Typical Signature Research Articles

BRAF Mutations and Dysregulation of the MAP Kinase Pathway Associated to Sinonasal Mucosal Melanomas.

Sinonasal mucosal melanoma (SNM) is a rare and aggressive type of melanoma, and because of this, we currently have a limited understanding of its genetic and molecular constitution. The incidence among SNMs of somatic mutations in the genes involved in the main molecular pathways, which have been largely associated with cutaneous melanoma, is not yet fully understood. Through a next-generation sequencing (NGS) approach using a panel of 25 genes involved in melanoma pathogenesis customized by our group, we performed a mutation analysis in a cohort of 25 SNM patients. Results showed that pathogenic mutations were found in more than 60% of SNM cases at a somatic level, with strikingly 32% of them carrying deleterious mutations in the BRAF gene. The identified mutations mostly lack the typical UV signature associated with cutaneous melanomas and showed no significant association with any histopathological parameter. Oncogenic activation of the BRAF-depending pathway, which may induce immune tolerance into the tumour microenvironment (i.e., by increasing the VEGF production) was poorly associated with mutations in genes that have been related to diminished clinical benefit of the treatment with BRAF inhibitors. Screening for mutations in BRAF and other MAPK genes should be included in the routine diagnostic test for a better classification of SNM patients.

P1941The nuclear receptor corepressor 1 blocks CD36-mediated foam cell formation in atherogenesis

Abstract Background Nuclear receptors and their cofactors regulate the expression of various target genes in different tissue and organs to orchestrate downstream (patho)physiological processes. Although the function of several nuclear receptors in atherosclerosis has been studied, very little is known about the role of nuclear receptor cofactors in atherosclerosis. Given its important role to suppress inflammatory processes, we speculated that macrophage nuclear receptor corepressor 1 (NCOR1) plays a protective function in atherosclerosis development. Purpose To evaluate the contribution of macrophage NCOR1 in atherosclerosis we used myeloid cell-specific Ncor1 knockout mice on an atherosclerosis-prone background. Methods and results 8-week-old male and female mice were exposed to a high high-cholesterol diet for 12 weeks. Our findings demonstrate that the lack of macrophage Ncor1 leads to a severe atherosclerotic phenotype in both sexes. These mice show a higher content of plaques along the thoraco-abdominal aortae as well as at the aortic sinus, which were characterized by larger necrotic cores and thinner fibrous caps, a typical signature of unstable plaques. Moreover, we found that the pro-atherogenic effects of the Ncor1 deletion are mediated via derepression of peroxisome proliferator-activated receptor gamma (PPARγ) target genes in mouse and human macrophages, especially the enhanced expression of the CD36 scavenger receptor and the subsequent rise in oxLDL uptake. Interestingly, while the expression of NCOR1 is reduced, the PPARγ signature is increased in human atherosclerotic plaques, and this signature is further pronounced in ruptured compared to stable carotid plaques. Conclusion Our findings suggest that macrophage NCOR1 blocks the pro-atherogenic functions of PPARγ in atherosclerosis and prevents the disease development. Acknowledgement/Funding The Swiss National Science Foundation, the Novartis Foundation, Olga-Mayenfisch Foundation, the OPO foundation

Update on Li-Fraumeni syndrome

The Li-Fraumeni syndrome (LFS, online Mendelian inheritance in man, OMIM #151623) is considered to be one of the currently known most aggressive cancer predisposition syndromes. The heterogeneous spectrum of tumors is dominated by bone and soft tissue sarcomas, various brain tumors, premenopausal breast cancer and adrenocortical carcinoma (ACC). Even in childhood the cancer risk is very strongly increased and it is not uncommon for people with LFS to develop synchronous and metachronous tumors. Typical histopathological findings and molecular genetic signatures can help towards the diagnosis. Inheritance is autosomal dominant and the penetrance appears to be more variable than previously thought. The prevalence of LFS is approximately 1:5000 with ahigh interregional variance. The LFS is caused by germline mutations in the TP53 gene coding for the protein p53, an essential cellular transcription factor that initiates antitumor responses to cellular stress, such as DNA damage. In people with LFS, due to the loss of functional p53, the protective mechanism of the cells is weakened resulting in asignificantly increased cancer risk. In order to improve the survival of people with LFS, structured tumor early recognition and surveillance strategies are recommended; however, national and international longitudinal observational studies are needed to evaluate the cost-effort-benefit balance. For this reason, the authors have established the LFS cancer predisposition registry in which all patients with LFS and other syndromes predisposing to cancer can be registered. Detailed information can be found at www.cancer-predisposition.org .

Seismic characterization of submarine gas-hydrate deposits in the Western Black Sea by acoustic full-waveform inversion of ocean-bottom seismic data

Evidence for gas-hydrate occurrence in the Western Black Sea is found from seismic measurements revealing bottom-simulating reflectors (BSRs) of varying distinctness. From an ocean-bottom seismic data set, low-resolution traveltime-tomography models of P-wave velocity [Formula: see text] are constructed. They serve as input for acoustic full-waveform inversion (FWI), which we apply to derive high-resolution parameter models aiding the interpretation of the seismic data for potential hydrate and gas deposits. Synthetic tests indicate the applicability of the FWI approach to robustly reconstruct [Formula: see text] models with a typical hydrate and gas signature. Models of S-wave velocity [Formula: see text] containing a hydrate signature can only be reconstructed when the parameter distribution of [Formula: see text] is already well-known. When we add noise to the modeled data to simulate field-data conditions, it prevents the reconstruction of [Formula: see text] completely, justifying the application of an acoustic approach. We invert for [Formula: see text] models from field data of two parallel profiles of 14 km length with a distance of 1 km. Results indicate a characteristic velocity trend for hydrate and gas occurrence at BSR depth in the first of the analyzed profiles. We find no indications for gas accumulations below the BSR on the second profile and only weak indications for hydrate. These differences in the [Formula: see text] signature are consistent with the reflectivity behavior of the migrated seismic streamer data of both profiles in which a zone of high-reflectivity amplitudes is coincident with the potential gas zone derived from the FWI result. Calculating saturation estimates for the potential hydrate and gas zones yields values of up to 30% and 1.2%, respectively.

Alteration of Particle Drift Resonance Dynamics Near Poloidal Mode Field Line Resonance Structures

AbstractWe examine the effect on drift‐resonant particle dynamics of a strongly peaked internally driven poloidal mode field line resonance (FLR; with specified frequency ω in the Pc5 range and azimuthal mode number m≫1). Using an analytic magneto‐hydrodynamic model in a dipole field to describe the ultra low frequency wave mode, we use the bounce‐averaged formalism of Northrop (1963) to obtain equations of motion for charged particles in the wave frame and find an analytic solution for the case of a temporally constant ultra low frequency wave amplitude profile. Focusing on equatorially mirroring electrons in this study, we demonstrate that, for sufficiently peaked radial profiles, multiple drift resonances appear that are associated with the FLR peak. These are in addition to the well‐known zeroth‐order drift resonance location, occurring when the unperturbed drift speed satisfies the resonance condition ( ). The additional resonances arise because the strongly peaked FLR wave field components provide sufficiently strong perturbations to the azimuthal drift speed to cause multiple zero crossings in the resonance condition. These additional resonances have trapping periods much lower than that of the zeroth‐order resonance and considerably complicate the electron dynamics. Further properties of these resonances and their measurable effect on electron dynamics are discussed. For example, their effect on observations of energetic electron flux on board satellites in the vicinity of an FLR is calculated and shown to significantly distort the typical signature associated with drift resonance (modulations in electron flux at the wave frequency with a 180° phase change across the resonant energy).

New Halonotius Species Provide Genomics-Based Insights Into Cobalamin Synthesis in Haloarchaea.

Hypersaline aquatic and terrestrial ecosystems display a cosmopolitan distribution. These environments teem with microbes and harbor a plethora of prokaryotic lineages that evaded ecological characterization due to the prior inability to cultivate them or to access their genomic information. In order to close the current knowledge gap, we performed two sampling and isolation campaigns in the saline soils of the Odiel Saltmarshes and the salterns of Isla Cristina (Huelva, Spain). From the isolated haloarchaeal strains subjected to high-throughput phylogenetic screening, two were chosen (F15BT and F9-27T) for physiological and genomic characterization due of their relatedness to the genus Halonotius. Comparative genomic analyses were carried out between the isolated strains and the genomes of previously described species Halonotius pteroides CECT 7525T, Halonotius aquaticus F13-13T and environmentaly recovered metagenome-assembled representatives of the genus Halonotius. The topology of the phylogenomic tree showed agreement with the phylogenetic ones based on 16S rRNA and rpoB′ genes, and together with average amino acid and nucleotide identities suggested the two strains as novel species within the genus. We propose the names Halonotius terrestris sp. nov. (type strain F15BT = CECT 9688T = CCM 8954T) and Halonotius roseus sp. nov. (type strain F9-27T = CECT 9745T = CCM 8956T) for these strains. Comparative genomic analyses within the genus highlighted a typical salt-in signature, characterized by acidic proteomes with low isoelectric points, and indicated heterotrophic aerobic lifestyles. Genome-scale metabolic reconstructions revealed that the newly proposed species encode all the necessary enzymatic reactions involved in cobalamin (vitamin B12) biosynthesis. Based on the worldwide distribution of the genus and its abundance in hypersaline habitats we postulate that its members perform a critical function by being able to provide “expensive” commodities (i.e., vitamin B12) to the halophilic microbial communities at large.

Analysis of a Case of Supercellular Convection over Bulgaria: Observations and Numerical Simulations

A long-lived supercell developed in Northwest Bulgaria on 15 May 2018 and inflicted widespread damage along its track. The first part of this article presents a detailed overview of the observed storm evolution. Doppler radar observations reveal that the storm acquired typical supercellular signatures and maintained reflectivity values in excess of 63 dBZ for more than 4 h. The thunderstorm was also analyzed through lightning observations that highlighted important characteristics of the overall supercell dynamics. In its second part, the study investigates the predictability of the severe weather outbreak. In the medium forecast ranges, the global European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble indicated the presence of favorable conditions for the development of deep moist convection 4 days prior to the event. A set of three convection-allowing ensemble simulations also demonstrated that the practical predictability of the supercell was approximately 12 h, which is considerably higher than some previously reported estimates. Nevertheless, the skill of the convective forecasts appears to be limited by the presence of typical model errors, such as the timing of convection initiation and the development of spurious convective activity. The relevance of these errors to the optimal ensemble size and to the design of future convection-allowing numerical weather prediction (NWP) systems is further discussed.

Geochemistry and Sr–Nd–Hf isotopes of granitoids from the Xiaotuergen porphyry Cu deposit, Altay orogenic Belt, Xinjiang, Northwest China: Implications for petrogenesis, tectonic setting, and mineralization

The Xiaotuergen deposit is the first porphyry Cu deposit to be identified in the northern Xinjiang Altay, Northwest China. Voluminous granitoids comprising granite porphyry, granodiorite porphyry, biotite monzogranite, and quartz porphyry are present in the ore district. Granodiorite porphyry hosts the main Cu mineralization, in disseminated, veinlet, veinlet-disseminated, and stockwork forms. The Xiaotuergen intrusions are weakly metaluminous to peraluminous calc-alkaline to alkaline granitic rocks, and exhibit typical subduction-related geochemical signatures comprising light rare earth element (LREE) enrichment, high field strength element (HFSE) depletion, and low Sr/Y and La/Yb ratios. They are depleted in Nb–Ta–Ti, P, and Eu–Sr, yield moderate Mg# values (41.10–55.38), and show negative but near-zero εNd(t) values (−2.0 to −0.1) and variable positive εHf(t) values (+1.52 to +11.08). Geochemical constraints indicate that the Xiaotuergen granitoids are highly evolved I-type granites which were derived from strong fractional crystallization of a parental magma, mixed with materials derived from partial melting of both subducting oceanic sediments and the overlying mantle wedge. The Xiaotuergen granitoids are products of the same tectono-magmatic activity as that which produced the synchronous magmatic rocks of the Xinjiang Altay, having been formed in a continental arc setting during the early Devonian. The Xiaotuergen ore-bearing porphyries are identified as the shoshonite series, rather than the adakite series. Mantle-derived contributions played a crucial role in the formation of magmas with Cu and S contents that were high enough to produce economic mineralization. The mature arc environment and long-lived magmatism provided favorable conditions for the development of porphyry Cu mineralization.

Neoproterozoic intrusions along the northern margin of South Qinling, central China: Geochemistry, zircon ages, and tectonic implications

We report whole-rock Sr–Nd isotopic compositions and U–Pb ages and Hf isotopic compositions of zircon grains from Neoproterozoic intrusive rocks exposed in northern South Qinling, central China. The rocks have diverse compositions and were emplaced at ca 751–714 Ma. On the basis of their distinct geochemical signatures, four compositional groups are recognized. High-Ti gabbros are tholeiitic, with low SiO2 and MgO, and high FeOT and TiO2 contents, and exhibit enrichment in large-ion-lithophile elements and absence of Nb and Ta negative anomalies. These gabbros have high εNd(t) values of +1.9 to +5.3 that are similar to the compositions of E-MORB or OIB, implying an origin from asthenospheric mantle. Low-Ti gabbros are calc-alkaline and have high SiO2 and MgO, and low FeOT and TiO2 contents. These gabbros have typical arc-like trace-element signatures and εNd(t) values that vary from −3.2 to +6.0, consistent with derivation from the partial melting of heterogeneous lithospheric mantle that was modified by subduction. Elemental and Nd–Hf isotopic compositions of I-type granitoids imply significant contributions from both mantle and crustal rocks. S-type granites originated from the partial melting of metasedimentary rocks with isotopic compositions similar to paragneisses of the basement in South Qinling. The extensive melting of both mantle and crustal rocks under relatively low pressures and high temperatures suggests an extensional environment during the Neoproterozoic. Our data, in combination with existing data from basement rocks and Neoproterozoic igneous rocks, constrain the crustal evolution of the northern Yangtze Block and South Qinling, in which subduction along the northern margin of the Yangtze Block prior to ca 800 Ma led to arc–continent collision, inducing high-grade metamorphism of the basement rocks of the Douling Complex. Subsequent protracted continental rifting was related to breakup of the supercontinent Rodinia.

A preliminary report on the Rare Earth Element + Yttrium (REE+Y) analysis from the Tlayúa Quarry Konservat-Lagerstätte (Tlayúa Formation; Lower Cretaceous, Albian) of Tepexi de Rodríguez, Puebla, Mexico: Results from Zone 13

The Tlayua Quarry Konservat-Lagerstatte (Albian, Lower Cretaceous; Tepexi de Rodriguez, Puebla, Mexico) is known worldwide for the preservation of its ubiquitous fossil remains. Major and trace element concentrations of selected limestone samples from zone 13 of the Tlayua Quarry were measured in order to understand the depositional conditions and source of REE + Y. The concentrations of SiO2, Al2O3, P and Zr show little contamination by terrigenous material and phosphates in this zone, at least to instances in which the REE + Y concentrations can be both shale-normalizable and reliable. REE + Y plots display typical modern seawater signals; namely, positive La and Gd anomalies, superchondritic Y/Ho ratios (between 46.421 and 67.777) and slight depletions of LREE and MREE with respect to HREE (x Pr/Yb = 0.201; x Nd/Yb = 0.305 and (x Dy/Yb = 0.683 respectively). Furthermore, sustained negative cerium anomalies could be identified (Ce/Ce* = 0.613), which would indicate oxidating conditions as in modern seawater. The observed REE + Y patterns, which constitute the first palaeoenvironmental inference by means of element analysis performed in Tlayua, suggest that the limestones from zone 13 still retain their original seawater pattern. Considering that terrigenous and phosphate contamination is overall low in the analysed samples, REE + Y (REY) patterns from the Tlayua Formation can be useful palaeoenvironmental proxies for the Cretaceous. All this allows the conclusion that, at least during the deposition of these limestones from zone 13, a typical marine signature can be seen. This does not exclude, however, the presence of a tidally or strongly monsoonic-influenced sedimentation in other sediments from zone 13 or from other zones in Tlayua, as previous works have suggested.

Tuning the interactions in the spin-ice materials Dy2Ge2−xSixO7 by silicon substitution

We report that the lattice constant of Dy$_2$Ge$_{2-x}$Si$_x$O$_7$ ($x=0, 0.02, 0.08, 0.125$) can be systematically reduced by substituting the non-magnetic germanium ion in the cubic pyrochlore oxide with silicon. A multi-anvil high-pressure synthesis was performed up to 16 GPa and 1100 $^\circ$C to obtain polycrystalline samples in a solid-state reaction. Measurements of magnetization, ac susceptibility, and heat capacity reveal the typical signatures of a spin-ice phase. From the temperature shift of the peaks, observed in the temperature-dependent heat capacity, we deduce an increase of the strength of the exchange interaction. In conclusion, the reduced lattice constant leads to a changed ratio of the competing exchange and dipolar interaction. This puts the new spin-ice compounds closer towards the phase boundary of short-range spin-ice arrangement and antiferromagnetic long-range order consistent with an observed reduction of the monopole energy scale.

Compressive deformation behavior of dendritic Mg–Ca(–Zn) alloys at high temperature

Mg-Ca(-Zn) alloys were subjected to hot compression at temperatures ranging from 350 ∘C to 450 ∘C and strain rates of 10−3 to 10 s−1. In the corresponding flow curves, the peak stress appeared at very low strain rates (less than 0.05) followed by steady state at a constant stress, indicating the occurrence of dynamic flow softening, which is a typical signature of dynamic recrystallization (DRX). The DRX was greatly affected by the deformation conditions and Ca/Zn contents, and optical and scanning electron microscopy analysis revealed that the DRX induced rearrangement of the complex dendritic microstructure during compression. Optimal parameters for the deformation were identified. These indicate deformation conditions where the processing is safe and easy. This in turn is likely to enable widening of the range of applications of Mg-Ca(-Zn) alloys.

MMS Measurements of the Vlasov Equation: Probing the Electron Pressure Divergence Within Thin Current Sheets

AbstractWe investigate the kinetic structure of electron‐scale current sheets found in the vicinity of the magnetopause and embedded in the magnetosheath within the reconnection exhaust. A new technique for computing terms of the Vlasov equation using Magnetospheric Multiscale (MMS) measurements is presented and applied to study phase space density gradients and the kinetic origins of the electron pressure divergence found within these current sheets. Crescent‐shaped structures in ∇⊥2fe give rise to bipolar and quadrupolar signatures in v·∇fe measured near the maximum ∇·Pe inside the current layers. The current density perpendicular to the magnetic field is strong (J⊥∼2 μA/m2), and the thickness of the current layers ranges from 3 to 5 electron inertial lengths. The electron flows supporting the current layers mainly result from the combination of E×B and diamagnetic drifts. We find nonzero J·E′ within the current sheets even though they are observed apart from typical diffusion region signatures.

Semi-Quantum Bi-Signature Scheme Based on W States

A semi-quantum bi-signature scheme based on W states is designed, in which two signers sign the same message. The unconditional security of the new semi-quantum bi-signature scheme is guaranteed with the teleportation of W states and semi-quantum key distribution (SQKD) protocol. From the aspects of hardware requirement and efficiency, the proposed semi-quantum bi-signature scheme is more efficient and convenient than many typical quantum signature schemes.

Design of a Remote-Controlled Platform for Green Roof Plants Monitoring via Hyperspectral Sensors

The combination of an appropriate design and careful management of green infrastructures may contribute to mitigate flooding (stormwater quantity) and pollutant discharges (stormwater quality) into receiving water bodies and to coping with other extreme climate impacts (such as temperature regime) on a long-term basis and water cycle variability. The vegetation health state ensures the green infrastructure’s effectiveness. Due to their remarkable spatial and spectral resolution, hyperspectral sensing devices appear to be the most suited for green infrastructure vegetation monitoring according to the peculiar spectral features that vegetation exhibits. In particular, vegetation health-state detection is feasible due to the modifications the typical vegetation spectral signature undergoes when abnormalities are present. This paper presents a ground spectroscopy monitoring survey of the green roof installed at the University of Calabria fulfilled via the acquisition and analysis of hyperspectral data. The spectroradiometer, placed on a fixed stand, was used to identify stress conditions of vegetation located in areas where drought could affect the plant health state. Broadband vegetation indices were employed for this purpose. For the test case presented, data acquired agreed well with direct observations on the ground. The analyses carried out showed the remarkable performances of the broadband indices Red Difference Vegetation Index (Red DVI), Simple Ratio (SR) and Triangular Vegetation Index (TVI) in highlighting the vegetation health state and encouraged the design of a remote-controlled platform for monitoring purposes.

Chitinozoan biostratigraphy of the Rheidol Gorge Section, Central Wales, UK: a GSSP replacement candidate for the Rhuddanian–Aeronian boundary

AbstractAs part of an international effort to evaluate potential replacement sections for the current Aeronian GSSP, the stratigraphy of the Rheidol Gorge section (central Wales, UK) is being restudied. A total of 28 samples from the Rhuddanian–Aeronian boundary interval at Rheidol Gorge were studied for chitinozoans. This famous Welsh Basin section, its stratigraphy rooted in the work of O.T. Jones and M. Sudbury, comprises a series of laminated black shales with abundant graptolites, alternating with grey mudstone intervals, deposited in anoxic to dysoxic/oxic seafloor conditions, respectively. The exposed section of c. 20 m spans the middle part of the upper Rhuddanian Pernerograptus revolutus Biozone through the lower Aeronian Neodiplograptus magnus Biozone of the lower to mid‐Llandovery Series (Cwmere and Derwenlas formations). Our chitinozoan analysis yielded an assemblage of over 2300 specimens distributed approximately uniformly throughout the entire succession. A total of 16 different taxa are identified, of which 12 remain in open nomenclature, reflecting the poor to moderately intact preservation of the specimens. Based on the presence of key species such as Spinachitina maennili and Conochitina iklaensis, the Rheidol Gorge section is referred to the Spinachitina maennili Biozone. This observation is in perfect alignment with the typical signature of other Rhuddanian–Aeronian boundary successions in the Welsh Basin and in other parts of the world.

Small heat shock proteins in the amphibian Pelophylax bergeri: Cloning and characterization of Hsp27 and Hsp30 cDNAs and their expression analysis in ex vivo skin exposed to abiotic stresses

Small Heat Shock Proteins (sHSP) are molecular chaperones that play an essential role in maintaining protein homeostasis and promoting cell survival. In this work, for the first time, multiple cDNAs encoding for small Hsp27 and Hsp30, designed, respectively, as PbHsp27-(1-2) and PbHsp30-(1-5), were cloned and characterized in the amphibian Pelophylax bergeri, which is a suitable model for studying biological responses to environmental perturbations. Domain architecture analysis showed that PbHsp27 and PbHsp30 cDNAs displayed the typical signature motifs of the sHSP family such as the conserved α-crystallin domain flanked by variable N-terminal and C-terminal regions. Phylogenetic analysis revealed that PbHsp27 and PbHsp30 clustered, respectively, with Hsp27 and Hsp30 members of other vertebrates, but more closely with amphibians. Overall PbHsp27 and PbHsp30 transcriptional activity, analyzed by qRT-PCR, evidenced that, in ex vivo skin exposed to thermal shock and cadmium treatment, PbHsp27 and PbHsp30 mRNAs were inducible and regulated differently. This study provides the basis for future research on the potential use of PbHsp27 and PbHsp30 as biomarkers of proteotoxic stress in amphibians.

The early Paleozoic Huangtupo VMS Cu—Zn deposit in Kalatag, Eastern Tianshan: Implications from geochemistry and zircon U—Pb geochronology of volcanic host rocks

The Tianshan in China forms the southern part of the Central Asian Orogenic Belt (CAOB) and also hosts important polymetallic resources. Here we investigate the Huangtupo medium–size copper–zinc deposit, located in the central part of the Kalatag copper Polymetallic Belt with a view to evaluate the nature and genesis of the early Paleozoic volcanogenic massive sulfide (VMS) Cu—Zn deposits. This deposit is correlated to intermediate–felsic volcano–sedimentary sequences of the early Paleozoic Daliugou Formation which are mainly composed of andesite, dacite, and rhyolite with minor basalt, as well as their pyroclastic equivalents. The ore bodies are hosted in the contact zone between andesitic volcanic breccia and tuff representing an eruptive hiatus between the two volcanic cycles with massive sulphide lens at the top and stockwork zone at lower part of the Daliugou Formation. We report new zircon U—Pb data, major and trace element geochemistry and Sr—Nd isotopes from the andesite, dacite and andesitic tuff in the Huangtupo deposit. Zircon from the dacite and the andesite occurring above the ore bodies yield and age of 440.1 ± 1.2 Ma and 439.7 ± 0.95 Ma, and that from the andesitic tuff in footwall shows and age of 442.0 ± 1.1 Ma. All samples show typical geochemical signatures of subduction–related calc–alkaline magmas with slight enrichment in LILE and LREE but depletion in Nb and Ti content relative to primitive mantle. The andesites are characterized by high MgO (7.6–10.8 wt%) contents and Mg# values (64–72) with low Sr/Y and La/Yb ratios, belonging to sanukite. Both dacite and tuff have low MgO (<2.5 wt%) and Al2O3 content (15–16.4 and 11.3–15.3 wt%) with Eu negative anomalies (Eu/Eu* = 0.71–0.75 and 0.44–0.6), showing their low–MgO affinity. All the volcanic rocks display similar Nd and Sr isotopic signature, with εNd(t) of 6.5 to 7.3 and moderately high (87Sr/86Sr)i ratios of 0.705274 to 0.706977. The geochemical characteristics and regional geology indicate that these volcanic rocks were formed in an intra–oceanic arc during southward subduction of the oceanic lithosphere in the northern part of the Eastern Tianshan. They were most likely derived from the partial melting of the mantle wedge with input and interaction with subducted–related melts and/or fluids. We also propose that the Huangtupo VMS deposit is analogous to Kuroko type VMS deposits developed within intra–oceanic rift.

Creep‐fatigue deformation micromechanisms of a directionally solidified nickel‐base superalloy at 850°C

AbstractIn the present exploration, it was attempted to understand the creep‐fatigue (CF) deformation micromechanisms of alloy CM 247 DS LC by conducting low‐cycle fatigue (LCF) and CF tests employing strain amplitude ranging from 0.6% to 1.0% at T = 850°C in the air and performing extensive electron microscopic examinations. The cyclic life of the alloy lessens for all CF tests conducted at 1 and 5 minute dwell time in comparison to LCF tests. Transmission electron microscopy (TEM) examinations confirmed that during CF tests substructure consists of dislocation loop, mixed dislocations, and γ' rafting, a typical creep deformation signature of nickel‐base superalloys, it also consists of features observed during fatigue deformation such as anti‐phase boundary (APB)‐coupled dislocations inside γ' precipitates and local tangles of dislocations. This confirms that the deformation of CF‐tested specimens is ascribed to the synergistic effect of both creep and fatigue. This fact was further verified by scanning electron microscopic (SEM) examinations.

Early Jurassic volcanic rocks in the Xiongcun district, southern Lhasa subterrane, Tibet: Implications for the tectono-magmatic events associated with the early evolution of the Neo-Tethys Ocean

Early Mesozoic (Late Triassic to Middle Jurassic) igneous rocks in the southern Lhasa subterrane, Tibet, record important information on the early tectono-magmatic evolution of the Neo-Tethys Ocean. This paper presents petrological, geochronological, and geochemical data for the Xiongcun Formation ignimbrites, to constrain the petrogenesis and tectonic setting of these rocks in the southern Lhasa subterrane. The Xiongcun Formation is dominated by andesitic and dacitic rocks. These rocks yield Early Jurassic (195–176 Ma) zircon UPb ages and display typical arc-like geochemical signatures, being enriched in large-ion lithophile elements (e.g., Rb, Ba, and U) and depleted in high-field-strength elements (e.g., Nb, Ta, and Ti). Sr–Nd–Pb–Hf isotopic compositions are highly depleted. These chemical and isotopic data suggest that the Xiongcun Formation ignimbrites probably formed in an intra-oceanic island arc setting related to the northward subduction of the Neo-Tethys oceanic slab. The parental magmas were derived from a depleted mantle source modified by fluids released from the Neo-Tethys oceanic slab. Combined with previously reported data, we suggest that the volcanic rocks in the Early Jurassic Xiongcun and Yeba formations of the southern Lhasa subterrane were generated by a single subduction system, but developed on oceanic and continental crust, respectively.