ABSTRACT
A diffuse reflectance near-infrared (NIR) spectrometer was evaluated as a noninvasive alternative to breath and blood measurements for in vivo alcohol testing. A hybrid partial least squares (PLS) calibration was constructed using a combination of in vivo and in vitro spectral data. This model was subsequently evaluated for its performance in quantifying alcohol concentrations in vivo using a prospective validation study involving subjects who did not participate in the calibration. The validation study entailed induction of alcohol excursions in ten human subjects and comparison of the noninvasive NIR alcohol measurements to blood and breath alcohol measurements. Blood and breath alcohol measurements were performed at the time of each noninvasive NIR measurement (N = 372), establishing the noninvasive NIR measurement standard error relative to blood alcohol at 4.9 mg/dL (0.0049%). Assessment of the hybrid calibration model's sensitivity and selectivity provided strong evidence that the hybrid calibration yielded measurements that were both sensitive to alcohol and independent of other absorbing analytes in human tissue.
Subject(s)
Algorithms , Diagnosis, Computer-Assisted/methods , Ethanol/analysis , Ethanol/metabolism , Models, Biological , Spectrophotometry, Infrared/methods , Substance Abuse Detection/methods , Breath Tests/methods , Feasibility Studies , Humans , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
Although not common, injuries that result in death do occur in youth baseball. Specifically, in the 5- to 14-year old age group a total of 68 deaths between 1973 and 1995 have been directly attributed to impacts from baseballs to the head and chest. The purpose of this work was to determine the effect of lowering ball modulus and ball mass on the likelihood of reducing impact injury. A theoretical model, based upon the assumption of ideal elastic behavior, was used to calculate the impact response of the head. At a constant ball velocity, lowering both modulus and mass had the greatest influence in decreasing peak head acceleration, Gadd Severity Index, and Head Injury Criterion. Independently lowering the modulus or the mass decreased the impact variables and the estimates of injury, but the decreases varied with the specific impact variable and injury criterion. To study the impact response of the ball and chest, an existing viscoelastic lumped-element model of the chest was used. Lowering ball modulus and mass had various effects, e.g., lowering ball modulus did not affect peak sternal displacement, but it did decrease peak sternal velocity. These theoretical models aid in illustrating that impact response depends upon ball modulus and mass, the physical properties of the target, and the specific impact variable studied. This theoretical model suggests that a softer and lighter than traditional baseball would be the most likely ball model to minimize impact injuries because this ball consistently reduced all impact response variables studied. Since impact injury criteria for youths are presently not validated, the degree to which impact injuries may be reduced remains uncertain.
Subject(s)
Baseball/injuries , Craniocerebral Trauma/prevention & control , Models, Biological , Thoracic Injuries/prevention & control , Adolescent , Child , Elasticity , Equipment Design , HumansABSTRACT
Mechanisms by which weak electromagnetic fields may affect biological systems are of current interest because of their potential health effects. Lednev has proposed an ion parametric resonance hypothesis (Lednev, 1991, Bioelectromagnetics, 12:71-75), which predicts that when the ac, frequency of a combined dc-ac magnetic field equals the cyclotron frequency of calcium, the affinity of calcium for calcium-binding proteins such as calmodulin will be markedly affected. The present study evaluated Lednev's theory using two independent systems, each sensitive to changes in the affinity of calcium for calmodulin. One of the systems used was the calcium/calmodulin-dependent activation of myosin light chain kinase, a system similar to that previously used by Lednev. The other system monitored optical changes in the binding of a fluorescent peptide to the calcium/calmodulin complex. Each system was exposed to a 20.9 microT static field superimposed on a 20.9 microT sinusoidal field over a narrow frequency range centered at 16 Hz, the cyclotron frequency of the unhydrated calcium ion. In contrast to Lednev's predictions, no significant effect of combined dc-ac magnetic fields on calcium/calmodulin interactions was indicated in either experimental system.
