N. Okasha - Academia.edu (original) (raw)

Papers by N. Okasha

Research paper thumbnail of Role of bicarbonate dialysis in prevention of serious arrhythmias in high-risk cardiac patients undergoing regular hemodialysis

Hemodialysis International, 2005

ABSTRACT Background: Cardiac arrhythmias are considered as one of the most important causes of mo... more ABSTRACT Background: Cardiac arrhythmias are considered as one of the most important causes of mortality in patients on hemodialysis. Arrhythmias frequently occur in patients with chronic renal failure on regular hemodialysis with reported incidences varying from 30–48% of patients. These abnormalities can span from supraventricular to severe ventricular arrhythmia. There is an increased frequency of occurrence and clustering of arrhythmias around the dialysis time. Aim of the study: To detect the difference between acetate and bicarbonate dialysis as regard to the type and frequency of arrhythmia in those patients. Study design: This study was done on 20 male patients age 51–73, all have history of heart disease. Patients were divided into 2 equal groups using acetate in group 1 and bicarbonate in group 2. All patients were on regular hemodialysis (4 hours, thrice weekly). Careful history and clinical examination were done. Pre-dialysis investigations included serum creatinine, blood urea nitrogen, serum sodium, potassium, calcium and phosphorus, serum albumin, hemoglobin, and arterial blood gases. Post-dialysis serum potassium and arterial blood gases were measured. ECG and forty-eight hours ambulatory monitor (Holter monitor)(before, during, and after hemodialysis, till the end of the dialysis day and throughout the following day) were performed. Results: Group 1 showed significantly less post-dialysis supraventricular arrhythmias than in dialysis day (210.9 ± 236 and 62.3 ± 14.4), respectively. Significantly less ventricular arrhythmias in post-dialysis than in dialysis day (30.7 ± 50.4, and 106.2 ± 128.4), respectively. While in Group 2 there were insignificant differences regarding supraventricular arrhythmias (21.9 ± 28.9 and 16.6 ± 36.3) and ventricular arrhythmias (22.9 + 7.8 and 29.6 + 12.8) in dialysis day than in post-dialysis day. There was significantly higher frequency of supraventricular and ventricular arrhythmias in the dialysis day in acetate hemodialysis in comparison to bicarbonate hemodialysis. Conclusion: Bicarbonate hemodialysis is less arrhythmogenic in comparison to acetate hemodialysis and has better effect on the blood pH and greater degree of base repletion. Continuous ambulatory ECG recording (Holter) is a useful tool in detecting arrhythmias in dialysis patients.

Research paper thumbnail of Crossover Between PEG and BT/NZF Magnetoelectric Nanocomposites for Tailoring Applicable Multiferroic Materials

Journal of Superconductivity and Novel Magnetism, 2015

ABSTRACT The composite materials with formula (1 − x) [Ni0.5Zn0.5Fe2O4 + BaTiO3] + (x) (PEG); 0 ≤... more ABSTRACT The composite materials with formula (1 − x) [Ni0.5Zn0.5Fe2O4 + BaTiO3] + (x) (PEG); 0 ≤ x ≤ 1 have been prepared via citrate autocombustion method. Physical properties of composite materials consisting of different ratios of polyethylene glycol powder were investigated. With the variation of x, typical magnetic hysteresis loops have been observed in the composites at room temperature. When PEG content increases, the saturation magnetization decreases. Meanwhile, the coercive force tends to be stable. Additionally, the dielectric constant (ε ′) and dielectric loss factor (ε ″) of composite materials shift toward higher frequency. The value of ε ′ decreased with increasing frequency, which indicates that the major contribution to the polarization comes from orientation polarization. The composites with doping PEG polymer may be useful for technological applications such as thermistors, transducers, magnetic probes, etc.

Research paper thumbnail of EFFECTS OF RARE EARTH OXIDES ON SOME PHYSICAL PROPERTIES OF Li-Zn NANOPARTICLE FERRITES

Modern Trends in Physics Research - Proceedings of the Third International Conference on Modern Trends in Physics Research, 2011

The spinel ferrite Li 0.2 Zn 0.6 La y Fe 2.2-y O 4 ; 0.01 ≤ y ≤ 0.1 were prepared by the usual ce... more The spinel ferrite Li 0.2 Zn 0.6 La y Fe 2.2-y O 4 ; 0.01 ≤ y ≤ 0.1 were prepared by the usual ceramic sintering technique. XRD confirmed the formation of the samples in single phase spinel structure for all the samples. The lattice parameters decreased with increasing the La-content. The d c resistivity was measured as a function of temperature. The obtained results indicate the semiconductor like behavior, where more than straight lines indicating the presence of different conductions mechanism exist. The density of states near Fremi level as a function of La-content and discussed based on the variable range hoping model. The dielectric constant and dielectric loss were measured as a function of temperature and frequency. The dispersion peak at low frequency (10 kHz) was splitted by increasing La-content up to the suggested absorber splitting.

Research paper thumbnail of Novelty Preparation, Characterization and Enhancement of Magnetic Properties of Nanoferrites Using Safety Binder (Egg White)

Modern Trends in Physics Research, 2013

Research paper thumbnail of EFFECTS OF RARE EARTH IONS ON THE QUALITY AND THE MAGNETIC PROPERTES OF Ag-FERRITES

Modern Trends in Physics Research - Proceedings of the Third International Conference on Modern Trends in Physics Research, 2011

ABSTRACT A set of compounds with the formula MgAg0.4R0.2Fe1.4O4 where R is Lanthanum (La3+), Terb... more ABSTRACT A set of compounds with the formula MgAg0.4R0.2Fe1.4O4 where R is Lanthanum (La3+), Terbium (Tb3+), and Yttrium (Y3+), were prepared by the flash combustion technique. The effect of rare earths ions on some properties of silver doped was investigated. The obtained data indicated that, by introducing a relatively small amount of rare earths ions instead of Fe2O3 ions, an important modification of both the structure and the magnetic properties can be obtained. The Curie temperature, effective magnetic moment and exchange interaction are affected by these substitutions. The effect of rare earth ions were explained both by their partial diffusion in the spinel lattice and by the formation of the crystalline secondary phase on the grain boundaries.

Research paper thumbnail of INFLUENCE OF ZINC SUBSTITUTION ON SOME PHYSICAL PROPERTIES OF Co-La FERRITE

Modern Trends in Physics Research - Proceedings of the Third International Conference on Modern Trends in Physics Research, 2011

ABSTRACT Co-Zn substituted ferrites with the formula Co1-xZnxLa0.025Fe1.975O4 with 0.1≤x ≤0.9 was... more ABSTRACT Co-Zn substituted ferrites with the formula Co1-xZnxLa0.025Fe1.975O4 with 0.1≤x ≤0.9 was prepared by conventional solid state reaction. X- ray diffraction (XRD), scanning electron microscope (SEM) and magnetic susceptibility (χ) are utilized in order to study the effect of variation in Zn content and its impact on crystal structure, magnetic properties such as (χ), Curie temperature (TC), and exchange interaction constant (J) between the different cations. The results of XRD reveal that, assured the single phase cubic spinel structure for all investigated samples with appearance of small peaks represented a secondary phase due to the presence of rare earth (La3+) ions. The particle size (t) varied with composition and heat treatment. The value of both TC and J decreases with increasing Zn content up to the critical concentration (0.5) then increases. The scanning electron micrographs indicate the distribution of grains in the sample with uniform size and agree well with the results of X- ray analyses. The influence of rare earth ions substitution on the structure and magnetic properties was examined.

Research paper thumbnail of The Formation and Characterization of Nanocrystalline -Ferrite From Magnetite

Modern Trends in Physics Research, 2013

Research paper thumbnail of Electrical transport properties of barium-titanium ferrite with a hollandite structure

A series of barium titanium oxide with various Ba/Ti ratios having a hollandite structure was obt... more A series of barium titanium oxide with various Ba/Ti ratios having a hollandite structure was obtained by ceramic technique. It was shown that barium titanium hollandites may adopt both oxygen excess and oxygen deficient stoichiometries within the structure. As a limiting case the barium titanium hollandites with only tetravalent titanium ions were obtained. Results of investigation samples in the general

Research paper thumbnail of Assessment of endothelial dysfunction in idiopathic pulmonary fibrosis

Egyptian Journal of Chest Diseases and Tuberculosis, 2013

ABSTRACT Background Idiopathic pulmonary fibrosis (IPF) is defined as a specific form of chronic ... more ABSTRACT Background Idiopathic pulmonary fibrosis (IPF) is defined as a specific form of chronic fibrosing interstitial pneumonia limited to the lung, with the histopathology of UIP on surgical lung biopsy. Recent epidemiological evidence indicates that patients with IPF have an increased risk of cardiovascular disease. The vascular endothelium acts to maintain vascular homeostasis through multiple mechanisms, and alteration in its function precedes the development, progression and clinical expression of atherosclerosis. Aim of the work To assess the prevalence of endothelial dysfunction in patients with idiopathic pulmonary fibrosis and its correlation with pulmonary hypertension. Subjects and methods The study included two groups. The patient group included 30 IPF patients subdivided into 2 subgroups: Subgroup I (15 IPF cases) with pulmonary hypertension; Subgroup II (15 IPF cases) without pulmonary hypertension. The control group included 10 normal healthy individuals. Patients were subjected to written informed consent, detailed history taking, thorough clinical examination, collagen profile, arterial blood gases (PaO2, SaO2), Pulmonary function tests (spirometry), 6 min walk test, HRCT chest scan, echocardiography, and brachial artery duplex to assess endothelial dysfunction. Results Subgroup (I) and Subgroup (II) showed a statistically highly significant difference in brachial artery flow mediated dilatation (BADFMD) and endothelium – reactive dilatation (ERD) which indicate endothelial dysfunction compared to the control group. Conclusion This work concluded that BADFMD and ERD more affected in IPF patients regardless of presence or absence of PH than normal population. So, endothelial dysfunction is a possible link between IPF and cardiovascular disease.

Research paper thumbnail of Stent for Life Initiative placed at the forefront in Egypt 2011

EuroIntervention, 2012

Myocardial infarction is a medical emergency in which 25 to 35% of patients will die before recei... more Myocardial infarction is a medical emergency in which 25 to 35% of patients will die before receiving medical attention. The Stent for Life registry was launched to access the current situation of the Egyptian population presenting with STEMI, and to determine what were the barriers to providing patients with cardiac problems appropriate care. This registry was conducted at 14 centres covered all the Egyptian regions including 1,324 consecutive patients presenting with STEMI during the period between January 1st, 2011 to November, 2011. Fourteen centres and 38 interventionalists participated in this registry; only six centres are Pilot Centres (fulfilling the criteria for a primary PCI centre) and were assigned at the end of 2011. Cardiovascular risk factors were mainly smoking (60.5%), dyslipidaemia (46.0%), diabetes (51.4%) and hypertension (56.0%). The mean age at presentation was 56.01±10.61years and 75.0% were male. Only 5% of the STEMI patients arrived via the emergency medical system. Thrombus aspiration was done in 42.7% of patients in primary PCI group and 25.9% in rescue PCI group. Bare metal stents (BMS) were used in 80.7% of the stented patients while drug eluting stents (DES) were used in 19.3% of the stented patients. In-hospital mortality was 2.9% (1.4% in primary PCI group, 1.1% in patients treated with thrombolysis and 0.4% in patients receiving no reperfusion therapy). Despite the logistical difficulties, excellent outcomes for acute interventional reperfusion strategy in STEMI can be achieved in our country, possibly similar to those seen in the West. There is a strong need for making the practice of PCI in STEMI more widespread in developing regions.

Research paper thumbnail of Effect of the La3+ ions substitution on the magnetic properties of spinal Li-Zn-ferrites at low temperature

Journal of Materials Research and Technology, 2013

Low temperature magnetization IR spectroscopy

Research paper thumbnail of Modification of Mn nanoferrite physical properties by gamma, neutron, and laser irradiations

Solid State Sciences, 2011

Manganese nanocrystalline ferrite powders were synthesized using citrate precursor technique. The... more Manganese nanocrystalline ferrite powders were synthesized using citrate precursor technique. The ferrite samples were subjected to different types of irradiation; gamma rays, neutrons, and laser photons to compare their effects on the physical properties of prepared ferrite. The samples were characterized by XRD and IR techniques. XRD shows a shift in all planes keeping the spinel structure stable. The magnetic and dielectric behavior for the irradiated and unirradiated samples was investigated at different temperatures. The data recommended the use of this nanoferrite as radiation detector.

Research paper thumbnail of Novelty, preparation, characterization and enhancement of magnetic properties of Mn nanoferrites using safety binder (egg white)

Solid State Sciences, 2011

ABSTRACT Nanocrystalline MnFe2O4 ferrite was prepared by using autocombustion technique (flash). ... more ABSTRACT Nanocrystalline MnFe2O4 ferrite was prepared by using autocombustion technique (flash). The microstructure and magnetic properties are studied. The results of XRD and TEM clarified that, this ferrite is nanosized with particle size (39 nm). Magnetic measurements showed a ferromagnetic behavior with TC = 613 K, the saturation magnetization Ms = 13.71 emu/g, remanent magnetization Mr = 0.1694 emu/g and, coercivity Hc = 25.6 Oe. Natural material, egg white used as an aqueous medium to extend prepare nanoparticles better than other chemical interesting materials.

Research paper thumbnail of Dramatic effect of rare earth ion on the electrical and magnetic properties of W-type barium hexaferrites

Physica B: Condensed Matter, 2010

A series of W-type hexaferrite samples with composition Ba1−yLayZn0.5Mg0.5CoFe16O27; 0≤y≤0.07 wer... more A series of W-type hexaferrite samples with composition Ba1−yLayZn0.5Mg0.5CoFe16O27; 0≤y≤0.07 were prepared using the solid state reaction to investigate their magnetic properties, AC and DC electrical conductivity and thermoelectric power as a function of composition and temperature. The X-ray diffraction was studied to identify the formation of the sample properly. Increasing of (a) and decreasing of (c) lattice parameters leads to a constant volume. The data of ac conductivity showed an increase with both temperature and frequency, and it becomes slightly independent of frequency at higher temperature, also the conduction mechanism depends on an La concentration. The results of the charge carrier mobility suggested that the hopping conduction mechanism of holes due to replacement of La3+ rare earth ions on the expense of Ba2+ ions is the predominant one. The transition temperature decreases with increasing La content. The values of dc electrical conductivity σdc at room temperature ranged 4.85×10−6–3.82×10−6(Ω−1cm−1) and the values of the calculated activation energies Edc ranged 0.215–0.137eV. The highest values of dielectric constant, electrical conductivity and Curie temperature, also the smallest value of porosity and effective magnetic moment are found at y=0.05. The thermoelectric power coefficient showed that the majority of charge carriers are P-type, except at y=0.03, 0.04 and 0.05 negative charge carriers (electrons) takes place at high temperature region.

Research paper thumbnail of Transport and magnetic properties of Co–Zn–La ferrite

Materials Chemistry and Physics, 2004

The dielectric constant (ε ) and dielectric loss factor (ε ) for the ferrite Co 1−x Zn x La y Fe ... more The dielectric constant (ε ) and dielectric loss factor (ε ) for the ferrite Co 1−x Zn x La y Fe 2−y O 4 ; 0.1 ≤ x ≤ 1.0 were measured at different frequencies (100 kHz to 5 MHz) and different temperatures (300-850 K). More than one type of polarization participates in the dielectric process, Maxwell Wagner polarization is the one participating in the high temperature region. The electrical conductivity measurement showed that there is more than one conduction mechanism participating in conductivity. The hopping mechanism either by holes or electrons or both is the predominant one. The increase in conductivity is due to the thermally activated mobility and not to thermal creation of additional mobile charge carriers. The replacement of Fe 3+ by La on octahedral sites and the presence of Co 2+ as well as Zn 2+ ions on the tetrahedral sites play a significant role in the electrical and magnetic properties behavior of the investigates samples. The values of the activation energy obtained indicate the semi-conducting behavior of the investigated ferrite.

Research paper thumbnail of Extraordinary role of rare-earth elements on the transport properties of barium W-type hexaferrite

Materials Chemistry and Physics, 2009

ABSTRACT The influence of R2O3 substitution on the electrical properties and the thermoelectric p... more ABSTRACT The influence of R2O3 substitution on the electrical properties and the thermoelectric power on the W-type hexaferrite Ba0.95R0.05 Mg0.5 Zn0.5 Co Fe16 O27; R = Y3+, Er3+, Ho3+, Sm3+, Nd3+, Gd3+, and Ce3+ ions as a function of the absolute temperature and frequency in the ranges 300–750 K and 100 kHz–4 MHz, respectively have been studied. The results obtained reveal that, by introducing a relatively small amount of R2O3 instead of Fe2O3, an important modification of both structure and physical properties can be obtained. The dielectric constant ɛ′, the dielectric loss factor ɛ″ and AC conductivity σ of the investigating samples have highest values in the case of Sm3+. The values of the calculated activation energy varied between (0.335 and 0.553 eV) and (0.106 and 0.232 eV), above and below the transition temperature, respectively which indicate the semiconducting properties of the prepared samples. The conduction mechanism for Ho3+ sample is associated with the small polaron whereas the hopping conduction mechanism is predominant mechanism for the samples doped with the rest of rare-earth ions. The thermoelectric power measurements indicated that the samples are n-type semiconductors except Er3+ and Y3+ samples, where the thermoelectric power of them is positive at low temperature but nearly above 480 and 375 K, respectively transits to negative. The charge carriers concentration n increases with slightly increasing RE ionic radius to critical value (≈1.04 Å), after that n becomes nearly constant.

Research paper thumbnail of Could Mg content control the conduction mechanism of Ba Co Zn-W-type hexagonal ferrites?

Journal of Magnetism and Magnetic Materials, 2009

Electrical properties as a function of composition, frequency and temperature for a series of W-t... more Electrical properties as a function of composition, frequency and temperature for a series of W-type hexagonal ferrites with the general formula BaCoZn 1Àx Mg x Fe 16 O 27 ; 0rxr0.6 prepared using the conventional ceramic method were studied. These samples are semiconductor-like materials, where the ac conductivity increases with increasing temperature. The results show that the conduction mechanism depends on the Mg 2+ substitution. The transition temperature (T s ) increases with increasing Mg content and gives a hump at x ¼ 0.5; after that T s decreases again. Both the ac conductivity and dielectric constant vary with Mg content and reach the highest value at x ¼ 0.5, due to the highest value of the ratio of Fe 2+ /Fe 3+ at x ¼ 0.5. The peak value of the dielectric constant depends on the Mg content x.

Research paper thumbnail of Role of Cu2+ concentration on the structure and transport properties of Cr–Zn ferrites

Journal of Magnetism and Magnetic Materials, 2009

ABSTRACT The influence of Cu concentration on the transport and microstructure characteristics of... more ABSTRACT The influence of Cu concentration on the transport and microstructure characteristics of CuyZn1−yCr0.8Fe1.2O4 with 0.2≤y≤1 ferrite was studied. X-ray, energy dispersive X- ray (EDAX) and infrared spectra (IR) were carried out to assure the formation of the sample in the proper form. The dielectric constant (ε′) and ac conductivity were measured at different frequencies ranging from 600 kHz to 5 MHz from room temperature up to 800 K. The obtained data reveals that, a single phase cubic spinel structure for all the concentrations. From the results of IR spectra, mainly two bands were observed. The dielectric constant and the dielectric loss tangent decrease with increasing frequency and Cu concentration. The dielectric constant shows a dispersion peak (ε′max) which shifts to higher frequency with increasing the temperature. The results are explained as due to the fact that the dielectric polarization process is similar to that of conduction. The appearance of the dispersion peak is related to the contribution of two types of charge carriers.

Research paper thumbnail of Influence of rare-earth ions on the structure and magnetic properties of barium W-type hexaferrite

Journal of Magnetism and Magnetic Materials, 2008

Barium W-type hexaferrite with composition Ba0.95R0.05Mg0.5Zn0.5CoFe16O27 where R=Y, Er, Ho, Sm, ... more Barium W-type hexaferrite with composition Ba0.95R0.05Mg0.5Zn0.5CoFe16O27 where R=Y, Er, Ho, Sm, Nd, Gd, and Ce ions has been prepared by the double-sintering ceramic technique. Structure of the prepared samples has been characterized by the X-ray diffraction (XRD) technique. The XRD patterns at room temperature show the presence of secondary phase with the intensity of the secondary phase increasing with increasing

Research paper thumbnail of The role of Mg substitution on the microstructure and magnetic properties of Ba Co Zn W-type hexagonal ferrites

Journal of Magnetism and Magnetic Materials, 2007

A series of W-type hexagonal ferrites with the composition BaCoZn 1Àx Mg x Fe 16 O 27 (0pxp0.6) w... more A series of W-type hexagonal ferrites with the composition BaCoZn 1Àx Mg x Fe 16 O 27 (0pxp0.6) were prepared by the conventional ceramic method to study their structural and magnetic properties as a function of temperature and composition. The characterization using X-ray diffraction indicated that a hexagonal W-type single-phase structure and the effect of composition on the unit cell parameters, density and porosity was studied. The variation of the magnetic susceptibility (w M ) with temperature for all the investigated samples in the temperature range (300-800 K) shows three regions of behavior that was explained on the basis of the distribution of Zn 2+ and Mg 2+ ions in the lattice and leads to the anomalous behavior of the effective magnetic moment m eff . The Curie temperature indicated that the critical concentration is at x ¼ 0.5. Paramagnetic nature of the samples above the Curie temperature is observed. The Curie Weiss constant y calculated from the plot of 1/w M vs. T (K) is in agreement with the expected value. The effective magnetic moment m eff decreases with increasing the intensity of magnetic field. The possible mechanisms contributing to these properties are discussed in the text. r 2007 Published by Elsevier B.V.

Research paper thumbnail of Role of bicarbonate dialysis in prevention of serious arrhythmias in high-risk cardiac patients undergoing regular hemodialysis

Hemodialysis International, 2005

ABSTRACT Background: Cardiac arrhythmias are considered as one of the most important causes of mo... more ABSTRACT Background: Cardiac arrhythmias are considered as one of the most important causes of mortality in patients on hemodialysis. Arrhythmias frequently occur in patients with chronic renal failure on regular hemodialysis with reported incidences varying from 30–48% of patients. These abnormalities can span from supraventricular to severe ventricular arrhythmia. There is an increased frequency of occurrence and clustering of arrhythmias around the dialysis time. Aim of the study: To detect the difference between acetate and bicarbonate dialysis as regard to the type and frequency of arrhythmia in those patients. Study design: This study was done on 20 male patients age 51–73, all have history of heart disease. Patients were divided into 2 equal groups using acetate in group 1 and bicarbonate in group 2. All patients were on regular hemodialysis (4 hours, thrice weekly). Careful history and clinical examination were done. Pre-dialysis investigations included serum creatinine, blood urea nitrogen, serum sodium, potassium, calcium and phosphorus, serum albumin, hemoglobin, and arterial blood gases. Post-dialysis serum potassium and arterial blood gases were measured. ECG and forty-eight hours ambulatory monitor (Holter monitor)(before, during, and after hemodialysis, till the end of the dialysis day and throughout the following day) were performed. Results: Group 1 showed significantly less post-dialysis supraventricular arrhythmias than in dialysis day (210.9 ± 236 and 62.3 ± 14.4), respectively. Significantly less ventricular arrhythmias in post-dialysis than in dialysis day (30.7 ± 50.4, and 106.2 ± 128.4), respectively. While in Group 2 there were insignificant differences regarding supraventricular arrhythmias (21.9 ± 28.9 and 16.6 ± 36.3) and ventricular arrhythmias (22.9 + 7.8 and 29.6 + 12.8) in dialysis day than in post-dialysis day. There was significantly higher frequency of supraventricular and ventricular arrhythmias in the dialysis day in acetate hemodialysis in comparison to bicarbonate hemodialysis. Conclusion: Bicarbonate hemodialysis is less arrhythmogenic in comparison to acetate hemodialysis and has better effect on the blood pH and greater degree of base repletion. Continuous ambulatory ECG recording (Holter) is a useful tool in detecting arrhythmias in dialysis patients.

Research paper thumbnail of Crossover Between PEG and BT/NZF Magnetoelectric Nanocomposites for Tailoring Applicable Multiferroic Materials

Journal of Superconductivity and Novel Magnetism, 2015

ABSTRACT The composite materials with formula (1 − x) [Ni0.5Zn0.5Fe2O4 + BaTiO3] + (x) (PEG); 0 ≤... more ABSTRACT The composite materials with formula (1 − x) [Ni0.5Zn0.5Fe2O4 + BaTiO3] + (x) (PEG); 0 ≤ x ≤ 1 have been prepared via citrate autocombustion method. Physical properties of composite materials consisting of different ratios of polyethylene glycol powder were investigated. With the variation of x, typical magnetic hysteresis loops have been observed in the composites at room temperature. When PEG content increases, the saturation magnetization decreases. Meanwhile, the coercive force tends to be stable. Additionally, the dielectric constant (ε ′) and dielectric loss factor (ε ″) of composite materials shift toward higher frequency. The value of ε ′ decreased with increasing frequency, which indicates that the major contribution to the polarization comes from orientation polarization. The composites with doping PEG polymer may be useful for technological applications such as thermistors, transducers, magnetic probes, etc.

Research paper thumbnail of EFFECTS OF RARE EARTH OXIDES ON SOME PHYSICAL PROPERTIES OF Li-Zn NANOPARTICLE FERRITES

Modern Trends in Physics Research - Proceedings of the Third International Conference on Modern Trends in Physics Research, 2011

The spinel ferrite Li 0.2 Zn 0.6 La y Fe 2.2-y O 4 ; 0.01 ≤ y ≤ 0.1 were prepared by the usual ce... more The spinel ferrite Li 0.2 Zn 0.6 La y Fe 2.2-y O 4 ; 0.01 ≤ y ≤ 0.1 were prepared by the usual ceramic sintering technique. XRD confirmed the formation of the samples in single phase spinel structure for all the samples. The lattice parameters decreased with increasing the La-content. The d c resistivity was measured as a function of temperature. The obtained results indicate the semiconductor like behavior, where more than straight lines indicating the presence of different conductions mechanism exist. The density of states near Fremi level as a function of La-content and discussed based on the variable range hoping model. The dielectric constant and dielectric loss were measured as a function of temperature and frequency. The dispersion peak at low frequency (10 kHz) was splitted by increasing La-content up to the suggested absorber splitting.

Research paper thumbnail of Novelty Preparation, Characterization and Enhancement of Magnetic Properties of Nanoferrites Using Safety Binder (Egg White)

Modern Trends in Physics Research, 2013

Research paper thumbnail of EFFECTS OF RARE EARTH IONS ON THE QUALITY AND THE MAGNETIC PROPERTES OF Ag-FERRITES

Modern Trends in Physics Research - Proceedings of the Third International Conference on Modern Trends in Physics Research, 2011

ABSTRACT A set of compounds with the formula MgAg0.4R0.2Fe1.4O4 where R is Lanthanum (La3+), Terb... more ABSTRACT A set of compounds with the formula MgAg0.4R0.2Fe1.4O4 where R is Lanthanum (La3+), Terbium (Tb3+), and Yttrium (Y3+), were prepared by the flash combustion technique. The effect of rare earths ions on some properties of silver doped was investigated. The obtained data indicated that, by introducing a relatively small amount of rare earths ions instead of Fe2O3 ions, an important modification of both the structure and the magnetic properties can be obtained. The Curie temperature, effective magnetic moment and exchange interaction are affected by these substitutions. The effect of rare earth ions were explained both by their partial diffusion in the spinel lattice and by the formation of the crystalline secondary phase on the grain boundaries.

Research paper thumbnail of INFLUENCE OF ZINC SUBSTITUTION ON SOME PHYSICAL PROPERTIES OF Co-La FERRITE

Modern Trends in Physics Research - Proceedings of the Third International Conference on Modern Trends in Physics Research, 2011

ABSTRACT Co-Zn substituted ferrites with the formula Co1-xZnxLa0.025Fe1.975O4 with 0.1≤x ≤0.9 was... more ABSTRACT Co-Zn substituted ferrites with the formula Co1-xZnxLa0.025Fe1.975O4 with 0.1≤x ≤0.9 was prepared by conventional solid state reaction. X- ray diffraction (XRD), scanning electron microscope (SEM) and magnetic susceptibility (χ) are utilized in order to study the effect of variation in Zn content and its impact on crystal structure, magnetic properties such as (χ), Curie temperature (TC), and exchange interaction constant (J) between the different cations. The results of XRD reveal that, assured the single phase cubic spinel structure for all investigated samples with appearance of small peaks represented a secondary phase due to the presence of rare earth (La3+) ions. The particle size (t) varied with composition and heat treatment. The value of both TC and J decreases with increasing Zn content up to the critical concentration (0.5) then increases. The scanning electron micrographs indicate the distribution of grains in the sample with uniform size and agree well with the results of X- ray analyses. The influence of rare earth ions substitution on the structure and magnetic properties was examined.

Research paper thumbnail of The Formation and Characterization of Nanocrystalline -Ferrite From Magnetite

Modern Trends in Physics Research, 2013

Research paper thumbnail of Electrical transport properties of barium-titanium ferrite with a hollandite structure

A series of barium titanium oxide with various Ba/Ti ratios having a hollandite structure was obt... more A series of barium titanium oxide with various Ba/Ti ratios having a hollandite structure was obtained by ceramic technique. It was shown that barium titanium hollandites may adopt both oxygen excess and oxygen deficient stoichiometries within the structure. As a limiting case the barium titanium hollandites with only tetravalent titanium ions were obtained. Results of investigation samples in the general

Research paper thumbnail of Assessment of endothelial dysfunction in idiopathic pulmonary fibrosis

Egyptian Journal of Chest Diseases and Tuberculosis, 2013

ABSTRACT Background Idiopathic pulmonary fibrosis (IPF) is defined as a specific form of chronic ... more ABSTRACT Background Idiopathic pulmonary fibrosis (IPF) is defined as a specific form of chronic fibrosing interstitial pneumonia limited to the lung, with the histopathology of UIP on surgical lung biopsy. Recent epidemiological evidence indicates that patients with IPF have an increased risk of cardiovascular disease. The vascular endothelium acts to maintain vascular homeostasis through multiple mechanisms, and alteration in its function precedes the development, progression and clinical expression of atherosclerosis. Aim of the work To assess the prevalence of endothelial dysfunction in patients with idiopathic pulmonary fibrosis and its correlation with pulmonary hypertension. Subjects and methods The study included two groups. The patient group included 30 IPF patients subdivided into 2 subgroups: Subgroup I (15 IPF cases) with pulmonary hypertension; Subgroup II (15 IPF cases) without pulmonary hypertension. The control group included 10 normal healthy individuals. Patients were subjected to written informed consent, detailed history taking, thorough clinical examination, collagen profile, arterial blood gases (PaO2, SaO2), Pulmonary function tests (spirometry), 6 min walk test, HRCT chest scan, echocardiography, and brachial artery duplex to assess endothelial dysfunction. Results Subgroup (I) and Subgroup (II) showed a statistically highly significant difference in brachial artery flow mediated dilatation (BADFMD) and endothelium – reactive dilatation (ERD) which indicate endothelial dysfunction compared to the control group. Conclusion This work concluded that BADFMD and ERD more affected in IPF patients regardless of presence or absence of PH than normal population. So, endothelial dysfunction is a possible link between IPF and cardiovascular disease.

Research paper thumbnail of Stent for Life Initiative placed at the forefront in Egypt 2011

EuroIntervention, 2012

Myocardial infarction is a medical emergency in which 25 to 35% of patients will die before recei... more Myocardial infarction is a medical emergency in which 25 to 35% of patients will die before receiving medical attention. The Stent for Life registry was launched to access the current situation of the Egyptian population presenting with STEMI, and to determine what were the barriers to providing patients with cardiac problems appropriate care. This registry was conducted at 14 centres covered all the Egyptian regions including 1,324 consecutive patients presenting with STEMI during the period between January 1st, 2011 to November, 2011. Fourteen centres and 38 interventionalists participated in this registry; only six centres are Pilot Centres (fulfilling the criteria for a primary PCI centre) and were assigned at the end of 2011. Cardiovascular risk factors were mainly smoking (60.5%), dyslipidaemia (46.0%), diabetes (51.4%) and hypertension (56.0%). The mean age at presentation was 56.01±10.61years and 75.0% were male. Only 5% of the STEMI patients arrived via the emergency medical system. Thrombus aspiration was done in 42.7% of patients in primary PCI group and 25.9% in rescue PCI group. Bare metal stents (BMS) were used in 80.7% of the stented patients while drug eluting stents (DES) were used in 19.3% of the stented patients. In-hospital mortality was 2.9% (1.4% in primary PCI group, 1.1% in patients treated with thrombolysis and 0.4% in patients receiving no reperfusion therapy). Despite the logistical difficulties, excellent outcomes for acute interventional reperfusion strategy in STEMI can be achieved in our country, possibly similar to those seen in the West. There is a strong need for making the practice of PCI in STEMI more widespread in developing regions.

Research paper thumbnail of Effect of the La3+ ions substitution on the magnetic properties of spinal Li-Zn-ferrites at low temperature

Journal of Materials Research and Technology, 2013

Low temperature magnetization IR spectroscopy

Research paper thumbnail of Modification of Mn nanoferrite physical properties by gamma, neutron, and laser irradiations

Solid State Sciences, 2011

Manganese nanocrystalline ferrite powders were synthesized using citrate precursor technique. The... more Manganese nanocrystalline ferrite powders were synthesized using citrate precursor technique. The ferrite samples were subjected to different types of irradiation; gamma rays, neutrons, and laser photons to compare their effects on the physical properties of prepared ferrite. The samples were characterized by XRD and IR techniques. XRD shows a shift in all planes keeping the spinel structure stable. The magnetic and dielectric behavior for the irradiated and unirradiated samples was investigated at different temperatures. The data recommended the use of this nanoferrite as radiation detector.

Research paper thumbnail of Novelty, preparation, characterization and enhancement of magnetic properties of Mn nanoferrites using safety binder (egg white)

Solid State Sciences, 2011

ABSTRACT Nanocrystalline MnFe2O4 ferrite was prepared by using autocombustion technique (flash). ... more ABSTRACT Nanocrystalline MnFe2O4 ferrite was prepared by using autocombustion technique (flash). The microstructure and magnetic properties are studied. The results of XRD and TEM clarified that, this ferrite is nanosized with particle size (39 nm). Magnetic measurements showed a ferromagnetic behavior with TC = 613 K, the saturation magnetization Ms = 13.71 emu/g, remanent magnetization Mr = 0.1694 emu/g and, coercivity Hc = 25.6 Oe. Natural material, egg white used as an aqueous medium to extend prepare nanoparticles better than other chemical interesting materials.

Research paper thumbnail of Dramatic effect of rare earth ion on the electrical and magnetic properties of W-type barium hexaferrites

Physica B: Condensed Matter, 2010

A series of W-type hexaferrite samples with composition Ba1−yLayZn0.5Mg0.5CoFe16O27; 0≤y≤0.07 wer... more A series of W-type hexaferrite samples with composition Ba1−yLayZn0.5Mg0.5CoFe16O27; 0≤y≤0.07 were prepared using the solid state reaction to investigate their magnetic properties, AC and DC electrical conductivity and thermoelectric power as a function of composition and temperature. The X-ray diffraction was studied to identify the formation of the sample properly. Increasing of (a) and decreasing of (c) lattice parameters leads to a constant volume. The data of ac conductivity showed an increase with both temperature and frequency, and it becomes slightly independent of frequency at higher temperature, also the conduction mechanism depends on an La concentration. The results of the charge carrier mobility suggested that the hopping conduction mechanism of holes due to replacement of La3+ rare earth ions on the expense of Ba2+ ions is the predominant one. The transition temperature decreases with increasing La content. The values of dc electrical conductivity σdc at room temperature ranged 4.85×10−6–3.82×10−6(Ω−1cm−1) and the values of the calculated activation energies Edc ranged 0.215–0.137eV. The highest values of dielectric constant, electrical conductivity and Curie temperature, also the smallest value of porosity and effective magnetic moment are found at y=0.05. The thermoelectric power coefficient showed that the majority of charge carriers are P-type, except at y=0.03, 0.04 and 0.05 negative charge carriers (electrons) takes place at high temperature region.

Research paper thumbnail of Transport and magnetic properties of Co–Zn–La ferrite

Materials Chemistry and Physics, 2004

The dielectric constant (ε ) and dielectric loss factor (ε ) for the ferrite Co 1−x Zn x La y Fe ... more The dielectric constant (ε ) and dielectric loss factor (ε ) for the ferrite Co 1−x Zn x La y Fe 2−y O 4 ; 0.1 ≤ x ≤ 1.0 were measured at different frequencies (100 kHz to 5 MHz) and different temperatures (300-850 K). More than one type of polarization participates in the dielectric process, Maxwell Wagner polarization is the one participating in the high temperature region. The electrical conductivity measurement showed that there is more than one conduction mechanism participating in conductivity. The hopping mechanism either by holes or electrons or both is the predominant one. The increase in conductivity is due to the thermally activated mobility and not to thermal creation of additional mobile charge carriers. The replacement of Fe 3+ by La on octahedral sites and the presence of Co 2+ as well as Zn 2+ ions on the tetrahedral sites play a significant role in the electrical and magnetic properties behavior of the investigates samples. The values of the activation energy obtained indicate the semi-conducting behavior of the investigated ferrite.

Research paper thumbnail of Extraordinary role of rare-earth elements on the transport properties of barium W-type hexaferrite

Materials Chemistry and Physics, 2009

ABSTRACT The influence of R2O3 substitution on the electrical properties and the thermoelectric p... more ABSTRACT The influence of R2O3 substitution on the electrical properties and the thermoelectric power on the W-type hexaferrite Ba0.95R0.05 Mg0.5 Zn0.5 Co Fe16 O27; R = Y3+, Er3+, Ho3+, Sm3+, Nd3+, Gd3+, and Ce3+ ions as a function of the absolute temperature and frequency in the ranges 300–750 K and 100 kHz–4 MHz, respectively have been studied. The results obtained reveal that, by introducing a relatively small amount of R2O3 instead of Fe2O3, an important modification of both structure and physical properties can be obtained. The dielectric constant ɛ′, the dielectric loss factor ɛ″ and AC conductivity σ of the investigating samples have highest values in the case of Sm3+. The values of the calculated activation energy varied between (0.335 and 0.553 eV) and (0.106 and 0.232 eV), above and below the transition temperature, respectively which indicate the semiconducting properties of the prepared samples. The conduction mechanism for Ho3+ sample is associated with the small polaron whereas the hopping conduction mechanism is predominant mechanism for the samples doped with the rest of rare-earth ions. The thermoelectric power measurements indicated that the samples are n-type semiconductors except Er3+ and Y3+ samples, where the thermoelectric power of them is positive at low temperature but nearly above 480 and 375 K, respectively transits to negative. The charge carriers concentration n increases with slightly increasing RE ionic radius to critical value (≈1.04 Å), after that n becomes nearly constant.

Research paper thumbnail of Could Mg content control the conduction mechanism of Ba Co Zn-W-type hexagonal ferrites?

Journal of Magnetism and Magnetic Materials, 2009

Electrical properties as a function of composition, frequency and temperature for a series of W-t... more Electrical properties as a function of composition, frequency and temperature for a series of W-type hexagonal ferrites with the general formula BaCoZn 1Àx Mg x Fe 16 O 27 ; 0rxr0.6 prepared using the conventional ceramic method were studied. These samples are semiconductor-like materials, where the ac conductivity increases with increasing temperature. The results show that the conduction mechanism depends on the Mg 2+ substitution. The transition temperature (T s ) increases with increasing Mg content and gives a hump at x ¼ 0.5; after that T s decreases again. Both the ac conductivity and dielectric constant vary with Mg content and reach the highest value at x ¼ 0.5, due to the highest value of the ratio of Fe 2+ /Fe 3+ at x ¼ 0.5. The peak value of the dielectric constant depends on the Mg content x.

Research paper thumbnail of Role of Cu2+ concentration on the structure and transport properties of Cr–Zn ferrites

Journal of Magnetism and Magnetic Materials, 2009

ABSTRACT The influence of Cu concentration on the transport and microstructure characteristics of... more ABSTRACT The influence of Cu concentration on the transport and microstructure characteristics of CuyZn1−yCr0.8Fe1.2O4 with 0.2≤y≤1 ferrite was studied. X-ray, energy dispersive X- ray (EDAX) and infrared spectra (IR) were carried out to assure the formation of the sample in the proper form. The dielectric constant (ε′) and ac conductivity were measured at different frequencies ranging from 600 kHz to 5 MHz from room temperature up to 800 K. The obtained data reveals that, a single phase cubic spinel structure for all the concentrations. From the results of IR spectra, mainly two bands were observed. The dielectric constant and the dielectric loss tangent decrease with increasing frequency and Cu concentration. The dielectric constant shows a dispersion peak (ε′max) which shifts to higher frequency with increasing the temperature. The results are explained as due to the fact that the dielectric polarization process is similar to that of conduction. The appearance of the dispersion peak is related to the contribution of two types of charge carriers.

Research paper thumbnail of Influence of rare-earth ions on the structure and magnetic properties of barium W-type hexaferrite

Journal of Magnetism and Magnetic Materials, 2008

Barium W-type hexaferrite with composition Ba0.95R0.05Mg0.5Zn0.5CoFe16O27 where R=Y, Er, Ho, Sm, ... more Barium W-type hexaferrite with composition Ba0.95R0.05Mg0.5Zn0.5CoFe16O27 where R=Y, Er, Ho, Sm, Nd, Gd, and Ce ions has been prepared by the double-sintering ceramic technique. Structure of the prepared samples has been characterized by the X-ray diffraction (XRD) technique. The XRD patterns at room temperature show the presence of secondary phase with the intensity of the secondary phase increasing with increasing

Research paper thumbnail of The role of Mg substitution on the microstructure and magnetic properties of Ba Co Zn W-type hexagonal ferrites

Journal of Magnetism and Magnetic Materials, 2007

A series of W-type hexagonal ferrites with the composition BaCoZn 1Àx Mg x Fe 16 O 27 (0pxp0.6) w... more A series of W-type hexagonal ferrites with the composition BaCoZn 1Àx Mg x Fe 16 O 27 (0pxp0.6) were prepared by the conventional ceramic method to study their structural and magnetic properties as a function of temperature and composition. The characterization using X-ray diffraction indicated that a hexagonal W-type single-phase structure and the effect of composition on the unit cell parameters, density and porosity was studied. The variation of the magnetic susceptibility (w M ) with temperature for all the investigated samples in the temperature range (300-800 K) shows three regions of behavior that was explained on the basis of the distribution of Zn 2+ and Mg 2+ ions in the lattice and leads to the anomalous behavior of the effective magnetic moment m eff . The Curie temperature indicated that the critical concentration is at x ¼ 0.5. Paramagnetic nature of the samples above the Curie temperature is observed. The Curie Weiss constant y calculated from the plot of 1/w M vs. T (K) is in agreement with the expected value. The effective magnetic moment m eff decreases with increasing the intensity of magnetic field. The possible mechanisms contributing to these properties are discussed in the text. r 2007 Published by Elsevier B.V.