Abrupt Reversal Research Articles

The Creation and Withdrawal of Spaces for Participatory Governance: The Case of Village Development Committees in West Bengal, India

This article examines how more democratic forms of state-citizen engagement can be engineered under less than favorable political conditions, through the case of the Village Development Committees under the Left Front government in West Bengal, India. Our research shows that these Committees embodied empowered participatory governance ideals and made meaningful contributions to citizens' participation within the local state, confirming the potential for well-designed institutions to deepen democratic engagement. However, this reform's abrupt reversal indicates that leftist parties are not automatically wholehearted supporters of empowered participatory governance, and that this reform needed to be connected to a wider set of claims about the Left Front's participatory successes, in order to build its legitimacy. Our wider argument is that research should examine not only the quality of participatory spaces themselves but also their political contexts, if we are to understand how experiments in empowered participatory governance can “scale up” and become durable.

Spatial patterns in ecological systems: from microbial colonies to landscapes.

Self-organized spatial patterns are ubiquitous in ecological systems and allow populations to adopt non-trivial spatial distributions starting from disordered configurations. These patterns form due to diverse nonlinear interactions among organisms and between organisms and their environment, and lead to the emergence of new (eco)system-level properties unique to self-organized systems. Such pattern consequences include higher resilience and resistance to environmental changes, abrupt ecosystem collapse, hysteresis loops, and reversal of competitive exclusion. Here, we review ecological systems exhibiting self-organized patterns. We establish two broad pattern categories depending on whether the self-organizing process is primarily driven by nonlinear density-dependent demographic rates or by nonlinear density-dependent movement. Using this organization, we examine a wide range of observational scales, from microbial colonies to whole ecosystems, and discuss the mechanisms hypothesized to underlie observed patterns and their system-level consequences. For each example, we review both the empirical evidence and the existing theoretical frameworks developed to identify the causes and consequences of patterning. Finally, we trace qualitative similarities across systems and propose possible ways of developing a more quantitative understanding of how self-organization operates across systems and observational scales in ecology.

Plasmonic diastereoisomer arrays with reversed circular dichroism simply controlled by deformation height

Chirality reversal between enantiomers is of great importance in both fundamental science and practical applications in chiroptics, biomedicine, and analytical chemistry. Here, we demonstrate an abrupt sign reversal of circular dichroism (CD) between artificial plasmonic diastereoisomers, which are a kind of stereo twisted metamolecules with different strength of deformations. The sign of the CD response is reversed in the same wavelength region by simply engineering the deformation height of nanostructures. Electromagnetic multipolar analysis shows that the sign of CD is determined by the phase-controlled handedness-dependent excitations of electric quadrupole modes. The numerical simulations are further verified by experiments using a nano-kirigami fabrication method. This work reveals that under certain circumstances, the CD response of the plasmonic diastereoisomers can be very close to that of enantiomers, which is useful for the exploration of profound chiroptics, as well as for the applications in chirality switching, chiral biosensing, and chiral separation.

Abrupt policy reversal amid Black Lives Matter: Starbucks’ grande employee dress code problem

Theoretical basis Organizational Justice Theory serves as a useful frame for discussion of this case, focusing on perceptions of fairness in the workplace. Such perceptions are shaped by outcomes, procedures, information and interpersonal treatment. Perceptions of justice in these four dimensions are associated with job performance, citizenship behaviors and some mental health outcomes. The Exit, Voice, Loyalty, Neglect (EVLN) Model outlines four potential responses (exit, voice, loyalty and neglect) to perceived job dissatisfaction, serving as a useful framework for students to discuss potential employee reactions to Starbucks’ decisions. Research methodology This case was developed from secondary sources, including news reports, company annual reports and websites. The case has been classroom tested with undergraduate students in Principles of Management (online and face-to-face) Human Resource Management (online asynchronous) and Labor/Management Relations (online synchronous). Case overview/synopsis In June 2020, Starbucks became immersed in controversy when its dress code policy conflicted with its public support for national protests over police brutality against Black Americans, including the death of George Floyd while in police custody. While publicly supporting the protests in a series of tweets, an internal memo forbidding employees from wearing Black Lives Matter attire was leaked to the press, generating national outcry, threats of a boycott and forcing Starbucks to reverse course immediately. This case examines the benefits and challenges of a corporate dress/uniform policy, and the implications of corporate involvement in social justice issues. Complexity academic level This case can be used in a wide range of undergraduate and graduate courses, but particularly in Principles of Management and Human Resources courses.

A Novel Method for Gaining New Insight on Flows Over Inundated Landscapes

AbstractWe present a novel approach for detecting surface water flows over flooded terrain. The approach requires a minimum of three stage measurements and can be applied to any inundated surface, across a range of temporal and spatial scales. This method creates new and robust opportunities for field observation and for validation of numerical simulations and remote sensing analyses. In this proof‐of‐concept study, we found that floodplain free surface gradients were particularly variable during sub‐bankfull inundation, including abrupt current reversals. Also, flow direction varied with stage and the rate of change in stage. The “triangular facet” approach provides a new type of mesoscale insight of flow processes over inundated landscapes, highlighting flow complexity. Moreover, the approach provides information on floods that represent a compromise between point velocimeter measurements and satellite remote sensing and it can provide substantial benefits to society by aiding in flood hazard and mitigation assessment and planning.

Propagation Vectors Facilitate Differentiation Between Conduction Block, Slow Conduction, and Wavefront Collision.

[Figure: see text].

Ferroelectric polarization reversal in multiferroic MnWO4 via a rotating magnetic field up to 52 T

A long-standing issue in multiferroic ${\mathrm{MnWO}}_{4}$ is the electric polarization reversal when magnetic field is applied along the magnetic easy axis $(H||u)$. In this work, we performed comprehensive ferroelectric polarization measurements on ${\mathrm{MnWO}}_{4}$ in fields up to 52 T and with rotating field direction in the $ac$ plane. When the field is rotated from $H||c$ to $H||u$, the induced high-field phase $(\ensuremath{-}P||b)$ favors a sign reversal relative to the low-field $+P||b$ phase, which is attributed to the vector spin chirality changing from one side of the spin connecting vector to the other. Particularly, further slight deviation of the field from the magnetic easy axis towards $H||a$ causes an abrupt reversal of the high-field phase from $\ensuremath{-}P||b$ to $+P||b$. We assume that this unusual angular dependence of polarization behavior can be understood by magnetic control of the helicity of the chiral plane with opposite conical spin structures. In addition, we also propose electric-field control of the chiral plane close to the ferroelectric phase transition at high fields. This study results in an overall understanding of this important multiferroic material and sheds light on field-induced polarization switching in related compounds.

The evolution of the irreversible transition from a free-swimming state to an immobile sessile state in aquatic invertebrates modelled in a chemostat

To better understand the environmental factors and ecological processes underlying the evolution of the irreversible transition from a free-swimming state to an immobile sessile state as seen in many aquatic invertebrates, we study the adaptive dynamics of the settling rate of a hypothetical microorganism onto the wall of a chemostat. The two states, floating or settled, differ in their nutrient ingestion, reproduction and death rate. We consider three different settling mechanisms involving competition for space on the wall: (i) purely exploitative competition where free-swimming individuals settle in vacant space only, (ii) mixed exploitative and interference competition where individuals attempt to settle in any place but fail and die if the space is already occupied, and (iii) mixed exploitative and interference competition, but now settling in occupied space is successful and the former occupant dies. In the simplified environment of the chemostat, the input concentration of nutrients and the dilution rate of the tank are the main environmental control variables. Using the theory of adaptive dynamics, we find that the settling mechanisms and environmental control variables have qualitatively different effects on the evolution of the settling rate in terms of the direction of evolution as well as on species diversity. In the case of purely exploitative competition a small change in the settings of the environmental control variables can lead to an abrupt reversal of the direction of evolution, while in the case of mixed exploitative and interference competition the effect is gradual. For all three settling mechanisms, periodic fluctuations in the nutrient input open the possibility of evolutionary branching leading to the long-term coexistence of an intermediate and an infinitely high settling rates (in the case of low-frequency fluctuations), and an intermediate and a zero settling rates (in the case of high-frequency fluctuations).

Steering magnonic dynamics and permeability at exceptional points in a parity\u2013time symmetric waveguide

Tuning the magneto optical response and magnetic dynamics are key elements in designing magnetic metamaterials and devices. This theoretical study uncovers a highly effective way of controlling the magnetic permeability via shaping the magnonic properties of coupled magnetic waveguides separated by a nonmagnetic spacer with strong spin–orbit interaction (SOI). We demonstrate how a spacer charge current leads to enhancement of magnetic damping in one waveguide and a decrease in the other, constituting a bias-controlled magnetic parity–time (PT) symmetric system at the verge of the exceptional point where magnetic gains/losses are balanced. We find phenomena inherent to PT-symmetric systems and SOI-driven interfacial structures, including field-controlled magnon power oscillations, nonreciprocal propagation, magnon trapping and enhancement as well as an increased sensitivity to perturbations and abrupt spin reversal. The results point to a new route for designing magnonic waveguides and microstructures with enhanced magnetic response.

The Chair’s Summing Up Independent Evaluation Office - IMF advice on Capital Flows Executive Board Meeting 20/93 September 18, 2020

Executive Directors welcomed the report of the Independent Evaluation Office (IEO) on IMF Advice on Capital Flows. Directors appreciated the high quality of the report, and its thematic and background country studies. Directors welcomed the finding that the adoption of the Institutional View (IV), along with the development of other frameworks and additional tools, had represented a major advance in the Fund’s policy framework to provide systematic advice to member countries on the management of capital flows and capital account liberalization. Directors also noted the conclusion that, in its application, the Fund had generally followed the IV and other policy frameworks to ensure that the advice was consistent, tailored to country circumstances, and evenhanded across countries. Directors welcomed that capital flow management measures (CFMs) have generally not been used to substitute for warranted policy adjustments. Directors also welcomed the finding that most authorities broadly support the IV’s sequenced framework to capital account liberalization and appreciated the Fund’s specific advice in many cases, especially in the context of technical assistance. More recently, faced with the abrupt capital flow reversals during the COVID-19 crisis, Directors noted that emerging markets and developing economies generally followed a multi-pronged approach broadly consistent with the IV framework and made relatively little use of CFMs.

Experimental exploration of dynamic phase transitions and associated metamagnetic fluctuations for materials with different Curie temperatures.

We study dynamic magnetic behavior in the vicinity of the dynamic phase transition (DPT) for a suitable series of samples that have different Curie temperatures T_{C}, which thus enables us to experimentally explore the role of the reduced temperature T/T_{C} in the DPT. For this purpose, we fabricate Co_{1-x}Ru_{x} epitaxial thin films with uniaxial in-plane anisotropy by means of sputter deposition in the concentration range 0.0≤x≤0.26. All samples are ferromagnetic at room temperature, exhibit an abrupt magnetization reversal along their easy axis, and represent a unique T_{C} and thus T/T_{C} ratio according to their Ru concentration. The dynamic magnetic behavior is measured by using an ultrasensitive transverse magneto-optical detection method and the resulting dynamic states are explored as a function of the applied magnetic field amplitude H_{0} and period P, as well as an additional bias field H_{b}, which is the conjugate field of the dynamic order parameter Q. Our experimental results demonstrate that the qualitative behavior of the dynamic phase diagram is independent of the T/T_{C} ratio and that for all T/T_{C} values we observe metamagnetic anomalies in the dynamic paramagnetic state, which do not exist in the corresponding thermodynamic phase diagram. However, quantitatively, these metamagnetic anomalies are very strongly dependent on the T/T_{C} ratio, leading to an about 20-fold increase of large metamagnetic fluctuations in the paramagnetic regime as the T/T_{C} ratio increases from 0.37 to 0.68. Also, the phase space range in which these anomalous metamagnetic fluctuations occur extends closer and closer to the critical point as T/T_{C} increases.

Glacier expansion on Baffin Island during early Holocene cold reversals

The North Atlantic was a key locus for circulation-driven abrupt climate change in the past and could play a similar role in the future. Abrupt cold reversals, including the 8.2 ka event, punctuated the otherwise warm early Holocene in the North Atlantic region and serve as useful paleo examples of rapid climate change. In this work, we assess the cryospheric response to early Holocene climate history on Baffin Island, Arctic Canada, using cosmogenic radionuclide dating of moraines. We present 39 new 10Be ages from four sets of multi-crested early Holocene moraines deposited by cirque glaciers and ice cap outlet glaciers, as well as erratic boulders along adjacent fiords to constrain the timing of regional deglaciation. The age of one moraine is additionally constrained by in situ14C measurements, which confirm 10Be inheritance in some samples. All four moraines were deposited between ∼9.2 and 8.0 ka, and their average ages coincide with abrupt coolings at 9.3 and 8.2 ka that are recorded in Greenland ice cores. Freshwater delivery to the North Atlantic that reduced the flux of warm Atlantic water into Baffin Bay may explain brief intervals of glacier advance, although moraine formation cannot be definitively tied to centennial-scale cold reversals. We thus explore other possible contributing factors, including ice dynamics related to retreat of Laurentide Ice Sheet outlet glaciers. Using a numerical glacier model, we show that the debuttressing effect of trunk valley deglaciation may have contributed to these moraine-building events. These new age constraints and process insights highlight the complex behavior of the cryosphere during regional deglaciation and suggest that multiple abrupt cold reversals—as well as deglacial ice dynamics—likely played a role in early Holocene moraine formation on Baffin Island.

A Forgotten Minority: The Return of the Auslandsdeutsche to Germany in 1919-20

This article examines the expulsion of Germans abroad (Auslandsdeutsche) from Allied countries and colonial empires in the aftermath of the First World War, and their somewhat negative reception in Weimar Germany in 1919-20. It does so against the background of what it identifies as a re-territorialisation of German national identity, beginning during the war itself and leading to an abrupt reversal of previous trends towards the inclusion of Germans abroad within broader transnational notions of Germanness (Deutschtum), rights to citizenship and aspirations to world power status. Re-territorialisation was not born out of the logic of de-territorialisation and Weltpolitik in any dialectical sense, however. Rather, its causes were largely circumstantial: the outbreak of global war in 1914, the worldwide economic and naval blockade of Imperial Germany, and its final defeat in 1918. Nonetheless, its implications were substantial, particularly for the way in which minority German groups living beyond Germany’s new borders were constructed in official and non-official discourses in the period after 1919-20.

Holocene hydroclimatic variability in the Zanskar Valley, Northwestern Himalaya, India

AbstractA 1.3-m-long sediment core from the Penzi-la pass, Zanskar Valley, provides a record of hydroclimatic conditions and abrupt climate changes over short time scales since the mid-Holocene. These climatic changes of centennial time scale are crucial to understanding the hydroclimatic variability in northwestern (NW) Himalaya. Relatively higher δ13C values complemented by total organic carbon, loss on ignition, grain size parameters, and lower Rubidium/Strontium ratios during the Late Northgrippian imply that the area had a dry climate during the period from ~6200–4500 cal yr BP. Subsequently, a relatively stable hydroclimatic environment was experienced between ~4500 and 3400 cal yr BP. After ~3400 cal yr BP the multiproxy data show gradual strengthening of hydroclimatic conditions, however, this trend is interrupted by high-amplitude abrupt reversals (dry events) with a stepwise decreasing intensity at ~3300, 2600, 1700, and 400 cal yr BP. The two most important climatic events of the last millennia (i.e., Medieval Climate Anomaly and the Little Ice Age) were also recorded from the sedimentary archive. Overall, our data show a progressive increase in the moisture availability in the Zanskar Valley and are in agreement with the late Holocene climatic trends of central and western Himalaya.

Belief reversals as phase transitions and economic fragility: a complexity theory of financial cycles with reflexive agents.

This paper aims to contribute to the analysis of expectations and belief reversals in a evolutionary and complexity economics framework. It formulates its analysis in terms of the concept of reflexivity, drawing on the ideas regarding reflexivity in financial markets of George Soros, and lays out a model of how a financial cycle expresses a systematic pattern of interacting feedback effects. The paper develops this analysis as a complex interaction between sets of heterogeneous expectations derived from the behavior of reflexive economic agents. Positive and negative feedback phases in a cycle are distinguished and associated with boom and bust stages of that cycle. A central role is played by agents’ beliefs and judgments underlying their expectations, and how those beliefs and judgments in uncertain circumstances are changeable and subject to abrupt reversals which can manifest themselves in “Minsky moments.” The paper argues that agents’ belief reversals result from their misconceptions about causal processes in booms and upswings, a misconception that reflects their tendency to think causally in terms of negative feedback patterns rather than positive ones.

A Complexity Theory of Financial Cycles With Reflexive Agents

This paper aims to contribute to the analysis of expectations and belief reversals in an evolutionary and complexity economics framework. It formulates its analysis in terms of the concept of reflexivity, drawing on the ideas regarding reflexivity in financial markets of George Soros, and lays out a model of how a financial cycle expresses a systematic pattern of interacting feedback effects. The paper develops this analysis as a complex interaction between sets of heterogeneous expectations derived from the behavior of reflexive economic agents. Positive and negative feedback phases in a cycle are distinguished and associated with boom and bust stages of that cycle. A central role is played by agents’ beliefs and judgments underlying their expectations, and how those beliefs and judgments in uncertain circumstances are changeable and subject to abrupt reversals which can manifest themselves in ‘Minsky moments.’ The paper argues that agents’ belief reversals result follow their misconception about causal processes in booms and upswings, a misconception that reflects their tendency to think causally in terms of negative feedback patterns rather than positive ones.

How Robust is the Asian Precipitation–ENSO Relationship during the Industrial Warming Period (1901–2017)?

AbstractInstrumental observations (1901–2017) are used to uncover the seasonality, regionality, spatial–temporal coherency, and secular change of the relationship between El Niño–Southern Oscillation (ENSO) and Asian precipitation (AP). We find an abrupt seasonal reversal of the AP–ENSO relationship occurring from October to November in a large area of Asia north of 20°N due to a rapid northward shift of the ENSO-induced subsidence from Indonesia to the Philippines. We identified six subregions that have significant correlations with ENSO over the past 116 years with |r| > 0.5 (p < 0.001). Regardless of the prominent subregional differences, the total amount of AP during a monsoon year (from May to the next April) shows a robust response to ENSO with r = −0.86 (1901–2017), implying a 4.5% decrease in the total Asian precipitation for 1° of SST increase in the equatorial central Pacific. Rainfall in tropical Asia (Maritime Continent, Southeast Asia, and India) shows a stable relationship with ENSO with significant 31-yr running correlation coefficients (CCs). However, precipitation in North China, the East Asian winter monsoon front zone, and arid central Asia exhibit unstable relationships with ENSO. Since the 1950s, the AP–ENSO relationships have been enhanced in all subregions except over India. A major factor that determines the increasing trends of the AP–ENSO relationship is the increasing ENSO amplitude. Notably, the AP response is asymmetric with respect to El Niño and La Niña and markedly different between the major and minor ENSO events. The results provide guidance for seasonal prediction and a metric for assessment of climate models’ capability to reproduce the Asian hydroclimate response to ENSO and projected future change.

In-situ Switchback Formation in the Expanding Solar Wind

Abstract Recent near-Sun solar-wind observations from Parker Solar Probe have found a highly dynamic magnetic environment, permeated by abrupt radial-field reversals, or “switchbacks.” We show that many features of the observed turbulence are reproduced by a spectrum of Alfvénic fluctuations advected by a radially expanding flow. Starting from simple superpositions of low-amplitude outward-propagating waves, our expanding-box compressible magnetohydrodynamic simulations naturally develop switchbacks because (i) the normalized amplitude of waves grows due to expansion and (ii) fluctuations evolve toward spherical polarization (i.e., nearly constant field strength). These results suggest that switchbacks form in situ in the expanding solar wind and are not indicative of impulsive processes in the chromosphere or corona.

Glacier expansion in central Patagonia during the Antarctic Cold Reversal followed by retreat and stabilisation during the Younger Dryas

The spatial-temporal footprint of millennial-scale climate events during the last glacial-interglacial transition can yield insights into the underlying drivers of climate change, but remains poorly resolved in Patagonia. Here, we assess the glacier response to abrupt cold events and palaeolake evolution using geomorphological mapping along with 10Be ages and optically stimulated luminescence ages from near Lago Belgrano (47.9° S) on the eastern side of Monte San Lorenzo. The former Belgrano glacier was sustained by a climatically sensitive ice cap, making the site ideal for investigating the glacier response to abrupt cold reversals. Our data reveal an extensive re-advance at 13.1 ± 0.6 ka, consistent with cooling and increased precipitation during the Antarctic Cold Reversal (ACR). Subsequently, ice retreated by at least 10 km and created an ice-dammed proglacial lake in the Belgrano valley. Rapid recession was punctuated by smaller advances/still-stands sufficient to maintain an ice-dam for the palaeolake and deposit a lateral moraine dated at 12.4 ± 0.3 ka during the Younger Dryas (YD). The final withdrawal of glaciers to the mountains allowed the palaeolake to drain and resulted in an Atlantic/Pacific drainage reversal. This marks the final separation of the Patagonian Ice Sheet into the individual ice fields at the YD-Holocene transition. Our data demonstrate the dominant ACR climate signal in central Patagonia, but also reveals a co-occurrence of the northern hemisphere YD signal, albeit of smaller magnitude. The ACR re-advance was primarily climatically controlled, but its relative magnitude was likely a consequence of ice divide migration and ice flow re-routing during the break-up of the Patagonian Ice Sheet.

Coercivity enhancement mechanism of Tb-diffusion Nd–Fe–B sintered magnets studied by magneto-optical Kerr optical microscope

The coercivity, microstructure, and magnetic domain structure of Nd–Fe–B sintered magnets by grain boundary diffusion process (GBDP) with TbH3 nanoparticles were systematically investigated. Compared to the original magnet, the coercivity (Hci) of the GBDP magnets improved from 1702 to 2374 kA·m−1 with few remanence reduced from 1.338 to 1.281 T. Electron probe micro-analysis (EPMA) analysis showed that Tb diffused along grain boundary, mainly concentrated in the boundary layer of the main phase, and formed a core–shell structure. Magneto-optical Kerr optical microscope (MOKE) analysis showed that there were two types of magnetic domain reversal in one grain: gradual reversal (GR) and abrupt reversal (AR). When the applied field decreased from saturated magnetic field, the reversal magnetic domain nucleated and then spread over the whole grain gradually, which was called GR. However, some grains kept the single domain state until Hh which was a value of reverse direction applied field in second quadrant in hysteresis loops. When the applied field increased above Hh, reversed magnetic domain would suddenly appear and occupy most of the area of the grain, which was called AR. That is because AR grains have higher reversed magnetic domain nucleation field (HRN2) than GR grains (HRN1). After GBDP, the area of AR region increased obviously and GR region decreased accordingly, indicating that the core–shell structure could change GR grain into AR grain. The core–shell structure could suppress flipping of the magnetization of the grains due to the large magnetic anisotropy of Tb-rich shell. Therefore, large AR area led to high coercivity.