Dominant Period Research Articles

Detections of Multi-Periodic Oscillations During a Circular Ribbon Flare

We present the analysis of three kinds of oscillating behavior using multi-wavelength observations of the 10 November 2013 (SOL2013-11-10T05:14) circular-ribbon flare. This event is a typical circular-ribbon flare with an outer spine structure and homologous jets. We found three kinds of oscillations (or perturbations): i) flux oscillation (or QPP) with a dominant period of about 20 seconds in X-ray, EUV, and microwave emissions, ii) periodic jets with an intermittent cadence of around 72 seconds, iii) an outer loop perturbing half a cycle with a duration of about 168 seconds. Similar to the periodic jets that could be produced by a nonthermal process, like repeated magnetic reconnection, the flare QPP detected in the thermal emissions could have the same origin as the oscillation seen in the nonthermal emissions. The outer-loop perturbation is possibly triggered by a blast wave driven by the circular-ribbon flare, or it might be modulated by the sausage wave or the slow magnetoacoustic wave. The results obtained provide data for further numerical studies on the physical origin of the flare oscillations.

Breakthrough COVID-19 Infection During the Delta Variant Dominant Period: Individualized Care Based on Vaccination Status Is Needed.

BackgroundThe clinical features of coronavirus disease 2019 (COVID-19) patients in the COVID-19 vaccination era need to be clarified because breakthrough infection after vaccination is not uncommon.MethodsWe retrospectively analyzed hospitalized COVID-19 patients during a delta variant-dominant period 6 months after the national COVID-19 vaccination rollout. The clinical characteristics and risk factors for severe progression were assessed and subclassified according to vaccination status.ResultsA total of 438 COVID-19 patients were included; the numbers of patients in the unvaccinated, partially vaccinated and fully vaccinated groups were 188 (42.9%), 117 (26.7%) and 133 (30.4%), respectively. The vaccinated group was older, less symptomatic and had a higher Charlson comorbidity index at presentation. The proportions of patients who experienced severe progression in the unvaccinated and fully vaccinated groups were 20.3% (31/153) and 10.8% (13/120), respectively. Older age, diabetes mellitus, solid cancer, elevated levels of lactate dehydrogenase and chest X-ray abnormalities were associated with severe progression, and the vaccination at least once was the only protective factor for severe progression. Chest X-ray abnormalities at presentation were the only predictor for severe progression among fully vaccinated patients.ConclusionIn the hospitalized setting, vaccinated and unvaccinated COVID-19 patients showed different clinical features and risk of oxygen demand despite a relatively high proportion of patients in the two groups. Vaccination needs to be assessed as an initial checkpoint, and chest X-ray may be helpful for predicting severe progression in vaccinated patients.

Spatiotemporal variability analysis of standardized precipitation indexed droughts using wavelet transform

Statistical drought characterization is critical for drought studies within the multivariate temporal and frequency domains. An efficient drought management can result in improved drought preparedness and risk management. In this study, Standardized precipitation indices (SPIs) over various timeframes were derived using precipitation data. The historical data for the hydrological stations and meteorological stations in Sabah and Sarawak, Malaysia were courtesy of the Department of Irrigation and Drainage, Malaysia. Based on the SPI index, the meteorological drought trends, periodicities, and the turning points were analysed using the Mann-Kendall (MK) test, Spearman rho (SR) test, sequential Mann-Kendall (SQMK) test, k-means clustering algorithm, and the Continuous wavelet transform (CWT). The MK and SR test were applied on a decade interval, for a period of years from 1989 to 2018. According to the findings, it was observed that there was a declining tendency shifting from the east to the west in Sabah, whereas in Sarawak, there was observed a declining trend across the state, particularly in its central area. The underlying trend of the droughts in Sabah reveals that the dominant periodicity of the SPI series that persisted throughout the study period at the Sabah stations varied between 2.5 and 5.5 years. However, the periodicity in Sarawak did not vary as much as it did in Sabah. The wavelet coherence analysis also reveals that significant coherence between SPI and climatic indices occurred intermittently for shorter periodicities. Furthermore, the longer dominating periodicities were shown to be associated with one or more climate phenomena.

Circulation type analysis of regional hydrology: the added value in using CMIP6 over CMIP5 simulations as exemplified from the MPI-ESM-LR model

AbstractThis study addresses the applicability of general circulation models (GCMs) in studying the impact of climate change on hydrology. The statistical downscaling of precipitation based on circulation types (CTs) derived from the fuzzy, i.e., more than one CTs can occur in a given day, obliquely rotated principal component analysis is suggested as a robust methodology in using climate models to research the impact of climate change on hydrology. The methodology allows understanding of the mechanism of atmospheric circulation in the study region, and the physical relationship between atmospheric circulation and the regional hydrological cycle. The capability of climate simulations from the Max Planck Institute Earth System Model (MPI-ESM) GCM to reproduce the observed CTs in the target region is examined in light of the uncertainty of atmospheric GCMs when used for circulation typing. The results were discussed and it showed that, generally, the analyzed GCM can reproduce the underlying physics of atmospheric circulation in the study region, represented by the CTs, together with their dominant periods, probability of occurrence, and annual frequency of occurrence with modest biases. Generally, the Coupled Model Intercomparison Project 6 (CMIP6) simulation indicates some improvement for the CT-based analysis relative to the CMIP5 counterpart; however, this depends on the analyzed CT.

Features of Intraseasonal Variability Observed in the Upper-Layer Current in the Northern South China Sea

This study reveals the features of the strong intraseasonal variability (ISV) of the upper-layer current in the northern South China Sea (NSCS) based on four long-time mooring observations and altimeter data. The ISV of the upper-layer current in the NSCS consists of two dominant periods of 10–65 days and 65–110 days. The ISV with period of 10–65 days is much strong in the Luzon Strait and decays rapidly westward along the slope. The ISV with the period of 65–110 days is relatively strong along the slope with two high cores at 115 and 119°E, whereas it is weak in the Luzon Strait. The 10–65-day ISV can propagate directly from the western Pacific into the NSCS for most of the time. However, due to its long wavelength, the 65–110-day ISV propagates into the NSCS indirectly, possibly similar to the wave diffraction phenomenon. The spatial differences between the two main frequency bands are primarily due to the baroclinic and barotropic instabilities. The spatial distribution of the upper-layer ISV is closely associated with the mesoscale eddy radius of the NSCS. The eddy radius is directly proportional to the strength of 65–110-day ISV, but it is inversely proportional to the strength of 10–65-day ISV.

Duration of Severe Acute Respiratory Syndrome Coronavirus 2 Natural Immunity and Protection Against the Delta Variant: A Retrospective Cohort Study.

BackgroundInfection with SARS-CoV-2 has been shown to be highly protective against reinfection and symptomatic disease. However, effectiveness against the highly transmissible Delta variant and duration of natural immunity remain unknown.MethodsThis retrospective cohort study included 325,157 patients tested for coronavirus disease 2019 (COVID-19) via polymerase chain reaction (PCR) from 09 March 2020 to 31 December 2020 (Delta variant analysis) and 152,656 patients tested from 09 March 2020 to 30 August 2020 (long-term effectiveness analysis) with subsequent testing through 09 September 2021. The primary outcome was reinfection, defined as a positive PCR test >90 days after initial positive test.ResultsAmong 325,157 patients tested before 31 December 2020, 50,327 (15.5%) tested positive. After 01 July 2021 (Delta dominant period), 40 (0.08%) of the initially positive and 1,494 (0.5%) of the initially negative patients tested positive. Protection of prior infection against reinfection with Delta was 85.4% (95% CI, 80.0-89.3). For the long-term effectiveness analysis, among 152,656 patients tested before 30 August 2020, 11,186 (7.3%) tested positive. After at least 90 days, 81 (0.7%) of the initially positive patients and 7,167 (5.1%) of the initially negative patients tested positive. Overall protection of previous infection was 85.7% (95% CI, 82.2-88.5) and lasted up to 13 months. Patients over age 65 had slightly lower protection.ConclusionsSARS-CoV-2 infection is highly protective against reinfection with the Delta variant. Immunity from prior infection lasts for at least 13 months. Countries facing vaccine shortages should consider delaying vaccinations for previously infected patients to increase access.

Influence of meteorological drought on environmental flows in mountain catchments

This study investigates the course of atmospheric drought to the response of the water resources availability taking into account the constraints arising from the need to maintain adequate environmental flows (e-flow) releases. For that purpose, eight catchments of southern Poland, namely, Skawa and Dunajec sub-basins (i.e., upper Vistula basin), were considered as study cases. The analysis was carried out as follows: trend analysis of streamflow rate and mean annual precipitation; determination of e-flows using the following methods: 25% mean multi-year flow (25%MAF), the minimum acceptable flow determined by Kostrzewa's method (Qn), the median of monthly mean flows (Qmed), flow with a guarantee of 90% (Q90%), and minimum mean 7-day flow with a recurrence period of 2 years (7Q2). The standardized precipitation index (SPI) and normal precipitation index (PNI) were used as meteorological drought indices to determine the relationship between meteorological drought and e-flow releases. The results revealed a lack of significant trends in annual precipitation and a significantly decreasing trend of streamflow rate in the Skawa sub-basin. For the Dunajec sub-basin, the significantly decreasing trend in streamflow was detected only for Biała; a significant increasing trend was for Biała and Sękówka catchments. The highest values of e-flows were obtained for Qmed and the lowest for 7Q2. The SPI values resulting from the multi-year analysis show that most of the period was dominated by meteorological drought. According to PNI values, the dominant period was normal years. Extremely wet years were found sporadically and were triggered by extremely high precipitation over southern Poland, like in 2010. The results demonstrate that the highest correlations between the SPI, PNI, and e-flows were obtained for 25%MAF and Qmed. Moreover, results exhibited a weak correlation between SPI, PNI values, streamflow rate, and a medium to high correlation for e-flows. The findings from this study showed that SPI and PNI indices could be a helpful tool in water resources management and planning, especially in predicting the influence of droughts on the e-flows deficit.

Correlation between PM2.5 and meteorological variables in Chiang Mai, Thailand

Air pollution is a major concern for the population in Chiang Mai, northern Thailand, as it is for most people in other large cities around the world. Hazy skies and pollution alert have become normal during late winter and entire summer almost every year. Prolonged expose to PM2.5 can have acute and chronic effects on the respiratory and cardiovascular systems. This research aims to study the correlations between PM2.5 and meteorological variables (rainfall and temperature) in Chiang Mai during 2017 and 2020. The cross wavelet transform (XWT) and wavelet coherence (WTC) have been used to examine these relations by assessing the presence of common power and the relative phase in the time-frequency space. The XWT between PM2.5 and rainfall shows a significant common power in two dominant period bands, one in the period between 10-14 months and the other one between 5-7 months. The first common power occurs during all observed time intervals, so it is obviously related to natural annual periodicities of PM2.5 and rainfall. The second band, which occurs only in the year 2019 may be connected with the beginning of the monsoon season which starts in May and brings a stream of warm moist air to Chiang Mai. Our data shows that PM2.5 typically begins to rise starting in November, and it remains high until March of the next year. The PM2.5 is low in rainy season since rain has a wet scavenging effect on PM2.5. The WTC, which is a measure of the correlation between two time series, indicate that there is a significant correlation between PM2.5 and rainfall in the 10-14 month band. The phase difference between these two time series is defined by arrows. The phase arrows pointing to the left indicated the anti-phase relation, when rainfall increases, PM2.5 decreases and vice versa. The correlation coefficient (r) between PM2.5 and rainfall in rainy season is equal to 0.8504. Our study also finds that there is a proven correlation between PM2.5 and temperature in a day time scale with the correlation coefficient equal to 0.9249. In a one-day period, PM2.5 is low in the day time and high at night. An understanding of how climate variability may impact PM2.5 concentration in Chiang Mai will help the government with better planning and preparation to prevent environmental hazard from PM2.5 pollution.

A computationally efficient dynamic model of human epicardial tissue.

We present a new phenomenological model of human ventricular epicardial cells and we test its reentry dynamics. The model is derived from the Rogers-McCulloch formulation of the FitzHugh-Nagumo equations and represents the total ionic current divided into three contributions corresponding to the excitatory, recovery and transient outward currents. Our model reproduces the main characteristics of human epicardial tissue, including action potential amplitude and morphology, upstroke velocity, and action potential duration and conduction velocity restitution curves. The reentry dynamics is stable, and the dominant period is about 270 ms, which is comparable to clinical values. The proposed model is the first phenomenological model able to accurately resemble human experimental data by using only 3 state variables and 17 parameters. Indeed, it is more computationally efficient than existing models (i.e., almost two times faster than the minimal ventricular model). Beyond the computational efficiency, the low number of parameters facilitates the process of fitting the model to the experimental data.

Circadian Rhythm Analysis Using Wearable Device Data: Novel Penalized Machine Learning Approach.

BackgroundWearable devices have been widely used in clinical studies to study daily activity patterns, but the analysis remains a major obstacle for researchers.ObjectiveThis study proposes a novel method to characterize sleep-activity rhythms using actigraphy and further use it to describe early childhood daily rhythm formation and examine its association with physical development.MethodsWe developed a machine learning–based Penalized Multiband Learning (PML) algorithm to sequentially infer dominant periodicities based on the Fast Fourier Transform (FFT) algorithm and further characterize daily rhythms. We implemented and applied the algorithm to Actiwatch data collected from a cohort of 262 healthy infants at ages 6, 12, 18, and 24 months, with 159, 101, 111, and 141 participants at each time point, respectively. Autocorrelation analysis and Fisher test in harmonic analysis with Bonferroni correction were applied for comparison with the PML. The association between activity rhythm features and early childhood motor development, assessed using the Peabody Developmental Motor Scales-Second Edition (PDMS-2), was studied through linear regression analysis.ResultsThe PML results showed that 1-day periodicity was most dominant at 6 and 12 months, whereas one-day, one-third–day, and half-day periodicities were most dominant at 18 and 24 months. These periodicities were all significant in the Fisher test, with one-fourth–day periodicity also significant at 12 months. Autocorrelation effectively detected 1-day periodicity but not the other periodicities. At 6 months, PDMS-2 was associated with the assessment seasons. At 12 months, PDMS-2 was associated with the assessment seasons and FFT signals at one-third–day periodicity (P<.001) and half-day periodicity (P=.04), respectively. In particular, the subcategories of stationary, locomotion, and gross motor were associated with the FFT signals at one-third–day periodicity (P<.001).ConclusionsThe proposed PML algorithm can effectively conduct circadian rhythm analysis using time-series wearable device data. The application of the method effectively characterized sleep-wake rhythm development and identified the association between daily rhythm formation and motor development during early childhood.

Modulation of centennial-scale hydroclimate variations in the middle Yangtze River Valley by the East Asian-Pacific pattern and ENSO over the past two millennia

Meteorological observations reveal an inverse relationship of summer monsoon rainfall between the tropical western North Pacific (WNP) and middle Yangtze River Valley (mid-YRV) on interannual and intraseasonal timescales. This seesaw-like pattern, named the East Asian-Pacific (EAP) pattern, is one of the major teleconnections that affect summer precipitation in the mid-YRV. However, due to the scarcity of long and continuous instrumental data, the behavior and mechanism of the EAP pattern on a long timescale are poorly understood. Here, we present a composite high-resolution summer monsoon rainfall record from 230 BC to 1810 AD, based on 1221 δ18O measurements and 22 230Th dates from two stalagmites (EB1 and EB5) in Shenqi Cave over the mid-YRV. Our new record shows that monsoon rainfall in the mid-YRV varies at a dominant periodicity of ∼100 years, probably linked to solar activity and ENSO variability. The multi-centennial fluctuations in the EB record, broadly consistent with the North Hemisphere temperature reconstruction, display strong similarities to two stalagmite δ18O records from nearby Heshang and Luoshui caves. To represent the integrated hydroclimate variations over the mid-YRV, we extracted the first principal component (PC1) of these three cave δ18O records by using the principal component analysis. We reveal a striking inverse relationship of wet/dry conditions between the mid-YRV and tropical WNP, suggesting that changes in the EAP pattern have an important impact on centennial-scale monsoon precipitation changes. Furthermore, we compile monsoon rainfall records from the mid-YRV and WNP to reconstruct a new EAP index. This EAP index exhibits a strong correlation with the ENSO proxy, confirming that the ENSO variability may play a key role in modulating the monsoon rainfall in the mid-YRV through the EAP teleconnection.

Dynamics of tethered membranes in inviscid flow

We investigate the dynamics of membranes that are held by freely-rotating rigid tethers in fluid flows. The tethered boundary condition allows periodic and chaotic oscillatory motions for certain parameter values. We characterize the oscillations in terms of deflection amplitudes, dominant periods, and numbers of local extrema of deflection along the membranes across the parameter space of membrane mass density, stretching modulus, pretension, and tether length. We determine the region of instability and the small-amplitude behavior by solving a nonlinear eigenvalue problem. We also consider an infinite periodic membrane model, which yields a regular eigenvalue problem, analytical results, and asymptotic scaling laws. We find qualitative similarities among all three models in terms of the oscillation frequencies and membrane shapes at small and large values of membrane mass, pretension, and tether length/stiffness.

Significant duration predictive models developed from strong‐motion data of thrust‐faulting earthquakes recorded in Mexico City

AbstractPredictive models for estimating strong‐motion duration in sites characterized by soft‐soil profiles are presented in this paper. The models were developed using a strong‐motion database that includes observations from subduction interface earthquakes that occurred from 1989 to 2020 and recorded in Mexico City, which is located at source‐to‐site distances up to 600 km. A linear mixed‐effects regression model, which is a statistical fitting procedure that allows to consider the correlation structure of grouped data, was used to develop the predictive models. Relative significant duration was selected to measure strong‐motion duration. This measure can be directly associated with the accumulation of energy of the ground movement. The proposed predictive models relate relative significant duration with moment magnitude, either hypocentral distance or closest distance to the rupture plane, and dominant period of the soil. Regression analyses were performed grouping the ground‐motion data by both seismic event and site class. Model assumptions, such as homoscedasticity, normality, and linearity of effects, were verified from residual analyses. From the results, the expected value of the natural logarithm of relative significant duration was found to be ∼1.2 times greater for an earthquake with a moment magnitude equal to 8.0 than for one of 6.0. An insightful discussion about the sources and character of the uncertainties detected in the proposed predictive models is also presented in this study. The predictive models proposed in this paper are of valuable application in seismic and structural engineering because they allow to circumscribe properly the dimension and randomness of strong‐motion duration.

Base isolation for mid-rise buildings in presence of soil-structure interaction

Base isolation has been commonly used for seismic protection of lowrise (short period) buildings on firm ground. For taller buildings on soft soil, however, the following concerns arise: soil-structure interaction (SSI) alters the resonant characteristics of the whole system and its dynamic response. The efficiency of base-isolation depends on the dynamic properties of the system and the shape of the site response spectrum. In this work, SSI effects on the dynamic response of base-isolated mid-rise buildings are examined. A discrete shear-building model with linear elastic elastomeric bearings and flexible foundation is analyzed by a suitable method for systems with non-classical damping. The model is applied to evaluate the feasibility of using seismic isolation at soft-soil sites of Mexico City, where typical buildings of 10–15 stories were the most damaged during the great 1985 Michoacán earthquake. It is concluded that base isolation can be effectively used to control the detrimental SSI effects anticipated for these buildings located at sites with dominant period longer than the fundamental fixed-base period of the superstructure.

Investigating Ionospheric Perturbations Following the 2020 Beirut Explosion Event

AbstractWe assess the detection of the August 4, 2020 chemical explosion in Beirut, Lebanon (33°N, 35°E). We use ionospheric total electron content (TEC) observations from a regional network of ground‐based Global Positioning System (GPS) receivers to study the ionospheric variability and wave perturbations generated by the Beirut explosion. Our analysis reveals that the induced wave structures arrived in the ionosphere 10 ± 2 min after the explosion, which is a strong indication of acoustic gravity wave activity. These wave structures are characterized with ΔTEC of 0.06 TECU moving at ∼750 m/s in south‐east direction away from the explosion epicenter. The continuous wavelet analysis we applied shows a dominant wave periodicity of 1.5–2.5 min (6.78–11 mHz) in the ionosphere. Furthermore, we use measurements from ERA‐interim analysis to establish the ambient neutral atmospheric conditions before the Beirut explosion event. Finally, the observed ionospheric wave perturbations appear to be in good agreement with the expected arrival of acoustic gravity waves generated following the explosion.

Development Prototype of Indonesia Seismic Microzonation Information System (Inasmis)

Indonesia has a high level of seismic vulnerability because located in the junction area of four large plates, namely the Eurasian plate, Indo-Australian plate, Pacific plate, and Philippine Plate, and also the number of active faults that stretch throughout its regions. One of the efforts to mitigate earthquake disasters is to conduct seismic hazard microzonation efforts. The Research and Development Center of BMKG has carried out ongoing research in the field of seismic microzonation to obtain information on the level of seismic hazard in some regions based on microtremor parameter values, including in the Sukabumi (2009), Bantul (2010), Padang (2011), Cilacap (2012), Kulonprogo (2014), Tasikmalaya (2017), Garut (2018) and Pangandaran (2019). This study tries to prototype the seismic microzonation information system in a web-based spatial information system called InaSMIS (Indonesia Seismic Microzonation Information System). InaSIMS contains information about the analysis of microtremor survey results, including the value of the dominant period (T0), Ground Shear Strain (GSS), and USGS Vs30, which states the level of seismic hazard in an area. InaSMIS is still being developed in the research stage and is not yet an operational service for BMKG. In the future, InaSMIS expected to be a source of public information to determine seismic hazards in Indonesian regions.

Diagnose the dominant climate factors and periods of spring phenology in Qinling Mountains, China

The important effect of climate factors on spring phenology has been confirmed by numerous studies, but its temporal variation remains unclear. Based on the daily meteorological observation data and annual vegetation phenology data from 1987 to 2016, this study proposes a Time Window Sliding Fitting (TWSF) method. Partial Least Squares (PLS) regression is used to investigate the relationship between spring phenology and five climate factors, including mean temperature, total precipitation, mean photoperiod, chilling index and forcing index, in all time windows from December to next May with 7-day interval in Qinling Mountains (QLMs) of China. The results show that: (1) Temperature in QLMs has an increasing trend with 0.41 °C/10a, and precipitation decreases with 400 mm/a. Moreover, spring phenology in QLMs is advancing with 4 days/10a. (2) Temperature is found having dominant effect on spring phenology in QLMs, and photoperiod has a significant effect on spring phenology in grassland area. (3) Temperature’s impact increases in cultivated land and grassland after March 25 but a consecutive decrease trend in forest, while photoperiod’s explanatory ability on grassland spring phenology is highlighted in early January, early February and early April. Chilling has the best explanatory ability on crop spring phenology in early March and early May. Additionally, forcing can significantly influence spring phenology in early March for cultivated land and late May for forest. The results of this study are beneficial to understand the mechanism of plant-climate interaction.

Institutional complexity and family business development: a case study of the Charoen Pokphand group

PurposeWith features of both “family” and “business,” family businesses must seek a balance between the emotional aspect of “family” and the economic aspect of “business” in its organizational and decision-making processes to ensure the sustainability of the family’s entrepreneurship. This study aims to focus on how internal institutional complexity combined evolves alongside the growth of the family business.Design/methodology/approachThe research looks, from the perspective of institutional logic, into the Charoen Pokphand Group, which is an epitome of overseas Chinese family businesses and proceeds to build a model of family business growth in the context of institutional complexity.FindingsThe research finds that as a family business grows, institutional complexity inside the organization would change from aligned period to sustaining period and then to dominant period. Then further elucidates the process of proactive response in different stages of the development of a family business. Attaching equal importance to the cultivation of entrepreneurship and to the continuation of family values and culture is the crucial mechanism by which Chinese family businesses seek a balance between family logic and business logic.Originality/valueThis paper unveils the change of institutional complexity in the evolution of family businesses and the process of action of its agency as an organization, and simultaneously partly reveals the features of entrepreneurship that overseas Chinese family businesses have as they grew, which is of positive significance for exploring and building a path of growth unique to Chinese family businesses.

Response and periodic variation of total atmospheric ozone to solar activity over Mountain Waliguan

Modern-Era Retrospective Analysis for Research and Applications, Version-2 (MERRA-2) total column ozone (TCO) data from 1980 to 2018 and ground based TCO data were used to investigate its responses to periodic variations concerning stratospheric dynamics such as tropopause heights and Quasi-Biennial Oscillations (QBO), and solar activity signatures of Magnesium II core-to-wing ratio (Mg II) and F10.7 cm solar radio flux (F10.7) observed over Mountain (Mt.) Waliguan (36.17°N, 100.53°E), China. Cross-correlation and wavelet analyses were used for carrying out the investigation. The MgII and F10.7 show a periodicity of around an 11-year solar cycle (SC) while the TCO trend is though periodic and it does not exhibit one to one correspondence with the 11-year SC. The highest value in TCO is 355.7 DU noted in February (1982) whereas, the lowest value of TCO is 256.02 DU in October (1988) during the entire study period. The average value in TCO is 291.17 ± 0.94 DU with an amplitude of variation of 99.68 DU (~28%). The trend of TCO depicts a persistent distinct seasonal pattern with maxima in winter/spring (December through April) and minima in summer/autumn (August through November). The long-term variability shows a notable decreasing trend in TCO by ~30%, 13%, and 5% per decade for SCs 21–23, where SC 24 represents an increasing trend of ~1% per decade. Hence, this illustrates the significant recovery of TCO over Mt. Waliguan, China which is as a result of the reduction of the ozone depletion agents arising as a positive outcome of the implementation of the Montreal regulatory policy. From wavelet analysis, the F10.7, MgII, tropopause height, QBO and TCO show a significant dominant periodicity of 10–12 months. It is concluded that the variations in mean TCO are strongly correlated with variations of the F10.7 cm and Mg-II solar indices, and the mean TCO responds rapidly to solar activity variations.

Reconstruction of Copper Smelting Technology Based on 18–20th-Century Slag Remains from the Old Copper Basin, Poland

This research was conducted on historical copper slags from Leszczyna and Kondratów in Lower Silesia, Poland. The area, formerly known as the Old Copper Basin, was a mining and smelting centre between the 18th and 20th centuries, with a dominant period in the 19th century. Cu-carbonates and residual chalcocite dominate local strata-bound copper deposits. Ore bodies are restricted to carbonate strata. A geochemical and mineralogical study of slag samples from four research sites allowed us to establish that a low amount of sulphur in slags results from S-poor ores, and pyrite with gypsum was implemented as reducing agents. Arkose sandstones served as a flux. During smelting, oxygen availability was limited, and temperature exceeded 1200 °C (18th- and 19th-century smelting) and 1400 °C (20th-century smelting). Calculated viscosity indexes mark the low efficiency of metal separation between the silicate and metallic phases. The skeletal and dendritic form of the crystals proved that slag melt was relatively rapidly cooled after formation, usually in air conditions. We estimated that approx. 2000 m3 of slag was created during the leading smelter (Stilles Glück) activity. The research provided various details of the historical copper smelting technological process in Leszczyna and Kondratów.