Subsequent Collision Research Articles

Ophiolite complex of Piedmont-Ligurian basin (Northern Apennines)

The Northern Apennines contain remnants of the Piedmont-Ligurian Basin (PLB) or ocean, which during the Late Mesozoic time (mainly in the Jurassic) separated the paleo-Europe (Iberian plate) from the southern paleocontinent Adria at the Africa promontory. The closure of the PLB and subsequent collision of Europe/Adria in Cretaceous-Cenozoic time led to the exhumation of the ophiolite complex of Northern Apennines in the Ligurian units. The paper gives information obtained by the authors during several field trips on the composition of the ophiolite complex of the Northern Apennines, representative of the composition and structure of the oceanic lithosphere. The latter, absent in the territory of Ukraine, is a key question to understanding the evolution of the oceanic crust, subduction processes, and formation of accretion wedges in the transitional zones to the continents. The Ligurian ophiolites of the PLB constitute an accessible and unique window to track the opening and evolution of the slow-spreading oceanic lithosphere. The Internal Ligurian ophiolites consist of km-scale gabbroic bodies intruded into depleted mantle peridotites and bear remarkable structural and compositional similarities to oceanic lithosphere from slow and ultra-slow spreading ridges. The External Ligurian ophiolites, associated with continental crust material and transition zone between the oceanic and continental crust, include mantle sequences retaining a subcontinental lithospheric origin. The gabbro-peridotite associations from the Internal Ligurian ophiolites were explored in the Bracco-Levanto ophiolite massif, which includes a km-scale gabbroic body, recalling the oceanic core complexes from modern spreading centres, intruded into the mantle peridotites. The peridotites and the gabbros from these ophiolites record a composite history involving deformation and alteration from high temperature to seafloor conditions. The top of the peridotites is covered by tectono-hydrothermal breccias (ophicalcites), radiolarites, and sedimentary breccias that testify to the exposure of peridotites at the seafloor. This succession is then covered by basalts pillow-lavas. Thus, the almost full section of the ophiolite complex is represented here.

Nature of early Mesoproterozoic magmatism in the Qilian-North Qaidam tectonic belt, NW China: Implications for prolonged extension processes and transition from Columbia to Rodinia

Precambrian basement rocks exposed in uplift zones and orogenic belts provide accessible opportunities for paleogeographic reconstruction, especially for microcontinents and cratons with thick covers. Here we report early Mesoproterozoic rifting-related mafic and granitic metaigneous rocks preserved in the Qilian-North Qaidam tectonic belt, NE Tibetan Plateau. Mafic rocks include garnet amphibolite emplaced at 1.40 Ga and metagabbro that were emplaced at 1.39 Ga, exposed in the North Wulan area. They are derived from low-degree (<7 %) partial melting of slab-modified lithospheric mantle lherzolites with Sp:Grt ranging from 90:10 to 60:40. The calculated low P-T conditions of mantle melting (Tpmax < 1472–1451 °C at P = 2.0 Ga) are also consistent with a thermal normal lithospheric mantle upwelling event. Granitic rocks comprise ca. 1.44 Ga garnet-bearing and ca. 1.41 Ga two-mica granites that were emplaced in the North Wulan and Central Qilian areas, respectively. They are S-type granites derived from crustal reworking of psammitic-rich and/or clay-rich metasedimentary rocks. In addition, the two-mica granites represent the oldest basement rocks yet identified in Central Qilian and indicate the existence of ancient basement rocks older than ca. 1.41 Ga. All the mafic and granitic rocks belong to a part of intense Mesoproterozoic rift-related magmatism in the composite Qilian-Quanji block (QQB), and subsequently underwent 1.18–0.9 Ga metamorphic modifications. The composite QQB in the NE Tibetan Plateau was involved in the long-term processes including crustal reworking and mantle upwelling (1.5–1.35 Ga) correspond to the breakup of Columbia followed by oceanic subduction (1.2–1.0 Ga) and subsequent collision and exhumation (0.9–0.8 Ga) at the periphery of Rodinia. Our results improve the understanding of the Mesoproterozoic tectonic evolution for the whole QQB and provide important constrains on the transition from Columbia to Rodinia.

Detrital record of sediment influx in the Triassic Chuxiong broken foreland basin in southeastern Tibetan Plateau

The Triassic Chuxiong basin represents a classic example of a foreland system that is thought to be associated with the closure of eastern branches of the Paleo-Tethys and subsequent Indosinian collision, yet how it was filled remains poorly understood. Here, we use paleocurrent measurements, sandstone petrology, and detrital zircon UPb geochronology to examine the patterns of basin fill. Paleocurrent reconstruction indicates that although some evidence exists for axial transport, the basin was mainly filled transversely with abundant sediment input from the Paleo-Tethyan suture to the west and the Kangdian High to the east. Qualitative determination of sandstone petrology shows that the lithic fragments contained within the Late Triassic strata are not of a uniform mode: volcanic lithics and glass grains are contained within nine Carnian and Rhaetian samples from the western part of the basin, but rarely observed in thirteen samples from the eastern basin. Similarly, detrital zircon UPb geochronology of sandstone samples from five sections reveals marked temporal and spatial changes in their age signatures that can be divided into three distinct types. Type-1 age spectra are represented by a narrow unimodal age probability peak at ca. 250 Ma that correlates with the Indosinian-aged arc sources developed along the Jinsha Jiang-Ailao Shan and Changning-Menglian sutures. Type-2 also shows a major zircon age population, but with a diagnostic peak at ∼780 Ma that corresponds to the Neoproterozoic basement outcropped in Kangdian High. Type-3 is generally characterized by multimodal distribution with major populations of ca. 200–350 Ma, ca. 400–500 Ma, ca. 700–900 Ma, ca. 1750–2000 Ma, and ca. 2350–2600 Ma. Comparing our new data with existing age spectra for the Triassic strata across the western Yangtze and the Indochina blocks demonstrates that the Chuxiong basin was primarily filled by a magmatic arc along the Paleo-Tethyan suture zone during the Carnian, and mostly fed by a reorganized drainage system by incorporating the fold-thrust belt and uplifted foreland basement as source area when the basin expanded eastward through the Norian and Rhaetian as the basin-fill onlaps onto the basement of Kangdian High. The patterns of sediment dispersal of the Triassic Chuxiong basin not only provide a new example of the interplay between orogen and craton sediment input in the peripheral setting but also highlight that the local basement-cored uplifts may dominate the provenance of a broken foreland system during underthrusting.

Effects of the third body (O and N) on the recombination of molecular nitrogen using quasi-classical trajectory methods

The investigation of the recombination reactions poses significant challenges due to the complexities involved in three-body collisions including simultaneous interaction of three bodies and multiple time scales. This work aims to investigate the complex dynamics involved in the recombination of atomic nitrogen to form molecular nitrogen using the quasi-classical trajectory method for the N3 and the N2O systems. The recombination pathways considered include a single-step direct reaction and a two-step mechanism that involves the formation of an intermediate with a finite lifetime which is stabilized through a subsequent collision with a third body. The latter is further classified as Lindemann or Chaperon mechanism based on the role played by the third body. The model uses a time-lag parameter to allow for a consistent treatment of all the reaction pathways. It is observed that the recombination probability is greatest for collisions involving low translational energies and low time lags. Recombination rate coefficients are evaluated using a novel rate coefficient expression developed for three-body collisions. Low temperature recombination rate coefficients, which can be computationally prohibitive to evaluate using traditional detailed balance methods, can be evaluated at a low computational cost. The recombination pathways are determined algorithmically by identifying the various interaction time scales. The direct mechanism is found to have a larger recombination probability, but a lower rate coefficient. The effect of the third body (oxygen and nitrogen atoms) on the recombination dynamics is explored in detail. It is observed that the recombination in excess of O atom leads to a larger population of the low internal energy states, as opposed to recombination in the excess of N atoms. The dominance of the Chaperon mechanism is seen in both systems.

Exploring paleoproterozoic metamorphism in the western Río de la Plata craton from drill-core evidence

Rhyacian basement is not exposed in the western part of the Río de la Plata craton, but deep borehole samples (depth of 1046–3340 m) provide information on its composition and metamorphic evolution. An amphibole schist sample from the Camilo Aldao borehole underwent two metamorphic stages: M1 and M2. The P-T conditions of M1 are not constrained whereas the M2 main metamorphic stage is characterized by conditions of 6.1–7.4 kbar and 575–605 °C. In contrast, an olivine gabbronorite sample from the Santiago Temple borehole records crystallization conditions of 1.7 ± 0.6 kbar and 1180 ± 10 °C based on clinopyroxene composition, and late magmatic to subsolidus low-pressure granulite facies metamorphism at 2.3 ± 1.2 kbar and 749 ± 85 °C based on multi-equilibrium thermobarometry. The Rhyacian evolution of the Río de la Plata craton is characterized by at least three thermo-tectonic orogenic stages: T1 (ca. 2200–2100 Ma), T2 (ca. 2100–2040 Ma), and T3 (ca. 2040–2010 Ma) that correspond respectively to: 1) early oceanic subduction and juvenile continental arc magmatism; 2) subsequent continental collision (clockwise intermediate P/T paths of metamorphism), and 3) final low-pressure metamorphism coeval with post-orogenic magmatism. The Camilo Aldao amphibole schist is representative of the T2 orogenic stage while the Santiago Temple gabbronorite is representative of T3 magmatism and metamorphism.

Role of crustal radiogenic heating in ultra-high temperature metamorphism of the Greater Himalayan Crystalline complex: Phase equilibrium and numerical modelling

Ultra-high temperature (UHT) metamorphism is a significant feature of the Greater Himalayan Crystalline complex (GHC), which constrains the dynamics of continental subduction and subsequent continental collision. However, the mechanism of such kind of UHT metamorphism is widely debated, including slab tearing-induced mantle upwelling, mechanical heating, radiogenic heating, and others. To better understand the UHT metamorphism and the thermal budget of collisional orogens, we first conduct a forward phase equilibrium modelling coupled with geochemical modelling to explore the variation of radiogenic heat production (RHP) of felsic melt, indicating that it may range from 4 μW/m3 to 9 μW/m3. Then, we incorporate the variable RHP into a thermo-mechanical model to study its effect on the thermal evolution of the collision zone. The numerical models reveal that a reasonably increased radiogenic heat production of 4 μW/m3 for the partially molten felsic crust contributes to UHT metamorphism after the continental collision for 30–35 million years. The model results are consistent with the structural observations, geochemical signatures, and P-T paths of the GHC. After the comparison with other mechanisms (e.g., the effects of mechanical heating and anomalous mantle heating), we propose that radiogenic heating could be a predominant heat source for the rapid UHT metamorphism of the GHC, whereas mechanical heating and heat flux from the mantle play secondary roles.

The ephemeral history of Earth’s youngest supra-subduction zone type ophiolite from Timor

Ophiolites occur widely in orogenic belts, yet their origins remain controversial. Here we present a modern example with a geodynamic model from Timor, eastern Indonesia, where Earth’s youngest supra-subduction zone (SSZ)-type ophiolitic fragments are exposed. Zircon U-Pb ages and geochemical data indicate a short timespan (~10 to 8 Ma) for the magmatic sequence with boninitic and tholeiitic arc compositions. We interpret the Timor ophiolite as part of the infant Banda arc-forearc complex, which formed with the opening of the North Banda Sea and subsequent arc-continent collision along the irregular Australian continental margin. Our study connects the occurrence of small, short-lived ocean basins in the western Pacific with orogens around the globe where ephemeral SSZ-type ophiolites occur. These orogenic ophiolites do not represent preexisting oceanic crust, but result from upper-plate processes in early orogenesis and thus mark the onset of collision zone magmatism.

Drug-induced eRF1 degradation promotes readthrough and reveals a new branch of ribosome quality control

Suppression of premature termination codons (PTCs) by translational readthrough is a promising strategy to treat a wide variety of severe genetic diseases caused by nonsense mutations. Here, we present two potent readthrough promoters-NVS1.1 and NVS2.1-that restore substantial levels of functional full-length CFTR and IDUA proteins in disease models for cystic fibrosis and Hurler syndrome, respectively. In contrast to other readthrough promoters that affect stop codon decoding, the NVS compounds stimulate PTC suppression by triggering rapid proteasomal degradation of the translation termination factor eRF1. Our results show that this occurs by trapping eRF1 in the terminating ribosome, causing ribosome stalls and subsequent ribosome collisions, and activating a branch of the ribosome-associated quality control network, which involves the translational stress sensor GCN1 and the catalytic activity of the E3 ubiquitin ligases RNF14 and RNF25.

Kinematics and geochronology of the Lancang metamorphic complex: Implications for the evolution of the Paleo-Tethys region

The Lancang metamorphic complex is a key component of the Three River Tethys Orogen in the SE Tibetan Plateau, with typical rock assemblages and deformation fabrics recording the subduction of the Paleo-Tethys Ocean and subsequent continental collision. In this study, we present new petrographic and structural observations, together with zircon U-Pb and mica 40Ar/39Ar geochronologic data, to reveal the deformation and kinematics of the Lancang metamorphic complex, thus providing insights into the Permian−Triassic evolution of the eastern Paleo-Tethys domain. The subduction of the Paleo-Tethys Ocean and subsequent collision resulted in a range of structural features, including penetrative regional foliations, thrusts, asymmetric folds at various scales, and ductile deformation fabrics such as asymmetric boudins and porphyroclasts. Zircon U-Pb dating of foliated gabbro and 40Ar/39Ar dating of mica schist and mylonite, which preserve shortening fabrics, suggest that the Paleo-Tethys Ocean was subducted during the Late Carboniferous to Permian−Early Triassic, and the collision of the Baoshan and Simao blocks mainly occurred during ca. 237−230 Ma in the SE Tibetan Plateau. Regional deformation likely shifted from shortening to extension ca. 230 Ma, as reflected by post-collision high-K calc-alkaline magmatism. Our results document regional structural patterns and place timing constraints on the evolution of the Paleo-Tethys Ocean.

Syncope and Traffic Crash: A Population-Based Case-Crossover Analysis

BackgroundAmong individuals with recent syncope, recurrence of syncope while driving might incapacitate a driver and cause a motor vehicle crash. Current driving restrictions assume that some forms of syncope transiently increase crash risk. We evaluated whether syncope is associated with a transient increase in crash risk. MethodsWe performed a case-crossover analysis of linked administrative health and driving data from British Columbia, Canada (2010 to 2015). We included licensed drivers who visited an emergency department with "syncope and collapse" and who were involved as a driver in an eligible motor vehicle crash, both within the study interval. Using conditional logistic regression, we compared the rate of emergency visits for syncope in the 28 days before crash (the "pre-crash interval") with the rate of emergency visits for syncope in 3 self-matched 28-day control intervals (ending 6, 12, and 18 months before the crash). ResultsAmong eligible crash-involved drivers, 47 of 3026 pre-crash intervals and 112 of 9078 control intervals had emergency visits for syncope, indicating syncope was not significantly associated with subsequent crash (1.6% vs 1.2%; adjusted odds ratio [OR], 1.27; 95% confidence interval [CI], 0.90-1.79; P = 0.18). There was no significant association between syncope and crash in subgroups at higher risk for adverse outcomes after syncope (eg, age > 65 years, cardiovascular disease, cardiac syncope). ConclusionsIn the context of prevailing modifications of driving behaviour after syncope, an emergency department visit for syncope did not transiently increase the risk of subsequent traffic collision. Overall crash risks after syncope appear to be adequately addressed by current driving restrictions.

An investigation of compliant contact force models applied for analysis of simultaneous, multi-zone impacts of particles

Compliant contact force models were developed and mainly used to investigate simple impacts of two bodies. It is therefore unclear how they will perform in more complex cases, where simultaneous, multi-zone impact may occur. The aim of this study is to investigate phenomena that occur in such impacts and to study the effectiveness of preselected contact force models in their modelling. For this purpose, the study addressed collisions that occur in a collinear system of 3 to 6 particles made of steel, aluminium, and bronze. The results obtained for each force model were referenced to the FEM analysis. To compare the performance of the models, the Benchmark Velocity Indicator (BVI) is proposed. The study showed that during simultaneous, multi-zone impact direct switch from the restitution to compression phases may occur and subsequent collision along the same normal may take place. Such phenomena are not incorporated in current compliant contact force models; therefore, the study showed the need for their further improvement. The best models proposed by Kogut and Etsion (KE) and Jackson and Green (JG) achieved average errors equal to 3.89% and 4.15%, respectively. However, the same models in their worst cases reached error values of 38.66% and 33.77%. The article concludes with proposals for future improvements.

Mass-dependent nickel isotopic variations in achondrites and lunar rocks

We present high-precision mass-dependent nickel isotopic data for a comprehensive suite of achondrites and lunar rocks, providing key insights into the early planetary differentiation and Earth-Moon system formation. The primitive achondrites display high Ni contents and invariant Ni isotopic compositions. Incomplete core-mantle differentiation in primitive achondrite parent bodies resulted in the retention of metal in the mantle, which dominated the Ni budget and accounted for the bulk chondritic Ni isotopic values. The highly reduced differentiated achondrites, aubrites and an ungrouped achondrite (NWA 8409), have variable, and extremely light Ni isotopic compositions. Acid leaching experiments demonstrate that the sulfides are a significant host of light Ni isotopes in aubrites. The most extreme Ni isotope values of aubrites may be due to large Ni isotope fractionation accompanied by silicate-sulfide-metal separation during differentiation of the parent bodies, and subsequent global disruptive collision and reassembly with variably high proportions of sulfides enriched in the mantle. The howardite-eucrite-diogenite (HED) meteorites show Ni isotopic variations that are positively correlated with Ni/Co ratios, a feature that cannot be produced by igneous differentiation. Late accretion of high-Ni and high-Ni/Co chondritic materials after core formation of their likely parent body, Vesta, could have accounted for this correlation. Thus, the primitive silicate mantle of Vesta may have sub-chondritic Ni isotopic compositions, implying possible Ni isotope fractionation during core-mantle differentiation of small planetary bodies. The lunar breccia meteorites have homogenously chondritic Ni isotope values, together with their high Ni/Co of bulk rock and metals therein, suggesting impact contamination. Lunar basalt meteorites have low Ni/Co ratios and are systematically isotopically lighter than the breccias, displaying a positive correlation between Ni isotope value and Ni/Co ratio, as that seen in the HEDs. Therefore, the Ni isotopic systematics in lunar rocks also indicates the effect of late accretion, with the primitive lunar mantle having sub-chondritic Ni isotope values. This implies that the Moon-forming impactor, Theia, was likely an aubrite-like differentiated planetary body whose mantle was enriched in light Ni isotopes. We suggest that there was significant Ni isotope fractionation between core and mantle during differentiation of early formed small planetary bodies, but this signature can be obscured by late accretion in the bulk achondrite records.

Investigation of thermal processes in the gap during explosion welding

This paper describes a thermocouple method for measuring the heat flux from the shock-compressed gas in the welding gap to the surfaces of the impacted plates during explosion welding. A set of experiments was conducted to determine the heat flux during explosion welding of copper plates at a distance of 0.4–0.6 m from the beginning of welding. The heat flux from the shock-compressed gas was found to be independent of the contact point velocity in the range of 1800–2500 m/s. As a result, the temperature of surface preheating before collision was found to be quantitatively dependent on the size and material of the welded plates. Thus, the effect of preheating the plates with shock-compressed gas in the gap can be commensurate with the energy released in the weld at the subsequent collision of the plates.

New age constraints on the break-up of Rodinia and amalgamation of southwestern Gondwana from the Choquequirao Formation in southwestern Peru

Abstract The Choquequirao Formation is a &gt;3 km-thick amphibolite-grade succession that outcrops in the Central Andes of southern Peru. To constrain its age and tectonostratigraphic setting, detrital zircon and metamorphic zircon, titanite, and rutile U–Pb isotopic analyses were conducted. Mantle-derived c. 640 Ma detrital zircons constrain the maximum age of the lower part of the succession and 550–490 Ma metamorphic zircon domains constrain its minimum age. The absence of early Paleozoic detrital zircons suggests that deposition predated early Paleozoic orogenesis in southwestern Gondwana. The close similarity of detrital zircon age spectra to those from sediments deposited on the Arequipa basement suggests that the Choquequirao Formation was deposited on the Arequipa Terrane. Metamorphic titanite dates are highly overdispersed, yet they overlap with c. 460 Ma peak metamorphism recorded by metamorphic zircon. Pb-loss pathways displayed by metamorphic titanite have a lower intercept that overlaps with c. 325 Ma metamorphic rutile, which corresponds to Hercynian orogenesis. A poorly constrained upper intercept of c. 510 Ma may correspond to Pampean and/or early Famatinian orogenesis. We interpret the Cryogenian–Ediacaran Choquequirao Formation as having been deposited during the opening of the Palaeo-Iapetus (Puncoviscana–Clymene) Ocean between eastern Arequipa and southern Kalahari prior to the subsequent collision with southwestern Amazonia during the Pampean Orogeny.

Selecting Features That Influence Vehicle Collisions in the Internet of Vehicles Based on a Multi-Objective Hybrid Bi-Directional NSGA-III

The smart platform of generating, collecting, managing and processing dynamic data from different sources in the Internet of Vehicles (IoV) pave the way for a large-scale dataset to be accumulated. The dataset can contain records running into hundreds of thousands and even millions of relevant, irrelevant and redundant features. Therefore, feature selection to select only the significant features for developing vehicle collision detection alarm systems for deployment in the IoV edge is critical. However, previous studies on vehicle collision detection in the IoV have not conducted rigorous feature selection. Limited studies have mainly applied Pearson correlation coefficient (PCC) to select subset features influencing vehicle collision in the domain of IoV. However, PCC can cause relevant features to be discarded if the correlation of the non-linear association is too small, thereby providing incorrect feature ranking, which, in turn, increases the chances of developing a model that will give a poor outcome. To close this gap, this paper proposed a multi-objective, filter-based hybrid non-dominated sorted genetic algorithm III with a gain ratio and bi-directional wrapper for the selection of subset features influencing vehicle collision in the IoV. The proposed approach selected the minimal most significant subset features for developing a vehicle collision detection classifier with maximum accuracy for deployment in the IoV. A comparative study proves that the proposed approach performs better than the compared algorithms across hybrid-, wrapper- and filter-based feature selection methods within the family of the NSGA. Further, a comparative analysis with other evolutionary algorithms proves the superiority of the proposal. This study can help researchers in the future by avoiding the use of large-scale computing resources in acquiring data to develop vehicle collision alert systems in the IoV. This can be achieved since only the subset features discovered in this study are collected, as opposed to collecting large features, thus saving time and resources in the subsequent vehicle collision detection data collection in the IoV.

Early Microjet Experimentation with Liquid Water in Vacuum.

ConspectusIn this brief look at the history of liquid microjets, I recollect some personal reminiscences on initial challenges for introduction of this method, as well as unexpected problems and exemplary results using this new tool for liquid evaporation and photoelectron spectroscopy studies.Many efficient and direct, atomic level diagnostic instruments in use at solid state surfaces and in gas-phase atom or cluster studies require high vacuum. They have therefore not been applied to investigations of aqueous solutions because liquid water both strongly evaporates and rapidly freezes in vacuum. Only fairly recently, over the past three decades, have liquid microjets been considered as practicable targets for research on liquid-water interfaces in vacuum. The working principle is analogous to the functioning of a free molecular beam source, where molecules enter through a small aperture into a vacuum without being disturbed by subsequent collisions in their original Maxwellian velocity distribution. Similarly, above a microjet surface in vacuum, water vapor molecules do not interact with each other, or with different probe particles, as long as the liquid jet diameter is small in relation to the mean free path of the liquids' vapor at equilibrium conditions. For pure liquid water, this constraint is Djet < λvap < 10 μm for 6.1 mbar vapor pressure at the triple point of water. A high streaming velocity of the liquid jet, >50 m/s, delays freezing and exposes a steadily renewed fresh vacuum surface for experiments.For experimental verification of the microjet free surface concept, H2O vapor velocities were measured in a molecular beam time-of-flight experiment. These studies showed Maxwellian velocity distributions with the expected local water-jet temperatures for 5 and 10 μm jets, whereas larger liquid jet diameters of 50 μm exhibit narrowed vapor velocity profiles. This narrowing is the known signature of incipient, collision dominated, supersonic hydrodynamic expansions in nozzle beam sources. As a completely unexpected new result in evaporation studies of carboxylic acid solutions, freely evaporating acetic acid dimers showed apparent non-equilibrium liquid surface source temperatures several hundred kelvin above the simultaneously measured monomer temperatures, a phenomenon shown to be correlated with surface tension.Continuing with improvements, the vacuum water microjets were implemented inside a photoelectron spectroscopy apparatus that was modified for handling large amounts of water vapor. After initial complications with liquid jet charging phenomena, the first partial liquid-water photoelectron spectra were recorded using 21 eV photons from a He I discharge lamp. In the next step, the equipment was taken to a synchrotron radiation beamline at BESSY II, resulting in substantial improvements of signal intensity and in photon tunability for narrow band monochromatic soft X-rays up to 1 keV. Two early examples of these continuing experiments are considered, briefly, for aqueous alkali halide salt solutions and for the pH-value dependent protonation of an NH2/NH3+ group in an amino acid directly in a photoelectron spectrum of a solution.In conclusion, liquid microjets have opened up a completely new approach to studies of arbitrary liquids with chemical and biological relevance.

Structures, deformation history and dynamic background of the Qianyingzi Coal Mine in the Huaibei Coalfield, eastern China

The Qianyingzi Coal Mine is located in the west of the Suxian Mining District of the Huaibei Coalfield, eastern China. The study on structural development patterns and genetic mechanisms in this mine lays an important foundation for safe and efficiently underground mining, and is also the key to understanding the regional tectonic evolution. In this study, based on the analysis of three-dimensional seismic, drilling and underground measured data and regional tectonic correlation, the structures, evolution history and dynamic background of the Qianyingzi Coal Mine are discussed. The Carboniferous-Permian coal measure strata in the mine are generally a gentle syncline with a NNE-trending axis, and cut by a series of faults. The faults developed in this mine are mainly medium- and small-sized with a throw of less than 20 m, and the number of reverse faults is significantly greater than that of normal faults. The strikes of reverse and normal faults are both mainly NE, followed by NNE and nearly N‒S. According to the characteristics of structural geometry, tectonic association, fault property and cross-cutting relation, the structural deformation of coal measure strata in the Qianyingzi Coal Mine can be divided into five stages, and the corresponding tectonic stress fields are NWW‒SEE compressive stress, nearly E‒W compressive stress, NW‒SE compressive stress, nearly E‒W and NW‒SE extensional stresses, respectively. It developed the Fengjia Syncline with a NNE-trending axis in the first stage and nearly N‒S-striking reverse faults in the second stage, which were the results of foreland deformation and subsequent continent-continent collision during the convergence of the North China Craton and South China Plate in the Indosinian period. The NNE-striking reverse sinistral faults and NE-striking reverse faults developed in the third stage is related to the rapid oblique subduction of the Izanagi Plate toward the East Asian continental margin at the beginning of the Early Cretaceous in the western Pacific region. Later, the fourth and fifth stages of the nearly N‒S- and NE-SW-striking normal faults were developed under the backarc extensional background in eastern China during the Early Cretaceous. These new results can be used to guide the rational arrangement for underground mining and also provide a new understanding for regional tectonic evolution of the Huaibei Coalfield.

The metabasites from the Texel Unit (Austroalpine nappe stack): markers of Cretaceous intracontinental subduction and subsequent collision

Abstract Eclogites in the Texel Unit (Austroalpine nappe stack; Eastern Alps, South Tyrol, Italy) represent the westernmost out-crops of the E-W striking Eoalpine High-Pressure Belt (EHB). East of the Tauern Window, the EHB forms part of a Cretaceous intracontinental south-dipping subduction/collision zone. The impetus of this contribution is to extend the geothermo-barometric data of the eclogites from the EHB using conventional geothermobarometry and multi-equilibrium calculations as well as Zr-in-rutile/titanite geothermometry and to put the P-T results of eclogites and amphibolites from the Texel Unit into the geodynamic framework. The investigated samples of this study are from the Spronser- and the Saltaus valleys (S-Tyrol) in the Austroalpine Texel Unit. The Texel Unit is composed mainly of paragneisses with minor intercalations of micaschists, orthogneisses, amphibolites and subordinately eclogites. The amphibolites from the Spronser valley contain the mineral assemblage amphibole + plagioclase + garnet + clinozoisite/epidote + quartz + titanite ± ilmenite ± rutile ± apatite ± calcite. Chemical zoning in plagioclase and amphibole shows two main growth stages: an older P-dominated stage (e.g. albite and barroisite cores) and a younger amphibolite-facies stage. The core of the amphiboles shows barroisite composition, the rim can be chemically classified as hornblende, edenite, tschermakite and pargasite. Geothermobarometric calculations with multi-equilibrium geothermobarometry (THERMOCALC v.3.21) yield temperatures of 600–654°C and pressures of 0.98–1.17 GPa for the same samples. The eclogites from the Saltaus valley contain the peak mineral assemblage omphacite + amphibole + garnet + clinozoisite/epidote + muscovite + quartz + titanite ± ilmenite ± rutile. Thermobarometric calculations, were performed in the system CaO-FeO-MgO-Na2O-Al2O3-FeO-SiO2-H2O with the assemblage clinopyroxene + garnet + amphibole + clinozoisite/epidote + muscovite + quartz ± H2O. The calculations involved an H2O-absent invariant point (mode-1 calculation) as well as two types of average P-T mode-2 calculations. The obtained average P-T H2O-absent mode 1 P-T conditions are 1.89 ± 0.18 GPa and 578 ± 60°C. Using the average P-T mode-2 two types of calculations were done: (1) calculations without amphiboles but with H2O present, which yield mean P-T conditions of 1.95 ± 0.28 GPa and 601 ± 55°C and (2) calculations with amphiboles but without H2O, which yield mean P-T conditions of 1.95 ± 0.26 GPa and 666 ± 77°C. Calculations using THERMOCALC v.3.33 yield similar results with slightly higher pressures of 0.3 GPa. Based on the present geothermobarometric data in conjunction with available mineral ages the eclogites represent the Eoalpine intracontinental subduction stage whereas the amphibolites reflect the subsequent, P-accentuated stage of decompression associated with the subsequent Eoalpine collisional stage.

Zircon geochronology of high-grade metamorphic rocks from outcrops along the Prince Olav Coast, East Antarctica: Implications for multi-thermal events and regional correlations

This paper reports laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) zircon U–Pb ages of a suite of high-grade metamorphic rocks collected from Sinnan Rocks, Akebono Rock, Niban Rock, Gobanme Rock, Tenmondai Rock, Akarui Point, Cape Omega, and Oku-iwa Rock along the Prince Olav Coast, in the Lützow-Holm Complex (LHC), East Antarctica. The dating results indicate that a newly detected ~ 990 Ma metamorphism of garnet–sillimanite–biotite gneiss from Niban Rock. A thermal event at 931.7 ± 9.8 Ma is recorded in zircon from staurolite-bearing garnet–gedrite–biotite–chlorite gneiss in Akebono Rock. The metamorphic zircon grains in other analyzed samples provide Ediacaran to Cambrian ages. Their multi-growth textures and age populations are possibly interpreted to exhibit three metamorphic stages during >600–580 Ma, 580–550 Ma, and 550–500 Ma. Combined with previous reports, the metamorphic rocks in Cape Hinode, Niban-nishi Rock of Niban Rock, and Akebono Rock might have experienced earlier high-temperature metamorphism at ~ 990–930 Ma without younger overprinting. Extensive high-grade metamorphism during ~ 650–500 Ma is recorded from not only the granulite-facies zone in the west of the LHC but also the amphibolite-facies zone in its east. The main metamorphic episode in the LHC is likely to be subdivided into a preceding thermal event (either independent single metamorphic event or prograde stage) at pre-580 Ma, near-peak condition stage during 580–560 Ma, and subsequent retrograde stage after 550 Ma. In regional context this indicates that the assembly at the central Gondwana started with the collision of early and late Neoproterozoic terranes prior to 580 Ma, as a part of the East Africa-Antarctic Orogeny. Subsequent collisions took place among late Neoproterozoic igneous terrane, above terranes collided at pre-580 Ma, and Neoarchean terrane, which were probably driven by the Kuunga Orogeny.

Reinforcement Learning-based Wi-Fi Contention Window Optimization

The collision avoidance mechanism adopted by the IEEE 802.11 standard is not optimal. The mechanism employs a binary exponential backoff (BEB) algorithm in the medium access control (MAC) layer. Such an algorithm increases the backoff interval whenever a collision is detected to minimize the probability of subsequent collisions. However, the increase of the backoff interval causes degradation of the radio spectrum utilization (i.e., bandwidth wastage). That problem worsens when the network has to manage the channel access to a dense number of stations, leading to a dramatic decrease in network performance. Furthermore, a wrong backoff setting increases the probability of collisions such that the stations experience numerous collisions before achieving the optimal backoff value. Therefore, to mitigate bandwidth wastage and, consequently, maximize the network performance, this work proposes using reinforcement learning (RL) algorithms, namely Deep Q Learning (DQN) and Deep Deterministic Policy Gradient (DDPG), to tackle such an optimization problem. In our proposed approach, we assess two different observation metrics, the average of the normalized level of the transmission queue of all associated stations and the probability of collisions. The overall network’s throughput is defined as the reward. The action is the contention window (CW) value that maximizes throughput while minimizing the number of collisions. As for the simulations, the NS-3 network simulator is used along with a toolkit known as NS3-gym, which integrates a reinforcement-learning (RL) framework into NS-3. The results demonstrate that DQN and DDPG have much better performance than BEB for both static and dynamic scenarios, regardless of the number of stations. Additionally, our results show that observations based on the average of the normalized level of the transmission queues have a slightly better performance than observations based on the collision probability. Moreover, the performance difference with BEB is amplified as the number of stations increases, with DQN and DDPG showing a 45.52% increase in throughput with 50 stations.