Expiratory muscle fatigue impairs exercise performance

High-intensity, exhaustive exercise may lead to inspiratory as well as expiratory muscle fatigue (EMF). Induction of inspiratory muscle fatigue (IMF) before exercise has been shown to impair subsequent exercise performance. The purpose of the present study was to determine whether induction of EMF also affects subsequent exercise performance. Twelve healthy young men performed five 12-min running tests on a 400-m track on separate days: a preliminary trial, two trials after induction of EMF, and two trials without prior muscle fatigue. Tests with and without prior EMF were performed in an alternate order, randomly starting with either type. EMF was defined as a ≥20% drop in maximal expiratory mouth pressure achieved during expiratory resistive breathing against 50% maximal expiratory mouth pressure. The average distance covered in 12min was significantly smaller during exercise with prior EMF compared to control exercise (2872±256 vs. 2957±325m; P=0.002). Running speed was consistently lower (0.13ms−1) throughout the entire 12min of exercise with prior EMF. A significant correlation was observed between the level of EMF (decrement in maximal expiratory mouth pressure after resistive breathing) and the reduction in running distance (r 2=0.528, P=0.007). Perceived respiratory exertion was higher during the first 800m and heart rate was lower throughout the entire test of running with prior EMF compared to control exercise (5.3±1.6 vs. 4.5±1.7 points, P=0.002; 173±10 vs. 178±7beatsmin−1, P=0.005). We conclude that EMF impairs exercise performance as previously reported for IM

Natural cement and monumental restoration

Natural cement, called "Roman” cement, was invented at the end of the 19th century and played an important role in the development of civil engineering works until the 1860s. More surprisingly, it was also used to restore historic buildings, such as gothic cathedrals. This paper deals with the mineralogy and the durability of natural cement in the particular case of the Bourges Cathedral in France. This study illustrates the interest of this material particularly adapted in stone repair or substitution. Contrary to traditional mortars, the present samples are made of neat cement paste, revealed by the absence of mineral additions as quartz or carbonate sand. Several combined techniques (SEM-EDS, TGA, XRD) were carried out to determine the composition of the hydraulic binder rich in calcium aluminate hydrates. The raw marl at the origin of the cement production contains oxidized pyrites which consist in a potential source of sulphate pollution of the surrounding limestone. The exposition of the cement in urban environment leads to some weathering features as atmospheric sulfation. Finally a petrophysical approach, based on water porosity, capillary sorption and compressive strength, has been performed to demonstrate the durability and the compatibility of natural cement applied as an historical building restoration morta

Kelp forest restoration in Australia

Kelp forests dominate the rocky coasts of temperate Australia and are the foundation of the Great Southern Reef. Much like terrestrial forests, these marine forests create complex habitat for diverse communities of flora and fauna. Kelp forests also support coastal food-webs and valuable fisheries and provide a suite of additional ecosystem services. In many regions of Australia and around the world, kelp forests are in decline due to ocean warming, overgrazing, and pollution. One potential tool in the conservation and management of these important ecosystems is habitat restoration, the science and practice of which is currently undergoing substantial expansion. We summarize the present state of Australian kelp forests and emphasize that consideration of the initial drivers of kelp decline is a critical first step in restoration. With a focus on Australian examples, we review methods, implementation and outcomes of kelp forest restoration, and discuss suitable measures of success and the estimated costs of restoration activities. We propose a workflow and decision system for kelp forest restoration that identifies alternative pathways for implementation and acknowledges that under some circumstances restoration at scale is not possible or feasible. As a case study, we then apply the Society for Ecological Restoration’s 5-star evaluation to Operation Crayweed, Australia’s primary example of kelp forest restoration. Overall, no single method of kelp forest restoration is suitable for all situations, but outcomes can be optimized by ameliorating the driver(s) of kelp decline and achieving ongoing natural recruitment of kelp. Whilst scalability of kelp forest restoration to the seascape-scale remains a considerable challenge, the present review should provide a platform for future restoration efforts. However, it is also crucial to emphasize that the challenges of restoration place a high value on preventative conservation and protection of existing kelp forest ecosystems – prevention is invariably better than cure

Structural Disorder Induced Polaron Formation and Magnetic Scattering in the Disordered Holstein-Double Exchange Model

In this paper we present results on the disordered Holstein-Double Exchange model, explicitly in three dimension and `metallic' densities, obtained by using a recently developed Monte Carlo approach. Following up on our earlier paper, cond-mat/0406085, here we provide a detailed microscopic picture of the thermally driven metal-insulator transition (MIT) that arises close to the ferromagnet to paramagnet transition in this problem. This paper is focused mainly on the `diagnostics', clarifying the origin of the effective disorder that drives the MIT in this system. To that effect, we provide results on the thermal evolution of the distributions of (i) lattice distortions, (ii) the net `structural disorder' and (iii) the `hopping disorder' arising from spin randomness feeding back through the Hunds coupling. We suggest a phenomenology for the thermally driven MIT, viewing it as an `Anderson-Holstein' transition.Comment: 6 pages, latex, JPSJ style, 7 eps figs. Style files included. Proceedings of the SPQS Meeting at Sendai, Japan, 2004. To appear in JPS

Propagation of social representations

Based on a minimal formalism of social representations as a set of associated cognems, a simple model of propagation of representations is presented. Assuming that subjects share the constitutive cognems, the model proposes that mere focused attention on the set of cognems in the field of common conscience may replicate the pattern of representation from context into subjects, or, from subject to subject, through actualization by language, where cognems are represented by verbal signs. Limits of the model are discussed, and evolutionist perspectives are presented with the support of field data

Phase diagrams of the 2D t-t'-U Hubbard model from an extended mean field method

It is well-known from unrestricted Hartree-Fock computations that the 2D Hubbard model does not have homogeneous mean field states in significant regions of parameter space away from half filling. This is incompatible with standard mean field theory. We present a simple extension of the mean field method that avoids this problem. As in standard mean field theory, we restrict Hartree-Fock theory to simple translation invariant states describing antiferromagnetism (AF), ferromagnetism (F) and paramagnetism (P), but we use an improved method to implement the doping constraint allowing us to detect when a phase separated state is energetically preferred, e.g. AF and F coexisting at the same time. We find that such mixed phases occur in significant parts of the phase diagrams, making them much richer than the ones from standard mean field theory. Our results for the 2D t-t'-U Hubbard model demonstrate the importance of band structure effects.Comment: 6 pages, 5 figure