584 research outputs found
Zircon U-Pb dating of Mesozoic volcanic and tectonic events in northwest Palmer Land and southwest Graham Land, Antarctica
New whole rock Rb-Sr and zircon U-Pb geochronological data and Sm-Nd isotopic data are presented from the central magmatic arc domain of the Antarctic Peninsula in the area of northwest Palmer Land and southwest Graham Land, Rb-Sr isochrons indicate an age of 169±6 Ma for basement orthogneisses and 132±9 to 71±9 Ma for plutons. A U-Pb age of 183 ± 2.1 Ma, with no detectable inheritance, on zircons from an orthogneiss from Cape Berteaux provides the first reliable age for the orthogneisses, which are interpreted as metamorphosed silicic volcanic rocks, and Sm-Nd data indicate derivation in a mature volcanic arc. The age indicates they may be correlatives of the Jurassic ‘Chon Aike’ volcanism of the eastern Antarctic Peninsula. A U-Pb zircon age of 107 ± 1.7 Ma on a terrestrial volcanic sequence overlying an uncomformity strongly suggests a mid-Cretaceous age for the extensive volcanic cover of northwest Palmer Land that was previously thought to be Jurassic. The unconformity is interpreted to have been a result of compressional uplift related to the Palmer Land event. This is the first date for the event in the western part of the central magmatic arc terrane of the Antarctic Peninsula
The CPSU and its members: between communism and postcommunism
Once dominant and unchallenged throughout the USSR, the Communist Party of the Soviet Union rapidly lost authority in the last two years of Soviet rule. Banned by Russian presidential decree after the failure of the attempted coup of August 1991, it was re-established in February 1993 and soon became the largest of the postcommunist parties. A 1992 survey of current and former party members as well as other Russians found that members were characterized by a relatively high degree of activism. They were disproportionately male, more affluent than non-members, and better provided with consumer goods. Younger respondents and religious believers were more likely to have left the party than their older colleagues. Those who still regarded themselves as party members were the most likely to oppose economic reform and support the collectivist principles of the communist era, particularly if they were activists; but the differences between members and non-members were not substantial, and both were found to hold generally pessimistic views on the postcommunist system. These findings suggest that, although former members will continue to be influential, CPSU membership is by itself likely to play a limited part in shaping the political direction of postcommunist Russia
Ion channel diversity, channel expression and function in the choroid plexuses
Knowledge of the diversity of ion channel form and function has increased enormously over the last 25 years. The initial impetus in channel discovery came with the introduction of the patch clamp method in 1981. Functional data from patch clamp experiments have subsequently been augmented by molecular studies which have determined channel structures. Thus the introduction of patch clamp methods to study ion channel expression in the choroid plexus represents an important step forward in our knowledge understanding of the process of CSF secretion
Is there a right way to teach physics?
An important development in university physics teaching in the last two decades has been the emergence of a worldwide Physics Education Research community. In physics departments at relatively large numbers of institutions throughout the world, particularly the USA and Europe, academic physicists are doing research into the difficulties associated with teaching their subject. Among the many directions this research has taken is the identification of 'misconceptions' (sometimes referred to as 'alternative conceptions'). These are ideas or concepts which students have constructed for themselves, based on their own experience of the natural world, which are often in conflict with the agreed view of practicing scientists. Research has
shown that these 'misconceptions' are very widely shared, very often in conflict with other concepts the student holds, and very difficult to change.
Following on from this research, as it were, a lot of work has been done to develop special diagnostic tests to uncover which, if any, of these misconceptions particular students hold. They normally consist of series of multiple choice questions, in which the 'right' answer is hidden among very tempting distracters, each one targeting one or more common misconceptions.Among the best known of these tests, in the subject area of kinematics and dynamics, are the Force Concept Inventory (FCI) and the Mathematics and Physics Concept Evaluation (MCPE)
This research has, in turn, prompted the development of teaching strategies which target specific classes of misconceptions - in the (understandable) belief that, if students can get the fundamental concepts 'right', they have a better chance of understanding the rest of the subject.The results of these strategies are reported in the literature, and there is coming to be a consensus within the physics education community that, for example, traditional (chalk and talk, lectures plus laboratories) teaching is relatively ineffective in changing misconceptions. On the other hand, one recent survey of over 7000 students in the USA has shown that teaching which employs interactive methods can result in significant increases in understanding (as measured by these diagnostic tests).
It would seem important therefore that teachers everywhere should take these findings seriously, and, where possible, test whether the same gain in understanding can be achieved in other teaching contexts
Going to Market with Deweyfish: The Journey from Partnership to Commercialisation
In 2016-7, The University of Western Australia Library partnered with researchers in the Australian Research Council’s Centre of Excellence in Plant Energy Biology to produce cropPAL2, a database providing the subcellular locations for proteins in crops significant for food production. The project was funded by the Australian National Data Service as part of its High Value Collections program, with the team consisting of computational biologists, software engineers and a librarian. The project involved many hours of manual article evaluation and data extraction by specialists in the plant species included in cropPAL, and the team decided that developing in-house software could make managing the process of article evaluation by multiple people much easier. Key software features were that it prevented assessing the same article twice, simplified finding and adding new articles to the database, provided real-time access by international group members, and the cut and drop function facilitated saving images and notes. Use of this software represented a 90% saving in time and therefore salaries.
The team realised the in-house software could be applied across many areas of research. Known as Team DeweyFish, the group embarked on the CSIRO’s ON Prime program in 2018 to learn how to commercialise the software. This process involved the team generating and testing 15 hypotheses about researcher behaviour through conducting 66 one on one interviews with potential users. This data lead to some significant insights, clarifying the needs of various user groups and refining the software specifications. An initial target market has been selected, and the team is now working towards developing a commercialisable prototype. This paper will discuss the role of the Library as a key player in this collaboration, a first for the University of WA, both in the innovative process and as a key driver in directing the development towards the wider benefit of researchers at UWA and beyond
The Brahmaputra tale of tectonics and erosion:early Miocene river capture in the Eastern Himalaya
The Himalayan orogen provides a type example on which a number of models of the causes and consequences of crustal deformation are based and it has been suggested that it is the site of a variety of feedbacks between tectonics and erosion. Within the broader orogen, fluvial drainages partly reflect surface uplift, different climatic zones and a response to crustal deformation. In the eastern Himalaya, the unusual drainage configuration of the Yarlung Tsangpo–Brahmaputra River has been interpreted either as antecedent drainage distorted by the India–Asia collision (and as such applied as a passive strain marker of lateral extrusion), latest Neogene tectonically-induced river capture, or glacial damming-induced river diversion events. Here we apply a multi-technique approach to the Neogene paleo-Brahmaputra deposits of the Surma Basin (Bengal Basin, Bangladesh) to test the long-debated occurrence and timing of river capture of the Yarlung Tsangpo by the Brahmaputra River. We provide U–Pb detrital zircon and rutile, isotopic (Sr–Nd and Hf) and petrographic evidence consistent with river capture of the Yarlung Tsangpo by the Brahmaputra River in the Early Miocene. We document influx of Cretaceous–Paleogene zircons in Early Miocene sediments of the paleo-Brahmaputra River that we interpret as first influx of material from the Asian plate (Transhimalayan arc) indicative of Yarlung Tsangpo contribution. Prior to capture, the predominantly Precambrian–Paleozoic zircons indicate that only the Indian plate was drained. Contemporaneous with Transhimalayan influx reflecting the river capture, we record arrival of detrital material affected by Cenozoic metamorphism, as indicated by rutiles and zircons with Cenozoic U–Pb ages and an increase in metamorphic grade of detritus as recorded by petrography. We interpret this as due to a progressively increasing contribution from the erosion of the metamorphosed core of the orogen. Whole rock Sr–Nd isotopic data from the same samples provide further support to this interpretation. River capture may have been caused by a change in relative base level due to uplift of the Tibetan plateau. Assuming such river capture occurred via the Siang River in the Early Miocene, we refute the “tectonic aneurysm” model of tectonic–erosion coupling between river capture and rapid exhumation of the eastern syntaxis, since a time interval of at least 10 Ma between these two events is now demonstrated. This work is also the first to highlight U–Pb dating on detrital rutile as a powerful approach in provenance studies in the Himalaya in combination with zircon U–Pb chronology
A constant Chinese Loess Plateau dust source since the late Miocene
© 2019 The Authors The Pliocene-Pleistocene boundary marks a major change in global climate and East Asian monsoon dynamic. However, the role of the global atmospheric dust-cycle over this time is unclear; in particular the degree to which changes in the dust cycle influenced climate change, were driven by climate change, and how these processes interacted. Chinese loess records past dust-cycle history and the influences of aridification and monsoon circulation over the last 40 Ma. Previous work on the Chinese Loess Plateau argue over whether changes in dust source occur at the Pliocene-Pleistocene boundary, or at 1.2 Ma, despite these intervals marking major shifts in monsoon dynamics. We present Sr, Nd and Hf isotope data from multiple sites and show that dust source largely remains unchanged across these boundaries. Shifts in geochemistry are due to changes in grain-size and weathering. While the transport pathway (river, deserts, direct aeolian) is unclear, these tracer isotopes show that dust was dominantly sourced from the Northern Tibetan Plateau, with some input from the local bedrock. This shows that a major established and constant dust source on the Tibetan Plateau has been active and unchanged since late Miocene, despite dramatically changing climate conditions. Changes in loess accumulation are a function of climate change in Tibetan Plateau source regions rather than effects from increased aridification over the Pliocene-Pleistocene boundary
The chicken type III GnRH receptor homologue is predominantly expressed in the pituitary, and exhibits similar ligand selectivity to the type I receptor
Two GnRH isoforms (cGnRH-I and GnRH-II) and two GnRH receptor subtypes (cGnRH-R-I and cGnRH-R-III) occur in chickens. Differential roles for these molecules in regulating gonadotrophin secretion or other functions are unclear. To investigate this we cloned cGnRH-R-III from a broiler chicken and compared its structure, expression and pharmacological properties with cGnRH-R-I. The broiler cGnRH-R-III cDNA was 100% identical to the sequence reported in the red jungle fowl and white leghorn breed. Pituitary cGnRH-R-III mRNA was ∼1400-fold more abundant than cGnRH-R-I mRNA. Northern analysis indicated a single cGnRH-R-III transcript. A pronounced sex and age difference existed, with higher pituitary transcript levels in sexually mature females versus juvenile females. In contrast, higher expression levels occurred in juvenile males versus sexually mature males. Functional studies in COS-7 cells indicated that cGnRH-R-III has a higher binding affinity for GnRH-II than cGnRH-I (Kd: 0·57 vs 19·8 nM) with more potent stimulation of inositol phosphate production (ED50: 0·8 vs 4·38 nM). Similar results were found for cGnRH-R-I, (Kd: 0·51 vs 10·8 nM) and (ED50: 0·7 vs 2·8 nM). The initial rate of internalisation was faster for cGnRH-R-III than cGnRH-R-I (26 vs 15·8%/min). Effects of GnRH antagonists were compared at the two receptors. Antagonist #27 distinguished between cGnRH-R-I and cGnRH-R-III (IC50: 2·3 vs 351 nM). These results suggest that cGnRH-R-III is probably the major mediator of pituitary gonadotroph function, that antagonist #27 may allow delineation of receptor subtype function in vitro and in vivo and that tissue-specific recruitment of cGnRH-R isoforms has occurred during evolution
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