High Frequency Cycles Research Articles

Modern and Holocene microbial mats and associated microbially induced sedimentary structures (MISS) on the southeastern coast of Tunisia (Mediterranean Sea)

AbstractOn the southeastern Tunisian coastline, very diverse living microbial mats colonize the lower supratidal and intertidal zones, and locally may extend into the upper infratidal zone. The interaction between the benthic cyanobacteria and their siliciclastic substratum leads to the development of several types of microbially induced sedimentary structures (MISS). The mapping of the microbial mats has allowed the identification of the types of MISS that characterize the different segments of the coastal environment. The modern microbial mats have been compared with those recorded at the top of the Holocene deposits, which are composed of biodegraded microbial black mats alternating with white laminae made of clastic and evaporitic sediments, indicative of very high frequency cycles of flood and drought. A hypothetic profile showing their occurrences along the different areas bordering the coastline is proposed as a guide for the reconstruction of the ancient depositional environment. The roles of tidal dynamics, storms, and climate in controlling their genesis and spatial distribution, are discussed and highlighted. The modern MISS of southeastern Tunisia are compared with their equivalents that are well documented through the different geological eras.

Cloud-Resolving Model Applied to Nowcasting: An Evaluation of Radar Data Assimilation and Microphysics Parameterization

AbstractThis research explores the benefits of radar data assimilation for short-range weather forecasts in southeastern Brazil using the Weather Research and Forecasting (WRF) Model’s three-dimensional variational data assimilation (3DVAR) system. Different data assimilation options are explored, including the cycling frequency, the number of outer loops, and the use of null-echo assimilation. Initially, four microphysics parameterizations are evaluated (Thompson, Morrison, WSM6, and WDM6). The Thompson parameterization produces the best results, while the other parameterizations generally overestimate the precipitation forecast, especially WDSM6. Additionally, the Thompson scheme tends to overestimate snow, while the Morrison scheme overestimates graupel. Regarding the data assimilation options, the results deteriorate and more spurious convection occurs when using a higher cycling frequency (i.e., 30 min instead of 60 min). The use of two outer loops produces worse precipitation forecasts than the use of one outer loop, and the null-echo assimilation is shown to be an effective way to suppress spurious convection. However, in some cases, the null-echo assimilation also removes convective clouds that are not observed by the radar and/or are still not producing rain, but have the potential to grow into an intense convective cloud with heavy rainfall. Finally, a cloud convective mask was implemented using ancillary satellite data to prevent null-echo assimilation from removing potential convective clouds. The mask was demonstrated to be beneficial in some circumstances, but it needs to be carefully evaluated in more cases to have a more robust conclusion regarding its use.

The co-movements between geothermal energy usage and CO2 emissions through high and low frequency cycles.

Geothermal energy is considered environmentally friendly than fossil fuel sources, and geothermal power plants are expected to have a low carbon footprint. It is renewable that can last million years. There exist, however, several gases stored under the earth's surface which are released into the atmosphere during digging (TWI 2020). This research paper aims at monitoring the potential positive and negative effects of geothermal on environmental quality (CO2 emissions) in the USA for the period January 1980 to August 2019. The paper employed wavelet and partial wavelet coherence computations to explore the impacts of geothermal energy usage on the environment. The concluding remarks from the estimations can be classified into short-term (1-3-year cycle) results and long-term (3-8-year cycle) results. It is found in the short term that (i) geothermal usage increased CO2 emissions during 1980-1983 and 1993-1997 and (ii) CO2 emissions caused geothermal usage to increase for the period 2000-2009 and after 2015. The paper reveals also that in the long term, (a) geothermal energy consumption increased CO2 emissions during the periods 1985-1990, 1993-1996, and 2013-2016 and (b) geothermal energy consumption decreased CO2 emissions for the period 1996-2008 in the USA. This research work eventually yields some relevant geothermal energy policy suggestions for US policymakers to make geothermal more environmentally friendly.

Causality between tourism and economic growth nexus

ABSTRACT The purpose of this paper is to use a multivariate wavelet approach to examine the causal relationship between tourism and economic growth in the 11 Asian regions for the period from 1995 to 2016. Results indicate from the time-domain view, we show strong evidence linkages among the real international tourism receipts, international tourist arrivals, capital formation and real gross domestic product variables. From the frequency-domain view, we uncover significant wavelet coherency and strong relationships which change over time, indicating low to high frequency cycles. Accordingly, it can be recommended that the government needs to increase and promote tourism demand and to further provide and nurture the expansion of tourism supply.

The Influence of Economic Policy Uncertainty on Piigs Tourism: Evidence from Three-dimensional Wavelet Analyses

This article aims at examining the relationship between economic policy uncertainty and tourism activities in Portugal, Ireland, Italy, Greece, and Spain using a three-dimensional wavelet analysis. Empirical results display that the relationships among the variables evolve through time and frequencies. The study finding reveals strong evidence of the relationships between these variables in terms of time domains. From the perspective of frequency domains, significant wavelet coherence and strong lead-lag relationships change over time are displayed in this study, indicating low to high frequency cycles over the whole sample period.

Decomposing a time-frequency relationship between economic policy uncertainty and tourism in the G8 countries through wavelet analysis

ABSTRACT This paper aims to examine the relationship between economic policy uncertainty (EPU) and tourism activities in the Group of Eight countries using wavelet transform context structures. This innovative technique allows the decomposition of time-series at different time frequencies. In this work, we used continuous wavelets, wavelet coherency and wavelet phase-difference based on Granger causality analysis to investigate the relationship between EPU and tourism. Results indicate that the relationship is generally negative but changes over time, displaying low to high frequency cycles. Moreover, the timing and frequency change when EPU co-moves with tourism. Accordingly, it can be recommended that the government increase and promote tourism demand and further provide and nurture the expansion of the tourism supply.

Stepwise optimization of a Flexible Microtube Plasma (FµTP) as an ionization source for Ion Mobility Spectrometry

The ionization source is the central system of analytical devices such as mass spectrometers or ion mobility spectrometers. In this study, a recently developed flexible microtube plasma (FμTP) is applied as an ionization source for a custom-made drift tube ion mobility spectrometer (IMS) for the first time. The FµTP is based on a highly miniaturized, robust and a small-footprint dielectric barrier discharge design with an outstanding ionization efficiency. In this study, the experimental setup of the FµTP was further improved upon to achieve optimal coupling conditions in terms of the ion mobility spectrometry sensitivity and the plasma gas consumption. One major focus of this study was the adjustment of the electrical operation parameters, in particular, the high voltage amplitude, frequency and duty cycle, in order to minimize the electric field disturbances and yield higher signals. Additionally, the consumption of helium plasma gas was reduced by refining the FµTP. It was found that the ionization efficiency could be significantly enhanced by increasing the plasma high voltage and through application of a duty cycle up to 90:10. Plasma gas flows could be reduced down to 3 mL min-1 by increasing the plasma high voltage amplitude. Furthermore, a smaller wire electrode design enables the operation of the FµTP with nitrogen and clean air. Moreover, detection limits of a homologous series of ketones in the range of 330 pptv (N2-FµTP, 2-decanone) down to 20 pptv (He-FµTP, 2-octanone) could be reached in the optimized setup. To sum up, this feasibility study demonstrates the potential of the optimized FµTP as a powerful ionization source for ion mobility spectrometry especially with regard to ionization efficiency.

Rock Magnetic Cyclostratigraphy of Permian Loess in Eastern Equatorial Pangea (Salagou Formation, South-Central France)

We present the findings from analysis and modeling of a stratigraphic series of magnetic susceptibility data measured with a portable magnetic susceptibility meter from the Permian Salagou Formation loessite (south-central France). The results reveal discernible Milankovitch-scale paleoclimatic variability throughout the Salagou Formation, recording astronomically-forced climate change in deep-time loessite of eastern equatorial Pangea. Optimal sedimentation rates are estimated to have ranged between 9.4 cm/kyr (lower Salagou Formation) and 13 cm/kyr (mid-upper Salagou Formation). A persistent 10-m-thick cyclicity is present that likely represents orbital eccentricity-scale (~100 kyr) variability through the middle to late Cisuralian (ca. 285—275 Ma). Subordinate, higher-frequency cycles with thicknesses of ~3.3—3.5 m and ~1.8 m appear to represent obliquity and precession-scale variability. If the driver of magnetic enhancement is pedogenic, then the ~10 m thick cyclicity that is consistent over ~1000 m of section may represent the thickness of loessite-paleosol couplets in the Salagou Formation. Laboratory rock magnetic data show generally low magnetic enhancement compared to analogous Eurasian Quaternary loess deposits. This is related to the predominance of hematite (substantially weaker signal than magnetite or maghemite) in the Salagou Formation which may be explained by different conditions of formation (e.g. syn depositional processes, more arid and/or oxidizing climate conditions) than in present Eurasia and/or post depositional oxidation of magnetite and maghemite.

Thermal effects on red muscle contractile performance in deep-diving, large-bodied fishes.

Bigeye thresher sharks (Alopias superciliosus) and swordfish (Xiphias gladius) are large, pelagic fishes, which make long-duration, diurnal foraging dives from warm, surface waters (18-24°C) to cold waters beneath the thermocline (5-10°C). In bigeye thresher sharks, the subcutaneous position of the red, aerobic swimming muscles (RM) suggests that RM temperature mirrors ambient during dives (i.e., ectothermy). In swordfish, the RM is closer to the vertebrae and its associated with vascular counter-current heat exchangers that maintain RM temperature above ambient (i.e., RM endothermy). Here, we sought to determine how exposure to a wide range of ambient temperatures (8, 16, 24°C) impacted peak power output and optimum cycle (i.e., tailbeat) frequency (0.25, 0.5, 1Hz) in RM isolated from both species. Bigeye thresher shark RM did not produce substantial power at high cycle frequencies, even at high temperatures; but it did produce relatively high power at slow cycle frequencies regardless of temperature. Swordfish RM produced more power when operating at a combination of fast cycle frequencies and higher temperatures. This suggests that swordfish RM benefits considerably more from warming than bigeye thresher shark RM, while the RM of both species was able to produce power at cold temperatures and slow cycle frequencies. Despite different thermal strategies (i.e., ectothermy vs. RM endothermy), the ability of the RM to power sustained swimming during foraging-related search behaviors may contribute to the unique ability of these fishes to successfully exploit food resources in deep, cold water.

Palaeoecological, sedimentological and stratigraphical insights into microbially induced sedimentary structures of the lower Cambrian successions of Iran

AbstractMicro‐organisms producing microbially induced sedimentary structures, particularly epibenthic cyanobacteria, are not facies‐dependent and could flourish in any environment if appropriate ecological conditions were provided. Hence, the changes in environmental parameters are the controlling factors on ecological tolerance of the producers. This study on the lower Cambrian successions of the Lalun Formation in Central Iran shows that paralic environments reacted differently to changes in parameters such as river and tide energy, palaeo‐topography, the rate of sediment supply and fluctuations in sea‐level, even though all were characterized by sandy substrates suitable for the development of microbially induced sedimentary structures. Therefore, the abundance and preservation of microbially induced sedimentary structures varied in the different paralic environments. From a sequence stratigraphic viewpoint, this study demonstrates that erosional discontinuities lacked the conditions required for the substrate stabilization by microbial communities. The distribution, size and type of microbially induced sedimentary structures within high frequency cycles generally follow the trends of changes in vertical facies stacking patterns. Within systems tracts, the pattern, morphological diversity and size of microbially induced sedimentary structures are not dependent on the type of systems tract, but on the type of depositional system developed such as delta, incised valley, coastal plain, estuaries and shoreline to shelf systems. Generally, estuarine and peritidal carbonates record an increase in the development of mat colonization during the transgressive systems tract, owing to decreased sedimentation rate as well as extended shallow water habitats. In contrast, the existence of microbially induced sedimentary structures depends on the pattern of shoreline shift in depositional systems developed during the highstand systems tract, such as open coast tidal flat and delta environments. If a shoreline regression was continuous (depositional trend and stacking pattern are a set of high frequency cycles), a greater increase in the aggradational component than the progradational component would cause intensified destructive processes hindering the development of microbial communities.

Probabilistic fatigue assessment of monitored railroad bridge components using long-term response data in a reliability framework

Fatigue is a primary concern for railroad bridge owners because railroad bridges typically have high live load to dead load ratios and high stress cycle frequencies. However, existing inspection and post-inspection analysis methods are unable to accurately consider the full influence of bridge behavior on the fatigue life of bridge components. Reliability-based fatigue analysis methods have emerged to account for uncertainties in analysis parameters such as environmental and mechanical properties. While existing literature proposes probabilistic fatigue assessment of bridge components, this body of work relies on train parameter estimates, finite element model simulations, or controlled loading tests to augment monitoring data. This article presents a probabilistic fatigue assessment of monitored railroad bridge components using only continuous, long-term response data in a purely data-driven reliability framework that is compatible with existing inspection methods. As an illustrative example, this work quantifies the safety profile of a fracture-critical assembly comprising of six parallel eyebars on the Harahan Bridge (Memphis, TN). The monitored eyebars are susceptible to accelerated fatigue damage because changes in the boundary conditions cause some eyebars to carry a greater proportion of the total assembly load than assumed during design and analysis; existing manual inspection practices aim to maintain an equal loading distribution across the eyebars. Consequently, the limit state function derived in this article accounts for the coupled behavior between fatigue and relative tautness of the parallel eyebars. The reliability index values for both the element (i.e. individual eyebars) and system (i.e. full eyebar assembly) reliability problems are assessed and indicate that under the conservative assumption that progressive failure is brittle, first failure within the parallel eyebar system is generally equivalent to system failure. The proposed method also serves as an intervention strategy that can quantify the influence of eyebar realignment on the future evolution of the reliability index.

Post-activation muscle potentiation and its relevance to cyclical behaviours

Muscle can experience post-activation potentiation (PAP), a temporary increase in force and rate of force development, when contractions are closely timed; therefore, cyclical behaviours are likely affected by PAP, as succeeding contraction cycles can lead to potentiation over several subsequent cycles. Here, we examined PAP during in situ cyclical contractions of the mallard lateral gastrocnemius (LG). Surface swimming, a cyclical behaviour, was mimicked with work-loops using in vivo LG length change and stimulation parameters. Tests were performed at mallards' preferred cycle frequency as well as at lower and higher frequencies. Like muscles from mammals, anurans and arthropods, the mallard LG exhibited PAP with increases in peak force, average force rate and net work. Staircase potentiation occurred over two or more work-loop cycles, resulting in gradual increases in PAP. The number of cycles needed to reach maximum work varied with cycle frequency, requiring more cycles at higher cycle frequencies. PAP occurred under in vivo-like stimulation parameters, suggesting a potentially important role of PAP in animal locomotion, especially in cyclical behaviours.

Internal anatomy of an erg sequence from the aeolian-fluvial system of the De La Cuesta Formation (Paganzo Basin, northwestern Argentina)

Permian red beds of the De La Cuesta Formation in the Sierra de Narvaez (Paganzo Basin, northwestern Argentina) are essentially composed of sandstones associated with mudstones and subordinate conglomerates. Facies distributions and stacking patterns indicate that these sediments resulted from the interaction between aeolian and ephemeral fluvial systems, and are represented by aeolian dune, dry aeolian interdune and aeolian sand sheet, mudflat, wet aeolian interdune, and fluvial deposits. The De La Cuesta Formation is characterised by aeolian (erg) sequences alternating with non-aeolian (terminal alluvial fan – mudflat) sequences. Each erg sequence is bounded at its base by a regionally extensive sand-drift surface and at the top by an extinction surface. A number of architectural elements, including aeolian dunes limited by interdunes, grouped crescentic aeolian dunes, longitudinal dunes, and draa with superimposed crescentic dunes are recognised in the erg sequences. The sand sea developed during phases of increasing aridity, whereas non-aeolian deposition might have occurred during more humid phases. Thus, the styles of aeolian-fluvial interaction are considered to result from cyclical climatic changes. Within the drier hemicycles, the rhythmic alternation between draa deposits and aeolian dune and interdune deposits indicates higher frequency cycles that could be attributed to subtle climatic oscillations and/ or changes in sand supply and availability. The development of the Permian sand sea in the inland Paganzo Basin seems to be related to the growth of a volcanic chain to the west. This topographic barrier separated the Paganzo Basin from the Chilean Basin, located along the western margin of Gondwana and characterised by shallow marine carbonate sedimentation. The correlation between the Permian erg and the shallow marine carbonates suggests a regional warming period during the Middle Permian in western Gondwana. 1

Defining the exploitation patterns of groundwater heat pump systems

Shallow geothermal systems are the most efficient and clean technology for the air-conditioning of buildings and constitutes an emergent renewable energy resource in the worldwide market. Undisturbed systems are capable of efficiently exchanging heat with the subsurface and transferring it to human infrastructures, providing the basis for the successful decarbonisation of heating and cooling demands of cities. Unmanaged intensive use of groundwater for thermal purposes as a shallow geothermal energy (SGE) resource in urban environments threatens the resources' renewability and the systems' performance, due to the thermal interferences created by a biased energy demand throughout the year. The exploitation regimes of 27 groundwater heat pump systems from an alluvial aquifer were firstly examined using descriptive statistics. Linear relationships between abstraction and injection temperatures of the systems were assessed by calculating Pearson's r correlation coefficient, and used as an evidence of thermal interferences. Then, time series of flow rate, operation temperature and energy transfer were modelled by means of spectral analysis and sinusoidal regression methods, followed by the definition of the relative exploitation patterns. The exploitation regimes examined presented a clear cooling bias and a similar cyclicality. The amplitudes correlated with the different end-user's activities (e.g. medical centres) when high frequency cycles were observed, while climatization strategies (e.g. constant flow rates and modulation of injection temperatures) did so when low frequency cycles were detected. The time series models allowed defining the relative operational pattern of a system and the groups of systems following such patterns. The biases in exploitation regimes of groundwater heat pump systems existing in Mediterranean areas require correction measures to ensure a more balanced exploitation of the SGE resources. The definition of the characteristic exploitation pattern proposed could be applied to guide resource managers by identifying unbalanced systems, understanding existent exploitation strategies and proposing corrective alternative plans.

The "In(de-)flated" Value Premium

The value premium has disappeared over the last decade and this paper provides a risk-based explanation for its disappearance. I document a positive linear relationship among the value premium and the expected inflation at both high frequency and lower business cycle frequency. A heterogeneous cash flow model featuring inflation non-neutrality is proposed to justify the observed pattern. The estimated results suggest that value firms are more exposed to high-frequency fluctuations in aggregate consumption growth but less exposed to the low-frequency consumption risk. This finding is consistent with the documented inflation-return relationship but it contrasts with the previous findings suggesting that value firms are more sensitive to long-run consumption risk. Simulation-based results show that the positive linear relationship among the value premium and the expected inflation can be recovered when inflation is non-neutral and the relationship turns into uncorrelated when inflation is neutral. Therefore we argue that inflation non-neutrality can justify the positive relationship among inflation and value premium. Meanwhile, value firms tend to under-perform growth firms when the inflation is in low range, and it leads to the disappearance of the value premium.

Tourism and House Prices: A Wavelet Analysis

ABSTRACT This paper aims to examine the relationship between tourism activities and house prices (HP) in first-tier cities of China (Beijing, Shanghai and Guangzhou) using the wavelet transform context structures. This innovative technique allows the decomposition of time-series at different time frequencies. In this work, we used continuous wavelets, wavelet coherence and wavelet phase difference based on Granger causality analysis to investigate the relationship between tourism activities and HP. Results indicate that the relationship is generally positive but changes over time, displaying low to high frequency cycles. There is a unidirectional causal influence of HP on tourism activities. Moreover, the timing and frequency changes when HP co-moves with tourism. Accordingly, it can be recommended that the government increases and promotes tourism demand and further provides and nurtures the expansion of tourism supply.

High-resolution sequence stratigraphy of a cretaceous mixed siliciclastic-carbonate platform succession of the Sergipe–Alagoas Basin, NE Brazil

The Sergipe–Alagoas Basin, in northeastern Brazil, has extensive exposures of carbonate rocks that may be studied as analogues to hydrocarbon reservoirs. The outcrops are equivalent to the pre-salt and post-salt reservoirs of the Campos and Santos basins, the most important hydrocarbon exploration targets nowadays in Brazil. Outcrops and well logs of the Riachuelo Formation, the most important for analogue studies of Cretaceous marine carbonate reservoirs of the Campos Basin due to the great variability of facies, are described and interpreted to identify the depositional cycles and stratigraphic sequences. Three unconformities formed during the initial drift phase of the basin are recognized. The depositional setting of the studied section changes from a siliciclastic-dominated continental to shallow-marine mixed siliciclastic-carbonate at the base to a shallow-marine carbonate platform in the upper part. The transgressive–regressive (T–R) sequence model was used for the stratigraphic analysis, leading to a stratigraphic framework of three third-order T–R sequences, with an estimated duration of approximately 2.0, 4.5 and 1.5 Ma, respectively. Consequently, the higher frequency cycles identified in the well logs represent a timing of circa 140,000 years, and are interpreted as fourth-order depositional cycles.

The source of real oil price fluctuations: a fresh view from the frequency domain

ABSTRACT This paper analyzes the role of different types of oil price shocks for real oil price fluctuations and contributes by exploiting insights from the frequency domain perspective. We find aggregate demand shocks are the most important contributor to real oil price fluctuations in the entire spectrum. Besides, oil-specific demand shocks have a relatively important impact on real oil price changes at high frequencies and business cycle frequencies, while oil supply shocks have a relatively important impact on real oil price changes at low frequencies and frequency zero.

Wind variability over the northern Indian Ocean during the past 4 million years – Insights from coarse aeolian dust (IODP exp. 359, site U1467, Maldives)

The lithogenic fraction of carbonate drift sediments from IODP Exp. 359 Site U1467 (Maldives) provides a unique record of atmospheric dust transport over the northern Indian Ocean during the past 4 Myr. Grain-size data provide proxies for dust flux (controlled by source area aridity) as well as wind transport capacity (wind speed). Entrainment and long-range transport of dust in the medium to coarse silt size range is linked to the strength of the Arabian Shamal winds and the occurrence of convective storms which prolong dust transport. Dust flux and the size of dust particles increased between 4.0 and 3.3 Ma, corresponding to the closure of the Indonesian seaway and the intensification of the South Asian Monsoon. There is no clear trend in dust flux between 3.3 and 1.6 Ma, whereas wind transport capacity decreased. Between 1.6 Ma and the Recent, dust flux increased and shows higher variability, especially during the last 500 kyr. Transport capacity increased between 1.2 and 0.5 Ma and slightly decreased since then. Frequency analysis shows that dust transport varies on orbital timescales, with eccentricity control being the most prominent (400 kyr throughout the record, 100 kyr between 2.0 and 1.3 Ma, and since 1.0 Ma). Higher frequency cycles (obliquity and precession) are more pronounced in wind transport capacity than in the amount of dust. This indicates that the amount of coarse dust in sediments from the Maldives as a far-field site is more prone to changes in transport mechanisms than to changes in dust source-area aridity.

Study on the Influence of Pulse Current Cathodic Protection Parameters of Oil Well Casing

Pulse current cathodic protection had obvious advantages over traditional DC cathodic protection, but when square-wave pulse current was used for cathodic protection of oil well casing, the influence of pulse protection parameters on potential distribution was not very clear. Therefore, according to the current situation of oil fields in China, the typical formation characteristic structure of oil wells was selected and the cathodic protection model of pulse current for oil well casing was established. Based on the established model, the effects of pulse current parameters (frequency and duty cycle) and anode distance on the cathodic protection effect of square-wave pulse current were studied. The results showed that better protection effect could be obtained by choosing appropriate anode distance, high frequency, and moderate duty cycle.