Ar g2 controlled stress rheometer

Blood samples were collected at three time points: 0 hour (at presentation to the Emergency Department), 2-6 hours and 24 hours atraumatically using a large bore needle. The initial 5mls of blood was discarded to avoid changes in the coagulation system that may be activated by injury to the blood vessel.
Fractal Analysis of clot microstructure 6.6mls of whole, unadulterated blood was transferred to the double concentric cylinder geometry on an AR-G2 controlled stress rheometer (TA Instruments, New Castle, DE, USA) at a temperature of 37 o C (±0.1 o C). The blood sample was then subjected to a shear stress at frequencies of 0.2Hz, 0.4309Hz, 0.9283Hz and 2Hz and the phase angle (δ) was measured with respect to time (s).The gel point analysis was obtained graphically from which the df can be determined as has been described previously [19] [20] [21] [22] . The relationship between df and clot mass at the gel point was assessed using a previously described computer model of random fractal aggregate growth and the relative normalised mass of the structure that is formed [23, 24] . This model of the relationship between df vs. clot mass is shown in Figure 1.

Viscosity for each formulation, before and after homogenization, was measured at 55°C. Reconstituted product at 12.5% (wt/wt) was measured at 20°C using an AR-G2 controlled stress rheometer (TA Instruments, Crawley, UK), equipped with concentric cylinder geometry in shear rate sweep mode. Samples were presheared at 500 s -1 for 1 min, followed by equilibration for 2 min. An ascending shear rate sweep was then applied from 5 to 500 s -1 over 3 min, followed by holding at 500 s -1 for 1 min. The average apparent viscosity measured at 500 s -1 was used to compare the formulations.

Oscillatory rheology tests of the hydrogels were performed with an AR-G2 controlled stress rheometer (TA Instruments), equipped with a Peltier temperature control system. A coneplate geometry of 40 mm diameter, a cone angle of 41 and a gap of 105 mm were used. Measurements were carried out at 25 1C and sample drying was prevented by using a solvent trap. Oscillation amplitude measurements were used to determine the linear viscoelastic region (LVR) of the hydrogel. Then, frequency measurements were performed within the LVR to ensure that the material response in terms of storage (G 0 ) and loss modulus (G 00 ) was independent of the strain magnitude. Data was analyzed using TRIOS software (TA Instruments, USA).