Stress concentration in periodically rough Hertzian contact: Hertz to soft-flat-punch transition.

We report on the elastic contact between a spherical lens and a patterned substrate, composed of a hexagonal lattice of cylindrical pillars. The stress field and the size of the contact area are obtained by means of numerical methods: a superposition method of discrete pressure elements and an iterative bisection-like method. For small indentations, a transition from a Hertzian to a soft-flat-punch behaviour is observed when the surface fraction of the substrate that is covered by the pillars is increased. In particular, we present a master curve defined by two dimensionless parameters, which allows one to predict the stress at the centre of the contact region in terms of the surface fraction occupied by pillars. The transition between the limiting contact regimes, Hertzian and soft-flat-punch, is well described by a rational function. Additionally, a simple model to describe the Boussinesq-Cerruti-like contact between the lens and a single elastic pillar, which takes into account the pillar geometry and the elastic properties of the two bodies, is presented.

Role of adhesion between asperities in the formation of elastic solid/solid contacts.

We investigated the formation of a contact between a smooth sphere of elastomer and a micro-patterned elastomer substrate. We focussed our attention on the transition between a contact only established at the top of the pillars, and a mixed contact with a central zone of full contact surrounded by a top contact corona, which was observed when the normal load was increased. The full contact zone always nucleated with a finite radius, and the transition appears to be a first-order transition, with a hysteresis due to the creation of an adhesive zone between the pillars. We propose to include the effect of the new inter-pillar adhesion to produce a realistic treatment of the mechanics of these complex contacts. This new approach quantitatively accounts for the evolution of the observed jump in the radius of the full contact with the geometrical parameters of the pattern.

Persistent export of 231Pa from the deep central Arctic Ocean over the past 35,000 years.

The Arctic Ocean has an important role in Earth's climate, both through surface processes such as sea-ice formation and transport, and through the production and export of waters at depth that contribute to the global thermohaline circulation. Deciphering the deep Arctic Ocean's palaeo-oceanographic history is a crucial part of understanding its role in climatic change. Here we show that sedimentary ratios of the radionuclides thorium-230 ((230)Th) and protactinium-231 ((231)Pa), which are produced in sea water and removed by particle scavenging on timescales of decades to centuries, respectively, record consistent evidence for the export of (231)Pa from the deep Arctic and may indicate continuous deep-water exchange between the Arctic and Atlantic oceans throughout the past 35,000 years. Seven well-dated box-core records provide a comprehensive overview of (231)Pa and (230)Th burial in Arctic sediments during glacial, deglacial and interglacial conditions. Sedimentary (231)Pa/(230)Th ratios decrease nearly linearly with increasing water depth above the core sites, indicating efficient particle scavenging in the upper water column and greater influence of removal by lateral transport at depth. Although the measured (230)Th burial is in balance with its production in Arctic sea water, integrated depth profiles for all time intervals reveal a deficit in (231)Pa burial that can be balanced only by lateral export in the water column. Because no enhanced sink for (231)Pa has yet been found in the Arctic, our records suggest that deep-water exchange through the Fram strait may export (231)Pa. Such export may have continued for the past 35,000 years, suggesting a century-scale replacement time for deep waters in the Arctic Ocean since the most recent glaciation and a persistent contribution of Arctic waters to the global ocean circulation.

Identifying the support needs of fathers affected by post-partum depression: a pilot study.

The purpose of this pilot study was to describe the experiences, support needs, resources, and barriers to support for fathers whose partners had post-partum depression (PPD) in preparation for a larger study. Qualitative methods and community-based research approaches were used in this exploratory/descriptive multi-site study, conducted in New Brunswick and Alberta. Telephone interviews were conducted with a total of 11 fathers in New Brunswick (n= 7) and Alberta (n= 4). Fathers experienced a number of depressive symptoms including: anxiety, lack of time and energy, irritability, feeling sad or down, changes in appetite, and thoughts of harm to self or baby. The most common barriers for fathers were lack of information regarding PPD resources and difficulty seeking support. This pilot study establishes the feasibility of the larger-scale exploration of fathers' experiences in supporting their spouses affected by PPD.

Wetting and dewetting transition: an efficient toolbox for characterizing low-energy surfaces.

The capillary bridge formed between a solid spherical surface and an infinite liquid bath is an efficient technique for characterizing the adhesion property of a solid surface. When the solid surface is pulled out of the liquid at a sufficiently high velocity, a thin liquid film is deposited on the solid and drains more slowly than the central capillary bridge. The retraction kinetics of this "pancake" and the critical velocity above which it appears are studied as a function of the viscosity of the liquid or the wettability of the solids. The dynamics of the liquid film follows the classical law of dynamic dewetting. This makes the capillary bridge test, used in the dynamical regime, a very efficient tool for discriminating between antiadhesive coatings.

Vo2 requirement at different displayed power outputs on five cycle ergometer models: a preliminary study.

BACKGROUND AND AIMS: The validity of five brands of cycle ergometers was evaluated by the comparison of the Vo(2) requirements at different displayed power. METHODS AND RESULTS: Five physically active men performed a continuous incremental exercise test on five ergometers (Ergomeca, Lifecycle, Monark, Polar S710 and CompuTrainer). The latter was also compared with a standard dynamometer in order to associate Vo(2) values with the real power. Every test started with a 5-min warm-up on the same cycle ergometer (Ergomeca) at 100 W to make sure that the Vo(2) differences do not come from Vo(2) measurement error. Only last minute steady-state Vo(2) values of each 2-min stage were used for the Vo(2)-watt curve. Large differences (5- 10 ml kg(-1) min(-1)) at the same displayed power indicate inaccuracy of displayed power output (PO). Using corrected power values from the dynamometer revealed that for the same Vo(2) the CompuTrainer underestimates PO by approximately 30 W between 100 and 300 W, whereas the Lifecycle overestimate it by 3-53 W from 100 to 300 W. The Monark and Polar S710 underestimate PO by 15 W and the Ergomeca by approximately 5 W. CONCLUSION: Inaccuracies between -10% and 18% in displayed PO of various cycle ergometers question their interchangeability.

The status of health-promoting schools in Hong Kong and implications for further development

An evaluation framework, called the Hong Kong Healthy Schools Award, has been developed to enable comprehensive collection and analysis of data reflecting the status of health-promoting schools (HPS) in Hong Kong. The key findings revealed a high prevalence of emotional problems, unhealthy eating habits, physical inactivity and risk-taking behaviours, leading to both intentional and unintentional injuries among students with higher prevalence among secondary school students. The results indicated a substantial lack of health policies in schools; it also indicated health services in schools not readily accessible to students and staff, and insufficient staff training in health promotion and education. However, most schools have made initiatives in environmental protection, established safety guidelines and strategies for managing students with emotional problems. The success of HPS depends largely on teachers' understanding of its building blocks. Evidence from the comprehensive mapping of the status of HPS in Hong Kong and from student surveys does show encouraging outcomes as well as identifying priority issues to be addressed in the next 5 years. (AU)

Anaerobic running capacity determined from a 3-parameter systems model: relationship with other anaerobic indices and with running performance in the 800 m-run.

The purpose of this study was to compare anaerobic running capacity (ARC, i.e., the distance that can be run using only stored energy sources in the muscle) determined from a 3-parameter systems model with other anaerobic indices and with running performance in the 800 m. Seventeen trained male subjects (.VO(2max) = 66.54 +/- 7.29 ml . min (-1) . kg (-1)) performed an incremental test to exhaustion for the determination of .VO(2max) and peak treadmill velocity (PTV), five randomly ordered constant velocity tests at 95, 100, 105, 110, and 120 % of PTV to compute ARC and oxygen deficit (O(2)def, at 110 % of PTV), and a 800-m time trial to determine running performance (mean velocity over the distance, V (800 m)) and peak blood lactate concentration ([La (-)] (b, peak)). ARC (467 +/- 123 m) was positively correlated with O(2)def (56.35 +/- 18.47 ml . kg (-1); r = 0.57; p < 0.05), but not with [La (-)] (b, peak) (15.08 +/- 1.48 mmol . l (-1); r = - 0.16; p > 0.05). The O(2) equivalent of ARC (i.e., the product of ARC by the energy cost of running; 103.74 +/- 28.25 ml . kg (-1)), which is considered as an indirect estimation of O(2)def, was significantly higher than O(2)def (p < 0.01, effect size = 1.99). It was concluded that ARC is partially determined by anaerobic pathway, but that it probably does not provide an accurate measure of anaerobic capacity, if, however, O(2)def can be considered as a criterion measure for it.

An on-ice aerobic maximal multistage shuttle skate test for elite adolescent hockey players.

The aim of this study was to design an on-ice test to predict V.O (2max) in ice hockey players. 30 elite hockey players (age 14.7 +/- 1.5 years) participated in this study. The oxygen uptake was assessed at submaximal and maximal velocities during an on-ice intermittent maximal multistage shuttle skate test with a 1-min/0.5-min work/rest ratio. The procedure consisted of skating back and forth on a distance of 45 m (stop and go) while following a pace fixed by an audible signal: initial velocity of 3.5 m . s (-1) with increments of 0.2 m . s (-1) every stage. The skating multistage aerobic test (SMAT) enabled the prediction of the V.O (2max) (ml . kg (-1) . min (-1)) from the maximal velocity (m . s (-1)) by means of the following regression equation: V.O (2max) = 18.07 x (maximal velocity) - 35.596 (r = 0.97, SEE = 3.01). The test-retest correlation was 0.92 and SEE = 0.56 stage (n = 23). Following the SMAT validation, an additional group of 112 elite male (age = 14.2 +/- 1.3 years) and 31 elite female (age = 14.0 +/- 1.2 years) ice hockey players performed both the 20-m shuttle run test and the SMAT, which was more specific and accurate to predict V.O (2max). The overall results suggest that the SMAT is highly specific, valid and reliable for the prediction of V.O (2max) of ice hockey players.

Adhesion enhancement through micropatterning at polydimethylsiloxane-acrylic adhesive interfaces.

Adhesion at polydimethylsiloxane (PDMS)-acrylic adhesive interfaces is shown to be enhanced through micropatterning of the PDMS substrate. By varying the geometry of the patterns (groves and hexagonal arrays of pillars of micrometer sizes, obtained through soft lithography techniques) and comparing rigid and deformable substrates, the respective roles of the geometry and the size and flexibility of the pattern features on the level of adhesion have been analyzed. For cylindrical pillars, two regimes are clearly identified: for a relatively low aspect ratio (h/r < 3, with h and r, respectively, the height and the radius of the pillars), soft patterned substrates are more efficient than rigid ones at increasing adhesion, pointing out the role of the elastic energy associated with the deformation of the pattern that is lost when the adhesive detaches from the substrate. Using scaling laws, the predominant contribution to that elastic energy can be further identified: deformation of the substrate underlying the pillars for h/r < 1.6 or bending of the pillars for h/r > 1.6.; for a high aspect ratio (h/r > 3), only rigid patterned substrates enhance adhesion, then the only possible contribution to energy dissipation comes from the enhanced viscoelastic losses associated with the pattern that induce modifications of the strain field within the adhesive layer. Soft, high aspect ratio patterns lose their efficiency even if still bent under the effect of the peel forces. This is because when bent, some of the pillars touch each other and remain stuck together, lying flat on the surface after the passage of the peel front. The bending elastic energy of the pillars (which is still lost) is then balanced by the corresponding gain in surface energy of the substrate in the peeled region. These systematic experiments demonstrate that the ability of the patterned surface to be deformed plays a crucial role in enhancing adhesion and allow us to propose a way to fine tune the level of adhesion at PDMS-acrylic adhesive interfaces, independently of the chemistry of the adhesive.

.VO2 kinetics during supramaximal exercise: relationship with oxygen deficit and 800-m running performance.

The aim of this study was to compare .VO2 kinetics of highly- versus recreationally-trained subjects during a constant velocity test of supramaximal intensity. Eighteen trained male subjects were recruited to one of two groups: highly trained (HT, n = 8, .VO(2max) = 70.1 +/- 6.5 ml . min (-1) . kg (-1)) and recreationally trained (RT, n = 10, .VO(2max) = 63.2 +/- 6.4 ml . min (-1) . kg (-1)). All subjects performed an incremental test to exhaustion for the determination of .VO(2max) and peak treadmill velocity (PTV), two constant velocity tests at 110 % of PTV to determine .VO2 kinetics and oxygen deficit (O(2)def), and a 800-m time trial to determine running performance (mean velocity over the distance, V (800 m)). We found significant differences between HT and RT for the on-transient of the .VO2 response (tau, 24.7 +/- 3.3 and 30.9 +/- 7.0 s, respectively), the amplitude of the .VO2 response (60.0 +/- 5.0 and 53.5 +/- 5.7 ml . min (-1) . kg (-1), respectively) and V (800 m) (6.27 +/- 2.1 and 5.45 +/- 0.38 m . s (-1), respectively). O(2)def (24.6 +/- 2.7 and 27.7 +/- 7.8 ml . kg (-1), respectively) and the gain of the .VO2 response (193 +/- 14 and 194 +/- 13 ml . kg (-1) . m (-1), respectively) were similar between groups. tau was associated with O(2)def (r = 0.90, p < 0.05), but not with V (800 m) (r = 0.30, p > 0.05). It was concluded that HT subjects exhibited faster on-kinetics and higher amplitude than their RT counterparts. The higher amplitude was not thought to reflect any difference in underlying physiological mechanisms. The faster tau, whose exact mechanisms remain to be elucidated, may have practical implications for coaches.

Nurses' voice: influencing the restructuring of the New Brunswick healthcare system.

Although nurses make up the largest group of professionals working in th healthcare field, they are often left out of the decisions that shape the restructuring of healthcare in Canada. A feminist philosophy guided this qualitative study, conducted in New Brunswick, to gain an in-depth knowledge of the impact of restructuring on nurses working in all types of healthcare facilities across the province. Sixty-five nurses were interviewed, and a number of themes, including "having a voice," emerged from the data. While many of the nurses interviewed reported that they were not invited to participate in decisions related to healthcare restructuring, others noted that when they did have an opportunity to participate, they were frequently not heard. However, a number of nurses also reported that they believed they had some influence and could continue to make a positive difference when they were asked to be involved at the outset of a change process.

Brainstem structures responsible for paradoxical sleep onset and maintenance.

This paper is dedicated to our mentor, Michel Jouvet who inspired our career and transmitted to us his passion for the study of the mechanisms responsible for paradoxical sleep genesis and also that of its still mysterious functions. We expose in the following the progresses in the knowledge in this field brought during 40 years by Michel Jouvet and his team and more recently by the members of a new CNRS laboratory in which we aim to pursue in the path opened by Michel Jouvet.

Molecular dynamics in thin grafted and spin-coated polymer layers.

Broadband Dielectric Spectroscopy is employed to study the molecular dynamics in thin layers of grafted and spin-coated polydimethylsiloxane (PDMS) and of the type-A polymer cis-1,4-polyisoprene (PI). Strong resemblance with low-molecular-weight systems is found but additionally the conformation of the chain and its extension becomes important. For PI a confinement-induced relaxation is found. It is observable if the layer thickness is comparable to the end-to-end vector of the chain and it depends strongly on the separation between interfaces. In contrast, the dynamic (and hence the calorimetric) glass transition is not affected by the geometrical confinement.

Night heart rate variability during overtraining in male endurance athletes.

AIM: The purpose of the study was to examine whether an unaccustomed increase in training volume would result in characteristics changes in heart rate variability (HRV), in order to determine if this marker can be used to diagnose overtraining. METHODS: Nine experienced endurance athletes increased their usual amount of training by 100% within 4 weeks. Night ECG was recorded before (baseline) and after (OVER) this period of overload, and after 2 weeks of recovery (REC). RESULTS: We diagnosed overtraining in 6 subjects using both physiological and psychological criteria. No difference was noted in heart rate for night periods (56+/-12, 55+/-10 and 53+/-15 bpm, respectively; p>0.05). We found no significant changes of LF/HF (1.10+/-0.92, 0.96+/-0.57 and 0.59+/-0.43, respectively; p>0.05) or HF expressed in normalized units (54.81+/-20.12, 53.81+/-11.35 and 66.15+/-15.12%, respectively; p>0.05). CONCLUSION: In the conditions of the present study, HRV during sleep does not seem to be a valid marker of overtraining in male endurance athletes. Before concluding to the uselessness of this tool in the monitoring of the syndrome, longitudinal studies with elite or sub-elite athletes are needed to determine if spontaneously developed overtraining results in the same response.

Blood lactate response to overtraining in male endurance athletes.

Many physiological markers vary similarly during training and overtraining. This is the case for the blood lactate concentration ([La-]b), since a right shift of the lactate curve is to be expected in both conditions. We examined the possibility of separating the changes in training from those of overtraining by dividing [La-]b by the rating of perceived exertion ([La-]b/RPE) or by converting [La-]b into a percentage of the peak blood lactate concentration ([La-]b,peak). Ten experienced endurance athletes increased their usual amount of training by 100% within 4 weeks. An incremental test and a time trial were performed before (baseline) and after this period of overtraining, and after 2 weeks of recovery (REC). The [La-]b and RPE were measured during the recovery of each stage of the incremental test. We diagnosed overtraining in seven athletes, using both physiological and psychological criteria. We found a decrease in mean [La-]b,peak from baseline to REC [9.64 (SD 1.17), 8.16 (SD 1.31) and 7.69 (SD 1.84) mmol.l-1, for the three tests, respectively; P < 0.05] and a right shift of the lactate curve. Above 90% of maximal aerobic speed (MAS) there was a decrease of mean [La-]b/RPE from baseline to REC [at 100% of MAS of 105.41 (SD 17.48), 84.61 (SD 12.56) and 81.03 (SD 22.64) arbitrary units, in the three tests, respectively; P < 0.05), but no difference in RPE, its variability accounting for less than 25% of the variability of [La-]b/RPE (r = 0.49). Consequently, [La-]b/RPE provides little additional information compared to [La-]b alone. Expressing [La-]b as a %[La-]b,peak resulted in a suppression of the right shift of the lactate curve, suggesting it was primarily the consequence of a decreased production of lactate by the muscle. Since the right shift of the curve induced by optimal training is a result of improved lactate utilization, the main difference between the two conditions is the decrease of [La-]b,peak during overtraining. We propose retaining it as a marker of overtraining for long duration events, and repeating its measurement after a sufficient period of rest to make the distinction with overreaching.

Schools, health literacy and public health: possibilities and challenges.

Health literacy is a concept that can be widely embraced by schools. Schools throughout the world contribute to the achievement of public health goals in conjunction with their educational commitments. In this paper, the interface between a school's core business of education and public health goals is identified, and examples provided in the area of nutrition demonstrating how these links can operate at school level. The structure and function of the health promoting school is described and the author proposes that there is a very close connection between the health promoting school and the enabling factors necessary in achieving health literacy. Major findings in the literature that provide evidence of good practices in school health education and promotion initiatives are described. Also, those factors that make schools effective and which facilitate learning for students are identified. There is a substantial overlap between the successful components of a health promoting school and effective schools. This enables schools to potentially achieve all three levels of health literacy, including level 3-critical health literacy. However, there are three challenges that must be addressed to enable schools to achieve this level: the traditional structure and function of schools, teachers practices and skills, and time and resources. Strategies are proposed to address all three areas and to reduce the impediments to achieving the goals of health literacy and public health using the school as a setting.

Anatomical distribution of serotonin-containing neurons and axons in the central nervous system of the cat.

By using a monoclonal antibody to serotonin (5-HT), an immunohistochemical study was undertaken to provide a comprehensive description of the 5-HT-containing neurons and of the distribution of their axonal processes in the cat brain and spinal cord. The localization of cell bodies was comparable to that previously reported in studies using formaldehyde-induced fluorescence and other 5-HT antibodies, with a large proportion of labeled neurons in the raphe nuclei and a minor, yet not negligible number, in the ventral, lateral, and dorsal reticular formation. The ascending efferent non-varicose axons were best visualized in sagittal sections and mainly seen taking a rostroventral direction through the tegmentum. The varicose axons could be grossly classified into thin and large fibers, according to the size and shape of the immunoreactive varicosities, which were elongated (up to 2 microm in length and 1 microm in width) or round (2-4 microm in diameter). Varicose axonal arborizations invaded almost every region of the gray matter and avoided large myelinated bundles except in the spinal cord. Variations in the density of the plexuses of immunoreactive fibers generally followed the anatomical divisions and were also observed within nuclei, especially in laminated structures. Only the superior olivary complex could be regarded as devoid of 5-HT-containing axons. A few areas contained extremely rich fiber plexuses. These were the olfactory tubercle, nucleus accumbens, ventral mesencephalon, periventricular gray from the hypothalamus to the pons, facial nucleus, subdivisions of the inferior olive, and the intermediolateral nucleus in the spinal cord. Varicose axons formed tight pericellular arrays in the neocortex, mainly the ectosylvian gyrus, and in the lateral septum and medullar magnocellular nucleus. These data, combined with those of the literature concerning the synaptic versus non-synaptic mode of termination of the 5-HT-immunoreactive varicosities and the high number of distinct receptors, are indicative of the multiple possible actions of serotonin in the central nervous system.