Solidification of bimary alloys with one dimensional heat flow

Imperial Users onl

A thermodynamic study of germanium sulfides

The vapour pressure of germanium monosulfide (liquid) was determined by a boiling point method. An expression for the vapour pressure as a function of temperature was obtained and the heat of vapourization calculated. Using the heat of sublimation data obtained by other investigators, the heat of fusion was calculated. The thermodynamic properties, change of standard free energy (Δ F°) heat content (Δ H°) and entropy (Δ S°); of germanium disulfide were determined by using an indirect method. The equilibrium H2S/H2O ratios are determined for the reaction: GeS2 (s) + 2H2O(g) = GeO2 (s) + 2H2S(g), in the temperature range of 410-560°C by using a flow method and extrapolating the values of H2/H2O ratios to zero flow rate. An expression for the standard free energy of the reaction as a function of temperature was obtained. Using the known values of standard free energy of formation of GeO2(s), H2S(g) and H2O(g) an expression for the dissociation of germanium disulfide was calculated. A detailed description is given for the methods and the apparatus used for both the vapour pressure and equilibrium studies. The methods used for the preparation of the compounds GeS2 and GeS and their properties are described. X-ray diffraction patterns are given for GeS2, GeS and GeO2 phases --Abstract, pages i-ii

Investigating contamination of dental-unit waterline systems and microbial biofilm ecology

Introduction: Biofilms within dental-unit waterlines (DUWLs) are acknowledged sources of contamination in the dental clinical environment and affect the quality of clinical treatment water. As a standard for reducing exposure to potentially harmful microorganisms, the Department of Health (DoH), UK suggests that water discharged from DUWL should contain 100 to 200 CFU/mL. However, local audits suggest that the quality of clinical treatment water often fails to meet the standards required. The aim: The aim was to be able to readily identify waterlines with higher levels of contamination via validation of a rapid existing “in-office” test and subsequently understand biofilm ecology. Materials and Methods: Water samples from 31 DUWLs in general dental practices were taken during the working day and cultured using the PetrifilmTM AC plate test as per manufacturer’s instructions and for extended incubation periods under laboratory conditions. The samples were also cultured using the laboratory based benchmark R2A agar. Further culture methods were employed for investigating spread of human pathogens with aerosolization and splatter of DUWL water; retraction valve failure; waterborne biofilm ecology and environment within a simulated laboratory DUWL (sDUWL) and whether amoebae were harboring nosocomial bacteria. Results: The bacterial concentration of the water samples cultured on R2A agar varied significantly (1 × 101 to 4.3 × 106); in surgeries (48%) which met DoH standards and those that failed (52%). A retest of water from surgeries which delivered safe and contaminated water revealed that approximately 55% of practices met the recommended threshold values whilst around 45% failed. The PetrifilmTM AC Plate method gave variable sensitivity values on different occasions with 100% specificity. Only the nosocomial clinical isolate of Serratia marcescens was recovered from one clinical water sample. The opportunistic yeast, Candida parapsilosis from 1 sample indicated possible retraction valve failure. The in-vitro sDUWL output water demonstrated a fully established biofilm community by day 2 consisting of bacteria, a fungus (Cladosporium cladosporioides), and one amoeba (Vermamoeba vermiformis) as the main organisms. When tested under laboratory culture conditions, V. vermiformis, appeared to feed on S. marcescens isolated from clinical water. Electron microscopy confirmed bacterial adherence characteristics for biofilm formation, and altered pattern of cell division in one Gram positive isolate from the in-vitro sDUWL. Despite the detection of a Legionella species, no metabolically active opportunistic human pathogens were observed within V. vermiformis in the sDUWL biofilm. Conclusions: This study demonstrates the importance of regular monitoring of DUWL water because even clean DUWLs can quickly become contaminated. One aim of this study was to find an in-office testing method for dental needs but it appears that improving the sensitivity of in-office tests is a challenge that needs addressing in the first instance. A more positive outcome was that, on the whole, clinical output water was not harbouring opportunistic human pathogens at the time of testing and that clinical surfaces were clean. Also when dental units are used there was no evidence that contaminants were being drawn back into the DUWLs. Overall, achieving a low level of microbial contamination consistently in water to 100 - 200 CFU/mL appeared to be difficult. In the short-term, if water could be tested more often this would help to understand the related challenges associated with conforming to national standards of delivering clean treatment water. The laboratory sDUWL model showed defective cell division and altered phenotype of specific bacterial species, and that V. vermiformis appeared unlikely to be harboring the late coloniser L. pneumophila, as it was out-with the size-range of bacteria, amoebae choose to feed upon. As the laboratory sDUWL model closely mimicked the heterogeneous biofilm development including the type of main microorganisms as those of the clinical DUWL it can be used to accurately accesses commercial biocides in the control of the biofilm independently as literature continues to question the efficacy of commercial disinfections in waterline cleansing protocols that fail to meet the required standards

Treatment of fevers prior to introducing rapid diagnostic tests for malaria in registered drug shops in Uganda.

BACKGROUND: Since drug shops play an important role in treatment of fever, introducing rapid diagnostic tests (RDTs) for malaria at drug shops may have the potential of targeting anti-malarial drugs to those with malaria parasites and improve rational drug use. As part of a cluster randomized trial to examine impact on appropriate treatment of malaria in drug shops in Uganda and adherence to current malaria treatment policy guidelines, a survey was conducted to estimate baseline prevalence of, and factors associated with, appropriate treatment of malaria to enable effective design and implementation of the cluster randomized trial. METHODS: A survey was conducted within 20 geographical clusters of drug shops from May to September 2010 in Mukono district, central Uganda. A cluster was defined as a parish representing a cluster of drug shops. Data was collected using two structured questionnaires: a provider questionnaire to capture data on drug shops (n=65) including provider characteristics, knowledge on treatment of malaria, previous training received, type of drugs stocked, reported drug sales, and record keeping practices; and a patient questionnaire to capture data from febrile patients (n=540) exiting drug shops on presenting symptoms, the consultation process, treatment received, and malaria diagnoses. Malaria diagnosis made by drug shop vendors were confirmed by the study team through microscopy examination of a blood slide to ascertain whether appropriate treatment was received. RESULTS: Among febrile patients seen at drug shops, 35% had a positive RDT result and 27% had a positive blood slide. Many patients (55%) had previously sought care from another drug shop prior to this consultation. Three quarters (73%) of all febrile patients seen at drug shops received an anti-malarial, of whom 39% received an ACT and 33% received quinine. The rest received another non-artemisinin monotherapy. Only one third (32%) of patients with a positive blood slide had received treatment with Coartem® while 34% of those with a negative blood slide had not received an anti-malarial. Overall appropriate treatment was 34 (95% CI: 28 - 40) with substantial between-cluster variation, ranging from 1% to 55%. CONCLUSION: In this setting, the proportion of malaria patients receiving appropriate ACT treatment at drug shops was low. This was due to the practice of presumptive treatment, inadequate training on malaria management and lack of knowledge that Coartem® was the recommended first-line treatment for malaria. There is urgent need for interventions to improve treatment of malaria at these outlets

Appropriate targeting of artemisinin-based combination therapy by community health workers using malaria rapid diagnostic tests: findings from randomized trials in two contrasting areas of high and low malaria transmission in south-western Uganda.

OBJECTIVE: To compare the impact of malaria rapid diagnostic tests (mRDTs), used by community health workers (CHWs), on the proportion of children <5 years of age receiving appropriately targeted treatment with artemisinin-based combination therapy (ACT), vs. presumptive treatment. METHODS: Cluster-randomized trials were conducted in two contrasting areas of moderate-to-high and low malaria transmission in rural Uganda. Each trial examined the effectiveness of mRDTs in the management of malaria and targeting of ACTs by CHWs comparing two diagnostic approaches: (i) presumptive clinical diagnosis of malaria [control arm] and (ii) confirmatory diagnosis with mRDTs followed by ACT treatment for positive patients [intervention arm], with village as the unit of randomisation. Treatment decisions by CHWs were validated by microscopy on a reference blood slide collected at the time of consultation, to compare the proportion of children <5 years receiving appropriately targeted ACT treatment, defined as patients with microscopically-confirmed presence of parasites in a peripheral blood smear receiving artemether-lumefantrine or rectal artesunate, and patients with no malaria parasites not given ACT. RESULTS: In the moderate-to-high transmission area, ACT treatment was appropriately targeted in 79.3% (520/656) of children seen by CHWs using mRDTs to diagnose malaria, vs. 30.8% (215/699) of children seen by CHWs using presumptive diagnosis (P < 0.001). In the low transmission area, 90.1% (363/403) children seen by CHWs using mRDTs received appropriately targeted ACT treatment vs. 7.8% (64/817) seen by CHWs using presumptive diagnosis (P < 0.001). Low mRDT sensitivity in children with low-density parasitaemia (<200 parasites/μl) was identified as a potential concern. CONCLUSION: When equipped with mRDTs, ACT treatments delivered by CHWs are more accurately targeted to children with malaria parasites. mRDT use could play an important role in reducing overdiagnosis of malaria and improving fever case management within iCCM, in both moderate-to-high and low transmission areas. Nonetheless, missed treatments due to the low sensitivity of current mRDTs in patients with low parasite density are a concern. For community-based treatment in areas of low transmission and/or non-immune populations, presumptive treatment of all fevers as malaria may be advisable, until more sensitive diagnostic assays, suitable for routine use by CHWs in remote settings, become available

Cost-effectiveness analysis of malaria rapid diagnostic tests for appropriate treatment of malaria at the community level in Uganda.

In Sub-Saharan Africa, malaria remains a major cause of morbidity and mortality among children under 5, due to lack of access to prompt and appropriate diagnosis and treatment. Many countries have scaled-up community health workers (CHWs) as a strategy towards improving access. The present study was a cost-effectiveness analysis of the introduction of malaria rapid diagnostic tests (mRDTs) performed by CHWs in two areas of moderate-to-high and low malaria transmission in rural Uganda. CHWs were trained to perform mRDTs and treat children with artemisinin-based combination therapy (ACT) in the intervention arm while CHWs offered treatment based on presumptive diagnosis in the control arm. Data on the proportion of children with fever 'appropriately treated for malaria with ACT' were captured from a randomised trial. Health sector costs included: training of CHWs, community sensitisation, supervision, allowances for CHWs and provision of mRDTs and ACTs. The opportunity costs of time utilised by CHWs were estimated based on self-reporting. Household costs of subsequent treatment-seeking at public health centres and private health providers were captured in a sample of households. mRDTs performed by CHWs was associated with large improvements in appropriate treatment of malaria in both transmission settings. This resulted in low incremental costs for the health sector at US$3.0 per appropriately treated child in the moderate-to-high transmission area. Higher incremental costs at US$13.3 were found in the low transmission area due to lower utilisation of CHW services and higher programme costs. Incremental costs from a societal perspective were marginally higher. The use of mRDTs by CHWs improved the targeting of ACTs to children with malaria and was likely to be considered a cost-effective intervention compared to a presumptive diagnosis in the moderate-to-high transmission area. In contrast to this, in the low transmission area with low attendance, RDT use by CHWs was not a low cost intervention

Health facility utilisation changes during the introduction of community case management of malaria in South Western Uganda: An interrupted time series approach.

This dataset contains all visits made to health facilities in Bwambara Sub-county, South Western Uganda as part of a cluster randomised trial. The anonymised dataset includes basic demographic details of the visit and the diagnosis made

Introducing rapid diagnostic tests for malaria into registered drug shops in Uganda: lessons learned and policy implications.

BACKGROUND: Malaria is a major public health problem in Uganda and the current policy recommends introduction of rapid diagnostic tests for malaria (RDTs) to facilitate effective case management. However, provision of RDTs in drug shops potentially raises a new set of issues, such as adherence to RDTs results, management of severe illnesses, referral of patients, and relationship with caretakers. The main objective of the study was to examine the impact of introducing RDTs in registered drug shops in Uganda and document lessons and policy implications for future scale-up of malaria control in the private health sector. METHODS: A cluster-randomized trial introducing RDTs into registered drug shops was implemented in central Uganda from October 2010 to July 2012. An evaluation was undertaken to assess the impact and the processes involved with the introduction of RDTs into drug shops, the lessons learned and policy implications. RESULTS: Introducing RDTs into drug shops was feasible. To scale-up this intervention however, drug shop practices need to be regulated since the registration process was not clear, supervision was inadequate and record keeping was poor. Although initially it was anticipated that introducing a new practice of record keeping would be cumbersome, but at evaluation this was not found to be a constraint. This presents an important lesson for introducing health management information system into drug shops. Involving stakeholders, especially the district health team, in the design was important for ownership and sustainability. The involvement of village health teams in community sensitization to the new malaria treatment and diagnosis policy was a success and this strategy is recommended for future interventions. CONCLUSION: Introducing RDTs into drug shops was feasible and it increased appropriate treatment of malaria with artemisinin-based combination therapy. It is anticipated that the lessons presented will help better implementation of similar interventions in the private sector