Throughout Earth's history, carbonate factories have been production systems which appeared, declined and re-appeared (in modified form) in function of biotic evolution and systemic stability. ...Reconstructing the history of these intricate systems requires a combined assessment of sedimentological, paleoecological, geochemical and diagenetic criteria. Here, the Ordovician of the western Tarim Basin (Darriwilian to Katian, ramp-platform to basin settings) is used as the case example to test a multiproxy approach, including statistical analysis of proxy data. We identify stratigraphic segmentation of these strata in terms of facies/mineralogy, diagenesis and a first comprehensive data set of component-specific carbon and oxygen isotope values. The published bulk carbon and oxygen isotope data are analysed in the second step to extract marine diagenetic versus burial/meteoric signatures (virtual bulk values, Monte-Carlo simulation). Finally, a synoptic chemo-chronostratigraphic plot for the Ordovician of the western Tarim Basin with segments lasting from tens of Myrs down to several 100 kyrs is proposed. A long-term trend of increasing δ13C values culminates in the early Katian at 3.2 ‰ followed by a steady decrease. A baseline shift, arguably due to the initiation of a bahamite-type factory, blurs the globally reported Guttenberg carbon-isotope excursion (GICE). A medium-term (Darriwilian to earliest Sandbian) negative δ13C isotope excursion coincides with the demise of the Darriwilian sponges-pelmatozoa factory (suecicus Event, term proposed in this study) and a positive δ18O excursion. This event might represent the effects of volcanism/SO2 outgassing during the switch from a passive to an active continental arc. The suecicus Event masquerades the middle Darriwilian carbon-isotope excursion (MDICE).
•Chronostratigraphic architecture (Wheeler diagram) of Ordovician deposits of the western Tarim Basin.•Integrated petrography including the spatial variation in diagenetic sequences.•First comprehensive data set of component-specific carbon and oxygen isotope values.•Statistical methods to qualify published bulk-rock geochemical data.•Synopsis addressing drivers of evolutionary and environmental change.
Sauropterygia was a taxonomically and ecomorphologically diverse clade of Mesozoic marine reptiles spanning the Early Triassic to the Late Cretaceous. Sauropterygians are traditionally divided into ...two groups representing two markedly different body plans - the short-necked, durophagous Placodontia and the long-necked Eosauropterygia - whereas Saurosphargidae, a small clade of armoured marine reptiles, is generally considered as the sauropterygian sister-group. However, the early evolutionary history of sauropterygians and their phylogenetic relationships with other groups within Diapsida are still incompletely understood. Here, we report a new saurosphargid from the Early Triassic (Olenekian) of South China -
gen. et sp. nov. - representing the earliest known occurrence of the clade. An updated phylogenetic analysis focussing on the interrelationships among diapsid reptiles recovers saurosphargids as nested within sauropterygians, forming a clade with eosauropterygians to the exclusion of placodonts. Furthermore, a clade comprising
and
is recovered as the sauropterygian sister-group within Sauropterygomorpha tax. nov. The phylogenetic position of several Early and Middle Triassic sauropterygians of previously uncertain phylogenetic affinity, such as
,
,
and
, is also clarified, elucidating the early evolutionary assembly of the sauropterygian body plan. Finally, our phylogenetic analysis supports the placement of Testudinata and Archosauromorpha within Archelosauria, a result strongly corroborated by molecular data, but only recently recovered in a phylogenetic analysis using a morphology-only dataset. Our study provides evidence for the rapid diversification of sauropterygians in the aftermath of the Permo-Triassic mass extinction event and emphasises the importance of broad taxonomic sampling in reconstructing phylogenetic relationships among extinct taxa.
The Paleo-Tethys experienced major geographic, tectonic, climatologic, and environmental changes during the Permian. A newly documented and complete Permian carbonate-dominated succession (>3 km) in ...the Xikou section, Zhen'an, Shaanxi, central China provides a unique opportunity to record its depositional environment evolution, sea-level fluctuation, and associated paleogeographic and paleoclimatic perturbation of the eastern Paleo-Tethys. Field observation and petrographic analysis document eighteen facies and indicate evolutional facies of a carbonate ramp within the Xikou section. The vertical distribution of those facies in the Xikou section indicates a fluctuated sea-level during the Permian, which reflected the global climatic changes and was associated with eastern Paleo-Tethys evolution. The relatively low sea-level accompanied by high-frequency fluctuations during the Asselian to Artinskian may be related to the expansion of glaciation (P1 and P2), while the followed significant rising at Kungurian may reflect the major deglaciation of the Late Paleozoic Ice Age (LPIA). The abrupt falling of sea-level at the end of the Capitanian was globally synchronous and may be relevant to mid-ocean ridge spreading and superimposed with global cooling (P4), which was in accord with the skeletal grain replacement of the fusulinaceans and dasyclads by small foraminifers and Gymnocodium, and was considered as a major reason for Middle Permian Extinction. The early Wuchiapingian characterized by densely mixed sequences of carbonate and siliciclastic intervals had a highly frequent fluctuating sea-level, which may be influenced by high frequent short-term climatic variations. The sea-level falling after it reached its highest stand during the middle Wuchiapingian, was suggested as a far-field response to the expansion of the Permian glaciation episode P4, or as a result of a regional tectonic transition from extension to compression relevant to the eastern Paleo-Tethys evolution. In addition, the overall rising trend of the sea-level and the thick succession in the Xikou area suggest that the South Qinling belt was primarily under an extensional setting during the Late Carboniferous to Early Triassic, in response to Tethys rifting, which may imply the subduction of Mianlue Ocean was possibly beyond the Permian.
The Late Ordovician succession of the Baltic Basin contains a characteristic fine-grained limestone, which is rich in calcareous green algae. This limestone occurs in surface outcrops and drill-cores ...in an extensive belt reaching from Sweden across the Baltic Sea to the Baltic countries. This limestone, which is known in the literature under several different lithological names, is described and interpreted, and the term “Baltic limestone facies” is suggested. The microfacies, from selected outcrops from the Åland Islands, Finland and Estonia, consists of calcareous green algae as the main skeletal component in a bioclastic mudstone-packstone lithology with a pure micritic matrix. Three types of calcitarch, which range in diameter from c. 100–180 μm, are common. Basinward, the youngest sections of the facies belt contain coral-stromatoporoid patch reefs and
Palaeoporella
-algal mounds. The Baltic limestone facies can be interpreted as representing the shallow part of an open-marine low-latitude carbonate platform.
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•Caffeic acid could decrease serum uric acid levels in hyperuricemia rats.•Reveal the mechanism of caffeic acid to reduce uric acid in vivo and in vitro.•Caffeic acid could adjust the ...transcription levels of uric acid transporters.•Caffeic acid could inhibit xanthine oxidase activity.
The mechanism underlying the reduction in uric acid levels in hyperuricemia rats by caffeic acid was investigated in this study. Different doses of caffeic acid (25, 50, and 100 mg/kg) were administered to hyperuricemia rats induced by the intraperitoneal injection of potassium oxonate. In vivo study showed that caffeic acid can down-regulate the transcription levels of URAT1 and GLUT9 mRNA and up-regulate the transcription levels of OAT1, UAT, and ABCG2 mRNA. In vitro study indicated caffeic acid competitively binds with xanthine oxidase to inhibit its activity, and the IC50 value was 53.45 µM. It was concluded that caffeic acid decreases serum uric acid levels in hyperuricemia rats by binding with xanthine oxidase and inhibiting its catalytic activity and by regulating the mRNA transcription of the renal uric acid transporters.
Chronic kidney disease is becoming a global public health problem, which will usually cause uremia at the end stage of chronic kidney failure. So far, kidney transplant is the most effective and ...proper therapy for uremia, however, the short supply of matched donor kidney has been a persistent bottleneck for transplantation. HLA matching of HLA-A, -B and -DRB1 loci is very important for the allocation of kidney transplants. In this study, we investigated genotypes of HLA-A, -B and -DRB1 loci based on 1,464 uremia patients and 10,000 unrelated healthy individuals in Henan province of China, and compared the frequency distribution of these HLA alleles and corresponding haplotypes between patient and healthy groups. We detected 23 HLA-A, 49 HLA-B and 17 HLA-DRB1 alleles in total. The predominant alleles of HLA-A, -B and -DRB1 loci in patients are the same as those in healthy group. The seven most frequent alleles account for about 87%, 50%, and 77% at HLA-A, -B and -DRB1 loci, respectively. The haplotypes (combinations of HLA-A, -B, and -DRB1) with significantly different frequency between patients and controls mostly account for less than 1%. Overall, this suggests that HLA matching is not a potential difficulty for kidney transplant of uremia patients. However, three of the top seven frequent HLA-DRB1 alleles have a significantly different distribution in patients and controls, while only one alleles for HLA-B and zero for HLA-A loci. These HLA-DRB1 alleles may be closely associated with uremia. This study sheds new lights on the composition and difference of HLA genotypes in uremia patients and healthy populations in Central China that can serve as a guide to HLA matching for kidney transplants and a resource for HLA typing-related studies.
Marine ecosystem recovery after the Permo-Triassic mass extinction (PTME) has been extensively studied in the shallow sea, but little is known about the nature of this process in pelagic ecosystems. ...Omphalosauridae, an enigmatic clade of open-water durophagous marine reptiles, potentially played an important role in the recovery, but their fragmentary fossils and uncertain phylogenetic position have hindered our understanding of their role in the process. Here we report the large basal ichthyosauriform Sclerocormus from the Early Triassic of China that clearly demonstrates an omphalosaurid affinity, allowing for the synonymy of the recently erected Nasorostra with Omphalosauridae. The skull also reveals the anatomy of the unique feeding apparatus of omphalosaurids, likely an adaptation for feeding on hard-shelled pelagic invertebrates, especially ammonoids. Morphofunctional analysis of jaws shows that omphalosaurids occupy the morphospace of marine turtles. Our discovery adds another piece of evidence for an explosive radiation of marine reptiles into the ocean in the Early Triassic and the rapid recovery of pelagic ecosystems after the PTME.
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•Slowly and fast evolving sites lead to the incongruent phylogenetic positions of tree shrews.•The monophyletic relationship between tree shrews and Glires is attributed to their fast ...substitution rates.•Sequence GC content is not informative to resolve the incongruent phylogenetic positions of tree shrews.•The closer phylogenetic affinity of tree shrews to Primates than to Glires is supported by confidence of tree selection.
Previous phylogenetic analyses have led to incongruent evolutionary relationships between tree shrews and other suborders of Euarchontoglires. What caused the incongruence remains elusive. In this study, we identified 6845 orthologous genes between seventeen placental mammals. Tree shrews and Primates were monophyletic in the phylogenetic trees derived from the first or/and second codon positions whereas tree shrews and Glires formed a monophyly in the trees derived from the third or all codon positions. The same topology was obtained in the phylogeny inference using the slowly and fast evolving genes, respectively. This incongruence was likely attributed to the fast substitution rate in tree shrews and Glires. Notably, sequence GC content only was not informative to resolve the controversial phylogenetic relationships between tree shrews, Glires, and Primates. Finally, estimation in the confidence of the tree selection strongly supported the phylogenetic affiliation of tree shrews to Primates as a monophyly.
Quasi-Steady-State Laws in Enzyme Kinetics Li, Banghe; Shen, Yuefeng; Li, Bo
The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory,
03/2008, Letnik:
112, Številka:
11
Journal Article
Recenzirano
To understand how enzymes work is essential for understanding life processes. And, in enzyme kinetics, a fundamental assumption is the so-called Quasi-Steady-State Assumption, which has the history ...of more than 80 years and has been proven very fruitful in analyzing the equations of enzyme kinetics. Many experimental results and numerical results have shown the validity of the assumption. So, an important problem is if it is always true. If it is always true, then it should be a law, not only an assumption. In this paper, we prove mathematically rigorously that it is indeed always true. Hence, it is a law, and we name it the Quasi-Steady-State Law. Actually, more precisely, we have two Quasi-Steady-State Laws. In one of them quasi-steady state means that the concentration of the enzyme−substrate complex remains approximately constant, and in the other it means that the change rate of the concentration of enzyme−substrate complex is extremely tiny.
Abstract This paper focuses on solving the routing optimization problem under the dynamic topology of the satellite communication network. With the rapid development of low-earth-orbit (LEO) ...satellite network communication technology, the dynamically changing topology of satellite networks has brought about frequent link switching and triggered a large number of routing updates. This paper proposes an improved routing algorithm named the Stable A-Star Routing (SASR) algorithm. The SASR algorithm is based on the A-star algorithm and aims to reduce path-switching frequency and enhance path stability by optimizing the path selection strategy. Through detailed simulation experiments and performance evaluation, we verified the performance advantages of the SASR algorithm in terms of the number of path switches, the number of path hops, the route convergence time, and the occurrences of congestion in business under different business volumes, and conducted comparative studies with classic algorithms. The results show that the SASR algorithm offers obvious advantages in key performance indicators. Compared with the Dijkstra algorithm and the A-star algorithm, the average number of path switches can be reduced by 22% and 10%, respectively. It shows more prominent advantages under a larger business volume, providing an efficient and reliable solution for routing optimization under the dynamic topology of satellite communication networks.
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