Chemistry Department

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Luteolin: a blocker of SARS-CoV-2 cell entry based on relaxed complex scheme, molecular dynamics simulation, and metadynamics
(Springer, 2021-07-08) Shadrack, Daniel M.; Deogratias, Geradius; Kiruri, Lucy W.; Onoka, Isaac; Vianney, John-Mary; Swai, Hulda; Nyandoro, Stephen S.
Natural products have served human life as medications for centuries. During the outbreak of COVID-19, a number of naturally derived compounds and extracts have been tested or used as potential remedies against COVID-19. Tetradenia riparia extract is one of the plant extracts that have been deployed and claimed to manage and control COVID-19 by some communities in Tanzania and other African countries. The active compounds isolated from T. riparia are known to possess various biological properties including antimalarial and antiviral. However, the underlying mechanism of the active compounds against SARS-CoV-2 remains unknown. Results in the present work have been interpreted from the view point of computational methods including molecular dynamics, free energy methods, and metadynamics to establish the related mechanism of action. Among the constituents of T. riparia studied, luteolin inhibited viral cell entry and was thermodynamically stable. The title compound exhibit residence time and unbinding kinetics of 68.86 ms and 0.014 /ms, respectively. The findings suggest that luteolin could be potent blocker of SARS-CoV-2 cell entry. The study shades lights towards identification of bioactive constituents from T. riparia against COVID-19, and thus bioassay can be carried out to further validate such observations.
Optical and electronic properties of para-functionalized triphenylamine-based dyes: a theoretical study
(Springer, 2021-11-09) Mkoma, Stelyus L.; Msambwa, Yohana; Jacob, Fortunatus R.; Kiruri, Lucy W.; Kinunda, Grace A.; Mlowe, Sixberth; Deogratias, Geradius
Molecular engineering of dyes has become a popular and most successful approach towards improvement of photovoltaic power conversion efficiency of dye-sensitized solar cells (DSSCs). We report the geometrical, optical, and electronic properties for para-substituted triphenylamine (TPA)-based dyes with D-π-π-A architecture. Results were realized through density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. We used B3LYP/6–31 + G(d,p) and CAM-B3LYP/6–31 + G(d,p) level of theory for DFT and TD-DFT, respectively. Six electron-donating (ED) and electron-withdrawing (EW) groups were symmetrically grafted to the para-direction of the phenyl rings. Two anchoring groups namely: cyanoacrylic acid (CA) and hydantoin (HY) were used. Excellent relationships between electronic energies and the Hammett constants (σp) have been reported. The results show that variation of both anchoring groups and substituents significantly affect the absorption of the dyes; maximum absorption for CA dyes was found ranging between 514–571 nm and 470–503 nm for ED and EW groups, respectively, while for HY dyes demonstrated maximum absorption between 502–537 nm and 480–496 nm for ED and EW, respectively. A linear correlation between σp and λmax with R2 > 0.97 was obtained. In addition, the mapping of the HOMO and LUMO energies suggests the intramolecular charge transfer and a strong electronic coupling between dye and semiconductor. Our theoretical calculations show that electron-donating substituents enhance the optoelectronic properties of the dyes. Analysis of chemical descriptors suggests that dyes containing alternative anchoring group HY substituted with –NH2 and –N(CH3)2 may demonstrate improved performance of DSSCs.
A Molecular Investigation of the Solvent Influence on Inter- and Intra-Molecular Hydrogen Bond Interaction of Linamarin
(MDPI, 2022-02-11) Paul, Lucas; Deogratias, Geradius; Shadrack, Daniel M.; Celestin N., Mudogo; Mtei, Kelvin M.; Machunda, Revocatus L.; Paluch, Andrew S.; Ntie-Kang, Fidele
Linamarin has been reported to have anticancer activities; however, its extraction and isolation using different solvents yield a low amount. Therefore, understanding the physical properties, such as solvents’ solubility, membrane permeability and lipophilicity and how they are associated with different solvents, is a paramount topic for discussion, especially for its potential as a drug. Linamarin has a sugar moiety with many polar groups responsible for its physical properties. Following current trends, a molecular dynamics simulation is performed to investigate its physical properties and how different solvents, such as water, methanol (MeOH), dimethyl sulfoxide (DMSO) and dichloromethane (DCM), affect such properties. In this work, we have investigated the influence of intermolecular and intramolecular hydrogen bonding and the influence of polar and non-polar solvents on the physical properties of linamarin. Furthermore, solvation free-energy and electronic structure analysis are performed. The structural analysis results show that the polar groups of linamarin have strong interactions with all solvents except the etheric oxygen groups. A detailed analysis shows intermolecular hydrogen bonding between polar solvents (water, MeOH and DMSO) and the hydroxyl oxygens of linamarin. Water exhibits the strongest interaction with linamarin’s functional groups among the investigated solvents. The findings show that within the first solvation shell, the number of water molecules is greatest, while MeOH has the fewest. Centrally to the structural analysis, solvation free energy confirms DMSO to be the best solvent since it prefers to interact with linamarin over itself, while water prefers to interact with itself. While the solute–solvent interactions are strongest between linamarin and water, the solvent–solvent interactions are strongest in water. As a result, the solvation free-energy calculations reveal that linamarin solvation is most favourable in DMSO.
Influence of heteroatoms on the optoelectronic properties of triphenylamine-based dyes for DSSCs application: A computational approach
(Elsevier, 2022-02-27) Kirenga, Peter; Mkoma, Stelyus L.; Mlowe, Sixberth; Msambwa, Yohana; Kiruri, Lucy W.; Jacob, Fortunatus R.; Mgaya, James E.; Kinunda, Grace A.; Deogratias, Geradius
A series of sensitizers with D-π-π-A architectural framework have been fine-tuned through a variation of heteroatoms (NH, O, Se, and Te) in the π-spacers. Cyanoacrylic acid and hydantoin were used as the acceptor groups. The geometrical and electronic properties were investigated through density functional theory (DFT) and time-dependent DFT (TD-DFT) , respectively. To determine stable dye-TiO2 configuration, the binding energies are reported. The driving force of charge injection and dye regeneration range between 0.00 to −0.77 eV and −0.133 to −1.60 eV, respectively, suggesting spontaneous processes. Chalcogen heteroatoms (S, Se, and Te) improved absorption within the visible and NIR regions. The binding energies of dye on (TiO2)6 cluster range between −8.32 to −9.62 eV and −7.77 to −8.98 eV for cyanoacrylic acid and hydantoin dyes, respectively. The findings suggest that the inclusion Se and Te heteroatoms may boost the performance of DSSCs when compared to parent materials containing S.
Hydrophobic π-π stacking interactions and hydrogen bonds drive self-aggregation of luteolin in water
(Elsevier, 2022-06-28) Deogratias, Geradius; Shadrack, Daniel M.; Munissi, Joan J.E.; Kinunda, Grace A.; Jacob, Fortunatus R.; Mtei, Regina P.; Masalu, Rose J.; Mwakyula, Issakwisa; Kiruri, Lucy W.; Nyandoro, Stephen S.
Luteolin is a flavonoid obtained from different plant species. It is known for its versatile biological activities. However, the beneficial effects of luteolin have been limited to small concentrations as a result of poor water solubility. This study aimed at investigating the hydrophobic interaction and hydration of luteolin towards the improvement of its solubility when used as a drug. We report the aggregation properties of luteolin in water by varying the number of monomers using atomistic molecular dynamics simulation. Results show that the equilibrium structure of luteolin occurs in an aggregated state with different structural arrangements. As the monomers size increase, the antiparallel flipped conformation dominates over T-shaped antiparallel, T-shaped parallel, and antiparallel conformations. The formation of intramolecular hydrogen bonding of 0.19 nm between the keto-enol groups results in hydrophobic characteristics. A larger cluster exhibits slow hydrogen bond dynamics for luteolin-luteolin than luteolin-water interaction. Water structure at large cluster size exhibited slow dynamics and low self-diffusion of luteolin. The existence of hydrophobic π-π and hydrogen bonds between luteolin molecules drives strong self-aggregation resulting in poor water solubility. Breakage of these established interactions would result in increased solubility of luteolin in water.
Oxygenated Cyclohexene Derivatives from the Stem and Root Barks of Uvaria pandensis
(ACS, 2021-11-21) Gasper, Maeda; Pieter, J. Gilissen; Anastasia, Rudenko; Jelle, van der Wal,; Catarina, Bourgard; Arvind, Kumar Gupta; Per, Sunnerhagen; Joan, J. E. Munissi; Stephen, S. Nyandoro; Máté, Erdélyi
Five new cyclohexene derivatives, dipandensin A and B (1 and 2) and pandensenols A–C (3–5), and 16 known secondary metabolites (6–21) were isolated from the methanol-soluble extracts of the stem and root barks of Uvaria pandensis. The structures were characterized by NMR spectroscopic and mass spectrometric analyses, and that of 6-methoxyzeylenol (6) was further confirmed by single-crystal X-ray crystallography, which also established its absolute configuration. The isolated metabolites were evaluated for antibacterial activity against the Gram-positive bacteria Bacillus subtilis and Staphylococcus epidermidis and the Gram-negative bacteria Enterococcus raffinosus, Escherichia coli, Paraburkholderia caledonica, Pectobacterium carotovorum, and Pseudomonas putida, as well as for cytotoxicity against the MCF-7 human breast cancer cell line. A mixture of uvaretin (20) and isouvaretin (21) exhibited significant antibacterial activity against B. subtilis (EC50 8.7 μM) and S. epidermidis (IC50 7.9 μM). (8′α,9′β-Dihydroxy)-3-farnesylindole (12) showed strong inhibitory activity (EC50 9.8 μM) against B. subtilis, comparable to the clinical reference ampicillin (EC50 17.9 μM). None of the compounds showed relevant cytotoxicity against the MCF-7 human breast cancer cell line.
Polyoxygenated Cyclohexene Derivatives and Flavonoids from Uvaria pandensis Leaves
(Elsevier, 2022-04) Gasper, Maeda; Pieter, J. Gilissen; Catarina, Bourgard; Jelle, van der Wal; Joan, J. E. Munissi; Stephen, S. Nyandoro; Máté, Erdélyi
Abstract Three new oxygenated cyclohexene derivatives, pandensenol D - F (1–3), two new flavanoids, pandensone A and B (4–5), and seven known compounds (6–12) were isolated from the methanol extract of the leaves of Uvaria pandensis Verdc. (Annonaceae). The structures were characterized by NMR spectroscopic and mass spectrometric analyses. The isolated metabolites were evaluated for their antibacterial activity against the Gram-positive bacteria Bacillus subtilis and Staphylococcus epidermidis, the Gram-negative bacteria Enterococcus raffinosus, Escherichia coli, Paraburkholderia caledonica, Pectobacterium carotovorum and Pseudomonas putida, and for cytotoxicity against the MCF-7 human breast cancer cell line. Out of the tested compounds, pandensenol D (1) and (6′,7′-dihydro-8'α,9'β-dihydroxy)-3-farnesylindole (12) showed weak activity, whereas (8'α,9'β-dihydroxy)-3-farnesylindole (11) strong activity against B. subtilis. Four of the isolated compounds (1, 4, 11 and 12) showed moderate cytotoxicity against MCF-7 breast cancer cells (EC50 > 100 μM).
Chemical Constituents and Antimicrobial Evaluation of Selected Aloe vera Branded Commercial Products in Tanzania
(CoNAS - UDSM, 2022-05) Stephen, S Nyandoro; Bahati, F Kyando; Joan JE, Munissi
Abstract Chemical compositions and antimicrobial activities of twenty-two Aloe vera branded commercial products in Tanzania, a case of marketed soaps, creams, lotions, petroleum jelly, toothpastes and hair conditioner products in Dar es Salaam, were investigated. Chemical compositions were analysed using gas chromatography-mass spectrometry (GC-MS) whereas antimicrobial activities were evaluated using agar dilution method against four bacteria species, namely Staphylococcus aureus, Escherichia coli, Klebsiella pneumoneae and Salmonella typhi) and two fungal species Candida albicans and Cryptococcus neoformans. The GC-MS analysis revealed the presence of seven non-polar constituents, namely methyl palmitate, 9-octadecenoic acid methyl ester, methyl stearate, tetratetracontane, hexacosane, and pentacosane and methyl tetradecanoate as the most common ingredients among the products. Eleven compounds were detected in both the commercial products and reference A. vera extracts. The commercial products AVC5 and AVL3 inhibited the growth of E. coli and S. typhi at minimum inhibitory concentrations (MICs) of 7.5 and 12.5% (v/v), respectively, whereas AVC2 and AVC5 inhibited the growth of C. albicans and C. neoformans at 5.0% (v/v). AVC6 had 7.5 and 15.0% (v/v) MICs for C. neoformans and C. albicans, respectively. Other commercial products and the reference A. vera extracts were inactive against the tested microbes at a screening concentration of 10.0 mg/mL.
Effect of Alternate Wetting and Drying Irrigation on Bioaccumulation of selected micronutrients in the Harvested Rice Grains
(DUCE - UDSM, 2021-12) Charles O, Joseph; Emanuel M, Sangu; Stephen S, Nyandoro
Abstract Alternate wetting and drying irrigation (AWDI) is a water saving strategy in rice farming. However, its impact on mineral bioaccumulation in the grain is not well understood. Thus, this study investigated the impact of AWDI on bioaccumulation of Zn, Se, Mn and Cu in rice grains. Six water regimes involving continuous flooding where water was maintained at 2cm above the soil, and delaying irrigation until water reaches 5, 10, 20, 30 and 40cm below the soil surface, were employed. The concentration of Zn, Mn and Se in the soil ranged between 2.05–6.9, 3.4–9.1 and 0.13–0.16 mgkg-1, respectively. In the harvested rice grains, the concentration of Zn, Mn, Cu and Se ranged between 8.20–11.90, 1.90– 3.50, 1.90–3.10 and 0.10–0.70 mgkg-1, respectively. These concentrations were not phytotoxic to plants. Re-flooding after every 2–5 days increased Zn, Mn and Cu bioaccumulation in rice grains by 65, 151 and 124% respectively, but reduced Se bioaccumulation by 95%. Re-flooding after every 8–12 days reduced bioaccumulation of all micronutrients in rice grains. Bioaccumulation factors indicated that Zn was absorbed and subsequently accumulated in rice grains. The estimated dietary daily intakes for Zn, Mn and Cu were higher in rice grown under mild AWDI, implying that AWDI can be used as a strategy to increase these micronutrients in human diets through rice consumption.
Structural, vibrational and thermodynamic properties of the isomers of the dimer molecules Ba2X4 (X=F, Cl, Br, or I)
(Springer, 2022-04-12) Fortunatus, Jacob
Geometrical parameters and vibrational spectra of the dimer Ba2X4 molecules were calculated; diferent isomeric structures were revealed. For the Ba2F4, Ba2Cl4, and Ba2Br4, three isomers of C3v, C2v, and C2h symmetries were confrmed to exist while for Ba2I4 only two isomers, C3v and C2h, were confrmed. For all halides, the bipyramidal C3v isomers possessed the lowest energy. The structural parameters and vibrational frequencies were employed in calculation of thermodynamic func tions and enthalpies of dissociation reactions of the species. The enthalpies of formation ∆fH(0) of the C3v isomers were obtained (in kJ mol−1):−1874 ± 2 (Ba2F4);−1236 ± 7 (Ba2Cl4);−1023 ± 8 (Ba2Br4);−787 ± 11 (Ba2I4). The relative abundance of the isomeric forms was evaluated for a broad temperature range, between 200 and 2000 K. It was shown that the concentrations of different isomers appeared to be comparable in saturated vapors at temperatures close to experimental conditions.
Quantum chemical study of structure, vibrational spectra and thermodynamic properties of molecular and ionic clusters existing in vapours over strontium dichloride
(Taylor and Francis, 2022-02-14) Sospeter, Imani; Fortunatus, Jacob
The cluster ions SrCl− 3 , Sr2Cl+ 3 , Sr3Cl+ 5 , Sr4Cl+ 7 and Sr5Cl+ 9 that were detected earlier in vapour over strontium dichloride at high temperatures ranging from 1100 to 1500 K have been studied theo retically. The equilibrium geometrical properties, vibrational spectra and thermodynamic properties were investigated by using the DFT, MP2 and MP4 methods. From the alternative structures consid ered, it was observed that the ions SrCl− 3 , Sr2Cl+ 3 , Sr3Cl+ 5 and Sr5Cl+ 9 correspond to D3h symmetry and Sr4Cl+ 7 corresponds to C2v configuration, no isomers were identified for all cluster ions from the considered alternative structures. The enthalpies of formation, fHo(0) of the cluster ions were deter mined (in kJ mol–1): −994 ± 3 (SrCl− 3 ), −410 ± 12 (Sr2Cl+ 3 ), −1202 ± 16 (Sr3Cl+ 5 ), −1962 ± 27 and −2718 ± 20.
Explicit Solutions for Real-time Reversible Inhibition Kinetics using Lambert W Function: Towards Progress Curve Analysis
(Tanzania Journal of Science, 2022-12) Geradius, Deogratias; Makungu, Madirisha; Fortunatus, Jacob
Accurate estimation of kinetic parameters is challenging due to the dynamics and mathematical nature of the chemical systems. This paper presents simple, yet efficient closed-form solutions for the enzymatic conversion of the substrate to the product in real-time derived using the Lambert W function. The real values of the Lambert W function were calculated from the Lambert package as implemented in MATLAB. The expressions exhibit remarkable robustness in estimating the parameters for randomized data at 1% to 4% variation in noise levels. Furthermore, unlike the initial rates method, the expressions estimate chemical kinetic parameters utilizing a full range of experimental data, thus minimizing the risk of missing information that would be detected at an extended time-span. Thus, the implementation of closed-form solutions presented in this paper for the estimation of kinetic parameters eliminates common pitfalls imposed by the initial rates and double reciprocal methods.
Hydrophobic π-π stacking interactions and hydrogen bonds drive self-aggregation of luteolin in water
(Elsevier, 2022-06-23) Deogratias, Geradius; Shadrack, Daniel M; Munissi, Joan J.E.; Kinunda, Grace A.; Jacob, Fortunatus R.; Mtei, Regina P.; Masalu, Rose J.; Mwakyula, Issakwisa; Kiruri, Lucy W.; Nyandoro, Stephen S.
Luteolin is a flavonoid obtained from different plant species. It is known for its versatile biological activities. However, the beneficial effects of luteolin have been limited to small concentrations as a result of poor water solubility. This study aimed at investigating the hydrophobic interaction and hydration of luteolin towards the improvement of its solubility when used as a drug. We report the aggregation properties of luteolin in water by varying the number of monomers using atomistic molecular dynamics simulation. Results show that the equilibrium structure of luteolin occurs in an aggregated state with different structural arrangements. As the monomers size increase, the antiparallel flipped conformation dominates over T-shaped antiparallel, T-shaped parallel, and antiparallel conformations. The formation of intramolecular hydrogen bonding of 0.19 nm between the keto-enol groups results in hydrophobic characteristics. A larger cluster exhibits slow hydrogen bond dynamics for luteolin-luteolin than luteolin-water interaction. Water structure at large cluster size exhibited slow dynamics and low self-diffusion of luteolin. The existence of hydrophobic π-π and hydrogen bonds between luteolin molecules drives strong self-aggregation resulting in poor water solubility. Breakage of these established interactions would result in increased solubility of luteolin in water.
Influence of heteroatoms on the optoelectronic properties of triphenylamine-based dyes for DSSCs application: A computational approach
(Elsevier, 2022-02-23) Kirenga, Peter; Mkoma, Stelyus L.; Mlowe, Sixberth; Msambwa, Yohana; Kiruri, Lucy W.; Jacob, Fortunatus R.; Mgaya, James E.; Kinunda, Grace A.; Deogratias, Geradius
A series of sensitizers with D-π-π-A architectural framework have been fine-tuned through a variation of het eroatoms (NH, O, Se, and Te) in the π-spacers. Cyanoacrylic acid and hydantoin were used as the acceptor groups. The geometrical and electronic properties were investigated through density functional theory (DFT) and time-dependent DFT (TD-DFT) , respectively. To determine stable dye-TiO2 configuration, the binding energies are reported. The driving force of charge injection and dye regeneration range between 0.00 to − 0.77 eV and − 0.133 to − 1.60 eV, respectively, suggesting spontaneous processes. Chalcogen heteroatoms (S, Se, and Te) improved absorption within the visible and NIR regions. The binding energies of dye on (TiO2)6 cluster range between − 8.32 to − 9.62 eV and − 7.77 to − 8.98 eV for cyanoacrylic acid and hydantoin dyes, respectively. The findings suggest that the inclusion Se and Te heteroatoms may boost the performance of DSSCs when compared to parent materials containing S.
Optical and electronic properties of para‑functionalized triphenylamine‑based dyes: a theoretical study
(Springer, 2021-11-09) Mkoma, Stelyus L.; Msambwa, Yohana; Jacob, Fortunatus R.; Kiruri, Lucy W.; Kinunda, Grace A.; Mlowe, Sixberth; Deogratias, Geradius
Molecular engineering of dyes has become a popular andmost successful approach towards improvement of photovoltaic power conversion efciency of dye-sensitized solar cells (DSSCs). We report the geometrical, optical, and electronic proper ties for para-substituted triphenylamine (TPA)-based dyes with D-π-π-A architecture. Results were realized through density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. We used B3LYP/6–31+G(d,p) and CAM-B3LYP/6–31+G(d,p) level of theory for DFT and TD-DFT, respectively. Six electron-donating (ED) and electron withdrawing (EW) groups were symmetrically grafted to the para-direction of the phenyl rings. Two anchoring groups namely: cyanoacrylic acid (CA) and hydantoin (HY) were used. Excellent relationships between electronic energies and the Hammett constants (σp) have been reported. The results show that variation of both anchoring groups and substituents significantly affect the absorption of the dyes; maximum absorption for CA dyes was found ranging between 514–571 nm and 470–503 nm for ED and EW groups, respectively, while for HY dyes demonstrated maximum absorption between 502–537 nm and 480–496 nm for ED and EW, respectively. A linear correlation between σp and λmax with R2>0.97 was obtained. In addition, the mapping of the HOMO and LUMO energies suggests the intramolecular charge transfer and a strong electronic coupling between dye and semiconductor. Our theoretical calculations show that electron-donating substituents enhance the optoelectronic properties of the dyes. Analysis of chemical descriptors suggests that dyes containing alternative anchoring group HY substituted with –NH2 and –N(CH3)2 may demonstrate improved performance of DSSCs.
Cluster ions in saturated vapor over barium difluoride: Structure and thermodynamic properties
(Elsevier, 2016-07-16) Jacob, Fortunatus; Pogrebnoi, Alexander M.; Pogrebnaya, Tatiana P.
Different cluster ions detected earlier in saturated vapor over barium fluoride have been studied here the oretically. The equilibrium geometrical parameters and vibrational spectra were obtained for the ions BaF3 , Ba2F3+, Ba3F5+, Ba4F7+, and Ba5F9+ . The DFT/B3P86 and MP2 methods were implemented with theTZVP basis sets including the diffuse and polarized basis functions. Along with cluster ions, the dimer molecule Ba2F4 properties were examined; the existence of isomeric forms was confirmed and the rela tive concentration of the isomers was evaluated. The enthalpies of ion molecular reactions were obtained both theoretically and based on experimental data. The enthalpies of formation DfHo(0) of the specieswere determined (in kJ mol 1): 1356 ± 4 (BaF3 ); 1039 ± 12 (Ba2F3+); 2179 ± 16 (Ba3F5+); 3277 ± 35(Ba4F7+); 4316 ± 22 (Ba5F9+); 1859 ± 7 (Ba2F4).
Structure and thermodynamic properties of cluster ions in saturated vapour over barium dibromide
(Elsevier, 2016-12-27) Jacob, Fortunatus; Pogrebnaya, Tatiana P.; Pogrebnoi, Alexander M.
The structure and thermodynamic properties of cluster ions detected earlier in saturated vapour over barium dibromide were studied theoretically. The equilibrium geometrical parameters and vibrational spectra were computed for the ions BaBr3 , Ba2Br3 + , Ba3Br5 + , Ba4Br7 + and Ba5Br9 + ; the DFT and MP2 methods with triple-zeta valence basis sets were used. The enthalpies of ion molecular reactions were obtained both theoretically through the total energies of participants and based on experimental data. The theo retical results were scrutinized with respect to methods of computation (DFT, MP2, and MP4). The enthalpies of formation DfHo (0) of the ions have been determined (in kJ mol 1 ): 858 ± 6 (BaBr3 ); 293 ± 10 (Ba2Br3 + ); 982 ± 20 (Ba3Br5 + ); 1644 ± 30 (Ba4Br7 + ); 2282 ± 17 (Ba5Br9 + ).
Ionic species in vapour over barium diiodide: Quantum chemical study of structure and thermodynamic properties
(Elsevier, 2017-08-22) Jacob, Fortunatus; Pogrebnaya, Tatiana P.; Pogrebnoi, Alexander M.
The cluster ions Ba2I3 + , Ba3I5 + and Ba4I7 + were detected earlier in saturated vapour over barium diiodide using high temperature mass spectrometric technique. In this work the structure and thermodynamic properties of the species BaI3 , Ba2I3 + , Ba3I5 + , Ba4I7 + , and Ba5I9 + have been studied theoretically by using the density functional theory (DFT/B3P86) and Møller–Plesset perturbation theory (MP2 and MP4) with triple-zeta valence basis sets. The enthalpies of ion molecular reactions have been determined both the oretically and based of available experimental data; the enthalpies of formation of the cluster ions are found as follows (in kJ mol 1 ): 709 ± 6, (BaI3 ), 96 ± 10 (Ba2I3 + ), 654 ± 15 (Ba3I5 + ), 1177 ± 20 (Ba4I7 + ) and 1686 ± 20 (Ba5I9 + ).
Polymer Reinforced Laterite for Building Materials
(International Journal of Engineering and Technology, 2015-02) Kalu, I.E.; Jossou, E.E.; Jacob, F.; Ilboudo, A.I.; Adedeji, A.F.; Soboyejo, W.O.
This paper focuses on the potential in locally available materials to produce alternative building materials at low cost. Laterite was reinforced with plastic particulates obtained from plastic wastes, and vulcanized rubber to improve flexural and compressive strength respectively. It was found that 20% volume fraction of fine grain plastic particulates mixed with matrix (60% laterite + 20% cement) had a better flexural and compressive strength respectively compared to the other samples of various proportions. In comparison with the traditional building material (river sand), it showed a higher compressive strength and very close flexural strength, hence can be used as alternative building material.
Potential of Kaolin Clay on Formulation of Water Based Drilling Mud Reinforced with Biopolymer, Surfactant, and Limestone
(College of Natural and Applied Sciences, University of Dar es Salaam, 2023-03-31) Paul M. Omary; Emanuel X. Ricky; Naswibu A. Kasimu; Makungu M. Madirisha; Kessy F. Kilulya; Esther H. J. Lugwisha
Drilling the wellbore into subsurface formations is the earliest stage in the life of a well that requires a suitable drilling fluid with good rheological and filtration control characteristics to achieve a successful drilling operation. This paper reports on the formulation of water-based drilling mud using kaolin clay reinforced with biopolymer, surfactant, and limestone from Tanzania. The raw materials used for the formulation were characterized using XRD, XRF, FTIR, and TGA techniques. The rheological properties, filtration loss, pH, and density of the formulated mud were measured using a viscometer, filter press, pH meter, and mud balance, respectively. The XRD results revealed kaolinite and quartz as the main minerals in all kaolin clay samples which were in agreement with the FTIR findings. The mineralogical composition of the kaolin was observed to vary with the mining sites and influenced the rheological and filtration control characteristics of the mud. The beneficiated drilling mud showed better rheological and filtration control characteristics than the commercially available bentonite mud in Dar es Salaam market and was comparable with the API standards. These results, therefore, are not only new but rather important and novel information on the potential of kaolin clay for the formulation of water based drilling mud.

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