The onset of deep recycling of supracrustal materials at the Paleo-Mesoarchean boundary

The recycling of supracrustal materials, and in particular hydrated rocks, has a profound impact on mantle composition and thus on the formation of continental crust, because water modifies the physical properties of lithological systems and the mechanisms of partial melting and fractional fractionation. On the modern Earth, plate tectonics offers an efficient mechanism for mass transport from the Earth''s surface to its interior, but how far this mechanism dates back in the Earth''s history is still uncertain. Here, we use zircon oxygen (O) isotopes to track recycling of supracrustal materials into the magma sources of early Archean igneous suites from the Kaapvaal Craton, southern Africa. The mean δ¹⁸O values of zircon from TTG (tonalite–trondhjemite–granodiorite) rocks abruptly increase at the Paleo-Mesoarchean boundary (ca. 3230 million years ago; Ma), from mantle zircon values of 5‰–6‰ to approaching 7.1‰, and this increase occurs in ≤3230 Ma rocks with elevated Dy/Yb ratios. The ¹⁸O enrichment is a unique signature of low-temperature water–rock interaction on the Earth''s surface. Because the later phase was emplaced into the same crustal level as the older one and TTG magmas would derive from melting processes in the garnet stability field (>40 km depth), we suggest that this evident shift in TTG zircon O isotopic compositions records the onset of recycling of the mafic oceanic crust that underwent seawater hydrothermal alteration at low temperature. The onset of the enhanced recycling of supracrustal materials may also have developed elsewhere in other Archean cratons and reflects a significant change in the tectonic realm during craton formation and stabilization, which may be important processes for the operation of plate tectonics on early Earth.     

Values—— A study of teacher and student perceptions in four countries

The study aimed to assess and compare the values prevalent among the students and teachers of Universities in Bangladesh, Japan, USA and Germany. The sample consisted of 480 students and 236 teachers. The sample included 120 undergraduate students Japan; 120 undergraduate students from Bangladesh; 120 undergraduate students from USA, and 120 undergraduate students from Germany. The faculty sample included 60 teachers from Japan, 60 teachers from Bangladesh; 60 teachers from USA, and 56 teachers from Germany. To identify the value preferences of the individuals a list of 10 values, pro-social, achievement, power over others, security, self direction, otherworldliness, fatalism, narcissism, inner directed, and conservative, based on previous values studies by Singh and Parek were prepared. The first five values were identified in previous studies as functional （Singh, 1975） and other five were identified as dysfunctional （Parek, 1988） in the context of national development of Asian cultures. The results revealed that Bangladeshi students held stronger preferences for values identified as functional values than for those identified as dysfunctional. Japanese students indicated stronger preferences for the values identified as functional values except narcissism. The American students indicated a preference for three of the five values identified as functional but also ranked narcissism and other worldliness as third and fifth preferred values respectively. German student showed a preference for functional values, except narcissism which they also ranked as third. Bangladeshi teachers＇ preferences for functional values were higher than dysfunctional values. Japanese teachers indicated a preference for functional values except narcissism. American teachers preferred functional values except other worldliness. German teachers＇ value preferences were also functional, except for narcissism which they ranked as fifth. Students and teachers in the four countries sampled indicate preferences for values identified as functional with few exceptions. This research suggests that value preferences among university students and teachers are more similar than different, suggesting a homogenizing effect （Boli, 2005） on human values.     

Peak Power Assessment of Isokinetic Knee Flexor and Extensor Tests – Pitfalls of a Dynamometer-based Assessment

ABSTRACT

Many sports demand high forces at high movement speeds. Joint power combines these two measures and is frequently analyzed by isokinetic tests. However, various concepts of assessing joint power lead to conflicting results. The aim was to examine different methods to calculate peak power during isokinetic knee tests of sixty-one healthy male participants (20 y, 182 cm, 76 kg). Unilateral movements of the eccentrically working hamstrings and the concentrically working quadriceps at 150°/s were captured by high-speed cameras. Peak power derived from isokinetic data was significantly higher (p < 0.01, d > 1.54) compared to the camera-based kinematic procedures. To achieve best accuracy, peak power should be derived from the camera-based joint angular velocity and the measured moment at time of peak power during the dynamometer’s isokinetic range of motion. A meaningful assessment of isokinetic joint power should incorporate a camera-based kinematic analysis to account for potential measuring inaccuracies owing to anatomical features, axis misalignment, and tissue deformation.     

Radicalism in composition pedagogy

For the Record

Radicalism in composition pedagogy     

Forschungs- und Entwicklungsprojekte

Ohne ZusammenfassungAxel Pfeiffer: Dipl.-Ing.,Patentanwalt     

Developmental changes in item and source memory: evidence from an ERP recognition memory study with children, adolescents, and adults

Event-related potential (ERP) correlates of item and source memory were assessed in 18 children (7-8 years), 20 adolescents (13-14 years), and 20 adults (20-29 years) performing a continuous recognition memory task with object and nonobject stimuli. Memory performance increased with age and was particularly low for source memory in children. The ERP difference between first presentations of objects and nonobjects, reflecting generic novelty processing, showed only small developmental changes. Regarding item memory, adults showed the putative ERP correlates of familiarity and recollection, whereas ERP effects in children and adolescents suggested a strong reliance on recollection. ERP correlates of source memory refined with age, suggesting maturation of strategic recollection between childhood and adolescence and the development of postretrieval control until adulthood.     

Transition partnerships: the views of education professionals and staff in support services for young people with learning disabilities

Transition to post-statutory education and employment for young people with learning disabilities has become a hotly debated issue among professionals in education and support services in the UK. Partnerships between educational institutions and voluntary sector providers are supposed to be ideal vehicles for delivering transition services and securing outcomes for young people with learning disabilities. In this article, Axel Kaehne and Stephen Bayer of the Welsh Centre for Learning Difficulties report the findings of a survey of the views of special educational needs co-ordinators and professionals who are involved at operational and strategic levels in the work of transition partnerships. The data show that undue emphasis is often placed, by all stakeholders, on the soft, rather than the concrete, outcomes of transition; that smooth transitions are still hampered by insufficient flow of information between collaborating agencies; and that there are still significant gaps in provision, in particular in the supported employment field, due to funding or referral restrictions. To deliver first-class transitions, argue Axel Kaehne and Stephen Bayer, partnerships that support young people with learning disabilities need to address these difficulties with some urgency.     

Quantification of improvement in triathlon swimming performance by textile speedsuits

To quantify swimwear-induced differences under triathlon-specific conditions, we compare the swimming performance, the metabolic cost, and the standardised passive drag of well-trained triathletes when wearing (1) five speedsuit models by different manufacturers from 2017, (2) usual swimming trunks/swimsuits (men/women), and (3) individually preferred competition trisuits. Because of the complexity of the underlying hydrodynamic and biomechanical effects, three separate experimental stages were realized, each with 6–12 well-trained short- and middle-distance triathletes (male and female, mean age 22?±?5 years) from the German national elite or junior elite level. All measurements were conducted on the basis of real athletes’ motion in the water to correctly account for all relevant effects, including skin and muscle vibrations. First, the athletes took part in a series of 100 m short-distance tests at maximal effort in a long-course pool to quantify swim-time differences in absolute terms. Second, the subjects completed multiple submaximal 400 m tests at 95% of their individual maximal speed in a swimming flume, with their swimwear-related differences in metabolic load being explored in terms of blood lactate and heart rate. Third, the passive drag of the triathletes was measured in the flume during a towing test under standardised conditions in velocity steps of 0.2 m/s within the triathlon-relevant range of 1.1–1.7 m/s. In all three test stages, the speedsuits exhibited performance advantages over trunks/swimsuits: in the 100 m maximal test, the mean swim time with speedsuits decreased by 0.99?±?0.30 s (????1.5%). During the 400 m submaximal flume test, the mean heart rate showed a reduction of 7?±?2 bpm (? ??4.0%), while the post-exercise blood lactate accumulation decreased by 1.0?±?0.2 mmol/L (? ??26.2%). Similarly, the passive drag in the towing test was lowered by 3.2?±?1.0 W (????6.9% as for normalised power and ??5.2% as for normalised force) for the speedsuits. Wearing speedsuits instead of usual trunks/swimsuits is shown to improve the swimming performance and to reduce the metabolic cost for well-trained triathletes under triathlon-specific test conditions. The reduction in passive drag of the passively towed athlete’s body due specific speedsuit surface textures seems to be only one reason for performance advantages: the effective reduction in muscular, soft tissue, and skin vibrations at the trunk and thighs during active propulsive motion of the swimmer seems to further contribute substantially.