232 research outputs found
Strategic Choices: The Case Of Management Accounting System
While the popularity of strategic management accounting (SMA) has been growing over the last decade, there is still not an extensive literature, which directly addresses the relationship between management accounting system and strategy. The Management Accounting Research (MAR) constructed a special issue on SMA and concluded that (1) there were less than 20 key articles on this subject in the mainstream academic journals; (2) there was a lack of comprehensive conceptual framework for SMA; and (3) there was limited empirical evidence. To explore this and related issues, a study of the relative significance of the use of cost information for strategic considerations in relation to two levels of competitive analysis - corporate competitive intelligent information, and business competitive intelligent information - was undertaken. The findings of the study relate managers’ perceptions of two dimensions of their environmental changes (stability and certainty) to the two levels of competitive analysis. In order to gain a wider understanding of this relationship, a random sample of 110 large Saudi companies were selected and data collected from senior managers. The results showed that (1) the perceptions of managers differ between their environmental certainty and stability; (2) the relative significance accorded to business competitive intelligent information was positively associated with rising instability; (3) the use of corporate competitive intelligent information was a common practice. An interpretation of the results is that market instability stimulates strategic movement and cost information is being used in management thinking to support strategic development in meeting competitive pressures and in restructuring and reconfiguration of business strategy
Synthesis, Characterization, and Application of Zirconia and Sulfated Zirconia Derived from Single Source Precursors
The objective of this research was the development of new methods for the synthesis of zirconium oxide and sulfated zirconium oxide based on the preparation and utilization of novel single-source precursors based on zirconium carboxylate and zirconium sulfonate complexes. A variety of carboxylate and sulfonate compounds were treated with zirconium salts to yield new precursors. The oxide products obtained form the thermal pyrolysis of the precursors were analyzed and characterized using several techniques such as powder X-ray diffraction, thermogravimetric analysis and infrared spectroscopy. Additionally, supported sulfated zirconia was successfully obtained by dispersion of the oxide over a high surface area porous silica support known as MCM-41. The ability of the produced sulfated zirconias to catalyze two different industrial reactions was addressed. The first was the alkylation reaction of benzene utilizing ethers such as dibenzyl ether, n-butyl ether, and benzyl methyl ether as alkylating agents. The seChemistry Departmen
High Performance Photocatalytic Activity of Mg2+ Doped Hexagonal ZnO Nanoparticles in the Methylene Blue Degradation under UV Irradiation.
Mg2+ doped hexagonal ZnO nanoparticles with different Mg2+contents (0%, 1%, 2%, 3%,4%, 5%, 10%, 15%, 20% and 25%) were prepared from oxalate precursors synthesized by direct reaction in the solid state between oxalic acid dihydrate (H2C2O4.2H2O), nitrate salts of zinc (Zn(NO3)2.6H2O) and magnesium (Mg(NO3)2.6H2O) at 150 °C. The resulting precursors were subsequently calcined at 500 °C to produce the corresponding oxides. In addition, the oxalates of the single metals were also prepared by heating at 180 °C to dehydrate the complexes, before using TGA thermal gravimetric analysis to determine the temperature range of the decomposition. The obtained oxides were characterized using X-ray Diffraction (XRD), Brunauer–Emmett–Teller technique (BET), transmission electron microscopy (TEM) and tested as photocatalysts in the degradation of methylene blue (MB) under UV irradiation. The results show a segregation of phases starting at an Mg2+ content of 10%. The crystallites’ sizes, calculated using Scherer formula from the XRD data, are in the nanoscale for all the samples (19.8 to 29.8 nm), in good agreement with the particle size observed in TEM (20 to 50 nm). However, larger particles sizes were obtained from BET, ranging from 70 to 123 nm, due the agglomerated state of the powder. On the other hand, the highest efficiency as a photocatalyst in the photodegradtion of MB was observed for samples 7 and 8 corresponding to 10% and 15% in Mg2+ content respectively. The reaction rates were found to be 0.57min-1 for undoped ZnO and 1.17 min-1 for samples 7 and 8. In this range, the substituted compounds are twice more efficient than the undoped ZnO
Synthesis, characterization, thermal analysis and biological study of new thiophene derivative containing o-aminobenzoic acid ligand and its Mn(II), Cu(II) and Co(II) metal complexes
New ligand containing 2-(2,4-dioxo-4-thiophen-2-yl-butyrylamino)-benzoic acid (HL) merged moiety was synthesized and characterized by FT-IR, elemental analyses, mass spectra and 1H-NMR spectral. In the present study, the attempts were carried to form complexes of HL ligand with some transition metal ions (MnII, CuII and CoII) of well-defined at the (1:1) ratio of the components in the dimethyl sulfoxide (DMSO) solvent. All complexes have been studied by FTIR spectra, elemental analyses, thermal analysis, molar conductivity, electronic spectra and magnetic moment. The HL ligand produced as a bidentate chelate with interactive metal ions. All the results suggested octahedral geometry to complexes and have the formulae [M(HL)(Cl)2(H2O)2].nH2O where M = Mn(II), Cu(II) and Co(II). The IR spectra of the complexes were assigned and compared with the data in literature. The kinetic and thermodynamic results such as E*, ΔH*, ΔS* and ΔG* were calculated based o the TGA/DTG curves using Coats and Redfern and Horowitz and Metzger approximation methods. Furthermore, the resultant complexes were evaluated for the anti-bacterial and anti-fungal potential.
KEY WORDS: 2-(2,4-Dioxo-4-thiophen-2-yl-butyrylamino)-benzoic acid, Transition metal complexes, FTIR, TGA, Antimicrobial test
Bull. Chem. Soc. Ethiop. 2021, 35(1), 129-140.
DOI: https://dx.doi.org/10.4314/bcse.v35i1.1
Solvent free synthesis of hydrazine carbothioamide derivatives as a precursor in the preparation of new mononuclear Mn(II), Cu(II), and Zn(II) complexes: Spectroscopic characterizations
ABSTRACT. Over the last few years considerable attention has been devoted to the study of Schiff base complexes of metal(II) containing nitrogen, oxygen and sulfur donor ligands due to their diverse biological activities. Therefore, the Schiff base thiosemicarbazone derivatives of 2-(2-hydroxy-3-methoxybenzylidene) hydrazine carbothioamide (HL1) and 2-(4-bromo-2-hydroxy-3-methoxybenzylidene) hydrazine carbothioamide (HL2) were synthesized with solvent free technique using silica gel as material support for the reaction. The structures of the precursor’s organic products confirmed with their 1H, 13C NMR, IR and microanalysis data. Six new manganese(II), copper(II), and zinc(II) complexes of HL1 and HL2 2-(2-hydroxy-3-methoxybenzylidene) hydrazinecarbothioamide derivatives with the general formulation [ML1Cl] and [ML2Cl], where M = Mn2+, Cu2+, and Zn2+ were prepared and well discussed by using elemental analyses, magnetic moments, molar conductance, infrared and electronic spectral techniques. The assignments data of spectroscopic analysis confirm that the synthesized thiosemicarbazone Schiff bases of acts as a tridentate ligand as sulfur-oxygen-nitrogen donating atoms. The values of magnetic moments agreed with the data of electronic spectra which both suggested a four-coordination geometry of the synthesized complexes.
KEY WORDS: Schiff base, Thiosemicarbazone, Manganese(II) complex, Copper(II) complex, Zinc(II) complex
Bull. Chem. Soc. Ethiop. 2021, 35(2), 413-424.
DOI: https://dx.doi.org/10.4314/bcse.v35i2.1
In situ acetonitrile/water mixed solvents: An ecofriendly synthesis and structure Explanations of Cu(II), Co(II), and Ni(II) complexes of thioxoimidazolidine
ABSTRACT. The bidentate oxoacetate derivative of 4-oxo-2-thiazolidine 4ligand (L1) synthesized by the reaction of 1-(1-(Pyridin-3-yl)ethylideneamino)-2-thioxoimidazolidin-4-one 3 with diethyl oxalate with both traditional and microwave irradiation methods. The metal ion complexes of mixed ligands L1 and L2 (acetonitrile) were prepared by condensation a solution mixture of Co(II) Ni(II), and Cu(ІІ) metal chloride salts with the ligands (L1 and L2) in distilled water with stirring. The complexes were characterized by the micro analysis (C, H, N), chloride content, FT-IR, UV-Vis spectra, thermal gravimetric analysis (TGA), molar conductivity as well as magnetic susceptibility measurement. According to the obtained data the suggested coordination geometries of these complexes were suggested as octahedral structure. All the synthesized complexes were found to be electrolyte due to the presence of chloride ions outside the coordination sphere. The antibacterial activity of the L1 ligand and their metal ion complexes have been studied by screening against various microorganisms, G+ bacteria (Bacillus subtillis, Streptococcus pneumonia, and Staphyloccoccus aurease), G-bacteria (E. coli, and Pesudomonas Sp.) and fungi (Aspergillus nigaer, and Penicillium Sp.). The metal ion complexes gave the formulae: [M(L1)(L2)2(H2O)2]Cl2where M = Co(II) Ni(II), and Cu(ІІ).
KEY WORDS: Imidazolidine, Microwave irradiation, Transition metals complexes, Biological activity
Bull. Chem. Soc. Ethiop. 2021, 35(2), 351-364.
DOI: https://dx.doi.org/10.4314/bcse.v35i2.1
Synthesis, characterization and microstructural evaluation of ZnO nanoparticles by William-Hall and size-strain plot methods
ABSTRACT. At various calcination temperatures 450, 550 and 650 °C, zinc oxide nanoparticles were produced. Calcinated ZnO has high surface area as the BET was 119.12 m2g–1 and the average particle radius was calculated to be 1.16 nm. The dimension of crystallites and straining in ZnO nanoparticles' diffraction peaks remained measured. The Williamson–Hall (W–H) technique besides the size–strain approach stayed used. For each of XRD reflection peaks, physical characteristics like strain and stress were computed. Towards regulate the magnitude of crystallites, the Williamson–Hall (W–H) approach besides the size–strain technique are used that is good agreement with the size that determine from SEM as it was 22.6, 26.6 and 32.6 nm for ZnO calcinated at 450, 550 and 650 oC, individually. Using the W–H plot to modify the subversion shape, assuming an unvarying distortion model (UDM), unvarying stress deformation model (USDM), unvarying deformation energy density model (UDEDM), and The size–strain plan (SSP) approach was used to determine this. The SEM and Scherrer methods match well with the crystal size of ZnO NPs determined using W–H plots and the SSP technique.
KEY WORDS: Zinc oxide nanosphere, Calcination, Physical characterization, W–H investigation, SSP technique
Bull. Chem. Soc. Ethiop. 2022, 36(4), 815-829.
DOI: https://dx.doi.org/10.4314/bcse.v36i4.8  
Favorable Changes in Fasting Glucose in a 6-month Self-Monitored Lifestyle Modification Programme Inversely Affects Spexin Levels in Females with Prediabetes
Spexin (SPX) is a novel peptide thought to have a role in various metabolic regulations. Given its presumed body-weight regulatory functions, we aimed to determine whether lifestyle intervention programs on weight loss and fasting glucose (FG) improvement among people with impaired glucose regulation also alter levels of circulating SPX. A total of 160 Saudi adult males and females with prediabetes were randomly selected from a larger cohort (N = 294) who underwent a 6-month lifestyle modification program to improve their glycemic status. Participants were split into two groups based on differences in glucose levels post-intervention, with the first 50% (improved group) having the most significant reduction in FG. SPX was measured at baseline and after 6 months. Changes in SPX was significant only in the improved group [baseline: median (Q1\u2013Q3) of 164 pg/ml (136\u2013227) vs follow-up: 176 pg/ml (146\u2013285); p < 0.01]. When stratified by sex, the significant increase was observed only in females [159 pg/ml (127\u2013252) vs 182.5 (152,369.1); p < 0.01]. Furthermore, SPX levels showed a significant inverse association with FG (\u3b2 = 120.22, p = 0.003) even after adjustment with age and BMI, again only in females. Circulating SPX levels increase over time in people with prediabetes, particularly women who responded favorably in a 6-month lifestyle intervention program. Whether an unknown mechanism regulating the sexual disparity seen in SPX levels post-intervention exists should be further investigated using a larger sample size
P-[N-(DiphenylÂphosphoÂrothioÂyl)isoÂpropylÂamino]-N-isopropyl-P-phenylÂthioÂphosphinic amide
The title compound, C24H30N2P2S2, was obtained by the reaction of Ph2PN(iPr)P(Ph)N(iPr)H with elemental sulfur in tetraÂhydroÂfuran. In the solid state, intraÂmolecular N—H⋯S hydrogen bonding influences the molÂecular conformation; a P—N—P—N torsion angle of 2.28 (9)° is observed. The two phenyl rings attached to one P atom form a dihedral angle of 74.02 (4)°
A new simple route for synthesis of cadmium(II), zinc(II), cobalt(II), and manganese(II) carbonates using urea as a cheap precursor and theoretical investigation
ABSTRACT. The MnCO3.H2O, CoCO3.4H2O, ZnCO3, and CdCO3, respectively, were synthesized through a new precise, easy pathway for the reaction of MnI2, CoI2, ZnI2, or CdI2 aqueous solutions with a cheap precursor-urea for 10 h at ~ 70 oC. The IR spectra of reaction products designate the presence of characteristic bands of ionic carbonate, CO32– and absence of the individual bands of urea. The (CO3)2- ion is planar and therefore, it belongs to the D3h symmetry. It is expected to display four modes of vibrations. The stretching vibrations of the type; n(C-O) is observed in the range of (1376-1503) cm-1 while another stretching vibration n(C-O) is observed in the region 1060-1079 cm-1. The out of plane of vibration d(OCO) is observed in the range of (833-866) cm-1 while, the angle deformation bending vibration d(OCO) appear in the range of (708-732) cm-1. The infrared spectra of metal carbonate, show that, this product clearly has an uncoordinated water. The band related to the stretching vibration n(O-H) of uncoordinated H2O is observed as expected in the range of ~ 3000 cm-1. A general mechanism explaining the synthesis of carbonate compounds of cadmium(II), zinc(II), cobalt(II), and manganese(II), are described. Moreover, the DFT outcomes using B3LYP/LanL2DZ (basis set) agree with the experimental results.
KEY WORDS: Carbonate, CoI2, Infrared spectra, Urea, DFT
Bull. Chem. Soc. Ethiop. 2022, 36(2), 363-372.
DOI: https://dx.doi.org/10.4314/bcse.v36i2.10  
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