Investigation of membrane de-clogging techniques in the Submerged Membrane Filtration Adsorption Hybrid System (SMFAHS)

Membrane clogging is a major obstacle to the successful operation of the membrane separation process. A submerged hollow fibre membrane with powdered activated carbon (PAC) adsorption (adsorption-membrane hybrid system) was used for the removal of organics from a synthetic wastewater representative of biologically treated sewage effluent. PAC usage successfully adsorbs the majority of the organics, and then the organic laden PAC is separated by the membrane reducing the direct organic loading to the membrane. However, membrane clogging still occurs. This study involved the development of an automation system and Supervisory Control and Data Acquisition (SCADA) system for performing an investigation and evaluation of three automated de-clogging techniques. The first de-clogging method involved the use of periodic relaxation, whereby permeate production for 12 minutes was periodically stopped for 3 minutes and the shear forces created by the aeration system and the absence of suction pressure during the relaxation period were used to de-clog the membrane. The second de-clogging method involved the use of a series of periodic back flush experiments with varied frequencies and durations to force permeate in the opposite direction out through the membrane pores. The optimal results in terms of de-clogging the membrane were achieved using a 15 second backflush after 15 minutes of permeate production. The third de-clogging method involved the application of an understanding of results of the periodic back flush series of experiments to design an automation system with a new approach to backflushing where an upper limit of a transmembrane pressure (TMP) increase each cycle was used to initiate the backflush. The transmembrane pressure represents the pressure measured across the membrane and it is a vital parameter indicating the degree of fouling of the membrane. A periodic backflush was found to be significantly more effective in terms of increasing the total quantity of wastewater treated than was achieved using periodic relaxation and was investigated in detail during the study. For the periodic backflush, an optimal frequency and duration was determined for treatment of wastewater with a fixed foulant concentration. The new approach to backflushing using more advances in the control system incorporating the TMP increase each cycle resulted in a 40% reduction in the number of backwashes required and was capable of self-optimising operating parameters under an unsteady foulant concentration of wastewater

Effect of different schedules of ten-valent pneumococcal conjugate vaccine on pneumococcal carriage in Vietnamese infants: results from a randomised controlled trial.

BACKGROUND: WHO recommends a three-dose infant pneumococcal conjugate vaccine (PCV) schedule administered as a two-dose primary series with booster (2 + 1) or a three-dose primary series (3 + 0). Data on carriage impacts of these and further reduced PCV schedules are needed to inform PCV strategies. Here we evaluate the efficacy against carriage of four different PCV10 schedules. METHODS: Participants within an open-label, randomised controlled trial in Ho Chi Minh City, Vietnam, were allocated to receive PCV10 in a 3 + 1 (2,3,4,9 months, n = 152), 3 + 0 (2,3,4 months, n = 149), 2 + 1 (2,4,9.5 months, n = 250) or novel two-dose (2,6 months, n = 202) schedule, or no infant doses of PCV (two control groups, n = 197 and n = 199). Nasopharyngeal swabs collected between 2 and 24 months were analysed (blinded) for pneumococcal carriage and serotypes. Trial registration: ClinicalTrials.gov NCT01953510. FINDINGS: Pneumococcal carriage prevalence was low (10.6-14.1% for vaccine-type (VT) at 12-24 months in unvaccinated controls). All four PCV10 schedules reduced VT carriage compared with controls (the 2 + 1 schedule at 12, 18, and 24 months; the 3 + 1 and two-dose schedules at 18 months; and the 3 + 0 schedule at 24 months), with maximum reductions of 40.1%-64.5%. There were no differences in VT carriage prevalence at 6 or 9 months comparing three-dose and two-dose primary series, and no differences at 12, 18, or 24 months when comparing schedules with and without a booster dose. INTERPRETATION: In Vietnamese children with a relatively low pneumococcal carriage prevalence, 3 + 1, 2 + 1, 3 + 0 and two-dose PCV10 schedules were effective in reducing VT carriage. There were no discernible differences in the effect on carriage of the WHO-recommended 2 + 1 and 3 + 0 schedules during the first two years of life. Together with the previously reported immunogenicity data, this trial suggests that a range of PCV schedules are likely to generate significant direct and indirect protection. FUNDING: NHMRC, BMGF

Field evaluation of the establishment potential of wmelpop Wolbachia in Australia and Vietnam for dengue control

BACKGROUND: Introduced Wolbachia bacteria can influence the susceptibility of Aedes aegypti mosquitoes to arboviral infections as well as having detrimental effects on host fitness. Previous field trials demonstrated that the wMel strain of Wolbachia effectively and durably invades Ae. aegypti populations. Here we report on trials of a second strain, wMelPop-PGYP Wolbachia, in field sites in northern Australia (Machans Beach and Babinda) and central Vietnam (Tri Nguyen, Hon Mieu Island), each with contrasting natural Ae. aegypti densities. METHODS: Mosquitoes were released at the adult or pupal stages for different lengths of time at the sites depending on changes in Wolbachia frequency as assessed through PCR assays of material collected through Biogents-Sentinel (BG-S) traps and ovitraps. Adult numbers were also monitored through BG-S traps. Changes in Wolbachia frequency were compared across hamlets or house blocks. RESULTS: Releases of adult wMelPop-Ae. aegypti resulted in the transient invasion of wMelPop in all three field sites. Invasion at the Australian sites was heterogeneous, reflecting a slower rate of invasion in locations where background mosquito numbers were high. In contrast, invasion across Tri Nguyen was relatively uniform. After cessation of releases, the frequency of wMelPop declined in all sites, most rapidly in Babinda and Tri Nguyen. Within Machans Beach the rate of decrease varied among areas, and wMelPop was detected for several months in an area with a relatively low mosquito density. CONCLUSIONS: These findings highlight challenges associated with releasing Wolbachia-Ae. aegypti combinations with low fitness, albeit strong virus interference properties, as a means of sustainable control of dengue virus transmission

Surjective word maps and Burnside's p^a q^b theorem

We prove surjectivity of certain word maps on finite non-abelian simple groups. More precisely, we prove the following: if N is a product of two prime powers, then the word map (x,y)↦xNyN is surjective on every finite non-abelian simple group; if N is an odd integer, then the word map (x,y,z)↦xNyNzN is surjective on every finite quasisimple group. These generalize classical theorems of Burnside and Feit–Thompson. We also prove asymptotic results about the surjectivity of the word map (x,y)↦xNyN that depend on the number of prime factors of the integer N