Effect of fabric mounting method and backing material on bloodstain patterns of drip stains on textiles.

Textiles may provide valuable bloodstain evidence to help piece together events or activities at violent crime scenes. However, in spite of over 75 years of research, there are still difficulties encountered in many cases in the interpretation and identification of bloodstains on textiles. In this study, we dripped porcine blood onto three types of fabric (plain woven, single jersey knit, and denim) that are supported in four different ways (hard, taut, loose, and semi-hard, i.e., fabric laid on denim). These four mounting methods represent different ways in which a textile may be present when blood from a violent act lands on it. This study investigates how the fabric mounting method and backing material affect the appearance of drip stains on textiles. We found that bloodstain patterns formed on fabric lying flat on a hard surface were very different from when the same fabric was suspended loosely. We also found that bloodstains formed on the technical back of single jersey knit were vastly different from those on the technical face. Interestingly, some drip stains showed blood passing through the textile and leaving a stain behind it that resembled insect stains. By observing, recording, and describing how a blood stained textile is found or presented at the scene, the analyst may be able to better understand bloodstains and bloodstain patterns on textiles, which could be useful to confirm or refute a witness's account of how blood came to be where it was found after a bloodshed event.

Development of in vitro performance tests and evaluation of nonabsorbable monofilament sutures for cardiovascular surgery.

There have been reports suggesting that polypropylene (PP) monofilament sutures are associated with mechanical failure. To overcome this problem, a new monofilament suture made from polyvinylidene fluoride, under the trade name of Teflene, has been developed. Few studies have measured the in vitro properties of Teflene sutures, and those that have, have been limited to a few tensile properties of the straight suture such as tensile strength, elongation, and creep behavior. The in vitro performance properties of Teflene sutures were evaluated and compared with those of commercial sutures made from PP such as Prolene and Surgilene in four sizes, 2-0, 3-0, 4-0, and 5-0. The performance properties of sutures included both the physical properties of straight sutures, such as suture diameter, tensile strength, elongation, surface roughness, coefficient of friction, bending stiffness, and tissue drag, and the knot characteristics, such as knot pull strength, knot run-down, and knot security. Existing standard test methods and testing instruments were used if available to measure certain suture properties such as diameter, tensile strength, knot pull strength, and some physical properties. The other novel test methods and unique accessory devices needed to perform the tests for measuring tissue drag, knot run-down, coefficient of friction, and knot security were developed in the authors' laboratories, and the comparative results are reported for the first time. From the test results, Teflene sutures were found in general to possess equivalent characteristics to those of existing PP commercial sutures, but some differences also were observed, such as greater elongation and less knot run-down. These differences may give them a unique feel and handling performance, especially in terms of making a knot, sliding it into position, and causing less damage to adjacent tissue.

Solution dimensions of the gramicidin dimer by dynamic light scattering.

Gramicidin is thought to form dimeric helical rods in alcohol solutions. In addition, there is evidence that the rod dimensions change upon addition of potassium ions. The present work reports values for the translational and rotational diffusion coefficients of gramicidin in methanol and 95% ethanol and in these same solvents with added KSCN. Solution dimensions are calculated from the diffusion coefficients. The results suggest that gramicidin exists primarily as dimers in these solutions and that the gramicidin rod does indeed become shorter upon addition of potassium ion. These results are consistent with those obtained from X-ray studies on single crystals grown from alcohol solutions.