Research Papers/Topics in Chemistry

M2(H2O)[μ10-C6H2(COO)4] (M = Ba2+, Pb2+) – Two Isotypic Three- Dimensional Coordination Polymers with a Layer-like Separation between Anions and Cations

Abstract. Z. Anorg. Allg. Chem. 641 (2015) 1150–1155. (DOI: 10.1002/zaac.201500050). Monoclinic single crystals of Ba2(H2O)[μ10-C6H2(COO)4] (1) and Pb2(H2O)[μ10- C6H2(COO)4] (2) were obtained using the silica gel method [space group C2/c (no. 15), Z = 4; 1: a = 780.89(4), b = 1756.19(8), c = 914.80(5) pm, β = 114.512(5)°; 2: a = 756.70(10), b =1772.8(2), c = 890.2(2) pm, β = 113.590(10)°]. There are two crystallographically independent M2+ ions (M = Ba, Pb). M(1) is surrounded by eigh...

Magnetic, Optical, Dielectric, and Sintering Properties of Nano-crystalline BaFe0.5Nb0.5O3 Synthesized by a Polymerization Method

Abstract A one-pot polymerization method using citric acid and glucose for the synthesis of nano-crystalline BaFe0.5Nb0.5O3 is described. Phase evolution and the development of the crystallite size during decomposition of the (Ba,Fe,Nb)-gel were examined up to 1100 °C. Calcination at 850 °C of the gel leads to a phase-pure nano-crystalline BaFe0.5Nb0.5O3 powder with a crystallite size of 28 nm. The shrinkage of compacted powders starts at 900 °C. Dense ceramic bodies (relative densit...

A Barium Germanium 1,2-ethanediolato Complex as Precursor for Barium Metagermanate

Abstract: Thermochim. Acta 457 (2007) 55-63. (DOI: 10.1016/j.tca.2007.02.021). The thermal behaviour of [Ba(HOC2H4OH)2Ge(OC2H4O)3] (2) as a BaGeO3 precursor, and its phase evolution during thermal decomposition in different atmospheres are described herein. The precursor complex decomposes in air to a finely divided mixture of BaCO3 and GeO2, which subsequently reacts above 650 °C to orthorhombic BaGeO3, transforming above 800 °C to hexagonal BaGeO3. The shrinkage behaviour of BaGeO3 co...

Synthesis and Characterization of a Nano-scaled Barium Cerate Perovskite Powder Using Starch as Polymerization Agent

Abstract. Solid State Ionics 203 (2011) 52–56. (DOI: 10.1016/j.ssi.2011.09.010). The preparation of nano-sized BaCeO3 powder using starch as a polymerization agent is described herein. Phase evolution during the decomposition process of a (BaCe)-gel was monitored by XRD. A phase-pure nano-sized BaCeO3 powder was obtained after calcining of the (BaCe)-gel at 920 °C. The resulting powder has a specific surface area of 15.4m2/g. TEM investigations reveal particles mainly in the size range ...

Sintering of a Fine-grained BaCeO3 Powder Obtained from a Co-precipitation Method

Abstract. J. Mater. Sci. 45 (2010) 6521–6527. (DOI: 10.1007/s10853-010-4741-8). The formation of BaCeO3 by a co-precipitation method is described herein. The coprecipitation route leads to an orange (BaCe)-precursor powder (1). To improve the sintering behaviour, a small amount of Ge4+ was incorporated, leading to a (BaCe0.95/Ge0.05)-precursor (2). Both precursor powders results in fine-grained preceramic powders (1A, 2A) after calcination. The shrinkage and sintering behaviour of resulti...

Experimental and Computational Modeling of H‑Bonded Arginine− Tyrosine Groupings in Aprotic Environments

ABSTRACT : H-bonds between neutral tyrosine and arginine in nonpolar environments are modeled by small-molecule phenol/guanidine complexes. From the temperature and concentration dependence of UV spectra, a value of ΔH° = −74 ± 4 kJ mol−1 is deduced for the formation of H-bonded parasol/dodecylguanidine in hexane. ΔE = −71 kJ mol−1 is computed with density functional theory (in vacuo). In dimethyl sulfoxide or crystals, (p-phenyl)alkylguanidines form head-to-tail homodimers with t...

Physico-Chemical Properties of Biodiesel from Jatropha and Castor Oils

Abstract - Biodiesel is becoming prominent among the alternatives to conventional petro-diesel due to economic, environmental and social factors. The quality of biodiesel is influenced by the nature of feedstock and the production processes employed. High amounts of free fatty acids (FFA) in the feedstock are known to be detrimental to the quality of biodiesel. In addition, oils with compounds containing hydroxyl groups possess high viscosity due to hydrogen bonding. American Standards and Te...

Prevalence And Factors Associated With Continual Opioid Use Among Patients Attending Methadone Clinic At Mwananyamala Hospital, Dar Es Salaam, Tanzania

A B S T R A C T Trends of continual drug use while under treatment have been reported worldwide. This paper assesses opioid use among patients receiving treatment in a methadone clinic for opioid addiction. A total of 126 urine samples were analyzed using LC–MS/FTMS. About 16% of patients were found to have a high prevalence level of opioids use. Prevalence level was significantly associated with the duration of treatment (p= 0.0121) and age (p =0.0328). About 125/126 patients were found t...

Efect of Nano-SiO2, Nano-TiO2 and Nano-Al2O3 Addition on Fluid Loss in Oil-Well Cement Slurry

Abstract  In this article, incorporation of nano-SiO2 (NS), nano-TiO2 (NT) and nano-Al2O3 (NA) particles and their binary and ternary blends on water fltration in oil-well cement slurry was examined. The nanoparticle contents were chosen at proportions corresponding to 1, 2, 3 and 4% based on the weight of cement. The experimental specimens were tested at three various temperatures of 70, 80 and 90 °C using a gas pressure of 1000 psi. The quantity of water fltrate collected was measured in ...

Anhydrous Monoalkylguanidines in Aprotic and Nonpolar Solvents: Models for Deprotonated Arginine Side Chains in Membrane Environments

ABSTRACT: In this study, the synthesis of crystalline dodecylguanidine free base and its spectroscopic characterization in nonpolar environments are described. IR as well as 1 H and 15N NMR spectra of the free base dissolved in aprotic solvents are substantially different from the previously reported spectra of arginine, or other monoalkylguanidinium compounds, at high hydroxide concentrations. The current results provide improved modelling for the spectroscopic signals that would be expecte...

Producing Sulphuric Acid In Tanzania And Potential Sources: A Review

Abstract Sulphuric acid is a backbone of chemical industry, agriculture and energy sectors. Tanzania has potential sources of producing its own sulphuric acid. The three most common methods: contact process, wet process and lead chamber process of producing sulphuric acid are reviewed. A modified lead chamber method can be a preferred method of producing the mineral acid by using local available raw materials according to Tanzania environment. Among of raw materials, pyrites from Samena area...

Phytochemical and Antimicrobial Properties of African peach (Sacocefalus latifolius)

Abstract This study includes phytochemical screening, quantification of secondary metabolites, thin-layer chromatography (TLC) and antimicrobial  assay of African peach (Sarcocephalus latifolius). The phytochemical analysis revealed the presence of alkaloid, flavonoid and saponin at various  quantities with saponin more abundant amongst others like tannin, glycoside and phenols that are present. All the extracts were tested for  antimicrobial activity with ethanol extract and water extract...

Phytochemical and Antimicrobial Properties of Lavandula angustifolia

Abstract: This present study deals with the quantitative and qualitative phytochemical  screening, the antimicrobial properties and thin layer chromatography of Lavandula angustifolia leaves extracts. These were achieved using the cold maceration method of  extraction involving hexane, water (aqueous) and ethanol, to ensure that a wide polarity  range of components are extracted. Alkaloid, phenol, flavonoids, tannins, terpenes,  glycosides and steroids were observed present in the leaves ...

Quantum chemical calculations on SiF4 and it's protonated analogues

Abstract: For every heteronuclear molecule, protonation can occur at more than one site  thus giving rise to more than one proton affinity. Experimentally, only one proton affinity  (PA) value is reported for a molecule and the experiment does not specify the site for the  protonation. In the present work, quantum chemical calculations are carried out on SiF4 and  its possible protonated analogues (HF4Si+ and HSiF4 + ) by employing several computational  chemistry methods including the M...

Kinetic studies of the biosorption of lead and zinc from solution using tea fibre

Abstract: This paper presents a biobsorption study on Zn and Pb(II) from dilute aqueous  solution using tea fiber as the biosorbent. The biosorption study was carried out as a function  of contact time, initial metal ion concentration and biosorbent dosage. The residual Zn and  Pb(II) in solution were determined using atomic absorption spectrophotometer. The  biosorption was also time dependent as maximum biosorption was obtained after 10 and 20  min, for both lead and zinc respectively....


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