulate I R . I R was stimulated with BPB and indomethacin and inhibited with TPA. These agents altered I R by a mechanism independent of c AMP, which can also modulate I R . The effects of these modulators are consistent with their actions on arachidonic acid (AA) metabolism in Aplysia nervous system, suggesting AA may constitutively inhibit I R . When ganglia were perfused for 12 hr with medium containing BSA to absorb extracellular fatty acids, I R was increased nearly twofold. This increase was partially inhibited by addition of AA to the perfusion medium, and completely inhibited by pretreatment of ganglia with BPB. Although no direct effect of shortterm exposure to exogenous AA was observed, long term exposure to exogenous AA and several other unsaturated fatty acids was accompanied by a decrease in I R .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48022/1/232_2005_Article_BF01868465.pd