8,210 research outputs found
On the genus Anchonus Schönherr in Florida (Coleoptera: Curculionidae)
Four species of Anchonus Schonherr occur in Florida: A. flol'idanus Schwarz, A. dul'yi Blatchley, A. blatchleyi Sleeper, and A. suillus (Fabricius), which is recorded from Florida and the continental United States for the first time. The species are distinguished in a key and illustrated. A lectotype is selected for A. floridanus
Reliability and reproducibility of Atlas information
We discuss the reliability and reproducibility of much of the information
contained in the Atlas of Finite Groups
Dynamic muscle quality of the plantar flexors is impaired in claudicant patients with peripheral arterial disease and associated with poorer walking endurance
Objective Peripheral arterial disease and intermittent claudication (PAD-IC) negatively affects physical activity and function. There is evidence for plantarflexor muscle dysfunction and weakness; however, the extent to which this dysfunction can be attributed to reduced muscle size or quality, or both, is not yet known. This study investigated whether in vivo plantarflexor muscle quality during static and dynamic contractions is altered by PAD-IC and whether such changes are associated with impaired walking endurance according to initial and absolute claudication distances. Methods The study recruited 22 participants, consisting of 10 healthy controls and 12 claudicant patients with occlusion of the superficial femoral artery (seven unilateral and five bilateral). Muscle quality of the combined gastrocnemius muscles during static contractions was calculated by normalizing the estimated maximal potential muscle force to the physiological cross-sectional area of the lateral and medial gastrocnemius. Muscle quality during dynamic contractions of the combined plantarflexor muscles was calculated as the ratio of peak voluntary concentric plantarflexor power and the summed volume of lateral and medial gastrocnemius. Results Dynamic muscle quality was 24% lower in the claudicating-limb and asymptomatic-limb groups compared with controls (P = .017 and P = .023). The differences were most apparent at the highest contraction velocity (180°/s). Dynamic muscle quality was associated with reduced walking endurance (R = 0.689, P = .006 and R = 0.550, P = .042 for initial and absolute claudication distance, respectively). The claudicating-limb group demonstrated a trend toward reduced static muscle quality compared with controls (22%, P = .084). The relative contribution of the soleus muscle to plantarflexion maximum voluntary contraction was significantly higher in the claudicating-limb and asymptomatic-limb groups than in controls (P = .012 and P = .018). Conclusions The muscle strength of the plantarflexors in those with PAD-IC appears to be impaired at high contraction velocities. This may be explained by some reduction in gastrocnemii muscle quality and a greater reliance on the prominently type I-fibered soleus muscle. The reduced dynamic capability of the plantarflexor muscles was associated with disease severity and walking ability; therefore, efforts to improve plantarflexor power through dynamic exercise intervention are vital to maintain functional performance
Biomechanical demands of the 2-step transitional gait cycles linking level gait and stair descent gait in older women
Stair descent is an inherently complex form of locomotion posing a high falls risk for older adults, specifically when negotiating the transitional gait cycles linking level gait and descent. The aim of this study was to enhance our understanding of the biomechanical demands by comparing the demands of these transitions. Lower limb kinematics and kinetics of the 2-step transitions linking level and descent gait at the top (level-to-descent) and the bottom (descent-to-level) of the staircase were quantified in 36 older women with no falls history. Despite undergoing the same vertical displacement (2-steps), the following significant (p<.05) differences were observed during the top transition compared to the bottom transition: reduced step velocity; reduced hip extension and increased ankle dorsiflexion (late stance/pre-swing); reduced ground reaction forces, larger knee extensor moments and powers (absorption; late stance); reduced ankle plantarflexor moments (early and late stance) and increased ankle powers (mid-stance). Top transition biomechanics were similar to those reported previously for continuous descent. Kinetic differences at the knee and ankle signify the contrasting and prominent functions of controlled lowering during the top transition and forward continuance during the bottom transition. The varying musculoskeletal demands encountered during each functional sub-task should be addressed in falls prevention programmes with elderly populations where the greatest clinical impact may be achieved. Knee extensor eccentric power through flexion exercises would facilitate a smooth transition at the top and improving ankle plantarflexion strength during single and double limb stance activities would ease the transition into level gait following continuous descent
Universal Properties of Galactic Rotation Curves and a First Principles Derivation of the Tully-Fisher Relation
In a recent paper McGaugh, Lelli, and Schombert showed that in an empirical
plot of the observed centripetal accelerations in spiral galaxies against those
predicted by the Newtonian gravity of the luminous matter in those galaxies the
data points occupied a remarkably narrow band. While one could summarize the
mean properties of the band by drawing a single mean curve through it, by
fitting the band with the illustrative conformal gravity theory with fits that
fill out the width of the band we show here that the width of the band is just
as physically significant. We show that at very low luminous Newtonian
accelerations the plot can become independent of the luminous Newtonian
contribution altogether, but still be non-trivial due to the contribution of
matter outside of the galaxies (viz. the rest of the visible universe). We
present a new empirical plot of the difference between the observed centripetal
accelerations and the luminous Newtonian expectations as a function of distance
from the centers of galaxies, and show that at distances greater than 10 kpc
the plot also occupies a remarkably narrow band, one even close to constant.
Using the conformal gravity theory we provide a first principles derivation of
the empirical Tully-Fisher relation.Comment: 6 pages, 15 figures. The paper is a comment on S. S. McGaugh, F.
Lelli, and J. M. Schombert, Phys. Rev. Lett. 117, 201101 (2016). Updated to
include a first principles derivation of the Tully-Fisher relation using the
conformal gravity theory. Submitted to Physics Letters
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In vitro Recapitulation of the Polymicrobial Communities Associated with Cystic Fibrosis Airway Infections
The airways of persons with cystic fibrosis (CF) are prone to lifelong colonisation with dense microbial ecosystems comprised of a diverse combination of bacteria and fungi. The role of interspecies interactions in modulating changes in gene expression and the metabolism of individual members of a polymicrobial community, compared with growth as an axenic population, is becoming increasingly apparent within the field of medical microbiology. In part, these poorly understood interactions explain why, regardless of intense research efforts, therapeutic treatments designed to clear such chronic airway infections often fail within the clinical setting. The paucity of existing in vitro and in vivo models used to study CF-associated infections greatly hinders research into the behaviours of polymicrobial communities. Species that coexist within the same in situ environment often outcompete one another when grown as a mixed population using traditional culture methods. The work presented in this dissertation redresses these problems. I describe the development and characterisation of a novel in vitro continuous-flow culture model. This experimental system permits the stable co-cultivation of distinctly different microbial species commonly-associated with CF airway infections; species that ordinarily readily outcompete one another in existing models. I demonstrate that the metabolic state and mutation rates of species cultured within the model remain stable for extended periods of time. Furthermore, I show that antimicrobial compounds display decreased efficacy against their target organism when grown as part of a polymicrobial community. I also show that different combinations of microbial species display different biofilm-forming potential. This work provides the basis of future research efforts aimed at the in vitro recapitulation of an entire polymicrobial community directly derived from persons with CF. Ultimately, this will help to bridge the bench-to-bedside gap for the development of more efficacious airway infection management regimens.NC3Rs studentship NC/P001564/1 and further consumables support from the UK Cystic Fibrosis Trust (Venture and Innovation Award) and the British Lung Foundation
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