Geophysical methods for detecting shallow sulphide mineralization in the Halifax Formation, Nova Scotia: a reconnaissance study

Construction activities have exposed sulphide-bearing slates of the Halifax Formation in southern mainland Nova Scotia. Under atmospheric conditions the sulphides break down and cause acid rock drainage (ARD) which adversely affects local ecosystems. These effects have been a major problem at the Halifax International Airport, causing fish kills and the expenditure of millions of dollars to ameliorate the ARD. A preferable alternative is to locate areas of sulphide mineralization in the construction area prior to excavation. Concentrated zones of sulphide mineralization can then be avoided, or treatment plans can be formulated in advance. Geophysical surveys provide possible means of detecting sulphides in slates of the Halifax Formation. To evaluate various geophysical methods, reconnaissance profiles were carried out in two areas near the Halifax International Airport utilizing ground conductivity, magnetic, VLF EM, spontaneous potential, and induced polarization measurements. The conductivity meter selected was specific to "construction depths" (i.e., its exploration depth limit is 6 m or less). Test pits were dug on one line in each area to sample bedrock coincident with and between conductivity anomalies. Bedrock samples collected in each test pit were analyzed for total sulphur, total carbon, Fe2+ and Fe3+ contents. On the first grid, increased total sulphur content was measured in rock specimens from a test pit coincident with a large ground conductivity anomaly. In contrast, extremely small total sulphur content was measured in rock specimens from a nearby hole which was deliberately situated where there is no conductivity anomaly. Similar results were obtained from the second grid. Magnetic anomalies are coincident with all but one of the sampled conductivity anomalies, indicative of the presence of pyrrhotite. Combined ground conductivity, magnetic and VLF EM surveys appear to be a practicable method for detecting near-surface sulphide mineralization in the Halifax Formation, and such surveys should be included in the Nova Scotia Environment Act. RÉSUMÉ Les activités de construction ont mis à nu des ardoises sulfuriferes de la Formation d'Halifax dans le sud intérieur de la Nouvelle-Écosse. Dans des conditions atmosphériques, les sulfures se décomposent et causent une exhaure de roches acides (ERA) qui a des effets nefastes sur les écosystèmes locaux. Ces effets ont constitué un problème de grande envergure à l'aéroport international d'Halifax, où ils ont causé la mort de poissons et exigé des investissements de plusieurs millions de dollars pour améliorer l'ERA. Une solution de rechange qu'on préfere consiste à délimiter les zones de minéralisation de sulfures à l'intérieur du secteur de construction avant les travaux de creusage. On peut ensuite éviter les zones concentrées de minéralisation de sulfures ou formuler des plans de traitement a l'avance. Les relevés géophysiques peuvent permettre de détecter les sulfures à l'intérieur des ardoises de la Formation d'Halifax. Les chercheurs ont, pour évaluer diverses méethodes géophysiques, dressé des profils de reconnaissance dans deux secteurs situés près de l'aéroport international d'Halifax au moyen d'études de polarisation induite, de diagraphie de polarisation spontanée et de conductivité ainsi que de relevés magnétiques et électromagnetiques. Le conductivimètre choisi était specifique aux " profondeurs de construction " (c.- à-d. que sa limite de profondeur d'exploration est de 6 m ou moins). lis ont creusé des trous d'exploration le long d'une ligne dans chaque secteur pour échantillonner le substrat rocheux correspondant aux anomalies de conductivité de même qu'entre celles-ci. Les chercheurs ont ensuite analysé la teneur en soufre total, en carbone total, en Fe2+ et en Fe3+ des échantillons de substrat rocheux prélevés dans chaque trou d'exploration. Dans le premier quadrillage, les chercheurs ont mesuré la teneur en soufre total des échantillons de roches provenant d'un trou d'exploration correspondant à une anomalie prononcée de conductivité du sol. Par contraste, on a relevé une teneur en soufre total extremement réduite dans les échantillons de roches provenant d'un trou à proximité délibérément creuse à un endroit où aucune anomalie de conductivité n'avait été relevée. On a obtenu des résultats semblables dans le deuxième quadrillage. Les anomalies magnétiques correspondaient à toutes les anomalies de conductivité échantillonnees indiquant la présence de pyrrhotine sauf une. La combinaison des études de conductivité du sol avec des relevés magnétiques et électromagnétiques semble constituer une méthode pratique pour détecter une minéralisation de sulfures à faible profondeur dans la Formation d'Halifax. La Loi sur l'environnement Nouvelle-&#xX9;cosse devrait prévoir la réalisation de ce genre de relevés. Traduit par la rédactio

The relationship of gross upper and lower limb motor competence to measures of health and fitness in adolescents aged 13–14 years

Introduction: Motor competence (MC) is an important factor in the development of health and fitness in adolescence. Aims: This cross-sectional study aims to explore the distribution of MC across 13-14 year old school students and the extent of the relationship of MC to measures of health and fitness across genders. Methods: A total of 718 participants were tested from three different schools in the UK, 311 girls, and 407 boys (aged 13-14 years), pairwise deletion for correlation variables reduced this to 555 (245 girls, 310 boys). Assessments consisted of, body mass index, aerobic capacity, anaerobic power, upper limb and lower limb MC. The distribution of MC and the strength of the relationships between MC and health/fitness measures were explored. Results: Girls performed lower for MC and health/fitness measures compared to boys. Both measures of MC showed a normal distribution and a significant linear relationship of MC to all health and fitness measures for boys, girls, and combined genders. A stronger relationship was reported for upper limb MC and aerobic capacity when compared to lower limb MC and aerobic capacity in boys (t= -2.21, df= 307, p = 0.03, 95%CI -0.253 -0.011). Conclusion: Normally distributed measures of upper and lower limb MC are linearly related to health and fitness measures in adolescents in a UK sample. Trial Registration: NCT0251733

Exploring the metabolic and perceptual correlates of self-selected walking speed under constrained and un-constrained conditions

Mechanisms underpinning self-selected walking speed (SSWS) are poorly understood. The present study investigated the extent to which SSWS is related to metabolism, energy cost, and/or perceptual parameters during both normal and artificially constrained walking. Fourteen participants with no pathology affecting gait were tested under standard conditions. Subjects walked on a motorized treadmill at speeds derived from their SSWS as a continuous protocol. RPE scores (CR10) and expired air to calculate energy cost (J.kg-1.m-1) and carbohydrate (CHO) oxidation rate (J.kg-1.min-1) were collected during minutes 3-4 at each speed. Eight individuals were re-tested under the same conditions within one week with a hip and knee-brace to immobilize their right leg. Deflection in RPE scores (CR10) and CHO oxidation rate (J.kg-1.min-1) were not related to SSWS (five and three people had deflections in the defined range of SSWS in constrained and unconstrained conditions, respectively) (p > 0.05). Constrained walking elicited a higher energy cost (J.kg-1.m-1) and slower SSWS (p 0.05). SSWS did not occur at a minimum energy cost (J.kg-1.m-1) in either condition, however, the size of the minimum energy cost to SSWS disparity was the same (Froude {Fr} = 0.09) in both conditions (p = 0.36). Perceptions of exertion can modify walking patterns and therefore SSWS and metabolism/ energy cost are not directly related. Strategies which minimize perceived exertion may enable faster walking in people with altered gait as our findings indicate they should self-optimize to the same extent under different conditions

The relationship of gross upper and lower limb motor competence to measures of health and fitness in adolescents aged 13-14 years

Introduction: Motor competence (MC) is an important factor in the development of health and fitness in adolescence. Aims: This cross-sectional study aims to explore the distribution of MC across 13-14 year old school students and the extent of the relationship of MC to measures of health and fitness across genders. Methods: A total of 718 participants were tested from three different schools in the UK, 311 girls, and 407 boys (aged 13-14 years), pairwise deletion for correlation variables reduced this to 555 (245 girls, 310 boys). Assessments consisted of, body mass index, aerobic capacity, anaerobic power, upper limb and lower limb MC. The distribution of MC and the strength of the relationships between MC and health/fitness measures were explored. Results: Girls performed lower for MC and health/fitness measures compared to boys. Both measures of MC showed a normal distribution and a significant linear relationship of MC to all health and fitness measures for boys, girls, and combined genders. A stronger relationship was reported for upper limb MC and aerobic capacity when compared to lower limb MC and aerobic capacity in boys (t= -2.21, df= 307, p = 0.03, 95%CI -0.253 -0.011). Conclusion: Normally distributed measures of upper and lower limb MC are linearly related to health and fitness measures in adolescents in a UK sample. Trial Registration: NCT0251733

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Motor impairment and its relationship to fitness in children.

Objectives The aim of this work was to explore the physiological and perceptual limits to exercise in children with varying degrees of motor impairment, and the relationships to measures of health. Design and methods In a group comparison design, 35 boys aged 12–15 years completed the Movement ABC test for the assessment of motor impairment, followed by an incremental cycle ergometer test to exhaustion for the assessment of maximal oxygen uptake (VO2peak), respiratory exchange ratio (RER), heart rate (HR) and rating of perceived exertion (RPE). Ten participants classified as having either high or no motor impairment also performed a maximal voluntary isometric contraction (MVIC) for the assessment of lower limb extensor strength. Results 18 boys were classified as having high motor impairment. There was a significant difference in Graphic peak (34.9 vs 48.5 mL kg/min), Graphic workload (12.5 vs 10.0 mL W), maximal HR (176 vs 188 bpm), maximal oxygen pulse (12.1 vs 15.9 mL beat) and MVIC (5.7 vs 9.1 Nm kg) between the high and non-motor impaired participants, respectively, (p<0.05). There was no significant difference in the RER or RPE between groups. Conclusions When performing cycling ergometry, perceived exertion was not a limiting factor in children with high motor impairment. The lower maximal HR, coupled with reduced movement efficiency and muscle strength reported in this group, suggests that exercise is limited by impairment at the muscular level. This finding was supported by high RER values despite low maximal HR values attained at exercise cessation and reduced maximal strength. Perception of effort is not heightened in children with high motor impairment and future-exercise interventions should be focused on improving muscular condition in these participants to enable them to be better prepared to engage in physical activity for health

Anomalous centre of mass energy fluctuations during treadmill walking in healthy individuals

Motorised treadmills are used to research and rehabilitate gait despite conflicting evidence that treadmill ambulation is equivalent to ground walking. It has been suggested that no mechanical differences should exist between these environments but there is little evidence to support this. During ground walking, the whole body centre of mass (COM) acts like an inverted pendulum recovering energy, thereby reducing the effort of locomotion. The energy recovery has a relationship with speed whereby maximum recovery occurs at intermediate speeds. In order to determine the relationship between energy recovery and speed during treadmill walking, we investigated estimated COM displacement in nine healthy individuals each walking on a treadmill at seven different speeds. In addition, we measured oxygen cost to determine the effort of walking. Our participants formed two distinct groups, those with normal COM energy recovery (N%R) that was similar to ground walking, and those with low COM energy recovery (L%R) that was different from typical ground walking. The low energy recovery in the L%R group was attributed to in-phase potential and kinetic energy fluctuations. Despite the low energy recovery values both groups produced the expected 'U'-shaped oxygen cost speed curve with no significant difference between groups (

RELATIONSHIPS BETWEEN MUSCLE FATIGUE CHARACTERISTICS AND MARKERS OF ENDURANCE PERFORMANCE

The aim of this study was to examine the relationship of a range of in-vivo whole muscle characteristics to determinants of endurance performance. Eleven healthy males completed a cycle ergometer step test to exhaustion for the determination of the lactate threshold, gross mechanical efficiency, peak power and VO2max. On two separate occasions, contractile and fatigue characteristics of the quadriceps femoris were collected using a specially designed isometric strength-testing chair. Muscle fatigue was then assessed by stimulating the muscle for 3 minutes. Force, rate of force development and rates of relaxation were calculated at the beginning and end of the 3 minute protocol and examined for reliability and in relation to lactate threshold, VO2max, gross mechanical efficiency and peak power. Muscle characteristics, rate of force development and relaxation rate were demonstrated to be reliable measures. Force drop off over the 3 minutes (fatigue index) was related to lactate threshold (r = -0.72 p < 0.01) but not to VO2max. The rate of force development related to the peak power at the end of the cycle ergometer test (r = -0.75 p < 0.01). Rates of relaxation did not relate to any of the performance markers. We found in-vivo whole muscle characteristics, such as the fatigue index and rate of force development, relate to specific markers of peripheral, but not to central, fitness components. Our investigation suggests that muscle characteristics assessed in this way is reliable and could be feasibly utilised to further our understanding of the peripheral factors underpinning performanc