Adherence of the rotating vortex lattice in the noncentrosymmetric superconductor Ru7B3to the London model.

The noncentrosymmetric superconductor Ru7B3has in previous studies demonstrated remarkably unusual behaviour in its vortex lattice (VL), where the nearest neighbour directions of the vortices dissociate from the crystal lattice and instead show a complex field-history dependence, and the VL rotates as the field is changed. In this study, we look at the VL form factor of Ru7B3during this field-history dependence, to check for deviations from established models, such as the London model. We find that the data is well described by the anisotropic London model, which is in accordance with theoretical predictions that the alterations to the structure of the vortices due to broken inversion symmetry should be small. From this, we also extract values for the penetration depth and coherence length.

Magnetic phase diagram of the helimagnetic spinel compound ZnCr2Se4 revisited by small-angle neutron scattering.

We performed small-angle neutron scattering (SANS) measurements on the helimagnetic spinel compound ZnCr2Se4. The ground state of this material is a multi-domain spin-spiral phase, which undergoes domain selection in a magnetic field and reportedly exhibits a transition to a proposed spin-nematic phase at higher fields. We observed a continuous change in the magnetic structure as a function of field and temperature, as well as a weak discontinuous jump in the spiral pitch across the domain-selection transition upon increasing field. From our SANS results we have established the absence of any long-range magnetic order in the high-field (spin-nematic) phase. We also found that all the observed phase transitions are surprisingly isotropic with respect to the field direction.

Magnon spectrum of the helimagnetic insulator Cu2OSeO3.

Complex low-temperature-ordered states in chiral magnets are typically governed by a competition between multiple magnetic interactions. The chiral-lattice multiferroic Cu2OSeO3 became the first insulating helimagnetic material in which a long-range order of topologically stable spin vortices known as skyrmions was established. Here we employ state-of-the-art inelastic neutron scattering to comprehend the full three-dimensional spin-excitation spectrum of Cu2OSeO3 over a broad range of energies. Distinct types of high- and low-energy dispersive magnon modes separated by an extensive energy gap are observed in excellent agreement with the previously suggested microscopic theory based on a model of entangled Cu4 tetrahedra. The comparison of our neutron spectroscopy data with model spin-dynamical calculations based on these theoretical proposals enables an accurate quantitative verification of the fundamental magnetic interactions in Cu2OSeO3 that are essential for understanding its abundant low-temperature magnetically ordered phases.

Climate variability and Ross River virus infections in Riverland, South Australia, 1992-2004.

Ross River virus (RRV) infection is the most common notifiable vector-borne disease in Australia, with around 6000 cases annually. This study aimed to examine the relationship between climate variability and notified RRV infections in the Riverland region of South Australia in order to set up an early warning system for the disease in temperate-climate regions. Notified data of RRV infections were collected by the South Australian Department of Health. Climatic variables and monthly river flow were provided by the Australian Bureau of Meteorology and South Australian Department of Water, Land and Biodiversity Conservation over the period 1992-2004. Spearman correlation and time-series-adjusted Poisson regression analysis were performed. The results indicate that increases in monthly mean minimum and maximum temperatures, monthly total rainfall, monthly mean Southern Oscillation Index and monthly flow in the Murray River increase the likelihood, but an increase in monthly mean relative humidity decreases the likelihood, of disease transmission in the region, with different time-lag effects. This study demonstrates that a useful early warning system can be developed for local regions based on the statistical analysis of readily available climate data. These early warning systems can be utilized by local public health authorities to develop disease prevention and control activities.

Timeliness of Salmonella notifications in South Australia.

OBJECTIVE: To evaluate the timeliness of Salmonella serotype and phage type notifications in South Australia. METHOD: We surveyed all notifications of Salmonella to the South Australian Department of Human Services between July 1995 and June 1996. We entered data onto an Epi Info 6.02 database and calculated the time interval between various stages of typing notification. RESULTS: The median time taken between collection of a faecal specimen and receipt of serotype notification was 10 days (range, 5-38), while phage type notification took a further seven days (range 0-40). The time interval between collection of a specimen and notification of a Salmonella final identity was 14 days (range 6-49). The internal mail system of the Department of Human Services delayed notification a median of two days. Environmental Health Officers supplied reports for 224 (58%) of 384 cases, 71% of which occurred before the final Salmonella isolate was known. CONCLUSIONS: We found that the internal departmental mail system delayed the notification of Salmonella. In South Australia, investigations should focus on clusters of cases of known Salmonella identity, rather than all notified cases. IMPLICATIONS: To improve communicable disease investigations, health agencies should evaluate the timeliness of surveillance systems and examine the feasibility of transferring laboratory data electronically.

Changing epidemiology of Ross River virus disease in South Australia.

OBJECTIVE: To investigate changes in epidemiology and symptoms of Ross River virus (RRV) disease in South Australia. DESIGN: Longitudinal questionnaire-based survey of notified cases from one to 36 months after infection. SUBJECTS: All patients with recent serologically confirmed RRV infection notified to the Communicable Disease Control Unit, South Australian Health Commission, between 1 October 1992 and 30 June 1993. OUTCOME MEASURES: Sociodemographic data, source of infection, symptoms and ability to carry out daily activities (at onset of illness and at time of questionnaire, up to 36 months after infection), symptom duration, economic impact of the illness, cases recovery time, factors predictive of delayed recovery. RESULTS: Information was obtained on the acute illness from 698 of the 821 subjects and at 15 months after infection from 436. At 15 months, 51% of respondents still had joint pain and 45% had persistent tiredness and lethargy. Other common symptoms included myalgia (34%), lymphadenopathy (25%), headache (23%) and depression (22%). These symptoms were still common 30 months after infection. Increasing age was the only statistically significant predictor of delayed recovery. Infections were acquired across the State, away from previously recognised RRV-endemic areas. CONCLUSIONS: For many people, RRV disease is debilitating, with long term symptoms similar to those of chronic fatigue syndrome. The geographic range of the infection has expanded in SA.

Locally acquired Brachylaima sp. (Digenea: Brachylaimidae) intestinal fluke infection in two South Australian infants.

Eggs of a small intestinal trematode were found in the faeces of two 21-month-old children from the same rural district of South Australia who presented 18 months apart with mild abdominal pain and diarrhoea. Treatment with praziquantel resulted in egg clearance and resolution of gastrointestinal symptoms. A brachylaimid intestinal trematode involving the common house mouse, poultry and introduced European helicid snails is well established in South Australia. Both infants had been seen eating raw snails, and snails from their environment were found to be infected with metacercariae of a brachylaimid trematode.

Mortality from influenza and allied infections in South Australia during 1968-1981.

Numbers of deaths from pneumonia and influenza and other causes were analysed for successive four-week periods in South Australia during 1968-1981. An overall excess in deaths from pneumonia or influenza of 74% was evident during the winter months and early spring, compared with summer and early autumn. An accompanying excess of 18% occurred for deaths assigned to other causes. There was a strong association between numbers of deaths from pneumonia and influenza and other deaths, suggesting that influenza may have a broad impact on mortality. This mostly applied to individuals aged 60 years and over. There is the need for medical practitioners to provide prophylactic care to protect aged patients against the effects of influenza. This should be done in autumn, and special attention should be given to individuals with underlying conditions.

Primaquine-chloroquine prophylaxis against malaria in Southeast-Asian refugees entering South Australia.

In 1980, the incidence of malaria among Southeast-Asian refugees arriving in South Australia rose substantially to 22.0 cases/1000 arrivals. All these cases were caused by Plasmodium vivax, and the majority occurred in the small proportion of refugees who had arrived by way of Indonesian camps of asylum (59.2 cases/1000 arrivals). The commencement of an eight-week prophylactic regimen with primaquine (22.5 mg/week) and chloroquine (300 mg/week; 600 mg first dose) by 1388 refugees proved significantly effective in reducing the incidence of malaria among this population. The regimen was administered without the assessment of glucose-6-phosphate dehydrogenase levels, and a transient haemoglobinuria occurred in only one refugee. Other side-effects were minimal when the administration of drugs was delayed until several days after the arrival of the refugee in Australia.

Determinants of the microbiological characteristics of South Australian swimming pools.

A survey of 100 swimming pools has been conducted to assess the effectiveness of disinfection practices against various microorganisms and to check compliance with recommended chlorine levels and pH. Microbiological quality was assessed from densities of total coliforms, Escherichia coli, and Pseudomonas aeruginosa, total colony counts, and the presence or absence of amoebae, including the pathogen Naegleria fowleri. Although a free chlorine residual of 1.0 mg/liter and a pH range of 7.0 to 7.6 are recommended by local health authorities, 41 pools had a lower free chlorine residual and 37 had a pH outside this range. Multiple logistic regression analysis was used to test the association of field measurements with the microbiological data. The analysis demonstrated a strong positive association of free chlorine with bacteriological quality and the absence of Naegleria spp. No other field measurement was predictive in this regard, although the absence of all amoebae was associated with a relatively low water temperature and pH. Using a mathematical model derived from this analysis, it was estimated that 99% of pools would have acceptable bacteriological quality and 94% would be free of Naegleria spp. at a free chlorine residual of 1.0 mg/liter. However, at the mean water temperature (23 degrees C) and pH (7.5) seen in this study, other amoebae would still be detectable in 500-ml samples taken from 40% of pools at this chlorine level.

Hepatitis B reservoirs and attack rates in an Australian community. A basis for vaccination and crossinfection policies.

Four different subpopulations in South Australia, which were expected to have high rates of hepatitis B infection (Asians, Aboriginals, homosexual men, and drug addicts) were examined for their contribution to the total reservoir of hepatitis B surface antigen (HBsAg) carriers and to the total annual incidence of acute hepatitis B infection in South Australia. Age-specific prevalence data were also examined to assess the ages at which infection is commonly acquired. It was found that the above four groups, which comprise 3% of the State's population, are likely to include about 75% of HBsAg carriers in the State, but contribute a minority of the total new infections each year; they are not likely to present a significant risk of infection to the community at large. Three different age-related patterns of acquisition of infection were recognized--among Southeast Asians and Aboriginals, homosexual men and drug addicts, and the general community, respectively. The above approach, and to some extent the general findings, should be applicable to other similar communities in the formulation of effective policies for the control and prevention of hepatitis B infection.

The epidemiology and control of primary amoebic meningoencephalitis with particular reference to South Australia.

This paper reviews the history, epidemiology and control of primary amoebic meningoencephalitis (PAM), caused by Naegleria fowleri, with particular reference to South Australia. The intention has been to outline misconceptions and uncertainties pervading the earlier literature. Although PAM infections elsewhere have been attributed to cysts in air-borne dust, we believe that contact with water in the domestic environment was not adequately considered as a potential source of these infections. Several reports have cast doubt on the effectiveness of chlorine in controlling N. fowleri, although there is laboratory and South Australian field experience to the contrary. These reports can be traced to a misunderstanding of the circumstances surrounding cases of PAM reported by other workers. Provided that a continuous free chlorine residual of 0.5 mg/l can be maintained in water accessible to N. fowleri, the risk of disease should be negligible. The failure of amphotericin B therapy to save recent victims of the disease, despite relatively prompt intervention, is disappointing. Possible reasons for this, and the reports that rifampin or tetracycline combined with amphotericin might be more successful, are discussed.