A review on mechanism and future perspectives of cadmium-resistant bacteria

Since the last few decades, cadmium anthropocentric sources have been increased drastically. Various chemical and physical approaches for cadmium remediation have been proposed, but these techniques are quite expensive, not healthy for the environment and not efficient at the low concentration of cadmium. Thus, in the last few years, the cadmium removal by biological approaches has received a great interest. Many bacteria can resist against high concentration of cadmium through different mechanisms. The cadmium-resistant bacteria can be grouped into three levels. The main group consists of bacteria which efflux the cadmium from the cells. The bacteria of the other two groups are capable of detoxifying or binding cadmium. The cadA and cadB gene systems are involved in efflux mechanism, and these encode different efflux pump proteins, while the functional groups such as amine, carboxyl, phosphate and hydroxyl facilitate cadmium binding to bacterial surface such as chemisorption. Many enzymes are involved in the detoxifying the cadmium and make the membrane impermeable against cadmium. This paper also reviews the industrial application of cadmium-resistant bacteria and the future perspectives of genetic engineering, bioelectrochemical system, microbial aggregates and biosorption of cadmium by algae.     

Integrated application of 2D resistivity and electromagnetic methods to investigate a metallic-sulfide deposit in Soap Gulch,Montana. A case study

Geoelectrical methods involving electrical resistivity tomography (ERT), self-potential (SP), frequency domain electromagnetic (FDEM), and very low frequency (VLF) methods have been used to provide valuable information in locating a known sulfide ore body in Soap Gulch, Montana. The study develops basis of comparison for the geophysical techniques employed. Ranges of resistivity along the area have been established using interpreted ERT which can help to understand the subsurface distribution of sulfides in the area. A sulfide body was delineated from the survey area corresponding to anomalously low resistivity values on the ERT section, negative SP, and high apparent current density zone in VLF. Depth to the localized ore zone ranges approximately from 10 to 20 m. FDEM data reflect the conductivity distribution of the shallow subsurface (less than 6 m deep); hence, the delineated sulfide zone had minimal contribution to FDEM measurements. The results of the study show that SP, VLF, and ERT methods provide significant information in localizing ore bodies. The survey revealed that the resistivity values obtained from ERT profile corroborate the FDEM, SP, and VLF from the area.     

Permian Calcareous algae from the Khachik Formation at the Ali Bashi Mountains,NW of Iran

Micropaleontological investigations on Permian successions in the NW of Iran based on algae led to the determination of taxa belonging to some families such as Ungdarellaceae (Ungdarella uralica), Gymnocodiaceae (Gymnocodium bellerophontis and Permocalculus sp.), Dasycladales (Mizzia cf. M. yabei), and some microproblematics (Vermiporella nipponica and Pseudovermiporella sodalica). These investigations are mainly focused on the Khachik Formation at the Ali Bashi Mountains. According to the algal community, a lagoon environment is offered for the studied successions.     

Dokhan volcanics of Gabal Monqul area,North Eastern Desert,Egypt: geochemistry and petrogenesis

The Dokhan volcanics are represented by a thick stratified lava flows succession of basalt, andesite, imperial porphyry, dacite, rhyodacite, rhyolite, ignimbrites, and tuffs. These lavas are interbanded with their pyroclastics in some places including banded ash flow tuffs, lithic tuffs, crystal lapilli tuffs, and agglomerates. They are typical calc–alkaline and developed within volcanic arc environment. All rocks show moderate enrichment of most large ion lithophile elements relative to high field strength elements (HFSE). The incompatible trace elements increase from basalt through andesite to rhyolite. The felsic volcanics are characterized by moderate total rare earth elements (REE) contents (162 to 392 ppm), less fractionated patterns {(Ce/Yb)_N = (1.24 to 10.93)}, and large negative Eu anomaly {(Eu/Eu*) = (0.15 to 0.92)}. The mafic volcanics have the lowest REE contents (61 to 192 ppm) and are relatively steep {(Ce/Yb)_N = (3.2 to 8.5)}, with no negative Eu anomalies {(Eu/Eu*) = (0.88 to 1)}. The rhyolite displays larger negative Eu anomaly (Eu/Eu* = 0.28) than those of other varieties, indicating that the plagioclase was an early major fractionating phase. The mineralogical and chemical variations within volcanics are consistent with their evolution by fractional crystallization of plagioclase and clinopyroxene.     

Automated Detection of Coronal Loops Using a Wavelet Transform Modulus Maxima Method

We propose and test a wavelet transform modulus maxima method for the automated detection and extraction of coronal loops in extreme ultraviolet images of the solar corona. This method decomposes an image into a number of size scales and tracks enhanced power along each ridge corresponding to a coronal loop at each scale. We compare the results across scales and suggest the optimum set of parameters to maximize completeness, while minimizing detection of noise. For a test coronal image, we compare the global statistics (e.g. number of loops at each length) to previous automated coronal-loop detection algorithms.     

Climate changes associated with high-amplitude <Emphasis Type="Italic">Sq</Emphasis> geomagnetic variations

When the solar irradiance propagates between the outer magnetospheric regions and the ionosphere, dynamic processes of the magnetosphere-ionosphere-thermosphere system are affected at the lower end of their paths by the interaction of radiation with the neutral troposphere. The main target of this work is to investigate the relationship between the diurnal magnetic field variations resulting from solar activities and the variation in the troposphere temperature. Meteorological and geomagnetic data acquired from different observatories located in Egypt, Portugal and Slovakia in a long-term and daily-term scales were analyzed.     

Spatial and Temporal Variability of Sediment Organic Matter Recycling in Two Temperate Eutrophicated Estuaries

This paper deals with the spatial and seasonal recycling of organic matter in sediments of two temperate small estuaries (Elorn and Aulne, France). The spatio-temporal distribution of oxygen, nutrient and metal concentrations as well as the organic carbon and nitrogen contents in surficial sediments were determined and diffusive oxygen fluxes were calculated. In order to assess the source of organic carbon (OC) in the two estuaries, the isotopic composition of carbon (δ ¹³C) was also measured. The temporal variation of organic matter recycling was studied during four seasons in order to understand the driving forces of sediment mineralization and storage in these temperate estuaries. Low spatial variability of vertical profiles of oxygen, nutrient, and metal concentrations and diffusive oxygen fluxes were monitored at the station scale (within meters of the exact location) and cross-section scale. We observed diffusive oxygen fluxes around 15 mmol m^?2 day^?1 in the Elorn estuary and 10 mmol m^?2 day^?1 in the Aulne estuary. The outer (marine) stations of the two estuaries displayed similar diffusive O₂ fluxes. Suboxic and anoxic mineralization was large in the sediments from the two estuaries as shown by the rapid removal of very high bottom water concentrations of NO _x ^? (>200 μM) and the large NH₄ ⁺ increase at depth at all stations. OC contents and C/N ratios were high in upstream sediments (11–15 % d.w. and 4–6, respectively) and decreased downstream to values around 2 % d.w. and C/N ≤ 10. δ ¹³C values show that the organic matter has different origins in the two watersheds as exemplified by lower δ ¹³C values in the Aulne watershed. A high increase of δ ¹³C and C/N values was visible in the two estuaries from upstream to downstream indicating a progressive mixing of terrestrial with marine organic matter. The Elorn estuary is influenced by human activities in its watershed (urban area, animal farming) which suggest the input of labile organic matter, whereas the Aulne estuary displays larger river primary production which can be either mineralized in the water column or transferred to the lower estuary, thus leaving a lower mineralization in Aulne than Elorn estuary. This study highlights that (1) meter scale heterogeneity of benthic biogeochemical properties can be low in small and linear macrotidal estuaries, (2) two estuaries that are geographically close can show different pattern of organic matter origin and recycling related to human activities on watersheds, (3) small estuaries can have an important role in recycling and retention of organic matter.     

Nuclear geophysical logging for Gondwana coal exploration: a case study at Phulbari Coal Basin, northern part of Bangladesh

Different methods of lithology predictions from geophysical data have been developed in the last 15 years, among which the conventional logs are as follows: sonic, neutron–neutron, natural gamma, and density (backscattered gamma–gamma). This article concentrates on the nuclear geophysical suite, in particular, gamma and gamma–gamma logging, which, to date, provide the most accurate geophysical means of identifying coal seams and estimating their thickness. From the gamma and gamma–gamma logs of boreholes AEN 002, 007, 044, 045, 063, 085, and 105, which were carried out at the Phulbari Coal Basin of Bangladesh, two coal seams—upper and main with two lower seams of limited occurrence and of varying thickness—were identified, together with their regional occurrence.     

Application of VES and TDEM techniques to investigate sea water intrusion in Sidi Abdel Rahman area, northwestern coast of Egypt

The present study is an approach to detect the sea/freshwater interface in Sidi Abdel Rahman area, northwestern coast of Egypt using both vertical electrical sounding and time domain electromagnetic. The measured vertical electrical soundings are interpreted in 1D and 2D manner. The 1D inversion is carried out using the commercial software (RESIST), whereas 2D resistivity nonlinear iterative inversion scheme based on the finite element technique and regularization method was used. The time domain electromagnetic stations are interpreted using Temixxl-4 software by Interpex Ltd. To have the advantages of the vertical electrical sounding in shallow depths and time domain electromagnetic in deep depths, a joint inversion algorithm is applied for the electric profile and the nearby electromagnetic profile. Very low resistivity values have been observed near the coast as well as a considerable salt/fresh water interface. The tip-top portion of the interface lies approximately 1,000 m from the shore line.     

A typical weathering profile of granitic rock in Johor,Malaysia based on joint characterization

Arabian Journal of Geosciences - One of the most important challenges in the study of slope stability, foundation, and excavation in rocks is understanding the weathering states. This issue is more...