Cambrian stratigraphy of Jordan

The lower and middle Cambrian succession (Ram Group) in Jordan is described in lexicon-style format to document an important phase of Earth history following the uplift and erosion of the Arabian-Nubian Shield (Aqaba Complex) during the late Neoproterozoic, and younger, but more localised, intrusive and volcanic/ volcaniclastic activity that formed the Araba Complex. The early Cambrian Ram Unconformity (ca. 530 Ma) marks the base of a predominantly fluvial siliciclastic succession derived from rapidly eroding Neoproterozoic (including Ediacaran) basement rocks, but includes a brief, but biostratigraphically significant, sequence of marine siliciclastics and carbonates, the early mid-Cambrian Burj Formation. Rapid uplift and erosion of the granitoid basement (Arabian-Nubian Shield or ANS) resulted in a peneplanation of the Aqaba Complex over millions of years duration (latest Neoproterozoic to Cambrian) in the Southern Desert of Jordan. Early Cambrian pebbly sandstones and locally derived conglomerates (Salib Formation) were deposited on an alluvial plain by high velocity-high discharge, northward flowing (NNE to NNW) braided rivers, characterised by trough crossbedding and erosive tabular sets. Brief, and rare, marine influence is represented, locally, by thin Skolithos-burrowed sandstones. A regional sea-level rise in the early mid-Cambrian marks a major marine transgressive-regressive cycle and southward thinning carbonate-siliciclastic wedge (Burj Formation) widely present in the subsurface across the Arabian Platform. During deposition of this transgressive marine sequence the palaeoshoreline was oriented WNW-ESE in southern Jordan. The transgressive phase (TST) is represented by tidal-dominated siltstones and fine-grained sandstones (Tayan Member) containing a diverse Cruziana/Rusophycus ichnofaunal assemblage. The overlying carbonate unit (Numayri Member) represents the highstand (HST) and maximum marine flooding surface (MFS), and comprises a carbonate ramp sequence of shelly wackestone, packstone and grainstone with ooids and oncolites, and a diverse shelly fauna including trilobites, brachiopods and hyolithids. A return to regressive tidal-influenced sandstone and siltstone (along with thin carbonates in central Jordan) (Hanneh Member) represents a regressive wedge (RST) deposited in response to renewed uplift of the ANS. Trilobites, represented by the Kingaspis campbelli and Redlichops faunules, suggest a biostratigraphical age of early mid-Cambrian for the carbonate MFS, which equates approximately to the base of the Cambrian Series 3 (Stage 5). This event probably represents the Cambrian marine flooding surface Cm20 (approximate geochronological age of 509 to 505 Ma). South of Feinan, in the Wadi Araba, the carbonates pass laterally to marine sandstone (Abu Khusheiba Sandstone) with extensive Skolithos burrows and Cruziana/Rusophycus traces. Traced southwards (palaeohinterland) the marine influence diminishes, so that the Burj/Abu Khusheiba units are absent in the Southern Desert

Prospectus, April 5, 1995

https://spark.parkland.edu/prospectus_1995/1010/thumbnail.jp

Magnetic excitations of the Cu2+^{2+} quantum spin chain in Sr3_3CuPtO6_6

We report the magnetic excitation spectrum as measured by inelastic neutron scattering for a polycrystalline sample of Sr$_3$CuPtO$_6$. Modeling the data by the 2+4 spinon contributions to the dynamical susceptibility within the chains, and with interchain coupling treated in the random phase approximation, accounts for the major features of the powder-averaged structure factor. The magnetic excitations broaden considerably as temperature is raised, persisting up to above 100 K and displaying a broad transition as previously seen in the susceptibility data. No spin gap is observed in the dispersive spin excitations at low momentum transfer, which is consistent with the gapless spinon continuum expected from the coordinate Bethe ansatz. However, the temperature dependence of the excitation spectrum gives evidence of some very weak interchain coupling.Comment: 9 pages, 5 figure

Hydrophobic gating of mechanosensitive channel of large conductance evidenced by single-subunit resolution

Mechanosensitive (MS) ion channels are membrane proteins that detect and respond to membrane tension in all branches of life. In bacteria, MS channels prevent cells from lysing upon sudden hypoosmotic shock by opening and releasing solutes and water. Despite the importance of MS channels and ongoing efforts to explain their functioning, the molecular mechanism of MS channel gating remains elusive and controversial. Here we report a method that allows single-subunit resolution for manipulating and monitoring “mechanosensitive channel of large conductance” from Escherichia coli. We gradually changed the hydrophobicity of the pore constriction in this homopentameric protein by modifying a critical pore residue one subunit at a time. Our experimental results suggest that both channel opening and closing are initiated by the transmembrane 1 helix of a single subunit and that the participation of each of the five identical subunits in the structural transitions between the closed and open states is asymmetrical. Such a minimal change in the pore environment seems ideal for a fast and energy-efficient response to changes in the membrane tension.

Tolerance aux fautes et systemes repartis : concepts et mecanismes

Projet REFLECSL'exigence de tolerance aux fautes est incontournable avec les systemes repartis. D'une part, la tolerance aux fautes est un besoin induit par la multiplicite des ressources et de nombreux travaux sur les systemes repartis ont pour but de garantir que la surete de fonctionnement de ces systemes n'est pas degradee par la repartition. Par ailleurs, la tolerance aux fautes peut etre en elle-meme un facteur motivant la repartition. En effet, la tolerance aux fautes ne peut etre assuree sans redondance et la repartition des traitements et des donnees sur des processeurs differents permet de structurer et gerer cette redondance. Dans ce rapport, nous presentons les concepts et mecanismes utilises dans les systemes repartis tolerants aux fautes. Une application repartie peut etre vue soit comme un ensemble de processus interagissant par echange de messages, soit comme un ensemble de transactions manipulant des donnees reparties. Les techniques connues de tolerance aux fautes sont fournies pour ces deux schemas de traitement. Nous introduisons ensuite les concepts de diffusion et de consensus reparti tolerant aux fautes

Regulation of procollagen amino-propeptide processing during mouse embryogenesis by specialization of homologous ADAMTS proteases: insights on collagen biosynthesis and dermatosparaxis

Mutations in ADAMTS2, a procollagen amino-propeptidase, cause severe skin fragility, designated as dermatosparaxis in animals, and a subtype of the Ehlers-Danlos syndrome (dermatosparactic type or VIIC) in humans. Not all collagen-rich tissues are affected to the same degree, which suggests compensation by the ADAMTS2 homologs ADAMTS3 and ADAMTS14. In situ hybridization of Adamts2, Adamts3 and Adamts14, and of the genes encoding the major. brillar collagens, Col1a1, Col2a1 and Col3a1, during mouse embryogenesis, demonstrated distinct tissue-specific, overlapping expression patterns of the protease and substrate genes. Adamts3, but not Adamts2 or Adamts14, was co-expressed with Col2a1 in cartilage throughout development, and with Col1a1 in bone and musculotendinous tissues. ADAMTS3 induced procollagen I processing in dermatosparactic. broblasts, suggesting a role in procollagen I processing during musculoskeletal development. Adamts2, but not Adamts3 or Adamts14, was co-expressed with Col3a1 in many tissues including the lungs and aorta, and Adamts2(-/-) mice showed widespread defects in procollagen III processing. Adamts2(-/-) mice had abnormal lungs, characterized by a decreased parenchymal density. However, the aorta and collagen fibrils in the aortic wall appeared normal. Although Adamts14 lacked developmental tissue-specific expression, it was co-expressed with Adamts2 in mature dermis, which possibly explains the presence of some processed skin procollagen in dermatosparaxis. The data show how evolutionarily related proteases with similar substrate preferences may have distinct biological roles owing to tissue specific gene expression, and provide insights into collagen biosynthesis and the pathobiology of dermatosparaxis

Linking the oceans to public health: current efforts and future directions

This is the final version of the article. Available from BioMed Central via the DOI in this recordWe review the major linkages between the oceans and public health, focusing on exposures and potential health effects due to anthropogenic and natural factors including: harmful algal blooms, microbes, and chemical pollutants in the oceans; consumption of seafood; and flooding events. We summarize briefly the current state of knowledge about public health effects and their economic consequences; and we discuss priorities for future research.We find that:* There are numerous connections between the oceans, human activities, and human health that result in both positive and negative exposures and health effects (risks and benefits); and the study of these connections comprises a new interdisciplinary area, "oceans and human health."* The state of present knowledge about the linkages between oceans and public health varies. Some risks, such as the acute health effects caused by toxins associated with shellfish poisoning and red tide, are relatively well understood. Other risks, such as those posed by chronic exposure to many anthropogenic chemicals, pathogens, and naturally occurring toxins in coastal waters, are less well quantified. Even where there is a good understanding of the mechanism for health effects, good epidemiological data are often lacking. Solid data on economic and social consequences of these linkages are also lacking in most cases.* The design of management measures to address these risks must take into account the complexities of human response to warnings and other guidance, and the economic tradeoffs among different risks and benefits. Future research in oceans and human health to address public health risks associated with marine pathogens and toxins, and with marine dimensions of global change, should include epidemiological, behavioral, and economic components to ensure that resulting management measures incorporate effective economic and risk/benefit tradeoffs.Funding was provided in part by the NSF-NIEHS Oceans Centers at Woods Hole, University of Hawaii, University of Miami, and University of Washington, and the NOAA Oceans and Human Health Initiative Centers of Excellent in Charleston, Seattle and Milwaukee, the National Center for Environmental Health (NCEH) of the Centers for Disease Control and Prevention (CDC), and the WHOI Marine Policy Center. Grant numbers are: NIEHS P50 ES012742 and NSF OCE-043072 (HLKP, RJG, PH); NSF OCE-0432368 and NIEHS P50 ES12736 (LEF); NIEHS P50 ES012762 and NSF OCE-0434087 (EMF, AT, LRY); NSF OCE04-32479 and NIEHS P50 ES012740 (BAW

Investigating the impact of nicotine on executive functions using a novel virtual reality assessment

Aims Nicotine is known to enhance aspects of cognitive functioning in abstinent smokers but the effects on specific areas of executive functions, and in non-smokers are inconclusive. This may be due in part to the poor sensitivity of tests used to assess executive functions. This study used a new virtual reality assessment of executive functions known as JEF (the Jansari assessment of Executive Functions) to address this issue. Design 2x2 design manipulating group (smokers and never-smokers) and drug (nicotine [4mg for smokers; 2mg for never smokers] vs placebo gum). Setting School of Psychology; University of East LondonParticipants 72 participants (aged 18 to 54). 36 minimally-deprived (2 hr) smokers and 36 never-smokers.Measurements Components of executive function were measured using the virtual reality paradigm JEF, which assesses eight cognitive constructs simultaneously as well as providing an overall performance measure. Results Univariate ANOVAs revealed that nicotine improved overall JEF performance, time-based prospective memory and event-based prospective memory in smokers (p < 0.01) but not in never-smokers. Action-based prospective memory was enhanced in both groups (p < 0.01) and never-smokers out-performed smokers on selective thinking and adaptive thinking (p < 0.01). Conclusions. Overall executive functioning and prospective memory can be enhanced by nicotine gum in abstinent smokers. That smokers were only minimally deprived suggests that JEFis a sensitive measure of executive functioning and that prospective memory is particularly susceptible to disruption by abstinence

The languages of peace during the French religious wars

The desirability of peace was a common topos in sixteenth-century political rhetoric, and the duty of the king to uphold the peace for the benefit of his subjects was also a long-established tradition. However, the peculiar circumstances of the French religious wars, and the preferred royal policy of pacification, galvanized impassioned debate among both those who supported and those who opposed confessional coexistence. This article looks at the diverse ways in which peace was viewed during the religious wars through an exploration of language and context. It draws not only on the pronouncements of the crown and its officials, and of poets and jurists, but also on those of local communities and confessional groups. Opinion was not just divided along religious lines; political imperatives, philosophical positions and local conditions all came into play in the arguments deployed. The variegated languages of peace provide a social and cultural dimension for the contested nature of sixteenth-century French politics. However, they could not restore harmony to a war-torn and divided kingdom