ABSTRACT
A rapid method of obtaining photoacoustic spectroscopic signals for trace amounts of surface adsorbed molecules using a nanostructured coupled resonator array is described. Explosive molecules adsorbed on a nanoporous anodic aluminum oxide cantilever, which has hexagonally ordered nanowells with diameters and well-to-well distances of 35 nm and 100 nm, respectively, are excited using pulsed infrared (IR) light with a frequency matching the common mode resonance frequency of the coupled resonator. The common mode resonance amplitudes of the coupled resonator as a function of illuminating IR wavelength present a photoacoustic IR absorption spectrum representing the chemical signatures of the adsorbed explosive molecules. In addition, the mass of the adsorbed molecules as an orthogonal signal for quantitative analysis is determined by measuring the variation of the localized, individual mode resonance frequency of a cantilever on the array. The limit of detection of the ternary mixture of explosive molecules (1:1:1 of trinitrotoluene (TNT), cyclotrimethylene trinitramine (RDX) and pentaerythritol tetranitrate (PETN)) is estimated to be ~ 100 ng cm(-2). These multi-modal signals enable us to perform quantitative and rapid chemical sensing and analysis in ambient conditions.
ABSTRACT
BACKGROUND: Full-dose prophylaxis is very effective at minimizing joint damage but is costly. Tailored prophylaxis has been proposed as a way of reducing costs while still protecting joints. OBJECTIVE: To report detailed findings in index joints of 56 subjects with severe hemophilia A entered into the Canadian Hemophilia Prophylaxis Study, and treated with tailored prophylaxis, after 13 years. METHODS: Boys with severe hemophilia A (< 2% factor) and normal joints were enrolled between the ages of 1 and 2.5 years. Initial treatment consisted of once-weekly factor infusions, with the frequency escalating in a stepwise fashion when breakthrough bleeding occurred. During the first 5 years, subjects were examined every 3 months using the modified Colorado Physical Evaluation (PE) scale; subsequently, every 6 months. The Childhood Health Assessment Questionnaire (CHAQ) was administered at each visit. RESULTS: Median age at study entry was 19 months (range 12-30 months); median follow-up was 92 months (range 2-156). The median PE score was 2, 3 and 3 at ages 3, 6 and 10 years. Persistent findings were related to swelling, muscle atrophy and loss of range of motion. The median score for each of these items (for the six index joints) was 0 at ages 3, 6 and 10 years. The median overall CHAQ score was 0 at ages 3, 6 and 10 years, indicating excellent function. CONCLUSIONS: Canadian boys treated with tailored primary prophylaxis exhibit minimal joint change on physical examination and minimal functional disability.
Subject(s)
Coagulants/administration & dosage , Factor VIII/administration & dosage , Hemarthrosis/prevention & control , Hemophilia A/drug therapy , Biomechanical Phenomena , Canada , Child , Child, Preschool , Coagulants/adverse effects , Disability Evaluation , Drug Administration Schedule , Factor VIII/adverse effects , Hemarthrosis/diagnosis , Hemarthrosis/etiology , Hemarthrosis/physiopathology , Hemophilia A/blood , Hemophilia A/complications , Hemophilia A/diagnosis , Humans , Infant , Joints/physiopathology , Kaplan-Meier Estimate , Linear Models , Male , Muscular Atrophy/etiology , Muscular Atrophy/prevention & control , Physical Examination , Range of Motion, Articular , Recombinant Proteins/administration & dosage , Severity of Illness Index , Surveys and Questionnaires , Time Factors , Treatment OutcomeABSTRACT
Despite its immediate applications, selective detection of trace quantities of surface adsorbed chemicals, such as explosives, without physically collecting the sample molecules is a challenging task. Standoff spectroscopic techniques offer an ideal method of detecting chemicals without using a sample collection step. Though standoff spectroscopic techniques are capable of providing high selectivity, their demonstrated sensitivities are poor. Here we describe standoff detection of trace quantities of surface adsorbed chemicals using two quantum cascade lasers operated simultaneously, with tunable wavelength windows that match with absorption peaks of the analytes. This standoff method is a variation of photoacoustic spectroscopy, where scattered light from the sample surface is used for exciting acoustic resonance of the detector. We demonstrate a sensitivity of 100 ng/cm(2) and a standoff detection distance of 20 m for surface adsorbed analytes such as explosives and tributyl phosphate.