Hydroclimatic variations over the last two glacial/interglacial cycles at Lake Urmia,Iran

A coarse-resolution, absolutely dated isotope record spanning the last 180 ka was constructed from aragonite-rich fecal pellets in a sediment core from Lake Urmia, Iran. The isotope record is not continuous as a consequence of detrital calcite that contaminates the pellets at certain depths. An isotopic correction was applied to samples > 50% aragonite, using the δ¹⁸O values of calcite-only pellets. Absolute dates were derived from U-Th analyses on pellets > 80% aragonite. The resultant δ¹⁸O record and sediment lithofacies confirm that the Penultimate Glacial was cold and dry, with pronounced interstadials at ca. 150 and >175 ka. Deglaciation began at ca. 130 ka, but climate was unstable and supported a probable no-analog vegetation assemblage. The onset of true interglacial conditions occurred at ca. 126 ka. Peak moisture conditions lasted for 5–6 ka before the climate became drier, with the loss of some tree taxa towards the end of the Last Interglacial. A period of greater moisture occurred between 116 and 108 ka, overlapping in timing with interstadial conditions recorded in the Soreq Cave speleothem record. In general, stadial to interstadial transitions (OIS 5d-5c, 5b-5a) are marked by decreasing δ¹⁸O values and rising lake levels. The nature of the OIS 5 to OIS 4 transition cannot be resolved in this study because of the loss of 5 m of core and imprecise dates. According to the present chronology, δ¹⁸O values, and inferred lake levels, arid conditions began at 60 ka and persisted until Termination I. Episodic increases in moisture, characterized by layers of aragonite-rich pellets, ostracodes, and the pollen of trees and/or aquatic plants, occurred during the Last Glacial. Deglaciation associated with the Late-glacial Interstadial began at 14 ka but was interrupted by a marked Younger Dryas event that resulted in renewed aridity. The Holocene began at approximately 10 ka. Despite large errors in the chronology, the overall timing and pattern of effective moisture matches the record from Soreq Cave, Israel, suggesting that the two regions were climatically in-phase.     

Multigene genetic programming for sediment transport modeling in sewers for conditions of non-deposition with a bed deposit

It is known that construction of large sewers based on consideration of flow with non-deposition without a bed deposit is not economical. Sewer design based on consideration of flow with non-deposition with a bed deposit reduces channel bed slope and construction cost in which the presence of a small depth of sediment deposition on the bed increases the sediment transport capacity of the flow. This paper suggests a new Pareto-optimal model developed by the multigene genetic programming (MGGP) technique to estimate particle Froude number (Fr_p) in large sewers with conditions of sediment deposition on the bed. To this end, four data sets including wide ranges of sediment size and concentration, deposit thickness, and pipe size are used. On the basis of different statistical performance indices, the efficiency of the proposed Pareto-optimal MGGP model is compared to those of the best MGGP model developed in the current study as well as the conventional regression models available in the literature. The results indicate the higher efficiency of the MGGP-based models for Fr_p estimation in the case of no additional deposition onto a bed with a sediment deposit. Inasmuch as the Pareto-optimal MGGP model utilizes a lower number of input parameters to yield comparatively higher performance than the conventional regression models, it can be used as a parsimonious model for self-cleansing design of large sewers in practice.     

Age, growth and reproduction of the sand smelt Atherina boyeri Risso, 1810 in the Gomishan wetland – southeast Caspian Sea

A total of 2256 specimens of Atherina boyeri caught in Gomishan wetland (a marsh lagoon located at the southeast Caspian Sea) during spawning season from February to August 2007 were examined for life-history attributes. The population has a 4-year life cycle. Length–weight relationship was estimated as W = 0.0053TL^3.0181 for males and W = 0.0050TL^3.063 for females, being allometrically positive for both sexes. The von Bertalanffy growth function fitted to back-calculated size at age data was: Lt = 155.17[1 − exp − 0.28(t + 0.738)] and Lt = 162.77[1 − exp − 0.27(t + 0.727)] for males and females respectively. The sex ratio was 1:1.30 in favor of females. The reproductive season, evaluated from GSI, extended from March to July, with a peak in March. The average absolute and relative fecundities were 2976 eggs and 874 eggs g⁻¹ of body weight respectively. The diameter of oocytes ranged from 0.03 to 0.20 mm with a mean value of 0.68. The life-history patterns of A. boyeri in the population under study imply that the population of this species in the southeast Caspian Sea differs markedly from those of other localities of its range distribution. The differences were thought to be due to differences in geographical locations.     

Leaching of an oxide gold ore with chloride/hypochlorite solutions

An oxide gold ore was subjected to chloride/hypochlorite leaching at room temperature. The effects of three factors, including Ca(OCl)₂ vs. NaOCl, OCl⁻ concentration, and HCl concentration on gold leaching performance were investigated. Due to formation of CaOCl⁺ complex in solution and hence less reactivity, calcium hypochlorite produces a sluggish gold leaching kinetics, taking twice the time (46 h) to achieve maximum gold recovery of 58% compared to sodium hypochlorite. 10 g/L of total initial hypochlorite species in solution produces reasonable gold recoveries. The amount of added HCl and hence the initial pH was found to have a major effect on gold leaching kinetics and maximum gold recovery. A high level of 9 g/L of added HCl causes HClO to be very reactive, producing very fast kinetics, reaching 67% gold extraction in 4 h. It also causes a faster consumption of hypochlorous acid, through catalytic decomposition (by NiO and CuO) and disproportionation. Hypochlorous acid reactions with sulfide and ferrous content of ore proceed very slowly in the pH range of 4–11. Gold–chloro complexes are strongly adsorbed on quartz component of ore. To minimize this undesirable adsorption of gold–chloro species, the aging time must be limited to a few hours only.     

Biofiltration of Hexane Vapor: Experimental and Neural Model Analysis

Biofiltration is a commonly practiced biological technique to remove volatile compounds from waste gas streams. From an industrial view‐point, biofilter (BF) operation should be flexible to handle temperatures and inlet load (IL) variations. A compost BF was operated at different temperatures (30–45°C) and at various inlet loading rates (ILR; 8–598 g m^?3 h^?1) under intermittent loading conditions. Complete removal of n‐hexane was observed at 30 and 35°C at ILRs up to 330 g m^?3 h^?1. Besides, 20–75% of the pollutant was removed at 40°C, corresponding to the different ILs applied to the BF. Increasing the temperature to 45°C decreased the removal efficiency (RE) significantly. A feed forward neural network was used to predict the RE of BF with temperature and ILR as the input variables. The experimental data was divided into training (2/3) and test datasets (1/3). The best structure of neural network was obtained by trial and error on the basis of the least differences between predicted and experimental values, as ascertained from their coefficient of regression (R²) values. The modeling results showed that a multilayer network with the topology 2?10?1 was able to predict BF performance effectively with R²‐value of 0.995 for the test data. The results from this study showed the predicting capability of ANNs which can be considered as an alternative for conventional knowledge‐based models.     

Mixed model for interoccurrence times of earthquakes based on the expectation-maximization algorithm

In this paper, the goodness-of-fit test based on a convex combination of Akaike and Bayesian information criteria is used to explain the features of interoccurrence times of earthquakes. By analyzing the seismic catalog of Iran for different tectonic settings, we have found that the probability distributions of time intervals between successive earthquakes can be described by the generalized normal distribution. This indicates that the sequence of successive earthquakes is not a Poisson process. It is found that by decreasing the threshold magnitude, the interoccurrence time distribution changes from the generalized normal distribution to the gamma distribution in some seismotectonic regions. As a new insight, the probability distribution of time intervals between earthquakes is described as a mixture distribution via the expectation-maximization algorithm.     

The Reissner–Sagoci problem for a transversely isotropic half‐space

A transversely isotropic linear elastic half‐space, z?0, with the isotropy axis parallel to the z‐axis is considered. The purpose of the paper is to determine displacements and stresses fields in the interior of the half‐space when a rigid circular disk of radius a completely bonded to the surface of the half‐space is rotated through a constant angle θ₀. The region of the surface lying out with the circle r?a, is free from stresses. This problem is a type of Reissner–Sagoci mixed boundary value problems. Using cylindrical co‐ordinate system and applying Hankel integral transform in the radial direction, the problem may be changed to a system of dual integral equations. The solution of the dual integral equations is obtained by an approach analogous to Sneddon's (J. Appl. Phys. 1947; 18 :130–132), so that the circumferential displacement and stress fields inside the medium are obtained analytically. The same problem has already been approached by Hanson and Puja (J. Appl. Mech. 1997; 64 :692–694) by the use of integrating the point force potential functions. It is analytically proved that the present solution, although of a quite different form, is equivalent to that given by Hanson and Puja. To illustrate the solution, a few plots are provided. The displacements and the stresses in a soil deposit due to a rotationally symmetric force or boundary displacement may be obtained using the results of this paper. Copyright © 2006 John Wiley & Sons, Ltd.     

The western Durkan Complex (Makran Accretionary Prism,SE Iran): A Late Cretaceous tectonically disrupted seamounts chain and its role in controlling deformation style

The Durkan Complex is a key tectonic element of the Makran accretionary prism (SE Iran) and it has been interpreted as representing a continental margin succession. We present here a multidisciplinary study of the western Durkan Complex, which is based on new geological, stratigraphic, biostratigraphic data, as well as geochemical data of the volcanic and meta-volcanic rocks forming this complex. Our data show that this complex consists of distinct tectonic slices showing both non-metamorphic and very low-grade metamorphic deformed successions. Stratigraphic and biostratigraphic data allow us to recognize three types of successions. Type-I is composed by a Coniacian – early Campanian pelagic succession with intercalation of pillow lavas and minor volcaniclastic rocks. Type-II succession includes a volcanic sequence passing to a volcano-sedimentary sequence with Cenomanian pelagic limestones, followed by a hemipelagic sequence. This succession is characterized by abundant mass-transport deposits. Type-III succession includes volcanic and volcano-sedimentary sequences, which are stratigraphically covered by a Cenomanian platform succession. The latter is locally followed by a hemipelagic sequence. The volcanic rocks in the different successions show alkaline geochemical affinity, suggesting an origin from an oceanic within-plate setting. Our new results indicate that the western Durkan Complex represents fragments of seamounts tectonically incorporated in the Makran accretionary wedge during the latest Late Cretaceous–Paleocene. We propose that incorporation of seamounts in the frontal prism caused a shortening of the whole convergent margin and possibly contributed to controlling the deformation style in the Makran Accretionary Wedge during Late Cretaceous–Paleocene times.