The effect of uniaxial compression in the behaviour of remanent and induced magnetizations for basaltic rocks from the western Sinai Peninsula, Egypt

Seventy oriented basaltic samples were collected from six sites from the Wadi Budra and Farsh El Azraq areas of the west-central part of Sinai. Rock magnetic properties such as Curie temperatures and hysteresis parameters, as well as microscopic observations, point to magnetite as the main carrier of the remanent magnetization. The stress sensitivity of basaltic rocks is relatively low. High stress produces an increase in the remanent and induced magnetizations perpendicular to the applied stress axis and a decrease parallel to it. The change of magnetization during stress action ranges from 1.1% to 3.5% for a stress of 100?bar. The differential total magnetic intensity field with time (within 2?years) was observed through 80 magnetic observation points set up on both sites of the basaltic sheet at the studied area. The observed temporal variations of magnetization can be interpreted as stress loading parallel to the regional stress field in the order of 50?±?20?bar, according to the stress sensitivity of the precursor basalt.     

Quasinormal modes and Hawking radiation of a Reissner-Nordström black hole surrounded by quintessence

We investigate quasinormal modes (QNMs) and Hawking radiation of a Reissner-Nordström black hole surrounded by quintessence. The Wentzel-Kramers-Brillouin (WKB) method is used to evaluate the QNMs and the rate of radiation. The results show that due to the interaction of the quintessence with the background metric, the QNMs of the black hole damp more slowly when increasing the density of quintessence and the black hole radiates at slower rate.     

Origin of Quartz Cement in the Paleogene Sandstone Reservoir of Shahejie Formation, Bohai Bay Basin, China

The precipitation of authigenic quartz plays a significant role to reduce the reservoir characteristics and enhance the stiffness of the rock.The Es₁ sandstone of Shahejie Formation is acting as a significant hydrocarbon producing rock in the Nanpu Sag.Various methods like thin section petrography,cathodoluminescence(CL),scanning electron microscope(SEM,with EDS),and electron microprobe analysis has been used to reveal the origin of quartz cement as well as to evaluate the effect of quartz cement on reservoir quality.The studied sandstone is classified as immature to mature feldspathic litharenite and lithic arkose and consists of quartz,feldspar,rock fragments and micas.Petrographic studies and SEM analysis shows that the authigenic quartz is acting a significant cement that reduces the reservoir quality.Whereas clay minerals(kaolinite and mixed layer illite to smectite)are dominant in the Es₁ sandstone,that can reduce the reservoir quality.SEM,CL and thin section analysis reveal that there are two stages of quartz cement in the studied samples;that are pore filling authigenic cement and quartz overgrowth cement.Fluid inclusion homogenization temperatures shows that stages of quartz cement were developed with continuous process from 70℃ to 130℃.Quartz cements were generally originated from I/S reaction,feldspar dissolution,conversion of rock fragments and pressure solution.Feldspar dissolution(K-feldspar)and kaolinite to illite reaction is an insignificant silica source for the silica cement which is internally precipitated in a close system with diffusion transporting mechanism.Overall,quartz cement significantly enhance the rock strengthen and brittleness effectively as well as it reduce the overall reservoir quality.     

Modeling in situ benzene bioremediation in the contaminated Liwa aquifer (UAE) using the slow-release oxygen source technique

Dissolved benzene was detected in the shallow unconfined Liwa aquifer, UAE, which represents the main freshwater source for the nearby residence Bu Hasa camp area. The main source of this contamination is believed to be the rejected water released from Bu Hasa liquid recovery plant. In this paper, a finite element model (METABIOTRANS) is used to simulate the fate and transport of the dissolved benzene plume in Liwa aquifer. Different remediation scenarios were simulated in which the slow-release oxygen source (SOS) technique is utilized to minimize benzene concentrations at the nearest camp supply wells downstream of the contamination zone. Results of the remediation scenarios show that the highest biodegradation rates occur when the oxygen source is placed near the plume center; where higher benzene concentrations exist. The nearest oxygen release source to the contamination zone caused higher stimulation to bacterial growth than further down-gradient oxygen sources. It also exhibited longer resident time of oxygen in the aquifer; and therefore, yielded higher reductions in benzene concentrations. However, using one central SOS proved to be insufficient as contaminant escaped laterally. Additional four transverse oxygen sources were necessary to capture benzene that laterally spread away from the contamination zone. These lateral SOSs were essential to reduce benzene concentrations at the supply wells that are located at the plume fringes. Finally, it was found that increasing oxygen release from one source did not always improve remediation; and that using several SOSs with lower release rates could be a more practical approach to enhance benzene biodegradation in the aquifer.     

Quasinormal modes of scalar perturbation around a quantum-corrected Schwarzschild black hole

In this paper, we evaluate quasinormal modes (QNMs) of scalar perturbations around a quantum-corrected Schwarzschild black hole by using the third order Wentzel-Kramers-Brillouin (WKB) approximation method. The results show that due to the quantum fluctuations in the background of the Schwarzschild black hole, the QNMs of the black hole damp more slowly when increasing the quantum correction factor (a), and oscillate more slowly.     

Coral bleaching and habitat effects on colonisation of reef fish assemblages: An experimental study

Degradation and mortality of corals is increasing worldwide and is expected to have significant effects on coral reef fish; hence studies on these effects are essential. In the present study, a field experiment was set up within Mafia Island Marine Park in Tanzania (East Africa) to examine the effects of bleaching and habitat structure on colonisation of coral reef fish assemblages. Live and bleached staghorn coral Acropora formosa was transplanted onto plots in a site dominated by sand and rubble, and the experimental design comprised of three treatments: live coral, bleached coral and eroded coral rubble. There was an immediate increase (within 24 h) in fish abundance and diversity in the two treatments with standing corals. Overall, live and bleached coral plots showed similar effects, but differed from the eroded coral plots which had a much lower abundance and diversity of fish. In general, fish species diversity changed with time over the study period while fish abundance did not. Multivariate analyses showed that while there were differences in fish assemblage structure between standing corals and the eroded coral treatment, there was neither a difference between live and bleached coral treatments nor any temporal effects on fish assemblage structure. Our findings suggest that physical structure and complexity of habitat have stronger effects on colonisation of reef fish assemblages than changes in coral health (such as bleaching) which do not affect coral structure. This may have important implications for appropriate coral reef management.     

Gravitational potential energy of interpenetrating spherical galaxies in Hernquist’s model

Hernquist’s (1990) mass model for spherical galaxies and bulges described by the deVaucouleur’s profile gives analytical expressions for the density profile and the potential. These have been used to derive a simple and exact analytical expression for the gravitational potential energy of a pair of interpene-trating spherical galaxies represented by this model. The results are compared with those for polytropic and Plummer models of galaxis.     

Error analysis of the NGS’ surface gravity database

Are the National Geodetic Survey’s surface gravity data sufficient for supporting the computation of a 1 cm-accurate geoid? This paper attempts to answer this question by deriving a few measures of accuracy for this data and estimating their effects on the US geoid. We use a data set which comprises ${\sim }1.4$ million gravity observations collected in 1,489 surveys. Comparisons to GRACE-derived gravity and geoid are made to estimate the long-wavelength errors. Crossover analysis and $K$ -nearest neighbor predictions are used for estimating local gravity biases and high-frequency gravity errors, and the corresponding geoid biases and high-frequency geoid errors are evaluated. Results indicate that 244 of all 1,489 surface gravity surveys have significant biases ${>}2$  mGal, with geoid implications that reach 20 cm. Some of the biased surveys are large enough in horizontal extent to be reliably corrected by satellite-derived gravity models, but many others are not. In addition, the results suggest that the data are contaminated by high-frequency errors with an RMS of ${\sim }2.2$  mGal. This causes high-frequency geoid errors of a few centimeters in and to the west of the Rocky Mountains and in the Appalachians and a few millimeters or less everywhere else. Finally, long-wavelength ( ${>}3^{\circ }$ ) surface gravity errors on the sub-mGal level but with large horizontal extent are found. All of the south and southeast of the USA is biased by +0.3 to +0.8 mGal and the Rocky Mountains by $-0.1$ to $-0.3$  mGal. These small but extensive gravity errors lead to long-wavelength geoid errors that reach 60 cm in the interior of the USA.     

Environmental impact assessment of a new nuclear power plant (NPP) based on atmospheric dispersion modeling

The US Environmental Protection Agency’s short-range atmospheric dispersion model (AERMOD 12345) is a good candidate for radiological dose calculations to the general public and the environment. It advanced capability should provide better confidence in the accuracy of offsite dose and risk assessment. The code has been used to compute the scaling factors for air concentration and ground level deposition of fission products based on routine and hypothetical accident releases from the NPP site in Geregu, Nigeria (7°33′N, 6°41′E). All computations were within the 16 km emergency planing zone of a generic reactor design considered by the study. The scaling factors have been used to assess the potential environmental risk of the NPP using an integrated approach to the assessment and management of environmental risks from ionizing radiation (D-ERICA). Obtained results should provide baseline information for decision making in terms of operation license provision for the pioneer NPP.     

Intensification of future heat waves in Pakistan: a study using CORDEX regional climate models ensemble

Future trends in the occurrence of heat waves (HW) over Pakistan have been presented using three regional climate models (RCMs), forced by three different global climate models (GCMs) runs under RCP8.5 scenarios. The results of RCMs are obtained from CORDEX (Coordinated Regional climate Downscaling EXperiment) database. Two different approaches for the assessment of HWs are defined, namely Fixed and Relative approaches. Fixed approach is defined for a life-threatening extreme event in which the temperature can reach more than 45 °C for a continuous stretch of several days; however, Relative approach events may not be directly life-threatening, but may cause snow/ice melt flooding and impact on food security of the country in summer and winter seasons, respectively. The results indicate a consistent increase in the occurrence of HWs for both approaches. For the Fixed approach, the increase is evident in the eastern areas of Pakistan, particularly plains of Punjab and Sindh provinces which host many big cities of the country. It is argued that the effect of HWs may also be exacerbated in future due to urban heat island effect. Moreover, summer time HWs for Relative approach is most likely to increase over northern areas of the country which hosts reservoirs of snow and glacier, which may result in events like glacial lake outburst flood and snow/ice melt flooding. Furthermore, the increase in winter time HWs for Relative approach may affect negatively on the wheat production, which in turn can distress the overall food productivity and livelihoods of the country. It is concluded that this study may be a useful document for future planning in order to better adapt to these threats due to climate change.