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The present work is based mainly on core rock samples investigation of CSS-38 well, northwest of Gulf of Suez, Egypt. The cores cover the whole the South Gharib Formation (upper Miocene). The stratigraphic succession of the Gulf of Suez includes three mega units, recorded from old to young as pre-rift, syn-rift, and post-rift sediments. The syn-rift sediments from old to young are Nukhul, Rudies, Kareem, Belayim Equivalent, South Gharib, and Zeit. The core samples reveal that South Gharib Formation is not a good reservoir. It consists of sulphate-rich beds with few carbonates intercalation, laminated dolomitic limestone and marly limestone. Patchy oil staining is detected in the thin streaks and basal laminated dolomitic limestone. The microfacies are found to be evaporites, carbonates, calcareous marl, and calcareous claystone. Evaporites microfacies are considered the most frequent microfacies. Gypsum and anhydrite are generally represented by nearly equal distribution with parallel variation in content. The core samples differentiated South Gharib Formation into seven zones of depositional environment; they are arranged from base to top as shallow sub-tidal, shallow lagoonal, intertidal, shallow lagoonal, intertidal, shallow lagoonal, and supra-tidal Sabkha cycles. Some samples from South Gharib Formation were measured electrically. We will try to highlight interrelations between electrical (conductivity, permittivity, and impedance) and petrophysical properties with petrography and mineral composition. Electrical properties were measured with a frequency range from 10 Hz to 100 kHz. The dielectric constant decreases with increasing frequency and increases with increasing conductor content (up to percolation threshold). The conductivity increases with the increase in conductor content and with increasing frequency. Many parameters can combine to affect electrical properties. The present research is a trial to relate the surface to subsurface measurements.

Clayey deposits' detailed mineralogical, electrical, and ceramic properties (El-Sheikh Fadl, El-Minya, Egypt) were determined to determine their potential use in the ceramic industry. The AC electrical properties of ceramic clay mineral mixtures change as their chemical composition (from clay to ceramic) and firing temperature change. The samples were electrically measured at room temperature as natural crude clay and then after firing at various temperatures (22, 1000, 1050, 1100, 1150, 1200 and 12500C). The measurements (electrical properties, X-ray, SEM, petrography, major and minor chemical characteristics, and chemical composition) show that the chemical composition (from clay to ceramic) and firing temperature have a significant impact on the mixture behavior and show how the properties of clay-ceramic products can be changed and improved. As temperature rises, so do conductivity and dielectric constant. Furthermore, water saturation (or humidity) affects the electrical properties significantly. Generally, the increase in ore mineral charges causes an increase in electrical properties. Excess ion exchange between grains, surface charge displacement, and diffusion polarization are all control mechanisms. The purpose of this research is to show how the electrical properties of ceramic clay mineral samples change with composition and temperature and to enhance the properties of the clay for industrial use.

Understanding basic petrophysical properties may enhance the recovery of residual oil saturation and help in reservoir management. Reservoir oil saturation is the fraction of the porosity of a zone occupied by oil. The trapping may increase with the increase of porosity. Oil reservoirs represent a significant fraction of the reservoirs in the world-wide. We try to make a reservoir evaluation using petrophysical analysis of well logs and core samples at Issaran Field, South Gharib Formation, West of the Gulf of Suez, southeast Egypt. This area was heavily influenced by the structural setting of the Gulf of Suez’s central province, which is characterized by major SW dipping faults with a regional stratigraphic dip toward the NE. The high structural blocks are located in the center of the research area, and the low structural region is located in the southwest. South Gharib Formation is primarily composed of carbonates with few sulfates that grade upwards into sulfate-rich beds in the upper part. Laminated dolomitic limestone, with evaporites grades, changes downward into laminated dolomitic limestone and marly limestone, in the lower part. The anhydrite and dolomite units near the bottom have spotty oil stains. The structural setup is continued by the spread and deposition of this formation. We try to make analytical examination, of some reservoirs, accomplished by analyzing both well log data and core rock samples, vertically and laterally. According to the study of the horizontal permeability to vertical permeability ratio (Permeability anisotropy; $$\lambda_{k}$$ λ k ), the reservoir is laminated rock ($$\lambda_{k} = 1.1 - 5$$ λ k = 1.1 - 5 ), with a few data samples nearly isotropic ($$\lambda_{k} = {1 \mathord{\left/ {\vphantom {1 {1.1}}} \right. \kern-\nulldelimiterspace} {1.1}}$$ λ k = 1 / 1.1 –1.1) and fractured ($$\lambda_{k} = {1 \mathord{\left/ {\vphantom {1 {2.5}}} \right. \kern-\nulldelimiterspace} {2.5}}$$ λ k = 1 / 2.5 –1/1.1). Reservoir data histograms show that the most typical values of the data are 20–30% oil saturation and 7–10% porosity. The net-pay zone varies from four to 71 feet at different depths (897–1414 feet). Due to low shale content, water saturation, high effective porosity values, hydrocarbon saturation, may show higher net-pay thickness. These results may help to enhance the oil recovery. The area in the middle of the research area is suggested for future hydrocarbon development and using more petrophysical analysis.

Some electrical, geochemical, and mineralogical investigations and analyses were made on some cubic oxidized Pyrite crystals (Gabal El-Sibai). Samples (chemically) are constituted from Fe2O3, SiO2,...

Alumina catalysts modified by platinum and nickel nanoparticles were prepared by chemical reduction and microwave stimulated techniques, and their relationship to electrical properties was studied. The structural and textural properties of such nanocatalysts were examined by XRD, DSC-TGA, N2 physisorption and TEM. The electrical properties of nanoparticle catalysts as functions of the increase of metal concentration are discussed. The electrical measurements were performed in the frequency domain. Three mechanisms are suggested for the electrical behaviour of all systems. The increment observed in conductivity with extra amounts of metal may be due to the expansion in the movement ability of uncontrolled transporters that disperse in the pores of the material. Upon arrival at the electrodes, these transporters evacuate their charge and, accordingly, increase the dispersion impedance. The results show high thermal stability up to 1000 °C. The isotherms obtained display almost the same behaviour for samples prepared by both the microwave and the chemical method. This may be linked to high-dispersion particles and their nanoscale metal concentration. The XRD results exhibit small diffraction line characteristics.

Background The pattern and impact of burnout among the medical staff are not yet well defined. However, the consequences of burnout are not limited to the healthcare providers but also may affect their family, colleagues and patients in a negative manner. We aimed to assess the characteristics and predictors of burnout among health professionals at two large tertiary hospitals. Methods We conducted a cross-sectional study during the period from July 2018 to 31 December 2018. Data, via Maslach Burnout Inventory survey, were collected from physicians and other healthcare workers in two hospitals. Results A total of 624 responses to questionnaires were analysed. Half of the respondents were physicians, and men constituted the majority. About 10% (95% CI, 7.8 to 12.5) of the respondents satisfied the criteria of burnout. Emotional exhaustion (EE) was observed in 45.7%, depersonalisation (DP) in 26.9% and personal accomplishment (PA) in 41.2% of the respondents. There was a positive correlation between EE and DP (r=0.627, p=0.001), and a weak negative correlation between DP and PA (r=−0.195, p=0.001). Young age, less experience, trauma surgery, lack of habits and getting depressed ≥1 time/week were predictors of burnout. Conclusions Burnout affects one-tenth of the health professionals in the tertiary hospitals in Qatar. Physicians are more likely to have higher DP and lower PA, whereas nurses prone to have higher EE. In this study, no gender discrepancy is appreciated and the junior medical staff is at a higher risk of burnout.

Electrical features of a humid kaolinite specimens was measured at various pressures and at various frequencies . Surface impedance is supposed on kaolinite particle surfaces (from humidity), chemi...

Six glass compositions based on basaltic rocks and some industrial wastes, Batches were melted in an electric furnace at temperature 1400 °C for 2 h and then casted into rods and discs shapes. Many important techniques were used in the present study including X- ray fluorescence, thermal expansion, dielectric properties, indentation micro hardness, bending strength, density and chemical durability, The expansion coefficient in the temperature range 25–300 °C lies in the range between 48.78 to 59.76 × 10−7 /°C and the temperatures of Tg started at 668.79 °C and ranging between 668.79–632.34 °C and Ts started at 737 °C and lies in the range and 737–711.6 °C respectively. The lower expansion glasses have higher transition and softening temperatures and vice versa. Bending strength and Vickers micro hardness show a gradual decrease from 118 to 56 MPa and 6120–4020 MPa respectively with increasing cement dust content. In the same time the density increases from 2.79 to 2.96 g/cm3 by increasing cement dust content.

The present work is conducted in the industrial district south of greater Cairo (ElTabbin area). Some heavy metals like Mn, Co, Ni, Cu, Zn, Pb, Cr, Ba, Cd, Mo were determined in polluted soils during May, 2018. At the study area, results displayed that average heavy metals concentrations differ considerably. They are decreased from Mn to Cd (Mn > Ba > Zn > Cr > Ni > Co > Pb > Cu > Mo > Cd). The average ranges as follows: Mn (255.8–31448.2 ppm); Ba (145.2–17545.6 ppm); Zn (53.3–1589.9 ppm); Cr (26.7–311.3 ppm); Ni (29.7–114.1 ppm); Co (13.2–39.8 ppm); Pb (5.7–77.4 ppm); Cu (7.6–35.2 ppm); Mo (0.1–15.9 ppm) and Cd (0–1.5 ppm), respectively. ElTabbin area has heavy manufacturing activity at Egypt. ElTabbin area was chosen as a model for that contamination. Electrical characteristics of some specimens from El- Tebbin area, Egypt, were taken and measured electrically at frequency range (10−3 to 100 kHz). Major and heavy elements were measured at specimens. Specimens were classified to three categories according to electrical properties. The changes were the consequence of change in minor and major mineral composition in the specimens. Electrical properties were able to recognize different specimens according to different levels of contaminants in the specimens. Texture, tortuosity and minor elements of heavy elements are the controlling factors that control electrical properties at specimens. High values concentration of Mn, Ni, and Zn heavy elements increases conductivity while the high concentration of Pb and Cu heavy elements decreases the conductivity. The mixing up of these different minor and major minerals and elements at specimen may lead to the change of conductivity values. The main controlling factors of the major elements are the Fe2O3 and SiO2, while the main controlling factors of the minor elements are the Mn and Pb. Our main objective is to study mixing up of the different minor and major minerals and elements on electrical properties of rocks., Physical chemistry, Geochemistry, Geology, Geophysics, Earth sciences, Hydrology, Condensed matter physics, Physics methods electrical conductivity, Dielectric constant, Impedance, Mineralogy.

The variation of salinity from Lake Quaroun, Fayium, Egypt may be a good indicator to differentiate between different levels of basins that have different concentrations of salts. There are four ponds (from the lake directly) that have different concentrated impurities and different soluble salts. According to the solubility product, some of the carbonate salts in addition to other impurities precipitate in the first pond. The rest of the carbonate minerals precipitate in second pond. Sulphate salts will precipitate in the third pond. Finally, chloride salts will precipitate in the fourth pond in the form of gel crystals. These chloride salts is pumped to plants to produce the nardite salt. The electrical properties were used in this study as a new tool to differentiate between the pollution of waste water and to define the pollution process. In addition, geochemical analyses, for bottom sediments, in the four ponds were done using XRF. Electrical properties were measured in frequency range of 42 Hz–5 MHz at room temperature. Slight changes were noticed between the samples taken from the different bonds. The changes in the electrical properties were found to be the result from changes in mineralogical composition in the different bonds. Most of the samples were composed of grains of clay-size fractions. The dielectric constant, generally, was found to decrease with discontinuous conduction paths and with frequency. Electrical conduction, usually, was found to increase with the increase of conductor continuous paths and with frequency.

Nickel oxide thin films were obtained by a cost-effective chemical spray pyrolysis approach on glass substrates using nickel chloride as starting precursor with different deposition times. The X-ray diffraction investigation indicated that the obtained films were polycrystalline cubic structure with preferred orientation along (111) plane. Scanning electron microscopy images for sprayed NiO layers at deposition time of 5 and 10 min exhibit a porous structure with randomly oriented honeycomb like morphology. The optical direct band-gap energy Eg of sprayed NiO films was around 3.4–3.5 eV for all deposited samples and optical transmittance decreases with increasing the deposition time. Gas sensing performance was tested for the detection of nitrogen dioxide (NO2) at different operating temperatures and NO2 concentrations. It was found that the sprayed NiO thin film at deposition time of 5 min shows the maximum sensitivity of 57.3% for 20 ppm NO2 at 200 °C as operating temperature with good stability and selectivity. This study suggests that the sprayed NiO thin film is a good candidate material for NO2 detection at a relatively low operating temperature.

Aim: Identification of BRCA1/2 mutations in Breast Cancer (BC) patients may help in providing genetic information to customize the therapeutic management of patients. Assessing liquid biopsies for BRCA1/2 somatic mutations could overcome the limitation of information gained from tissue biopsy. Consequently, this study aimed to identify the frequencies of pathogenic BRCA1 & BRCA2 somatic mutations in both liquid and tissue biopsies in Egyptian BC patients. Material and methods: The study was conducted on 45 BC patients. Liquid and tissue biopsies were collected from each patient and they were profiled for BRCA1/2 mutations using next generation sequencing (NGS). Qiaseq UMI-based targeted panel was used for performing libraries. Ion proton platform was used for sequencing. The detected genetic variants at depth of coverage 500x were annotated against Cosmic, dbSNP, and Exac all databases. Polyphen-2, Sift prediction tools and Clinvar database were used to detect the biological function of the detected variants using IVA software. Results: Variants analysis revealed that Among 45 patients, 37 (82.2%) patients were carrying one or more damaging BRCA1/2 somatic mutations. A total number of BRCA1/2 somatic variants detected was 24 and they were classified to 13 pathogenic, 7 likely pathogenic and 4 benign variants. Tissue and plasma samples of BC patients were found to harbor one detectable pathogenic somatic mutation in BRCA1 gene; c.1961delA with frequencies of 75.5% vs 17.7%, respectively. While, both samples had 8 detectable pathogenic BRCA2 somatic variants, the top 3 most frequent mutations among them were: c.5351delA (82.2% vs 40%), c.2957delA (75.56% vs 42.2%) and c.9253delA (68.89% vs 24.4%). One deleterious variant was detected merely in tissue sample; c.8940delA (55.5%). Whereas, 3 damaging variants were detected merely in plasma samples: c.8053delA (22.2%), c.6762delT (20%), c.4631delA (6.6%).Likely pathogenic BRCA2 somatic variants were also identified in both samples; c.7177delA (71.1% vs 53.3%) and c.10248delA (37.7% vs 11.1%). Moreover, 5 likely pathogenic variants were merely found in plasma samples. The most frequently detected variant among them was c.1114A>C (42.2%). Our data showed that exon 10 in BRCA1 and exon 11 in BRCA2 are the most affected exons as they harbored the most frequent detected pathogenic variants. Conclusion: Our preliminary results showed the most frequent pathogenic and likely pathogenic BRCA1/2 somatic mutations in liquid and tissue biopsies in Egyptian BC patients. This data may help in developing personalized targeted therapies that efficiently target the BRCA1/2 mutations. Citation Format: Mai M. Lotfy, Amira Salah El-Din Youssef, Auhood Nassar, Mahmoud Kamel, Zeinab K. Hassan, Amany Abd-Elhameed Abou-Bakr, Ahmed Farahat, Mohamed M. Gomaa, Abdel Rahman N. Zekri. Identification of Somatic BRCA1/2 mutation profile in tissue-based and liquid biopsy-based next generation sequencing in Egyptian patients with breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2175.

Few reports are displayed on relation between electrical characteristics of rocks and pressure. The objective of this article is the interpretation and modeling of experimental kaolinite specimens under various pressures (0- ~4.5 Kb, at ~50% humidity), and frequency (10 Hz - 10 kHz). Complex impedance measurements were performed for samples. At low pressure range (≤1 Kb); the reliance of the experimental capacitance and conductance on the pressure displays a considerable dependence on the applied pressure. Constant conductances are present at higher pressures. With rising pressure the capacitance decreases. These behaviors are interpreted by percolation theory. With the rise of pressure, the pore spaces decrease and conducting paths between grains increase. The behavior of capacitance and conductance with frequency is comparable with other reports as it will be discussed. Due to existence of water, it was supposed there is impedance at the kaolinite grain surfaces. Also, it was supposed the presence of charge movement and chemical reaction at surface grains. Renormalization group model as a member of the percolation group methods was used to interpret and model experimental data. We developed a model using four phases to analyze the probable deviations in electrical features that may control pressure.

Dolostones of Um Bogma and Um Gheig Formations were studied using mineralogical and geochemical characterizations. The present work has tried to identify the origin, environment, pollution, and their electrical properties for the two formations. Also, the environmental geochemistry that resulted from the trace element concentration is examined here and we will try to differentiate between them. The study samples are fissile and highly fossiliferous dolomites. The two formations are classified as dolostones and nearly ordered. The mineralogy and geochemistry studies indicated that the two formations were formed under mixing zone at the near-surface oxidizing environment. The diagenetic features of both formations demonstrate many processes with clear effects. Dolostones of both formations may be precipitated from two different solutions. Meteoric water is the main supply, while the other solution may be resulted from the deep hydrothermal solutions that come up from deep faults. The distribution of Sr and Y content of dolostones at Um Bogma Formation indicated that they are precipitated at 110–150 °C, while those in Um Gheig are deposited at

Realization of electrical and petrography of rocks is absolutely necessary for geophysical investigations. The petrographical, petrophysical and electrical properties of sandstone rocks (El-Maghara Formation, North Sinai, Egypt) will be discussed in the present work. The goal of this paper was to highlight interrelations between electrical properties in terms of frequency (conductivity, permittivity and impedance) and petrography, as well as mineral composition. Electrical properties including (conductivity and dielectric constant) were measured at room temperature and humidity of (∼35%). The frequency range used will be from 10 Hz to 100 kHz. Slight changes between samples in electrical properties were found to result from changes in composition and texture. Electrical properties generally change with grain size, shape, sorting, mineralogy and mineral composition. The dielectric constant decreases with frequency and increases with increasing clay content. The conductivity increases with the increase in conductor channels among electrodes. Many parameters can combine together to lead to the same electrical properties. The samples are mainly composed of sand with clay and carbonate.

Electrical properties of some sandstone rocks (conductivity and dielectric constant) were investigated as a function of frequency (100 Hz to 100 kHz). Such heterogeneous specimens contain semiconducting constituents (silt and clay) and insulating constituents (sand, air, and carbonates). A theoretical pseudo-random renormalisation group method was used to predict the electrical properties of such random mixture. Four phases were used in the model to consider the detailed texture of the constituent materials. The measured electrical properties (conductivity and dielectric constant) versus frequency of these samples were analysed to predict the texture or connections of these four phases. From the analysis, these four phases were suggested to be (1) carbonates, (2) sand coated with clay and coated with air, (3) carbonates coated with clay and coated with air, and (4) pure sand. The forward problem predicts the electrical properties versus frequency using the pseudo-random renormalisation group method for certain concentrations of the constituent materials distributed among the random four phases. The forward model is used to fit the measured response to obtain the expected concentrations of rock constituents in the proposed four phases using a parameter search method (inverse problem). The obtained accordance between the experimental and modelled characteristics in much of the frequency band used suggests that the pseudo-random renormalisation group method with the supposed four phases reasonably represents the main mineralogical composition of the rock.

Influence of TiO2 and Ta2O5 on crystallisation for ceramic based on Li–Ca–Al–Si was studied. Sintering of glass-ceramics leads to the formation of β-eucryptite, anorthite and Ca-olivine. These phas...

Electrical properties of carbonate rocks from North Sinai, Egypt, were investigated experimentally in the frequency domain (100 Hz to 100 kHz). Changes between electrical properties were attributed to changes in mineral composition and texture of samples. Asymmetric mixture laws cannot describe electrical behavior of heterogeneous rocks in the mentioned frequency range. A theoretical pseudo-random renormalization group (PRNG) method was developed to model electrical behavior of rock mixtures. The main goal of this paper is to make forward and inverse modeling using PRNG method for the electrical properties as a function of frequency for carbonate rocks with texture. In PRNG method four phases were used to take into account the texture in the samples. Four phases are the best that we could use in the model. We are trying to increase the competence of the model in the near future. In these four phases mainly conducting constituents (silt and clay) and mainly insulating constituents (sand, air and carbonate) may coat each other. With appropriately chosen coatings for the four phases, the PRNG method can reasonably model the electrical properties of the samples in the measured frequency range. Thus, an inverse problem is used to find the detailed structure of the four phases, which leads to the measured electrical properties of the samples, taking into account the measured concentrations of the different constituents of the samples. The inverse problem is based on minimizing the misfit between the measured frequency response for the conductivity and the dielectric constant and those obtained theoretically from the PRNG method. It was shown that the texture plays an important role in determining the A.C. electrical properties of heterogeneous samples.

Effects of temperature, frequency, and molarity on electrical conductivity have been studied for sand-clay samples contaminated by water and gasoline. Electrical properties change according to frequency, contaminant type, and structure of components at the sample. A comparison was performed for these contaminated sand-clay samples. Changes of dielectric constant (is an element of '), conductivity (sigma), and complex impedance with frequency (0.1 Hz 2x10(7) Hz), with different contaminant concentration (at constant room temperature similar to 21 degrees C), have been studied. The sand-clay samples were mutually wetted gradually using gasoline and distilled water. Then, electrical properties were measured sequentially. Water is 30a conductive liquid and the contaminant gasoline is an insulator. The experimental results indicate that conductivity of samples increases with increase of water concentration while with the additions of the contaminant gasoline, the sample conductivity decreases. The permittivity decreases with reduction of conductive links between grains and with the progressive increase of frequency. The conduction of electrical conductivity, commonly, increases with increase of connectivity between different links between grains. Also, conduction increases with progressive increase of frequency. Comparison of both outcomes from lab electrical measurements gives 30a speculation about the picture in the field.

The effect of CaO∖SiO2 molar ratio on the electrical properties of some glass materials was examined, using the impedance spectroscopy, at different frequency ranges, from 100 Hz up to 5 MHz. Also, a trial was accomplished to study the influence of CaO∖SiO2 molar ratio on some physical properties such as density, micro-hardness and bending strength. Six glass batches, based on Sinai basaltic rocks and bypass cement dust, were prepared with different CaO/SiO2 molar ratios (0.2–0.93 mol %). Accordingly, the electrical properties (conductivity dielectric constant and dielectric loss) of these samples show noticeable change. Electrical results show that the samples with relatively low (CaO/SiO2) molar ratio have relatively higher electrical conductivity, compared to the other samples with higher (CaO/SiO2) molar ratios, at different frequencies. Also, at the same time, the bending strength and Vickers micro-hardness show a gradual increase from 56 to 118 MPa and from 4020 to 6120 MPa, respectively, with decreasing CaO/SiO2 molar ratio. The density of the samples shows a successive increase from 2.79 to 2.96 gm/cm3 with the successive additions of bypass cement dust.

Detailed mineralogical and geochemical studies were carried out on the middle members of the black shales of the Duwi Formation (Quseir–Safaga province) to define their source rock, paleo-weathering, pollution impact and provenance of the sources. The studied black shales are highly fossiliferous and fissile. They are texturally classified as phosphatic marly mudstone microfacies. The black shale mineral composition is mainly composed of calcite, apatite, quartz, pyrite and clay minerals. The average values of Cu, Ni, Zn, Cr, V, As and Se and the ratios Rb/Sr and Cr/Ni in black shale are enriched compared to those of the Post-Archean Australian Shale (PAAS) values. Electrical properties of samples were measured using a non-polarizing electrode, at room temperature (∼18 °C), and relative atmospheric humidity of (∼35%), in the frequency range from 42 Hz to 5 MHz. The changes in electrical properties were argued to be due to the change in mineral composition. Generally, the electrical properties of rocks are changed due to many factors such as grain size, mineral composition, grain shape and inter-granular relations between grains. The dielectric constant decreases with frequency, and increases with conductor concentration. Also, the conductivity increases with the increase of conductor continuous paths between electrodes.

Nickel oxide thin films were prepared by chemical bath deposition (CBD) and by chemical spray pyrolysis from the same precursor onto glass substrate. The sprayed NiO thin films are polycrystalline in cubic phase structure with (111) preferred orientation. While the chemical bath deposited as a nickel hydroxide phase and transfer to polycrystalline NiO with annealing. The annealed CBD-films are polycrystalline NiO with cubic phase structure and preferred orientation (200). Sprayed and CBD-NiO films have optical transmittance in the visible region 70 and 46 %, respectively. Sprayed and CBD-NiO thin films have optical band gap 3.54 and 3.62 eV, respectively. Sprayed NiO thin films can be used as transparent materials in invisible electronics applications.

A frequency-domain membrane polarization impedance formula was suggested previously by Marshall and Madden for a sequence of ion selective and non-selective regions of equal cross-sections. We generalized the formula for the case of non-equal cross-sections and small Debye lengths (common case). This formula is a simplification of a general analysis of the impedance, given by Buchheim and Irmer, which is tedious for computations and does not give physical insight into the process. The obtained results are physically consistent for the effect of the different cross-sections on the limiting resistance at high frequencies. It is, also, consistent in behaviour with the chargeability formula given by Titov. The impedance model considering regions of non-equal cross-sections may be useful for modeling complex impedance of partially and fully water-saturated rocks. Our study also gives, in detail, the essential equations not given in Buchheim and Irmer derivation, while the lengthy intermediation steps are omitted. Some typing errors in the equations of the previous derivation are rectified. Our approach and formula for the impedance is more rigourous than the formula given by Bucker and Hordt.

Chemical spray pyrolysis is utilized to deposit ZnO thin films with varied vanadium (V) contents, offering a simple, low cost and large-scale production deposition process. The effect of introducing V on structural, morphological, optical, electrical and magnetic properties of ZnO thin films is studied. XRD measurements reveal single phase ZnO polycrystalline layers with hexagonal wurtzite structure and high texturing along {002} plane. The incorporation of V into the ZnO lattice is confirmed through the XRD peaks shift towards a higher angle. Further, the SEM micrographs indicate morphological transformation from hexagonal nanoplates to spherical particles when increasing the V content from 2% to 10% nominally. All films are optically transparent in VIS and NIR spectral regions and the optical transmittance is strongly decreasing with increasing the V percentage. The magnetic measurement data shows paramagnetic behavior for the ZnO layer doped with 2% V while ZnO layer doped with 10% V shows a small ferromagnetic behavior. Additionally, the magnetoresistance measurement at 1.6 T shows positive values at room temperature and increased from 6% to 12% when increasing V amount.

The Electrical properties of substances respond quickly to slight changes according to the manner at which particles or grains are dispersed everywhere in the material (texture). Also, they react quickly to their conductor component concentrations. In this article, we will try to preserve the homogeneity of specimens. So, the sample elements (pure sand and pure hematite) are crushed separately, and different successive hematite (conductor) concentrations (East Aswan, in the Eastern Desert, Cairo, Egypt) mixed with pure sand. Different homogenous combinations and quantities of hematite put together, and electrical properties were measured. Measurements made for electrical properties at dry state condition at constant temperature (~20 °C). The frequency range used was 0.1 Hz - 10 5 Hz. The electrical spectrum, of the measurements, varies substantially according to measured frequency range and as stated by the composition or constitution or arrangement of specimens (sample texture). There are two conduction regions, as asserted by the conductivity that is determined by the frequency (two slopes). Permittivity increases linearly with increasing concentration. Permittivity is becoming smaller with the rising of the spectrum at a special rate. Electrical properties show universal Jonscher's law. The change in the specimens is the hematite conductor concentration (distributed homogeneously around sand grains) and probably the difference in the texture of specimens. Percolation theory is used to interpret the electrical properties of mixtures. Classical mixture formulas can be suggested to understand these homogeneous mixture samples.

The effect of CaO∖SiO2 molar ratio on the electrical properties of some glass materials was examined, using the impedance spectroscopy, at different frequency ranges, from 100 Hz up to 5 MHz. Also, a trial was accomplished to study the influence of CaO∖SiO2 molar ratio on some physical properties such as density, micro-hardness and bending strength. Six glass batches, based on Sinai basaltic rocks and bypass cement dust, were prepared with different CaO/SiO2 molar ratios (0.2–0.93 mol %). Accordingly, the electrical properties (conductivity dielectric constant and dielectric loss) of these samples show noticeable change. Electrical results show that the samples with relatively low (CaO/SiO2) molar ratio have relatively higher electrical conductivity, compared to the other samples with higher (CaO/SiO2) molar ratios, at different frequencies. Also, at the same time, the bending strength and Vickers micro-hardness show a gradual increase from 56 to 118 MPa and from 4020 to 6120 MPa, respectively, with decreasing CaO/SiO2 molar ratio. The density of the samples shows a successive increase from 2.79 to 2.96 gm/cm3 with the successive additions of bypass cement dust.

Efficient ammonia gas sensor devices were fabricated based on nickel oxide (NiO) nanostructures films. Two chemical synthesis approaches were used: chemical spray pyrolysis (CSP) and chemical bath deposition (CBD), aiming at obtaining highly developed surface area and high chemical reactivity of NiO. Crystal structure, morphology, and composition of NiO films and nanostructures were investigated by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. CSP method results in the synthesis of NiO films with pure cubic crystalline structure of preferred orientation along (111) direction. The type of the precursors used (nickel acetate, nickel chloride and nickel nitrate) affects the morphology and crystallites average size of the deposited films. CBD method consisted of two stages: (i) deposition of nickel hydroxide phase and (ii) thermal annealing of nickel hydroxide at 450 A degrees C in air for 4 h. Resulted structures were nanoflakes, vertically arranged in a "wall-like" morphology. Fabricated structures were found to be sensitive to ammonia differently, depending on the synthesis approach and material morphology. NiO films deposited by CBD demonstrated a stable response to ammonia with maximum magnitude at the operating temperature of 300 A degrees C. The highest average response for the CBD-NiO sample was 114.3-141.3% for 25 and 150 ppm NH3, respectively, whereas the response range observed for the film processed by spray pyrolysis using nickel chloride was 31.7-142.5% for 25 and 150 ppm NH3, respectively. Funding Agencies|Egyptian Ministry for Higher Education and Scientific Research; Swedish Research Council [VR 348-2013-6782]; Angpanneforeningens Forskningsstiftelse [14-517]; Swedish Research Council (VR) Marie Sklodowska Curie International Career Grant [2015-00679]

The Jurassic sedimentary section in north Sinai is of a special interest in particular for its economic potentiality. The understanding of petrographical and electrical properties of these rocks is essential for investigating minerals and oil and water exploration. This paper presents a study of the petrographical and A. C. electrical properties of Jurassic carbonates. Electrical measurements have been conducted for twenty-nine (18) carbonate samples. The slight changes between samples in electrical properties were attributed to the changes in mineral composition, texture pore spaces and pore throat distribution of the samples. Electrical properties generally change with many factors (grain size, mineral composition, grain shape and facies). The dielectric constant decreases with frequency and increases with the presence of conductive solids (silt and clay) and its composition. The conductivity increases with the increase of conductor paths between electrodes. The main goal of this paper is to shed more light on interrelations between electrical properties (conductivity, dielectric constant and impedance as a function of frequency), petrography and mineral composition (carbonates that contain clays and quartz grains).

The geochemical, petrographical, and electrical properties of rocks are essential to the investigation of the properties of minerals. In this paper we will try to present a study of the A. C. electrical properties of carbonate rock samples and their relation to petrographical and geochemical properties. Samples were collected from four formations from the Bir Dungul area, in the South Western Desert, Egypt. The electrical properties of the samples were measured using a non-polarizing electrode, at room temperature (~28 °C), and at a relative atmospheric humidity of (~45%), in the frequency range from 42 Hz to 5 MHz. The changes in the electrical properties were argued to the change in mineral composition. Generally, the electrical properties of rocks are changed due to many factors e.g., grain size, mineral composition, grain shape and inter-granular relations between grains. The dielectric constant of samples decreases with frequency, and increases with conductor concentration. Also, the conductivity increases with an increase of continuous conductor paths between electrodes. The petrographical and geochemical studies reveal that the deposition of the tufa deposits occurred in shallow lakes accompanied by a high water table, an alkaline spring recharge and significant vegetation cover. Diagenetically, tufa deposits were subjected to early and late diagenesis. Petrography and geochemistry studies indicated that the area of tufa deposits was deposited under the control of bacterial activity. Geochemically, the Sr content indicates that the tufa deposits formed from dissolved bicarbonate under the control of microbes and bacterial activity.

In this study, Pt (of 0.3, 0.6 and 0.9 wt% loadings) was supported on a mesoporous silica surface via a microwave-assisted solution (MAS) method or rotary chemical evaporation (RCE) method in the in situ reduction step. The as-synthesized Pt nanocatalysts were characterized through XRD, XRF, TGA/DSC, TEM, N2-adsorption–desorption, H2-pulse titration and electrical conductivity techniques. The samples prepared by MAS method exhibited higher surface area and a better dispersion profile of Pt NPs, of average sizes not exceeding 10 nm with increasing the Pt loading. In contrast, although RCE method showed higher efficacy in decomposing the used precursor, an uneven distribution of larger Pt nanoparticles (≥33 nm) was determined. Electrical properties in terms of AC conductivity and dielectric constant confirmed the enhancement of an even distribution of smaller Pt NPs with a higher concentration of grain boundaries effected by microwave electromagnetic radiations. Highly mobile electrons and lattice vibrations (phonons) were favored, as compared with aggregated NPs produced during RCE method. The TOF values calculated for reactions to selectively produce ethylene (from ethanol) or benzene (from cyclohexane) decreased with Pt loading on the catalyst samples synthesized by MAS method. The highly dispersed NPs (of 3–7 nm) seemed to be responsible for the activity in both reactions, probably tending to be structure insensitive. However, samples reduced by RCE method, with enlarged average sizes of surface Pt NPs (approaching 15.5 nm), exhibited increasing TOF values with Pt loading, i.e., causing the reactions most probably to be structure sensitive.

Nickel oxide thin films were deposited by a simple and low-cost spray pyrolysis technique using three different precursors: nickel nitrate, nickel chloride, and nickel acetate on corning glass substrates. X-ray diffraction show that the NiO films are polycrystalline and have a cubic crystal structure, although predominantly with a preferred 111-orientation in the growth direction and a random in-plane orientation. The deconvolution of the Ni 2p and O 1s core level X-ray photoelectron-spectra of nickel oxides produced by using different precursors indicates a shift of the binding energies. The sprayed NiO deposited from nickel nitrate has an optical transmittance in the range of 60-65% in the visible region. The optical band gap energies of the sprayed NiO films deposited from nickel nitrate, nickel chloride and nickel acetate are 3.5, 3.2 and 3.43 eV respectively. Also, the extinction coefficient and refractive index of NiO films have been calculated from transmittance and reflectance measurements. The average value of refractive index for sprayed films by nickel nitrate, nickel chloride and nickel acetate are 2.1, 1.6 and 1.85 respectively. It is revealed that the band gap and refractive index of NiO films by using nickel nitrate corresponds to the commonly reported values. We attribute the observed behavior in the optical band gap and optical constants as due to the change of the Ni/O ratio. Funding Agencies|Swedish Research Council [VR 348-2013-6782]; Egyptian Ministry for Higher Education and Scientific Research; Angpanneforeningens Forskningsstiftelse [14-517]; Swedish Research Council (VR) Marie Sklodowska Curie International Career "GREEN 2D FOX" [2015-00679]

The effect of increasing SiO 2 at the expense of B 2 O 3 on the internal structure of xSiO 2-(40-x) B 2 O 3-60Bi 2 O 3 glass matrix (where x=0, 10, 20, 30 and 40 mole %) was investigated. The glass structure was indicated that Bi 3+ cations are incorporated in the glass structure as pyramidal [BiO 3] and [BiO 6] octahedral units and boron ions are incorporated in BO 3 and BO 4 units. The presence of distorted [BiO 6] octahedral units in the glass network was observed and the degree of distortion was found to be decreased on progressive substitution of B 2 O 3 by SiO 2. The results revealed that increase of SiO 2/B 2 O 3 replacements, led to increase the density, microhardness and chemical durability of the studied glasses. However, the molar volume was decreased. The increase of SiO 2/B 2 O 3 replacements generally decreased the AC conductivity. That decrease may be due to the decrease in distortion of [BiO 6] octahedral units in glass network on progressive substitution of B 2 O 3 by SiO 2. Dielectric constants of the samples are complex, which may be an indication of the distortion (number of free charges or broken bonds) in the network of the glass. The obtained experimental data were argued to the internal structure of glass network and the change of the structure of the samples from pyramidal to octahedral and the presence of boron ions in BO 3 and BO 4 units.

Electrical methods are used in a wide range of applications including groundwater, geothermal, mineral discovery, oil and gas exploration, and deep tectonic processes. The Jurassic sedimentary section in North Sinai is of a special interest in particular for its economic potentiality and environmental conditions such as continental, marine, fluviomarine. The understanding petrographical and electrical properties of these rocks are essential for investigating minerals, oil, and water exploration. This paper presents a study of the petrographical and AC electrical properties of the Jurassic carbonates. Electrical measurements have been conducted for twenty nine (29) carbonate samples. The slight changes between samples in electrical properties were attributed to the changes in mineral composition, texture pore spaces, and pore throat distribution of the samples. Electrical properties generally change with many factors (grain size, mineral composition, grain shape, and facies). The dielectric constant decreases with frequency and increases with the presence of conductive solids (silt and clay) and its composition. The conductivity increases with the increase of conductor paths between electrodes. The main goal of this paper is to shed more light on interrelations between electrical properties (conductivity, dielectric constant and impedance as a function of frequency), petrography, and mineral composition (carbonates that contain clays and quartz grains). This is the first time to make some complex electrical properties on the carbonate rocks at this area as a prelude to make forward and inverse modeling.

The influence of adding Fe2O3 at the expense of Na2O in sodium lead borate glasses on the structural, physical and electrical properties have been investigated. Results obtained from Fourier transform infrared (FTIR) spectra indicated that Fe2O3 plays an important role in converting three coordinated boron atoms [BO3] to four coordinated boron atoms [BO4]. The physical properties such as density and molar volume helped to evaluate the compact structure of the prepared glass samples due to presence of [BO4] groups. The increase of Fe2O3/Na2O replacements led to increasing the microhardness values and decreasing the thermal expansion coefficients of the studied glasses. The increase of Fe2O3/Na2O replacements generally decreased the AC conductivity. That decrease might be due to converting of the three coordinated boron atoms [BO3] to four coordinated boron atoms [BO4]. Dielectric constants of the samples might be an indication of the distortion in the coordinated boron atoms. The obtained experimental data indicated the internal structure of glass network and the change of the structure of the samples from three [BO3] to four coordinated boron atoms [BO4].

Dopants of transition metal ions in II-VI semiconductors exhibit native 2+ valency. Despite this, 3+ or mixed 3+/2+ valency of iron ions in ZnO was reported previously. Several contradictory mechanisms have been put forward for explanation of this fact so far. Here we analyze Fe valency in ZnO by complementary theoretical and experimental studies. Our calculations within the generalized gradient approximation (GGA+$U)$ indicate that the Fe ion is a relatively shallow donor. Its stable charge state is ${\mathrm{Fe}}^{2+}$ in ideal ZnO, however, the high energy of the (+/0) transition level enhances the compensation of ${\mathrm{Fe}}^{2+}$ to ${\mathrm{Fe}}^{3+}$ by nonintentional acceptors in real samples. Using several experimental methods like electron paramagnetic resonance, magnetometry, conductivity, excitonic magnetic circular dichroism, and magnetophotoluminescence we confirm the 3+ valency of the iron ions in polycrystalline (Zn,Fe)O films with the Fe content attaining 0.2%. We find a predicted increase of $n$-type conductivity upon the Fe doping with the Fe donor ionization energy of $0.25\ifmmode\pm\else\textpm\fi{}0.02$ eV consistent with the results of theoretical considerations. Moreover, our magneto-optical measurements confirm the calculated nonvanishing s,p-d exchange interaction between band carriers and localized magnetic moments of the ${\mathrm{Fe}}^{3+}$ ions in the ZnO, being so far an unsettled issue.

SUMMARY Therehasbeenincreasinginterestintheelectricalpropertiesofrocksatdifferenttemperatures. Studies of the electrical properties under high temperatures became important to understand the materials within the earth’s interior. This paper reports on the development of forward and inverse modelling of the electrical properties of the samples considering their internal texture. Sediments in Hammamat area, Egypt, containing magnetite, were extensively heated by intruded magma. As a result, magnetite was altered to hematite with different degrees according to the distance from the intrusion. Complex impedance measurements in the frequency range from 10Hz to 100kHz were performed on samples taken at different distances from the magmatic intrusion. It is supposed that the conductivity will decrease with increasing distance from the intrusion due to the decrease of the conductive magnetite and increase of the much less conductive hematite, but our results show the opposite trend. Conventional mixture laws cannot interpret this abnormal behaviour. A new pseudo-random renormalization group method was developed to model the samples properties with four supposed constituents to match the experimental results. The four constituents are magnetite blocked by air, hematite blocked by air, sand covered by hematite and magnetite covered by hematite. Thefitting results with the experimental data show that as the samples are more heated, volume of the air pores, blocking the hematite and magnetite, decreases due to partial or complete melting, causing an increase in the sample conductivity in spite of the decrease of the magnetite content. This shows that the pseudo-random renormalization group method can model the abnormal properties of the samples. The texture represented mainly by blocking air has a larger effect on the samples conductivity than the concentration of the conductive magnetite.

The structure of soda-calcia-magnesia-silicate glasses doped with rare-earth fluoride (NdF3) was investigated by Fourier transform infrared spectrometer. The density and microhardness have been investigated in order to study the effect of doping NdF3 on the physical properties of the studied glasses. The results showed that the density of glasses increases with the increase in NdF3 contents. While, the increase of NdF3 contents led to decrease the microhardness values of the studied samples. The AC electrical properties of samples were measured in the frequency interval 100 Hz up to 1 MHz. The increase of NdF3 doping generally increases the conductivity and dielectric constants of the samples slightly. The obtained experimental data from samples were discussed based on the internal structure of the glass and the distribution of its constituents, connectivity and number of free charges or broken bonds.

Understanding petrographical, geochemical and electrical properties of rocks is essential for investigating minerals. This paper presents a study of the petrographical, geochemical and A.C. electrical properties of carbonate rock samples. The samples collected show six lithostratigraphic rock units. Electrical properties were measured using a non-polarizing electrode at room temperature (∼20°C) and a relative atmospheric humidity of ∼50% by weight in the frequency range from 42 Hz to 5 MHz. The difference in electrical properties between the samples was attributed to the change in composition and texture between the samples. Electrical properties generally change with many factors (grain size, chemical composition, grain shape and facies). The dielectric constant decreases with frequency and increases with conductor composition. The conductivity increases with the increase of conductor paths between electrodes. Many parameters can contribute to the same result of the electrical properties. The main objective of the present study is to shed more light on the relation between the texture and geochemical composition of measured samples (carbonates that contain clays and quartz grains) through electrical laboratory measurements (conductivity and dielectric constant as a function of frequency).

Electrode polarization is a major problem in the determination of dielectric properties of samples, particularly at low frequencies. Understanding of these interfacial phenomena is essential in order to measure correctly the electrical properties of a sample of interest. This paper presents a comparative study of the effect of electrode contact impedance on A.C. electrical properties of a partially and fully saturated hematitic sandstone sample. The electrical properties of the sample were first measured using stainless steel electrodes with high contact impedance, and measured again with a four terminal Cu–CuSO4 electrode of low contact impedance. Complex impedance measurements at room temperature (~16°C) were performed in the frequency range from 1 Hz to 100 kHz. Measured electrical spectra vary strongly with the electrode type. The difference in the electrical properties between the two electrode types (stainless steel and Cu–CuSO4) may be attributed to the surface contact impedance between the sample and the electrode. Experimental data indicate that the electrical properties vary strongly with water saturation. The dielectric constant decreases with frequency and increases with saturation up to a certain saturation limit then decreases. Charge transport can occur either through the bulk of the solid matrix (hematite or sand) or along the grain boundaries of aggregates (water). When soil minerals are exposed to water, exchangeable ions go into solution. Most of the ionic or covalent bonded rock forming minerals such as quartz, mica, and feldspars are nonconductors. When the surfaces of these minerals come into contact with liquid water, electrolytes are formed and ionic drift associated with the electrical field causes electrical conduction. The anomalous dielectric properties of partially saturated rocks can be interpreted using percolation theory. This theory predicts that when the conductive fraction (water) increases, clustering of conductive inclusions develops, and the thickness of insulating gaps between conductive clusters decreases, causing a large increment in the capacitance of the sample. Further increases in the conductive component causes the shunting of insulating capacitive gaps.

This paper is devoted to study the effect of saturation, with distilled water, on AC electrical conductivity and dielectric constant of a fully and partially saturated hematitic sandstone sample (Aswan area, Egypt). The saturation of the sample was changed from full saturation to partial saturation by air drying. Complex resistivity measurements at room temperature (∼16 ◦ C) were performed in the frequency range from 10 Hz to 100 kHz. We used non-polarizing Cu/CuSO4 gel electrodes. Experimental electrical spectra indicate, generally, that the electrical conductivity and dielectric constant vary strongly with water saturation and frequency. The low-frequency electrical conductivity and dielectric constant are supposed to be mainly controlled by surface conduction and polarization of the electrical double layer. Power law behaviours with frequency were noticed. The change in electrical conductivity and dielectric constant with increasing water content is fast at low saturations and slow at high saturations. The behaviour of the electrical conductivity and dielectric constant, with increasing water content, was argued to be the orientational polarization of bound water for very low saturations, displacement of the excess surface charges for relatively low saturations and free exchange of excess ions in double layer with the bulk electrolyte and generation of transient diffusional potentials, which lag behind the applied field for high saturations in addition to membrane polarization on clay and at inter-grain and grain surface water throats having selective charge transport properties. Also, from the data a semi-percolation behaviour was found that has a peak of dielectric constant at a certain concentration and an abrupt change in conductivity at another saturation.

Electrical properties and X-ray diffraction of 20 hematite sandstone samples of the most economically interesting Egyptian iron ore deposits have been investigated. Samples were collected from two different areas in Egypt (Aswan and Bahariya). Complex impedance measurements in the frequency range from 10 Hz to 100 kHz were performed at room temperature (∼20 °C). The observed dielectric behavior was characterized by Maxwell–Wagner interfacial polarization at low frequencies and bulk polarization at relatively higher frequencies. The frequency dependence on conductivity shows a classical relaxation behavior followed Jonscher’s universal law. The measured electrical properties vary strongly with the frequency and sample composition. The difference in the electrical properties may be attributed to the fluctuations in the concentration of the sample constituents and to the degree of heterogeneity of the grains. The XRD-patterns of Egyptian iron ore deposits prove that the main phases are hematite and quartz.

AC electrical conductivity analysis for silica gel and silica gel-supported nickel (via 2, 5 and 8 wt.% Ni) and γ-alumina and γ-alumina-supported platinum (viz., 0.3 and 0.6 wt.% Pt) is carried out. Measurements were carried out in the frequency range from 0.1 Hz up to 100 kHz at room temperature (20 °C) and 1 V for estimating the effect of increasing Ni or Pt on its supports namely silica gel and γ-alumina. Electrical properties of such mesoporous materials reflect directly its ion exchange and interfacial catalytic activity. Assuming that Ni or Pt particles are optimally dispersed over the surface of its supports, this may give rise to an increase in the conductivity and dielectric constant of the studied system. Electrical properties of pure γ-Al2O3 and silica gel supports depend on metal content and frequency of the applied field. The observed increase in conductivity with the increase in metal loadings may be due to the increase in the mobility of the free charge carriers. These charge carriers diffuse in the bulk of pores and reach electrodes and discharge there giving rise to diffusion impedance (Warburg impedance). An equivalent circuit is deduced to describe the electrical behavior of the systems studied. It constitutes elements forming three mechanisms: ion exchange at interfaces, diffusion in the pores and high frequency effect (beyond the scope of this work). The study evidenced that the increase of metal content has a great effect on the electrical properties of the studied system.

The thermal effects of magmatic intrusion on the conductivity and dielectric constant of magnetic rocks from Hammamat sediments, NE desert, Cairo, Egypt (latitude ∼27° and longitude ∼33°) were investigated experimentally in the laboratory using non-polarizing electrodes. Granitic magma was intruded into the Hammamat sediments, which are a mixture of mainly magnetite with sandstone and due to the thermal effect the area around was extensively heated and altered to different degrees. Due to this magma intrusion, magnetite was transformed (by heating) to hematite to different degrees according to its location from the intrusion. Complex impedance measurements were performed in the frequency range of 10 Hz to 100 KHz at normal temperature (∼20°C) and at a relative humidity of ∼50% RH. Samples were collected at different locations perpendicular to the core of the magma intrusion. Experimental data indicate that the electrical properties vary strongly as we move away (with distance) from the magma intrusion. The conductivity of hematite is ∼10- 2 S/m and that of magnetite is ∼10 4 S/m. As we move from magnetite to hematite (to the core of the magma intrusion) it is supposed that the conductivity will decrease but it was found that the conductivity increases (which is supposed to be abnormal). The conductivity increases with increasing frequency from ∼10 -8 S/m to ∼10 -5 S/m with almost power-law dependence on frequency. The conductivity increases in the order of one decade due to the variation from magnetite to hematite. The increase of conductivity, as we move from magnetite to hematite, was argued to be due to the heating that partially or completely melts the samples, thus the porosity of the samples was decreased and accordingly the conductivity and dielectric constant increased. It was also supposed that the grains of the conductor in the samples are coated or isolated with insulator material. A percolation behaviour for the conductivity and dielectric constant, characteristic of random conductor-insulator mixtures, was found with distance, where continuous paths of the conductive material occur accompanied by peaking of the dielectric constant. Complex impedance plots show that as we move in the direction of altered samples (towards hematite) the relation between real and imaginary impedance changes from a linear form to an arc of a depressed semicircle and increases in depression as we move in the direction of the altered samples, which is consistent with the above interpretation.

The AC electrical data, measured in the frequency range 0.1 Hz–5 MHz, were used to study the electrical response of lithium barium titanium alumino borosilicate glass-ceramics containing strontium or magnesium. Complex plane plot from these electrical data for various glass ceramic samples reveal contributions from simultaneously operating polarization mechanisms to overall dielectric behaviour. The SrO/BaO or MgO/Al2O3 replacements resulted in the increase of the conductivity and dielectric constant of the corresponding glass-ceramic materials. The relationships between the crystalline phases formed and dielectric values of studied glass-ceramics are complicated. The complex impedance of the crystalline materials generally decreases with the addition of SrO instead of BaO and with increase of MgO at the expense of Al2O3. The obtained data were correlated to the internal microstructure, crystalline phases formed, glassy matrix and glass to crystal interface region. β-Spodumene together with varieties of Ba-containing phases [e. g. orthorhombic celsian—BaAl2Si2O8, fresnoite—Ba2(TiO)Si2O7], barium silicate Ba2Si3O8, lithium borate—Li6B4O9, lithium metasilicate—Li2SiO3 strontium titanate—SrTiO3, and magnesium borate—MgB4O7 phases were mostly developed in the crystallized glasses. The microhardness characteristics of the crystalline glasses have been investigated by Knoop microhardness. The SrO/BaO or MgO/Al2O3 replacements resulted into decreasing the microhardness values. The obtained data of the glass-ceramic specimens were explained in relation to the crystalline phases, microstructure formed and the glassy matrix.

The catalytic activity of silica gel and silica gel—supported nickel (2, 5, and 8 wt% Ni) and γ-alumina—supported platinum (0.3 and 0.6 wt% Pt) was studied for n-hexane or n-pentane cracking and cyclohexane dehydrogenation adopting pulse technique. The results showed that Pt/γ-alumina could be a selective catalyst for cyclohexane dehydrogenation reaction. Ni/silica gel catalyst was a good cracking catalyst, the activity of which increased by increasing the metal content up to 8% Ni. For cyclohexane, dehydrogenation over Ni/silica gel, the activity increased by increasing the metal loading. N2 sorption characterizations showed that both silica gel- and γ-alumina—supported catalyst samples exhibited mesoporous structures. Silica gel and silica gel—supported samples have ink-bottle type pores while γ-alumina and γ-alumina—supported platinum samples have platelike pores. BET surface area and total pore volume decreased by increasing metal loading for both catalyst samples. Electrical properties of pu...