In this study, we investigated corticospinal excitability during mental simulation of a leg extension movement with the technique of transcranial magnetic stimulation. Motor evoked potentials were ...recorded in both knee extensors (quadriceps) and flexors (biceps femoris) in 19 trained participants (healthy volunteers). The amplitude and latency of motor evoked potentials were compared in three conditions: (1) at rest, (2) during motor imagery, and (3) at rest, immediately after motor imagery. The results showed a significant effect (p < 0.001) of conditions on motor evoked potentials amplitude in the quadriceps but not in the biceps femoris. During motor imagery, the size of motor evoked potentials in the quadriceps increased significantly (p < 0.001) compared with rest and post-imagery conditions. Changes in motor evoked potentials latency across conditions were not significant, however. These results are consistent with previous studies in the upper limb and suggest that corticospinal excitability can be enhanced during motor imagery to facilitate responses in specific lower limb muscles.
Paying for performance is however not an easy solution for organisational performance problems. As stated by Wright (1991: 16), "even the most ardent supporters of performancebased reward systems ...recognise that it is extraordinarily difficult to manage well". There is also a school of thought that rejects the claims made of performance-based rewards. A recent survey of British Telecom executives carried out by the Society of Telecom Executives (1991: 35) revealed that only 6 per cent of those responding to the survey thought that performance-based rewards improved their performance compared with an overwhelming 70 per cent who thought it had not. Research conducted by Carmen and Wood (1992: 8) on behalf of the Institute of Personnel Management and the National Economic Development Office into payment schemes, did not confirm that performance-based pay was a motivator. Face-to-face interviews were conducted with 40 personnel directors and managers from large and medium organisations. They concluded that the personnel managers interviewed were by no means certain that performancebased rewards succeed in motivating people. Most were not convinced they could unequivocally identify that performance-based rewards was increasing either individual or organisational performance. When these research findings are closely investigated, it can normally be established that specific reasons contribute to the failure of the performance-based reward systems to increase motivation and organisational performance. Armstrong and Murlis (1994: 252) believe these reasons are mostly: A failure to involve employees sufficiently in the design and implementation of the system; A mistaken belief that the performance-based reward system on its own will achieve the expected increase in motivation and performance; and The poor people skills of those managers that are responsible for managing implemented performance-based reward systems.
Surface Fires： No Wind, No Slope, Marginal Burning Jacques-Henry Balbi Domingos Xavier Viegas Jean-Louis Rossi Carlos Rossa Francois Joseph Chatelon Dominique Cancellieri Albert Simeoni Thierry Marcelli
环境科学与工程：A,
2014, Volume:
3, Issue:
2
Journal Article
The first aim of this work is to provide an analytical expression to calculate the rate of spread of surface fires under no wind and no slope conditions. A previous simplified model was improved for ...this particular case of fire propagation. The test of this proposed model was performed by using two complete sets of experimental results with several fuel beds and variable parameters such as moisture content or bulk density. The second aim of this article is to highlight two conditions that allow stopping a fire： the low leaf area and the high value of the moisture content.
In order to better understand what controls carbonate weathering rates, we report results from the Jura Mountains （East France）, an area exclusively composed of carbonate rocks. This region presents ...an altitude gradient increasing from 250 m to 1300 m. Over the basin, this gradient generates climatic contrasts of 5℃ and a runoff three times higher in altitude. This place offers a good opportunity for understanding the controlling factors of carbonate weathering. Contrary to thermodynamic calculations that predict the highest concentrations at low temperature, we observe that carbonate dissolution is two times higher at low elevation than in the mountains. This observation can only be explained by a variation in soil pCO2. In order to better constrain the observed variation in cation contents （principally Ca and Mg） of rivers, we used the ASPECTS ecological model （Rasse et al., 2001）. Based on both hourly climatic data, vegetation type and soil type, ASPECTS may reconstruct pCO2 in soil.
Atmospheric carbon dioxide concentrations are believed to drive climate changes from glacial to interglacial modes, although geological and astronomical mechanisms have been invoked as ultimate ...causes. Additionally, it is unclear whether the changes between cold and warm modes should be regarded as a global phenomenon, affecting tropical and high-latitude temperatures alike, or if they are better described as an expansion and contraction of the latitudinal climate zones, keeping equatorial temperatures approximately constant. Here we present a reconstruction of tropical sea surface temperatures throughout the Phanerozoic eon (the past ∼550 Myr) from our database of oxygen isotopes in calcite and aragonite shells. The data indicate large oscillations of tropical sea surface temperatures in phase with the cold-warm cycles, thus favouring the idea of climate variability as a global phenomenon. But our data conflict with a temperature reconstruction using an energy balance model that is forced by reconstructed atmospheric carbon dioxide concentrations. The results can be reconciled if atmospheric carbon dioxide concentrations were not the principal driver of climate variability on geological timescales for at least one-third of the Phanerozoic eon, or if the reconstructed carbon dioxide concentrations are not reliable.
Data from the 1990 San Joaquin Valley Air Quality Study/ Atmospheric Utility Signatures, Predictions, and Experiments (SJVAQS/AUSPEX) field program in California's San Joaquin Valley (SJV) suggest ...that both urban and rural areas would have difficulty meeting an 8-hr average O
3
standard of 80 ppb. A conceptual model of O
3
formation and accumulation in the SJV is formulated based on the chemical, meteorological, and tracer data from SJVAQS/ AUSPEX. Two major phenomena appear to lead to high O
3
concentrations in the SJV: (1) transport of O
3
and precursors from upwind areas (primarily the San Francisco Bay Area, but also the Sacramento Valley) into the SJV, affecting the northern part of the valley, and (2) emissions of precursors, mixing, transport (including long-range transport), and atmospheric reactions within the SJV responsible for regional and urban-scale (e.g., downwind of Fresno and Bakersfield) distributions of O
3
. Using this conceptual model, we then conduct a critical evaluation of the meteorological model and air quality model. Areas of model improvements and data needed to understand and properly simulate O
3
formation in the SJV are highlighted.
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