Lawrence J. Myers

The scientific foundation and efficacy of the use of canines as chemical detectors for explosives

This article reviews the use of dogs as chemical detectors, and the scientific foundation and available information on the reliability of explosive detector dogs, including a comparison with analytical instrumental techniques. Compositions of common military and industrial explosives are described, including relative vapor pressures of common explosives and constituent odor signature chemicals. Examples of active volatile odor signature chemicals from parent explosive chemicals are discussed as well as the need for additional studies. The specific example of odor chemicals from the high explosive composition C-4 studied by solid phase microextraction indicates that the volatile odor chemicals 2-ethyl-1-hexanol and cyclohexanone are available in the headspace; whereas, the active chemical cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX) is not. A detailed comparison between instrumental detection methods and detector dogs shows aspects for which instrumental methods have advantages, a comparable number of aspects for which detector dogs have advantages, as well as additional aspects where there are no clear advantages. Overall, detector dogs still represent the fastest, most versatile, reliable real-time explosive detection device available. Instrumental methods, while they continue to improve, generally suffer from a lack of efficient sampling systems, selectivity problems in the presence of interfering odor chemicals and limited mobility/tracking ability.

Evaluation of fatal dog bites: the view of the medical examiner and animal behaviorist

The multidisciplinary evaluation of fatal dog bites in the context of a case is discussed. This approach emphasizes detailed examination of the animals including matching of bite marks, autopsy, and canine behavioral analysis. It further provides details such as contributory medical conditions, past animal behavior and physical evidence linking the dogs to the attack. Such information is important in the legal proceedings that usually accompany these events.

Effects of steroids on the olfactory function of the dog

Twenty-four (24) mature, mixed breed, healthy dogs weighing from 14.6 kg to 27.6 kg were used to study the effects of various steroids on the olfactory function of the dog using olfactory detection threshold as an index. Two odorants were used, viz; benzaldehyde and eugenol. Of the various steroids used, only dexamethasone produced classical signs of Cushings syndrome in the dogs. However, all dogs that received either dexamethasone alone or hydrocortisone plus DOCA exhibited a significant elevation in the olfactory detection threshold for both odorants without any observable structural alteration of the olfactory tissue using light microscopy. On the other hand, neither DOCA, hydrocortisone alone, nor any of the vehicles used in the study significantly altered the olfactory function of the dogs. The results show that Cushings syndrome can be experimentally produced in dogs using exogenous steroids and that this condition diminishes the olfactory capability of the dog without producing classical signs of the disease.

CMOS implementation of a pulse-coupled neuron cell

Recent applications of pulse-coupled neural networks have demonstrated the need for a simple pulse-coupled neuron circuit which can easily be implemented in CMOS technology. The proposed cell uses a positive feedback circuit with two capacitors. One capacitor corresponds to the external sodium ion potential, and the other to the internal potassium ion potential. This cell body circuit is also used as a neural segment in an artificial axon. When linked by large resistors, these neural segments display many properties expected in a biological axon. SPICE simulations verify proposed circuit operation.

Effect of dietary fat source and exercise on odorant-detecting ability of canine athletes

Eighteen male English Pointers (2-4 years of age, 23.94+/-0.54 kg body weight) were allotted to three diet and two physical conditioning groups to evaluate the effect of level and source of dietary fat on the olfactory acuity of canine athletes subjected to treadmill exercise. Diet groups (6 dogs/diet) consisted of commercially prepared diets (minimum of 26% crude protein) containing 12% fat as beef tallow (A), 16% fat provided by equivalent amounts of beef tallow and corn oil (B), or 16% fat provided by equivalent amounts of beef tallow and coconut oil (C). This dietary formulation resulted in approximately 60% of the total fatty acid being saturated for diets A and C, while approximately 72% of the total fatty acids were unsaturated in diet B. One-half of the dogs within each dietary group were subjected to treadmill exercise 3 times per week for 30 min (8.05 km/h, 0% grade) for 12 weeks. All dogs were subjected to a submaximal exercise stress test (8.05 km/h, 10% slope for 60 min) every four weeks beginning at week 0. Olfactory acuity was measured utilizing behavioral olfactometry before and after each physical stress test. Non-conditioned (NON) dogs displayed a greater decrease (P<0.05) in olfactory acuity following exercise, while physically conditioned (EXE) dogs did not show a change from pre-test values. A diet by treatment interaction (P<0.10) was detected over the course of the study. NON dogs fed coconut oil had decreased odorant-detecting capabilities when week 4 values were compared with week 12 values. Feeding a diet that is predominately high in saturated fat may affect the odorant-detecting capabilities of working dogs. Additionally, these data indicate that utilization of a moderate physical conditioning program can assist canine athletes in maintaining olfactory acuity during periods of intense exercise.

Determination of canine olfactory thesholds using operant laboratory methods

This paper reports the results of a study using operant conditioning methods under laboratory conditions to determine the absolute threshold of dogs to an explosive compound. Testing was conducted in a behavioral laboratory setting consisting of a fully enclosed experimental chamber in which each dog worked, an olfactometer permitting the presentation of odors in precise concentrations expressed in terms of dilution of saturated vapor, and a computer that controlled all stimuli presented to the dog and recorded data. A series of daily sessions consisting of repeated trials of this procedure were conducted with 10 dogs. Throughout each session, the dilution of a saturated vapor in the air stream was systematically varied among dilutions above and below threshold, randomly alternating with clear air, until a threshold was determined. These procedures permitted the determination of absolute olfactory thresholds for a number of compounds. Data are reported regarding the variability of threshold performance across dogs for a single compound. Possible application of this testing technology to other questions are also discussed.

Dog-handler team as a detection system for explosives: a tail to be told

The dog-handler team as an explosive detection system is critically reviewed. The probable means of detection, olfaction or the sense of smell, is described to understand how sensitive and selective the dog-handler team can be. The empirical and experimental data available at this time regarding the means by which the teams are selected, trained, deployed, and maintained are presented and evaluated. The dog-handler team is recognized as a very effective system for detection of explosives with considerable potential for improvement. The need for more valid data relating to the mechanisms of detection, of training, and of selection are expressed and explained. Potential means of improving the system are proposed.