Exercise-induced respiratory muscle work: Effects on blood flow, fatigue and performance

This is the post print version of this article. The official published version can be obtained from the link below.In healthy subjects, heavy intensity endurance exercise places substantial demands on the respiratory muscles as breathing frequency, ventilation and the work of breathing rise over time. In the highly trained subject working at high absolute work rates, the ventilatory demand often causes varying degrees of expiratory flow limitation, sometimes accompanied by lung hyperinflation and, therefore, increased elastic work of breathing. Time-dependant increases in effort perceptions for both dyspnea and limb discomfort accompany these increased ventilatory demands. Similar responses to endurance exercise but at much lower exercise intensities also occur in patients with COPD and CHF. Note that these responses significantly influence exercise performance times in both health and disease. This effect was demonstrated by the marked reductions in the rate of rise of effort perceptions and the enhanced exercise performance times elicited by unloading the respiratory muscles using pressure support ventilation or proportional assist mechanical ventilation. In healthy fit subjects, unloading the inspiratory work of breathing by about one half increased performance by an average of 14% (Harms et al. 2000), and in CHF and COPD patients performance time more than doubled with respiratory muscle unloading (O’Donnell et al. 2001). Why are effort perceptions of limb discomfort markedly reduced and exercise performance increased when the respiratory muscles are unloaded? Our hypothesis is shown in Fig. 1

PMHS impact response in low and high-speed nearside impacts

Lateral impact tests were performed using seven male post-mortem human subjects (whole, unembalmed cadavers) to further characterize the response of the body, and in particular the force-deflection response of the lower abdomen, to lateral impact. All tests were performed using a dual-sled, side-impact test facility. A multi-segmented impactor was mounted on a sled that was pneumatically accelerated into a second, initially stationary sled on which a cadaver subject was seated facing perpendicular to the direction of impact. Sizes and heights of impactor segments were adjusted for each subject so that forces applied to different anatomic regions including thorax, abdomen, greater trochanter, iliac wing, and thigh could be independently measured on each cadaver. For all tests, the impactor contact surfaces were located in the same vertical plane except that the abdomen plate was offset 5.1 cm toward the subject. Each subject was first impacted on one side of the body using an initial impactor speed of 3 m/s. Following the five of these tests that did not result in injury, the contralateral side of the body was impacted at a speed of either 8 m/s or 10 m/s. The masses of the sleds and the force-deflection characteristics of the energy-absorbing material that acted as the interface between the sleds were set so that the velocity history of the impactor sled matched the average driver door velocity history produced in a series of side NCAP tests. Impactor padding was also selected so that average ATD pelvis and thorax responses from the same series of side NCAP tests were reproduced when the ATD used in these tests was impacted using the average door-velocity history. Results of these tests were used to develop force-deflection response targets for the abdomen, force history response targets for the pelvis (iliac wing and greater trochanter), the midthigh, and the thorax at each of the three impact velocities. Response targets for the lateral acceleration of the pelvis were also developed. Future work will compare side impact ATD responses to these response targets.NHTSA, Human Injury Research Divisionhttp://deepblue.lib.umich.edu/bitstream/2027.42/91957/1/102871.pd

On the estimation of temporal mileage rates

Peer reviewedPostprin

Detection and attribution of urbanization effect on flood extremes using nonstationary flood-frequency models

This study investigates whether long-term changes in observed series of high flows can be attributed to changes in land use via nonstationary flood-frequency analyses. A point process characterization of threshold exceedances is used, which allows for direct inclusion of covariates in the model; as well as a nonstationary model for block maxima series. In particular, changes in annual, winter, and summer block maxima and peaks over threshold extracted from gauged instantaneous flows records in two hydrologically similar catchments located in proximity to one another in northern England are investigated. The study catchment is characterized by large increases in urbanization levels in recent decades, while the paired control catchment has remained undeveloped during the study period (1970–2010). To avoid the potential confounding effect of natural variability, a covariate which summarizes key climatological properties is included in the flood-frequency model. A significant effect of the increasing urbanization levels on high flows is detected, in particular in the summer season. Point process models appear to be superior to block maxima models in their ability to detect the effect of the increase in urbanization levels on high flows

On nuclear matrix element uncertainties in short range 0vBB decay

The evaluation of short range contributions to neutrinoless double beta decay has been challenged due to critics of the ansatz of the nuclear matrix element calculations. We comment on the critics and uncertainties of these calculations and the effect on the derived limits.Comment: 3 pages, Latex, new arguments adde

Report on the Distribution of Dwarf Birches and Present Pollen Rain, Baffin Island, N.W.T., Canada

A distribution map for the dwarf birches is presented for the region from Frobisher Bay northward to Cumberland Peninsula. These shrubs are restricted to favourable habitats which, at the northern limit of the species (67 deg. 40 sec. N), are found on south-facing slopes above the immediate local cooling influence of the sea. Pollen studies within the zone of scattered dwarf birch indicate that pollen dispersal from these low, prostrate shrubs is minimal. Samples of moss collected beneath the bushes have 5-36% Betula pollen; whereas sites no more than 50 m away from Betula shrubs have percentages of <2%. These data will be useful in considering the Holocene and Pleistocene histories of these Low Arctic shrubs in the Eastern Canadian Arctic

Anharmonic parametric excitation in optical lattices

We study both experimentally and theoretically the losses induced by parametric excitation in far-off-resonance optical lattices. The atoms confined in a 1D sinusoidal lattice present an excitation spectrum and dynamics substantially different from those expected for a harmonic potential. We develop a model based on the actual atomic Hamiltonian in the lattice and we introduce semiempirically a broadening of the width of lattice energy bands which can physically arise from inhomogeneities and fluctuations of the lattice, and also from atomic collisions. The position and strength of the parametric resonances and the evolution of the number of trapped atoms are satisfactorily described by our model.Comment: 7 pages, 5 figure

The Construction of Double-Ended Classical Trajectories

In the present paper we describe relaxation methods for constructing double-ended classical trajectories. We illustrate our approach with an application to a model anharmonic system, the Henon-Heiles problem. Trajectories for this model exhibit a number of interesting energy-time relationships that appear to be of general use in characterizing the dynamics.Comment: (12 pages, submitted to Chemical Physics Letters. Figures are too large for convenient e-mail access. they are available via anonymous ftp on willie.chem.brown.edu and reside in the directory pub/chem-ph/9407 as the compressed tar file 9407001.tar.Z. If you have difficulty retrieving the figures, please contact J. Doll ([email protected]) for assistance