Hair as Forensic Evidence of Explosive Handling

Hair has the ability to assimilate a variety of chemical compounds. The analysis of hair for determining first‐hand exposure to illegal drugs is a popular forensic technique [1–6]. Molecules such as explosives can also become trapped in hair due to external exposure and detected at trace levels [7–12]. Hair analysis could prove a powerful, non‐invasive method for the detection of individual exposure to illicit explosives. Previous studies showed that in a sealed vessel with adequate headspace, military explosives such as PETN, TNT, and RDX were sorbed to human hair. These organic explosives persisted on hair even after the hair was washed with detergents or solvent [7, 8]. Such sorption was influenced by hair color, and the levels of contamination were on the order of micrograms per gram hair after thousands of hours of exposure. It was assumed that in the “real‐world” explosives would sorb to hair through the condensation of vapors or by the deposition of solid particulates. This study involved the sampling of hair from students and instructors attending field classes for handling explosives at Fort A. P. Hill, Fredericksburg, VA and Redstone Arsenal, AL. Hair was sampled using combs fitted with cheesecloth, and the cheesecloth was extracted and analyzed by GC‐ECD for PETN, TNT, and RDX. On average, 80% of the participants were contaminated with PETN, found in detonating cord, after daily field exercises. Average participant contamination with TNT and RDX in hair ranged from 30 to 50%.     

Pulse experiments on electroformed mim structures

Voltage pulses of amplitude from 0 to 10 V, width 1 μs to 10 ms and with a wide range of repetition frequencies have been applied to electroformed Al-SiO_x-Au devices and the pulsed current-voltage characteristics have been examined. The peak currents observed were up to 28 times larger than those obtained under d.c. bias conditions. It is argued that these results can be understood in terms of the filamentary model of conduction in electroformed devices but are in quantitative disagreement with the theory in its present form. Attempts to estimate the energy required for switching a device into a high impedance state were made using single 1 μs voltage pulses. These are compared with similar experiments reported in the literature. It is suggested that the present experiments yield the only unequivocal upper limit for the energy required to switch a device into a high impedance state.     

The examination of some thermosetting polymers by inelastic electron tunnelling spectroscopy

This paper first discusses the principles of Inelastic Electron Tunnelling Spectroscopy (IETS) and describes the experimental procedures needed to obtain spectra. Spectra are presented for an epoxide resin and two aliphatic amine-hardeners, and for epoxideamine mixtures both before and after a heat curing schedule. From the latter it can be seen that the normal curing reaction between amine and epoxide groups does not take place within an IETS junction. A possible reason for this is the adsoprtion of amines onto the aluminium oxide surface of the substrate.     

Ion transport diagnostics in a microsecond pulsed Grimm-type glow discharge time-of-flight mass spectrometer

A Grimm-type glow discharge ion source, operated in the microsecond pulsed mode, has been interfaced to a commercial time-of-flight mass spectrometer. Ion transport from the source to the mass spectrometer, an inherent limitation of a Grimm source and mass spectrometer combination, was evaluated. The primary discharge operating conditions found to influence transport efficiency were gas flow rate and source pressure. The configuration of the Grimm-type source also influenced ion transport, including use of a gas-directing sleeve device. The effect of transport efficiency was separated into two components: (1) total ion signal and (2) temporal resolution. The latter is an advantage afforded by use of a pulsed glow discharge source and time-of-flight spectrometer, which allows discrimination against interfering gaseous background ions by appropriate ion sampling time. Shown as an example is the identification of trace magnesium from potential background interference using an optimized source configuration based on this temporal resolution method.     

Space, time and nesting Integrated Assessment Models

Integrated Assessment Modelling in the field of air pollution has advanced greatly since the 1985 Helsinki Protocol on the reduction of Sulphur emissions and their transboundary fluxes. With subsequent protocols and increased understanding of the inter-relationships between local air quality, transboundary air pollution and climate change, a variety of spatio-temporal issues must be addressed in order to model the multi-scalar processes involved and nest Integrated Assessment Models. We describe the state-of-the-art in Integrated Assessment Modelling using a conceptual framework which locates the research activities driving integrated assessment in relation both to each other and to flows of information between activities, and identify inter-relationships with scientific and policy domains beyond the scope of the UN/ECE Convention on Long Range Transboundary Air Pollution, recognising the utility of social science in understanding the effects of policy on socio-cultural behaviours. We discuss how the issues identified are being captured by integrated assessment models, with particular focus on the treatment of non-technical pollution abatement measures, noting current developments at the micro-scale addressing the dynamics of behavioural responses to abatement policies. Finally, we identify three key challenges for issue-driven Integrated Assessment Modelling: (i) capturing the dynamics of behavioural responses to value-driven policy mechanisms designed to promote non-technical abatement measures; (ii) the development of new tools to handle the delay times, inter-dependencies and multi-pollutant effects of abatement measures; and (iii) the identification of boundaries between knowledge domains and the effective transfer of multi-disciplinary scientific and socio-cultural knowledge to an increasingly trans-disciplinary policy domain.     

Energetic Material/Polymer Interaction Studied by Atomic Force Microscopy

The interactions of energetic materials and polymers have important implications in safety, long‐term storage, and performance of explosives and explosive mixtures. Atomic force microscopy was used to investigate adhesion forces at the molecular scale of nine energetic materials, organic explosives and energetic salts, on eleven common polymers (polyethylene, polyvinylalcohol, poly(vinyl chloride), polycarbonate, polystyrene, poly(methyl methacrylate), styrene‐butadiene rubber, poly(4‐vinyl phenol), poly(2,6‐dimethylphenylene oxide), poly(2,6‐diphenyl‐p‐phenylene oxide) (Tenax®), and polytetrafluoroethylene (Teflon®)). Teflon was the least adhesive polymer to all energetic materials, while no distinct trend could be elucidated among the other polymers or energetic materials.     

Determining the Vapor Pressures of Diacetone Diperoxide (DADP) and Hexamethylene Triperoxide Diamine (HMTD)

The vapor signature of diacetone diperoxide (DADP) and hexamethylene triperoxide diamine (HMTD) were examined by a gas chromatography (GC) headspace technique over the range of 15 to 55 °C. Parallel experiments were conducted to redetermine the vapor pressures of 2,4,6‐trinitrotoluene (TNT) and triacetone triperoxide (TATP). The TNT and TATP vapor pressures were in agreement with the previously reported results. Vapor pressure of DADP was determined to be 17.7 Pa at 25 °C, which is approximately 2.6 times higher than TATP at the same temperature. The Clapeyron equation, relating vapor pressure and temperature, was LnP (Pa)=35.9−9845.1/T (K) for DADP. Heat of sublimation, calculated from the slope of the line for the Clapeyron equation, was 81.9 kJ mole⁻¹. HMTD vapor pressure was not determined due to reduced thermal stability resulting in vapor phase decomposition products.