Identification and comparison of electrical tapes using instrumental and statistical techniques: I. Microscopic surface texture and elemental composition

Comparisons of polyvinyl chloride electrical tape typically rely upon evaluating class characteristics such as physical dimensions, surface texture, and chemical composition. Given the various techniques that are available for this purpose, a comprehensive study has been undertaken to establish an optimal analytical scheme for electrical tape comparisons. Of equal importance is the development of a quantitative means for sample discrimination. In this study, 67 rolls of black electrical tape representing 34 different nominal brands were analyzed via scanning electron microscopy and energy dispersive spectroscopy. Differences in surface roughness, calendering marks, and filler particle size were readily apparent, including between some rolls of the same nominal brand. The relative amounts of magnesium, aluminum, silicon, sulfur, lead, chlorine, antimony, calcium, titanium, and zinc varied greatly between brands and, in some cases, could be linked to the year of manufacture. For the first time, quantitative differentiation of electrical tapes was achieved through multivariate statistical techniques, with 36 classes identified within the sample population. A single-blind study was also completed where questioned tape samples were correctly associated with known exemplars. Finally, two case studies are presented where tape recovered from an improvised explosive device is compared with tape recovered from a suspect.     

Selection and Incentives in the Electoral Security‐Constituency Communication Relationship

The relative importance of selection and incentives is essential for understanding how elections structure politicians’ behavior. I investigate the relative magnitudes of these two effects in the context of US House members’ constituency communication. Consistent with previous research, I find that there is a negative cross‐sectional relationship between electoral security and the intensity of constituency communication. The negative relationship holds in a panel‐data setting where only within‐legislator variation in electoral security is used to identify the effect of electoral security on legislator behavior. Due to the likely presence of myopic voters, the impact of electoral security increases as the election approaches. Point estimates suggest that the total effect is almost entirely driven by incentives, and I am able to reject the hypothesis that the incentive effect is zero at conventional levels of statistical significance.     

Application of solvent microextraction to the analysis of amphetamines and phencyclidine in urine

A fast and simple method to detect some commonly abused illicit drugs, amphetamine, methamphetamine, 3,4-methylendioxy-amphetamine (MDA), 3,4-methylendioxy-methamphetamine (MDMA), 3,4-methylendioxy-N-ethylamphetamine (MDEA) and phencyclidine (PCP) in urine using solvent microextraction (SME) combined with gas chromatography (GC) analysis has been developed. The extraction is conducted by suspending a 2 μl drop of chloroform in a 2 ml urine sample. Following 8 min of extraction, the organic solvent is withdrawn into the syringe and injected into a GC with a pulsed discharge helium ionization detector (PDHID).The effects of different extraction solvents and times, pH and sample preparation were studied. The optimized method was capable of detecting drugs in urine at concentrations below Substance Abuse and Mental Health Services Administration (SAMHSA) established cut-off values for preliminary testing. Good linearity and reproducibility of extraction were obtained. The limits of detection were 0.5 μg/ml for amphetamine, 0.1 μg/ml for methamphetamine and MDA, 0.05 μg/ml for MDMA, 0.025 μg/ml for MDEA and 0.015 μg/ml for PCP. Relative standard deviation (R.S.D.) values ranged between 5 and 20% for the studied drugs.