Sharp Reversal Research Articles

Magnetostratigraphy and rock magnetic studies on the Cretaceous‐Paleogene transition strata along the Um Sohryngkew River, Therriaghat, Meghalaya, India

A combination of magnetic polarity and rock magnetic analysis on the well‐documented section of the Um Sohryngkew River (USR) in the south Shillong Plateau, NE India, produced a sharp reversal marking the C29r‐C29n geomagnetic polarity transition at approximately 65.688 Ma. The rock magnetic studies indicate ferrimagnetic dominant mineralogy with abundance of SSD grains, with an anomalous peak in susceptibility coinciding with Ir‐rich limonitic layer. The magnetic reversal occurs precisely 61 m above the Ir‐rich distinct in situ limonitic layer, indicating that the C29r‐C29n geomagnetic reversal post‐dates the widely accepted Ir‐anomaly based K‐Pg boundary by approximately 355 Ka. Furthermore, the rock magnetic studies indicate its frequency dependence coinciding with the Ir‐rich limonitic layer suggesting a possible dust/aerosol source, while akaganéite is reported from the interval approximately 1 m below peak susceptibility, indicating signature of Deccan volcanism. This study infers the completeness of the USR section with a high rate of sedimentation of approximately 17 cm/ka among the marine K‐Pg boundary sections in the world.

Abrupt, climate-induced increase in wildfires in British Columbia since the mid-2000s

In the province of British Columbia, Canada, four of the most severe wildfire seasons of the last century occurred in the past 7 years: 2017, 2018, 2021, and 2023. To investigate trends in wildfire activity and fire-conducive climate, we conducted an analysis of mapped wildfire perimeters and annual climate data for the period of 1919–2021. Results show that after a century-long decline, fire activity increased from 2005 onwards, coinciding with a sharp reversal in the wetting trend of the 20th century. Even as precipitation levels remain high, moisture deficits have increased due to rapid warming and increased evaporative demand. Bottom-up factors further influence fire activity, as the legacy of past wildfires, insect outbreaks, and land-use practices continually influence fire regimes. The compound effects of climate-induced moisture changes and altered fuels now force British Columbians to confront the harsh reality of more frequent years of intense and prolonged wildfire activity.

Geochemical Anatomy of the Main Magnetitite Layer, Bushveld Complex, South Africa

ABSTRACT The mafic layered Bushveld Complex, South Africa, contains numerous examples of monomineralic layers within its succession. The Upper Zone (UZ) contains approximately 24 magnetitite layers, the genesis of which has been extensively debated. The Main Magnetitite Layer (MML) is approximately 2 m thick and is traceable around its edge across >60 000 km2. Its basal contact with underlying anorthosite is planar and sharp, but the top contact grades upward with increasing plagioclase content. Sampling at a vertical spacing of a very few centimetres from seven profiles in the east over many tens of kilometres and one other 300 km to the west reveals concentrations of Cr in magnetite that decrease extremely rapidly upward (typically from >8000 to 1000 ppm within 30–60 cm from the base), punctuated by sharp concentration reversals and rare decreases. Here, we describe an outcrop where the MML splits into three sub-layers, separated by magnetite–plagioclase rocks. Twelve profiles across this zone of splitting have been similarly analysed. Lateral variations in Cr profiles across a few metres are observed at this locality. We offer the suggestion that magnetite formation may have been induced by shock wave nucleation on the bottom of the chamber accounting for the abrupt appearance of magnetitite over such a wide area. Bottom growth of magnetite lowered the density and Cr content of the evolving magma, causing turbulence and convective overturn near the base of the chamber that created inhomogeneities in Cr on various scales, preserved in the ensuing magnetite compositions both vertically and laterally. Intermittent and abrupt (on a scale of 1–2 cm) upward increases in the Cr contents of up to 3000 ppm in magnetite profiles resulted from convective overturn impinging on the floor. The tops of the magnetitite sub-layers grade up into magnetite–plagioclase rocks and continue the upward decrease in Cr content in magnetite, typically at 900 ppm Cr, demonstrating upward continuity of fractionation. In contrast, there are reversals in Cr content between the magnetite–plagioclase rocks and the overlying magnetitite sub-layers that we attribute to convective overturn, with an increase in the Cr content. Two profiles through the MML show abrupt upward discontinuities to lower Cr contents that we attribute to physical erosional events. Anorthosite fragments in magnetitite and magnetitite fragments in anorthosite layers further attest to such processes. The anorthite contents of plagioclase do not change across the MML, suggesting that magma addition was not responsible for the formation of magnetitite layers. Primary topographic variations at the base of the chamber also preclude addition of dense magma for the formation of magnetitite layers. Upward infiltration metasomatism, slightly resetting Cr contents, is limited to <3 cm.

The US Policy of Sanctions and Restrictions against China. Beijing’s Tactical Countermeasures and Strategic Counteraction Potential

A sharp reversal of the Chinese vector of the US foreign policy inevitably came with the election of Donald Trump to the presidency in 2017, whose entire election campaign was accompanied by accentuated anti-Chinese rhetoric. Beijing’s response to the powerful pressure of the Trump administration was not the curtailment of state industrial development programs (Made in China – 2025, etc.) required by Washington, but the proclamation of a course to ensure the country’s economic security, increase the level of technological self-sufficiency, further strengthen the role of the domestic market and reduce dependence on exports. In particular, the latest provisions were included in the “double circulation” policy adopted in October 2020. By now, Washington has imposed on China, though sensitive, still limited sanctions which generally do not have a significant impact on the socio-economic development of the country. Even with the WH’s firm political will, effective sanctions potential of the US against China is significantly limited due to enormous interdependence of the two largest world economies. In general, the US sanctions of recent years against China can be divided into two large blocks: officially justified by the interests of US national security (restrictions on telecommunications companies, the ban of Chinese software, etc.) and related to accusations of human rights violations (restrictions on Xinjiang Uygur Autonomous Region of the PRC and Hong Kong SAR). However, in some cases the real reason for the restrictions imposed is the desire of the United States to contain China in the context of general political, economic and technological rivalry of the two countries.

Leverage cycles, growth shocks, and sudden stops in capital inflows

Using a quarterly panel of 98 advanced as well as emerging and developing countries from 1990 to 2018, this paper examines covariates of sudden stops in capital inflows. It shows that domestic variables are related to the probability of incurring sharp reversals in capital inflows controlling for global push factors. In particular, negative growth shocks combined with high levels of leverage in the domestic private sector are significantly correlated with sudden stops. This is in line with real business cycle models including an occasionally binding credit constraint and income trend shocks.

Signatures of the long-range phase transition in topological Josephson junctions

The extended Kitaev models spark a recent surge of interest due to its unprecedented topological phase with fractional invariants. In this extended model of topological superconductors, long-range pairing interactions can induce a pair of subgap massive edge modes (MEMs), posing novel challenges to the unambiguous detection of Majorana bound states (MBSs) sustained by the same model in the short-range limit. Here we investigate the effect of a power-law decayed long-range pairing on the dc and ac Josephson currents between two Majorana nanowires. By varying the magnetic field and long-range pairing, the nanowires can be driven into different phases hosting MEMs, MBSs, or trivial Andreev bound states (ABSs), which considerably modulate the Josephson current. For weakly linked Josephson junctions, we show that the MEMs emerging in the long-range phases can induce a zigzag profile in the dc current-phase relation featured by two sign reversals deviating from the point where the superconducting phase difference $\ensuremath{\phi}=\ensuremath{\pi}$. In contrast, the Josephson current indicates a sharp sign reversal at $\ensuremath{\phi}=\ensuremath{\pi}$ in the short-range phase that hosts MBSs, while a smooth sinelike dc Josephson current appears in the presence of ABSs. In the nonequilibrium junction biased by a voltage, we identify a $4\ensuremath{\pi}$ ac Josephson current in the short-range phases, indicating a MBSs-mediated tunneling process dominating the supercurrents. Differently, when the system enters MEMs-hosted long-range phases, the ordinary ac Josephson current with $2\ensuremath{\pi}$ periodicity can be restored. In addition, we find the ac Josephson current induced by MEMs is significantly suppressed under the strong long-range pairing interactions. These signatures can serve as probes to discriminate MBSs from MEMs and ABSs.

Combining hardness measurements of a heat-treated crankshaft bearing with cross-sectional residual stress and retained austenite distributions measured by HEXRD

Surface hardening is commonly used to modify mechanical properties of crankshaft bearings. In this work, residual stress and hardness distributions across the crankshaft bearings cross-sections are evaluated using synchrotron high-energy X-ray diffraction and hardness testing. It is shown that the measured hardening depth correlates with a point of sudden sharp reversal of the stress gradient from compressive to tensile. This point is linked to the microstructure and does not shift with subsequent tempering or trimming of the sample. The superimposed data is used to interpret the evolution of stresses during the quenching and tempering cycle and gain understanding of the hardening process for such complex geometries. Within the hardened zone retained austenite is found to increase with depth to over 15%, which is attributed to reduced quenching effects as the material is further away from the surface. All measured properties agree in the determined hardening depth of 3.5mm to 4.5mm, which in turn fits well with optical evaluation of metallographic microsections.

Weather risks in grain production

Grain production depends primarily on weather conditions. The paper provides a comparative detailing of meteorological factors affecting the productivity of grain production in the world. The main global factors in the context of climate change that affect the world indicators of the productivity of grain production are natural and climatic conditions with the corresponding Rhesus (risk-extreme values): air temperature during the growing season of grain crops (abnormal heat/frosts); precipitation in the spring-summer period (drought/showers). Based on the analysis of the group of meteorological factors that affect the productivity of grain production, presented by the authors, we can conclude that there are factors of global warming, which leads to a change in productivity and has sharp reversals in the form of “recession/rise". Moreover, speaking about the further development of these agricultural systems, one can state the presence of uncertainty in factors, both objective and external (precipitation, temperature). In this case, by risk we mean the randomness and uncertainty of results in the agricultural sector of the grain-producing territories of the world, which is higher than in other areas of human life.

J-EĞRİSİ MODELİ: TÜRKİYE’DEKİ KOLLEKTİF HOŞNUTSUZLUĞU ANLAMAK İÇİN ALTERNATİF BİR YOL

The contemporary world is marked by deep collective discontent that is difficult to define. Various theories have been put forward to explain collective discontent. One of them is Davies's J-curve model. According to this model, collective discontent is most likely to occur when a prolonged period of economic and social development is followed by a short period of sharp reversal. The present study aims to explain widespread and deepening collective discontent in Turkey with the J-curve model by associating it with the social and political conditions of the country. The data used in the study were obtained from the Turkish Statistical Institute. In the present study, data on gross national income per capita, cost of living, number of suicides, and unemployment rates between 2002 and 2021 were analyzed. All data clearly show that the period of 2002-2021 is graphically compatible with the J-curve. Accordingly, significant economic and social progress took place in Turkey between 2002 and 2012/2013. Since 2012/2013, this progress left its place to regression. The J-curve model has only been studied in an industrial context in Turkey. This study is the first to evaluate the J-curve model in relation to social and political events.

Trade Union Resurgence in Ethiopia

Despite a global trend of declining trade unionism, the Ethiopian trade union movement is resurgent. Having fought off a harsh labour bill and forced industrial parks to open to trade union organising in the past few years, it has scored some of its most momentous achievements, acquiring in the process momentum and leverage. Membership has grown substantially in the last few years, and a sharp increase in workplace-level collective action has occurred over the same period. This article seeks to examine the factors that have enabled the rapid resurgence of trade unionism in Ethiopia, and thus the seeming paradox of a buoyant trade union movement emerging in a context where structural vulnerabilities prevail, at a historical time of global decline in the power and influence of labour organisations. It does so by comparing contemporary trade union strategies to historical iterations. It identifies willingness and capacity to engage in class contestation as the most important factors, and finds that they are premised upon and propelled by pressures and activity from below. The article finds the situation of Ethiopian trade unions to be at once pregnant with possibilities of further advances and serious risks of sharp reversals. ­­­­­­­­­­­­­­­­­­KEYWORDS: trade unions; labour movements; Confederation of Ethiopian Trade Unions

Impact of N-Aryl- and NHC Core-Substituents on the Coupling of Alkylzinc Nucleophiles: Is Bigger always Better?

Bulky Pd-N-heterocyclic carbene (NHC) catalysts (e. g., N-(di-2,6-(3-pentyl)phenyl), IPent) have been shown to have significantly higher reactivity in a wide variety of cross-coupling applications (i. e., C-C, C-S, C-N) than less hindered variants (e. g., N-(di-2,6-(isopropyl)phenyl), IPr). Further, chlorinating the backbone of the NHC ring sees an even greater increase in reactivity. In the cross-coupling of (hetero)aryl electrophiles to secondary alkyl nucleophiles, making the N-aryl groups larger reduces the amount of β-hydride elimination leading to alkene byproducts and chlorinating the NHC core had an even greater effect, all but eliminating alkene formation. In the present study involving the cross-coupling of primary alkyl electrophiles and nucleophiles, a sharp and surprising reversal of all of the above trends was observed. Bulkier catalysts had generally slower rate of reaction and β-hydride elimination worsened leading to extensive amounts of alkene byproducts.

Leverage Cycles, Growth Shocks, and Sudden Stops in Capital Inflows

Using a quarterly panel of 98 advanced as well as emerging and developing countries from 1990 to 2017, this paper shows that domestic variables are significantly related to the probability of incurring sharp reversals in capital inflows controlling for global push factors. In particular, negative growth shocks combined with high levels of leverage in the domestic private sector are a significant determinant of sudden stops. This is in line with real business cycle models including an occasionally binding credit constraint and income trend shocks.

Parameters of Sand-Tyre Chips Mixture for Hardening Soil Small Constitutive Model

Hardening Soil model with the small strain extension (HSS) is lately one of the most popular constitutive models to describe soil behaviour. It is versatile – includes the phenomena of shear strength, stress history, dilatancy, volumetric and shear hardening, hyperbolic stress-strain relationship in axial compression, stiffness dependency on stress and its degradation with strain, as well as the regain of the high stiffness after sharp loading reversals. Even though the model is advanced and complex, accordingly to its authors, it is relatively easy to calibrate based on results of standard tests and empirical formulas. In this paper an attempt was undertaken to estimate the parameters of untypical anthropogenic soils – mixtures of sand and scrap tyre rubber in order to build a database for future numerical analyses. A literature review was conducted and, eventually, the material parameters were determined based on results of a series of laboratory tests (cyclic and monotonic triaxial with bender elements, direct shear) published by researchers of Wollongong University of Australia.

The Largest, Metropolitan, and Global Centers in the World Arena: Matching Networks

—The article compares the leadership of the world’s cities in terms of their size, capital status, global economic functions, and spatial structure of their networks. The global network of 210 largest centers is polycentric but coincides with the network of capitals by only one-third. Giant countries, except for Indonesia and Russia, are characterized by bi- or even polycentrism and active competition of the leading cities. They are dictated by geographic, political, and other factors. Smaller countries, far more numerous in the world, as a rule (but not without exceptions), have monopolistic centers, most often represented by their capitals as absolute and unrivaled leaders. Lists of just large and global cities almost equal in length coincide by 60%. It is difficult for small and poor countries to create global centers; it is easier for them to grow a global center from a capital or largest city. Shifts of urban networks to the south at the planetary level are caused by both global and (often) internal forces, including sharp reversals in countries with transitional economies.

Spatiotemporal development of coexisting wave domains of Rho activity in the cell cortex

The Rho family GTPases are molecular switches that regulate cytoskeletal dynamics and cell movement through a complex spatiotemporal organization of their activity. In Patiria miniata (starfish) oocytes under in vitro experimental conditions (with overexpressed Ect2, induced expression of Δ90 cyclin B, and roscovitine treatment), such activity generates multiple co-existing regions of coherent propagation of actin waves. Here we use computational modeling to investigate the development and properties of such wave domains. The model reveals that the formation of wave domains requires a balance between the activation and inhibition in the Rho signaling motif. Intriguingly, the development of the wave domains is preceded by a stage of low-activity quasi-static patterns, which may not be readily observed in experiments. Spatiotemporal patterns of this stage and the different paths of their destabilization define the behavior of the system in the later high-activity (observable) stage. Accounting for a strong intrinsic noise allowed us to achieve good quantitative agreement between simulated dynamics in different parameter regimes of the model and different wave dynamics in Patiria miniata and wild type Xenopus laevis (frog) data. For quantitative comparison of simulated and experimental results, we developed an automated method of wave domain detection, which revealed a sharp reversal in the process of pattern formation in starfish oocytes. Overall, our findings provide an insight into spatiotemporal regulation of complex and diverse but still computationally reproducible cell-level actin dynamics.

Inside the Mind of Investors During the COVID-19 Pandemic: Evidence from the StockTwits Data

The authors study investor beliefs—sentiment and disagreement—about stock market returns during the COVID-19 pandemic using a large number of investor messages, about 3.7 million, on a social media investing platform, StockTwits. The rich and multimodal features of StockTwits data allow the authors to explore the evolution of sentiment and disagreement within and across investors, sectors, and even industries. The authors find that sentiment (disagreement) has a sharp decrease (increase) across all investors with any investment philosophy, horizon, and experience between February 19, 2020, and March 23, 2020, when a historical market high was followed by a record drop. Surprisingly, these measures have a sharp reversal toward the end of March. However, the performance of these measures across various sectors is heterogeneous. Financial and healthcare sectors are the most pessimistic and optimistic divisions, respectively. <b>TOPICS:</b>Security analysis and valuation, quantitative methods, big data/machine learning, financial crises and financial market history, performance measurement <b>Key Findings</b> ▪ Daily time series of the sentiment and disagreement is not a stationary process. ▪ Sentiment (disagreement) has a sharp decrease (increase) across all investors with any investment philosophy, horizon, and experience between February 19, 2020, and March 23, 2020, when a historical market high was followed by a record drop. ▪ The financial and healthcare sectors are the most pessimistic and optimistic divisions, respectively.

Magneto-optical surface plasmon resonances on perpendicular magnetic thin films consisting of CoPt/ZnO/Ag stacked nanolayers

Magneto-plasmonic phenomena on CoPt/ZnO/Ag stacked nanolayers were investigated in polar Kerr excitation geometry. The nanolayer displays an ideal square-shaped out-of-plane magnetic hysteresis loop with a large polar Kerr activity. The surface plasmon resonances (SPRs) induce drastic magneto-optical (MO) responses with a narrow linewidth and a sharp reversal of the Kerr polarity. The CoPt/ZnO/Ag nanolayer is a candidate for high-performance chemical sensor elements. For example, an MO‒SPR sensor with a Pd surface layer was applied for hydrogen detection. The Pd layer acts as a transducer for both hydrogen detection and plasmon response. Substantial MO responses to the exposure of hydrogen gas can be observed. The results show that the polarized sensing signal is not affected by the intensity of the incident light. The use of the new type of MO‒SPR element with polar Kerr activity leads to a stable chemical sensing system with a simple measurement configuration.

From Baroque drama to tragedy: the first and third editions of the play "Der Turm" by Hugo Laurenz August Hofmann von Hofmannsthal

The problems of genre typology of two editions of the play "Der Turm" (1925, 1927) by the famous Austrian poet and playwright Hugo Laurenz August Hofmann von Hofmannsthal (1874-1929) are studied for the first time. The first edition of the “Der Turm” embodies the author's "Austrian idea", which is a concept of a "conservative revolution" and is aimed at establishing a monarchical order in society. The first play, based on Baroque drama "Life Is a Dream" (1634) by Pedro Calderón de la Barca asserts the power of the "spiritual" principle of Prince Sigismund in resolving the conflict caused by astrological predictions, and develops without Prince's willful participation. He becomes a just ruler, and then gives power to the Child king (from the Bible). In the third edition, the picture of the world changes dramatically. The events of impending Nazism in Germany and Austria changed Hofmannsthal's utopian ideas. The new edition completely changes the motivation of the characters' actions: Prince Sigismund becomes an active participant in the events, and the real power is possessed by the soldier Olivier, who organises the murder of the king and Prince. The author creates a tragic development of the conflict and condemns the sole dictatorship. A sharp reversal from the recognition of the supremacy of the monarch to the image of the victim of dictatorial arbitrariness changed the dialogue of consent of the first edition to the imperative picture of the world of the third edition.

Seismic Attenuation Monitoring of a Critically Stressed San Andreas Fault

AbstractWe show that seismic attenuation ( ) along the San Andreas fault (SAF) at Parkfield correlates with the occurrence of moderate‐to‐large earthquakes at local and regional distances. Earthquake‐related anomalies are likely caused by changes in permeability from dilatant static stress changes, damage by strong shaking from local sources, and pore unclogging/clogging from mobilization of colloids by dynamic strains. We find that, prior to the 2004 M6 Parkfield earthquake, prefailure conditions for some local events of moderate magnitude correspond to positive anomalies of on the Pacific side, with local and regional earthquakes producing sharp attenuation reversals. After the 2004 Parkfield earthquake, we see higher anomalies along the SAF, but low sensitivity to local and regional earthquakes, probably because the mainshock significantly altered the permeability state of the rocks adjacent to the SAF, and its sensitivity to earthquake‐induced stress perturbations.

Event study on the reaction of the developed and emerging stock markets to the 2019-nCoV outbreak

With a sample of 49 stock market indices of the developed and emerging markets in the world using the standard event methodology, this paper aims to examine the impacts of the 2019-nCoV outbreak on the global stock markets. Previous studies have supported that macroeconomic news and firm-specific news do impact the stock market returns. This study provides evidence for global stock market reactions to epidemics. The study concludes that the 2019-nCoV outbreak has significantly impacted the global stock markets with the Asian stock markets being hit the hardest. Further, the study also analyzed the impacts of lockdowns/restrictions imposed by the economies to contain the 2019-nCoV outbreak. This study evidences that early lockdowns/restrictions imposed by the nations have yielded positive results in containing the spread of the novel coronavirus, thus, rebuilding the investor’s confidence and sharp reversal in the stock market returns. The statistical results establish a high and moderate negative correlation between the cumulative abnormal returns (CARs) and the cumulative cases and deaths both country-wise and that of the world indicating that the cross-country variation in the evolution of cases and fatality rates led to such stock market reactions impacting the market sentiments and anticipation for the future.