The use of modified urea-formaldehyde resins in soil binder systems

Please read the abstract in the section 00front of this documentDissertation (M Eng (Chemical Engineering))--University of Pretoria, 2007.Chemical Engineeringunrestricte

Laboratorium optimisasie van ‘n urea-formaldehied

The Indirect Tensile Strength (ITS) was used to characterise the soil stabilising properties of a urea-formaldehyde (UF) resin. The test soil was brown shale gravel. Synergistic strength improvements were obtained when combining the resin with anionic bitumen emulsion and dosing both at 2%. Performance levelled off above these concentrations. For full strength development, the soil moisture content must be reduced to below 3%. Optimum indirect tensile strength is obtained at formaldehyde to urea molar ratio of 2:1. Soil strength increases as the reaction pH is lowered but the need for adequate application times restricts it to pH > 4,5. The experimental results also suggest that the presence of appropriate organic matter is critical for effective soil stabilisation with UF resin.Die Indirekte Treksterkte (ITS) is gebruik om die grondstabilisasie-eienskappe van ‘n urea-formaldehied hars (UF) te kwantifiseer. Die toetsgrond was ‘n bruin skaliegruis. Kombinasie van die hars met ‘n anioniese bitumen emulsie toon sinergistiese sterkteverbetering wanneer beide doseer word op die 2% vlak. Werkverrigting plat af bokant hierdie konsentrasies. Vir volle sterkteontwikkeling moet die grondvogtigheid verlaag word tot onder 3%. Optimale indirekte treksterktes word behaal met ‘n formaldehied-tot-urea molverhouding van 2:1. Grondsterkte neem ook toe soos die reaksie pH verlaag word maar vir pH < 4,5 word die beskikbare aanwendingstyd ontoereikend. Die eksperimentele resultate dui ook daarop dat die teenwoordigheid van ‘n geskikte organiese fraksie in die grond krities is vir effektiewe stabilisasie met UF hars.The THRIP program of the Department of Trade and Industry and the National Research Foundation of South Africa as well as Megadev Pty. (Ltd.)http://www.saiche.co.za/article.aspam201

ESTABLISHING A PLATFORM FOR SPRAY DRYING INHALABLE VACCINES IN SOUTH AFRICA

Mycobacterium bovis BCG is the current vaccine for tuberculosis (TB). However, BCG as it is currently administered shows highly variable efficacy in protecting adults against TB. The natural route of infection of TB is via inhalation of bacilli-containing aerosols and it is postulated that immunization by the natural route of infection may lead to a greater immunity given the fact that the lungs are the primary target of infection. By eliciting both local and systemic immune responses, it is anticipated that an inhaled form of BCG will offer greater protection against pulmonary TB. Current commercial BCG vaccine preparations are filled as bacterial suspensions in vials, dried through lyophilization and stabilized through refrigeration with a one year shelf life. However, freeze-dried BCG does not exhibit a particle form conducive for delivery via the aerosol route and must be injected. Spray drying studies by Harvard University and Medicine in Need (MEND) scientists have demonstrated that BCG could be spray dried into a viable aerosol with up to 1 year of stability under refrigerated conditions, with the potential for room temperature stability. To support the further preclinical development of the BCG aerosol for application in the developing world, MEND established a state-of-the-art Biosafety level 3 spray drying facility with local expertise in South Africa, where the vaccine will be produced for an IND-enabling toxicology study meeting OECD Good Laboratory Practice (GLP) requirements. Frozen BCG bulk is spray dried and the resulting dry powder is characterized in terms of viability and aerosol properties. The dried BCG aerosol is then aseptically filled into capsules using a semi-automatic filling device for delivery using a low-cost hand-held inhaler. In conclusion, the spray drying technology was successfully transferred from Harvard University to the MEND facility in Pretoria. MEND is developing local expertise and infrastructure to support further preclinical and clinical development of BCG for inhalation

Effects of clofazimine on planktonic and biofilm growth of Mycobacterium tuberculosis and Mycobacterium smegmatis

Mycobacteria form lipid-rich biofilms that restrict the efficacy of antimicrobial chemotherapy, possibly necessitating the use of lipophilic antibiotics. In the current study, the activity of one such agent, clofazimine, against Mycobacterium tuberculosis and Mycobacterium smegmatis planktonic cells and biofilms was investigated. Minimum inhibitory concentrations (MICs) of clofazimine were determined for planktonic cultures, whilst minimum bactericidal concentrations (MBCs) were determined for planktonic, biofilm-producing and biofilm-encased organisms using standard bacteriological proce- dures. The effects of clofazimine on biofilm formation and the stability of pre-formed biofilm were measured using a crystal violet-based spectrophotometric procedure. In the case of M. smegmatis, clofazimine was found to be active against planktonic phase (MICs and MBCs of 2.5 mg/L and >20 mg/L, respectively) and biofilm-producing organisms (MBC of 2.5 mg/L); clofazimine demonstrated greater activity against M. tuberculosis, corresponding values of 0.06, 5 and 0.3 mg/L. Although clofazimine inhibited biofilm production both by M. tuberculosis and M. smegmatis (P < 0.05 at 0.07 mg/L and 0.3 mg/L, respectively) and appeared to reduce the pre-formed M. tuberculosis biofilm, addition of antimicrobial agent to pre-existing biofilm matrices failed to kill biofilm-encased organisms. In conclusion, clofazimine is more effective against M. tuberculosis than against M. smegmatis, exhibiting bactericidal activity both for actively growing and slowly replicating bacilli but not for non-replicating organisms of both species.South African Medical Research Council.http://www.elsevier.com/locate/jgar2016-05-31hb201

Clofazimine : current status and future prospects

Clofazimine, a lipophilic riminophenazine antibiotic, possesses both antimycobacterial and anti-inflammatory activities. However, its efficacy has been demonstrated only in the treatment of leprosy, not in human tuberculosis, despite the fact that this agent is impressively active in vitro against multidrug-resistant strains of Mycobacterium tuberculosis. Recent insights into novel targets and mechanisms of antimicrobial and antiinflammatory activity coupled with the acquisition of innovative drug delivery technologies have, however, rekindled interest in clofazimine as a potential therapy for multidrug- and extensively multidrug-resistant tuberculosis in particular, as well as several autoimmune diseases. The primary objective of this review is to critically evaluate these recent developments and to assess their potential impact on improving the therapeutic efficacy and versatility of clofazimine.The South African Medical Research Council. Research into the spray-dried formulations of clofazimine is supported by the K-RITH collaborative grant (Howard Hughes Medical Institute and the University of KwaZulu-Natal).http://jac.oxfordjournals.org

Inhaled microparticles containing clofazimine are efficacious in treatment of experimental tuberculosis in mice

Inhalable clofazimine-containing dry powder microparticles (CFM-DPI) and native clofazimine (CFM) were evaluated for activity against Mycobacterium tuberculosis in human monocyte-derived macrophage cultures and in mice infected with a low-dose aerosol. Both formulations resulted in 99% killing at 2.5 g/ml in vitro. In mice, 480 g and 720 g CFM-DPI inhaled twice per week over 4 weeks reduced numbers of CFU in the lung by as much as log10 2.6; 500 g oral CFM achieved a log10 0.7 reduction.The Indian work was funded by a grant from CSIR, India (NWP0035). R.K.V., A.K.S., and A.K.A. received research fellowships from CSIR, India, and M.M. received one from ICMR, India. The South African work was supported by The South African Medical Research Council (M.P.M., M.C., R.A.) and a K-RITH collaborative grant (Howard Hughes Medical Institute and the University of KwaZulu-Natal, to P.B.F. and W.A.G.).http://aac.asm.org/am2014ay201

A laboratory study of soil stabilisation with an urea-formaldehyde resin

The aim of this paper is to present laboratory results on the effectiveness of a proprietary urea-formaldehyde (UF) resin as a soil stabiliser. The Indirect Tensile Strength (ITS) was used to characterise the soil stabilising properties of the resin. A brown shale gravel with an ITS dry strength of 160 kPa was used as test soil. Treated samples were compacted at the optimum moisture content (OMC) of the soil (ca. 9,5%) using the Marshall apparatus. Dry strength was evaluated after the samples were left to air-dry for 7 or 21 days. The wet strength was determined following a 24-hour water-soak of the air-dried samples. In this system, cement and lime were ineffective soil stabilisers even at the 6% dosage level. In contrast, the addition of 2% UF resin was sufficient to raise the dry strength to 340 kPa but wet strength was still poor. This problem was solved by a further addition of a suitable bitumen emulsion. At a 2% dosage it increased both the wet and dry strengths to ca. 450 kPa. Unconfined Compressive Strength (UCS) measurements on this as well as other soil types confirmed the soil stabilisation utility of the UF resin. These tests also showed that the system performed better in siliceous than in calcareous aggregates.http://www.journals.co.za/ej/ejour_civileng.htmlhb201