Effects of Temperature and Angular Velocity on Eccentric Force of an Intrinsic Thumb Muscle

Temperature and velocity have significant effects on muscle contractile properties. For example, it is well known that changing angular velocity and altering muscle temperature can change the force-producing capacity of muscle. It is typically understood that with increasing shortening velocity and cooler temperature force decreases. However, the influence of temperature and angular velocity on force during lengthening contractions is less understood.  The purpose of this study was to determine whether temperature and/or velocity has an effect on the eccentric to isometric force ratio of the adductor pollicis muscle in young males. Ten young (~25y) male subjects performed lengthening (0-40°) electrically-evoked contractions of the left adductor pollicis muscles at ~50% of maximum voluntary force at angular velocities ranging from 0-320°/s. This procedure was performed initially at room temperature (21˚C), and then repeated two more times after a 20min bath, first in a cold (15°C) water and then in a warm (43°C) water bath in order to change the muscle temperature. The eccentric to isometric ratio was significantly greater in the cold compared to the normal condition (P<0.05), but was not different from normal for the warm condition (P>0.05). The eccentric to isometric ratio was significantly greater at 80, 160 and 320°/s (P<0.05) than at 20°/s, but was not different at velocities slower than 80°/s (P>0.05).  Instantaneous stiffness was measured 1 s after attaining maximum stretch. There was a significant (~38%) increase in active stiffness in the cold muscle compared to normal. No significant difference (~15%) in stiffness was observed for the warm compared with the normal condition, and no significant difference (~20%) was found between warm and cold muscles. The findings suggest that there is an increased force per cross-bridge as temperature approaches normal physiological temperature, but decreases when temperature deviates from normal

Stable and unstable equilibrium states in a fishery-aquaculture model

This is the pre-peer reviewed version of the following article: Bergland, H., Pedersen, P.A. & Wyller, J. (2018). Stable and unstable equilibrium states in a fishery-aquaculture model. Natural Resource Modeling, which has been published in final form at https://doi.org/10.1111/nrm.12200. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.We study interactions between fishery and aquaculture using a 3D generalized Lotka–Volterra model, where we assume that the aquaculture production may affect the growth rate in the fish stock and the productivity in harvesting. In addition, input demands from both marine industries may result in effort competition. We identify conditions for the coexistence of a unique equilibrium state inside the first octant of the phase space and equilibrium states on its boundary. Conditions for stability and instability of these states are also given, thus showing the possibility of having bistability. The equilibrium point inside the first octant is stable if the growth impact on fishery from sea farming is below the potential productivity in harvesting. In the complementary case, we have an unstable interior equilibrium, and we may then end up in stable equilibrium states on the boundary, where either the fishery or the aquaculture is wiped out

Intra- and inter-individual cognitive variability in schizophrenia and bipolar spectrum disorder: an investigation across multiple cognitive domains

Abstract There is substantial cognitive heterogeneity among patients with schizophrenia (SZ) and bipolar disorders (BD). More knowledge about the magnitude and clinical correlates of performance variability could improve our understanding of cognitive impairments. Using double generalized linear models (DGLMs) we investigated cognitive mean and variability differences between patients with SZ (n = 905) and BD spectrum disorders (n = 522), and healthy controls (HC, n = 1170) on twenty-two variables. The analysis revealed significant case-control differences on 90% of the variables. Compared to HC, patients showed larger intra-individual (within subject) variability across tests and larger inter-individual (between subject) variability in measures of fine-motor speed, mental processing speed, and inhibitory control (SZ and BD), and in verbal learning and memory and intellectual functioning (SZ). In SZ, we found that lager intra -and inter (on inhibitory control and speed functions) individual variability, was associated with lower functioning and more negative symptoms. Inter-individual variability on single measures of memory and intellectual function was additionally associated with disorganized and positive symptoms, and use of antidepressants. In BD, there were no within-subject associations with symptom severity. However, greater inter-individual variability (primarily on inhibitory control and speeded functions) was associated with lower functioning, more negative -and disorganized symptoms, earlier age at onset, longer duration of illness, and increased medication use. These results highlight larger individual differences in patients compared to controls on various cognitive domains. Further investigations of the causes and correlates of individual differences in cognitive function are warranted