Development of a Mesoscale Pulsed Discharge Helium Ionization Detector for Portable Gas Chromatography.

Miniaturization of gas chromatography (GC) instrumentation enables field detection of volatile organic compounds (VOCs) for chembio-applications such as clandestine human transport and disease diagnostics. We fabricated a mesoscale pulsed discharge helium ionization detector (micro-PDHID) for integrating with our previously described mini-GC hardware. Stainless steel electrodes fabricated by photochemical etching and electroforming facilitated rapid prototyping and enabled nesting of inter-electrode insulators for self-alignment of the detector core during assembly. The prototype was ∼10 cm(3) relative to >400 cm(3) of a commercial PDHID, but with a comparable time to sweep a VOC peak from the detector cell (170 ms and 127 ms, respectively). Electron trajectory modeling, gas flow rate, voltage bias, and GC outlet location were optimized for improving sensitivity. Despite 40-fold miniaturization, the micro-PDHID detected 18 ng of the human emanation, 3-methyl-2-hexenoic acid with <3-fold decrease in sensitivity relative to the commercial detector. The micro-PDHID was rugged and operated for 9 months without failure.

Diagnostic potential of the pulsed discharged helium ionization detector (PDHID) for pathogenic Mycobacterial volatile biomarkers.

Pathogenic Mycobacteria cause diseases in animals and humans with significant economic and societal consequences. Current methods for Mycobacterial detection relies upon time- and labor-intensive techniques such as culturing or DNA analysis. Using gas chromatography and mass spectrometry, four volatile compounds (methyl phenylacetate, methyl p-anisate, methyl nicotinate and o-phenyl anisole) were recently proposed as potential biomarkers for Mycobacteria. We demonstrate for the first time the capabilities of a field-deployable, pulsed discharge helium ionization detector (PDHID) for sensing these volatiles. We determined the analytical performance of the PDHID toward these Mycobacterial volatiles. Detector performance was moderately affected over the temperature range of 150 to 350 °C. The linear dynamic range for all four analytes exceeded three orders of magnitude. The limits of detection (LOD) and quantitation (LOQ) were calculated as 150 and 450 pg respectively, for all compounds, except methyl phenylacetate (LOD and LOQ, 90 and 270 pg, respectively). Control charts revealed that the PDHID detection system was generally stable, and deviations could be traced to common causes and excluded special causes. Grob tests and ionization potential data suggest that the PDHID is capable of detecting Mycobacterial volatiles in a complex milieu such as culture headspace or breath samples from tuberculosis patients. The diagnostic potential of the PDHID is critical to our goal of a handheld, field-deployable 'sniffer' system for biological pathogens and chemical warfare agents.

Sleep, sex, and the Web: surveying the difficult-to-reach clinical population suffering from sexsomnia.

One major advantage of Web-based research lies in its ability to reach and study people who have rare conditions of interest. Another advantage is that, due to the anonymity of the survey situation, the Internet is particularly suited for surveys on sensitive topics. Sexsomnia is a newly identified medical condition whose sufferers engage in sexual behavior during their sleep. Problematic cases are highly distressing and have forensic implications. The consensus among opinion leaders in sleep medicine is that sexsomnia may be quite common but that it often goes unreported because of shame and embarrassment. Thus, little is known about this condition's demographics and clinical features. This article reports findings from a sample analysis of 20 years of research on sexsomnia and discusses the results, strengths, and weaknesses of a recent Web-based survey conducted on the difficult-to-reach clinical population that suffers from sexsomnia.

A phenomenology of problematic sexual behavior occurring in sleep.

First-person reports of individuals' experiences of problematic "sleep sex" were collected in an Internet-based study. Qualitative analysis of 121 reports yielded 6 distinct themes: (1) fear and a lack of emotional intimacy; (2) guilt and confusion; (3) a sense of repulsion and feelings of sexual abandonment; (4) shame, disappointment, and frustration; (5) annoyance and suspicion; (6) embarrassment and a sense of "self-incrimination." Results suggest that sleep sex can elicit negative emotions and cognitions that may become a source of personal and relational distress. Clinician familiarity with problematic sleep sex may foster more effective communication with individuals presenting with such complaints.