Stages Of Contraction Research Articles

The reverse-encapsulation and core-release process of a compound droplet under thermocapillary effects

This work demonstrates that a core-shell compound droplet can undergo separation into two different phase droplets or be transformed into a reverse-encapsulation droplet under the influence of thermocapillary effects. This study comprehensively investigates the thermocapillary effects on the migration, reverse-encapsulation, and core-release dynamics of compound droplets, with particular emphasis on the interactions among key dimensionless parameters, including the Marangoni number, Reynolds number, and the radius ratio of the inner to the middle fluid of a core-shell compound droplet. Using a reduction-consistent phase field model for incompressible N-phase flows, this research provides an in-depth analysis of the reverse-encapsulation and core-release processes of a compound droplet. The reverse-encapsulation process is characterized by three distinct stages: The initial acceleration stage, the encapsulation stage, and the post-transformation stage. Similarly, the core-release process also has three stages: The initial acceleration stage, the middle fluid contraction stage, and the independent movement stage. The results indicate that the Marangoni number has little influence on the migration velocity, while the tangential surface force (thermocapillary force) is the cause of these processes. The Reynolds number has a significant effect on the encapsulation dynamics, with higher values leading to slower and more turbulent processes. In addition, the radius ratio plays a critical role in determining the reverse-encapsulation and core-release processes, as well as migration behaviors. These findings advance our understanding of multiphase fluid dynamics and have significant implications for applications in microfluidics, targeted drug delivery, and advanced materials synthesis.

Experiments on the effect of wall distances for bubble collapse characteristics

At present, the energy released by bubble collapse can be used for the surface treatment of workpieces and can also be used to degrade pollutants. However, the mechanism of action between bubble collapse and a nearby wall has yet to be accurately explained. In order to grasp the relationship between the wall distance and collapse characteristics, the methods of spark discharge, high-speed photography, and pressure acquisition are used to study bubble shapes and the dynamic variation during pressure release with different wall distances in this paper. The results show that with the increasing of the distance L, the shape of a bubble changes from oblate to spherical and its collapse time shortens. The proportion of the total collapse time consumed by the slow collapse stage shows an increasing trend. In an experiment with two contractions, the time proportion of the slow collapse stage of the first contraction is much larger than that of the second contraction. The existence of the wall delays the collapse of the bubble. As the distance L increases, the bubble goes from undergoing one collapse to two collapses and then to one collapse again. The proportion of the duration of the slow collapse stage of the first contraction decreases rapidly, and the proportion of the slow collapse stage of the second contraction increases slowly, but the time proportion of second contraction decreases. When the distance L increases from 4.5 mm to 11 mm, the pressure received by the wall gradually decreases 28.19 MPa to 18.01 MPa. With an increase in the distance S from 0 to 8 mm, the maximum pressure received by the wall gradually decreases from 19.77 MPa to 9.37 MPa. The relationship found between the slow collapse stage (ta), the second contraction (tb), and the distance (L) can provide guidance for the effective application of the energy released by bubble collapse.

Is the Cyclic Model of the Universe Possible in the Relativistic Theory of Gravitation?

For the flat FLRW model of Universe evolution in RTG a new model of Dark Energy is proposed. It is a global scalar field Φ with the quadratic potential. It ensures cosmological acceleration at the present time and a bounce at the latе times. At the contraction stage Kazner-like growing anisotropy of Riemannian metrics will break a mass-of- the-graviton bounce mechanism near the Big Bang in FLRW case. There is also noncyclic option, when small enough graviton-mass-terms are significant only at the end of expansion. After bounce, during next contraction epoch, an anisotropy grows and the matter density finally reaches the Planck one.

Vibration-Induced Pancake Bouncing of Impacting Droplets on Hydrophobic Surfaces.

Rapid detachment of impacting droplets from solid surfaces is fundamentally interesting and important in many practical applications, including self-cleaning, anti-icing, and energy harvesting. The droplet pancake bouncing is strongly preferred for the reduced contact time and high bouncing velocity. However, the trigger conditions for pancake bouncing are rigorous. Driven by this, this work circumvents the limitations via solid surface vibration. Our results show that the impacting droplet patterns are highly sensitive to the surface vibration parameters (i.e., the vibration amplitude and frequency), and only a reasonable design of vibration parameters enables the impacting droplets to bounce in a pancake shape without the contraction stage. Intriguingly, the pancake bouncing induced by surface vibration exhibits a significant reduction of solid-liquid contact time (up to ≈80%) compared to the traditional bouncing pattern, and the bouncing velocity has been dramatically enhanced. Furthermore, the critical conditions for the pancake bouncing on the hydrophobic surface and the underlying dynamic mechanism are also identified. This work provides an effective method to achieve well-controlled pancake bouncing of impacting droplets for extensive applications.

Paleogene stratigraphy in the central area of the Fuegian fold and thrust belt, Austral Basin, Argentina: Implications for the chronology of thrust-belt deformation

We combine extensive field data with calcareous nannofossils and dinocysts analysis and detrital zircon U-Pb ages to identify six Paleocene-Oligocene stratigraphic units in a previously poorly studied area in the external fold and thrust belt of the Fuegian Andes. Detailed petrographic analysis coupled with detrital zircon ages indicate three main provenance peaks, which reflect that 1) the lowermost upper Cretaceous was already exhumed during the Paleocene-early Eocene, 2) the upper Cretaceous rocks were a continuous source at least until the late Eocene, 3) volcanism was coetaneous with the deposition of middle Eocene successions. Three contractional stages known elsewhere in the thrust-belt are identified in the study area in the Danian, the early Eocene-early middle Eocene, and the latest Eocene-early Oligocene. This suggests synchronicity along strike during the evolution of the Fuegian fold and thrust belt.

Radiomics features of the cardiac blood pool to indicate hemodynamic changes in pulmonary hypertension (PH) due to heart failure with preserved ejection fraction (PH-HFpEF).

To test the hypothesis that cine MRI-derived radiomics features of the cardiac blood pool can represent hemodynamic characteristics of pulmonary hypertension-heart failure with preserved ejection fraction (PH-HFpEF). Nineteen PH-HFpEF patients (9 male, 57.8 ± 14.7 years) and 19 healthy controls (13 male, 50.3 ± 13.6 years) were enrolled. All participants underwent a cardiac MRI scan. One hundred and seven radiomics features (7 classes) of the blood pool in the left and right ventricles/atrium (LV/RV/LA/RA) were extracted from 4-chamber cine (2D images) at the stages of systole, rapid filling, diastasis, and atrial contraction within a cardiac cycle. For PH-HFpEF patients, features acquired from LV/LA were related to the pulmonary capillary wedge pressure (PCWP); features acquired from RV/RA were related to the mean pulmonary artery pressure (mPAP) using the Pearson correlation coefficient (r). Logistic regression, receiver operating characteristic (ROC) curve and the area under the curve (AUC) were used to test the capability of radiomics features in discriminating 2 subject groups. Features acquired from different chambers at various periods present diverse properties in representing hemodynamic indices of PH-HFpEF. Multiple radiomics features blood pool were significantly related to PCWP and/or mPAP (r: 0.4-0.679, p < 0.05). In addition, multiple features of blood pools acquired at various time points within a cardiac cycle can efficiently discriminate PH-HFpEF from controls (individual AUC: 0.7-0.864). Cine MRI-derived radiomics features of the cardiac blood pool have the potential to characterize hemodynamic abnormalities in the context of PH-HFpEF.

Supervised learning to covering cost risk through post-construction evaluation of transportation projects by project delivery methods

PurposeThe main objectives of this study are to (1) develop and test a cost contingency learning model that can generalize initially estimated contingency amounts by analyzing back the multiple project changes experienced and (2) uncover the hidden link of the learning networks using a curve-fitting technique for the post-construction evaluation of cost contingency amounts to cover cost risk for future projects.Design/methodology/approachBased on a total of 1,434 datapoints collected from DBB and DB transportation projects, a post-construction cost contingency learning model was developed using feedforward neural networks (FNNs). The developed model generalizes cost contingencies under two different project delivery methods (i.e. DBB and DB). The learning outputs of generalized contingency amounts were curve-fitted with the post-construction schedule and cost information, specifically aiming at uncovering the hidden link of the FNNs. Two different bridge projects completed under DBB and DB were employed as illustrative examples to demonstrate how the proposed modeling framework could be implemented.FindingsWith zero or negative values of change growth experienced, it was concluded that cost contingencies were overallocated at the contract stage. On the other hand, with positive values of change growth experienced, it was evaluated that set cost contingencies were insufficient from the post-construction standpoint. Taken together, this study proposed a tangible post-construction evaluation technique that can produce not only the plausible ranges of cost contingencies but also the exact amounts of contingency under DBB and DB contracts.Originality/valueAs the first of its kind, the proposed modeling framework provides agency engineers and decision-makers with tangible assessments of cost contingency coupled with experienced risks at the post-construction stage. Use of the proposed model will help them evaluate the allocation of appropriate contingency amounts. If an agency allocates a cost contingency benchmarked from similar projects on aspects of the base estimate and experienced risks, a set contingency can be defended more reliably. The main findings of this study contribute to post-construction cost contingency verification, enabling agency engineers and decision-makers to systematically evaluate set cost contingencies during the post-construction assessment stage and achieving further any enhanced level of confidence for future cost contingency plans.

Clinical experience of JIAO Lin in treatment of knee osteoarthritis with manual mobilization of meridian muscle regions

The paper introduces JIAO Lin's clinical experience in treatment of knee osteoarthritis (KOA) by manual mobilization of meridian muscle regions. Professor JIAO Lin believes that the key to the occurrence and development of KOA lies in the disorder of meridian muscle regions (sinews/fascia). In pathology, four stages are divided, i.e. the acute stage, the blockage stage, the contraction stage and the atrophy stage of muscle regions, characterized as multi-layer, multi-dimensional and multi-morphological distribution. In treatment, based on the principle, "taking pain sites as stimulating points", the sites, with reduced pain threshold and distributed along the meridian muscle regions, are regarded as "acupoints" for intervention. Manual mobilization of meridian muscle regions is the dominant approach, combined with routine acupuncture, heat-sensitive moxibustion, cupping and bloodletting corresponding to the features of syndromes and meridian manifestation at different stages. The comprehensive treatment may restore and reconstruct the physiological functions of the meridian muscle regions around knee joints by "nourishing tendons, strengthening bones and benefiting joints".

Polyphased gold enrichment as a key process for high-grade gold formation: Insights from the 10 Moz Jundee-Bogada camp (Yilgarn Craton, Western Australia)

High-grade (> 10 g/t) gold mineralization in orogenic gold deposits is of significant economic importance. Understanding the formation of such enriched ore zones is critical for gold exploration success. The world-class Jundee-Bogada gold camp in the Yilgarn Craton of Western Australia comprises both high-grade (avg. > 10 g/t, Jundee deposit) and low-grade (avg. < 3 g/t, Bogada prospect) lodes, despite shared host stratigraphy. The paragenetic framework established for the Jundee gold deposit suggests that the overall gold endowment developed over three deformation events. An early episode of low-grade gold mineralization is associated with colloform-crustiform veins that formed during extensional deformation (DJB2A). A switch to transtensional deformation (DJB2B) resulted in brecciation of the colloform-crustiform veins and coeval deposition of native gold. Late reverse faults record evidence for a third mineralization stage resulting from a NE-SW-directed shortening (DJB3). Mineralization during this late stage was dominantly low-grade, with local occurrences of ultra-high-grade ore zones (> 100 g/t). Each event records transient changes in fluid chemistry during continued hydrothermal activity that spanned local deformation histories. We argue that at the Jundee gold deposit, protracted gold enrichment during three polyphased mineralization episodes resulted in the formation of high-grade gold ores. Whereas the complete metallogenic history is recorded at the Jundee deposit, gold within the Bogada prospect was introduced solely during the late contractional stage (DJB3), resulting in a bulk low-grade endowment. We hypothesize that gold enrichment in high-grade orogenic gold deposits is a direct consequence of the spatial superimposition of protracted ore-forming events.

Study on flame quenching characteristics inside the Tesla valve structure flame arrester unit

Flame arrester is a kind of safety device designed to prevent the spread of flames. In order to achieve a more efficient flame arrester unit structure, this paper proposes a flame arrester unit based on the Tesla valve structure. A comparative study of the quenching characteristics of deflagration flames of propane-air premixtures in traditional crimped ribbon and Tesla valve structure flame arrester units is conducted through numerical simulations and experiments. The results indicate that the flame arrester unit based on the Tesla valve structure exhibits more efficient flame quenching performance compared to the crimped ribbon flame arrester unit. The flame quenching process fusion image shows that the flame quenching length of Tesla valve flame arrester unit with the same cross-sectional area is only 61% of the crimped ribbon flame arrester unit. In addition to heat transfer and wall effect, the collision of airflow in the branched pipe and main pipe within the Tesla valve structure flame arrester unit also plays a significant role in hindering the further advancement of flames. The quenching process of the Tesla valve structure flame arrester unit can be divided into four stages: expansion, diversion, convergence, and contraction stages. Among the five structural parameters that make up the Tesla valve structure flame arrester unit, the angle is the most critical factor affecting quenching performance, with the angle and entrance structure having a significant impact on flow performance. Furthermore, experimental evidence confirms the typical morphological changes the flame front structure undergoes during flame propagation: spherical (hemispherical),finger-shaped and tulip-shaped. However, tulip-shaped flames do not always propagate continuously to the end of the pipeline.

Analysis of Full Lifecycle Cost Management of Construction Projects in the Construction Phase

The purpose of this article is to conduct an in-depth analysis of the comprehensive cost management of engineering construction projects during the construction phase, discussing its significance and application in project management. Through an introduction outlining the research background and objectives, the concept, role, as well as relevant theories and methods of comprehensive cost management throughout the project lifecycle are introduced. Subsequently, a detailed presentation of the main aspects of comprehensive cost management during the construction phase is provided, including the budgeting stage, contract stage, implementation stage, and closing stage. This is followed by an analysis of the key factors that influence comprehensive cost management, covering both internal and external factors. Finally, optimization and improvement strategies are suggested, along with a discussion of future research directions and development trends.

The Spatiotemporal Variation Characteristics and Influencing Factors of Green Vegetation in China

Green vegetation is one of the main objects of ecological environment restoration and protection, objectively reflecting the quality of regional ecological environments. Studying its spatial distribution characteristics is of great significance to the formulation of ecological environment restoration policies. Based on data on urban green vegetation in China from 2000 to 2022, this study attempts to analyze the destruction and protection patterns of urban green vegetation in China from the perspectives of total changes in green vegetation contraction and growth and spatial evolution characteristics and trends, and it explores the driving factors affecting the change in green vegetation area. The results show the following: (1) Green vegetation growth and contraction occurred alternately in China from 2000 to 2022. Vegetation contraction showed a “point–line–plane” evolution pattern, forming a contraction stage of point-like aggregation, linear series, and planar spread. Vegetation growth has always presented a frontal pattern. (2) The growth and contraction of green vegetation in China showed a north–south differentiation phenomenon. The vegetation contraction phenomenon spread in the Central Plains urban agglomeration and its surrounding areas and showed an expanding trend. The growth trend is obviously moving northward, mainly concentrated in Inner Mongolia, Ningxia, Gansu, Xinjiang, and other northern provinces, which also coincides with the key ecological restoration policies in northern China in recent years. (3) City scale, economic level, population scale, agro-industrial structure, and water resources content have significant effects on the spatial distribution of green vegetation.

Cretaceous extensional and contractional stages in the Colombian Andes unraveled by a source-to-sink geochronological and thermochronological study in the Upper Magdalena Basin

Extensional and flexural basins can evolve through multiple stages under the same plate tectonic regime over tens of millions of years. The Cretaceous tectonic evolution of the Colombian Andes is characterized by shifts between contractional and extensional tectonics. The upper plate response to these changes is recorded in the Cretaceous sedimentary rocks along the Western, Central, and Eastern cordilleras, and their adjacent basins, including the Upper Magdalena hinterland basin. We integrated field observations, petrography, geochronology, and thermochronology in the Cretaceous sedimentary units in the southern Upper Magdalena Basin and in the adjacent crystalline basement to decipher the provenance of these units and the exhumation patterns of the source areas. These results suggest that the source areas were exhumed between the Late Jurassic to Early Cretaceous, which may have resulted from the combination of Jurassic contraction and the Early Cretaceous extension. Between ∼120 and 100 Ma, a major stage of crustal extension is recorded in the Caballos Formation. Subsequently, between ∼100 and 80 Ma, sedimentation in the Villeta Group marks the end of the extension and the onset of contraction. This contractional phase was characterized by minor rock uplift within the basin. Basin modification continued between 80 and 65 Ma, involving two successive contractional stages that changed the sedimentary patterns, leading to the burial of a previously exhumed horst block and the appearance of new source areas. These major changes in source areas and sedimentary systems are the result of deformation episodes during prolonged extensional and contractional phases. This geologic evolution highlights the stages that characterize extensional to contractional settings.

Conflict Handling Styles used by Design Team Leaders During Post Contract Stage of Building Construction Projects in Sri Lanka

In comparison to other industries, construction sector encompasses a distinct, complex, and a competitive environment. It enriches the community with improvements when individuals with diverse perspectives, abilities, and degrees of construction expertise collaborate with each other. In this highly competitive multiparty context, conflicts have been labeled as one of the key constraints that prevent the `success of construction projects. Conflict is a fact that everyone must deal with on a regular basis. Construction projects are therefore not an exception. It entails different types of conflicts. To handle these different types of conflicts, construction professionals use different conflict handling styles. Therefore, the aim of this study is to investigate design team leaders’ preference of conflict handling styles and its impact on team spirit of the members of the design team during the post contract stage of building construction projects in Sri Lanka. To collect data, an e-based, closed-ended questionnaire was used incorporating the conflict handling styles introduced in Rahim's Dual Concern theory. The questionnaire was answered by 56 professionals who have the experience of working in the design team during the post contract stage. The study was limited to the building construction projects in Sri Lanka. To analyze the gathered data, descriptive statistics such as mean, percentage, count correlation co-efficient etc. were used. The study has revealed that during the post contract stage, the design team leaders use all five conflict handling styles of Rahim’s Dual concern theory: integrating style, obliging style, dominating style, avoiding style, and compromising style in different frequencies to handle conflicts among design team professionals. The design team professionals often use compromising style and rarely use integrating style, obliging style, dominating style, and avoiding style to handle conflicts among the design team professionals during the post contract stage respectively. Furthermore, the study indicates that these styles bring different levels of impact to the team spirit of design team professionals during the post contract stage of building construction projects in Sri Lanka. The team spirit of design team members is shown to be strongly affected by the compromising style. In contrast, the other four conflict handling styles, integrating style, obligating style, dominating style, and avoiding style, were identified to moderately impact team spirit. Moreover, findings revealed that all these five conflicts handling styles show a strong relationship with the team spirit of design team members during the post-contract stage of building construction projects in Sri Lanka. The research findings may assist construction industry design team leaders and other stakeholders to manage conflicts in a more efficient way and provide an insight to the way to handle conflicts to improve the team spirit of the design team during the post-contract stage of building construction projects in Sri Lanka. KEYWORDS: Conflicts, Conflict Handling Styles, Building Projects, Design team, Construction industry, Post contract stage.

Ciclos econômicos e pagamentos de dividendos: Um estudo no mercado brasileiro

ABSTRACT Purpose: To analyze the behavior of the dividend distribution of publicly traded Brazilian companies according to the effects of the business cycles, comparing the stages of recovery, expansion, recession, and contraction (Schumpeter, 1935) with the stages of expansion and recession according to the National Bureau of Economic Research (NBER). Originality/value: According to Schumpeter (1935), classifying the stages of the business cycle presents greater details to the NBER method because the four stages show different characteristics that are not observed when only the two stages of the NBER model are used. Design/methodology/approach: Information was collected from 243 publicly traded companies listed on the Brazilian Stock Exchange between 1997 and 2021 to achieve the research objective. Data were obtained from the Refinitiv database, using panel data regression models with random effects to analyze two hypotheses defined in this study. The hypotheses state that the behavior of the relationship between the payment of dividends and the stages of the NBER’s bearish (high) business cycles is different from the recession and contraction stages (recovery and expansion), according to Schumpeter. Findings: The results indicated the non-rejection of the hypotheses, reinforcing the importance of the analysis of the four stages of the business cycles and complementary form by investors, analysts, managers, and other users when analyzing the payment of dividends by publicly held companies at the different levels of economic activity in the country.

Effect of inorganic cation on dynamic characteristics of bubble generation

Understanding the effect of inorganic cations on dynamic bubble generation is an important precursor for predicting the bubble characteristics in actual coal flotation. Using the high-speed motion acquisition system, we investigated the bubble growth in different inorganic salt solutions. The bubble generation process was divided into Formation, Expansion, and Contraction stages according to the contact angle between the bubble and the capillary as 90°. Na+, Mg2+, Ca2+, and Al3+ were found to promote bubble growth during the Formation and Expansion stages while restraining the growth during the Contraction stage. Al3+ roughly presented the most obvious promotion of the bubble generation. The dynamic bubble width and length during different bubble growth stages were analyzed to discuss the bubble pressure. The internal pressure increased as the bubble grew. The pressure difference inside and outside the bubble generally followed the order Na+ > Mg2+ > Ca2+ > Al3+. The forces acting on the bubble were attempted to be discussed. The net force acting on the bubble first kept constant and then decreased with the concentrations of Na+, Mg2+, and Ca2+, while it first decreased and then increased in the presence of Al3+. Our results can provide valuable insight into the development of the technology for mineral flotation.

Coupled effects of temperature and relative humidity on desiccation curling of a clayey soil

Soil curling caused by drying is a common phenomenon in nature, and it can vary depending on different atmospheric effects. To investigate the coupled effects of temperature and relative humidity on soil curling, a sequence of desiccation experiments were performed by using elongated strip soil samples in the laboratory. The soil curling process is divided into five stages: vertical settlement stage, lateral contraction stage, concave-up curling stage, curling recovery stage and convex-up curling stage. In this study, the soil evaporation characteristic and curvature curves are obtained under different temperature and relative humidity conditions. The findings revealed that a lower relative humidity results in a higher evaporation rate and a smaller maximum concave-up curling curvature for soil samples. Additionally, as the temperature increased, the water content associated with concave curling decreased. The maximum concave-up curling curvature was determined by the transition from the appearance of concave-up curling to the maximum curvature of concave-up curling. Under the coupled effect of temperature and relative humidity, all the water content associated with the occurrence of concave-up curling, maximum concave-up and convex-up curling appearance are reduced with increasing temperature and decreasing relative humidity. As the temperature ranged from 20 °C to 40 °C, the maximum concave-up curling curvature initially decreased and then increased. Conversely, the maximum concave-up curling curvature increased within the relative humidity range of 30% to 45%.

Peraluminous leucogranites generation during different stages of the Brasiliano Orogeny in the Borborema Province, NE Brazil

The Mamanguape pluton comprises muscovite, biotite syeno-to monzogranite intruded in metasedimentary rocks. Geochemically, the studied samples of the Mamanguape pluton peraluminous granites are ferroan and alkali-calcic. Furthermore, trace element distribution diagrams are characterized by troughs at Ba, Nb, Sr, P and Ti. The REE patterns are fractionated showing (Ce/Yb)N ratios ranging from 12 to 15, and deep negative Eu anomalies, with Eu/Eu* ratios varying between 0.18 and 0.25. The geochemistry of the two-mica granites of the Mamanguape pluton shows similarities with peraluminous leucogranites from the Borborema Province with crystallization ages related to the contractional (640–600 Ma) and transcurrent (590–545 Ma) stages of the Brasiliano/Pan-African Orogeny. Peraluminous, two-mica and biotite-leucogranites were emplaced through all Borborema Province with ages within 640–600 Ma and 590–545 Ma intervals. Their generation is interpreted as the result of partial melting of metasedimentary rocks involving muscovite dehydration. The crystallization age (574 ± 2 Ma) of the Mamanguape two-mica granites suggest intrusion related to the transcurrent stage of the Brasiliano Orogeny. Zircon grains extracted from two samples of a two-mica leucogranites of the Jurema and Jupi Plutons, Pernambuco-Alagoas Domain, show a large variation of εHf(t) values (−45 to −5) and Hf TDM model age between 1.2 and 3.9 Ga. Archean Hf TDM model ages were recorded in Cryogenian/Ediacaran zircon grains as well as Paleoproterozoic grains, suggesting contribution of an Archean component in the source of the granites. One sample of the Mamanguape Pluton, Transversal subprovince, have εHf(t) values ranging between −13.7 and + 1.4 and Hf TDM model age between 1.4 and 2.2 Ga, suggesting that the magma was generated by partial melting of metasedimentary rocks that received a large contribution of Neoproterozoic and Paleoproterozoic igneous sources. Small amount of mantle melt contributing to the source of the two-mica granites is supported by the presence of mafic enclaves and positive εHf(t) values.

Devonian to Early Carboniferous Retreating—Advancing Subduction Switch in the Northwestern Patagonia Accretionary Orogen: U‐Pb and Lu‐Hf Isotopic Insights

AbstractIn this contribution, we present new early middle Devonian igneous and metaigneous units with a major juvenile magmatic source input in the North Patagonian Massif, which were discovered through U‐Pb and Lu‐Hf zircon analyses. Afterward, we assessed their tectonic implications for northwestern Patagonia and then for southern South America, combining our results with available database information consisting of igneous crystallization ages and isotopic data of the Devonian to early Carboniferous magmatic units, tectonic‐metamorphic analyses, and thermochronologic record. This study allows for distinguishing retreating and advancing subduction switching in northwestern Patagonia (38°30′ to 44°S) and a contrasting coetaneous evolution for basement outcrops exposed further north (27°30′ and 37°30′S). The early middle Devonian (400–380 Ma) northwestern Patagonian magmatism is characterized by widespread magmatism and positive εHf–εNd linked to forearc and backarc magmatism that evolved within a retreating subduction stage. A tectonic switching toward advancing orogeny stage began in the late Devonian, evidenced by a lull in magmatic activity with a negative εHf–εNd trend, possibly contemporaneous with the first tectonic‐metamorphic event in western Patagonia. An early Carboniferous magmatic gap, followed by the subsequent development of the main foliation in the basement during the Carboniferous‐Permian period, denotes the acme of this contractional stage. In contrast, the Devonian period in the northern segment is characterized by mostly negative εHf–εNd values, reverse shear zone activity in the foreland, and an inboard magmatism migration, evidencing a compressive tectonic setting that changed to an extensional configuration in the early Carboniferous with widespread arc magmatism development.

Multifractal scaling analyses of the spatial diffusion pattern of COVID-19 pandemic in Chinese mainland

Revealing spatio-temporal evolution regularity in the spatial diffusion of epidemics is helpful for preventing and controlling the spread of epidemics. Based on the real-time COVID-19 datasets by prefecture-level cities, this paper is devoted to exploring the multifractal scaling in spatial diffusion pattern of COVID-19 pandemic and its evolution characteristics in Chinese mainland. The ArcGIS technology and box-counting method are employed to extract spatial data and the least square regression based on rescaling probability (μ-weight method) is used to calculate fractal parameters. The results show multifractal distribution of COVID-19 pandemic in China. The generalized correlation dimension spectrums are inverse S-shaped curves, but the fractal dimension values significantly exceed the Euclidean dimension of embedding space when moment order q«0. The local singularity spectrums are asymmetric unimodal curves, which slant to right. The fractal dimension growth curves are shown as quasi S-shaped curves. From these spectrums and growth curves, the main conclusions can be drawn as follows: First, self-similar patterns developed in the process of COVID-19 pandemic, which seems to be dominated by multifractal scaling law. Second, the spatial pattern of COVID-19 across China can be characterized by global clustering with local disordered diffusion. Third, the spatial diffusion process of COVID-19 in China experienced four stages, i.e., initial stage, the rapid diffusion stage, the hierarchical diffusion stage, and finally the contraction stage. This study suggests that multifractal theory can be utilized to characterize spatio-temporal diffusion of COVID-19 pandemic, and the case analyses may be instructive for further exploring natural laws of spatial diffusion.