Polymer packaging of I2 producing pyrotechnic biocides

ABSTRACT

Finding a straightforward counter to infectious biological agents, such as Bacillus anthracis, is of great interest. We have found that a pyrotechnic mixture of iodate salts and aluminum is highly effective at producing heat and elemental iodine, both of which are considered as effective biocides. What is required is a general method of application. This paper outlines an approach to creating sprayable pyrotechnics. Polyurethane foams (energetic and non-energetic), nitrocellulose, and glycidyl azide polymer (GAP) have been applied as binders to pyrotechnic mixtures. Heat produced upon burning these formulations was quantified by bomb calorimetry, while iodine output was quantified by ultraviolet-visible spectroscopy (UV-Vis). The nitrocellulose-pyrotechnic formulation in acetone created a sprayable matrix, which dried to paint-like consistency. While the polyurethane-pyrotechnic was also sprayable, it was dried to a rigid, flammable foam. Properly formulated, all produced significant heat and iodine even under inert atmosphere.     

Gas production from thermal decomposition of explosives: Assessing the thermal stabilities of energetic materials from gas production data

Abstract

The gas formation associated with the thermal decompositions of nineteen energetic materials was determined at three temperatures (120°C, 220°C and 320°C). Although there was considerable variability within classes, among the largest producers of gas were the nitrate esters. PETN (pentaerythritol nitrate) generated about 6.3mole gas per mole, while nitrocellulose, produced almost no gas. Second in gas production were the nitramines, followed by nitroarenes and lastly, energetic salts. NTO (5-nitro-2, 4-dihydro-3H-1, 2, 4-triazol-3-one), which does not fit into the four main classes of energetic materials, exhibited gas production (2.13 mole gas per mole NTO) comparable with some nitroarenes and the energetic salt, ammonium dinitramide (ADN). For selected compounds gas evolution data was used to construct first-order plots, from which Arrhenius parameters were determined and compared with previously reported values.     

The evolution of productivity performance on China’s dairy farms in the new millennium

China’s dairy farm structure has experienced fundamental changes across farm types. As the number of backyard farms has dramatically declined, the share of dairy cows from backyard farms has decreased by 22.4% from 2003 to 2008. However, the herd numbers of larger dairy farms have increased. In particular, the share of dairy cows has risen by 18.8% on small farms, by 22.2% on medium farms, and by 80.8% on large farms over the same period. Total factor productivity was decomposed into technical efficiency and technological change on China’s dairy farms using the stochastic production frontier framework. The estimated results indicate that patterns of productivity growth appear to have shifted in the 2000s compared with the 1990s, from generally driven by technological change to exclusively driven by technological change on backyard and small farms and uniquely driven by the improvement of technical efficiency on large farms. Tests of the econometric assumption indicate that the variations in total factor productivity growth patterns across farm types and regions are likely caused by the feed input biases and cropping production practice.     

X-band TRAPATT amplifiers

A 2-stage, class-C. X-band pulsed trapatt amplifier has been demonstrated, giving a maximum gain of 9·5 dB over a 1 dB bandwidth of 200 MHz at a centre frequency of 9.4GHz. The trapatt diodes have a silicon p+?n?n+ structure with silver integral heatsinks and gold-button heat reservoirs. Single-stage amplifiers have been operated with input pulse widths of 0·5 ?s and gains of 5 dB, with 11%3 dB bandwidths centred at 9·2 GHz.     

Constructing structural VAR models with conditional independence graphs

In this paper graphical modelling is used to select a sparse structure for a multivariate time series model of New Zealand interest rates. In particular, we consider a recursive structural vector autoregressions that can subsequently be described parsimoniously by a directed acyclic graph, which could be given a causal interpretation. A comparison between competing models is then made by considering likelihood and economic theory.     

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%.     

Backpropagation of an Image Similarity Metric for Autoassociative Neural Networks

Autoassociative Neural Networks (AANNs) are most commonly used for image data compression. The goal of an AANN for image data is to have the network output be ‘similar’ to the input. Most of the research in this area use backpropagation training with Mean-Squared Error (MSE) as the optimisation criteria. This paper presents an alternative error function called the Visual Difference Predictor (VDP) based on concepts from the human-visual system. Using the VDP as the error function provides a criteria to train an AANN more efficiently, and results in faster convergence of the weights, while producing an output image perceived to be very similar by a human observer. Received: 02 December 1998, Received in revised form: 28 June 1999, Accepted: 05 August 1999     

Explosive foil injection (EFI) pre-accelerator for electromagneticlaunchers

The use of an explosive foil injection system (EFI) for imparting an initial velocity on a projectile prior to its entering the breech of a railgun is demonstrated. This will substantially reduce the dwell time of the main arc at the breech end of the rails, which will greatly reduce the rail and dielectric ablation of the bore when compared to standing start systems. The preinjection system uses a small capacitor bank (6 kJ at 15 kV) to explode a fine nickel chrome wire and a disk of aluminum foil. The explosive energy produced is harnessed in a 99.5% pure aluminum driving plate assembly, which is free to move in the direction of the projectile only. The projectile (9.9 mm cube of Lexan) is in contact with the driving plate via a driving slug and is thus propelled along a flight tube into the breech of the main railgun. Preinjection velocities of up to 300 m/s have been obtained with a stored energy of only 2.7 kJ     

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.