E.A. Hassan

Synthesis, antitubercular activity and pharmacokinetic studies of some Schiff bases derived from 1-alkylisatin and isonicotinic acid hydrazide (INH).

N′-(1-alkyl-2,3-dihydro-2-oxo-1H-3-indolyliden)-4-pyridinecarboxylic acid hydrazide derivatives,3(a-g), were synthesized in a trial to overcome the resistance developed with the therapeutic uses of isoniazid (INH). The lipophilicity of the synthesized derivatives supersedes that of the INH as expressed by Clog p values. The synthesized compounds and INH were tested against bovin, human sensitive and human resist strains of Mycobacterium tuberculosis. Compounds3a, 3d, 3f and3g with 1-unsubstituted, 1-propyl, 1-propynyl and 1-benzyl groups respectively exhibited equipotent growth inhibitory activity (MIC 10 μmol) against the tested strains as compared with INH however the later has no activity against human resist strain. Pharmacokinetic study revealed that the rate and extent of absorption of the tested derivatives (3d and3f) significantly higher than that of INH (p<0.05). The relative bioavailabilities (FR%) were 183.15 and 443.25 for3f and3d respectively as compared to INH. These results preliminary indicate the possible use of the prepared derivatives for treatment of tuberculosis infections in order to overcome the resistance developed with INH.

Active surface centres in a heterogeneous CdO catalyst for ethanol decomposition

Abstract The dehydration of ethanol was studied over pure CdO. The kinetics of the dehydration reaction and the effect of pretreatment of the catalysts, lattice structure and specific surface areas were studied. On the basis of these experimental data, a mechanism of ethanol dehydration was proposed. The proposed mechanism depends entirely on the presence of oxygen ion vacancies and the interstitial cadmium atoms as active sites in the heterogeneous catalytic reaction.

Electrical conductivity and thermogravimetric studies of the thermal decomposition of doped cobalt carbonate

Abstract The effect of CdO on the thermal decomposition of cobaltous carbonate was studied. Measurements were carried out using thermogravity and electrical conductivity. The results show that addition of CdO retards the decomposition process via annihilation of holes created in cobaltic oxide. The non-stoichiometry and activity of the thermal decomposition products up to 500 °C were measured by means of the decomposition of N2H4 and H2O2 using a gasometric technique. The results show that the Co2+ ions are the active centres. The increase in activity when the CdO content is increased to 5 mol.% is attributed to an enhancement in the transition from Co3+ ions to Co2+ ions. The decomposition mechanism for H2O2 is proposed.

Role of the Structural and Electronic Properties of Molybdenum Trioxide Catalysts on the Structure-Sensitive Oxidation of Methanol to Formaldehyde

SummaryAs catalysts for selective oxidation, molybdenum trioxide catalysts—prepared by two different methods—have been investigated. The results of vapor-phase oxidation of methanol are discussed on the basis of the acidic property, oxidizing functions, and the crystallographic structure of the catalysts. It was found that the acidic property is not the sole factor deciding the catalytic activity. Electrical conductivity measurements proved that molecular oxygen in the gas feed is necessary for maintaining the catalysts active. The difference in the catalytic activity and selectivity were reasonably interpreted in view of the structure sensitivity of those catalysts. A redox mechanism is also discussed in this paper.ZusammenfassungAuf zwei verschiedene Arten hergestellte Molybdäntrioxidkatalysatoren wurden für selektive Oxidationen untersucht. Die Ergebnisse der Dampfphasenoxidation von Methanol werden auf Basis der sauren Eigenschaften, der oxidierenden Funktionen und der kristallographischen Struktur der Katalysatoren diskutiert. Es wurde festgestellt, daß die sauren Eigenschaften zur Erklärung der entscheidenden Wirksamkeit der Katalysatoren nicht alleine verantwortlich sind. Elektrische Leitfähigkeitsmessungen zeigten, daß molekularer Sauerstoff im zugeleiteten Gas zur Erhaltung der katalytischen Aktivität notwendig ist. Die Unterschiede in der Katalysatoraktivität und der Selektivität sind aus der Struktur der Katalysatoren zu erklären. Es wird ein adäquater Redox-Mechanismus diskutiert.

Effect of oxide additives on the thermal decomposition of KClO4

Abstract The decomposition of KClO4 was used as a test reaction to study the effect of catalyst properties such as surface area, non-stoichiometry and electrical characteristics. Such studies were carried out using thermogravimetric analysis to monitor the thermal decomposition process. The results indicate that p-type oxides enhance the decomposition process more than n-type oxides do. However, oxides with both p-type and n-type properties, e.g. Cr2O3, can effectively decompose KClO4 at lower temperatures. The effect of p-type and n-type semiconductor properties on the decomposition mechanisms is discussed.

A study on the thermal decomposition of iron-cobalt mixed hydroxides

Thermal decomposition of pure Fe(OH)3 and mixed with Co(OH)2 were studied using TG, DTA, kinetics of isothermal decomposition and electrical conductivity measurements. The thermal products were characterized by X-ray diffraction and IR spectroscopy. The TG and DTA analysis revealed the presence of Co2+ retards the decomposition of ferric hydroxide and the formation of α-Fe2O3. The kinetics of decomposition showed that the mixed samples need higher energy to achieve thermolysis. The investigation of thermal products of mixed samples indicated the formation of cobalt ferrite on addition ofx=1 or 1.5 cobalt hydroxide. The electrical conductivity accompanying the thermal decomposition decreases in presence of low ratio of Co2+ (x=0.2) via the consumption of holes created during thermal analysis. The continuous increase in σ values on increasing of Co2+ concentration corresponded to the electron hopping between Fe2+ and Co3+.ZusammenfassungMittels TG, DTA und der Kinetik von Messungen der isothermen Zersetzung und der elektrischen Leitfähigkeit wurde die Zersetzung von Fe(OH)3 in reinem Zustand und vermengt mit Co(OH)2 untersucht. Die thermischen Produkte wurden mittels Röntgendiffraktion und IR-Spektroskopie charakterisiert. TG und DTA zeigen, daß die Zersetzung von Eisen(III)-hydroxid und die Bildung von -Fe2O3 durch Gegenwart von Co2+ verzögert wird. Die Zersetzungskinetik zeigt, daß die Mischproben mehr Energie für die Thermolyse benötigen. Die Untersuchung der thermischen Produkte zeigt die Bildung von Cobaltferrit bei Zusatz vonx=1 oder 1,5 Cobalthydroxid. Die elektrische Leitfähigkeit nimmt bei der thermischen Zersetzung in Gegenwart von niedrigen Co2+-Konzentrationen (x=0.2) durch Verbrauch der bei der Thermoanalyse geschaffenen Löcher ab. Das monotone Ansteigen der -Werte bei steigender Co2+-Konzentration stimmt mit dem Überspringen von Elektronen zwischen Fe2+ und Co3+ überein.

A study of the effect of lithium and aluminium on the thermal decomposition of nickel hydroxide

Abstract The decomposition of Ni(OH)2 in air was monitored thermogravimetrically. It was found that the cationic vacancies and holes created and doping of the parent material with either Li+ or Al3+ ions affect the thermal decomposition rate. The doping appears to influence the surface properties of the final products. The variation with doping percentage in vacuum of the value of SBET for the final products is discussed.

Patterns of Candida biofilm on intrauterine devices.

Biofilms are colonies of microbial cells encased in a self-produced organic polymeric matrix and represent a common mode of microbial growth. Microbes growing as biofilm are highly resistant to commonly used antimicrobial drugs. We aimed to screen and characterize biofilm formation by different isolates of Candida on removed intrauterine devices (IUDs), to perform experimental biofilm formation with isolated strains, and to examine biofilm by the crystal violet and XTT reduction assays and scanning electron microscopy (SEM). A total of 56 IUDs were examined for biofilm formation using Sabourauds dextrose chloramphenicol agar. Suspected colonies were identified by different methods. Antifungal susceptibility testing with fluconazole (FLU) and amphotericin B for the isolated strains and in vitro experimental biofilm formation was carried out. The biofilm was quantified by crystal violet, XTT reduction assay and SEM. Among the 56 IUDs investigated, 26 were Candida positive (46.4 %). Candida albicans was recovered from 15 isolates. The biofilm MIC of FLU was increased 64 to 1000 times compared to the MIC for planktonic cells. The XTT method results were dependent on the Candida species; biofilm formation was highest in Candida krusei and Candida glabrata strains, followed by C. albicans and Candida tropicalis. SEM of Candida biofilm revealed a heterogeneous thick biofilm with a mixture of micro-organisms. The main conclusion from this study was non-albicans Candida represents more than a half of the Candida biofilm. Better understanding of Candida biofilms may lead to the development of novel therapeutic approaches for the treatment of fungal infections, especially resistant ones among IUD users.

Influence of additives to chromium oxide catalysts for the thermal decomposition of KClO4

Abstract The effect of doping on the catalytic behaviour of Cr 2 O 3 was studied using the thermal decomposition of KClO 4 as a test reaction. The doping of the catalysts was effected using 5 mol.% Li + , Zr 4+ or U 6+ ions and calcination at 600 °C for 5 h. Studies were carried out using thermogravimetric analysis and electrical conductivity measurements. The results showed that Cr 2 O 3 was more effective in enhancing the decomposition process when it was doped with U 6+ ions than when it was doped with Li + or Zr + ions. Mechanisms of doping were discussed and the role of defects in the catalytic reaction was interpreted.

Action of chromium oxide as a catalyst in the course of KMnO4 decomposition

Abstract The enhancing influence of chromium oxide as a catalyst for the decomposition of KMnO 4 has been studied. Its action was attributed to the presence of surface holes in accepting the released electrons from the intermediate step. There is an indication that a solid-state interaction occurs between the catalyst and the products of decomposition. The reaction products were identified using IR spectroscopy. The inhibition of either Zr 4+ or U 6+ cations is attributed to the doping effect via the consumption of surface as well as bulk holes.