Andrew J. Vreugdenhil

The application of silicon sol–gel technology to forensic blood substitute development: Mimicking aspects of whole human blood rheology

Solution-gelation chemistry has promising applications in forensic synthetic blood substitute development. This research offers a silicon-based sol-gel approach to creating stable materials that share similar rheological properties to that of whole human blood samples. Room temperature, high water content, silicon sol-gels were created using the organosilane precursors 3-glycidoxypropyltrimethoxysilane and tetraethylorthosilicate along with various concentrations of filler and pigment. Shear-thinning non-Newtonian properties were observed within most formulations of the presented materials. The effects of colloidal concentration, temperature, age and filler addition on the viscosity of the sol-gels were investigated. SEM-EDS analysis was used to identify the behavior of the fillers within the film and support their inclusion for basic bloodstain pattern simulation. A final proposed candidate sol-gel was assessed using a previously reported passive drip simulation test on a hard, dry surface and passed. This works represents encouraging development in providing safe material alternatives to using whole human blood for forensic training and research.

An Impact Velocity Device Design for Blood Spatter Pattern Generation with Considerations for High-Speed Video Analysis.

A mechanical device that uses gravitational and spring compression forces to create spatter patterns of known impact velocities is presented and discussed. The custom‐made device uses either two or four springs (k1 = 267.8 N/m, k2 = 535.5 N/m) in parallel to create seventeen reproducible impact velocities between 2.1 and 4.0 m/s. The impactor is held at several known spring extensions using an electromagnet. Trigger inputs to the high‐speed video camera allow the user to control the magnets release while capturing video footage simultaneously. A polycarbonate base is used to allow for simultaneous monitoring of the side and bottom views of the impact event. Twenty‐four patterns were created across the impact velocity range and analyzed using HemoSpat. Area of origin estimations fell within an acceptable range (ΔXav = −5.5 ± 1.9 cm, ΔYav = −2.6 ± 2.8 cm, ΔZav = +5.5 ± 3.8 cm), supporting distribution analysis for the use in research or bloodstain pattern training. This work provides a framework for those interested in developing a robust impact device.

Novel silica sol–gel passive sampler for mercury monitoring in aqueous systems

A novel passive sampler for mercury monitoring was prepared using organosilica sol-gel materials. It comprises a binding layer with thiol groups for mercury complexation and a porous diffusive layer through which mercury can diffuse and arrive at the binding layer. Our study demonstrated that this new sampler follows the principle of passive sampling. The mass of mercury accumulated in the binding layer depends linearly on the mercury concentration in solution, the sampling rate and the exposure time. A typical sol-gel sampler is characterized by a diffusive layer of 1.2 μm, in which mercury ions diffuse with a coefficient of D=0.09×10(-6) cm(2) s(-1), resulting in an uptake R(s) of 8.8 mL h(-1). The capacity for mercury uptake is approximately 0.64 μg cm(-2). Mercury diffusion and binding in the passive sampler are independent of the type of mercury-chloride complex, which potentially opens the door to use this device for mercury monitoring in a wide range of natural waters.

Investigation of Physical Effects of Acid Yellow 7® Enhancement on Dark and Non-Porous Surfaces in Impact Pattern Area of Origin Estimation

Abstract Impact patterns that are generated on dark surfaces can become camouflaged creating difficulties with conventional photographic methods that are used when estimating the area of origin. Chemical enhancement is an alternative technique that can be used to visualize these latent bloodstains. The application of Acid Yellow 7 to already fixed bloodstains provides a robust enhancement protocol which yields minimal stain distortion. Image J software was utilized to count stains, resulting in an approximate 5% increase in small stain detection post-enhancement. Area analyses also performed with Image J demonstrates that the average area of a single stain increases by a factor of approximately 1.24 post-enhancement. When using the BackTrack™ suite of programs this enlargement does not significantly affect the calculated impact angle of an enhanced bloodstain when compared to that of its original deposition (P= 0.585). As a result, the area of origin can be estimated within the accepted error of ± 7 cm from the known blood source.

The application of silicon sol–gel technology to forensic blood substitute development: Investigation of the spreading dynamics onto a paper surface

This work investigates the spreading dynamics of three candidate sol-gel solutions, of ranging viscosities, surface tensions and densities, and compares them with water and two commercial blood substitute products. Droplets were created with different sizes (10 to75μL) and impact velocities (1.4 to 6.0m/s) to strike 176gsm cardstock. Over 2200 droplets were created using the six different fluids and their final dried stain diameter was measured. Droplet spread was plotted using the Scheller and Bousfield correlation and uses effective viscosity as a parameter for non-Newtonian fluids. Comparing the results to an expected whole human blood range validated the spread of the candidate FBS sol-gel material in passive drip bloodstain pattern simulation. These findings complement the practical application of the material as a safe substitute for demonstrating droplet spread under controlled conditions on hard paper surfaces.

Three physical factors that affect the crown growth of the impact mechanism and its implications for bloodstain pattern analysis

This research uses high-speed video analysis of bloodstain impact events to investigate the influence of impact velocity, fluid depth and free-space on the characteristics of the mechanism. We focus on the changes in the crown growth over time. This work demonstrates qualitative differences in the impact mechanism under a range of impact conditions. These differences are further explained quantitatively as a function of measured crown width and height lengths over time. Fluid dynamic explanations of this growth are featured in the results and discussion. A comparison to water dynamics is reported. Our image analysis demonstrates that droplets are consistently formed at points which are different from the impactor/fluid interface and that this difference is fluid dependent. This fluid dependency demonstrates the importance of accurately modeling fluid dynamics of blood when designing and deploying blood substitutes in forensics applications.

Waterborne epoxy-thiol decorated silica sol-gel coatings: impact of crosslinking on corrosion prevention

AbstractOrganic–inorganic hybrid coatings of crosslinked epoxy and thiol silicates (TGST) were synthesized for the corrosion protection of low carbon steel via a waterborne sol-gel route. The coatings were synthesized in two stages; in the first step two separate aqueous formulations of epoxy and thiol decorated silica colloids were prepared and subsequently crosslinked in a 1:1 ratio in the second stage. The structure and rate of crosslinking was monitored using Raman spectroscopy. Formulation stability was measured based on viscosity changes and pot-life assessment. The novel material was characterized for its particle size using dynamic light scattering. Viscosity average molecular weight was calculated using Fikentscher’s equation and using polyethylene oxide molecular weights as a calibration standard. The covalently bonded epoxy-thiol silicate thin-film coating was uniform and defect free. Accelerated corrosion resistance was tested by exposing the panels to standard salt solution tests. TGST showed a 96% improvement in corrosion inhibition over the non-crosslinked formulations in a corrosive environment. The synthesis and characterization of TGST using a simple approach, revealed key synthetic parameters for generating optimized sol-gel corrosion prevention materials. Schematic representation of the crosslinking of the epoxy (TG) and thiol (ST) decorated silica colloids by the waterborne sol-gel route at room temperature to form the crosslinked TGST formulation effective for the corrosion prevention of low carbon steel substratesHighlightsCrosslinked epoxy-thiol decorated silicate coatings for corrosion prevention were synthesized.Green, non-toxic formulations were prepared via a waterborne sol-gel route at room temperature.Enhanced barrier properties showing 96% improved corrosion resistance of crosslinked coatings over the non-crosslinked formulations on low carbon steel were achieved.Coatings were smooth, defect-free, and showed easy applicability to suit dip or spray coating.The two-component coating system showed a commercially attractive pot-life.

High-speed video analysis of crown formation dynamics of controlled weapon-head impacts on to three surface types

ABSTRACT This work explores the crown formation dynamics of blunt force impact onto a thin film of sheeps blood. Three weapons – a hammer head, a simulant baseball bat, and a metal bar – were used to impact blood on fibreboard, cloth, and sponge. Impact velocity was controlled using a custom impact device. High-speed videos were collected and analyzed with motion tracking and computing software. Interestingly, crowns were not observed to form in seven out of nine trials where each weapon struck the bloodied sponge. The widths and heights where observable crowns formed were measured and ranged between 0 to 105 mm and –0.4 to 36 mm, respectively. Bloodied material type was observed to influence the size and shape of the crown; however, the weapon heads used in this study did not. Three unusual cases of rim instability were observed where droplets were sent in the opposite direction of the expanding crown. This work supports the idea that the formation dynamics of mechanisms caused by blunt force impact are complex. Observable crowns can form with a range of geometries and subsequently produce droplets that originate at points different from the contact interface between the weapon head and blood.

Design and Thermal Properties of Interpenetrating and Intercrosslinked Biosilicate Materials

Biosilicate hybrid materials represent a tremendously broad range of materials from inorganic matrices hosting small proteins (Gill und Ballesteros, J Am Chem Soc 120:8587–8598, 1998) to chitosan scaffolds with small silicate inclusions. (Silva et al., J Mater Chem 15:3952–3961, 2005) In this chapter, we will focus on the chemical interactions within a biosilicate hybrid and the effect that these interactions have on the thermal properties of the material. Broadly, we can consider biosilicate hybrids to be a material made up of both an inorganic and a bioorganic polymeric network with varying degrees of chemical interaction. These binary network materials are an interesting area of research as the nature of the two dissimilar networks can be used to temper the properties of the resulting hybrid not only by their content and their particular chemical composition but also in their degree of chemical interaction.