Sharp Shifts Research Articles

Subseafloor Archaea reflect 139 kyrs of paleodepositional changes in the northern Red Sea.

The vertical distribution of subseafloor archaeal communities is thought to be primarily controlled by in situ conditions in sediments such as the availability of electron acceptors and donors, although sharp community shifts have also been observed at lithological boundaries suggesting that at least a subset of vertically stratified Archaea form a long-term genetic record of coinciding environmental conditions that occurred at the time of sediment deposition. To substantiate this possibility, we performed a highly resolved 16S rRNA gene survey of vertically stratified archaeal communities paired with paleo-oceanographic proxies in a sedimentary record from the northern Red Sea spanning the last glacial-interglacial cycle (i.e., marine isotope stages 1-6; MIS1-6). Our results show a strong significant correlation between subseafloor archaeal communities and drastic paleodepositional changes associated with glacial low vs. interglacial high stands (ANOSIM; R=.73; p= .001) and only a moderately strong correlation with lithological changes. Bathyarchaeota, Lokiarchaeota, MBGA, and DHVEG-1 were the most abundant identified archaeal groups. Whether they represented ancient cell lines from the time of deposition or migrated to the specific sedimentary horizons after deposition remains speculative. However, we show that the majority of sedimentary archaeal tetraether membrane lipids were of allochthonous origin and not produced in situ. Slow post-burial growth under energy-limited conditions would explain why the downcore distribution of these dominant archaeal groups still indirectly reflect changes in the paleodepositional environment that prevailed during the analyzed marine isotope stages. In addition, archaea seeded from the overlying water column such as Thaumarchaeota and group II and III Euryarchaeota, which were likely not have been able to subsist after burial, were identified from a lower abundance of preserved sedimentary DNA signatures, and represented direct markers of paleoenvironmental changes in the Red Sea spanning the last six marine isotope stages.

Atomic-Scale Studies of Overlapping Grain Boundaries between Parallel and Quasi-Parallel Grains in Low-Symmetry Monolayer ReS2

Summary Grain boundaries (GBs) are significant microstructures that dominate properties of polycrystalline two-dimensional (2D) materials. Low-symmetry rhenium disulfide monolayers provide an ideal platform to investigate diverse configurations of GBs and their orientation-dependent characteristics. Here, we utilize the preferential deposition of platinum-based nanoparticles on grain edges to rapidly locate nanoscale-wide overlapping GBs during microscopic-scale observation. Atomic-resolution investigations by aberration-corrected annular dark-field scanning transmission electron microscopy reveal diverse overlapping GBs constructed by parallel grains with transversal displacement. They prefer to align along several primary lattice directions with different interlayer atomic registries. Calculations show that the electronic band structures of overlapping GBs are strongly direction dependent, suggesting their potential in tunable electronic and photonic devices. Incommensurate overlapping GBs formed by quasi-parallel grains with ultrasmall twist angles are also observed. These results unveil the rich polymorphism of GBs and new opportunities to tailor properties of anisotropic 2D materials via GB engineering.

An eleven-year cohort of bloodstream infections in 552 febrile neutropenic patients: resistance profiles of Gram-negative bacteria as a predictor of mortality.

Antimicrobial stewardship is of major importance in patients with febrile neutropenia (FN). In this study, we aimed to investigate the trends in resistance and the relationship with mortality rates in patients with FN. The single-center surveillance data of inpatients with FN and diagnosed as microbiologically confirmed bloodstream infections (BSIs) between 2006 and 2016 were reviewed retrospectively. A total of 950 episodes in 552 patients with BSIs were analyzed. Of whom, 55.9% were male, the median age was 43years, and 35.6% had acute myeloid leukemia. In total, 1016 microorganisms were isolated from blood cultures. Gram-negatives accounted for 42.4% (n = 403) of the episodes. Among Gram-negatives, Enterobacteriaceae accounted for 346 (86%) (E. coli, n = 197; 34% extended-spectrum β-lactamases (ESBL) producers, and Klebsiella spp., n = 120; 48.3% ESBL producers). Also, 24 (20.0%) of Klebsiella spp. had carbapenemase activity. There were 6 (5.0%) colistin-resistant Klebsiella spp. Thirteen (26.5%) of Pseudomonas spp. and 17 (60.7%) of Acinetobacter spp. had carbapenemase activity. There were 2 (5.6%) colistin-resistant Acinetobacter spp. The 30-day mortality rates were 12.0%, 21.5%, 34.6%, and 29.0% in BSIs due to Gram-positive, Gram-negative bacterial, fungal, and polymicrobial etiology respectively (p = 0.001). BSIs with ESBL-producing (p = 0.001) isolates, carbapenem (p < 0.001), and colistin-resistant isolates (p < 0.001) were associated with increased mortality risk. The tremendous rise in resistance rates among Gram-negatives is dreadfully related to increasing mortality and leads to sharp shifts toward extreme restrictions of unnecessary antibiotic uses. Antimicrobial stewardship in patients with FN requires vigilance and tailoring of treatment upon local surveillance data.

Variations in lithic artefact density as a tool for better understanding Middle Palaeolithic human behaviour: The case of Nesher Ramla (Israel)

Variability in the composition of lithic assemblages stems from the combined action of different agents. In this study we used shifts in the relation between lithic artefact density and lithic technological organisation as a tool to better understand the underlying causes of lithic techno-typological variability throughout the archaeological sequence of Nesher Ramla (Israel). Nesher Ramla is a Middle Palaeolithic open-air site found in a karst sinkhole, where human occupation took place in situ. The upper part of the site's sequence (Units II-I, dated to Marine Isotope Stage 5), is characterised by sharp shifts in lithic artefact densities, concomitant with changes in the composition of the lithic assemblages. Using lithic artefact density as a proxy, we were able to partially dissect palimpsests at the site as well as isolate which components of the lithic assemblages are affected by the length of the site occupation and which are possibly the outcome of different activities performed on-site (i.e., the site function) or result from the stylistic preferences of the site inhabitants. We suggest that the role played by the site within past hunter-gatherers’ mobility systems changed from the occupation of Unit IIB-Lower, when it was possibly repeatedly used for hunting and processing animal resources, to Unit I, when it was only sporadically visited for more general purposes. Morphological changes in the karst sinkhole over time are suggested as the major causes of change in site use.

THE EFFECTS OF FOREIGN PLAYER REGULATIONS ON PLAYER PRODUCTIVITY IN THE TURKISH SUPER LEAGUE

This study investigates the effects of foreign player regulations on the labor productivity in the Turkish Super League. The initial hypothesis is that the productivity of the new foreign entrants will decrease as the number of foreign players allowed increases since most clubs tend to transfer foreign players that they would not make good use of. To test this hypothesis, data was collected for all the new foreign entrants to the Turkish Super League between the seasons 1999/2000 – 2004/2005 and 2009/2010 – 2014/2015. Regression Discontinuity Design is used as a tool for testing the initial prediction to reveal whether there are sharp shifts in the player productivity. The results displayed that productivity of the new foreign entrants diminished as the number of foreign players allowed increased. The possible spillover effects of the regulation changes on the number of Turkish players transferred to overseas clubs and the productivity of the domestic youngsters playing in the league are investigated in detail. Empirical evidence was found to state that foreign player regulations are influential of domestic youngsters’ overall productivity however no evidence could be found that the regulations are affecting the number of Turkish players transferred abroad.

Memory in Early Modern Europe, 1500–1800, by Judith Pollmann

The central insight that lies at the heart of Judith Pollmann’s concise and stimulating book is that because memory is ‘a form of cognition that interacts with social processes’ it ‘also has a history’ (p. 3). By contrast with the attention that scholars of the Middle Ages and the twentieth century have lavished on this topic, early modernists have been surprisingly slow to place it under the microscope. But questions about how, what and why people remembered—and forgot—between 1500 and 1800 are now rising to the top of the agenda. This, then, is a timely think-piece that maps out the terrain of this emerging subfield and sets some points on the compass for future studies. Its principal aim is to initiate a conversation between students of memory before and after 1800 and to engage critically with claims that the age of revolutions catalysed profound changes in the ways in which memory was practised. Reacting to a theoretical literature predicated on the assumption that historical consciousness was radically transformed by nationalism, state-formation and the emergence of new media of communication, Pollmann’s book calls upon historians to take a longer view. It sets aside linear and teleological models of development in favour of recognising the continuity and co-existence of multiple modes of apprehending the past across this caesura. In place of sharp paradigm shifts it posits a more cumulative process of evolution. This is a history of memory that both recognises the dangers of the modernity narratives that have underpinned previous accounts and is energised by them.

Distinct Biogeography of Different Fungal Guilds and Their Associations With Plant Species Richness in Forest Ecosystems

Author(s): Wang, P; Chen, Y; Sun, Y; Tan, S; Zhang, S; Wang, Z; Zhou, J; Zhang, G; Shu, W; Luo, C; Kuang, J | Abstract: Plant pathogens are increasingly considered as important agents in promoting plant coexistence, while plant symbionts like ectomycorrhizal fungi (EMF) can facilitate plant dominance by helping conspecific individuals to defend against plant pathogens. However, we know little about their relationships with plants at large scales. Here, using soil fungal data collected from 28 forest reserves across China, we explored the latitudinal diversity gradients of overall fungi and different fungal functional guilds, including putative plant pathogens, EMF, and saprotrophic fungi. We further linked the spatial patterns of alpha diversities of putative plant pathogens and EMF to the variation of plant species richness. We found that the relationships between latitude and alpha diversities of putative plant pathogens and EMF were region-dependent with sharp diversity shifts around the mid-latitude (~35°N), which differed from the unimodal diversity distributions of the overall and saprotrophic fungi. The variations in the diversities of putative plant pathogens and EMF were largely explained by the spatial regions (south vs. north/subtropical zone vs. temperate zone). Additionally, the alpha diversities of these two fungal guilds exhibited opposing trends across latitude. EMF could alter the relationship between diversities of putative plant pathogens and plants in the south/subtropical region, but not vice versa. We also found that the ratio of their alpha diversities (EMF to putative plant pathogens) was negatively related to plant species richness across the spatial regions (north to south), and explained ~10% of the variation of plant species richness. Overall, our findings suggest that plant-microbe interactions not only shape the local plant diversity but also may have non-negligible contributions to the large-scale patterns of plant diversity in forest ecosystems.

Soil aggregate size modifies the impacts of fertilization on microbial communities

Soil microorganisms play an essential role in the redistribution of soil aggregate sizes due to the microenvironmental changes, but little is known about the changes in microbial communities (especially fungi) and their activities within different microenvironments due to agronomic managements. Here, we examined the influence of fertilization (inorganic and inorganic plus organic amendments) on soil aggregate distribution and the microbial communities within aggregates at the site of a long-term fertilization experiment. Significant impacts on soil aggregate distribution and distinct changes in fungal and bacterial communities in soil aggregates due to fertilization were observed, with the fungal community exhibiting more marked changes compared with the bacterial community. Soil carbon and nitrogen contents in aggregates were the most closely related to changes in microbial communities associated with soil aggregates. The changes of microbial taxa abundance in aggregates were generally accompanied by the redistributions of these taxa among all size aggregates, showing the preference for specific ecological niches for these taxa under fertilizations. Both applications of nitrogen alone (N) and inorganic plus organic amendment (NPKM) contributed to mega-aggregate formation. N treatment caused the low total fungal counts in mega-aggregates and carbon depletion, whereas it increased the abundance of N2O-producing fungi in both mega- and macro-aggregates, denitrifying bacteria in micro-aggregates and nitrifying bacteria in macro-aggregates. In contrast, NPKM treatment mitigated/prevented the sharp shifts of the abundance of these microbes mentioned above with nitrogen fertilization, and increased the ectomycorrhizal fungi abundance in all soil fractions as well as carbon accumulation in soil. Our results suggest that the responses of soil bacteria and fungi to fertilizations are modified by their ecological niches, which responses are responsible for the variation of ecosystem services.

Gendering the State of Emergency Regime in Turkey

Since the 20th of July 2016, Turkey has been under the state of emergency. Reiteration of the hegemonic relationship between power, masculinity and violence for the reassertion of political rule is the central feature of state of emergency regimes. In Turkey, we experience sharp and sudden shifts of power within the political and legal sphere, and these shifts impact on gender norms and gender policies. This article aims to present the effects of the security state on women’s and LGBTI individuals’ life spaces, in order to gender Turkey’s state of emergency rule. It will discuss how the weakening of the separation of powers, and the granting of extreme powers to the executive, almost completely prevent any opportunities for advancing the women and LGBTI movements’ agenda through different modalities of the three branches of the state. The emergency measures ravage many of the women and LGBTI movement’s long-term struggles and achievements. The article will also discuss the government’s interventions in Kurdish municipalities and the closing down of women’s organizations, shelters and solidarity centers; such interventions meant the violent interruption of the institutional solidarity networks that had gained women’s trust with their long-term work. Moreover, public spaces are becoming extremely insecure for women and LGBTI individuals under the regime of the security state. The conservative and militarist individuals and groups that took over public spaces are supported by the sexist rhetoric of government officials. Encouraged by their new powers, conferred to them by the state of emergency regime, the police use extensive physical violence against women during gatherings and demonstrations. Sexual harassments and torture while under custody, against female and male detainees, are widespread.The article aims to analyze the state of emergency as a mechanism that works against all kinds of anti-oppression solidarities and alliances. However, I also establish that despite all of the draconian governmental measures, and the rising sexist violence in all segments of society, women and LGBTI groups resist the state of emergency regime in solidarity.

ТРАНСФОРМАЦИИ ГЛОБАЛЬНОЙ МИГРАЦИИ НАСЕЛЕНИЯ

Sharp and unpredictable shifts in population movements, imperfection and incompleteness of international migration statistics, regular revisions by the UN Population Division of previous estimates of the international migrant stock complicate assessing the current state and forecasting future developments in this field. Nevertheless, there are obvious changes in geography, dynamics, composition and forms of modern migration occurring in the context of the polycentric and, at the same time, transnational and increasingly interconnected world entering the period of globalization reformatting, economic turbulence and uncertainty, the growth of socio-political conflict, the establishment of postmodern social values and attitudes. These shifts outline the contours of a new model emerging in the global migration space. The territorial mobility of people is growing in the whole, but this process is multi-speed. The non-migration mobility is increasing noticeably. However, modern flows of long-term migrants are weakening, and the growth in their number is slowing. This indicates a decrease in migration activity. The role of settlement is likely to decline in the new migration paradigm. Migration is becoming increasingly fluid and incomplete. With the spread of temporary and circular movements occurring generally in developed regions, in the EU in particular, frontier and hybrid patterns of movements arise. They combine elements of short-term and long-term migration and those of non-migration mobility. The diversity of migrants and receiving population is growing. The development of these processes requires an improvement of migration statistics, as well as reforming the integration policies. A new geography of migration is being construed. It is characterized by the shift of human flows to the global South and their regionalization on the basis of integration platforms. The regionalization of movements in the South requires working-out and implementation of immigration and integration policies by developing states and the development of sub-global mechanisms for regulating human flows as well. Moreover, the architecture design of the global population movements&rsquo; governance should be adjusted to the emerging migration model.&nbsp;&nbsp

Testing Hysteresis in Unemployment in G7 Countries Using Quantile Unit Root Test with both Sharp Shifts and Smooth Breaks

We apply a Quantile unit root test with both Sharp Shifts and Smooth Breaks to revisit hysteresis in unemployment for G7 countries using data for the period 1980–2017. Results from the conventional unit root tests indicate that hysteresis in unemployment does hold in half of these G7 countries during the period 1980–2017. A quantile Kolmogorov–Smirnov test fails to reject hysteresis in the unemployment hypothesis for our quarterly data but not in monthly data in G7 countries. Empirical results from our proposed quantile unit root test considering both sharp shifts and smooth breaks indicate that hysteresis in unemployment can be rejected over certain quantiles. A quantile Kolmogorov–Smirnov test results demonstrating hysteresis in unemployment does not hold in G7 countries for both monthly and quarterly data. These empirical findings have important policy implications in G7 countries.

"Science in action": The politics of hands-on display at the New York Museum of Science and Industry.

This article analyzes the changing politics of hands-on display at the New York Museum of Science and Industry by following its urban deambulation within Midtown Manhattan, which went hand in hand with sharp shifts in promoters, narrative, and exhibition techniques. The museum was inaugurated in 1927 as the Museum of the Peaceful Arts on the 7th and 8th floors of the Scientific American Building. It changed its name in 1930 to the New York Museum of Science and Industry while on the 4th floor of the Daily News Building, and it was close to being renamed the Science Center when it finally moved in 1936 to the ground floor of the Rockefeller Center. The analysis of how the political agenda of the different promoters of the New York Museum of Science and Industry was spatially and performatively inscribed in each of its sites suggests that the 1930s boom of visitor-operated exhibits had nothing to do with an Exploratorium-like rhetoric of democratic empowerment. The social paternalistic ideology of the vocational education movement, the ideas on innovation of the early sociology of invention, and the corporate behavioral approach to mass communications are more suitable contexts in which to understand the changing politics of hands-on display in interwar American museums of science and industry.

Can the interaction between a single long-term attractor and heterogeneous trading explain the exchange rate conundrum?

Over the last 15 years, exchange rate movements were relatively smooth, despite sharp shifts in the fundamental variables. In the large literature dealing with the high frequency exchange rate dynamics, the model that assumes heterogeneous trading strategies, where ‘fundamentalists’ coexist with ‘chartists’, plays a relevant if puzzling role.We study the US dollar, the British pound and the Japanese yen vs the euro over the period 2002–2016 using weekly data and we find that both types of agents react to the same transition variable, viz. the absolute distance of the actual exchange rate to its relative PPP value. The spot foreign currency demand of fundamentalists is driven by the size of the misalignment both directly and through a transition function, which models the adoption of fundamental strategies by newcomers. The number of chartists also varies according to the absolute distance of the exchange rate change from its fundamental PPP value. Evidence supports the existence of stabilizing and destabilizing behaviour not only by chartists but also by fundamentalists.

Archaeogenetics of Late Iron Age Çemialo Sırtı, Batman: Investigating maternal genetic continuity in north Mesopotamia since the Neolithic.

North Mesopotamia has witnessed dramatic social change during the Holocene, but the impact of these events on its demographic history is poorly understood. Here, we study this question by analysing genetic data from the recently excavated Late Iron Age settlement of Çemialo Sırtı in Batman, southeast Turkey. Archaeological and radiocarbon evidence indicate that the site was inhabited during the second and first millennia BCE. Çemialo Sırtı reveals nomadic items of the Early Iron Age, as well as items associated with the Late Achaemenid and subsequent Hellenistic Periods. We compare Çemialo Sırtı mitochondrial DNA profiles with earlier and later populations from west Eurasia to describe genetic continuity patterns in the region. A total of 16 Çemialo Sırtı individuals' remains were studied. PCR and Sanger sequencing were used to obtain mitochondrial DNA HVRI-HVRII sequences. We studied haplotype diversity and pairwise genetic distances using FST , comparing the Çemialo Sırtı population with ancient and modern-day populations from west Eurasia. Coalescent simulations were carried out to test continuity for specific population comparisons. Mitochondrial DNA (mtDNA) haplotypes from 12 Çemialo Sırtı individuals reveal high haplotype diversity in this population, conspicuously higher than early Holocene west Eurasian populations, which supports the notion of increasing population admixture in west Eurasia through the Holocene. In its mtDNA composition, Çemialo Sırtı shows highest affinity to Neolithic north Syria and Neolithic Anatolia among ancient populations studied, and to modern-day southwest Asian populations. Based on population genetic simulations we cannot reject continuity between Neolithic and Iron Age, or between Iron Age and present-day populations of the region. Despite the region's complex sociopolitical history and indication for increased genetic diversity over time, we find no evidence for sharp shifts in north Mesopotamian maternal genetic composition within the last 10,000 years.

Does the Efficient Market Hypothesis Fit Military Enterprises in China?

This paper investigates whether the efficient market hypothesis (EMH) fits the Chinese military market using the Sequential Panel Selection Method (SPSM) and the Panel KSS unit root test with a Fourier function. We obtain evidence for structural shifts and non-linearity in the stock prices of the military industry in the Chinese stock market. Because sharp shifts and structural breaks are taken into account, the unit root hypothesis for most listed companies is rejected. Our result suggests that the Chinese military market is inefficient because of such factors as defense reforms, friction in the stock market, and irrational investors. We provide investment implications to enable future stock price movements to be predicted based on past behavior and enable trading strategies to be developed to earn abnormal returns. Meanwhile, Chinese defense enterprises should continue to implement industrial reforms, change their bureaucratic culture, and develop a market-oriented workforce.

Atomically sharp interlayer stacking shifts at anti-phase grain boundaries in overlapping MoS2 secondary layers.

When secondary domains nucleate and grow on the surface of monolayer MoS2, they can extend across grain boundaries in the underlying monolayer MoS2 and form overlapping sections. We present an atomic level study of overlapping antiphase grain boundaries (GBs) in MoS2 monolayer-bilayers using aberration-corrected annular dark field scanning transmission electron microscopy. In particular we focus on the antiphase GB within a monolayer and track its propagation through an overlapping bilayer domain. We show that this leads to an atomically sharp interface between 2H and 3R interlayer stacking in the bilayer region. We have studied the micro-nanoscale "meandering" of the antiphase GB in MoS2, which shows a directional dependence on the density of 4 and 8 member ring defects, as well as sharp turning angles 90°-100° that are mediated by a special 8-member ring defect. Density functional theory has been used to explore the overlapping interlayer stacking around the antiphase GBs, confirming our experimental findings. These results show that overlapping secondary bilayer MoS2 domains cause atomic structure modification to underlying anti-phase GB sites to accommodate the van der Waals interactions.

PPP in the 34 OECD countries: evidence from quantile-based unit root tests with both smooth and sharp breaks

ABSTRACTConventional unit root tests have mostly failed to validate the PPP. Quantile-based unit root tests by previous research have provided some support for the PPP. In this article, we take an additional step and incorporate sharp shifts and smooth breaks into the quantile-based unit root test and re-examine the PPP in each of the 34 OECD countries over the period 1994:01–2016:03. We find support for the PPP in 18 countries of Austria, Chile, Estonia, Finland, France, Germany, Italy, Korea, Mexico, Netherlands, New Zealand, Poland, Portugal, Slovenia, Sweden, Switzerland, Turkey and the United Kingdom.

Shifts in sediment provenance across a hierarchy of bounding surfaces: A sequence-stratigraphic perspective from bulk-sediment geochemistry

Geochemical differentiation of sediment packages framed by surfaces of chronostratigraphic significance represents an effective tool to unravel the stratigraphic architecture of multi-sourced sediment-supply systems on a variety of temporal scales and through a wide spectrum of lithofacies assemblages. Sediment provenance shifts were examined across three-orders of bounding surfaces, arranged in a hierarchy of 105 to 103years sediment packages, from late Quaternary alluvial, deltaic, coastal and shallow-marine strata of the Po Basin, where controlling factors of sedimentary evolution are firmly constrained by strong age control. A total of 150 samples were analyzed for bulk-sediment geochemistry by X-ray fluorescence spectrometry (XRF). Geochemically unique catchment lithologies, such as ultramafic rocks and dolostones, were used as end-member grain assemblages to assess clear geochemical signatures, and chemostratigraphic correlations were generated on the basis of key element abundances and ratios.Sequence boundaries originating in response to tectonic uplift and related to 105 years sediment packages are associated with marked, basin-wide changes in sediment composition that reflect phases of substantial basin rearrangement, with strong modification of the drainage patterns. On an intermediate temporal scale (104years depositional units), large magnitude sea-level fluctuations had a major impact on sediment pathways, producing sharp provenance shifts on a systems tract scale. The Holocene transgressive surface records a substantial change in clastic sediment flux, as the alluvial system turned into a wave-dominated estuary. On the other hand, no notable changes in composition were observed across the maximum flooding surface. Finally, identifiable provenance variations developed on a short-term, facies tract scale (103years sediment packages) and revealed by lower-rank bounding surfaces denote dramatic changes in sediment dispersal patterns in response to simple autogenic processes, such as channel avulsion and delta lobe switching. In the stratigraphic context provided by the ancient record, such provenance shifts could easily be misinterpreted as the sedimentary expression of higher-rank bounding surfaces.This study supports the robustness of a comprehensive geochemical approach to an improved interpretation of the subsurface geological record across a hierarchy of depositional elements. It shows, however, that provenance shifts at chemofacies boundaries alone cannot be used to infer allogenic or autogenic controls on sedimentation. High-resolution facies analysis within stratigraphically constrained time intervals needs to be considered before promoting predictive relationships between provenance shifts and basin evolution.

Can the Interaction between a Single Long-Term Attractor and Heterogeneous Trading Explain the Exchange Rate Conundrum?

Over the last 15 years, exchange rate movements have been smoother and slower than expected, given the entity of the sharp shifts in the fundamental variables brought about by the international financial crisis. Since the beginning of the ’90s researchers have explored different approaches in order to understand high frequency exchange rate dynamics. Among them the model that assumes heterogeneous trading strategies, where ‘fundamentalists’ coexist with ‘chartists’ in nonlinear transitional specifications, plays an increasingly relevant if puzzling role. We study the US dollar, the British pound and the Japanese yen vs the euro over the period 2002 to 2016 using weekly data. The most important contribution of this paper is that we find empirical evidence that both types of agent react to the same transition variable, viz. the absolute distance of the actual exchange rate to its relative PPP value. The spot foreign currency demand of fundamentalists is driven by the size of the misalignment both directly and through a transition function, which models the adoption of fundamental strategies by newcomers. The number of chartists also varies according to the absolute distance of the exchange rate change from its fundamental value. Evidence supports the existence of stabilizing and destabilizing behaviour not only by chartists but also by fundamentalists.

Denoising Signals Used in Gas Turbine Diagnostics with Ant Colony Optimized Weighted Recursive Median Filters

Accurate fault detection and isolation requires signal processing of measurement signals which are contaminated with noise. Typically, gas turbine faults are revealed by sharp trend shifts in the signals and these trend shifts should be preserved during signal processing. Linear filters can smooth out the sharp trend shifts while removing noise. However, nonlinear filters such as the weighted recursive median (WRM) filters show good noise reduction while preserving key signal features if their integer weights are determined optimally. We propose the ant colony optimization (ACO) method coupled with local search to calculate the integer weights of WRM filters. It is found that the filter weight optimization problem is mathematically equivalent to the quadratic assignment problem which can be solved by ACO. Optimal parameters for the ACO are found using numerical experiments. The WRM filter is demonstrated for abrupt and gradual faults in gas turbines and is found to yield noise reduction of 52–64% for simulated noisy signals considered in this paper.