Hajjah University

Ḩajjah, Yemen

Hajjah University

Ḩajjah, Yemen
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Alsabah Y.A.,Neelain University | Alsabah Y.A.,King Saud University | Alsabah Y.A.,Hajjah University | AlSalhi M.S.,King Saud University | And 2 more authors.
Journal of Alloys and Compounds | Year: 2017

We studied the structural and optical properties of Ba2Zn1-xNixWO6 (0 ≤ x ≤ 1) double perovskites prepared by a solid-state reaction route using various tools, such as X-ray diffraction (XRD), scanning electron microscopy/energy dispersive X-ray (SEM/EDX), ultraviolet (UV)-visible diffuse reflectance, and photoluminescence. Rietveld refinement of the powder XRD data revealed that the compounds were highly crystalline and had a cubic crystal structure within the space group Fm-3m. The XRD results were consistent with EDX spectra results. SEM images exhibited large variation in the particle size with increasing zinc (Zn2+) and nickel (Ni2+) cations. The band gap of Ba2Zn1-xNixWO6 oxides calculated from the diffuse reflection spectra using Tauc plot was found between 3.18 and 3.53 eV, which indicated a wide-band gap semiconductor behavior in all samples. Finally, the photoluminescence study was performed at room temperature. Due to the high reflectance of the prepared double perovskite, we suggest that the material can be used for sunglass fabrication or photovoltaic energy conservation. © 2017 Elsevier B.V.


Alsabah Y.A.,Neelain University | Alsabah Y.A.,King Saud University | Alsabah Y.A.,Hajjah University | AlSalhi M.S.,King Saud University | And 2 more authors.
Materials | Year: 2017

The effect of Sr2+ substitution on the morphology, crystal structure, and optical properties of double perovskite oxide Ba2-xSrxZnWO6 (x = 0.00, 0.25, 0.50, 0.75, 1.00) were investigated. Scanning electronic microscopy demonstrated that all samples have similar microstructure morphology but differ in the range of grain sizes. X-ray diffraction measurements indicated that these materials crystallize in a (Fm-3m) cubic crystal structure, and also confirmed the tolerance factor. Rietveld analysis revealed that the lattice parameter decreased from 8.11834 to 8.039361 Å when the substitution of Ba2+ with Sr2+ cations increased from zero to 100%. Fourier transform infrared (FTIR) and Raman spectroscopies displayed a symmetric stretching vibration of WO6 octahedra at 825 cm-1, and an anti-symmetric stretching mode of WO6 was observed by FTIR at 620 cm-1. A strong peak at 420 cm-1 was also observed in the Raman spectra and is due to theW-O-W bending vibration modes. UV-Vis diffuse reflectance spectroscopy was carried out for the series, and the band gap energy decreased from 3.27 eV for Ba2ZnWO6 to 3.02 and 3.06 eV for Ba1.75Sr0.25ZnWO6 and Ba1.5Sr0.5ZnWO6, respectively. The excitation and emission photoluminescence properties were investigated at room temperature. © 2017 by the authors.


Sattar A.A.,Ain Shams University | El-Sayed H.M.,Ain Shams University | Alsuqia I.,Hajjah University
Journal of Magnetism and Magnetic Materials | Year: 2015

CoFe2O4/NiFe2O4 core/shell magnetic nanocomposite was synthesized by using hydrothermal method.The analysis of XRD indicated the coexistence of CoFe2O4, NiFe2O4as core/shell composite. The core/shell structure of the composite sample has been confirmed by HR-TEM images, EDX and FT-IR measurements. The size of obtained core/shell nanoparticles was 17 nm in core diameter and about 3 nm in shell thickness. The magnetization measurements showed that both the coercive field and the saturation magnetization of the resulting core/shell nanocomposite were slightly decreased compared to those of the CoFe2O4 core but the thermal stability is of the magnetization parameter was enhanced. Furthermore, superparamagnetic phase is established at temperatures higher than the room temperature. The results were discussed in terms of the surface pinning and the magnetic interaction at the interface between the core and shell. © 2015 Elsevier B.V.All rights reserved.


El Sawaf B.M.,Ain Shams University | Kassem H.A.,Ain Shams University | Mogalli N.M.,Hajjah University | El Hossary S.S.,Ain Shams University | Ramadan N.F.,Ain Shams University
Acta Tropica | Year: 2016

This report presents the results of the first entomological survey of the sand fly fauna in northwestern Yemen. Sand flies were collected using sticky paper traps and CDC light traps from Hajjah governorate, a cutaneous leishmaniasis focus due to Leishmania tropica. Six Phlebotomus species: P. alexandri, P. arabicus. P. bergeroti, P. orientalis, P. papatasi, P. sergenti and ten Sergentomyia species: S. africana, S. antennata, S. christophersi, S. dolichopa, S. dreyfussi, S. fallax, S. multidens, S. taizi, S. tiberiadis, S. yusafi were identified. P. alexandri was the most predominant Phlebotomus species and P. papatasi was a scarce species. S. fallax was the principal Sergentomyia species and S. dolichopa was the least species encountered. The diversity of the sand fly fauna within and among three altitudinal ranges using Simpson index and Jaccard's diversity coefficient respectively were measured. High species diversity was found in all altitude ranges. There seemed to be more association between sand fly fauna in higher altitudes with fauna from moderate altitudes. Sand fly seasonal activity showed a mono-modal trend in the lowland and a confluent bimodal trend in the highlands. Leishmania DNA could not be detected from 150 Phlebotomus females using PCR-RFLP. A possible zoonotic cutaneous transmission cycle due to Leishmania tropica in northwestern Yemen would involve P. arabicus as the sand fly vector and the rock hyrax as the reservoir host. The vector competence for P. alexandri as a vector of visceral leishmaniasis in Hajjah governorate is discussed. © 2016 Elsevier B.V.


PubMed | Ain Shams University and Hajjah University
Type: | Journal: Acta tropica | Year: 2016

This report presents the results of the first entomological survey of the sand fly fauna in northwestern Yemen. Sand flies were collected using sticky paper traps and CDC light traps from Hajjah governorate, a cutaneous leishmaniasis focus due to Leishmania tropica. Six Phlebotomus species: P. alexandri, P. arabicus. P. bergeroti, P. orientalis, P. papatasi, P. sergenti and ten Sergentomyia species: S. africana, S. antennata, S. christophersi, S. dolichopa, S. dreyfussi, S. fallax, S. multidens, S. taizi, S. tiberiadis, S. yusafi were identified. P. alexandri was the most predominant Phlebotomus species and P. papatasi was a scarce species. S. fallax was the principal Sergentomyia species and S. dolichopa was the least species encountered. The diversity of the sand fly fauna within and among three altitudinal ranges using Simpson index and Jaccards diversity coefficient respectively were measured. High species diversity was found in all altitude ranges. There seemed to be more association between sand fly fauna in higher altitudes with fauna from moderate altitudes. Sand fly seasonal activity showed a mono-modal trend in the lowland and a confluent bimodal trend in the highlands. Leishmania DNA could not be detected from 150 Phlebotomus females using PCR-RFLP. A possible zoonotic cutaneous transmission cycle due to Leishmania tropica in northwestern Yemen would involve P. arabicus as the sand fly vector and the rock hyrax as the reservoir host. The vector competence for P. alexandri as a vector of visceral leishmaniasis in Hajjah governorate is discussed.


PubMed | Ain Shams University, Hajjah University and Saudi Hospital
Type: | Journal: Acta tropica | Year: 2016

The clinicoepidemiologic profile of 143 cases (93 males and 50 females) with cutaneous leishmaniasis from 18 villages of Hajjah governorate, Yemen was studied. Dry-type lesions were seen in 98.6% and wet-type lesions in 1.4% of patients. Lesions were localized in all cases with different morphological patterns. Microscopic examination of Giemsa-stained slit smears revealed amastigotes in 74.1% of patients with dry-type lesions and 0% in patients with wet-type lesions. The burden of the parasites in the lesions was high indicating active transmission of the disease. Most cases were from villages with moderate altitude range (8001-1600m). All age groups were affected, but most cases were seen in ages from 5 to 15 years. Leishmania species identification was done for all cases by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The biopsic material was scraped from both Giemsa-stained and methanol-fixed smears. The molecular characterization of Leishmania species revealed Leishmania tropica as the causative agent of cutaneous leishmaniasis in Hajjah, Yemen. The risk factors associated with the transmission of the disease and recommendations for improving case detection were discussed.


Berenblyum A.S.,Lomonosov Moscow University of Fine Chemical Technology | Al-Wadhaf H.A.,Hajjah University | Katsman E.A.,Lomonosov Moscow University of Fine Chemical Technology | Shamsiev R.S.,Lomonosov Moscow University of Fine Chemical Technology | Koroleva A.A.,Lomonosov Moscow University of Fine Chemical Technology
Petroleum Chemistry | Year: 2014

The reduction reaction of Pd(II) diacetate, a precursor in nanocatalyst synthesis, with molecular hydrogen on silica gel has been studied. A kinetic model involving the autocatalytic mechanism of Pd(II) reduction to Pd(0) and adequately describing the experimental data has been proposed. Similarities and dissimilarities in the mechanism of this process on silica gel and carbon have been revealed. On the basis of quantum-chemical simulation data, it has been suggested that the differences are due to both a high bond energy of the precursor with the support and modifications in geometry of various Pd(II) diacetate species adsorbed on the surface. The controllable reduction of the precursor makes it possible to manufacture materials with a metal particle size of 1.7-2.8 nm according to transmission electron microscopy data. The materials catalyze the reaction of phenylacetylene hydrogenation to styrene with a high activity and selectivity at 25°C and 1 atm of hydrogen. © 2014 Pleiades Publishing, Ltd.


Gadallah A.-S.,Cairo University | Alhijry I.A.,Mansoura University | Alhijry I.A.,Hajjah University | Abdelkader H.I.,Mansoura University | Abou Kana M.T.H.,Cairo University
Optics and Laser Technology | Year: 2015

Abstract The influence of [Ag NPs: PM567] complex formation on optical properties of parent PM567 laser dye in 2-hydroxyethyl methacrylate (homomonomer, homopolymer) and 2-hydroxyethyl methacrylate/methyl methacrylate (comonomer, copolymer) hosts was studied at room temperature. The silver nanoparticles were synthesized by chemical reduction method. Its size and concentration was determined by high resolution transmission electron microscope and UV/VIS absorption spectroscopy. The experimental results showed that the optical properties of dye were remarkably enhanced with optimum concentrations of NPs and dye. The effect of different nanoparticle concentrations on the optical properties of complex based not only on NPs and dye concentrations, but also on nature of milieu. Whereas, [1 × 10-4 mol/L PM567:40% C Ag NPs] and [1 × 10-3 mol/L PM567:40% C Ag NPs] were the optimum complexes in case of monomer and polymer hosts respectively. Also, at optimum concentration of PM567 dye in polymeric samples (1 × 10-3 mol/L), the gain values of dye in HEMA were 1.9 and 2.4 with respect to absence and presence of Ag NPs. While in HEMA/MMA copolymer, the gain values were 1.8 and 2.45 respectively. In a deeper study, [1 × 10-3 mol/L: 40% C Ag NPs] complex in HEMA/MMA copolymer host had preferable ASE Slope efficiencies and photostabilities, compared with complex in HEMA homopolymer host. © 2015 Elsevier Ltd.


The selective hydrogenation of phenylacetylene (PhA) into styrene (St) in the presence of a palladium nanocatalyst has been investigated. Salient features of this reaction have been revealed, such as independence of the PhA hydrogenation and St hydrogenation (after exhaustion of PhA) rates from the PhA and St concentrations, respectively; their nearly first-order dependence on the hydrogen pressure; and the first order in catalyst loading. The experimental results obtained according to a special plan have been processed using computer programs for various reaction mechanisms. It has been found that adequate description is achieved for the only scheme involving the adsorption one to two PhA and/or St molecules and one to two hydrogen molecules on the active site of the same type. The presence of one hydrogen molecule on the active site leads to the hydrogenation of PhA to St or St to ethylbenzene (EB). In the presence of two adsorbed hydrogen molecules, PhA is selectively hydrogenated to St and nonselectively hydrogenated directly to EB. It has been shown that the nature of the selectivity of the palladium catalyst is determined by the thermodynamics of competitive adsorption of PhA and St. The activation energies of the individual steps of the process have been determined. © 2014 Pleiades Publishing, Ltd.


Al-Wadhaf H.A.,Hajjah University
Catalysis in Industry | Year: 2015

Silica-supported palladium materials containing 4.0 and 9.1 wt % Pd have been synthesized. It has been demonstrated by electron microscopy that these materials are nanosized systems, with a Pd particle size of 1.70 ± 0.72 and 1.30 ± 0.64 nm, respectively. The effects of Pd content and precursor (palladium(II) acetate) reduction conditions on the catalytic properties of Pd/SiO2 in the selective hydrogenation of phenylacetylene into styrene at 25°C have been investigated. Increasing the palladium content from 4.0 to 9.1% and raising the reduction temperature from 50 to 120°C do not cause any significant coarsening of the Pd particles and, accordingly, exert only a weak effect on the rate and selectivity of phenylacetylene hydrogenation. The nanosized Pd/SiO2 systems have been demonstrated to be efficient catalysts for phenylacetylene hydrogenation, an industrially important process. They afford a high styrene selectivity of 96.75 and 90.3% at conversions of about 50 and 100%, respectively, which is well above the maximum selectivity that was earlier attained in alkyne hydrogenation (at most 75% at ∼100% conversion). © 2015 Pleiades Publishing, Ltd.

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