Mohammed Suleiman

Phase transition and lattice expansion during hydrogen loading of nanometer sized palladium clusters

Abstract In situ X-ray diffraction (XRD) measurements for Pd-clusters (3.8 and 6.0 nm) are performed during hydrogen loading and unloading. The lattice parameter increases as a function of the hydrogen partial pressure. The expansion is smaller than that of bulk palladium and is shown to be cluster-size dependent. An (α–α′) phase transition was observed for the large clusters but small clusters do not show this transition. XRD analysis of the as-prepared clusters show that the 3.8-nm sized clusters predominantly have an icosahedral structure, while the 6.0-nm sized clusters have a cubic structure. The effect of size and structure of the cluster on the lattice expansion and on the phase transition will be discussed.

Anticonvulsant Effects of Some Arab Medicinal Plants

AbstractThe effect of the aqueous extracts of leaves and stems of Rosmarinus officinalis, Pimpinella anisun, Matricaria chamomilla, Artemisia vulgaris. Origanum vulgare, Lupinus albus and Olea europaea, were studied on the Picrotoxin-induced seizures in mice. In this study, the effect on the mortality rate, onset of convulsion, and γ-aminobutyric acid (GABA) content, were monitored. Extracts of Rosmarinus officinalis, Pimpinella anisum, Matricaria chamomilla and Artemisia vulgaris were found to delay the onset of picrotoxin-induced seizures and to decrease the mortality rate. On the other hand, extracts of Origanum vulgare, Lupinus albus and Olea europaea were found to have no effect on the onset of convulsions or on the mortality rate.

One Step Synthesis of NiO Nanoparticles via Solid-State Thermal Decomposition at Low-Temperature of Novel Aqua(2,9-dimethyl-1,10-phenanthroline)NiCl2 Complex

[NiCl2(C14H12N2)(H2O)] complex has been synthesized from nickel chloride hexahydrate (NiCl2·6H2O) and 2,9-dimethyl-1,10-phenanthroline (dmphen) as N,N-bidentate ligand. The synthesized complex was characterized by elemental analysis, infrared (IR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy and differential thermal/thermogravimetric analysis (TG/DTA). The complex was further confirmed by single crystal X-ray diffraction (XRD) as triclinic with space group P-1. The desired complex, subjected to thermal decomposition at low temperature of 400 ºC in an open atmosphere, revealed a novel and facile synthesis of pure NiO nanoparticles with uniform spherical particle; the structure of the NiO nanoparticles product was elucidated on the basis of Fourier transform infrared (FT-IR), UV-vis spectroscopy, TG/DTA, XRD, scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDXS) and transmission electron microscopy (TEM).

Electrochemical Reduction of Metronidazole and Its Determination in Pharmaceutical Dosage Forms by D.C. Polarography

Abstract A simple d.c. polarographic method has been developed for the determination of metronidazole in dosages forms. In Robinson - Britton buffer (pH 4.38) and in presence of 1.60 × 10−3 % Triton X-100, the drug produced a well defined 4-electron polarographic wave followed by another wave of about half the height of the first wave. The current is proportional to the concentration and permits the drug to be determined by d.c. polarography in the concentration range 5.0 × 10−5 -7.0 × 10−4 M. Results obtained by the proposed method are in excellent agreement with that provided by the USP-XX method. A rapid, sensitive and accurate polarographic method for the determination of metronidazole in the tablets which are produced locally is proposed.

Hypotensive Effect of Crataegus oxyacantha

AbstractThe hypotensive effect of the herb Crataegus oxyacantha was investigated in vivo using normal anaesthetised rats. An aqueous extract of Crataegus oxyacantha leaves was found to produce a significant decrease in the systolic, diastolic and mean blood pressure, but no effect was noticed on heart rate. The hypotensive effect was dose dependent and reversible with a median effective dose of 31 mg/kg. It seems that the hypotensive effect of Crataegus oxyacantha is not mediated via adrenergic, muscarinic or histaminergic receptors.

The influence of harmaline on the movements of sodium ions in smooth muscle of the guinea pig ileum

SummaryThe effect of changing the extracellular concentration of both Na+ and K+ on the longitudinal muscle of the guinea-pig ileum was studied in the presence and absence of harmaline. A decrease in extracellular Na+ concentration was found to produce a dose-dependent contractile response, which may suggest the existence of a Na...Ca exchange mechanism in this muscle. Harmaline (2 × 10−4 M) was found to reversibly inhibit this contraction and was also found to selectively block the tonic component of high-K induced contradictions. In view of the fact that harmaline is a non-competitive inhibitor of Ca-induced contractions (Hider et al., Europ. J. Pharmacol., 71, 87, 1981), the action of harmaline was interpreted as being a specific inhibitor of the Na... exchange mechanism, binding specifically to Na+ coordination sites.

N-[(1E)-(3-Bromophenyl)methylene]-N-(2-piperidin-1-ylethyl)amine

N-[(1E)-(3-Bromophenyl)methylene]-N-(2-piperidin-1-ylethyl)amine Schiff base was prepared in good yield and characterized by the reflux of equivalent amounts of 2-(piperidin-1-yl)ethanamine with 3-bromobenzaldehyde. The structure of the desired Schiff base was analyzed based on: elemental analysis, EI-MS, TG/DTG, UV-visible, FT-IR, 1H and 13C-NMR spectral analysis. The condensation reaction was monitored by FT-IR.

Size and Structure of Palladium Clusters Determined by XRD and HREM

Abstract Scherrer formula is often applied to X-ray-diffraction profiles for the size determination of small size clusters. However, for small clusters this often leads to conflicting results in comparison to other methods. A series of Pd-clusters of different size is studied by X-ray diffraction analysis and transmission electron microscopy. The influence of size and structure on the results is presented and discussed in comparison with theoretical calculations. It will be shown that the different structure of small size systems are one main origin of the conflicts. The structure problem can be overcome by using Fourier Transform of the X-ray diffraction pattern. The importance of the knowledge of the cluster structure was demonstrated by showing its strong influence on the hydrogen solubility.

Design, Synthesis, Characterization of Novel Ruthenium(II) Catalysts: Highly Efficient and Selective Hydrogenation of Cinnamaldehyde to (E)-3-Phenylprop-2-en-1-ol

In this contribution, two novel supported and non-supported ruthenium(II) complexes of type [RuCl2(dppme)(NN)] where [dppme is H2C=C(CH2PPh2)2 and NN is N1-(3-(trimethoxysilyl)propyl)ethane-1,2-diamine] were prepared. The NN co-ligand caused release of one of the dppme ligands from [RuCl2(dppme)2] precursor to yield complex 1. The process of substitution of dppme by NN was monitored by 31P{1H}-NMR. Taking advantage of the presence of trimethoxysilane group in the backbone of complex 1, polysiloxane xerogel counterpart, X1, was prepared via sol-gel immobilization using tetraethoxysilane as cross-linker. Both complexes 1 and X1 have been characterized via elemental analysis, CV and a number of spectroscopic techniques including FT-IR, 1H-, 13C-, and 31P-NMR, and mass spectrometry. Importantly, carbonyl selective hydrogenation was successfully accomplished under mild conditions using complex 1 as a homogenous catalyst and X1 as a heterogeneous catalyst, respectively.

Hydrogen absorption in 3.1 nanometre sized palladium samples: does structure matter?

Abstract In this work the hydrogen absorption behaviour of two types of Pd-clusters, different in structure but similar in size (3.1 nm), will be presented. First, icosahedral Pd clusters stabilised in surfactants; second, cubic Pd clusters stabilised in a Teflon-AF matrix. The phase transition in these samples was monitored by in-situ X-ray diffraction. It will be shown that the hydrogen uptake ability depends strongly on the lattice structure, which is affected by the type of stabiliser. Teflon AF stabilised clusters (cubic clusters) show the phase transition which is common for bulk Pd, whereas the surfactant stabilised clusters (icosahedral clusters) show only weak lattice dilatation upon hydrogen absorption. Pressure – lattice parameter isotherms show that the cubic clusters absorb large amounts of hydrogen in comparison to the icosahedral clusters. The measured lattice expansion is 0.130 Å at 105 Pa and 300 K, which is about 320 % the amount measured for icosahedral clusters (0.04 Å). This suggests that surface sites are available for hydrogen in the Pd – Teflon-AF samples which are not accessible for Pd – surfactant-clusters, and that the icosahedral lattice absorbs less hydrogen for similar external pressures.