PubMed · 12980893
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E R BALLINGER. 1952. Human experiments in subgravity and prolonged acceleration.. https://pubmed.ncbi.nlm.nih.gov/12980893/
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STUDY DESIGN: Seventeen healthy volunteers were subjected to right and left lateral impacts 5.0, 6.8, 9.2, and 16.8 m/s acceleration while positioned in a Volvo car seat with lap and shoulder seat belt restraint in laboratory setting. OBJECTIVES: The purpose of this study was to determine the effect of using a standard 3-point lap and shoulder seat belt and Volvo car seat on the response of the cervical muscles to increasing low-velocity lateral impacts. SUMMARY OF BACKGROUND DATA: A previous study of lateral impacts in a 5-point harness restraint with head and trunk in neutral posture suggests that the burden of impact is borne primarily by the splenius capitis muscle contralateral to the direction of impact. That study, however, used a nonstandard harness for automobiles, and other studies suggest that a lap-and-shoulder seat belt may increase the risk of whiplash injury. METHODS: Triaxial accelerometers recorded the acceleration of the 1) sled, 2) torso at the shoulder level, and 3) head of the participant, while bilateral electromyograms of the sternocleidomastoids, trapezii, and splenii capitis were also recorded. RESULTS: For participants experiencing a right or left lateral impact, the muscle responses increased with increasing levels of acceleration (P < 0.05). The time to onset and time to peak electromyogram for most muscles also showed a trend to progressively decrease with increasing levels of acceleration. The peak head accelerations relative to the sled ranged from 2.5 to 10.6 m/s. When the impact was a right lateral impact, at the highest sled acceleration, the left splenius capitis generated 47% of its maximal voluntary contraction (MVC), and the left trapezius also 46% of its MVC; the left and right sternocleidomastoid, right splenius capitis, and right trapezius generated 29% or less of their MVC. For the highest level of acceleration in a left lateral impact, the right splenius capitis generated 48% of its MVC and the right trapezius 57% of the MVC, the left and right sternocleidomastoid, left splenius capitis, and left trapezius generated 29% or less of their MVC. In both directions of impact, the contralateral splenius capitis and trapezius showed a statistically significant difference in the EMG response compared with other muscles (P < 0.05). For participants experiencing a frontal impact, whether straight-on, right or left anterolateral, the muscle responses increased with increasing levels of acceleration (P < 0.05). The time to onset and time to peak electromyogram for most muscles also showed a trend to progressively decrease with increasing levels of acceleration. In a straight-on frontal impact, the trapezii (TRPs) muscles showed the greatest EMG response compared with the remaining muscles (P < 0.05). CONCLUSIONS: Compared with previously reported impact studies with a 5-point harness and rigid seat, the use of a 3-point lap and shoulder seat belt with car seat does not appear to adversely affect the cervical muscle response. In very-low- and low-velocity impact experiments, seat belt and seat type may thus not be particularly relevant to cervical EMG and kinematics.
Five parkinsonian subjects with chronic bilateral stimulation of the subthalamic nucleus and five sex- and age-matched healthy controls grasped, lifted, and held an instrumented object. The grip-lift task was either performed at self-determined speed or in response to an auditory cuing signal. Parkinsonian subjects performed the task with subthalamic nucleus stimulation switched ON and OFF. In Parkinson's disease, stimulation of the subthalamic nucleus and the presentation of auditory timing cues improved akinesia of both the grasp and lift components of the task. The finding that auditory timing cues improve akinesia in the absence of subthalamic nucleus stimulation suggests that the basal ganglia are less involved in the control of movements made in response to environmental cues. However, subthalamic nucleus stimulation caused parkinsonian subjects to apply excessive grip forces, regardless of whether the movement was made under self-determined or externally guided speed conditions. This implies that subthalamic nucleus stimulation produces a generalized upregulation in the gain of all components of a movement without the subtlety of focused control that is required to normalize performance.
Exact masses of monoisotopic ions, and the relative isotopic abundances (RIAs) of ions greater in mass by 1 and 2 Da than the monoisotopic ion, are independent and complementary physical properties useful for distinguishing among elemental compositions of ions possible for a given nominal mass. Using these properties to determine elemental compositions of product ions and neutral losses increases the masses of precursor ions for which unique compositions can be determined. Compositions of the precursor ion, product ion, and neutral loss aid mass spectral interpretation and guide modest chemical literature searches for candidate standards to be obtained for confirmation of tentative compound identifications. This approach is essential for compound characterization or identification due to the absence of commercial libraries of electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) product ion spectra. For a series of 34 exact mass measurements, an orthogonal acceleration time-of-flight mass spectrometer provided 34 and 29 values accurate to within 2 and 1 mDa, respectively, for ions from eight simulated unknowns with [M+H](+) ion masses between 166 and 319 Da. Of 36 RIA measurements for +1 Da or +2 Da ions, 35 were accurate to within 20% of their predicted values (or to within 0.4 RIA % when the RIA value was less than 1%) in the absence of obvious interferences, in cases where the monoisotopic ion peak areas were at least 1.7 x 10(5) counts and the ion masses exceeded 141 Da. An ion correlation program (ICP) provided the unique and correct compositions for all but three of the 34 ions studied. Manual inspection of the data eliminated the incorrect compositions. To test the utility of the ICP for deconvoluting composite product ion spectra, all 34 ions were tested for correlation. Six of eight precursor ions were identified as such, while two were compositional subsets of others and were not properly identified. The six precursor ion compositions were still found by the ICP even though ions with masses less than 158 Da were not considered since they could no longer be correlated with a single precursor ion. Finally, two unidentified analytes were characterized, based on data published by others and using the ICP together with mass spectral interpretation.