Generalization Across Acetone Peroxide Homemade Explosives by Detection Dogs

Effective explosives detection requires dogs to generalize their response to untrained variations of targets that are related to those with which they were trained. Previous research suggests that dogs tend to be highly specific to their trained odors, and are sensitive to alterations in odor profiles. Triacetone triperoxide (TATP) is an increasingly popular homemade explosive due to the widespread accessibility of starting materials. The large variety of reagent sources and production approaches yields high variability in deployed formulations. Whether dogs trained with pure forms of TATP generalize to other variations is unknown, representing a potentially significant security gap. In the current study, we tested dogs (n = 11) previously trained to detect pure TATP with four variants: diacetone diperoxide (DADP), a homologue often created as a TATP byproduct, and three different clandestine TATP formulations designed to emulate those used by terrorists or insurgents. On average, dogs detected each untrained variant at rates equivalent to the trained TATP (ps > 0.07), with individual variability in first-trial alerts for some of the variants. Chemical analyses paralleled the canine results, showing distinct similarities and differences. For the TATP samples, the laboratory-grade was the purest sample tested and did not contain DADP or the TATP homologue that the three clandestine versions showed in their respective headspace profiles. The headspace results showed that each sample could be clearly identified as TATP, yet they showed recognizable differences due to their individual syntheses. These findings suggest that training on pure TATP may be effective for generalization to untrained variants. Further research is necessary to identify factors that influence individual variation in generalization between dogs, as well as other explosives.

Peroxide Based Organic Explosives

In recent years progressively increasing terrorist activities, which use homemade explosives; such as acetone peroxide and other cyclic organic peroxides have led to worldwide awareness by security and defense agencies. Then the development of methodologies for the detection of cyclic organic peroxides have become an urgent need. Until quite recently, most of the current technology in use for trace detection of explosives had been unable to detect these energetic compounds. Differences in physical properties between cyclic organic peroxides is the main barrier for the development of a general method for analysis and detection of the peroxide explosives. In this short review, the most relevant contributions related to preparation, characterization and detection of the most important cyclic organic peroxides have been presented. It also includes few recent investigations about the toxicity and metabolism of some peroxide explosives.

Study on the metabolites of DH-e, a Halomonas marine bacterium, against three toxic dinoflagellate species

Algicidal bacteria play an important role in mitigating harmful algal blooms (HABs). In the study, five bacterial strains were isolated from the East China Sea. One strain of algicidal bacterium, named DH-e, was found to selectively inhibit the motor ability of Prorocentrum donghaiense, Alexandrium tamarense (ATDH-47) and Karenia mikimotoi Hansen. Both 16S rDNA sequence analysis and morphological characteristics revealed that the algicidal DH-e bacterium belonged to Halomonas. Furthermore, results showed that the metabolites in the DH-e cell-free filtrate could kill algae directly, and the minimum inhibitory concentrations (MICs) of the bacterial metabolites on the cells of the three dinoflagellate species ranged from 35.0–70.0 μg/mL. Following short-term inhibitory tests, the dinoflagellates in mixed crude extract solution (0.7 mg/mL) ceased movement after 5 min. The algicidal mechanism of the metabolites was investigated through enzyme activities, including that of catalase (CAT), alkaline phosphatase (AKP), acetone peroxide (T-ATP) synthetase and nitrite reductase (NR). Results indicated that metabolites did not disrupt the energy or nutrient routes of the algae (P > 0.05), but did initiate an increase in free radicals in the algal cells, which might explain the subsequent death of sensitive algae. Thus, the metabolites of the DH-e bacterium showed promising potential for controlling HABs.