Observations of the OH radical in comets at 18 cm wavelength

We present recent observations of the OH radical at λ 18 cm with the Nançay radio telescope in comets Meier (1978 XXI), Bradfield (1979 X), Meier (1980q), P/Encke (1980), and Bradfield (1980t). The analysis of the OH radio line shape is a powerful tool to study the kinematics of the coma. The expansion velocity of the OH molecules is found to be ≈1.5 km sec^?1 at r_h = 1 AU, and decreases with increasing heliocentric distance. The line profile is generally asymmetric, which demonstrates the Greenstein effect on the fluorescent excitation mechanism and/or anisotropic outgassing of the nucleus. In several cases, especially for comet Meier (1978 XXI), an asymmetry is also found in the east-west brightness distribution of the OH line, showing again the Greenstein effect and/or anisotropic outgassing. An excitation model by uv pumping and fluorescence of the OH radical, which agrees with the observations at least in the first order, and the application of Haser's model lead to the production rate of the parent molecule of OH. There is a close correlation between this gas production rate and the visual brightness of the comet. Our estimates of gas production rates are smaller than or equal to those obtained from uv measurements, but both radio and uv estimates depend heavily on the parameters used in Haser's models.     

New data on mantle seismicity of the Caspian region and their geological interpretation

The results of detailed seismological observations with bottom recording systems carried out in 2004 and 2006 near the Dagestan coast of the Middle Caspian are considered. The records of more than 550 micro- and weak earthquakes with M_L = 0.1–4.7 (M_LH = ?0.7 to 4.3) were obtained during 165 days of recording; a fifth of these earthquakes occurred in the upper mantle at a depth of 50–200 km. Over the entire period of instrumental recording since the 1930s, only 10 mantle earthquakes with M_LH = 3.5?6.3 have been recorded by on-land systems. The highest density of earthquake epicenters with source depths down to 50 km is established on the Middle Caspian coast between Derbent and Izberbash and in the adjacent water area. The mantle earthquakes with hypocenters at a depth of 60–80 km cluster beneath the western wall of the Derbent Basin, whereas deeper hypocenters are located beneath both the wall of this basin and the Middle Caspian coast. The sporadic mantle earthquakes recorded in 2004 (about 30 shocks), determined by a network of systems with a small aperture, depicted a zone plunging beneath the Greater Caucasus with indications of a peculiar “subduction” of the Scythian Plate beneath the Caucasus. Subsequent observations based on a more extensive network were carried out in 2006. They substantially changed the pattern of mantle earthquake hypocenters. According to this evidence, the sources of mantle earthquakes make up a dispersed cloud extended in the vertical direction beneath the Middle Caspian coast and water area, which may be regarded as a relic of tectonic activity of a bygone tectonic epoch. A comprehensive tectonic interpretation of the detected seismological phenomenon is given.     

Multi-step water quality forecasting using a boosting ensemble multi-wavelet extreme learning machine model

The use of electrical conductivity (EC) as a water quality indicator is useful for estimating the mineralization and salinity of water. The objectives of this study were to explore, for the first time, extreme learning machine (ELM) and wavelet-extreme learning machine hybrid (WA-ELM) models to forecast multi-step-ahead EC and to employ an integrated method to combine the advantages of WA-ELM models, which utilized the boosting ensemble method. For comparative purposes, an adaptive neuro-fuzzy inference system (ANFIS) model, and a WA-ANFIS model, were also developed. The study area was the Aji-Chay River at the Akhula hydrometric station in Northwestern Iran. A total of 315 monthly EC (µS/cm) datasets (1984–2011) were used, in which the first 284 datasets (90% of total datasets) were considered for training and the remaining 31 (10% of total datasets) were used for model testing. Autocorrelation function (ACF) and partial autocorrelation function (PACF) demonstrated that the 6-month lags were potential input time lags. The results illustrated that the single ELM and ANFIS models were unable to forecast the multi-step-ahead EC in terms of root mean square error (RMSE), coefficient of determination (R²) and Nash–Sutcliffe model efficiency coefficient (NSC). To develop the hybrid WA-ELM and WA-ANFIS models, the original time series of lags as inputs, and time series of 1, 2 and 3 month-step-ahead EC values as outputs, were decomposed into several sub-time series using different maximal overlap discrete wavelet transform (MODWT) functions, namely Daubechies, Symlet, Haar and Coiflet of different orders at level three. These sub-time series were then used in the ELM and ANFIS models as an input dataset to forecast the multi-step-ahead EC. The results indicated that single WA-ELM and WA-ANFIS models performed better than any ELM and ANFIS models. Also, WA-ELM models outperformed WA-ANFIS models. To develop the boosting multi-WA-ELM and multi-WA-ANFIS ensemble models, a least squares boosting (LSBoost) algorithm was used. The results showed that boosting multi-WA-ELM and multi-WA-ANFIS ensemble models outperformed the individual WA-ELM and WA-ANFIS models.     

Stochastic analysis of Lake Superior elevations for computation of relative crustal movement

Using Lake Superior mean monthly elevations as recorded at five gauges around the lake, time series of elevations and differences in elevations between pairs of gauges were analysed for trends, periodicities and autoregressive components. It was found that the variance of the time series of elevations consisted of 4–12% linear trends, 35–44% periodicities in the mean, 0.23–0.66% periodicities in the variance, a 43–54% autoregressive component and a 5% random component. On the other hand, the time series of differences in lake elevations were found to consist of 30–52% linear trends, 5–35% periodicities in the mean and variance, up to a 30% autoregressive component and a random component of 21–31%. Rates of crustal movement were computed from the trends in gauge differences.     

Late Cretaceous-Eocene marginal seas in the Black Sea-Caspian region: Paleotectonic reconstructions

A series of seven reconstructions is presented to illustrate the evolution of marginal seas in the Black Sea-South Caspian segment of the margin of the Tethys Ocean from the Late Jurassic to the middle Eocene. After Middle Jurassic inversion and until the Aptian Age, no marginal (backarc) basins were formed in the region, while the Pontides-Rhodope margin developed in the passive regime. The retained relict of the Late Triassic-Early Jurassic backarc basin includes the southeastern part of the Greater Caucasus, the northern part of the South Caspian Basin, and the shallow-water Kopetdagh Basin. The basins of the southern slope of the Greater Caucasus, Balkans (Nish-Trojan Trough), and Dobrogea developed as flexural foredeeps in front of the Middle Jurassic fold systems. The next, Aptian-Turonian epoch of opening of marginal seas was related to the origination of subduction zones at the Pontides-Rhodope margin and to the incipient consumption of the Vardar Basin lithosphere with formation of the West Black Sea Basin and its western continuation in the Bulgarian Srednogorie. The backarc rifting in the Greater Caucasus resulted in transformation of the foredeep into the backarc basin. Two basins approximately 2000 km in total extent were separated by the bridge formed by the Shatsky and Andrusov rises. The last, late Paleocene-middle Eocene epoch of the formation of backarc basins was associated with the newly formed subduction zone south of the Menderes-Taurus Terrane that collided with the active margin in the early Paleocene. The Greater Caucasus Basin widened and deepened, while to its south the East Black Sea Basin, the grabens in the Kura Depression, and the Talysh Basin, all being separated by a chain of uplifts, opened. The Paleogene South Caspian Basin opened in the course of the southward motion of the Alborz volcanic arc at the late stage of closure of the Iranian inner seas.     

Development of a short-term river flood forecasting method for snowmelt driven floods based on wavelet and cross-wavelet analysis

In this study, a new method of stand-alone short-term spring snowmelt river flood forecasting was developed based on wavelet and cross-wavelet analysis. Wavelet and cross-wavelet analysis were used to decompose flow and meteorological time series data and to develop wavelet based constituent components which were then used to forecast floods 1, 2, and 6 days ahead. The newly developed wavelet forecasting method (WT) was compared to multiple linear regression analysis (MLR), autoregressive integrated moving average analysis (ARIMA), and artificial neural network analysis (ANN) for forecasting daily stream flows with lead-times equal to 1, 2, and 6 days. This comparison was done using data from the Rideau River watershed in Ontario, Canada. Numerical analysis was performed on daily maximum stream flow data from the Rideau River station and on meteorological data (rainfall, snowfall, and snow on ground) from the Ottawa Airport weather station. Data from 1970 to 1997 were used to train the models while data from 1998 to 2001 were used to test the models. The most significant finding of this research was that it was demonstrated that the proposed wavelet based forecasting method can be used with great accuracy as a stand-alone forecasting method for 1 and 2 days lead-time river flood forecasting, assuming that there are no significant trends in the amplitude for the same Julian day year-to-year, and that there is a relatively stable phase shift between the flow and meteorological time series. The best forecasting model for 1 day lead-time was a wavelet analysis model. In testing, it had the lowest RMSE value (13.8229), the highest R² value (0.9753), and the highest EI value (0.9744). The best forecasting model for 2 days lead-time was also a wavelet analysis model. In testing, it had the lowest RMSE value (31.7985), the highest R² value (0.8461), and the second highest EI value (0.8410). It was also shown that the proposed wavelet based forecasting method is not particularly accurate for longer lead-time forecasting such as 6 days, with the ANN method providing more accurate results. The best forecasting model for 6 days lead-time was an ANN model, with the wavelet model not performing as well. In testing, the wavelet model had an RMSE of 57.6917, an R² of 0.4835, and an EI of 0.4366.     

Lithological and biogeochemical features of carbonate sedimentation in the Tsimlyansk Reservoir

Sources of carbonates delivered to the Tsimlyansk Reservoir, pathways of their withdrawal and distribution over the area, as well as morphological and structural features of minerals, are studied. It has been established that the Tsimlyansk Reservoir is characterized by imbalance between rates of carbonate material delivery to the reservoir and rates of its sedimentation. It is shown that the whole carbonate material is utilized by mollusks that make shells from aragonite. The mollusks accelerate the redistribution of chemical elements in carbonates, reconstruct their crystalline structures, discard Mg, and assimilate Sr.