RESUMO
The possibility to grow in zincblende (ZB) and/or wurtzite (WZ) crystal phase widens the potential applications of semiconductor nanowires (NWs). This is particularly true in technologically relevant III-V compounds, such as GaAs, InAs, and InP, for which WZ is not available in bulk form. The WZ band structure of many III-V NWs has been widely studied. Yet, transport (that is, carrier effective mass) and spin (that is, carrier g-factor) properties are almost experimentally unknown. We address these issues in a well-characterized material: WZ indium phosphide. The value and anisotropy of the reduced mass (µ exc) and g-factor (g exc) of the band gap exciton are determined by photoluminescence measurements under intense magnetic fields (B, up to 28 T) applied along different crystallographic directions. µ exc is 14% greater in WZ NWs than in a ZB bulk reference and it is 6% greater in a plane containing the WZ c axis than in a plane orthogonal to c. The Zeeman splitting is markedly anisotropic with g exc = |ge| = 1.4 for Bâ¥c (where ge is the electron g-factor) and g exc = |ge - gh,//| = 3.5 for B//c (where gh,// is the hole g-factor). A noticeable B-induced circular dichroism of the emitted photons is found only for B//c, as expected in WZ-phase materials.
RESUMO
BACKGROUND: Guidelines for optimal exercise doses in people with multiple sclerosis (MS) have to be established. We need to ascertain the basic physiological and perceptual response and adaptation to different exercise doses in this clinical population. AIM: The aim of this paper was to explore the response during maximal and sub-maximal exercise in people with MS prior to and following two different twelve week exercise programmes. DESIGN: Sub-analysis of per protocol exercise data of a two group, single blinded, randomised control trial. SETTING: Multicentre (community leisure and rehabilitation centres). POPULATION: Participants with MS assigned to a continuous (N.=12; mean±SE age=52.3±2.08; Barthel index median & range=19&13-20) or interval (N.=9; mean±SE age=49.3±3.5; Barthel index median & range=19&18-20) exercise programme. METHODS: Cardiovascular, respiratory and perceptual exercise response and adaption was measured at maximal and sub-maximal levels of physical exercise prior to and following a twelve week exercise programme, delivered at different intensities. RESULTS: Irrespective of the type of exercise programme followed, there was a significant increase in peak power (z=-1.98; P=0.05) and normalised oxygen uptake during unloaded cycling (z =-2.00; P=0.05). At discharge from the exercise programmes, the cardiovascular response to sub-maximal exercise had significantly changed (t(360) =-4.62; p<0.01). CONCLUSION: The response in people with MS at maximal and sub-maximal levels of physical exercise following a twelve week programme is analogous to non-diseased adults. CLINICAL REHABILITATION IMPACT: Cardiovascular adaptation in people with MS following a twelve week exercise programme suggests deconditioning rather than autonomic dysfunction caused by the disease.